【作者】 高文俊；

【导师】 刘增文；

【作者基本信息】 西北农林科技大学 ， 水土保持与荒漠化防治， 2007， 硕士

【摘要】 人工纯林的长期经营会引发诸多生态问题,如地力衰退、林地生产力下降,森林的抗逆性差,抗御自然灾害的能力低下等问题,这不仅影响森林物质生产和多种服务功能的发挥,而且严重威胁着森林生态系统的可持续发展。本项研究以位于秦岭山脉中段的黑河上游安沟小流域境内的四种典型森林(日本落叶松、油松、灰楸和锐齿栎)为研究对象,通过对林地进行外源增施C、N、枯落物客置和客土改造等人为干扰的定位试验,研究不同森林的土壤生物化学性质及其对各种干扰的响应,进一步探讨不同树种的种间关系,为指导当地人工纯林的管理和更新改造提供理论科学依据。所取得的主要结论如下:(1)不同林地的土壤生物化学性质比较结果表明:灰楸和锐齿栎林地的土壤有机C和全氮含量均高于日本落叶松和油松林地。日本落叶松、灰楸、锐齿栎和油松等四种林地土壤酶活性随土层的增加逐渐减小,0-10cm土壤酶活性是10-20cm层的1.18～2.83倍,是20-30cm的1.37～6.55倍。灰楸林地土壤酶活性动态变化为增大。土壤微生物量C(MB-C)和微生物量N(MB-N)随土层深度的增加而逐渐减小,灰楸和锐齿栎林地土壤MB-C高,而MB-N则比落叶松和油松的低。四林地凋落物分解速率表现为灰楸>锐齿栎>日本落叶松>油松。(2)外源增施C、N干扰表明:外源性C干扰使四种林地0-10cm土壤酶活性增大,使灰楸林地20-30cm土壤过氧化氢酶降低了26.9%,使林地0-10cm土层土壤MB-C上升。N干扰对日本落叶松林地土壤酶有抑制,降低了林地MB-C。C、N同时干扰使四林地林地0-10cm土壤脲酶和蔗糖酶增加,使油松林地土壤MB-C上升。日本落叶松林地不宜施N。不同林地对C、N复合干扰的响应不同。凋落物在外源性C、N干扰的作用下,失重率随分解年限的延长而增大,分解50%和95%所需要的时间分别缩短。(3)枯落物客置是将针叶(油松、日本落叶松)林与阔叶(灰楸、锐齿栎)林枯落叶置换。研究结果表明:该措施使灰楸和锐齿栎枯落叶放置在落叶松林地后的土壤酶活性和土壤MB-C降低,其他客置处理的土壤酶活性升高。枯落物客置干扰后,除落叶松和油松枯落叶客置于灰楸林地处理外,枯落物的分解率增大,分解50%需要的时间缩短了2～19个月,分解95%需要的时间缩短了3～7年。日本落叶松和灰楸的混交还有得进一步研究。(4)土壤客置改造干扰是将针叶(油松、日本落叶松)与阔叶(灰楸、锐齿栎)林地的腐殖质按不同比例混合后客置。试验结果表明:0-10cm土层酶活性实测结果都要比预测值大1.03～2.01倍。方差分析表明,土壤酶活性预测值和实测值之间差异极显著,说明客土改造对土壤酶活性的影响较大。日本落叶松林地土壤与灰楸和锐齿栎林地的土壤以1/3或1/1的比例混合对土壤MB-C有一定的抑制。土壤客置改造使林地枯落物的分解率增大,分解50%的时间缩短了6～24个月,分解95%的时间缩短了2～8年。结合枯落物客置的结果,说明日本落叶松不宜与灰楸混交。楸树与油松、油松与锐齿栎、落叶松与锐齿栎有一定的混交可行性,但混交比例还需进一步的研究。更多还原

【Abstract】 Long term management of pure plantation may cause a series of ecological problems, such as fertility degradation, decrease of land productivity, deterioration of forest resistance to natural disasters. This may not only affect production and service function of forest, but also seriously threaten the sustainable development of forest ecosystem. This study took four kinds of typical forestlands with different tree species (Larix kaempferi,Pinus tabulaeformis,Catalpa fargesii,Q. aliena var. acuteserrata) in Angou watershed , upper reaches of Heihe river, middle of Qinling Mountain as subjects, carried out experiments about human disturbance including extra C and N application, litter exchange and soil exchange, analyzed the biochemical characteristic of soil and its response to human disturbance in different forestlands. The interspecific relationship between tree species was investigated in order to offer theoretical direction for pure plantation management and forest renewal in that area. The main results includes :(1) Comparation of biochemical characteristic of soil in different forestlandsThe amount of organic C and total N in Catalpa fargesii and Q.aliena var.acuteserrata lands was higher than in Larix kaempferi and Pinus tabulaeformis lands, but soil bulk density was lower. Soil enzyme activity of four kinds of forestlands decreased with soil depth. The soil enzyme activity in 0-10 layer was 1.18-2.83 times and 1.37-6.55 times higher than 10-20 layer and 20-30 layer, respectively. The soil enzyme activity in Catalpa fargesiiland was increasing. The soil microbial biomass C(MB-C) and soil microbial biomass N(MB-N) decreased with soil depth. Catalpa fargesii and Q.aliena var.acuteserrata lands had higher MB-C but lower MB-N than Larix kaempferi and Pinus tabulaeformis lands. The litter decomposition rates in four kinds of forest lands follow this sequence: Catalpa fargesii>Q.aliena var.acuteserrata>Larix kaempferi>Pinus tabulaeformis.(2) Disturbance of extra C and N applicationExtra C increased soil enzyme activity and MB-C in 0-10 layer in four kinds of lands, but decreased the soil catalase activity in 20-30 layer by 26.9% in Catalpa fargesiiland. Extra N had inhibitory effect on soil enzyme and decreased MB-C in Larix kaempferi land. Application of C and N jointly increased urase and sucrase activity in 0-10 layer in four kinds of lands, and increased MB-C in Pinus tabulaeformis land. It was not suitable to applied N in Larix kaempferi land. The response to C and N joint disturbance was different for different lands. Under extra C and N disturbance, the litter weight loss rate increased as decomposition continued. Time for 50% and 95% decomposition decreased both.(3)Llitter exchange: exchange the litter of conifer(Pinus tabulaeformis,Larix kaempferi) and broadleaf tree(Catalpa fargesii,Q.aliena var.acuteserrata)After putting litter of Catalpa fargesii and Q.aliena var.acuteserrata into Larix kaempferi land, soil enzyme activity and MB-C decreased. Enzyme activity under other exchange treatments all increased. After litter exchange, decomposition rate all increased except putting litter of Larix kaempferi and Pinus tabulaeformis into Catalpa fargesii land. Time for 50% and 95% decomposition shortened by 2-19 months and 3-7 years respectively. Mixed plantation of Larix kaempferi and Catalpa fargesii was not feasible.(4) Soil exchange: exchange the humus layer soil of conifer(Pinus tabulaeformis,Larix kaempferi) and broadleaf tree(Catalpa fargesii,Q.aliena var.acuteserrata) lands after mixed the soil with different ratiosThe measured value of soil enzyme activity in 0-10 layer was 1.03-2.01 times higher than predicted value. Analysis of variance showed that the difference between predicted value and measured value of soil enzyme activity was significant, which implied soil exchange had a considerable effect on soil enzyme activity. The mixing of soil in Larix kaempferi land with soil in Catalpa fargesii and Q.aliena var.acuteserrata land with ratio of 1/3 or 1/1 had an inhibitory effect on MB-C to a certain extent. Soil exchange improved litter decomposition. Time for 50% and 95% decomposition shortened by 6-24 months and 2-8 years respectively. Combined with results of litter exchange, this study showed that Larix kaempferi was not suitable to be planted with Catalpa fargesii。Mixing plantation of Catalpa fargesii and Pinus tabulaeformis,Pinus tabulaeformis and Q.aliena var.acuteserrata, Larix kaempferi and Q.aliena var.acuteserrata is feasible to a certain extent, but mixing ratio needs to be more studies.更多还原