亚高山草甸植物群落物种多样性与群落C、N、P生态化学计量的关系

通过测定祁连山东部亚高山草甸256个群落样方的群落物种数和地上植物的C、N、P元素含量, 探究了该地区高产草地和低产草地植物群落物种多样性与植物群落C、N、P生态化学计量特征的关系。结果表明: 高产样地植物群落C、N、P含量的平均值分别为53.05%、1.99%、0.22%; 而低产样地植物群落C、N、P含量的平均值分别为52.51%、2.28%、0.19%。高产和低产样地植物群落C、N、P元素含量均呈现显著差异。高产样地上植物群落的物种数与N含量和N:P呈显著正相关关系, 与C:N呈显著负相关关系, 但与C、P含量和C:P无明显相关关系; 低产样地上植物群落的物种数与N、P含量呈极显著负相关关系, 与C:N和C:P呈显著正相关关系, 但与C含量和N:P无明显相关关系。说明高产草地和低产草地植物群落物种多样性与养分元素化学计量特征显示出一定的分异性, 高产样地上植物群落的物种数主要受N含量的限制, 与N含量呈正相关关系; 低产样地上植物群落的物种数则受N、P含量共同限制, 与N、P含量呈负相关关系。

Relationships between species diversity and C,N and P ecological stoichiometry in plant communities of sub-alpine meadow

Aims Our objective was to investigate relationships between species diversity of pasture and C, N and P stoichiometry characteristics of plants at the community level.
Methods This field survey focused on plant nutrient stoichiometry of two-level yields in alpine meadow in Eastern Qilian Mountain, China was conducted in early August 2012. Two survey sites were identified as high-yield grassland and low-yield grassland. At each survey site, two 8 m × 8 m plots were selected and divided into 64 1 m × 1 m subplots. For each subplot, the number of species was counted, and newly matured leaves were randomly selected after collecting the aboveground parts by clipping the plant at the soil surface. The collected leaves were sun-dried in the field and oven-dried at 80 °C to constant weight. All samples were finely ground and passed through a 40-mesh screen. Plant C concentration was analyzed by ash determination, plant N concentration was tested by Kjeldahl acid-digestion method and plant P concentration was analyzed by phosphorus vanadium molybdate yellow colorimetric method. Pearson’s bivariate correlation was used to test the relationship between plant C, N, and P stoichiometric traits and number of species. Two-tailed Student’s t-tests were used to compare plant stoichiometric variables.
Important findings Mean values of plant C, N and P concentrations in high-yield grassland were 53.05%, 1.99%, and 0.22%, respectively, and those in low-yield grassland were 52.51%, 2.28% and 0.19%, respectively. In high-yield grassland, the number of species was significantly positively correlated with plant N concentration and N:P ratio, while significantly negatively correlated with plant C:N ratio. In low-yield grassland, the number of species was significantly negatively correlated with N and P concentrations, but significantly positively correlated with C:N and C:P. Results indicated that the species of high-yield grassland were primarily limited by N concentration and positively correlated with N concentration. However, the species of low-yield grassland was co-limited by N and P concentrations and negatively correlated with N and P concentrations, thus indicating heterogeneity in C, N and P stoichiometry characteristics between high- and low-yield grasslands.