Spatial relationships among species, above-ground biomass, N, and P in degraded grasslands in Ordos Plateau, northwestern China |
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| Authors: | X Cheng S An J Chen B Li Y Liu S Liu |
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| Institution: | aSchool of Life Science, Nanjing University, Nanjing 210093, PR China;bDepartment of Earth, Ecological and Environmental Science, University of Toledo, Toledo, OH 43606, USA;cMinistry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, Institute of Biodiversity Science, Fudan University, Shanghai 200433, PR China;dInstitute of Forest Ecology, Environment and Protection, Chinese Academy Forestry, Beijing 100091, PR China |
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| Abstract: | We chose five communities, representing a mild to severe gradient of grassland desertification in a semi-arid area of Ordos Plateau, northwestern China, to explore the spatial relationships among plant species, above-ground biomass (AGB), and plant nutrients (N and P). Community 1 (C1) was dominated by Stipa bungeana; Community 2 (C2) by a mix of S. bungeana and the shrub Artemisia ordosica; Community 3 (C3) by A. ordosica; Community 4 (C4) by a mix of Cynanchum komarovii and C. komorovii; and Community 5 (C5) by C. komorovii. Quantitative methods, including geostatistics, were used to compare community composition, structure, and indicators of ecosystem function (i.e. AGB, plant N and P) in five 16-m2 plots. The highest AGB, plant nitrogen (N) and plant phosphorus (P) were found in lightly degraded community C2. With increasing desertification effects from C3 to C5, the AGB, N, and P decreased significantly while plant density remained unchanged. The spatial variations of AGB were higher in shrub-dominated communities (C1 and C5) than in grass-dominated communities (C2–C4). Strong spatial relationships were detected within and among the communities, with stronger relationships between AGB and density than between AGB and species richness. Spatial patterns of plant N and P were different from those of AGB, reflecting different N and P contents of individual plants and different species that can redistribute soil resources in these communities. The AGB was positively correlated with soil nutrients (TOC, TN, TP, and IN), except for soil AP. We concluded that several specific aspects of ecosystem properties were directly associated with the conversion of the grass and shrub “functional types” in these degraded grasslands. |
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| Keywords: | Spatial heterogeneity Desert vegetation Plant nutrients Disturbed prairie Geostatistics |
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