Ecosystem-scale carbon dynamics in desert Shrublands: Unraveling the complex interplay among leaf functional and physiological traits and environment

Understanding the relationships and dynamics of environmental variables, leaf traits, and photosynthetic parameters in determining gross ecosystem productivity (GEP) is fundamental to assessing the carbon (C) cycle. However, existing knowledge in this area, especially concerning desert ecosystems, remains entirely inadequate. In this study, we used near-continuous eddy covariance, foliar, and photosynthetic data acquired from an Artemisia ordosica-dominated shrubland over a seven-year period (2013–2019). The study proceeded to assess: (i) the influence of environmental variables on GEP as a function of leaf phenology, (ii) the role of foliar traits and photosynthetic parameters in regulating GEP, and (iii) resource use strategies adopted by A. ordosica in response to adverse environmental conditions. Analysis of controlling factors indicated that various environmental and photo-physiological factors influenced GEP to different extents, depending on leaf phenology. During the leaf-expanding phase, GEP was largely controlled by maximum carboxylation rate (V_cmax). With leaf expansion, the leaf dark respiration rate (R_d), stomatal conductance (G_s), and light compensation point (LCP) played pivotal roles in an upregulation of GEP. However, during the leaf-coloring phase, GEP was limited by the maximum electron transport rate (J_max). Our findings accentuate A. ordosica's conservative strategy in nitrogen resource investment, which influences the shrubland's role as a C sink. These insights emphasize the importance of considering both climatic and plant physiological controls, especially as it pertains to photosynthesis, when seeking to understand broader C dynamics in desert ecosystems.