Experimental evidence that the Ornstein-Uhlenbeck model best describes the evolution of leaf litter decomposability.

Xu Pan,Andreas Prinzing,Johannes H C Cornelissen,Guo-Fang Liu,William K Cornwell,Wei-Wei Zhao,Yu-Kun Hu,Ming Dong

doi:10.1002/ece3.1115

Abstract

Leaf litter decomposability is an important effect trait for ecosystem functioning. However, it is unknown how this effect trait evolved through plant history as a leaf ‘afterlife’ integrator of the evolution of multiple underlying traits upon which adaptive selection must have acted. Did decomposability evolve in a Brownian fashion without any constraints? Was evolution rapid at first and then slowed? Or was there an underlying mean-reverting process that makes the evolution of extreme trait values unlikely? Here, we test the hypothesis that the evolution of decomposability has undergone certain mean-reverting forces due to strong constraints and trade-offs in the leaf traits that have afterlife effects on litter quality to decomposers. In order to test this, we examined the leaf litter decomposability and seven key leaf traits of 48 tree species in the temperate area of China and fitted them to three evolutionary models: Brownian motion model (BM), Early burst model (EB), and Ornstein-Uhlenbeck model (OU). The OU model, which does not allow unlimited trait divergence through time, was the best fit model for leaf litter decomposability and all seven leaf traits. These results support the hypothesis that neither decomposability nor the underlying traits has been able to diverge toward progressively extreme values through evolutionary time. These results have reinforced our understanding of the relationships between leaf litter decomposability and leaf traits in an evolutionary perspective and may be a helpful step toward reconstructing deep-time carbon cycling based on taxonomic composition with more confidence.

Highlights

Leaf litter decomposition is a key process in terrestrial ecosystems, as it regulates carbon and nutrient recycling in the soil (Berg and Laskowski 2005) and releases CO2 back to the atmosphere and controls the carbon fluxes between the biosphere and atmosphere (Sitch et al 2003; Cornwell et al 2008)
We found that species traits were good predictors (Table 1, Fig. 1) for k based on the results of either multiple regression or simple regression analysis
We found the phylogenetic half-life for leaf litter decomposability to be relatively short, but it is possible that half-life would be much longer if one considered comprehensively a much larger clade such as the entire spermatophytes, In that case numerous Gymnosperms would be included besides Angiosperms and the ancient differentiation of decomposability between these two groups would strongly influence the calculated half-life time

Summary

Introduction

Leaf litter decomposition is a key process in terrestrial ecosystems, as it regulates carbon and nutrient recycling in the soil (Berg and Laskowski 2005) and releases CO2 back to the atmosphere and controls the carbon fluxes between the biosphere and atmosphere (Sitch et al 2003; Cornwell et al 2008). It is well known that variation in leaf litter decomposability among extant plant species depends on a set of leaf traits, which determine rates a 2014 The Authors. The Evolution of Leaf Litter Decomposability and mechanisms of leaf litter decomposition of different species at present (Cornelissen 1996; Cornwell et al 2008; Zhang et al 2008). While we can assume similar mechanisms have operated in the past, little is known about how leaf litter decomposability changed through plant evolutionary history and whether and how such changes in leaf litter decomposability related to the evolution of multiple leaf traits

Methods

Results

Discussion

Conclusion