Functional Matrix: A Conceptual Framework for Predicting Multiple Plant Effects on Ecosystem Processes

Abstract

▪ Abstract Plant species differ in how they influence many aspects of ecosystem structure and function, including soil characteristics, geomorphology, biogeochemistry, regional climate, and the activity and distribution of other organisms. Attempts to generalize plant species effects on ecosystems have focused on single traits or suites of traits that strongly covary (functional groups). However, plant effects on any ecosystem process are mediated by multiple traits, and many of these traits vary independently from one another. Thus, most species have unique combinations of traits that influence ecosystems, and there is no single trait or functional-group classification that can capture the effects of these multiple traits, or can predict the multiple functions performed by different plant species. We present a new theoretical framework, the functional matrix, which builds upon the functional group and single trait approaches to account for the ecosystem effects of multiple traits that vary independently among species. The functional matrix describes the relationship between ecosystem processes and multiple traits, treating traits as continuous variables, and determining if the effects of these multiple traits are additive or interactive. The power of this approach is that the ecosystem effects of multiple traits are the underlying mechanisms determining species effects, how the effects of an individual species change across seasons and under varying environmental conditions, the nonadditive effects of plant species mixtures, and the effects of species diversity.

Tree patch distribution drives spatial heterogeneity of soil traits in cork oak woodlands

“…Oak savannas have been established through the thinning of the natural oak forest, and they are characterized by a sparse tree cover and a diversity of understory vegetation that ranges from shrubs to grasses (Olea and San Miguel-Ayanz 2006). Under this structure, scattered oaks have a positive effect on chemical and physical soil fertility by the accumulation of organic matter (Eviner and Chapin 2003;Gallardo 2003;Rhoades 1997) and improving soil moisture, water availability and soil enzyme activity (Gallardo et al 2000;Garcia et al 2002). This spatial pattern allows the coexistence of plant species with different competition abilities (Ludwig et al 2004;Moreno et al 2005 and ultimately improves the production, quality, and diversity of herbaceous species (Marañón 1986).…”

“…We did not find any relationship between tree cover and soil texture. The main effect of trees on soil structure is due to root disaggregation of rock fragments; thus, differences in belowground traits such as root morphology, C inputs, or associated soil biota are more likely to be related with the heterogeneity of soil texture than the mere presence of trees (Eviner and Chapin 2003).…”

Comment les arbres affectent-ils l’hétérogénosité spatio-temporelle du cycle des nutriments dans une prairie méditerranénne annuelle?

“…The nutrient content of upper soil organic matter (OM) increases below the canopy along with total nitrogen (N), calcium (Ca), potassium (K) and magnesium (Mg), although the results of previous studies differ as regards the effect of trees on variables such as soil pH or phosphorus (P) content (e.g. Eviner and Chapin III, 2003;Ludwig et al, 2001;Rhoades, 1997). Trees reduce solar radiation availability to understory vegetation as trees intercept light.…”

“…biomass, nutrients, etc). These interactions affect biogeochemical cycles (Eviner and Chapin III, 2003) and therefore influence not only plant growth and distribution but also livestock and wildlife management, and even greenhouse gas (GHG) cycles, as in the case of N or C. Explaining the variation in the levels of certain elements is not an easy task since the nutrient cycle may differ according to a number of factors such as plant community type (e.g. annuals, perennials), climate or soil bedrock (Ludwig et al, 2001;Rodá et al, 1999).…”

Plant Colonizers Shape Early N-dynamics in Gopher-mounds

“…Plant species differ in the amount and form of N they take up (Aerts and Chapin, 2000), and these speciesspecific patterns of uptake modify the pools of N available to soil microbes and to other plants (Jackson et al, 1989;Jaeger et al, 1999a;Stark and Hart, 1997). Plants also indirectly affect N dynamics through their influence on microbial activity (Bardgett and Shine, 1999;Hobbie, 1992;Jackson et al, 1988) via root exudation, above-and below-ground litter inputs, and effects on microclimate (Eviner and Chapin, 2003b;Hodge et al, 1998;Jaeger et al, 1999b). While the effects of litter quantity and quality are not apparent until litter accumulates and decomposes in the soil (Jingguo and Bakken, 1997;Vinton and Burke, 1995), root exudates and species effects on microclimate may affect the soil microbial community from the early stages of plant growth.…”