Soil microbial communities regulate global biogeochemical cycles and respond rapidly to changing environmental conditions. However, understanding how soil microbial communities respond to climate ...change, and how this influences biogeochemical cycles, remains a major challenge. This is especially pertinent in alpine regions where climate change is taking place at double the rate of the global average, with large reductions in snow cover and earlier spring snowmelt expected as a consequence. Here, we show that spring snowmelt triggers an abrupt transition in the composition of soil microbial communities of alpine grassland that is closely linked to shifts in soil microbial functioning and biogeochemical pools and fluxes. Further, by experimentally manipulating snow cover we show that this abrupt seasonal transition in wide-ranging microbial and biogeochemical soil properties is advanced by earlier snowmelt. Preceding winter conditions did not change the processes that take place during snowmelt. Our findings emphasise the importance of seasonal dynamics for soil microbial communities and the biogeochemical cycles that they regulate. Moreover, our findings suggest that earlier spring snowmelt due to climate change will have far reaching consequences for microbial communities and nutrient cycling in these globally widespread alpine ecosystems.
Climate change is disproportionately impacting mountain ecosystems, leading to large reductions in winter snow cover, earlier spring snowmelt and widespread shrub expansion into alpine grasslands. ...Yet, the combined effects of shrub expansion and changing snow conditions on abiotic and biotic soil properties remains poorly understood. We used complementary field experiments to show that reduced snow cover and earlier snowmelt have effects on soil microbial communities and functioning that persist into summer. However, ericaceous shrub expansion modulates a number of these impacts and has stronger belowground effects than changing snow conditions. Ericaceous shrub expansion did not alter snow depth or snowmelt timing but did increase the abundance of ericoid mycorrhizal fungi and oligotrophic bacteria, which was linked to decreased soil respiration and nitrogen availability. Our findings suggest that changing winter snow conditions have cross‐seasonal impacts on soil properties, but shifts in vegetation can modulate belowground effects of future alpine climate change.
Climate change is disproportionately impacting mountain ecosystems, leading to large reductions in winter snow cover, earlier spring snowmelt and widespread shrub expansion into alpine grasslands. Using complimentary field experiments, we show that earlier snowmelt and reductions in snow cover have cross‐seasonal impacts on soil microbial communities and their functioning, with consequences for soil nutrient pools and fluxes. However, we also show that shifts in vegetation can modulate the belowground effects of future alpine climate change.
The seasonal coupling of plant and soil microbial nutrient demands is crucial for efficient ecosystem nutrient cycling and plant production, especially in strongly seasonal alpine ecosystems. Yet, ...how these seasonal nutrient cycling processes are modified by climate change and what the consequences are for nutrient loss and retention in alpine ecosystems remain unclear. Here, we explored how two pervasive climate change factors, reduced snow cover and shrub expansion, interactively modify the seasonal coupling of plant and soil microbial nitrogen (N) cycling in alpine grasslands, which are warming at double the rate of the global average. We found that the combination of reduced snow cover and shrub expansion disrupted the seasonal coupling of plant and soil N‐cycling, with pronounced effects in spring (shortly after snow melt) and autumn (at the onset of plant senescence). In combination, both climate change factors decreased plant organic N‐uptake by 70% and 82%, soil microbial biomass N by 19% and 38% and increased soil denitrifier abundances by 253% and 136% in spring and autumn, respectively. Shrub expansion also individually modified the seasonality of soil microbial community composition and stoichiometry towards more N‐limited conditions and slower nutrient cycling in spring and autumn. In winter, snow removal markedly reduced the fungal:bacterial biomass ratio, soil N pools and shifted bacterial community composition. Taken together, our findings suggest that interactions between climate change factors can disrupt the temporal coupling of plant and soil microbial N‐cycling processes in alpine grasslands. This could diminish the capacity of these globally widespread alpine ecosystems to retain N and support plant productivity under future climate change.
Seasonal transfers of nutrients between plants and soil microbes are crucial for nutrient retention in alpine ecosystems. Here, we show that two important climate change factors in alpine ecosystems, reduced snow cover and shifts in vegetation, interactively disrupt these seasonal transfers of nutrients. Future climate change could therefore diminish the capacity of globally widespread alpine ecosystems to retain nutrients, with far‐reaching consequences for nutrient cycling and plant productivity.
BACKGROUND AND AIMS: The carbon (C) sequestration potential of land-use practices is increasingly important. Trees sequester atmospheric C into biomass and above and belowground litter but may also ...prime the decomposition of soil organic matter (SOM). We compared the influence of Acer pseudoplatanus (Sycamore) and Larix x. europlepsis (Hybrid Larch) on soil C decomposition. METHODS: We used natural abundance ¹³C to partition soil-surface CO₂ efflux into root and SOM sources. CO₂ was sampled from incubated root-free soil and from live tree roots using in-situ chambers. Combined surface efflux δ¹³CO₂ was measured using dynamic chambers and cavity-ringdown spectroscopy. RESULTS: Under Sycamore, CO₂ emissions were dominated (80–90 %) by root respiration. SOM contributed 10–20 % with a mean residence time of centuries. Under Larch, 24–33 % of total CO₂ efflux was root respiration, the remainder originating from an SOM pool with a turnover time of decades. Total soil C stocks were similar between the two plot types. Root-respired δ¹³CO₂ was consistently different by c. 2 ‰ between the species. CONCLUSIONS: The decomposition rate of soil C and its mean residence time are markedly different under the two tree species. Species differences in root-respired δ¹³CO₂ may reflect plant C allocation or respiratory fractionation.
BACKGROUND AND AIMS: Root-respired δ¹³CO₂ can be useful for exploring plant carbon allocation and root respiratory fractionation as well as for partitioning soil-surface CO₂ emissions into plant root ...and soil organic matter (SOM) sources, a necessary measure for calculating the contribution of heterotrophic respiration of soil carbon to net ecosystem exchange. Root CO₂ is usually sampled from excised roots, however, excision alters respiration rate and isolates the root sample from aboveground plant processes. METHODS: To improve the integrity of root efflux δ¹³CO₂ measurements, we designed a chamber for sampling root-respired CO₂ in situ from minimally disturbed tree roots. We compared root δ¹³CO₂ values from excised and attached roots in the field and we pruned mature Scots pine trees to induce a measureable change in root δ¹³CO₂. RESULTS: Excised root samples containing root wounds gave more ¹³C-depleted measurements of root-respired δ¹³CO₂ than intact roots by 1.8 ‰. Using chambers to sample CO₂ from attached roots, we measured a diurnal change in root-respired δ¹³CO₂ of 3–4 ‰, triggered by pruning foliage from the trees. CONCLUSIONS: This chamber system permits high-frequency sampling of live root-respired δ¹³CO₂ that enables greater insight into plant respiratory processes and more accurate partitioning of soil-surface CO₂ emissions.
The carbon (C) sequestration potential of land-use practices is increasingly important. Trees sequester atmospheric C into biomass and above and belowground litter but may also prime the ...decomposition of soil organic matter (SOM). We compared the influence of Acer pseudoplatanus (Sycamore) and Larix x. europlepsis (Hybrid Larch) on soil C decomposition. We used natural abundance super(13)C to partition soil-surface CO sub(2) efflux into root and SOM sources. CO sub(2) was sampled from incubated root-free soil and from live tree roots using in-situ chambers. Combined surface efflux delta super(13)CO sub(2) was measured using dynamic chambers and cavity-ringdown spectroscopy. Under Sycamore, CO sub(2) emissions were dominated (80-90 %) by root respiration. SOM contributed 10-20 % with a mean residence time of centuries. Under Larch, 24-33 % of total CO sub(2) efflux was root respiration, the remainder originating from an SOM pool with a turnover time of decades. Total soil C stocks were similar between the two plot types. Root-respired delta super(13)CO sub(2) was consistently different by c. 2 ppt between the species. The decomposition rate of soil C and its mean residence time are markedly different under the two tree species. Species differences in root-respired delta super(13)CO sub(2) may reflect plant C allocation or respiratory fractionation.
Background and aims The carbon (C) sequestration potential of land-use practices is increasingly important. Trees sequester atmospheric C into biomass and above and belowground litter but may also ...prime the decomposition of soil organic matter (SOM). We compared the influence of Acer pseudoplatanus (Sycamore) and Larix x. europlepsis (Hybrid Larch) on soil C decomposition. Methods We used natural abundance ^sup 13^C to partition soil-surface CO2 efflux into root and SOM sources. CO2 was sampled from incubated root-free soil and from live tree roots using in-situ chambers. Combined surface efflux δ^sup 13^CO2 was measured using dynamic chambers and cavity-ringdown spectroscopy. Results Under Sycamore, CO2 emissions were dominated (80-90 %) by root respiration. SOM contributed 10-20 % with a mean residence time of centuries. Under Larch, 24-33 % of total CO2 efflux was root respiration, the remainder originating from an SOM pool with a turnover time of decades. Total soil C stocks were similar between the two plot types. Root-respired δ^sup 13^CO2 was consistently different by c. 2 per thousand between the species. Conclusions The decomposition rate of soil C and its mean residence time are markedly different under the two tree species. Species differences in root-respired δ^sup 13^CO2 may reflect plant C allocation or respiratory fractionation.
Background and aims The carbon (C) sequestration potential of land-use practices is increasingly important. Trees sequester atmospheric C into biomass and above and belowground litter but may also ...prime the decomposition of soil organic matter (SOM). We compared the influence of Acer pseudoplatanus (Sycamore) and Larix x. europlepsis (Hybrid Larch) on soil C decomposition. Methods We used natural abundance .sup.13C to partition soil-surface CO.sub.2 efflux into root and SOM sources. CO.sub.2 was sampled from incubated root-free soil and from live tree roots using in-situ chambers. Combined surface efflux δ.sup.13CO.sub.2 was measured using dynamic chambers and cavity-ringdown spectroscopy. Results Under Sycamore, CO.sub.2 emissions were dominated (80-90 %) by root respiration. SOM contributed 10-20 % with a mean residence time of centuries. Under Larch, 24-33 % of total CO.sub.2 efflux was root respiration, the remainder originating from an SOM pool with a turnover time of decades. Total soil C stocks were similar between the two plot types. Root-respired δ.sup.13CO.sub.2 was consistently different by c. 2 â° between the species. Conclusions The decomposition rate of soil C and its mean residence time are markedly different under the two tree species. Species differences in root-respired δ.sup.13CO.sub.2 may reflect plant C allocation or respiratory fractionation.
Root-respired δ^sup 13^CO2 can be useful for exploring plant carbon allocation and root respiratory fractionation as well as for partitioning soil-surface CO2 emissions into plant root and soil ...organic matter (SOM) sources, a necessary measure for calculating the contribution of heterotrophic respiration of soil carbon to net ecosystem exchange. Root CO2 is usually sampled from excised roots, however, excision alters respiration rate and isolates the root sample from aboveground plant processes. To improve the integrity of root efflux δ^sup 13^CO2 measurements, we designed a chamber for sampling root-respired CO2 in situ from minimally disturbed tree roots. We compared root δ^sup 13^CO2 values from excised and attached roots in the field and we pruned mature Scots pine trees to induce a measureable change in root δ^sup 13^CO2. Excised root samples containing root wounds gave more ^sup 13^C-depleted measurements of root-respired δ^sup 13^CO2 than intact roots by 1.8 per thousand. Using chambers to sample CO2 from attached roots, we measured a diurnal change in root-respired δ^sup 13^CO2 of 3-4 per thousand, triggered by pruning foliage from the trees. This chamber system permits high-frequency sampling of live root-respired δ^sup 13^CO2 that enables greater insight into plant respiratory processes and more accurate partitioning of soil-surface CO2 emissions.
PDF
