Slowed Biogeochemical Cycling in Sub-arctic Birch Forest Linked to Reduced Mycorrhizal Growth and Community Change after a Defoliation Event

Parker, Thomas C.; Sadowsky, Jesse; Dunleavy, H.; Subke, Jens‐Arne; Frey, Serita D.; Wookey, Philip A.

doi:10.1007/s10021-016-0026-7

Cited by 35 publications

(49 citation statements)

References 74 publications

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“…It was, however, in disagreement with the field study by Kaukonen et al (2013) finding decreasing soil fungi:bacteria after repeated defoliations, suggesting that in the field, plant ? symbiont feedbacks (Saravesi et al 2015;Parker et al 2016) may be more important than the direct effects of litter degradation studied here. Similarly, our findings contradict the general trends for field studies in temperate and boreal forests (Frey et al 2004;Treseder 2008), where chronic inorganic N fertilisation had a negative impact on fungal biomass, while bacteria showed no response.…”

Section: Discussionmentioning

confidence: 83%

“…For example, studies have reported enhanced resource turnover and decreased fungal:bacterial ratios (Kaukonen et al 2013), slowed biogeochemical cycling linked to changes in ectomycorrhizal (ECM) associations (Parker et al 2016), and decreased ECM-abundances and richness benefitting saprotrophic decomposers (Saravesi et al 2015). Moreover, the substantial short-term N-enrichment following outbreaks in the Subarctic mountain birch system (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, the substantial short-term N-enrichment following outbreaks in the Subarctic mountain birch system (e.g. Parker et al 2016) may also increase the likelihood of N-inhibition of microbial activity (Fog 1988;Berg 2000;DeForest et al 2004). Furthermore, labile organic matter addition may over time shift the organic matter use by decomposers to components richer in N; hence decreasing overall soil organic matter mineralisation (Ehtesham and Bengtson 2017;Rousk et al 2016).…”

Section: Introductionmentioning

confidence: 99%

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The biogeochemical consequences of litter transformation by insect herbivory in the Subarctic: a microcosm simulation experiment

2018

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Warming may increase the extent and intensity of insect defoliations within Arctic ecosystems. A thorough understanding of the implications of this for litter decomposition is essential to make predictions of soil-atmosphere carbon (C) feedbacks. Soil nitrogen (N) and C cycles naturally are interlinked, but we lack a detailed understanding of how insect herbivores impact these cycles. In a laboratory microcosm study, we investigated the growth responses of heterotrophic soil fungi and bacteria as well as C and N mineralisation to simulated defoliator outbreaks (frass addition), long-term increased insect herbivory (litter addition at higher background N-level) and non-outbreak conditions (litter addition only) in soils from a Subarctic birch forest. Larger amounts of the added organic matter were mineralised in the outbreak simulations compared to a normal year; yet, the fungal and bacterial growth rates and biomass were not significantly different. In the simulation of long-term increased herbivory, less litter C was respired per unit mineralised N (C:N of mineralisation decreased to 20 ± 1 from 38 ± 3 for pure litter), which suggests a directed microbial mining for N-rich substrates. This was accompanied by higher fungal dominance relative to bacteria and lower total microbial biomass. In conclusion, while a higher fraction of foliar C will be respired by insects and microbes during outbreak years, predicted longterm increases in herbivory linked to climate change may facilitate soil C-accumulation, as less foliar C is respired per unit mineralised N. Further work elucidating animal-plant-soil interactions is needed to improve model predictions of C-sink capacity in high latitude forest ecosystems.

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Section: Discussionmentioning

confidence: 83%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The biogeochemical consequences of litter transformation by insect herbivory in the Subarctic: a microcosm simulation experiment

2018

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“…R soil was also negatively correlated with total browning, further reflecting the slowdown in below‐ground processes which follows a reduction in aboveground productivity (Supporting Information Figure S3; Litton et al, ; Parker et al, ). However, contrary to hypothesis (iv), no overall correlation between total browning and R eco was identified.…”

Section: Discussionmentioning

confidence: 97%

“…This supports previous work showing that vegetation damage following climatic and biological extreme events reduces R soil (Moore et al, ; Olsson, Heliasz, Jin, & Eklundh, ; Zhao, Peichl, & Nilsson, ), and further demonstrates that vegetation stress may have qualitatively similar effects to damage (albeit of a lesser magnitude). Reductions in R soil following vegetation damage have previously been attributed to diminished microbial activity and deceleration of soil processes due to reduced transfer of carbon below ground (Litton, Raich, & Ryan, ; Parker et al, ). Here, decomposition data are consistent with this mechanism, given that decomposed fraction of green tea (labile litter) was lower in damaged plots, indicating reduced microbial activity.…”

Section: Discussionmentioning

confidence: 99%

Arctic browning: Impacts of extreme climatic events on heathland ecosystem CO₂ fluxes

Treharne

Bjerke

Tømmervik

et al. 2018

Global Change Biology

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Extreme climatic events are among the drivers of recent declines in plant biomass and productivity observed across Arctic ecosystems, known as “Arctic browning.” These events can cause landscape‐scale vegetation damage and so are likely to have major impacts on ecosystem CO2 balance. However, there is little understanding of the impacts on CO2 fluxes, especially across the growing season. Furthermore, while widespread shoot mortality is commonly observed with browning events, recent observations show that shoot stress responses are also common, and manifest as high levels of persistent anthocyanin pigmentation. Whether or how this response impacts ecosystem CO2 fluxes is not known. To address these research needs, a growing season assessment of browning impacts following frost drought and extreme winter warming (both extreme climatic events) on the key ecosystem CO2 fluxes Net Ecosystem Exchange (NEE), Gross Primary Productivity (GPP), ecosystem respiration (Reco) and soil respiration (Rsoil) was carried out in widespread sub‐Arctic dwarf shrub heathland, incorporating both mortality and stress responses. Browning (mortality and stress responses combined) caused considerable site‐level reductions in GPP and NEE (of up to 44%), with greatest impacts occurring at early and late season. Furthermore, impacts on CO2 fluxes associated with stress often equalled or exceeded those resulting from vegetation mortality. This demonstrates that extreme events can have major impacts on ecosystem CO2 balance, considerably reducing the carbon sink capacity of the ecosystem, even where vegetation is not killed. Structural Equation Modelling and additional measurements, including decomposition rates and leaf respiration, provided further insight into mechanisms underlying impacts of mortality and stress on CO2 fluxes. The scale of reductions in ecosystem CO2 uptake highlights the need for a process‐based understanding of Arctic browning in order to predict how vegetation and CO2 balance will respond to continuing climate change.

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The spatial distribution of tree–tree interaction effects on soil microbial biomass and respiration

Christel,

Bruelheide,

Cesarz

et al. 2024

Ecology and Evolution

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The capacity of forests to sequester carbon in both above‐ and belowground compartments is a crucial tool to mitigate rising atmospheric carbon concentrations. Belowground carbon storage in forests is strongly linked to soil microbial communities that are the key drivers of soil heterotrophic respiration, organic matter decomposition and thus nutrient cycling. However, the relationships between tree diversity and soil microbial properties such as biomass and respiration remain unclear with inconsistent findings among studies. It is unknown so far how the spatial configuration and soil depth affect the relationship between tree richness and microbial properties. Here, we studied the spatial distribution of soil microbial properties in the context of a tree diversity experiment by measuring soil microbial biomass and respiration in subtropical forests (BEF‐China experiment). We sampled soil cores at two depths at five locations along a spatial transect between the trees in mono‐ and hetero‐specific tree pairs of the native deciduous species Liquidambar formosana and Sapindus saponaria. Our analyses showed decreasing soil microbial biomass and respiration with increasing soil depth and distance from the tree in mono‐specific tree pairs. We calculated belowground overyielding of soil microbial biomass and respiration – which is higher microbial biomass or respiration than expected from the monocultures – and analysed the distribution patterns along the transect. We found no general overyielding across all sampling positions and depths. Yet, we encountered a spatial pattern of microbial overyielding with a significant microbial overyielding close to L. formosana trees and microbial underyielding close to S. saponaria trees. We found similar spatial patterns across microbial properties and depths that only differed in the strength of their effects. Our results highlight the importance of small‐scale variations of tree–tree interaction effects on soil microbial communities and functions and are calling for better integration of within‐plot variability to understand biodiversity–ecosystem functioning relationships.

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Slowed Biogeochemical Cycling in Sub-arctic Birch Forest Linked to Reduced Mycorrhizal Growth and Community Change after a Defoliation Event

Cited by 35 publications

References 74 publications

The biogeochemical consequences of litter transformation by insect herbivory in the Subarctic: a microcosm simulation experiment

The biogeochemical consequences of litter transformation by insect herbivory in the Subarctic: a microcosm simulation experiment

Arctic browning: Impacts of extreme climatic events on heathland ecosystem CO₂ fluxes

The spatial distribution of tree–tree interaction effects on soil microbial biomass and respiration

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Slowed Biogeochemical Cycling in Sub-arctic Birch Forest Linked to Reduced Mycorrhizal Growth and Community Change after a Defoliation Event

Cited by 35 publications

References 74 publications

The biogeochemical consequences of litter transformation by insect herbivory in the Subarctic: a microcosm simulation experiment

The biogeochemical consequences of litter transformation by insect herbivory in the Subarctic: a microcosm simulation experiment

Arctic browning: Impacts of extreme climatic events on heathland ecosystem CO2 fluxes

The spatial distribution of tree–tree interaction effects on soil microbial biomass and respiration

Contact Info

Product

Resources

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Arctic browning: Impacts of extreme climatic events on heathland ecosystem CO₂ fluxes