Shrub encroachment in Arctic tundra: Betula nana effects on above- and belowground litter decomposition (original) (raw)
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Ecosystems, 2015
The Arctic climate is projected to change during the coming century, with expected higher air temperatures and increased winter snowfall. These climatic changes might alter litter decomposition rates, which in turn could affect carbon (C) and nitrogen (N) cycling rates in tundra ecosystems. However, little is known of seasonal climate change effects on plant litter decomposition rates and N dynamics, hampering predictions of future arctic vegetation composition and the tundra C balance. We tested the effects of snow addition (snow fences), warming (open top chambers), and shrub removal (clipping), using a full-factorial experiment, on mass loss and N dynamics of two shrub tissue types with contrasting quality: deciduous shrub leaf litter (Salix glauca) and
Ecology, 2014
Climate warming in arctic tundra may shift dominant vegetation from graminoids to deciduous shrubs, whose functional traits could, in turn, alter biotic and abiotic controls over biogeochemical cycling of carbon (C) and nitrogen (N). We investigated whether shrub-induced changes in microclimate have stronger effects on litter decomposition and nutrient release than changes in litter quality and quantity. In arctic tundra near Toolik Lake, Alaska, USA, we incubated a common substrate in a snow-addition experiment to test whether snow accumulation around arctic deciduous shrubs altered the environment enough to increase litter decomposition rates. We compared the influence of litter quality on the rate of litter and N loss by decomposing litter from four different plant functional types in a common site. We used aboveground net primary production values and estimated decay constant (k) values from our decomposition experiments to calculate community-weighted mass loss for each site. Snow addition had no effect on decomposition of the common substrate, and the site with the highest abundance of shrubs had the lowest decomposition rates. Species varied in their decomposition rates, with species from the same functional type not always following similar patterns. Community-weighted mass loss was 1.5 times greater in the high shrub site, and only slightly decreased when adjusted for soil environment, suggesting that litter quality and quantity are the primary drivers of community decomposition. Our findings suggest that on a short time scale, the changes in soil environment associated with snow trapping by shrubs are unlikely to influence litter nutrient turnover enough to drive positive snow-shrub feedbacks. The mechanisms driving shrub expansion are more likely to do with shrub-litter feedbacks, where the higher growth rates and N uptake by shrubs allows them to produce more leaves, resulting in a larger litter N pool and faster internal cycling of nutrients.
Short-term root and leaf decomposition of two dominant plant species in a Siberian tundra
Pedobiologia
In tundra ecosystems, global warming is expected to accelerate litter decomposition and to lead to shifts in vegetation composition. To understand these shifts, it is important to understand the interactions between global warming, vegetation composition, litter quality and decomposition in the tundra. In addition, it is important to consider root litter since roots are the major part of plant biomass in the tundra. In order to increase our understanding of decomposition, and root decomposition in particular, we performed a litter transplant experiment in northeastern Siberia, in which we measured mass loss for leaf and root litter (live and dead material) of the two dominant plant species, graminoid Eriophorum vaginatum and shrub Betula nana, in three vegetation types (E. vaginatum or B. nana dominated and mixed vegetation) during the growing season. Our results show that although leaf decomposition did not differ between the two species, root decomposition showed significant differences. Mass loss of live roots was higher for E. vaginatum than for B. nana, but mass loss of E. vaginatum dead roots was lowest. In addition, we found evidence for home-field advantage in litter decomposition: litter of a plant decomposed faster in vegetation where it was dominant. Mass loss rates of the litter types were significantly correlated with phosphorus content, rather than nitrogen content. This indicates that phosphorus limits decomposition in this tundra site. The low decomposition rate of B. nana live roots compared to E. vaginatum live roots suggests that the acceleration of decomposition in the Arctic may be partly counteracted by the expected expansion of shrubs. However, more information on litter input rates and direct effects of climate change on decomposition rates are needed to accurately predict the effects of climate change on carbon dynamics in tundra ecosystems.
Science of the Total Environment, 2020
Aims Litter decomposition is an important driver of soil carbon and nutrient cycling in nutrient-limited Arctic ecosystems. However, climate change is expected to induce changes that directly or indirectly affect decomposition. We examined the direct effects of long-term warming relative to differences in soil abiotic properties associated with vegetation type on litter decomposition across six subarctic vegetation types. Methods In six vegetation types, rooibos and green tea bags were buried for 70–75 days at 8 cm depth inside warmed (by open-top chambers) and control plots that had been in place for 20–25 years. Standardized initial decomposition rate and stabilization of the labile material fraction of tea (into less decomposable material) were calculated from tea mass losses. Soil moisture and temperature were measured bi-weekly during summer and plant-available nutrients were measured with resin probes. Results Initial decomposition rate was decreased by the warming treatment. Stabilization was less affected by warming and determined by vegetation type and soil moisture. Soil metal concentrations impeded both initial decomposition rate and stabilization. Conclusions While a warmer Arctic climate will likely have direct effects on initial litter decomposition rates in tundra, stabilization of organic matter was more affected by vegetation type and soil parameters and less prone to be affected by direct effects of warming.
Litter decomposition in two subalpine forests during the freeze–thaw season
Acta Oecologica, 2010
Mass loss and nutrient release of forest litter during the freezeethaw season could play an essential role in C and nutrient cycling in cold regions, but few studies in some key ecosystems have been available. In order to characterize litter decomposition during the freezeethaw season in a subalpine forest region of western China, a field experiment using the litterbag method was conducted on the decomposition of foliar litter of two dominant species, fir (Abies faxoniana) and birch (Betula platyphylla) under their respective forests. Over the freezeethaw season following leaf-fall, about 18% and 20% of mass, 13% and 14% of lignin, 30% and 26% of cellulose, 14% and 21% of C, 30% and 27% of N, 17% and 15% of P, and 17% and 13% of K were lost from fir and birch litters, respectively. The lost mass and components accounted for more than 64% and 65% of mass, 72% and 69% of lignin, 75% and 60% of cellulose, 49% and 59% of C, 56% and 71% of N, 62% and 37% of P, and 38% and 37% of K in 1 year net loss rate of fir and birch litter, respectively. In addition, the loss of mass, lignin, cellulose and component bio-elements during the freezeethaw season correlated closely with the initial substrate type and the levels of the individual bioelements. The results demonstrated that litter decomposition during the freezeethaw season contributes significantly to the first year decomposition in these subalpine forests.
Ecology Letters, 2007
Whether climate change will turn cold biomes from large long-term carbon sinks into sources is hotly debated because of the great potential for ecosystem-mediated feedbacks to global climate. Critical are the direction, magnitude and generality of climate responses of plant litter decomposition. Here, we present the first quantitative analysis of the major climate-change-related drivers of litter decomposition rates in cold northern biomes worldwide. Leaf litters collected from the predominant species in 33 global change manipulation experiments in circum-arctic-alpine ecosystems were incubated simultaneously in two contrasting arctic life zones. We demonstrate that longer-term, large-scale changes to leaf litter decomposition will be driven primarily by both direct warming effects and concomitant shifts in plant growth form composition, with a much smaller role for changes in litter quality within species. Specifically, the ongoing warminginduced expansion of shrubs with recalcitrant leaf litter across cold biomes would constitute a negative feedback to global warming. Depending on the strength of other (previously reported) positive feedbacks of shrub expansion on soil carbon turnover, this may partly counteract direct warming enhancement of litter decomposition.
Analysis of litter decomposition in an alpine tundra
Canadian Journal of Botany, 1998
Decomposition of plant litter regulates nutrient cycling and transfers of fixed carbon to soil organic matter pools in terrestrial ecosystems. Climate, as well as factors of intrinsic litter chemistry, often govern the rate of decomposition and thus the dynamics of these processes. Initial concentrations of nitrogen and recalcitrant carbon compounds in plant litter are good predictors of litter decomposition rates in many systems. The effect of exogenous nitrogen availability on decay rates, however, is not well defined. Microclimate factors vary widely within alpine tundra sites, potentially affecting litter decay rates at the local scale. A controlled factorial experiment was performed to assess the influence of landscape position and exogenous nitrogen additions on decomposition of surface foliage and buried root litter in an alpine tundra in the Front Range of the Rocky Mountains in Colorado, U.S.A. Litter bags were placed in three communities representing a gradient of soil moisture and temperature. Ammonium nitrate was applied once every 30 days at a rate of 20 g N·m -2 during the 3-month growing season. Data, as part of the Long-Term Inter-site Decomposition Experiment Team project, were analyzed to ascertain the effects of intrinsic nitrogen and carbon fraction chemistry on litter decay in alpine systems. Soil moisture was found to be the primary controlling factor in surface litter mass loss. Root litter did not show significant mass loss following first growing season. Nitrogen additions had no effect on nitrogen retention, or decomposition, of surface or buried root litter compared with controls. The acid-insoluble carbon fraction was a good predictor of mass loss in surface litters, showing a strong negative correlation. Curiously, N concentration appeared to retard root decomposition, although degrees of freedom limit the confidence of this observation. Given the slow rate of decay and N loss from root litter, root biomass appears to be a long-term reservoir for C and N in the alpine tundra.
Litter quality outweighs climate as a driver of decomposition across the tundra biome
2023
, the staff and research commission of the Swiss National Park, BioGeoClimate Modelling Lab. We thank the innumerable field technicians, logistics teams, graduate and undergraduate assistants for help with data collection. Special thanks to the Tea Bag Index core-team. Finally, we thank parks, wildlife refuges, field stations and the local and Indigenous people for the opportunity to conduct research on their land.
Plant and Soil, 2013
Aims Climate-induced changes in snow cover are likely to affect cold arctic and alpine ecosystems functioning and major processes such as wintertime plant litter decomposition. However, it remains poorly studied in subalpine systems where the snowpack may be irregular. In this paper we explored the dynamic of the winter plant litter decomposition process, its magnitude and its relationship with the snowpack properties. Methods In subalpine grasslands of the Central French Alps, we performed a litter bag experiment monitoring over a whole winter the litter decomposition from the exploitative Dactylis glomerata and the conservative Festuca paniculata, under two contiguous experimental sites with snowpacks differing in depth and physical properties. Results Litter decomposition rates were stable during winter and 3-fold higher under deeper and permanent snowpack with higher thermal resistance. Litter quality appeared only significant under thinner snowpack with higher decomposition rates for the exploitative species. A snowpack with higher thermal resistance created an insulating layer promoting the decomposition process. Conclusion These results suggest that the temporal (permanence vs. intermittency) and physical (depth Plant Soil (2013) 363:215-229