民勤绿洲荒漠过渡带人工梭梭群落与水土因子的关系

Relationships between artificial Haloxylon ammodendron communities and soilwater factors in Minqin oasis-desert ecotone

作为绿洲可持续发展的重要生态屏障,人工梭梭群落的演替关系着民勤绿洲的生态安全。以民勤绿洲边缘人工梭梭群落为研究对象,在野外调查的基础上,采用双向指示种分类(TWINSPAN)和典范对应分析(CCA)数量生态学方法分析了人工梭梭群落与水土环境因子的关系。结果表明:(1)TWINSPAN方法将人工梭梭群落划分为4个群丛类型:群丛I梭梭+白刺-沙蒿-盐生草(Haloxylon ammodendron+Nitraria tangutorum-Artemisia frigida-Halogeton glomeratus)、群丛Ⅱ梭梭+沙拐枣-沙米(Haloxylon ammodendron+Calligonum mongolicum-Agriophyllum squarrosum)、群丛Ⅲ梭梭+白刺-芦苇(Haloxylon ammodendron+Nitraria tangutorum-Phragmites australis)、群丛Ⅳ梭梭+柽柳+盐爪爪(Haloxylon ammodendron+Tamarix ramosissima+Kalidium foliatum);(2)CCA排序第1轴代表生境水分及有机质梯度的变化,第2轴代表生境土壤盐分的环境梯度。Monte Carlo检验和前项选择结果表明,人工梭梭群落演替的环境调控因子排序为土壤水分(10%)>有机质(9.7%)>pH(8.8%)>速效磷(8.4%)>土壤沙粒(7.8%)>地下水埋深(7.8%)>样方距离绿洲之间的距离(7.2%)>全氮(6.9%)>电导率(6.7%)。TWINSPAN分类结果在CCA样方-环境因子排序图中有较好的反映,分类和排序结果较为吻合。(3)土壤含水量、酸碱度、沙粒体积百分比、速效磷、有机质、全氮、电导率与空间因子样方与绿洲的距离解释了物种格局变化的19.8%,其中土壤因子占15.6%,地下水因子占1.1%,土壤与地下水因子交互作用解释部分占3.1%。对于50%以上未能被解释的变异部分,可能归咎于未被选取的环境因子如降水、风蚀沙埋、封禁或者随机过程。

The ecological safety of Minqin oasis depends on the evolution of artificial Halxylon ammodendron communities that acts as important barriers and promotes the continual development of the oasis. The relationship between artificial H.ammodendron communities and environmental factors was evaluated and analyzed using the quantitative ecology methods, two-way indicator species analysis （TWINSPAN） and canonical correspondence analysis （CCA） in this research. The results showed that （1） there were 4 types of associations in artificial H.ammodendron communities using TWINAPAN：AssociationⅠH. ammodendron＋Nitraria tangutorum-Artemisia arenaria-Halogeton glomeratus; AssociationⅡH.ammodendron＋Calligonum mongolicum-Agriophyllum squarrosum; Association Ⅲ H. ammodendron＋Nitraria tangutorum＋Phragmites australis; Association Ⅳ H. ammodendron＋Tamarix ramosissima ＋Kalidium foliatum. （2） The first axis of CCA ordination represented the environmental gradient of water and soil organic matter, meanwhile soil electrical conductivity was reflected by second axis of CCA ordination. Forward selection and Monte Carlo test suggested that the ordination of environmental factors determining species distribution of artificial H. ammodendron communites was soil water content（10%） 〉 soil organic matter（9.7%） 〉 pH（8.8%） 〉 available phosphorus（8.4%） 〉 sand（7.8%） 〉 groundwater depth（7.8%） 〉 distance between oasis and desert（7.2%） 〉 total nitrogen（6.9%） 〉 electrical conductivity（6.7%）.The classification results of TWINSPAN were exactly reflected in the CCA two-dimensional ordination diagram for samples and environmental variables. （3） PCCA revealed that soil factors such as soil water content, organic matter, sand, electrical conductivity, available phosphorus, total nitrogen, pH, and groundwater factors together explained 19.8% of the variance in species distribution of artificial H. ammodendron communities. Soil factors alone explained 15.6% of the variance, groundwater factors accounted for 1.1% of the variance, and the interaction between soil and groundwater factors explained 3.1% of the variance. The partitioning of variance using the PCCA helped identify the important habitat factors regulating species distribution of artificial H. ammodendron communities at the study site. However, the fact that more than half of the variance was unaccounted for by the factors studied suggested that other influences that were not examined could also play a role in determining the occurrence and distribution of artificial H. ammodendron communities, such as rain events, wind erosion, and sand burying, as well as banned and random events.