Tesi sul tema "Seedling regeneration"

Abstract The aims were to examine the importance of regeneration by seeds, the influence of plant traits and disturbances, and the role of seed-seedling conflicts in regeneration and in the determination of vegetation structure. The study was carried out at in a subarctic alpine area (Kilpisjärvi 69°01'N 20°50E', Finland). Seed bank and seedling densities were high in many plant communities (ranges 99 -1109 viable seeds/m2 and 0.2-227 seedlings/m2, respectively). Effective seedling recruitment is reflected in vegetation as a high proportion of plants with poor or no vegetative reproduction ability. This development may take place in meadows and snowbeds where herbs (e.g. Gnaphalium supinum, Sibbaldia procumbens, Veronica alpina and Viola biflora) are abundant. On the other hand, the low proportion of these plants in heath vegetation reflects ineffective seedling recruitment. Floristic similarities between the consecutive phases in the regeneration pathway may be low despite effective seedling recruitment. Clonality, large and small seed sizes and appendaged diaspores limit the movement of species from phase to phase. Generally, disturbances facilitate effective regeneration by seeds. Grazing promotes species with large seed banks and is therefore one reason for high seed bank densities. Freezing and melting processes negate a negative influence of altitude on seed bank densities in the phase of seedlings. However, if disturbances are severe and continuous and the soil is compact, unstable or dry, disturbances are not beneficial. The same is true if there is a shift in the species composition of seedlings from gaps to closed vegetation. This phenomenon occurred in a rich meadow. Seed-seedling conflicts limit regeneration by seeds in low-herb snowbeds and Ranunculus glacialis-Gymnomitrion snowbeds. Vegetative reproduction and infrequent pulses of seedling recruitment negate an influence of short-term seedling recruitment on the spatial structure of vegetation. Extreme conditions, such as low temperatures, instability of the soil and late snowmelt modify the influence of factors that are important in more moderate conditions. To conclude, all transitions limit regeneration by seeds. However, favourable conditions (e.g. moist conditions in a meadow) partly eliminate the obstacles against seedling emergence. Regeneration by seeds therefore has a major impact on the dynamics and structure of vegetation. In heath vegetation, where bare soils are dry and the moss cover is thick, large seed banks and seed rains do not guarantee effective seedling recruitment. The regeneration process is reduced in the early phases, and plants that reproduce primarily by seeds have a minor role in vegetation. The accumulation of seed banks is effective in these circumstances.

Drought-induced tree mortality is a phenomenon affecting many forest ecosystems and is predicted to increase under ongoing climate change. Forest stability partly depends on regeneration: the process of renewing mature forest with subsequent generations. As seedlings are more susceptible to drought effects than mature trees, mortality of the seedling bank can represent a major bottleneck controlling forest structure and species composition. Scots Pine (Pinus sylvestris L.) is the most widely distributed of the Pinus species, covering a broad latitudinal gradient of ecological conditions. The thesis aims to deepen understanding of drought-induced mortality, while analysing intra-specific variation in the phenotypic and metabolic profile of Pinus sylvestris seedlings subjected to drought stress. I also consider the relevance of the results to the broader conceptual framework of drought-induced mortality. The experiments utilise seeds from different populations of origin (provenances) across the north-south axis of the European range of Pinus sylvestris, in order to determine the extent of regeneration capacity in this species under drought. Seeds were collected from different populations (provenances) that, along with other climatic and edaphic differences, span a gradient of water availability: from wet (Scotland) to intermediate (Austria, Poland) to dry (Spain). In Chapter 2, the effects of osmotic stress on the initial seedling establishment stage were studied by comparing phenotypic responses across provenances. Seedling germination, early growth, osmotic stress tolerance and survival were investigated using a polyethylene glycol irrigation treatment as a proxy for rapid and severe drought. Treatment, provenance and interaction effects were found for rate of germination, final proportion of seeds germinated, seedling size, and superoxide dismutase activity (an antioxidant enzyme). Root investment was affected by both provenance and time to germination. Although there was no significant effect of provenance on survival, a trend towards increased probability of survival under osmotic stress was indicated for the southernmost (driest) as compared with the northernmost (wettest) provenance. Chapter 3 investigates the responses of older seedlings (at 10 months) to a drying down of soil moisture for 40 days. Morphological and physiological data were collected to assess intra-specific and intra-population variation in the seedling stress response under drought. A metabolomics analysis using Ultra performance Liquid chromatography followed by mass spectrometry (UPLC/MS) was carried out to investigate whether metabolic markers could be identified that are suggestive of heightened oxidative stress and whether populations in different climatic and edaphic environments show variation in metabolic activity under drought. Preliminary results suggest large intra-population variability yet clear differentiation in metabolic responses to drought over the time course of the experiment. Univariate and multivariate analyses indicated that among the most significant increases in response to drought were those involved in osmoprotective and antioxidant capabilities, including the free amino acid proline and a quercetin derivative (a flavonoid). Interestingly, provenances, either under experimental drought or not, did not show significantly different metabolite profiles, even though provenance and its interaction with drought treatment did significantly affect seedling biomass and photochemical efficiency. In Chapter 4 the effects of provenance, maternal parentage and seed weight on germination rate, final germination percentage, as well as seedling drought responses in biomass allocation and the expression of selected antioxidant genes were analysed. Seed weights were measured individually and seed weight was found to have a strong positive effect on: germination rate, seedling dry weights, and number of needles. Expression of two antioxidant enzymes increased under drought. Seed weight was strongly determined by provenance and maternal parentage as well as their interaction. However, root to shoot biomass allocation depended on provenance and maternal effects that were not mediated by seed weight effects. Principal component analysis indicated that the Spanish provenances could be characterised by a higher root to shoot ratio and stem weight. Specific leaf area was also found to be lowest for the Spanish provenances.

Many studies have reported deficient or intermittent patterns of natural regeneration in temperate deciduous woodland. The present study aimed to assess the relative impact of herbivore-mediated plant mortality on the natural regeneration dynamics of representative tree species (Acer pseudoplatanus, Betula pendula, Fraxinus excelsior, Ilex aquifolium, Sorbus aucuparia, Taxus baccata and Ulmus glabra) in representative temperate deciduous woodland (Shipley Wood and Derwent Gorge, County Durham). Sapling density and the density, spatial association and size distribution of adult tree populations varied significantly between tree species and study sites, reflecting contrasting patterns of current and historical regeneration. Rates of post-dispersal seed predation and seedling herbivory were quantified using field-based 'cafeteria' trials. Rodents were the principal agents responsible for seed predation, whereas seedling herbivory was attributable to a mixed suite of herbivores including invertebrates, rodents and larger mammals. Rates of seed predation and seedling herbivory varied significantly between tree species, most likely reflecting individualistic, trade-off responses to chemical and physical attributes. Fine-scale spatial variation most likely reflected the preferential foraging of rodents beneath protective vegetation cover. There was no consistent evidence to support the hypothesis that dispersed seeds may escape disproportionately high offspring mortality beneath parent plants resulting from increased herbivore activity. Natural seedling density varied significantly between years and between tree species, according to the abundance of viable seeds produced by conspecific adult trees. Although seedling survivorship varied significantly between species, the survivorship of each species was similar between years and between cohorts of the same year. Canopy cover, field layer cover or correlated factors were significant determinants of seed germination and seedling emergence, establishment and survival, according to age- and species-specific tolerances. In relative terms, patterns of natural regeneration were primarily herbivore- limited (Acer and Taxus), microsite-limited (Betula, Fraxinus, Ilex and Ulmus) or limited by herbivores and microsites (Sorbus). The availability of viable seeds may have also limited the recruitment of Ilex, Sorbus, Taxus and Ulmus. Vegetative expansion, mast seeding, seed bank regeneration and repeated, prolonged reproduction may have reduced the actual impact of herbivory on natural regeneration, such that long-lived iteroparous tree species were unlikely to have been critically dependent on current recruitment.

Effects of fungi and overstory composition on tree seedling survival and growth were investigated in closed canopy upland forests in the coastal plain of South Carolina. Seedlings of Quercus alba, Cornus florida and Pinus taeda were planted in the understory of two forest types -naturally regenerated hardwood and planted pine. Fungal species composition and biomass were experimentally manipulated with a treatment of the fungicide captan. In contrast with other studies conducted in different systems (sand dune, grassland, and old field), the effects of soil fungi were minor in a closed canopy forest. Only Q. alba showed a significant response to the fungicide (p < 0.05) treatment with increased growth. Overstory composition had no significant effect on growth or survival for any of the species. Both of the commercially desirable species (Q. alba and P. taeda) had reasonable survival ( @ 60%). Both also maintained positive, though modest, growth. This suggests that an advance regeneration pool could be established successfully by artificial regeneration.
Master of Science

Glaze damage to canopy trees, gap size and seedling regeneration was surveyed relating to site topographic features after a major glaze storm at Fishburn Forest in the central Appalachian mountain region. The survey sites were stratified according to aspect and landform, and sample plots were randomly assigned to each topographic category. The canopy trees in the plots were tallied and their damage was visually classified. The results demonstrated that different species had different susceptibilities to glaze damage and susceptibility of species varied as topography changed. Virginia pine was the most susceptible species. In general, trees had the greatest damage on steep slopes and eastern aspects, and least damage on toe-slopes. Some species varied greatly in their susceptibility to glaze damage across the topographic categories, such as red maple, while some species varied little, like blackgum. Basal area was reduced 6% and varied due to species and topography. Where glaze damage was severe, gaps in the forest canopy were created. Gap sizes and the effects of gap size and topography on seedling regeneration within gaps caused by glaze damage were assessed. Seedlings were tallied by species and height in microplots within each sample plot and in the nearest gap, where gap size was measured. Gap size varied from 14,000 m2 to less than 20 m2. Average gap size was 255 m2. Canopy tree damage, forest type and topography were the most important factors affecting gap size. Gaps tended to be larger on steep backslopes. Common seedling species in both gaps and understory were sassafras, serviceberry and red maple. Disturbance affected both seedling height and density, as did topography. However gap size had effect only on seedling height. The future forest in this area is unlikely to change significantly, as species composition of seedlings was largely unaffected by the glaze storm damage.
Master of Science

Rosebay rhododendron (Rhododendron maximum L.) is an evergreen ericaceous shrub that plays a dynamic role in the southern Appalachian forests. Commonly located on mesic sites, this understory shrub forms dense thickets that greatly reduce the amount of light available to herbaceous and woody plants found on the forest floor. Past research has shown that silvicultural methods can be used to eradicate R. maximum, however it is unclear which of these methods is most efficient and what effects other than stem mortality may occur. In this study, treatments involving prescribed fire, mechanical cutting, and herbicide applications were applied to R. maximum dominated forests in southwestern Virginia to determine what effect seven different silvicultural treatments had on 1) controlling of R. maximum as a forest weed 2) fuel loading inside of a R. maximum thicket, and 3) canopy tree seedling regeneration. Mechanical cutting treatments were successful in reducing R. maximum basal area per acre; however stump sprouting and increased fuel loading occurred. Herbicide applications were successful in controlling only the smallest diameter class of R. maximum stems. Prescribed fire reduced litter layers and caused delayed mortality on R. maximum stems three years following treatment. Hemispherical photographs taken within each plot showed that silvicultural treatments that successfully increased the amount of light entering each plot were influential in seedling establishment three years following treatments. Results from this study can be used to further perfect silvicultural applications that alleviate R. maximum cover on the forest landscape.
Master of Science

During the late 19th and early 20th centuries, extensive logging reduced the forests of red spruce (Picea rubens) by nearly 99% through portions of West Virginia. In the wake of this disturbance, red spruce has begun regenerating on the ridge and mountaintop areas of Canaan Valley, West Virginia, where heath and grassland communities have both persisted in natural barrens and expanded into formerly forested areas. To understand abiotic and biotic conditions guiding the advance of the red spruce stand, I conducted a broad-scale assessment of thirty-one demographics plots spread across two sites (north Cabin Mountain and Bear Rocks/Dolly Sods), and a more focused assessment of red spruce species associations within thirty-two paired plots at Cabin Mountain. At the 15m x 15m demographics plots, I conducted a count of all P. rubens present, measured specimen height, DBH or diameter at ground level (DGL) for specimens < 1.37m tall, and assessed the relative percent cover of rock, shrub, herbaceous, and tree cover. These data, along with additional abiotic components derived from a DEM, formed the basis of my assessment using a generalized linear mixed model (GLMM) to identify the most significant biophysical variables related to P. rubens count. In the paired plots, I used the relative interactions index (RII) to compare the total cover of each present non-graminoid vascular species and the grouped cover types Rock, Graminoid, Lichen, Litter, and Moss in one 45cm-radius plot with a < 1.37m P. rubens specimen, and one paired 45cm-radius plot in open heath. The significance of differences in total cover were assessed with the Wilcoxon test and Tukey HSD. The GLMM identified percent rock cover and distance from the nearest P. rubens stand to be important correlates of P. rubens count at the demographic plots. Graminoid cover was found to be higher in P. rubens 45cm-radius plots than in paired heath plots, and Vaccinium angustifolium cover was found to be concentrated in 45cm radius plots beyond the first 15cm from the P. rubens stem. These findings reinforce a complex interplay between both the biotic and abiotic characteristics of a microsite and the successful germination and regeneration of a red spruce seedling in the heathland.
Master of Science

The New Zealand alpine zone has many fleshy-fruited plant species, but now has a relatively depauperate animal fauna. The key question is, therefore, are native alpine plants still being dispersed, if so where to and by what? I first measured fruit removal rates among nine common species using animal-exclusion cages to compare natural fruit removal by all animals, and by lizards only. Over two years, mean percent of fruit removed by early winter ranged from 25–60% among species. Speed of fruit removal also varied depending on species. Secondly, I quantified which animals disperse (or predate) seeds of those fruits, into which habitats they deposit the seeds, and the relative importance of each animal species for dispersal, in two ways. A 2-year study using fixed-area transects to monitor faecal deposition showed that introduced mammals (especially possums, rabbits, hares, sheep, pigs and hedgehogs) were abundant and widespread through alpine habitat. Of the 25,537 faeces collected, a sub-sample of 2,338 was dissected. Most mammals dispersed most (> 90%) seeds intact. However, possums (numerically the important disperser) moved most seeds into mountain beech (Nothofagus solandri) forest, while rabbits, hares, and sheep dispersed seeds mainly into open grassland dominated by thick swards of exotic grasses (e.g. Agrostis capillaris and Anthoxanthum odoratum); all are less suitable microsites. Kea (Nestor notabilis), the largest and most mobile of only three remaining native alpine bird species, are potentially useful as a long-distance seed disperser, even though parrots are typically seed predators. I found that kea are numerically more important than all other birds combined, damage very few seeds, and are probably responsible for most dispersal of seeds between mountain ranges. Finally, I investigated the effects of seed deposition microsite (shady/high-light), pulp-removal (whole/cleaned), competition (soil dug/not-dug) and predation (caged/ not) on germination, growth and survival of eight subalpine plant species. There were strong positive effects of shady microsites for seed germination and seedling survival to 3.5 years for six of the eight species. Effects of other treatments were less important and varied among species and stages. Hence, both native birds and introduced mammals are dispersing alpine seeds, but the mammals often deposit seeds in habitats unsuitable for establishment. Any evaluation of the dispersal effectiveness of frugivores must consider their contribution towards the long-term success for plant recruitment through dispersal quantity and quality.

The non-native Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) has been grown to a limited extent in the southern part of Sweden since the early 1900s. A more extensive use has probably been curtailed by its known susceptibility to damage by frost, pine weevil and other pests. Limited access to vital seedlings of suitable provenances has also restricted its more widespread growth. The need for valuable species that will grow well through ongoing climate change has increased the interest for Douglas fir in Sweden. This thesis addresses a number of important questions relating to the planting of Douglas fir in Sweden: seedling storability, freezing tolerance, timing of bud burst, frost damage and seedling response to site preparation. Seven Douglas fir provenances originating from British Columbia, Canada were used in the experiments and where applicable, compared with a local provenance of Norway spruce (Picea abies (L.) Karst.). The early bud burst of interior Douglas fir provenances, observed both in greenhouse tests and in the field, results in a high risk of damage by late spring frost. This type of damage does not seem, however, to be fatal and does not obviously retard the early growth of seedlings. The difference in growth between coastal and interior provenances was insignificant, but survival was greater for interior than for coastal provenances. All the provenances of Douglas fir studied showed a later development of freezing tolerance of shoots and roots in the autumn than Norway spruce, with the coastal provenances developing such tolerance even later than interior provenances. This could be a contributory cause for the severe damage by winter desiccation observed on seedlings of coastal origin. A thorough site preparation proved to be an effective way to increase survival and root growth. Interior provenances of Douglas fir became ready for storage earlier in autumn than coastal provenances. When freezing tolerance of shoots had increased sufficiently, Douglas fir seedlings could safely be kept in frozen storage using the same procedures used for Norway spruce. The results emphasise the need to gain further knowledge about how the remaining obstacles to establishment of Douglas fir could be reduced with different silviculture methods.

Abstract The restoration of degraded landscapes has become one of our most valuable tools for conservation, however there are many factors which can restrict natural regeneration and impede active restoration attempts. The purpose of this study was to investigate three key processes which commonly limit the establishment of forest tree species into abandoned pasture in tropical forests: i) dispersal limitation, ii) seed predation, and iii) competition from the grass sward. Seed dispersal I identified 59 species of birds that were using the grassland habitat. Through 216 hours of focal tree observations I established that isolated trees in the grassland that had larger canopies, and those that were providing a food source (i.e. flowers or fruit) had significantly higher bird visitation rates and average stay lengths. I found evidence of the “perch effect” as patches of remnant trees encouraged more birds into areas of grassland, and the density of seedlings under tree canopies was significantly positively correlated with bird visitations. 95% of the seedlings found beneath tree canopies in grassland were of a different species to that of the tree canopy above them, demonstrating the dispersal of seeds from elsewhere into these microhabitats. 98% of these seedlings are grassland or forest edge species showing forest core species are still dispersal or microsite limited despite the effect of these trees. Seed predation Removal rates of seeds from experimentally laid out seed piles varied among seed species, the habitat the pile was in, and the predator guild able to access the piles. Preliminary results indicate that these trends are driven by the ecology of the seed predator. Removal of seeds by vertebrates was highest in the core forest, while ant predation was constant across all habitats. Vertebrates removed the larger seeds (Entandrophragma angolense and Sterculia tragacantha) while ants preferred the smaller Celtis gomphophylla and Croton macrostachyus. Overall predation rates in grassland were lower than those in the forest, and the presence of remnant trees did not influence predation rates, a positive sign for regeneration and the survival of seeds dispersed into these areas. Competition from the grass sward While the grass sward provides shade for seedlings of forest tree species it is also a harsh environment for them, as the grass competes with seedlings for water. Removing the grass and covering planted seedlings with artificial shading structures significantly increased both the survival and growth of these seedlings. Recommendations From this study I was able to make recommendations for a low input restoration program at Ngel Nyaki. Planting seedlings in small „islands‟ takes advantage of the natural increase in dispersal of seeds under isolated trees, while low seed predation rates increase the chance of survival of these seeds to germination. Planting these seedlings under shade will lead to increases both their growth rates and their survival. Once the secondary forest develops, under-planting seedlings of core forest trees will introduce them to the system, as the natural establishment of these seeds appears to be limited in the current environment. This study has also served to remind us how little we know about this particular forest-grassland system, and has led to the development of ideas for further investigations into several more aspects of regeneration.

Conventional Appalachian surface-mine reclamation techniques repress natural forest regeneration, and tree plantings are often necessary for reforestation. Reclaimed Appalachian surface mines harbor a suite of mammal herbivores that forage on recently planted seedlings. Anecdotal reports across Appalachia have implicated herbivory in the hindrance and failure of reforestation efforts, yet empirical evaluation of herbivory impacts on planted seedling vitality in this region remains relatively uninitiated. First growing-season survival, height growth, and mammal herbivory damage of black locust (Robinia pseudoacacia L.), shortleaf pine (Pinus echinata Mill.), and white oak (Quercus alba L.) are presented in response to varying intensities of herbivore exclusion. Seedling survival was generally high, and height growth was positive for all species. The highest herbivory incidence of all tree species was observed in treatments offering no herbivore exclusion. While seedling protectors lowered herbivory incidence compared with no exclusion, full exclusion treatments resulted in the greatest reduction of herbivore damage. Although herbivory from rabbits, small mammals, and domestic animals was observed, cervids (deer and elk) were responsible for 95.8% of all damaged seedlings. This study indicates that cervids forage heavily on planted seedlings during the first growing-season, but exclusion and tree species selection is effective at reducing herbivory.

Fire has influenced species composition within the Central Hardwood Forest for millennia. Since the last glacial retreat, Native Americans followed by European settlers used fire as a tool to manipulate their environment. This fire use by humans helped maintain the dominance of well-adapted oak-hickory species across eastern forests. By the 1940's, land fragmentation from increased settlement and actively enforced suppression policies effectively eliminated fire from the landscape. Without the disturbance of recurrent fire that alters succession, the fertile loess-capped hills of southern Illinois have undergone several decades of compositional and structural change manifested by encroachment of mixed mesophytic competitors that are maladapted to fire. Today, land managers seek practical methods to restore declining oak-hickory forests. Southern Illinois forests in particular are lacking information on how cutting and prescribed fire techniques can be applied to encourage regeneration of oak-hickory species. In 2002, five sites were chosen across the Greater Shawnee Hills geographic region for similar ecological characteristics. A factorial combination of thinning and a fire treatment consisting of two burns was used to test the response of understory components including: seedling density, seedling height, seedling diameter, non-tree cover and available sunlight. Results showed a distinct improvement in oak-hickory seedling competitive position as compared to non oak-hickory species. Seedlings of sassafras out-competed all other groups in this study and were the only species to increase in both density and height following repeated fire. The non-tree vegetation layer increased as a result of thin from below treatments, while burning had no effect on the amount of available sunlight. Generally, woody seedlings benefited from thinning based on their physiological adaptations and fire essentially acts as a filter selecting for traits of disturbance-prone vegetation.

As características da regeneração natural no sub-bosque de comunidades florestais em processo de restauração expressam os principais indicadores de sucesso dos projetos de restauração ecológica, sendo que a ausência ou a baixa qualidade de regeneração natural são os principais gargalos para a perpetuação de projetos inseridos em paisagens muito fragmentadas. No entanto, condições adversas de micro-sítio de regeneração sob plantios de restauração podem restringir a colonização do sub-bosque por espécies nativas, comprometendo a sua perpetuação no tempo. O objetivo desse estudo foi avaliar se, e como, as condições físico-químicas do micro-sítio de regeneração, no sub-bosque de áreas em processo de restauração com diferentes idades, podem limitar o estabelecimento de espécies arbóreas nativas, restringindo assim, a restauração da dinâmica florestal. O estudo foi desenvolvido em três áreas em processo de restauração com diferentes idades (10, 22 e 55 anos), implantadas via reflorestamentos de alta diversidade. Foi realizada a caracterização físico-química do micro-sitio de regeneração das áreas de estudo, avaliando-se o grau de compactação, porosidade, umidade, conteúdo de matéria orgânica e nutrientes e granulometria do solo, bem como a massa seca de serapilheira, e a cobertura do dossel. Em cada área de estudo, foram alocados 10 blocos experimentais, cada um constituído por 4 parcelas de 1 m x 1 m, onde foram semeadas nove espécies arbóreas nativas regionais. Nessas parcelas foram estabelecidos três tratamentos e um controle: A) semeadura na condição natural da área, sem qualquer alteração das características do micro-sítio de estabelecimento (serapilheira autóctone), B) semeadura sobre a serapilheira e o solo transplantados de floresta nativa (serapilheira alóctone), C) semeadura sobre bagaço de cana triturado e compostado e D) controle (sem semeadura). A coleta dos dados de emergência e mortalidade de plântulas foi feita por um período de 6 meses. Ocorreu um gradiente de aumento da cobertura do dossel, da porosidade, da umidade, do conteúdo de argila e matéria orgânica e uma diminuição da compactação do solo das áreas restauradas mais novas para as mais velhas. A emergência de plântulas não diferiu entre as áreas de estudo, porém, a sobrevivência de plântulas foi significativamente menor na restauração mais antiga, de 55 anos. Constatou-se uma correlação positiva entre a mortalidade de plântulas com o aumento da cobertura do dossel e com a quantidade de matéria orgânica no solo. A emergência e a sobrevivência de plântulas foram estatisticamente maiores no tratamento onde as sementes foram aplicadas sobre serapilheira autóctone. Assim, conclui-se que apesar das condições de micro-sítio de regeneração de florestas em restauração tornarem-se, com o tempo, mais semelhantes à de florestas naturais, tornam-se cada vez mais restritivas ao estabelecimento de plântulas. Além disso, o estabelecimento de plântulas é favorecido nas condições locais de substrato de florestas em processo de restauração florestal, sem limitação evidente para que a sucessão secundária avance. Conseqüentemente, a limitação de dispersão deve ter influência maior nessas condições para o avanço inicial da restauração do que a limitação de micro-sítios favoráveis de estabelecimento.
The characteristics of the natural regeneration of restoration plantings understory express the main indicators of success of ecological restoration projects, in which the absence of regeneration indicates a bottleneck for the perpetuation of forest communities inserted into highly fragmented landscapes. Nevertheless, adverse conditions of the micro-site of regeneration in restoration plantings may hamper the colonization of the understory by native species, which in turn collapse its perpetuation along the time. We sought to evaluate if, or how, the physical-chemical conditions of the micro-site of regeneration of restoration plantings with different ages can limit native tree species establishment and therefore, the dynamic of forest restoration. The study was developed in three areas under restoration with different ages (10, 22 and 55 years). The physical-chemical characterization of the micro-site of regeneration of the study areas was carried out by evaluating the soil compression level, porosity, humidity, organic matter and nutrients content and granulometry, as well as litter dry mass and canopy cover. In each area, we set 10 experimental blocks, each one consisting of four 1 m x 1 m plots, in which nine tree species were sown. In each plot we established three treatments: A) direct seeding in the natural condition of the area, without any alteration in the characteristics of the micro-site (indigenous leaf litter), B) direct seeding on the leaf litter and soil transplanted from a native forest (allochthonous leaf litter), C) direct seeding on grounded and composted sugarcane bagasse and D) control (no seeding). Seedling emergence and mortality were observed through six months. An increase on the canopy cover and soil porosity, humidity, clay and organic matter content were observed in the oldest areas, as well as a decrease in soil compression. Seedling emergence did not differ among the studied areas; however, seedling survival was significantly lower in the oldest reforestation, with 55 years. A positive correlation was observed between seedling mortality with the increase of canopy cover and soil organic matter content. Seedling emergence and survival were statistically higher in the treatment A (indigenous leaf litter). Thus, although the micro-site conditions for seedling establishment become even more similar to reference ecosystems as restoration planting evolve, it also becomes more restrictive. In addition, seedling establishment was favored in the conditions of local substrate of restoration plantings, without evidence of limitation for the progress of secondary succession. Consequently, dispersal limitation may play a higher influence in this condition for the advance of restoration process.

This thesis quantifies aspects of shade tolerance in tree seedlings of species native to the Caledonian pinewood ecosystems of Glen Affric (Highland Region, Inverness-shire). Growth, allocation and morphological responses of 15 species to irradiance under simulated forest canopy light were investigated in a nursery-based shade house experiment. The same responses of four of the 15 species (Ilex aquifolium, Alnus glutinosa, Sorbus aucuparia and Betula pubescens) to different developmental stages of Pinus sylvestris woodland were investigated in the field. The spatial and temporal growth responses of naturally regenerating S. aucuparia seedlings to shade and gap microhabitats were also studied. Data from the shade house experiment enabled further detailed exploration of the relationship between relative growth rates (RGR) and irradiance and potential cross-overs of ranks of growth in high and low light conditions.

- Ziele der Arbeit - Das primäre Ziel der vorliegenden Arbeit bestand in einer möglichst umfassenden Be-schreibung einzelner Entwicklungsstadien im Verjüngungszyklus von Betula pendula Roth. Dabei waren die lokalen Bestandes- und Standortsbedingungen im Untersuchungsgebiet in besonderer Weise zu berücksichtigen. Des Weiteren sollten Optionen zur waldbaulichen Integration der Sand-Birkenverjüngung in bestehende Behandlungskonzepte für in Auflösung befindliche Fichtenaltbestände aufgezeigt werden. - Untersuchungsgebiet - Der Tharandter Wald liegt im Freistaat Sachsen (50° 55’-50° 00’n. Br., 13° 25’-13° 35’ ö. L.) und umfasst eine Fläche von etwa 6.000 ha. Das von der Baumart Fichte dominierte Gebiet kolliner bis submontaner Höhenstufe (350 - 420 m ü. NN) wird der „Unteren Nordostab-dachung des Erzgebirges“ zugeordnet. Als Untersuchungsflächen wurden wechselfeuchte (wechselfrische) Standorte mittlerer Trophie gewählt, die von einschichtigen Fichtenbe-ständen in einem Alter von ≥ 80 Jahren bestockt waren. Einzeln bis truppweise eingemischte Samenbäume der Sand-Birke (B. pendula) bildeten eine Grundvoraussetzung für die Flächen-auswahl. - Methodisches Vorgehen - Das methodische Vorgehen konzentrierte sich auf die verjüngungsökologisch relevanten Entwicklungsstadien (fruktifizierender Samenbaum, Diaspore, Keimling, Sämling und eta-blierte Verjüngungspflanze) der Sand-Birke. Die Wachstumsparameter der vorhandenen Samenbäume wurden durch Untersuchungen zum Fruchtbehang unterlegt. Der mehrstufige Versuchsansatz zur Erfassung einzelner Verjüngungsstadien stützte sich auf Bestandesauf-nahmen, Gefäß- und Laborversuche. Erhebungen auf Bestandesebene erfassten die Diaspo-renausbreitung mithilfe von Samenfallen und dokumentierten die Keimlings- und Ver-jüngungsstadien von B. pendula auf entsprechend etablierten Aufnahmeplots (1 m x 1 m). Darüber hinaus umfassten die Aufnahmen Strahlungs- und Feuchtemessungen und die Charakterisierung der Bodenvegetation. Für die Einschätzung des mikrostandörtlichen Um-feldes wurden exemplarisch Bodendeckungsvarianten (Mineralboden, Nadelstreuauflage, Calamagrostis villosa CHAIX (GMEL.) und Deschampsia flexuosa L. (TRIN.)) ausgewählt, die als besonders repräsentativ für reine Fichtenbestände des Erzgebirges gelten. Für die räumliche Modellierung der Diasporen und Keimlinge auf Bestandesebene stand das Pro-gramm WALDSTAT (NÄTHER & WÄLDER 2003) zur Verfügung. Im Rahmen des Mitscherlich-Gefäßversuchs wurden gleichermaßen quantitative und qualitative Entwicklungen von Sand-Birkenkeimlingen und -sämlingen erhoben. Der Einfluss ausgewählter Bodendeckungs-varianten wurde in diesen Betrachtungen berücksichtigt. Neben zahlreichen Pflanzenpara-metern (Spross-, Blatt- und Wurzelentwicklung, Allokationen, Allometrien) war die kleinstandörtliche räumliche Verteilung dieser Verjüngungspflanzen von vorrangiger Be-deutung. Als Verteilungs- und Konkurrenzmaße auf Ebene des Mikrostandortes dienten Tessellationsmodelle, der Aggregationsindex nach CLARK & EVANS, der Gini-Koeffizient und das “Constant Yield Law“. - Ergebnisse - - Die Erfassung der Samenbaumparameter von B. pendula führte zu flächenspezifischen und signifikanten Unterschieden in der Dimension, Höhe und soziologischen Stellung. Für die Darstellung der Durchmesser-Höhenverteilungen erwiesen sich logarithmische und quadra-tische Funktionen gleichermaßen geeignet. Das Kronenprozent ereichte im Mittel Werte zwi-schen 37 % und 49 %. Die einzelnen Kronenparameter (Kronendurchmesser, Kronenlänge und Kronenmantelfläche) zeigten straffe lineare Zusammenhänge. Innerhalb der Kronen-strukturen (z. B. Blatt- und Zweigtrockenmasse) ließen sich zum Teil allometrische Be-ziehungen nachweisen. Im Rahmen der Vollbaumbeerntung war ein durchmesserabhängiger Fruchtbehang nachweisbar, der für den Einzelbaum eine Anzahl zwischen 2,3 und 4,2 Millionen Diasporen erreichte. - Mit den Erhebungen zur zeitlichen Ausbreitungsdynamik der Diasporen waren durch mehrjährige Untersuchungszeiträume, auch für eine Pionierbaumart wie B. pendula, stärkere Samenjahre nachzuweisen. Die räumliche Modellierung der anemochoren Diasporenaus-breitung belegte erwartungsgemäß bessere Modellanpassungen für den anisotropen (richtungsgebundenen) Modellansatz. Dennoch zeichneten sich sowohl jahres- als auch flächenspezifisch deutliche Unterschiede in der Modellgüte ab. Als maximale Diasporen-dichte pro m² wurde ein Wert von 20.700 Diasporen ermittelt. Die mittleren Ausbreitungs-distanzen (MDD - “Mean Dispersal Distances“) lagen nach Modellschätzung für die ge-samten Beprobungszeiträume und unter Berücksichtigung aller Versuchsflächen zwischen 37 m und 90 m. Die durchschnittliche Diasporenproduktion eines Einzelbaumes lag nach Anga-ben des Modells in einem Bereich von 180.000 bis 7.400.000. Die Qualitätsansprache an den Diasporen ergab einen Anteil von etwa 5 % bis 8 % äußerlich Schadhaften. Der unmittelbare Windeinfluss auf Hauptausbreitungsrichtung und -entfernung konnte ebenfalls nachgewiesen werden. - Untersuchungen zum Keimlingsstadium zeigten deutliche Abhängigkeiten zwischen den ausgewählten Bodendeckungsvarianten, der Keimlingsdichte und dem Keimlingswachstum. Sand-Birkenkeimlinge waren sowohl unter Bestandesbedingungen als auch unter den freif-lächenähnlichen Bedingungen des Mitscherlich-Gefäßversuchs auf der Variante mit Mine-ralboden besonders dicht aufgelaufen, blieben jedoch stark in ihrer weiteren Entwicklung zurück. Als besonders wüchsig erwiesen sich Keimlinge auf den Bodendeckungsvarianten mit Nadelstreuauflage und in D. flexuosa. Sand-Birkenkeimlinge der Bodendeckungsvarianten ohne Konkurrenz durch Bodenvegetation (Mb, Nd) besaßen eine längere Hauptwurzel und eine höhere Wurzelmasse (56 % - 60 % der Gesamtmasse). Die oberirdische Allokation (Blatt- und Sprossmasse) fiel hingegen für Sand-Birkenkeimlinge in den Bodendeckungs-varianten mit C. villosa und D. flexuosa höher aus. Verteilungs- und Konkurrenzerhebungen in den Gefäßversuchen erbrachten signifikante Zusammenhänge zwischen Keimlingsdichte, Standraum und Wachstum der Einzelpflanze. - Das Sämlingsstadium und die älteren Verjüngungspflanzen wiesen einen deutlichen Rückgang in der Mortalität auf. Die Erhebungen im Bestand ergaben ein unterschiedliches Durchschnittsalter für Sand-Birken auf den einzelnen Bodendeckungsvarianten (C. villosa 7,6 Jahre, D. flexuosa 6,2 Jahre und Nadelstreu 4,7 Jahre). Die wachstumsrelevanten Umweltbe-dingungen wie Strahlungsverfügbarkeit, Feuchteregime und Entfernung zum nächsten Alt-baum unterschieden sich außerdem in Abhängigkeit von den als repräsentativ eingestuften Bodendeckungsvarianten unter Bestandesbedingungen. Das bestandesbezogene Wachstum der Sand-Birken in einem Alter von 2 bis 6 Jahren ließ sich durch eine exponentielle Funktion mit hoher Anpassungsgüte (p ≤ 0,000) abbilden. Innerhalb des Mitscherlich-Gefäßversuchs haben sich ebenfalls Unterschiede in der Individuendichte, den Mortalitäts- und Wachstums-raten in Abhängigkeit von den Bodendeckungsvarianten ausgebildet. Höchste Verjüngungs-dichten wurden nach einem 2,5jährigen Entwicklungszeitraum auf der Bodendeckungs-variante Nadelstreuauflage erreicht. Die Allokationen in der Trockenmasse näherten sich hingegen in den unterschiedlichen Varianten stärker an. Ein dichteabhängiges Wachstum konnte in der letzten Aufnahme nicht mehr nachgewiesen werden. Abschließend bleibt festzuhalten, dass die ermittelten Untersuchungsergebnisse in Abhängig-keit vom jeweiligen Verjüngungsstadium die zeitliche und räumliche Präsenz, Konkurrenz- und Entwicklungsfähigkeit der Sand-Birke in Fichtenaltbeständen des Tharandter Waldes charakterisieren. Sie belegen eine kleinstandörtliche Heterogenität in den untersuchten Beständen, die sich nachhaltig auf die Etablierung der hier untersuchten Pionierbaumart auswirkt. Anhand der räumlichen Modellierung lässt sich die zu erwartende Verteilung von Diasporen und Keimlingen in Abhängigkeit von den Positionen der Samenbäume prognostizieren. Insgesamt ergibt sich aus den vorliegenden Ergebnissen ein vergleichsweise hohes Verjüngungspotenzial für B. pendula, das sich durch waldbauliche Maßnahmen effizient nutzen ließe. Ein detailliertes Wissen über die einzelnen Verjüngungsstadien bietet zudem die Möglichkeit einer gezielten waldbaulichen Steuerung der Baumart und zur Risikoabschätzung des Verjüngungserfolgs unter den gegebenen Rahmenbedingungen. Bei einer wachsenden waldbaulichen Unsicherheit im Umgang mit unterschiedlichsten Klima-prognosen, die sich in ihrer Wirkung regionalspezifisch erheblich unterscheiden können, sollte die Sand-Birke als Misch- und Vorwaldbaumart unbedingt berücksichtigt werden. Um dem viel zitierten Anspruch an die Nachhaltigkeit waldbaulichen Handelns gerecht zu werden, muss die Option zur Integration von B. pendula gewährleistet bleiben, auch für künftige Generationen und bei sich wandelnden Ansprüchen an den Wald
- Objectives - The main goal of this study was to describe comprehensively the particular stages of the regeneration cycle of Betula pendula Roth. Investigations were carried out in local stand and site conditions of a research area in South-East Germany (Tharandter Forest) are considered. In this context options for integrating Silver birch regeneration into silvicultural management concepts of old Spruce stands (Picea abies L.) with lacking vitality are pointed out. - Research area - The Tharandter Forest is located (50°00’N, 13°35’E.) in Saxony (South-East Germany) with an area of around 6.000 ha. It is dominated by Norway spruce stands, and ranges from colline to submontane altitudinal belt (350 to 420 m a.s.l.). These sites are part of the northern declivity of the Ore Mountains. Mono-layered Norway spruce stands with soils of medium trophy and well drained, but featured highly variable soil moisture levels during the growing season were selected for this study. The stand age was ≥ 80 years. Seed trees of Silver birch were mixed as single trees or small groups. - Methodical aspects - The methodical work was concentrated on relevant regeneration aspects like fructification of seed trees, seeds, seedlings, saplings and established regeneration of Silver birch. Growth parameters of seed trees and the amount of fructification were used to quantify allometric relationships. The multi-level research design was based on measurements under stand conditions, pot and laboratory experiments. Seed traps and plots (1m x 1m) were located in spruce stands with regard to different stages of Silver birch development. Therefore micro-environmental growth conditions like soil humidity and photosynthetic active radiation were measured, and plants of ground cover characterized. As examples of ground cover variants with highest presence in homogeneous spruce stands mineral soil, needle litter, Calamagrostis villosa CHAIX (GMEL.) und Deschampsia flexuosa L. (TRIN.) were chosen. Using the program WALDSTAT (NÄTHER & WÄLDER 2003) spatial distribution of dispersed seeds (diaspores) and seedlings could be modelled. Additionally pot experiments were done to compare quantitative and qualitative development of birch seedlings between stand and open site conditions. Regeneration density, number of leaves, shoot and root growth and allocations were measured as important growth parameters to evaluate single plant development under different environmental conditions. Finally, spatial distribution of seedlings in microsites and intraspecific competition were calculated by tessellation models, aggregation indices after CLARK & EVANS, Gini-coefficient and ‘constant yield law’. - Main results - - Measurements on seed trees of B. pendula indicate stand specific differences significantly in dimension, height and biosocial position of trees within the birch population (crown classes). For specific height-dbh curves logarithmic and quadratic equations were adapted. The relative crown length for seed trees was located between 37 % and 49 %. Allometric relationships between crown parameters (e.g. crown diameter, crown length and crown surface) were strongly correlated. In specific cases crown structures (e.g. dry mass of leaves and twigs) were also correlated, certainly with different grades. Direct seed counting of felled seed trees provided the relationships between dbh and number of seeds. Counted seeds for single Silver birch trees ranged between 2.300.000 - 4.200.000. - As one result of seed trapping huge varieties in seed production of Silver birch were detectable between years with different seed potential. Spatial modeling of seed dispersal supported strong influences caused by wind (direction and speed). Hence, best fitted model estimations were found for anisotropic scenarios. The maximum in seed density was recorded with 20.700 seeds per m². As data for ‘Mean Dispersal Distances’ (MDD) the program WALDSTAT calculated between 37 m and 90 m. Furthermore the amount of seeds produced by a single tree was estimated with 180.000 - 7.400.000 depending on dbh. Physical quality evaluations for seeds have shown a mean proportion of damaged and not germinable seeds between 5 % and 8 %. - Direct effects of ground cover variants have been identified for seedling density and growth. Seedling density was highest on mineral soil for both, stand conditions and pot experiment, but these birch seedlings developed slowly compared with individuals in the other ground cover variants. The best growth was realized by birch seedlings in needle litter and D. flexuosa. Regarding to root length and mass, birches in ground cover variants without grass competition (mineral soil and needle litter) have shown a significant better development of underground parts. Root dry mass of these birch seedlings reached proportions between 56 % and 60 % of whole plant dry mass. By contrast the aboveground dry mass (leaves and shoot) was higher for birches competing with grasses. Overall results of birch seedling distribution and competition were significant correlations between densities, space, and growth per single plant. - For saplings and established birch regeneration a notable decrease in mortality rates were found. According to regeneration analyses under stand conditions age distributions in Silver birch regeneration have been controlled by ground cover variants and their environment conditions. The average age of Silver birch seedlings was high in areas with C. villosa (7.6 years) and low in needle litter (4.7 years). Furthermore growth influencing environmental conditions like light, humidity, and distance of old spruce trees have shown differences between variants in ground cover. The growth of regenerated Silver birches at the age of 2 to 6 years under those stand conditions can be described by an exponential function with high degree of adaptation (p ≤ 0,000). There were also differences in sapling densities, mortality and growth rates caused by ground cover variants in the pot experiments. After 2.5 years maximum regeneration densities in pots were registered on ground covers with needle litter. Allocations in regeneration dry mass were less influenced by ground cover variants than in previous stages. Density dependent growth rates could not be proved during last measurements. Finally, the presented results provide the opportunity to characterize temporal and spatial presence of different regeneration stages of Silver birch, its potential of competition and further development in old Norway spruce stands of the Tharandter Forest. They document heterogeneous structures of micro-environmental conditions in these spruce stands, which have sustainable effects on regeneration establishment of this studied pioneer tree species. On the basis of spatial modeling it is possible to estimate spatial distribution of seeds and seedlings depending on seed tree positions. Overall the results involve a high potential of successful regeneration in Silver birch, which opens up promising vistas for silvicultural management. More detailed knowledge in particular regeneration stages induces possibilities for selective control in silviculture with Silver birch. Additionally, estimating the regeneration risks and the success under given surrounding conditions will be more precisely. Considering uncertainty in giving prognoses for climate change Silver birch should be integrated in silvicultural strategies because of its role as admixed tree species and pioneer crop combined with comparably high resilience against warming

Restoring longleaf pine ecosystems is essential for managing rare plant and animal species and protecting biological diversity in the southeastern Coastal Plain of the United States. Natural longleaf pine ecosystems range from xeric uplands to poorly-drained flatwoods and savannas. Most existing stands, however, occur on xeric to dry-mesic sites and approaches to restoring longleaf pine to wetter sites traditionally utilize intensive practices. There is little information available on the efficacy of these practices to establish longleaf pine seedlings on poorly-drained sites and their impacts on soil properties, seedling survival and growth, and the understory plant community. A research project was established at Marine Corps Base Camp Lejeune, NC to evaluate the effects of site preparation methods for returning longleaf pine on hydric soils with no natural seed source. Various site preparation treatments were evaluated in a field experiment, and results revealed greater growth and earlier emergence from the grass stage with more intensive site preparation. There was a marginal increase in soil nutrients, and a slight increase in foliar nutrients found with the more intensive treatments. Site preparation influenced seedling growth in the short-term and this was likely due to the cumulative effects of controlling competition and modifying the planting site. Marine Corps Base Camp Lejeune and other Department of Defense installations include both former and remnant longleaf pine ecosystems that support federally protected plants and animals such as the red-cockaded woodpecker - and thus face the challenge of restoring former, poorly-drained longleaf pine ecosystems. A land use history revealed that, largely due to its poorly-drained status and inaccessibility, the majority of disturbance on the research area occurred after the 1920âs and was largely due to forestry activities. Since purchasing the land area of the project in 1996, the Marine Corpsâ challenge has been to balance the mission of training and readiness with the need for restoration and long-term management of longleaf pine ecosystems. The results of this work provide natural resource managers with a scientific foundation for assessing choices to assist in this restoration and management effort.

Predictions of microsite requirements for seven common Afromontane forest tree species were made by testing above ground relative growth rate (RGR) and photosynthetic response of seedlings of the respective species under different light intensities. Virgilia oroboides and Halleria lucida, with either a very high photosynthetic rate or RGR, were regarded to be pioneer species. Podocarpus latifolius was regarded to be a deep shaded species due to its low photosynthetic and RGR's. Rapanea melanophloeos, Ilex mitis, Olea capensis sub Ssp. macrocarpa and Kiggelaria africana either had moderately high RGR or photosynthetic rate and were regarded to be light shaded species. Predictions were tested in Grootvadersbosch (34ᵒ05's,20ᵒ50'E) forest, where frequency of seedlings beneath the canopy and under a canopy gap were recorded and tested using a x²-goodness of fit test, against the null hypothesis that there are equal frequencies of seedlings beneath the canopy and canopy gaps. Results confirmed predictions made for latifolius, O. capensis sub sp. macrocarpa, and R. melanophloeos. Low seedling frequencies for the other species, either due to a restricted distribution of adult trees (e.g. V. oroboides) or high levels of herbivore attack, made it difficult to test predictions. Significantly higher frequencies of seedlings of P. latifolius and O. capensis sub sp. macrocarpa beneath the canopy than in the gap of dry forest suggest that gaps in drier forests are stressful sites for regeneration. This led to the hypothesis of expecting a greater dominance of shade tolerant species in the canopy of dry forests than in moist forests. McKenzie's (1978) findings support this hypothesis. It was concluded that Afromontane forests are largely made up of deep or light shaded tree species, with pioneer species confined to forest margins. The role of canopy gaps can be seen to play a minor role promoting regeneration.

Kyoto University (京都大学)
0048
新制・課程博士
博士(農学)
甲第13907号
農博第1722号
新制||農||957(附属図書館)
学位論文||H20||N4374(農学部図書室)
UT51-2008-C823
京都大学大学院農学研究科地域環境科学専攻
(主査)教授 二井 一禎, 教授 武田 博清, 教授 縄田 栄治
学位規則第4条第1項該当

Magistro darbe įvertintos Varėnos rajone Na augavietėje augančių pušynų atsikūrimo galimybės praėjus 2-7 metams po atvejinių kirtimų pirmo atvejo. Darbo objektas – atvejiniais kirtimais išretinti 0,6-0,7 skalsumo pušynai Varėnos miškų urėdijos Zervynų, Ūlos, Marcinkonių ir Musteikos girininkijose. Į apskaitą pateko 7 sklypai, kurių plotas svyravo nuo 0,8 iki 22,7 hektarų. Pušies medynų amžius buvo 100-130 metų, bonitetas II-IV. Darbo tikslas – įvertinti pušynų žėlimo galimybes Varėnos miškų urėdijos pušies medynuose, kirstuose supaprastintais dviejų atvejų atvejiniais kirtimais. Darbo metodai. Matavimai buvo atliekami sistemiškai išdėstytose kvadratinėse 2x2 m apskaitos aikštelėse. Iš viso 7-iuose išretintuose pušies medynuose buvo išskirta 220 apskaitos aikštelių. Kiekvienoje tyrimo aikštelėje buvo nustatomas perspektyvių ir neperspektyvių 2-7 metų savaiminukų skaičius, miško paklotės storis, žolinės dangos agresyvumas žėlimui ir vyraujančios rūšys, trako rūšinė sudėtis ir kiekis aikštelėje, kitų medžių rūšių (B) žėlinių skaičius. Taip pat kiekviename tirtame sklype nustatytas paliktų priedangos medžių skaičius. Darbo rezultatai. Du tirti prieš 2-3 metus išretinti pušies medynai laikomi neatkurtais, juose perspektyvių pušies savaiminukų tankis siekė 1,1-1,4 tūkst. vnt./ha. Kiti trys prieš 4-5 metus išretinti pušies medynai laikomi atkurtais patenkinamai, juose perspektyvių pušies žėlinių skaičius buvo 3,2-3,6 tūkst. vnt./ha. Likę du prieš 6-7 metus išretinti medynai... [toliau žr. visą tekstą]
In this Master's thesis were determined pine's forest capability to restore naturally in mineral soils of normal humidity in Varena district after shelterwood cuttings during 2-7 years period. Also shelterwood trees density, soil scarification, litter thickness and herbaceous plants cover influence to pine's regeneration were estimated. Object of work – pine's forests in seven different sites of Varena district. These pine's forests occupied from 0,8 to 22,7 hectars, were 100-130 years old, 0,6-0,7 stands density and II-IV bonitete. Aim of work – to estimate pine's forests capability to restore naturally in Varena district after shelterwood cuttings. Methods of work. The measurements were performed in 2 to 2 meters accounting fields. In each field perspective and nonperspective pine's seedlings, litter thickness, herbaceous plant's species, undergrowth density and other tree species seedlings were determined. Shelterwood trees density in all pine's forests were determined too. Results. Two pine's forests were not regenerated when 2-3 years period after shelterwood cuttings have passed. In these forests the density of perspective pine's seedlings were 1100-1400 units per ha. Other three pine's forests were regenerated sufficiently when 4-5 years period after shelterwood cuttings have passed. In these forests the density of perspective pine's seedlings were 3200-3600 units per ha. Last two pine's forests were regenerated well when 6-7 years period after shelterwood cuttings... [to full text]

Central to the issue of harvest feasibility on the outer BC coast (CWHvh) is the question of whether sites, once harvested, can be regenerated, and whether the time period for replacement and subsequent growth is economically and environmentally acceptable. Since low productivity sites have not been harvested in the past, there is a lack of data to answer this question. We tried to provide an answer by assessing regeneration following natural disturbances. Small scale gap disturbances are the norm within old-growth stands. If regeneration is not a problem in gaps, then we have some evidence that regeneration should not be a problem upon implementation of our management practices. The objectives of this study were: (1) to develop baseline information on the mechanisms and the patterns of regeneration across a sequence of forest types; (2) to assess regeneration success with respect to productivity; and (3) to estimate future growth and productivity.

As communities and managers become aware of the long-term impacts of mangrove loss, estimated at 1-2% per year, interest in sediment erosion and mangrove rehabilitation has increased substantially. In this thesis project I 1) examine erosion rates within coastal fringing Rhizophora mangle ecosystems following mangrove clearing and compare these rates to accretion rates in intact mangroves; and 2) investigate the abiotic factors influencing mangrove seedling survival and regeneration of naturally colonizing R. mangle, in historic mangrove habitat after anthropogenic clearing. Differences in erosion were compared between patches of open-coast intact and anthropogenically cleared R. mangle to quantify the sediment trapping function provided by mangroves and its loss following clearing over a 24 month period. Growth rates of mangrove seedlings in intact forest were compared to seedlings in cleared areas. Seedling growth indicators were measured on 100 seedlings at five sites (50 in the intact and 50 in the cleared areas). To examine the limiting factors on seedling growth rates, nutrient addition and wave protection treatments were applied to seedlings in three disturbed areas. Sites within intact mangroves had sediment accretion (M= +3.83 mm) while areas cleared of mangroves had sediment erosion (M= -7.30 mm). Seedling growth (height) over the 2 year study period significantly differed between intact mangrove (M = 15.6 cm) and cleared (M = 10.24 cm) areas. Seedling mortality from the cleared areas (31%) differed from the intact areas (13%). Average seedling growth (height) was: greater with both nutrient/wave (M = 18.4 cm) and nutrient (M = 17.65 cm) treatments compared to controls (M = 10.8 cm), which suggests that providing nutrients and/or wave protection result in growth outputs comparable to seedlings found in intact mangroves. This study may prove to be useful in identifying areas that are most vulnerable to erosion following mangrove removal and ideal location of restoration following mangrove removal. Areas cleared of mangroves can lead to intensified erosion in areas where fringing reefs are not continuous. When managers are determining areas to focus resources for restoration, focusing on areas with nutrient rich habitat may result in higher survival rates and growth outputs.

Esta dissertação teve como objetivo analisar a dinâmica de regeneração natural de três formações florestais de restinga (uma Floresta de Restinga Alta Seca - RAS; uma Floresta de Restinga Alta Alagada - RAA; e uma Floresta de Restinga Baixa - RB) com diferentes condições edáficas, composições florísticas e estruturas, da Ilha do Cardoso, Cananéia, SP. Ao longo de um ano, procuramos entender os mecanismos que promovem as variações na composição e estrutura arbórea desses três sistemas. Para isso, entre fevereiro de 2007 e janeiro de 2008 nós acompanhamos a chuva de sementes das três florestas através 90 coletores de sementes de 0,5 m² (30 em cada floresta; Capítulo 1) e a comunidade de plântulas 50 cm de espécies arbóreas, através de 270 parcelas de 1 m² (90 em cada floresta; Capítulo 2). A dinâmica de regeneração natural das florestas foi analisada a partir dos dados de chuva de sementes, da dinâmica de plântulas (três censos em 12 meses), dos dados pré-coletados dos indivíduos arbóreos com DAP 5 cm das três florestas mais os dados ambientais de abertura de dossel (disponibilidade de luz) e teor de matéria orgânica (MO) no solo (Capítulo 3). Em relação à chuva de sementes, a RB apresentou quase o dobro de sementes do que as outras florestas. Por outro lado, a RAS e a RAA apresentaram uma diversidade de espécies significativamente maior do que a RB e uma elevada similaridade florística e estrutural. Quanto à síndrome de dispersão, mais de 95% das sementes e das espécies amostradas foram zoocóricas, indicando a importância da zoocoria para a manutenção e estruturação dessas florestas. As espécies de sementes apresentaram uma alta correspondência com as espécies da comunidade arbórea adulta adjacente aos coletores, sugerindo que as semelhanças e as diferenças de diversidade, de composição florística e de estrutura entre a chuva de sementes da RAS, da RAA e da RB observadas são reflexo da diversidade, da composição florística e da estrutura da comunidade de espécies arbóreas local das três formações florestais. Além disso, como as sementes apresentaram um padrão de deposição agregado e próximo à planta-mãe, propusemos que as espécies das florestas estudadas são principalmente limitadas em relação ao local adequado para a germinação de suas sementes e não à dispersão. Para as plântulas, encontramos uma maior diversidade e riqueza por 3 m² na RB, o oposto do que era esperado, já que a Floresta de Restinga Alta é conhecida por ser uma formação mais complexa e com maior diversidade, em relação aos adultos arbóreos, do que a Floresta de Restinga Baixa. Propusemos, portanto, um modelo hipotético de estruturação dessas comunidades no qual as florestas são estruturadas de formas distintas devido a filtros ecológicos, como a disponibilidade de luz e de nutrientes e eventos estocásticos, que limitam a germinação e o estabelecimento de plântulas, juvenis e adultos. Predizemos também que a inversão de diversidade entre as comunidades de plântulas e de adultos deve-se a processos dependentes da densidade decorrentes do estabelecimento diferenciado na fase de plântula. No Capítulo 3 foi possível testar algumas partes do modelo hipotético de estruturação das comunidades proposto no Capítulo 2. Concluímos que a dinâmica de regeneração natural e seus filtros bióticos e abióticos realmente são importantes para estruturação das comunidades de restinga estudadas. A RB apresentou uma maior abertura de dossel (maior disponibilidade de luz) do que a RAS e a RAA. O recrutamento, a densidade e a riqueza (em 3 m²) de plântulas estiveram positivamente relacionados com a abertura de dossel. No entanto, a RAS e a RAA apresentaram um maior teor de MO do que a RB, e a diversidade da comunidade arbórea adulta esteve positivamente relacionada com a MO. Assim, a disponibilidade de luz parece ser um filtro abiótico importante na germinação e no estabelecimento das plântulas, levando a maiores recrutamentos, densidades e riqueza por 3m² na RB quando comparado à RAS e à RAA. Entretanto, na passagem de plântula/juvenil para adulto a menor densidade de indivíduos e a maior disponibilidade de nutrientes na RAS e na RAA beneficiariam a permanência das espécies, levando à maior diversidade de espécies encontrada nessas florestas.
The goal of this dissertation was to analyze the natural regeneration dynamics of three restinga forests (Tall Restinga Forest TR; Tall Seasonal Swamp Restinga Forest TSR and Short Restinga Forest SR) with different edaphic conditions, floristic composition and structure in Ilha do Cardoso, Cananéia, SP. During a year, we attempted to understand the mechanisms that promote the floristic composition and structure variations in these three systems. For that, between February 2007 and January 2008 we accompanied the forests seed rain using 90 seed traps of 0,5 m² (30 in each forest; Chapter 1) and the seedlings community (tree species; 50 cm) using 270 plots of 1 m² (90 in each forest; Chapter 2). The natural regeneration dynamics was analyzed using the seed rain and the seedling dynamics (three census in 12 months) data, the individuals tree species with DAP 5 cm data and the environment data (canopy openness and organic matter - OM; Chapter 3). In relation to the seed rain, SR presented twice as many seeds as TR and TSR. On the other hand, TR and STR presented a significantly higher diversity than SR and also floristic composition and structure similarity. In respect to the dispersion syndrome, more than 95% of the seeds and species were animal dispersed, indicating the importance of zoochoric dispersal to the maintenance and structuring of these forests. The seeds species showed a higher correspondence with the adult community adjacent to the seed traps, suggesting that diversity, floristic composition and structure similarities and differences among the forests seed rain are a reflection of the forests local adult community diversity, floristic composition and structure. Besides, as the seeds presented an aggregated and close to the parent tree pattern of deposition , we proposed that the forests species are limited mainly by safe sites for seed germination and not by dispersion. For the seedlings, we founded a higher diversity and richness per 3 m² in SR, the opposite of what we had expected since the Tall Restinga Forest is known to be a more complex vegetation, with higher values of richness and diversity for adult trees when compared to Short Restinga Forest. We proposed a hypothetical model of community structuring in which these forests are structured in different ways due to ecological filters, as light and nutrients availability and stochastic events, that limit germination and seedling, juveniles and adults establishment. We predicted, as well, that the diversity inversion between the seedlings and adults community is due to density-dependence factors that are responsible for the differentiated seedling establishment. In Chapter 3, we were able to test some parts of the hypothetical model of community structuring proposed in Chapter 2. We concluded that natural regeneration dynamics and biotic and abiotic filters really are important to the forests community structuring. SR presented a higher canopy openness (higher light availability) than TR and STR. Seedling recruitment, density and richness (in 3 m²) were positively related to the canopy openness. Nevertheless, TR and STR presented higher organic matter contents than SR, and the diversity was positively related to the canopy openness and the OM. Thus, light availability seems to be an important abiotic filter acting in the germination and in the seedling establishment, leading to higher values of recruitment, density and richness per 3 m² in the SR when compared to TR and STR. However, in the seedling/juvenile turn to adult the lower individuals density and the higher nutrients availability in TR and STR would benefit the species permanence, leading to the higher species diversity found in those forests.

Orientador: Veridiana de Lara Weiser Bramante
Resumo: O Cerrado é considerado um dos 25 hotspots mundiais, uma das áreas prioritárias para a conservação da biodiversidade mundial, por apresentar uma alta biodiversidade, um alto grau de endemismo e suas espécies estarem ameaçadas de extinção. Sendo assim, é fundamental o desenvolvimento de estudos na vegetação de cerrado para subsidiar trabalhos de conservação, manejo e restauração ecológica. O presente estudo visou conhecer as espécies que constituem o estrato de regeneração natural de uma área de cerradão na Gleba II do Refúgio de Vida Florestal Aimorés, em Bauru, centro-oeste do estado de São Paulo, sudeste do Brasil. Por meio do método de parcelas, realizamos o inventário da regeneração natural em duas classes de altura. A classe I (H ≤ 50 cm), chamamos de banco de plântulas e amostramos em subparcelas de 2 m x 2 m e a classe II (50 cm < H ≤ 1 m) chamamos de jovens regenerantes, amostramos em subparcelas de 5 m x 5 m. Alocamos as duas subparcelas no canto inferior esquerdo de 25 parcelas permanentes de 10 m x 10 m. Para cada classe de altura da regeneração natural analisamos os parâmetros de riqueza e abundância, calculamos o índice de diversidade de Shannon (H’) e equabilidade (J), os índices de regeneração natural por classe (RNC) e total (RNT).Utilizamos o índice de Sorensen para avaliar a similaridade florística entre as classes de altura da regeneração natural e entre a regeneração natural como um todo e o estrato arbóreo amostrado em dois períodos, 2005 e 2019. Amostram... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The Cerrado is considered one of the 25 hotspots, one of the priority areas for the conservation of global biodiversity, as it presents a high biodiversity, a high degree of endemism and its species are threatened with extinction. Therefore, it is essential to develop studies in the cerrado vegetation to support conservation, management and ecological restoration work. The present study aimed to know the species that constitute the natural regeneration stratum of woodland cerrado area in the Wildlife Refuge Aimorés, in Bauru, middle west of the state of São Paulo, southeastern Brazil. Using the plot method, we carried out the inventory of natural regeneration in two height classes. Class I (H ≤ 50 cm), we call the seedling bank and sample in subplots of 2 m x 2 m and class II (50 cm Mestre

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FAPEAM - Fundação de Amparo à Pesquisa do Estado do Amazonas
On the importance of the Amazon Biome and its role in the maintenance of terrestrial biodiversity and ecological balance of the planet, the control of deforestation has been a constant challenge in the management of environmental conservation. Thus, the revegetation of degraded areas through initiatives of reforestation with native tree species or by conduct of natural regeneration are potential strategies for the reintroduction of these areas to ecological and productive processes. This study had as main objective to investigate the effectiveness of two methods of regeneration for the recovery of altered areas in the Fazenda Experimental of the Universidade Federal do Amazonas (FAEXP-UFAM). The study area had its forest cover removed and after abandoning two experiments were implemented, namely: 1) conduct of natural regeneration and 2) planting of eleven native forest species belonging to different ecological groups, pioneers (six) and no pioneers (five). In experiment 1 were sampled in 9 x 15 m plots all trees individuals with height above 10 cm. The experiment 2 was installed in randomized blocks design, being five blocks with 50 saplings each. Monitoring the survival and height growth, diameter and crown area was held for 10 months. In the analysis of natural regeneration (experiment 1) showed a total of 148 individuals distributed into eight botanical families, nine genera and 13 species, being the species Vismia gracilis, Vismia cayennensis and Vismia guianensis, the species had the highest importance value. Individuals have focused predominantly on the class of intermediate size (0.3 < 1.5 m tall) of natural regeneration. Ten months after planting in the field (experiment 2), high (≥ 80%) survival of the species in both the ecological groups, with the exception of pioneer species Sclerolobium paniculatum (40%) and species not pioneer Cedrela odorata (67%). Among the pioneering species, the largest growths were observed for Ochroma pyramidale and Trattinickia rhoifolia. For the ecology group of not pioneer species, the best growth performances were achieved by Parkia velutina, Hymenaea courbaril, Cedrela odorata and Endlicheria anomala. The study area is in early stages of succession, and enrichment planting of species of better survival and growth could be most effective strategy for forest recovery to a lesser period of time.
Diante da importância do Bioma Amazônia e o seu papel para a manutenção da biodiversidade terrestre e para o equilíbrio ecológico do planeta, o controle do desmatamento tem sido um constante desafio na gestão da conservação ambiental. Assim, a revegetação de áreas degradadas por meio de iniciativas de reflorestamento com espécies arbóreas nativas ou pela condução da regeneração natural constituem estratégias potenciais para a reintrodução dessas áreas aos processos ecológicos e produtivos. O presente estudo teve como objetivo principal investigar a eficiência de dois métodos de regeneração para a recuperação de áreas alteradas na Fazenda Experimental da Universidade Federal do Amazonas (FAEXP-UFAM). A área de estudo teve sua cobertura florestal removida e após o abandono foram implantados dois experimentos, a saber: 1) condução da regeneração natural e 2) plantio de mudas de onze espécies florestais nativas pertencentes aos grupos ecológicos, pioneiras (seis) e não pioneiras (cinco). No experimento 1 foram amostrados em parcelas de 9 x 15 m todos os indivíduos arbóreos acima de 10 cm de altura. O experimento 2 foi instalado em delineamento de blocos casualizados, sendo cinco blocos com 50 mudas cada. O monitoramento da sobrevivência e do crescimento em altura, diâmetro e área de copa foi realizado durante dez meses. Na análise da regeneração natural (experimento 1) observou-se um total de 148 indivíduos distribuídos em oito famílias botânicas, nove gêneros e 13 espécies arbóreas, sendo as espécies Vismia gracilis, Vismia cayennensis e Vismia guianensis, as espécies que apresentaram maior Valor de Importância. Os indivíduos concentraram-se predominantemente na classe de tamanho intermediária (0,3 < 1,5 m de altura) da regeneração natural. Aos dez meses após o plantio em campo (experimento 2), observou-se alta sobrevivência (≥ 80%) das espécies em ambos os grupos ecológicos, à exceção da espécie pioneira Sclerolobium paniculatum (40%) e da espécie Não Pioneira Cedrela odorata (67%). Dentre as espécies pioneiras, os maiores crescimentos foram observados para Ochroma pyramidale e Trattinickia rhoifolia. No grupo ecológico das espécies não pioneiras, os melhores desempenhos em crescimento foram alcançados por Parkia velutina, Hymenaea courbaril, Cedrela odorata e Endlicheria anomala. A área estudada encontra-se em estágio inicial de sucessão, sendo o plantio de enriquecimento das espécies de melhor sobrevivência e crescimento estratégia mais efetiva para a recomposição florestal em menor período de tempo

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
This study evaluated the mechanisms of natural regeneration represented by seeds rain, seeds bank of the soil and the regeneration vegetation, considering the seedlings bank and the established regeneration, in a fragment of Estacional Decidual Forest. The evaluation was made with 70 randomized samplings in 14 parcels inside four bands, with systematic distribution in the area. The seeds rain was studied using 70 collectors with 1 m x 1 m, the collected material was analyzed monthly, during a year. In the seeds bank was collect 70 samplings using an iron collector (25 x 25 cm) on the soil surface and adjusting the studied samplings to 5 cm of deep. The collected material was taken to the Laboratory of Silvicultura of the Departament of Ciências Florestais of the Federal University of Santa Maria, where it was evaluated during seven months. The seeds bank was evaluated in 70 sampling units of 2 x 2 m where was identified and measured all plants with h ≥ 30 cm and DBH < 1 cm, the natural regeneration in the area was evaluated in 70 sampling units of 5 x 5 m, in which were identified and measured all plants with 1cm ≤ DBH ≤ 5 cm. The regeneration mechanisms were analyzed in groups formed in the adult vegetation. In the seeds rain it was observed the presence of 73 species, mainly trees. The seeds bank of the soil show predominance of herbaceous species, and some trees and bush-like species, pioneer species and secondary species. In the seedlings bank, was observed the presence of light demanding tree species and eciofiles species, while in the established natural regeneration the predominance was of shadow species. The seed bank of the soil and the established natural regeneration show different comportment for the group 1 and 2 in the adult vegetation, while the seeds rain and seedlings bank show uniformity in the forest. The species with the bigger probability to perpetuate in the studied forest reminiscent and in the near areas were Gymnanthes concolor, Soroceae bonplandii, Eugenia rostrifolia, Trichilia claussenii, Trichilia elegans, Myrocarpus frondosus, Cupania vernalis, Nectandra megapotamica and Dasyphylum spinescens, these species can be used to enrichment and recuperation of the forest. The most restricted species were Cordia tricotoma, Luehea divaricata, Sebastiania commersoniana and Syagrus rommanzoffiana, these species may grow in the forest if used the right treatments to their perpetuation. The indicative species in the adult vegetation groups have the seeds rain and the seedlings bank as the main mechanisms for their conservation in the forest reminiscent.
Este estudo avaliou os mecanismos de regeneração natural, representada pela chuva de sementes, banco de sementes do solo, e vegetação em regeneração, considerando banco de plântulas e regeneração natural estabelecida, em remanescente de Floresta Estacional Decidual. A avaliação foi realizada em 70 subparcelas, aleatorizadas em 14 parcelas, dentro de 4 faixas distribuídas sistematicamente, na área. A chuva de sementes foi estudada em 70 coletores de 1 m x 1 m, cujo material era coletado mensalmente para avaliação, no curso de um ano. No banco de sementes do solo foram coletados 70 amostras, a partir de um gabarito de ferro (25 x 25 cm), que colocado sob a superfície do solo permitia a padronização da área para coleta em 5 cm de profundidade. O material coletado foi levado para o Laboratório de Silvicultura do Departamento de Ciência Florestais da Universidade Federal de Santa Maria, onde foi avaliado durante 7 meses. O banco de plântulas foi avaliado em 70 unidades amostrais de 2 x 2 m, onde identificaram-se e mediram-se todos os indivíduos com h ≥ 30 cm e DAP < 1 cm. A regeneração natural estabelecida foi avaliada em 70 unidades amostrais de 5 x 5 m. Nestas, identificaram-se e mediram-se todos os indivíduos com 1cm ≤ DAP < 5 cm. Os mecanismos de regeneração foram analisados em agrupamentos, formados na vegetação adulta. Na chuva de sementes, observou-se a presença de 73 espécies, principalmente, arbóreas. O banco de sementes do solo teve predomínio de espécies herbáceas, além de arbóreas e arbustivas, espécies pioneiras e secundárias iniciais. No banco de plântulas observou-se a presença de espécies heliófilas e eciófilas, enquanto na regeneração natural estabelecida foi verificado o predomínio de espécies de sombra. O banco de sementes do solo e a regeneração natural estabelecida apresentaram comportamento diferente para o grupo 1 e 2 da vegetação adulta, enquanto a chuva de sementes e banco de plântulas apresentaram uniformidade na floresta. As espécies com maior potencialidade para perpetuar no remanescente de floresta estudado foram Gymnanthes concolor, Soroceae bonplandii, Eugenia rostrifolia, Trichilia claussenii, Trichilia elegans e Dasyphylum spinescens, sendo indicadas para enriquecimento. As espécies com maior restrição, foram Cordia tricotoma, Myrocarpus frondosus, Cupania vernalis, Nectandra megapotamica, Luehea divaricata, Sebastiania commersoniana e Syagrus rommanzoffiana, dependendo de tratamentos silviculturais na floresta para garantir sua perpetuação. As espécies indicadoras dos agrupamentos, na vegetação adulta, têm a chuva de sementes e banco de plântulas como principais mecanismos de conservação das espécies no remanescente.

O acúmulo significativo de conhecimento sobre a ecologia de restauração nos últimos anos tem conduzido a mudanças na orientação dos programas de manejo e restauração florestal. A escolha ou criação de um modelo de restauração é um processo em constante aprimoramento, exigindo a necessidade de estudos que não apenas diminuam os custos envolvidos, mas também, que garantam a efetividade do objetivo proposto. Neste sentido, este trabalho testa novas metodologias de restauração visando a obtenção de informações técnicas sobre: A) a expressão do banco de sementes autóctone e alóctone na restauração florestal de diferentes situações de degradação antrópica.; B) o resgate de plântulas e indivíduos de espécies arbustivo-arbóreas regenerantes; C) a eficiência de um modelo de plantio que utiliza conceitos de Preenchimento e Diversidade e; D) a evolução da paisagem. Para análise dos bancos de sementes autóctone e alóctone foram feitos levantamentos da densidade e das espécies arbustivo-arbóreas regeneradas. No resgate de indivíduos de espécies arbustivo-arbóreas regenerantes, as plântulas e indivíduos jovens foram resgatadas em uma floresta e levadas para adapatação em viveiro, onde tiveram seus indivíduos e espécies contabilizados em termos de densidade e sobrevivência. No modelo de plantio estudado, as espécies foram reunidas em grupos de Preenchimento e Diversidade e tiveram a cobertura de copa de cada indivíduo quantificada. A evolução da paisagem foi realizada através de fotointerpretação e principalmente checagem de campo periódica. Os principais resultados dessas metodologias foram: A) As situações identificadas na Fazenda Intermontes apresentaram diferentes expressões de regeneração natural em função do número de indivíduos germinados banco de sementes autóctone. O aproveitamento dessa expressão poderá ser realizado através de metodologias diferenciadas de restauração para cada situação estudada: B) No estudo do Banco de sementes alóctone, a densidade dos indivíduos germinados se foi de 409.334 indivíduos/ha, revelando a possibilidade de uso no programa de restauração. Os indivíduos arbóreos apresentaram na área adubada um acréscimo de 137,3 % em sua altura média em relação aos indivíduos da área não adubada. C) No resgate de plântulas e indivíduos de espécies arbustivo-arbóreas regenerantes, a densidade dos indivíduos foi muito próxima para as duas épocas do ano, sendo 38.700 ind./ha e 37.900 ind./ha, mas com uma diferença significante para os indivíduos sobreviventes que apresentaram 16.500 ind./ha e 26.600 ind./ha para os meses de julho e dezembro de 2002, respectivamente. A técnica de resgate utilizada se mostrou viável uma vez que foi possível alcançar até 70,9% de sobrevivência para os indivíduos resgatados; D) No estudo sobre o modelo de plantio foram amostrados 143 espécies, demonstrando que a função do grupo da diversidade vem sendo mantida e aumentando as chances de efetivação dos processos de sucessão. Os resultados mostraram que o grupo de Preenchimento apresentou-se com uma porcentagem de cobertura significativamente maior que a do grupo de Diversidade, sendo 73,6% e 83,3% para 1,5 e 2,5 anos respectivamente.
Significant accumulation of know-how about restoration ecology has been changing forest restoration management programs’ trends during the last years. Choosing or elaborating a restoration model is a process that requires constant improvement and ecological studies that not only reduces the costs involved but also warrants the achievement of the aimed proposal. This study explores new restoration methodologies, searching for technical information about: A) autochthonous and allochthonous seed bank expression on forest restoration at different situations degraded by anthropogenic disturbances; B) seedlings and woody growing individuals rescue; C) efficiency of a planting model based on fulfillment and diversity concept; D) landscape development. The autochthonous and allochthonous seed bank were analyzed through regenerating woody species and density scouting. For the rescue of regenerating woody species, seedling and young individuals were taken from a forest and transferred to a plant nursery for adjustment, where number and species were counted regarding density and survival. In this studied planting model, species were organized and gathered into a fulfillment or diversity group, and each individual had its crown area quantified. Landscape development was analyzed by photointerpretation and specially by periodical field checking. Results from these methodologies showed that: A) Identified degraded situations at Intermontes farm displayed distinguished natural regeneration expression, influenced by the number of germinated seeds of the autochthonous seed bank. Advantage can be taken from these different outcomes by using distinct restoration methodologies for each studied situation. B) For the autochthonous seed bank study, germinated seed density was 409,334 ind./ha, indicating its potential role on restoration programs. Woody individuals at fertilized sites had a medium height enhancement of 137,7% when compared to those at non fertilized sites. C) For seedlings and woody growing individuals rescue, individual density was similar for both seasons (38700ind./ha and 37900ind./ha) but significantly distinct for individual survivor, with values of 16500ind./ha for July and 2600ind./ha for December. Rescue technique turned out to be a viable possibility since it achieved survival of 70,9% for rescued individuals. D) This planting model study registered 143 species, indicating that the diversity group’s role has been maintained and enhances the chance of successional process success. The fulfilling group had a significant higher percentage of crown area than the diversity group, with 73,6% and 83,3% for 1,5 and 2,5 years, respectively.

碩士
國立臺灣大學
植物學研究所
83
Seedling dynamics were studied in thirty small piots of 5×1㎡ in a 3-ha permanent plot established in Nanjenshan subtropical rain forest on Hengchun peninsula, tagged, identified, measured and recensused every month. A total of 3500 seedlings in 73 species were analyzed by 14censuses and survivorship of all tagged seedlings was 69.94%. Survivorship of the first census was 80.75%, comprising 1673 individuals of mixed ages and species. The density varied seasonally by birth and death of seedlings. There were two main birth seasons, one is between winter to spring, i.e. December to March, and the other is during summer between June to July. Most seedlings were dead within first three months after birth, and the peaks were concentrated form April to August. Seedling density was higher in the windward habitat than in the leedward habitat. The intermediate habitat had the highest diversity. The leedward habitat showed a seasonal variation. The Highest survivorship was found in the intermediate habitat, while the leedward habitat was the lowest. Canonical Correspondence Analysis (CCA) suggested that seedlings composition and distribution were influenced by aspect, soil moisture and vegetation type. Prior to my study, seedling assemblage of compostition and structure appeared to reflect the adult community at Nanjenshan. Different habitats and regeneration strategy were the main factors influencing seedlings establishment.

碩士
國立屏東科技大學
森林系所
99
Abstract Student ID: M9712016 Title of Thesis: Characteristics of Seed Germination and Seedling Regeneration of Leucaena leucocephala Total Page: 52 Name of Institute: Department of Forest, National Pingtung University of Science and Technology Graduate Date: July 8, 2011 Degree Conferred: Master Name of student: Chi- Chen Lin Adviser: Dr. Yan-Lun Kuo The Contents of Abstract in This Thesis: Leucaena leucocephala is among the 100 of the World's Worst Invasive Alien Species, and its invasiveness in Hengchun is extremely severe—with large areas of pure forest being formed. In order to understand the required light conditions for L. leucocephala regeneration, seeds and seedlings of L. leucocephala were placed under 8 different light treatments, and seed germination ratio, seedling height growth and seedling biomass allocation were compared among different light treatments. In addition, to understand the natural regeneration at different stands we investigated the amount of L. leucocephala seeds in soil seed banks from 10 L. leucocephala stands along the Hengchun west coast, while sample areas were set to monitor the dynamics of seedling survival in different months. Germination time of L. leucocephala can be reduced by soaking seeds in hot water, but if affected by worm bites the percentage of seed germination will be reduced to around 30%. Seed germination experiments were carried out in October 2009, under 8 different light treatments. Result showed that germination percentage of L. leucocephala seeds under 100% and 70% full-sun was 33.5% and 29.5%, respectively. These were significantly lower than germination percentage of 40~0.2% full-sun treatments (43.0~54.5% germination). However, same experiment carried out in December 2009 showed that full-sun condition resulted in significantly higher seed germination than the other 7 lower light treatment s. These two results contradict with each other. Possible explanations include variations in temperature of different month interact with light conditions—which affect seed germination performance—and seed quality. From shading experiments of L. leucocephala seedlings, we found that seedling survival was lowered under 20% full-sun, and death within two months under extremely low light of 0.2%. L. leucocephala seedlings had significantly higher height, ground diameter, and biomass under 70% full-sun, whilst 100% full-sun condition didn’t produce the tallest seedlings. In addition, 40% full-sun or lower was not favorable for seedling growth. Soil seed banks investigation in 10 L. leucocephala stands along west coast of Hengchun showed that the density of L. leucocephala seed on surface soil was 40~950 seeds per m-2; the 5 cm-thick subsoil contained 70~1,020 seeds per m-2. In total, these two soil horizons contained 1,900 L. leucocephala seeds per m-2 to the most. As for seedling density of L. leucocephala, Dayuanshan stand had the highest seedling density among all stands—145 seedlings per m-2 in July 2010—with all the other nine stands under 40 seedlings per m-2 each. There were major differences in L. leucocephala seedling density between dry and wet seasons: the seeds underwent mass sprouting during wet season, but seedling density was rapidly lower when it came to August. Results showed that there was a positive correlation between the numbers of L. leucocephala seedling and seed counts from soil seed banks.

Forest gaps play a major role in forest dynamics because increased resource availability favors plant species that differ from those in undisturbed forest. This dissertation investigates the spatial heterogeneity of resource availability in gaps, how it varies by site, and how it affects regeneration. Gap effects on resource availability and seedling growth were studied at three sites, which differed in drainage, using large gaps (108 m × 30 m) where light ranged from understory shade to full sun. Light levels in plots were measured using hemispherical photos; soil moisture, with a capacitance probe; soil temperature, with a portable thermocouple; and nitrogen, with buried-bag incubations. The strong asymmetric, light-induced temperature gradient drove nitrogen mineralization rates. Patterns of mineralization were modified by variation in soil moisture within sites and increased with the average moisture levels among sites. Nitrogen availability was highest in the center of gaps, while root uptake reduced nitrogen availability at the north edge. Contrary to predictions, relative height growth of Betula lenta growing in the north center of gaps was greater than that of B. papyrifera. For both species, the difference between understory and gap growth increased from least to most fertile sites. To separate the effects of resources on plant- and leaf-level responses in the two species, a greenhouse experiment was conducted with high and low levels of light, nitrogen, and water. High nitrogen increased height growth even in shade. Nitrogen also increased leaf area through greater leaf initiation and retention. High rates of growth in gaps is caused by nitrogen effects on leaf display and light effects on realized carbon gain. This research shows that increased nitrogen availability only occurs if gaps are large enough to increase soil temperatures that drive mineralization and to overcome the effects of root uptake near gap edges. It also highlights how the effects of canopy openings varies by site and how this can influence the regeneration of gap-dependent species.