Increased precipitation leads to earlier green-up and later senescence in Tibetan alpine grassland regardless of warming

Pengfei Ma; Jingxue Zhao; Haoze Zhang; Lin Zhang; Tianxiang Luo

doi:10.1016/j.scitotenv.2023.162000

Increased precipitation leads to earlier green-up and later senescence in Tibetan alpine grassland regardless of warming

Sci Total Environ. 2023 May 1:871:162000. doi: 10.1016/j.scitotenv.2023.162000. Epub 2023 Feb 3.

Authors

Pengfei Ma¹, Jingxue Zhao², Haoze Zhang¹, Lin Zhang³, Tianxiang Luo⁴

Affiliations

¹ Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China; University of Chinese Academy of Sciences, Beijing 100049, China.
² College of Ecology, Lanzhou University, Lanzhou 730000, China.
³ Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China.
⁴ Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100101, China. Electronic address: luotx@itpcas.ac.cn.

PMID: 36739031
DOI: 10.1016/j.scitotenv.2023.162000

Abstract

It is debatable whether warming or increased precipitation primarily drives the changes of spring and autumn phenology in alpine grasslands at high elevations like the Tibetan Plateau. We aim to test the hypothesis that increased precipitation and soil moisture rather than warming significantly advance spring green-up dates (GUD) of dominant species in a semiarid alpine grassland, while both increases of temperature and precipitation delay their autumn senescence dates (SD). We conducted a 2-year manipulative experiment with infrared warming (ambient, +2 °C) and precipitation increase for each of rainfall events (ambient, +15 %, +30 %) during the growing season in a Tibetan alpine grassland. GUD and SD of three dominant species and the relevant soil temperature (ST) and moisture (SM) were observed. Rainy season onset as well as Pre-GUD or Pre-SD (30 days before GUD or SD) mean air-temperature (T_-30d) and precipitation (P_-30d) and relevant soil temperature (ST_-30d) and moisture (SM_-30d) were calculated for each experimental treatment. GUD dates of the three dominant species were advanced by increased precipitation rather than by warming, which showed a robust positive correlation with rainy season onset. SD dates were independently delayed by both increases of temperature and precipitation. There was no interactive effect of warming and increased precipitation on GUD and SD across species and years. In general, GUD had a significant negative correlation with Pre-GUD P_-30d (SM_-30d) but not with Pre-GUD T_-30d (ST_-30d), while SD showed a significant positive correlation with Pre-SD T_-30d and P_-30d or Pre-SD ST_-30d and SM_-30d. Our data support the hypothesis, indicating that spring and autumn phenology of monsoon-adapted alpine vegetation are more sensitive to precipitation change than to warming. The prolonged growing season length under increased temperature and precipitation is more depended on the delay of autumn senescence than the advance of spring green-up.

Keywords: Alpine grassland; Autumn senescence; Climate change; Monsoon climate; Rainy season onset; Spring green-up.