中国植物细根碳、氮、磷化学计量学的空间变化及其影响因子

Spatial changes and influencing factors of fine root carbon, nitrogen and phosphorus stoichiometry of plants in China

为了研究中国陆地植物细根碳(C)、氮(N)、磷(P)的空间变化模式,揭示细根在"温度-植物生理假说"及"生长速率假说"等方面的规律,该文收集已发表的有关中国陆地植物细根研究的文献,从中提取细根C、N、P元素含量及其相关数据,分析了细根C、N、P含量及其比例与经纬度之间的关系。结果表明:细根N、P元素含量均随纬度增加而增加,P含量随经度增加而降低,N:P随经度增加而增加。细根N、P含量与年平均气温、年降水量均呈负相关关系,与土壤养分呈正相关关系。在土壤养分、温度、降水量3个非生物因素中,土壤养分对细根N、P含量的影响最大。该文中细根和粗根的C:P、N:P差异变化不完全支持"生长速率假说"。根系和叶片一样,N、P含量与纬度呈正相关关系,支持"温度-植物生理假说",反映了植物对自然环境的适应策略。

Aims Fine roots and leaves are important below- and above-ground functional organs. It is widely recognized that leaf nitrogen （N） and phosphorus （P） stoichiometry displays significant latitudinal variations, and two com- peting theories （i.e. Temperature-Plant Physiological Hypothesis and Growth Rate Hypothesis） have been pro- posed to explain this phenomenon. Although considerable efforts have been made to test these theories, compara- tively few data have been reported for the plants in China to examine the latitudinal and longitudinal variations in fine root carbon （C）, N and P stoichiometry. Accordingly, we compiled an extensive data set of root C, N and P stoichiometry, our objective was to address three main issues： （1） whether the C, N and P stoichiometric latitu- dinal patterns for roots conform to those reported for leaves, （2） how exactly does root C, N and P stoichiometry changes as a function of longitude, and （3） whether the Temperature-Plant Physiological Hypothesis or Growth Rate Hypothesis can account for the latitudinal pattems observed for fine root stoichiometry. Methods We compiled data on fine root C, N and P contents, climate, and geographic location, and analyzed the correlations among these variables. Important findings The N and P contents were higher in fine roots as opposed to coarse roots. The N and P contents in fine roots increased with increasing latitude. P content in fine roots declined with increasing longitude, whereas the N：P of fine roots increased with increasing longitude. The N and P contents in fine roots were nega- tively correlated with mean annual temperature and mean annual precipitation, but positively correlated with soil nutrient. Among the three abiotic factors （i.e. soil N and P contents, temperature and precipitation）, soil N and P levels had the greatest effect on the N and P contents in fine roots. The variations observed in fine and coarse root C：P and N：P were inconsistent with the Growth Rate Hypothesis, whereas the positive correlations between root N and P contents and latitude were the same as those observed for leaves, which support Temperature-Plant Physio- logical Hypothesis, reflecting an adaptive strategy to environmental conditions.