Nitrogen enrichment delays the drought threshold responses of leaf photosynthesis in alpine grassland plants

Yicheng He; Ruiyang Zhang; Pengyu Li; Lu Men; Meng Xu; Jinsong Wang; Shuli Niu; Dashuan Tian

doi:10.1016/j.scitotenv.2023.169560

Nitrogen enrichment delays the drought threshold responses of leaf photosynthesis in alpine grassland plants

Sci Total Environ. 2024 Feb 25:913:169560. doi: 10.1016/j.scitotenv.2023.169560. Epub 2023 Dec 27.

Authors

Yicheng He¹, Ruiyang Zhang², Pengyu Li³, Lu Men⁴, Meng Xu², Jinsong Wang², Shuli Niu⁵, Dashuan Tian⁶

Affiliations

¹ Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China; College of Grassland Science and Technology, China Agricultural University, Beijing 100193, China.
² Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China.
³ Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China; School of Grassland Science, Beijing Forestry University, Beijing 100083, China.
⁴ Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China; Institute of Qinghai-Tibetan Plateau, Southwest Minzu University, Chengdu 610041, China.
⁵ Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China.
⁶ Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China. Electronic address: tiands@igsnrr.ac.cn.

PMID: 38154633
DOI: 10.1016/j.scitotenv.2023.169560

Abstract

Extreme drought is found to cause a threshold response in photosynthesis in ecosystem level. However, the mechanisms behind this phenomenon are not well understood, highlighting the importance of revealing the drought thresholds for multiple leaf-level photosynthetic processes. Thus, we conducted a long-term experiment involving precipitation reduction and nitrogen (N) addition. Moreover, an extreme drought event occurred within the experimental period. We found the presence of drought thresholds for multiple leaf-level photosynthetic processes, with the leaf light-saturated carbon assimilation rate (A_sat) displaying the highest threshold (10.76 v/v%) and the maximum rate of carboxylation by Rubisco (Vc_max) showing the lowest threshold (5.38 v/v%). Beyond the drought thresholds, the sensitivities of leaf-level photosynthetic processes to soil water content could be greater. Moreover, N addition lowered the drought thresholds of A_sat and stomatal conductance (g_s), but had no effect on that of Vc_max. Among species, plants with higher leaf K concentration traits had a lower drought threshold of A_sat. Overall, this study highlights that leaf photosynthesis may be suppressed abruptly as soil water content surpasses the drought threshold. However, N enrichment helps to improve the resistance via delaying drought threshold response. These new findings have important implications for understanding the nonlinearity of ecosystem productivity response and early warning management in the scenario of combined extreme drought events and continuous N deposition.

Keywords: Drought threshold; Extreme drought; Functional trait; Leaf photosynthesis; Nitrogen addition.

MeSH terms

Droughts
Ecosystem*
Grassland*
Nitrogen
Photosynthesis / physiology
Plant Leaves / physiology
Soil
Water

Substances

Nitrogen
Water
Soil