Carbon Sink Function Research Articles

Influence of Terrain on MODIS and GLASS Leaf Area Index (LAI) Products in Qinling Mountains Forests

Leaf Area Index (LAI), as a pivotal parameter in characterizing the structural properties of vegetation ecosystems, holds significant importance in assessing the carbon sink function. Given the availability of multiple long-term LAI products, validating these LAI products with consideration of topographic factors is a prerequisite for enhancing the quality of LAI products in mountainous areas. Therefore, this study aims to evaluate the performance of MODIS LAI and GLASS LAI products from 2001 to 2021 by comparing and validating them with ground-measured LAI data, focusing on the spatio-temporal and topographic aspects in the Qinling Mountains. The results show that the GLASS LAI product is a better choice for estimating LAI in the Qinling Mountains. The GLASS LAI product has better completeness and generally higher values compared to the MODIS LAI product. The time-series curve of the GLASS LAI product is more continuous and smoother than the MODIS LAI product. Both products, however, face challenges in quantifying LAI values of evergreen vegetation during winter. The MODIS and GLASS LAI products exhibit differences between sunny and shady slopes, with mean LAI values peaking on sunny slopes and reaching their lowest on shady slopes. When the slope ranges from 0 to 10°, the mean values of GLASS LAI product show a higher increasing trend compared to the MODIS LAI product. At elevations between 1450 and 2450 m, the mean LAI values of the GLASS LAI product are higher than the MODIS LAI product, primarily in the southern Qinling Mountains. Compared to ground-measured LAI data, the GLASS LAI product (R² = 0.33, RMSE = 1.62, MAE = 0.61) shows a stronger correlation and higher accuracy than the MODIS LAI product (R² = 0.24, RMSE = 1.61, MAE = 0.68).

Reducing CO2 emissions from rivers around bare land contributes to improving the carbon sink function of the Qinghai–Tibetan Plateau

River CO2 fluxes (FCO2) play an important role in the carbon cycle of the Qinghai‒Tibet Plateau (QTP). However, the carbon budget of river water is ignored in the assessment of the carbon sources and sinks of ecosystems on the QTP, which makes the assessment of the carbon sinks of ecosystems uncertain on the QTP. Here, we selected rivers around alpine steppe, alpine meadow, forestland and bare land areas on the QTP to determine their FCO2 values and control factors during thaw, rainy and freezing periods. The results revealed that river water around the alpine steppe absorbed CO2 during the thaw and freezing periods, making it a carbon sink. The influencing factors of FCO2 around different ecosystems significantly differed across the different periods. The pCO2 was the most direct factor affecting the FCO2 of river water. During the thaw period, the FCO2 of rivers around the alpine steppe and bare land was affected mainly by dissolved organic carbon (DOC) and precipitation, respectively. The FCO2 of rivers around the alpine meadow and forestland was affected by dissolved inorganic carbon (DIC). During the rainy period, the FCO2 of the rivers around the alpine steppe and bare land was affected mainly by total nitrogen (TN) and salinity, respectively. The FCO2 of rivers around the alpine meadow and forestland was affected by dissolved oxygen (DO) and DOC. During the freezing period, the FCO2 of the rivers around the alpine steppe and bare land was affected mainly by TN and pCO2, respectively. The FCO2 of rivers around the forestland and alpine meadow was affected by precipitation, runoff and DIC. The FCO2 in rivers around vegetated areas were affected by rock weathering, aquatic ecosystem biology and hydrological processes to varying degrees at different times. However, rivers around bare ground were less affected by these processes. The FCO2 values around the alpine steppe, alpine meadow, forestland and bare land were 1.40 g C/m2/d, 1.12 g C/m2/d, 2.29 g C/m2/d and 4.20 g C/m2/d, respectively. The river water around bare land released a large amount of CO2. Therefore, to reduce the CO2 emissions of rivers on the QTP, it is urgent that we restore bare-land vegetation and promote the transfer of bare land to steppe, which is an effective way to increase the carbon sink of the ecosystems on the QTP.

Current status and research prospects of terrestrial ecosystem carbon sink in Northeast China.

Increasing the carbon sink capacity of terrestrial ecosystems is a primary strategy to mitigate climate change and achieve the "carbon neutrality" goal. Clarifying the status and future dynamics of carbon sink of terrestrial ecosystems in Northeast China is crucial for achieving "carbon neutrality" as this region is a core contributor to carbon sink in China's terrestrial ecosystems. Here, we systematically summarized current research on carbon sink of terrestrial ecosystems across Northeast China, including the measurements and spatial-temporal patterns of carbon sinks, driving mechanisms of carbon sinks, the assessments of carbon sink potential, and technologies for increasing carbon sequestration. There are substantial uncertainties in quantifying terrestrial ecosystem carbon sink in Northeast China due to differences in data sources and methods, especially for forest carbon sink measurements, ranging from 0.020 to 0.157 Pg C·a-1. Carbon sink function depends on carbon exchange processes across plant-soil-atmosphere interfaces. The key pathways to enhance carbon sequestration in Northeast China under different temporal and spatial scales remains unclear. Improving terrestrial ecosystem quality is the key and core of carbon sequestration and sink enhancement. However, there is an urgent need to develop a multi-ecosystem collaborative carbon sequestration and sink enhancement technology system for the "dual carbon" goal. Future research needs to develop an accurate carbon sink measurement system that integrates multi-source data and multi-scale technologies to accurately assess the function and potential of carbon sink in Northeast China, focus on the multi-scale driving mechanism of carbon sink functions, develop new technical systems for coordinated enhancement of carbon sink for the Northeast terrestrial ecosystems, and carry out demonstrations of carbon sink enhancement technologies. These efforts will provide the scientific and technological supports for achieving the "carbon neutrality" goal.

From case study to general principle: An analysis of the development mechanism and policy optimization of mangrove carbon sinks

Mangroves, as a crucial coastal ecosystem, possess significant carbon sink functions and play a key role in mitigating global climate change. This paper, based on the Zhanjiang Mangrove Afforestation Project in Guangdong, explores the development mechanisms and economic and ecological benefits of mangrove carbon sink projects through the lens of collective action theory and system dynamics modeling. The study finds that the primary reason for the unsustainable progression of mangrove carbon sink projects is the lack of intrinsic motivation among local villagers to engage in collective action. By constructing a system dynamics model, this paper quantifies the long-term impacts of mangrove carbon sink projects on local socio-economic welfare and proposes policy optimization recommendations. These recommendations include expanding income sources for local villagers, establishing carbon trading and ecological compensation mechanisms, and involving international non-governmental organizations. The findings of this study not only provide guidance for mangrove carbon sink projects in China but also offer valuable insights for the promotion of similar projects globally.

Carbon stocks in mangrove ecosystems of Sri Lanka: Average contributions and determinants of sequestration potential

Mangroves are crucial in carbon sequestration despite covering only a small percentage of the Earth's surface. Latitudinal gradient primarily determines the distribution of climatic zones of distinct sunlight, temperature, and precipitation patterns, which influence the community structure of the mangrove ecosystem. The tropical climate of Sri Lanka contributes to the island's lush mangrove forests. The present study estimated that the average island's carbon sequestration capacity of Sri Lankan mangrove ecosystems is 524.25 t/ha representing a substantial volume of carbon storage that contributes to offset greenhouse effect due to increasing atmospheric CO2. Our results substantiated that rainfall positively influences total carbon sequestration capacity of mangrove ecosystems.It was also revealed that a positive relationship exists between vegetation structural complexity and sediment organic carbon, highlighting the influence of vegetation structure, that is primarily dependent on climatic conditions, on production of organic matter and sediment carbon sequestration. Globally, the carbon sink function of mangrove ecosystems is reported to be highest in the tropical areas and it declines towards sub-tropical higher latitudes while those in the southern hemisphere perform better carbon sinks than those in the northern hemisphere.The vertical distribution of total organic matter content in mangrove sediments was revealed to be in a descending order, manifesting the weak tidal removal of surface organic matter under the microtidal conditions in Sri Lankan marine waters, thus qualifying mangrove ecosystems in microtidal coasts as effective carbon sinks.

Multi-scale geographically weighted regression estimation of carbon storage on coniferous forests considering residual distribution using remote sensing data

The Above-Ground Carbon (AGC) is an important indicator reflecting the carbon sink function of forest ecosystems. The area of coniferous forests in China accounts for about 50 % of the national forest area. Accurately estimating the AGC of coniferous forests plays an important role in evaluating forest carbon sink function. This study takes coniferous forests in Chun’an, Zhejiang Province as an example, using Landsat 8 OLI as the remote sensing data source, and innovatively proposes a multi-scale Geographically Weighted Regression model (MGWR) combined with Co-Kriging (COK), namely MGWR-COK and Ordinary Kriging (OK), namely MGWR-OK, for AGC estimation. This method first processes Landsat8 OLI remote sensing data, extracts and screens variables, and then constructs an MGWR model with AGC survey samples to estimate AGC and calculate residuals; Afterwards, two models, COK and OK, were used to spatially estimate the residuals; Finally, the AGC estimation results are overlaid with the residual estimation results to obtain the spatial distribution of AGC in coniferous forests. The study indicates that: (1) The selected remote sensing feature variables such as Optimized Soil-Adjusted Vegetation Index (OSAVI), Normalized Difference Vegetation Index (NDVI), Entropy (B3_ent_1 and B2_ent_2), Correlation (B4_corr and B5_corr_2) of texture information, B754 with band combination and elevation have a significant impact on AGC estimation. (2) The AGC accuracy R2 estimated by MGWR-OK and MGWR-COK are 0.837 and 0.857, respectively, which are 6 % and 8 % higher than the MGWR model, and the root mean square error is also reduced by 10 % and 12 %, respectively. This indicates that the combination of MGWR and Kriging interpolation can effectively reduce its spatial estimation error. (3) The range of AGC values estimated by the MGWR-COK model is 0.189–62.591 Mg ∙ hm−2, with a mean of 28.795 Mg ∙ hm−2. The spatial distribution shows a characteristic of high in the southeast and low in the northwest, which is consistent with the actual situation in the study area.

Widespread crab burrows enhance greenhouse gas emissions from coastal blue carbon ecosystems

Fiddler crabs, as coastal ecosystem engineers, play a crucial role in enhancing biodiversity and accelerating the flow of material and energy. Here we show how widespread crab burrows modify the carbon sequestration capacity of different habitats across a large climatic gradient. The process of crab burrowing results in the reallocation of sediment organic carbon and humus. Crab burrows can increase more greenhouse gases emissions compared to the sediment matrix (CO2: by 17–30%; CH4: by 49–141%). Straightforward calculations indicate that these increased emissions could offset 35–134% of sediment carbon burial in these two ecosystems. This research highlights the complex interactions between crab burrows, habitat type, and climate which reveal a potential lower carbon sink function of blue carbon ecosystems than previously expected without considering crab burrows.

Spatial–Temporal Evolution and Influencing Factors of Arable Land Green and Low-Carbon Utilization in the Yangtze River Delta from the Perspective of Carbon Neutrality

Arable land green and low-carbon utilization (ALGLU) is an important pathway to safeguard food safety and achieve the green transformation and progress of agriculture, playing a crucial role in promoting agricultural ecological protection and economic sustainability. This study takes the Yangtze River Delta region (YRD), where rapid urbanization is most typical, as the study area. On the basis of fully considering the carbon sink function of arable land, the study measures the green and low-carbon utilization level of arable land in the region using the Super-slack and based measure (Super-SBM) model, and analyzes its spatial and temporal evolution using the spatial autocorrelation model, the center of gravity, and the standard ellipsoid model, and then analyzes its impact with the help of the geographic detector and the geographically weighted regression model. We analyzed the multifactor interaction and spatial heterogeneity of the factors with the help of the geodetector and geographically weighted regression model. Results: (1) The ALGLU in the YRD has shown a fluctuating upward tendency, increasing from 0.7307 in 2012 to 0.8604 in 2022, with a growth rate of 17.75%. The phased changes correspond to national agricultural development policies and the stages of socio-economic development. (2) There are significant spatial differences in the level of ALGLU in the YRD, with high levels distributed in the southwest of Jiangsu, northern Zhejiang, and northwest Anhui, while low levels are distributed in the southwest of the YRD. Positive spatial autocorrelation exists in the level of ALGLU in the YRD. The spatial transfer trends of the gravity and standard deviation ellipses essentially align with changes in the spatial pattern. (3) The level of ALGLU in the YRD is affected by many factors, with the intensity of interaction effects far exceeding that of individual factors. When considering single-factor effects, precipitation, topography, and farmers’ income levels are important factors influencing the level of ALGLU. In scenarios involving multiple-factor interactions, agricultural policies become the primary focus of interaction effects. Furthermore, the driving effects of influencing factors exhibit spatial heterogeneity, with significant differences in the direction and extent of driving effects of each factor in different cities. This study can provide valuable insights for future ALGLU in the YRD and regional sustainable development.

Temporal patterns of carbon-water coupling of a subalpine peatland in subtropics: Insights from a seven-year eddy covariance monitoring

Study regionA well-preserved subalpine peatland in the subtropics, the Dajiuhu peatland, in Shennongjia, Hubei Province, China. Study focusOver a seven-year period, constant in-situ carbon flux monitoring was conducted using the eddy covariance method. The patterns of CO2 and H2O fluxes were analyzed, encompassing both daytime and nocturnal period observations, spanning both growing and non-growing seasons, and the interconnection between carbon and water within the Dajiuhu peatland. Furthermore, this investigation identified meteorological parameters shaping these flux dynamics. New hydrological insights for the regionThe water source function was more resilient to the effects of extreme weather events and showed higher stability when compared to the carbon sink function. Daytime carbon-water coupling presented a pronounced negative correlation during the growing season, contrasting with a more complex trinomial relationship evident during the non-growing season; however, nocturnal periods did not reveal any apparent correlation. Relative humidity (RH), water table depth (WTD), and evapotranspiration (ET) emerged as key variables impacting jointly on both CO2 and H2O fluxes. Furthermore, net radiation (Rn) magnifies the hysteresis loops associated with net ecosystem exchanges of CO2 (NEE) during the growing season, with WTD being the prime determinant influencing seasonal fluctuations in hysteresis related to H2O fluxes. These findings exemplify the complexities inherent in the management of carbon and water resources within subalpine peatlands, underscored by their intricately intertwined and inseparable relationship.

A deep learning approach for high‐resolution mapping of Scottish peatland degradation

AbstractPeat makes up approximately a quarter of Scotland's soil by area. Healthy, undisturbed, peatland habitats are critical to providing resilient biodiversity and habitat support, water management, and carbon sequestration. A high and stable water table is a prerequisite to maintain carbon sink function; any drainage turns this major terrestrial carbon store into a source that feeds back further to global climate change. Drainage and erosion features are crucial indicators of peatland condition and are key for estimating national greenhouse gas emissions. Previous work on mapping peat depth and condition in Scotland has provided maps with reasonable accuracy at 100‐m resolution, allowing land managers and policymakers to both plan and manage these soils and to work towards identifying priority peat sites for restoration. However, the spatial variability of the surface condition is much finer than this scale, limiting the ability to inventory greenhouse gas emissions or develop site‐specific restoration and management plans. This work involves an updated set of mapping using high‐resolution (25 cm) aerial imagery, which provides the ability to identify and segment individual drainage channels and erosion features. Combining this imagery with a classical deep learning‐based segmentation model enables high spatial resolution, national scale mapping to be carried out allowing for a deeper understanding of Scotland's peatland resource and which will enable various future analyses using these data.

Partitioned Simulation of Land Use Change Based on Carbon Neutrality Zoning and Its Multiscale Effect on Carbon Emissions in the Xia–Zhang–Quan Metropolitan Circle, China

Urbanization significantly affects the global carbon balance. Therefore, clarifying the effect of urbanization-induced land use change on carbon emissions and proposing the zonal-based policy implementation became crucial. In this study, we estimated the future land use carbon emissions in three scenarios by adopting the partitioned Patch-generating Land Use Simulation Model (PLUS) in the Xiamen–Zhangzhou–Quanzhou (XZQ) metropolitan circle, China. The results showed that (1) the region could be divided into two sub-areas (carbon sink function zone and high-carbon optimization zone); the partitioned PLUS model had a higher accuracy in the developed areas, whereas it had a lower accuracy in the undeveloped areas; (2) the main characteristic of land use change was the construction on the land that was previously farmland, spanning 260.2 km2; the land used for construction would continue to expand, with 215.5 km2 (8.2%), 261.0 km2 (9.9%), and 129.5 km2 (4.9%) in the natural development scenario (ND), economic development scenario (ED), and carbon neutrality scenario (CN), respectively; (3) the amount of carbon emissions would increase by 196.2 × 104 tons and 235.4 × 104 tons in the ND and ED, respectively, whereas, it would decrease by 49.0 × 104 tons in the CN. This study made a beneficial attempt at partitioning based on carbon neutrality by improving the PLUS model simulation results and carbon emission assessment, which could provide methods and references for future similar studies. The findings suggest a method for the coordinated development between the carbon sink function zone and the high-carbon optimization zone. In addition, comprehensively understanding the land use change and its effects on carbon emissions, from this study, could provide important insights into carbon neutrality and regional sustainable development for urban planners and policymakers. In future research, the zoning research could be conducted at a finer scale, since the partition results were relatively coarse in this study.

Topsoil dilution by subsoil admixture had less impact on soil organic carbon stock development than fertilizer form and erosion state

Enhancing the agroecosystems carbon (C) sink function for climate mitigation faced challenges, particularly with traditional measures with limited suitability for increasing soil organic carbon (SOC) stocks. Inducing a SOC undersaturation in the topsoil by abrupt subsoil admixture is a way to create an additional C sink. However, the deep tillage traditionally used for this topsoil dilution was not always successful. It was due to a lack of knowledge and suitable approaches to record the effect of all relevant factors in SOC recovery, including soil conditions and fertilizer forms.We addressed these problems by establishing a three-factorial experiment: I) “moderate topsoil dilution,” II) “N fertilization form,” and III) “soil erosion state,” representing three soil types in the hummocky ground moraine landscape of NE Germany. SOC dynamics were determined over a year of winter rye cropping using a novel robotic chamber system capable of measuring CO2 exchange on 36 experimental plots with a reduced methodological bias than previous measuring systems.The averaged net ecosystem carbon balance, a proxy for SOC stock change, indicated that topsoil dilution only reduced further SOC losses. The N fertilizer form had a significantly stronger and more differentiated effect. While the mineral N fertilization consistently produced only C sources, the organic fertilization, in combination with the diluted topsoil, led to a C sink. This C-sink function was, however, more pronounced in the eroded soil than in the non-eroded soil. Overall, the results have made clear that the impact of topsoil dilution on the further development of the SOC stock is only possible if the effect of other relevant factors, such as N fertilizer form and erosion state, are taken into account.

Biomass Allocation and Allometric Relationship of Salix gordejevii Branches in Sandy Habitats Heterogeneity in Northern China

The patterns of biomass allocation are crucial for understanding the growth, reproduction, and community functions of plant individuals. We investigated the allometric growth characteristics and biomass allocation patterns of Salix gordejevii fascicular branches in various habitats of the Hunshandake Sandy Land to delve into their adaptability to environmental changes and role in the carbon cycle. We discovered the following: (1) The base diameter-to-branch length of S. gordejevii fascicular branches exhibited allometric growth relationships in mobile dunes and interdune lowlands, whereas it showed isometric growth relationships in semifixed and fixed dunes. As the soil moisture gradient increased, the length growth rate of S. gordejevii fascicular branches became faster than the base diameter growth rate in mobile dunes, demonstrated isometric growth in semifixed and fixed dunes, and was slow in interdune lowlands. (2) The biomasses of S. gordejevii fascicular branches significantly varied across different habitats, with the biomass of each component showing an increasing trend as habitat conditions improved. This study revealed the resource utilization strategies and adaptability of S. gordejevii fascicular branches in different habitats, providing new insights into the carbon sink function of desert ecosystems in semiarid regions.

Optimizing restoration duration to maximize CO2 uptake on the Tibetan Plateau

Grasslands cover one-third of the terrestrial area, though half of them have been degraded and primarily due to overgrazing. The Tibetan Plateau (TP) is home to the largest area of alpine grassland on Earth, experiencing a typical degradation-restoration story over the past three decades. With the large-scale implementation and long-term duration of ecological projects aimed at restoring degraded grasslands by fencing across the TP, there is considerable uncertainty regarding the direction and magnitude of changes in the carbon (C) sink function. To address this, we combined ten pairs of systematic field observations at the site scale with literature compilation, aiming to clarify whether restoration still contributes to C uptake and its driving factors. Our results show that after a decade of restoration, living biomass was enhanced by over 80 %, and litter accumulation increased by 3.68 ± 1.25 times across all ecosystem types, although these changes were barely reflected in soil C. Litter caused consistent negative impacts on CO2 uptake across all vegetation types, despite restoration having increased CO2 uptake by half in alpine steppes and alpine meadows. This negative impact was more evident in alpine wetlands, where the quantity of litter was double the living biomass. The thick layer of litter produced a shading effect that further limited the photosynthetic yield of living plants, regulating the restoration-induced CO2 gain or loss. Combining 246 cases across the TP further highlights the need to shorten the duration of restoration to maximize CO2 uptake while also benefitting sustainability, which is deserving of attention from both the scientific community and policy-makers.

How will permafrost carbon respond to future climate change? A new assessment for future thaw trends of permafrost carbon on the Tibetan Plateau

Permafrost degradation on the Tibetan Plateau (TP) is anticipated to result in the thaw of permafrost carbon. Existing studies have been conducted to assess the future thaw of frozen carbon on the TP, primarily focusing on the deepening of the active layer while neglecting the impact of permafrost area shrinkage. This oversight may lead to a significant underestimation of the potential thaw of frozen carbon. Our research underscores the pivotal role of permafrost area shrinkage in estimating the future thaw of frozen carbon. Our findings reveal that when the combined effects of permafrost area shrinkage and active layer deepening are considered, the thaw rates of frozen carbon in various radiative forcing scenarios are nearly four times those based on active layer deepening alone. Notably, our results demonstrate substantial thaw of frozen organic carbon in the TP permafrost area under all four future scenarios: In the low radiative forcing scenario SSP1-2.6, it is predicted that 55.4 % of the organic carbon in the permafrost area 0–10 m soils will be in a state of thaw by 2100, and more than 90 % in the high radiative forcing scenario SSP5-8.5. This substantial thaw is poised to diminish the TP's current carbon sink function significantly. Our study emphasizes that as global warming persists, frozen carbon in permafrost areas will play a more active role in global carbon cycle processes in the future. Furthermore, we stress the importance of considering permafrost area shrinkage in understanding the thaw of frozen carbon, providing valuable insights for carbon balance studies on the TP.

Analysis of the spatial mismatch pattern of net carbon in agriculture and its influencing factors

Agricultural production has dual functions as a carbon emitter and sink, and fully exploiting the carbon sink function of agriculture is highly valuable for ensuring carbon neutrality. The layout of net carbon in agriculture shows an imbalance, i.e., underscaling in areas with a net carbon advantage or overscaling in areas with a net carbon disadvantage, which restricts the fulfillment of agricultural carbon sinks. Clarifying the global pattern of net carbon imbalances in agriculture and their drivers is highly important for improving the overall net carbon. In this regard, this paper focuses on the global net carbon in agriculture in 155 countries and regions, and a spatial mismatch index of net carbon in agriculture (MNCA) is constructed based on the relative difference between net carbon and cultivated land. Spatial autocorrelation analysis and the standard deviation ellipse are used to reflect its spatiotemporal evolution pattern. In addition, through geographically weighted regression, we explored the effects of agricultural structure, agricultural economic development, the scale of labor and cultivated land and organized the mismatches into carbon and area effects. The results show that (1) global agricultural production represents net carbon emissions, while developing countries represent net carbon sinks, and there is a mismatch of net agricultural carbon in most regions; (2) the MNCA is characterized by low-low clustering in North America, Asia and Europe, with its center of gravity falling in western Africa and migrating northeastward; and (3) the main factors influencing the MNCA are the agricultural structure and economic level. Underscaling in areas with a net carbon advantage is a major problem. To increase the global agricultural carbon sink capacity, we suggest that North America, South Asia and other regions strictly implement agricultural emission reduction policies and that Central America, South America and Africa tentatively upgrade agricultural technology and their economies to alleviate farmland pressure through transnational cooperation. In this paper, the global net carbon imbalance in agriculture is identified and the overall implementation path of increasing carbon sinks is explored to provide a reference for achieving carbon neutrality. SynopsisThis study reports a global mismatch in net carbon in agriculture and identifies the wasted carbon sink advantage of developing countries as the root problem.

Soil microbial functional diversity is primarily affected by soil nitrogen, salinity and alkalinity in wetland ecosystem

Wetland ecosystems, recognized as important carbon sinks, face challenges due to climate change. Although wetland soil microorganisms play a major role in the wetland carbon cycle, the mechanisms influencing their spatial distribution remain elusive. Here, we investigate the impact of soil properties on the spatial distribution of soil microorganisms across five saline-alkali wetlands (Xianghai [XH], Niuxintaobao [NX], Momoge [MMG], Zhalong [ZL], and Halahai [HLH]) within the Songnen Plain, China. We utilized the Biolog-ECO method to assess the carbon metabolic activity, microbial diversity, and carbon source utilization preference of soil microorganisms. Using the structural equation model, we analyzed factors influencing microbial carbon metabolic activity and microbial diversity. Results indicate that southern wetlands harbor soil microbial communities exhibiting higher carbon metabolic activity, Shannon index, and substrate richness, compared to their northern counterparts. Specifically, soil microorganisms in NX and XH wetlands demonstrate a preference for labile organic carbon, whereas those in HLH and ZL wetlands preferred to use recalcitrant carbon. Furthermore, soil microbial carbon metabolic activity is primarily regulated by soil total nitrogen content, whereas soil microbial diversity is primarily regulated by soil salinity and alkalinity. Our findings revealed the distribution characteristics and influencing factors of soil microorganisms in the Songnen Plain wetland, contributing to understanding the maintenance mechanism of wetland carbon sink function.

Effects of Enhanced UV-B Radiation on Decomposition and Nutrient Release Rates of Litter from Cunninghamia lanceolata (Lamb.) Hook

In order to explore the effects of enhanced UV-B radiation on the decomposition and nutrient cycling characteristics of Cunninghamia lanceolata (Lamb.) Hook litter, we collected material from C. lanceolata in a middle-aged forest (16 years) and over-mature forest (49 years). Four different UV-B radiation enhancement gradient treatments of CK, CK + 30 uw/cm2 (T1), CK + 45 uw/cm2 (T2), and CK + 60 uw/cm2 (T3), with natural light (CK) as the baseline, were conducted to determine the impact of UV-B radiation indoor simulation enhancement on the litter decomposition and nutrient release of C. lanceolata at various developmental stages. The results indicate that UV-B radiation increases the dry weight decomposition rate and the nutrient decomposition rate of C. lanceolata litter, and the decomposition rate of C. lanceolata litter in an over-mature forest is always greater than that in a middle-aged forest litter, with observable influences on its chemical composition. Such changes significantly alter the nutrient release pattern of N, P, and K in litter in middle-aged forests and N in litter from over-mature forests, and promote the release of C, which may affect the nutrient cycle and carbon sink function of C. lanceolata plantations.

Appropriateness Evaluation Study of Land Reclamation of Pre-drilling Project in Southwest China Under Dual-carbon Background

Cultivated land and forest land are important carbon sink systems in the context of dual-carbon, so it is necessary to do a suitability evaluation study of pre-drilling project land reclamation to support the restoration of carbon sink function of the temporarily occupied farmland. In this paper, the suitability evaluation model of pre-drilling engineering land reclamation was established by adopting hierarchical analysis method and TOPSIS multi-attribute decision-making method, and the suitability evaluation study of pre-drilling engineering land reclamation was carried out on a drilling platform in Southwest China.

Peatland evaporation across hemispheres: contrasting controls and sensitivity to climate warming driven by plant functional types

Abstract. Peatlands store disproportionally large amounts of carbon per unit area, a function that is dependent on maintaining high and stable water tables. Climate change is likely to negatively impact carbon storage in peatlands, in part due to increases in vapour pressure deficit (VPD) driving higher evaporation (E) rates. However, the response of E to increasing VPD depends on the dominant vegetation type within peatlands. In this study, we used multiple years of eddy covariance (EC) measurements to compare E regimes at two peatlands with contrasting vegetation types – Kopuatai bog in Aotearoa / New Zealand, dominated by the vascular wire rush Empodisma robustum, and Mer Bleue bog in Canada, a “typical” shrub- and moss-dominated Northern Hemisphere peatland. We examined seasonal variability in E and equilibrium E (Eeq), energy balance partitioning, and the response of E, evaporative fraction (EF), and canopy conductance (gc) to VPD. Mean annual E was 45 % lower than mean annual Eeq at Kopuatai but only 16 % lower at Mer Bleue, demonstrating much greater limitations on E at Kopuatai. In addition, the mean midday (10:00–14:30 local standard time) dry-canopy Bowen ratio (β) at Kopuatai was 2.0 compared to 0.8 at Mer Bleue; therefore, the sensible heat flux (H) dominated over the latent heat flux (LE) at Kopuatai and vice versa at Mer Bleue. The responses of E, EF, and gc to increasing VPD at Kopuatai demonstrated stronger limitations on evaporative water loss for VPD > 0.7 kPa compared to Mer Bleue. The observed limitations at Kopuatai were attributed to strong stomatal control by E. robustum due to the rapid decrease in gc with increasing VPD; however, surface E could also be limited by its dense standing litter. At Mer Bleue, however, E was only weakly limited at VPD > 2 kPa, likely due to weak stomatal control over transpiration by the sparse shrub canopy and relatively large surface E from Sphagnum carpets. As such, the results of this study suggest that E. robustum drives a greater “hydrological resistance” to increasing VPD than the vegetation at Mer Bleue, leading to greater water retention at Kopuatai. This may enable greater resilience of the carbon sink function at Kopuatai to climatic warming and drying than at Mer Bleue.