Leaf Functional Traits Of Current-year And Former-year Leaves Of Pinus Tabulaeformis In Songshan,Beijing

Plant functional trait has become a hot research in the field of ecology in recent years,reflecting the response of plants to the environment.In natural and artificial forests,Songshan Nature Reserve,we measured five leaf functional traits of Pinus tabulaeformis including specific leaves area(SLA),leaf dry matter content(LDMC),leaf nitrogen concentration(LNC),leaf phosphorus concentration(LPC)and N:P ratio across age,slope aspect and diameter class.In addition,six leaf photosynthetic physiological traits were also measured.The objective of this study was to reveal the survival strategy,resource utilization efficiency and physiological adaptation mechanism of Pinus tabulaeformis,than provide scientific reference for the protection of Pinus tabulaeformis in natural forests and the management of Pinus tabulaeformis in artificial forests.The conclusions are as follows.1.SLA of current and former-year leaves from natural forests were significantly greater than current-year leaves that from artificial forests(P<0.05).LDMC of former-year leaves from natural forests were significantly greater than current and former-year leaves that from artificial forests(P<0.05).The N:P ratio of former-year leaves were significantly greater than current-year leaves(P<0.05).Natural forests have greater environmental resource utilization efficiency and stronger environmental adaptability than artificial forests.2.SLA from north-facing slopes was significantly greater than that from south-facing slopes(P<0.05).LDMC from north-facing slopes was significantly lower than that from south-facing slopes(P<0.05).LNC and LPC in natural forests were mainly controlled by their own development.Besides,the slopes had no effect on both of them.3.SLA of small class diameter were significantly greater than medium diameter and large diameter classes.The average of LNC and N:P ratio of current-year were greater than those of former-year leaves,while LPC was the opposite.Both current-year and former-year leaves were found to be limited by nitrogen,and the current-year leaves were more susceptible to the lack of nitrogen.In order to promote the development of Pinus tabulaeformis in Songshan area,nitrogen fertilizer may be properly applied.4.SLA was significantly negatively correlated with LDMC(P<0.01).LPC was significantly negatively correlated with N:P ratio(P<0.01).LNC in natural forests was significantly positively correlated with N:P ratio(P<0.01).In artificial forests,LNC of former-year leaves was significantly positively correlated with N:P ratio(P<0.01),and LNC of current-year leaves was significantly positively correlated with LPC(P<0.01).5.Photosynthetic potential of current-year leaves was stronger than former-year leaves'.However,former-year leaves had a better ability to absorb the weak light.The curves of diurnal variation of net photosynthetic rate(Pn)and transpiration rate(Tr)were both displayed "double-peak" curves.In the whole day,compared with former-year leaves,current-year leaves have faster metabolism and breathe,greater transpiration,and stronger photosynthetic capacity.Furthermore,photosynthetic active radiation was common environmental factor of the photosynthesis of current-year and former-year leaves.