Chen Xi, Chen Fu-sheng, Ye Su-qiong, Yu Su-qin, Fang Xiang-min, Hu Xiao-fei
Ying Yong Sheng Tai Xue Bao. 2015 Jan;26(1):1-8.
Tea (Camellia sinensis) plantation in hilly red soil region has been long impacted by acid deposition, however its effects on nitrogen (N) and phosphorus (P) transformations in rhizosphere soils remain unclear. A 25-year old tea plantation in a typical hilly red soil region was selected for an in situ simulation experiment treated by pH 4.5, pH 3.5, pH 2.5 and control. Rhizosihere and bulk soils were collected in the third year from the simulated acid deposition experiment. Soil mineral N, available P contents and major enzyme activities were analyzed using the chemical extraction and biochemical methods, and N and P mineralization rates were estimated using the indoor aerobic incubation methods. Our results showed that compared to the control, the treatments of pH 4.5, pH 3.5 and pH 2.5, respectively decreased 7.1%, 42.1% and 49.9% NO3(-)-N, 6.4%, 35.9% and 40.3% mineral N, 10.5%, 41.1% and 46.9% available P, 18.7%, 30.1% and 44.7% ammonification rate, 3.6%, 12.7% and 38.8% net N-mineralization rate, and 31.5%, 41.8% and 63.0% P mineralization rate in rhizosphere soils; however, among the 4 treatments, rhizosphere soil nitrification rate was not significantly different, the rhizosphere soil urease and acid phosphatase activities generally increased with the increasing intensity of acid rain (P<0.05). In bulk soil, compared with the control, the treatments of pH 4.5, pH 3.5 and pH 2.5 did not cause significant changes in NO3(-)-N, mineral N, available P as well as in the rates of nitrification, ammonification, net N-mineralization and P mineralization. With increasing the acid intensity, the rhizosphere effects of NH4+-N, NO3(-)-N, mineral N, ammonification and net N-mineralization rates were altered from positive to negative effects, those of urease and acid phosphatease showed the opposite trends, those of available P and P mineralization were negative and that of nitrification was positive. In sum, prolonged elevated acid rain could reduce N and P transformation rates, decrease their availability, alter their rhizosphere effects, and have impact on nutrient cycling in tea plantation.
丘陵红壤地区的茶园长期受到酸沉降的影响，但其对根际土壤中氮（N）和磷（P）转化的影响尚不清楚。选择典型丘陵红壤地区的一个25年生茶园进行原位模拟实验，设置pH 4.5、pH 3.5、pH 2.5处理及对照。在模拟酸沉降实验的第三年采集根际土和非根际土。采用化学提取和生化方法分析土壤矿质氮、有效磷含量及主要酶活性，采用室内好气培养法估算氮磷矿化率。结果表明，与对照相比，pH 4.5、pH 3.5和pH 2.5处理分别使根际土壤中NO3(-)-N含量降低7.1%、42.1%和49.9%，矿质氮含量降低6.4%、35.9%和40.3%，有效磷含量降低10.5%、41.1%和46.9%，氨化率降低18.7%、30.1%和44.7%，净氮矿化率降低3.6%、12.7%和38.8%，磷矿化率降低31.5%、41.8%和63.0%；然而，4种处理中根际土壤硝化率差异不显著，根际土壤脲酶和酸性磷酸酶活性总体上随酸雨强度增加而升高（P<0.05）。在非根际土壤中，与对照相比，pH 4.5、pH 3.5和pH 2.5处理对NO3(-)-N、矿质氮、有效磷以及硝化、氨化、净氮矿化和磷矿化速率均未引起显著变化。随着酸强度增加，根际土壤中NH4+-N、NO3(-)-N、矿质氮、氨化和净氮矿化速率的根际效应由正效应转变为负效应，脲酶和酸性磷酸酶的根际效应呈相反趋势，有效磷和磷矿化的根际效应为负，硝化的根际效应为正。总之，长期酸雨增加会降低氮磷转化率，减少其有效性，改变其根际效应，影响茶园养分循环。
