Analyzing the spatial structure of a Sri Lankan tree species with multiple scales of clustering.

Clustering at multiple critical scales may be common for plants since many different factors and processes may cause clustering. This is especially true for tropical rain forests for which theories explaining species coexistence and community structure rest heavily on spatial patterns. We used point pattern analysis to analyze the spatial structure of Shorea congestiflora, a dominant species in a 25-ha forest dynamics plot in a rain forest at Sinharaja World Heritage Site (Sri Lanka), which apparently shows clustering at several scales. We developed cluster processes incorporating two critical scales of clustering for exploring the spatial structure of S. congestiflora and interpret it in relation to factors such as competition, dispersal limitation, recruitment limitation, and Janzen-Connell effects. All size classes showed consistent large-scale clustering with a cluster radius of approximately 25 m. Inside the larger clusters, small-scale clusters with a radius of 8 m were evident for recruits and saplings, weak for intermediates, and disappeared for adults. The pattern of all trees could be divided into two independent patterns: a random pattern (nearest neighbor distance > 8 m) comprising approximately 12% of the trees and a nested double-cluster pattern. This finding suggests two independent recruitment and/or seed dispersal mechanisms. Saplings were several times as abundant as recruits and may accumulate several recruit generations. Recruits were only weakly associated with adults and occupied about half of the large-scale clusters, but saplings almost all. This is consistent with recruitment limitation. For approximately 70% (95%) of all juveniles the nearest adult was less than 26 m away (53 m), suggesting a dispersal limitation that may also be related to the critical large-scale clustering. Our example illustrates the manner in which the use of a specific and complex null hypothesis of spatial structure in point pattern analysis can help us better understand the biology of a species and generate specific hypotheses to be further investigated in the field.

[1]  Stephen J. Wright,et al.  Light-Gap disturbances, recruitment limitation, and tree diversity in a neotropical forest , 1999, Science.

[2]  Aubière Cedex,et al.  Avoiding misinterpretation of biotic interactions with the intertype K 12 -function: population independence vs. random labelling hypotheses , 2003 .

[3]  Thorsten Wiegand,et al.  Extending point pattern analysis for objects of finite size and irregular shape , 2006 .

[4]  A. Baddeley,et al.  Non‐ and semi‐parametric estimation of interaction in inhomogeneous point patterns , 2000 .

[5]  T. Whitmore,et al.  On the influence of soil properties on species distribution in a Malayan lowland Dipterocarp rain forest. , 1970 .

[6]  Stephen P. Hubbell,et al.  Diversity of canopy trees in a neotropical forest and implications for conservation , 1983 .

[7]  D. Stoyan,et al.  Fractals, random shapes and point fields : methods of geometrical statistics , 1996 .

[8]  J. Silvertown,et al.  Community structure in a desert perennial community , 1994 .

[9]  S. Levin.  The problem of pattern and scale in ecology , 1992 .

[10]  M. Crawley.  The Structure of Plant Communities , 2009 .

[11]  B. Abeywickrama,et al.  Flora of Ceylon@@@A Revised Handbook to the Flora of Ceylon , 1974 .

[12]  B. Ripley.  Modelling Spatial Patterns , 1977 .

[13]  Dietrich Stoyan,et al.  Estimating Pair Correlation Functions of Planar Cluster Processes , 1996 .

[14]  S. Hubbell,et al.  Spatial patterns in the distribution of tropical tree species. , 2000, Science.

[15]  Tropical Rain Forests of the Far East. , 1985 .

[16]  P. Ashton,et al.  Ecological studies in the mixed dipterocarp forests of Brunei state , 1967 .

[17]  M. Turner,et al.  LANDSCAPE ECOLOGY : The Effect of Pattern on Process 1 , 2002 .

[18]  Douglas A. Maguire,et al.  Modeling the spatial structure of topical forests , 1998 .

[19]  D. Janzen.  Herbivores and the Number of Tree Species in Tropical Forests , 1970, The American Naturalist.

[20]  Kyle E. Harms,et al.  Pervasive density-dependent recruitment enhances seedling diversity in a tropical forest , 2000, Nature.

[21]  W. Bossert,et al.  Habitat heterogeneity and niche structure of trees in two tropical rain forests , 2004, Oecologia.

[22]  Robert Haining,et al.  Statistics for spatial data: by Noel Cressie, 1991, John Wiley & Sons, New York, 900 p., ISBN 0-471-84336-9, US $89.95 , 1993 .

[23]  J. Connell.  On the role of the natural enemies in preventing competitive exclusion in some marine animals and in rain forest trees , 1971 .

[24]  Kevin J Gaston,et al.  Estimating Species Abundance from Occurrence , 2000, The American Naturalist.

[25]  M. Thomas.  A generalization of Poisson's binomial limit for use in ecology. , 1949, Biometrika.

[26]  Erkki Tomppo.  Models and methods for analysing spatial patterns of trees. , 1986 .

[27]  M. S. Bartlett,et al.  The spectral analysis of two-dimensional point processes , 1964 .

[28]  P. Grubb.  THE MAINTENANCE OF SPECIES‐RICHNESS IN PLANT COMMUNITIES: THE IMPORTANCE OF THE REGENERATION NICHE , 1977 .

[29]  P. Dixon.  Ripley's K Function , 2006 .

[30]  D. Burslem,et al.  Species–habitat associations in a Sri Lankan dipterocarp forest , 2006, Journal of Tropical Ecology.

[31]  S. Hubbell,et al.  A unified theory of biogeography and relative species abundance and its application to tropical rain forests and coral reefs , 1997, Coral Reefs.

[32]  J. Møller,et al.  Statistical Inference and Simulation for Spatial Point Processes , 2003 .

[33]  Zhe Jiang,et al.  Spatial Statistics , 2013 .

[34]  Jérôme Chave,et al.  Cluster Analysis of Spatial Patterns in Malaysian Tree Species , 2002, The American Naturalist.

[35]  Frank M. Schurr,et al.  Spatial pattern formation in semi-arid shrubland: a priori predicted versus observed pattern characteristics , 2004, Plant Ecology.

[36]  S. Levin.  THE PROBLEM OF PATTERN AND SCALE IN ECOLOGY , 1992 .

[37]  R. Pélissier,et al.  Avoiding misinterpretation of biotic interactions with the intertype K12-function: population independence vs. random labelling hypotheses , 2003 .

[38]  T. Wiegand,et al.  Spatial ecology of a root parasite – from pattern to process , 2007 .

[39]  P. Ashton,et al.  Speciation among tropical forest trees: some deductions in the light of recent evidence , 1969 .

[40]  J. Plotkin,et al.  Species-area curves, spatial aggregation, and habitat specialization in tropical forests. , 2000, Journal of theoretical biology.

[41]  C. Wills,et al.  Similar non–random processes maintain diversity in two tropical rainforests , 1999, Proceedings of the Royal Society of London. Series B: Biological Sciences.

[42]  J. Proctor,et al.  Tropical Rain Forests of the Far East. , 1977 .

[43]  Jessica Gurevitch,et al.  Integrating the Statistical Analysis of Spatial Data in Ecology , 2022 .

[44]  B. Ripley.  The Second-Order Analysis of Stationary Point Processes , 1976 .

[45]  Thorsten Wiegand,et al.  Rings, circles, and null-models for point pattern analysis in ecology , 2004 .