title: Do shallow soil, low water availability, or their combination increase the competition between grasses with different root systems in karst soil?
abstract: Uneven soil depth and low water availability are the key limiting factors to vegetation restoration and reconstruction in limestone soils such as in vulnerable karst regions. Belowground competition will possibly increase under limited soil resources. Here, we investigate whether low resource availability (including shallow soil, low water availability, and shallow soil and low water availability combined) stimulates the competition between grasses with different root systems in karst soil, by assessing their growth response, biomass allocation, and morphological plasticity. In a full three-way factorial blocked design of soil depth by water availability by neighbor identity, we grew Festuca arundinacea (deep-rooted) and Lolium perenne (shallow-rooted) under normal versus shallow soil depth, high versus low water availability, and in monoculture (conspecific neighbor) versus mixture (neighbor of the other species). The key results were as follows: (1) total biomass and aboveground biomass in either of the species decreased with reduction of resources but were not affected by planting patterns (monoculture or mixture) even at low resource levels. (2) For F. arundinacea, root biomass, root mass fraction, total root length, and root volume were higher in mixture than in monoculture at high resource level (consistent with resource use complementarity), but lower in mixture than in monoculture at low resource levels (consistent with interspecific competition). In contrast for L. perenne, either at high or low resource level, these root traits had mostly similar values at both planting patterns. These results suggest that deep-rooted and shallow-rooted plant species can coexist in karst regions under current climatic regimes. Declining resources, due to shallow soil, a decrease in precipitation, or combined shallow soil and karst drought, increased the root competition between plants of deep-rooted and shallow-rooted species. The root systems of deep-rooted plants may be too small to get sufficient water and nutrients from dry, shallow soil, while shallow-rooted plants will maintain a dominant position with their already adaptive strategy in respect of root biomass allocation and root growth.
authors.affiliation: Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), Chongqing Key Laboratory of Plant Ecology and Resources Research in Three Gorges Reservoir Region, School of Life Sciences, Southwest University, Chongqing, 400715, China.
authors.forename: Yajie
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), Chongqing Key Laboratory of Plant Ecology and Resources Research in Three Gorges Reservoir Region, School of Life Sciences, Southwest University, Chongqing, 400715, China.
authors.forename: Zhou
authors.initials: Z
authors.lastname: Li
authors.affiliation: Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), Chongqing Key Laboratory of Plant Ecology and Resources Research in Three Gorges Reservoir Region, School of Life Sciences, Southwest University, Chongqing, 400715, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), Chongqing Key Laboratory of Plant Ecology and Resources Research in Three Gorges Reservoir Region, School of Life Sciences, Southwest University, Chongqing, 400715, China.
authors.forename: Haiyan
authors.initials: H
authors.lastname: Song
authors.affiliation: Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), Chongqing Key Laboratory of Plant Ecology and Resources Research in Three Gorges Reservoir Region, School of Life Sciences, Southwest University, Chongqing, 400715, China.
authors.forename: Qianhui
authors.initials: Q
authors.lastname: Liang
authors.affiliation: Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), Chongqing Key Laboratory of Plant Ecology and Resources Research in Three Gorges Reservoir Region, School of Life Sciences, Southwest University, Chongqing, 400715, China.
authors.forename: Jianping
authors.initials: J
authors.lastname: Tao
authors.affiliation: Systems Ecology, Department of Ecological Science, Faculty of Earth and Life Sciences, VU University, De Boelelaan 1085, 1081 HV, Amsterdam, The Netherlands.
authors.forename: Johannes H C
authors.initials: JH
authors.lastname: Cornelissen
authors.affiliation: Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), Chongqing Key Laboratory of Plant Ecology and Resources Research in Three Gorges Reservoir Region, School of Life Sciences, Southwest University, Chongqing, 400715, China. jinchun@swu.edu.cn.
authors.forename: Jinchun
authors.initials: J
authors.lastname: Liu
mesh_terms: D018533:Biomass; D018517:Plant Roots; D006109:Poaceae; D012987:Soil; D014867:Water
chemical_list: D012987:Soil; D014867:Water
keywords: Biomass accumulation; Biomass allocation; Competition; Deep-rooted plant; Drought; Limestone; Root growth; Shallow-rooted plant; Soil heterogeneity