Analysis of forest canopy density based on textural features of high resolution imagery and airborne laser scanning data Abstract The objective of this thesis is to assess the forest canopy density in the Šumava Mountains, Czech Republic. The spruce forests in this area have been suffering from the bark beetle outbreak for almost 20 years resulting in a mixture of dead and young trees, mature forest stands and peat bogs. The canopy density was evaluated using a very high spatial resolution panchromatic imagery and low point density LiDAR, combined with an object oriented approach. The classification based on three GLCM texture measures (contrast, entropy and correlation), which were derived from the image objects, resulted in a kappa index of accuracy of 0.45. Adding the information from the LiDAR data, the accuracy of the classification improved up to 0.95.

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.

Graduation date: 2006 / Canopy gap formation is a major factor contributing to maintenance of overstory species diversity and stand structure in forests and may be integral to development of understory shrub and herb layers as well. Acknowledgement of gap formation as a fundamental feature of natural forests has led to consideration of gaps as an option in forest management regimes. This study examined understory vegetation communities across canopy gaps created as a part of the Density Management Study (DMS), which investigates the effectiveness of a thinning regime in promoting late-successional habitat development in young Douglas-fir forests of western Oregon. Patterns in understory vegetation community composition in and around 0.1 and 0.4ha gaps created as a part of the DMS treatment were investigated. The primary goal of this research was to investigate the potential role of canopy gap creation in fostering heterogeneity in understory vegetation communities, and to examine the extent of gap influence on the surrounding thinned forest matrix. Tree species distributions have been shown to partition across gaps in tropical forest systems through differential responses of species to gradients in resource availability, a pattern known as gap partitioning. In temperate forests, understory vegetation communities are much more diverse than the overstories, and display a greater array of habitat requirements. Therefore, understory communities may be more likely than overstories to exhibit gap partitioning in these forests. Patterns in understory community composition across gaps suggest that gap partitioning has occurred. The strength of this partitioning effect appears to differ between gap sizes, as smaller gaps showed a less powerful effect. Abundance of ruderal species was strongly related to gap partitioning in larger gaps, while smaller gaps were dominated by competitor species. Partitioning may be related to an interactive relationship between harvest-related ground disturbance and resource gradients. Therefore, considerations of gap partitioning processes should take into account intensity and spatial distribution of ground disturbance in relation to resource gradients. In addition, conditions necessary for the expression of gap partitioning in understory vegetation communities may be rare in natural gaps in this region. The influence of gaps on understory vegetation communities in the surrounding forest appears to be relatively small. This small influence extent may help explain the lack of a stand level response to gap formation in these stands. Larger gaps exhibit a slight influence on the understory plant community in the surrounding forest to the north of the gap. In small gaps, there seemed to be an influence of the surrounding forest on gap interiors, resulting in an area of influence smaller than the physical gap area. This relationship may indicate that the area of gap influence on understory vegetation may not scale linearly with physical gap size. Species diversity was higher in gap interiors than in surrounding thinned forests. However this effect was partially due to the presence of exotic species, which showed an affinity for gap interiors. Late successional associated species were negatively related to gap interiors, but only in the larger gap size. Gap creation appears to be promoting small scale species diversity in these stands, but creation of large gaps may also promote the establishment of exotic species and may have a negative effect on late successional associated species. However, any and all of these effects may be transient, as understory communities will be strongly affected by overstory re-establishment, and related changes in resource availability. In general, gap formation may influence small-scale stand heterogeneity as evidenced by understory plant communities, but this effect may rely strongly on the nature of gap formation and intensity of disturbance related to this formation.

The Mountain Hemlock (MH) zone includes all subalpine forests along British Columbia’s coast. It occurs at elevations where most precipitation falls as snow and the growing season is less than 4 months long. The zone includes the continuous forest of the forested subzones and the tree islands of the parkland subzones (Figure 1). Old-growth stands are populated by mountain hemlock, Pacific silver fir, and Alaska yellow-cedar, and are among the least-disturbed ecosystems in the world. Canopy trees grow slowly and are commonly older than 600 years, while some Alaska yellow-cedars may be up to 2000 years old. Early regeneration failures followed slashburning and the planting of unsuitable species. Currently, the most successful and feasible option for reforesting cutovers is natural regeneration with a mix of the three main tree species, but uncertainties remain about the temporal and spatial pattern of regeneration, changes in species composition, and the time required for stand establishment after cutting. Our study addressed these concerns by examining regeneration patterns on 6 sites that were clearcut 11-12 years prior to sampling and left to regenerate naturally. The sites were located at the lower limits of the zone in the Tetrahedron Range, near Sechelt, at elevations from 1060-1100m.

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.

The objective of this thesis was to understand the spatial patterns and processes responsible for canopy and understorey spider (Arachnida: Araneae) diversity at multiple spatial scales in north-temperate hardwood forests. I sampled tree trunks (sticky traps) and foliage (beating) of sugar maple and American beech tree canopies and their understorey saplings in old growth forests near Montreal, Quebec. Results show the composition of canopy and understorey assemblages differed significantly, and so did sugar maple and American beech canopy assemblages. Each stratum was also dominated by different species. The rank-abundance distribution of species from each habitat wsa also verticaly stratified because it fit different distribution models. Different factors likely structure assemblages in both habitats, particularly since the canopy is a less stable environment. Spiders from canopy and understorey foliage were tested in a laboratory for their propensity to balloon. General linear models indicated that small sized web-building spiders of the RTA and Orbicularia clades have the highest propensity to balloon. Small bodied species initiated ballooning regardless of the habitat they were collected in or their developmental stage. My results support the mixed evolutionarily stable strategy theory and indicate the absence of risk-spreading in the dispersal strategy of canopy spiders. My last chapter focused on dispersal capacity and diversity patterns of spiders at multiple spatial scales. Analyses of the species diversity of limited and high dispersal capacity species subsets through nested-multivariate ANOVA, additive diversity partitioning, and species-abundance distribution curves all point towards species-sorting processes as the main driver of local community spider diversity at the tree and stand spatial scales. Mass-effects and patch-dynamic processes drive site and regional scale diversity patterns. This thesis demonstrates that spiders provide good models to test many biological hypotheses. The research chapters of this thesis test hypotheses on the vertical stratification of forest spider diversity, the evolution of local dispersal adaptations, and the importance of dispersal capacity on species diversity patterns through a metacommunity framework.

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.

No description available.

A method was developed for extending a fine-scaled forest gap model to a watershed-scaled landscape, using the Eastern Cross Timbers ecoregion as a case study for the method. A topographic wetness index calculated from digital elevation data was used as a measure of hydrologic across the modeled landscape, and the gap model modified to have with a topographically-based hydrologic input parameter. The model was parameterized by terrain type units that were defined using combinations of USDA soil series and classes of the topographic wetness index. A number of issues regarding the sources, grid resolutions, and processing methods of the digital elevation data are addressed in this application of the topographic wetness index. Three different grid sizes, 5, 10, and 29 meter, from both LiDAR-derived and contour-derived elevation grids were used, and the grids were processed using both single-directional flow algorithm and bi-directional flow algorithm. The result of these different grids were compared and analyzed in context of their application in defining terrain types for the forest gap model. Refinements were made in the timescale of gap model’s weather model, converting it into a daily weather generator, in order to incorporate the effects of the new topographic/hydrologic input parameter. The precipitation model was converted to use a Markov model to initiate a sequence of wet and dry days for each month, and then daily precipitation amounts were determined using a gamma distribution. The output of the new precipitation model was analyzed and compared with a 100-year history of daily weather records at daily, monthly, and annual timescales. Model assumptions and requirements for biological parameters were thoroughly investigated and questioned. Often these biological parameters are based on little more than assumptions and intuition. An effort to base as many of the model’s biological parameters on measured data was made, including a new technique for estimating optimal volumetric growth rate by measuring tree rings. The gap model was set up to simulate various terrain types within the landscape.

Thesis (MSc(For))--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Recognizing the biological significance of gaps, the South African Department of Water Affairs and Forestry (DWAF) in 1989 initiated a Gap Dynamics Project in the indigenous forests of Tsitsikamma (Eastern Cape, South Africa). This consists of three sub-projects: Koomansbos (9300 m2), created by a ground fire in 1989; Plaatbos (1600 m2), made by a Podocarpus falcatus (Thunb.) R. Br. ex Mirb. (Podocarpaceae) windfall in 1994; and nine gaps of different sizes, artificially created by selective tree felling in 1995: three small (100-150 m2), three medium (300-500 m2) and three large (800-1000 m2). All the gaps were surveyed after creation and permanent plots were established for subsequent monitoring. The current timber harvesting system practiced in South African indigenous forests attempts to minimize gap size. It has been proposed by Euston-Brown et al. (1996) that this practice is likely to benefit the more shade tolerant species, but may inhibit the regeneration of less shade tolerant plants in the forest. Therefore, the present study aimed to verify two hypotheses: gaps may close in a process that is determined by their size, their origin and the plant species characteristics; soil quality might change inside those gaps. For the purpose of the study, the gaps cited above were re-surveyed between 2002 and 2003. It was found that: 1) there was little clear difference in the community structure of plant species between gaps of different sizes and origins; as expected from the species-area relationship, large gaps had higher species richness, plant diversity and herbaceous percentage cover than medium and small gaps; diversity indices were higher in the large windfall gap than in the large fire and artificial gaps; generally, context and stochastic events were largely more important in determining gap diversity and regeneration than gap sizes and origins; 2) diversity indices in the gaps were higher than recorded previously; 3) soil pH and Electrical Conductivity were respectively lower and higher inside the gaps than adjacent to them; these variations were statistically significant. Present data on the vegetation in the gaps were compared to past measurements, and future vegetation structure has been predicted, as a function of current gap vegetation. Recommendations have been made for sustainable management of the indigenous forest of Tsitsikamma. / AFRIKAANSE OPSOMMING: Voortspruitend uit die erkenning van die biologiese belang van gapings, het die Suid-Afrikaanse Departement van Waterwese en Bosbou (DWB) in 1989 'n projek oor gapingsdinamika in die inheemse woude van Tsitsikamma (Oos-Kaap, Suid-Afrika) geïnisieer. Dit bestaan uit drie subprojekte: die gaping in Koomansbos (9300 m2) wat in 1989 deur 'n grondvuur geskep is; die gaping in Plaatbos (1600 m2) wat veroorsaak is toe bome van die spesie Podocarpus falcatus (Thunb.) R. Br. ex Mirb. (Podocarpaceae) in 1994 omgewaai is; en nege gapings van verskillende groottes wat in 1995 kunsmatig deur geselekteerde boomkappery geskep is: drie is klein (100-150 m2), drie mediumgrootte (300-500 m2) en drie groot (800-1000 m2). Alle gapings is ná hulle ontstaan opgemeet en ondersoek en permanente terreine is vir daaropvolgende monitering gevestig. Die stelsel wat tans vir die oes van hout in Suid-Afrikaanse inheemse woude gebruik word, poog om die grootte van gapings te minimaliseer. Euston Brown et al. (1996) doen aan die hand dat hierdie praktyk spesies wat meer skaduweeverdraagsaam is waarskynlik sal bevoordeel, maar die regenerasie van plante in die woud wat minder skaduweeverdraagsaam is, kan inhibeer. Hierdie studie het dus ten doel gehad om twee hipoteses te verifieer: Gapings kan toegroei in 'n proses wat deur hul grootte, oorsprong en die eienskappe van die plantspesies bepaal word; en die gehalte van die grond binne daardie gapings kan verander. Die gapings waarna hierbo verwys is, is vir die doel van hierdie studie tussen 2002 en 2003 weer gemonitor. Daar is bevind dat: 1) daar min duidelike verskille was tussen die gemeenskapstruktuur van plantspesies tussen gapings van verskillende groottes en oorsprong; soos van die verhouding tussen spesies en area verwag kan word, het groter gapings 'n hoër spesierykheid, plantdiversiteit en persentasie niehoutagtige dekking as medium- en klein gapings gehad; diversiteitsindekse was hoër in die groot Plaatbosgaping as in die groot Koomansbosgaping of die kunsmatige gapings; in die algemeen was konteks en stochastiese gebeure grootliks belangriker in die bepaling van gapingsdiversiteit en -regenerasie as gapingsgrootte of -oorsprong; 2) diversiteitsindekse in die gapings was hoër as wat voorheen aangeteken is; en 3) grond-pH en elektriese geleidingsvermoë was onderskeidelik laer en hoër binne die gapings as neffens hulle; hierdie variasies was statisties beduidend. Huidige data oor die plantegroei in die gapings is met vorige metings vergelyk, en 'n toekomstige plantegroeistruktuur is as 'n funksie van huidige gapingsplantegroei voorspel. Aanbevelings is gemaak rakende die volhoubare bestuur van Tsitsikamma se inheemse woud.