祁连山不同类型植被物候变化及其对温度的响应

本文基于GIMMS NDVI数据，采用遥感物候法提取了生长季开始日期（SOS）、生长季结束日期（EOS）和生长季长度（LGS）3个植被物候指标，并借助Theil-Sen斜率与Mann-Kendall检验等统计方法和偏最小二乘分析法（PLS），分析了祁连山不同类型植被物候空间分布规律、时间变化趋势及其对温度的响应．结果表明:1）自东南到西北方向，祁连山植被类型从灌丛逐渐过渡到草甸、草原再到高山植被，物候指标SOS逐渐推迟，EOS逐渐提前，LGS逐渐缩短．2）草甸和灌丛2种植被的物候变化最为剧烈，研究期内该2种植被的SOS均显著提前（分别为0.19和0.25 d·（10 a）?1），EOS显著推迟（分别为0.20、0.21 d·（10 a）?1），LGS显著延长（分别为0.39、0.46 d·（10 a）?1）；祁连山全境及主要植被的SOS均在1997—2000年发生转折，EOS和LGS的转折点均发生在2003年．3）上年秋末冬初温度对草甸与灌丛植被SOS具有正向影响，物候期前的春季温度对SOS具有显著负影响；夏秋季温度对EOS和LGS具有显著正影响．此外，最高温对物候的影响显著强于最低温，且在春夏季的个别月份，二者对物候的影响方向不同．植被物候的变化提示当地牧民在牧草种植与放牧上的调整． 

Vegetation phenology change and response to temperature in the Qilian Mountains from 1982 to 2014

The Qilian Mountains in the northeast of Qinghai Tibet Plateau are endowed with diverse vegetation types and significant climate change．Understanding vegetation phenology change in Qilian Mountains is of great significance for ecology and development of animal husbandry industry．GIMMS NDVI data and satellite-derived method were used to extract phenology indicators of Qilian from 1982 to 2014: start of the growing season (SOS), end of the growing season (EOS) and length of the growing season (LGS)．The phenological characteristics and their responses to temperature were then examined in different vegetation type regions using Theil-Sen slope, Mann-Kendall test and partial least-square method (PLS)．It was found that the vegetation types in Qilian Mountains from the southeast to the northwest transitioned gradually from shrubs to meadows and grasslands and then to alpine vegetation; SOS was delayed, EOS advanced, LGS shortened gradually．Meadow and shrub were found to be the vegetation types with the most drastic phenology change．From 1982 to 2014, SOS of meadow and shrub was significantly advanced (0.19 days per decade, 0.25 d·(10 a)?1), EOS delayed (0.20, 0.21 d·(10 a)?1), LGS extended (0.39, 0.46 d·(10 a)?1), all significantly．For the whole Qilian Mountains and major vegetation types, the SOS had a turning point from 1997 to 2000, turning points of EOS and LGS both occurred in 2003．After these turning points, phenology trends became insignificant．Temperature at the end of autumn and beginning of winter was found to have a positive effect on SOS in meadows and shrubs, temperature in spring before the phenology date had a significant negative effect on SOS．Temperature in summer and autumn had significant positive effect on EOS．The effect of maximum temperature on phenology was found to be significantly stronger than minimum temperature; in the individual months in spring and summer, effects of maximum and minimum temperature on phenology showed opposite directions．Changes in vegetation phenology will help to remind local herdsmen to adjust their forage planting and grazing．