黄河三角洲湿地柽柳灌丛周围有机质富集及水分运动研究

为研究滨海湿地柽柳灌丛水分推动下的土壤养分富集作用,对黄河三角洲单株柽柳个体周围不同位点、不同土层土壤有机质含量及土壤水、地表水和黄河水同位素进行分析。结果表明:(1)土壤有机质在灌木主干周围出现富集现象,形成深度为20cm,半径为1.5m的富集圈层,有机质含量空间分布呈现冠幅下明显高于冠幅边缘和株间空地,且随土层深度增加而降低,表现出非常明显的肥岛效应。(2)不同土壤剖面水分同位素值出现差异:0~5cm表层土δD、δ18 O同位素值表现为冠幅下冠幅边缘株间空地,而5~10cm土层δD、δ18 O同位素值为冠幅下冠幅边缘株间空地。0~5cm表层土同位素值大于5~10cm土层同位素值。(3)水分运动对柽柳灌丛周围有机质含量产生影响,沿灌木主干流下的雨水冲刷和黄河水侧渗作用是影响灌丛下土壤有机质含量冠幅下冠幅边缘株间空地的原因之一。有机质等土壤养分在肥岛效应及水分运动影响下向柽柳主干周围聚集,这种土壤养分的小尺度空间异质性促进了柽柳自身及附近其他植物的生长,改变了土壤的理化性质。本研究结果同时可以作为黄河三角洲盐碱地土壤改良和植被恢复的参考依据。

Study of the enrichment of soil organic matter and water movement around the Tamarix chinensis shrubs in the coastal wetlands of the Yellow River Delta

To investigate the promoting effect of water movement on soil nutrients beneath the Tamarix chinensis shrubs in the coastal wetlands,we analyzed the soil organic matter at different locations and soil layers around a Tamarix chinensis and the isotopes of soil water,surface water,and Yellow River water.The results showed that:(1) Soil organic matter is enriched around the trunk of Tamarix chinensis shrubs,forming a 20 cm-deep enriched circle-layer with a 1.5-m radius.Soils under shrub canopy have significantly higher content of organic matter compared to those under the canopy edge and at the open spaces between plants.Deeper soils have less content,showing prominent "fertile island" effects.(2) The hydrogen and oxygen stable isotopes at different soil profiles were different.In the 0-5cm topsoil,the δD and δ18O isotopic values are from large to small under shrub canopy,under canopy edge,and at the open spaces.In the 5-10cm soil layer,the δD and δ18O isotopic values are from small to large under shrub canopy,under canopy edge,and at the open spaces.The isotopic values in the 0～5 cm topsoil are greater than those in the 5～10 cm soil layer.(3) Water movement has an effect on the content of organic matter.The nutrients carried by stemflow and the lateral seepage of the Yellow River are two of the reasons why the content of organic matter is from large to small under shrub canopy,under canopy edge,and at the open spaces.The enrichment of soil organic matter has changed the physicochemical properties of the soil around the plant.The small-scale spatial heterogeneity of soil nutrients has promoted the growth of the Tamarix chinensisis and the surrounding plants.The research results can provide reference for the saline soil reclamation and vegetation recovery in the Yellow River Deltta.