Elevation-dependent patterns of temporally asymmetrical vegetation response to climate in an alpine basin on the Qinghai-Tibet Plateau

Abstract

The temporally asymmetric effects of vegetation growth response to climate, e.g., time-lag, time-accumulation, and their combination effects, have been widely reported. However, their elevation-dependent spatial distribution patterns in alpine basins of the Qinghai-Tibet Plateau remain unclear, especially in different seasons. This study investigated the temporal response of vegetation to precipitation and temperature throughout the whole growing season and its two subphases (growth phase and senescence phase) in the Lhasa River Basin (LRB). The results showed that alpine vegetation responds to climate in all seasons with obvious time-accumulation and relatively weak time-lag, and during the senescence phase and whole growing season, there is no significant lag in vegetation response to both precipitation and temperature, while the accumulation is about 3 ∼ 4 weeks and 2 weeks, respectively. Comparatively, there are enhanced lag and accumulation during the growth phase, with a similar lag of about 2 weeks, and 6-week and 4-week accumulation for precipitation and temperature, respectively. The whole LRB is subdivided into four elevation zones, each with different hydrothermal condition and temporal response characteristic. Across different elevation zones, it is found that stronger water-deficit stress on vegetation results in shorter lag and longer accumulation to precipitation, while stronger heat-deficit stress leads to shorter lag and accumulation to temperature, which is determined by both the vegetation’s hydrothermal demands and ambient environment. These findings shed light on the relationship between vegetation and climate and provide potential theoretical support for vegetation conservation in alpine basins.

Keywords

• Vegetation growth
• Precipitation
• Temperature
• Time-lag effects
• Time-accumulation effects
• Alpine environment