模拟酸雨对不同土壤有机碳和作物秸秆分解的影响

为研究酸雨对不同pH值水稻土中有机碳分解的影响，选择酸性（pH 5.48）、碱性（pH 8.18）和中性（pH 6.70）水稻土（分别设置施用秸秆0、15 g·kg^-1土处理）在20 ℃条件下进行40 d的培养试验，各土壤组分别用pH值为6.0、4.5、3.0的模拟雨水将土壤含水量调为400 g·kg^-1(以风干土计).结果表明：秸秆、酸雨和土壤共同对土壤系统CO₂释放产生影响，秸秆的添加可显著提高土壤CO₂释放速率.培养期间，酸雨未显著影响土壤有机碳分解，但对土壤中作物秸秆的分解影响显著. pH 3.0酸雨处理下酸性和碱性土壤中秸秆40 d总分解量比pH 6.0处理高8%;酸雨抑制了中性水稻土中秸秆的分解，pH 3.0酸雨处理下秸秆40 d总分解量比pH 6.0处理低15%.pH 3.0酸雨处理下，酸性水稻土有机碳分解速率分别比中性和碱性水稻土高43%和50%（P<0.05），秸秆在中性水稻土中分解量分别比其在酸性和碱性水稻土中低17%和16%（P<0.05）.

Effects of simulated acid rain on decomposition of soil organic carbon and crop straw.

To evaluate the effects of acid rain on the organic carbon decomposition in different acidity soils, a 40-day incubation test was conducted with the paddy soils of pH 548, 670 and 818. The soils were amended with 0 and 15 g·kg-1 of rice straw, adjusted to the moisture content of 400 g·kg-1 air-dried soil by using simulated rain of pH 60, 45, and 30, and incubated at 20 ℃. The results showed that straw, acid rain, and soil co-affected the CO2 emission from soil system. The amendment of straw increased the soil CO2 emission rate significantly. Acid rain had no significant effects on soil organic carbon decomposition, but significantly affected the straw decomposition in soil. When treated with pH 30 acid rain, the amount of decomposed straw over 40-day incubation in acid (pH 5.48) and alkaline (pH 818) soils was 8% higher, while that in neutral soil (pH 670) was 15% lower, compared to the treatment of pH 60 rain. In the treatment of pH 30 acid rain, the decomposition rate of soil organic C in acid (pH 548) soil was 43% and 50% (P<005) higher than that in neutral (pH 670) and alkaline (pH 818) soils, while the decomposition rate of straw in neutral soil was 17% and 16% (P<005) lower than that in acid and alkaline soils, respectively.