Effect of soil heterogeneity and endogenous processes on plant spatial structure

Abstract

Within communities, organisms potentially self‐organize through endogenous processes that create nonrandom spatial structure as they interact with one another or modify the abiotic environment. In contrast, exogenous processes such as environmental heterogeneity or variable immigration are thought to be dominant processes controlling these spatial patterns. Although both endogenous and exogenous processes likely occur, their relative importance is still largely unknown because of limited analytical tools and the lack of experimental evidence, particularly those that address exogenous sources of environmental heterogeneity. Here, we used a soil heterogeneity experiment to examine the relative effect of endogenous and exogenous processes on plant spatial structure after five years of community assembly. Soil heterogeneity was manipulated by splitting the vertical soil profile into three soil‐types that were randomly assigned to 40 × 40 cm patches within 2.4 × 2.4 m plots. Homogeneous plots were created by mixing all soils before filling each patch. Thirty‐four grassland species were then sown into all plots and allowed to grow for five years after which the location of all plants was mapped using a 5 × 5 cm grid. Results from point‐pattern spatial analysis indicated that, even in the absence of soil heterogeneity and with initial seed arrival, spatial structure was primarily generated by endogenous processes. Although soil heterogeneity increased species aggregation at certain scales, most of the spatial structure was created by endogenous processes. These results suggest that endogenous processes may be more important than expected for generating spatial structure and can develop much faster than anticipated.

Analysing and modelling spatial patterns to infer the influence of environmental heterogeneity using point pattern analysis, individual-based simulation modelling and landscape metrics

“…Abiotic and biotic processes were shown to act simultaneously and to interact in many plant populations (e.g. Adler et al, 2007;Chase and Myers, 2011;Chisholm and Pacala, 2010; Filho et al, 2012;Furniss et al, 2017;Getzin et al, 2008;John et al, 2007;Legendre et al, 2009;Mitchell et al, 2017;Schouten and Houseman, 2019;Shen et al, 2013;van Waveren, 2016). Because both abiotic and biotic processes can result in similar spatial patterns of individuals, it can be challenging, yet not impossible, to study the relative importance of biotic and abiotic processes and disentangle possible interactions.…”

“…Because both abiotic and biotic processes can lead to similar spatially clustered patterns, there is a long-lasting and ongoing discussion about the relative importance of the two contrasting processes and how to disentangle them in plant populations (e.g. Adler et al, 2007;Chase and Myers, 2011;Chisholm and Pacala, 2010;Diniz-Filho et al, 2012;Furniss et al, 2017;John et al, 2007;Legendre et al, 2009;Mitchell et al, 2017;Schouten and Houseman, 2019). While biotic processes including competition (Coates et al, 2009;Wang et al, 2010a), limited seed dispersal (Martínez and González-Taboada, 2009) ENVIRONMENTAL…”

“…There are several methods to analyse the influence of abiotic processes and possible interactions with biotic processes, including analytical approaches (Chisholm and Pacala, 2010), spatial autocorrelation analysis (Diniz-Filho et al, 2012), species-habitat associations analysis (Furniss et al, 2017;Harms et al, 2001), principle coordinates of neighbour matrices (Legendre et al, 2009), linear regression models (Mitchell et al, 2017), point pattern analysis (Ramon et al, 2018;Shen et al, 2013) or experimental setups (Schouten and Houseman, 2019). Many methods have in common that conclusions about the acting processes are based on descriptive and inferential analyses of observed field data.…”

Tales from the underground: Soil heterogeneity and not only above‐ground plant interactions explain fine‐scale species patterns in a Mediterranean dwarf‐shrubland

“…Contradicting this conceptual framework, recent studies suggest that soil heterogeneity may affect plant distribution at the same spatial scales where biotic interactions take place (Luzuriaga, González, & Escudero, 2015; Mudrák et al, 2016; Schouten & Houseman, 2019; Tamme, Gazol, Price, Hiiesalu, & Pärtel, 2016). Indeed, strong relationships between soil variation and species distribution at relatively fine scales have been found in tropical forests (Baldeck et al, 2013; Chang, Zelený, Li, Chiu, & Hsieh, 2013; John et al, 2007; Xia, Chen, Schaefer, & Detto, 2015), and some authors have shown the effects of fine‐scale environmental heterogeneity on plant responses (Hutchings, John, & Stewart, 2000).…”

“…Indeed, strong relationships between soil variation and species distribution at relatively fine scales have been found in tropical forests (Baldeck et al, 2013; Chang, Zelený, Li, Chiu, & Hsieh, 2013; John et al, 2007; Xia, Chen, Schaefer, & Detto, 2015), and some authors have shown the effects of fine‐scale environmental heterogeneity on plant responses (Hutchings, John, & Stewart, 2000). Note, however, that plants can also modify soil conditions generating fine‐scale spatial or temporal heterogeneity (Ehrenfeld, Ravit, & Elgersma, 2005; van Breemen, 2013), whose effect, without experimental studies, cannot be separated of heterogeneity caused directly by the soil abiotic factors (Schouten & Houseman, 2019). Therefore, until recently, neither the effects of fine‐scale environmental, and particularly soil, heterogeneity on community assembly (Baldeck et al, 2013; Letten, Keith, Tozer, & Hui, 2015; Tamme et al, 2016) nor their role on the spatial distribution of individual species within the community have been explicitly considered (Shen et al, 2013; Xia et al, 2015).…”