不同土地利用方式对黄河三角洲土壤物理特性的影响

黄河三角洲是我国成土最快的河口三角洲之一,探索其土地利用过程中不同土地利用方式对土壤物理性质的影响,对该区土壤肥力保持和土地资源的持续利用具有重要意义。选择黄河三角洲棉田、麦田、苇地、碱蓬地和裸地等5种不同的土地利用方式,通过野外调查与室内分析,研究不同土地利用方式下土壤主要物理特性的变异特征及影响因素。结果显示,与裸地土壤相比,有植被土地利用方式土壤容重降低,土壤孔隙度、团聚体水稳性、饱和含水量与毛管含水量也有相应的提高;土壤有机碳和速效氮、有效磷含量均有显著增加,土壤总盐分含量呈显著降低趋势。在所研究土壤中,土壤物理性质依麦田-棉田-苇地-碱蓬地-裸地的次序从最佳向最差过渡。逐步回归分析和相关分析表明土壤容重、团聚体平均重量直径和毛管孔隙度是土壤毛管含水量的主要影响因子,团聚体水稳性主要由大于0.25 mm水稳性团聚体含量和毛管孔隙度决定,土壤总盐分含量影响土壤饱和导水率;大于0.25 mm水稳性团聚体含量分别与土壤有机碳含量(r=0.8323)、速效氮含量(r=0.7558)和有效磷含量(r=0.9049)具有正相关关系。因此,黄河三角洲地区土地利用应以增加有机质的投入,提高土壤水稳性团聚体形成为基础,促进土壤良好结构形成。这些结果为该区土壤肥力提高和土壤资源可持续利用提供参考依据。

Effect of different land-use patterns on physical characteristics of the soil in the Yellow River delta region

The Yellow River delta is one of the three major pedogenic river deltas in China and is the fastest forming delta that has important reserved land resources. Anthropogenic behavior and natural development play an important role in the physical and chemical properties of the soil during pedogenic processes. In order to maintain soil fertility and ensure sustainable utilization of land resources, it is necessary to investigate the effect of various types of land uses on physical properties of the soil. In this study, disturbed and undisturbed soil samples were collected from soil covered by different vegetation. Arable soil was considered to be soil cultivated with wheat and cotton, while land covered with reeds and suaeda was considered to be natural vegetation and bare land was classified as recently formed land. These soils were considered to be trends of mature soils in the Yellow River delta region. The physical properties of undisturbed soil samples were as follows: bulk density and porosity of the soil, water-stable aggregates, and saturated moisture. The organic carbon content, available nitrogen and phosphorus content, and total salt content in the soil were probed as chemical indexes. Field research along with lab analyses was conducted at different genesis stages in order to illustrate the changing trends in soil physical characteristics and to identify the causative factors. Compared with bare land soil, the soil covered with vegetation had significantly higher soil porosity, aggregate water stability, and saturated and capillary water content. Soil organic carbon content and available nitrogen and phosphorus content were higher in vegetation soil than in bare land soil. On the other hand, the total salt content and soil bulk density were significantly lower in soil with vegetation than in bare land soil. The trends in soil properties improved with different vegetation in the following order wheat>cotton>reed>suaeda>bare land. Stepwise regression and correlation analysis identified that the main factors of soil capillary water content are soil bulk density, soil aggregate mean weight diameter, and soil capillary porosity. The aggregate soil water stability was determined as>0.25-mm water-stable aggregate content and capillary porosity. The total salt content in the soil significantly affected the soil saturated hydraulic conductivity, while>0.25-mm water-stable aggregates had a significantly positive correlation with the soil organic carbon content (r=0.8323), available nitrogen content (r=0.7558), and available phosphorus content (r=0.9049) in the soil. Therefore, proper land-use management and optimization systems were established to preserve organic carbon accumulation and water-stable aggregate formation in the soil, thereby resulting in the development of soil structure. In this study, agricultural management was determined to be the best approach for maintaining the physical properties of the soil. Therefore, improvement in soil fertility and sustainable utilization of soil resources in the Yellow River delta region is critical.