喀斯特区次生林土壤和优势树种叶片的化学计量特征及季节变化

Stoichiometric characteristics and seasonal variation of soils and dominant plant leaves in secondary forest in karst area

【目的】探究黔中喀斯特地区次生林林分土壤和优势树种叶片的化学计量特征及其季节变化规律,为退化喀斯特地区植被恢复提供参考依据。【方法】在秋(10月)、冬(1月)、春(4月)和夏(7月)季对黔中喀斯特地区针叶林、阔叶林和针阔混交林3种林分土壤和优势树种叶片进行野外采样,测定分析其碳(C)、氮(N)、磷(P)含量及其计量比C/N、C/P和N/P。【结果】黔中喀斯特地区次生林3种林分土壤中的C、N、P含量及C/N、C/P和N/P的总平均值分别为47.98 g/kg、1.71 g/kg、0.77 g/kg、29.50、68.93和2.34,3种林分优势树种叶片的C、N、P含量及C/N、C/P和N/P总平均值分别为461.66 g/kg、13.75 g/kg、1.76 g/kg、38.75、387.70和9.57,反映出林分优势树种叶片的C、N和P含量较高。3种林分土壤中的C、N和P含量均在春季最低,N和P含量最高值出现于秋季,C含量最高值出现于夏季;除针叶林的N/P最低值出现在春季外,其余林分C/N、C/P和N/P的最低值均出现在秋季。3种林分优势树种叶片的C和N含量呈冬季低夏季高的变化趋势,P含量最高和最低值出现的季节在3个林分中各异,C/N、C/P和N/P在春、夏季最高,在秋、冬季最低。相关性分析结果表明,林分优势树种叶片C含量、C/P、N/P与土壤C含量呈极显著正相关(P<0.01)或显著正相关(P<0.05,下同),叶片N/P与土壤C/P及二者的C/P和N/P间也呈显著正相关。【结论】季节变化对喀斯特地区次生林林分的土壤化学计量特征有一定程度影响,对林分优势树种叶片化学计量特征的影响较明显,且呈春、夏季高,秋、冬季低的变化趋势;该地区次生林植被生长主要受N限制,可将N/P作为判断植物N和P营养元素受限制的指标。

【Objective】The stoichiometric characteristics of soils and dominant plant leaves in stands of secondary forest in karst area of central Guizhou in China were explored.And the seasonal variation regularity of their stoichiometricratiowas also researched,in order to provide reference for vegetation restoration in degraded karst area.【Method】Field sampling method was used to collect soils and leaves in three stands of coniferous forest,broad-leaved forest and coniferous and broad-leaved mixed forest in the karst area of central Guizhou.And then the contents of carbon(C),nitrogen(N)and phosphorus(P)in samples and their stoichiometric ratios,including C/N,C/P and N/P,were determined and analyzed.【Result】The gross average value of C,N and Pcontents were 47.98,1.71 and 0.77 g/kg,respectively in soils of three standsof secondary forest in karst area of central Guizhou.And the gross average value of indicators containing C/N,C/P and N/P were 29.50,68.93,2.34. The gross average value of C,N and P contents were 461.70,13.75 and 1.76 g/kg respectively in leaves of three stands;the gross average value of C/N,C/P and N/P were 38.75,383.70,9.57 respectively in leaves of three stands. These results reflected that the contents of C,N and P in leaves of stands were relatively high.The contents of C,N and P in soils reached the lowest value in spring,but the contents of N and P reached the maximum value in autumn and the content of C reached the maximum value in summer. Except that the minimum value of N/P in coniferous forest appeared in spring,the minimum values of C/N,C/P and N/P in other stands appeared in autumn. In leaves of three stands,there was a trend that the contents of C and N were low in winter and high in summer. Besides,the maximum and minimum content of P in three stands occurred in different seasons. The C/N,C/P and N/P were high in spring and summer and low in autumn and winter. The results of correlation analysis showed that the content of C,C/P and N/P in leaves of stands had extremely significant positive correlation(P<0.01)or significantpositive correlation with the content of C in soils(P<0.05,the same below). The N/P in leaves had significant positive correlation with the C/P in soils;and the C/P in leaves and soils also had significant positive correlation with the N/P in leaves and soils.【Conclusion】Season has certain influence on the stoichiometry characteristics value of soils in stands of secondary forest in karst area. But seasonal influence on the ecological stoichiometry characteristics value of leaves is very obvious.And there is a trend that stoichiometry characteristics value of leaves is relatively high in spring and summer and is relatively lowin autumn and winter. The vegetation growth of secondary forest in central Guizhou is mainly restricted by N. N/P value can be used as indicatorsto determine the restriction of N and P nutrients in plants.