Root functional parameters along a land‐use gradient: evidence of a community‐level economics spectrum

Abstract

1. There is a fundamental trade-off between leaf traits associated with either resource acquisition or resource conservation. This gradient of trait variation, called the economics spectrum, also applies to fine roots, but whether it is consistent for coarse roots or at the plant community level remains untested. 2. We measured a set of morphological and chemical root traits at a community level (functional parameters; FP) in 20 plant communities located along land-use intensity gradients and across three climatic zones (tropical, mediterranean and montane). We hypothesized (i) the existence of a root economics spectrum in plant communities consistent within root types (fine, < 2 mm; coarse, 2-5 mm), (ii) that variations in root FP occur with soil depths (top 20 cm of soil and 100-150 cm deep) and (iii) along land-use gradients. 3. Root FP covaried, in line with the resource acquisition-conservation trade-off, from communities with root FP associated with resource acquisition (e.g. high specific root length, SRL; thin diameters and low root dry matter contents, RDMC) to root FP associated with resource conservation (e.g. low SRL, thick diameters and high RDMC). This pattern was consistent for both fine and coarse roots indicating a strong consistency of a trade-off between resource acquisition and conservation for plant roots. 4. Roots had different suites of traits at different depths, suggesting a disparity in root function and exploitation capacities. Shallow, fine roots were thinner, richer in nitrogen and with lower lignin concentrations associated with greater exploitation capacities compared to deep, fine roots. Shallow, coarse roots were richer in nitrogen, carbon and soluble concentrations than deep, coarse roots. 5. Fine root parameters of highly disturbed, herbaceous-dominated plant communities in poorer soils were associated with foraging strategies, that is greater SRL and lower RDMC and lignin concentration than those from less disturbed communities. Coarse roots, however, were less sensitive to the land-use gradient. 6. Synthesis. This study demonstrates the existence of a general trade-off in root construction at a community level, which operates within all root types, suggesting that all plant tissues are controlled by the trade-off between resource acquisition and conservation.

High organic inputs explain shallow and deep SOC storage in a long-term agroforestry system – combining experimental and modeling approaches

“…Each transect was made up of three subplots, 2 m north from the tree, 2 m south from the tree, and 6.5 m from the tree (middle of the alley). In March 2012, a 2 m deep pit was opened in the agricultural control plot (Prieto et al, 2015), and the root biomass was quantified to the maximum rooting depth (1.5 m). The root : shoot ratio of durum wheat was measured in the control plot.…”

Fine-root trait plasticity of beech (Fagus sylvatica) and spruce (Picea abies) forests on two contrasting soils

“…On the one hand, following the resource economics hypothesis (Grime 1977;Craine 2009), poor soils select for species with thick fine-roots that live long, so that valuable plant resources are conserved (Eissenstat and Yanai 1997;Aerts and Chapin 2000;Wahl and Ryser 2000;Pérez-Ramos et al 2012;Reich 2014); such relationships between fine-root traits and the soil environment might also exist within species. A contrasting hypothesis, however, predicts thinner fine-roots on poor soils, because these roots grow fast and can more efficiently exploit the soil for resources (Eissenstat 1992;Ryser and Lambers 1995;Eissenstat and Yanai 1997;Ostonen et al 2007b;Holdaway et al 2011;Prieto et al 2015). Both hypotheses have been corroborated and refuted with empirical data (e.g.…”

Root structure–function relationships in 74 species: evidence of a root economics spectrum related to carbon economy

“…Experimental evidence of such an acquisitionconservation trade-off for fine roots across species is missing as a consequence of the scarcity of data related to root functioning and in particular with regard to resource acquisition and life span. Recent multivariate comparative root studies have generally focused on covariation of morphological and chemical fine-root traits (Chen et al, 2013;Fort et al, 2013Fort et al, , 2015Kong et al, 2014;Prieto et al, 2015), but how these syndromes are related to root functioning remains poorly understood. In a recent review, Reich (2014) suggested the existence of an RES representing a trade-off between root growth and persistence in fine roots.…”