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模拟酸雨淋溶对缙云山针阔混交林与常绿阔叶林凋落物分解的影响
北京林业大学 水土保持学院 重庆缙云山三峡库区森林生态系统国家定位观测研究站，北京 100083
广东省林业科学研究院 广东省森林培育与保护利用重点实验室， 广东 广州 510520
中图分类号: S718.5
Three-gorges Reservoir Area (Chongqing) Forest Ecosystem Research Station, School of Soil and Water Conservation, Beijing Forestry University, Beijing 100083, China
Guangdong Provincial Key Laboratory of Silviculture, Protection and Utilization, Guangdong Academy of Forestry, Guangzhou 510520, Guangdong, China
图12种典型林分凋落物干质量残留率动态
Figure1Changes in dry weight remaining of leaf litter decomposition of three typical tree species
图22种典型林分凋落物干质量平均损失率
Figure2Average dry weight loss rate of litter of two typical forests
表1样地基本情况
Table1.Basic situation of the sample plot
表2凋落物分解的Olson负指数衰减模型
Table2.Olson negative exponential decay model of litter decomposition
中图分类号:S718.5
摘要: 目的 探讨缙云山针阔混交林与常绿阔叶林凋落物分解在酸雨过程中的特点和规律，为优化缙云山森林管理，指导林分配置提供科学依据。 方法 以重庆缙云山2种典型林分为研究对象，进行4个不同酸碱度：pH 4.50(对照)、pH 4.00、pH 3.25和pH 2.50的酸雨模拟实验，结合Olson负指数衰减模型，分析针阔混交林与常绿阔叶林的凋落物分解速率并计算分解系数，定量分析模拟酸雨下2种典型林分的凋落物分解变化规律。 结果 ①经过0.5 a的分解，对照、pH 4.00、pH 3.25和pH 2.50处理下针阔混交林质量残留率均高于常绿阔叶林，分别高4.60%、3.78%、4.22%和5.39%。其中，对照针阔混交林凋落物损失率达到半衰期与全衰期的时间为1.62、6.98 a，常绿阔叶林为1.29和5.56 a；不同酸碱度酸雨淋溶下针阔混交林凋落物损失率达50%和95%的时间分别为1.47~2.00 和6.35~8.43 a，常绿阔叶林分别为1.23~1.50和5.33~6.48 a。②对照、pH 4.00、pH 3.25和pH 2.50各处理下针阔混交林的分解常数k值分别为0.43、0.47、0.40 和0.35，常绿阔叶林则分别为0.54、0.56、0.51和0.46，k值随着处理pH的降低呈下降趋势。③研究区pH 4.00的模拟酸雨一定程度上对林内凋落物的分解有促进作用；pH 2.50和pH 3.25的模拟酸雨一定程度上抑制不同林下调落物的分解。 结论 重庆缙云山模拟不同酸碱度酸雨对2种典型林分的凋落物分解速率影响显著，常绿阔叶林分解速率总体高于针阔混交林，温度制约凋落物分解速率。图2表2参32
Abstract: Objective This study, with an investigation of the characteristics and laws of litter decomposition in mixed coniferous and broad-leaved forest and evergreen broad-leaved forest during acid rain in Jinyun Mountain, is aimed to provide scientific basis for the optimization of forest management and the guidance in forest stand allocation. Method With two typical forests of Jinyun Mountain in Chongqing selected, four acid rain simulation experiments with different concentrations were conducted. Then, with the employment of the Olson negative exponential decay model, the decomposition rate of litter of two forest stands was assessed, and the laws of litter decomposition in two typical forest stands under simulated acid rain were analyzed. Result (1) After a six-month decomposition, in comparison, the mass residue rate of the mixed coniferous and broad-leaved forest treated with acid rain of pH 4.50(ck), pH 4.00, pH 3.25, and pH 2.50 was higher than those of the evergreen broad-leaved forest under the same conditions by 4.60%, 3.78%, 4.22% and 5.39%. (2) The time for the control group to reach half-life and full-life of litter decomposition in the coniferous and broad-leaved mixed forest was 1.62 a and 6.98 a whereas that for evergreen broad-leaved forest was 1.29 and 5.56 a; the time for the material loss rate to reach 50% and 95% for the coniferous and broad-leaved mixed forest litter under different concentrations of acid rain is 1.47−2.00 a and 6.35−8.43 a whereas that for the evergreen broad-leaved forest is 1.23−1.50 a and 5.33−6.48 a. (3) The k values of the mixed coniferous and broad-leaved forests treated with ck, pH 4.0, pH 3.25, and pH 2.5 were 0.43, 0.47, 0.40, and 0.35, respectively while those of the evergreen broad-leaved forest were 0.54, 0.56, 0.51, and 0.46, respectively, and the overall k value shows a downward trend as the pH value of the treatment decreases. (4) The simulated acid rain with pH 4.00 in the study area promoted the decomposition of litter in the forest to a certain extent whereas the simulated acid rain with pH 2.50 and pH 3.25 inhibited the decomposition of falling objects in different forests to a certain extent. Conclusion In Jinyun Mountain of Chongqing, simulated acid rain of different concentrations had a significant effect on the decomposition rates of litters in the two typical stands and the decomposition rate of evergreen broad-leaved forest was higher than that of coniferous and broad-leaved mixed forest. [Ch, 2 fig. 2 tab. 32 ref.]
研究区位于三峡库区(重庆段)重庆市缙云山国家级自然保护区，嘉陵江小三峡之温塘峡西岸。缙云山位于重庆市西北部的北碚、沙坪坝、壁山3个区县境内(29°41′~29°52′N，106°17′~106°24′E)，海拔为175.0~951.5 m，总面积为76 km2。缙云山具有典型的亚热带季风湿润性气候特征，雨量丰富，年均降水量为1 611.8 mm，年均相对湿度为85%以上，年均酸雨pH 4.53，年均日照时数1 293 h。缙云山地形平缓，土层较薄，主要土壤为黄壤和水稻土两大类，土壤pH 3.5~4.5。保护区内植物资源丰富，森林覆盖率高，林分凋落物保护较好，经营性活动如采伐、施肥、抚育等基本停止。主要植被类型为常绿阔叶林、针阔混交林、常绿阔叶灌丛、暖性针叶林、针阔混交林、竹林，以及亚热带灌草丛等。主要树种为马尾松、四川大头茶Gordonia acuminate、杉木Cunninghamia lanceolata、四川山矾Syraplocos setchuanensis、白毛新木姜子Neolitea aurata等。
表 1样地基本情况
Table 1.Basic situation of the sample plot
其中：t0.5为凋落物分解至50%(半衰期)需要的时间(a)，t0.95为凋落物分解至95%(全衰期)需要的时间(a)。
采用Excel 2019软件整理数据，采用SPSS 26.0软件进行统计分析，采用LSD最小差异显著法多重比较。
图 12种典型林分凋落物干质量残留率动态
Figure 1.Changes in dry weight remaining of leaf litter decomposition of three typical tree species
图 22种典型林分凋落物干质量平均损失率
Figure 2.Average dry weight loss rate of litter of two typical forests
在相同pH值酸雨处理下，针阔混交林、常绿阔叶林凋落物在6—7月(即30~60 d)干质量残留率曲线平缓，8—9月(即94~122 d)曲线下降幅度较大，表明在相同pH值处理下，针阔混交林、常绿阔叶林在6—7月分解缓慢，5月、8—9月凋落物分解较为迅速。随着时间的推移，针阔混交林在9月(122 d)后凋落物分解速率降低，呈平缓趋势，常绿阔叶林在9月后凋落物分解速率仍达到较高水平，下降明显。在相同月份下，凋落物干质量残留率在pH 2.50处理下最高，pH 4.00处理最低。
表 2凋落物分解的Olson负指数衰减模型
Table 2.Olson negative exponential decay model of litter decomposition
综上，重庆缙云山针阔混交林和常绿阔叶林凋落物质量残留率、半衰期和全衰期的变化特征受不同酸碱度酸雨影响显著，模拟酸雨pH 4.00处理时凋落物分解速率最大，常绿阔叶林分解速率总体高于针阔混交林。在同一区域范围内，除酸雨酸碱度、凋落物种类之外，凋落物分解速率还受到温度条件的制约。