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Modeling the spatial structure of topical forests
Abstract
The spatial structure of tropical forest stands under different management conditions was modeled as a series of different spatial point processes. Spatial patterns were first assessed by K-function analyses to help choose a point process appropriate for observed patterns. The homogenous Neyman-Scott process accurately described live tree distribution in clear cut areas, where tree patterns tended to be aggregated. Parameters were estimated by minimizing Diggle's modified least squares criterion, and goodness-of-fit was assessed by comparison to confidence envelopes constructed by Monte Carlo simulation.
Parameter estimates can be interpreted to help understand the ecological processes influencing re-colonization of disturbed areas. The inhomogeneous Poisson process was investigated for simulating the spatial pattern of ingrowth trees in lower canopy strata. The intensity function of this process was inversely proportional to variables representing canopy density. As assessed by Monte Carlo generation of confidence envelopes, the inhomogeneous Poisson process successfully portrayed the influence of canopy structure on understory plant distribution in most stands. Tree mortality was modeled as a thinning process in which the probability of individual tree mortality was conditional on subject tree attributes and competitive environment. The thinning function took the form of a generalized linear model with a binomial error distribution and logit link function. In
most stands, tree neighborhood variables were powerful predictors of mortality, but they were not important predictors in all plots. This suggests that the surrounding forest structure of a subject tree has considerable influence on its morality, but competition is not the sole cause of tree morality in tropical forests.
... Spatial patterns and interactions play a central role in many ecological theories of biological communities and populations (Legendre & Fortín, 1989;Dale, 1999;Condit et al., 2000). Knowledge of these patterns and interactions allows understanding of the ecological processes of spatiotemporal structuring of tropical forests (Fangliang, Legendre, & Lafrankie, 1997;Batista & Maguire, 1998;Silva et al., 2014;Rockwell et al., 2017), becoming essential for the developing strategies for conservation and management of tree species in the long-term (Myster & Malahy, 2012). ...
... K-function has as main advantage the possibility of evaluating the spatial patterns of a series of points in different scales, varying the radius of the formed circles (Batista & Maguire, 1998;Capretz et al., 2012). This function considers as null hypothesis (H 0 ) the complete spatial randomness (CSR) of a series of points. ...
... This function considers as null hypothesis (H 0 ) the complete spatial randomness (CSR) of a series of points. Thus, the spatial pattern is classified as random, if the observed values ( ) are within the limits of the reliable envelopes; aggregate, when outside the reliable envelopes and with positive values; and regular, when outside the envelopes and with negative values (Batista & Maguire, 1998;Capretz et al., 2012). K-function is described by a simple quadratic equation (K (r)), although its transformation to linear form ( ) results in variance stabilization and better graphic interpretation of spatial patterns (Batista & Maguire, 1998). ...
Knowledge of spatial patterns and interactions of tree species allows for understanding the ecological processes of spatiotemporal structures of tropical forests, becoming essential for the establishment of strategies for the conservation and management of their resources in long term. The aim of this study was to investigate spatial patterns and interactions of Astronium lecointei, Dinizia excelsa and Peltogyne paniculata, three dominant timber tree species in Jamari National Forest, Brazilian Amazon. Kernel estimator was used aiming to verify the possible influence of first-order factors on species distributions and Inhomogeneous K-function was applied to analyze spatial patterns and interactions of the species by means of second-order factors. Univariate analyses revealed different scale-dependent spatial patterns for the species. Aggregation related to ecological characteristics, such as preferential habitat and dispersal limitation, was verified for A. lecointei and P. paniculata. D. excelsa presented a random spatial pattern, explained by specific features of its establishment, such as the need for clearings due to light requirement. Interspecific associations were evidenced by bivariate analyses, in which the spatial attraction of the species resulted from the same preference for microhabitats and the repulsion was a result of niche segregation.
... Inventorying forest plots, including mapping of trees, is not an easy task. Mapping trees is necessary for developing spatial individual-based models, and it has been used to study the spatial patterns of tropical trees (Pelissier 1998, Condit et al. 2000, Plotkin et al. 2002, forest dynamics (Batista & Maguire 1998) and spatial dependence between trees and habitats (Harms et al. 2001, John et al. 2007, Ledo et al. 2013. It has also been used to study mechanisms that allow species coexistence (Dislich et al. 2010, Bagchi et al. 2011, aboveground biomass in the forest (Chave et al. 2003) and develop and propose efficient management strategies (Batista & Maguire 1998). ...
... Mapping trees is necessary for developing spatial individual-based models, and it has been used to study the spatial patterns of tropical trees (Pelissier 1998, Condit et al. 2000, Plotkin et al. 2002, forest dynamics (Batista & Maguire 1998) and spatial dependence between trees and habitats (Harms et al. 2001, John et al. 2007, Ledo et al. 2013. It has also been used to study mechanisms that allow species coexistence (Dislich et al. 2010, Bagchi et al. 2011, aboveground biomass in the forest (Chave et al. 2003) and develop and propose efficient management strategies (Batista & Maguire 1998). ...
... Plot size (ha) Dbh (cm) Type of forest Arévalo and Fernandez-Palacios (2003) 0.06 4 Cloud forest Batista and Maguire (1998) 0.5 10 Atlantic Brazilian forest Lawes et al. (2008) 1 10 Moist tropical forest Li et al. (2009) 20 1 Subtropical forest Pelissier (1998) 0.4 30 Rainforest Condit (1998) 1 to 50 1 Rainforest, moist forest Wiegand et al. (2007) 25 1 Rainforest Proposed method 1 0.5 Cloud forest Table 1 Comparisons between tropical inventories using mapped plots, including plot size, diameter cut-off at 1.3 m height (dbh) and type of forest a large-scale network for the study of species richness and biomass in the Amazon. Talbot et al. (2014) and Arellano (2013) also provided discussion on plots where the trees were not mapped. ...
Inventorying field mapped plots can be difficult in tropical forest because visibility and access are limited due to high density of woody plants. Additionally, steep slopes and frequent presence of fog further complicate field measurements in mountain areas. The objective of this study was to propose a detailed field census protocol. The method described allowed inventory of mapped 1-ha plots in a montane cloud forest with little cost and time. The inventory also included the recording of some environmental conditions, namely, light, soil coverage temperature and humidity. A detailed explanation dealing with species identification in the forest is also included. The method can be extended to different tropical as well as temperate forest ecosystems. Finally, a summary and comparison with different inventories focusing on mapped trees are given, along with a number of recommendations.
... The relationship between r and K(r) (Fig. 3) indicates that the distribution of lead-zinc deposits in the study area is concentrated because the observed value of K is greater than the predicted value of K. The prediction curve intersects the upper envelope trace at 20 km, indicating that the deposits show a random distribution if the spacing distance is less than or equal to 20 km and an aggregate distribution if the spacing distance is greater than 20 km (Batista and Maguire 1998). ...
... The lengths of the orebodies range from 120 to 2200 m, and the grades of Pb and Zn are higher than those of most of the lead-zinc orebodies in other parts of the world (Table 1, Fig. 5). Ag is present in varying grades ranging from 0.12 to Fig. 5 Zn, Pb, and Ag grade-ore tonnage scatter diagrams of the ore grades and tonnage totals in this study and the literature (adapted from Batista and Maguire (1998) and Singer et al. (2009)). (A) Zn-Pb; (B) Ag-Zn; (C) Ag-Pb; and (D) cumulative frequency of the ore tonnage. ...
This study explores the spatial relationship between the spatial distribution features and the fracture distribution of deposits in northeastern Yunnan based on spatial point pattern statistics and the Fry analysis method. The K(r) function value of the spatial point pattern analysis shows that the spatial distribution of lead-zinc deposits displays cluster features. Fry analysis shows that the spatial distribution of lead-zinc deposits can be divided into three distinct scales: the 5-km deposit scale, 20-km ore belt scale, and 100-km regional scale. With a change in the measured scale, the dominant direction in the spatial distribution of the lead-zinc deposits changes from northwest at a scale of 5 km to east-northeast and approximately northeast at a scale of 20 km to nearly north-south at a scale of 100 km. At the deposit and ore belt scales, northwest-southeast-striking faults may control lead-zinc mineralization. At the regional scale, north-south-striking faults affect the spatial distribution of lead-zinc deposits. The seven main orebodies in the Xiaohe lead-zinc deposit in Qiaojia County are used to analyze the features of the Xiaohe lead-zinc orebody. The orebodies at the deposit scale are distributed along a northwest-southeast direction, which seems to confirm the relationship between the northwest-southeast-striking faults and the lead-zinc deposits at the mining area scale, which is also consistent with the Fry analysis results.
... Keywords Ripley's K function · Spatial patterns · Forest communities 1 Introduction O padrão espacial de árvores é uma questão chave para estudos de ecologia orestal que permite analisar a estrutura da comunidade em si, conhecer processos ecológicos importantes, como competição, herbivoria e dispersão de sementes (Barot et al 1999;Schwarz et al 2003) e observar a inuência de recursos limitantes. Variáveis abióticas, histórico de perturbações, a dinâmica do dossel e a complexidade da estrutura vertical também reetem-se no padrão espacial das árvores de uma oresta (Armesto et al 1986;Haase et al 1997;Batista and Maguire 1998;Anjos et al 1998;Coomes et al 1999;Kuuluvainen and Rouvinen 2000). ...
... A função K de Ripley (Ripley 1977) é uma forma de caracterizar as propriedades de segunda ordem de padrões pontuais estacionários e istrópicos, que possui a vantagem de ser facilmente estimada a partir de um conjunto de dados, sem a necessidade de denição de modelos paramétricos para o padrão estudado (Diggle 2003). Tratase, portanto, de uma ferramenta estatística apropriada para estudos sobre mapas de árvores, cujas principais vantagens são a possibilidade de detectar o padrão espacial em diferentes escalas simultaneamente (Getis and Franklin 1987;Batista and Maguire 1998) e testar a independência espacial entre grupos de árvores quaisquer (Ripley 1977;Batista 1994;Anjos et al 1998). ...
Investigating tree's spatial patterns according to their size classes and according to their more abundant species can provide evidences about the structure of the vegetal community, since the spatial pattern is a key question for forestry ecology studies. The tree spatial organization patterns on the environment depend on several ecological processes and on the specific characteristics of each environment, so that the best understanding of this frame provides important elements for the knowledge on forestry formation. This paper aimed to study tree spatial patterns, according to the diameter classes and from four most abundant species in different forests, in order to provide evidences regarding to the ecology of each vegetal community. The spatial pattern description in each forestry formation was developed using Ripley's K function. The studied forestry formations were: Ombrophilous Forest, Cerradao, Seasonal Forest and Restinga Forest. In this work, a 10.24 ha plot was installed in each forestry formation, and every tree, with a circumference at breast height (CBH) larger than 15 cm were measured, georeferenced and identified. The obtained data highlights the aggregated character in tropical forests, as observed in every studied forest. The 'Cerradão' and 'Restinga' forest trees showed close aggregate patterns. In the Ombrophilous forest, for all distance scales, the aggregate pattern was meaningful. In the seasonal forest, a random tendency was observed, although a meaningful aggregation was observed in all short distances. The spatial pattern by diameter classes was generally aggregated for trees smaller than 10 cm of diameter and between 10 and 20 cm and random for the others, proving the existence of a tendency which in young trees is more aggregated than in old ones. The spatial pattern of the dominant species is always strongly similar to the general pattern of each forestry formation. The differences between the spatial patterns of two or three coincident species, among the forestry formations, indicate that its pattern is influenced by each different environment. This stands out the importance of its self-ecology and of its ecological processes, intrinsic of each community that can explain the observed patterns.
... Keywords Ripley's K function · Spatial patterns · Forest communities 1 Introduction O padrão espacial de árvores é uma questão chave para estudos de ecologia orestal que permite analisar a estrutura da comunidade em si, conhecer processos ecológicos importantes, como competição, herbivoria e dispersão de sementes (Barot et al 1999;Schwarz et al 2003) e observar a inuência de recursos limitantes. Variáveis abióticas, histórico de perturbações, a dinâmica do dossel e a complexidade da estrutura vertical também reetem-se no padrão espacial das árvores de uma oresta (Armesto et al 1986;Haase et al 1997;Batista and Maguire 1998;Anjos et al 1998;Coomes et al 1999;Kuuluvainen and Rouvinen 2000). ...
... A função K de Ripley (Ripley 1977) é uma forma de caracterizar as propriedades de segunda ordem de padrões pontuais estacionários e istrópicos, que possui a vantagem de ser facilmente estimada a partir de um conjunto de dados, sem a necessidade de denição de modelos paramétricos para o padrão estudado (Diggle 2003). Tratase, portanto, de uma ferramenta estatística apropriada para estudos sobre mapas de árvores, cujas principais vantagens são a possibilidade de detectar o padrão espacial em diferentes escalas simultaneamente (Getis and Franklin 1987;Batista and Maguire 1998) e testar a independência espacial entre grupos de árvores quaisquer (Ripley 1977;Batista 1994;Anjos et al 1998). ...
http://dx.doi.org/10.5902/198050986622Investigar o padrão espacial das árvores, segundo suas classes de tamanho e segundo suas espécies mais abundantes pode fornecer evidências sobre a estrutura da comunidade vegetal, sendo que, o padrão espacial é uma questão-chave para estudos de ecologia florestal. O nível de organização espacial das árvores no ambiente depende de diversos processos ecológicos e características próprias de cada ambiente, de modo que a melhor compreensão deste quadro fornece subsídios importantes para o conhecimento sobre formações florestais. Neste trabalho objetivou-se estudar o padrão espacial das árvores, segundo suas classes de diâmetro e das quatro espécies mais abundantes em diferentes florestas, visando fornecer evidências sobre a ecologia de cada comunidade vegetal. A descrição do padrão espacial em cada formação florestal foi realizada segundo a Função K de Ripley. As formações florestais estudadas foram: Floresta Ombrófila, Cerradão, Floresta Estacional e Restinga. Instalou-se uma parcela de 10,24 ha em cada formação florestal, e todas as árvores com circunferência na altura do peito (CAP) a partir de 15 cm foram medidas, georreferenciadas e identificadas. Os resultados obtidos ressaltam o caráter agregado em florestas tropicais, como foi observado em todas as florestas estudadas. As árvores do Cerradão e da Restinga apresentaram padrões de agregação muito próximos. Para a Floresta Ombrófila, o padrão agregado foi significativo em toda a escala de distâncias estudada. Na Floresta Estacional, foi observada tendência à aleatoriedade, embora, uma agregação significativa tenha sido notada para curtas distâncias. O padrão espacial por classes de diâmetro foi, em linhas gerais, agregado para árvores menores que 10 cm de diâmetro, e entre 10 e 20 cm, e aleatório para as demais, evidenciando uma tendência de que árvores jovens são mais agregadas do que árvores adultas. O padrão espacial das espécies dominantes é sempre muito semelhante ao padrão geral de cada formação florestal. As diferenças entre o padrão espacial das espécies dominantes coincidentes entre as formações florestais indicam que seu padrão é influenciado por cada ambiente. Ressaltando-se assim, a importância da sua autoecologia e dos processos ecológicos intrínsecos a cada comunidade que podem explicar os padrões observados.
... The remaining 17 species had patterns that could not be distinguished from random. Since then, several other studies confirmed the predominance of clumped or random dispersion patterns, the latter with much lower frequency (e.g. Batista & Maguire, 1998). The analysis of spatial pattern in biology, and specifically of vegetation, is an important tool to help in the understanding of the arrangement of the system. ...
... Random distributions may result either from processes directly producing such a distribution, or from the combined effects of agents tending to turn aggregated patterns into regular patterns or vice versa. Spatial Pattern has been analysed quite extensively in humid and wet tropical forests (Sterner et al., 1986; Wong et al., 1990; Batista & Maguire, 1998; Pellisier, 1998; Pelissier & Goreaud, 2001) and African savannas (Skarpe, 1991; Caylor et al., 2003), but has received little attention in seasonally dry tropical forests (SDTF). In fact, an extensive literature search yielded only two publications, apart from reports of studies in deciduous forests in India (Sagar et al., 2003). ...
A study to reveal spatial distribution patterns in four characteristic dry forest tree species was undertaken in six one-hectare plots in the Cerros de Amotape National Park, northwestern Peru. The modified Ripley's K statistic was used. Eriotheca ruizii (K. Schum.) A. Robyns (Bombacaceae), Bursera graveolens (Kunth) Triana & Planch. (Burseraceae), Caesalpinia glabrata Kunth (Leguminosae) and Cochlospermum vitifolium (Willd.) Spreng. (Cochlospermaceae) present in 11 out of 17 cases, patterns that are not significantly different from a completely random pattern. At the analysed spatial scale, this disagrees with the widely held notion that tropical tree species present clumped patterns. The different factors that may contribute to the observed patterns are discussed.
... The reconstitution of tree spatial distribution in forest inventory datasets using a model calibrated with spatially explicit plots has many applications in forest management (Batista and Maguire, 1998;Pommerening and Stoyan, 2008). For example, the use of spatial information about trees has been recommended to model and analyze complex forest structures (Vanclay, 1994) because dynamically relevant parameters of the populations (tree growth, mortality and recruitment) are influenced by the availability of resources shared through competitive processes among individuals. ...
... However, contrary to usual tree measurements, obtaining spatial information is very labour intensive and is thus rarely collected in large scale forest inventories used for growth and yield modeling. Therefore, the assignment of spatial coordinates to trees from non-spatialised, large-scale forest inventories is an interesting alternative to field measurements (Tomppo, 1986;Pretzsch, 1997;Batista and Maguire, 1998;Pommerening, 2006). Pairwise interacting point processes form a class of spatial models that were successfully used to represent tree spatial arrangements showing repulsion, but not attraction among trees (Diggle et al., 1994;Grabarnik and Särkkä, 2009). ...
The spatial structure of complex forest stands results from competitive interactions among trees which is one of the most important ecological processes influencing forest development. The aim of the study is to incorporate in a new class of random point process models a coherent representation of the competition process driving forest stand dynamics to establish a direct link between pattern and ecological processes. The resulting area-saturation model was defined by a set statistic characterised by overlapping discs representing tree interactions. Unlike previous approaches, this new spatial model has the advantage of allowing a straightforward interpretation of its parameters in terms of inter-tree competition. A 60 m × 60 m plot of even-aged Scots pines was used to illustrate the potential of this approach in modelling the spatial structure of a plant community. The social status of each tree was taken into account, leading to a multivariate point pattern exhibiting various spatial properties (regularity, clustering and randomness) at different scales. We considered a hierarchical structure of interactions to account for the fact that competition for light is size-asymmetric. According to the analysis, the generalised area-saturation model has the required flexibility to capture complex spatial tree patterns.
... In general, a thinning operation or rule [Illian et al., 2008] determines which points in the basic process are deleted. For example, such thinnings drive the evolution of plant communities due to competition-induced mortality [Batista and Maguire, 1998]. ...
Mat\'ern's hard-core processes are valuable point process models in spatial statistics. In order to extend their field of application, Mat\'ern's original models are generalized here, both as point processes and particle processes. The thinning rule uses a distance-dependent probability function, which controls deletion of points close together. For this general setting, explicit formulas for first- and second-order characteristics can be given. Two examples from materials science illustrate the application of the models.
... We used spatial point processes (also known as point process models; PPMs) to model the spatial distribution of species individuals under the null hypothesis of dispersal assembly [17,[51][52][53][54][55]. The locations of the individuals of a species constitute a spatial point pattern, which can be regarded as the realization of a spatial point process [56]. ...
Soil phosphorus (P) partitioning could contribute to species diversity and structure in plant communities, but field-scale evidence for P partitioning remains scarce. We hypothesized that the presence of P partitioning could be inferred from statistical associations between the spatial distributions of plants and chemical forms of bioavailable soil P. We investigated this in a diverse tropical tree community on Barro Colorado Island, Panama. We quantified potentially bioavailable forms of soil P by extraction in 2 mM citric acid followed by treatment with phosphatase enzymes. We then linked these P forms to the distribution of 189 tree species in a 50 ha forest dynamics plot by testing species–P associations against null models of random dispersal. We found that 20% of tree species were significantly (α = 0.05) associated with the depletion of at least one soil organic P fraction, although around half of these associations might be false rejections of the null hypothesis due to type I error. Species in the Fabaceae (legumes), which are known to express high rates of phosphatase in their roots, were most frequently associated with soil P fractions. We interpret our findings as evidence of widespread P partitioning at the community scale, affecting a relatively small proportion of tree species in this moderately fertile forest. We predict that stronger evidence of partitioning will be found at sites with lower P availability.
... Application of nearest neighborhood analysis to spatial mapping has been previously and extensively developed in the field of ecology, particularly in studies considering the spatial structures and diversity of forests [34][35][36][37] . More recently, it has been adapted by numerous groups for multiplex imaging applications as a way to mathematically model single cell data within a preserved spatial context 38,39 , however, the neighborhood size cutoff varies widely and often lacks biological rationale. ...
Direct interactions between tumor and immune cells mediate the antitumor effect of all modern cancer immunotherapeutic agents. Simultaneously, tumor cells have evolved mechanisms of evasion, including the downregulation of HLA-I, potentially disrupting the mechanism of action employed by many immune checkpoint inhibitors. And yet, the in situ interplay between these cells within the tumor immune microenvironment (TIME) remains elusive. Recent advances in histologic multiplex bioimaging platforms have enabled in-depth molecular characterization of single cells within spatially preserved and clinically archived tumor tissues. Herein, we applied multiplex immunofluorescence to excisional lymph node biopsies from 14 patients with metastatic melanoma who experienced clear objective responses to immunotherapy (7 complete response; 7 progressive disease) to determine distinguishing features of the TIME in the pretreatment setting. Distinct regions of the TIME were evaluated using 35 proteins probing tumor, immune, and vasculature components across 323 fields of view. Single-cell compositional analysis confirmed established prognostic immune cell types including increased prevalence of cytotoxic T cells within the tumor core fields of view of responders. Integrating single-cell quantification with the spatial arrangement of cellular neighborhoods surrounding tumor cells revealed novel, spatial immune signatures capable of stratifying TIME based on clinical response. Our analysis revealed dynamic cellular composition of the tumor-centric cellular neighborhood (TCCN) based on anatomic subregion, functional expression of HLA-I by the index tumor cell and ultimately clinical response to immunotherapy. Overall, this study provides an analytic framework to resolve the cellular complexity of the TIME, increasingly relevant to the outcomes of modern cancer immunotherapy.
Significance
Findings from this work propose a novel approach to resolving clinical heterogeneity of the TIME by objectively quantifying the cellular interactions occurring in metastatic melanoma lymph node tissue utilizing multiplex immunofluorescence. This study provides an analytic and biologically derived unit of measure, the TCCN which is customizable for studying critical paracrine interactions within spatially preserved tissue of various cancers and across the spectrum of multiplex imaging modalities.
... We analysed which biotic and abiotic factors influenced sapling density at plot level. For that, we fitted an inhomogeneous Poisson model (Baddeley et al. 2015;Batista & Maguire, 1998) to the intensity (i. e., density of saplings). ...
Despite noticeable concern about the deforestation rate worldwide, the forest surface in Europe has considerably expanded over the past centuries as a consequence of the rural exodus and abandonment of agrarian practices. Tree recruitment associated with forest regrowth is a multi-stage process influenced by several biotic and abiotic factors. Yet, it is uncertain whether their influence on recruitment patterns and dynamics varies along a gradient of forest expansion. Similarly, for dioceious species, the influence of tree sex in recruitment is not entirely understood. Here, we aim to elucidate what drives Spanish juniper recruitment in expanding forests. Specifically, we hypothesized that facilitation by conspecifics and heterospecific woody species would occur at the expanding front, where environmental conditions are harsher and that recruitment would be preferably associated to female trees because of the likelihood of mature cones produced by them germinating in the nearby area. The study was conducted in Mediterranean forests of Juniperus thurifera in central Spain. A total of 17 plots were delimited along a gradient of forest expansion including three stages: i) old forests, ii) an intermediate zone and iii) novel forests at the expanding front. Within each plot all J. thurifera individuals (saplings and adults) were mapped. We also recorded bio-volumetric characteristics and tree sex for all adult trees and estimated the percentage of cover of heterospecific woody species within the area of influence of each adult individual. We analysed the spatial pattern of J. thurifera individuals for each stand (plot). Using a novel spatial approach, we evaluated how conspecific (female and male tree sizes) and heterospecific (woody cover) vegetation influenced sapling density along a forest expansion gradient. We also studied the effects of the stage of the forest expansion gradient and the sex of adult trees on the spatial association between adults and saplings. Our results showed that sapling recruitment was negatively influenced by conspecific adult size along the whole gradient, while the effect of heterospecific woody vegetation was always positive. Conspecific facilitation of recruitment in J. thurifera forests occurred at their expanding front where saplings were associated to male adult trees. Despite having been overlooked in conservation policies, recently colonised areas in extreme environments are key targets to implement management measures aimed at achieving forest restoration, which aligns with the Aichi targets and the biodiversity policies of the European Union.
... We analysed which biotic and abiotic factors influenced sapling density at plot level. For that, we fitted an inhomogeneous Poisson model (Baddeley et al. 2015;Batista & Maguire, 1998) to the intensity (i. e., density of saplings). ...
Despite noticeable concern about the deforestation rate worldwide, the forest surface in Europe has considerably expanded over the past centuries as a consequence of the rural exodus and abandonment of agrarian practices. Tree recruitment associated with forest regrowth is a multi-stage process influenced by several biotic and abiotic factors. Yet, it is uncertain whether their influence on recruitment patterns and dynamics varies along a gradient of forest expansion. Similarly, for dioceious species, the influence of tree sex in recruitment is not entirely understood. Here, we aim to elucidate what drives Spanish juniper recruitment in expanding forests. Specifically, we hypothesized that facilitation by conspecifics and other woody species would occur at the expanding front, where environmental conditions are harsher and that recruitment would be preferably associated to female trees because of the likelihood of mature cones produced by them germinating in the nearby area. The study was conducted in Mediterranean forests of Juniperus thurifera in central Spain. A total of 17 plots were delimited along a gradient of forest expansion including: i) old forests, ii) an intermediate zone and iii) novel forests at the expanding front. Within each plot all J. thurifera individuals (saplings and adults) were mapped. We also recorded bio-volumetric characteristics and tree sex for all adult trees and estimated the percentage of cover of woody species within the area of influence of each adult individual. We analysed the spatial pattern of J. thurifera individuals for each stand (plot). Using a novel spatial approach, we evaluated how conspecific (female and male tree sizes) and heterospecific (woody cover) vegetation influenced sapling density along a forest expansion gradient. We also studied the effects of the stage of the forest expansion gradient and the sex of adult trees on the spatial association between adults and saplings. Our results showed that sapling recruitment was negatively influenced by conspecific adult size along the whole gradient, while the effect of heterospecific woody vegetation was always positive. Conspecific facilitation of recruitment in J. thurifera forests occurred at their expanding front where saplings were associated to male adult trees. Despite having been overlooked in conservation policies, recently colonised areas in extreme environments are key targets to implement management measures aimed at achieving forest restoration, which aligns with the Aichi targets and the biodiversity policies of the European Union.
... Some of these were either comparable or higher than our findings, which might be because of variation in site quality factors and climatic conditions. Species diversity is a comprehensive reflection of species richness, distribution and evenness, which also reflects the community structure types, organization levels, development stages, stability and habitat difference of the plant assemblages (Whittaker 1972;Kuuluvainen et al. 1996;Batista and Maguire 1998;Ai 2006;Dash et al. 2009). The studies of tree spatial patterns in forest stands have become a relevant tool in the analysis of the structure and dynamics of forest communities and provide a measure of habitat quality (Pommerening 2002;Skov and Svenning 2003;Pragasan and Parthasarthy 2010). ...
This study was conducted at the Chilapatta Reserve Forest of West Bengal to analyse the woody species diversity and their distribution pattern. The dominant forest stands of Tectona grandis (TGDFS), Shorea robusta (SRDFS), Michelia champaca (MCDFS), Lagerstroemia parviflora (LPDFS) and mixed vegetation forest stand (MVFS) were evaluated. The stratified random nested quadrat sampling method was adopted. The species are native and commercially highly valued timber species of the region. The tree species richness, the species diversity index, the Shannon-Wiener diversity index, concentration of dominance and the evenness index were higher in MVFS than in the sole-species dominant stands. In all these studied stands, species were evenly distributed with dominance dispersed. The distribution pattern was mostly random in all the stands. Overall, the MVFS was denser than sole-species dominant stands due to higher species richness. The IVI of mixed- and sole-species dominant stands varied widely because of the dominance of the lead species in terms of numerical strength in sole-species dominant stands, whereas numerical strength in mixed-species stands was more or less similar for all component species. Plantation with these high-value timber species outside forests is recommended in the region for carbon-farming initiatives.
... The distance between a tree and its closest neighbours has important implications in forest ecology and management [1,2]. As forest dynamics (growth, mortality, and recruitment) are influenced by competitive processes between neighbouring trees for access to resources [3], the use of spatial information can significantly improve the understanding of forest structure [4]. ...
Research Highlights: The spatial distribution of trees results from several ecological processes that can be difficult to measure. We applied a point process modelling approach that uses the diameter and species of neighbouring trees to represent inter-tree interactions through repulsive and attractive processes. Thinning treatments slightly influence the tree spatial distribution of trees in white spruce plantations. Integrating this “spatialiser” into growth models could help improve stand simulations following various thinning treatments over larger areas and longer periods. It could also allow for the use of spatially explicit models when tree position is not available. Background and Objectives: Tree spatial patterns result from several ecological processes and have important implications in forest ecology and management. The use of spatial information can significantly improve our understanding of forest structures. However, this implies intensive field work that is rarely integrated into forest inventories. The aims of this study were to develop a spatial distribution simulator of trees in white spruce plantations and to evaluate the influence of thinning treatments. Materials and Methods: A point process modelling approach was used to represent inter-tree interactions through repulsive and attractive process in white spruce (Picea glauca (Moench) Voss) plantations in eastern Quebec, Canada, that had been commercially thinned five years ago. Balsam fir (Abies balsamea (L.) Mill.) and hardwoods together can represent 30–40% of the basal area of these plantations. Results: The diameter and species of each tree’s two closest neighbours were found to be the most important predictors in explaining the observed distances between trees. Despite the short period since thinning treatments, results showed that the treatment had slight significant effects on tree interactions. However, their impact on the global spatial distribution of stands is quite limited. Conclusions: Using only a few readily-available variables (species and diameter of trees), this “spatialiser” will make it possible to assign spatial coordinates to trees and generate realistic stand spatial structures even after various silvicultural treatments.
... Para averiguação da homogeneidade na densidade de distribuição da população de pequi, as coordenadas coletadas foram analisadas pelo estimador de densidade de Kernel (CÂMARA; CARVALHO, 2004). A análise da distribuição espacial foi realizada a partir da Função K de Ripley (RIPLEY, 1981), com o intuito de detectar o padrão espacial em diferentes escalas simultaneamente e testar a independência espacial entre grupos de árvores (BATISTA; MAGUIRE, 1998). ...
Objetivou-se determinar a distribuição espacial de árvores nativas de pequi e a produção de pasto na estação seca e chuvosa. Na área de estudo realizou-se o inventário e mapeamento de indivíduos de pequi e sua distribuição espacial foi verificada pelo teste k de Ripley sobre a população total e em função de classes de área de copa. Para a análise do rendimento da matéria seca, foram coletadas amostras de forragem sob a copa das árvores e nas áreas de pastagem a pleno sol, separadas em lâmina de folha, bainha + colmo e material senescente, no final das estações chuvosa e seca. Os dados foram submetidos ao teste F e teste t, ambos com significância de 10%. Foram observadas 139 árvores remanescentes de pequi com área de copa média de 148 m2, distribuídas de modo agregado, com tendência aleatoriedade nas classes de menor e maior área de copa. Na condição sombreada houve incremento de forragem independente das estações estudadas. O sombreamento favorece a produção do pasto nos períodos de seca e chuva, com redução do material senescente.
Palavras-chave: Caryocar brasiliensis Camb., teste k de Ripley, pasto sombreado, integração.
FORAGE PRODUCTION AND SPATIAL DISTRIBUTION OF PEQUI TREES IN THE SILVIPASTORIL SYSTEM
ABSTRACT:
The objective was to determine the spatial distribution of pequi native trees and pasture production in dry and rainy seasons. In the study area, the inventory and mapping of pequi individuals was performed and their spatial distribution was verified by the Ripley k test on the total population and as a function of crown area classes For the analysis of the dry matter yield, forage samples were collected under the canopy of the trees and in the pasture areas in full sun, separated in leaf blade, sheath + stem and senescent material, at the end of the rainy and dry seasons. Data were submitted to the F test and t test, both with a significance of 10%. A total of 139 remaining pequi trees with a median canopy area of 148 m2, distributed in an aggregate manner, were observed, with a tendency to randomness in the classes of smaller and larger crown area. In the shaded condition there was increment of forage independent of the studied stations. Shading favors pasture production during periods of drought and rain, with reduction of senescent material.
Keywords: Caryocar brasiliensis Camb., Ripley's k test, shaded grass, integration.
... In the current section, an attempt to model the intensity of building damage using the spatial relationships identified in the previous step is presented. The most suitable family of models for describing the spatial structures of point patterns is the stochastic point process models (Batista and Maguire 1998). An attractive feature of these purely spatial models is that they typically require only a few parameters; however their difficult validation represents the main drawback for their use. ...
Just 4 days after the earthquake, Haitians could send SMS messages on their location and urgent needs through the on-line mapping platform Ushahidi. The real-time crowd-sourcing of crisis information provided direct support to key humanitarian actors on the ground including Search and Rescue teams. In addition to its use as a knowledge base for rescue operations, the spatial distribution of geolocated SMS messages could represent an interesting early indicator on the distribution and on the intensity of building damage. This work explores the relationship between the spatial patterns of SMS messages and building damage. The latter correspond to the detailed damage assessments of individual buildings conducted on post-earthquake airborne photos. The interaction between SMS messages and building damage is studied by analyzing the spatial structure of the corresponding bivariate patterns. This is performed through the implementation of cross Ripley¿s K-function which is suitable for characterizing the spatial structure of a bivariate pattern, and more precisely the spatial relationship between two types of points located in the same study area. The results show a strong attraction between the patterns exhibited by SMS messages and building damages. They also prove that the distributions of SMS messages and building damages are not spatially independent. The interactions identified between the two patterns suggest that the geolocated SMS can be used as early indicators of the spatial distribution of building damage. Accordingly a statistical model has been developed allowing to map the distribution of building damage from the geolocated SMS. The preliminary results will be presented and discussed.
... O padrão espacial foi avaliado para as cinco classes demográficas e para os indivíduos mortos da coorte 2013, pela Função K Univariada (Ripley, 1977), a qual permite detectar o padrão espacial em diferentes escalas simultaneamente (Batista & Maguire, 1998). O raio (h) utilizado para obter o K (h) foi de um metro, com distância máxima de 150 m para as classes Imaturos, Masculinos e Femininos, e 80 m para as classes Plântulas, Jovens e indivíduos Mortos, considerada a metade do menor lado da parcela. ...
... Furthermore, it carries information about the ecological processes which operated in the past and the processes which will take place in the future since a number of these ecological processes such as competition, facilitation, mortality, and dispersal tend to follow specific types of spatial patterns in a forest stand (Cale et al., 1989;Stoyan and Penttinen, 2000;Law et al., 2009). These ecological relationships and processes are also key drivers that markedly affect forest structure and functioning that should be considered when developing efficient guidelines for their conservation and management (Batista and Maguire, 1998;Pommerening, 2002). ...
... 在大径级的个体中, 个体死亡概率依赖于其本 身生长发育情况和竞争环境( Batista & Maguire, 1998)。如果个体是随机死亡的, 死亡后的活立木空 间格局应该保持不变, 而密度依赖死亡会减弱聚集 程度( Condit et al., 2000), ...
... Indeed, several studies provide a detailed description of forest stands linked to underlying mechanisms and dynamic stages (Picard et al., 2009;Condit, 2000). In forest systems, it has been shown that regeneration is most successful in gaps where the influence of canopy trees is lowest, and where light and nutrient conditions are favourable (Batista and Maguire, 1998). Seedlings cluster in canopy gaps and regeneration occurs in clusters. ...
An agroecological way to improve the provision of ecosystem services in agroecosystems consists in combining several plant species in the same plot. In this context, tropical agroforests, characterized by high plant diversity, are subject of an increasing interest. This work focuses on natural pest and disease regulation service in complex agroecosystems. Our hypothesis was that complex agroforest structures (composition and spatial structure) influence pest and disease attack intensity of the main crop. Host composition in agroforest has an impact on pest and disease due to resource dilution or amplification. Plant spatial structure (vertical and horizontal) in agroforest has an impact on pest and disease through its impact on microclimatic variations. Moreover, resource and microcli- matic variations interact under natural condition. Indeed, microclimatic variations can affect the vegetative growth of the host plant and thereby the amount of resource for pest and disease. However, the relative importance of host composition effects on pest and disease intensity due to resource dilution or amplification, and plant spatial structure effects due to microclimatic variations, is still unknown. Our objectives were (1) to characterize plant composition and spatial structure in cacao agroforests and (2) to quantify their interactions with pest and disease attack intensity on a plot scale. The study was conducted on two cacao diseases and one pest chosen for their contrasting spread and development characteristics : in Costa Rica, Frosty Pod Rot (FPR) intensity was studied in cacao agroforests in the Talamanca region ; in Cameroon, Black Pod (BP) intensity and mirid density were studied in cacao agroforests in the Centre region. Firstly, we characterized host composition and shade tree spatial structure in cacao agroforests. In Costa Rica, a diversity of forest tree spatial structures was identified ranging from significant aggregation to significant regularity depending on agroforest plots probably due to a management intensity gradient between plots. In Cameroon, we also identified a diversity of spatial structure between stands of the same plot. Indeed, forest trees are randomly distributed or aggregated while fruit trees are randomly or regularly distributed across the plot which suggests a difference in management intensity between these two stands. Secondly, we identified and classified host composition, amount of sensitive tissue and spatial structure characteristics of the associated plants, according to their explanatory power in explaining FPR intensity, BP intensity and mirid density in cacao agroforests. FPR intensity and mirid density decrease with a decreasing in sensitive tissues amounts and when forest trees are regularly or randomly distributed rather than aggregated or in low density at the plot scale. In another hand, FPR intensity decreases with an increasing in cacao tree density and BP intensity decreases with an increasing in cacao tree abundance which is in contrast to the resource dilution assumption. Overall, our results showed that the amount of sensitive tissue rather than the host composition variables explained the increase in pest and disease in complex agroecosystems. Moreover, the spatial structure of forest trees, never described in our level of accuracy, was a crucial characteristic of agroforests in explaining pest and disease regulation. Spatial structure optimization could be a way of agroecological management of FPR intensity and mirid density in cacao agroforests. In the context of agroecology, this work improves our understanding of ecological mechanisms involved in natural pest and disease regulation in cacao agroforests on a plot scale and opens prospects for their agroecological management.
... La simulation d'un peuplement virtuel passe ainsi par l'utilisation d'un processus ponctuel marqué pour modéliser une répartition spatiale observée. La modélisation proprement dite de répartitions spatiales d'arbres par des processus ponctuels est le plus souvent limitée aux positions des arbres, modélisées par des processus non marqués (Rathbun & Cressie, 1994;Moeur, 1997;Batista & Maguire, 1998;Neeff et al., 2005). Les processus les plus couramment adoptés pour modéliser des répartitions agrégées sont les processus de Cox, et plus précisément les processus de Neyman-Scott, de Cox log-normal ou de Cox « shot noise » (Brix & Chadoeuf, 2002;Møller & Waagepetersen, 2004), tandis que les processus de Gibbs ont la préférence pour les répartitions régulières (Møller & Waagepetersen, 2004;Neeff et al., 2005). ...
La modélisation de la dynamique des forêts naturelles tropicales peut reposer sur deux niveaux de description : l'arbre ou la distribution en taille des arbres au sein du peuplement. Mes travaux ont porté essentiellement sur le lien entre ces deux niveaux de description, que ce soit d'un point de vue théorique ou appliqué. La théorie de l'agrégation permet ainsi de basculer du niveau détaillé de l'arbre au niveau agrégé de la distribution. Lorsque les interactions entre arbres ne sont pas dépendantes des distances, l'agrégation est asymptotiquement parfaite. Dans le cas contraire, il est essentiel de pouvoir modéliser la relation rétro-active de la dynamique sur la répartition spatiale des arbres. La méthode des moments apporte alors une solution approximative à la question de l'agrégation. La question peut également être abordée dans le sens inverse (désagrégation), le modèle de dynamique étant vu comme un algorithme de simulation d'un processus ponctuel marqué (la marque étant la taille des arbres). Ces questions se transposent pour traiter le cas de la diversité spécifique propre aux forêts tropicales. La théorie de l'agrégation peut à nouveau être mise en oeuvre pour regrouper les multiples espèces en groupes ayant des caractéristiques de dynamique communes.
... This hypothesis is usually tested building Monte Carlo envelopes from the "succesful" patterns resulting from a random labelling of a "binomially"- marked point pattern (this is equivalent to a random thinning of the whole pattern irrespective of the marks). As tree mortality is rarely random but instead can be modelled as a function of a certain number of covariates, the most natural alternative to the random mortality hypothesis is the logistic mortality hypothesis, that can be tested thinning the original pattern of trees with retention probabilities defined by the fitted values of a logistic model ( Batista andMaguire 1998, Olano et al. 2008). ...
Some wrappers, functions and data sets for spatial point pattern analysis (mainly based on spatstat), used in the book "Introduccion al Analisis Espacial de Datos en Ecologia y Ciencias Ambientales: Metodos y Aplicaciones''
... The distribution pattern of plants in space as a consequence of diverse regulatory mechanisms involved within the community has received considerable attention from numerous investigators (Greig-Smith, 1983;Dale, 1999). Identifying and characterizing spatial pattern of plant populations is often necessary as various ecological processes may be explained with reference to the current spatial patterns (Greig-Smith, 1983;Legendre and Fortin, 1989;Batista and Maguire, 1998;Shaukat et al., 2012;2014). Pattern inherent in a population may be defined as a quantitative description of the horizontal distribution individuals of a population in space. ...
The investigation focuses on species composition, spatial heterogeneity, diversity and interspecific associations in an early successional plant community. A total of twenty species were recorded of which five were grasses while the rest were undershrubs or perennial herbs. Out of 11 species investigated for spatial pattern using variance/ mean ratio and Morisita’s index, ten exhibited aggregated distribution pattern which was presumably caused by topographic-edaphic heterogeneity or by limited seed dispersal. Test for species richness pattern within the community showed variability in species richness which can be attributed to environmental heterogeneity. Species diversity (H´) was moderate (H´ = 2.442), equitability was also moderate (J´= 0.815) while species richness (d) was 0.575. Dominance-diversity curve approached geometric distribution. Dominance (D) was low. Ten different species association coefficients (or similarity indices) were tested and compared of which three including those proposed by Jaccard, Soenesen & Dice and Ochiai provided consistent results in terms of disclosing the degree of interspecific association. These three measures are recommended for application in ecology.
... Indeed, several studies provide a detailed description of forest stands linked to underlying mechanisms and dynamic stages (Picard et al., 2009;Condit, 2000). In forest systems, it has been shown that regeneration is most successful in gaps where the influence of canopy trees is lowest, and where light and nutrient conditions are favourable (Batista and Maguire, 1998). Seedlings cluster in canopy gaps and regeneration occurs in clusters. ...
An agroecological way to improve the provision of ecosystem services in agroecosystems consists in combining several plant species in the same plot. In this context, tropical agroforests, characterized by high plant diversity, are subject of an increasing interest. This work focuses on natural pest and disease regulation service in complex agroecosystems. Our hypothesis was that complex agroforest structures (composition and spatial structure) influence pest and disease attack intensity of the main crop. Host composition in agroforest has an impact on pest and disease due to resource dilution or amplification. Plant spatial structure (vertical and horizontal) in agroforest has an impact on pest and disease through its impact on microclimatic variations. Moreover, resource and microclimatic variations interact under natural condition. Indeed, microclimatic variations can affect the vegetative growth of the host plant and thereby the amount of resource for pest and disease. However, the relative importance of host composition effects on pest and disease intensity due to resource dilution or amplification, and plant spatial structure effects due to microclimatic variations, is still unknown.
Our objectives were (1) to characterize plant composition and spatial structure in cacao agroforests and (2) to quantify their interactions with pest and disease attack intensity on a plot scale. The study was conducted on two cacao diseases and one pest chosen for their contrasting spread and development characteristics : in Costa Rica, Frosty Pod Rot (FPR) intensity was studied in cacao agroforests in the Talamanca region ; in Cameroon,
Black Pod (BP) intensity and mirid density were studied in cacao agroforests in the Centre region.
Firstly, we characterized host composition and shade tree spatial structure in cacao agroforests. In Costa Rica, a diversity of forest tree spatial structures was identified ranging from significant aggregation to significant regularity depending on agroforest plots probably due to a management intensity gradient between plots. In Cameroon, we also identified a diversity of spatial structure between stands of the same plot. Indeed, forest trees are
randomly distributed or aggregated while fruit trees are randomly or regularly distributed across the plot which suggests a difference in management intensity between these two stands.
Secondly, we identified and classified host composition, amount of sensitive tissue and spatial structure characteristics of the associated plants, according to their explanatory power in explaining FPR intensity, BP intensity and mirid density in cacao agroforests. FPR intensity and mirid density decrease with a decreasing in sensitive tissues amounts and when forest trees are regularly or randomly distributed rather than aggregated or in
low density at the plot scale. In another hand, FPR intensity decreases with an increasing in cacao tree density and BP intensity decreases with an increasing in cacao tree abundance which is in contrast to the resource dilution assumption. Overall, our results showed that the amount of sensitive tissue rather than the host composition variables explained the increase in pest and disease in complex agroecosystems. Moreover, the spatial structure of forest trees, never described in our level of accuracy, was a crucial characteristic of agroforests in explaining pest and disease regulation. Spatial structure optimization could be a way of agroecological management of FPR intensity and mirid density in cacao agroforests.
In the context of agroecology, this work improves our understanding of ecological mechanisms involved in natural pest and disease regulation in cacao agroforests on a plot scale and opens prospects for their agroecological management.
... Neste trabalho foi analisado o efeito de desvios da Completa Aleatoriedade Espacial (CAE), (Batista & Maguire 1998), em direção a padrões agrupados e regulares, sobre a estimativa da densidade obtida pelo método de quadrantes para populações com diferentes densidades, bem como a influência do tamanho da amostra sobre as estimativas. As hipóteses deste trabalho são que os padrões espaciais regulares apresentem superestimativas de densidade, ao passo que os agrupados apresentem subestimativas de densidade, podendo gerar erros que inviabilizam a aplicação indiscriminada do método sem o conhecimento prévio do padrão espacial das árvores da floresta. ...
O método de quadrantes tem sido bastante utilizado em levantamentos fitossociológicos de florestas tropicais. O método pressupõe que as árvores tenham padrão espacial completamente aleatório para que a estimativa da densidade (árvores ha-1) não apresente viés. Neste trabalho, analisou-se através de simulação de Monte Carlo de florestas hipotéticas, o efeito de desvios da Completa Aleatoriedade Espacial (C AE) em direção a padrões agrupados e regulares, sobre a estimativa da densidade obtida pelo método de quadrantes para populações com diferentes densidades, bem como a influência do tamanho da amostra sobre as estimativas. O aumento do tamanho da amostra não mostrou efeito significativo na redução de viés. Entre os padrões de distribuição dos indivíduos testados através de simulação, o viés na estimativa da densidade obtida pelo método de quadrantes oscilou entre +70,3% (distribuição perfeitamente regular, correspondente ao padrão em lattice) e -75,7% (distribuição fortemente agrupada, correspondente ao padrão agrupado com raio médio de agrupamento de 25 m). Com exceção das florestas com padrão espacial completamente aleatório e com padrão regular em lattice aleatorizado, em todos os outros padrões espaciais testados não houve relação clara entre a densidade da floresta e a precisão da estimativa de densidade efetuada pelo método de quadrantes. O método de quadrantes superestima a densidade em florestas com padrão regular, e subestima a densidade em florestas com padrão agrupado. Seria importante saber, a priori, o padrão espacial dos indivíduos na floresta para que fosse possível aplicar o método de quadrantes e interpretar corretamente os seus resultados, sem viés.
... Estas técnicas comenzaron a aplicarse en el estudio de bosques tropicales para analizar el patrón espacial en selvas tropicales en Costa Rica (Clark & Clark 1992), se han empleado también para estudiar y modelizar una selva tropical en Brasil, midiendo durante tres años consecutivos parcelas rectangulares de 0,5 ha donde se registran las posiciones y diámetros de todos los pies con un diámetro mayor a 10 cm (Batista & Maguire 1998); para estudiar el patrón espacial en diferente áreas de un bosque en la India, con tres parcelas de 1 ha, considerando todos los pies con diámetro mayor o igual a 30 cm (Pélissier 1998). También se han empleado técnicas del momento de segundo orden para analizar el patrón espacial en la Laurisilva canaria (Arévalo & Fernandez-Palacios 2003); en el estudio de la dependencia entre los huecos que aparecen en la masa y la riqueza de especies en un bosque montano en Argentina (Grau 2002) y en los trabajos de patrón espacial y dinámica forestal en la Guayana Francesa (Picard et al. 2009). ...
This paper reviews the different indices used to describe and characterize the horizontal structure or spatial pattern in forest stands, with particular emphasis on those which have been applied to the study of tropical forests. These indices have been classified according to their data-inventory requirements. A number of aspects concerned with the statistical properties of the most commonly employed indices (Fisher and Morisita indices, LQV techniques and SADIE in the quadrats group; Clark-Evans, Pielou and Byth-Ripley in the nearest-neighbour group; The empirical L(d) and O-ring functions in the mapped data group) and their applicability to tropical stands, have been tested in experimental plots located in an Andean tropical forest.
... Tropical forests are generally considered to be ecological systems well suited for species-area and spatial-aggregation research [48,28]. Subtropical forests display a relatively high diversity of tree species, therefore providing suitable conditions for ecological analyses. ...
The species-area relationship is one of the most important topic in the study of species diversity, conservation biology and landscape ecology. The species-area relationship curves describe the increase of species number with increasing area, and have been modeled by various equations. In this paper, we used detailed data from six 1-ha subtropical forest communities to fit three species-area relationship models. The coefficient of determination and F ratio of ANOVA showed all the three models fitted well to the species-area relationship data in the subtropical communities, with the logarithm model performing better than the other two models. We also used the three species-abundance distributions, namely the lognormal, logcauchy and logseries model, to fit them to the species-abundance data of six communities. In this case, the logcauchy model had the better fit based on the coefficient of determination. Our research reveals that the rare species always exist in the six communities, corroborating the neutral theory of Hubbell. Furthermore, we explained why all species-abundance figures appeared to be left-side truncated. This was due to subtropical forests have high diversity, and their large species number includes many rare species.
... The Poisson cluster process, sometimes also called the Thomas process, is an explicit clustering mechanism. The Thomas process assumes that (1) the parent events follow a CSR process with intensity q, (2) each parent produces a random number of offspring according to a Poisson distribution, and (3) the locations of the offspring, relative to the parent individuals, have a bivariate, Gaussian distribution [10,[43][44][45][46]. The pair-correlation function for the Thomas process is given by ...
A considerable challenge in plant ecology is to understand how interactions, such as competition or facilitation, shape the spatial distribution of plants. The “stress gradient hypothesis” predicts that facilitation and competition will vary inversely across gradients of abiotic stress or consumer pressure. Surprisingly, few previous studies have explored how the balance between facilitation and competition affects spatial patterns along gradients of stress in a plant population based on field experiments. In order to investigate the effects of consumer pressure, facilitation, and competition on the spatial pattern of plant populations, we conducted a restoration succession series field experiment in the Inner Mongolian steppe in which sample sites of graded consumer pressure, specifically grazing stress, were established. We chose to examine the spatial patterns of Leymus chinensis, a dominant species in our experimental site. In order to test the “stress gradient hypothesis,” we applied the univariate O-ring statistic to analyze local neighborhood density at different spatial scales. We used the pair-correlation function to detect the characteristics of point patterns using complete spatial randomness, the Poisson cluster process, and the nested double-cluster process. We found that the local densities of L. chinensis were higher under high stress than lower stress environments. This demonstrated the “stress gradient hypothesis” in that facilitation and competition varied inversely across gradients of consumer pressure. However, we found no differences in the spatial patterns of L. chinensis based on complete spatial randomness when interactions shifted from facilitation to competition along gradients of consumer pressure. Furthermore, we detected the characteristics of point patterns using the Poisson cluster and nested double-cluster processes. The results showed the spatial patterns of L. chinensis to fit well with the nested double-cluster model under highly stressful conditions, while in lower stress environments they were best approximated by the Thomas process. Our results illustrate that a shift in interactions from facilitation to competition along gradients of consumer pressure can shape spatial patterns and that a combination of the Poisson cluster process and nested double-cluster process can detect spatial pattern characteristics which cannot be detected by complete spatial randomness.
This paper aimed to investigate and analyse the diametric and spatial distribution of Prunus avium populations in Tunisia. This study may help us document better information about the ecological processes and its functioning. Dendrometric and ecological data were collected on four square plots of an area of 1 ha each within two forests, Tabarka and Ain Draham, in northwest Tunisia. The results presented in this work show that P. avium individuals present a diametrical structure in the form of an “inverted J” translated by the dominance of the seedlings compared to the other classes. The analysis of the spatial distribution shows that wild cherry is identified by its aggregates and variable size (approximately 5 m and 20 m). It is coherent with the mode of vegetative propagation by suckering and the dispersal of fruits by birds.
This investigation opens insight into other species to ensure good sustainable management of natural resources.
Los bosques nativos brindan una amplia variedad de bienes y servicios ecosistémicos, otorgando oportunidades sociales y económicas, por lo que es necesario desarrollar una silvicultura integrada que responda a tales fines, por ejemplo, producción maderera, no maderera y conservación. En este Capítulo se presentan propuestas y estrategias para mejorar la implementación del manejo sostenible de los bosques nativos en la Argentina, basadas en el actual desarrollo del conocimiento de la silvicultura, tomando como base al manejo adaptativo, el agregado de valor a los productos obtenidos del bosque, y la necesidad de la restauración de los bosques nativos para recuperar potencialidades perdidas. Asimismo, se plantean los principales desafíos para los próximos años como el manejo multipropósito a distintas escalas del paisaje, la adaptación del manejo silvícola a las modificaciones del clima, y la implementación de indicadores y sistemas de monitoreo. Por último, se presenta en forma sintética las principales recomendaciones sobre la silvicultura y manejo del bosque nativo para los tomadores de decisiones de las diferentes regiones forestales del país.
The spatial distribution of vegetation in sandy lands is closely related to micro-topography. Point pattern analysis of vegetation distribution from ground surveys and satellite images is a commonly used method but does not capture the influence of spatial heterogeneity at small scales. This study examined long-term ecological observation sites of elm (Ulmus pumila) sparse forest in the Otindag Sandy Land, China. Elevation models from unmanned aerial vehicles (UAVs) and ground survey data on vegetation structure from 3768 elms were used to classify the terrain of sampled sites using a decision tree classification. It combined terrain factors, including slope, aspect, and small-scale altitude differences. Plots were divided into five topographic types: sand flat (53%), sand lowland (17%), sunny slope (13%), shady slope (10%), and sandy ridges (7%). Elm densities varied from 141.7 trees hm⁻² on shady slopes to 17.0 trees hm⁻² on sand lowland. A 2D Poisson fitting method was applied to the diameter at breast height, crown width, and other vegetation growth characteristics to simulate and verify the distribution of elms in the plots. Multivariate analysis was undertaken to confirm the effect of topographic factors on variation of tree characteristics. The integrated terrain approach could better characterize the spatial distribution of sparse forests. This research demonstrated that UAVs were a useful tool to measure spatial heterogeneity of sand micro-topography. Simulations of the distribution of plant characteristics indicated that the terrain classification matched the spatial pattern analysis of elms in semi-arid regions. Simulation of vegetation distribution is a useful technique for analyzing arid regions. This study will assist with further research on ecological restoration and vegetation protection in semi-arid areas.
This paper reviews the point process theory focusing on applications to spatial ecology when data are given by a tree distribution map, often together with additional information such as tree size, species, and genotype.Beginning with a rather intuitive definition of point processes, this paper explains several functions that are useful for illustrating the basic characteristics of tree spatial patterns, followed by remarks about the basic assumption of stationality and isotropy.A variety of convenient statistics that express spatial patterns for additional information are introduced with reference to tree sizes, species, and genotypes.When such exploratory analysis reveals some characteristic spatial patterns, the nest step is to construct mathematical models that can explain a given tree distribution, then checking the model fitting by simulation.Currently, the point process theory itself is at the developmental stage and its practical power in ecology is uncertain.However, it can, at least, be applied to exploratory analysis for finding basic characteristics in spatial patterns.Point processing can be expected to have various other applications for analyzing mapped data.
Inventories of plant populations are fundamental in ecological research and monitoring, but such surveys are often prone to field assessment errors. Presence/absence (P/A) sampling may have advantages over plant cover assessments for reducing such errors. However, the linking between P/A data and plant density depends on model assumptions for plant spatial distributions. Previous studies have shown, for example, how that plant density can be estimated under Poisson model assumptions on the plant locations. In this study, new methods are developed and evaluated for linking P/A data with plant density assuming that plants occur in clustered spatial patterns.
New theory was derived for estimating plant density under Neyman–Scott‐type cluster models such as the Matérn and Thomas cluster processes. Suggested estimators, corresponding confidence intervals and a proposed goodness‐of‐fit test were evaluated in a Monte Carlo simulation study assuming a Matérn cluster process. Furthermore, the estimators were applied to plant data from environmental monitoring in Sweden to demonstrate their empirical application.
The simulation study showed that our methods work well for large enough sample sizes. The judgment of what is' large enough’ is often difficult, but simulations indicate that a sample size is large enough when the sampling distributions of the parameter estimators are symmetric or mildly skewed. Bootstrap may be used to check whether this is true. The empirical results suggest that the derived methodology may be useful for estimating density of plants such as Leucanthemum vulgare and Scorzonera humilis .
By developing estimators of plant density from P/A data under realistic model assumptions about plants' spatial distributions, P/A sampling will become a more useful tool for inventories of plant populations. Our new theory is an important step in this direction.
Since its beginnings in the late 18th century the result of modelling in forest science has always been intriguing, because it allows studying plant populations as they travel through space and time in a time-lapse mode, whereas field and lab-based studies of plant development usually take much time. On the other hand models can only approximate reality. For individual-based forest ecology and management models are of particular importance, since this field involves large, complex ecological systems with slow dynamics, where the main lessons can only be learned from simulations based on agent- or individual based models that pull theory and experimental results together and synthesise them.
Este manual metodológico es una contribución importante realizada por el Instituto
de investigación de Recursos Biológicos Alexander von Humboldt, en asocio con el
Instituto Smithsoniano de Investigaciones Tropicales (STRI), contando con la participación
de instituciones colombianas. El uso de parcelas permanentes para el estudio
de los bosques no es algo nuevo en Colombia. Los ingenieros forestales han
establecido y utilizado parcelas para medir el crecimiento de especies de importancia
económica durante varias décadas, los botánicos lo han hecho para realizar inventarios,
y los ecólogos las han usado para estudiar las interacciones entre distintas especies.
Durante el proceso de preparación del manual se identificaron cerca de 190 parcelas
permanentes de diferentes tamaños en Colombia; pero desafortunadamente los
métodos empleados en su establecimiento varían mucho, lo cual limita la comparación
de los resultados entre ellas, y han sido pocos los esfuerzos para consolidar y
comparar esta información con miras a obtener un mayor valor agregado. Confío en
que este documento sirva para fomentar el establecimiento de nuevas parcelas permanentes
en Colombia, incentivar el mantenimiento de las actuales, propiciar la
utilización de métodos comparables, y obtener una mayor cooperación que promueva
compartir la información generada en ellas.
The spatial pattern of regeneration of Aspidosperma polyneuron Müll. Arg. was studied in a remnant sector of the Paranaense forest in the Misiones province, Argentina. All individuals were mapped in a 210 m × 100 m area (2,1 ha). Univariate and bivariate point pattern analyses were used by means of Wiegand and Moloney O ring index. Regeneration showed clumped pattern to scales up to10 m and clusters of 30 m of diameter. No association was found between regeneration and both adult trees of A. polyneuron and standing death trees, whereas a small scale relationship between regeneration and adult trees of all species was observed. These results revealed that the regeneration of Aspidosperma polyneuron is strongly restricted to the presence of conspecific adult trees. On the other hand, the recruitments are associated with individuals from different species with DBH > 10 cm and infrequent in open sites.
The aim is to determine the ecological characteristics of Pinus massoniana Lamb and Cunninghamia lanceolata (Lamb) Hook, which co-dominate a natural coniferous forest in the Huangshan region of Anhui Province, eastern China, we examined the spatial patterns, size structure, and tree height-diameter relationship of both species. P. massoniana dominated the canopy layer, but smaller individuals were scarce. In contrast, C. lanceolata co-dominated the sub-canopy layer and had a considerable number of saplings and sprouting from the root collar of larger individuals. The spatial pattern of P. massoniana tended to be overdispersed at small scales, but became random-overdispersed at intermediate to larger scales. The spatial pattern of C. lanceolata was clumped at small scales. In a young stand, tree height at a given stem diameter was larger for P. massoniana than for C. lanceolata. Based on these results, we inferred several ecological characteristics of these two dominant species: Cunninghamia lanceolata is a relatively slow-growing shade-tolerant species. P. massoniana is a fast-growing shade-intolerant species that has high mortality rates if suppressed and regenerates only after large-scale disturbances.
The present research aimed to analyze and describe spatial patterns and quali-quantitative features of natural regeneration of tree species of Ocotea odorifera (Vell.) Rohwer (canela-sassafrás) in a fragment of Mixed Ombrophyllous Forest (Araucarian Forest) located at the National Forest of Irati, Paraná State, Southern Brazil. Three plots of one hectar each were sampled and height, diameter and location informations were collected for all plants of canela-sassafrás with total height ≥ 30 cm. Univariate analyzes using K-function of Ripley were done in order to describe spatial patterns of plants at different regeneration phases as well as of canela-sassafrás adults. Generally, this species presented an aggregated spatial pattern at all considered scales of regeneration, suggesting to be a typical pattern at initial phases of this species. The change from aggregated to random spatial pattern was tested analyzing different size classes of canela-sassafrás. Some inferences were made considering subjacent processes that could be associated to obtained results. It is possible to say that the studied species presents potencialities for its management and conservation with excellent natural regeneration capacity.
The quantitative estimation of hair follicle patterns for a leather surface was investigated by point pattern analysis for use as a possible method for correct identification of leather materials. The Lfunction was used as a point pattern analysis. In the case of goatskins, the L-function correctly indicated the distribution patterns of guard hair follicles. Moreover, it was found that the density of hair follicles and the microscope magnification affect the estimation of the L-function. It was demonstrated that hair follicle patterns of leather surface could be estimated quantitatively by point pattern analysis with optimum conditions. This result suggested that leather materials could be identified objectively by this method.
Several methods for analyzing uni- and bivariate point patterns, commonly used in ecology, are reviewed in this work. The refined nearest neighbor method, the Ripley’s K function and the SADIE technique were used to analyze simulated and real spatial point patterns. A random pattern, three clumped patterns with radius of 3, 5 and 10 m, and three random patterns with inhibition distances of 2, 4 and 6 m, were simulated to check the efficiency of the methods. Real patterns were measured in two deciduous forests in the Cantabrian lowlands and a coniferous forest in the Cebollera-Urbión Range. All techniques were able to distinguish between random, clumped and regular patterns. Nearest neighbor method and K function displayed inhibition distances in regular patterns, but K function alone detected the clump size. Juveniles showed clumped spatial patterns, while adults displayed a random distribution. For bivariate analyses, some simulated patterns displayed significant evidence of spatial attraction or repulsion. Real patterns indicated spatial repulsion between juveniles and adults, and attraction between differently sized juveniles. The results were interpreted according to the available information on forest ecology. The use of appropriate methods for edge effect correction, and null models alternative to the complete spatial randomness, is also discussed.
The spatial pattern of regeneration of Aspidosperma polyneuron Müll.Arg. was studied in a remnant sector of the Paranaense forest in the Misiones province, Argentina. All individuals were mapped in a 210 m x 100 m area (2,1 ha). Univariate and bivariate point pattern analyses were used by means of Wiegand and Moloney O ring index. Regeneration showed clumped pattern to scales up to10 m and clusters of 30 m of diameter. No association was found between regeneration and both adult trees of A. polyneuron and standing death trees, whereas a small scale relationship between regeneration and adult trees of all species was
observed. These results revealed that the regeneration of Aspidosperma polyneuron is strongly restricted to the presence of conspecific adult trees. On the other hand, the recruitments are associated with individuals from different species with DBH > 10 cm and infrequent in open sites.
Marsh was the major wetland type. The soil of marsh is oxygen-poor due to permanently inundate which has formed a special environmental conditions and vegetation types. The Sanjiang Plain is one of the largest freshwater marshes with area of approximately approximately 10400km2. The dominant plants are grass species which both have cloned habits such as Carex lasiocarpa, Carex pseudocuraica, Deyeuxia angustifolia and Glyceria spiculosa. To study the spatial distribution pattern of plant populations in marsh is supplementary for spatial pattern theory because the distinctive environmental conditions. Meanwhile, it is very significance for revealing plant populations characteristics in marsh environment. Thus, we analysis the spatial distribution pattern of main dominant species (C. lasiocarpa, C. pseudocuraica, D. angustifolia and G. spiculosa) by point pattern analysis based on different null models. The study site is located at the Ecological Experiment Station of Mire Wetland in Sanjiang Plain, Chinese Academy of Sciences (47°35′N,133°31′E, 56m above sea level), Northeast of China. In September 2012, we mapped a 4×4 m representative area in the permanently inundated marsh community which the surface are smooth and have uniform physiognomy. The plot was divided into 256 contiguous 25×25 cm quadrats, as the basic unit of vegetation survey, using the bamboo pole and the white rope. The relative position of each plant individual or plexus projection of grass was expressed in the coordinates which represent the distance. All analyses were conducted using the grid-based estimators in the Programita software package. Nineteen Monte-Carlo simulations were used to generate 95% confidence envelopes. Our results showed that: The four main dominant species mainly depart from complete spatial randomness (CSR) and shows aggregation in 0-200cm scales, but have varying degrees of deviation; The C. lasiocarpa, C. pseudocuraica and G. spiculosa depart from poisson cluster process (NS) in small-scale, except D. angustifolia; The C. lasiocarpa andG. spiculosa depart from nested double-cluster process (DC) in a very small-scale, but not significant. The C. pseudocuraica accordance with nested double-cluster process in 0-200cm scales, completely; The measured value of population farther departed from complete spatial randomness (CSR) are more likely accordance with poisson cluster process (NS), and farther depart from poisson cluster process (NS) are more likely accordance with nested double-cluster process (DC); The aggregation of 4 species in 0-200cm scales is caused by vegetative propagation which could help to adapt the perennial water environment. Much ramet system can form a cluster in large scale, while the one ramet system forms a cluster in small scale. On the other side, the aggregation intensity of population would reduce due to strong intraspecific competition in has formed cluster.
Understanding spatial distribution patterns has been a central focus of plant ecology since its inception. Spatial patterns of individuals within populations are closely linked to processes; determining these underlying processes remains a major objective of ecological research. Spatial patterns are often determined using a point pattern, a data set consisting of a series of mapped point locations within a study area. The simplest and most widely used null model for analyzing point patterns is the complete spatial randomness (CSR) model. In fact, other null models are rarely used. This paper aims to provide guidance to ecologists when quantifying the underlying processes responsible for spatial patterns of ecological phenomena using point patterns and null models. Photography orientation was used to estimate the point pattern of Leymus chinensis in different restored successional stages in a typical steppe, and complete spatial randomness, Poisson and double-cluster processes were used to analyze spatial patterns of L. chinensis based on this data set. In the early stages of succession, the distribution of L. chinensis fit well with the nested double-cluster process for all scales in the community block of 10 m×10 m. Over time, the distribution fits better with the Thomas process at all scales. This ecological succession phenomenon may be induced by intra-specific competition, but cannot be explained by density interactions. Population territory density could possibly explain the phenomenon. Our study is an important example of successful analysis of population spatial patterns using point patterns and complex null models.
Spatial aspects of changes in species composition of natural forest stands
in Białowieża National Park: ingrowths establishment, their survival and advance
to the canopy. The paper describes spatial aspects of changes in tree species
composition of Białowieża National Park in the period between 1936 and 2003
when massive disturbances in canopy strata of investigated stands were not observed.
The main subject of investigations were differences in response of relatively
young specimens of different species on the infl uence of surrounding trees
on their ability to achieve DBH of 50 mm (receiving the status of ingrowth) and
their survival and advance to the canopy strata. The investigations concentrate on
the ingrowths cohort recorded between 1955 and 1959 because their establishment
took place in the period of exceptionally low density of ungulates in Białowieża
Primeval Forests and it could be assumed that tree stand conditions had the prevailing
infl uence on their fortune.
Data were collected by the Department of Silviculture, Warsaw University of
Life Science SGGW on permanent research plots of total area 15.60 ha placed in
the oldest best preserved part of Białowieża National Park referred to as Reserve.
In the year 1936 on fi ve plots the placement of trees with DBH more than 50mm
was mapped. During fi ve censuses between 1955 and 2003 tree mortality and
ingrowths were recorded. Tree diameter, vitality and relative height ware also
recorded.
Spatial aspects of ingrowths establishment were analysed in bigger (forest
stand) spatial scale as well in smaller concerning only trees from the nearest
neighbourhood. Analyses in bigger spatial scale comprise graphical analysis of
changes in tree stand openness as well in spatial distribution of sub-canopy trees
and ingrowths registered during second and third censuses. The infl uence of tree
stand conditions on density of ingrowths was analysed with the use of classifi cation
trees (CART algorithm). Both the ingrowths density and tree stand characteristics
were assessed on the squares (40 × 40 m) placed on research plots. Stand
conditions were described by 24 characteristics such as: tree density, basal area,
mean value of DBH calculated for all trees and separately for canopy and subcanopy
trees. As explanatory variables were used the changes in the values of before mentioned variables observed between fi rst and second censuses as well
the importance value of trees species forming canopy in investigated fragments
and site condition type.
Local aspects of ingrowths establishment, their survival and advance to the
canopy were described by the use of infl uence (competition) indices. In the work
were used simple indices as local tree density or local basal area as well more
complicated indices built on distances between central trees and trees in the neighbourhood
and their DBH. To assess the extent of perception zones of ingrowths
the analysis comprises infl uence indices calculated for the neighbourhood of
radii from 1 to 10 meters with increment of 1 m. To assess the role of local species
composition three variants of analysis were carried on: one without distinguishing
species of neighbours, second with dividing neighbours in con-specifi c
and hetero-specifi cs groups and third in which three groups of neighbours were
distinguished according to their ability of casting shadow. Because the ingrowths of some species were very sparse, the rare events logistic
regression was used to model the infl uence of local neighbourhood on their
establishment. The Kaplan-Meirer estimator and Cox proportional hazard model
ware used to model survival and advance to the canopy of ingrowths recorded during
the second census. For species with more numerous ingrowths analyses were
performed separately for different site conditions types.
Spatial and temporal variability of stand openness in Reserve, as well as
spatial variability of ingrowths and sub-canopy trees distribution during the fi rst
and second census was to a large extent infl uenced by the wild and domesticated
ungulates. Probably the domination of spruce in sub-canopy on poorer site-conditions
observed during fi rst census was connected with cattle grazing which
took place even before the year 1889. Exceptionally high density of ungulates in
the period 1889–1914 was the cause of high openness of tree stands observed on
the fi rst census in the year 1936. Rapid and strong decrease in quantity of ungulates
after the year 1914 promoted the establishment of natural regeneration of
many tree species which developed into ingrowths observed during the second
census. The analyses showed that the most constraining infl uence on establishment
of ingrowths had trees growing in the immediate neighbourhood of radius 5–7 m.
Survival analysis of trees recorded as ingrowths during the second census showed
that the radius of perception zone of a tree grows as the size of tree grows. The
likelihood of ingrowths establishment was inversely proportional to the value of
indices describing the neighbourhood infl uence. The prognostic ability of models
describing ingrowths establishment decreased as increased the shade tolerance of modelled species. For the modelling of ingrowths establishment the most useful
was relatively simple index: local tree density but for the modelling of survival
and advance to the canopy were better indices built on distances between central
trees and trees in the neighbourhood and their DBH.
For the ingrowths of light demanding species could be assumed the equivalence
of infl uence of different species from the neighbourhood. Tree species
with higher crown openness (light demanding species) growing in the neighbourhood
constrained establishment of hornbeam, ash, lime, alder, spruce and elm
ingrowths less than more shade tolerant species with lower crown openness. The
survival was also inversely proportional to light demand of analysed species but
this dependence was weaker than in the case of establishment. The comparison
of establishment and survival of different species suggests that in a longer period
of low intensity disturbances in the canopy and simultaneous low pressure from
ungulates the changes in species composition of analysed tree stands would tend
to dominance of shade tolerant species, especially of hornbeam which very well
tolerates conditions present in sub-canopy strata and can stay there for a longer
period. Negative infl uence of older (canopy) hornbeams on the establishment
of its own ingrowths, which was observed in bigger and in smaller spatial scale
may constrain the possibility of this species dominance. The second potential dominant
would become lime, which tries to achieve the position in canopy layer.
The survival analysis of spruce ingrowths suggest that the process of withdrawal
of this species from analysed tree stands started with the decrease of their openness.
The objective of this research was to analyze the spatial distribution of a Mixed Ombrophylus Forest fragment, as well as of three species pertaining to distinct successional groups belonging to the same, by the Ripley's K function. The data came from a census carried out in a fragment located in the Campus Botanical Garden, UFPR, Curitiba - PR, Brazil, where all trees with DBH above 10cm were georeferenced. One plot with 4 ha was used for the analysis of the spatial distribution of the forest and individually for the species of Araucaria angustifolia (Bertol.) O. Kuntze, Casearia Sylvestris Sw. and Cedrela fissilis Vell. The spatial relationship between species, as well as the spatial relationship between diameter classes of the same were also analyzed. The forest showed a random spatial distribution, however, the three selected species showed an aggregate spatial distribution when analyzed individually. The Casearia Sylvestris presented an attraction relationship with Araucaria angustifolia and Cedrela fissilis, and these trees in turn, were related to repulsion between them. The spatial relationship between DBH classes of Araucaria angustifolia was attraction between individuals of smaller classes with larger individuals. This result reflects the form of seed dispersal of species, where regeneration occurs in the proximity to the parental trees. For the Casearia Sylvestris and Cedrela fissilis, aggregation occurred only between the smaller individuals.
The natural regeneration in forest environments is dynamic, variable in space and time and it is in the development cycle of forests. In seasonal tropical forests, due to seasonal climatic changes, natural regeneration depends mainly on availability of soil moisture, which affects patterns of seed production and germination, survival and development of seedling as well. The objective of this study was to analyze the dynamics of natural regeneration in a seasonal semideciduous secondary forest in Pirenópolis, Goiás, Brazil, by analyzing the changes in floristic composition of seedlings and small trees over time and relating them to environmental factors of plots in the study area by using Canonical Correspondence Analysis (CCA). The results indicated that seedlings were more dynamic than small trees mainly because of climate. This occurred because of the greater susceptibility of the seedling to soil water stress and the increase of solar radiation and temperature in the dry season. It was found a high floristic similarity (± 50%) among population of natural regeneration and the tree community, indicating an advanced stage of natural regeneration of the forest, with Diversity Index higher than 3.0 nats.indv -1. Canonical Correspondence Analysis grouped the species according to the environmental gradient of moisture and shade versus soil cover, placing near to each other, species of humid environments versus species of typical cerrado dry environments.
As a partial explanation for the maintenance of high tree diversity in wet tropical forests, Janzen (1970) and Connell (1971) independently hypothesized that natural enemies act to increase spacing within these tree populations through disproportionately high attack on progeny near adults. A minimum critical distance effect occurs because of 100% progeny mortality within a given distance of adults. Data describing the spacing dynamics of Dipteryx panamensis support both hypotheses. From 7 mo to 2 yr postgermination, seedling survival was positively correlated with distance to adult and negatively correlated with local conspecific seedling density. Partial correlation was used to separate the effects of density and distance. Seedling density was the only significant factor in this case. No seedlings or juveniles survived within 8 m of an adult bole. A review of 24 data sets on tropical woody plants showed that most evidence indicates either density-dependence or distance-dependence in progeny mortality. Some positive evidence also exists for the minimum critical distance effect for tropical trees. -from Authors
The spatial structure of vegetation and soil properties of a patchy Scots pine (Pinus sylvestris L.) forest of 1 ha was described and examined in relation to the height growth of pine seedlings in the understory. Measured ecosystem properties included the distribution and sizes of canopy trees, within-stand radiation regime, composition of understory vegetation, and topsoil and mineral soil properties. The joint distance dependent effects of large trees were described as the influence potential, derived from the ecological field theory approach. The variation in understory vegetation and soil characteristics was described as score values, derived from multivariate analyses, summarizing the variation of multiple measured variables; factor analysis was used for topsoil and mineral soil properties and canonical correspondence analysis was used for understory species composition. The spatial variation of variables was examined and mapped using geostatistical techniques. The influence potential of canopy trees, as determined by their size and spatial distribution, correlated most strongly with seedling growth, so that the height growth of seedlings was retarded in the vicinity of trees. Correlations suggest that canopy trees also affected seedlings indirectly through their dominating effect on the properties of understory vegetation and humus layer. The mineral soil nutrient content showed a weak positive correlation with seedling height growth. All the factors related to seedling growth showed substantial small-scale variation across the 1-ha study site. The analysis suggests that the variation in seedling height growth in the understory of the studied Scots pine stand is largely caused by the spatial heterogeneity of both above- and below-ground factors and by the joint effect of their complex interaction.
Moeur, M. 1993. Characterizing spatial patterns of trees using
stem-mapped data. Forest Science 39: 756-775.
Procedures for stem-mapping trees on fixed area plots are described. Two statistical procedures for analyzing spatial patterns of the completely mapped tree data are presented. These procedures, known as nearest neighbor analysis and Ripley's K(d) function, consider the cumulative distributions of distances between trees, compared to a distance distribution for a point pattern generated by a random process. Nearest neighbor uses tree-to-nearest-tree distances, and Ripley's K(d) considers distances between all pairs of trees. Both procedures include edge correction schemes for trees near plot boundaries. The two analyses were applied to stem-mapped data from several old-growth study plots to investigate spatial interactions within and between groups of canopy trees. Patterns for trees in different mortality, size, and competitive classes were analyzed separately. Results showed that between-tree competitive interactions drive forest pat- terns from clustering toward regularity. There was also evidence that canopy gaps are an important mechanism in the regeneration process. The examples illustrate how spatial pattern analysis can be useful in describing and interpreting complicated development processes that result from competitive interactions between individual trees. For. Sci. 39(4):756-775.
A high number of tree species, low density of adults of each species, and long distances between conspecific adults are characteristic of many low-land tropical forest habitats. I propose that these three traits, in large part, are the result of the action of predators on seeds and seedlings. A model is presented that allows detailed examination of the effect of different predators, dispersal agents, seed-crop sizes, etc. on these three traits. In short, any event that increases the efficiency of the predators at eating seeds and seedlings of a given tree species may lead to a reduction in population density of the adults of that species and/or to increased distance between new adults and their parents. Either event will lead to more space in the habitat for other species of trees, and therefore higher total number of tree species, provided seed sources are available over evolutionary time. As one moves from the wet lowland tropics to the dry tropics or temperate zones, the seed and seedling predators in a habitat are hypothesized to be progressively less efficient at keeping one or a few tree species from monopolizing the habitat through competitive superiority. This lowered efficiency of the predators is brought about by the increased severity and unpredictability of the physical environment, which in turn leads to regular or erratic escape of large seed or seedling cohorts from the predators.
An investigation of spatial pattern in relatively sparse Pinus ponderosa-P. Jeffreyi stands showed that a simple Poisson model of random distribution described the pattern at 5 to 50 m scales in the denser stands examined when allowance is made for inhibition between nearest neighbors. There is evidence for a clumped distribution in large quadrats for the sparsest stands, which concurs with prior work where a mixed Poisson model was fit to the data. The technique used was innovative in that it involved digitally recording tree locations from high resolution aerial photos, which allowed for the automatic application of several statistical techniques in order to determine how pattern varies with plot density and scale. Point locations were recorded for six 11.3 ha plots in three density regions of a 340 ha study area in northeastern California, USA. The inter-event distance distribution, and one- and two-dimensional power spectra were calculated, and variable quadrat analysis was performed for the data sets. The second order and spectral analyses showed no evidence of a distinctive clumped pattern at any scale, and all analyses showed that the pattern was regular at the scale of the average inter-plant distance in the denser stands. For the sparser stands, the counts in large quadrats did not fit a Poisson distribution, but were better fit by a mixed Poisson model describing aggregated pattern.
Patterns of tree abundance and dispersion in a tropical deciduous (dry) forest are summarized. The generalization that tropical trees have spaced adults did not hold. All species were either clumped or randomly dispersed, with rare species more clumped than common species. Breeding system was unrelated to species abundance or dispersion, but clumping was related to mode of seed dispersal. Juvenile densities decreased approximately exponentially away from adults. Rare species gave evidence of poor reproductive performance compared with their performance when common in nearby forests. Patterns of relative species abundance in the dry forest are compared with patterns in other forests, and are explained by a simple stochastic model based on random-walk immigration and extinction set in motion by periodic community disturbance.
S ummary
Spatial point processes may be analysed at two levels. Quadrat and distance methods were designed for the sampling of a population in the field. In this paper we consider those situations in which a map of a spatial pattern has been produced at some cost and we wish to extract the maximum possible information. We review the stochastic models which have been proposed for spatial point patterns and discuss methods by which the fit of such a model can be tested. Certain models are shown to be the equilibrium distributions of spatial–temporal stochastic processes. The theory is illustrated by several case studies.
Interaction between mature trees and young seedlings could lead to partial mortality of seedlings. Species distribution was also related to environment, particularly topography and frequency of gaps. The patch structure observed for Eperua falcata corresponded to the rapid "turnover rate' focused on the poorest sites. -from English summary
(1) Quararibea asterolepis (Bombacaceae), a common canopy tree in the old forest on Barro Colorado Island, Panama, was the only species defoliated during an outbreak of Eulepidotis (Noctuidae) larvae in May and June 1985. (2) The level of defoliation among 460 potentially reproductive trees (⩾ 16 cm dbh) over a 50-ha plot was related to local conspecific density and to the severity of defoliation of the three nearest neighbours. (3) Young leaves suffered greater damage than mature leaves in the same Quararibea crown. Trees with mostly young leaves before the outbreak suffered heavier defoliation than those with mostly mature leaves. Trees that escaped defoliation had either all or mostly mature leaves. (4) When sapling pairs were matched with respect to leaf age, saplings near an infested adult suffered heavier defoliation than distant saplings. The distance effect was reversed, however, when near saplings had mature leaves and far saplings had young leaves. (5) Heavily defoliated crowns of large (⩾ 64 cm dbh) Quararibea trees produced significantly fewer flowers and fruits than lightly defoliated crowns. Flowering also occurred later and was less synchronized for heavily defoliated trees. This difference in reproductive output did not persist beyond the outbreak year.
For isolated parents of Platypodium elegans (Leguminosae), high seedling mortality nearer the parent tree due to fungal pathogens caused the median distance of surviving 3-month old seedlings to be greater than that of germinated seeds. After 1 yr the median distance of surviving offspring either increased further or decreased, depending on the location of light-gaps, in which survival and growth were greatly enhanced. Saplings were further from the parent than either dispersed seeds or 1-yr old seedlings. Thus recruitment distances of a given cohort were not constant through time. Mortality distributed uniformly in space or between individuals does not cause a shift in the location of recruitment. Any observed shift is an indication of density- or distance-dependent mortality. -from Author
(1) Spatial patterns of the mortality of tropical trees were investigated using maps of four species on an 80 × 80-m site of primary rainforest in Costa Rica. Using new statistical methodology, designed specifically for complete maps of individuals, models of clustering or uniformity were fitted to different size classes, and the relative uniformity of the different size classes compared. The data for the extant juveniles were then used to predict what the extent adult spatial distribution would be given random mortality of the juveniles. The actual adult distribution was compared to this hypothetical distribution to see if they were more or less uniform than predicted. (2) For three of the four species, the spatial models which fit the adults were more uniform than the models which fit the juveniles. The adults of these three species were significantly more uniformly distributed than expected from the random mortality of their extant juveniles. The fourth species had adults with a similar distribution to randomly thinned extant juveniles. (3) Post-germination survival leads toward a uniform distribution. During the lifespan of three of the four species, repulsion occurs between individuals. At small scales, clumping, when present, may be more the result of patchy dispersal of seeds or seedling germination than the patchy survival of germinated individuals.
The local spatial arrangement of the coniferous trees Pinus edulis and Juniperus osteosperma was mapped in two woodland stands and measured in two shrub-dominated stands in the semiarid Piceance Basin of northwest Colorado. In the woodlands, small trees were often clumped, while medium and large trees were either randomly or uniformly dispersed. Significant regressions were obtained between a tree's basal area or canopy area and the area of its Dirichlet domain (the region closer to it than to any other tree). Both findings from the woodland stands accord with results obtained by other workers in other vegetation. Like earlier workers, we interpret these patterns to indicate density-dependent mortality and density-dependent depression of growth rates among the trees in the woodlands. In contrast, the trees in the shrub-dominated stands are located at random with respect to each other. However, they are strongly associated with shrub cover. Apparently, tree seeds arrive in these stands primarily by long-distance dispersal, and the establishment of seedlings is more likely in the shade of shrubs.
The spatial pattern of Pinus banksiana individuals (459 live, 257 standing dead, 659 stumps) in a pure, even-aged, naturally established stand was mapped. Three maps corresponding to different stages of stand development were recognized: live + dead (initial pattern, n = 1375), live (following self-thinning, n = 459), and live + standing dead (survivors plus most recent mortality, n = 716). The Dirichlet-Thiessen tessellations of these maps indicated that the distribution of tile areas (area potentially available) becomes increasingly equitable over time. A significant positive correlation between diameter at breast height or surviving trees and their area potentially available was found for each map; this correlation was highest for the life tessellation. In the live + dead and live + standing dead tessellations, the mean tile area of dead trees was significantly smaller than that of survivors. Larger trees tend to have large neighbours and smaller trees have small ones. Results suggest a model of differential mortality in which the smaller individuals in a stand, particularly those surrounded by larger individuals, are most likely to die over a given time interval. -from Authors
The hypothesis that seed or seedling predation by host-specific herbivores can explain the coexistence of the large number of tree species in tropical forests, and produce a low density and uniform dispersion of adults of these tree species, is examined. On theoretical grounds, it is shown that spacing of conspecific adults can account for only a very small fraction of the observed tree species richness in tropical forests unless interadult distances are quite large. Moreover, in growing or declining populations, seed predation will not result in large-scale uniformity in adult dispersion patterns throughout the population. It results in uniformity in equilibrium populations only if the same spacing rule applies to all adult trees. However, adult trees differ enormously in seed production from year to year, and from young (small) to old (large) adults. High variance in seed production from tree to tree and year to year leads to heterogeneity in the intensity of seed predation and in the spacing distance between adults. This explains why the adults of most tropical tree species are clumped or randomly dispersed, and not uniformly spaced, in spite of heavy seed predation in many species. Because tree species are not everywhere as dense as whould be predicted from observed nearest neighbor distances, it is concluded that other factors than seed predation limit the abundance of tropical tree species and prevent single-species dominance. /// Проверяли гипотезу о том, что потребление семян или проростков фитофагами, специализированными к определенному виду кормового растения, может объяснить сосуществование большого числа видов деревьев в тропических лесах, низкую плотность и равномерное распределение зрелых деревьев этих видов. На теоретической основе показано, что пространственное распределение взрослых деревьев одного вида определяется лишь небольной частью всего видового богатства деревьев в тропическом лесу, хотя расстояния между эрелыми деревьями относительно большие. Более того, в развивающихся или угасающих популяциях выедание семян не приводит к крупномасштабной равномерности в характере пространственного распределения взрослых деревьев в пределах распространения популяции. Это приводит равномерности в уровновешенных популяциях лишь в случае, если характер пространственного распределения одинаков у всех взрослыхдеревьев. Однако взрослых деревья сильно различаются по продукции семян в разные годы и в разном возрасте. Большие колебания в продукции семян в разные годы, а таюже индивидуальные колебания приводят к возникновению различий в интенсивности потребления семян и неравномерности распределения взрослых деревьев. Это объясняет, почему распределения взрослых деревьев большинства тропических видов агрегировано или случайно и неравномерно, несмотря на интенсивное отчуждение семян фитофагами у многих видов. Так как отдельные виды деревьев не везде встречаются в той плотности, которую можно предсказать по расстоянию между ближайшими соседними деревьями, сделано заключение, что обилие тропических деревьев лимитируется рядом друтих факторов, помимо выедания семян, которые препетствуют и доминированию отдельных видов.
The paper presents a method for the second-order analysis of point processes, and, basing on it, for their orientation analysis. For the reduced second moment measure of stationary and of stationary and isotropic point processes a new estimator is given, which has some advantages in comparison to RIPLEY's estimator. Three examples illustrate the use of the statistical techniques.
For the reduced second moment measure of stationary point processes several estimators are presented. In order to show the most general conditions under which the estimators are applicable, some properties of non-stationary point processes are introduced making it possible to reduce the second moment measure as in the stationary case. For the stationary Poisson process variances of the estimators are given.
Spatial point processes may be analysed at two levels. Quadrat and distance methods were designed for the sampling of a population in the field. In this paper we consider
those situations in which a map of a spatial pattern has been produced at some cost and we wish to extract the maximum possible information. We review the stochastic models which have been proposed for spatial point patterns and discuss methods by which the fit of such a model can be tested. Certain models are shown to be the equilibrium distributions of spatial-temporal stochastic processes. The theory is illustrated by several case studies.
Trees in a forest interact and therefore have to be considered as a system of dependent random variates from an unknown stochastic process. One such mathematical model which considers the spatial dependence among trees in a forest and their characteristics is a marked point process. The "points" are the tree positions and the "marks" are tree characteristics such as stem diameters or tree species. Statistical methods for marked point processes can give valuable information on the spatial interaction of trees. They are applied in this paper to describe spatial dependence of stem diameters in a spruce forest, of heights of trees in a stand of pine saplings, and of heights, stem diameters, and crown lengths in a mixed birch-pine forest area. For. Sci. 38(4):806-824.
Spatial statistics were used to examine the pattern of self-thinning in a 0.25-ha even-aged (65 yr old), pure stand of jack pine in the boreal forest near Elk Lake, Ontario, Canada. The positions of 459 living and 916 dead trees were recorded, and refined nearest neighbor analysis [G( w)] and second-order spatial statistics [L(t)] were used to examine distributional deviations from both the Poisson expectation and the hypothesis of random mortality. The results indicate that the initial (live + dead, n = 1375) distribution was locally random. By contrast, the distribution of live trees was locally highly regular, while the dead trees were significantly more clumped than random mortality would dictate. It is suggested that the development of a strong regular pattern in the survivors is attributable to differential mortality involving two distinct competitive phases: an early scramble phase involving two-sided competition for soil resources, and a later contest phase involving one-sided competition for light. Analysis of L(t) for the live trees indicated a mean “area of influence” for each individual of an ~ 3.5 m radius, suggesting that trees may compete directly only with their immediate neighbors.
Analysis of stand structure and spatial patterning indicates that Lagarostrobos franklinii (Huon pine) regenerates intermittently in response to canopy disturbance. Its ability to resprout rapidly from fallen trees is likely to be important in the continued dominance of gaps by this species in competition with faster-growing tree species. The largely riverine distribution pattern of this species is best explained by rapid vegetative spread down river systems and slow dispersal into canopy gaps away from river edges. The probability of recurrent disturbance within the lifespan of this species is high, implying that competitive exclusion of Huon pine is unlikely once it establishes at a site.
The analysis of spatial patterns is one of the ways to estimate the role of competition among trees in forest dynamics. Three hypotheses concerning distribution patterns in old‐growth stands were tested: (1) fine‐scale spatial patterns of trees are regular; (2) patterns do not differ significantly from a random distribution, and (3) spatial patterns at larger scales are clumped because of site heterogeneity. Old‐growth forest stands in Poland and the Czech Republic were analysed with a modified Ripley K function, using distribution maps of tree stems.
Fine‐scale spatial patterns (with distances among trees not exceeding 15 m) were usually intermediate between random and regular. Trends towards a regular distribution occurred more often among dead than among live individuals. No significant relationships between tree species were found at smaller scales; however, at larger scales (distances from 15–25 m) negative associations between some species were found. This reflects site heterogeneity rather than any direct influence of one tree species upon another.
The pattern of spatial arrangement of trees at scales up to 20 m is examined in 12 plots of even-aged monoculture of tall-open Eucalyptus obliqua L'Herit. forest, aged 30–57 years, in Tasmania. In general, trees were randomly arranged on the plots. In four plots there was a tendency towards regular spacing amongst the 50% largest diameter trees of the plots, these trees being the more successful competitors. There was evidence that this occurred simply because crown spread prevents dominant trees being too close together. There were slight tendencies in some plots for larger trees to be further from their nearest neighbouring tree than smaller trees and to have smaller nearest neighbours than smaller trees. These results are considered in relation to suggestions that competition in monoculture should impose spatial regularity on successful competitors and that dominant trees suppress near by trees. It is suggested that inter-tree root grafting or variability in the shape of root and crown systems may reduce the tendency for these effects to apply, consistent with the results of the present work.
The spatial distribution of woody plants was studied in an arid savanna in Botswana. The study included stands of mixed species and sizes as well as monospecific even-sized stands of different size classes of the tree Acacia erioloba and the shrub Acacia mellifera. In the case of A. mellifera both dense stands on overgrazed land and more open stands were included. The analysis used all plant-to-plant distances, and individuals were represented with a realistic canopy extension. The mixed stands showed aggregated distribution of individuals, mainly caused by strong clumping of small shrubs. In A. erioloba saplings were aggregated, small trees were randomly or regularly distributed and large trees were randomly spaced. In open stands of A. mellifera aggregation increased with size of the shrubs, while in dense stands with overgrazing aggregation decreased with increasing size. The different patterns are discussed in relation to the relative importance of inter- and intraspecific competition for water and of disturbance by fire as regulatory mechanisms for total amount and spatial distribution of woody plants in this savanna.
Spatial pattern analysis based on Ripley's K-function is a second-order analysis of point patterns in a twodimensional space. The method is increasingly used in studies of spatial distribution patterns of plant communities, but the statistical methods involved are sometimes poorly understood or have been modified without evaluating the effects on results. The procedures of field data acquisition, statistical analysis, and the test for the null hypothesis of complete spatial randomness are described and the presentation of results is discussed. Different methods of edge correction were tested on a computer-generated random pattern and a mapped distribution of a Mediterranean shrubland. The inclusion of buffer zones around mapped plots describes the spatial pattern most accurately, but may not warrant the additional labour involved. Three variations of the weighted edge correction yielded comparable results for the distribution patterns tested. The toroidal edge correction may give biased results for non-random patterns. Recommendations for standardisation of the statistical procedures and data presentation are given.
Effects of spatial processes on temperate deciduous forest structure and dynamics were investigated with a spatial simulator derived from a forest gap model. The multi-species neighborhood model accounted for competitive interactions and endogenous disturbance in the form of small canopy gaps. Simulated and actual spatial pattern of old-growth stands were compared. The 400 yr simulations produced a pattern scale (0.07–0.2 ha patches) similar to that of an actual stand; simulated pattern intensity was greater than actual intensity, however. Distances to nearest neighbor were somewhat similar for trees in the simulated and actual stands; yet the frequency distributions of distance to nearest neighbor values differed substantially. The simulated stand patterns were generally less random than the actual patterns. Spatial pattern changed markedly during the course of simulated succession. Pattern approached a random dispersion in early succession. Intensity peaked at mid-succession (ca. 150 yr) with a hyperdispersed overstory and a strongly clumped understory. Pattern intensity diminished in late succession as a mixed size structure developed. Old-growth patch size was greater than the neighborhood (or gap) size, suggesting the gap-sized areas do not behave independently.
Spatial pattern was analyzed in seventeen stands of oak-dominated forest to address the hypothesis that species tended to be aggregated under favorable conditions and widely spaced in xeric, nutrient poor conditions. Trees were sampled at 80–100 points in each stand with the distance-to-nearest neighbor method. Soil samples were collected in each stand for analysis of total nitrogen, total phosphorus, total potassium, soil pH, soil texture, and soil organic matter. Growing season precipitation was also recorded from climate stations near each stand. Quercus stellata (Wang.) dominated 10 stands, Q. marilandica (Muenchh.) dominated three stands and these species were codominant in four stands. Principal components analysis identified a soil texture/fertility gradient across the study area. Quercus stellata and all species combined were aggregated in most stands, whereas Q. marilandica was mostly randomly distributed within a stand. Small trees of all species combined tended to be aggregated and large trees were randomly dispersed in all but two stands, suggesting competition. Mean distance between large-large pairs was always greater than mean distance between small-small pairs in all stands, but this difference was only significant in one stand. Correlations between nearest neighbor distance and combined size of nearest neighbors were significant and positive in 12 of 17 stands. In all cases, however, slopes were shallow suggesting that competition is weak in these communities and has a limited effect on spacing of neighboring trees. Contrary to our hypothesis, trees were more aggregated on coarse-textured soils with low organic matter content. For all species combined, degree of aggregation was unrelated to growing season precipitation. Aggregation appears to be common in these forests because environmental stress in many stands reduces growth rates. Trees have not yet reached a size at which competition or other interactions can greatly increase interplant distances and reduce the degree of aggregation. A simple graphical model is developed to describe the relationship between patterns, stress and competition in plant communities.
Des inventaires de régénération naturelle ont été effectués en 1986 et 1988 par échantillonnage systématique au taux de 1 % de la surface et sur 33 espèces de la forêt tropicale humide de Guyane au sein du périmètre sylvicole de Paracou. Cette étude est consacrée à la modélisation de la répartition spatiale de 3 espèces : Qualea rosea Aublet, Eperua falcata Aublet, Symphonia globulifera Linnaeus f. Les principaux paramètres d'abondance et de dispersion sont présentés : densité des semis, précision relative, indice de dispersion. Ce dernier met en évidence l'existence d'agrégats. Deux méthodes mathématiques sont utilisées dans l'étude des structures spatiales (variogrammes et indices non paramétriques). Trois modèles différents apparaissent : agrégats (Qualea rosea Aublet), plaques (Eperua falcata Aublet), paquets (Symphonia globulifera Linnaeus f). Ces structures sont en rapport avec la répartition des arbres adultes. Les interactions entre ces deux strates sont décrites, les semenciers pouvant accentuer la mortalité des régénérations à leur proximité. Le milieu exerce également une action sur la répartition des espèces, en particulier la topographie et la fréquence des chablis. Les structures en plaques observées pour Eperua falcata Aublet définissent un type de peuplement à renouvellement rapide, localisé sur les milieux les plus pauvres. Natural regeneration of rainforest in French Guyana: spatial distribution of 3 species, Qualea rosea Aublet, Eperua falcata Aublet, Symphonia globulifera Linnaeus f. A natural regeneration survey concerning a systematic sampling of 1% of the area was carried out from 1986 to 1988 on 33 species from the French Guyana rainforest in the Paracou sylviculture and research area. The present study has focused on spatial distribution modeling of 3 species: Qualea rosea Aublet, Eperua falcata Aublet and Symphonia globulifera Linnaeus f. Abundance and dispersion parameters were as follows: seedling density, relative precision, dispersion index. The latter showed the presence of clusters. Two mathematical methods were applied for spatial structure (variograms and non-parametric indices). Three different patterns were found: tight agregates, loose agregates and patches. These structures were related to mature tree distribution. It was found that interaction between mature trees and young seedlings could lead to partial mortality of seedlings. Species distribution was also related to environment, particularly topography and frequency of gaps. The patch structure observed for Eperua falcata Aublet corresponded to the rapid "turnover rate" focused on the poorest sites.
Rate of herbivory and defensive characteristics of young and mature leaves were measured for saplings of 46 canopy tree species in a lowland tropical rain forest (Barro Colorado Island, Panama). Grazing rates were determined in the field for sample periods in the early wet, late wet, and dry seasons. Leaf properties such as pubescence, toughness, water, protein, fiber, and phenolic contents explained over 70% of the variation among plant species in the rates of herbivory on mature leaves. Leaf toughness was most highly correlated with levels of herbivory, followed by fiber content and nutritive value. Phenol content and phenol : protein ratios were not significantly correlated with damage. Journal Article
Thesis (Ph. D.)--University of Washington, 1994. Vita. Includes bibliographical references (p. [306]-327).
Libro de texto sobre la estadística de los datos espaciales, dirigido a científicos e ingenieros.
According to the Janzen-Connell hypothesis for the maintenance of species diversity, recruitment is inhibited in the immediate vicinity of adults by herbivores and pathogens. This reduces the per capita ability of abundant species to reproduce, relative to less common species, and gives rare or competitively inferior species a greater chance to persist. We tested this hypothesis in a 50-ha mapped plot of tropical moist forest on Barro Colorado Island, Panama, by investigating the spatial patterns of sapling recruitment in 80 species of trees and shrubs. Two censuses of adults and saplings were carried out, in 1982 and in 1985. Recruits were defined as saplings of 1-8 cm dbh (diameter breast height) appearing in the 1985 census that were not present in 1982. The distance from each recruit to its nearest conspecific adult neighbor was measured. At various distances from adults, the number of conspecific recruits and the number of recruits of all species were tallied. The ratio of recruits of species i to all recruits was taken as an estimate of the probability that species i would occupy that site as an adult. A few species showed a significant reduction in recruitment probability close to adults, but more species showed a significant increase, and many other species showed no significant spatial pattern. Among canopy trees, about a third of the species showed some sign of local reduction in recruitment, but the distance over which the effect extended was usually less than 5 m; however, the most abundant canopy tree, Trichilia tuberculata, showed a sharp reduction in recruitment probability up to 10 m from adults. In treelets and shrubs, most species showed strong peaks in recruitment probability close to adults. Thus, most recruitment patterns did not fit the prediction of Janzen and Connell; however, two to three of the most common species may have reached densities at which a depression in local recruitment is regulating abundance.
Factors related to seedling growth in a boreal scots pine stand: a spatial analysis of vegetation-soil system. Canad Horizontal structure of uneven-aged mixed species forests modeled as an Inhomogeneous Poisson process
- T Kuuluvainen
- T J Hokkanen
- Ja Èvinen
- E Pukkala
- T Maguire
- D Batista
- J L F Mckenzie
Kuuluvainen, T., Hokkanen, T.J., Ja Èvinen, E., Pukkala, T., 1993. Factors related to seedling growth in a boreal scots pine stand: a spatial analysis of vegetation-soil system. Canad. J. For. Res. 23, 2101±2109. Maguire, D., Batista, J.L.F., McKenzie, D., 1993. Horizontal structure of uneven-aged mixed species forests modeled as an Inhomogeneous Poisson process. In: Reynolds, K. (Ed.). Proc. IUFRO S4.11 Conf. on Stochastic Spatial Models in Forestry. University of Greenwich, Thessaloniki, Greece, pp. 163±170.
All trees with DBH<10 cm and DBH>80 cm were removed, as well as 30% of the remaining basal area, starting from the largest residual trees
- Lower
- Upper
Lower and upper cut: All trees with DBH<10 cm and DBH>80 cm were removed, as well as 30% of the remaining basal area, starting from the largest residual trees.
Marked point process in forest statistics Modelling spatial pattern Spatial patterns and dynamics of woody vegetation in an arid savanna
- A Penttinen
- D Stoyan
- H M Henttonen
- ±
- B Ripley
Penttinen, A., Stoyan, D., Henttonen, H.M., 1992. Marked point process in forest statistics. For. Sci. 38(4), 806±824. Ripley, B., 1977. Modelling spatial pattern. J. Roy. Statist. Soc. 39, 172±242. Rizzini, C.T., 1979. Tratado de Fitogeografia do Brasil. Higitec/ Universidade de Sa Äo Paulo, Sa Äo Paulo. Skarpe, C., 1991. Spatial patterns and dynamics of woody vegetation in an arid savanna. J. Veg. Sci. 2, 565±572.
A spatial model of forest dynamics Spacing dynamics of a tropical rain forest trees: evaluation of the Janzen±Connell model Herbivory and defensive characteristics of tree species in a lowland tropical forest
- R Busing
Busing, R., 1991. A spatial model of forest dynamics. Vegetatio 92, 167±179. Clark, D.A., Clark, D.B., 1994. Spacing dynamics of a tropical rain forest trees: evaluation of the Janzen±Connell model. Am. Naturalist 124(6), 769±788. Coley, P.D., 1983. Herbivory and defensive characteristics of tree species in a lowland tropical forest. Ecol. Monogr. 53(2), 209± 233.