Three Tibetan grassland plant species tend to partition niches with limited plasticity in nitrogen use
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Niche complementarity theory explains how species coexist by using different resources. Two pathways to partition resource have been demonstrated: classical niche differentiation and plasticity in resource use. We aimed to determine N-uptake patterns in three Tibetan Plateau grassland species, and to examine how N-partitioning is driven by neighbor interactions.
We conducted a transplantation experiment using ten plant communities, each comprising a different combination of Kobresia humilis, Stipa aliena, and Saussurea superba. Soil was sprayed uniformly with a mixture of (NH4)2SO4, KNO3, and glycine (C2H5NO2) (1:1:1 by mass of N, each containing one form of 15N) after growing for 45 days.
Across three species, the N-uptake pattern was NO3− > NH4+ > glycine (NO3−: 58.47%; NH4+: 26.91%; glycine: 14.62%). Neighbor presence had species-specific effects on 15N recovery. Kobresia humilis took up more 15N-NO3− when it was in competition with other species, whereas Stipa aliena and Saussurea superba took up more 15N-NH4+ and 15N-glycine, respectively.
Plasticity in N resource utilization of the three species was limited. The species competed for N resources proportionally to the availability of these sources, and tended to partition niches. These findings provide important insights into how plant species grow together in alpine grasslands.
KeywordsNiche complementarity Kobresia humilis Stipa aliena Saussurea superba 15N Resource competition
This work was done at the Haibei National Field Research Station of Alpine Grassland Ecosystem. We thank Tanfeng Yin and Yu Guo for their help in the field.
This study was supported by the National Key Research and Development Program of China (Grant No. 2016YFC0501802; 2017YFA0604802), the National Natural Science Foundation of China (31470560; 41671263) as well as Qinghai innovation platform construction project (2017-ZJ-Y20).
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