【作者】 丁新新；

【导师】 洪伟； 吴承祯；

【作者基本信息】 福建农林大学 ， 水土保持与荒漠化防治， 2009， 硕士

【摘要】 全球变化是当前人们所关注的热点问题,近年来特别是19世纪工业革命以来,人类的生产活动对地球系统产生重大的影响,突出表现为大气二氧化碳浓度的升高,生物多样性的减少,生态系统遭到严重的破坏等方面,其中大气二氧化碳浓度的升高是导致全球气候变暖的主要因素。大气二氧化碳浓度的升高主要是由于大量化石燃料的燃烧,森林资源的大量砍伐和土地利用方式的改变造成的。目前土地利用/土地覆盖变化成为人们研究人类活动对全球二氧化碳浓度变化的主要方向。由于人口的增加、人类活动的不断增强,土地利用和土地覆被发生了巨大变化,从而使更多的碳素释放大气中,土地利用变化影响下相应CO2的释放已不容忽视。据报道,每年因土地利用变化所释的CO2约占全球CO2释放量的25%。毛竹(Phyllostachys pubesens)是我国南方重要的森林资源之一,分布地域广阔,栽培历史悠久。据不完全统计,中国现有毛竹林总面积300万hm2以上,约占全世界竹林总面积的20%,并且近年来种植面积有不断扩大的趋势。毛竹林不仅为我国提供了大量的商品用材,而且在维护生态平衡方面发挥了重要的作用。本文在福建省建阳市选择了毛竹纯林、毛竹阔叶树混交林、毛竹油茶混交林、毛竹油桐混交林、毛竹杉木混交林五种闽北典型的毛竹林混交类型,通过野外定位观测和实验室分析,研究了混交模式变化对土壤碳库、可溶性有机碳、轻组有机碳、微生物生物量碳以及土壤呼吸的影响。主要研究结果如下:(1)不同混交模式下土壤有机碳含量总体上随着土壤深度的增加而减少。混交模式变化对表层土壤的影响显著高于底层土壤,0-5cm土层有机碳含量和储量受混交模式变化的影响最大,而20-40cm土层土壤有机碳储量占0-100cm土层的28.1%-49.1%,成为贮存有机碳的主要层次,20cm以下土层有机碳含量与储量受混交模式变化的影响很小。(2)0-100cm土层土壤有机碳储量大小顺序为:毛竹阔叶树混交林>毛竹油茶混交林>毛竹杉木混交林>毛竹纯林>毛竹油桐混交林,毛竹阔叶树混交林、毛竹油茶混交林、毛竹杉木混交林的0-100cm土层土壤有机碳含量分别比毛竹纯林提高了27.67%,7.33%和7.31%。但毛竹油桐混交林的土壤含碳量有所降低。(3)不同混交模式下土壤可溶性有机碳含量总体上随土层加深而降低,0-5cm土层DOC含量为40-60cm土层的1.2倍左右,在该层次上毛竹阔叶树混交林的可溶性有机碳的含量最高为1274.41mg·kg-1,毛竹油桐的含量最低为523.25mg·kg-1。(4)不同混交模式的林分随土壤剖面深度增加,轻组含量、轻组有机碳占总有机碳比例均明显下降,混交模式变化对轻组垂直分布的影响与植物根系分布深度相对应。轻组的碳含量在12.62%-16.25%之间,碳氮比范围约为20.45-34.67,均高于全土的碳含量及碳氮比。轻组在土壤表层富集。(5)毛竹阔叶树混交林土壤微生物生物量碳含量最大,各土层间的差异也较大;毛竹油桐混交林含量最小,不同土层间土壤微生物有机碳含量接近,差异较小。毛竹油桐混交林土壤微生物有机碳占土壤总有机碳的比例约在1.24%-4.04%之间,平均比例最大;而毛竹杉木混交林MBC占SOC的比例在1.02%-2.49%之间,所占比例最小且变化幅度较小,随土层加深MBC占SOC的比例变化不明显。(6)对轻组含量与土壤容重进行回归分析,轻组含量与土壤容重具有极显著的负相关(R2=0.513,P<0.01)。微生物生物量碳的垂直分布与轻组垂直分布之间有着密切的联系。对轻组含量与微生物生物量碳含量进行了回归分析,微生物量碳的垂直分布对轻组垂直分布具有显著的负相关(R2=0.6903,P<0.05)。因为微生物对轻组的形成具有重要作用,而且也是轻组的来源之一。(7) 5种不同混交模式下土壤容重的范围在0.83-1.40g/cm3,其中毛竹油桐混交林各个层次的土壤容重均比其他林分同等层次的土壤容重大,5种不同混交模式下毛竹林的总孔隙度的范围在50.80V%-69.75V%。表层土壤的最大持水量和毛管持水量的平均值呈现出毛竹杉木混交林>毛竹油茶混交林>毛竹阔叶树混交林>毛竹纯林>毛竹油桐混交林的规律。(8)不同的混交模式土壤呼吸具有明显的季节变化,一般为夏季>春季>秋季>冬季。总体的规律表现为1到4月份随着气温、地温的升高的趋势,土壤呼吸速率也是逐渐增大。4月份到7月份随着气温继续增大。在7月底达到年呼吸速率的最大值3.12-5.52μmol·m-2·s-1,此后随温度的降低而呈逐渐递减的趋势,直到次年的1月份,达呼吸速率最低值为2.0-2.25μmol·m-2·s-1。更多还原

【Abstract】 Global chang has become the hot issue which we talk about everyday.In recent years,especially since the Industrial Revolution of the 19th century, human activities have a major impact on the earth system.The outstanding performance is that the increased concentrations of carbon dioxide, the reduction of biological diversity, damage to ecosystems and so on. Most passages show that the increased concentrations of carbon dioxide lead the global warming.As the economy development,we use more and more fossil fuel and lots of forest are felled, we chang the land-use types frequently. All of those human activities deteriorate our living environment.Due to the growth of population and the human’s active, the land use and land cover have been changed greatly. So more carbon was released to atmosphere and people has attached importance to the release of CO2 lead by the change of land use. It was reported that the CO2 released by land use change was about 25% of the globe.Phyllostachys edulis is one of the important forest species in South China. It is widely distributed and has a long planting history. Partly estimated, the area of Phyllostachys heterocycla plantation is more than 3.0×106hm~2 in China, accounting for about 20% of the total bamboo forests area all over the world. The cultivated area has been increasing gradually these years, thus not only supplied a lot of commercial timber for the country, but also played an important role in the maintenance of ecological balance.In view of this situation ,background in subtropical area was chosen nearly consistently, Therefore we chose different mixed forests modes including : Phyllostachys heterocycla、mixed forest of Phyllostachys heterocycla and broadleaf tree、mixed forest of Phyllostachys heterocycla and Camellia oleifera、mixed forest of Phyllostachys heterocycla and Vernicia fordii、mixed forest of Phyllostachys heterocycla and Cunninghamia 1anceolata in Jianyang City of Fujian Province. We researched the effect of land use changes on the soil carbon pool、dissoveled organic carbon、light fraction organic carbon、microbial biomass carbon and soil respiration.The major results were summarized as follows:(1)Soil organic carbon contents decreased with soil depth increasing in different land utilization types, The effect of land use change on the surface layer soil was more significant than on the substrate soil, in which the influence to soil organic content and storage in 0-5cm soil layer is the most great. Soil organic carbon storage in 20-40cm was 28.1%-49.1% in 0-100cm soil layer, so the soil layer of 0-20cm is main. The influence to SOC content and storage below 20cm soil layer is large.(2)The order of soil organic storage in 0-100cm soil layer:mixed forest of Phyllostachys heterocycla and broadleaf tree> mixed forest of Phyllostachys heterocycla and Camellia oleifera> mixed forest of Phyllostachys heterocycla and Cunninghamia 1anceolata> Phyllostachys heterocycla> mixed forest of Phyllostachys heterocycla and Vernicia fordii.The storage of Phyllostachys heterocycla is 27.67%、7.33% and 7.33% fewer respectively than mixed forest of Phyllostachys heterocycla and broadleaf tree, mixed forest of Phyllostachys heterocycla and Camellia oleifera, mixed forest of Phyllostachys heterocycla and Cunninghamia 1anceolata. However, the carbon storage of mixed forest of Phyllostachys heterocycla and Vernicia fordii has become lower than the forest of Phyllostachys heterocycla.(3)The soil dissolved organic carbon content decreased with soil depth increasing in different different mixed forests,in which the DOC content in 0-5cm was 1.2 times of that in 40-60cm.The DOC content in 0-5cm soil layer of mixed forest of Phyllostachys heterocycla and broadleaf tree was highest (1274.41mg·kg-1) and that of mixed forest of Phyllostachys heterocycla and Vernicia fordii was lowest(523.25mg·kg-1).(4)Content of LFOC and the proportion of organic C present as LFOC both decreased with depth, corresponding distribution of roots.In addition,accumulation rate of LFOC was faster than that of SOC, which was important for soil sustainability and carbon management.The content of the LOFC is in the range of 12.62%-16.25%,C/N of soil light fraction is higher than the value of the soil.(5)Microbial biomass carbon (MBC) in mixed forest of Phyllostachys heterocycla and broadleaf tree was highest and Microbial biomass carbon (MBC) in mixed forest of Phyllostachys heterocycla and Vernicia fordii was highest.The difference among soil layers was big. The content of MBC in steep farmland was lowest and the different among soil layers was close. The proportion of MBC to SOC in mixed forest of mixed forest of Phyllostachys heterocycla and Vernicia fordii is between 1.24% and 4.04%, of which the average was the biggest and in mixed forest of Phyllostachys heterocycla and Cunninghamia 1anceolata in all land use types and the proportion changed indistinctly with depth.(6)There is the most significant positive relationship between LFOC and soil bulk density(R2=0.513,P<0.01)and there is the significant positive relationship between LFOC and MBC(R2=0.6903,P<0.05) Microbial biomass play an important role in the formation of the LFOC,and it is the main source of LFOC.(7)The range of the soil bulk densities in different land utilization types is from 0.83 g/cm~3 to 1.40g/cm3,and the soil bulk of mixed forest of Phyllostachys heterocycla and Vernicia fordii is the biggest in all of the levels.Soil total porosity of 5 different mixed modes from 50.80V% to 69.75V%, and non capillary porosity occupied nearly 1/5-2/7 of total porosity.The max moisture capacity, the capillary moisture capacity of the soil were in descensive order as follows: mixed forest of Phyllostachys heterocycla and Cunninghamia 1anceolata> mixed forest of Phyllostachys heterocycla and Camellia oleifera> mixed forest of Phyllostachys heterocycla and broadleaf tree > Phyllostachys heterocycla> mixed forest of Phyllostachys heterocycla and Vernicia fordii.(8)The seasonal change of soil respiration speed was significant in all land use types, the order : summer>spring>autumn>winner.The main laws is that the average soil respiration from January to April in these differernt land utilization types increased as the soil temperature increase.In July the soil respiration is the highest ,which is 3.12-5.52 umol / ( m~2·s).As the temperature gradually reduced ,The soil respiration of these minxed forest has reduced.更多还原