Response of plant community structure and primary productivity to experimental drought and flooding in an Alaskan fen

2015 ◽  
Vol 45 (2) ◽  
pp. 185-193 ◽  
Author(s):  
Amber C. Churchill ◽  
Merritt R. Turetsky ◽  
A. David McGuire ◽  
Teresa N. Hollingsworth
Keyword(s):  
Plant Species ◽  
Water Table ◽  
Primary Productivity ◽  
Net Primary Productivity ◽  
Species Abundance ◽  
Total Biomass ◽  
Climate Control ◽  
Green Area ◽  
Northern Peatlands

Northern peatlands represent a long-term net sink for atmospheric CO2, but these ecosystems can shift from net carbon (C) sinks to sources based on changing climate and environmental conditions. In particular, changes in water availability associated with climate control peatland vegetation and carbon uptake processes. We examined the influence of changing hydrology on plant species abundance and ecosystem primary production in an Alaskan fen by manipulating the water table in field treatments to mimic either sustained flooding (raised water table) or drought (lowered water table) conditions for 6 years. We found that water table treatments altered plant species abundance by increasing sedge and grass cover in the raised water table treatment and reducing moss cover while increasing vascular green area in the lowered water table treatment. Gross primary productivity was lower in the lowered treatment than in the other plots, although there were no differences in total biomass or vascular net primary productivity among the treatments. Overall, our results indicate that vegetation abundance was more sensitive to variation in water table than total biomass and vascular biomass accrual. Finally, in our experimental peatland, drought had stronger consequences for change in vegetation abundance and ecosystem function than sustained flooding.

scholarly journals Climate-related changes in peatland carbon accumulation during the last millennium

2013 ◽  
Vol 10 (2) ◽  
pp. 929-944 ◽  
Author(s):  
D. J. Charman ◽  
D. W. Beilman ◽  
M. Blaauw ◽  
R. K. Booth ◽  
S. Brewer ◽  
...  
Keyword(s):  
Carbon Sequestration ◽  
Carbon Cycle ◽  
Primary Productivity ◽  
Net Primary Productivity ◽  
Carbon Accumulation ◽  
Total Carbon ◽  
Sequestration Rate ◽  
Northern Peatlands ◽  
Carbon Sequestration Rate

Abstract. Peatlands are a major terrestrial carbon store and a persistent natural carbon sink during the Holocene, but there is considerable uncertainty over the fate of peatland carbon in a changing climate. It is generally assumed that higher temperatures will increase peat decay, causing a positive feedback to climate warming and contributing to the global positive carbon cycle feedback. Here we use a new extensive database of peat profiles across northern high latitudes to examine spatial and temporal patterns of carbon accumulation over the past millennium. Opposite to expectations, our results indicate a small negative carbon cycle feedback from past changes in the long-term accumulation rates of northern peatlands. Total carbon accumulated over the last 1000 yr is linearly related to contemporary growing season length and photosynthetically active radiation, suggesting that variability in net primary productivity is more important than decomposition in determining long-term carbon accumulation. Furthermore, northern peatland carbon sequestration rate declined over the climate transition from the Medieval Climate Anomaly (MCA) to the Little Ice Age (LIA), probably because of lower LIA temperatures combined with increased cloudiness suppressing net primary productivity. Other factors including changing moisture status, peatland distribution, fire, nitrogen deposition, permafrost thaw and methane emissions will also influence future peatland carbon cycle feedbacks, but our data suggest that the carbon sequestration rate could increase over many areas of northern peatlands in a warmer future.

scholarly journals Climate-related changes in peatland carbon accumulation during the last millennium

2012 ◽  
Vol 9 (10) ◽  
pp. 14327-14364 ◽  
Author(s):  
D. J. Charman ◽  
D. W. Beilman ◽  
M. Blaauw ◽  
R. K. Booth ◽  
S. Brewer ◽  
...  
Keyword(s):  
Carbon Sequestration ◽  
Carbon Cycle ◽  
Primary Productivity ◽  
Net Primary Productivity ◽  
Carbon Accumulation ◽  
Total Carbon ◽  
Sequestration Rate ◽  
Northern Peatlands ◽  
Carbon Sequestration Rate

Abstract. Peatlands are a major terrestrial carbon store and a persistent natural carbon sink during the Holocene, but there is considerable uncertainty over the fate of peatland carbon in a changing climate. It is generally assumed that higher temperatures will increase peat decay, causing a positive feedback to climate warming and contributing to the global positive carbon cycle feedback. Here we use a new extensive database of peat profiles across northern high latitudes to examine spatial and temporal patterns of carbon accumulation over the past millennium. Opposite to expectations, our results indicate a small negative carbon cycle feedback from past changes in the long-term accumulation rates of northern peatlands. Total carbon accumulated over the last 1000 yr is linearly related to contemporary growing season length and photosynthetically active radiation, suggesting that variability in net primary productivity is more important than decomposition in determining long-term carbon accumulation. Furthermore, northern peatland carbon sequestration rate declines over the climate transition from the Medieval Climate Anomaly (MCA) to the Little Ice Age (LIA), probably because of lower LIA temperatures combined with increased cloudiness suppressing net primary productivity. Other factors including changing moisture status, peatland distribution, fire, nitrogen deposition, permafrost thaw and methane emissions will also influence future peatland carbon cycle feedbacks, but our data suggest that the carbon sequestration rate could increase over many areas of northern peatlands.

scholarly journals A process-based <i>Sphagnum</i> plant-functional-type model for implementation in the TRIFFID Dynamic Global Vegetation Model

2019 ◽  
Author(s):  
Richard Coppell ◽  
Emanuel Gloor ◽  
Joseph Holden
Keyword(s):  
Water Table ◽  
Primary Productivity ◽  
Photosynthetically Active Radiation ◽  
Land Surface ◽  
Net Primary Productivity ◽  
Type Model ◽  
Surface Model ◽  
Dynamic Global Vegetation Model ◽  
Active Radiation ◽  
Global Vegetation

Abstract. Peatlands are important carbon stores and Sphagnum moss represents a critical peatland genus contributing to carbon exchange and storage. However, gas fluxes in Sphagnum-dominated systems are poorly represented in Dynamic Global Vegetation Models (DGVMs) which simulate, via incorporation of Plant Functional Types (PFTs), biogeochemical and energy fluxes between vegetation, the land surface and the atmosphere. Mechanisms characterised by PFTs within DGVMs include photosynthesis, respiration and competition and, in more recent DGVMs, sub-daily gas-exchange processes regulated by leaf 10 stomata. However, Sphagnum, like all mosses, are non-vascular plants and do not exhibit stomatal regulation. In order to achieve a level of process detail consistent with existing vascular vegetation PFTs within DGVMs, this paper describes a new process-based non-vascular-PFT model that is implemented within the TRIFFID DGVM used by the JULES land surface model. The new PFT model was tested against extant published field and laboratory studies of peat assemblage-net primary productivity, assemblage-gross primary productivity, assemblage respiration, water-table position, incoming 15 photosynthetically active radiation, temperature, and canopy dark respiration. The PFT model’s parameters were roughly tuned and the PFT model easily produced curves of the correct shape for peat assemblage-net primary productivity against water-table position, incoming photosynthetically active radiation and temperature, suggesting that it replicates the internal productivity mechanism of Sphagnum for the first time. Minor modifications should also allow it to be used across a range of other bryophytes enabling this non-vascular PFT model to have enhanced functionality.

Long-Term Trends in Forest Net Primary Productivity: Cascade Mountains, Washington

Ecology ◽  
1989 ◽  
Vol 70 (2) ◽  
pp. 405-410 ◽  
Author(s):  
Lisa J. Graumlich ◽  
Linda B. Brubaker ◽  
Charles C. Grier
Keyword(s):  
Primary Productivity ◽  
Net Primary Productivity ◽  
Cascade Mountains ◽  
Long Term Trends

Soil processes dominate the long-term response of forest net primary productivity to increased temperature and atmospheric CO2 concentration

2000 ◽  
Vol 30 (6) ◽  
pp. 873-888 ◽  
Author(s):  
Belinda E Medlyn ◽  
Ross E McMurtrie ◽  
Roderick C Dewar ◽  
Mark P Jeffreys
Keyword(s):  
Time Scales ◽  
Primary Productivity ◽  
Net Primary Productivity ◽  
N Uptake ◽  
Forest Growth ◽  
Equilibrium Analysis ◽  
Soil Processes ◽  
Growth Responses ◽  
Term Response

Predicting the responses of forest growth to elevated temperature (T) and atmospheric CO2 concentration ([CO2]) on decadal time scales presents a formidable challenge because of the many interacting processes involved. A key uncertainty concerns the relative importance of plant and soil processes to the overall long-term response. In this study, the plant-soil model G'DAY was used to simulate forest growth responses to T and [CO2] on different time scales for forests in cool and warm climates. An equilibrium-based graphical analysis was used to distinguish the roles played by plant and soil processes in determining the response. Doubled [CO2] caused a large initial increase (~20%) in net primary productivity (NPP), but this did not persist in the long term. By contrast, a 2°C increase in T caused a persistent long-term increase in NPP of approximately 10-15%. These responses were similar at cool and warm sites. The equilibrium analysis indicated that soil processes dominated the long-term responses predicted by the model. In particular, the predicted long-term increase in NPP under elevated T reflected an increase in predicted N mineralization and plant N uptake, assuming that a constant fraction of mineralized N is taken up by plants. The analysis highlights key uncertainties for future research.

scholarly journals Pastoralism in the highest peaks: Role of the traditional grazing systems in maintaining biodiversity and ecosystem function in the alpine Himalaya

PLoS ONE ◽  
2021 ◽  
Vol 16 (1) ◽  
pp. e0245221
Author(s):  
Tenzing Ingty
Keyword(s):  
Species Richness ◽  
Plant Species ◽  
Ecosystem Function ◽  
Primary Productivity ◽  
Net Primary Productivity ◽  
Diversity Index ◽  
Shannon Index ◽  
Pastoral System ◽  
Evenness Index ◽  
Biodiversity And Ecosystem Function

Rangelands cover around half of the planet’s land mass and provide vital ecosystem services to over a quarter of humanity. The Himalayan rangelands, part of a global biodiversity hotspot is among the most threatened regions in the world. In rangelands of many developing nations policies banning grazing in protected areas is common practice. In 1998, the Indian state of Sikkim, in the Eastern Himalaya, enacted a grazing ban in response to growing anthropogenic pressure in pastures and forests that was presumably leading to degradation of biodiversity. Studies from the region demonstrate the grazing ban has had some beneficial results in the form of increased carbon stocks and regeneration of some species of conservation value but the ban also resulted in negative outcomes such as reduced household incomes, increase in monocultures in lowlands, decreased manure production in a state that exclusively practices organic farming, spread of gregarious species, and a perceived increase in human wildlife conflict. This paper explores the impact of the traditional pastoral system on high elevation plant species in Lachen valley, one of the few regions of Sikkim where the grazing ban was not implemented. Experimental plots were laid in along an elevation gradient in grazed and ungrazed areas. Ungrazed areas are part of pastures that have been fenced off (preventing grazing) for over a decade and used by the locals for hay formation. I quantified plant species diversity (Species richness, Shannon index, Simpson diversity index, and Pielou evenness index) and ecosystem function (above ground net primary productivity ANPP). The difference method using movable exlosure cages was used in grazing areas to account for plant ANPP eaten and regrowth between grazing periods). The results demonstrate that grazing significantly contributes to greater plant species diversity (Species richness, Shannon index, Simpson diversity index, and Pielou evenness index) and ecosystem function (using above ground net primary productivity as an indicator). The multidimensional scaling and ANOSIM (Analysis of Similarities) pointed to significant differences in plant species assemblages in grazed and ungrazed areas. Further, ecosystem function is controlled by grazing, rainfall and elevation. Thus, the traditional transhumant pastoral system may enhance biodiversity and ecosystem function. I argue that a complete restriction of open grazing meet neither conservation nor socioeconomic goals. Evidence based policies are required to conserve the rich and vulnerable biodiversity of the region.

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