Abstract
Influence of long-term changes in climate and CO2 concentration on intrinsic water-use efficiency (iWUE), defined as the ratio between net photosynthesis (A) and leaf conductance (g), and tree growth remain not fully revealed in humid subtropical China, which is distinct from other arid subtropical areas with dense coverage of broadleaf forests. This study presented the first tree-ring stable carbon isotope (δ13C) and iWUE series of Pinus massoniana from 1865 to 2013 in Fujian province, humid subtropical China, and the first tree-ring width standard chronology during the period of 1836–2013 for the Niumulin Nature Reserve (NML). Tree-ring width growth was limited by precipitation in July-August (r = 0.40, p < 0.01). The tree-ring carbon isotope discrimination (Δ13C) was mainly controlled by the sunshine hours (r = -0.66, p < 0.001) and relative humidity (r = 0.58, p < 0.001) in September-October, a season with rapid latewood formation in this area. The iWUE increased by 42.6% and the atmospheric CO2 concentration (ca) explained 92.6% of the iWUE variance over the last 150 years. The steady increase in iWUE suggests an active response with a proportional increase in intercellular CO2 concentration (ci) in response to increase in ca. The contribution of iWUE to tree growth in the study region is not conspicuous, which points to influences of other factors such as climate.
Highlights
Global warming and increase in CO2 concentration have profound influences on forests growth by directly modulating their physiological processes, e.g. photosynthesis, and indirectly by changing the forests structures
Li et al [12] revealed that the growths of tree-rings of Pinus massoniana were mainly controlled by the July-September precipitation in Fuzhou area in the eastern of Fujian province
This study presented the first tree-ring width chronology in NML over the period of 1836– 2013 and first tree-ring δ13C series from 1865 to 2013 in the humid subtropical area in Fujian province, southeast China
Summary
Global warming and increase in CO2 concentration have profound influences on forests growth by directly modulating their physiological processes, e.g. photosynthesis, and indirectly by changing the forests structures. These changes can in turn feedback climate change via modulating carbon cycles since forests are important carbon sink [1,2,3]. Interactions among temperature, CO2 concentration and forests growth vary from region to region, which is PLOS ONE | DOI:10.1371/journal.pone.0172045. IWUE and tree growth in humid subtropical China in Research and Higher Education The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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