{"title":"Effects of a warmer climate and forest composition on soil carbon cycling, soil organic matter stability and stocks in a humid boreal region","authors":"D. Paré, J. Laganière, G. Larocque, R. Boutin","doi":"10.5194/soil-8-673-2022","DOIUrl":null,"url":null,"abstract":"Abstract. The maintenance of the large soil organic carbon (SOC) stocks of the boreal\nforest under climate change is a matter of concern. In this study, major\nsoil carbon pools and fluxes were assessed in 22 closed-canopy\nforests located along an elevation and latitudinal climatic gradient\nexpanding 4 ∘C in mean annual temperature (MAT) for two important boreal\nconifer forest stand types: balsam fir (Abies balsamea), a fire avoider, and black spruce\n(Picea mariana), a fire-tolerant species. SOC stocks were not influenced by a warmer\nclimate or by forest type. However, carbon fluxes, including aboveground\nlitterfall rates, as well as total soil respiration (Rs) and heterotrophic\n(Rh) and autotrophic soil respiration (Ra), were linearly related\nto temperature (cumulative degree days >5 ∘C). The\nsensitivity of soil organic matter (SOM) degradation to temperature, assessed by comparing\nQ10 (rate of change for a T increase of 10 ∘C) of soil respiration\nand Rs10 (soil respiration rates corrected to 10 ∘C), did not vary\nalong the temperature gradient, while the proportion of bioreactive carbon\nand nitrogen showed higher values for balsam fir and for warmer sites.\nBalsam fir forests showed a greater litterfall rate, a better litter quality\n(lower C : N ratio) and a higher Rs10 than black spruce ones,\nsuggesting that their soils cycle a larger amount of C and N under a similar\nclimate regime. Altogether, these results suggest that a warmer climate and\na balsam fir forest composition induce a more rapid SOC turnover. Contrary\nto common soil organic matter stabilisation hypotheses, greater litter input\nrates did not lead to higher total SOC stocks, and a warmer climate did not\nlead to the depletion of bioreactive soil C and N. Positive effects of\nwarming both on fluxes to and from the soil as well as a potential\nsaturation of stabilised SOC could explain these results which apply to the\ncontext of this study: a cold and wet environment and a stable vegetation\ncomposition along the temperature gradient. While the entire study area is\nsubject to a humid climate, a negative relationship was found between\naridity and SOM stocks in the upper mineral soil layer for black spruce\nforests, suggesting that water balance is more critical than temperature to\nmaintain SOM stocks.\n","PeriodicalId":22015,"journal":{"name":"Soil Science","volume":"75 1","pages":""},"PeriodicalIF":0.0000,"publicationDate":"2022-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Soil Science","FirstCategoryId":"97","ListUrlMain":"https://doi.org/10.5194/soil-8-673-2022","RegionNum":4,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"Agricultural and Biological Sciences","Score":null,"Total":0}
引用次数: 0
Abstract
Abstract. The maintenance of the large soil organic carbon (SOC) stocks of the boreal
forest under climate change is a matter of concern. In this study, major
soil carbon pools and fluxes were assessed in 22 closed-canopy
forests located along an elevation and latitudinal climatic gradient
expanding 4 ∘C in mean annual temperature (MAT) for two important boreal
conifer forest stand types: balsam fir (Abies balsamea), a fire avoider, and black spruce
(Picea mariana), a fire-tolerant species. SOC stocks were not influenced by a warmer
climate or by forest type. However, carbon fluxes, including aboveground
litterfall rates, as well as total soil respiration (Rs) and heterotrophic
(Rh) and autotrophic soil respiration (Ra), were linearly related
to temperature (cumulative degree days >5 ∘C). The
sensitivity of soil organic matter (SOM) degradation to temperature, assessed by comparing
Q10 (rate of change for a T increase of 10 ∘C) of soil respiration
and Rs10 (soil respiration rates corrected to 10 ∘C), did not vary
along the temperature gradient, while the proportion of bioreactive carbon
and nitrogen showed higher values for balsam fir and for warmer sites.
Balsam fir forests showed a greater litterfall rate, a better litter quality
(lower C : N ratio) and a higher Rs10 than black spruce ones,
suggesting that their soils cycle a larger amount of C and N under a similar
climate regime. Altogether, these results suggest that a warmer climate and
a balsam fir forest composition induce a more rapid SOC turnover. Contrary
to common soil organic matter stabilisation hypotheses, greater litter input
rates did not lead to higher total SOC stocks, and a warmer climate did not
lead to the depletion of bioreactive soil C and N. Positive effects of
warming both on fluxes to and from the soil as well as a potential
saturation of stabilised SOC could explain these results which apply to the
context of this study: a cold and wet environment and a stable vegetation
composition along the temperature gradient. While the entire study area is
subject to a humid climate, a negative relationship was found between
aridity and SOM stocks in the upper mineral soil layer for black spruce
forests, suggesting that water balance is more critical than temperature to
maintain SOM stocks.
期刊介绍:
Cessation.Soil Science satisfies the professional needs of all scientists and laboratory personnel involved in soil and plant research by publishing primary research reports and critical reviews of basic and applied soil science, especially as it relates to soil and plant studies and general environmental soil science.
Each month, Soil Science presents authoritative research articles from an impressive array of discipline: soil chemistry and biochemistry, physics, fertility and nutrition, soil genesis and morphology, soil microbiology and mineralogy. Of immediate relevance to soil scientists-both industrial and academic-this unique publication also has long-range value for agronomists and environmental scientists.