The Lenglongling Mountains （LLM） located in northeastern part of the Tibet Plateau, belong to a marginal area of the East Asian summer monsoon （EASM） and are sensitive to monsoon dynamics. Two tree-ring width chronologies developed from six sites of Picea crassifolia in the LLM were employed to study the regional drought variability. Correlation and temporal correlation analyses showed that relationships between the two chronologies and self-calibrated Palmer Drought Severity Index （sc_PDSI） were significant and stable across time, demonstrating the strength of sc_PDSI in modeling drought conditions in this region. Based on the relationships, the mean sc_PDSI was reconstructed for the period from 1786 to 2013. Dry conditions prevailed during 1817-1819, 1829-1831, 1928-1931 and 1999-2001. Relatively wet periods were identified for 1792-1795 and 1954-1956. Spatial correlations with other fourteen precipitation/drought reconstructed series in previous studies revealed that in arid regions of Northwest China, long-term variability of moisture conditions was synchronous before the 1950s at a decadal scale （1791-1954）. In northwestern margin of the EASM, most of all selected reconstructions had better consistency in low-frequency variation, especially during dry periods, indicating similar regional moisture variations and analogous modes of climate forcing on tree growth in the region.
通过分析河西走廊花海古湖泊沉积物中的盐类矿物组成，结合年代序列，重建了花海晚冰期以来湖泊演化过程及其对气候变化的响应。结果表明：晚冰期及新仙女木时期，花海湖泊以芒硝沉积为主，属硫酸盐型湖泊，湖水的盐度较高且周期性波动频繁；全新世早期（10.47 cal ka BP以前），湖泊以洪泛堆积和风成沉积为主，揭示了湖泊萎缩、甚至干涸；全新世早期至全新世中期（10.47～8.87 cal ka BP）盐类矿物以碳酸盐沉积为主，为碳酸盐型湖泊，湖水淡化，湖泊水位开始逐渐回升；全新世中期（8.87～5.50 cal ka BP）盐类矿物呈现一定的波动变化，其中，8.8 cal ka BP 时期盐类矿物以硫酸盐沉积为主，湖泊由碳酸盐型转化为硫酸盐型，湖水咸化，盐度升高；随后盐类矿物以碳酸盐沉积为主，湖泊由硫酸盐型转化为碳酸盐型，湖水盐度降低、湖泊扩张；全新世中晚期（5.50 cal ka BP以来）出现沉积间断，表明中晚全新世时期湖泊逐渐萎缩。在全新世期间，花海湖泊千年尺度演化过程揭示了该区域气候干湿状况受亚洲季风和西风共同控制的影响。
An understanding 0f variati0ns in vegetati0n c0ver in resp0nse t0 climate change is critical f0r predicting and managing future terrestrial ec0system dynamics. Because scientists anticipate that m0untain ec0systems will be m0re sensitive t0 future climate change c0mpared t0 0thers, 0ur 0bjectives were t0 investigate the impacts 0f climate change 0n variati0n in vegetati0n c0ver in the Qilian M0untains （QLM）, China, between 2000 and 2011. T0 acc0mplish this, we used linear regressi0n techniques 0n 250-m MODIS N0rmalized Difference Vegetati0n Index （NDVI） datasets and mete0r0l0gical rec0rds t0 determine spati0temp0ral variability in vegetati0n c0ver and climatic fact0rs （i.e. temperature and precipitati0n）. Our results sh0wed that temperatures and precipitati0n have increased in this regi0n during 0ur study peri0d. In additi0n, we f0und that gr0wing seas0n mean NDVI was mainly distributed in the vertical z0ne fr0m 2,700 m t0 3,600 m in elevati0n. In the study regi0n, we 0bserved significant p0sitive and negative trends in vegetati0n c0ver in 26.71% and 2.27% 0f the vegetated areas. C0rrelati0n analyses indicated that rising precipitati0n fr0m May t0 August was resp0nsible f0r increased vegetati0n c0ver in areas with p0sitive trends in gr0wing seas0n mean NDVI. H0wever, there was n0 similar significant c0rrelati0n between gr0wing seas0n mean NDVI and precipitati0n in regi0ns where vegetati0n c0ver declined thr0ugh0ut 0ur study peri0d. Using spatial statistics, we f0und that veeetati0n c0ver freauentlvdeclined in areas within the 2,500-3,100 m vertical z0ne, where it has steep sl0pe, and is 0n the sunny side 0f m0untains. Here, the p0sitive influences 0f increasing precipitati0n c0uld n0t 0ffset the drier c0nditi0ns that 0ccurred thr0ugh warming trends. In c0ntrast, in higher elevati0n z0nes （3,900-4,500 m） 0n the shaded side 0f the m0untains, rising temperatures and increasing precipitati0n impr0ved c0nditi0ns f0r vegetati0n gr0wth. Increased precipitati0n als0 facilitated vegetati0n gr0wth in are
DENG Shao-fuYANG Tai-baoZENG BiaoZHU Xi-fenXU Hao-jie
