三峡水库消落带柳树(Salix matsudana)种植初期对土壤碳、氮、磷含量的影响

Soil C,N and P Contents After Short-Term Revegetation by Salix matsudanain the Water-Level-Fluctuation Zone of Three Gorges Reservoir

以三峡库区汝溪河流域165-170m和170-175m两个海拔段的人工种植柳树土壤为研究对象,比较两个海拔段土壤的化学性质在一个淹水周期前后的变化特征,包括土壤pH值、有机质（OM）、碳氮比（C/N）、全氮（TN）、硝态氮（NO-3-N）、铵态氮（NH＋4-N）、全磷（TP）和有效磷（AP）含量,并设置裸地土壤作为空白对照.结果显示,三峡水库消落区不同海拔高程的柳树生长状况良好,水淹后生长于高海拔的柳树较低海拔的柳树冠幅和胸径分别高出22.2%和48.8%;对于裸地土壤,经过淹水后其pH值趋向中性变化,全氮和铵态氮含量增加,硝态氮含量下降;与裸地相比,栽植柳树的土壤全磷含量显著升高,碳氮比、有效磷、有机质、铵态氮含量显著下降.研究表明,柳树良好的适应能力使其能在三峡库区消落带大量存活,但是由于其土壤N,P营养元素含量的增加而对水体富营养化问题的产生存在一定的贡献潜力也是不容忽视的.

Soils at two altitudes （165-170 m and 170-175 m） located in the water-level fluctuating zone of Three Gorges Reservoir （TGR） under Salix matsudana vegetation were selected as the study objects. The dynamics of soil chemical properties （pH, C/N, TN, NO3^-N, NH4^＋-N, TP and AP） before and after flooding were contrastively studied in the Ruxi water basin area. Blank soils with no vegetation at each altitude were set up as the control （CK）. S. matsudana seedlings growing in the TGR were in good condition, and their canopy and diameter at breast height （DBH） after flooding were 22.2% and 48.8% higher at 170-175 m than at 165-170 m, respectively. For the CK, pH increased in acid soil, but decreased in alkaline soil, and the contents of total nitrogen and NH4^＋-N increased, while NO3^-N content decreased significantly after flooding. Compared with the CK, the TN content in the soil under S. matsudana vege- tation significantly increased, while C/N ratio, AP, OM, and NH4^＋-N significantly decreased. It can be seen from the above results that after planting S. rnatsudana in the riparian areas of the Three Gorges Reservoir, water eutrophication might be aggravated due to the increase of soil N and P contents.