Aims In contrast to temperate regions,the reasons for growth reductions of individual tree species along elevational gradients in tropical mountain ranges are poorly known,especially for tropical conifers.We aimed at ...Aims In contrast to temperate regions,the reasons for growth reductions of individual tree species along elevational gradients in tropical mountain ranges are poorly known,especially for tropical conifers.We aimed at testing whether climatic or edaphic conditions are responsible for the reduced growth of Pinus kesiya,a widely distributed pine species of southern and south-eastern Asia,at higher elevations.Methods We analysed the stem diameter increment and the isotope discrimination against ^(13)C(△^(13)C)in tree rings of P.kesiya along an elevational gradient of~900 to~2000 m a.s.l.in the mountain ranges of South-Central Vietnam,and related growth to△^(13)C and to climatic and edaphic variables.Important findings We found no consistent correlation patterns between the basal area increment(BAI)of the trees and temperature or precipitation.In contrast,across the elevational gradient,we obtained significantly negative correlations of BAI with△^(13)C and with the C/N ratios and theδ^(15)N signature of the upper mineral soil.BAI was positively correlated with the concentrations of plant-available phosphorus(P_(a))and of“base”cations(calcium,magnesium,potassium)in the soil.We conclude that lower temperatures at higher elevations exert an indirect effect on tree growth by inducing higher C/N ratios and by reducing the rate of nitrogen(N)and P mineralization,which may be further hampered by lower concentrations of“base”cations(upon enhanced leaching by precipitation)and a negative feedback from low availability of mineralized N and P at higher elevations.Our results may be transferable to the uppermost growth limit of P.kesiya and to other montane regions of the species’occurrence.展开更多
基金supported by the State of Vietnam through a PhD grant to L.T.H.(Grant No.4358/QĐ-BGDĐT)by the Deutscher Akadamischer Austauschdienst(DAADProject No.57163751)through covering travel costs of R.S.and F.M.T.
文摘Aims In contrast to temperate regions,the reasons for growth reductions of individual tree species along elevational gradients in tropical mountain ranges are poorly known,especially for tropical conifers.We aimed at testing whether climatic or edaphic conditions are responsible for the reduced growth of Pinus kesiya,a widely distributed pine species of southern and south-eastern Asia,at higher elevations.Methods We analysed the stem diameter increment and the isotope discrimination against ^(13)C(△^(13)C)in tree rings of P.kesiya along an elevational gradient of~900 to~2000 m a.s.l.in the mountain ranges of South-Central Vietnam,and related growth to△^(13)C and to climatic and edaphic variables.Important findings We found no consistent correlation patterns between the basal area increment(BAI)of the trees and temperature or precipitation.In contrast,across the elevational gradient,we obtained significantly negative correlations of BAI with△^(13)C and with the C/N ratios and theδ^(15)N signature of the upper mineral soil.BAI was positively correlated with the concentrations of plant-available phosphorus(P_(a))and of“base”cations(calcium,magnesium,potassium)in the soil.We conclude that lower temperatures at higher elevations exert an indirect effect on tree growth by inducing higher C/N ratios and by reducing the rate of nitrogen(N)and P mineralization,which may be further hampered by lower concentrations of“base”cations(upon enhanced leaching by precipitation)and a negative feedback from low availability of mineralized N and P at higher elevations.Our results may be transferable to the uppermost growth limit of P.kesiya and to other montane regions of the species’occurrence.
