Vegetation canopy structure mediates the response of gross primary production to environmental drivers across multiple temporal scales

Yaoyao Zheng; Weiqing Zhao; Anping Chen; Yue Chen; Jiana Chen; Zaichun Zhu

doi:10.1016/j.scitotenv.2024.170439

Vegetation canopy structure mediates the response of gross primary production to environmental drivers across multiple temporal scales

Sci Total Environ. 2024 Mar 20:917:170439. doi: 10.1016/j.scitotenv.2024.170439. Epub 2024 Jan 26.

Authors

Yaoyao Zheng¹, Weiqing Zhao¹, Anping Chen², Yue Chen¹, Jiana Chen¹, Zaichun Zhu³

Affiliations

¹ School of Urban Planning and Design, Shenzhen Graduate School, Peking University, Shenzhen 518055, China; Key Laboratory of Earth Surface System and Human-Earth Relations, Ministry of Natural Resources of China, Shenzhen Graduate School, Peking University, Shenzhen 518055, China.
² Department of Biology and Graduate Degree Program in Ecology, Colorado State University, Fort Collins, CO, USA.
³ School of Urban Planning and Design, Shenzhen Graduate School, Peking University, Shenzhen 518055, China; Key Laboratory of Earth Surface System and Human-Earth Relations, Ministry of Natural Resources of China, Shenzhen Graduate School, Peking University, Shenzhen 518055, China. Electronic address: zhu.zaichun@pku.edu.cn.

PMID: 38281630
DOI: 10.1016/j.scitotenv.2024.170439

Abstract

Gross primary production (GPP) is a critical component of the global carbon cycle and plays a significant role in the terrestrial carbon budget. The impact of environmental factors on GPP can occur through both direct (by influencing photosynthetic efficiency) and indirect (through the modulation of vegetation structure) pathways, but the extent to which these mechanisms contribute has been seldom quantified. In this study, we used structural equation modeling and observations from the FLUXNET network to investigate the direct and indirect effects of environmental factors on terrestrial ecosystem GPP at multiple temporal scales. We found that canopy structure, represented by leaf area index (LAI), is a crucial intermediate factor in the GPP response to environmental drivers. Environmental factors affect GPP indirectly by altering canopy structure, and the relative proportion of indirect effects decreased with increasing LAI. The study also identified different effects of environmental factors on GPP across time scales. At the half-hourly time scale, radiation was the primary driver of GPP. In contrast, the influences of temperature and vapor pressure deficit took on greater prominence at longer time scales. About half of the total effect of temperature on GPP was indirect through the regulation of canopy structure, and the indirect effect increased with increasing time scale (GPP_NT-based models: 0.135 (half-hourly) vs. 0.171 (daily) vs. 0.189 (weekly) vs. 0.217 (monthly); GPP_DT-based models: 0.139 vs. 0.170 vs. 0.187 vs. 0.215; all values were reported in gC m^-2 d^-1 °C^-1, P < 0.001); while the indirect effect of radiation on GPP was comparatively lower, accounting for less than a quarter of the total effect. Furthermore, we observed a direct, negative-to-positive impact of precipitation on GPP across timescales. These findings provide crucial information on the interplay between environmental factors and LAI on GPP and enable a deeper understanding of the driving mechanisms of GPP.

Keywords: Driving factors; Gross primary production; Leaf area index; Multiple temporal scales; Structural equation model; Vegetation canopy structure.

MeSH terms

Carbon Cycle
Ecosystem*
Photosynthesis*
Seasons
Temperature