| Carbon storage and changes of terrestrial ecosystem is an important issue in globalclimate change research. Land use/cover change has major influence on carbon circling ofterrestrial ecosystem. The changes of land utilization due to human activities and naturalfactors, such as deforestation, reclamation of cultivated land and town construction etc, makelots of natural ecological process alert, thus affect the physical and chemical properties of soil.All of them contribute to the change of soil carbon storage. Therefore, correctly estimating thecorrelation between LUCC, soil and vegetation carbon storage at regional scale can offer auseful reference for us to understand the carbon circling of terrestrial ecosystem in the pastand future. The ecological environment in Loess Plateau of north Shaanxi Province changesviolently in recent twenty years. As a result, this research based on three phases of TMimagery data in1990,2000and2010, the second soil profiles survey data and sample fielddata, analyzed land use/cover change, vegetation and soil carbon storage dynamic changesfrom1990to2010in the study area by using RS and GIS technology. The results indicatedthat:The change of land use types was significant during1990to2010. Also cultivated landchanged with different periods, it was still the primary land use type in the study area. Thetotal area of cultivated land has decreased by443.15km~2in twenty years, which interconvertinto forestland, scrubland and grassland strongly in Hancheng City, Heyang County andYichuan County. Forestland was the second largest land use type. Under the policy of"returning farmland to forests", it increased by362.93km~2from1990to2010, which mostlytransformed from cultivated land and scrubland in soil rock mountainous region of HuanglongCounty and northern Baota District. Grassland area has increased form1651.67km~2in1990to1719.80km~2in2010, with68.13km~2increased in twenty years. Over the past two decadesthe area of scrubland was on the decrease, with185.44km~2reduced which mostly changedinto cultivated land, scrubland and grassland. The area of residential land in2010had beendoubled compared with1990because of the population explosion and expansion of towns.The area of other land and water area had little changed due to their small area and thedifficulty of exploitation and utilization. The area of vegetation in1990,2000and2010was15432.62km~2,15277.45km~2and15226.09km~2respectively. Vegetation carbon storage was36.76Tg in1990,35.01Tg in2000and38.18Tg in2010. From1990to2010, with the increase of forestland, vegetation carbonstorage increased by1.42Tg, which was "carbon sequestration". Vegetation carbon storage onloess remnant-beam hill was bigger than other physiognomies, followed by soil rockmountainous region. Because loess tableland and loess platform had little forest land, theirvegetation carbon storage was relatively low.The total soil organic carbon storage was estimated by soil taxonomy method integrationwith GIS. It varied from27.27Tg in1990to29.24Tg in2010, with1.97Tg increased, whichwas "carbon sequestration" for soil. Another method called vegetation types also used toassess it and the result was28.66Tg, which was slightly lower than the result of soiltaxonomy method. The main reason for the difference may be that vegetation types methodtook into account the impact of different vegetation types on upper soil organic carbon.Choose the Loess Plateau ecologically fragile areas to explore land use/cover changeand its effect on vegetation-soil carbon storage could not only enrich the research andtheoretical method of ecosystem carbon balance in north Shaanxi Loess Plateau, but also helpto provide data foundation and scientific basis for the study of carbon cycle in typical region. |
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