黄河三角洲刺槐群落土壤优先流及养分分布特征

Abstract

黄河三角洲湿地面临严重的水资源短缺、湿地退化、土壤盐碱化等问题，湿地土壤干旱缺水，土壤收缩产生裂隙等优先流路径，在小尺度上改变湿地内部以及湿地板块之间水文连通性，小尺度水文效应往往制约大尺度水文连通性，基于当前社会对湿地修复的迫切需求，从小尺度对水文连通研究有必要加以重视。然而，目前的研究多集中在大尺度水文连通的阐述，为进一步明确黄河三角洲湿地小尺度水文连通和养分随优先流路径运移分布情况，以此区域典型刺槐群落为研究对象，基于室外染色示踪实验和室内图像处理技术，分析土壤优先流形态和分布特征，并探究优先流和土壤养分含量之间的关系。结果表明：（1）刺槐群落染色面积比随土壤深度变化主要包括2个阶段，第一阶段：优先流和基质流相互影响作用显著，第二阶段：优先流和基质流相互作用不显著，优先流强度逐渐增强，明显存在指流现象，极少部分管流现象。（2）刺槐群落染色面积比、基质流深度和百分之五十染色深度的数值较大，优先流区染色面积比较小，基质流深度发生在土壤深10-15 cm区间，该类型植被群落水流均匀入渗深度较大，优先流和基质流相互作用程度大，水文连通性较高。（3）优先流区土壤有机碳、有机质、全氮、全磷和有效磷含量值均高于基质流区；（4）土壤优先流区染色面积比与5种养分指标均呈负相关关系，有机碳、有机质和有效磷含量受优先流路径影响显著。（5）土壤中有机碳、有机质和有效磷含量在一定程度上可以衡量土壤优先流发育水平。研究结果可为黄河三角洲湿地生态系统保护和管理提供参考。;More serious environmental problems including water shortage, wetland degradation, and soil salinization are gradually recognized in the Yellow River Delta wetland. Due to water deficiency of wetland soils, preferential pathways including soil cracks occur as soil shrinkage which changes the hydrological connectivity of inside wetlands or between wetlands at small scale, and small scale hydrological processes tend to affect the large scale hydrological cycle, depending on our urgent needs to restore wetlands, it is necessary to pay attentions to the study of hydrological connectivity research from microcosmic perspectives to promote the understanding of connotation of hydrological connectivity. However, most of the current studies focused on the hydrological connectivity from macroscopical perspectives. In order to clarify the small-scale hydrological connectivity in the Yellow River Delta, the morphology and distribution characteristics of preferential flow in soil were analyzed based on outdoor dyeing tracer experiment and indoor image processing technology. The relationship between preferential flow and soil nutrient content was explored. The results show that:(1) There are two stages in the variation of the dry coverage of Robinia pseudoacacia Linn community with soil depth. The first stage:the interaction between preferential flow and matrix flow is significant; the second stage:the interaction between preferential flow and matrix flow is not significant, and the intensity of preferential flow is gradually increasing, finger flow phenomenon and a small part of pipe flow phenomenon is observed. (2) Vertical soil-profile indexes (dry coverage, dry coverage of preferential pathway, depth of diffusion area, and depth of 50% dry coverage) reveal a strong interaction between preferential flow and matrix flow, and depth of diffusion area occurs in the range of 10-15cm in the soil, which indicates that this type of vegetation community has large depth of water infiltration flow uniformly and the hydrological connectivity is high; (3) The contents of soil organic carbon, organic matter, total nitrogen, total phosphorus and available phosphorus in preferential flow area were higher than those in matrix flow area; (4) The dye coverage ratio of preferential flow area was negatively correlated with the five nutrient indexes, and the contents of organic carbon, organic matter and available phosphorus were significantly affected by preferential pathway. (5) The content of organic carbon, organic matter and available phosphorus in soil can measure the development level of preferential flow to a certain extent. These results can provide references for wetland ecosystem protection and management in the Yellow River Delta.