环境变化对兴安落叶松氮磷化学计量特征的影响

兴安落叶松(Larix gmelinii)为我国北方人工林优势树种,采集地理和气候差异明显的6个种源种子,在分布区南界的均一立地条件下进行播种,形成了32a林分。采集新老枝、新老叶和不同径级的根样品,测定其氮(N)和磷(P)浓度,比较种源间差异以及其随月份的变化和各器官NP元素之间的相关性。结果表明:老枝叶(P0.05)、1—2 mm根(P0.01)和2—5 mm根(P0.05)N浓度在种源间差异显著,变化范围分别为21.1—24.2 mg/g、5.9—7.8 mg/g和4.7—6.5 mg/g。P浓度在老枝叶(P0.05)和新枝叶(P0.05)中都表现出种源间的差异显著,变化范围分别为4.5—5.8 mg/g和4.5—6.5 mg/g。根系和枝叶的N/P皆存在种源间显著性差异(P0.05)。叶片和根系的NP浓度的月份变化呈现先减小再增加的趋势,而新枝则呈现增加-减小-增加的不同趋势。新老枝、新老叶和根系的N和P浓度之间显著相关;新老枝、新老叶和根系之间的N浓度显著相关。不同种源兴安落叶松因对不同环境的长期适应而产生NP化学计量特征的遗传差异。

Influence of environmental changes on stoichiometric traits of nitrogen and phosphorus for Larix gmelinii trees

To understand response and adaptation of nitrogen (N) and phosphorus (P) stoichimetry to environmental changes, we conducted a provenance experiment on Larix gmelinii, the dominant boreal tree species in northeastern China. We collected seeds from six provenances with different geographical and climatic conditions and planted the seeds at a homogenous site in the southern boundary of the distribution range of this species for 32 years. Our objectives were to (1) examine variations in the concentrations of N and P in different organs among provenances, (2) explore monthly dynamics in the concentrations, and (3) explore correlations between N and P concentrations in different organs. The results showed that the N concentrations in the needles on old branch, fine roots (diameter 1-2 mm), and medium roots (diameter 2-5 mm) showed significantly different among the provenances (P < 0.05, P < 0.01, and P < 0.05, respectively), with the concentrations ranging from 21.1 to 24.2 mg/g, from 5.9 to 7.8 mg/g, and from 4.7 to 6.5 mg/g, respectively. The P concentrations in the needles on old branch and needles on new twig were significantly different (P < 0.05) among the provenances, with the concentrations ranging from 4.5-5.8 mg/g and from 4.5-6.5 mg/g, respectively. The N/P in the roots, branches and needles showed significantly different among the provenances (P < 0.05). The seasonal variations in the concentrations of N and P in the needles and roots trended to decrease first and then increase as the growing season proceeded, while those in the twigs showed a trend of increasing-decreasing-increasing. There were significant correlations between N and P concentrations in branches, needles, fine roots and medium roots. There were significant correlations between the N concentrations in the needles on twigs and on branches, twigs, branches and roots. The results suggest that the adaptation of Larix gmelinii trees to different environments in the six provenances lead to genetic differentiation in their stoichiometric traits of N and P.