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冻融循环对五台山典型植被土壤微团聚体的影响
李杨波1, 刘楠1, 韩进斌2, 郭勇强2, 李变华2, 申彦科3
1.太原理工大学 水利科学与工程学院, 山西 太原 030024;2.山西省林业厅, 山西省五台山树木园, 山西 忻州 035500;3.中水北方勘测设计研究有限责任公司, 天津 300220
摘要:
[目的]研究气候变化背景下季节性冻融对土壤微团聚体的作用,为影响林线附近土壤地球生物化学过程的相关研究提供参考。[方法]选择五台山林线附近3种典型植被:草甸、华北落叶松(Larix principis-rupprechtii)和云杉(Picea meyeri)覆盖下的土壤,通过土柱野外原位培养,测定不同时期土壤各粒径微团聚体含量以及土壤分形维数(D)。[结果]在培养期内,3个样地的2~0.25 mm和0.25~0.05 mm团聚体含量变化趋势各不相同; 0.05~0.02 mm (先降后增再降),0.02~0.002 mm (先降后增,华北落叶松样地除外),<0.002 mm (先增后降)团聚体含量变化趋势基本一致。在初冻期和融化期,季节性冻融导致3个样地土壤微团聚体含量发生显著变化(p<0.05),深冻期无显著变化(p>0.05)。生长季同样发生了土壤微团聚体含量的显著变化(p<0.05)。不同样地植被组成的差别造成了土壤微团聚体含量差异显著(p<0.05),体现在初冻期和融化期。季节性冻融期间,土壤微团聚体分形维数逐渐增加,而此时云杉样地土壤微团聚体分形维数最低;生长季期间,微团聚体分形维数逐渐降低,草甸样地土壤微团聚体分形维数最低,但在生长季末期,则是华北落叶松样地最低;但3个样地土壤微团聚体分形维数仅在生长季末期存在显著差异(p<0.05),且培养期结束时的土壤分形维数与开始时无显著差异(p>0.05)。[结论]季节性冻融对3个样地土壤微团聚体含量都具有显著影响,且3种植被下土壤结构对季节性冻融的响应也明显不同,主要发生在初冻期和融化期;在培养期内,虽在冻融作用下土壤微团聚体分形维数增加,但进入生长季后都逐渐减少至培养前水平,3个样地土壤结构性和团聚能力均呈周期性变化,具有一定的自我恢复能力。
关键词:  冻融循环  林线  土壤微团聚体  分形  五台山
DOI:10.13961/j.cnki.stbctb.2018.05.004
分类号:S714;S718.5
基金项目:国家自然科学基金项目“基于水文过程和冻融循环的高山植被土壤氮动态研究”(31400618);国家留学基金管理委员会资助(201708140203,留金法[2017]5087号);国家自然科学基金项目(41572239,41502243)
Effects of Freeze-thaw Cycles on Soil Micro-aggregates in Typical Vegetations of Wutai Mountain
LI Yangbo1, LIU Nan1, HAN Jinbin2, GUO Yongqiang2, LI Bianhua2, SHEN Yanke3
1.College of Water Resources Science and Engineering, Taiyuan University of Technology, Taiyuan, Shanxi 030024, China;2.Shanxi Provincial Department of Forestry, Shanxi Wutai Mountain Arboretum, Xinzhou, Shanxi 035500, China;3.Beifang Investigation, Design & Research Co. Ltd, Tianjin, 300222, China
Abstract:
[Objective] The effect of seasonal freeze-thaw on soil micro-aggregates in the context of climate change was studied in order to provide references for the reserch of soil biochemical processes near the timberline.[Methods] Soil samples from three typical vegetation types (meadow, Larix principis-rupprechtii and Picea meyeri) near the timberline of Wutai Mountain were collected for soil column in situ experiment. Soil micro-aggregates contents and fractal dimensions (D) were measured.[Results] The variations of 2~0.25 mm and 0.25~0.05 mm aggregate contents were different among the three plots. The content of 0.05~0.02 mm aggregate reduced initially, then increased and finally reduced. The content of 0.02~0.002 mm aggregate reduced initially and then increased (except in Larix principis-rupprechtii plot), and the content of <0.002 mm micro-aggregates increased firstly and then reduced. The content of micro-aggregates changed significantly (p<0.05) due to seasonal freeze-thaw events in initial freezing and thawing periods, while there was no significant change in deep freezing period (p>0.05). Soil micro-aggregate contents also changed significantly (p<0.05) in the growing season. Different vegetation compositions caused significant differences (p<0.05) among micro-aggregate contents in three plots, especially, in initial freezing and thawing periods. During the freezing-thawing period, D values were increased, and that of Picea meyeri plots was the lowest. In growing season, D values were decreased, and that of meadou plots was the lowest. Significant differences (p<0.05) of D values among three researched plots were only observed in the late growing season, and the least D value is obtained in H. principis-rupprechtii.[Conclusion] Freeze-thaw cycles have great impacts on soil micro-aggregate contents. The responses of soil structures to seasonal freeze-thaw events are significantly different, and mainly occur in initial freezing period and thawing period. The D values of all plots are increased by freeze-thaw cycles. Although the D value of soil microaggregates increased during the incubation period, it gradually decreased to the pre-incubation level after entering the growing season. Soil aggregations and structures of all three plots vary periodically and have certain self-recovery capabilities.
Key words:  freeze-thaw cycles  timberline  soil micro-aggregates  fractal  Wutai Mountain