不同利用方式下草地优势植物的生态化学计量特征

在内蒙古温带草原围封、放牧和割草3种不同利用方式下,测定了大针茅、冷蒿和羊草3种优势种植物的化学计量元素,探讨了草地不同利用方式下优势种植物的化学计量特征响应机制。结果表明,3种优势种植物的C、N、P含量及其计量比在不同利用方式下均有明显的季节变化;不同利用方式、不同物种以及二者的交互作用均对N、P含量及C∶N、C∶P和N∶P有显著的影响,其中,C含量比较稳定,不同的利用方式对其无显著影响,N含量在整个生长季内总体呈下降趋势,放牧样地3种植物叶片的N、P含量均高于割草和围封样地,说明放牧增加了植物N、P的含量。植物生长普遍受到N的限制,土壤养分特征在不同利用方式间也存在一定的差异,围封样地表现为更加缺N,而放牧样地更加缺P。放牧样地有机质、C、N和P含量均高于割草和围封样地,说明适度放牧能提高土壤养分的含量,有利于植物的生长。

The ecological stoichiometry of dominant species in different land uses type of grassland

The stoichiometric elements of three dominant species, namely Stipa grandis, Artemisia frigida and Leymus chinensis were measured in different land use (grazing-exclusion, grazing and mowing) in the temperate grassland in Inner Mongolia. The seasonal variations of stoichiometric characteristic of plants and soil under different grassland uses were discussed. The stoichiometric characteristic response mechanisms of the plants and the nutrient limiting conditions were analyzed. The results show that obvious seasonal variations in C, N, P concentrations and their mass ratio of the three species exist in each grassland use type. Grassland use type, species and their interactions have significant impacts on N, P concentrations and the ratios C∶N, C∶P and N∶P, among which C concentration is relatively stable in the whole growing season and different uses show no significant impact on it. N concentration reduces overall. N and P concentrations in leaves are higher in grazing plot than those in grazing-exclusion and mowing plots. It shows that grazing can increased N and P concentrations. On the whole, plant growth is limited by N. Characteristics of soil nutrients among different grassland uses have certain differences, where comparably more serious N deficiency happens in the enclosed plot and P deficiency in the grazing plot. Generally the organic matter, C, N and P concentrations in the grazing plot are higher than those in the mowing and enclosed plots. It shows that soil nutrients can be increased which can promote plants growth in grazing plot.