Changes In Terrestrial Ecosystems Research Articles

Soil degradation and herbicide pollution by repeated cassava monoculture within Thailand's conservation region.

In a national park in Northeast Thailand, agricultural land has been converted from natural forest by small-scale farmers for cassava agriculture. We hypothesise that long-termed cassava monoculture leads to the degradation of soil properties. To test the hypothesis, we conducted a five-year (2016-2020) study on the physical and chemical properties of soil in cassava farmland, and also examined the soil properties of its adjacent natural forests, as a control. The examined cassava farmland was converted from the natural forest during the five years from 2011 to 2015. The significant decrease in organic carbon and the increases in exchangeable potassium and bulk density were found in 2016, indicating that these soil properties varied quickly following the farmland conversion. On the other hand, the significant increase in soil nitrogen and the decrease in pH were found later in 2020, indicating that these soil properties were gradually altered by repeated agricultural activities, such as fertilizer application and trampling. In contrast, there were no significant differences in available phosphate, electrical conductivity, cation exchange capacity, and the soil texture (the fractions of sand, silt, and clay) among the forest and farmland soils. The cation exchange capacity was positively correlated to the fraction of clay, the organic carbon, and pH. The use of glyphosate and paraquat herbicides is prohibited within national parks in Thailand. However, in 2020, glyphosate was detected in farmland soil (up to 5.0 mg kg-1) during both the rainy and dry seasons, and glyphosate (up to 2.5 mg l-1) was detected in stream water from the farmland during the dry season at least in 2020. Soil degradation and herbicide pollution may carry a high risk of causing irreversible changes in terrestrial ecosystems. We discuss the root causes of this issue from perspectives of agricultural production, economy, and the environmental impact, and propose effective policy measures.

Microbial hydrogenation of cholesterol to coprostanol by anaerobic bacteria: evidence from Antarctic lacustrine sediment

Fecal sterols are traditionally ascribed as important biomarkers for animal excrement, and have been widely used to identify the source of organic matter and to reconstruct paleoecological changes in Antarctic terrestrial, aquatic, and marine ecosystems. However, the in situ microbial hydrogenation of cholesterol to coprostanol could have significance as a proxy to infer paleoenvironmental studies in Antarctica, particularly in anoxic sediment. Here, we report that abundant coprostanol, which was traditionally deemed as a biomarker for human sewage contamination, was found in three anoxic sediment profiles (AC2, BI, and CH1), which were strongly influenced by animal excrement at North Victoria Land, western Ross Sea, Antarctica. Our results suggest that the high concentrations of coprostanol in these three sediment profiles were not due to animal excrement, since coprostanol is not present in penguin guano and is a minor component in seal excrement. Coprostanol/cholesterol and coprostanol/(coprostanol + cholestanol) ratios suggest that coprostanol in the sediment cores of AC2 and BI was primarily derived from bacterial hydrogenation of cholesterol introduced by penguin guano. Coprostanol in CH1 sediments is related to human sewage due to intensive research activities from 1968 to 2006 in this region. However, the low abundance of coprostanol and the ratios of coprostanol/cholesterol and coprostanol/(coprostanol + cholestanol) in a relatively oxidizing sediment core (IIL1) infer that coprostanol was likely contributed by seal settlement. Together with high-throughput sequencing of the 16S rRNA gene, the conversion of cholesterol to coprostanol by anaerobic bacteria (e.g., Eubacterium coprostanoligenes) could occur in anoxic aquatic systems. Our results suggest that the presence of coprostanol in Antarctic lacustrine sediment with anoxic conditions does not necessarily indicate seal activity and human waste as the microbial hydrogenation of cholesterol to coprostanol should also be considered.

Assessing land-use changes and carbon storage: a case study of the Jialing River Basin, China

Land-use change is the main driver of carbon storage change in terrestrial ecosystems. Currently, domestic and international studies mainly focus on the impact of carbon storage changes on climate, while studies on the impact of land-use changes on carbon storage in complex terrestrial ecosystems are few. The Jialing River Basin (JRB), with a total area of ~ 160,000 km2, diverse topography, and elevation differences exceeding 5 km, is an ideal case for understanding the complex interactions between land-use change and carbon storage dynamics. Taking the JRB as our study area, we analyzed land-use changes from 2000 to 2020. Subsequently, we simulated land-use patterns for business-as-usual (BAU), cropland protection (CP), and ecological priority (EP) scenarios in 2035 using the PLUS model. Additionally, we assessed carbon storage using the InVEST model. This approach helps us to accurately understand the carbon change processes in regional complex terrestrial ecosystems and to formulate scientifically informed land-use policies. The results revealed the following: (1) Cropland was the most dominant land-use type (LUT) in the region, and it was the only LUT experiencing net reduction, with 92.22% of newly designated construction land originating from cropland. (2) In the JRB, total carbon storage steadily decreased after 2005, with significant spatial heterogeneity. This pattern was marked by higher carbon storage levels in the north and lower levels in the south, with a distinct demarcation line. The conversion of cropland to construction land is the main factor driving the reduction in carbon storage. (3) Compared with the BAU and EP scenarios, the CP scenario demonstrated a smaller reduction in cropland area, a smaller addition to construction land area, and a lower depletion in the JRB total carbon storage from 2020 to 2035. This study demonstrates the effectiveness of the PLUS and InVEST models in analyzing complex ecosystems and offers data support for quantitatively assessing regional ecosystem services. Strict adherence to the cropland replenishment task mandated by the Chinese government is crucial to increase cropland areas in the JRB and consequently enhance the carbon sequestration capacity of its ecosystem. Such efforts are vital for ensuring the food and ecological security of the JRB, particularly in the pursuit of the “dual-carbon” objective.

An earliest Triassic riparian ecosystem from the Bulgo Sandstone (Sydney Basin), Australia: palynofloral evidence of a high-latitude terrestrial vertebrate habitat after the end-Permian mass extinction

A landmark change in terrestrial ecosystems took place after the end-Permian mass extinction (EPME). This was marked by disappearance of the iconic latest Permian Glossopteris forests in Australian continental successions dated to 252.10 ± 0.06 Ma (mega-annum). Pioneering earliest Triassic spore-producing plants then spread following catastrophic wildfires, soil erosion and algal blooms. These ruderal plant communities were later replaced by vast Dicroidium ‘seed fern’ forests, which established under warm, seasonally dry conditions. By contrast, evidence of coeval vertebrate assemblages is scarce in Australia. The Bulgo Sandstone (Narrabeen Group) fossil biota in the Sydney Basin is, therefore, important as a rare example of associated plant and animal communities from the Early Triassic. The fossils include imprints and organic remains of lycopsid roots and attributed leaves (microphylls), Dicroidium and Lepidopteris foliage, and both erythrosuchid and smaller-bodied archosauromorphs, capitosaurians and other temnospondyls, actinopterygian fishes and sharks. Here, we undertake a palynofloral analysis of the vertebrate fossil-bearing bed within the Bulgo Sandstone to determine the assemblage age and palaeoenvironment. We identified a low-diversity miospore suite that is overwhelmingly dominated by lycopsids (42%), and especially quillworts (Isoëtales/Pleuromeiales) represented by Densoisporites and Aratrisporites. Bryophyte (moss), sphenopsid (horsetail) and ground fern spores are also present. Pollen (14%) comprises forms mainly associated with voltzialean conifers. The non-taeniate bisaccate Falcisporites (Alisporites) produced by Dicroidium is comparatively rare (3%). Based on this taxic composition, we correlate the vertebrate-bearing layer of the Bulgo Sandstone with the lower part of the Protohaploxypinus samoilovichii Oppel Zone and suggest a late Induan to early Olenekian age. Calculated sedimentation rates indicate that the 400 m of sediments between the top of the Vales Point Coal and the base of the Bulgo Sandstone were laid down within a time span of 40–400 ka (kilo-annum). Furthermore, the high portion of spores (37%) implies a parautochthonous organic accumulation that would have derived from local vegetation. This was likely riparian, with Dicroidium (and associated gymnosperm) cuticles (ca 20%) being over-represented because of a deciduous seasonal cycle. Notably, the Bulgo Sandstone accumulated on a high-palaeolatitude floodplain (ca 66–69°S) with dense vegetation flanking waterways that might have provided both shelter and forage for terrestrial vertebrates living less than 1 Ma after the EPME ecosystem collapse. Vivi Vajda* [vivi.vajda@nrm.se], Swedish Museum of Natural History, Svante Arrhenius väg 9, Stockholm 11414, Sweden; Benjamin P. Kear [benjamin.kear@em.uu.se], The Museum of Evolution, Uppsala University, Norbyvägen 16, Uppsala 75236, Sweden.

The Growth and Carbon Sink of Tundra Peat Patches in Arctic Alaska

AbstractRecent amplified climate warming in the Arctic has caused profound changes in terrestrial ecosystems, with the potential for strong feedback on climate change. Arctic tundra landscapes have developed patchy and thin organic soil (peat) layers at the surface that may continue to grow into mature peatlands and become a larger carbon sink under future warming. Here we use paleoecological analyses of multiple soil and peat cores collected from the North Slope of Alaska to document and understand the formation and development histories of tundra peat patches and permafrost peatlands. We find a consistent peat development sequence for peat patches, first from mineral soils to sedge peat during the Little Ice Age, and then to Sphagnum peat during the recent warming with high carbon accumulation rates. These findings suggest that climate cooling is likely critical for the initial peat buildup on tundra soils due to reduced decomposition, whereas climate warming triggers the regime shift into an increased abundance of Sphagnum mosses that are likely central to enhancing their carbon sink capacity. Additionally, peat patches become similar to permafrost peatlands in the vicinity in terms of ecosystem processes and carbon dynamics, and therefore may have developed the same ecohydrological feedback system to maintain their long‐term stability. This study implies that the potential future expansion of peat patches into peatlands may strongly alter the carbon balance of Arctic tundra, supporting the new United Nations Environment Programme's report that calls for incorporating widespread shallow peat into understanding the peatland–carbon–climate nexus.

Characteristics, Sources, and Mechanisms of Soil Respiration under Simulated Rainfall in a Native Karst Forest in Southwestern China

Rainfall significantly affects soil respiration rates by altering microbial activity and organic matter decomposition. In karst regions, it also impacts carbonate dissolution and precipitation, further influencing soil CO2 flux. Investigating the mechanism of rainfall’s impact on soil respiration is essential for accurately evaluating and predicting changes in terrestrial ecosystems. However, our understanding of the interaction between rainfall and soil respiration in the extensive karst ecosystems of southwestern China remains limited. This study conducted field-based simulated rainfall experiments to examine variations in soil respiration rates and elucidate the associated control mechanisms through stable carbon isotope composition analysis. Simulated rainfall significantly increased the CO2 release via soil respiration. We observed significant differences in the δ13C value of soil-respired CO2 before and after simulated rainfall. Following the rain, the δ13C of soil-respired CO2 was enriched compared to that before the rain. Through isotope data analysis, we found that the increased soil CO2 emissions were primarily driven by heterotrophic respiration, likely stimulated via changes in soil moisture, affecting microbial growth conditions. Furthermore, the variation in soil moisture affected carbonate dissolution and precipitation, potentially increasing the soil CO2 release after rainfall. In conclusion, these findings expand our understanding of rainfall’s effects on soil respiration in the native karst forests of southwestern China, contributing to the prediction of carbon cycling processes in such ecosystems. The data from this study have significant implications for addressing the release of greenhouse gases in efforts to combat climate change.

Updating knowledge of vegetation belts on a complex oceanic island after 20 years under the effect of climate change

Climate change is causing major changes in terrestrial ecosystems and biomes around the world. This is particularly concerning in oceanic islands, considered reservoirs of biodiversity, even more in those with a significant altitudinal gradient and high complexity in the vegetation they potentially harbour. Here, in Tenerife (Canary Islands), we have evaluated the changes in potential vegetation belts during the last 20 years by comparing them with a previous study. Considering the intimate linkage between vegetation and climate, we used a methodology based on phytosociological knowledge, ordination techniques and geostatistics, using multivariate spatial interpolations of bioclimatic data. This has allowed us to spatially detect the variations experienced by eight vegetation units during the last 20 years and incorporating a set of vulnerability metrics. New bioclimatic and vegetation cartography are provided according to the current scenario studied (1990–2019). Our results indicate that summit vegetation, humid laurel forest and thermo-sclerophyllous woodland are the habitats that have experienced a very high area loss and mismatch index, strong changes, if we consider that we are only comparing a period of 20 years. Simultaneously, the more xeric vegetation belts, the dry laurel forest and the pine forest would have benefited from this new warmer and drier climate, by gaining area and experiencing strong upward movements. These changes have not been spatially uniform, indicating that the elevational gradient studied not explain completely our results, showing the influence of the complex island topography. Effective landscape management should consider current remnants, transition capacity and movement limitations to better understand current and future vegetation responses in a global change context.

Soil erosion in the United States: Present and future (2020–2050)

Brought on by anthropogenic actions, accelerated soil erosion inflicts extreme changes in terrestrial and aquatic ecosystems. These field-scale (30 m) changes have neither been fully surveyed in the present, nor predicted for a probable future. Water-driven soil erosion (i.e., sheet and rill erosion) rates across the contiguous United States were estimated for the present, and then predicted for the future using three alternative Shared Socioeconomic Pathway and Representative Concentration Pathway (SSP-RCP) scenarios (2.6, 4.5, and 8.5) of the Coupled Model Intercomparison Project Phase 6 (CMIP6). The G2 erosion model which is integrated with Machine Learning (ML) and Remote Sensing (RS) techniques were used to estimate soil erosion based on gauge observations of long-term precipitation, and climate and land use land cover (LULC) scenarios. The baseline model (2020) estimated soil erosion rates of 2.32 Mg ha−1yr−1 under current conservation agriculture practices (CPs). Maintaining current CPs, future scenarios predict an 8 % to 21 % increase in soil erosion under different combinations of SSP-RCP climate and LULC change scenarios. The findings of this study can help policy makers for future conservation planning on maintaining soil fertility, mitigating environmental impacts, and promoting food security.

Elaboration of the Land use Land Cover Plan of the Subdivision of Monatele in Cameroon

Over the past years, humans have directly or indirectly affected the Earth’s surface through various activities. These changes in terrestrial ecosystems are closely linked with the issue of the sustainability of socio- economic development since they affect essential parts of our natural capital such as climate, soils, vegetation, water resources and biodiversity. Land Cover has undergone several changes in Cameroon since its independence in 1960. One of the major drivers of this change is urbanization. Uncontrolled, rapid urbanization has had many negative impacts on the center region of Cameroon, around the continuum of its headquarter and in Cameroon metropolises such as anarchical constructions, pollution and traffic congestions. Faced with these urbanization issues, planners need to know the spatiotemporal trends of Land Use Land Cover for the past, present and have predictions of possible future patterns in order to better orient their planning. This is possible through the establishment of Land Use Land Cover maps. Remote sensing and Geographic Information Systems represent a cost-effective method for accomplishing this. In this work, we examine the case of Monatélé, a growing city around the Yaoundé metropolis. Satellite images from 2010, 2017, 2022 were downloaded and classified into five classes using the Support Vector Machine algorithm of image classification. It was found that between 2010 and 2022, settlements have increase continuously from 1.61% to 4.28%, water has decreased continuously from 9.81% to 6.72%, forest has experienced a net decrease from 73.77% to 68.25%, agriculture has experienced a net increase from 12.44% to 16.92%, while Bare Land has had a net increase from 2.38% to 3.82%. of the total surface area of the subdivision of Monatélé. Predictions made for 2029 and 2035 show that by 2035, settlements would have increased to 6.58%, water would have decreased to 4.58%, forest would have decreased to 61.22%, agriculture will take 25.19%, and bare land would have almost remained unvaried, taking up 2.43% of the surface area from 2010 to 2035. This will represent for Monatélé an increase in anarchical settlements, an increased loss in biodiversity, an increased pollution, an increase in demand for basic commodities, and an increased pressure on natural resources, if no planning measures are put in place, though it may represent an increase in human capital, an increase in local employment opportunities, a reduction of groceries expenditures.

Inversion of soil carbon, nitrogen, and phosphorus in the Yellow River Wetland of Shaanxi Province using field in situ hyperspectroscopy

Soil nitrogen and phosphorus are directly related to soil quality and vegetation growth and are, therefore, a common research topic in studies on global climate change, material cycling, and information exchange in terrestrial ecosystems. However, collecting soil hyperspectral data under in situ conditions and predicting soil properties, which can effectively save time, manpower, material resources, and financial costs, have been generally undervalued. Recent optimization techniques have, however, addressed several of the limitations previously restricting this technique. In this study, hyperspectral data were taken from surface soils under different vegetation types in the wetlands of the Shaanxi Yellow River Wetland Provincial Nature Reserve. Through in situ original and first-order differential transformation spectral data, three prediction models for soil carbon, nitrogen, and phosphorus contents were established: partial least squares (PLSR), random forest (RF), and Gaussian process regression (GPR). The R2 and RMSR of the constructed models were then compared to select the optimal model for evaluating soil content. The soil organic carbon, total nitrogen, and total phosphorus content models established based on the first-order differential had a higher accuracy when modeling and during model validation than those of other models. Moreover, the PLSR model based on the original spectrum and the Gaussian process regression model had a superior inversion performance. These results provide solid theoretical and technical support for developing the optimal model for the quantitative inversion of wetland surface soil carbon, nitrogen, and phosphorus based on in situ hyperspectral technology.

Rapid recovery of desert shrubs is attributed to imbalance of water supply to demand after disturbance in Northwest China

BackgroundDisturbance is a key driver of changes in terrestrial ecosystems, especially in water limited regions. In the desert ecosystem of Northwest China, shrubs are often foraged by camels and this causes the shrubs lost their aboveground tissues. Although the aboveground tissue could recover after the disturbance, the mechanisms of resprouts’ recovery after the disturbance are still poorly understood. We investigated the morphological and physiological characteristics and root water uptake sources of resprouts and non-disturbed seedlings of four desert shrub species that were often foraged by camels.ResultsThe results showed that the resprouts grew rapidly after the removal of aboveground tissue. The height and aboveground biomass of resprouts reached the level of 5-year-old seedlings following a growing season. Compared to un-disturbed seedlings, higher leaf water potential, leaf hydraulic conductance and photosynthesis rate were observed in resprouts, indicating that resprouts grew rapidly after disturbance. Furthermore, we found that the root water uptake source did not change after disturbance. This indicated that the roots of resprouts kept intact water uptake capacity after disturbance, which could keep supplying sufficient water to the aboveground tissue. Due to the removal of aboveground tissue of the resprouts, the water demand of aboveground tissue decreased, which induced an imbalance of water supply from roots to demand of aboveground tissues of resprouts. This explained the improved physiological performance and rapid recovery of resprouts after disturbance.ConclusionsThe imbalance of water supply to demand contributes to the rapid recovery of desert shrubs after disturbance. The findings provide insight into the eco-physiological mechanism for the maintenance of desert ecosystems that are facing disturbance.

Disentangling the variability of symbiotic nitrogen fixation rate and the controlling factors.

Symbiotic nitrogen (N) fixation (SNF), replenishing bioavailable N for terrestrial ecosystems, exerts decisive roles in N cycling and gross primary production. Nevertheless, it remains unclear what determines the variability of SNF rate, which retards the accurate prediction for global N fixation in earth system models. This study synthesized 1230 isotopic observations to elucidate the governing factors underlying the variability of SNF rate. The SNF rates varied significantly from 3.69 to 12.54 g N m-2 year-1 across host plant taxa. The traits of host plant (e.g. biomass characteristics and taxa) far outweighed soil properties and climatic factors in explaining the variations of SNF rate, accounting for 79.0% of total relative importance. Furthermore, annual SNF yield contributed to more than half of N uptake for host plants, which was consistent across different ecosystem types. This study highlights that the biotic factors, especially host plant traits (e.g. biomass characteristics and taxa), play overriding roles in determining SNF rate compared with soil properties. The suite of parameters for SNF lends support to improve N fixation module in earth system models that can provide more confidence in predicting bioavailable N changes in terrestrial ecosystems.

Creation and environmental applications of 15-year daily inundation and vegetation maps for Siberia by integrating satellite and meteorological datasets

As a result of climate change, the pan-Arctic region has seen greater temperature increases than other geographical regions on the Earth’s surface. This has led to substantial changes in terrestrial ecosystems and the hydrological cycle, which have affected the distribution of vegetation and the patterns of water flow and accumulation. Various remote sensing techniques, including optical and microwave satellite observations, are useful for monitoring these terrestrial water and vegetation dynamics. In the present study, satellite and reanalysis datasets were used to produce water and vegetation maps with a high temporal resolution (daily) and moderate spatial resolution (500 m) at a continental scale over Siberia in the period 2003–2017. The multiple data sources were integrated by pixel-based machine learning (random forest), which generated a normalized difference water index (NDWI), normalized difference vegetation index (NDVI), and water fraction without any gaps, even for areas where optical data were missing (e.g., cloud cover). For the convenience of users handling the data, an aggregated product is provided, formatted using a 0.1° grid in latitude/longitude projection. When validated using the original optical images, the NDWI and NDVI images showed small systematic biases, with a root mean squared error of approximately 0.1 over the study area. The product was used for both time-series trend analysis of the indices from 2003 to 2017 and phenological feature extraction based on seasonal NDVI patterns. The former analysis was used to identify areas where the NDVI is decreasing and the NDWI is increasing, and hotspots where the NDWI at lakesides and coastal regions is decreasing. The latter analysis, which employed double-sigmoid fitting to assess changes in five phenological parameters (i.e., start and end of spring and fall, and peak NDVI values) at two larch forest sites, highlighted a tendency for recent lengthening of the growing period. Further applications, including model integration and contribution to land cover mapping, will be developed in the future.

Extreme environments simplify reassembly of communities of arbuscular mycorrhizal fungi.

The ecological impacts of long-term (press) disturbance on mechanisms regulating the relative abundance (i.e., commonness or rarity) and temporal dynamics of species within a community remain largely unknown. This is particularly true for the functionally important arbuscular mycorrhizal (AM) fungi; obligate plant-root endosymbionts that colonize more than two-thirds of terrestrial plant species. Here, we use high-resolution amplicon sequencing to examine how AM fungal communities in a specific extreme ecosystem-mofettes or natural CO2 springs caused by geological CO2 exhalations-are affected by long-term stress. We found that in mofettes, specific and temporally stable communities form as a subset of the local metacommunity. These communities are less diverse and dominated by adapted, "stress tolerant" taxa. Those taxa are rare in control locations and more benign environments worldwide, but show a stable temporal pattern in the extreme sites, consistently dominating the communities in grassland mofettes. This pattern of lower diversity and high dominance of specific taxa has been confirmed as relatively stable over several sampling years and is independently observed across multiple geographic locations (mofettes in different countries). This study implies that the response of soil microbial community composition to long-term stress is relatively predictable, which can also reflect the community response to other anthropogenic stressors (e.g., heavy metal pollution or land use change). Moreover, as AM fungi are functionally differentiated, with different taxa providing different benefits to host plants, changes in community structure in response to long-term environmental change have the potential to impact terrestrial plant communities and their productivity.IMPORTANCEArbuscular mycorrhizal (AM) fungi form symbiotic relationships with more than two-thirds of plant species. In return for using plant carbon as their sole energy source, AM fungi improve plant mineral supply, water balance, and protection against pathogens. This work demonstrates the importance of long-term experiments to understand the effects of long-term environmental change and long-term disturbance on terrestrial ecosystems. We demonstrated a consistent response of the AM fungal community to a long-term stress, with lower diversity and a less variable AM fungal community over time under stress conditions compared to the surrounding controls. We have also identified, for the first time, a suite of AM fungal taxa that are consistently observed across broad geographic scales in stressed and anthropogenically heavily influenced ecosystems. This is critical because global environmental change in terrestrial ecosystems requires an integrative approach that considers both above- and below-ground changes and examines patterns over a longer geographic and temporal scale, rather than just single sampling events.

The impacts of rising vapour pressure deficit in natural and managed ecosystems.

An exponential rise in the atmospheric vapour pressure deficit (VPD) is among the most consequential impacts of climate change in terrestrial ecosystems. Rising VPD has negative and cascading effects on nearly all aspects of plant function including photosynthesis, water status, growthand survival. These responses are exacerbated by land-atmosphere interactions that couple VPD to soil water and govern the evolution of drought, affecting a range of ecosystem services including carbon uptake, biodiversity, the provisioning of water resourcesand crop yields. However, despite the global nature of this phenomenon, research on how to incorporate these impacts into resilient management regimes is largely in its infancy, due in part to the entanglement of VPD trends with those of other co-evolving climate drivers. Here, we review the mechanistic bases of VPD impacts at a range of spatial scales, paying particular attention to the independent and interactive influence of VPD in the context of other environmental changes. We then evaluate the consequences of these impacts within key management contexts, including water resources, croplands, wildfire risk mitigationand management of natural grasslands and forests. We conclude with recommendations describing how management regimes could be altered to mitigate the otherwise highly deleterious consequences of rising VPD.

Soil enzyme activity and stoichiometry in response to precipitation changes in terrestrial ecosystems

Soil extracellular enzymes play a key role in catalyzing organic matter decomposition, and enzymatic stoichiometry is a critical metric for reflecting shifts in soil microbial functions. Changes in precipitation can influence belowground ecosystem processes by regulating soil microbial functions under global change. However, the effects of increased (+PRE) and decreased precipitation (–PRE) on soil enzyme activity and stoichiometry remain poorly understood. In this study, we performed a global meta-analysis using 167 observations from 61 field studies to investigate the effects of precipitation changes on soil enzyme activity and stoichiometry. The results showed that + PRE increased the N- and P-acquiring enzyme activities by an average of 26% and 13%, respectively. +PRE led to a decrease in the enzymatic C:N ratio in the forests and dry areas. The –PRE had no general effect on soil C- and N-acquiring enzymes or their ratios. Soil N-acquiring enzyme activity, enzymatic C:N and N:P ratios were sensitive to slight + PRE, suggesting that moderate precipitation is conducive to enzyme production by microbial communities. Soil enzyme activity and stoichiometry were predominantly influenced by the experimental duration of precipitation changes, and their response to precipitation were closely associated with root biomass and the fungi-to-bacteria ratio. Collectively, precipitation changes may have a general impact on N-acquiring enzyme activity with consequences for the stoichiometry of soil resource recycling under global changes.

Spatial and Temporal Evolution and Prediction of Carbon Storage in Kunming City Based on InVEST and CA-Markov Model

Land use/cover change is an important driving factor for carbon stock changes in terrestrial ecosystems and affects the carbon cycle of the whole ecosystem. Taking Kunming City as a case study, based on the modified carbon density coefficient, this study analyzed the spatio-temporal characteristics of carbon storage changes in the terrestrial ecosystem under different land use scenarios from 2000 to 2020 and "three-line" constraints by coupling the carbon storage module of the InVEST model and CA-Markov model. The results showed that:① cultivated land, forest land, and grassland were the main types of land use in Kunming City, and land use transfer also occurred among the three types. ② From 2000 to 2020, the overall carbon storage in Kunming City was low in the south and high in the north, and the carbon storage decreased yearly with a cumulative loss of 5.27×106 t. The degradation of forest land and grassland was the main reason for the decrease in carbon storage. ③ From 2020 to 2030, the carbon storage of the four scenarios should decrease, and the decline in carbon storage in the inertia development scenario was the most obvious, which was mainly caused by the rapid expansion of construction land. The cultivated land protection scenario effectively slowed down the reduction in carbon storage compared with the inertia development scenario. The ecological protection scenario could enhance the carbon sequestration capacity of the study area, with carbon storage reaching 262.49×106 t, but could not effectively control the reduction in cultivated land area. The scenario of preventing urban expansion effectively inhibited the disorderly expansion of construction land and indirectly prevented further reduction in carbon storage. Therefore, the cultivated land protection scenario, ecological protection scenario, and urban expansion prevention scenario can be considered comprehensively in the study area, which could not only increase the carbon sink space of the study area but also ensure food and ecological security.

Quantitative analysis of fractional vegetation cover in southern Sichuan urban agglomeration using optimal parameter geographic detector model, China

Vegetation is a main part of ecosystems and an essential indicator for monitoring changes in terrestrial ecosystems. It is crucial for us to discover the temporal and spatial features and potential drivers of vegetation change to promote regional ecological environment protection and management. However, it can be difficult to pinpoint the causes of vegetation change when considering both human activity and climate change. We used trend and stability method to study the temporal and spatial patterns of vegetation evolution in the South Sichuan Urban Agglomeration (SSUA) from 2001 to 2021 with the Google Earth Engine (GEE) platform. An optimal parameter-based geographical detector (OPGD) model was applied to optimize the spatial scale and zoning effect of geographic data, effectively solving the problem of spatial data heterogeneity. It compensates for the inadequacies of conventional approaches that neglect the modifiable areal units problem (MAUP), and improving the science and accuracy of quantitative analysis and identification of vegetation drivers. We studied demonstrate that (1) During the last 21 years, Fractional Vegetation Cover (FVC) has generally been in good condition, with a multi-year average FVC greater than 0.4 of 71.74 %, and the vegetation is significantly characterized by a low fluctuation of 78.16 %. However, there is a significant trend of vegetation degradation, accounting for 8.89 %, mainly in the main urban areas of Neijiang and Zizhong County, Lu County of Luzhou City, Gao County of Yibin City, and other areas with rapid urbanization. In general, FVC is low in the built-up areas of towns and along transportation roads, while the mountainous and agricultural areas have a high level of vegetation cover. (2) The OPGD model detection showed the optimal spatial scale of vegetation cover in this study region was 2 km. Optimal discrete parameter combinations for slope, elevation, temperature and GDP are quantile breaks with 9 intervals, which contribute to improved scientific accuracy and precision in studies of vegetation change and its drivers. (3) The explanatory power of urbanization rate, land use type, slope, GDP, population density, and average annual precipitation were all above 20 % and were the main drivers of vegetation change. Moreover, any two factors interacted in a nonlinear enhancement and a bi-variable enhancement, increasing the impact on vegetation spatial variation. When the slope is 26.9°∼87.4°, the elevation is 967 m ∼ 4207 m, the average annual temperature is 0.18 °C ∼ 13.6 °C, the average annual precipitation is 328 mm ∼ 439 mm, the GDP is 4.07 ∼ 5.23 million yuan km−2, the population density is 12.7 ∼ 21.1 people/km2, the urbanization rate is 33.4 %∼37.7 %, and the land-use type is forest land, the FVC value is the highest and suitable for vegetation growth. The study showed that using the OPGD model to detect the zoning effects and spatial scale of the explanatory variables solves for the shortcomings of the previous methods for variable regional units and discrete methods, may more precisely explore the features of temporal and spatial changes in the vegetation and the driving mechanisms, offers scientific references for environmental conservation and long-term economic growth in the region.

Neolithic human activity caused eutrophication in small central European lakes

Human activities during the Early Neolithic have had major influences on central European terrestrial ecosystems through deforestation, burning, animal husbandry and agriculture. However, much less is known about how these landscape-scale changes affected aquatic ecosystems. In this study, we examined diatom assemblages preserved in radiocarbon dated and intermittently laminated sediment cores collected at Burgäschisee and Moossee, two small lakes on the Swiss Plateau, and compared the results with archaeological evidence for Neolithic lakeshore settlements and palaeobotanical records indicating distinct catchment scale phases of changing land use. The new diatom records were used to reconstruct changes to the lake ecosystem and of lake water nutrient concentrations from 6600 to 3800 calibrated radiocarbon years BP (cal yr BP). Blooms of small sized Stephanodiscus spp. together with algal remains (Cyanobacteria, Chlorophyta) indicate distinct phases of lake nutrient enrichment particularly during a land use and settlement phase associated with the Cortaillod culture (5800–5500 cal yr BP). In contrast, other land use phases were not associated with clear indications of water quality changes. Diatom response to human impact in the catchment was more pronounced at Burgäschisee relative to Moossee, notably for the phase corresponding to the Cortaillod culture.The new results agree with previous studies that provided evidence of Neolithic human impact on lake ecosystems in central Europe. For small lakes, such as Moossee and Burgäschisee, the establishment of Neolithic lakeside settlements and land uses did not only lead to pronounced terrestrial ecosystem changes in the catchment but apparently influenced the lake ecosystems themselves. The different response of the diatom assemblages in the two lakes also suggests that the impact of land use on nutrient concentrations and algal communities varied between lakes during the Neolithic, presumably due to different intensities of human impact at different sites, but likely also due to differences in geographical and hydrological settings of the lakes (basin morphologies, stratification, and mixing regimes).

High-resolution chronostratigraphy of late Mesozoic sequences in northern North China: Implications for the linkages among intracontinental orogeny, volcanism, Jehol Biota, and Pacific plate subduction

Abstract Subduction of the paleo-Pacific plate during the late Mesozoic is thought to have been responsible for the destruction of the North China craton, manifested by intense volcanism, lithospheric deformation, and dramatic changes in surface morphology and terrestrial ecosystems. However, the timing and correlations of these consequential events remain obscure. This issue was addressed here by carrying out a high-resolution geochronologic study on the Upper Jurassic–Lower Cretaceous sequences of the Luanping basin, northern Hebei Province, China. Secondary ion mass spectrometry (SIMS) and chemical abrasion–isotope dilution–isotope ratio mass spectrometry (CA-ID-IRMS) zircon U-Pb ages from samples near the boundaries of the stratigraphic units help to redefine the chronostratigraphic framework of this basin and more importantly reveal that the second phase of the Yanshanian orogeny, representing a tectonic transition from flat to steep subduction of the paleo-Pacific plate, occurred within 0.87 ± 0.10 m.y. between 134.162 ± 0.091 Ma and 133.295 ± 0.043 Ma. Crustal extension then followed and resulted in development of rift basins and vigorous volcanism. The Jehol Biota came into being in Lower Cretaceous successions formed after ca. 130 Ma. The late Mesozoic Luanping basin therefore records how the subduction of the paleo-Pacific plate drove intracontinental orogeny, volcanism, basin development, and ecosystem evolution.