喀斯特生态脆弱区典型小生境土壤团聚体稳定性比较研究

Comparative study on the stability of soil aggregates in typical microhabitats in karst ecologically fragile areas

为探究喀斯特小生境类型对土壤团聚体稳定性影响,揭示小生境土壤团聚体主要失稳机制,选取研究区内石缝、石沟、石槽、石土面和土面5种典型小生境为研究对象,采用干筛法、Elliott湿筛法和Le Bissonnais法测定土壤团聚体稳定性。结果表明:湿筛后,团聚体分布以水稳性团聚体(WR;)为主,含量在81.26%以上,团聚体破坏率(PAD)介于8.93%—17.39%之间,平均重量直径(MWD)在1.94—2.85 mm间,均小于干筛,团聚体稳定性表现为石槽最好,土面最差,石土面次之。LB法处理后,MWD值变化趋势为慢速湿润(SW)>预湿润后扰动(WS)>快速湿润(FW),即小生境土壤团聚体最大破坏机制为大雨或暴雨时快速湿润FW产生的消散作用,团聚体稳定性同样以石槽最好,土面最差,石土面次之。相关性分析显示,LB法测定的MWD均与湿筛法的WR;呈显著正相关,与PAD呈显著负相关,即LB法和湿筛法具有良好的相关性,LB法用于测定喀斯特地区土壤团聚体稳定性是可行的(P<0.05)。LB法FW处理的MWD值与有机质呈显著正相关,即有机质对团聚体稳定性有重要影响;全氮、全磷、全钾与WR;、SW处理的MWD值呈显著正相关,与PAD呈显著负相关,即稳定的团粒结构对养分蓄积有正向效应(P<0.05)。综合不同测定方法的结果表明,土面、石土面易造成土壤流失,应加强雨季对喀斯特生态脆弱区土面、石土面小生境的防护。

In order to investigate the influence of karst microhabitat types on the stability of soil aggregates and to reveal main destabilization mechanisms of soil aggregates in microhabitats, five typical microhabitats in the study area, namely stone crevices, stone ditch, stone sink, stone and earth surfaces, and earth surface are selected. The dry sieve method, Elliott wet sieve method, and Le Bissonnais method are used to determine the stability of soil aggregates. The results show that after wet sieving, the distribution of agglomerates is dominated by water-stable agglomerates(WR;) with a content of over 81.26%, the percentage of aggregate destruction(PAD)ranged from 8.93% to 17.39%, the mean weight diameter(MWD)ranged from 1.94 to 2.85 mm, all smaller than the MWD of the dry sieving method, and the stability of the agglomerates shows that the stone sink is the best, the earth surface is the worst, and stone and earth surfaces is the second worst. The trend of MWD values after Le Bissonnais method treatment is slow wetting(SW)>pre-wetting and strirring(WS)>fast wetting(FW), indicating that the maximum damage mechanism of soil agglomerates in microhabitats is the dissipative effect of fast wetting FW during heavy or stormy rainfall, and the stability of the agglomerates is shown to be best in the stone sink, worst in the earth surfaces and stone and earth surfaces is the second worst. Correlation analysis shows that the MWD determined by the Le Bissonnais method are all significantly positively correlated with WR;for the wet sieve method and negatively correlated with PAD(P<0.05), indicating that the Le Bissonnais method and the wet sieve method have good correlation and that the Le Bissonnais method is feasible for determining the stability of soil aggregates in karst areas(P<0.05). The MWD under the FW treatment in the Le Bissonnais method is significantly positively correlated with organic matter, indicating that organic matter has an important effect on agglomerate stability;total N, total P and total K is significantly positively correlated with MWD under WR;and SW treatments, and negatively correlated with PAD, indicating that a stable agglomerate structure has a positive effect on nutrient accumulation(P < 0.05). The results of the different measurement methods show that earth surface and stone and earth surfaces microhabitats are prone to soil erosion and that protection of them in karst ecologically fragile areas should be strengthened during the rainy season.