治沙措施通过植物群落的质量效应驱动土壤因子变化——以玛曲高寒草甸沙化区为例

Sand control measures drive changes in soil factors through the mass effect of plant communities:A case study of severe desertification area in Maqu alpine meadows

沙漠化是玛曲高寒草甸面临的主要生态问题之一,研究沙障固定+种草植灌+围封共同构建的综合性治沙措施对不同调查区(县城南岸与河曲马场)玛曲高寒草甸严重沙漠化区域(流动沙地)植物群落和土壤因子的影响,以及植物群落驱动土壤因子变化的生态机制,有助于科学合理的开展沙漠化防治与生态恢复工作。结果表明:治沙措施实施后,植物群落的主要优势种由青藏苔草(Carex moorcroftii)转变为垂穗披碱草(Elymus nutans)与青藏苔草并重。不受调查区制约,治沙措施能够显著改善植物群落数量特征与物种多样性,表现为县城南岸与河曲马场的地上生物量大幅提高至18.04 g/m^(2)和24.67 g/m^(2)(P<0.05),盖度分别为23.8%和31.1%,较流动沙地显著提高了487.3%和589.2%(P<0.05),物种丰富度和Shannon多样性指数的变化规律与盖度相近。土壤因子方面,除pH值外,治沙措施能够显著提高县城南岸与河曲马场的土壤全氮、全碳、全磷、速效磷和速效钾。线性混合效应模型表明,治沙措施实施后,地上生物量是驱动土壤有机质、全氮和全碳变化的主导因素,其对以上土壤养分的积极效应亦达到显著水平。相较而言,物种多样性对土壤因子变化的贡献率较低,说明植物群落主要通过“质量效应”而不是“多样性效应”来改善土壤有机质、全氮和全碳等主要养分。

Desertification is one of the main ecological issues faced by Maqu alpine meadows.Therefore,in order to carry out local desertification control and ecological restoration scientifically and rationally,we studied the effect of comprehensive sand control measures(sand barrier fixation+grass planting and irrigation+enclosure)on the plant community and soil factors in the severe desertification area(mobile sandy land)of Maqu alpine meadow in different survey areas(the south bank of the Yellow River in Maqu and Horse ranch at the first Meander of Yellow River).The results showed that after implementation of the sand control measures,the dominant species of the plant community changed from Carex moorcroftii to both Elymus nutans and Carex moorcroftii.Regardless of the survey area,the desertification control measures could significantly improve the quantitative characteristics and species diversity of plant communities.It showed that the aboveground biomass of the south bank of the Yellow River in Maqu and the Horse ranch at the first Meander of Yellow River increased significantly to 18.04 g/m^(2) and 24.67 g/m^(2)(P<0.05),and the coverage was 23.8% and 31.1%,respectively,which was significantly increased by 487.3% and 589.2% compared with the mobile sandy land(P<0.05).The variation law of species richness and Shannon diversity index was similar to that of coverage.In terms of soil properties,in addition to pH value,sand control measures could significantly increase soil total nitrogen,total carbon,total phosphorus,available phosphorus and available potassium in the south bank of the Yellow River in Maqu and Horse ranch at the first Meander of Yellow River.The linear mixed effects model showed that after the implementation of sand control measures,the aboveground biomass was the dominant factor driving changes in soil organic matter,total nitrogen and total carbon,and its positive effects on the above soil nutrients also reached a significant level.In comparison,the contribution rate of species diversity to soil property change was lower,indicating that plant communities mainly improved soil organic matter,total nitrogen and total carbon through the mass effect rather than the diversity effect.