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藏北高寒草地生长季变化及其对气候的响应
Alternative TitleThe Variation of Growing Season in Alpine Grassland and its Response to Climate Change in Northern Tibet
Language中文
张晓克
Thesis Advisor王小丹
2015
Degree Grantor中国科学院研究生院
Place of Conferral北京
Degree Name博士
Degree Discipline自然地理学
Keyword生长季 Ndvi 气候因子 高寒草地 藏北
Abstract植被生长季是长期适应环境季节性变化而形成的生长发育节律,是陆面过程模型以及植被生产力模型的重要参数,对生长季的研究不仅有助于增进植被对气候变化响应的理解,而且对于提高气候-植被之间物质与能量交换的模拟精度、准确地评估植被生产力与碳收支具有重要意义。藏北地区位于青藏高原“世界第三极”腹地,高寒草地生长季对气候变化的扰动极为敏感,研究植被生长季变化及其驱动机制对于其生态安全的维护具有重要意义。 本文以藏北高寒草地为研究对象,以MODIS NDVI影像数据及气象站点数据为主要数据源,通过Timesat及CASA模型模拟,地面数据验证等综合研究手段,获取了01-13年生长季及NPP的时间序列数据,解析了2001-2013年藏北高寒草地不同类、组、型生长季节开始时间、结束时间及生长季长度的时空格局与演变趋势;探讨了生长季变化与生态功能的关系,阐明了不同草地类型生长季对气温、降水变化的响应方式;初步揭示了在高寒特殊环境中生长季变化的驱动机制,并进一步预测了未来气候情景下高寒草地生长季的可能变化。论文研究工作的主要结论如下: (1)藏北地区温度自南向北逐渐降低,呈带状分布,年均温度-3℃,整体以0.549℃/10a (p = 0.063) 的速度增加。年降水空间分布从西北到东南呈增加趋势,平均年降水量285 mm,降水增幅16.50mm/10a (p = 0.063)。总体上藏北地区北部、西部是暖湿化倾向,南部及东南部暖干化倾向。NDVI与该地区的水热条件和植被类型的地带性分异规律是一致的,自东南至西北递减。近十几年来,12.37%的面积是显著增加,分布在西部及北部人类活动较少区域;6.41%的面积是显著减少,分布在那曲、班戈、革吉、改则等部分区域。总体上NDVI是增加趋势。 (2)藏北高寒草地总体上生长季开始时间提前1 days/10a,生长季结束时间提前2.4 days/10a,生长季长度缩短的1.4 days/10a。生长季长度缩短是生长季结束时间提前引起。不同类型的高寒草地生长季变化不同,近十几年来,高寒草甸草原生长季开始时间推后,为0.9 days/10a,其他类型提前;高寒草原生长季结束时间是推后,为0.2days/10a,其他类型提前;高寒草原生长季长度延长,为0.9 days/10a,其他类型缩短。 (3)高寒草地类、型、组生长季差异显著,高寒草甸草原、高寒草原和高寒荒漠草原中半灌木组的生长季开始时间较早,生长季结束时间最晚,生长季长度最长;相比较矮禾草组,小莎草组开始时间较早。高寒草甸小莎草组中矮生嵩草、高寒草甸草原矮禾草组中微药羊茅波伐早熟禾和高寒草原中羊茅状早熟禾生长季开始时间最早,结束时间最晚,高寒荒漠中垫状驼绒藜生长季结束时间较早,生长季长度较短。不同类、型、组高寒草地生长季变化的差异既反映高寒植物生物学特性,也受生境条件影响。 (4)藏北高寒草地总体生长季开始时间与5月份温度正相关,生长季结束时间与9月温度正相关,9月温度的降低引起生长季结束时间的提前。高寒草甸生长季开始时间影响因子比较复杂,半干旱、干旱地区草地与夏季和生长季开始时间前累积降水显著负相关,降水越多,生长季开始时间越提前;高寒草甸、高寒草甸草原生长季结束时间与9月及秋季温度显著正相关,高寒荒漠草原和高寒荒漠与9月温度正相关,高寒草原与9月温度和降水正相关。 (5)在RCP2.6、RCP4.5和RCP8.5未来气候变化情景下,2050年藏北高寒草地生长季开始时间分别为第139、138、137天,结束时间分别为第271、272、275天,与2001-2013年均值相比,生长季长度分别是延长7天、9天和13天。未来气候变化情景下,藏北地区生长季开始时间提前。生长季结束时间,高寒草原及高寒荒漠草原提前的;高寒草甸推后,随着温度升高推后幅度变大。在高寒环境中,未来温度升高有利于湿润地区草地的生长。
Other AbstractVegetation growing season is the formation of the growth rhythm over a long period of seasonal change for adaptability to the environment, is an important parameter of land surface process model as well as vegetation productivity model. The study of growing season will not only help improve the understanding of plant response to climate change, but also has of great significance for the improvement of simulation precision for material and energy exchange between climate and vegetation and accurately assesses the vegetation productivity and carbon balance. The Northern Tibet located in the Qinghai–Tibet plateau called the “Third Pole”. The growing season of alpine grassland is extremely sensitive to climate change. So the research of vegetation growing season variation and its driving mechanism is of great significance for the maintenance of the ecological security. In this paper, the research object is alpine grassland in Northern Tibet, MODIS NDVI image data and meteorological site data is as the main data source. We obtained the time series of 01-13 growing season and NPP through the Timesat and CASA model with ground data validation. We analyzed the pattern of space and the evolution trend of start of growing season, end of growing season time and growing season length for different alpine grassland classes, type and groups in Northern Tibet grassland during 2001-2013, discussed the relationship between the growing season change and the ecological function, illustrated the growing season of different alpine grassland classifications response to temperatures and precipitation, preliminary revealed the driving mechanism of growing season change in alpine special environment, and further predicted possible changes of the growing season for alpine grassland under future climate scenarios. The main conclusion in this paper is as follows: (1) In Northern Tibet, the spatial distribution of temperature reduces gradually from south to north, showing a zonal distribution. The annual average temperature is 3℃, at a speed of 0.549℃/10a (p = 0.063) increasing. The spatial distribution of annual precipitation increases from the northwest to the southeast, is 285 mm. Precipitation has a larger interannual fluctuation, at a speed of 16.50mm/10a (p = 0.063) increasing. On the whole, the west and north region has a warmer and wetter tendency, the southeast region has a warmer and drier tendency. The NDVI distribution is strongly correlated with the regional spatial distribution of temperature and precipitation, descending from southeast to northwest. Recently, 16.44% of the region showed a significant increasing trend that mainly distributed in northwest of Northern Tibet and 6.06% of that showed a significant decreasing trend that mainly distributed in some regions of Nakchu, Palgon, Gertse and so on. On the whole, the NDVI showed an increasing trend. (2) The start of growing season for alpine grassland experienced a continuous advancing trend at a rate of 0.1 days/a, the end of growing season experienced a continuous advancing trend at a rate of 0.24 days/a, the growing season length experienced a continuous shortening trend at a rate of 0.14 days/a in the Northern Tibet from 2001 to 2013. The growing season length shortening was caused by end of growing season advancing. In recent years, the start of growing season for alpine meadow steppe experienced a continuous postponing trend at a rate of 0.09 days/a, the others experienced a continuous advancing trend. The end of growing season for alpine steppe experienced a continuous postponing trend at a rate of 0.02 days/a, the others experienced a continuous advancing trend. The growing season length for alpine steppe experienced a continuous prolonging trend at a rate of 0.09 days/a, the others experienced a continuous shortening trend. (3) The growing season of class, type and group has significant difference, not only reflects alpine plants biological characteristics, but also affected
Document Type学位论文
Identifierhttp://ir.imde.ac.cn/handle/131551/15033
Collection山地表生过程与生态调控重点实验室
Affiliation中国科学院成都山地灾害与环境研究所
Recommended Citation
GB/T 7714
张晓克. 藏北高寒草地生长季变化及其对气候的响应[D]. 北京. 中国科学院研究生院,2015.
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