Environmental Filtering and Positive Plant Litter Feedback Simultaneously Explain Correlations Between Leaf Traits and Soil Fertility
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- Laughlin, D.C., Richardson, S.J., Wright, E.F. et al. Ecosystems (2015) 18: 1269. doi:10.1007/s10021-015-9899-0
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Plant traits covary with soil fertility, but determining whether this is the outcome of environmental filtering or plant feedback is not straightforward, especially in long-lived plant communities such as rain forests. Without explicitly accounting for the potential of plant litter to influence soil properties, it is difficult to interpret with confidence that covariation between soil nutrients and plant traits is the outcome of environmental filtering. We estimated abundance-weighted mean leaf dry matter content (LDMC), senesced leaf litter nitrogen resorption proficiency (litter N %), wood tissue density, and multiple metrics of soil fertility (pH, C:N ratio, and organic P concentrations) on 241 temperate rain forest plots throughout New Zealand. A non-recursive structural equation model indicated that environmental filtering and plant litter feedback were equally important reciprocal processes that explain covariation between leaf traits and soil fertility. Plant communities with high resorption proficiency, high LDMC, and high stem tissue density were strongly associated with low-fertility soils. Both structural (LDMC) and chemical (litter N %) leaf traits influenced soil fertility, but stem tissue density did not exhibit feedback effects. Here, we show that it is not a matter of ‘either–or’ when determining the relative importance of environmental filtering and plant feedback, but rather that both processes are equally important and occur simultaneously in temperate forest ecosystems. Although both leaf and wood traits were filtered by soil fertility, only leaf traits exhibited significant feedback effects on soil fertility.