Accurate measurements of the associated vegetation phenological dynamics are crucial for understanding the relationship between climate change and terrestrial ecosystems. However, at present, most vegetation phenologi...Accurate measurements of the associated vegetation phenological dynamics are crucial for understanding the relationship between climate change and terrestrial ecosystems. However, at present, most vegetation phenological calculations are based on a single algorithm or method. Because of the spatial, temporal, and ecological complexity of the vegetation growth processes, a single algorithm or method for monitoring all these processes has been indicated to be elusive. Therefore, in this study, from the perspective of plant growth characteristics, we established a method to remotely determine the start of the growth season(SOG) and the end of the growth season(EOG), in which the maximum relative change rate of the normalized difference vegetation index(NDVI) corresponds to the SOG, and the next minimum absolute change rate of the NDVI corresponds to the EOG. Taking the Three-River Headwaters Region in 2000–2013 as an example, we ascertained the spatiotemporal and vertical characteristics of its vegetation phenological changes. Then, in contrast to the actual air temperature data, observed data and other related studies, we found that the SOG and EOG calculated by the proposed method is closer to the time corresponding to the air temperature, and the trends of the SOG and EOG calculated by the proposed method are in good agreement with other relevant studies. Meantime, the error of the SOG between the calculated and observed in this study is smaller than that in other studies.展开更多
草地碳汇/源是植被生态系统中碳收支和碳平衡的一个重要内容,区分碳汇和碳源对气候变化的响应可为减源增汇提供科学依据。基于MODIS NPP数据和土壤呼吸模型量化了2001—2019年青藏高原草地净生态系统生产力(NEP)的时空变化和碳汇/源格局...草地碳汇/源是植被生态系统中碳收支和碳平衡的一个重要内容,区分碳汇和碳源对气候变化的响应可为减源增汇提供科学依据。基于MODIS NPP数据和土壤呼吸模型量化了2001—2019年青藏高原草地净生态系统生产力(NEP)的时空变化和碳汇/源格局,利用通径分析方法分析了青藏高原气候变化对草地碳汇/源的影响。结果表明:青藏高原草地NEP呈现东高西低的分布格局,年平均值为54.41 g C m^(-2)。草地整体上以碳汇功能为主。碳汇区面积约为72.26万km^(2),碳源区面积约为47.82万km^(2),净碳汇总量65.35 Tg C a^(-1)。近19年青藏高原草地NEP以增加趋势为主,青藏高原气候暖湿化趋势有利于草地NEP的增加,增强碳汇;而暖干化趋势对NEP的影响在不同生态地理区差异较大。展开更多
基金supported by National Natural Science Foundation of China (Grant No. 41801099)
文摘Accurate measurements of the associated vegetation phenological dynamics are crucial for understanding the relationship between climate change and terrestrial ecosystems. However, at present, most vegetation phenological calculations are based on a single algorithm or method. Because of the spatial, temporal, and ecological complexity of the vegetation growth processes, a single algorithm or method for monitoring all these processes has been indicated to be elusive. Therefore, in this study, from the perspective of plant growth characteristics, we established a method to remotely determine the start of the growth season(SOG) and the end of the growth season(EOG), in which the maximum relative change rate of the normalized difference vegetation index(NDVI) corresponds to the SOG, and the next minimum absolute change rate of the NDVI corresponds to the EOG. Taking the Three-River Headwaters Region in 2000–2013 as an example, we ascertained the spatiotemporal and vertical characteristics of its vegetation phenological changes. Then, in contrast to the actual air temperature data, observed data and other related studies, we found that the SOG and EOG calculated by the proposed method is closer to the time corresponding to the air temperature, and the trends of the SOG and EOG calculated by the proposed method are in good agreement with other relevant studies. Meantime, the error of the SOG between the calculated and observed in this study is smaller than that in other studies.
文摘草地碳汇/源是植被生态系统中碳收支和碳平衡的一个重要内容,区分碳汇和碳源对气候变化的响应可为减源增汇提供科学依据。基于MODIS NPP数据和土壤呼吸模型量化了2001—2019年青藏高原草地净生态系统生产力(NEP)的时空变化和碳汇/源格局,利用通径分析方法分析了青藏高原气候变化对草地碳汇/源的影响。结果表明:青藏高原草地NEP呈现东高西低的分布格局,年平均值为54.41 g C m^(-2)。草地整体上以碳汇功能为主。碳汇区面积约为72.26万km^(2),碳源区面积约为47.82万km^(2),净碳汇总量65.35 Tg C a^(-1)。近19年青藏高原草地NEP以增加趋势为主,青藏高原气候暖湿化趋势有利于草地NEP的增加,增强碳汇;而暖干化趋势对NEP的影响在不同生态地理区差异较大。
