title: Impacts of leguminous shrub encroachment on neighboring grasses include transfer of fixed nitrogen.
abstract: Shrub encroachment induced by global change and human disturbance strongly affects ecosystem structure and function. In this study, we explore the degree to which invading leguminous shrubs affected neighboring grasses, including via the transfer of fixed nitrogen (N). We measured N concentrations and natural abundance (15)N of shoot tissues from three dominant grasses from different plant functional groups across seven distances along a local transect (up to 500 cm) to the leguminous shrub, Caragana microphylla. C. microphylla did transfer fixed N to neighboring grasses, but the amount and distance of N transferred were strongly species-specific. Shoot N concentrations decreased significantly with distance from C. microphylla, for a rhizomatous grass, Leymus chinensis, and a bunchgrass, Achnatherum sibiricum. However, N concentrations of another bunchgrass, Stipa grandis, were higher only directly underneath the shrub canopy. Shoot δ(15)N values of L. chinensis were enriched up to 500 cm from the shrub, but for S. grandis were enriched only below the shrub canopy. In contrast, δ(15)N of A. sibiricum did not change along the 500-cm transect. Our results indicated the rhizomatous grass transferred fixed N over long distances while bunchgrasses did not. The presence of C. microphylla increased the shoot biomass of L. chinensis but decreased that of S. grandis and A. sibiricum. These findings highlight the potential role of nutrient-acquisition strategies of neighboring grasses in moderating the interspecific variation of fixed N transfer from the leguminous shrub. Overall, leguminous shrubs have either positive or negative effects on the neighboring grasses and dramatically affect plant community composition and structure.
authors.affiliation: State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, 110164, China. zhanghaiyang798@gmail.com.|Max Planck Institute for Biogeochemistry, 07745, Jena, Germany. zhanghaiyang798@gmail.com.
authors.forename: Hai-Yang
authors.initials: HY
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, 110164, China. turfyu@gmail.com.|Department of Biology, Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO, 80523, USA. turfyu@gmail.com.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Yu
authors.affiliation: State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, 110164, China.
authors.forename: Xiao-Tao
authors.initials: XT
authors.lastname: Lü
authors.affiliation: Max Planck Institute for Biogeochemistry, 07745, Jena, Germany.
authors.forename: Susan E
authors.initials: SE
authors.lastname: Trumbore
authors.affiliation: State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, 110164, China.
authors.forename: Jun-Jie
authors.initials: JJ
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, 110164, China. xghan@ibcas.ac.cn.
authors.forename: Xing-Guo
authors.initials: XG
authors.lastname: Han
mesh_terms: D018533:Biomass; D032602:Caragana / Q000254:growth & development* / Q000378:metabolism; D004463:Ecology; D017753:Ecosystem; D007887:Fabaceae / Q000254:growth & development / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism*; D009586:Nitrogen Fixation; D018520:Plant Shoots / Q000254:growth & development / Q000378:metabolism; D006109:Poaceae / Q000254:growth & development* / Q000378:metabolism; D027343:Rhizome; D013045:Species Specificity
chemical_list: D009584:Nitrogen
keywords: Nitrogen transfer; Plant competition; Plant facilitation; Shrub encroachment; Species-specific