【作者】 陈光升；

【导师】 胡庭兴；

【作者基本信息】 四川农业大学 ， 森林培育， 2008， 博士

【摘要】 凋落物分解是森林生态系统最为关键的生态过程之一,对森林的生物地球化学循环起着重要的作用。凋落物是植被—土壤之间的联系纽带,同时,凋落物也能通过分解过程改善森林生态系统的生态功能。华西雨屏区是为我国降雨量最丰富的区域之一,也是四川省实施退耕还林的重点区域,在退耕还林后形成了大面积的人工林。本文以位于华西雨屏区（洪雅县柳江镇）的5种植被恢复模式（慈竹林、光皮桦林、苦竹+光皮桦混交林、苦竹林、撑绿杂交竹林）为研究对象,针对其凋落物的特征及生态功能进行了研究。以期为该区域人工林的生物地球化学循环研究提供必要的基础数据,并从凋落物的生态功能的角度评价该区域退耕还林地的生态效益。主要研究内容包括几种植被恢复模式凋落物的凋落动态和分解动态,凋落物及表层土壤的水源涵养功能,凋落物对土壤理化性质、土壤微生物生物量和土壤酶活性、土壤碳库、土壤呼吸的影响等。主要研究结果如下:在几种植被恢复模式中,凋落物蓄积量和年凋落量的大小顺序均为撑绿杂交竹林＞苦竹+光皮桦混交林＞苦竹林＞慈竹林＞光皮桦林。光皮桦林凋落量月动态为单峰曲线,9月凋落量占年凋落量的48%。几种竹林的凋落量在5月最大,其后趋于平稳。凋落量主要还受自身生物节律的支配,与气温和降雨量没有明显的相关关系。运用凋落袋法研究了几种植被恢复模式凋落物的分解动态。结果表明,光皮桦林的分解速率最快;竹林分解速率的大小关系为:慈竹林＞苦竹林＞杂交竹林。几种林地凋落物在经过330 d的分解后,质量损失率均没有超过50%,光皮桦林达到了46.2%,而杂交竹林仅为30.6%。凋落物质量损失率与降雨量有明显的回归关系。几种林地凋落物的分解动态符合Olson模型,根据模型推算出几种植被恢复模式凋落物分解95%所需时间在4～7 a之间。光皮桦林和混交林的分解速率较快,可能是其凋落物中初始N浓度较高和初始C/N较小所致。几种林地凋落物C在分解40 d后基本都表现为净释放。不同林地凋落物的N浓度变化几乎均呈现出淋溶—累积—释放的规律。凋落物的P、Ca浓度波动都较小,而K、Mg浓度在系统中的流动性大。作为凋落物分解的预测指标,C/N优于木质素/N。对凋落物及表层土壤的水源涵养功能的研究结果表明:叶凋落物持水量的大小关系为:慈竹林＞混交林＞苦竹林＞杂交竹林,光皮桦林的持水量介于慈竹林和混交林之间。几种叶凋落物持水量与浸泡时间的关系符合指数函数的模型,持水速率与浸泡时间的关系符合幂函数的模型。通过野外原位实验和室内模拟实验相结合的方法,系统研究了凋落物对土壤理化性质、微生物生物量和土壤酶活性以及碳库的影响,野外实验采用凋落袋法,室内试验控制光照、温度、湿度等环境因子。研究结果表明,土壤的水分—物理性质的变化较小,可能原因是实验周期较短。5种林地土壤的pH值范围在4.12～5.42之间。3种竹林凋落物分解会造成pH值的降低,但并没有表现出随凋落袋放置时间（分解时间）加长,而pH值变化增大的趋势。总体而言,凋落物会提高土壤全N含量。NO₃^--N、NH₄⁺-N、碱解N和水溶性N等有效态N是影响植物生长发育的关键因子。研究表明,野外实验和室内实验均证明了凋落物会增加土壤碱解N和水溶性N含量,因此,在研究区域,碱解N和水溶性N可能是更好地研究林地凋落物对土壤有效N影响的指标。凋落物分解会增加几种林地的土壤有效P含量。野外实验和室内实验均表明,慈竹林、光皮桦林、混交林和苦竹林的凋落物对土壤速效K含量有正效应。凋落物的存在均会增加几种林地土壤微生物生物量碳（MBC）、土壤微生物生物量氮（MBN）和土壤酶活性。光皮桦林和混交林凋落物的C/N较小,分解速率较大,故凋落物对土壤微生物生物量影响也大。几种竹林凋落物对土壤酶活性的影响较大,在华西雨屏区的几种竹林中,凋落物对土壤蔗糖酶、过氧化氢酶、多酚氧化酶、脲酶活性的影响大小与凋落物的分解速率基本一致;而纤维素酶和酸性磷酸酶的活性同凋落物分解速率没有很好地吻合。竹林的有机碳总量和易氧化碳含量均高于光皮桦林和混交林。室内培养实验结果表明,添加凋落物会增加土壤有机碳、易氧化碳、水溶性碳和溶解性碳。将不同林地凋落物对土壤碳库的影响程度进行比较,混交林优于其它几种林地。采用动态密闭气室红外CO₂分析法（IRGA）对几种植被恢复模式凋落物对土壤呼吸的影响进行了研究。结果表明,5种林地的土壤呼吸速率的日变化均表现为单峰曲线,在8:00-10:00的土壤呼吸速率最低,在14:00-16:00达到最大。5种林地土壤呼吸速率的观测值均在8月最大,到10月中旬急剧下降。从7月开始,5种林地均表现为凋落物增加了土壤呼吸速率。慈竹林凋落物对土壤呼吸的贡献最大,而苦竹林和杂交竹林凋落物的贡献较小。土壤呼吸与地表温度的关系基本为指数函数关系。土壤呼吸速率与土壤易氧化C有显著的正相关关系,而与土壤微生物生物量C、N没有明显的相关关系。通过本研究,对华西雨屏区（洪雅县柳江镇）的5种植被恢复模式凋落物的一些生态学过程有了初步的了解,为该区域人工林生态系统的生物地球化学循环积累了基础数据,并且证明凋落物对林地水源涵养功能及土壤质量的改善起着重要的作用。更多还原

【Abstract】 Litter decomposition is the most key one of the ecological process of forest ecosystem, and plays an important role in nutrients recycling of forest.Litter is the link between vegetation and soil,and can improve ecological function of forest ecosystem by decomposition.The rainy area of Western China is one of the plentiful rainfall areas of China and is also the key area of Grain for Green project in Sichuan province.Now,there are many artificial forests in this area.In this study,we examined litter production, decomposition and ecological function in several patterns of vegetation restoration （Pleioblastus plantation,Bambusa pervariabilis×Dendrocala mopsis plantation,Neosinocalamus affinis plantation,Pleioblastus+Betula luminifera plantation and Betula luminifera plantation）in rainy area of Western China.This study can provide necessary data for nutrients recycling of forest and evaluate ecological benefit of the area by ecological function of litter.The major subject include the dynamics of litter production,the dynamics of litter decomposition,the water conservation function of litter and surface layer soil and the effects of litter on quality of soil,for instance,pyhsicochemical characteristics,microbial biomass and enzyme activity,carbon pool,soil respiration.It is showed that:The amount of litter layer and annual litter production of the plantations were in a order of Bambusa pervariabilis×Dendrocala mopsis＞Pleioblastus+Betula luminifera＞Pleioblastus＞Neosinocalamus affinis＞Betula luminifera.The peak of monthly litter production of Betula luminifera plantation occurred in September,and it was 48%of annual litter production.But the litter of several bamboo plantations mostly occurred the in May,then smoothly decreased and kept stable.No significant difference of litter production between air temperature and rainfalls was detected.So,litter production was chiefly affected by biorhythm of the species.By using litter bag method,experiment was made to study the dynamics of litter decomposition.The results showed that the orders of litter decomposition rate of several plantations were Betula luminifera＞Pleioblastus+Betula luminifera＞Neosinocalamus affinis＞Pleioblastus＞Bambusa pervariabilis×Dendrocala mopsis.The mass loss of several plantations was lower than 50%in 330 d,Betula luminifera plantation was 46.2%, and Bambusa pervariabilis×Dendrocala mopsis plantation was 30.6%.The mass loss of leaf litter was significantly correlated with rainfall.It was found that the modles were fit the data.Litter decomposition processes were simulated Olson’s exponential models. which were found the best of fits to the data.According to the models,it needs 4-7 years to reach the 95%of decay rate for the investigated plantations in the experimental region. Decay rates of leaf litter were significantly correlated with the initial leaf litter nitrogen content and C/N but not with other index,and species with high nitrogen contents and C/N exhibited relatively faster decomposition rates.The release rates of carbon showed a continuously increasing pattern in 40 d in all the plantations.At the earlier decomposition stage,the absolute content of nitrogen was decreased in all plantations.Among all there was the most significant nitrogen accumulation,then released at the later decomposition. The variation of phosphorus and calcium concentration of leaf litter was little.The potassium and magnesium of leaf litter moved easily.C/N was superior to lignin/N as calculation index of litter decomposition in the plantations.The order of water-holding capacity of leaf litter in different plantations was Neosinocalamus affinis＞Betula luminifera＞Pleioblastus+Betula luminifera＞Pleioblastus＞Bambusa pervariabilis×Dendrocala mopsis.The model between the water-holding capacity of the leaf litter and the immerse time accorded with exponential function.The model between the water absorption speed and the immerse time was accord with power function.The effect of litter on the soil pyhsicochemical characteristics,microbial biomass and the activity of soil enzyme,carbon pool was studied both in field and laboratory.Litter bags were used in the field to examine the effect.At the same time,the effect was also investigated in the laboratory by constant temperature,illumination and relative humidity. The results were as follows:probably short experiment period,there was not significant variation of soil water-physical properties.The pH value of 5 plantations ranged from 4.12 to 5.42.With decomposition processes of litter in bamboo plantations,pH value decreased. But this variation did not increase with decomposition time.Litter could increase the content of soil total nitrogen.But the variation of soil total nitrogen was not great.NO₃^--N, NH₄⁺-N,available N and water-soluble N are some key factors for growth and development of plant.Litter increased the content of available N and water-soluble N in field and laboratory.Therefore,available N and water soluble-N were more valid index than NO₃^--N and NH₄⁺-N to study the effect of litter on soil nitrogen.The content of available phosphorus and potassium increased with decomposition of litter.Adding leaf litter into soil could obviously increase soil microbial biomass C,N and soil enzyme activity.The litter of Betula luminifera and Pleioblastus+Betula luminifera affected soil microbial biomass more than other plantations because of their lower C/N and quicker decomposition rate.In three bamboo plantations,variation of sucrase,catalase, polyphenol oxidase and urease activity in the litter decomposition processes accorded with decay rate of litter.But celluase and acid phosphatase activity had no law mentioned above.The content of soil total organic carbon and labile carbon of bamboo plantations was greater than Betula luminifera plantation and Pleioblastus+Betula luminifera plantation. According with the result of laboratory incubation experiment,adding litter into soil could increase the content of soil total organic carbon,labile carbon,water-soluble organic carbon and dissolved organic carbon.The effect of litter on soil carbon pool of Pleioblastus+Betula luminifera plantation was superior to other plantations.Soil respiration and the effect of litter on it in several plantations were measured by means of closed-chamber IRGA technique from March 2007 to October 2007.The diurnal variation of soil respiration showed normal distribution,with the minimum value occurring around 8:00-10:00 hours and the maximum value around 14:00 to 16:00 hours.Soil respiration rate was the greatest in August in five plantations,and decreased sharply in October.After July 2007,litter could increase soil respiration rate in the plantations.The order of contribution of litter to soil respiration in different plantations was: Neosinocalamus affinis＞Betula luminifera＞Pleioblastus+Betula luminifera＞Pleioblastus＞Bambusa pervariabilis×Dendrocala mopsis.The soil respiration was positively correlated to ground surface temperature（from the surface to 10 cm depth）in the plantations,and the corrections could be described by exponential function.There was positively relationship between the soil respiration rate and soil labile carbon,but no obviously relationship with microbial biomass carbon and nitrogen.The overall results from this study provided necessary and basic datasets for nutrient cycling,and for contributing to a preliminary understanding of ecological processes of litter of several plantations in rainy area of Western China.Moreover,litter played an important role in improving water-holding and soil quality of the plantations.更多还原