Increasing Impact of Precipitation on Alpine-Grassland Productivity over Last Two Decades on the Tibetan Plateau

Abstract

Understanding the importance of temperature and precipitation on plant productivity is beneficial, to reveal the potential impact of climate change on vegetation growth. Although some studies have quantified the response of vegetation productivity to climate change at local, regional, and global scales, changes in climatic constraints on vegetation productivity over time are not well understood. This study combines the normalized difference vegetation index (NDVI) and the net primary production (NPP) modeled by CASA during the plant-growing season, to quantify the interplay of climatic (growing-season temperature and precipitation, GST and GSP) constraints on alpine-grassland productivity on the Tibetan Plateau, as well as the temporal dynamics of these constraints. The results showed that (1) 42.2% and 36.3% of grassland NDVI and NPP on the Tibetan Plateau increased significantly from 2000 to 2019. GSP controlled grassland growth in dryland regions, while humid grasslands were controlled by the GST. (2) The response strength of the NDVI and NPP to precipitation (partial correlation coefficient RNDVI-GSP and RNPP-GSP) increased substantially between 2000 and 2019. Especially, the RNDVI-GSP and RNPP-GSP increased from 0.14 and 0.01 in the first 10year period (2000–2009) to 0.83 and 0.78 in the second 10-year period (2010–2019), respectively. As a result, the controlling factor for alpine-grassland productivity variations shifted from temperature during 2000–2009 to precipitation during 2010–2019. (3) The increase in precipitation constraints was mainly distributed in dryland regions of the plateau. This study highlights that the climatic constraints on alpine-grassland productivity might change under ongoing climate change, which helps the understanding of the ecological responses and helps predict how vegetation productivity changes in the future.

Warm Early Summer Compensated Reduction in Photosynthesis Caused by 2022 Late Summer Extreme Drought Over the Tibetan Plateau

“…Similarly, the increased vegetation photosynthesis in spring over the Northern Hemisphere during 1982-2011 triggered an additional SW deficit extending into summer, as demonstrated in a previous study (Lian et al, 2020). In addition, Angert et al (2005) figured out that warming does not necessarily lead to higher CO 2 uptake, even in temperature-limited ecosystems (Zha et al, 2022).…”

“…In addition, Angert et al. (2005) figured out that warming does not necessarily lead to higher CO 2 uptake, even in temperature‐limited ecosystems (Zha et al., 2022).…”

Has the Dominant Climatic Driver for the Carbon Budget of Alpine Grassland Shifted from Temperature to Precipitation on the Qinghai–Tibet Plateau?

“…However, after 2010, it appears that precipitation may have replaced temperature and become the primary climatic driving factor of the carbon budget, while the rising temperature hindered the growth of the carbon budget, especially for the GPP and NEP. A recent study on the net primary productivity (NPP) of grasslands on the QTP also reached a similar conclusion, indicating a shift from temperature to precipitation as the controlling factor for alpine grassland productivity from 2000-2009 to 2010-2019 [57].…”

The Relative Effects of Climate Change and Phenological Change on Net Primary Productivity Vary with Grassland Types on the Tibetan Plateau

“…Solar radiation also plays an essential role in regulating carbon uptake by influencing the availability and interception of photosynthetically active radiation [7,8]. Identifying the primary factor among these climatic variables and quantifying its contributions to vegetation productivity is essential for predicting how vegetation will respond to current and future climate conditions [9]. To achieve this goal, numerous studies have investigated the effects of climate change on NPP variations at different spatial and temporal scales [8][9][10].…”

“…Identifying the primary factor among these climatic variables and quantifying its contributions to vegetation productivity is essential for predicting how vegetation will respond to current and future climate conditions [9]. To achieve this goal, numerous studies have investigated the effects of climate change on NPP variations at different spatial and temporal scales [8][9][10]. However, there are still some ambiguities.…”