Lateral detrital C transfer across a Spartina alterniflora invaded estuarine wetland

Background The lateral movements of mass and energy across the terrestrial-aquatic interface are being increasingly recognized for their importance in the carbon (C) balance of coastal/estuarine wetlands. We quantified the lateral flux of detrital C in the Yangtze estuary where invasive Spartina alterniflora has substantially and extensively altered the ecosystem structure and functions. Our overall objective was to close the C budget of estuarine wetlands through field sampling, tower-based measurements, and modeling. Methods A lateral detrital C exchange evaluation platform was established in a case study of the Yangtze River Estuary to investigate the effect of ecosystem structural changes on lateral detrital C transfer processes. This study estimated the lateral detrital C exchange based on the gross primary production (GPP) by performing coupled modeling and field sampling. Tower-based measurements and MODIS time series and CH4 outgassing and biomass simultaneously measured the lateral detrital C flux to characterize the relative contributions of lateral (i.e., detritus) C fluxes to the annual marsh C budget. Results The C pools in the plants and soil of Spartina marshes were significantly higher than those of the native community dominated by Phragmites australis. The GPP based on MODIS (GPPMODIS) was 472.6 g C m−2 year−1 and accounted for 73.0% of the GPP estimated from eddy covariance towers (GPPEC) (646.9 ± 70.7 g C m−2 year−1). We also detected a higher GPPMODIS during the pre-growing season, which exhibited a similar lateral detrital C flux magnitude. On average, 25.8% of the net primary production (NPP), which ranged from 0.21 to 0.30 kg C m−2 year−1, was exported during lateral exchange. The annual C loss as CH4 was estimated to be 17.9 ± 3.7 g C m−2 year−1, accounting for 2.8% of the GPPEC. The net positive detrital C flux (i.e., more detritus leaving the wetlands), which could exceed 0.16 kg C m−2 day−1, was related to daily tides. However, the observed lateral detrital C flux based on monthly sampling was 73.5% higher than that based on daily sampling (i.e., the sum of daily sampling), particularly in March and October. In addition, spatiotemporal granularities were responsible for most of the uncertainty in the lateral detrital C exchange. Conclusion This research demonstrated that an integrated framework incorporating modeling and field sampling can quantitatively assess lateral detrital C transport processes across the terrestrial-aquatic interface in estuarine wetlands. However, we note some limitations in the application of the light-use efficiency model to tidal wetlands. Spartina invasion can turn the lateral C balance from a C source (209.0 g C m−2 year−1) of Phragmites-dominated marshes into a small C sink (-31.0 g C m−2 year−1). Sampling over a more extended period and continuous measurements are essential for determining the contribution of different lateral detrital C flux processes to closing the ecosystem C budgets. The sampling spatiotemporal granularities can be key to assessing lateral detrital C transfer.

Melatonin Maintains Anabolic-Catabolic Equilibrium and Regulates Circadian Rhythm During Osteoarthritis Development in Animal Models: A Systematic Review and Meta-analysis

Background: The driving force behind osteoarthritis (OA) pathogenesis is an anabolic-catabolic (a/c) imbalance. Melatonin (MT) is a key player in maintaining a/c stability and mitigates OA pathogenesis, but mechanisms underlying its effects remain poorly understood.Objectives: We performed a systematic review analyzing the experimental data that support the clinical applicability of MT in the treatment of OA pathogenesis, placing particular emphasis on the regulation of circadian rhythms and a/c balance.Methods: Major electronic databases and grey literature were used to identify related original articles. Methodological quality of all selected studies was evaluated using the SYRCLE risk of bias tool. Pooled mean differences (MDs)/standardized mean differences (SMDs) with 95% confidence intervals (CIs) were calculated to estimate the effect size.Results: Eleven trials were included in this systematic review. Compared with the control group, MT significantly decreased the levels of interleukin-1β (IL-1β; SMD = −5.45; 95% CI [−6.78, −4.12]; p < 0.00001, and histological grading scale (SMD = −3.46; 95% CI, [−5.24, −1.68]; p < 0.0001). MT significantly increased the transforming growth factor-β1 (TGF-β1; SMD = 1.17; 95% CI [0.31, 2.03]; p < 0.0007). Furthermore, core circadian clock genes Per2 and Cry1 mRNA levels were regulated by MT treatment in OA progression.Conclusion: MT may maintain a/c balance and regulate circadian rhythms during OA development. MT could be used in as adjunct with other interventions to manage pain and OA severity.

The carbon budget of the managed grasslands of Great Britain constrained by earth observations

Grasslands cover around two thirds of the land area of Great Britain (GB) and are important reservoirs of terrestrial biological carbon (C). Outside a few well-monitored sites the quantification of C dynamics in managed grasslands is made complex by the spatio-temporal variability of weather conditions combined with grazing and cutting patterns. Earth observation (EO) missions produce high-resolution frequently-retrieved proxy data on the state of grassland canopies but synergies between EO data and biogeochemical modelling to estimate grassland C dynamics are under-explored. Here, we show the potential of model-data fusion (MDF) to provide robust near-real time analyses of managed grasslands of GB (England, Wales andScotland). We combine EO data and process-based modelling to estimate grassland C balance and to examine the role of management. We implement a MDF algorithm to (1) infer grassland management from vegetation reduction data (Proba-V), (2) optimise model parameters by assimilating leaf area index (LAI) data (Sentinel-2) and (3) simulate livestock grazing, grass cutting, and C allocation and loss to the atmosphere. The MDF algorithm was applied for 2017 and 2018 at 1855 fields sampled from across GB. The algorithm was able to effectively assimilate the Sentinel-2 based LAI time series (overlap = 80 %, RMSE = 1 gCm−2, bias = 0.35 gCm−2) and predict livestock densities per area that correspond with independent census-based data (r = 0.68). The mean total removed biomass across all simulated fields was 6 (±1.8) tDM ha−1 y−1. The simulated grassland ecosystems were on average C sinks in 2017 and 2018; the GB-average net ecosystem exchange (NEE) and net biome exchange (NBE) for 2017 was −232 ± 94 and for 2018 was −120 ± 103 gCm−2 y−1. The 2018 summer drought reduced C sinks, with a 9-fold increase in the number fields that were C sources (NBE > 0) in 2018 compared to 2017. We conclude that management in the form of sward condition and the timing, intensity and type of defoliation are key determinants of the C balance of managed grasslands. Nevertheless, extreme weather, such as prolonged droughts, can convert grassland C sinks to sources.

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

Wildfires 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.

Insights into the carbon dynamics of a wasted peatland under long term drainage and intensive agriculture.

<p>Lowland fen peatlands in East Anglia, United Kingdom (UK), have had a long history of drainage and agricultural use, with some having been drained for several centuries. This has led to the loss of up to 4.0 m of the original peat layer through initial consolidation and subsequent decomposition.</p><p>Today, the primary land use of these peatlands is intensive arable and horticultural agriculture, resulting in continued loss and degradation of the remaining peat layer. This has led to the classification of a large part of these peatlands as ‘wasted’ - i.e. the peat-forming vegetation has been lost along with a significant depth of peat and the underlying mineral layer increasingly determining soil properties.</p><p>Despite a significant fraction of the UK lowland peatlands being classified as wasted (1922 km<sup>2</sup> or 13.5%), there have been no previous studies of the carbon (C) emissions from these peatlands. Studies on non-wasted ‘deep’ agricultural peatlands (peat depths > 1m) suggest emission factors of 5.2 to 8.3 t CO<sub>2</sub>-C ha<sup>-1</sup> yr<sup>-1</sup> indicating the potential for wasted peatlands, despite having a lower soil organic C content, to still generate large emissions representing a significant component of the UK’s national greenhouse gas inventory.</p><p>Using Eddy Covariance, the CO<sub>2</sub> emissions of two co-located fen peatlands within East Anglia under similar intensive agriculture were quantified throughout 2018-2020.  The first site, EN-SP3, is a wasted fen peatland where the surface organic layer has been depleted to <40cm. The second site, EF-DA, is a deep peat with an organic soil layer >1m deep. We present initial analysis of C emissions data from EN-SP3, which represent the first emission estimates from a wasted agricultural fen peatland in the UK, in comparison with data collected from EF-DA, the co-located deep peat agricultural fen peatland, over the last ~6 years.</p><p>Preliminary analysis of the first full year of emissions data from the wasted peat site (EN-SP3) indicates an approximate net C balance of  5.4 t C ha<sup>-1 </sup>yr<sup>-1 </sup>(17<sup>th</sup> May 19 – 17<sup>th</sup> May 20, Celery crop following a Phacelia & Buckwheat cover crop), whilst there was a higher estimated rate of emission during the previous year under a maize crop (222 days; 4<sup>th</sup> May 18 – 11<sup>th</sup> Dec 18) indicating a net C balance of 4.7 t C ha<sup>-1</sup> over the 222 day period. These data compare with 7.8 - 11.2 t C ha<sup>-1 </sup>yr<sup>-1 </sup>from between 2012-2019 from the deep peat site (EF-DA). We highlight key differences between sites, enabling us to draw early insights into how C dynamics may differ between shallow and deep lowland agricultural peat soils.</p>

LATEST CARBON BALANCE SURVEYS AND MONITORING AT THE KURSK BIOSPHERE STATION OF THE INSTITUTE OF GEOGRAPHY, RAS, IN THE FRAMEWORK OF THE NOVEL CONCEPT OF LAND DEGRADATION NEUTRALITY

The paper focuses on the applicability and adaptation of the novel international concept of Land Degradation Neutrality (LDN) of the United Nations, as applied to the territory of Russian Federation, taking into account the large variety of its soil and climatic conditions and economic approaches, as well as the historical past. In particular, in this publication, a team of authors made an attempt to assess to what extent the estimates of the carbon balance and its main components for the study area can be used as one of the indicators of the LDN in relation to the most fertile chernozem agrolandscapes in the south of the European part of Russia (Kursk region). Field work and modelling have been carried out in natural ecosystems and agrolandscapes in the neighbourhood of the Kursk Biosphere Station (KBS) of the Institute of Geography, Russian Academy of Sciences. This valuable russian scientific research station has a long and rich history of geo(eco)system observations with LDN and net C-balance monitoring of age-old agrolandscapes, becoming one of its present focuses. Using simulation models DNDC, RothC, T&P, C-calculators, as well as long-term field measurements of soil CO2 efflux and carbon net exchange, it was found that individual software tools are not able to adequately assess carbon exchange processes of the complex landscape, but correctly selected ensembles consisting of C-balance simulations and C-calculators supported by field data are able to meet such challenges more successfully. On this condition the area's carbon net balance can serve as an alternative to the recommended global LDN indicators.

Fire as carbon sink? The global biome-dependent wildfire carbon balance

Wildfires generally result in biospheric recovery approximating the pre-disturbance state. However legacy carbon(C) gains and losses that have until now been overlooked in global-scale theory and modelling indicate that post-fire C gains through pyrogenic carbon (PyC) production, and losses via fire regime shifts, post-fire mortality, topsoil loss and inland water export, may be central to whether 20th century fires have imposed a net terrestrial C source or sink. Here, we integrate PyC production and soil accumulation into a global terrestrial model (ORCHIDEE-MICT) and estimate wildfire C-gains and losses over 1901-2010, quantifying the fire-C balance at global, regional and vegetation scales. Excluding the effect of PyC mineralisation, fires provide a land storage of +177 TgC yr-1 (63% PyC production), dominated by grasslands. The global balance is nuanced, with forest fires resulting in strong terrestrial net C loss:gain ratios (>-2:1) that are greatest in tropical regions (>-3:1). Frequent tropical grassland fires are responsible for the bulk of the land PyC sink and its environmental persistence, whose theoretical minimum mean residence time we quantify at 2760yrs. We highlight the dependency of the global fire-C balance on vegetation coverage and the potential role of preserving grasslands, particularly those in the tropics, in that regard.

Lagged effects regulate the inter-annual variability of the tropical carbon balance

Inter-annual variations in the tropical land carbon (C) balance are a dominant component of the global atmospheric CO2 growth rate. Currently, the lack of quantitative knowledge on processes controlling net tropical ecosystem C balance on inter-annual timescales inhibits accurate understanding and projections of land–atmosphere C exchanges. In particular, uncertainty on the relative contribution of ecosystem C fluxes attributable to concurrent forcing anomalies (concurrent effects) and those attributable to the continuing influence of past phenomena (lagged effects) stifles efforts to explicitly understand the integrated sensitivity of a tropical ecosystem to climatic variability. Here we present a conceptual framework – applicable in principle to any land biosphere model – to explicitly quantify net biospheric exchange (NBE) as the sum of anomaly-induced concurrent changes and climatology-induced lagged changes to terrestrial ecosystem C states (NBE = NBECON+NBELAG). We apply this framework to an observation-constrained analysis of the 2001–2015 tropical C balance: we use a data–model integration approach (CARbon DAta-MOdel fraMework – CARDAMOM) to merge satellite-retrieved land-surface C observations (leaf area, biomass, solar-induced fluorescence), soil C inventory data and satellite-based atmospheric inversion estimates of CO2 and CO fluxes to produce a data-constrained analysis of the 2001–2015 tropical C cycle. We find that the inter-annual variability of both concurrent and lagged effects substantially contributes to the 2001–2015 NBE inter-annual variability throughout 2001–2015 across the tropics (NBECON IAV = 80 % of total NBE IAV, r = 0.76; NBELAG IAV = 64 % of NBE IAV, r = 0.61), and the prominence of NBELAG IAV persists across both wet and dry tropical ecosystems. The magnitude of lagged effect variations on NBE across the tropics is largely attributable to lagged effects on net primary productivity (NPP; NPPLAG IAV 113 % of NBELAG IAV, r = −0.93, p value < 0.05), which emerge due to the dependence of NPP on inter-annual variations in foliar C and plant-available H2O states. We conclude that concurrent and lagged effects need to be explicitly and jointly resolved to retrieve an accurate understanding of the processes regulating the present-day and future trajectory of the terrestrial land C sink.

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

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.