Pervasive increase in tree mortality across the Australian continent.

A regression model was built for the relationship between carbon density, temperature, and precipitation in the terrestrial ecosystem of Anhui Province in the base year （2010）. Based on the actual changes in climate and land cover from 2010 to 2020, the carbon density of various land types in 2020 was calculated while the changes in carbon storage were simulated quantitatively in the province under the dual driving forces of nature and human activities. Using the four future climate scenarios proposed by CMIP6 and the future land cover simulated by the PLUS model, the carbon storage of terrestrial ecosystems in Anhui Province in 2030 and 2060 was predicted. The results indicate that： ① This multiple linear regression equation （R2=0.886 75） better confirmed the existing research conclusions that the interannual temperature rise accelerated soil organic carbon decomposition, and the increase in precipitation promoted vegetation biomass accumulation in the transition zone from warm temperate to northern subtropical regions in eastern China. ② From 2010 to 2020, the overall temperature in Anhui Province slightly decreased, and precipitation slightly increased, resulting in an increase of 89.81 Tg in carbon storage caused by climate change. The main trend of land cover change was the outward expansion of construction land, which occupied surrounding arable land, resulting in a reduction of 6.11 Tg in carbon storage. As a result, the carbon storage of terrestrial ecosystems in Anhui Province increased from 2 097.07 Tg in 2010 to 2 180.77 Tg in 2020, with an average annual carbon sequestration rate per unit area （calculated as C） of 59.76 g·（m2·a）-1. ③ From 2020 to 2030, under the SSP1-2.6 （low emission） scenario, the overall temperature in Anhui Province decreased narrowly, and precipitation increased, resulting in a slight increase in carbon density in all six land types. Driven by both climate change （91.6% contribution） and human activities （8.4% contribution）, carbon storage increased by 142.84 Tg over the next 10 years, reaching 2 323.61 Tg in 2030, with an average annual carbon sequestration rate per unit area （calculated as C） of 101.96 g·（m2·a）-1. In the SSP2-4.5 （medium emission）, SSP3-7.0 （competition）, and SSP5-8.5 （high emission） scenarios, there were varying degrees of warming, resulting in a corresponding decrease in carbon density and carbon storage by 2030. The SSP3-7.0 （competition） scenario had the smallest relative decrease. ④ From 2030 to 2060, due to the further increase in temperature under the four scenarios, carbon density in all six land types was predicted to decrease. In addition, relatively high-density carbon sequestration farmland would continue to be significantly transformed into low-density carbon sequestration towns, resulting in a significant decrease in carbon storage in all four scenarios. In the SSP3-7.0 （competitive） scenario in 2060, carbon storage was relatively highest compared to that in the other three scenarios.

Canada's boreal forests, which occupy approximately 30% of boreal forests worldwide, play an important role in the global carbon budget. However, there is little quantitative information available regarding the spatiotemporal changes in the drought-induced tree mortality of Canada's boreal forests overall and their associated impacts on biomass carbon dynamics. Here, we develop spatiotemporally explicit estimates of drought-induced tree mortality and corresponding biomass carbon sink capacity changes in Canada's boreal forests from 1970 to 2020. We show that the average annual tree mortality rate is approximately 2.7%. Approximately 43% of Canada's boreal forests have experienced significantly increasing tree mortality trends (71% of which are located in the western region of the country), and these trends have accelerated since 2002. This increase in tree mortality has resulted in significant biomass carbon losses at an approximate rate of 1.51 ± 0.29 MgC ha-1 year-1 (95% confidence interval) with an approximate total loss of 0.46 ± 0.09 PgC year-1 (95% confidence interval). Under the drought condition increases predicted for this century, the capacity of Canada's boreal forests to act as a carbon sink will be further reduced, potentially leading to a significant positive climate feedback effect.

Against the background of "carbon neutrality" and sustainable development goals, it is of great significance to assess the carbon storage changes and sustainability of terrestrial ecosystems in order to maintain the coordinated sustainable development of regional ecological economies and the balance of terrestrial ecosystems. In this study, the terrestrial ecosystem carbon storage in Guizhou from 2010 to 2020 was assessed with the InVEST model. Using the PLUS model, the distribution of terrestrial ecosystem carbon storage by 2030 and 2050 was predicted. The current sustainable development level of the terrestrial ecosystem of Guizhou was evaluated after establishing an index system based on SDGs. The results showed the following: (1) From 2010 to 2020, the terrestrial ecosystem carbon storage decreased by 1106.68 × 104 Mg. The area and carbon storage of the forest and farmland ecosystems decreased while the area and carbon storage of the grassland and settlement ecosystems increased. (2) Compared with 2020, the terrestrial ecosystem carbon storage will be reduced by 4091.43 × 104 Mg by 2030. Compared with 2030, the terrestrial ecosystem carbon storage will continue to decrease by 3833.25 × 104 Mg by 2050. (3) In 2020, the average score of the sustainable development of the terrestrial ecosystem was 0.4300. Zunyi City had the highest sustainable development score of 0.6255, and Anshun had the lowest sustainable development score of 0.3236. Overall, the sustainable development of the terrestrial ecosystem of Guizhou was found to be high in the north, low in the south, high in the east, and low in the west. The sustainable regional development of the terrestrial ecosystem of Guizhou was found to be unbalanced, and the carbon storage of the terrestrial ecosystem will keep decreasing in the future. In order to improve the sustainable development capacity of the terrestrial ecosystem, the government needs to take certain measures, such as returning farmland to forests and grasslands, curbing soil erosion, and actively supervising.

Simulation and attribution analysis of terrestrial ecosystem carbon storage of Hainan Island from 2015 to 2050

A widespread increase in tree mortality has been observed around the globe, and this trend is likely to continue because of ongoing climate-induced increases in drought frequency and intensity. This raises the need to identify regions and ecosystems that are likely to experience the most frequent and significant damages. We present SurEau-Ecos, a trait-based, plant-hydraulic model designed to predict tree desiccation and mortality at scales from stand to region. SurEau-Ecos draws on the general principles of the process-based, soil-plant-atmosphere SurEau model. It also introduces a simplified representation of plant architecture and alternative numerical schemes; both additions made to facilitate model parameterization and large-scale applications. In SurEau-Ecos, the water fluxes from the soil to the atmosphere are represented through two plant organs (a leaf and a stem, which includes the volume of the trunk, roots and branches) as the product of an interface conductance and the difference of water potentials. Each organ is described by its symplasmic and apoplasmic compartments. The dynamics of plant’s water status beyond the point of stomatal closure are explicitly represented via residual transpiration flow, plant cavitation and solicitation of plants’ water reservoirs. In addition to the "explicit” numerical scheme of SurEau, we implemented a “semi-implicit” and “implicit” scheme. Both schemes led to a substantial gain in computing time compared to the “explicit” scheme (>10,000 times), and the implicit scheme was the most accurate. We also observed similar plant water dynamics between SurEau-Ecos and SurEau but slight disparities in infra-daily variations of plant water potentials that we attributed to the differences in the representation of plant architecture between models. A global model’s sensitivity analysis revealed that factors controlling plant desiccation rates differ depending on whether leaf water potential is below or above the point of stomatal closure. Total available water for the plant, leaf area index, and the leaf water potential at 50 % stomatal closure mostly drove the time needed to reach stomatal closure. Once stomata are closed, resistance to cavitation, residual cuticular transpiration and plant water stocks mostly determined the time to hydraulic failure. Finally, we illustrated the potential of SurEau-Ecos to simulate regional drought-induced mortality over France. SurEau-Ecos is a promising tool to perform regional-scale predictions of drought-induced hydraulic failure, determine the most vulnerable areas and ecosystems to drying conditions, and asses the dynamics of forest flammability.

Abstract. A widespread increase in tree mortality has been observed around the globe, and this trend is likely to continue because of ongoing climate-induced increases in drought frequency and intensity. This raises the need to identify regions and ecosystems that are likely to experience the most frequent and significant damage. We present SurEau-Ecos, a trait-based, plant hydraulic model designed to predict tree desiccation and mortality at scales from stand to region. SurEau-Ecos draws on the general principles of the SurEau model but introduces a simplified representation of plant architecture and alternative numerical schemes. Both additions were made to facilitate model parameterization and large-scale applications. In SurEau-Ecos, the water fluxes from the soil to the atmosphere are represented through two plant organs (a leaf and a stem, which includes the volume of the trunk, roots and branches) as the product of an interface conductance and the difference between water potentials. Each organ is described by its symplasmic and apoplasmic compartments. The dynamics of a plant's water status beyond the point of stomatal closure are explicitly represented via residual transpiration flow, plant cavitation and solicitation of plants' water reservoirs. In addition to the “explicit” numerical scheme of SurEau, we implemented a “semi-implicit” and “implicit” scheme. Both schemes led to a substantial gain in computing time compared to the explicit scheme (>10 000 times), and the implicit scheme was the most accurate. We also observed similar plant water dynamics between SurEau-Ecos and SurEau but slight disparities in infra-daily variations of plant water potentials, which we attributed to the differences in the representation of plant architecture between models. A global model's sensitivity analysis revealed that factors controlling plant desiccation rates differ depending on whether leaf water potential is below or above the point of stomatal closure. Total available water for the plant, leaf area index and the leaf water potential at 50 % stomatal closure mostly drove the time needed to reach stomatal closure. Once stomata are closed, resistance to cavitation, residual cuticular transpiration and plant water stocks mostly determined the time to hydraulic failure. Finally, we illustrated the potential of SurEau-Ecos to simulate regional drought-induced mortality over France. SurEau-Ecos is a promising tool to perform regional-scale predictions of drought-induced hydraulic failure, determine the most vulnerable areas and ecosystems to drying conditions, and assess the dynamics of forest flammability.

Estimating terrestrial ecosystem carbon storage change in the YREB caused by land-use change under SSP-RCPs scenarios

Rola zaburzeń w kształtowaniu struktury i dynamiki naturalnych lasów bukowo-jodłowo-świerkowych w Karpatach Zachodnich

Land use change drives carbon storage in terrestrial ecosystems. Understanding the spatio-temporal varia-tion of land use and carbon storage is important for improving carbon sink capacity and achieving the carbon neutrality goal. With InVEST-PLUS model, we evaluated spatio-temporal variation of land use change and ecosystem carbon storage in Hebei Province, explored their variations from 2000 to 2020, and predicted land use changes and carbon storage in 2040. The results showed that cultivated land, forest, and grassland were dominant vegetation types from 2000 to 2020. The area of cultivated land decreased by 7011.1 km2, and the construction land increased by 7479.6 km2. The conversion of cultivated land to construction land was the predominant form of land transfer. Carbon storage in Hebei decreased by 3.6×107 t from 2000 to 2020, with the conversion of cultivated land and grassland to construction land being the main reason for such rapid decline of carbon storage. Carbon storage was higher in the northwest and lower in the southeast. From 2020 to 2040, under natural development scenario, ecological protection scenario, and economic development scenario, the carbon storage of Hebei Province would increase by 4.0×107, 5.1×107, and 5.9×107 t, respectively. The main carbon pools will still be cultivated land, forest, and grassland. In the future, it would be necessary to protect carbon sequestration resources such as forest and grassland, optimize land use pattern with the goal of reducing carbon emissions, and protect areas with high carbon density to further enhance their carbon sequestration capacity.

This paper is a critical synthesis of the causes, effects and challenges of the Sahelian droughts. The results show that the four main causes of the Sahelian droughts are as follows: sea surface temperature changes, vegetation and land degradation, dust feedbacks and human-induced climate change. However, human-induced climate change is seen as the major drought-determining factor because it controls sea surface temperatures, dust feedbacks and vegetation degradation. Increase rainfall and greening have been observed in the Sahel since the 1990s; yet, food yields remain low while tree mortality rates are high. The implication of this is that the rainfall is not available for agriculture since various human-induced climate change processes such as deforestation and the expansions of arable farms do not make the moisture available for agriculture. The increase in tree mortality has also been found to increase atmospheric CO2 in the study area. However, this study hypothesizes that the increase in CO2 might be responsible for the increase in greening and rainfall observed. This can be explained by an increased aerial fertilization effect of CO2 that triggers plant productivity and water management efficiency through reduced transpiration. Also, the increase greening can be attributed to rural–urban migration which reduces the pressure of the population on the land. The remittances from migrant urban workers may make farming more sustainable in the rural areas, thus enhancing greening. The principal challenges in overcoming the effects of the droughts are HIV/AIDS and Malaria, political instability, data availability, proliferation of extensive non-mechanized farms and lack of adequate observations.

(1) Terrestrial ecosystems are critical carbon sinks, and the accurate assessment of their carbon storage is vital for understanding global carbon cycles and formulating climate change mitigation strategies. (2) This study integrated vegetation indices, meteorological factors, land use data, soil/vegetation types, field sampling, and a convolutional neural network (CNN) model to estimate the carbon storage of terrestrial ecosystems in Guangdong Province. (3) Total carbon storage increased by 0.11 Pg from 2000 to 2021, with vegetation carbon gains (+0.19 Pg) offsetting soil carbon losses (−0.08 Pg), with the latter primarily being driven by reduced soil carbon in forest ecosystems. (4) Northern and eastern Guangdong exhibit high potential for enhancing carbon storage capacity, which is crucial for achieving regional carbon peaking and neutrality targets.

<title>Abstract</title> Carbon storage in vegetation sustains climate regulation by facilitating carbon sequestration (CS). varying abilities of plant species to sequester, retain, and emit carbon make their collective functional traits pivotal in deriving carbon storage in terrestrial ecosystems. However, combined impacts of stand structures and functional traits on multi-layered above-ground carbon storage across forest strata, and their shifts along the altitudinal gradients in single-species forests, remain understudied. Using data from 195 quadrates (20 × 20m²) across five monodominant <italic>Quercus incana</italic> forests in Hindu Himalayas, we analyzed relationship between stand structures, functional traits, and yearly CS. SEM used to assess direct and indirect influences of elevation, stand structural attributes DBH, H, CA, FB, and functional traits on carbon storage. The results showed that stand structures strongly influenced carbon storage, with significant correlations in Zone2 (1524 m; β = 0.144, p = 0.04), Zone3 (2000–2300 m; β = 0.272, p = 0.001), and Zone5 (2400-2700m; β = 0.306, p = 0.001). Functional traits exhibited elevation specific effects, BT and WD correlated positively with carbon in Zone3,5 (p = 0.001) but weakened in Zone1,2 (p &gt; 0.05). Leaf traits LDMC, LT showed significant positive correlation in Zone5 (p = 0.001), while SLA had inconsistent effect, including slightly negative in Zone4 (p ~ 0.05). Our study illustrates that the effect of stand structures and functional traits on carbon storage are forest strata and elevation mediated, serving as key predictors of CS across elevations. Prioritizing these factors bid a robust framework for modeling how traits derive under climate change, particularly monodominant forests. This approach augments predictive accuracy in assessing climate carbon feedback and informs targeted ecosystem management.

An analysis of regional carbon stock response under land use structure change and multi-scenario prediction, a case study of Hefei, China

Rising atmospheric CO2 may stimulate future forest productivity, possibly increasing carbon storage in terrestrial ecosystems, but how tropospheric ozone will modify this response is unknown. Because of the importance of fine roots to the belowground C cycle, we monitored fine-root biomass and associated C fluxes in regenerating stands of trembling aspen, and mixed stands of trembling aspen and paper birch at FACTS-II, the Aspen FACE project in Rhinelander, Wisconsin. Free-air CO2 enrichment (FACE) was used to elevate concentrations of CO2 (average enrichment concentration 535µl l-1) and O3 (53nl l-1) in developing forest stands in 1998 and 1999. Soil respiration, soil pCO2, and dissolved organic carbon in soil solution (DOC) were monitored biweekly. Soil respiration was measured with a portable infrared gas analyzer. Soil pCO2 and DOC samples were collected from soil gas wells and tension lysimeters, respectively, at depths of 15, 30, and 125cm. Fine-root biomass averaged 263g m-2 in control plots and increased 96% under elevated CO2. The increased root biomass was accompanied by a 39% increase in soil respiration and a 27% increase in soil pCO2. Both soil respiration and pCO2 exhibited a strong seasonal signal, which was positively correlated with soil temperature. DOC concentrations in soil solution averaged ~12mg l-1 in surface horizons, declined with depth, and were little affected by the treatments. A simplified belowground C budget for the site indicated that native soil organic matter still dominated the system, and that soil respiration was by far the largest flux. Ozone decreased the above responses to elevated CO2, but effects were rarely statistically significant. We conclude that regenerating stands of northern hardwoods have the potential for substantially greater C input to soil due to greater fine-root production under elevated CO2. Greater fine-root biomass will be accompanied by greater soil C efflux as soil respiration, but leaching losses of C will probably be unaffected.

Interactions between photosynthetic substrate supply and temperature in determining the rate of three respiration components (leaf, belowground and ecosystem respiration) were investigated within three environmentally controlled, Populus deltoides forest bays at Biosphere 2, Arizona. Over 2 months, the atmospheric CO2 concentration and air temperature were manipulated to test the following hypotheses: (1) the responses of the three respiration components to changes in the rate of photosynthesis would differ both in speed and magnitude; (2) the temperature sensitivity of leaf and belowground respiration would increase in response to a rise in substrate availability; and, (3) at the ecosystem level, the ratio of respiration to photosynthesis would be conserved despite week‐to‐week changes in temperature. All three respiration rates responded to the CO2 concentration‐induced changes in photosynthesis. However, the proportional change in the rate of leaf respiration was more than twice that of belowground respiration and, when photosynthesis was reduced, was also more rapid. The results suggest that aboveground respiration plays a key role in the overall response of ecosystem respiration to short‐term changes in canopy photosynthesis. The short‐term temperature sensitivity of leaf respiration, measured within a single night, was found to be affected more by developmental conditions than photosynthetic substrate availability, as the Q10 was lower in leaves that developed at high CO2, irrespective of substrate availability. However, the temperature sensitivity of belowground respiration, calculated between periods of differing air temperature, appeared to be positively correlated with photosynthetic substrate availability. At the ecosystem level, respiration and photosynthesis were positively correlated but the relationship was affected by temperature; for a given rate of daytime photosynthesis, the rate of respiration the following night was greater at 25 than 20°C. This result suggests that net ecosystem exchange did not acclimate to temperature changes lasting up to 3 weeks. Overall, the results of this study demonstrate that the three respiration terms differ in their dependence on photosynthesis and that, short‐ and medium‐term changes in temperature may affect net carbon storage in terrestrial ecosystems.