三峡水库城区消落带人工草本植被土壤养分含量研究

为研究三峡水库城区消落带人工植被种植后,经不同淹水时间土壤的化学特性变化规律,及探讨城区消落带植被重建对库区水质的潜在影响,分别对2012年6月、2013年3月、2013年5月、2013年7月、2013年9月城区消落带扁穗牛鞭草(Hc)、狗牙根(Cd)、小巴茅(Ss)和裸地土壤的pH值和养分含量进行了调查研究。结果表明,植被类型对土壤pH值、碱解氮(AN)、有效磷(AP)、全磷(TP)含量有显著影响。综合而言,与裸地相比,人工草本植被土壤pH值和养分含量无显著差异。该区土壤pH值在6.5~8.5间波动。不同淹水时间的城区消落带土壤营养元素含量间存在较大差异。随取样时间的延长,裸地和人工植被土壤pH值、有机质含量呈波动变化。AN含量在2013年3月、2013年9月消落带刚开始落干时较高。然而,AP含量在2012年6月最大,此时,裸地、扁穗牛鞭草、狗牙根、小巴茅土壤AP含量分别为(2.62±0.30),(3.92±0.34),(1.08±0.16),(1.24±0.06) mg/kg。土壤全磷、全钾含量则在研究后期有所增加。研究表明,除地表植被、水文因素外,城市污水排放、强烈人为干扰、地表径流带来的点/面源污染等也影响该城区消落带土壤营养元素含量。对于三峡库区长江重庆主城区河段而言,由人工草本植被构建造成的水体富营养化程度有限。

Nutrient content of soils under artificial grass vegetation in the urban hydro-fluctua-tion belt of the Three Gorges Reservoir Region

A study has been undertaken to explore the dynamics of soil chemical properties under different water-logging durations following re-vegetation in the urban hydro-fluctuation belt of the Three Gorges Reservoir Region. The study also aimed to determine the potential impact of vegetation reconstruction on water quality. Soil samples were taken from Hemarthria compressa, Cynodon dactylon and Saccharum spontaneum communities, and from non-vegetated areas in a hydro-fluctuation belt located in downtown Chongqing, in June 2012, March 2013, May 2013, July 2013 and September 2013. Analysis was undertaken of soil pH, organic matter (OM), alkali hydrolysable nitrogen (AN), available phosphorus (AP), available potassium (AK), total nitrogen (TN), total phosphorus (TP) and total potassium (TK). Results showed that vegetation type significantly influenced soil pH values and AN, AP and TP contents. No significant differences were found in the tested properties between soils without vegetation and those beneath the three types of artificial grasses. However, there were significant soil differences under different water-logging durations. pH values and OM contents fluctuated throughout the experiment. Soil pH ranged from 6.5 to 8.5. AN contents were relatively higher in March and September 2013, when the water level dropped, while maximum AP contents were found in June 2012. At that time, AP contents under bare areas, H. compressa, C. dactylon, and S. spontaneum were (2.62±0.30), (3.92±0.34), (1.08±0.16), and (1.24±0.06) mg/kg respectively. TP and TK contents increased in the later phases of the experiment. The study also showed that, besides vegetation and hydrological factors, other factors such as urban sewage discharge, human disturbance and point or non-point source pollution caused by surface runoff influenced soil pH and nutrients. For the Yangtze River in Chongqing urban areas of the Three Gorges Reservoir Region, the potential risk of water eutrophication caused by artificial grasses might be lower.