Aims As extreme climatic events including droughts and heat waves become more common in a changing climate,tree mortality has increased across the globe.In order to determine whether certain species have a competitive...Aims As extreme climatic events including droughts and heat waves become more common in a changing climate,tree mortality has increased across the globe.In order to determine whether certain species have a competitive advantage over others,we explored the water-relations and leaf-gas exchange of four co-occurring spe-cies in a forest in northern Aotearoa-New Zealand.We studied the ecologically and culturally significant foundation species,Agathis australis(a conifer),two additional conifers,Phyllocladus tricho-manoides and Podocarpus totara and the angiosperm Knightia excelsa.Methods We measured sap flow,leaf-gas exchange and xylem water poten-tials of leaves and terminal branches with concurrent measures of micrometeorological data on days with very few clouds.We derived whole tree hydraulic conductance and instantaneous water-use efficiency(WUEi)at our remnant forest in west Auckland during February 2015(southern hemisphere summer).Important Findings The four species behaved similarly in their diurnal curves of gas exchange and water potential.Rates of assimilation,stomatal con-ductance and WUEi were similar among trees of different species.Whole tree hydraulic conductance was also similar among species.These results indicate functional convergence in water relations,possibly driven by low nutrient soils at the site.Our results suggest that there is no species with a clear adaptive advantage over the others in the context of climate change.展开更多
基金This research was funded by a grant from the Marsden Fund(UOA1207),administered by the Royal Society of New Zealand to C.M.
文摘Aims As extreme climatic events including droughts and heat waves become more common in a changing climate,tree mortality has increased across the globe.In order to determine whether certain species have a competitive advantage over others,we explored the water-relations and leaf-gas exchange of four co-occurring spe-cies in a forest in northern Aotearoa-New Zealand.We studied the ecologically and culturally significant foundation species,Agathis australis(a conifer),two additional conifers,Phyllocladus tricho-manoides and Podocarpus totara and the angiosperm Knightia excelsa.Methods We measured sap flow,leaf-gas exchange and xylem water poten-tials of leaves and terminal branches with concurrent measures of micrometeorological data on days with very few clouds.We derived whole tree hydraulic conductance and instantaneous water-use efficiency(WUEi)at our remnant forest in west Auckland during February 2015(southern hemisphere summer).Important Findings The four species behaved similarly in their diurnal curves of gas exchange and water potential.Rates of assimilation,stomatal con-ductance and WUEi were similar among trees of different species.Whole tree hydraulic conductance was also similar among species.These results indicate functional convergence in water relations,possibly driven by low nutrient soils at the site.Our results suggest that there is no species with a clear adaptive advantage over the others in the context of climate change.
