Climate Change And Its Impact On Crop Potential Productivity Production Space In Tibet

Climate change has direct impact on human survival and development of economy andsociety, especially has an important impact on agricultural production. Tibet is the main partof the Qinghai-Tibet Plateau. Due to its unique geographical location and the complexity ofthe plateau climate, its climate change has great influence on China and even the whole ofAsia. Therefore, Tibet has become the focus of global climate change research. Because ofTibet’s fragile ecological conditions and poor adoption ability, its agricultural production canbe greatly influenced by the climate change.In this study, the characteristics of Tibet climate change, the light-temperature andclimatic potential productivity as well as the production space of barley and wheat for6agricultural production regions in semi arid (Lhasa, Shigatse, Changdu, Zedang) and semihumid (Linzhi, Bomi) in the past40years were analyzed using the linear trend method basedon meteorological data from6representative weather stations and the practical yield datafrom1971to2010. The results show that:(1) During the40years from1971to2010, the temperature showed a significantlyincrease trend in the major agricultural production areas of Tibet. The average temperature of6agricultural production area increased by1.42℃, which is far greater than the averagetemperature increase rate (0.44℃) of whole state, this is the most obvious especially in thesemi-arid agricultural region. And the changes of precipitation in different periods showdifferent trends, namely increased in first30years (1971-2000) and then decreased in10years (2001-2010) after that;(2) Along with the rise of temperature, light-temperature potential productivity of barleyand wheat also significantly increased. The average increase speed of barley and wheatreached45.6kg/hm2and75.4kg/hm2respectively in the semi arid agricultural areas, and27.2kg/hm2and44.9kg/hm2respectively in the semi humid agricultural areas. Climatepotential productivity showed a different trend with the variation of precipitation at differenttime. The climatic potential productivity of barley and wheat increased yearly by50.1kg/hm2and80.5kg/hm2, respectively in semi-arid agricultural areas in the first30years (1971~2000) and decreased yearly64.6kg/hm2and76.9kg/hm2respectively in the10years (2001~2010)after that, whereas in the semi humid agricultural areas the climatic potential productivity ofbarley and wheat increased yearly82.6kg/hm2and112.7kg/hm2, respectively in the first30years (1971~2000) and decreased75.5kg/hm2and58.4kg/hm2in the10years (2001~2010)after that.(3) The real productivity in the major agricultural areas of Tibet generally did notsignificantly change in the resent10years. In the semi-arid agricultural areas, the barley realproductivity reduced with an average annual rate of0.95kg/hm2, wheat real productivityincreased with average annual rate of59.3kg/hm2and a maximum yield of7580kg/hm2in2006; in the semi-humid agricultural areas, barley and wheat real productivity showed alightly decreasing trend with the average annual decrease rate of38.5kg/hm2and51.6kg/hm2respectively, the lowest yield of barley and wheat was3786.6kg/hm2and3837.6kg/hm2respectively, appeared in2009. In this year, a wide range of drought occurred in the region,therefore barley and wheat productivity was the lowest in the major agricultural areas inrecent10years, which was especially more obvious in semi-humid agricultural areas. Thatsuggests that the precipitation is the one of main factors that restricts crop yield enhance ofmain agricultural areas in Tibet;(4) In view of the production space, light-temperature production space of barley andwheat showed a significant increasing trend. Light-temperature production space of barleyand wheat increased at an average annual rate of167.5kg/hm2and215.9kg/hm2, respectivelyin the semi-arid agricultural areas, and increased at an average annual rate of102.7kg/hm2and157.8kg/hm2, in the semi-humid agricultural areas. The climate production space of two cropsshowed a significant decreasing trend. In the semi-arid agricultural areas decreased averagelyby63.6kg/hm2and136.2kg/hm2annually, the minimum climate production space of barleyand wheat still reached1048.6kg/hm2and1223.6kg/hm2, respectively, occurring in2006, thereal yield accounted for only84%and86%of climate potential productivity of barley andwheat. In the semi-humid agricultural areas, the climate production space of barley and wheatalso showed a weak decreasing trend, the largest climate production space reached1048.6kg/hm2and1223.6kg/hm2in2010, respectively for barely and wheat, whichaccounted for only46%and29%of the climatic potential productivity of barley and wheat;(5) The actual crop productivity in the main agricultural area was positively correlatedwith the temperature of March, negatively correlated with the temperature of June and July,significantly positively correlated with the precipitation of this period, and not stronglycorrelated with temperature and precipitation of other months.