Larix Chinensis's NDVI Variation And Its Response To Climate Change

Qinling Mountains is China's important geographic boundaries; Taibai Mountain is the highest mountain of Qinling Mountains. As special tree specie in the insensitive area to climate change-timberline region, Larix chinensis is important for the research on the changes of vegetation and response to climate. In this paper, Based on the data of 15 meteorological stations from 1959 to 2013 around Taibai Mountain,11 alpine meteorological stations from 2012 to 2014 inside Taibai Mountain Nature Reserve area, remote sensing images in four different years, continuous MODIS and spot NDVI, and DEM images, authors used spatial analysis methods to analyzed the characters and diversity of climate change on different spatial and temporal scales, Larix chinensis variation and its response to climate nearly 14 years, and distribution of upper limit in Larix chinensis area and its climate response nearly 24 years in this study area. The results showed:(1) For 55 years, there were an upward trend of annual averaged temperature and a insignificant decrease of precipitation in the Reserved area of Taibai Mountain and high altitude areas. But it was a warmer and more humid nearly 14 years.From 1959 to 2013, the rising rate of temperature in Taibai Mountain nature Reserved area was 0.329 ?/10a (P<0.05). There was a warming mutation appeared in 1998, and primary cycle of temperature change was 20 years. Annual averaged precipitation change rate was -8.045 mm/10a, and primary cycle of precipitation was 27 years.The rate temperature change in high altitude area was 0.244?/10a (P<0.05). A warming mutation occurred in 2001, and primary change cycle was 30 years. The annual averaged precipitation change rate was -7.943mm/10a which had one increase and one decrease mutation occurred in 1969 and 1985 respectively, and its main change cycle was 25 years.From 2000a to 2014a, the climate showed a warmer and more humid with temperature and precipitation increasing in Taibai Mountain Nature Reserved area.(2) The proportion of warming area increased significantly after mutations in the study area. Temperature rise rate in northern slope was higher than that in southern slope. Annual averaged precipitation increased after mutations.In 1959-2013a, the proportion of significant and extremely significant rise in Taibai Mountain nature reserved areas increased from 43.59 to 86.76% and from 49.71 to 80.43% in high-altitude region. Temperature change rate in the high altitude area was fower than the rate of overall reserved area before and after warm abrupt. The warming rate reduced in the western and central regions warmed significantly. Fall regions of annual total precipitation reached 25.23% of the study area. After the mutation, it showed an increase trend which was not significant.The climate in the northern slope was warmer than that in the southern slope, but its rise rate was fower in the northern slope. The proportion of significant and extremely significant warming increased from 37.61 to 88.27% in northern slope and from 32.73 to 76.53% in southern slope. Warming rate increased gradually from north to south in northern slope, and it showed an east-west differences in the southern slope. Precipitation grew rapidly in northeast region and reduced in western region.(3) In recent 14 years, NDVI showed an upward trend in the study area, and the growing season of Larix chinensis extended.The NDVI of the upper and lower in Larix chinensis regions raised, while the central region's NDVI decreased. The NDVI grew fastest in the semi-shady.From 2000a to 2013a, annual average NDVI increased at a rate of 0.01/10a, and winter's increasing rate was the fastest. Rise rate of NDVI in high altitude area was (altitude?2800 m) over that of the Reserve area. The NDVI in the northern slope showed increasing trend while the southern slope decreased. The Growing season of Larix chinensis began at the fifteenth ten days and ended at the thirtieth ten days, and it extended 17 days per 10 years approximately.Larix chinensis distributes mainly at the elevation areas about 3150-3300 m in Taibai Mountain. Vegetation coverage degree at 2800m is the highest and annual average NDVI increased. The NDVI decreased in the region between 2800 and 3300m and grew at the rate of 0.015/10a above 3300m. Larix chinensis spreads mainly in semi-shady and rise rate of the NDVI was 0.021/10a. But it declined in shady and semi-sunny.(4) In 24 years, the upper limit of Larix chinensis and 0? isotherm moved higher consistently every year.From 1990 to 2013, the eastern, middle and western sections in Larix chinensis's upper limit raised 60.24,32.56 and 43.62m where was about 79%?63.14% and 50.49%, respectively. Average elevation of 0? isotherm raised 408.91 m. The variation ranges of temperature was 1.85,1.93 and 1.28 ?/24a, and precipitation decreased 100.18mm, 72.86mm and 25.24 mm in the three sections(5) Temperature was more important than precipitation to Larix chinensis, and spring drought inhibited the growth of Larix chinensis.From 2000a to 2013a, the areas of positively correlations between annual average temperature and NDVI accounted for 76.53% in the study area, of which 31.3% reached significant level. There was a 3-4 month lag phase of month average NDVT's response to the month average temperature. Positive correlation coefficient in Eastern region was the max. It reduced and became negative gradually from east to west. The southern slope has a higher correlation coefficient than the northern slope.Area of positive correlations between average annual precipitation and NDVI accounted for 63.55% in the study area, of which 0.98% reached significant level. Most correlation coefficient was negative in the southern slope, while most correlation coefficient was positive in the northern slope.For 14 years, there was an insignificant negative correlation between annual average NDVI and dryness index. Average temperature in April and annual average dryness index had a significant negative impact on Larix chinensis. The formula was:NDVI= 0.36+ 0.656X annual temperature - 0.01X average Apriltemperature - 1.812X annual dryness index+0.009X. average July temperature.The warming and drying trend in spring can inhibit the growth of Larix chinensis.