| As a material basis and source of wealth for human survival, land are suffering from the most intense impact of human activities in the history. Due to unreasonable land use behavior, the soil resources and environment is facing tremendous pressure, such as the decline of soil fertility quality, deterioration of ecological environment, the decline of land productivity. This study includes researches based on soil sampling, statistic materials collecting and field investigation on land use structure changes in Fuyang County in the period from1979to2009year, such as cropland quality, spatial and temporal variability of soil primary nutrient factors, risk assessment of soil heavy metal pollution, source identification of soil heavy metal pollution, total soil organic carbon (SOC) stock changes and carbon balance evaluation of land use plan. However, all these researches systematically analyze the dynamic changes of land productivity in Fuyang County. The objective of this study is to assess the influence of land use changes (LUCs) on land productivity in urbanization process, and summarize the influence patterns and to predict the future variation trends. The information gathered could provide a scientific way for land use management, and effectively in industrial distribution optimization, soil fertility policy-making and cropland protection. The main contents and results are as follows:(1) Soil fertility levels are the basis of land productivity. Firstly, the study analyzed temporal and spatial variability of primary soil fertility factors in the land use changing process in Fuyang County by the use of traditional statistics and geostatistics methods. Results showed that soil organic matter, total nitrogen, available phosphorus and available potassium increased significantly with large regional variability in Fuyang County from1979to2006year. Different land use types had significantly influence on soil fertility levels. The general content sequence was listed as vegetable land> paddy field-dry land-woodland> orchard> vacant land. Agricultural LUCs and transition from agricultural to construction land were two driving forces in variations in soil fertility. Extensive use of organic manure and chemical fertilizer, unreasonable disposal of industrial and municipal waste were the direct reasons to the different levels of soil nutrients. Secondly, on the basis of the quality evaluation system of cropland, we compared the quality of construction requisition to compensation cropland from1996to2006year and predicted the trend from2006to2020year in Fuyang County using quality benchmark values of cropland. Results indicated that the quality of construction requisition cropland was better than compensation cropland from1996to2006year and from2006to2020year despite some quality issues exits.(2) Soil heavy metal pollution is an important negative factor for land productivity, which caused by the development of industry and economy. Firstly, the Nemero Synthesis Index evaluation method was performed to quantify the pollution risk of soil heavy metals in each town. Results showed that most of the towns in Fuyang County had low pollution risk, except towns such as Huanshan had different degrees of pollution risk. Secondly, the CART decision tree method was used to generate sets of decision rules on the region which facing a big pollution risk after done the research on environmental factors, such as industrial emission, transportation, agricultural activities and urban living. Soil pH value and organic matter content significantly influenced the distribution of these heavy metals. After quantitative comparison of the importance of nine environmental factors included in decision rules, industrial emission was selected as the most important heavy metal pollution source. Finally, results indicated that CART had significantly advantages after comparing to multivariate statistics or ordinary kriging method on the research scope of soil heavy metal pollution.(3) Soil organic carbon is an important indicator of land productivity evaluation and is considered as the largest carbon stock in most terrestrial ecosystems which significantly affecting the global climate change. The objective of this research was to investigate the dynamics of vegetation carbon (VC) and SOC stock changes during1979to2006integrating data of land use, soil sampling and literatures review. Results showed that total VC stocks estimated in Fuyang were3.680Tg in1979and3.407Tg in2006. The total amount of carbon in the depth of0-20cm soil in Fuyang was estimated with8.847Tg in1979and8.076Tg in2006. LUCs between1979and2006have generated a VC decreasing of273.44Gg, which translate into source of55.61x10-3Mg C ha-1year-1Due to land use change of built-up land, cropland and woodland, a SOC was decreased with771.01Gg, which translates into source of156.81×10-3Mg C ha-1year-1mainly. Additionally, due to the expansion of cropland area and reduction of woodland and orchard area, the Fuyang Land Use Master Planning (2006-2020) would lead to potential carbon sources of25.93×10-3Mg C ha-1yea-1of vegetation. And for soil, there are27.48×10-3Mg C ha-1year-1between2006and2020. |
