Soil resource availability shapes community trait structure in a species‐rich dipterocarp forest

Abstract

Summary 1.Habitat filtering and limiting similarity have been proposed as two opposing forces structuring community memberships. Community assembly theory proposes habitat filtering as a mechanism restricting community membership according to the ecological strategies of species in a given environment. Limiting similarity posits that some species exclude others that are ecologically similar. 2. We quantified nine ecophysiological and life-history traits for 80 dipterocarp species in the 52-ha Lambir Forest Dynamics Plot (FDP; Lambir Hills National Park, Sarawak, Malaysia). We studied forests on four soil types differing in fertility and moisture, focusing on soil resource availabilities as environmental determinants of habitat filtering processes. We used a null-model approach to detect the strengths of habitat filtering and limiting similarity. We quantified the relative contributions of soil resources (nutrients and water) to habitat filtering by comparing the strength of habitat filtering processes (i.e. effect sizes) at the overall plot scale and at the individual soil-type scale. We also compared the strengths of assembly processes among soil types. 3. Compared to a null model at microscale (20 · 20 m), trait range and variance were reduced for seven of nine functional traits, suggesting the importance of habitat filtering in the dipterocarp community. We also found a broader distribution of five traits, and more even spacing for seven traits (20 · 20 m), which is consistent with the concept of limiting similarity. Randomizations that swapped species occurrences within soil types (i.e. null models removing soil effects in assembly processes) were much closer to observed values, and there were no phylogenetic constraints on habitat association. Hence, soil resource availability acted as a habitat filtering mechanism in the FDP; relative contributions to habitat filtering ranged from 35% for seed mass to 77% for relative growth rate. Furthermore, soil types apparently affected the strengths of habitat filtering and limiting similarity. 4. Synthesis. We demonstrate that soil resource availability is a crucial determinant of habitat filtering in this species-rich tropical rain forest; the strengths of assembly processes differed among soil types. Variation in soil resource availability can shape the distribution of traits through community assembly processes, promoting trait diversification and species coexistence.

Temperate rain forest species partition fine-scale gradients in light availability based on their leaf mass per area (LMA)

“…The different patterns observed in the two forest types in this study suggest that functional traits may mediate species coexistence according to the limiting factors of a given site: light in temperate rain forests and probably soil moisture in Mediterranean forests. Our findings are in accordance with the results of other studies showing significant relationships between LMA and other leaf traits and patterns of species abundance or occurrence at much coarser spatial scales (Katabuchi et al, 2012;Laurans et al, 2012;Mason et al, 2012). Previous studies have also shown that species' leaf traits in a given community vary significantly across light environments (e.g.…”

The Influence of Variable Rainfall Frequency on Germination and Early Growth of Shade-Tolerant Dipterocarp Seedlings in Borneo

“…Large-seeded species may preferentially establish in wetter areas which sustain consistent soil moisture such as lowland riparian zones, and small-seeded species may persist in sites with well-drained soils which have a more fluctuating water table. Recent work done in Lambir Hills National Park, Sarawak, Malaysia found an increase in mean seed mass along a soil moisture and fertility gradient with the largest seed masses found on fine clayey soil textures [41], which supports our seed size-sensitivity relationship.…”

Environmental factors predict community functional composition in Amazonian forests

“…terra firme forests). Our study thus extends on previous research showing the importance of environmental filtering in tropical forests (ter Steege et al 2006;Engelbrecht et al 2007;Kraft, Valencia & Ackerly 2008;Paine et al 2011;Katabuchi et al 2012) to demonstrate that environmental gradients underlie directional shifts in community functional composition across lowland Amazonian forests.…”

“…Kraft, Valencia & Ackerly 2008;Cornwell & Ackerly 2009;Ingram & Shurin 2009). Several recent studies have specifically used functional traits to demonstrate the importance of environmental filtering in determining the assembly of species-rich tropical forests (ter Steege et al 2006;Engelbrecht et al 2007;Kraft, Valencia & Ackerly 2008;Swenson & Enquist 2009;Paine et al 2011;Katabuchi et al 2012). However, these studies included only a few functional traits (ter Steege et al 2006) or species (Engelbrecht et al 2007), or covered relatively small areas (Kraft, Valencia & Ackerlybetter understanding of this issue is critical to improve predictions of the response of community functional composition and associated ecosystem functioning to global change (Lavergne et al 2010;Reu et al 2011).…”