Paludification reduces black spruce growth rate but does not alter tree water use efficiency in Canadian boreal forested peatlands  

作　　者：Joannie Beaulne Étienne Boucher Michelle Garneau Gabriel Magnan 

机构地区：[1]Geotop Research Center,Université du Québec à Montréal,Montréal,Québec H3C 3P8,Canada [2]Department of Geography,Université du Québec à Montréal,Montréal,Québec H3C 3P8,Canada [3]GRIL-UQAM,Université du Québec à Montréal,Québec H3C 3P8,Canada [4]Centre d'études nordiques,Université Laval,Montréal,Québec G1V 0A6,Canada

出　　处：《Forest Ecosystems》2021年第2期373-386,共14页森林生态系统（英文版）

基　　金：Scholarships to J.B.were provided by the Natural Sciences and Engineering Research Council of Canada(NSERC-CGS M);the Fonds de recherche du Québec–Nature et technologies(FRQNT);funded by the Natural Sciences and Engineering Research Council of Canada through discovery grants to M.G.andÉB。

摘　　要：Background:Black spruce(Picea mariana(Mill.)BSP)-forested peatlands are widespread ecosystems in boreal North America in which peat accumulation,known as the paludification process,has been shown to induce forest growth decline.The continuously evolving environmental conditions(e.g.,water table rise,increasing peat thickness)in paludified forests may require tree growth mechanism adjustments over time.In this study,we investigate tree ecophysiological mechanisms along a paludification gradient in a boreal forested peatland of eastern Canada by combining peat-based and tree-ring analyses.Carbon and oxygen stable isotopes in tree rings are used to document changes in carbon assimilation rates,stomatal conductance,and water use efficiency.In addition,paleohydrological analyses are performed to evaluate the dynamical ecophysiological adjustments of black spruce trees to site-specific water table variations.Results:Increasing peat accumulation considerably impacts forest growth,but no significant differences in tree water use efficiency(iWUE)are found between the study sites.Tree-ring isotopic analysis indicates no iWUE decrease over the last 100 years,but rather an important increase at each site up to the 1980 s,before iWUE stabilized.Surprisingly,inferred basal area increments do not reflect such trends.Therefore,iWUE variations do not reflect tree ecophysiological adjustments required by changes in growing conditions.Local water table variations induce no changes in ecophysiological mechanisms,but a synchronous shift in iWUE is observed at all sites in the mid-1980 s.Conclusions:Our study shows that paludification induces black spruce growth decline without altering tree water use efficiency in boreal forested peatlands.These findings highlight that failing to account for paludification-related carbon use and allocation could result in the overestimation of aboveground biomass production in paludified sites.Further research on carbon allocation strategies is of utmost importance to understand the carbon sink capac

关 键 词：Black spruce growth Boreal biome Carbon allocation Ecophysiological mechanisms Forested peatland Paludification Stable isotope Water use efficiency 

分 类 号：S718.5[农业科学—林学]