Responses of functional traits to seven-year nitrogen addition in two tree species: coordination of hydraulics, gas exchange and carbon reserves

Hongxia Zhang; Fenghui Yuan; Jiabing Wu; Changjie Jin; Alexandria L Pivovaroff; Jinyuan Tian; Weibin Li; Dexin Guan; Anzhi Wang; Nate G McDowell

doi:10.1093/treephys/tpaa120

Responses of functional traits to seven-year nitrogen addition in two tree species: coordination of hydraulics, gas exchange and carbon reserves

Tree Physiol. 2021 Feb 2;41(2):190-205. doi: 10.1093/treephys/tpaa120.

Authors

Hongxia Zhang^{1

2}, Fenghui Yuan¹, Jiabing Wu¹, Changjie Jin¹, Alexandria L Pivovaroff³, Jinyuan Tian^{1

2}, Weibin Li⁴, Dexin Guan¹, Anzhi Wang¹, Nate G McDowell^{3

5}

Affiliations

¹ Key Laboratory of Forest Ecology and Management, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China.
² University of Chinese Academy of Sciences, Beijing 100049, China.
³ Atmospheric Sciences & Global Change Division, Pacific Northwest National Laboratory, Richland, WA 99354, USA.
⁴ State Key Laboratory of Grassland and Agro-ecosystems, Key Laboratory of Grassland Livestock Industry Innovation, Ministry of Agriculture and Rural Affairs, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou 730020, China.
⁵ School of Biological Sciences, Washington State University, Pullman, WA 99164-4236, USA.

PMID: 33313912
DOI: 10.1093/treephys/tpaa120

Abstract

Atmospheric nitrogen (N) deposition has been observed to impact plant structure and functional traits in terrestrial ecosystems. Although the effect of N deposition on plant water use has been well-evaluated in laboratories and in experimental forests, the linkages between water and carbon relations under N deposition are unclear. Here, we report on hydraulics, gas exchange and carbon reserves of two broad-leaved tree species (Quercus mongolica and Fraxinus mandshurica) in mature temperate forests after a seven-year experiment with different levels of N addition (control (CK), low (23 kg N ha-1 yr-1), medium (46 kg N ha-1 yr-1) and high (69 kg N ha-1 yr-1)). We investigated variation in hydraulic traits (xylem-specific hydraulic conductivity (Ks), native percentage loss of conductivity (PLC) and leaf water potential), xylem anatomy (vessel diameter and density), gas exchange (maximum net photosynthesis rate and stomatal conductance) and carbon reserves (soluble sugars, starch and total nonstructural carbohydrates (NSC)) with different N addition levels. We found that medium N addition significantly increased Ks and vessel diameter compared to control, but accompanied increasing PLC and decreasing leaf water potential, suggesting that N addition results in a greater hydraulic efficiency and higher risk of embolism. N addition promoted photosynthetic capacity via increasing foliar N concentration but did not change stomatal conductance. In addition, we found increase in foliar soluble sugar concentration and decrease in starch concentration with N addition, and positive correlations between hydraulic traits (vessel diameter and PLC) and soluble sugars. These coupled responses of tree hydraulics and carbon metabolism are consistent with a regulatory role of carbohydrates in maintaining hydraulic integrity. Our study provides an important insight into the relationship of plant water transport and carbon dynamics under increasing N deposition.

Keywords: hydraulic architecture; hydraulic conductivity; nitrogen fertilization; nonstructural carbohydrates; photosynthetic rate; vessel diameter.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Carbon
Ecosystem
Nitrogen*
Plant Leaves
Trees*
Water
Xylem

Substances

Water
Carbon
Nitrogen