519 research outputs found
Climate and species affect fine root production with long-term fertilization in acidic tussock tundra near Toolik Lake, Alaska
Author Posting. © The Author(s), 2007. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Oecologia 153 (2007): 643-652, doi:10.1007/s00442-007-0753-8.Long-term fertilization of acidic tussock tundra has led to changes in plant species
composition, increases in aboveground production and biomass and substantial losses of soil
organic carbon (SOC). Root litter is an important input to SOC pools, though little is known
about fine root demography in tussock tundra. In this study, we examined the response of fine
root production and live standing fine root biomass to short- and long-term fertilization, as
changes in fine root demography may contribute to observed declines in SOC. Live standing
fine root biomass increased with long-term fertilization, while fine root production declined,
reflecting replacement of the annual fine root system of Eriophorum vaginatum, with the long-lived
fine roots of Betula nana. Fine root production increased in fertilized plots during an
unusually warm growing season, but remained unchanged in control plots, consistent with
observations that B. nana shows a positive response to climate warming. Calculations based on
a few simple assumptions suggest changes in fine root demography with long-term fertilization
and species replacement could account for between 20 and 39% of observed declines in SOC
stocks.This project was supported by National Science Foundation research grants 9810222,
9911681, 0221606 and 0528748
Carbon cycling and budget in a forested basin of southwestern Hokkaido, northern Japan
Quantification of annual carbon sequestration is very important in order to assess the function of forest ecosystems in combatting global climate change and the ecosystem responses to those changes. Annual cycling and budget of carbon in a forested basin was investigated to quantify the carbon sequestration of a cool-temperate deciduous forest ecosystem in the Horonai stream basin, Tomakomai Experimental Forest, northern Japan. Net ecosystem exchange, soil respiration, biomass increment, litterfall, soil-solution chemistry, and stream export were observed in the basin from 1999–2001 as a part of IGBP-TEMA project. We found that 258 g C m–2 year–1 was sequestered annually as net ecosystem exchange (NEE) in the forested basin. Discharge of carbon to the stream was 4 g C m–2 year–1 (about 2% of NEE) and consisted mainly of dissolved inorganic carbon (DIC). About 43% of net ecosystem productivity (NEP) was retained in the vegetation, while about 57% of NEP was sequestered in soil, suggesting that the movement of sequestered carbon from aboveground to belowground vegetation was an important process for net carbon accumulation in soil. The derived organic carbon from aboveground vegetation that moved to the soil mainly accumulated in the solid phase of the soil, with the result that the export of dissolved organic carbon to the stream was smaller than that of dissolved inorganic carbon. Our results indicated that the aboveground and belowground interaction of carbon fluxes was an important process for determining the rate and retention time of the carbon sequestration in a cool-temperate deciduous forest ecosystem in the southwestern part of Hokkaido, northern Japan
Temperature-Induced Increase in Methane Release from Peat Bogs: A Mesocosm Experiment
Peat bogs are primarily situated at mid to high latitudes and future climatic change projections indicate that these areas may become increasingly wetter and warmer. Methane emissions from peat bogs are reduced by symbiotic methane oxidizing bacteria (methanotrophs). Higher temperatures and increasing water levels will enhance methane production, but also methane oxidation. To unravel the temperature effect on methane and carbon cycling, a set of mesocosm experiments were executed, where intact peat cores containing actively growing Sphagnum were incubated at 5, 10, 15, 20, and 25°C. After two months of incubation, methane flux measurements indicated that, at increasing temperatures, methanotrophs are not able to fully compensate for the increasing methane production by methanogens. Net methane fluxes showed a strong temperature-dependence, with higher methane fluxes at higher temperatures. After removal of Sphagnum, methane fluxes were higher, increasing with increasing temperature. This indicates that the methanotrophs associated with Sphagnum plants play an important role in limiting the net methane flux from peat. Methanotrophs appear to consume almost all methane transported through diffusion between 5 and 15°C. Still, even though methane consumption increased with increasing temperature, the higher fluxes from the methane producing microbes could not be balanced by methanotrophic activity. The efficiency of the Sphagnum-methanotroph consortium as a filter for methane escape thus decreases with increasing temperature. Whereas 98% of the produced methane is retained at 5°C, this drops to approximately 50% at 25°C. This implies that warming at the mid to high latitudes may be enhanced through increased methane release from peat bogs
Depleted 15N in hydrolysable-N of arctic soils and its implication for mycorrhizal fungi–plant interaction
Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Biogeochemistry 97 (2009): 183-194, doi:10.1007/s10533-009-9365-1.Uptake of nitrogen (N) via root-mycorrhizal associations accounts for a significant portion of
total N supply to many vascular plants. Using stable isotope ratios (δ15N) and the mass balance
among N pools of plants, fungal tissues, and soils, a number of efforts have been made in recent
years to quantify the flux of N from mycorrhizal fungi to host plants. Current estimates of this
flux for arctic tundra ecosystems rely on the untested assumption that the δ15N of labile organic
N taken up by the fungi is approximately the same as the δ15N of bulk soil. We report here
hydrolysable amino acids are more depleted in 15N relative to hydrolysable ammonium and
amino sugars in arctic tundra soils near Toolik Lake, Alaska, USA. We demonstrate, using a
case study, that recognizing the depletion in 15N for hydrolysable amino acids (δ15N = -5.6 ‰ on
average) would alter recent estimates of N flux between mycorrhizal fungi and host plants in an
arctic tundra ecosystem.This study was funded by NSF-DEB-0423385and NSF-DEB 0444592.
Additional support was provided by Arctic Long Term Ecological Research program, funded by
National Science Foundation, Division of Environmental Biology
Shallow water marine sediment bacterial community shifts along a natural CO2 gradient in the Mediterranean Sea off Vulcano, Italy.
The effects of increasing atmospheric CO(2) on ocean ecosystems are a major environmental concern, as rapid shoaling of the carbonate saturation horizon is exposing vast areas of marine sediments to corrosive waters worldwide. Natural CO(2) gradients off Vulcano, Italy, have revealed profound ecosystem changes along rocky shore habitats as carbonate saturation levels decrease, but no investigations have yet been made of the sedimentary habitat. Here, we sampled the upper 2 cm of volcanic sand in three zones, ambient (median pCO(2) 419 μatm, minimum Ω(arag) 3.77), moderately CO(2)-enriched (median pCO(2) 592 μatm, minimum Ω(arag) 2.96), and highly CO(2)-enriched (median pCO(2) 1611 μatm, minimum Ω(arag) 0.35). We tested the hypothesis that increasing levels of seawater pCO(2) would cause significant shifts in sediment bacterial community composition, as shown recently in epilithic biofilms at the study site. In this study, 454 pyrosequencing of the V1 to V3 region of the 16S rRNA gene revealed a shift in community composition with increasing pCO(2). The relative abundances of most of the dominant genera were unaffected by the pCO(2) gradient, although there were significant differences for some 5 % of the genera present (viz. Georgenia, Lutibacter, Photobacterium, Acinetobacter, and Paenibacillus), and Shannon Diversity was greatest in sediments subject to long-term acidification (>100 years). Overall, this supports the view that globally increased ocean pCO(2) will be associated with changes in sediment bacterial community composition but that most of these organisms are resilient. However, further work is required to assess whether these results apply to other types of coastal sediments and whether the changes in relative abundance of bacterial taxa that we observed can significantly alter the biogeochemical functions of marine sediments
Medicinal Plant Use and Health Sovereignty: Findings from the Tajik and Afghan Pamirs
Medicinal plants are indicators of indigenous
knowledge in the context of political volatility and sociocultural
and ecological change in the Pamir Mountains of
Afghanistan and Tajikistan. Medicinal plants are the
primary health care option in this region of Central Asia.
The main objective of this paper is to demonstrate that
medicinal plants contribute to health security and sovereignty
in a time of instability. We illustrate the nutritional
as well as medicinal significance of plants in the daily
lives of villagers. Based on over a decade and half of
research related to resilience and livelihood security, we
present plant uses in the context of mountain communities.
Villagers identified over 58 cultivated and noncultivated
plants and described 310 distinct uses within
63 categories of treatment and prevention. Presence of
knowledge about medicinal plants is directly connected to
their use
Recovery and resilience of tropical forests after disturbance
The time taken for forested tropical ecosystems to re-establish post-disturbance is of widespread interest. Yet to date there has been no comparative study across tropical biomes to determine rates of forest re-growth, and how they vary through space and time. Here we present results from a meta-analysis of palaeoecological records that use fossil pollen as a proxy for vegetation change over the past 20,000 years. A total of 283 forest disturbance and recovery events, reported in 71 studies, are identified across four tropical regions. Results indicate that forests in Central America and Africa generally recover faster from past disturbances than those in South America and Asia, as do forests exposed to natural large infrequent disturbances compared with post-climatic and human impacts. Results also demonstrate that increasing frequency of disturbance events at a site through time elevates recovery rates, indicating a degree of resilience in forests exposed to recurrent past disturbance
Climate change and outdoor regional living plant collections: an example from mainland Portugal
Original PaperClimate change threatens not only plant species occurring naturally, but also
impacts on regional living plant collections, which play an important role in ex situ
conservation strategies. In the last few years, several global circulation models have been
used to predict different global climate change scenarios. Due to their coarse resolutions,
and while more detailed regional approaches are not available, downscaling techniques
have been proposed, as a very simple first approach to increase detail. We analysed seven
sites on mainland Portugal with potential for species conservation (four botanic gardens
and three universities), in the light of downscaled climate change scenarios, using an
environmental envelope approach and a predefined bioclimatic neighbourhood for each
site. Thresholds for the bioclimatic neighbourhood were based on Rivas-Martı´nez’s Bioclimatic
Classification of the Earth. For each site, the expected geographical shift of its
original bioclimatic neighbourhood (1950–2000) was mapped for 2020, 2050 and 2080.
Analysing those shifts enabled us to delineate knowledge-transfer paths between sites,
according to the analysed scenarios. We concluded that, according to the Intergovernmental
Panel on Climate Change A2 scenario, all considered sites will be outside the
predefined bioclimatic neighbourhood by 2080, while according to the B2 scenario all of
them will be inside that neighbourhood, although sometimes marginally so. Therefore, the
implementation of global sustainability measures as considered in the B2 scenario family
can be of great importance in order to delay significantly the impacts of climate change,
giving extra time for the adaptation of the outdoor regional living plant collectionsinfo:eu-repo/semantics/publishedVersio
- …