模拟酸雨对南亚热带典型森林土壤N2O排放的影响

基于长期模拟酸雨森林样地,利用箱式法同步测定了不同酸雨强度处理下森林土壤N₂O排放通量,研究了模拟酸雨对我国南亚热带针阔叶混交林和季风常绿阔叶林两种代表性森林土壤N₂O排放的影响。结果表明: 连续5年(2014—2018年)观测周期内,两种林型土壤N₂O排放通量在各模拟酸雨处理下均表现出明显的季节变化特征,湿季排放通量高于干季,并且年际变化较大。受2017—2018年度降水减少的影响,此期间两种林型土壤N₂O排放通量普遍较低。两种林型土壤N₂O排放通量与土壤温度和土壤湿度呈显著正相关。季风常绿阔叶林对照样方土壤N₂O排放通量为12.6 μg N₂O m^-2·h^-1,与对照相比,pH 3.5和pH 3.0条件下土壤N₂O排放通量分别上升42.9%和61.1%,模拟酸雨显著增加了季风常绿阔叶林土壤N₂O排放通量;模拟酸雨同样有促进针阔叶混交林土壤N₂O排放的趋势,但各处理间差异不显著。在酸雨依旧严峻的形势下,我国南亚热带典型森林土壤N₂O排放通量将增加,且不同林型的增幅不同。

Effects of simulated acid rain on soil N2O emission from typical forest in subtropical sou-thern China.

Based on a long-term simulated acid rain experiment, soil N₂O emission fluxes were measured using static chambers and the gas chromatography method in a coniferous and broadleaved mixed forest and a monsoon evergreen broadleaved forest in southern China. During the five-year observation periods (2014-2018), soil N₂O emission fluxes in the two forests showed obvious seasonal variation. The soil N₂O emission fluxes in wet season were significantly higher than that in dry season, with a large annual variation. Due to the decreases of precipitation, soil N₂O emission fluxes of the two forests in 2017 and 2018 were generally low. Soil N₂O emission flux was positively correlated with soil temperature and soil moisture. In the monsoon evergreen broadleaved forest, soil N₂O emission flux in the control plot was 12.6 μg N₂O·m^-2·h^-1. Soil N₂O emission fluxes under the pH 3.5 and pH 3.0 treatments increased by 42.9% and 61.1%, respectively. Soil N₂O emission was significantly increased under simulated acid rain in the monsoon evergreen broadleaved forest. Acid rain promoted soil N₂O emission in the coniferous and broadleaved mixed forest, but without significant difference among the treatments. Under the scenario of increasing acid rain, soil N₂O emission fluxes in typical subtropical southern China forests would increase, and the magnitude of such increase was different among forest types.