| 摘 要： |
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 (5 g N m(-2) yr(-1)), +N-10 (10 g N m(-2) yr(-1)), +P-5 (5 g P m(-2) yr(-1)), +N-5 + P-5, +N-10 + P-5, and control (N-0 + P-0). 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 car-bohydrates 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. |
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