Understory plant diversity and composition across a postfire tree density gradient in a Siberian Arctic boreal forest

Paulson, Alison K.; Pena, H.; Alexander, Heather D.; Davydov, S. P.; Loranty, M. M.; Mack, Michelle C.; Natali, Susan M.

doi:10.1139/cjfr-2020-0483

Cited by 17 publications

(37 citation statements)

References 47 publications

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“…Additionally, recent albedo trends suggest a fire regime shift may be underway (Webb et al, 2021). If these fire regime shifts are sustained, the potential impacts on forest cover associated with recruitment dynamics (Alexander et al, 2012(Alexander et al, , 2018Paulson et al, 2021) have important implications for cryospheric climate feedbacks. The extent to which increases in winter albedo immediately postfire (Chen et al, 2018;Stuenzi and Schaepman-Strub, 2020) are reversed during postfire succession will depend on the density of forest regrowth (Talucci et al, 2020;Paulson et al, 2021;Walker et al, 2021).…”

Section: Discussion Of Emerging Ecosystem Changes With Implications For Cryospheric Climate Feedbacksmentioning

confidence: 99%

“…If these fire regime shifts are sustained, the potential impacts on forest cover associated with recruitment dynamics (Alexander et al, 2012(Alexander et al, , 2018Paulson et al, 2021) have important implications for cryospheric climate feedbacks. The extent to which increases in winter albedo immediately postfire (Chen et al, 2018;Stuenzi and Schaepman-Strub, 2020) are reversed during postfire succession will depend on the density of forest regrowth (Talucci et al, 2020;Paulson et al, 2021;Walker et al, 2021). Similarly, forest impacts on surface energy exchange exert a series of interrelated controls on permafrost and snow thermal dynamics (Loranty et al, 2018;Stuenzi et al, 2021).…”

Section: Discussion Of Emerging Ecosystem Changes With Implications For Cryospheric Climate Feedbacksmentioning

confidence: 99%

“…Similarly, forest impacts on surface energy exchange exert a series of interrelated controls on permafrost and snow thermal dynamics (Loranty et al, 2018;Stuenzi et al, 2021). Variation in forest recovery within a single fire perimeter near Cherskiy has resulted in even-aged stands with canopy cover ranging from ∼10-95% (Paulson et al, 2021), and winter albedos of ∼0.3 and ∼0.7 at representative highand low-density stands (Kropp and Loranty, 2018;Kropp et al, 2019). Corresponding to post-fire tree density, summer and winter soil temperatures are warmer at sites with lower tree cover (Figure 1B) as a result of lower canopy shading and insulation from organic soils, and snow redistribution, respectively.…”

Section: Discussion Of Emerging Ecosystem Changes With Implications For Cryospheric Climate Feedbacksmentioning

confidence: 99%

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Siberian Ecosystems as Drivers of Cryospheric Climate Feedbacks in the Terrestrial Arctic

et al. 2021

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Climate warming is altering the persistence, timing, and distribution of permafrost and snow cover across the terrestrial northern hemisphere. These cryospheric changes have numerous consequences, not least of which are positive climate feedbacks associated with lowered albedo related to declining snow cover, and greenhouse gas emissions from permafrost thaw. Given the large land areas affected, these feedbacks have the potential to impact climate on a global scale. Understanding the magnitudes and rates of changes in permafrost and snow cover is therefore integral for process understanding and quantification of climate change. However, while permafrost and snow cover are largely controlled by climate, their distributions and climate impacts are influenced by numerous interrelated ecosystem processes that also respond to climate and are highly heterogeneous in space and time. In this perspective we highlight ongoing and emerging changes in ecosystem processes that mediate how permafrost and snow cover interact with climate. We focus on larch forests in northeastern Siberia, which are expansive, ecologically unique, and studied less than other Arctic and subarctic regions. Emerging fire regime changes coupled with high ground ice have the potential to foster rapid regional changes in vegetation and permafrost thaw, with important climate feedback implications.

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Section: Discussion Of Emerging Ecosystem Changes With Implications For Cryospheric Climate Feedbacksmentioning

confidence: 99%

Section: Discussion Of Emerging Ecosystem Changes With Implications For Cryospheric Climate Feedbacksmentioning

confidence: 99%

Section: Discussion Of Emerging Ecosystem Changes With Implications For Cryospheric Climate Feedbacksmentioning

confidence: 99%

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Siberian Ecosystems as Drivers of Cryospheric Climate Feedbacks in the Terrestrial Arctic

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“…Stands of larch in our study system are underlain by carbon‐rich, Pleistocene‐age, Yedoma permafrost with high ice content (Strauss et al, 2017). The active layer thickness across the stands is impacted by climate but also sensitive to tree density and canopy cover (Paulson et al, 2021; Walker et al, 2021) more so than variation in soil organic layer thickness unlike the ecosystem‐protected permafrost (Shur & Jorgenson, 2007) further south. Understorey vegetation is composed of tall (>1 m) deciduous, EcM shrubs, short (<1 m) ericaceous shrubs that host ericoid mycorrhizal fungi (ErM), forbs, grasses, lichens and mosses.…”

Section: Methodsmentioning

confidence: 99%

“…We investigated the relationships between tree density, the characteristics of larch roots and root‐associated fungi important to N acquisition, and above‐ground productivity and N cycling parameters of larch located along a natural gradient where larch density increased and active layer thickness decreased in northeastern Siberia (Paulson et al, 2021; Walker et al, 2021). Here, increasing stand productivity was coupled with greater demand for N above‐ground as density increased (Hewitt, Alexander, et al, 2022, Hewitt et al, in press).…”

Section: Introductionmentioning

confidence: 99%

Root‐associated fungi not tree density influences stand nitrogen dynamics at the larch forest–tundra ecotone

et al. 2022

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Greater tree density and forest productivity at the tundra–taiga ecotone (TTE) are expected with climate warming, with potential feedbacks to the climate system. Yet, competition for nitrogen (N) may impact TTE dynamics. Greater tree density will likely increase N demand, while reducing N supply through soil shading and slower decomposition rates. We explored whether characteristics of roots and root‐associated fungi important to N acquisition responded to changes in density at the TTE and were related to above‐ground stand productivity and N cycling. We measured rooting depth, uptake of N forms among soil layers and ectomycorrhizal (EcM) colonization and composition along a natural tree density gradient of monodominant larch Larix cajanderi in northeastern Siberia. We tested relationships between larch root and fungal characteristics, above‐ground productivity and stand‐level N cycling parameters. Overall, there was preferential uptake of ammonium compared to glycine or nitrate. Nitrogen uptake was greatest in shallow soils of the organic horizon and related to root chemistry, root‐associated fungi and above‐ground N cycling parameters, but the direction of these relationships depended on N form. Uptake of different N forms, rooting depth and EcM colonization and composition were not related to tree density, but fungal composition was correlated with root N chemistry and above‐ground N cycling parameters. In addition to EcM, the abundance of dark septate endophytes and other ascomycetous taxa was positively related to N uptake and above‐ground N cycling parameters. Synthesis. There was little impact of tree density on root and fungal parameters related to N acquisition suggesting intraspecific larch competition for N was not amplified with increased density. There was, however, a strong impact of root‐associated fungi on N uptake and stand N dynamics regardless of tree density. Together, this suggests an important role of root‐associated fungi on broadscale patterns of N cycling in TTE larch forests independent of changes in tree density expected with climate warming.

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Increasing tree density accelerates stand‐level nitrogen cycling at the taiga–tundra ecotone in northeastern Siberia

et al. 2022

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As climate warms, tree density at the taiga–tundra ecotone (TTE) is expected to increase, which may intensify competition for belowground resources in this nitrogen (N)‐limited environment. To determine the impacts of increased tree density on N cycling and productivity, we examined edaphic properties indicative of soil N availability along with aboveground and belowground tree‐level traits and stand characteristics related to carbon (C) and N cycling across a tree density gradient of monodominant larch (Larix cajanderi) at the TTE in far northeastern Siberia. We found no consistent evidence from soil, tree, or stand‐level N cycling characteristics of lower N availability or greater intraspecific competition for N with increased density. Active layer thickness declined, but resin‐sorbed N and soil organic layer thickness did not covary with increased tree density. There was, however, greater allocation belowground to stand‐level coarse and fine roots with increased tree density, an allocation pattern suggestive of limited soil resources. Foliar traits related to C (%C, δ13C, and resorption) were responsive to density indicating the importance of non‐nutrient resources, like light, to foliar stoichiometry. As tree density increased and individual trees had lower productivity, tree‐level N and biomass pools aboveground and belowground declined tracking decreases in N uptake, N resorption, N use efficiency, and allocation to slow cycling tissues like wood. At the stand level, our findings show high N turnover with increased N acquisition, allocation to short‐lived tissues with relatively high N content and reduced N residence time, and greater stand productivity as tree density increased. Yet, these positive relationships were curtailed at the highest tree densities. Our observations of shifts in biomass, C and N allocation, and loss aboveground, along with greater root density with increased tree density, could have strong impacts on C and N cycling and should be represented in models of TTE dynamics and feedbacks to climate.

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Understory plant diversity and composition across a postfire tree density gradient in a Siberian Arctic boreal forest

Cited by 17 publications

References 47 publications

Siberian Ecosystems as Drivers of Cryospheric Climate Feedbacks in the Terrestrial Arctic

Siberian Ecosystems as Drivers of Cryospheric Climate Feedbacks in the Terrestrial Arctic

Root‐associated fungi not tree density influences stand nitrogen dynamics at the larch forest–tundra ecotone

Increasing tree density accelerates stand‐level nitrogen cycling at the taiga–tundra ecotone in northeastern Siberia

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