Spatiotemporal patterns of remotely sensed phenology and their response to climate change and topography in subtropical bamboo forests during 2001-2017: a case study in Zhejiang Province, China

Vegetation phenology has long been adapted to environmental change and is highly sensitive to climate change. Shifts in phenology also affect feedbacks of vegetation to environmental factors such as topography and climate by influencing spatiotemporal fluctuations in productivity, carbon fixation, and the carbon water cycle. However, there are limited studies which explores the combined effects of the climate and terrain on phenology. Bamboo forests exhibit the outstanding phenological phenomena and play an important role in maintaining global carbon balance in climate change. Therefore, the interaction mechanisms of climate and topography on bamboo forest phenology were analyzed in Zhejiang Province, China during 2001–2017. The partial least squares path model was applied to clarify the interplay between the climate and terrain impacts on phenology under land cover/use change. The results revealed that the average start date of the growing season (SOS) significantly advanced by 0.81 days annually, the end date of the growing season (EOS) was delayed by 0.27 days annually, and the length of the growing season (LOS) increased by 1.08 days annually. There were obvious spatial differences in the partial correlation coefficients between the climate factors and phenological metrics. Although the SOS, EOS and LOS were affected by different climatic factors, precipitation was the dominant factor. Due to the sensitivity of the SOS and EOS to precipitation, a 100 mm increase in regional annual precipitation would cause the average SOS to advance by 0.18 days and the EOS to be delayed by 0.12 days. Regarding the terrain factors affecting climate conditions, there were clear differences in the influences of different altitudes, slopes and aspect gradients on bamboo forest phenology. This study further showed that topographic factors mainly affected the interannual variations in phenological metrics under land cover/use change by affecting precipitation. This study clarified the spatial pattern of bamboo forest phenology and the interactive mechanisms between vegetative phenology and environmental conditions, as this information is crucial in assessing the impact of phenological change on the carbon sequestration potential of bamboo forests.