Features Of The Soil Organic Matter Fractions Of Different Land Use Patterns In The Karst Areas

The tremendous storage of soil organic carbon is likely to be the carbon source or the carbon sink, a minor change of which will affect the emission of carbon into the atmosphere, and thus affects the global climate change. The storage and change of soil organic carbon is closely related to different land use patterns. Thus, the change of land use pattern may cause the change of the concentration of CO2in the atmosphere. To understand the features of the soil organic matter fractions of different land use patterns and the organic Mechanism of carbon sequestration are significant to mitigate climate change. The studies of how land use patterns affect the change of soil carbon storage and the fractions of soil organic matter, however, are few, especially for the Karst areas in Chongqing. Therefore, this thesis, concentrating on the area of Chongqing Zhongliang Mountain, combining the approaches of sampling outdoors and laboratory analysis, develops a study of the influences of land use patterns upon active soil organic carbon pool,slow soil organic carbon pool and inertia soil organic carbon pool and aggregate organic carbon, and has a preliminary discussion of the regular effects of soil carbon under different land use patterns in the Karst areas and the mechanisms involved, offering a scientific basis for the promotion of land productivity and carbon sequestration.The main results are as follows:(1) The average performance of the size of the soil organic carbon content:woodland (12.33g/kg)> vegetable land (11.67g/kg)> grassland (9.51g/kg)> garden (the6.99g/kg)> abandoned farmland (4.45g/kg). Soil organic carbon content decreased with soil depth. Soil vegetation cover, human tillage and fertilization were important factors to affect the distribution of soil organic carbon, under different land use patterns(2) The performance of soil dissolved organic carbon (DOC) content:woodland> grassland> garden> the abandoned farmland> vegetable land. The peak appeared in the woodland; different land use patterns of soil soluble organic carbon (DOC) content of the vertical distribution of performance tended to decrease with the increase of soil depth, the Garden to the biggest drop. Soil Dissolved Organic Carbon proportion of total soil organic carbon as follows:abandoned farmland> grassland> woodland> Garden> the vegetable land. Abandoned farmland and vegetable land were extremely different. Soil easily oxidized organic carbon content (EOC) performance:woodland> vegetable land> grass> Garden> abandoned farmland; vertical distribution of soil EOC content of different land use patterns showed decreases with increasing soil depth, which Garden the biggest drop. The soil easily oxidized organic carbon proportion of total soil organic carbon:woodland> abandoned farmland> Garden> the vegetable land> grassland. Representative active organic carbon DOC and EOC showed that the content increased with soil decreasing trend, in which the biggest drop in the Garden. Active organic carbon was more vulnerable to human disturbance, and reacted sensitively. Abandoned farmland in active organic carbon accounted for a higher proportion of total organic carbon of the abandoned soil organic carbon was unstable and easily lost.(3) The content of the soil coarse particulate organic carbon (CPOC):the garden> grassland> vegetable land> woodland> abandoned farmland. The differences among different land use patterns were obvious. The highest value was in the Garden, the lowest in the abandoned farmland. The CPOC of soil was sensitive to human farming methods and fertilization treatments. The peak of FPOC was in the surface layer of woodland and grassland, and the increase of organic sources would improve soil FPOC. Light soil organic carbon (LFOC) content performance:grassland> woodland> garden> vegetable land> abandoned farmland. The lowest value was in the abandoned farmland. The highest value appeared in the table lower layer (20-40cm) in the vegetable land, indicating that the base fertilizer can improve soil LFOC content. The lowest value of POC and LFOC content appeared in abandoned farmland, indicating that the long-term farming will exacerbate the loss of this part of the carbon.(4) An inert organic carbon pool indicators of soil mineral-bound organic carbon (MOC) and the recombinant organic carbon (HFOC) content:woodland> vegetable land> grass> Garden> abandoned farmland. It was identical to the soil organic carbon (TOC) content trends. The topsoil was greater than the soil layers, the input of exogenous organic matter is conducive to the increase of the soil inert organic carbon content. The higher content of woodland and grassland indicated that it’s more conducive to the accumulation of inert organic carbon. Abandoned arable land compared to other land use patterns of soil organic carbon in an inert carbon. (5) Different land use patterns of soil showed all>0.25mm large aggregate content were higher, especially concentrated in the5-2and1-0.5mm. Woodland and grassland were higher in5-2mm aggregates; garden, vegetable land and abandoned farmland were higher in-0.5mm aggregates. Soil water stable aggregates mean weight diameter and geometric mean diameter: woodland> grassland> garden> vegetable> abandoned farmland. Human intervention would affect the stability of the aggregates. In addition to the vegetable garden and garden, different land use patterns showed the trend of larger particle size, the higher the organic carbon content, among which woodland and grassland particle size aggregates organic carbon content was significantly higher than the garden and abandoned farmland. The large aggregates of organic carbon with different land use patterns were higher than micro-aggregates proportion of organic carbon, among which organic carbon in aggregates were mostly in the1-0.5mm,1-2mm and2-5mm aggregates. In terms of different land use patterns, the highest proportion was the woodland organic carbon in aggregates (96.72%and97.56%, respectively), which was conducive to increase of soil organic carbon in aggregates. The correlation coefficient of the soil organic carbon in aggregates and total organic carbon indicates that the increase in organic carbon accumulation of soil organic carbon is more prominent in the1-2mm,0.5-1.0mm and0.5-0.25mm particle size aggregates.(6) Five types of land use soil are characterized by:content of inert carbon pool> the chronic carbon pool content> content of active carbon pool. Woodland soil total organic carbon is higher, the highest soil inert carbon content was in the woodland, indicating that the woodland is advantageous to the increase of soil "carbon sinks" effect. vegetable field soil, increase organic-inorganic fertilizer on increasing chronic organic carbon content has very good effect, is advantageous to the "carbon sinks" effect. The content of abandoned farmland soil total organic carbon is the lowest, inert carbon in the soil due to not easily affected by the outside world, the decomposition and consumption is less, show the inert organic carbon to total organic carbon ratio is higher than that of woodland and grassland. Abandoned farmland due to affected by tillage activated carbon in the soil for a long time before abandon and chronic carbon loss is serious; don’t use the accumulation of organic carbon. Thus, returning farmland to forest has been promoted, which was more conducive to the soil increasing carbon sink in Karst.