DOI: 10.5061/dryad.cz8w9gj0d
title: Data from: Neighbourhood-dependent root distributions and the consequences on root separation in arid ecosystems

description: 1. Inter-specific root separation is an important example of spatial niche
 differentiation that drives species coexistence in many ecosystems.
 Particularly under water-stressed conditions, it is believed to be an
 inevitable outcome of species interactions. However, evidence for and
 against this idea has been found. So far, studies aiming at reconciling
 the debate mainly focus on abiotic determinants. It remains unclear if and
 to what extent root separation depends on the type and growth form of
 interacting plants. 2. We conducted a detailed field study in three
 adjacently located (with pairwise distances &lt; 500 m) arid patchy
 communities where a common tussock grass species Achnatherum splendens
 grew in association with either a tree (Elaeagnus angustifolia), a shrub
 (Nitraria tangutorum) or a perennial forb species (Sophora alopecuroides).
 In each community, roots and soils were sampled along the soil layers from
 five depths (0-10, 10-30, 30-60, 60-100 and 100-150 cm) in the patches and
 in the adjacent bare ground outside the patches. 3. Significant vertical
 inter-specific root separation occurred in the species-association patches
 of tree-grass and forb-grass communities, but not in the shrub-grass
 community. As the neighbour changed going from trees to shrubs and to
 forbs, rooting profiles of the grass Achnatherum became progressively
 deeper, with progressively less roots allocated in the upmost 10 cm soil
 layer and more in the subsequent two layers. After controlling for the
 differences in soil water and nutrient conditions among the three
 communities, the effects of neighbour type on grass rooting profiles
 remained robust. 4. Synthesis. We found that the root distributions of
 plants in the dryland strongly depend on the type of neighbour plants,
 which can, at least partially, determine the extent of inter-specific root
 separation at the community scale. Our work poses new questions about
 plasticity in root distribution and helps to better understand species
 interactions and coexistence under stressful conditions.
description: The data sheet contains eight columns. They are
 <strong>community</strong>,
 <strong>replicate</strong>,
 <strong>position</strong>, <strong>layer</strong>,
 <strong>groots</strong>, <strong>nroots</strong>,
 <strong>som</strong> and
 <strong>swc</strong>. 
 <strong>community</strong>: 'TG', tree-grass
 community; 'SG', shrub-grass community; 'FG',
 forb-grass community. 
 <strong>replicate</strong> (i.e. the patch replicate in the
 communities): take 'TGR1' for example, it means patch
 replicate 1 in the tree-grass community. 
 <strong>position</strong> (i.e. the position of soil
 monolith): 'in', the soil monolith inside the patch;
 'out', the soil monolith in the adjacent bare ground outside the
 patch. <strong>layer</strong> (i.e. soil
 layer): 'L1', 0-10 cm; 'L2', 10-30 cm; 'L3',
 30-60 cm; 'L4', 60-100 cm; 'L5', 100-150
 cm. <strong>groots</strong>, i.e. grass
 root mass (g). <strong>nroots</strong>,
 i.e. fine root mass (g) of the woody-tap-root-system neighbours (i.e.
 <em>Elaeagnus</em> in the tree-grass community,
 <em>Nitraria</em> in the shrub-grass community, and
 <em>Sophora</em> in the forb-grass community).
 <strong>som</strong>, i.e. soil organic matter
 content (g·kg<sup>-1</sup>). 
 <strong>swc</strong>, i.e. soil water content
 (g·cm<sup>-3</sup>).