Dynamics Of Carbon Accumulation Research Articles

Development and carbon accumulation dynamics of a minerotrophic fen during the last millennium, northeast China

Peatlands are terrestrial ecosystems with high carbon sequestration efficiency, providing critical feedback on climate change. It is crucial to understand how peatland development and carbon accumulation respond to various factors to reveal the future direction of carbon reservoirs under changing climatic conditions. To assess the impact of climate and hydrological conditions on the development and carbon accumulation of peatlands, 15 peat core samples were analyzed to examine the processes of lateral expansion in the Dongfanghong (DFH) peatland, a minerotrophic fen located in the Changbai Mountains of northeast China. Accelerator Mass Spectrometry 14C, total organic carbon, dry bulk density, testate amoebae, δ13C of α-cellulose in Carex spp. and plant macrofossil analyses were conducted on a high-resolution peat core. The proxies were used to calculate carbon accumulation rate (CAR) and reconstruct water table depth as well as surface moisture and vegetation development of the DFH peatland. Our findings indicated that the DFH peatland was initiated at 1011 cal. CE and experienced paludification during the last millennium. The expansion of the DFH peatland was primarily determined by hydrological conditions rather than climatic factors such as total solar irradiance and regional temperature. The rapid expansion between 1500 and 1700 cal. CE was likely resulted from relatively low precipitation and a decrease in water table/surface moisture. CAR generally correlated with total solar irradiance, regional temperature, and precipitation, suggesting that climate may be crucial for CAR in DFH peatlands over multi-centennial timescales. However, the increased CAR under relatively dry conditions suggested that the CAR were regulated by hydrological conditions over a centennial timescale. This study highlighted the important roles of climate and hydrological conditions in the lateral expansion and CAR of the peatland in minerotrophic fen and that there may be a threshold for hydrology during the process of peatland development and carbon accumulation.

Early Dynamics of Carbon Accumulation as Influenced by Spacing of a Populus deltoides Planting

The fast-growing tree, eastern cottonwood (Populus deltoides), currently is being planted to catalyze native forest restoration on degraded agricultural sites in the southeastern United States. Many of these restoration sites are appropriate for short rotation woody crop (SRWC) culture that addresses climate mitigation objectives, but information needed to optimize climate mitigation objectives through such plantings is limited. Therefore, we established a 10-year experiment on degraded agricultural land located in the Mississippi Alluvial Valley, USA, aiming to quantify the dynamics of aboveground carbon (AGC) accumulation in a cottonwood planting of four replicated spacing levels (3.7 × 3.7 m, 2.7 × 1.8 m, 2.1 × 0.8 m, and (0.8 + 1.8) × 0.8 m) aligned with SRWC systems targeting various ecosystem services. Annual sampling revealed a substantial range in increments of AGC and year 10 carbon stocks among stands of different densities. Mean annual increments for AGC (MAIAGC) were similar for the two tightest spacing levels, peaking higher than for the other two spacings at about 7.5 Mg ha−1 y−1 in year 7. Year 10 AGC ranged between 22.3 Mg ha−1 for stands spaced 3.7 × 3.7 m and 70.1 Mg ha−1 for stands of the two tightest spacings, leading us to conclude that a spacing between 2.1 × 0.8 m and 2.7 × 1.8 m would maximize aboveground carbon stocks through year 10 on sites of similar agricultural degradation. Increments and accumulation of AGC on the degraded site trended lower than values reported from more productive sites but illustrate that quick and substantial transformation of the carbon stock status of degraded agricultural sites can be achieved with the application of SRWCs to restore forests for climate mitigation and other compatible ecosystem services.

OVERGROWN AGRICULTURAL LANDS AS A POTENTIAL FOR NATURAL DECARBONIZATION OF OIL AND GAS FIELDS

In the north-western part of the Republic of Bashkortostan there are a large number of oil and gas fields, which are located on abandoned agricultural lands. Taking into account the increased level of impact on forest phytocenoses of natural and artificial origin in this zone, it becomes necessary to study the volume of carbon uptake by woody vegetation. To fulfill this goal, the tasks of carrying out an inventory of overgrown agricultural lands, entering coordinates of the boundaries of oil and gas fields into geoinformation projects and applying the results of digitization of overgrown agricultural lands to the boundaries of oil and gas fields are set. The study covers 18 municipal districts: Askinsky, Bakalinsky, Baltachevsky, Belebeyevsky, Bizhbulyaksky, Blagoveshchensky, Buraevsky, Dyurtyulinsky, Ilishevsky, Kaltasinsky, Karaidelsky, Krasnokamsky, Kushnarenkovsky, Mishkinsky, Tatyshlinsky, Tuymazinsky. Sharansky, Yanaulsky. The Q-GIS program defines the areas of overgrown areas. According to satellite images, 4 stages of overgrowth have been identified: the fourth (the age of trees is 20 years or more), the third (the age of trees is about 15 years), the second (the age of trees is about 10 years) and the first (the age of trees is up to 5 years). The main breeds that ensure overgrowth are pine and birch. The results of the study demonstrate an increase from 1985 to 2022 for the forest area by 20.41% for the north of the Republic of Bashkortostan. Calculation of accumulated carbon with subsequent conversion into carbon units and assessment of their value showed that at the moment the stand of overgrown agricultural land has already accumulated about 182 thousand tons of carbon units. About 135 thousand tons of carbon units are deposited annually. The high dynamics of carbon accumulation by woody vegetation allows us to assume with a high degree of probability that agricultural lands overgrown with forest, when implementing certain forestry measures, can be the basis for the implementation of costeffective climate projects for both owners of licensed plots and other interested parties. According to the results of our work, the use of the Severo-Kushkul and Mishidinsky license areas of oil and gas fields is promising for forest-climatic projects.

Carbon accumulation dynamics and development processes of peatland established after the Changbaishan Millennium eruption

The Changbaishan Millennium eruption (946–947 CE) was one of the strongest volcanic activities over the past 2000 years, which greatly influenced the nearby wetland ecosystems. However, the carbon accumulation dynamics and development processes of these peatlands have rarely been investigated. This study tried to reveal the carbon accumulation dynamics and development processes of peatland established after the Changbaishan Millennium eruption. Here we selected the Yueliangwan peatland as study object. Results suggest that the Yueliangwan basin was a lake after the Changbaishan Millennium eruption. Then, a arid climate event occurred between 1250 and 1300 CE and dried out the water of this basin. During 1300–1384 years CE, the carbon accumulation rate (CAR) was low because of the peat initiation process. During 1384–1600 years CE, the CAR reached the highest over the past 700 years. Peat plants further rapidly expanded on the flat areas. During 1600–1750 years CE, the CAR showed a decreasing trend. The lateral expansion rate significantly slowed down because of the restriction of complex morphology. During 1750–1850 years CE, the CAR reached the lowest values. The lateral expansion of this peatland was over. During 1850–2019 years CE, the Yueliangwan peatland developed into bog stage. The CAR slightly increased during this period. These processes suggest that peatlands can rapidly develop after volcanic eruption. Additionally, correlation analyses indicate that regional precipitation controlled by the total solar irradiance and El Niño Southern-Oscillation (ENSO) activity played an important role in influencing the carbon accumulation dynamics and vegetation succession of the peatlands in Northeast China. This study would expand our understanding of long-term interactions between carbon accumulation dynamics and lateral expansion of peatlands, hydroclimate and volcanic activity.

Fruiting patterns impact carbon accumulation dynamics in cotton

Fruiting patterns impact carbon accumulation dynamics in cotton

Carbon accumulation dynamics of the Klukva peatland at the southern boundary of broad-leaved forest zone in European Russia

The study is focused on reconstructing the carbon accumulation rate of the peatland Klukva (1 ha) situated at the southern boundary of broad-leaved forest zone within the Oka river basin in European Russia. The age of the peatland is about 9400 cal years BP and it is one of the oldest peatlands within the Central Russian Upland. The results of our experimental study showed that the rate of peat accumulation is ranged from 0.15 to 0.9 mm/year and it was strongly influenced by climatic factors. Two main stages were distinguished in the peatland genesis. The longest was the mesotrophic stage, which began in the Early Holocene at about 9400 cal years BP and ended in the Late Holocene at about 1500 cal years BP. Since 1500 cal years BP there has been a gradual transition of the peatland from mesotrophic to oligotrophic type. The mean carbon accumulation rate during the peatland Klukva development was about 20 gC/(m2yr). This process was most actively going between 2500 and 6300 cal yrs BP, when the rates of peat accumulation increased to 26-29 gC/(m2yr). Nowadays, the carbon stock in the peat deposit of the peatland Klukva is amounted to 175 kgC/m2 and it is comparable with the carbon stocks of boreal peatlands in Northern Eurasia. This means that the oligotrophic peatlands situated at the southern boundary of broad-leaved forest zone, despite the small areas, continue to be a large stock of atmospheric carbon.

Identification of the dynamics of carbon accumulation in the Verkh-Invenskoe peatland by the method of Loss on Ignition

Abstract. The Perm Kama region is characterized by numerous promising paleoar chives, and the paleoecological knowledge of the region is uneven. Identification of the dynamics of organic carbon accumulation in peat is included in the complex of studies used to reconstruct the state of the natural environment in the past. We have studied peat deposits of the Verkh-Invenskoe bog in the western part of the region. For this, depth measurements, sampling of a peat column, and laboratory analysis of samples throughout the thickness were performed. As a result, indicators were determined: Bulk Density (further BD), Organic Matter Bulk Density (further OMBD), Loss on Ignition (further LOI), Long term average rate of carbon accumulation (LORCA). For the first time for the western part of the Perm Kama region, numerical data on the dynamics of carbon accumulation over the last 10.9 thousand years have been obtained.

14,000-year Carbon Accumulation Dynamics in a Siberian Lake Reveal Catchment and Lake Productivity Changes

A multi-proxy paleolimnological analysis of a sediment core sequence from Lake Malaya Chabyda in Central Yakutia (Eastern Siberia, Russia) was conducted to investigate changes in lake processes, including lake development, sediment and organic carbon accumulation, and changes in primary productivity, within the context of Late Pleistocene and Holocene climate change. Age-depth modeling with 14C indicates that the maximum age of the sediment core is ∼14 cal kBP. Three distinct sedimentary units were identified within the sediment core. Sedimentological and biogeochemical properties in the deepest section of the core (663–584 cm; 14.1–12.3 cal kBP) suggests a lake environment mostly influenced by terrestrial vegetation, where organic carbon accumulation might have been relatively low (average ∼100 g OC m−2 a−1), although much higher than the global modern average. The middle section of the core (584–376 cm; 12.3–9.0 cal kBP) is characterized by higher primary productivity in the lake, much higher sedimentation, and a remarkable increase in OC delivery (average ∼300 g OC m−2 a−1). Conditions in the upper section of the core (<376 cm; < 9.0 cal kBP) suggest high primary productivity in the lake and high OC accumulation rates (average ∼200 g OC m−2 a−1), with stable environmental conditions. The transition from organic-poor and mostly terrestrial vegetation inputs (TOC/TNatomic ratios ∼20) to conditions dominated by aquatic primary productivity (TOC/TNatomic ratios <15) occurs at around 12.3 cal kBP. This resulted in an increase in the sedimentation rate of OC within the lake, illustrated by higher sedimentation rates and very high total OC concentrations (>30%) measured in the upper section of the core. Compact lake morphology and high sedimentation rates likely resulted in this lake acting as a significant OC sink since the Pleistocene-Holocene transition. Sediment accumulation rates declined after ∼8 cal k BP, however total OC concentrations were still notably high. TOC/TNatomic and isotopic data (δ13C) confirm the transition from terrestrial-influenced to aquatic-dominated conditions during the Early Holocene. Since the mid-Holocene, there was likely higher photosynthetic uptake of CO2 by algae, as suggested by heavier (isotopically enriched) δ13C values (>−25‰).

Vegetation Determines Lake Sediment Carbon Accumulation during Holocene in the Forest–Steppe Ecotone in Northern China

To understand the past carbon accumulation of forest–steppe ecotone and to identify the main drivers of the long-term carbon dynamics, we selected Huangqihai Lake and analyzed the sediment records. We measured the organic carbon content (TOC; %) of sedimentary samples and quantified the carbon accumulation rate (CAR; g C m−2 yr−1). Furthermore, the climate, soil erosion, and vegetation development of the past 6800 years were reconstructed using physicochemical parameters and pollen records. Human activities were also obtained from a 2200-year history record. Our results showed that the CAR was high during 5800~4100 cal yr BP (40~60 g C m−2 yr−1), which is mainly attributed to the high sediment accumulation rate (SAR) during this period. Pearson’s correlation, redundancy analysis and hierarchical variation partitioning analyses suggested that the CAR was influenced by the SAR and TOC, while vegetation dynamics (broadleaved tree percentage and vegetation coverage) and local soil erosion were the main drivers of the TOC and SAR. Especially when the vegetation was dominated by broadleaved forests, the CAR was significantly high due to the high gross primary productivity and carbon density of forest compared with steppe. Our study highlights the direct influence of local vegetation and soil erosion on the CAR, whereas climate might influence indirectly by changing local vegetation and soil conditions. Moreover, our results showed that human activities had positive influences on the carbon accumulation dynamics in this region since 2200 cal yr BP by influencing the SAR.

Dynamics of Carbon Accumulation in Tropical Dry Forests under Climate Change Extremes

We analyze here how much carbon is being accumulated annually by secondary tropical dry forests (TDFs) and how structure, composition, time since abandonment, and climate can influence the dynamics of forest carbon accumulation. The study was carried out in Santa Rosa National Park in Guanacaste province, Costa Rica and Mata Seca State Park in Minas Gerais, Brazil. Total carbon storage and carbon accumulation were obtained for both sites from the sum of the aboveground carbon and belowground carbon gain plus the annual litterfall. Carbon accumulation of these TDFs varied from 2.6 Mg C ha−1 y−1 to 6.3 Mg C ha−1 y−1, depending on the age of the forest stands. Time since abandonment and number of stems per plot were the best predictors for carbon storage, annual carbon gains, and losses. Mortality rates and carbon losses were also associated with seasonal climate variability. We found significant correlations between tree mortality, carbon losses and mean seasonal temperature, mean seasonal precipitation, potential evapotranspiration, and the Oceanic Niño Index. Carbon dynamics in tropical dry forests are driven by time since abandonment and forest structure; however, rising temperature and El Niño Southern Oscillation (ENSO) events can have a significant impact on tree mortality and carbon losses. Depending on their location and land-use history, some dry forests are more impacted by climatic extremes than others, and differences between secondary stages are expected.

Sources of Particulate Organic Matter across Mangrove Forests and Adjacent Ecosystems in Different Geomorphic Settings

Mangrove forests are among the world’s most productive ecosystems and provide essential ecosystem services such as global climate regulation through the sequestration of carbon. A detailed understanding of the influence of drivers of ecosystem connectivity (in terms of exchange of suspended particulate organic matter), such as geomorphic setting and carbon stocks, among coastal ecosystems is important for being able to depict carbon dynamics. Here, we compared carbon stocks, CO2 fluxes at the sediment-air interface, concentrations of dissolved organic carbon and suspended particulate organic carbon across a mangrove-seagrass-tidal flat seascape. Using stable isotope signatures of carbon and nitrogen in combination with MixSIAR models, we evaluated the contribution of organic matter from different sources among the different seascape components. Generally, carbon concentration was higher as dissolved organic carbon than as suspended particulate matter. Geomorphic settings of the different locations reflected the contributions to particulate organic matter of the primary producers. For example, the biggest contributors in the riverine location were mangrove trees and terrestrial plants, while in fringing locations oceanic and macroalgal sources dominated. Anthropogenic induced changes at the coastal level (i.e. reduction of mangrove forests area) may affect carbon accumulation dynamics in adjacent coastal ecosystems.

Terrestrial organic carbon storage modes based on relationship between soil and lake carbon, China

Terrestrial ecosystems have received considerable attention as a significant sink for organic carbon at regional to global scales. Previous studies were focused on assessment and quantification of carbon sinks for one ecotype, and few have worked on the interconnection of terrestrial sinks. In this paper, we synthesized the data from China's second national soil survey and direct measurements from 54 lakes. Meanwhile, we investigated the controlling factors of carbon accumulation dynamics in soils and lakes. Results showed varied spatial distribution of soil and lake organic carbon in different regions, and three storage modes were found. The storage mode of watershed collection was observed in the region of the Qinghai-Tibetan Plateau, while the northeast China and Yunnan-Guizhou Plateau revealed another storage mode of autochthonous deposition, and the mode of human activities affection was represented by the East Plain and Mongolia-Xinjiang Plateau. The spatial difference throughout China was regulated by various climate patterns, geological conditions and anthropogenic interference. Our results provide insights into carbon storage modes in various regions, and also inform strategies for enhancing global carbon sequestration and future mitigation policies towards global climate change.

Energy stock seasonal dynamics in the pine forest beddings of Holosiivsky National Nature Park

The article presents the results of research of the energy stock in the components of pine forest bedding of National nature park Holosiivsky. The study was aimed on measurement and comparison of the carbon accumulation in the components of forest litter in natural and artificial forest ecosystems. The results of this study can be used to predict the stability of forest phytocoenoses. It is established that the energy supply of forest litter is an important element of the energy flows of the forest ecosystem and provides support for its stability. The study of seasonal dynamics of carbon accumulation was conducted on two monitoring plots of 50 m×50 m size. The first plot (D1) is represented by the association Dicrano-Pinetum Preising and Knapp 1942 ( Dicrano-Pinion Union (Libbert 1933) and located in a pine forest formed by Pinus sylvestris artificial plantations. The second plot (D2) is natural forest represented by the association Serratulo-Pinetum (W. Mat. 1981) with Pinus sylvestris aged 100–120 years in the first tier. The energy stock of artificial litter in artificial pine phytocoenoses exceeded the energy supply of natural pine litter. The average energy potential of artificial pine forest litter was 50857.75 kJ/m2, and it was 23910.00 kJ/m2 in natural pine phytocoenoses. The seasonal dynamics of the organic matter of the forest litter of the natural pine forest was smoother with the presence of one peak in the month of May, and for artificial pine characterized by periodic changes during the vegetation period with peaks in June, September and November. Insignificant fluctuations during the year of the energy potential of the forest litter of the natural pine forest showed a greater stability compared to artificial ones. Overall, the study confirmed the importance of monitoring the accumulation of carbon in various components of forest ecosystems.

Impact of Gobal Climate Change on the Dynamics of Carbon Balance of Plant Communities in South Asia

Assessment of the status of ecosystems experiencing anthropogenic impact is based on the ability of plant communities in such ecosystems to withstand these disturbances or to mitigate their effects fast enough. The aim of this paper is to analyze the impact of global climate change on carbon balance of plant communities of South Asia. To achieve this objective, the spatial model of global carbon cycle developed by the Computing Center of the Russian Academy of Sciences (RAS CC) was used to calculate the impact of industrial CO2 emissions as well as the main causes of carbon losses in the investigated region (deforestation and soil erosion) on the dynamics of carbon accumulation in the humus and phytomass of forest ecosystems. India was selected as a model country to assess and compare the compensatory functions of plant communities. On the basis of the spatial mathematical model of the global carbon cycle in the biosphere, changes in CO emissions as a result of burning fossil fuels, deforestation, and soil erosion associated with improper land use in South Asia were estimated. The impact of deforestation and soil erosion on climate change in South Asia is forecast up to the year 2060. A comparison of regulatory functions of different types of plant communities was performed for the study area. The calculations data revealed some regularities occurring in the ecosystems of South Asia under the impact of CO2 emissions, deforestation, and soil erosion due to improper land use. Mathematical modelling has shown the dependence of growth of humus and phytomass of vegetation on the amount of CO2 in the atmosphere. Quantitative forecast of the dynamics of the ecosystem characteristics of plant communities depending on the growing region has been performed.

Large-scale patterns in forest growth rates are mainly driven by climatic variables and stand characteristics

Comparing the growth rate of natural forest and plantation forest may be useful to better understand rates of carbon sequestration and carbon turnover. However, the large-scale patterns of biomass growth rates in China’s forests are still not well defined. We analyzed the growth rates of forest leaves, branches, stems, and roots across forest communities in China by using data collection, collation, and systematic analysis of published research and our unpublished data. The biomass growth rates in all forests exhibited negative latitudinal trends and negative altitudinal trends, with significant influence from climatic variables and stand characteristics. Stand characteristics explained more variation in growth rates of forest biomass than did climatic variables, and growth rates of forest leaves, branches, stems, and roots varied in relation to climate, stand characteristics, and forest origin. The cross-validated results of stepwise multiple regression (SMR) models and neural network models (NNM) indicated that the prediction accuracy of growth rate of forest biomass by NNM was better than that of the SMR models. Our results improve understanding of the environmental factors affecting Chinese forest growth and inform efforts to model dynamics of carbon accumulation in China’s forests.

Dendroecological Approach to Assessing Carbon Accumulation Dynamics in TwoPinusSpecies from Northern Mexico

Global climate change will alter forests by shifting species ranges, which has implications for their ecological functions. Annual tree-ring widths and wood density are useful proxies for carbon cycle studies across a range of species. Here, using a dendroecological approach we sought to understand the carbon accumulation rates of two representative pine species growing on contrasting wet (P. arizonica) and dry (P. cembroides) sites and reveal how such species cope with climate variability. Although the rate of carbon gain was not significantly different across sites, we found that variations in carbon accumulation responded differently to specific hydroclimate drivers, site conditions, or to functional features of each species, which are still to be explored. Overall, annual carbon accumulation (C) was less sensitive to climate variability than ring width and wood density. Annual C was more sensitive to rainfall in the cold season (P. arizonica) and to the start of spring (both species). Our species-specific approach provided a suitable basis for modeling projections in the long-term carbon balance in these forests. Using species-specific tree-ring data has the potential to yield better estimations given that tree rings reflect fine spatial and temporal resolution, thereby reducing the uncertainty in forest carbon budgets.

Accumulation of carbon and age of thinning of the tree component in agroforestry systems

Agroforestry systems (AFS) are considered large sinks of greenhouse gases (GHG) in the atmosphere. However, little is known about the dynamics of carbon accumulation in tree individuals over the years and the Age Thinning Technique (ATT) to potentialize GHG mitigation. The objective of the study was to predict the growth in carbon and determine the age thinning Technique of the tree component in 3 AFS in the municipality of Viçosa, MG, Brazil, in which System A is composed of eucalypt (Eucalyptus saligna) + pasture (Brachiaria decumbens) and systems B and C with eucalypt (Eucalyptus urophylla x Eucalyptus grandis) + pasture (Brachiaria decumbens). The Gompertz and Logistic models were employed to predict the timber volume and carbon growth. The ATT was determined based on the maximum productivity in timber volume per unit area. The curve asymptotic values of the systems A, B and C were 450, 221 and 226 m3 ha-1 for the volume and 104, 51 and 52 MgC ha-1 for the carbon, respectively. Stabilization of carbon accumulation will occur close to 100 months for systems A and B and at 80 months for system C. As the ATT ranged 64-80 months, the thinning is recommended before this age to promote the carbon accumulation of the remaining arboreal individuals.

The dynamics of carbon accumulation in Eucalyptus and Acacia plantations in the Pearl River delta region

Plantation type and age strongly influence the quantity of carbon stored in forest ecosystems. The marked increase in total ecosystem carbon stock achieved over time by the Eucalyptus and Acacia plantations has confirmed that the afforestation of degraded soils can contribute positively to carbon sequestration. Reforestation has been widely conducted to restore and protect the eroded red soil in south China in recent decades. The question as to whether the content of soil organic carbon (SOC) can be boosted by establishing plantations of fast-growing tree species remains unresolved. We addressed whether the afforestation of degraded soils can contribute positively to carbon sequestration, and whether the accumulation of SOC is more effective under a nitrogen fixing species such as Acacia than under Eucalyptus. Here, a study was undertaken to measure the quantity of total ecosystem carbon (TEC) accumulated by plantations of both Eucalyptus and Acacia spp. in the Pearl River Delta region of southern China. The quantity of TEC increased significantly with stand age in both plantation types (P < 0.05). The largest single component of TEC was SOC, with stand age having a considerable effect on both SOC and overall biomass. The accumulation of SOC in the top 100 cm of the soil profile was higher under Acacia than under Eucalyptus (P < 0.05). In terms of carbon sequestration, the afforestation of Eucalyptus and Acacia represent an effective forest management practice. The accumulation of SOC is more effective under Acacia than under Eucalyptus.

Carbon accumulation in Dahu Swamp in the eastern Nanling Mountains (south China) and its implications for hydroclimatic variability over the past 47 000 years

Wetlands act as persistent natural carbon sinks over long time scales. Understanding the response of these carbon reservoirs to climate change is critical to assessing potential climate feedbacks. We conducted a study of an 860‐cm‐long sediment core in Dahu Swamp in south China to determine how the carbon accumulation rate (CAR) has varied as a function of palaeohydrology and palaeoclimate over the past 47 000 years. From an orbital time scale, our results show that the CAR in Dahu Swamp is relatively low in the wet periods of Marine Isotope Stage 3 (MIS 3) (mean: 46.7 gC m−2 a−1) and MIS 1 (mean: 28.2 gC m−2 a−1), compared to the dry periods of MIS 2 (mean: 59.9 gC m−2 a−1). At centennial and millennial scales, the highest CARs of Dahu Swamp mainly occur in organic‐rich silt or clay (gyttja) layers, which correspond to the relatively dry climate (e.g. c. 48 000–41 000, c. 33 000–32 000, c. 15 800–14 900 and c. 4400–4250 cal. a BP). The CAR of Dahu Swamp is mainly controlled by local hydrological variations that are closely related to the East Asian summer monsoon (EASM) intensity, which may be co‐influenced by orbitally induced summer insolation forcing and internal feedback processes (e.g. Atlantic Meridional Overturning Circulation and El Niño/Southern Oscillation). Based on comparison with the CARs in monsoonal regions of China, we consider that precipitation may be the key factor for wetland CAR in EASM areas, whereas temperature is more important in Qinghai–Tibetan Plateau regions under Indian summer monsoon influence. The CAR of Dahu Swamp provides valuable records of wetland carbon accumulation dynamics in subtropical monsoon regions, which contradict the traditional patterns in global northern wetlands.

A six thousand‐year record of climate and land‐use change from Mediterranean seagrass mats

Summary The Mediterranean seagrass Posidonia oceanica maintains a biodiverse ecosystem and it is a world‐wide important carbon sink. It grows for millennia, accumulating organic‐rich soils (mats) beneath the meadows. This marine habitat is protected by the European Union; however, it is declining rapidly due to coastal development. Understanding its response to disturbances could inform habitat restoration, but many environmental impacts predate monitoring programs (&lt;50 years). This research explores the palaeoecological potential of Posidonia mats to reconstruct six thousand years of environmental change that could have affected Posidonia meadows and, in turn, left an imprint on the mats. Palynological, microcharcoal, magnetic susceptibility and glomalin‐related soil protein (GRSP) analyses on Posidonia mats enabled us to detect climate‐ and human‐induced environmental processes impacting on the seagrass during the Late Holocene. The pollen and microcharcoal records reconstructed anthropogenic disturbances attributed to agriculture. The record of GRSP shows that agrarian activities affected continental soil quality. Changes in magnetic susceptibility reveal that enhanced soil erosion was caused by both climate (major flooding events in the NW Mediterranean) and humans (cultivation) which impacted on the Posidonia mat. Finally, increased human impact is linked to eutrophication of coastal waters since Roman‐Medieval times. Synthesis. This study shows that climate and land‐use changes in the western Mediterranean resulted in enhanced loadings of terrigenous material to the coastal zone since the Late Holocene, likely disturbing the Posidonia meadows and their mat carbon accumulation dynamics. Under the current global change scenario in which CO2 emissions are projected to increase, restoring carbon sinks is a priority. Seagrass habitat restoration should consider not only the coastal perturbations, but also the continental ones at a catchment scale to preserve the socio‐economic ecosystem services provided by seagrasses.