Studies on Ecological Degradation Mechanism of Representative Karst Mountains in Chongqing
|School||Southwest Agricultural University|
|Keywords||Karst Mountains Land use patterns Soil quality Soil seed bank Fragile ecosystems|
Karst area as early as 1983, we have a fragile environment and the edge of the desert. Past studies largely ignored the impact of land use patterns in the karst habitat degradation process to explore and limited to large-scale or single factor, the lack of to clarify the karst habitat loss caused by the recovery mechanism from the perspective of small and medium-scale and ecosystem. Investigate the the karst ecosystem degradation process, characteristics and mechanism helps to understand the laws governing the operation of the karst ecosystem degraded the karst ecosystem restoration and reconstruction, land use structure optimization basis. Chongqing covers an area of ??82,400 km 2, carbonate rocks out the exposed area 32038.14km, covers an area of ??38.9%, mainly concentrated in the northeast of Chongqing, and Chongqing and southeast of the district cities and counties. In this thesis, Beibei Guanyinxia anticlines low mountains, Foshan, nanchuan gold, Qianjiang, Wushan four locations as a typical representative of Chongqing Karst Mountains choose from 10 land use patterns: (original) woodland, secondary woodland, Plantation, shrub , grassland, abandoned shortage of farming early (abandoned 2 years, 5 years, 10 years), sloping land, early vegetable, bare land. Through field investigation and laboratory analysis, four karst mountain different land use types on soil physical and chemical properties, soil seed bank composition, biomass and biodiversity, the purpose is to clarify the change of soil fertility, quality and quantity of soil seed bank the relationship between the change, biodiversity and biomass and land use: analysis of the karst habitat degradation and recovery factor, aspects and indicators. The results showed that: 1. Karst environment of soil particle composition is mainly affected by the impact of the parent material, vegetation and land use its also have a great impact. Long-term tillage and soil erosion can affect the surface soil particles. The sandy topsoil phenomenon is very common in the karst environment, but different land use patterns vary greatly. Become secondary vegetation succession of natural vegetation or artificial reclamation, the the karst mountain soil surface of sand. After of reclamation, the karst environment soil surface of sand phenomenon is more pronounced. Aggregate stability analysis showed that the different land use patterns into the water stable aggregates larger changes, the ratio of the levels of water stable aggregates should be able to better reflect the quality of the soil aggregates, aggregates failure rate may indicate degree of soil aggregate stability, the wet sieve the Beibei, Qianjiang, gold, Foshan, Wushan aggregates structural damage range from 2.9% to 35.1%, from 9.2 to 85.8%, 2.2% to 48.8%, 2.2% to 21.8% aggregates structural damage rate average of 15.1%, 35.9%, 13.6%, 10.2%, and between the different regions of the karst mountain, the large differences in the same area of ??different land use water stability of soil aggregates. Soil surface> 5mm of water stable aggregate content: grassy slopes> virgin forest orchard> woodland> abandoned farmland> farmland> 2mm water stable aggregates content: original forest> grassland> woodland> orchard> abandoned farmland> arable land, > 0.25mm water stable aggregate content: grassland> original forest> forest> abandoned farmland orchard and arable land. Woodland, grassland interspersed with the soil surface and subsurface water-stable aggregates gt; 2mm orchards, abandoned farmland, farmland 2mm water stable aggregates relatively small proportion. This shows that human farming activity is large water stable aggregates, the karst area of ??woodland, shrub-grass land reclamation after the destruction of water stable aggregates decreased, thereby affecting its corrosion resistance and storability, exacerbated by habitat drought, slope farmland farmland aggregates can to some extent be restored. In order to further compare the different use of the karst environmental soil aggregate stability, a number of soil samples CD reagent processing, soaked in water for 30 min (soil and water ratio of 4:1), oscillation for 10 minutes (150 times / min) and then by H. The И Javier Ivanov wet sieving step the sieving results show that the intensity of land use, less organic matter involved in the formation of aggregates of cropland, orchards, vegetable, the abandoned farmland 0.25mm water stable aggregates decreased by a big margin, and woodland (6,10,4), low shrub - grass soil> 0.25 mm water stable aggregates the content of decline. Correlation analysis showed that the organic matter in water stable aggregates greater than clay, woodland, grassland reclamation, soil organic matter content should be decreased soil aggregate water stability decreased and the main reason for the decrease in the number, total N content number of water-stable aggregates have a good relationship. Low mountains in North alkaline limestone, soil water stable aggregates body and the correlation coefficient of the organic matter, followed by is CaCO; the clay less affected; karst area in Qianjiang, soil water stable aggregates body with organic matter and CaCO. The correlation coefficient; the Jinfo Mountain limestone soil because of its high content of organic matter, soil water stable aggregates by cosmid and CaCO. Obvious; the Wushan karst mountain soil water stable aggregates with cosmid, CaCO. The correlation coefficient is higher. The grass surface Guests soil total porosity, orchards, farmland, arable land correspondingly lower porosity, soil bulk density trend is the opposite. Grassland (plots 3,9), woodland (4,6,10), vegetable plot (plot 7), a more uniform pore size distribution of the arable land (plot 1), especially in the capillary porosity (0 knife 02 ~ 0 knife zmm) and aeration porosity (> 0 knife Zmm) this benign porosity dominant, the proportion of the total porosity of 56% or more; abandoned arable land (plot 2), orchard (plot 5,8) non-active pore a higher proportion of abandoned arable land (plot 2) capillary porosity than arable land, orchards high. Different land use patterns of these two types of pores varied because aggregate stability and organic matter content of the soil is quite different. Under different land use patterns in soil moisture characteristic curve changes, mainly in the aeration of changes in land use and management, greater soil aeration porosity. The relationship between the mathematical model (a · S-') to simulate soil water suction (kPa) and water content (cm' / m '), the soil moisture characteristic curve fitting equation derivation, soil moisture another The important parameter than the water capacity of C (s) = the d 0/ds =-ah. s-'''', which largely reflects the water supply capacity of a soil release properties of the soil moisture plots beans, water supply capacity; 3,6 plots not only water-holding capacity, water supply capacity better; plots poor water-holding capacity, poor water supply capacity; plots 4,10 better water holding capacity, but for?