Dissertations / Theses on the topic 'Herbivore grazing'

Degradation of terrestrial habitats with high conservation value has resulted in strategic efforts to cease or reverse their declines. Broad habitat management can restore ecological processes and large herbivores can provide ecological function in some terrestrial systems. Following years of decline and fragmentation, owing to factors such as cessation of traditional practices, lowland heathland has become an internationally important habitat with strategic protection. Free-ranging grazing aims to assist in mitigating such losses to habitat and vegetation communities, but quantifying the grazing regime and its associated impacts is necessary to ensure protection of these vulnerable systems. Reviews of herbivore impacts on lowland heath provide detailed evaluations and recognise the absence of experimental assessments and baseline monitoring. This research aimed to assess ecological activity and impacts (herbage removal, trampling and dunging) of horses and cattle on a lowland heath system to determine their influence on changing vegetation and to inform grazing management. This mixed regime is commonly adopted for restoration of semi-natural habitats but a failure to understand the separate vegetation impacts can be detrimental for the system as a whole. Behavioural activity was quantified using scan-sampling assessing spatial and temporal variation in behaviour, habitat selection and niche overlap, spatial occupancy and diet. A factorial design was set up to quantify the impacts of herbage removal, trampling and dunging to vegetation separately. Assessments vegetation community composition and architecture in treatment and control areas were undertaken. Analyses incorporated non-parametric and general linear models. Animals utilised their environments in different ways, varying for feeding and showed high habitat selectivity, based on physiology and foraging strategy primarily. Herbage removal strongly influenced vegetation architecture and heterogeneity owing to selection for graminoids and the plants’ competitive traits; effects on other plants were not as well defined due to minimal abundance. Trampling modified the vegetation structure due to reduced canopy density maintaining colonising gaps, but increased graminaceous cover and showed a capacity for lateral expansion. Dunging regime was highly influential for enhancing plant architecture and modified vegetation composition based on nutrient availability and competition. Worming regime was influential on architectural parameters and may be due to retarded dung degradation; further research is required. The findings contributed knowledge to lowland heath grazing management, validating the use of mixed regimes at low densities, for generating vegetation heterogeneity, for the control of dominating plants and for understanding the impacts of different animal-management practices. Expanding the reach of this research to comparable systems is necessary to develop the knowledge of grazing-management impacts. The work addressed an absence of experimental evaluation on these systems and also illustrated the importance of separately quantifying the impacts of large herbivores.

Estimating herbivore density is an important part of understanding their impact on vegetation.  Many studies have been carried out on the impact of reindeer and other herbivores on arctic and sub-arctic vegetation, but they are difficult to compare as they typically use different methods to estimate herbivore activities.  The aim of this study was to compare three methods that were based on the recent International Tundra Experiment herbivory protocol to measure the activities of three herbivore groups: reindeer, rodents and invertebrates. The robustness of the methods themselves was then evaluated.  Fieldwork was carried out at 12 sites in the Fennoscandian mountain area, with controls inside reindeer exclosures.  The results showed that the methods were the most robust when measuring reindeer activities.  The reindeer measurements were also well correlated with a reindeer-density estimate calculated from official reindeer population data.  This study recommends considering the use of photographs to increase the time-efficiency of pellet-counts.  The rodent activity estimates were good, but the patterns inside exclosures differed to the patterns outside exclosures.  The results for invertebrates were deemed to be less reliable as the measurements for one method were not recorded at an appropriate scale.  In conclusion, the findings of this study will help improve the comparability of future studies on the impact of reindeer herbivory and other herbivores, and gives suggestions for more accurate ways of measuring herbivore pressure in arctic and sub-arctic vegetation.

Plant-herbivore interactions play a significant role in the structure and functioning of ecosystems. Co-evolutionary theory suggests that plant defenses evolved due to herbivores and herbivore pressure can shape the genetic composition of their food resources. We used interactions between North American porcupines (Erethizon dorsatum) and trembling aspens ( Populus tremuloides) as a system to investigate this theory's important assumption that herbivores select food sources based on genetically controlled traits. We confirmed that porcupines exhibit intra-specific food selection and that this is linked to the genetic composition of the aspens. We also demonstrated that variation in phenolic glycosides and condensed tannins are strong components of this selection, thereby creating an important link between genetics, plant chemistry, and mammalian herbivory. We investigated potential impacts of porcupine herbivory on aspen using fluctuating asymmetry, however we did not detect any stress on heavily eaten trees, thereby questioning the validity of this tool for this study system.

Vegetation in semi-arid regions is subject to change when heavily utilised by herbivores. Changes in species richness, species and growth form composition, total cover and plant palatability in response to rest (fenced) and grazing (open) treatments was investigated in Sanbona Wildlife Reserve over five years (2004-2008). This reserve is over 55 000 ha and has four dominant vegetation types: Little Karoo Quartz Vygieveld, Western Little Karoo, Montagu Shale Renosterveld and previously transformed Renosterveld classified here as Old Lands. There was no significant change in vegetation dynamics between the fenced or open plots. There were significant differences between years in some vegetation types. All vegetation types showed both treatments having similar shifts in floristic composition. Floristic composition deviated the greatest in 2008 in all vegetation types. This was attributed to an increase in summer and winter rainfall in 2008, as all plots were similarly affected. There was no observed impact of herbivores although disturbance from small rodents and baboons was observed in a few plots. The lack of detectable difference between the fenced and open sites was attributed to low stocking rates, good rainfall and insufficient time.

Along the coast of temperate oceans brown algae of the genus Fucus form dense stands on rocky shores and are keystone species of the coastal ecosystem. These large seaweeds are perennial and function as substrate for many sessile marine organisms, provide shelter for fauna and juvenile fish, and are food source. A number of abiotic (e.g. wave-exposure, salinity and substrate) and biotic (e.g. herbivory and competition) factors structures these communities and determines the abundance and composition of fucoids at each specific site. Earlier studies have shown that herbivores may reduce growth of fucoids, thus affecting their distribution, and at high densities eliminate the species from previously occupied sites. In my thesis I focused on investigating herbivore-seaweed interactions and whether such interactions could influence the geographical range limits of Fucus species. A set of laboratory bioassays and a field survey were conducted (1) to investigate the resistance to grazing by a generalist gastropod between introduced (to Sweden) and native (Iceland) Fucus evanescens (Paper I),  (2) to study the distribution pattern of F. radicans and F. vesiculosus along the Swedish coast and specifically the southern limit of F. radicans, (3) to examine the abundance of herbivores in these two species, and (4) to test the hypothesis that Idotea baltica may contribute to restrict F. radicans to the Bothnian Sea (objective 2-4; Paper II). Fucus evanescens, a species that was introduced to the Swedish coast about 100 years ago, was found to be more resistant to grazing by L. littorea compared to F. evanescens from the native Icelandic populations.  It was also shown to contain a higher amount of phlorotannins; a putative chemical defence to herbivory. This indicates that development of resistance to herbivory could be important for a successful introduction and survival in a new range. No gradual change in the proportion, measured as % cover of either F. radicans or F. vesiculosus was found inside the range of F. radicans and its southernmost limit was abrupt without any corresponding abrupt change in any abiotic factor, e.g. salinity. Herbivores, i.e. Idotea spp., Gammarus spp. and Theodoxus fluviatils were found to be more abundant in F. radicans than in F. vesiculosus thalli indicating a habitat preference for F. radicans.  Further, Idotea baltica, whose range only overlaps with that of F. radicans in the south, was shown to prefer F. radicans over F. vesiculosus, possibly due to its lower content of phlorotannins. Based on these findings I propose that Idotea species may contribute in restricting the southern range of F. radicans, although further experiments, especially regarding competition with the larger F. vesiculosus need to be performed. In conclusion, biotic interactions e.g. the ability of to resist herbivore grazing by e.g. high phlorotannin content or having a structure less attractive as habitat to herbivores may be of importance in determining the geographic range of fucoids.
Längs kusterna i de tempererade haven bildar brunalger av släktet Fucus täta bestånd på klippiga stränder och är ofta nyckelarter i kustekosystemen. Dessa tångarter är fleråriga och utgör substrat för många fastsittande organismer, ger skydd åt små rörliga djur och fiskyngel, samt utgör föda för betare så som gastropoder, amphipoder och isopoder. Faktorer som vågexponering, bottentyp, salthalt, näringshalter, bete och konkurrens strukturerar tångsamhällen och avgör hur vanlig varje tångart är på en viss lokal. I min avhandling har jag fokuserat på interaktionen mellan betare och tång, samt hur viktig denna interaktion är för att avgöra den geografiska utbredningen av tångarter. Tidigare studier har visat att betare kan minska tillväxten hos tång och på så sätt påverka dess utbredning. I höga densiteter kan de beta ner hela bestånd av tång så att den försvinner från lokaler där de tidigare vuxit. Resistens mot bete hos Fucus evanescens, ishavstång, som är introducerad till Skagerrak, Kattegat och sydvästra Östersjön och inhemsk i norra Atlanten och norra Stilla Havet undersöktes i betesförsök (Artikel I). En betare, generalisten Littorina littorea, strandsnäcka, som är inhemsk i Sverige, dit F. evanescens har introducerats, föredrog att äta F. evanescens från Island där den är inhemsk, framför F. evanescens från Sverige. Det här skulle kunna tyda på att ett välutvecklat försvar är viktigt för att alger som blir introducerade till nya områden ska kunna etablera sig i det nya området. Jag undersökte även utbredningen av den nyligen beskrivna tångarten Fucus radicans, smaltång (Artikel II). Resistensen mot betare hos F. radicans jämfördes med resistensen mot bete hos F. vesiculosus, blåstång, som växer tillsammans med F. radicans, genom att undersöka preferensen mellan de två arterna hos Idotea baltica, tånggråsugga (Artikel II). Det fanns ingen gradient i förekomsten av F. radicans eller F. vesiculosus inom F. radicans utbredningsområde. Istället observerades en ganska abrupt gräns för utbredningen av F. radicans i söder. Eftersom I. baltica, vars utbredning överlappar F. radicans utbredning i söder, föredrog att äta F. radicans framför F. vesiculosus, skulle F. radicans utbredning kunna påverkas av I. baltica. Både I. baltica och två andra betare, Gammarus spp. och Theodoxus fluviatilis, var vanligare i F. radicans än i F. vesiculosus i plantor insamlade i fält. Det innebär att de vanligaste betarna, även i fält, föredrar att uppehålla sig i F. radicans och antagligen konsumerar mer av F. radicans. Slutsatsen från de båda studierna är att betare och tångens försvar mot bete har potentialen att påverka utbredning av olika tångarter.

There is limited knowledge and understanding of the role of nutrients and effect of herbivore grazing on epilithon production in Australian upland rivers. Before investigating these processes, a method was required that will allow the study of factors (physical, chemical and biological) that affect epilithon abundance and distribution in lotic systems. The Thredbo River, Kosciusko National Park, New South Wales, provided an opportunity to conduct this investigation because it: is relatively undisturbed; has been intensely studied; is easily accessed; and is of appropriate width and depth to conduct in-stream experiments. The specific goals of this research were the: (1) validation of the nutrient-diffusing substrate method for investigating epilithon responses to nutrients; (2) development of experimental channels in which to investigate nutrient/epilithon dynamics in an upland stream; (3) development of a method to inhibit macroinvertebrate grazing from in situ experimental channels, so that epilithon responses to nutrients with and without grazing pressure can be studied; and (4) assessment of the ecological implications of nutrient/ epilithon/macroinvertebrate interactions assessed from in-stream experiments. Major achievements of my research, that advance the study of stream ecology, are as follows: · The investigation of the features of nutrient release from terracotta nutrientdiffusing substrates showed that phosphorus does not readily diffuse through terracotta clay, probably because terracotta contains known binding agents for phosphorus, such as iron, and because pores are easily blocked. I concluded that this type of substrate is inappropriate for studying nutrient dynamics and epilithon responses to the nutrient(s) limiting growth. The outcomes of this research has implications for future research using nutrient-diffusing substrates, and of how nutrient limitation information is interpreted from past research using terracotta nutrient-diffusing substrates. · I designed and tested in-stream experimental channels that were functional and provided near natural conditions for studying the interactions between nutrients/ epilithon/macroinvertebrates, without affecting physical variables not tested for. The in situ method developed was successful in simulating 'real world' complexities. Clay paving bricks were used as standardized common surface for community development because their colour, size and surface texture are similar to those of natural stones. · I developed a technique for successfully inhibiting macroinvertebrate grazing from designated areas, using electricity, without affecting flow and light. This technique will enable in-stream herbivory studies to assess the effects of macroinvertebrate grazing pressure on epilithon under natural conditions, including variability in flow, temperature, light and nutrients. It will allow the vexed question of whether epilithon biomass is controlled by bottom-up or top-down processes to be objectively addressed. The construction of in situ experimental channels that simulate natural conditions, combined with the non-intrusive methods of macroinvertebrate exclusion and nutrient addition, resulted in a study design that will facilitate the investigation of biotic responses to nutrients in Australian upland streams. Using the method developed, I showed that variable flows in the upper Thredbo River appear high enough to slough epilithon, but not high enough to dislodge macroinvertebrates. This may mean that in systems such as the Thredbo River that experience frequent low level disturbance, the epilithon is unable to reach equilibrium. There is strong top-down control of epilithon in this stream, with nutrients, temperature and light playing a secondary role. I concluded that natural variability may be more important than previously considered and perhaps this, rather than constancy, should be studied. This thesis adds support to the continuance of multiple factor investigations, and advocates that such studies be conducted under natural conditions so that the results are more relevant to natural systems than from studies conducted in controlled laboratory and outdoor artificial streams. Clearly, the in-stream channels, developed as part of the current research, will allow research that contributes to our understanding of community responses to the physical, chemical and biological processes operating in lotic environments.

Abstract The area of traditionally managed semi-natural meadows is declining throughout Europe. Knowledge of how to restore their species richness is urgently needed. Community manipulations by means of grazing and mowing and, on the other hand, knowledge of species-level responses as well as the responses of functional plant groups to management may help in planning appropriate restoration tools. The restoration of species richness was studied in two community-level experiments: in a sheep grazing experiment and in a mowing experiment. Three species-level studies were conducted to test the compensatory capacity of monocarpic, herbaceous plants (Gentianella amarella, Erysimum strictum, Euphrasia stricta) to simulated herbivory (10–50% of stem being cut). The perennial Linaria vulgaris was used to study whether there is any benefit of clonal integration in the tolerance of simulated herbivory. This topic was studied in a growth experiment and a 13C tracer study. In both grazing and mowing experiments, small herbs gained more space, while the dominant tall herbs subsided. The species number increased by 30% on the grazed plots, but mowing did not affect species richness, probably indicating seed limitation. At sites of this kind, seed addition could be used to promote restoration. Functional plant groups appeared to be useful in predicting the effects of grazing on plant communities. Early season grazing and mowing seem to be proper management tools in overgrown/degraded meadows. In species-level studies, all the species had relatively good compensatory capacity to repair small damage. Overcompensation was observed in response to apical damage, especially when the growing conditions were favourable, supporting the compensatory continuum hypothesis. The studied monocarpic plant species may share a common unbranched growth form where incidental apical damage leads to activation of uninitialized meristems and slight overcompensation. These responses may represent consequences of adaptation to above-ground competition, rather than adaptation to predictable herbivory. In Linaria, damaged ramets were not supported, but the neighbouring ramets seemed to compete with each other for root resources. While growing in disturbed habitats, it is more profitable for this species to invest in new ramets. The present studies showed that, while the appearance and structure of a traditional grassland rich in small-growing herbs can be restored in five years, it is more difficult to increase species diversity by mere mowing or grazing. Knowledge of the tolerance of individual species for herbivory could provide useful information for planning management practices. More studies on the effects of different management tools on different meadow types are urgently needed for the maintenance of the diversity of these valuable environments
Tiivistelmä Perinteisellä tavalla hoidettujen luonnonniittyjen pinta-ala vähenee kaikkialla Euroopassa. Tarvitsemme enemmän tietoa siitä, miten näiden elinympäristöjen lajiston monimuotoisuus voitaisiin turvata. Tietämys laidunnuksen ja niiton vaikutuksesta kasviyhteisöihin ja toisaalta yksittäisiin kasvilajeihin tai toiminnallisiin kasviryhmiin voi auttaa tehokkaiden hoito- ja ennallistamistapojen löytämisessä. Tässä työssä tutkittiin niittyjen lajirikkauden palauttamista kahdessa yhteisötason kokeessa: lammaslaidunkokeessa ja kokeessa, jossa eri niittotapojen vaikutuksia selvitettiin. Kolmessa lajitason kokeessa testattiin monokarppisten ruohokasvien (rantaukonnauris, horkkakatkero, ketosilmäruoho) kompensaatiokykyä simuloituun herbivoriaan (10–50 % varresta poistettiin). Monivuotista kannusruohoa käytettiin tutkittaessa onko klonaalisesta integraatiosta hyötyä herbivorian siedossa. Tätä selvitettiin kasvukokeella ja hiili-13-merkkiainekokeella. Sekä laidun- että niittokokeessa matalat ruohokasvit saivat kasvutilaa korkeiden ruohojen valta-aseman vähentyessä. Laidunnus lisäsi lajimäärää 30 % koealaa kohti, mutta niitto ei vaikuttanut lajirikkauteen. Molemmissa kokeissa kasviyhteisö oli luultavasti siemenrajoitteinen. Tällaisissa kohteissa siementen lisäystä voitaisiin käyttää ennallistamiskeinona. Toiminnalliset kasviryhmät olivat käyttökelpoisia ennustettaessa laidunnuksen vaikutuksia kasviyhteisöön. Aikaisin kasvukaudella tapahtuva niitto/laidunnus näyttää sopivalta hoitokeinolta umpeenkasvaneilla niityillä. Lajitason kokeissa kaikki tutkitut kasvilajit kykenivät melko hyvin kompensoimaan vähäisiä vaurioita. Ylikompensaatiota havaittiin vasteena kärkivaurioihin erityisesti, kun kasvuolot olivat edulliset. Tämä tuki ns. kompensaatiojatkumohypoteesiä. Tutkituilla lajeilla voi olla yhtenäinen haaraton kasvumuoto, jossa ajoittaiset kärkivauriot johtavat lepotilassa olevien silmujen aktivoitumiseen ja lievään ylikompensaatioon. Nämä vasteet voivat olla seurausta sopeutumisesta valokilpailuun pikemmin kuin sopeutumisesta ennustettavissa olevaan herbivoriaan. Kannusruoholla vaurioituneita versoja ei autettu, vaan kloonin sisällä versot näyttävät kilpailevan keskenään juuriresursseista. Koska laji kasvaa häirityillä paikoilla, sille näyttää olevan edullisempaa investoida uusiin versoihin. Tämä työ osoitti, että vaikka perinteisen matalakasvuisen lajirikkaan niityn ulkonäkö ja rakenne voidaan palauttaa viidessä vuodessa, on vaikeampaa lisätä lajirikkautta pelkän niiton tai laidunnuksen avulla. Tietämys yksittäisten kasvilajien vasteista biomassan menetykseen voi auttaa sopivien hoitotapojen suunnittelussa. Lisää kokeita eri hoitotapojen vaikutuksista ja eri niittytyypeillä tarvitaan pikaisesti näiden arvokkaiden elinympäristöjen monimuotoisuuden ylläpitämiseksi

Master of Science
Department of Animal Sciences and Industry
KC Olson
Our objective was to determine the effects of supplemental corn steep liquor (CSL) on voluntary selection of sericea lespedeza (SL) by beef cows grazing native tallgrass range. Dietary botanical composition of cows (n = 145; initial BW = 579 ± 91 kg) was evaluated during a 150-d grazing period (5/1 to 10/1). Native pastures (n = 9; 50 ± 17 ha) infested by SL (average SL biomass = 37% of total forage biomass) were assigned randomly to 1 of 2 treatments: grazing by unsupplemented cows or grazing by cows supplemented with CSL (1.79 kg DM • cow-1 • d-1; 45% DM, 34% CP). Cows were assigned randomly to treatment and pasture (stocking rate = 0.5 ha/AUM). Concentration and protein-binding capacity of condensed tannins (CT) in SL were measured monthly. Fecal samples were collected from each cow on 6/1, 7/1, 8/1, 9/1, and 10/1. Herbivory of SL was estimated along line transects in October. Plant fragments in fecal samples were quantified via a microhistological technique; fragment prevalence in fecal material was assumed to equal botanical composition of the diet. Concentration and protein-binding capacity of CT in SL were greatest (P < 0.01) on 8/1 and 9/1, respectively. The proportion of individual SL plants showing evidence of herbivory tended to be greater (P = 0.09) on pastures grazed by supplemented cows compared to pastures grazed by unsupplemented cows (94 vs. 80% of SL stems, respectively). Prevalence of SL in beef cow diets was influenced (P < 0.01) by CSL supplementation and by month. Prevalence of SL in beef cow diets was not different (P ≥ 0.35) between treatments when concentration and protein-binding capacity of CT were relatively low (6/1, 7/1, and 10/1). In contrast, supplemented cows selected more (P < 0.01) SL than unsupplemented cows when concentration and protein-binding capacity of CT were greatest (8/1 and 9/1). We interpreted these data to suggest that voluntary selection of SL by beef cows was inversely related to concentration of CT; moreover, supplemental CSL stimulated voluntary selection of SL during periods of high CT concentration. Supplemental CSL did not influence selection of other plant species that were monitored.

The importance of resource supply and herbivory in driving competitive interactions among species has been an important but contentious issue within ecology. These variables exhibit different effects on species competition when manipulated in isolation but interact when manipulated together. I tested the direct and interactive effects of nutrient addition and simulated grazing (clipping) on the competitive performance of primary producers and community structure of a seagrass bed in South Florida. One square meter experimental plots were established in a mixed seagrass meadow from August 2007 to July 2009. The experiment was a 3 x 3 factorial experiment: 3 fertility treatments: control, medium (2.4 mg N d-1 and 80 µg P day-1) and high (4.8 mg N d-1 and 160 µg P day-1) x 3 clipping intensities (0, 25% and 50 % biomass removal (G)) x 5 replicates for each treatment = 45 plots). Nutrient additions and simulated grazing were done every two months. Fertilization and simulated grazing decreased sexual reproduction in S. filiforme. Fertilization increased competitive dominance within the primary producers while simulated grazing counteracted this effect by removal of the dominant species. Fertilization ameliorated the negative impacts of simulated grazing while simulated grazing prevented competitive exclusion in the fertilized plots. Nutrient addition and simulated grazing both exerted strong control on plant performance and community structure. Neither bottom up nor top down influences was eliminated in treatments where both factors where present. The effects of fertilization on plant performance were marked under all clipping intensities indicating that the system is regulated by nutrient availability both in the presence or absence of grazers. Clipping effects were strong under both fertilized and unfertilized conditions indicating that the seagrass bed can be simultaneously under top-down control by grazers.

Abstract In northernmost Fennoscandia, grazing by reindeer (Rangifer tarandus L.) has a substantial impact on the vegetation of boreal forests and arctic-alpine tundra heaths, which are reflected in below-ground processes, such as nutrient mineralization and soil organic matter decomposition. In the present thesis, the effects of reindeer grazing on soil nutrient cycling were studied by comparing grazed situation with an ungrazed control area in ten boreal forests and six arctic-alpine tundra heaths. In boreal forests, reindeer grazing reduced microbial respiration in both the oligotrophic and mesotrophic study areas, indicating a deficiency of labile substrates for the soil microbes due to reindeer grazing. Simultaneously, there was heterogeneity in the impact on nitrogen mineralization rates as at some sites, mineralization was enhanced by grazing. The fertilization effect of urine and faeces can therefore be strong enough a factor to outweigh a reduction in quality of soil organic matter. In the oligotrophic forests, low soil moisture content in the grazed areas could sometimes limit the mineralization rates even when the potential for mineralization was enhanced by grazing. In the tundra ecosystems, there was spatial variation in the impact of grazing on microbial respiration and nitrogen mineralization. Low grazing intensity occurring outside the growing season had a retarding impact on nutrient cycling in both unfertilized, nutrient-poor and fertilized, nutrient-rich conditions. In contrast, a relatively high grazing intensity enhanced the mineralization rates in two nutrient-poor and two nutrient-rich tundra heaths. When three different grazing intensities were compared in one oceanic, nutrient-rich and one continental, nutrient-poor tundra heath, the strongest positive effect of grazing on soil nutrient cycling occurred in the heavily grazed areas. The data do not support the assumption that soil nutrient availability regulates whether herbivores enhance or retard nutrient cycling in the soil. Instead, the net effect of grazing is determined by the balance between the underlying mechanisms that may work at opposite directions. The most important of these mechanisms are the grazer-mediated impact on the decomposability of the dominant vegetation and fertilization by urine and faeces. The duration, intensity and seasonal timing of the grazing seem to be important factors that regulate whether reindeer grazing enhances or retards soil nutrient cycling in each specific area. Due to the high spatial and temporal variation in the effects of grazing observed in this study, it is not possible to generalize the overall impact of grazing. Further study is required in order to determine the exact conditions under which grazing enhances or it retards soil nutrient cycling.

Abstract In this thesis I studied responses of three biennial, monocarpic plants Erysimum strictum, Gentianella amarella, and G. campestris, to various aspects in resource availability (i.e. competition, mineral nutrition, neighbor removal) and environmental stress (early frost) at adult or rosette stages and how these effects are related to grazing tolerance. I also studied how manipulations in resource availability affected arbuscular mycorrhizal colonization of the roots. All three species were relatively tolerant to simulated grazing and in most cases plants were able to compensate quite well for minor biomass losses. According to the compensatory continuum hypothesis, tolerance is most pronounced in resource-rich conditions, but this was not always the case in the present experiments. Erysimum strictum compensated for defoliation at the rosette stage but the reproductive output of adult plants was reduced markedly in the next year. This reduction was strongest among fertilized plants. Moreover, apex removal at the adult stage resulted in overcompensation (i.e. clipped plants were more productive) but only in the absence of fertilization and in the presence of competition, which is against the compensatory continuum hypothesis. In E. strictum a potential cost of compensation appeared as delayed flowering and fruit maturation among clipped plants. However, in spite of early frost treatment clipped plants were still able to overcompensate. In Gentianella amarella and G. campestris, apex removal reduced growth and reproductive performance in most cases. Effects on root fungal parameters were positive or neutral. This pattern suggests that simulated above-ground herbivory tends to increase carbon limitation, and therefore regrowing shoots and the fungal symbionts may appear as alternative, competing sinks for the limited carbon reserves of the host plant. Both shoot architecture and resource availability modify the responses of the study plants to apical damage at both rosette and adult stages. In addition, different environmental stress factors affect success in compensatory growth.

Doctor of Philosophy
Department of Biology
Brett K. Sandercock
Habitat heterogeneity is a key driver of biodiversity in many ecosystems. In native ecosystems, habitat heterogeneity can arise from multiple drivers including nutrients, topoedaphic conditions, and ecological disturbance. Historically, the prairies of North America existed as a heterogeneous mosaic of habitat conditions created by the interaction of fire and grazing by native ungulates. The focus of many grazing systems has been to minimize disturbance caused by grazing by promoting uniform distributions of grazing animals across management units. Patch-burn grazing is an alternative rangeland management practice that has been proposed to restore historical patch dynamics and biodiversity to rangelands by simulating historical disturbance processes. In my dissertation research, I tested the hypothesis that patch- burn grazing restores habitat heterogeneity to rangelands, and that the resulting habitat heterogeneity can promote biodiversity of native wildlife. I focus on responses of small mammals and coyotes to patch-burn grazing to gain a better understanding of wildlife responses to rangeland management, and because grassland mammals are an ecologically important group. My 3.5-year field study of habitat and small mammal responses to rangeland management showed that: 1) patch-burn grazing created greater heterogeneity in vegetative structure and composition of plant functional groups than in positive and negative controls; 2) habitat heterogeneity created by the interaction of fire and grazing increased small mammal richness and diversity compared to a negative control managed for uniform grazing distributions; 3) the interaction of fire and grazing structured small mammal communities in tallgrass prairie; and 4) population dynamic responses of small mammals to fire and grazing disturbance were species- specific. My 3-year study of coyote survival and resource selection revealed that: 1) rangeland management influences resource selection by coyotes in seasons when they depend on small mammal prey, but not during other seasons; and 2) anthropogenic sources of mortality are important for coyotes at a protected area, even in the absence of harvest. My field results show that restoring the drivers of historical patch dynamics to managed rangelands and publicly held grasslands that are not currently grazed could have profound effects on biodiversity conservation in North America, while continuing to provide ecosystem services to society.

Studies in tropical regions have shown that trees and grasses respond differently to fire, grazing and browsing. In African savannas, the responses to fire, grazing and browsing are different, determined by negative or positive correlations. Browsing may have other consequences than grazing because instead of increasing woody biomass it reduces it, causing increase in grass growth, leading to increase in fuel that results in more intense fires and decrease in woody biomass. Fire and herbivory are an important interactive disturbance factors affecting vegetation succession and the tree-grass dynamics in savanna environment. Several of the fire-herbivory interactions are landscape level effects, which is shown in 2 models. My hypothesis is that the tree-grass balances are determined by interactions of both grazing and fire. There have come new scientific data about fire and herbivory and the interaction effects on tree-grass dynamic and succession in the savanna. By analyzing my hypothesis through a comparison between hypotheses, Intermediate disturbance hypothesis, Janzen-Connell hypothesis and the Huston hypothesis, I propose several scenarios of the savanna tree-grass dynamics in East Africa, as a result of this comparison.

Acropora cervicornis, commonly known as the staghorn coral has historically been a major contributor to reef structural complexity, providing habitat for many functionally important fish species throughout Florida and the Caribbean. Unfortunately, due to disease, bleaching, and local anthropogenic stressors, A. cervicornis populations have suffered drastic declines that have negatively impacted associated reef fish populations. In order to promote recovery, A. cervicornis fragments can be cultivated in nurseries and outplanted back onto reefs. This practice can effectively increase A. cervicornis abundance, but the long-term effects on local fish assemblages, and specifically functionally important grazing fishes, has not been assessed. Fish assemblages at natural (control) sites were compared to outplanted A. cervicornis sites in Southeast Florida. Fish surveys were conducted each summer at four locations from 2012 to 2017. Each location contained three outplanted A. cervicornis and one or two control sites. Outplant sites were defined by 50 A. cervicornis colonies in a 36 m2 area. Control sites occupied the same area but did not contain outplanted colonies. The fish assemblage structure was assessed in terms of composition, demography, and functional temporal trends as well as with the increasing structural complexity of the outplanted corals, defined as total linear extension (TLE). Significant temporal trends were recorded for total fish abundance, grazer abundance, and diversity. Structural complexity (outplanted A. cervicornis measured in TLE m-2) was found to be a significant predictor of total fish abundance, grazer abundance and diversity. Fishes 2-5 cm total length were most numerous indicating that the outplant sites may be providing habitat for juvenile reef fishes, particularly algae consumers. These findings suggest that A. cervicornis restoration may be creating a positive feedback loop in which outplanted corals create habitat for grazing fishes that in turn reduce algae competition, potentially providing new habitat for coral settlement.

Doctor of Philosophy
Department of Biology
Brett K. Sandercock
Habitat heterogeneity is a key driver of biodiversity in many ecosystems. In native ecosystems, habitat heterogeneity can arise from multiple drivers including nutrients, topoedaphic conditions, and ecological disturbance. Historically, the prairies of North America existed as a heterogeneous mosaic of habitat conditions created by the interaction of fire and grazing by native ungulates. The focus of many grazing systems has been to minimize disturbance caused by grazing by promoting uniform distributions of grazing animals across management units. Patch-burn grazing is an alternative rangeland management practice that has been proposed to restore historical patch dynamics and biodiversity to rangelands by simulating historical disturbance processes. In my dissertation research, I tested the hypothesis that patch- burn grazing restores habitat heterogeneity to rangelands, and that the resulting habitat heterogeneity can promote biodiversity of native wildlife. I focus on responses of small mammals and coyotes to patch-burn grazing to gain a better understanding of wildlife responses to rangeland management, and because grassland mammals are an ecologically important group. My 3.5-year field study of habitat and small mammal responses to rangeland management showed that: 1) patch-burn grazing created greater heterogeneity in vegetative structure and composition of plant functional groups than in positive and negative controls; 2) habitat heterogeneity created by the interaction of fire and grazing increased small mammal richness and diversity compared to a negative control managed for uniform grazing distributions; 3) the interaction of fire and grazing structured small mammal communities in tallgrass prairie; and 4) population dynamic responses of small mammals to fire and grazing disturbance were species- specific. My 3-year study of coyote survival and resource selection revealed that: 1) rangeland management influences resource selection by coyotes in seasons when they depend on small mammal prey, but not during other seasons; and 2) anthropogenic sources of mortality are important for coyotes at a protected area, even in the absence of harvest. My field results show that restoring the drivers of historical patch dynamics to managed rangelands and publicly held grasslands that are not currently grazed could have profound effects on biodiversity conservation in North America, while continuing to provide ecosystem services to society.

Abstract Air temperatures in high-latitude regions are anticipated to rise by several degrees by the end of the century and result in substantial northward shifts of species. These changes will likely affect the source and sink dynamics of greenhouse gases and possibly lead to a net carbon release from high-latitude soils to the atmosphere. However, regional differences in carbon cycling depend highly on the vegetation community composition, which may be controlled by the abundance of herbivores. I investigated whether mammalian herbivores, mainly reindeer and rodents, alter ecosystem carbon storage through their impacts on vegetation and on dominant plant functional traits. I combined observations of recent changes in ecosystem carbon with experimental field manipulations of both herbivory and climate change and measured carbon storage in vegetation and soil, the uptake and release of carbon dioxide, microbial activity and compared these to plant community composition. Results of my PhD thesis show that under ambient conditions, the impacts of herbivory on both above- and belowground carbon storage ranged from positive to negative. Herbivory altered dominant plant functional traits and these were fairly good predictors of the changes in soil carbon. When combined with experimental warming, herbivory continued to exert control on the dominant plant functional traits but the strong effects of warming on ecosystem carbon storage mostly concealed the impact of herbivory. Interestingly, herbivory–nutrient interactions that were not linked to dominant functional traits determined the consequences of warming on soil carbon. Taken together, I show clear and site-specific impacts of herbivores on vegetation and ecosystem carbon storage and the processes that govern them. Therefore, I suggest that an improved understanding of the role of herbivory in the global carbon cycle could improve estimations of global carbon–climate feedbacks
Tiivistelmä Vuosisadan loppuun mennessä arktisten alueiden lämpötilan odotetaan nousevan usealla asteella ja johtavan lajien siirtymiseen yhä pohjoisemmaksi. Nämä muutokset todennäköisesti muuttavat pohjoisten ekosysteemien kykyä vapauttaa ja sitoa ilmakehän hiiltä ja saattavat johtaa siihen, että yhä enemmän hiiltä vapautuu tundramailta ilmakehään. Kuitenkin paikallisesti hiilenkierto on riippuvainen kasviyhteisöstä ja erityisesti kasvien funktionaalisista ominaisuuksista. Väitöskirjassani tutkin, voivatko herbivorit, pääasiassa porot sekä jyrsijät, muokata hiilenkiertoa muuttamalla kasvillisuutta. Tutkimuksissani seurasin kuinka alueen laidunnushistoria on muokannut hiilivarastoja ja hiilenkiertoa tällä hetkellä ja pyrin arvioimaan herbivorien vaikutusta lämpenevässä ilmastossa kokeiden avulla, joissa manipuloidaan sekä herbivoriaa että lämpötilaa tai ravinteiden saatavuutta. Tulokseni perustuvat arvioihin hiilen varastoista, hiilidioksidin vapautumisesta ja sitoutumisesta sekä mikrobien aktiivisuudesta, joita vertaan kasviyhteisöön. Tulokseni osoittavat, että herbivoria voi joko lisätä tai vähentää ekosysteemin hiilivarastoja sekä maan päällä että maan alla. Muutokset hiilivarastoissa selittyivät varsin hyvin herbivorien tuottamilla kasvillisuusmuutoksilla ja valtalajien funktionaalisilla ominaisuuksilla. Herbivoria muokkasi kasviyhteisöä myös kokeellisen lämmityksen yhteydessä, mutta lämmityksen välittömät vaikutukset hiilivarastoihin peittivät suureksi osaksi alleen herbivorian vaikutukset. Kuitenkin herbivorian ja lannoituksen kasvillisuusmuutoksista riippumattomat yhdysvaikutukset määrittivät lämpenemisen seuraukset maan hiileen. Kaiken kaikkiaan, tutkimukseni osoittaa, että herbivorit voivat paikkakohtaisesti muokata kasvillisuutta, ekosysteemin hiilivarastoja sekä hiilenkierron prosesseja. Näiden tulosten myötä ehdotan, että parempi ymmärrys herbivorian vaikutuksista maailmanlaajuisesti voisi parantaa nykyisiä ennusteita siitä, kuinka ilmaston lämpeneminen muuttaa hiilenkiertoa

The object of this thesis was to study plant community structure, especially in relation to vertebrate herbivory, in an altitudinal gradient in the Fennoscandian mountain chain. A sowing experiment in a high alpine Ranunculus glacialis population showed that seeds germinated better in cleared microsites than under established individuals. This is contrasted with a hypothesis that predicts positive plant-plant interactions in high alpine environments. It was concluded that plant-plant interactions in die studied population varied from neutral to negative, whereas no indications for positive interactions were found. An exclosure experiment in a snow-bed showed that a lemming population consumed 33 % of the available graminoids and 66 % of the mosses from August to June during a population peak. The results shows that grazing needs to be considered as a structuring factor in snow-bed vegetation. The vegetation in exclosures in another snow-bed changed from a graminoid-dominated to a herb-dominated plant community during a long-term (six years) experiment No changes of the same magnitude were seen in a tall herb meadow on a lower altitude. Survival of transplanted adult shoots from the tall herb meadow was equally high in the snow-bed as on the meadow, and germination was also high on bare ground in the snow-bed. Grazing seemed to be a more important structuring factor in the snow-bed than in the more productive tall herb meadow. Raising the grazing pressure during one growing season by introducing microtine rodents into enclosures did not cause any large short-term effects on plant community structure in a tall hob meadow or in a snow-bed. Marked shoots showed that some preferred plant species had a high shoot mortality, but biomass for pooled categories of plants was not significantly affected. It was predicted that the tall herb meadow would be more grazing sensitive than die snow-bed, but productivity on the meadow seemed to be sufficiently high for the plants to compensate for the grazing during the growing season. A greenhouse experiment showed that voles, when grazing freely, have the potential to deplete productive field layer vegetation contrary to predictions from plant defence theories. A nitrogen-based defence did not prevent heavy shoot mortality for toxic tall herbs.

Diss. (sammanfattning) Umeå : Umeå universitet, 1993, härtill 5 uppsatser.

digitalisering@umu.se

Cette thèse s'intéresse aux liens fonctionnels existants entre les grands herbivores et les << grazing lawns >> (ou gazons par pâturage ) : une formation végétale crée et maintenue par l'action de ces mêmes herbivores. Les grazing lawns sont des espaces de savane (ou d'autres écosystèmes paturés) ou une forte activité de pâturage maintient une herbe courte dans un état de croissance précoce à haute valeur nutritive. Ces formations, qui résultent d'un rétrocontrôle positif entre l'intensité du pâturage et l'attractivité de la ressource, représentent un cas extrême dans l'interaction entre herbivores et structure de la végétation. Contrairement au surpâturage, les grazing lawns sont des formations durables, dont beaucoup s'interrogent si elles améliorent la qualité de l'environnement pour les herbivores qui les exploitent. L'objectif de cette thse est de comprendre comment les liens dynamiques et fonctionnels entre végétation et grands herbivores au sein des grazing lawns influencent le statut de ces formations en tant que ressource alimentaire. La production et la consommation de la ressource herbacée au sein des grazing lawns restent fortement synchronisées dans le temps. Les nutriments ne restent que très peu de temps sous forme de biomasse végétale. Je nomme ce type d'exploitation de la ressource exploitation d'une << ressource de flux >>, par opposition à l'exploitation d'une << ressource de stock >> dans laquelle la matière et les nutriments s'accumulent sous forme de biomasse végétale. Si le maintien d'une ressource de flux permet aux herbivores d'entretenir un couvert herbacé de grande valeur nutritive, il contraint également la disponibilité de cette ressource à une régularité des précipitations. Au sein de ces écosystèmes pâturés ayant connu une longue histoire évolutive entre herbivores paisseurs et végétation herbacée, les grazing lawns peuvent être vus comme des formations végétales stables. Des transitions plus ou moins violentes peuvent cependant faire disparaître ces formations si la densité locale d'herbivores diminue (envahissement par les hautes herbes) ou bien augmente trop (perte du couvert végétal par surpâturage). Les grazing lawns représentent pour les herbivores des espaces de savane dont ils exploitent les propriétés particulières en les intégrant au sein de leurs stratégies alimentaires. Même présente en faible quantité, la ressource disponible dans les grazing lawns a une valeur nutritive élevée et peut avantageusement être associée à d'autres ressources moins nutritives au cours de la journée. De ces associations entre différents types de ressources peuvent naître des interactions alimentaires positives avantageuses pour l'herbivore. Il est donc nécessaire de replacer l'utilisation des grazing lawns dans un contexte plus général de mise en place de stratégies alimentaires sur un ou plusieurs jours et d'exploitation de l'ensemble des espaces alimentaires disponibles dans le domaine vital. En contrôlant la surface de grazing lawns disponible dans l'environnement, les gestionnaires d'aires protégées peuvent en modifier la mosaïque herbacée et diversifier l'habitat des grands herbivores, ce qui permet à ces derniers de complexifier leur stratégie alimentaire afin de mieux tirer partie de leur environnement.

Reindeer appear to have strong positive effects on plant productivity and nutrient cycling in strongly nutrient-limited ecosystems. While the direct effects of grazing on vegetation composition have been intensively studied, much less is known about the indirect effect of grazing on plant-soil interactions. This thesis investigated the indirect effects of ungulate grazing on arctic plant communities via soil nutrient availability and plant nutrient uptake. At high density, the deposition of dung alone increased plant productivity both in nutrient rich and nutrient poor tundra habitats without causing major changes in soil possesses. Plant community responses to dung addition was slow, with a delay of at least some years. By contrast, a 15N-urea tracer study revealed that nutrients from reindeer urine could be rapidly incorporated into arctic plant tissues. Soil and microbial N pools only sequestered small proportions of the tracer. This thesis therefore suggests a strong effect of dung and urine on plant productivity by directly providing nutrient-rich resources, rather than by stimulating soil microbial activities, N mineralization and ultimately increasing soil nutrient availability. Further, defoliation alone did not induce compensatory growth, but resulted in plants with higher nutrient contents. This grazing-induced increase in plant quality could drive the high N cycling in arctic secondary grasslands by providing litter of a better quality to the belowground system and thus increase organic matter decomposition and enhance soil nutrient availability. Finally, a 15N natural abundance study revealed that intense reindeer grazing influences how plants are taking up their nutrients and thus decreased plant N partitioning among coexisting plant species. Taken together these results demonstrate the central role of dung and urine and grazing-induced changes in plant quality for plant productivity. Soil nutrient concentrations alone do not reveal nutrient availability for plants since reindeer have a strong influence on how plants are taking up their nutrients. This thesis highlights that both direct and indirect effects of reindeer grazing are strong determinants of tundra ecosystem functioning. Therefore, their complex influence on the aboveground and belowground linkages should be integrated in future work on tundra ecosystem N dynamic.

Thesis (MSc)--University of Stellenbosch, 2004.
ENGLISH ABSTRACT: West Coast Renosterveld is one of the most threatened vegetation types in South Africa. Less than 5% of the original extent of this vegetation type remains, of which 80% is on private land. In addition to fragmentation, much of the vegetation has been ploughed for crop production and then abandoned and invaded by alien plants. Restoration of transformed areas may improve the conservation status of this vegetation type. Indigenous species do not return to abandoned agricultural fields for decades even if these are adjacent to natural areas since their return is limited either by seed dispersal or seedling establishment. The aim of this study was to examine the recovery of indigenous vegetation on abandoned fields. Renosterveld, as we know it today, is an asteraceous shrubland, dominated mainly by renosterbos (Eytropappus rhinocerotis), but might have been a grassland or a grassland-shrubland mosaic. Historical records indicate that species of large game were common in the Western Cape when the early settlers arrived, but most of these have since disappeared. It is thus impossible to reconstruct exactly the ecological processes and functioning of Renosterveld. The first part of the study was designed to examine the effects of grass competition, grazing by indigenous large herbivores, and interaction of these two factors on the establishment, growth and survival of transplanted Renosterveld seedlings on an abandoned agricultural field. Experimental transplanting of indigenous shrubs into an old field showed that most of the plants investigated competed for resources with lawn grasses on the field, and competition affected the seedlings throughout the experiment. Mortality was higher, and growth was reduced for seedlings exposed to grass competition. With the exception of wild olive (Olea europaea spp.africana), herbivory alone had no significant impact on the target species. Herbivory was at a low intensity (20 ha/large animal unit); higher grazing pressures might have given different results. No interaction between competition and herbivory was found for the species investigated; competition and grazing therefore seem to influence the seedlings independently. The second part of this study was conducted to examine the effects of different management strategies, viz: brush cutting, burning and herbicide application on plant species recruitment and community composition and to ascertain their applicability by farmers for large scale restoration of Renosterveld. My comparison of the different strategies for controlling annual alien grasses indicated that these did not differ significantly in their effects on species richness. Burning reduced shrub cover and increased overall species richness and diversity. Burning also reduced grass biomass, and increased recruitment of indigenous seedlings. The use of herbicide resolved the problem of grass biomass invasion and increased shrub species richness. The herbicide application did not appear to have long-term negative effects on the soil quality. Brush cutting did not remove grass biomass on the old field. Experimental re-seeding with an indigenous grass and shrub species into treated plots resulted in low recruitment. My conclusion is that grass can reduce recruitment and growth of many indigenous shrub species. My recommendation for the restoration of old fields in West Coast Renosterveld is to apply herbicide to remove grass competition, and then, after the herbicide has degraded, to oversow the field with seeds of indigenous shrub and grass species of early successional stages to increase overall species diversity.
AFRIKAANSE OPSOMMING: Weskus Renosterveld is een van die mees bedreigde plantegroei soorte in Suid Afrika. Minder as 5% van die oorspronklike omvang van hierdie plantegroei tipe is oor, en dit hoofsaaklik (80%) op privaatlande. Saam met fragmentasie, is baie Renosterveld areas ook omgeploeg vir boerdery en dan net so gelos, met die gevolg dat uitheemse plante hierdie areas ingedring het. Restorasie of herstelling van sulke bewerkte lande kan dalk die bewaringsstatus van hierdie plantegroei tipe verbeter. Natuurlike vestiging van Renosterveld spesies op sulke ou bewerkte lande gebeur nie, selfs al is daar Renosterveld direk langs so ‘n ou veld. Die hervestiging van inheemse spesies is dus tot saadverspreiding or saailingbevestiging beperk. Die doel van hierdie studie is om die stadige terugkoms van inheemse plantegroei na verlate bewerkte velde te verduidelik. Renosterveld is ‘n struikveld waarin die renosterbos (Eytropappus rhinocerotis) domineer, maar kan ook ‘n grasveld of ‘n grasveld-struikland mengsel wees. Groot herbivore was algemeen in die Wes Kaap toe die eerste settelaars gearriveer het, maar intussen het omtrent al die groot wild spesies verdwyn. Dit is dus ontmoontlik om die ekologiese prosesse en funksionering van Renosterveld presies so te herstel. Die eerste deel van hierdie studie bestudeer die effek van graskompetisie, weiding deur inheemse groot herbivore, en die interaksie tussen hierdie twee faktore op die vestiging, groei en oorlewing van oorgeplante Renosterveld saailinge in ‘n verlate ou veld. Die eksperimentele oorplanting van inheemse struike in ‘n ou land het gewys dat die meeste van hierdie plante kompeteer vir hulpbronne met kweekgras wat op die ou veld groei. Kompetisie het die saailinge deur die hele eksperiment geaffekteer. ‘n Hoër mortaliteit en verminderede groei in saailinge wat aan gras kompetisie blootgestel was, is waargeneem. Met die uitsondering van Olea europaea spp. africana, het herbivorie alleen geen betekenisvolle impak op plant spesies gehad nie. Weidingsdruk was laag (20 ha/groot vee eenheid); ‘n groter weidingsdruk sou miskien ‘n ander uitkoms gehad het. Geen interaksie tussen kompetisie en herbivorie is waargeneem in die bestudeerde plantspesies nie. Dit wil dus voorkom of kompetisie en weiding die saailinge onafhanklik van mekaar beïnvloed. Die tweede deel van hierdie studie was onderneem om die effek van verskillende behandelings (kontrole, sny, brand en herbisied toediening) op plantspesie vestiging en samestelling te bestudeer asook om bestuurmetodes te toets was deur boere op groot skaal gebruik kan word om Renosterveld te herstel. In ‘n vergelyking van verskillende bestuur metodes (kontrole, besnoeiing, brand en herbisied) om eenjarige uitheemse gras te beheer, is gewys dat die behandlings nie betekenisvol van mekaar verskil in hulle effek op spesierykheid nie. Vuur het struikbedekking verminder en totale spesies rykheid en diversitiet verhoog. Die gebruik van ‘n herbisied het die probleem van grasindringing opgelos en het ook struikspesiesrykheid verhoog. Die herbisied het nie lang termyn negatiewe effekte op grond kwaliteit gehad nie. Sny het nie gras biomassa verlaag op die ou land nie. Eksperimentele plant van inheemse grasse en struike in die behandelde areas, het lae vestiging tot gevolg gehad. My algemene afleiding is dus dat gras die hervestinging en groei van baie inheemse struikspesies verminder. Ek stel voor dat herbisied gebruik moet word om gras kompetisie te verminder. Nadat herbisied residue in die grond afgebreek is, moet die ou land met inheemse struik en grasspesies, wat in vroeë suksessie stadiums is, beplant word om sodoende totale spesiediversiteit te verhoog en uiteindelik ou bewerkte lande in Weskus Renosterveld te herstel.

L'expérience de pâturage menée sur les digues du Rhône permet de répondre à un triple objectif : gestion des terrains artificiels de la Compagnie Nationale du Rhône, amélioration de la dynamique écologique, floristique et faunistique, et conservation de races rustiques à effectif réduit. Le suivi comportemental de trois herbivores - juments Pottok, vaches Bretonnes Pie Noire et brebis Solognotes - a été mené ainsi que l'étude de leur impact sur la flore et les populations lombriciennes. Après trois années de pâturage, on constate la bonne adaptation des animaux à leur territoire et un effet positif sur la diversité biologique. Les populations de lombriciens augmentent, notamment celles des anéciques, et la flore s'enrichit et se diversifie. Si l'intérêt des animaux pour restaurer des milieux abandonnés est maintenant bien connu, il apparaît également que les herbivores peuvent être de bons gestionnaires de milieux artificiels et répondre à des objectifs écologiques, aussi bien qu'économiques.

Coral reefs are one of the world’s most diverse yet heavily impacted marine ecosystems. As a result of many direct and indirect stressors, coral reefs have experienced major degradation over the last several decades. Declines in coral reefs in the Caribbean have been particularly acute and generally associated with the loss of key herbivores and an increase in algae. Herbivorous fishes such as parrotfishes can positively impact coral reefs by removing algae that compete with corals for light and space. However, many parrotfishes are also important coral predators. Predation on corals, known as corallivory, can adversely affect coral growth, reproduction and survivorship. In this time of changing environments and coral reef decline, understanding the context-dependent nature of parrotfish foraging behavior is of critical importance to scientists and managers. Knowledge of the responses of parrotfishes across a range of resource abundance will help scientists and managers better predict the impacts that these herbivores have on benthic communities as both herbivores and corallivores. In Chapter 1, we examined how six different species of coral reef herbivores (i.e. parrotfishes), all of which belong to a single feeding guild but represent a range of dietary specialization, respond to changes in the abundance of preferred food items. We conducted behavioral observations of parrotfishes in two regions of the Greater Caribbean, and compared consumption rates, diet preferences, and foraging territory size in relation to natural variation across sites in preferred resource abundance. We found that the more-specialized parrotfishes increased their dietary specialization, had smaller foraging territories, and increased their feeding rate with increased preferred resource abundance. In contrast, less-specialized species exhibited constant foraging traits regardless of the abundance of their preferred resources. This study suggests that differences in dietary preference, specialization, and subsequent nutritional demand may drive a differential response in foraging behavior by generalists and specialist herbivores to changes in resource abundance. Recognizing that generalists and specialists differ in the degree to which their foraging behaviors are context-dependent can allow researchers to better predict how herbivores shape the structure and function of marine and terrestrial ecosystems. In Chapter 2, we determined if and how corallivory rates and intensity by parrotfishes differ between two regions of the Greater Caribbean that vary in coral and parrotfish community composition and abundance. We found that more species of parrotfishes than previous studies suggest contribute to corallivory. However, corallivory rates and selectivity for coral species by parrotfishes were largely context-dependent, particularly with regards to the relative abundance of preferred corals and diversity of corallivores at a given site. Although we found that corallivory rates decrease with coral cover, it appears that areas of low coral cover may have high corallivory intensity and coral tissue loss, in part due to the relatively high abundance of corallivores in these areas. The impact of high corallivory intensity and tissue loss requires further knowledge regarding the fate of bite scars on corals.This information will help predict the positive and negative consequences of parrotfishes on coral persistence in the Caribbean. Evidence provided in this thesis furthers our understanding of the dual role of parrotfishes as herbivores and corallivores. Additionally, it reveals the implications of changing coral reef habitats on parrotfish behavior and subsequent coral reef health and resilience.

L’étude des interactions entre système fourrager, santé et croissance des lapins contribuera à proposer de nouvelles pratiques pour des systèmes d’élevage cunicole alternatifs, tels que ceux en agriculture biologique (AB) incluant une gestion intégrée de la santé. Mais cette stratégie est limitée par le manque de références sur la cuniculture AB, i) sur l'alimentation au pâturage (ingestion de fourrages verts, qualités nutritionnelles pour les lapins, etc) ; et ii) sur les risques sanitaires notamment le parasitisme, identifié comme un frein important au développement de la cuniculture AB. L’emploi de plantes riches en tannins condensés (TCs) comme le sainfoin, permettrait de diminuer l’utilisation d’antiparasitaires comme cela a été montré chez les petits ruminants, tant pour la gestion des nématodes que celle des coccidies. Mais le potentiel d’activité des TCs chez le lapin, tout comme le niveau d’ingestion et les performances de croissance, restent à explorer, et pourra servir la cuniculture AB et conventionnelle. Ce travail de thèse a pour objectif i) d’étudier l’intérêt du sainfoin comme ressource pour l’alimentation du lapin, et pour ses propriétés antiparasitaires, ii) définir le niveau d’ingestion au pâturage des lapins et les conséquences sur la production et iii) d’évaluer, le risque parasitaire au pâturage pour des lapins en production. Nous avons montré qu’un aliment enrichi en sainfoin distribué à partir du sevrage, avec une teneur en tannins de 1,8% d’équivalent d’acide tannique, n’a pas réduit l’installation de L3s de Trichostrongylus colubriformis, ni la fertilité des vers adultes, mais a réduit le potentiel d’éclosion des oeufs (-27 points), contribuant à réduire l’infestation de l’environnement. Un aliment enrichi en sainfoin contenant 1,2% d’équivalent d’acide tannique, distribué aux mères et aux lapins en croissance a eu un effet coccidiostatique : l’excrétion oocystale fécale de lapins nourris avec un aliment enrichi en sainfoin a été réduite de 60% par rapport à ceux ayant reçus l’aliment témoin. Si la réduction de l’excrétion oocystale de l’espèce Eimeria magna n’a pas pu être démontrée, en revanche, la réduction d’oocystes toutes espèces confondues dans l’environnement pourrait contribuer à diminuer le risque de coccidiose en élevage. Comparé à la luzerne, le sainfoin, plus riche en lignines, a une forte concentration en énergie (11,2 MJ/kg) et en protéines digestibles (110 g/kg). Au pâturage, lorsque la quantité d’herbe offerte dépasse 85 g MS/kg0,75, il semble que l’ingestion d’herbe soit régulée d’une part lorsque la teneur en énergie digestible de l’herbe dépasse 9 MJ/kg (régulation chémostatique), ou d’autre part si la teneur en lignocellulose (ADF) dépasse 350 g d’ADF/kg (régulation physique : encombrement digestif). Mais la quantité d'herbe disponible dépasse rarement 85 g MS/kg0,75. C’est-à-dire que dans la majorité des cas, une surface pâturable de 0,4 m² (minimum réglementaire) n’a pas permis de combler la capacité d’ingestion et les besoins énergétiques de lapin en croissance. De plus, si l’offre d’herbe est limitante, le lapin ne peut pas exprimer une préférence alimentaire vers des plantes plus jeunes et riches en protéines. La limitation de l’ingestion de protéines a aussi pour conséquence de réduire les potentialités de croissance des lapins et d’allonger la période d’engraissement. Au cours de trois saisons successives de pâturage (université de Perpignan), la pression parasitaire (nématodes et coccidies) a augmenté, avec des infestations par Trichostrongylus sp. et de Graphidium strigosum. Si le délai d'attente entre deux pâturages n’a pas eu d’effet visible sur l’infestation par des nématodes, cela influerait le niveau d’infection par les coccidies. Nos travaux établissent l’intérêt de l’incorporation du sainfoin dans l’alimentation du lapin et ouvrent des perspectives pour établir des pratiques innovantes et bénéfiques à la production cunicole biologique et conventionnelle
The study of the interactions between grazing systems, health and growth in organic rabbit farming (ORF) will contribute to propose new practices including integrated management of health. However, this strategy is limited by the lack of references on ORF and in particular on rabbit intake of green fodder when grazing, nutritional qualities of forages for rabbits, the supply of grass in relation with animal’s density (stocking rate), the related parasitic challenge, etc. The acquisition of such references is a key issue for the development of ORF. The use of plants rich in condensed tannins (CTs), such as sainfoin, could reduce the use of antiparasitic agents, as shown in small ruminants, both for the management of nematodes and for coccidia. However, the potential for CTs containing resources in rabbits, as well as the intake levels and the effects on growth performances, remain to be explored in both OF and conventional rabbit breeding. The aim of this thesis was (i) to investigate the interest of sainfoin as a resource for rabbit feeding and its antiparasitic properties, (ii) to define the intake level in grazing rabbit and the consequences on production and (iii) to evaluate the parasitic risk associated with pasture for rabbits’ production. We have shown that a sainfoin-enriched diet distributed from weaning, with a feed containing 1.8% of tannic acid equivalent, did not reduce neither the establishment of Trichostrongylus colubriformis L3s, nor the fertility of adult worms. In contrast, the development of nematode’s egg to infective larvae was compromised and may reduce the risk of environmental contamination. Besides, a sainfoin-enriched diet containing 1.2% tannic acid equivalent, distributed to does and growing rabbits, had a coccidiostatic effect. With an overall fecal oocyst excretion in rabbits fed with sainfoin reduced by 60% compared to control diet. Although, the pathogenic species Eimeria magna was not concerned by these decrease, such a general reduction in oocyst excretion in the environment could help to reduce on long term the risk of coccidiosis in the rearing units. Sainfoin could constitute a real alternative to dehydrated alfalfa, since it has high digestible energy (DE, 11.12 MJ DE/kg), and protein (110 g/kg), and provide a high supply of lignins. At grazing, when the herbage allowance exceeded 85 g DM/kg0,75, it appeared that the herbage intake was limited by an increase in the DE content when it exceeds 9 MJ / kg, or else by a lignocellulose content higher than 350 g of ADF/kg. However, herbage allowance, rarely exceeds 85 g DM/kg0,75. In other words, in the majority of cases access to a 0.4 m² grazing area did not allow sufficient supply to reach the intake capacity and energy requirements of the rabbits. In addition, rabbits with limited supply cannot express their dietary preference to young and high protein plants. Limiting the intake of proteins also reduced the growth potential of rabbits and extended the fattening period. During the first three grazing seasons (University of Perpignan), the parasitic pressure (nematodes and coccidia) increased, particularly with cases of Trichostrongylus sp. and Graphidium strigosum. While rotation rhythms had no visible effects on nematode infestation, it had an influence on coccidian infection. This work enabled us to establish the advantage of sainfoin enriched diet for the rabbit. It gives prospects to further research projects regarding the establishment of beneficial and innovative practices for organic and conventional rabbit breeding

Green sea turtles in Bermuda are overgrazing the seagrasses on which later life stages are thought to specialize. I hypothesized that larger green turtles in Bermuda would display individual diet specializations during seagrass scarcity. Stable isotope methods were used to determine the diet composition of green sea turtles from the Bermuda Platform as a function of size class and in turtles captured in successive years. Individual turtles had a wide range of diets, however, the variation in diets was driven by differences among size class rather than within the size classes of larger turtles, indicating that green turtles undergo a dietary ontogenetic shift during their residency on the Bermuda Platform and no clear specialization of diets among late-stage individuals. The apparent lack of dietary specialization of larger turtles indicates that older turtles are not diversifying their diets in response to the drastic reductions in seagrass in Bermuda.

Rewilding aims at the restoration of lost ecosystems by re-introducing large herbivores. In northern Siberia, the demise of the mammoth steppe ecosystem at the end of the Pleistocene has been related to the loss of megafauna due to human overhunting. Others argue that climate change at the beginning of the Holocene has triggered the shift from dry, cold steppe vegetation to wet and low productive tundra and taiga vegetation. Despite many different opinions and ongoing discussions on the topic, few case studies are available to test the proposed hypotheses. In this thesis I try to bridge the theoretical backgrounds of palaeoecology and contemporary grazing ecology, and apply these to new data from grazed steppes and surrounding vegetation in Yakutia. This study region is suitable to shed light on the importance of grazers for the (mammoth) steppe vegetation because Yakutia was dominated by mammoth steppe in Pleistocene glacials, and the extrazonal steppes of today are considered potential relics; permafrost deposits in close proximity to these steppes allow palaeobotanical reconstructions of vegetation from the same area; and two game parks, one in Central Yakutia, one in northeastern Yakutia, allow to study grazing impact on contemporary vegetation, specifically steppes. The first part of the thesis focuses on current grassland and steppe vegetation in Russia in general and in Yakutia specifically. Chapter highlights the biological diversity of Russia´s grasslands under diverse climatic and edaphic consditions. It highlights the value of Russian steppes for nature conservation, shows that most grasslands are of agricultural origin and that cessation of land use can pose a threat to both natural and secondary grasslands. Chapter 2 focuses on the phytosociology of extrazonal steppes and other grasslands of Yakutia, and on the harsh climatic and the special edaphic conditions they inhabit. It demonstrates relationships to southern zonal steppes, despite lower species diversity and unique associations with a high contribution of alpine plants. The second part of the thesis addresses the evidence of grazing in the palaorecord as well as effects and importance of grazing for contemporary vegetation. Chapter 3 aims at a comparison of current vegetation with Pleistocene fossil remains in order to find the closest analogues of mammoth steppe vegetation. It demonstrates that meadow steppes formed large parts of the vegetation in both cold and warm stages, only shifting in proportions. Disturbance indicators from grazing animals were more common in the fossil record than today. Chapter 4 discusses the influence of grazing on current vegetation under the given harsh climate; on plant species and trait composition, as well as on vegetation productivity. Climate and soil conditions seem to be the most important determinants of steppe and surrounding vegetation. Large grazers like bison can alter vegetation structure and plant communities on the local scale, but do not alter composition dramatically nor do they increase vegetation productivity in the given settings. In summary, steppes are an important part of biodiversity in Russia and specifically in Yakutia today. The extrazonal steppes of Yakutia are no direct relics of the mammoth steppe, and are not dependent on grazing. However, grazing of large herbivores, such as bison, can locally open up vegetation, and in a continental climate, drive grasslands towards a more steppic character. Further research is needed to investigate the details of these processes and how they could translate to the landscape scale.:Chapter 1: General Introduction 1 1.1. Large mammal extinctions and the onset of the Anthropocene 1 1.2. The 'mammoth steppe' 3 1.2.1. Definitions and concepts 3 1.2.2. Environmental conditions 4 1.2.3. Vegetation of the mammoth steppe 6 1.2.4. Megafauna and suggested ecosystem processes of the mammoth steppe 7 1.2.5. The demise of the mammoth steppe 9 1.3. Grazing ecology 11 1.3.1. Effects of herbivores on vegetation 11 1.3.2. Effects of herbivores on ecosystem processes 14 1.4. Study area 15 1.4.1. Central and northeastern Yakutia 15 1.4.2. Pleistocene Park and the Ust-Buotoma Bisonary 18 1.5. Chapter outline 19 Chapter 2: Land Use of Natural and Secondary Grasslands in Russia 20 2.1. Introduction 21 2.2. Origin and types of grasslands 26 2.2.1. Natural grasslands 26 2.2.1.1. Steppes 26 2.2.1.2. Alpine grasslands 32 2.2.1.3. Azonal grasslands 33 2.2.2. Secondary grasslands 34 2.3. Agronomic Use of grasslands 34 2.3.1. History of land use 34 2.3.2. Current practice of grassland management 38 2.4. Ecological and economic value of grasslands 40 2.5. Threats to grasslands 43 2.6. Conservation of grasslands 48 2.6.1. Legal aspects 48 2.6.2. Prioritization 50 2.6.3. Conservation of grasslands: Protected Areas (PAs) 51 2.7. Conclusions 53 Chapter 3: Extrazonal steppes and other temperate grasslands of northern Siberia - Phytosociological classification and ecological characterization 55 3.1. Introduction 57 3.2. Methods 60 3.3. Results 61 3.3.1. Overview: classification and ordination 61 3.3.2. Description of communities 67 3.3.2.1. Meadows and wet grasslands 67 3.3.2.2. Steppes 68 3.3.3. Phytosociological synopsis 73 3.4. Discussion 75 3.4.1. Meadows 75 3.4.2. Steppes 76 3.4.3. Tundra steppes 80 3.5. Conclusions 81 Cahpter 4: Woodlands and steppes: Pleistocene vegetation in Yakutia´s most continental part recorded in the Batagay permafrost sequence 82 4.1. Introduction 84 4.1.1. Regional setting 86 4.2. Material and methods 87 4.2.1. Material 87 4.2.2. Sampling and preparation 90 4.2.3. Macrofossil preparation and identification 91 4.2.4. Charcoal 91 4.2.5. Palynology preparation and identification 91 4.2.6. Invertebrate sampling and identification 92 4.2.7. Reconstruction of palaeo-vegetation 92 4.3. Results 94 4.3.1. Vegetation of the last cold stage 95 4.3.2. Vegetation of the last interglacial 107 4.3.3. History of local vegetation and environment throughout the sequence 113 4.3.3.1. Unit IV 113 4.3.3.2. Unit III 114 4.3.3.3. Unit II 114 4.4. Discussion 121 4.4.1. Steppes persistent throughout the investigated timespan 121 4.4.2. Steppes in northeast Siberia: Pleistocene survivors or Holocene immigrants? 124 4.4.3. Climatic implications 126 4.5. Conclusions 129 Chapter 5: Grazing at the limit 􀂱 effects of large herbivore grazing on relics of presumed mammoth steppe in NE-Siberia 131 5.1. Introduction 133 5.2. Methods 137 5.2.1. Field sampling and data collection 137 5.2.2. Data analysis 138 5.2.2.1. Species composition 138 5.2.2.2. Plant trait composition 138 5.2.2.3. Taxonomic and functional diversity 139 5.2.2.4. Productivity and chemical composition of vegetation 139 5.3. Results 139 5.3.1. Species composition 140 5.3.2. Trait composition 142 5.3.3. Taxonomic and functional diversity 143 5.3.4. Productivity and chemical composition of vegetation 144 5.4. Discussion 145 5.4.1. Effect of microclimate 145 5.4.2. Grazing effects 146 5.4.3. Implications for rewilding in Siberia 149 Chapter 6: Synthesis - Yakutian steppes and rewilding the mammoth steppe 151 6.1. Contemporary grasslands and herbivore pastures in Yakutia 151 6.2. Contemporary steppes and tundra steppes 152 6.2.1. Relics of the mammoth steppe?! 154 6.3. The role of grazers today - and their proposed role in the mammoth steppe 157 6.4. Outlook on rewilding 166 Chapter 7: Conclusions 174 Chapter 8: Summary 175 Chapter 9: Zusammenfassung 177 II. References 179 III. Appendix 207 IV. List of abbreviations 263 V. Curriculum vitae 270
Mit der Auswilderung von Großherbivoren wird oft das Ziel verfolgt, ein lange vergangenes Ökosystem wiederherzustellen. In Nordsibirien ist das die Mammutsteppe, deren Verlust auf die Ausrottung der Großherbivoren-Fauna durch menschliche Überjagung zurückgeführt wurde. Andererseits könnte auch der Klimawandel am Beginn des Holozäns für den Vegetationswandel von trockener, kalter Steppe zu feuchter und wenig produktiver Tundra und Taiga verantwortlich sein. Das Thema wird von verschiedenen Meinungen beherrscht und die Diskussion darüber dauert an; doch konkrete Studien, die diese Hypothesen überprüfen würden, sind selten. In meiner Dissertation versuche ich, eine Brücke zwischen Theorien aus der Paläoökologie und der rezenten Beweidungsökologie zu schlagen und diese auf die beweideten Steppen Yakutiens und deren umgebende Vegetation anzuwenden. Diese Studie liefert Erkenntnisse zur Bedeutung von Weidetieren für die (Mammut-)steppenvegetation, da Yakutien in Pleistozänen Kaltzeiten von Mammutsteppe bedeckt war und die rezenten, extrazonalen Steppen als potenzielle Reliktvegetation angesehen werden; Permafrostaufschlüsse in direkter Umgebung dieser Steppen die paläobotanische Rekonstruktion des selben Gebietes erlauben; und zwei Wildparks, einer in Zentralyakutien, einer im Nordosten Yakutiens, die Erforschung von Beweidungseffekten auf die rezente Vegetation, vor allem Steppenvegetation, ermöglichen. Der erste Teil meiner Dissertation bezieht sich auf die rezente Grasland- und Steppenvegetation Russlands mit Fokus auf Yakutien. Kapitel 1 stellt die biologische Vielfalt der Russischen Grasländer unter verschiedensten klimatischen und edaphischen Bedingungen heraus. Dabei steht die Bedeutung der Russischen Steppen für den Naturschutz im Fokus. Es wird deutlich, dass der Großteil der Grasländer auf landwirtschaftliche Nutzung zurückzuführen ist und dass eine Nutzungsaufgabe sowohl natürliche als auch sekundäre Grasländer bedroht. Kapitel 2 beschäftigt sich mit der Pflanzensozologie der extrazonalen Steppen und anderer Grasländer Yakutiens, sowie mit den speziellen klimatischen und edaphischen Bedingungen, unter denen sie existieren. Ich zeige die verwandtschaftlichen Beziehungen dieser Steppen mit den südlichen, zonalen Steppen, trotz ihrer geringeren Artenvielfalt und ihrer einzigartigen Assoziationen mit hohem Anteil alpiner Arten. Der zweite Teil meiner Dissertation beschäftigt sich mit den Hinweisen auf Beweidung in paläobotanischen Rekonstruktionen der Vegetation, sowie der Bedeutung von Beweidung in der rezenten Vegetation. Kapitel 3 stellt einen Vergleich zwischen der Artenzusammensetzung Pleistozäner Pflanzenfossilien mit denen rezenter Pflanzengesellschaften an, um die Vegetation zu definieren, die der Mammutsteppe am ähnlichsten ist. Dieser Vergleich zeigt, dass Wiesensteppen sowohl in Kalt- als auch in Warmzeiten vorkamen und nur in ihrem Anteil an der Gesamtvegetation schwankten. Störungszeiger für Beweidung waren häufiger in den fossilen Pflanzenresten zu finden als in rezenten Pflanzengesellschaften. Kapitel 4 diskutiert schließlich den Einfluss von Beweidung auf die rezente Vegetation unter den gegebenen extremen Klimaverhältnissen; auf die Zusammensetzung von Arten und Artmerkmalen einer Pflanzengesellschaft, sowie auf deren Produktivität. Die klimatischen und edaphischen Bedingungen scheinen ausschlaggebend für die Steppen- und umgebende Vegetation zu sein. Großherbivoren wie das Bison können allerdings lokal Veränderungen in der Vegetationsstruktur und Pflanzengesellschaften bewirken, wenn auch, unter den gegebenen Umständen, weder Artenzusammensetzung noch Produktivität drastisch verändert wurden. Steppen stellen einen bedeutenden Anteil der Russischen, und besonders Yakutischen, Biodiversität dar. Die extrazonalen Steppen Yakutiens sind keine unmittelbaren Relikte der Mammutsteppe und sind heute nicht auf Beweidung angewiesen. Trotzdem können Großherbivoren wie das Bison lokale Veränderungen bewirken: sie vermögen Baumbestände aufzulichten und, unter kontinentalem Klima, Wiesen hin zu einem mehr steppen-artigen Charakter zu verändern. Weitere Forschung ist nötig, um die Details der beobachteten Prozesse zu erkunden und ihre Übertragbarkeit auf die Landschaftsebene zu überprüfen.:Chapter 1: General Introduction 1 1.1. Large mammal extinctions and the onset of the Anthropocene 1 1.2. The 'mammoth steppe' 3 1.2.1. Definitions and concepts 3 1.2.2. Environmental conditions 4 1.2.3. Vegetation of the mammoth steppe 6 1.2.4. Megafauna and suggested ecosystem processes of the mammoth steppe 7 1.2.5. The demise of the mammoth steppe 9 1.3. Grazing ecology 11 1.3.1. Effects of herbivores on vegetation 11 1.3.2. Effects of herbivores on ecosystem processes 14 1.4. Study area 15 1.4.1. Central and northeastern Yakutia 15 1.4.2. Pleistocene Park and the Ust-Buotoma Bisonary 18 1.5. Chapter outline 19 Chapter 2: Land Use of Natural and Secondary Grasslands in Russia 20 2.1. Introduction 21 2.2. Origin and types of grasslands 26 2.2.1. Natural grasslands 26 2.2.1.1. Steppes 26 2.2.1.2. Alpine grasslands 32 2.2.1.3. Azonal grasslands 33 2.2.2. Secondary grasslands 34 2.3. Agronomic Use of grasslands 34 2.3.1. History of land use 34 2.3.2. Current practice of grassland management 38 2.4. Ecological and economic value of grasslands 40 2.5. Threats to grasslands 43 2.6. Conservation of grasslands 48 2.6.1. Legal aspects 48 2.6.2. Prioritization 50 2.6.3. Conservation of grasslands: Protected Areas (PAs) 51 2.7. Conclusions 53 Chapter 3: Extrazonal steppes and other temperate grasslands of northern Siberia - Phytosociological classification and ecological characterization 55 3.1. Introduction 57 3.2. Methods 60 3.3. Results 61 3.3.1. Overview: classification and ordination 61 3.3.2. Description of communities 67 3.3.2.1. Meadows and wet grasslands 67 3.3.2.2. Steppes 68 3.3.3. Phytosociological synopsis 73 3.4. Discussion 75 3.4.1. Meadows 75 3.4.2. Steppes 76 3.4.3. Tundra steppes 80 3.5. Conclusions 81 Cahpter 4: Woodlands and steppes: Pleistocene vegetation in Yakutia´s most continental part recorded in the Batagay permafrost sequence 82 4.1. Introduction 84 4.1.1. Regional setting 86 4.2. Material and methods 87 4.2.1. Material 87 4.2.2. Sampling and preparation 90 4.2.3. Macrofossil preparation and identification 91 4.2.4. Charcoal 91 4.2.5. Palynology preparation and identification 91 4.2.6. Invertebrate sampling and identification 92 4.2.7. Reconstruction of palaeo-vegetation 92 4.3. Results 94 4.3.1. Vegetation of the last cold stage 95 4.3.2. Vegetation of the last interglacial 107 4.3.3. History of local vegetation and environment throughout the sequence 113 4.3.3.1. Unit IV 113 4.3.3.2. Unit III 114 4.3.3.3. Unit II 114 4.4. Discussion 121 4.4.1. Steppes persistent throughout the investigated timespan 121 4.4.2. Steppes in northeast Siberia: Pleistocene survivors or Holocene immigrants? 124 4.4.3. Climatic implications 126 4.5. Conclusions 129 Chapter 5: Grazing at the limit 􀂱 effects of large herbivore grazing on relics of presumed mammoth steppe in NE-Siberia 131 5.1. Introduction 133 5.2. Methods 137 5.2.1. Field sampling and data collection 137 5.2.2. Data analysis 138 5.2.2.1. Species composition 138 5.2.2.2. Plant trait composition 138 5.2.2.3. Taxonomic and functional diversity 139 5.2.2.4. Productivity and chemical composition of vegetation 139 5.3. Results 139 5.3.1. Species composition 140 5.3.2. Trait composition 142 5.3.3. Taxonomic and functional diversity 143 5.3.4. Productivity and chemical composition of vegetation 144 5.4. Discussion 145 5.4.1. Effect of microclimate 145 5.4.2. Grazing effects 146 5.4.3. Implications for rewilding in Siberia 149 Chapter 6: Synthesis - Yakutian steppes and rewilding the mammoth steppe 151 6.1. Contemporary grasslands and herbivore pastures in Yakutia 151 6.2. Contemporary steppes and tundra steppes 152 6.2.1. Relics of the mammoth steppe?! 154 6.3. The role of grazers today - and their proposed role in the mammoth steppe 157 6.4. Outlook on rewilding 166 Chapter 7: Conclusions 174 Chapter 8: Summary 175 Chapter 9: Zusammenfassung 177 II. References 179 III. Appendix 207 IV. List of abbreviations 263 V. Curriculum vitae 270

Knowledge of scale-dependent factors that affect the distribution of ungulate herds, such as cattle, is essential for the development of more accurate predictive models of animal movement and the management of sustainable agriculture. Our objectives were to evaluate the seasonal and diurnal patterns of herd spread, explore grouping dynamics, and the influence of dominance ranks, seasonal changes in forage biomass, use of shade, water and supplemental feed areas on cattle distribution. Positional and activity information of eleven free-ranging Bonsmara, Bos taurus, cows were obtained at five minute intervals using Global Positioning System collars. We conducted a total of 12 trials each of three weeks from August 2007 to August 2009 in a 457ha shrub-dominated savanna in South Texas. Spread was obtained by calculating the average Euclidean distance of individuals to the center of the herd. The association software package, ASSOC1, was used to analyze spatio-temporal interactions. Normalized Difference Vegetation Index, an indicator of available forage biomass, was calculated using satellite imagery. Number of GPS fixes was used as an indicator of animal use of shade patches and water and supplemental feeding areas. In this semi-arid environment, herd spread was greatest and subgroup division occurred during summer when forage biomass was high. Herd spread was the least and shade patches were used more during winter when forage biomass was low. Throughout the year spread was smallest and use of shade patches highest during the midday period compared to other periods of the day. Location of individuals in the center of the herd was not associated with their dominance ranking. There was no significant overall pattern of seasonal changes in cattle use of water and supplemental feeding areas. Seasonal forage availability and shade patches seem to have a greater influence on herd dispersion patterns and grouping dynamics than any effect of social dominance. Herd distribution is likely related to changes in forage biomass and temperature fluctuations which drive compensatory night-time feeding and thermoregulatory actions. Accurate ethological studies of herds depend on our ability to understand herd dynamics at multiple scales that affect and are relevant to animal's response to the landscape.

Herbivores have a significant influence on their environment. Factors that influence herbivore distribution in a landscape are important for conservation. Artificial water provision is one such factor, with water sources being focal points of herbivore activity. Variation between herbivore utilisation of different waterhole types and habitat integrity surrounding the different waterholes is assessed in this study. Correlations are drawn between herbivore utilisation and habitat integrity to quantify the impact that artificial waterholes have on the landscape. A scoring system is devised to investigate the various factors affecting vegetation around artificial waterholes. Results show that there are significant variations between herbivore utilisation for different artificial waterhole types, as well as significant variation in habitat integrity surrounding the different waterhole types. Distance between waterholes and drainage lines, and utilisation by specific herbivore species have a significant impact on habitat integrity - specifically affecting veld condition and disturbance observed on woody plant species. A habitat score that was created by combining data from both the herbaceous and woody layers is not affected by waterhole type, distance from waterholes, or the different herbivore species utilising the different waterhole types. Earth dams have the greatest impact on surrounding vegetation and are the most utilised waterhole type. Closures of earth dams are not recommended due to their importance to herbivores. Less utilised waterhole types are also important, mitigating the impact of herbivore damage to vegetation at earth dams.
Environmental Sciences
M. Sc. (Nature Conservation)

How so many species coexist while utilizing the same resources is both of ecological interest and important for the management of wildlife communities and parks. This thesis endeavours to understand how grazing herbivores co-exist, with special emphasis on understanding the mechanisms of competition and facilitation over temporal and spatial scales. I compared the dry season use of grasslands, grass species, grass height and grass greenness by white rhino and three other ungulate species, zebra, wildebeest, and impala. I was specifically interested in the extent to which white rhinos, with their capacity to graze both short and tall grass, either competed with or facilitated other grazers. In Chapter Two, I clarify the mechanisms of facilitation and competition in terms of temporal and spatial scales, and discuss why there is little evidence in the literature to support these mechanisms. I conclude that evidence for facilitation through stimulation of grass re-growth during the growing season appears stronger than that for increased resource access through removal of obstructing grass structures during the dormant season. Facilitation may benefit the nutritional gains obtained by certain species in the short term, but these benefits do not appear to be translated into the expected population consequences. In collaboration with co-author Norman Owen-Smith, we suggested this could be due to seasonal tradeoffs between facilitation and competition, as well as to restrictions on the spatial extent of trophic overlap. In Chapter 3 Norman Owen-Smith and I compared the grass height use in relation to body size. We expected that the grass height favoured would increase with the body size of the herbivore species, as suggested from past studies of resource partitioning among large mammalian herbivores. Instead we found that the largest of these species, white rhino, concentrated on the shortest grass, while the smallest species, impala, favoured grass heights intermediate between those grazed by wildebeest and zebra. Results suggest that the scaling of mouth width relative to body size, and hence metabolic demands, is the primary factor governing grass height selection, rather than body size alone. Hence grazing successions governed by body size differences may not be a typical feature of their ecology, contrary to past suggestions. Furthermore, there was considerable overlap in grass height grazed among these four species, indicating that niche separation by grass height is inadequate alone to explain their coexistence. More attention needs to be paid to other aspects such as the grass species selected and habitat structure favoured. Chapter Four compared the overlap in grassland use and grass species use, as well as grass height and grass greenness of swards utilized by the herbivores as the dry season advances. I show that all species prefer grazing lawns during times of abundance, and that zebra leave grazing lawns before other species, and wildebeest leave grazing lawns before white rhino and impala. This suggests zebra and wildebeest may be competitively excluded from grazing lawns through a reduction in grass height, by white rhino and impala, during the dry season. However, white rhino are also potentially the ‘supreme’ facilitator increasing the availability of nutritious grazing lawns, as well as increasing the quality of those lawns through grazing in the wet season. A better understanding of the trade-off between “habitat facilitation” and competitive exclusion by white rhino, allows us to better understand how grazing herbivores co-exist.

The influence of herbivory, grass competition and grazing system on emergence, growth and survival of Acacia seedlings in burnt and unburnt areas was investigated in their first growing season, from September 1997 to May 1998. The study was aimed at determining possible reasons for the increase in woody plant density in semi-arid savannas, specifically the effect of excluding small-mouthed herbivores from domestic and livestock systems, and switching from continuous grazing to rotational grazing systems. The effect of fire intensity and maximum fire temperature on seed viability, germination and mortality, specifically with regard to back versus head fires and seed size , were investigated. Variability among species in the number of seedlings emerging generally resembled differences in viability. Emergence of Acacia karroo and Acacia tortilis was poorer than that of Acacia nilotica under grass competition. Emergence was lower in burnt and open areas, the latter depending on Acacia species. Herbivory did not affect seedling emergence, in both domestic and wildlife systems. Seedling survival and growth was adversely affected by small-mouthed herbivores in both domestic and livestock systems, whilst large-mouthed herbivores exerted no direct effects on woody seedlings, except to a small degree by trampling. Seedlings showed better growth and survival under low grass competition, which also resulted in greater leaf-to-height ratios , indicating that grass interference with irradiance affects woody seedlings. This effect appeared to be greater for cattle and rotational grazing, and for burning, in domestic and wildlife systems respectively. Woody seedling establishment was also better in burnt areas. Whilst seedling growth was better under rotational than continuous grazing, survival was not significantly different. Grass competition influenced seedling establishment to a greater extent than herbivory, whilst burning made a greater impact than grass competition. Seed mortality in response to maximum fire temperature was inversely related to seed size, and trends in seed germination and mortality, although very variable, appeared to be influenced by threshold fire intensities and maximum temperatures. Back fires had hotter maximum temperatures and fire intensities at ground level than head fires, which result in greater seed mortality following fire. Based on the current study it is likely that the removal of grass competition, burning, and a change from continuous to rotational grazing systems, and small-mouthed to large-mouthed herbivores, will result in an increase in woody seedling establishment.
Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2001.

A study was conducted to determine what impact high white-tailed deer (Odocoileus virginianus) densities were having on the native grasslands of a tallgrass: aspen forest tract embedded within an agro-urban setting. Due to excessive spring moisture, row-crops were unavailable the first year. Using microhistological fecal analysis to determine dietary composition, deer were assessed to be placing the site’s favoured native plant species at risk of extirpation. Measuring woody stem abundance and height along and near the prairie: forest ecotone, deer were found to restructure woody growth but not directly influence encroachment rates. Indirectly, however, deer facilitated forest encroachment and prairie degradation through seed dispersal, nitrogen deposition, gap-dynamics, and trampling. Comparing dietary composition to nutritional data, deer grazed to maximize fitness, selecting foods high in IVDMD, minimizing energy expenditure, and optimizing CP. High crop CP was offset by intensively grazing particular native plants. ADF was an effective nutritional marker, not AIA.

Hairy prairie-clover (Dalea villosa Nutt. (Spreng) var. villosa), a rare plant species, grows in the Canadian Prairies. Populations of Dalea in Canada are threatened by the loss of sand dune habitat because of changes in land use and altered ecological processes such as grazing and fire. Local populations of Dalea are further threatened by one or more specific threats, including herbivory from native and domestic ungulates and invasion of habitats by exotic plants. The overall objective of this thesis was to gain more knowledge about Dalea and to determine the impact of threats and management practices to the Saskatchewan populations and their habitats. Observational studies were conducted at each of two sites in Saskatchewan supporting Dalea. First, at the Dundurn Sandhills site, structural equation modeling was used to examine landscape, ecological, and management factors associated with high rates of herbivory on Dalea and with reductions in the long-term survival and productivity of Dalea. The conditions which deer (Odocoileus hemionus and Odocoileus virginianus) or cattle (Bos taurus) were responsible for the most intense rates of herbivory to Dalea plants and patches were determined. Generally, deer appeared responsible for the most herbivory, whereas cattle grazing on Dalea increased with stocking densities. At the same time, new hypotheses about ecological processes affecting Dalea productivity in the Dundurn Sandhills were explored. In particular, it appeared that deer may be responding to cattle grazing in Dalea habitat by avoiding those areas, and that mid-season germination and recruitment of many Dalea plants may occur following precipitation events. Second, at the Mortlach site, the costs and benefits of using grazing management to control leafy spurge (Euphorbia esula L. var. esula) were assessed, especially in consideration of the potential negative effects of intense herbivory on Dalea productivity. Aspects of the grazing regime including stocking density and the livestock species influenced herbivory on Dalea and its reproductive output, but there were no apparent links between the abundance of leafy spurge abundance and the reproductive output of Dalea. The findings of these two studies are relevant for the conservation and management of Dalea in Saskatchewan.

As alterações nos efetivos das populações de herbívoros, um pouco por toda a Europa, provocaram desequilíbrios nos ecossistemas, associados a situações de sub pastoreio e sobre pastoreio. Por um lado, assistiu-se ao abandono da atividade pastoril em áreas marginais para o pastoreio, com redução do efetivo ou menor esforço de gestão, por outro, assistiu-se a uma intensificação do pastoreio extensivo, com aumento do efetivo e/ou da densidade de encabeçamento. O controlo eficaz da movimentação dos animais promove o seu papel de regulação ecológica, otimizando-os ao mesmo tempo que diminui os seus impactos sobre habitats sensíveis. Esta tese usa uma metodologia de revisão sistemática para avaliar o estado da arte do uso de um novo sistema de vedação, o virtual fencing, e o seu potencial para ser implementado gestão e restauro de ecossistemas naturais. O virtual fencing é cada vez mais alvo de atenção por parte de científicas de todo o muindo. Nesse aspeto, a Austrália, Inglaterra e Estados Unidos foram os países que mais contribuíram com publicações para esta tese. Nestes países, os artigos abordam maioritariamente a gestão de gado (na Austrália e Estados Unidos) e ovelhas (em Inglaterra) em sistemas de pastagem extensiva, montanhas e florestas, sendo os principais objetivos de estudo o desenvolvimento de software a gestão de valores naturais. Esta solução mostrou ser eficaz na manutenção de animais na área definida pelo sistema de GPS, um aspeto essencial para a gestão e conservação de ecossistemas degradados.
Changes in herbivore populations across Europe have led to ecosystem disturbances associated with under and overgrazing. On one hand, pastoral activity was abandoned in marginal grazing areas, with a reduction in the number of herds or a lower management effort. On the other hand, there was an intensification of extensive grazing, with the increase of livestock and / or stocking density. Effective control of animal movement promotes their ecological regulatory role while optimizing their impact on sensitive habitats. This thesis uses a systematic review methodology to assess the state of the art of the use of a new fencing system, virtual fencing, and its potential for implementing natural ecosystem management and restoration. Virtual fencing is increasingly receiving attention from scientists around the world. Australia, England and the United States were the countries with more publications for this thesis. In these countries, the articles focus mainly on the management of cattle (in Australia and the United States) and sheep (in England) in extensive pasture, mountain and forest systems. This solution has been shown to be effective to maintain animals in the area defined by the GPS system which corresponds to an essential aspect for the management and conservation of degraded ecosystems. Cattle were also successfully excluded from sensitive areas, generally responding positively to audio cues and electrical stimulus, after a learning period. There are, however, some issues associated with animal welfare and behavioural variability among individuals and between species, which should be tackled as opportunities to motivate future technological developments.