氮沉降下滇中高原森林凋落物分解特征对其持水性的影响

研究模拟氮沉降下凋落物分解特征对其持水性的影响,旨在为氮沉降背景下森林生态系统养分循环和水分循环相关研究提供理论依据。以滇中高原常绿阔叶林和高山栎林为研究对象,在野外开展模拟氮沉降下凋落叶、枝原位分解研究试验,设置0(对照CK),10(低氮LN),20(中氮MN),25(高氮HN) g/(m²·a)N共4种处理,利用尼龙网袋法和室内浸泡法,探究不同处理下凋落叶、枝质量残留率、持水量和持水率及吸水速率变化特征。结果表明：(1) 2种林分凋落叶、枝质量残留率随分解时间延长而减少;与CK质量残留率相比,LN处理2种林分凋落叶、枝无显著影响(p>0.05),MN和HN处理使常绿阔叶林凋落叶分解第16,19,23,24个月和HN处理高山栎林凋落叶分解第16个月分别增加5.05%～7.45%,7.88%～8.62%,4.72%。(2)与CK分解95%所需时间相比,LN处理使常绿阔叶林凋落叶、枝和高山栎林凋落枝分别增加0.549,0.366,0.402年,高山栎林凋落叶则减少1.011年,MN和HN处理使2种林分落叶、枝增加0.236～3.638年。(3)分解时间和氮沉降...

Influence of Decomposition Characteristics of Forest Litter on Water Holding Capacity Under Nitrogen Deposition in Central Yunnan Plateau

To study the influence of decomposition characteristics of litter on their water holding capacity under simulated nitrogen (N) deposition so as to provide a theoretical basis for the study of nutrient and water cycling in forest ecosystem under N deposition. The evergreen broad-leaved forest and Quercus semicarpifolia forest in central Yunnan Plateau were selected to conduct in situ leaf litter and twig decomposition experiment with four N treatment levels of 0 (control check CK), 10 (low nitrogen LN), 20 (medium nitrogen MN) and 25 (high nitrogen HN) g/(m²·a)N. Litterbag method and the laboratory immersion method were used to explore the variation characteristics of mass remaining rate, water holding capacity, water holding rate and water absorption rate of leaf litter and twig litter under different treatment. The results showed that: (1) The mass remaining rate of leaf litter and twig litter in two forest types decreased with the extension of decomposition time. Compared with the mass remaining rate of CK, LN treatment had no significant effect on leaf litter and twig litter in two forest types. MN and HN treatments increased leaf litter decomposition in evergreen broad-leaved forest at 16, 19, 23, 24 months and HN treatment increased leaf litter decomposition in Q. semicarpifolia forest at 16 months by 5.05%~7.45%, 7.88%~8.62% and 4.72%, respectively. (2) Compared with the CK, LN treatment increased the time required for 95% decomposition of leaf litter and twig litter in evergreen broad-leaved forest and twig litter in Q. semicarpifolia forest by 0.549, 0.366 and 0.402 years, respectively, while that of leaf litter in Q. semicarpifolia forest decreased by 1.011 years, and that of leaf litter and twig litter in two forest types under MN and HN treatment increased by 0.236~3.638 years. (3) The decomposition time, nitrogen deposition and their interaction significantly affected the maximum water holding capacity, maximum water holding rate, maximum water absorption of leaf litter and twig litter (p<0.001). Compared with the CK, the maximum water holding capacity, maximum water holding rate, maximum water absorption of leaf litter in evergreen broad-leaved forest under LN and MN treatments decreased by 21.99%,6.47%,54.47%,16.14%,4.15% and 1.25%, respectively, and those under HN treatment increased by 0.24%, 0.80%, and 0.96%, respectively, and in LN and MN and HN treatments, those of twig litter in evergreen broad-leave forest and leaf and twig litter in Q. semicarpifolia forest increased by 8.03%~38.22%, 5.47%~60.00% and 0.46%~5.72%, respectively. (4) The relationship between water holding capacity and the water holding rate of leaf litter and twig litter in two forest types and immersion time was a logarithmic function (m=a+bln t), and the water absorption rate was exponentially related to immersion time (v=at^-b). (5) The mass remaining rate of leaf litter in evergreen broad-leaved forest and that of twig litter in Q. semicarpifolia forest were significantly and positively correlated with their maximum water holding capacity, maximum water holding rate and maximum water absorption rate, respectively (p<0.05). In conclusion, the water holding capacity of litter was affected by the decomposition stage and nitrogen deposition.