Co-Innovation Center for Sustainable Forestry in Southern China, Jiangsu Province Key Laboratory of Soil and Water Conservation and Ecological Restoration, Nanjing Forestry University, 159 Longpan Road, Nanjing, Jiangsu 210037, China.
Jiangsu Province Key Laboratory of Ecological Engineering, Nanjing Forestry University, Nanjing 210037, China.
Sci Total Environ. 2018 Mar 15;618:336-346. doi: 10.1016/j.scitotenv.2017.11.073. Epub 2017 Nov 10.
The influence of acid rain on forest trees includes direct effects on foliage as well as indirect soil-mediated effects that cause a reduction in fine-root growth. In addition, the concentration of NO in acid rain increases with the rapidly growing of nitrogen deposition. In this study, we investigated the impact of simulated acid rain with different SO/NO (S/N) ratios, which were 5:1 (S), 1:1 (SN) and 1:5 (N), on fine-root growth from March 2015 to February 2016. Results showed that fine roots were more sensitive to the effects of acid rain than soils in the short-term. Both soil pH and fine root biomass (FRB) significantly decreased as acid rain pH decreased, and also decreased with the percentage of NO increased in acid rain. Acid rain pH significantly influenced soil total carbon and available potassium in summer. Higher acidity level (pH=2.5), especially of the N treatments, had the strongest inhibitory impact on soil microbial activity after summer. The structural equation modelling results showed that acid rain S/N ratio and pH had stronger direct effects on FRB than indirect effects via changed soil and fine root properties. Fine-root element contents and antioxidant enzymes activities were significantly affected by acid rain S/N ratio and pH during most seasons. Fine-root Al ion content, Ca/Al, Mg/Al ratios and catalase activity were used as better indicators than soil parameters for evaluating the effects of different acid rain S/N ratios and pH on forests. Our results suggest that the ratio of SO to NO in acid rain is an important factor which could affect fine-root growth in subtropical forests of China.
酸雨对森林树木的影响包括对树叶的直接影响以及通过土壤间接造成的影响，后者会导致细根生长减少。此外，随着氮沉积的迅速增加，酸雨的氮氧化物浓度也会增加。在本研究中，我们调查了不同 SO/NO（S/N）比值的模拟酸雨（S/N 比分别为 5:1、1:1 和 1:5）对 2015 年 3 月至 2016 年 2 月间细根生长的影响。结果表明，短期内细根比土壤对酸雨的影响更为敏感。随着酸雨 pH 值的降低，土壤 pH 值和细根生物量（FRB）均显著下降，而酸雨的氮氧化物百分比也随之下降。酸雨 pH 值在夏季显著影响土壤总碳和有效钾。较高的酸度水平（pH=2.5），尤其是 N 处理，对夏季后土壤微生物活性的抑制作用最强。结构方程模型结果表明，酸雨 S/N 比和 pH 值对 FRB 的直接影响大于通过改变土壤和细根特性的间接影响。在大多数季节，细根元素含量和抗氧化酶活性都受到酸雨 S/N 比和 pH 值的显著影响。细根铝离子含量、Ca/Al、Mg/Al 比值和过氧化氢酶活性比土壤参数更适合作为评价不同酸雨 S/N 比和 pH 值对森林影响的指标。我们的结果表明，酸雨的 SO 与 NO 比值是影响中国亚热带森林细根生长的一个重要因素。
