旱化对浙江山地沼泽湿地土壤与植物碳氮磷含量的影响

因受到气候变暖、人为干扰等因素的影响,浙江省山地沼泽湿地面临着缺水旱化的问题,泥炭藓沼泽、草本沼泽逐渐退化成旱化的沼泽。在山地沼泽旱化的过程中,山地沼泽湿地土壤碳、氮、磷含量及其生态化学计量比的变化趋势尚不明确。本研究选取浙江5块不同旱化程度的山地沼泽湿地,分析土壤表层0~60 cm剖面上土壤有机碳(SOC)、全氮(TN)、全磷(TP)、土壤pH值、土壤容重等,以及植物样方地上生物量、植物粉碎混合样的有机碳(OC)、TN、TP。结果表明: 浙江山区沼泽湿地SOC、TN含量丰富,但TP含量低;随着山区沼泽湿地的旱化,容重、pH值、地上生物量上升,而SOC、TN、TP、C∶N、C∶P、N∶P呈下降趋势,容重、pH值与SOC、TN、TP均呈显著线性负相关;不同旱化程度的浙江山区沼泽湿地土壤C、N、P等元素的累积量与植物凋落物输入量、湿地氧气条件、凋落物分解的难易程度等因素有关。浙江山地沼泽湿地旱化趋势明显,土壤C、N、P等营养元素的含量下降,而植物由湿生群落向中性群落演替,植物中C、N、P含量随着植物种类的变化而变化,与土壤C、N、P含量的变化关系不耦合。

Effects of aridity on carbon,nitrogen, and phosphorus contents in soils and plants of mountain swamps,Zhejiang, China

Mountain swamps in Zhejiang Province have been suffered from severe drouhgt threats because of climate change and artificial interruption. Sphagnum bogs and swamps were gradually degraded into arid swamps. However, the effects of arid processes on the C, N, P contents of soils and their stoichiometry in mountain swamps are still unclear. We measured C, N and P concentrations, pH values, and bulk density in the upper 0-60 cm soil layers in the stands of five mountain swamps with the different arid levels. Moreover, the aboveground biomass and the C, N, P concentrations in the crushed plant mixture were also measured. The results showed that the soils of mountain swamps in Zhejiang Province were rich in soil organic carbon (SOC), total nitrogen (TN), but infertile in phosphorus (TP). Aboveground biomass, soil pH, bulk density increased, while SOC, TN, TP, C:N, C:P, N:P decreased with aridity. Soil pH and bulk density had significant negative correlations with SOC, TN, and TP in soils, respectively. The differences in the C, N, P accumulation in the soils were probably associated with litterfall production, the oxygen condition of wetlands, and the degree of plant decomposition at the different types of mountain swamps. In all, arid trends were obvious at the mountain swamps in Zhejiang Province. Soil nutrients, such as C, N, P, deceased, while plant community succeeded from the wet swamp to the mesophyte vegetation with the arid processes. The contents of C, N and P in the plants varied across species, and were not coupled with those in the soils.