濒危植物大别山五针松枝叶NPK化学计量特征季节动态

为了解我国特有珍稀濒危植物大别山五针松(Pinus dabeshanensis)枝和叶的养分状况及其季节变化特征,连续12个月对其开展野外取样和室内分析,探讨了枝叶N、P、K含量及其化学计量比的动态变化及其在器官间的差异性。结果表明,器官和月份对大别山五针松化学计量特征有显著影响,其中器官的影响最大。枝和叶化学计量特征的季节变化不规律,N∶K变异系数最大(枝叶分别为26.75%和28.00%),其余均属弱变异(变异系数<25%)。叶N、P、K平均含量(10.40、1.43及5.15 mg·g-1)显著高于枝(6.56、1.26及4.80 mg·g-1),叶N∶P(7.27)也显著高于枝(5.18),但枝和叶N∶P均远低于14,呈严重N限制。枝和叶N∶P、N∶K及P∶K分别受制于N、K和K(即相关系数最大)。枝和叶N、P和K之间(枝N-K除外)具有显著的相关性和异速生长关系,其中叶N分配速率高于枝而P分配速率低于枝。降水和温度对枝叶化学计量特征有不同影响。降水量具有明显的时间尺度效应,短时间尺度降水多影响叶而长时间尺度多影响枝。在各时间尺度下,温度均与叶P含量呈显著负相关而与枝K含量呈显著正相关。综合来看,大别山五针松枝、叶间化学计量特征差异显著,且具有明显的季节变异,在一定程度上受降水和温度的影响。

Seasonal Dynamics of N,P,and K Stoichiometry in Twigs and Needles of Pinus dabeshanensis,An Endangered Gymnosperm Species

In order to understand the nutrient status and seasonal variations in the twigs and needles of Pinus dabeshanensis,a rare and endangered plant in China,the dynamics of N,P and K contents and theirstoichiometric ratios in twigs and needles,and the differences between organs were explored,the field samplingand N,P,K analyses in laboratory were carried out in 12 consecutive months.The results showed that organ andmonth represented significant influences on the stoichiometric characteristics of P.dabeshanensis,and the organshowed the greatest influence.The seasonal changes of stoichiometric characteristics in twigs were irregular;theN∶K showed the greatest variation(the variation coefficients for twig and needle were 26.75%and 28.00%,respectively)and the rest stoichiometric indices belonged to weak variation(variation coefficients<25%).Theaverage contents of N,P and K in needles(10.40,1.43 and 5.15 mg·g-1,respectively)showed significantlyhigher than that in twigs(6.56,1.26 and 4.80 mg·g-1,respectively),and the mean N∶P in needles(7.27)wasalso significantly higher than that in twigs(5.18).However,both of the two N∶P ratios were far lower than 14,showed a serious N-limitation.The N∶P,N∶K and P∶K ratios were dominated by N,K,and K,respectively,inboth needles and twigs(i.e.,the highest correlation coefficients were observed between them).Significantallometric scaling relationships were detected among N,P,and K in both needles and twigs(except for N-K intwigs);the partitioning rate of needle N was higher than that of twigs,while the partitioning rate of P was lowerthan that of twigs.The precipitation and temperature showed different influences on stoichiometriccharacteristics in twigs and needles.The precipitation presented significantly obvious temporal-scale effect.Theshort temporal-scale precipitation mostly affected needles,while the long temporal-scale precipitation mostlyaffected twigs.At all temporal-scales,temperature was negatively correlated with P content in needles,butpositively correlated with K content in twigs.As a whole,there were significant differences in the stoichiometriccharacteristics between needles and twigs of P.dabeshanensis,and they exhibited obvious seasonal variation,andwere affected by precipitation and temperature to some extent.