新疆植被物候时空变化特征

基于MODIS-NDVI数据,提取新疆2001—2016年典型植被物候期,分析新疆不同生态分区的山地-绿洲系统植被物候期的时空演变趋势和空间分异特征,并结合同期气象数据,探讨植被物候与气候变化的响应关系。结论为:(1)新疆植被物候具有明显的纬向分布和垂直地带性分布特征,海拔在物候的地域分异中扮演着重要作用。新疆植被生长季开始时间(Start of season,SOS)集中于3月中旬至5月上旬,生长季结束时间(End of season,EOS)集中于10月中旬至12月下旬。(2)与全球大背景下典型植被物候特征变化趋势相反,新疆植被SOS呈推迟趋势,推迟幅度为1.9d/10a;EOS呈提前趋势,提前幅度为3.66d/10a;生长季长度(Length of season,LEN)呈缩短趋势,缩短幅度为5.6d/10a。除东疆地区外,全疆及不同分区均呈现出绿洲及平原SOS较早,山地区域较迟;全疆及不同分区均呈现出山地EOS结束较早,绿洲结束较迟;除东疆地区外,全疆及不同分区的LEN均为绿洲及平原区域山地,同样显示出垂直地带性分布的特征。(3)通过冗余分析(Redundancy analysis,RDA)解释了物候特征与气象因子关系的绝大部分信息,生长季开始时间受春季气温、前一年冬季降水量和日照时数的显著影响。夏季和秋季降水量是新疆植被生长季结束时间的重要影响因素,在总体上受气温和日照时数的影响较小。

Spatiotemporal variation of vegetation phenology in Xinjiang from 2001 to 2016

Typical phenological metrics (start of the season, SOS; end of the season, EOS; and length of the season, LEN) were estimated using moderate resolution imaging spectroradiometer (MODIS)-normalized difference vegetation index (NDVI) data from 2001 to 2016. Then, the phenological interannual variation trend and its spatial pattern were analyzed for the ecological mountain-oasis-desert system (MODS) in Xinjiang and its sub-regions, and the relationship between the vegetation changes and the climate variations were discussed in combination with the meteorological data. The following results were obtained in this study. The phenological characteristics in Xinjiang exhibited obvious zonal and vertical zonal distribution characters, and the altitude plays an important role in the regional differentiation of phenology. The SOS and EOS ranged from mid-March to early-May, and mid-October to late-December, respectively. Contrary to the global phenological change direction, the SOS was delayed in Xinjiang with a delayed amplitude of 1.9 days in every 10 years, the EOS was advanced with an advanced amplitude of 3.66 days in every 10 years, and the shortened LEN amplitude was 5.6 days in every 10 years. The SOS was earlier at the oasis and plain regions but later in the mountain area in the entire Xinjiang area except for the Eastern part. The EOS occurred earlier in the mountain and later in the oasis region of the entire Xinjiang area and different partition zones. The LEN range changed from the oasis and plain to the mountain areas except for the eastern part and showed a vertical zoning character. Based on the redundancy analysis (RDA), which explains most of the relationship information between the phenological characters and the climate factors, the SOS was remarkably influenced by spring temperatures, the year before the winter rainfall and sunshine duration. Summer and autumn precipitation was the important influencing factor for the EOS, which was affected by the temperature and sunshine duration, although the effect was limited. We may have to consider the changing amplitude as the main and secondary factor that affects the phenology metrics when studying the associated interannual variation. This is because various influencing factors may have different effects and change the direction of the advanced or delayed vegetation phenology, which ultimately affects the phenological characteristics of the interannual trend.