密度调控对川西山地云杉人工林地被物及土壤水文特征的影响

Effects of density adjustment on ground cover and soil hydrological function of Picea asperata plantation in the subalpine region of western Sichuan Province,China

【目的】研究不同密度调控(对照(未疏伐)、密度调控Ⅰ(疏伐强度65%)、密度调控Ⅱ(疏伐强度75%))对川西山地云杉(Picea asperata Mast.)人工林地被物及土壤水文特征的影响。【方法】通过典型抽样法获取了不同处理方式下林地苔藓、枯落物和土壤的水文指标,并开展相关指标的比较分析。【结果】疏伐不但促进了云杉人工林的单株生长量,还促进了林下植被的生长,各调控处理促进效果从强到弱依次为调控Ⅱ、调控Ⅰ、对照;林下苔藓的最大持水率介于558%~594%之间,显著低于天然林,但在3个处理间不存在显著差异;就苔藓蓄积量和最大持水量而言,密度调控Ⅱ显著高于另两种处理,这可能与林下苔藓多样性和生物量随着光照条件的改善而增加有关;3个处理间,林下枯落物的蓄积量、最大持水率和最大持水量均无显著差异;云杉人工林林下土壤密度介于0.87~0.93 g/cm^3之间,显著高于天然次生林以及原始林土壤密度,但无论是在各个层次间还是不同的处理类型下均无显著的差异。两种密度调控处理的土壤毛管持水量、最小持水量和最大持水量均较对照组显著增加,但两密度调控组间则无显著差异,这可能是因为林分地下生物量的增加,促进土壤层有机质含量以及土壤动物活动等,进而促进土壤层孔隙度增加并改善渗透能力。【结论】从6 a的短期效应看,两种调控处理均对云杉人工林的地被物和土壤的持水能力产生了一定的正面效应,且密度调控Ⅱ的影响更大些,长期影响仍有待于进一步研究。

【Objective】To determine the effects of density adjustment on ground cover and soil hydrological function of Picea asperata plantations in the subalpine region of western Sichuan Province,China.【Method】Moss,litter and soil of Picea asperata plantations with different density adjustment modes（no disturbance,0%; adjustment Ⅰ,65%; adjustmentⅡ,75%） were measured and sampled,and hydrological functions of soils were analyzed.【Result 】The results showed that thinning increased not only the net primary production of planted Picea asperata plantations but also the growth of understory（adjustmentⅡ 〉adjustment Ⅰ 〉no disturbance）.The maximal water holding rate（MWHR） of moss under Picea asperata plantations was between 558% and 594%,which was significantly lower than that of natural forests.There were no significant differences among the three modes.Cumulated mass（CM） and the maximal water holding capacity（MWHC） from the adjustment Ⅱ mode was significantly greater than that of the other modes,which might have been caused by the increase indiversity and biomass of mosses with improved light conditions.However,there were no significant differences in MWHR,CM,and MWHC in the litters among the three modes.Soil bulk density of planted forests was from 0.87 to 0.93 g/cm^3,and was significantly higher than that of the natural forest.There were no significant differences in soil bulk density between levels or among different modes.Capillary water holding capacity,the lleast water holding capacity（LWHC）,and MWHC from thinned forests increased significantly compared with that of the undisturbed forest.This maybe caused by improved soil porosity and soil penetrability resulting from increased soil organic content and activity of soil animals after thinning.【Conclusion】Six years after the treatments,two modes of density adjustment had positive effects on ground cover and soil in Picea asperata plantations; 75% reduction in density led to greater effects than did 65% reduction.A long-term study is needed to further investigate the hydrological and ecological effects of different density adjustments to Picea asperata plantations.