广州市典型绿地土壤水分入渗特征

Abstract

绿地对于缓解城市洪涝灾害具有非常重要的作用，对其土壤入渗的定量化研究是评价城市绿地雨洪调蓄能力的关键。受城市土壤空间异质性的影响，不同功能区绿地土壤水分入渗速率的差异较大。采用双环入渗仪对广州海珠国家湿地公园典型乔草和灌草绿地的土壤水分入渗特征进行测定，并对其影响因素进行分析，结果表明：（1）广州海珠国家湿地公园的绿地土壤水分入渗性能处于中等至较高水平，但受机械和人为压实作用，绿地土壤容重偏大，总孔隙率偏低，加上外来客土影响，土壤物理性黏粒含量高，且有人为侵入体混入等，从而抑制了绿地表层土壤的水分入渗；（2）灌草相对于乔草对绿地表层土壤水分入渗的改善更为明显，这主要与前者的根系分布较浅有关，此外灌草绿地的凋落物更易留存，且其细根分解较快，这均有助于表层土壤有机质的及时返还，从而促进了绿地表层土壤的水分入渗；（3）广州海珠国家湿地公园绿地土壤的水分累积入渗量随时间变化更符合Kostiakov模型。未来广州市绿地的建设及管理应减少土壤压实及外来客土混入，适当增加灌草比例，使其兼顾旅游休闲和雨洪蓄积功能，从而有助于海绵城市的高效建设。;Rapid soil water infiltration in green space plays an important role in the alleviation of flood hazard in urban areas, so its accurate measurement is very critical for the assessment of flood storage capacity in cities. However, the soil infiltration rate of green space in different functional zones varied greatly due to the high spatial heterogeneity in urban soil. In this paper, soil infiltration rate was measured using a double ring infiltrometer and its influencing factors were analyzed in Haizhu National Wetland Park, Guangzhou city. The results indicated that:(1) soil water infiltration capacity in green space of the Haizhu National Wetland Park could be classified as the middle to relatively high level. However, the soil physical clay content and bulk density in our study area were relatively higher, while soil non-capillary porosity was relatively lower in green space soil compared with the natural soil, which could be attributed to its soil source mainly transported from other places, such as pond sludge. Moreover, heavy soil compactions from both mechanical and human activities, as well as mixture of anthropogenic intrusions due to the mismanagement of urban solid waste, which all contributed to the inhibition of soil water infiltration in urban green space. (2) Plantation of shrubs and grasses could greatly improve the soil water infiltration capacity in surface soil of urban green space compared with the plantation of trees and grasses, which was due to the relatively shallow root distribution of shrubs in soils. In addition, more difficulty in cleaning the leaf and branch litter, and higher decomposition rate with finer roots were more commonly observed in urban green space with shrubs and grasses, which both contributed to the rapid feedback of litter from leaves, branches and roots, facilitated the increase of the surface soil organic content, and further enhanced the soil water infiltration capacity in urban green space. (3) With higher R² and lower RMSE, the variation of cumulative infiltration of soil water into the urban green space could be better simulated through the Kostiakov model. The establishment and management of urban green space should focus more on the combined plantation of trees, shrubs and grasses, especially the increase of shrub plantations, while reduce the use of soil from other places, particularly the soil with high physical clay content, and weaken the soil compaction by building the specified passage and recreation area, which will balance the functions between leisure and flood storage in urban green space, and facilitate the development of sponge city in Guangzhou.