不同梯度氮沉降对亚热带甜槠林凋落物及养分的影响

Effects of Nitrogen Deposition on Litterfall and Its Nutrient in Subtropical Evergreen Broad-leaved Castanopsis Eyrei Forest

[目的] 分析不同梯度氮沉降作用下亚热带常绿阔叶甜槠（Castanopsis eyrei）林凋落物量及养分变化规律，从而为亚热带地区氮沉降研究提供数据参考与理论依据。[方法] 对安徽省仙寓山地区设置不同梯度施氮对照试验，长期实地监测甜槠林凋落物量及其养分的响应状况。[结果] 凋落物量大小顺序为：高氮加磷（HN＋P） 〉 低氮（LN） 〉 高氮（HN） 〉 对照CK，不同处理间的差异未达到显著水平；但是落叶量LN与CK之间差异显著（p=0.023）。各处理凋落物量的月变化模式均呈双峰型，分别在4和11月达到峰值；凋落物中各组分所占比例从大到小均为：叶 〉 果 〉 枝 〉 碎屑 〉 花 〉 皮；施肥处理不同程度上改变了落果量的比重：HN＋P（27%） 〉 HN（25%） 〉 CK=LN（23%）。甜槠林C，N，P，K，Ca，Mg这6种大量元素的养分年归还量共计：HN＋P 4.62 t/（hm^2·a） 〉 CK 4.44 t/（hm^2·a） 〉 HN 4.17 t/（hm^2·a） 〉 LN 3.96 t/（hm^2·a）；不同处理各养分（K除外）归还量均表现为上述关系，且HN＋P与CK之间的N，P的养分归还量差异显著（p=0.047；0.023）。对于各组分而言，落叶的养分归还量占年养分归还量的52%～58%。[结论] 模拟不同梯度的氮沉降处理在一定程度上改变了甜槠林凋落物总量的大小及其组成比例，且影响到其他养分的吸收及归还量。

[Objective] This essay provided data reference and theoretical basis for nitrogen deposition in subtropical regions by analyzing effects of nitrogen deposition on litterfall and its nutrient in a subtropical evergreen broad-leaved Castanopsis eyrei forest.[Methods] Different gradient nitrogen control experiments were set up in Xianyu mountain area of Anhui Province to monitor C. eyrei forest litterfall and nutrient response status for a long time.[Results] The order of the annual litterfall were as follows：high nitrogen and phosphorus（HN＋P） 〉 low nitrogen（LN） 〉 high nitrogen（HN） 〉 control check（CK）. There was no significant difference among the treatments. There was significant difference in foliar litter between LN and CK treatments（p=0.023）. The total litterfall showed a bimodal type with the peaks appeared in April and November. The order of the proportion of the different litter components for the four treatments ranked as leaf 〉 fruit 〉 branch 〉 miscellaneous 〉 flower 〉 bark. HN＋P and HN treatments changed the fruit percentage to a certain degrees：HN＋P（27%） 〉 HN（25%） 〉 CK=LN （23%）. The annual amount of total nutrient-returns of the six macro-elements（C, N, P, K, Ca, Mg） was as follows：HN＋P 4.62 t/（hm^2·a） 〉 CK 4.44 t/（hm^2·a） 〉 HN 4.17 t/（hm^2·a） 〉 LN 3.96 t/（hm^2·a）. The similar patterns appeared for C, N, P, Mg, Ca returns in the four treatments. There was significant differences in annual returns of N and P between HN＋P and CK treatments（p=0.047; p=0.023）. The nutrient return from foliar litter covered 52%～58% of the annual total.[Conclusion] We simulated different gradient of nitrogen settlement and found that it changed the C. eyrei forest total litter amount and composition proportion in a certain extent and affected the absorption of other nutrients and return amount.