Wang Fangchao, Chen Fu-Sheng, Fang Xiang-Min, Wang Huimin, Hu Xiaofei
Postdoctoral Research Station of Management Science and Engineering, Nanchang University, Nanchang 330031, China; Key Laboratory of National Forestry and Grassland Administration on Forest Ecosystem Protection and Restoration of Poyang Lake Watershed, Jiangxi Agricultural University, Nanchang 330045, China.
Key Laboratory of National Forestry and Grassland Administration on Forest Ecosystem Protection and Restoration of Poyang Lake Watershed, Jiangxi Agricultural University, Nanchang 330045, China.
Sci Total Environ. 2022 Dec 15;852:158230. doi: 10.1016/j.scitotenv.2022.158230. Epub 2022 Aug 22.
Forest productivity is generally limited by nutrient scarcity. This study aims to reveal seasonal interactions among leaf carbon (C), nitrogen (N) fractions and tree growth driven by nutrient addition in a subtropical forest. Here, a field nutrient addition experiment was conducted with six treatments, namely, +N (5 g N m yr), +N (10 g N m yr), +P (5 g P m yr), +N + P, +N + P, and control (N + P). C fractions (structural and non-structural carbohydrates) and N fractions (soluble N, nucleic N and protein N) in needles as well as tree growth indicated by basal area increment (BAI) were measured in growing and dormant seasons. Total N and protein N in old needles were significantly increased by P addition, while no significant differences of non-structural carbohydrates in young (<1-year old) and old needles (>1-year old) were detected among the treatments in both seasons. N and P addition increased the structural carbohydrates of old needles in dormant season. P addition decreased and increased tree growth in growing and dormant seasons, respectively. The variation of BAI was explained 18.3 % by total N and 17.8 % by protein N in growing season, and was explained 33.9 % by total N and 34.2 % by protein N in dormant season. Our study suggested that the P addition effect on Chinese fir growth mostly depends on needle N fractions. This study highlights tree seasonal growth driven by nutrient alteration might be characterized by leaf N fractions rather than C fractions in subtropical forests.
森林生产力通常受养分稀缺的限制。本研究旨在揭示亚热带森林中养分添加驱动的叶片碳（C）、氮（N）组分与树木生长之间的季节性相互作用。在此，进行了一项田间养分添加实验，有六种处理，即 +N（5 克氮/平方米·年）、+N（10 克氮/平方米·年）、+P（5 克磷/平方米·年）、+N + P、+N + P 和对照（不添加 N 和 P）。在生长季和休眠季测量了针叶中的 C 组分（结构性和非结构性碳水化合物）和 N 组分（可溶性 N、核酸 N 和蛋白质 N）以及以胸径生长量（BAI）表示的树木生长情况。添加 P 显著增加了老针叶中的总 N 和蛋白质 N，而在两个季节的各处理中，未检测到幼叶（<1 年生）和老叶（>1 年生）中非结构性碳水化合物有显著差异。添加 N 和 P 增加了休眠季老针叶的结构性碳水化合物。添加 P 分别降低和增加了生长季和休眠季的树木生长。在生长季，BAI 的变化分别有 18.3%由总 N 解释，17.8%由蛋白质 N 解释；在休眠季，分别有 33.9%由总 N 解释，34.2%由蛋白质 N 解释。我们的研究表明，添加 P 对杉木生长的影响主要取决于针叶 N 组分。本研究强调，在亚热带森林中，由养分变化驱动的树木季节性生长可能以叶片 N 组分而非 C 组分为特征。
