Record ID No. |
2540 |
Author(s) |
Wu TianXiang., Huang JianHui. , 2010 |
Affiliation |
State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China. jhhuang@ibcas.ac.cn |
Title |
Effects of grazing on the delta 15N values of foliage and soil in a typical steppe ecosystem in Inner Mongolia, China |
Source. Vol.(no):Page |
Journal of Plant Ecology (Chinese Version). 34(2):160-169p. |
Categories |
Arbuscular Mycorrhiza |
Subjects |
Biochemistry |
Sub-subjects |
Nitrogen metabolism |
Host |
Caragana microphylla, Astragalus galactites, Melilotoides ruthenica [Medicago ruthenica],Leymus chinensis, Stipa grandis, Heteropappus altaicus, Potentilla acaulis, Kochia prostrata |
Organism |
AMF |
Country |
China, Asia |
Abstracts |
Stable N isotope signature ( delta 15N) in both plant and soil is potentially an important parameter to evaluate N cycling in grassland ecosystems. Grazing is a dominant land use in northern China grasslands and might have greatly changed N cycling. Our objective was to determine the 15N signature of leaves and soils in grazed and fenced plots of a typical steppe to investigate how delta 15N values in an ecosystem are affected by grazing. We collected foliar and soil samples in a nearly 20 years fenced plot and an adjacent freely grazed plot in Inner Mongolia. The foliar samples came from eight dominant species, including three perennial legumes (Caragana microphylla, Astragalus galactites and Melilotoides ruthenica [Medicago ruthenica]), two grasses (Leymus chinensis and Stipa grandis), two forbs (Heteropappus altaicus and Potentilla acaulis) and a semi-shrub (Kochia prostrata). We also sampled 0-10 and 10-20 cm rhizosphere soils of C. microphylla and K. prostrata. Nitrogen isotope ratios were determined with a Thermal Finnigan MAT Deltaplus XP isotope-ratio mass spectrometer. Although the delta 15N value of leaves of different plant species varied greatly, the observed pattern of variability was consistent in both grazed and fenced plots, i.e., semi-shrub > forbs and grasses > legumes. Long-term grazing reduced foliar delta 15N values of forbs, semi-shrub and S. grandis significantly while changing little or even increasing that of potential biological N fixers (legumes and L. chinensis). As the only arbuscular mycorrhiza non-infected plant species, K. prostrata was enriched in 15N (with delta 15N values of 4.34 per mil +or- 0.35 per mil and 2.04 per mil +or- 0.20 per mil in fenced and grazed plots, respectively) compared with the depletion of other species. Mycorrhizal association may be considered to play an important role in plant nutrient transfer in those N-limited grassland ecosystems. In contrast to results of previous studies, soil delta 15N values decreased significantly with grazing. |