title: Woody plant encroachment into grasslands: spatial patterns of functional group distribution and community development.
abstract: Woody plant encroachment into grasslands has been globally widespread. The woody species invading grasslands represent a variety of contrasting plant functional groups and growth forms. Are some woody plant functional types (PFTs) better suited to invade grasslands than others? To what extent do local patterns of distribution and abundance of woody PFTs invading grasslands reflect intrinsic topoedaphic properties versus plant-induced changes in soil properties? We addressed these questions in the Southern Great Plains, United States at a subtropical grassland known to have been encroached upon by woody species over the past 50-100 years. A total of 20 woody species (9 tree-statured; 11 shrub-statured) were encountered along a transect extending from an upland into a playa basin. About half of the encroaching woody plants were potential N2-fixers (55% of species), but they contributed only 7% to 16 % of the total basal area. Most species and the PFTs they represent were ubiquitously distributed along the topoedaphic gradient, but with varying abundances. Overstory-understory comparisons suggest that while future species composition of these woody communities is likely to change, PFT composition is not. Canonical correspondence analysis (CCA) ordination and variance partitioning (Partial CCA) indicated that woody species and PFT composition in developing woody communities was primarily influenced by intrinsic landscape location variables (e.g., soil texture) and secondarily by plant-induced changes in soil organic carbon and total nitrogen content. The ubiquitous distribution of species and PFTs suggests that woody plants are generally well-suited to a broad range of grassland topoedaphic settings. However, here we only examined categorical and non-quantitative functional traits. Although intrinsic soil properties exerted more control over the floristics of grassland-to-woodland succession did plant modifications of soil carbon and nitrogen concentrations, the latter are likely to influence productivity and nutrient cycling and may, over longer time-frames, feed back to influence PFT distributions.
authors.affiliation: Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden, Chinese Academy of Sciences, Wuhan, China ; Department of Ecosystem Science and Management, Texas A&M University, College Station, Texas, United States of America.
authors.forename: Feng
authors.initials: F
authors.lastname: Liu
authors.affiliation: School of Natural Resources and the Environment, University of Arizona, Tucson, Arizona, United States of America.
authors.forename: Steven R
authors.initials: SR
authors.lastname: Archer
authors.affiliation: Department of Wildlife and Fisheries Sciences, Texas A&M University, College Station, Texas, United States of America.
authors.forename: Frances
authors.initials: F
authors.lastname: Gelwick
authors.affiliation: State Key Laboratory of Forest and Soil Ecology, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang, China.
authors.forename: Edith
authors.initials: E
authors.lastname: Bai
authors.affiliation: Department of Ecosystem Science and Management, Texas A&M University, College Station, Texas, United States of America.
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Boutton
authors.affiliation: Department of Ecosystem Science and Management, Texas A&M University, College Station, Texas, United States of America.
authors.forename: Xinyuan Ben
authors.initials: XB
authors.lastname: Wu
mesh_terms: D000704:Analysis of Variance; D003247:Conservation of Natural Resources; D058865:Introduced Species; D006109:Poaceae; D012922:Social Change; D012987:Soil / Q000737:chemistry; D062206:Spatial Analysis; D013781:Texas; D014934:Wood / Q000254:growth & development*
chemical_list: D012987:Soil