scholarly journals Carbon dioxide flux and net primary production of a boreal treed bog: Responses to warming and water-table-lowering simulations of climate change

2015 ◽  
Vol 12 (4) ◽  
pp. 1091-1111 ◽  
Author(s):  
T. M. Munir ◽  
M. Perkins ◽  
E. Kaing ◽  
M. Strack
Keyword(s):  
Climate Change ◽  
Carbon Dioxide ◽  
Primary Production ◽  
Water Level ◽  
Water Table ◽  
Forest Floor ◽  
Net Primary Production ◽  
Control Site ◽  
Co2 Uptake ◽  
Experimental Site

Abstract. Midlatitude treed bogs represent significant carbon (C) stocks and are highly sensitive to global climate change. In a dry continental treed bog, we compared three sites: control, recent (1–3 years; experimental) and older drained (10–13 years), with water levels at 38, 74 and 120 cm below the surface, respectively. At each site we measured carbon dioxide (CO2) fluxes and estimated tree root respiration (Rr; across hummock–hollow microtopography of the forest floor) and net primary production (NPP) of trees during the growing seasons (May to October) of 2011–2013. The CO2–C balance was calculated by adding the net CO2 exchange of the forest floor (NEff-Rr) to the NPP of the trees. From cooler and wetter 2011 to the driest and the warmest 2013, the control site was a CO2–C sink of 92, 70 and 76 g m−2, the experimental site was a CO2–C source of 14, 57 and 135 g m−2, and the drained site was a progressively smaller source of 26, 23 and 13 g CO2–C m−2. The short-term drainage at the experimental site resulted in small changes in vegetation coverage and large net CO2 emissions at the microforms. In contrast, the longer-term drainage and deeper water level at the drained site resulted in the replacement of mosses with vascular plants (shrubs) on the hummocks and lichen in the hollows leading to the highest CO2 uptake at the drained hummocks and significant losses in the hollows. The tree NPP (including above- and below-ground growth and litter fall) in 2011 and 2012 was significantly higher at the drained site (92 and 83 g C m−2) than at the experimental (58 and 55 g C m−2) and control (52 and 46 g C m−2) sites. We also quantified the impact of climatic warming at all water table treatments by equipping additional plots with open-top chambers (OTCs) that caused a passive warming on average of ~ 1 °C and differential air warming of ~ 6 °C at midday full sun over the study years. Warming significantly enhanced shrub growth and the CO2 sink function of the drained hummocks (exceeding the cumulative respiration losses in hollows induced by the lowered water level × warming). There was an interaction of water level with warming across hummocks that resulted in the largest net CO2 uptake at the warmed drained hummocks. Thus in 2013, the warming treatment enhanced the sink function of the control site by 13 g m−2, reduced the source function of the experimental by 10 g m−2 and significantly enhanced the sink function of the drained site by 73 g m−2. Therefore, drying and warming in continental bogs is expected to initially accelerate CO2–C losses via ecosystem respiration, but persistent drought and warming is expected to restore the peatland's original CO2–C sink function as a result of the shifts in vegetation composition and productivity between the microforms and increased NPP of trees over time.

scholarly journals Carbon dioxide flux and net primary production of a boreal treed bog: responses to warming and water table manipulations

2014 ◽  
Vol 11 (9) ◽  
pp. 12937-12983 ◽  
Author(s):  
T. M. Munir ◽  
M. Perkins ◽  
E. Kaing ◽  
M. Strack
Keyword(s):  
Carbon Dioxide ◽  
Primary Production ◽  
Water Level ◽  
Water Table ◽  
Forest Floor ◽  
Net Primary Production ◽  
Carbon Dioxide Flux ◽  
Water Levels ◽  
Co2 Uptake ◽  
Experimental Site

Abstract. Mid-latitude treed bogs are significant carbon (C) stocks and are highly sensitive to global climate change. In a dry continental treed bog, we compared three sites; control, recent (1–3 years; experimental) and older drained (10–13 years; drained) with water levels at 38, 74 and 120 cm below the surface, respectively. At each site we measured carbon dioxide (CO2) fluxes and tree root respiration (Rr) (across hummock-hollow microtopography of the forest floor) and net primary production (NPP) of trees during the growing seasons (May to October) of 2011–2013. The carbon (C) balance was calculated by adding net CO2 exchange of the forest floor (NEff–Rr) to the NPP of the trees. From cooler and wetter 2011 to driest and warmest 2013, The control site was a~C sink of 92, 70 and 76 g m−2, experimental site was a C source of 14, 57 and 135 g m−2, and drained site was a progressively smaller source of 26, 23 and 13 g m−2, respectively. Although all microforms at the experimental site had large net CO2 emissions, the longer-term drainage and deeper water level at the drained site resulted in the replacement of mosses with vascular plants (shrubs) at the hummocks and lichens at the hollows leading to the highest CO2 uptake at drained hummocks and significant losses at hollows. The tree NPP was highest at the drained site. We also quantified the impact of climatic warming at all water table treatments by equipping additional plots with open-top chambers (OTCs) that caused a passive warming on average of ∼1 °C and differential air warming of ∼6 °C (at mid-day full sun) across the study years. Warming significantly enhanced the shrub growth and CO2 sink function of the drained hummocks (exceeding the cumulative respiration losses at hollows induced by the lowered water level × warming). There was an interaction of water level with warming across hummocks that resulted in largest net CO2 uptake at warmed drained hummocks. Thus in 2013, the warming treatment enhanced the sink function of control by 13 g m−2, reduced the source function of experimental by 10 g m−2, and significantly enhanced the sink function of the drained site by 73 g m−2. Therefore, drying and warming in continental bogs is expected to initially accelerate C losses via respiration but persistent drought and warming is expected to restore the peatland's original C sink function as a result of transitional shift of vegetation between the microforms and increased NPP of trees over time.

scholarly journals Short-term Effects of Grazing Exclusion on Net Ecosystem CO2 Exchange and Net Primary Production in a Pannonian Sandy Grassland

2012 ◽  
Vol 40 (2) ◽  
pp. 67 ◽  
Author(s):  
Szilard CZOBEL ◽  
Orsolya SZIRMAI ◽  
Zoltan NEMETH ◽  
Csaba GYURICZA ◽  
Judit GAZI ◽  
...  
Keyword(s):  
Carbon Sequestration ◽  
Primary Production ◽  
Net Primary Production ◽  
Plant Productivity ◽  
Co2 Exchange ◽  
Co2 Uptake ◽  
Aboveground Phytomass ◽  
Grazing Exclusion ◽  
Sequestration Potential ◽  
Sandy Grassland

Using portable, non-destructive own developed chambers (d=60 cm) and infrared gas analyses, the in situ field investigation was performed to study the seasonal and inter-annual dynamics of the stand level CO2-flux and production of sandy grassland that has been extensively grazed for decades. Furthermore, NEE measurements and biomass samples were used to identify the initial effects of grazing exclusion on CO2 exchange, aboveground phytomass and potential plant productivity in years of significantly different precipitation levels. A considerable inter-annual variation in all of the studied parameters was found both in the non-grazed and grazed stands. As a result of the grazing exclusion the CO2 uptake potential of the non-grazed stand increased by 13% compared to the grazed stand. It was more significant in the extreme dry year (220%), however, in wet year slightly lower average carbon sequestration was detected at the non-grazed stand (-13%), than that of the grazed area. Significant carbon sequestration potential was only detected during wet periods in both stands. The rate of CO2 uptake was found to be nearly six times higher in the non-grazed stand in the wet year than in the previous extremely dry year. The drought in 2003 significantly reduced the CO2 uptake of both stands, leading to lower annual net primary production and potential plant productivity. The annual net primary production dropped by almost 40% in the extremely dry year but then it rose by nearly two and a half times in the subsequent year with adequate rainfall.

scholarly journals Desertification in Forest, Range and Desert Landuses of Tehran Province, Under the Impact of Climate Change

2016 ◽  
Author(s):  
Hadi Eskandari Dameneh ◽  
Moslem Borji ◽  
Hassan Khosravi ◽  
Ali Salajeghe
Keyword(s):  
Climate Change ◽  
Primary Production ◽  
Net Primary Production ◽  
Degradation Process ◽  
Early Warning Systems ◽  
Land Uses ◽  
Emission Scenarios ◽  
Desert Ecosystems ◽  
Tehran Province ◽  
The Impact

Abstract. Persistence of widespread degradation in arid and semi-arid region of Iran necessitates using of monitoring and evaluation systems with appropriate accuracy to determine the degradation process and adoption of early warning systems; because after transition from some thresholds, effective reversible function of ecosystems will not be very easy. This paper tries to monitor the degradation and desertification trends in three land uses including range, forest and desert lands affected by climate change in Tehran province for 2000s and 2030s. For assessing climate changes of Mehrabad synoptic stations the data of two emission scenarios including A2 and B2 were used using statistical downscaling techniques and data generated by SDSM model. The index of net primary production resulting from MODIS satellite images was employed as an indicator of destruction from 2001 to 2010. The results showed that temperature is the most effective driver force which alters the net primary production in rangeland, forest and desert ecosystems of Tehran province. On the basis of monitoring findings under real conditions, in the 2000s, over 60 % of rangelands and 80 % of the forests have been below the average production in the province. On the other hand, the long-term average changes of NPP in rangeland and forests indicated the presence of relatively large areas of these land uses with production rate lower than the desert. The results also showed that, assuming the existence of circumstances of each emission scenarios, the desertification status will not improve significantly in the rangelands and forests of Tehran province.

scholarly journals Responses of carbon dioxide flux and plant biomass to water table drawdown in a treed peatland in northern Alberta: a climate change perspective

2014 ◽  
Vol 11 (3) ◽  
pp. 807-820 ◽  
Author(s):  
T. M. Munir ◽  
B. Xu ◽  
M. Perkins ◽  
M. Strack
Keyword(s):  
Climate Change ◽  
Water Table ◽  
Plant Biomass ◽  
Carbon Dioxide Flux ◽  
Control Site ◽  
Change Scenario ◽  
Vegetation Growth ◽  
Growing Seasons ◽  
C Stocks ◽  
Incremental Growth

Abstract. Northern peatland ecosystems represent large carbon (C) stocks that are susceptible to changes such as accelerated mineralization due to water table lowering expected under a climate change scenario. During the growing seasons (1 May to 31 October) of 2011 and 2012 we monitored CO2 fluxes and plant biomass along a microtopographic gradient (hummocks-hollows) in an undisturbed dry continental boreal treed bog (control) and a nearby site that was drained (drained) in 2001. Ten years of drainage in the bog significantly increased coverage of shrubs at hummocks and lichens at hollows. Considering measured hummock coverage and including tree incremental growth, we estimate that the control site was a sink of −92 in 2011 and −70 g C m−2 in 2012, while the drained site was a source of 27 and 23 g C m−2 over the same years. We infer that, drainage-induced changes in vegetation growth led to increased biomass to counteract a portion of soil carbon losses. These results suggest that spatial variability (microtopography) and changes in vegetation community in boreal peatlands will affect how these ecosystems respond to lowered water table potentially induced by climate change.

Impact of climate change on net primary production (NPP) in south Iran

2020 ◽  
Vol 192 (6) ◽  
Author(s):  
Zahra Azhdari ◽  
Elham Rafeie Sardooi ◽  
Ommolbanin Bazrafshan ◽  
Hossein Zamani ◽  
Vijay P. Singh ◽  
...  
Keyword(s):  
Climate Change ◽  
Primary Production ◽  
Net Primary Production ◽  
Impact Of Climate Change

scholarly journals Holocene wildfire regimes in forested peatlands in western Siberia: interaction between peatland moisture conditions and the composition of plant functional types

2021 ◽  
Author(s):  
Angelica Feurdean ◽  
Andrei-Cosmin Diaconu ◽  
Mirjam Pfeiffer ◽  
Mariusz Gałka ◽  
Simon M. Hutchinson ◽  
...  
Keyword(s):  
Climate Change ◽  
Water Level ◽  
Water Table ◽  
Western Siberia ◽  
Fire Regime ◽  
Tree Cover ◽  
Pinus Sibirica ◽  
Vegetation Composition ◽  
Forest Density ◽  
Peatland Hydrology

Abstract. Wildfire is the most common disturbance type in boreal forests and can trigger significant changes in forest composition. Waterlogging in peatlands determines the degree of tree cover and the depth of the burning horizon associated with wildfires. However, interactions between peatland moisture, vegetation composition and flammability, and fire regime in forested peatland in Eurasia remain largely unexplored, despite their huge extent in boreal regions. To address this knowledge gap, we reconstructed the Holocene fire regime, vegetation composition, and peatland hydrology at two sites in Western Siberia near Tomsk Oblast, Russia. The palaeoecological records originate from forested peatland areas in predominantly light taiga (Pinus-Betula) with the increase in dark taiga communities (Pinus sibirica, Picea obovata, Abies sibirica) towards the east. We found that the past water level fluctuated between 8 and 30 cm below the peat surface. Wet peatland conditions promoted broadleaf trees (Betula), whereas dry peatland conditions favoured conifers and a greater forest density (dark-to-light-taiga ratio). The frequency and severity of fire increased with a declining water table that enhanced fuel dryness and flammability and at an intermediate forest density. We found that the probability of intensification in fire severity increased when the water level declined below 20 cm suggesting a tipping point in peatland hydrology at which wildfire regime intensifies. On a Holocene scale, we found two scenarios of moisture-vegetation-fire interactions. In the first, severe fires were recorded between 7.5 and 4.5 ka BP with lower water levels and an increased proportion of dark taiga and fire avoiders (Pinus sibirica at Rybanya and Abies sibirica at Ulukh Chayakh) mixed into the dominantly light taiga and fire-resister community of Pinus sylvestris. The second occurred over the last 1.5 ka and was associated with fluctuating water tables, a declining abundance of fire avoiders, and an expansion of fire invaders (Betula). These findings suggest that frequent high-severity fires can lead to compositional and structural changes in forests when trees fail to reach reproductive maturity between fire events or where extensive forest gaps limit seed dispersal. This study also shows prolonged periods of synchronous fire activity across the sites, particularly during the early to mid-Holocene, suggesting a regional imprint of centennial to millennial-scale Holocene climate variability on wildfire activity. Increasing human presence in the region of the Ulukh-Chayakh Mire near Teguldet over the last four centuries drastically enhanced ignitions compared to natural background levels. Frequent warm and dry spells predicted for the future in Siberia by climate change scenarios will enhance peatland drying and may convey a competitive advantage to conifer taxa. However, dry conditions, particularly a water table decline below the threshold of 20 cm, will probably exacerbate the frequency and severity of wildfire, disrupt conifers’ successional pathway and accelerate shifts towards more fire-adapted broadleaf tree cover. Furthermore, climate-disturbance-fire feedbacks will accelerate changes in the carbon balance of forested boreal peatlands and affect their overall future resilience to climate change.

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