Dissertations / Theses on the topic 'Temperate rain forest'

Using a forested headwater stream system as a model, the effects of inter-annual variation in summer discharge regimes on aquatic insect communities were investigated. More specifically, the benthic invertebrate community response to the intensity, minimum discharges, frequency, duration and abruptness of summer low-flow events were examined. We hypothesized that intensification of summer low-flow events, both in duration and magnitude, have some negative impacts on benthic macroinvertebrate communities in riffles. Examples of negative impacts include reduction in their abundance and/or biodiversity. First, the abundance and functional trait data of the benthic macroinvertebrates in the three streams in the Malcolm Knapp Research Forest, British Columbia, Canada, were analyzed with respect to the low-flow events. Second, population models were built to simulate the potential responses of lotic aquatic insect communities to future climate change scenarios that differ in the rate of intensifications in extreme flow events: a low-flow event scenario within the current range versus 10% increase in intensity. The summer low-flow events were found to have a significant relationship with benthic macroinvertebrate communities through three-table ordinations of the empirical data. The community structure was correlated with a major ocean-atmosphere regime shift (Pacific Decadal Oscillation). The intensity and duration of low-flow events explained the observed shift in community structure favouring r-selected traits (e.g. short life cycle, high reproduction rate). The two low-flow severity scenarios showed the significant differential impacts on the aquatic insect community structures when individual populations were modeled according to their traits. Aquatic insects could be separated into three groups according to their sensitivities, measured by extinction rates, toward the two scenarios.

Rain forest canopies are renowned for their very high biodiversity and the critical role they play in key ecological processes and their influence on global climate. Despite that New Zealand supports one of the most diverse and extensive epiphyte flora of any temperate forest system, few studies have investigated epiphyte communities and their invertebrate fauna along with factors that influence their distribution and composition. This thesis represents the first comprehensive study of entire epiphyte communities and their resident invertebrate fauna in the canopy of New Zealand’s indigenous forests. The aim of this study was to determine spatial patterns of epiphyte and invertebrate species richness, abundance and community composition in relation to abiotic variables, and in particular, the responses of these communities to elevated temperature and rainfall. This study was carried out in coastal lowland podocarp-broadleaved forests at two sites on the West Coast of the South Island of New Zealand. Samples from 120 mat-forming epiphyte assemblages located on inner canopy branches of 40 northern rata (Metrosideros robusta) trees were studied to characterise the component flora and fauna. Additionally, biomass, branch and tree characteristics and community responses to treatments designed to elevate temperature and rainfall to simulate predicted climate change were measured. This investigation revealed astonishing diversity and functional complexity of epiphyte and invertebrate life in this ecosystem. The 30.6 kg (dry weight) of epiphyte material collected contained a total of 567 species, 170 epiphyte and 397 invertebrate (excluding immature specimens and mites) species, including at least 10 species new to science and many undescribed species Epiphyte communities were found to be dominated by non-vascular plants (80 % of the total species richness), particularly liverworts and invertebrate communities were dominated with respect to abundance (~ 80 % of the total individuals) by Acari, Collembola and Hymenoptera (primarily ants) and functionally by scavengers and ants. Epiphyte and invertebrate communities were highly variable with respect to spatial patterning of species richness, abundance and composition across sites, among trees within sites and among branches within trees. Overall, a highly significant proportion, > 75 %, of the variance could be attributed to differences at the branch level, but these differences could not be explained by the environmental factors measured. There were no consistent relationships between the spatial pattern of epiphytes and invertebrates, or between vascular and non-vascular plants. However, there were significant positive correlations between epiphyte biomass and invertebrate species richness (r = 0.472; p < 0.0001) and abundance (r = -0.395; p < 0.0001), as well as non-living epiphyte biomass and scavenger species richness (r = 0.4; p < 0.0001). Microclimatic measurements taken on epiphyte mats were also highly variable with respect to temperature and relative humidity at similar physical locations within the same tree as well as across trees within sites. There was also considerable variation in the intensity and frequency of climatic extremes, although potentially harmful climatic conditions were experienced by all the epiphyte mats for which weather variables were measured. Negative correlations existed between both epiphyte and invertebrate community composition and increased temperatures expressed as cumulative degree days above 5˚C. However, variability was such that there was no direct evidence that increased temperature and rainfall treatments had an effect on invertebrate species richness, abundance or diversity. Northern rata host trees harbour an astonishingly diverse and complex canopy flora and fauna that is characterised by high spatial variability. Such variability highlights that to determine species distribution and community dynamics in canopy habitats in response to disturbance caused either by climate change or invasive species the structure of entire communities at different taxonomic and spatial scales, along with their responses to microclimatic factors, need to be studied. If such complexities are not taken into account, inappropriate interpretation may result in poor decisions concerning the conservation status, vulnerability and subsequent management of such unique ecosystems.

The relationships between the tree-rings of the white fir (Abies alba Mill.) and climate in the French internal Alps are indicated by correlation functions. This fir shows an accurate response to climate as well as long term persistence for at least six years (MS =0.18, R1 =0.65, and R6= 0.27). Its growth is strongly influenced by the previous year's climate, especially by prior August rainfall, which enhances ring size, or by high temperatures, which show the opposite effect. The most critical period extends from prior July to prior September. This species responds positively to warm temperature from current January to April, followed by rainfall in May and June, which leads to a longer growth period. A favorable water balance seems to be decisive. Abies alba can be affected by frost and seems to prefer a low thermal amplitude as demonstrated by the analysis of the extreme temperature data. Moreover, even a few days of excessive heat can reduce its growth.

O papel da Floresta Amazônica na ciclagem do carbono tem sido`freqüentemente relatado, no entanto, pouco se sabe sobre os aspectos que regula nos processos de assimilação e liberação de carbono da biosfera para a atmosfera. O objetivo deste trabalho foi descrever as respostas dos processos de respiração e fotossíntese com a variação da temperatura foliar, utilizando características biofísicas e dados micro-meteorológicos, para predizer a taxa assimilatória de CO2 de um indivíduo ou da comunidade em estudo. A pesquisa foi conduzida na Estação Experimental de Silvicultura Tropical (núcleo ZF-2), área de pesquisa da Coordenação de Pesquisa de Silvicultura Tropical (CPST) do Instituto Nacional de Pesquisas da Amazônia (INPA), utilizando-se de 4 torres para o acesso as copas. Os elementos climáticos foram monitorados por estações micro-meteorológicas Li-1401. As medidas de temperatura foliar foram realizadas com o auxilio de termopares de cobre-contantan, sendo a fotossíntese e a respiração avaliadas com um analisador de gases por infravermelho, com o qual foram obtidas curvas de respostas da fotossíntese a variação de radiação fotossinteticamente ativa (A-RFA), e a variação da concentração interna de CO2 em 4 diferentes temperaturas (A-Ci-T). Os resultados mostraram que: a temperatura foliar está relacionada com a radiação fotossinteticamente ativa (RFA) e a umidade relativa do ar (UR); a temperatura ótima da fotossíntese foi de 31,1 oC, onde a comunidade apresentou 7,6 µmol.m-2.s-1 de assimilação líquida de CO2, e a partir desta temperatura houve uma diminuição da fotossíntese máxima; valores de temperaturas foliares maiores que 34,5 oC diminuíram a velocidade máxima de carboxilação e as acima de 35,7 oC diminuíram a capacidade máxima de transporte de elétrons; a condutância estomática decresceu com o aumento da temperatura foliar, dentro do intervalo de temperatura estudado, indicando que a limitação estomática pode ser o fator que mais afeta a fotossíntese; e a respiração contribuiu para que o balanço de carbono fosse menor com o aumento da temperatura foliar devido a respiração estar positivamente relacionada com a temperatura foliar. A taxa assimilatória de CO2 foi diminuída devido a aumentos da temperatura foliar, sendo principalmente afetada pela diminuição da condutância estomática e do mesofilo e depois por aumentos da respiração foliar.
The role of the Amazon Rain Forest in the carbon budget has been often reported, however little is known about the aspects regulating the processes of carbon assimilation and its release from the biosphere to the atmosphere. The objective of this work was to describe the responses of respiration and photosynthesis processes related to leaf temperature variations by using biophysics characteristics and micro-meteorological data in order to predict CO2 assimilation rates on individual or community level. The research was conducted at the Experimental Station for Tropical Forest research (ZF-2) of the National Institute of Research of the Amazon (INPA). For this study four towers were used to access the canopy. Climatic parameters were monitored by micrometeorological stations Li-1401. The leaf temperature was measured using copper-contantan thermocouples. Photosynthesis and respiration were evaluated with an infra-red gas analyzer, generating light and CO2 curves responses. The results showed that: the leaf temperature was related to the photosynthetic active radiation (PAR) and to the relative air humidity (UR). The optimal photosynthesis temperature was 31,1 ºC where the tree community presented 7,6 µmol.m-2.s-1 of net CO2 assimilation. Above this temperature a reduction of the maximal photosynthesis was determined. Leaf temperatures higher than 34,0 ºC decreased the maximal velocity of RuBP carboxilation and temperatures higher than 35,7ºC decreased the maximal capacity of electrons transportation. The stomatal conductance decreased with increasing leaf temperatures within the temperature interval studied. The results indicated that the stomatal limitation probably represent the main factor that effects photosynthesis. The respiration contributes to reduce the carbon assimilation due to the increase of the leaf temperature because respiration is positively related to leaf temperature. Thus, the CO2 assimilation rates decreased with an increase of leaf temperature and is mainly affected by a decrease of stomatal and mesophyll conductance and by an increase of leaf respiration.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
The objective of the research was to analyze the rainfall on a the regional scale and compare the temperature, air relative humidity and rain at local scale at points outside of semideciduous seasonal forests (FES) and inside the FES, on the area of Barra dos Coqueiros and Caçu hydropower plants (UHEs), in the lower course of the Rio Claro river e, in the cities of Cachoeira Alta and Caçu, in the state of Goiás. The rainfall data were obtained from four rainfall stations of the National Water Agency (ANA), (Cachoeira Alta, Itarumã, Quirinópolis and Pombal) between 1977-2011 and experiment points out of semideciduous seasonal forests (FES), with measurement of temperature and relative humidity and rainfall and inside the FES with temperature and relative humidity of September 2011 to September 2012.The methodological procedures were performed at regional, local and microclimate, with calculation of standard years, statistical calculations, analysis of land use, exposure of the slopes and comparison of climatic elements between points outside and inside the FES, starting from a point reference. On a regional scale, in 35 years of averages of the four seasons, we identified that 66% were standard years rainy, tending to rainy and habitual; the spatial variability of rainfall shows higher concentration northwest and southwest basins and climate trends indicated a trends of increase in stations and Cachoeira Alta Pombal and decrease in Itarumã and Quirinópolis. On a local scale, in relation to land use, the total area of 965 km2 of the two basins, it was found that the greatest change occurred by increasing the area occupied by water in 2009 was 0.6% and in 2011 becomes occupy 7.4%, which represented an increase of 1200%, with loss of native vegetation and habitat. Regarding climatic elements, temperature and relative humidity, on the reference point outside the FES (P1) differences occurred in the absolute maximum temperature of 10.6 °C and the absolute minimum of 7.8 °C, relative humidity was maximum absolute differences less than 1% and the minimum absolute difference of 8%, relative to rainfall, the largest difference was 927 mm. At the point of reference within the FES (P15), the largest difference in maximum air temperature was 10.5 °C and minimum 2.4 °C, the relative humidity was 3% absolute maximum and minimum of 8%. In microclimatic scale, points out the FES, mainly focused on the areas: north, east, west, northwest and southwest, which receive greater insolation showed higher maximum temperatures between 52.7 to 46.9 °C, while the points located within the FES, independent of the exposure of the strands had the absolute maximum temperature between 36.7 to 47.2 ° C and absolute minimum between 3.8 and 6.5 °C. Therefore, the points inside the FES showed dampening effect on the microclimate, and the absolute maximum temperatures and temperature were lower and the minimum absolute and relative humidity were high.
O objetivo da pesquisa foi analisar as chuvas em escala regional e comparar a temperatura, a umidade relativa do ar e a chuva em escala local em pontos fora das Florestas Estacionais Semideciduais (FES) e no interior das FES, na área das bacias das Usinas Hidrelétricas (UHEs) de Barra dos Coqueiros e Caçu, no baixo curso do rio Claro, nos municípios de Cachoeira Alta e Caçu no Estado de Goiás. Os dados de chuva foram obtidos de quatro estações pluviométricas da Agência Nacional das Águas (ANA), (Cachoeira Alta, Itarumã, Quirinópolis e Pombal) entre 1977 a 2011 e do experimento em pontos fora das Florestas Estacionais Semideciduais (FES), com mensuração de temperatura e umidade relativa do ar e chuvas e no interior das FES com temperatura e umidade relativa do ar de setembro de 2011 a setembro de 2012. Os procedimentos metodológicos foram realizados nas escalas regional, local e microclimática, com cálculo dos anos padrão, cálculos estatísticos, análise do uso da terra, exposição das vertentes e comparação dos elementos climáticos entre os pontos fora e interior das FES, partindo de um ponto de referência. Na escala regional, em 35 anos das médias das quatro estações, identificaram-se que 66% foram anos padrão chuvosos, tendentes a chuvosos e habituais; a variabilidade espacial das chuvas apresentou maior concentração a noroeste e sudoeste das bacias e a tendência climática indicou tendência de acréscimo nas estações de Cachoeira Alta e Pombal e decréscimo em Itarumã e Quirinópolis. Na escala local, em relação ao uso do solo, da área total de 965 km2 das duas bacias, verificou-se que a maior mudança ocorreu pelo aumento da área ocupada por água, em 2009 era de 0,6% e em 2011 passa a ocupar 7,4%, o que representou um aumento de 1200%, com perda de vegetação nativa e habitat. Em relação a temperatura e umidade relativa do ar, no ponto de referência fora da FES (P1) ocorreram diferenças na temperatura máxima absoluta de 10,6 °C e na mínima absoluta de 7,8 °C; a umidade relativa máxima absoluta teve diferenças menores de 1% e na mínima absoluta diferenças de 8%; em relação às chuvas, a maior diferença foi de 927 mm. No ponto de referência no interior da FES (P15), a maior diferença na temperatura máxima absoluta foi de 10,5 °C e a mínima 2,4 °C; a umidade relativa do ar máxima absoluta foi 3% e a mínima de 8%. Na escala microclimática, os pontos fora das FES, principalmente os voltados para as vertentes: norte, nordeste, oeste, noroeste e sudoeste, as quais recebem maior insolação, apresentaram temperaturas máximas maiores entre 52,7 a 46,9 °C, enquanto os pontos localizados no interior das FES, independente da exposição das vertentes, tiveram a temperatura máxima absoluta entre 36,7 a 47,2 °C e a mínima absoluta entre 3,8 a 6,5 °C. Assim, os pontos no interior das FES apresentaram efeito atenuador no microclima, sendo que as temperaturas máximas absolutas e a amplitude térmica foram menores e as mínimas absolutas e umidade relativa do ar foram elevadas.

As florestas tropicais representam grande parte do carbono armazenado na forma de biomassa. São caracterizadas por uma alta taxa de produtividade primária, no entanto, não é muito claro o entendimento de como as florestas tropicais respondem ao balanço de carbono com o avanço das mudanças climáticas. Um dos efeitos relacionados ao aumento de concentração de dióxido de carbono na atmosfera e ao aumento da temperatura ambiental, que pode contribuir para ocorrência de distúrbios na função de assimilação ou emissão deste composto dentro das florestas tropicais, é a temperatura. A temperatura tem sido apontada, como influenciadora nas trocas gasosas das plantas, afetando a fotossíntese e a respiração. Neste sentido, estudos que visam melhorar o entendimento dos processos fisiológicos das plantas, principalmente os que estão envolvidos com a ciclagem do C, são importantes para gerar informações sobre os efeitos das mudanças globais nos padrões de respostas da assimilação de CO2 das plantas ou ecossistemas. O objetivo deste trabalho foi determinar as respostas dos processos de fotossíntese e respiração em função da temperatura foliar de um indivíduo e comunidade em estudo. O trabalho foi desenvolvido na Floresta Nacional (FLONA) dos Tapajós (2º 51 Sul (S), 54º 58 Oeste (O)) localizada ao sul da cidade de Santarém, próximo ao marco km 67 e 83 da rodovia Santarém-Cuiabá BR-163. Para realização das medidas nas folhas das plantas na copa do dossel florestal foram utilizadas cinco torres. Para quantificação da fotossíntese e respiração foliar, utilizou-se um analisador de gás por infravermelho (IRGA) modelo (LI- 6400). Para cada folha observada, obteve-se uma curva de resposta da fotossíntese à radiação fotossinteticamente ativa (A-RFA) e quatro curvas de respostas da fotossíntese em relação a concentração interna de CO2 (A-Ci), em quatro grupos de temperaturas foliares (Tfoliar). As curvas de resposta a radiação fotossinteticamente ativa (RFA), Tfoliar e concentração interna de CO2 (Ci) foram realizadas entre os horários de 07:00 e 14:00 horas. Para o ciclo diurno quantificou-se a fotossíntese (A), condutância estomática (gs), transpiração (E) e déficit de pressão de vapor da folha (DPVf), as medidas foram realizadas ao longo de um dia entre 10:00 e 18:00 horas. A temperatura ótima média da fotossíntese foi de 29,9 oC, e a população apresentou taxa assimilatória líquida ótima de CO2 de 7,2 µmol.m-2.s-1. Valores de temperaturas foliares superiores a 32,9 oC e 32,5 oC, diminuíram a capacidade máxima de transporte de elétrons e a velocidade máxima de carboxilação, respectivamente. A eficiência de carboxilação começou a diminuir a partir de 31 oC. A concentração interna de CO2 diminuiu 32,6% aos 42 oC. Na avaliação do ciclo diurno A e gs decresceram significativamente a partir das 16:00 e 15:00 horas, respectivamente. Quando houve um aumento de 0,34 kPa no DPVf a transpiração diminuiu em 64%. A condutância estomática decresceu com o aumento da temperatura foliar e a respiração foliar foi positivamente relacionada com o aumento da temperatura foliar.
Tropical forests hold large stores of carbon as biomass. They are characterized by large net primary productivity, however, it is not well understood how carbon budgets of tropical forests respond to the advance of climatic changes. Temperature is one of the agents related to the increase of carbon dioxide concentration in the atmosphere and ambient temperatures can contribute to alterations in assimilation or emission of CO2 in tropical forests. Temperature has been pointed as responsible for gas exchange rates in plants, affecting the photosynthesis and respiration. Thus, studies aimed at better understanding of physiological processes of plants, particularly those which involve carbon cycling, are important to generate information on the effects of the global changes in the trends of CO2 assimilation response in plants or in ecosystems. The objective of this work was to determine the photosynthesis processes and respiration responses as a function of leaf temperature of an individual and of the community in study. The study was carried out at the Tapajós National Forest (FLONA, 2º 51` S 54º 58` W) located in the south of Santarém municipality, at kms 67 and 83 of the Santarém- Cuiabá highway (BR-163). Five towers were used to support measurements in leaves in the forest canopy. An infra-red gas analyzer (IRGA, LI-6400 model) was utilized for quantification of leaf photosynthesis and respiration. For each observed leaf, a curve relating the photosynthesis response to the photosynthetically active radiation (PAR) was obtained together with four curves of photosynthesis response in relation to the internal CO2 concentration (Ci) in four groups of leaf temperatures (Tleaf). The response curves of PAR, Tleave and internal CO2 concentration (Ci) were obtained between 07h00 and 14h00. For the diurnal cycle it was quantified photosynthesis (A), stomatal conductance (gs), transpiration (E) and vapor pressure deficit of the leaf (VPDf), and measurements were carried out throughout one day between 10h00 and 18h00. The main optimum temperature of photosynthesis was 29.9 °C, and the community presented optimum CO2 net assimilation rate of 7.2 µmol.m-2.s-1. Leaf temperature values above 32.9 °C and 32.5 °C decreased the maximum capacity of electron transport and the maximum speed of carboxylation, respectively. The carboxylation efficiency starts to decreased at 31 °C. The internal CO2 concentration diminished 32.6% at 42 °C In the evaluation of the diurnal cycle, photosynthesis and stomatal conductance decreased significantly after 16h00 and 15h00 hours, respectively. An increase of 0.34 kPa in VPDf diminished transpiration in 64%. The stomatal conductance decreased with increase of leaf temperature and leaf respiration was positively related to the increase of leaf temperature.

Une etude phytoecologique et cartographique des chenaies vertes tetraclinaies et pineraies a ete abordee a grande echelle dans trois sites tests afin d'inventorier les principales series de vegetation et de degager les grandes tendances de leur evolution. La repartition spatiale entre chenaies (chene vert, chene liege et chene zeen), resulte d'un ensemble de facteurs: bioclimatiques, edaphiques et biotiques favorables. L'approche dendroecologique a pour objectif de contribuer a une meilleure comprehension des relations cernes-climat. La fonction de reponse de chaque population precise le role respectif des temperatures et des precipitations mensuelles sur la croissance radiale. L'etude dendrometrique et de cubage du chene liege a permis d'evaluer la production subereuse en volume. L'etude de la biomasse et du volume du chene vert a conduit a elaborer des modeles mathematiques a partir des peuplements scleriphylles obtenus sur plusieurs cepees moyennes abattues et permettre l'elaboration de tarifs poids-secs

碩士
國立臺灣大學
植物學研究所
90
Abstarct From 1990 to 1994, a permanent 1-ha plot of warm-temperate rain forest was estabilished at Mt. Lopei, North Taiwan. All free-standing woody plants in this plot with DBH ≥ 1cm were identified, tagged, and mapped. A total of 70 tree species ( 12875 stems ), belonging to 31 families and 79 genera were recorded. The total basal area was about 47.53 m2/ha. The forest was dominant by Cyclobalanopsis longinux (17.58%), Illicium arborescens (13.79%), Cyclobalanopsis sessilifolia (11.68%), Machilus thunbergii (10.64%), and Meliosma squimulata (5.54%). Cumulative important value of these five species reached 58.75%. TWINSPAN analysis revealed four distinct groups of quadrats. Sites of the first and second group were located at the north-eastern hillside and the hilltop. These two groups was thought to be a windward community because of its high density, low canopy and specific species composition, while the other two group was thought to be the oppsite. Tree species was divided into three types, north-eastern, western, and random, by their distribution. Most species were patchily distributed, showing high correlation with aspect and elevation. Spatial patterns of tree species were studied by Ripley’s K analysis and L-function. Out of the 44 species occuring with ≥ 15 individuals in whole plot, 81.82% had an aggregated distribution, 15.91% were randomly distributed and just 2.27% showed regular distribution. But in each habitat, obviously, most species were randomly distributed. We suggest that habitat factors, such as wind and topography, played an important role in spatial distribution of tree species, and they may cause the difference between whole plot and each habitat. Spatial patterns of canopy trees showed a regular distribution between 2 to 5 meters. Adult trees of dominant groups also showed a regular distribution in 4 meters, and as tree individuals grew, this range became wider. It is revealed that tree individuals, especially adult ones, compete anainst each other for some recources, such as space or light, etc. Spatial relationships between conspecific adults and juveniles mostly showed a regular pattern between 2 to 7 meters, or longer. We are confident that adults affect the survival of juveniles. It could caused by some factors such as resource limiting, competition, herbivores, and pathogens, etc. This study suggest that this forest is subjected to multiple factors, eg., topography, wind, inter- and intra-specific competition, seed dispersal and germination. The importance of each factor changes across spatial and temporal scales.

In the Pacific Northwest (PNW), concern about the impacts of climate and land cover change on water resources, flood-generating processes, and ecosystem dynamics emphasize the need for a mechanistic understanding of the interactions between forest canopies and hydrological processes. A detailed measurement and modeling program during the 1999 and 2000 hydrologic years characterized hydrological conditions and processes in a 500-600 year old Douglas fir-western hemlock seasonal temperate rainforest. The measurement program included sub-canopy arrays of radiometers, tipping bucket rain gauges, and soil temperature and moisture probes, to supplement a vertical temperature and humidity profile within the forest canopy. Analysis of the precipitation interception characteristics of the canopy indicated that the mean direct throughfall proportion was 0.36, and the mean saturation storage was 3.3 mm. Evaporation from small storms insufficient to saturate the canopy comprised 19% of the net interception loss, and canopy drying and evaporation during rainfall accounted for 47% and 33% of the net loss, respectively. Results of the measurement program were used to modify the Simultaneous Heat and Water (SHAW) model for forested systems. Changes to the model include improved representation of interception dynamics, stomatal conductance, and within-canopy energy transfer processes. The model effectively simulated canopy air and vapor density profiles, snowcover processes, throughfall, soil water content profiles, shallow soil temperatures, and transpiration fluxes for both a calibration period and for an uncalibrated year. Soil warming at bare locations was delayed until most of the snowcover ablated due to the large heat sink associated with the residual snow patches. During the summer, simulated evapotranspiration decreased from a maximum monthly mean of 2.17 mm day����� in July to 1.34 mm day����� in September, as a result of declining soil moisture and net radiation. Our results indicate that a relatively simple parameterization of the SHAW model for the vegetation canopy can accurately simulate seasonal hydrologic fluxes in this environment. Application and validation of the model in other forest systems will establish similarities and differences in the interactions of vegetation and hydrology, and assess the sensitivity of other systems to natural and anthropogenic perturbations.
Graduation date: 2002

Sustainable use of species-rich moist forests is hampered by an insufficient understanding of their dynamics and long-term response to different wood harvesting strategies. This thesis contributes to a better understanding of natural forest dynamics, explores the productivity of native forests subjected to different management strategies, and quantifies the ecological impacts of these strategies. The thesis focuses on two study regions: tropical montane cloud forest (TMCF) in central Veracruz, Mexico, and Valdivian temperate rain forest (VTRF) in northern Chiloé Island, Chile. The process-based forest growth model FORMIND is applied to study natural forest succession, to assess long-term ecological implications of fuelwood extraction on TMCF, to explore the potential of secondary TMCF for provision of ecosystem services and fuelwood, and to compare potential harvesting strategies for VTRF regarding forest productivity and ecological consequences.Simulation results show that both forest types have a high potential for wood production. As wood extraction increases, the forest structure becomes simplified because large old trees disappear from the forest. The species composition shifts to tree species that are favoured by the respective harvesting strategy. The overall ecological impact increases linearly with the amount of extracted wood. Simulation results allow to define management strategies that balance conservation and production objectives, promote the regeneration of desired tree species, or minimise shifts in the species composition of the forest. Process-based forest models enhance our understanding of the dynamics of species-rich moist forests and are indispensable tools to assess long-term implications of anthropogenic disturbances on forest ecosystems. Thereby they contribute to the conservation and sustainable use of native forests outside protected areas.