scholarly journals North American boreal forests are a large carbon source due to wildfires from 1986 to 2016

2020 ◽  
Author(s):  
Bailu Zhao ◽  
Qianlai Zhuang ◽  
Narasinha Shurpali ◽  
Kajar Köster ◽  
Frank Berninger ◽  
...  
Keyword(s):  
Net Primary Production ◽  
Net Ecosystem Production ◽  
Ecosystem Dynamics ◽  
Fire Disturbance ◽  
Burn Severity ◽  
Fire Emissions ◽  
Terrestrial Ecosystem Model ◽  
C Balance ◽  
Ecosystem Production ◽  
The Impact

Abstract Wildfires are a major disturbance to forest carbon (C) balance through both immediate combustion emissions and post-fire ecosystem dynamics. Here we use a process-based biogeochemistry model, the Terrestrial Ecosystem Model (TEM), to simulate C budget in Alaska and Canada during 1986-2016, as impacted by fire disturbances. We extracted the data of difference Normalized Burn Ratio (dNBR) for fires from Landsat TM/ETM imagery and estimated the proportion of vegetation and soil C combustion. We observed that the region is a C source of 2.74 Pg C during the 31-year period. The observed C loss, 57.1 Tg C yr-1, was attributed to fire emissions, overwhelming the net ecosystem production (1.9 Tg C yr-1) in the region. Our simulated during-fire emissions for Alaska and Canada are within the range of field measurements and other model estimates. As burn severity increases, combustion emission tended to switch from vegetation origin towards soil origin. Burn severity regulates post-fire C dynamics. Low severity fires increase soil temperature and decrease soil moisture and thus, enhance soil respiration. However, the opposite trend was found under moderate or high burn severity. The proportion of post-fire soil emission in total emissions increased with burn severity. Net nitrogen mineralization gradually recovered after fire, enhancing net primary production. Net ecosystem production recovered fast under higher burn severities. The impact of fire disturbance on the C balance of northern ecosystems and the associated uncertainties can be better characterized with long-term, prior, during- and post-disturbance data across the geospatial spectrum. Our findings suggest that the regional source of carbon to the atmosphere will persist if the observed forest wildfire occurrence and severity continues into the future.

scholarly journals North American Boreal Forests Are a Large Carbon Source Due to Wildfires From 1986 to 2016

2020 ◽  
Author(s):  
Bailu Zhao ◽  
Qianlai Zhuang ◽  
Narasinha Shurpali ◽  
Kajar Köster ◽  
Frank Berninger ◽  
...  
Keyword(s):  
Net Primary Production ◽  
Net Ecosystem Production ◽  
Ecosystem Dynamics ◽  
Fire Disturbance ◽  
Burn Severity ◽  
Fire Emissions ◽  
Terrestrial Ecosystem Model ◽  
C Balance ◽  
Ecosystem Production ◽  
The Impact

Abstract Wildfires are a major disturbance to forest carbon (C) balance through both immediate combustion emissions and post-fire ecosystem dynamics. Here we use a process-based biogeochemistry model, the Terrestrial Ecosystem Model (TEM), to simulate C budget in Alaska and Canada during 1986-2016, as impacted by fire disturbances. We extracted the data of difference Normalized Burn Ratio (dNBR) for fires from Landsat TM/ETM imagery and estimated the proportion of vegetation and soil C combustion. We observed that the region is a C source of 2.74 Pg C during the 31-year period. The observed C loss, 57.1 Tg C yr-1, was attributed to fire emissions, overwhelming the net ecosystem production (1.9 Tg C yr-1) in the region. Our simulated during-fire emissions for Alaska and Canada are within the range of field measurements and other model estimates. As burn severity increases, combustion emission tended to switch from vegetation origin towards soil origin. When dNBR is below 300, fires increase soil temperature and decrease soil moisture and thus, enhance soil respiration. However, the opposite trend was found under moderate or high burn severity. The proportion of post-fire soil emission in total emissions increased with burn severity. Net nitrogen mineralization gradually recovered after fire, enhancing net primary production. Net ecosystem production recovered fast under higher burn severities. The impact of fire disturbance on the C balance of northern ecosystems and the associated uncertainties can be better characterized with long-term, prior, during- and post-disturbance data across the geospatial spectrum. Our findings suggest that the regional source of carbon to the atmosphere will persist if the observed forest wildfire occurrence and severity continues into the future.

scholarly journals North American boreal forests are a large carbon source due to wildfires from 1986 to 2016

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Bailu Zhao ◽  
Qianlai Zhuang ◽  
Narasinha Shurpali ◽  
Kajar Köster ◽  
Frank Berninger ◽  
...  
Keyword(s):  
Soil Respiration ◽  
Net Primary Production ◽  
Net Ecosystem Production ◽  
Ecosystem Dynamics ◽  
Burn Severity ◽  
Fire Emissions ◽  
Terrestrial Ecosystem Model ◽  
C Balance ◽  
Ecosystem Production ◽  
The Impact

AbstractWildfires are a major disturbance to forest carbon (C) balance through both immediate combustion emissions and post-fire ecosystem dynamics. Here we used a process-based biogeochemistry model, the Terrestrial Ecosystem Model (TEM), to simulate C budget in Alaska and Canada during 1986–2016, as impacted by fire disturbances. We extracted the data of difference Normalized Burn Ratio (dNBR) for fires from Landsat TM/ETM imagery and estimated the proportion of vegetation and soil C combustion. We observed that the region was a C source of 2.74 Pg C during the 31-year period. The observed C loss, 57.1 Tg C year−1, was attributed to fire emissions, overwhelming the net ecosystem production (1.9 Tg C year−1) in the region. Our simulated direct emissions for Alaska and Canada are within the range of field measurements and other model estimates. As burn severity increased, combustion emission tended to switch from vegetation origin towards soil origin. When dNBR is below 300, fires increase soil temperature and decrease soil moisture and thus, enhance soil respiration. However, the post-fire soil respiration decreases for moderate or high burn severity. The proportion of post-fire soil emission in total emissions increased with burn severity. Net nitrogen mineralization gradually recovered after fire, enhancing net primary production. Net ecosystem production recovered fast under higher burn severities. The impact of fire disturbance on the C balance of northern ecosystems and the associated uncertainties can be better characterized with long-term, prior-, during- and post-disturbance data across the geospatial spectrum. Our findings suggest that the regional source of carbon to the atmosphere will persist if the observed forest wildfire occurrence and severity continues into the future.

scholarly journals Precipitation legacy effects on dryland ecosystem carbon fluxes: direction, magnitude and biogeochemical carryovers

2016 ◽  
Vol 13 (2) ◽  
pp. 425-439 ◽  
Author(s):  
W. Shen ◽  
G. D. Jenerette ◽  
D. Hui ◽  
R. L. Scott
Keyword(s):  
Plant Biomass ◽  
Net Primary Production ◽  
Ecosystem Respiration ◽  
Ecosystem Dynamics ◽  
Legacy Effects ◽  
Previous Period ◽  
Legacy Effect ◽  
Ecosystem Production ◽  
Legacy Impacts ◽  
The Impact

Abstract. The precipitation legacy effect, defined as the impact of historical precipitation (PPT) on extant ecosystem dynamics, has been recognized as an important driver in shaping the temporal variability of dryland aboveground net primary production (ANPP) and soil respiration. How the PPT legacy influences whole ecosystem-level carbon (C) fluxes has rarely been quantitatively assessed, particularly at longer temporal scales. We parameterized a process-based ecosystem model to a semiarid savanna ecosystem in the southwestern USA, calibrated and evaluated the model performance based on 7 years of eddy-covariance measurements, and conducted two sets of simulation experiments to assess interdecadal and interannual PPT legacy effects over a 30-year simulation period. The results showed that decreasing the previous period/year PPT (dry legacy) always increased subsequent net ecosystem production (NEP) whereas increasing the previous period/year PPT (wet legacy) decreased NEP. The simulated dry-legacy impacts mostly increased subsequent gross ecosystem production (GEP) and reduced ecosystem respiration (Re), but the wet legacy mostly reduced GEP and increased Re. Although the direction and magnitude of GEP and Re responses to the simulated dry and wet legacies were influenced by both the previous and current PPT conditions, the NEP responses were predominantly determined by the previous PPT characteristics including rainfall amount, seasonality and event size distribution. Larger PPT difference between periods/years resulted in larger legacy impacts, with dry legacies fostering more C sequestration and wet legacies more C release. The carryover of soil N between periods/years was mainly responsible for the GEP responses, while the carryovers of plant biomass, litter and soil organic matter were mainly responsible for the Re responses. These simulation results suggest that previous PPT conditions can exert substantial legacy impacts on current ecosystem C balance, which should be taken into account while assessing the response of dryland ecosystem C dynamics to future PPT regime changes.

Decade of permafrost thaw in a subarctic palsa mire alters carbon fluxes without affecting net carbon balance

2020 ◽  
Author(s):  
Carolina Olid ◽  
Jonatan Klaminder ◽  
Sylvain Monteux ◽  
Margareta Johansson ◽  
Ellen Dorrepaal
Keyword(s):  
Global Climate ◽  
Net Ecosystem Production ◽  
Climate System ◽  
Winter Warming ◽  
Permafrost Thaw ◽  
C Storage ◽  
C Balance ◽  
Ecosystem Production

<p>Snow depth increases observed in some artic regions and its insulations effects have led to a winter-warming of permafrost-containing peatlands. Permafrost thaw and the temperature-dependent decomposition of previously frozen carbon (C) is currently considered as one of the most important feedbacks between the artic and the global climate system. However, the magnitude of this feedback remains uncertain because winter effects are rarely integrated and predicted from mechanisms active in both surface (young) and thawing deep (old) peat layers.</p><p>Laboratory incubation studies of permafrost soils, in situ carbon flux measurements in ecosystem-scale permafrost thaw experiments, or measurements made across naturally degrading permafrost gradients have been used to improve our knowledge about the net effects of winter-warming in permafrost C storage. The results from these studies, however, are biased by imprecision in long-term (decadal to millennial) effects due to the short time scale of the experiments. Gradient studies may show longer-term responses but suffer from uncertainties because measurements are usually taken during the summer, thus ignoring the long cold season. The need for robust estimates of the long-term effect of permafrost thaw on the net C balance, which integrates year-round C fluxes sets the basis of this study.</p><p>Here, we quantified the effects of long-term in situ permafrost thaw in the net C balance of a permafrost-containing peatland subjected to a 10-years snow manipulation experiment. In short, we used a peat age modelling approach to quantify the effect of winter-warming on net ecosystem production as well as on the underlying changes in surface C inputs and losses along the whole peat continuum. Contrary to our hypothesis, winter-warming did not affect the net ecosystem production regardless of the increased old C losses. This minimum overall effect is due to the strong reduction on the young C losses from the upper active layer associated to the new water saturated conditions and the decline in bryophytes. Our findings highlight the need to incorporate long-term year-round responses in C fluxes when estimating the net effect of winter-warming on permafrost C storage. We also demonstrate that thaw-induced changes in moisture conditions and plant communities are key factors to predicting future climate change feedbacks between the artic soil C pool and the global climate system.</p>

scholarly journals Land Cover and Land Use Change Decreases Net Ecosystem Production in Tropical Peatlands of West Kalimantan, Indonesia

Forests ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1587
Author(s):  
Imam Basuki ◽  
J. Boone Kauffman ◽  
James T. Peterson ◽  
Gusti Z. Anshari ◽  
Daniel Murdiyarso
Keyword(s):  
Land Use ◽  
Land Use Change ◽  
Soil Respiration ◽  
Primary Production ◽  
Oil Palm ◽  
Net Primary Production ◽  
Net Ecosystem Production ◽  
Carbon Sinks ◽  
Peat Swamp ◽  
Ecosystem Production

Deforested and converted tropical peat swamp forests are susceptible to fires and are a major source of greenhouse gas (GHG) emissions. However, information on the influence of land-use change (LUC) on the carbon dynamics in these disturbed peat forests is limited. This study aimed to quantify soil respiration (heterotrophic and autotrophic), net primary production (NPP), and net ecosystem production (NEP) in peat swamp forests, partially logged forests, early seral grasslands (deforested peat), and smallholder-oil palm estates (converted peat). Peat swamp forests (PSF) showed similar soil respiration with logged forests (LPSF) and oil palm (OP) estates (37.7 Mg CO2 ha−1 yr−1, 40.7 Mg CO2 ha−1 yr−1, and 38.7 Mg CO2 ha−1 yr−1, respectively), but higher than early seral (ES) grassland sites (30.7 Mg CO2 ha−1 yr−1). NPP of intact peat forests (13.2 Mg C ha−1 yr−1) was significantly greater than LPSF (11.1 Mg C ha−1 yr−1), ES (10.8 Mg C ha−1 yr−1), and OP (3.7 Mg C ha−1 yr−1). Peat swamp forests and seral grasslands were net carbon sinks (10.8 Mg CO2 ha−1 yr−1 and 9.1 CO2 ha−1 yr−1, respectively). In contrast, logged forests and oil palm estates were net carbon sources; they had negative mean Net Ecosystem Production (NEP) values (−0.1 Mg CO2 ha−1 yr−1 and −25.1 Mg CO2 ha−1 yr−1, respectively). The shift from carbon sinks to sources associated with land-use change was principally due to a decreased Net Primary Production (NPP) rather than increased soil respiration. Conservation of the remaining peat swamp forests and rehabilitation of deforested peatlands are crucial in GHG emission reduction programs.

scholarly journals The Influence of Ozone on Net Ecosystem Production of a Ryegrass–Clover Mixture under Field Conditions

Atmosphere ◽  
2021 ◽  
Vol 12 (12) ◽  
pp. 1629
Author(s):  
Thomas Agyei ◽  
Stanislav Juráň ◽  
Magda Edwards-Jonášová ◽  
Milan Fischer ◽  
Marian Švik ◽  
...  
Keyword(s):  
Trifolium Pratense ◽  
Arable Land ◽  
Growing Season ◽  
Net Ecosystem Production ◽  
Terrestrial Vegetation ◽  
The Czech Republic ◽  
Linear Mixed Effects ◽  
Ecosystem Production ◽  
Summer Maximum ◽  
The Impact

In order to understand the effect of phytotoxic tropospheric ozone (O3) on terrestrial vegetation, we quantified the impact of current O3 concentration ([O3]) on net ecosystem production (NEP) when compared to the conditions of the pre-industrial era. We compared and tested linear mixed-effects models based on [O3] and stomatal O3 flux (Fsto). The managed ryegrass–clover (Lolium perenne and Trifolium pratense) mixture was grown on arable land in the Czech Republic, Central Europe. Values of [O3] and Fsto were measured and calculated based on resistance analogy, respectively, while NEP was calculated from eddy covariance CO2 fluxes. We found the Fsto-based model more precise when compared to measured NEP. High Fsto was found even at low [O3], while broad summer maximum of [O3] was not necessarily followed by significant NEP decline, due to low soil water content leading to a low stomatal conductivity and Fsto. Comparing to low pre-industrial O3 conditions, current levels of O3 resulted in the reduction of cumulative NEP over the entire growing season, up to 29.7 and 13.5% when the [O3]-based and Fsto-based model was applied, respectively. During the growing season, an O3-induced reduction of NEP ranged between 13.1% in May and 26.2% in July when compared to pre-industrial Fsto levels. Looking to the future, high [O3] and Fsto may lead to the reduction of current NEP by approximately 13.3% on average during the growing season, but may increase by up to 61–86.6% in autumn, indicating further O3-induced acceleration of the senescence. These findings indicate the importance of Fsto and its inclusion into the models estimating O3 effects on terrestrial vegetation. The interaction between environmental factors and stomatal conductance is therefore discussed in detail.

Temporal changes of forest net primary production and net ecosystem production in west central Canada associated with natural and anthropogenic disturbances

2003 ◽  
Vol 33 (12) ◽  
pp. 2340-2351 ◽  
Author(s):  
Zhong Li ◽  
Michael J Apps ◽  
Werner A Kurz ◽  
Ed Banfield
Keyword(s):  
Primary Production ◽  
Net Primary Production ◽  
Anthropogenic Disturbances ◽  
Temporal Variations ◽  
Net Ecosystem Production ◽  
Forest Sector ◽  
Natural Disturbances ◽  
Carbon Budget Model ◽  
West Central ◽  
Ecosystem Production

Temporal variations of net primary production (NPP) and net ecosystem production (NEP) in west central Canadian forests over the period of 1920–1995 and their responses to natural and anthropogenic disturbances were simulated using the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS2). The results show that forest NPP in the region was 215 g C·year–1·m–2 in 1920, varied between 105 and 317 g·C year–1·m–2 depending on ecoclimatic province, but gradually increased to 330 (158 to 395) g C·year–1·m–2 in the early 1980s before declining to 290 (148 to 395) g C·year–1·m–2 by 1995. Forest NEP was estimated to be 53 (–13 to 88) g C·year–1·m–2 in 1920–1924, increased to 75 (5 to 98) g C·year–1·m–2 in 1960, and then declined to 26 (–14 to 53) g C·year–1·m–2 in 1991–1995. Natural disturbances played a greater role than harvest in determining the temporal pattern of forest NPP and NEP during the period because of the larger area affected by natural disturbances. This study also indicated that ignoring disturbances would lead to an overestimation of forest NPP and NEP in ecosystem modeling.

scholarly journals Scaling net ecosystem production and net biome production over a heterogeneous region in the western United States

2007 ◽  
Vol 4 (2) ◽  
pp. 1093-1135 ◽  
Author(s):  
D. P. Turner ◽  
W. D. Ritts ◽  
B. E. Law ◽  
W. B. Cohen ◽  
Z. Yang ◽  
...  
Keyword(s):  
United States ◽  
Remote Sensing ◽  
Interannual Variation ◽  
Carbon Stocks ◽  
Net Ecosystem Production ◽  
The State ◽  
Western United States ◽  
Fire Emissions ◽  
Ecosystem Production ◽  
Heterogeneous Region

Abstract. Bottom-up scaling of net ecosystem production (NEP) and net biome production (NBP) was used to generate a carbon budget for a large heterogeneous region (the state of Oregon, 2.5×105 km2) in the western United States. Landsat resolution (30 m) remote sensing provided the basis for mapping land cover and disturbance history, thus allowing us to account for all major fire and logging events over the last 30 years. For NEP, a 23-year record (1980–2002) of distributed meteorology (1 km resolution) at the daily time step was used to drive a process-based carbon cycle model (Biome-BGC). For NBP, fire emissions were computed from remote sensing based estimates of area burned and our mapped biomass estimates. Our estimates for the contribution of logging and crop harvest removals to NBP were from the model simulations and were checked against public records of forest and crop harvesting. The predominately forested ecoregions within our study region had the highest NEP sinks, with ecoregion averages up to 197 gC m−2 yr−1. Agricultural ecoregions were also NEP sinks, reflecting the imbalance of NPP and decomposition of crop residues. For the period 1996–2000, mean NEP for the study area was 17.0 TgC yr−1, with strong interannual variation (SD of 10.6). The sum of forest harvest removals, crop removals, and direct fire emissions amounted to 63% of NEP, leaving a mean NBP of 6.1 TgC yr−1. Carbon sequestration was predominantly on public forestland, where the harvest rate has fallen dramatically in the recent years. Comparison of simulation results with estimates of carbon stocks, and changes in carbon stocks, based on forest inventory data showed generally good agreement. The carbon sequestered as NBP, plus accumulation of forest products in slow turnover pools, offset 51% of the annual emissions of fossil fuel CO2 for the state. State-level NBP dropped below zero in 2002 because of the combination of a dry climate year and a large (200 000 ha) fire. These results highlight the strong influence of land management and interannual variation in climate on the terrestrial carbon flux in the temperate zone.

scholarly journals Precipitation legacy effects on dryland ecosystem carbon fluxes: direction, magnitude and biogeochemical carryovers

2015 ◽  
Vol 12 (13) ◽  
pp. 9613-9650 ◽  
Author(s):  
W. Shen ◽  
G. D. Jenerette ◽  
D. Hui ◽  
R. L. Scott
Keyword(s):  
Plant Biomass ◽  
Ecosystem Respiration ◽  
Model Performance ◽  
Ecosystem Dynamics ◽  
Legacy Effects ◽  
Previous Period ◽  
Legacy Effect ◽  
Ecosystem Production ◽  
Legacy Impacts ◽  
The Impact

Abstract. The precipitation legacy effect, defined as the impact of historical precipitation (PPT) on extant ecosystem dynamics, has been recognized as an important driver in shaping the temporal variability of dryland aboveground primary production (ANPP) and soil respiration. How the PPT legacy influences whole ecosystem-level carbon (C) fluxes has rarely been quantitatively assessed, particularly at longer temporal scales. We parameterized a process-based ecosystem model to a semiarid savanna ecosystem in southwestern US, calibrated and evaluated the model performance based on 7 years of eddy covariance measurements, and conducted two sets of simulation experiments to assess interdecadal and interannual scale PPT legacy effects over a 30 year simulation period. The results showed that decreasing the previous period/year PPT (dry legacy) always imposed positive impacts on net ecosystem production (NEP) whereas increasing the previous period/year PPT (wet legacy) had negative impacts on NEP. The simulated dry legacy impacts were mostly positive on gross ecosystem production (GEP) and negative on ecosystem respiration (Re) but the wet legacy impacts were mostly negative on GEP and positive on Re. Although the direction and magnitude of GEP and Re responses to the simulated dry and wet legacies were influenced by both the previous and current PPT conditions, the NEP responses were predominantly determined by the previous PPT characteristics including rainfall amount, seasonality and event size distribution. Larger PPT difference between periods/years resulted in larger legacy impacts, with dry legacies fostering more C sequestration and wet legacies more C release. By analyzing the resource pool (C, N, and H2O) responses to the simulated dry and wet legacies, we found that the carryover of soil N between periods/years was mainly responsible for the GEP responses while the carryovers of plant biomass, litter and soil organic matter were mainly responsible for the Re responses. These simulation results suggest that previous PPT conditions can exert substantial legacy impacts on current ecosystem C balance, which should be taken into account while assessing the response of dryland ecosystem C dynamics to future PPT regime changes.

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