围封对天山高寒草原4种植物叶片和土壤化学计量学特征的影响

以中国科学院巴音布鲁克草原生态系统研究站长期围栏内外的羊茅(Festuca ovina)、天山赖草(Leymus tiansecalinus)、二裂委陵菜(Potentilla bifurca)和鹅绒委陵菜(Potentilla anserine)4种植物叶片和土壤为研究对象,分析了放牧与围封对植物叶片和土壤C、N、P的化学计量特征的影响。结果表明,围封样地土壤养分浓度整体高于放牧样地(P0.05),全氮(TN)浓度除外。围封显著增加羊茅叶片C、N浓度(P0.05),对P浓度影响不显著;围封显著增加鹅绒委陵菜叶片的C浓度,但是显著降低叶片的N和P浓度(P0.05),围封对天山赖草和二裂委陵菜养分含量影响不显著。围封显著增加鹅绒委陵菜C∶N和C∶P(P0.05);围封显著降低羊茅C∶N、C∶P和增加N∶P(P0.05);围封显著降低二裂委陵菜C∶N(P0.05),对天山赖草的化学计量特征影响不显著。不同植物对围封的响应不同,意味着长期围封可能会改变天山高寒草原生态系统的结构。围封降低优势种(羊茅)的固碳能力,增加退化期出现的代表性植物(鹅绒委陵菜)的固碳能力,表明在长期围封下植物凋落物中的杂类草(鹅绒委陵菜)可能更多的为土壤提供碳来源,也能促进优势禾本科物种的氮含量和碳含量的增加。

Effects of enclosure on leaves of four plants and soil stoichiometry in an alpine grassland of Tianshan Mountains

To determine effects of grazing and enclosure on the ecological stoichiometry characteristics, we evaluated the carbon(C),nitrogen(N),and phosphorus(P) contents in soil and leaves of four plants, which were Festuca ovina, Leymus tiansecalinus, Potentilla bifurca and Potentilla anserine, inside and outside the fence of the Bayinbuluk Grassland Ecological Research Station, Chinese Academy of Sciences. The results showed that soil nutrient content of enclosed grassland was significantly higher than that of grazing site, except total nitrogen (TN) content (P<0.05). The enclosure significantly increased the content of C and N in the leaves of Festuca ovina (P<0.05), but it did not significantly affect the content of P. The enclosure significantly increased the C content (P<0.05), but it significantly reduced the N and P content in the leaves of Potentilla anserine. Effects of the enclosure on the nutrient content of Leymus tiansecalinus and Potentilla bifurca were not significant. The enclosure significantly increased C:N and C:P of Potentilla anserine (P<0.05), while it significantly reduced C:N, C:P and increased N:P of Festuca ovina(P<0.05). The enclosure significantly reduced C:N of Potentilla bifurca(P<0.05), but it had no significant effect on the stoichiometric characteristics of Leymus tiansecalinus. The different species had different responses to the enclosure, meaning that long-term enclosure may change the structure of the Tianshan alpine grassland ecosystem. The enclosure reduced the carbon sequestration capacity of the dominant plant species (Festuca ovina) and increased the carbon sequestration capacity of the forb (Potentilla anserine) in the degradation stage. In long-term enclosure, Potentilla anserine may provide more carbon for the soil, and it also could promote nitrogen and carbon content of the dominant grass species.