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- Harden, Jennifer W., et al.
(författare)
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Field information links permafrost carbon to physical vulnerabilities of thawing
- 2012
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 39, s. L15704-
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Tidskriftsartikel (refereegranskat)abstract
- Deep soil profiles containing permafrost (Gelisols) were characterized for organic carbon (C) and total nitrogen (N) stocks to 3 m depths. Using the Community Climate System Model (CCSM4) we calculate cumulative distributions of active layer thickness (ALT) under current and future climates. The difference in cumulative ALT distributions over time was multiplied by C and N contents of soil horizons in Gelisol suborders to calculate newly thawed C and N. Thawing ranged from 147 PgC with 10 PgN by 2050 (representative concentration pathway RCP scenario 4.5) to 436 PgC with 29 PgN by 2100 (RCP 8.5). Organic horizons that thaw are vulnerable to combustion, and all horizon types are vulnerable to shifts in hydrology and decomposition. The rates and extent of such losses are unknown and can be further constrained by linking field and modelling approaches. These changes have the potential for strong additional loading to our atmosphere, water resources, and ecosystems. Citation: Harden, J. W., et al. (2012), Field information links permafrost carbon to physical vulnerabilities of thawing, Geophys. Res. Lett., 39, L15704, doi: 10.1029/2012GL051958.
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| 2. |
- Mayor, Jordan R., et al.
(författare)
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Nitrogen Isotope Patterns in Alaskan Black Spruce Reflect Organic Nitrogen Sources and the Activity of Ectomycorrhizal Fungi
- 2012
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Ingår i: Ecosystems. - : Springer Science and Business Media LLC. - 1432-9840 .- 1435-0629. ; 15:5, s. 819-831
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Tidskriftsartikel (refereegranskat)abstract
- Global patterns in soil, plant, and fungal stable isotopes of N (delta N-15) show promise as integrated metrics of N cycling, particularly the activity of ectomycorrhizal (ECM) fungi. At small spatial scales, however, it remains difficult to differentiate the underlying causes of plant delta N-15 variability and this limits the application of such measurements to better understand N cycling. We conducted a landscape-scale analysis of delta N-15 values from 31 putatively N-limited monospecific black spruce (Picea mariana) stands in central Alaska to assess the two main hypothesized sources of plant delta N-15 variation: differing sources and ECM fractionation. We found roughly 20% of the variability in black spruce foliar N and delta N-15 values to be correlated with the concentration and delta N-15 values of soil NH4 (+) and dissolved organic N (DON) pools, respectively. However, N-15-based mixing models from 24 of the stands suggested that fractionation by ECM fungi obscures the N-15 signature of soil N pools. Models, regressions, and N abundance data all suggested that increasing dependence on soil DON to meet black spruce growth demands predicates increasing reliance on ECM-derived N and that black spruce, on average, received 53% of its N from ECM fungi. Future research should partition the delta N-15 values within the soil DON pool to determine how choice of soil delta N-15 values influence modeled ECM activity. The C balance of boreal forests is tightly linked to N cycling and delta N-15 values may be useful metrics of changes to these connections.
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