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The existence of global warming is common knowledge. However, it can be predicted that there may be cooling zones worldwide based on the mechanism of terrestrial biophysical processes. Here, the Theil–Sen median trend, the Mann–Kendall trend test method, continuous wavelet transformation, and the Hurst exponent were used to study the cooling trends, abrupt change times, periodicity, and future sustainability of temperature changes in different cooling zones since the 1900s based on the CRU dataset. We found an amazing result; 8,305,500 km2 of land surface had been cooling since the 1900s, covering five continents and 32 countries, accounting for 86% of land area in China, and distributed over 16 zones. The average cooling rate of the cooling zones was −0.24 °C/century. The maximum cooling rate was −1.40 °C/century, and it was 1.43 times the average rate of global land warming (0.98 °C/century). The cooling zones near the sea were greatly influenced by ocean currents and were mainly affected by a small time scale periodicity of less than 30 years, whereas the cold zones located relatively far from the sea and less affected by ocean currents were mainly affected by medium time scales of more than 30 years. Moreover, 32.33% of the cooling zones, involving 2,684,900 km2, will be continuously cooling in the future, and the rest will probably warm up in 2114, 2041, 2096, 2099, 2119, 2073, 2048, and 2101, respectively. The study will help us to further understand the essential characteristics of global climate change, and to find more theoretical bases for mitigating global warming and exploring surface cooling mechanisms. [ABSTRACT FROM AUTHOR]

Identifying the response of runoff changes to extreme climate evolution was of great scientific significance for the rational regulation of watershed water resources and the prevention of hydrological disasters. However, the time–frequency response relationships were not clear. The Yinjiang River watershed, a typical watershed with karst trough valley areas, was chosen to identify the impact of different climatic driving factors on runoff changes from 1984 to 2015. Continuous wavelet transform (CWT), cross-wavelet transform (XWT), and wavelet coherence transform (WTC) were performed to study the response relationship and time–frequency effect between runoff changes and extreme climate change at different time scales. The main results showed that: (1) Twelve extreme climate indices (ECIs) were detected to have a significant impact on runoff changes, mainly on a 6-year time scale; (2) The R10 and Rx1day in extreme precipitation index and SU34.4 and TNx in the extreme temperature index were the main driving factors of runoff changes, which had relatively large impacts on runoff changes in high and low energy vibration regions. However, the remaining eight ECIs that passed the 0.05 confidence level showed relatively large impacts on runoff changes only in low energy vibration regions; (3) The transition of the interaction between ECIs and runoff changes in high and low time–frequency scales was related to the abrupt change characteristics of the ECIs. The correlation of abrupt change was an important reason for the emergence of highly correlated regions that trigger high and low energy vibrations; (4) As a whole, the extreme precipitation events were ahead of runoff changes at the high time–frequency scale and exhibited small lag effects at the low time–frequency scale, while extreme temperature events were mainly ahead of runoff changes. This study has effectively revealed the impact of climate factors at different scales on runoff changes, and provides a theoretical understanding for regulating and managing water resources in karst basins. [ABSTRACT FROM AUTHOR]

The Yinjiang River watershed is a typical karst watershed in Southwest China. The present study explored runoff change and its responses to different driving factors in the Yinjiang River watershed over the period of 1984 to 2015. The methods of cumulative anomaly, continuous wavelet analysis, Mann-Kendall rank correlation trend test, and Hurst exponent were applied to analyze the impacts of climate change and human activities on runoff change. The contributions of climate change and human activities to runoff change were quantitatively assessed using the comparative method of the slope changing ratio of cumulative quantity (SCRCQ). The following results were obtained: (1) From 1984 to 2015, runoff and precipitation exhibited no-significant increasing trend, whereas evaporation exhibited significant decreasing trend. (2) In the future, runoff, precipitation, and evaporation will exhibit weak anti-persistent feature with different persistent times. This feature indicated that in their persistent times, runoff and precipitation will continuously decline, whereas evaporation will continuously increase. (3) Runoff and precipitation were well-synchronized with abrupt change features and stage characteristics, and exhibited consistent multi-timescale characteristics that were different from that of evaporation. (4) The contribution of precipitation to runoff change was 50%–60% and was considered high and stable. The contribution of evaporation to runoff change was 10%–90% and was variable with a positive or negative effects. The contribution of human activities to runoff change was 20%–60% and exerted a low positive or negative effect. (5) Climatic factors highly contributed to runoff change. By contrast, the contribution of human activities to runoff change was low. The contribution of climatic factors to runoff change was highly variable because of differences among base periods. In conclusion, this paper provides a basic theoretical understanding of the main factors that contribute to runoff change in a karst watershed. [ABSTRACT FROM AUTHOR]

• We quantify the contributions of CC and HA to karst vegetation productivity. • We identify the critical control areas in which CC and HA contribute to NPP changes. • A major decline in NPP was detected in the areas where NDVI increased. • CC weakens the positive effect of HA on vegetation productivity in southern China. China has conducted large-scale eco-afforestation projects in karst areas for mitigating rocky desertification in recent decades. However, the benefits of karst vegetation productivity restoration and the contributions of influencing factors are unclear. We analyzed the impacts of climate change (CC) and human activity (HA) on vegetation productivity change based on the net primary productivity (NPP) by using the partial derivatives and designing eight different scenarios. Results demonstrated that the average NPP over the entire vegetation-covered karst area exhibited an unremarkable increasing trend (0.92 g C m−2 yr−1) and a major decline in NPP was detected in the areas where NDVI increased from 2000 to 2015 (0.44 million km2, 29.07%). Solar radiation (−0.91 g C m−2 yr−1) was the preponderant climatic factors exhibiting negative contribution to NPP changes. A significant positive contribution was caused by HA (1.53 g C m−2 yr−1) on NPP variations, while a negative contribution was induced by CC (−0.61 g C m−2 yr−1). CC and HA showed the more similar contribution proportion to NPP increasing (51.94% vs 48.06%), but with great difference (68.43% vs 31.57%) for NPP decreasing. 39.83% of the areas involved in NPP decreasing was attributed to the accelerating consumption of autotrophic respiration while the rest (60.17%) was contributed by rapid decrease of gross primary productivity, respectively. In southern karst area, HA showed a positive impact (59.07%) on NPP increasing. However, the negative contribution from CC (70.72%) due to the rapid and constant decline of solar radiation completely counteracted this, leading to a greater NPP decrease. This study stresses the importance of negative effect from CC on karst vegetation productivity change and provides location guidance for further implementation of ecological protection projects in southern China. [ABSTRACT FROM AUTHOR]

Carbonate rock chemical weathering carbon sinks reduce the rate of increase of the atmospheric CO2 concentration and global warming. However, uncertainty still exists in the estimation results of carbonate rock chemical weathering carbon sink fluxes (CCSF), and the contributions of climate change and ecological restoration to the CCSF are not clear. To this end, we compiled published site data on ion concentrations in different watersheds in China and used a classical thermodynamic dissolution model to reassess the potential and spatial and temporal patterns of the CCSF in China from 1991 to 2020. We quantified the contributions of temperature (MAT), precipitation (MAP), evapotranspiration (ET), soil water (SM), and the normalized difference vegetation index (NDVI) to the CCSF. The results revealed that (1) China's CCSF was 22.76 t CO2 km−2 yr−1, which was higher than the global average (15.771CO2 km−2 yr−1). The total carbonate rock chemical weathering carbon sink (CCS) was 4772.67×104 t CO2, contributing 14.91% of the global CCS through a carbonate rock area of 252.98×104 km−2. (2) China's CCSF decreased gradually from southeast to northwest, with values of 33.14, 12.93, and 7.27 t CO2 km−2 yr−1 in the southern karst, Qinghai-Tibetan karst, and northern karst regions, respectively. (3) The overall CCSF in China exhibited an increasing trend from 1991 to 2020, with a rate of increase of 0.16 t CO2 km−2 yr−1. (4) The contributions of the MAP, MAT, ET, SM, and NDVI to the CCSF were 63.3%, 3.02%, 27.5%, 3.1%, and 3.05%, respectively. Among them, the increase in precipitation was the main contributor to the increase in the CCSF in China over the last 30 years, while the enhancement of ET offset part of the positive contribution of the increase in precipitation to the CCSF. In conclusion, the results of this study provide a systematic quantification of the magnitude, the patterns, and the influencing factors of CCS over a long time series in China. The results are of great significance and provide a reference for the diagnosis and gap analysis of the national and global carbon neutrality capacities. [ABSTRACT FROM AUTHOR]

Karst rocky desertification (KRD) has become one of the most serious ecological and environmental problems in karst areas. At present, mapping KRD with a high accuracy and on a large scale is still a difficult problem in the control of KRD. In this study, a random forest (RF) based on maximum information coefficient and correlation coefficient feature selection is proposed to predict KRD. Nine predictors stood out as feature factors to estimate KRD. Rock exposure was the most important predictor, followed by fractional vegetation cover for the prediction of KRD processes. The kappa and classification accuracy indexes were to evaluate the performance of the model. We recorded overall accuracy rate and kappa index values of 94.7% and 0.92 for the testing datasets respectively. The RF model was then used to predict the KRD in 2001, 2011, 2016, and 2020, and it was found that the KRD in the study area has exhibited a positive trend of improvement. Therefore, the use of multisource remote sensing data combined with the RF model can obtain better prediction results of KRD, thereby providing a new idea for large-scale estimation of the KRD in peak-cluster depression. [ABSTRACT FROM AUTHOR]

Ecosystem services (ESs) synergies have been broadly studied, whose synergy control areas and driving mechanisms were still not fully understood. Here, We analyzed soil conservation (SC), water yield (WY), net primary productivity (NPP) and food supply (FS) on the basis of geospatial analysis techniques from 1992 to 2015. The results showed that the SW karst areas contributed 23.7% of SC and 14.56% of NPP with only 8.4% of China's continent. 49.28% of China's land was synergy control areas, while accounted for 82.23% in the SW karst areas. The cause of this phenomenon was twofold, one was the significant increase in NDVI was mainly due to human activities (HA), and the coincidence rates between the HA dominated areas and the synergies control areas up to 90.7%. These results emphasized that ecological engineering was a key factor of the synergy among multi-ESs, the synergy control areas should be priority for ecological restoration. [ABSTRACT FROM AUTHOR]

Cropland area has long been used as a key indicator of food security. However, grain yield is not solely controlled by the area of the cropland. Therefore, we proposed a new indicator to assess food security. Results show that from 1992 to 2004, the global cropland area increased by 840 200 km2 (99.4%), but the grain yield increased only by 310 million t (29.1%); and from 2004 to 2015, the cropland area decreased by 39 000 km2 (4.64%), but the grain yield increased by 370 million t (70.84%). This result showed that grain yield was not linearly correlated with cropland area, and delimiting the threshold of cropland protection may not guarantee food security. Combined with further correlation analysis, we found that the increase in the global grain yield was more closely related to the harvested area (R2 = 0.94), which indicated that the harvested area is a more scientific and accurate indicator than cropland area in terms of guaranteeing food security. Therefore, if governments want to ensure the food security, they should choose a new and more accurate indicator: harvested area rather than cropland area. [ABSTRACT FROM AUTHOR]

Stated preference valuation of ecosystem services involves participants answering hypothetical questions to express preferences. Participants tend to respond to the hypothetical questions separately, without any deliberation (the process of considering and discussing within a group). However, a relatively recent development in deliberation research involves asking participants to state preferences via deliberation. Deliberation is historically conducted in-person but can now also be done online. This paper covers the strengths and limitations of integrating online deliberation into stated preference valuation, including: (1) comparison between stated preference valuation with and without deliberation, (2) comparison between in-person and online deliberation, and (3) comparison between online deliberation media, such as typing, video meetings, and voice calls. Conducting deliberation can broaden participants' understanding of the target ecosystem services and others' preferences. However, this requires participants' willingness to deliberate and increases time investment. Online deliberation has lower costs and travel restrictions and higher time efficiency and confidentiality of personal information than in-person deliberation. However, people with low abilities or willingness to use online media are disadvantaged. Differences in the online deliberation media may reduce or improve the inclusiveness, engagement, and openness of deliberations in ways that affect valuation results. We also provide suggestions for selecting deliberation media and mitigating deliberation bias derived from the choice of deliberation media. Further research should explore how to improve time efficiency and affordability of online deliberation, how to promote inclusiveness, engagement, and openness of online deliberation, and how different deliberation media affect deliberation quality and valuation results. • Preferences for ecosystem services can be stated via online deliberation. • Deliberation promotes information sharing and mutual learning. • Online deliberation may be more flexible and confidential than in-person deliberation. • Effective deliberation should be inclusive, engaging, and open. • Deliberation media (e.g., typing, video meetings) may affect deliberation effectiveness. [ABSTRACT FROM AUTHOR]

Soil moisture restricts the ecological restoration in karst, but studies on soil moisture storage (SMS) in karst are lacking. Thus, this study analyzed the characteristics of SMS in the karst area of China (K) and revealed the relationships of SMS with its influencing factors. The main results are as follows: (1) Average SMS in K is higher than that in the non-karst area (N). However, when SMS is below the thresholds 12 mm (0–7 cm) and 563.6 mm (0–289 cm), SMS in K is lower than that in N. (2) SMS in K experienced a decreasing trend in 1979–2017. (3) SMSs of K and N increase with precipitation class, but the SMS in K is more sensitive to precipitation. (4) SMSs of Agriculture and Forest landcovers in K significantly reduced in 1979–2017. Overall, the SMSs in K are high, but the soil water is easily lost due to serious soil erosion. [ABSTRACT FROM AUTHOR]

Karst Rocky Desertification (KRD) has become the most serious ecological disaster in Southwest China. We used the data of Thematic Mapper (TM) images from 1990, 1995, 2000, 2004, and 2011 and the 2016 Operational Land Imager (OLI) image. These sensing images were pre-processed by removing non-karst areas based on lithology and cutting away the land types impossibly generating KRD from land use maps. Then, we used a Classification And Regression Tree (CART) to classify the KRD. We want to improve the interpretation accuracy of KRD through the above steps. The results were as follows: (1) The KRD experiences the evolution process of 'first deterioration and then improvement'. The rate is −4.94 km2.a−1 over a period of 1990 to 2004, and the rate is 36.48 km2.a−1 from 2004 to 2016; (2) The most influential factors causing KRD formation are the lithology and the resident population density, with contribution rates of 30.17% and 25.86%, respectively. [ABSTRACT FROM AUTHOR]

• Average start of the photosynthetic period in China was on the 123rd day of the year. • The average start of the photosynthetic period advances at a rate of 4.3 d (10 a)−1. • 64% of the region is temperature controlled, others are precipitation controlled. • Importance of temperature and precipitation determined by pre-season precipitation. • Climate change increases NPP by advancing the start of the photosynthetic period. In the context of global warming, the advancement of spring phenology in northern and temperate regions due to increased temperatures has been widely reported. Early and delayed start of the photosynthetic period (SOP) directly affects the vegetation net primary productivity (NPP). However, the interrelationship between climate change, the SOP, and the NPP is unclear. In this paper, we use the dynamics of decadal daily solar-induced chlorophyll fluorescence data to calculate the response of Chinese vegetation photosynthetic phenology to climate change and its impact on the NPP over the last 20 years. The results found that over the last 20 years, the average SOP in China was on the 123rd day of the year, and the SOP has advanced at an average rate of 4.3 d (10 a)−1, with a faster trend of SOP advancement in highland and high-altitude areas. 64% of SOP in China is controlled by temperature; 36% of the SOP in China is controlled by precipitation, and the relative importance of temperature and precipitation was reversed as the precipitation gradient decreased, with SOP dominated by temperature when pre-season precipitation ≧300 mm, and SOP dominated by precipitation when pre-season precipitation ≦300 mm. Finally, we find that climate change indirectly increases vegetation NPP by advancing SOP. Our study emphasizes the importance of precipitation on phenology. It provides a scientific basis for understanding and predicting the response of spring photosynthetic phenology to climate change and the contribution of spring phenology to carbon estimation in terrestrial ecosystems. [ABSTRACT FROM AUTHOR]

The rapid and accurate grasp of changes in residences is crucial for urban planning and urbanisation. However, the traditional methods for extracting residences exists several problems, which lead to inaccurate extraction results. In this study, the Landsat image is used to establish a new method for extracting the residences quickly and accurately. The specific steps are as follows: (1) We calculate surface albedo to exclude the interference of waters and shadows; (2) Using single-band threshold method, we eliminate the interference of shadows; (3) Normalized Difference Vegetation Index is calculated to exclude the effects of vegetation; (4) Roads are removed by calculating the shape index. Verification shows that the accuracy of this extraction method is 92.81%, which is more accurate than the traditional methods and solves the problems existed in the traditional methods. This novel method is a new reference for other land cover research on the technical aspect. [ABSTRACT FROM AUTHOR]

Most of the ions in rivers come from the migration of weathering products of continental rocks. However, there is no clear understanding of the dynamic changes in ions derived from the chemical weathering of rocks and their feedback to climate change. This affects our comprehension of the evolution of life and the cycle of matter on Earth. In the present study, we established a dataset with a 0.25° × 0.25° spatial resolution for the major dissolved ions and their total fluxes in the riverine transported (ICWR) at the global scale from 1980 to 2020 using the Lechuga-Crespo model and the random forest algorithm. The results show that from 1980 to 2009, the total amount of the ICWR was 5.4·109 Mg yr−1, of which alkalinity accounted for 45%, Ca2+ accounted for 17%, SO 4 2− accounted for 14%, Na+ accounted for 9%, Cl− accounted for 8%, Mg2+ accounted for 6%, and K+ accounted for 2%. In addition, the ICWR increased at a rate of 6.47·106 Mg yr−1. The most obvious trend was in the area with high ionic activity coefficients between 30° N and 30° S. The growth trend of the ICWR during 2010–2020 was seven times that during 1980–2009, resulting in a 30% increase in the ICWR over the past 40 years. This study highlights the critical role of climate change in the transport and evolution of the ICWR, and explores their impact on vegetation change. It has important reference value for responding to the eco-environmental problems caused by climate change. [Display omitted] • Climate change has caused a 30% increase in the ICWR. • The rate of change in alkalinity was the fastest, and the rate of change in Mg2+ was the slowest. • Runoff, nitrogen deposition, and soil moisture were important factors affecting the changes in the ICWR. • A dataset was created for the riverine transported ICWR on a global scale, from 1980 to 2020. • The positive effect of ICWR on NPP was greater than the negative effect. [ABSTRACT FROM AUTHOR]

Carbonate carbon sequestration (CS) can aid in solving the problem of terrestrial residual carbon sinks and imbalances in the global carbon budget. Thus, complete understanding of the magnitude, spatiotemporal distribution, and evolution of this sequestration is highly desirable. On the basis of random forest regression and maximal potential dissolution model for carbonate, we estimated the CS of typical carbonate weathering in China from 2000 to 2014, that is, the sequestration of limestone weathering, using long-term ecologic, meteorological, hydrological raster data, and monitored data from 44 watersheds in China and surrounding regions. We extended our analyses by systematically exploring the spatiotemporal pattern and evolution trend of the flux and total sequestration. High levels of ionic activity coefficients of Ca2+ and HCO3− in limestone regions were observed to be mainly distributed in Northern and Northwestern China with a clear gradient from northwest to southeast. With a contrary spatial pattern, the annual average CS flux (CSF) of limestone weathering in China was estimated to be 4.28 t C km−2 yr−1, with high values mainly in the karst zones in Southeastern China. The mean CSF in different latitudes showed that Southern China (south of 28.14°N) was the region with the largest interannual fluctuation of flux and CSF increases as latitude decreases. The mean CSF in subtropical and tropical (TR) regions was the maximum of all major climate types, and for the frigid (F), mid-temperate (MTE), warm temperate (WTE), and temperate (TE) major climates; the CSF in the desert (D) subdivided climate was the minimum of these climates. By contrast, the values in grassland (G) and broad-leaved forest subdivided climate were the maximum. The pixel-based trend analysis indicated that the CSF of limestone weathering in China was slightly increasing in the period 2000–2014 with a rate of 0.036 t C km−2 yr−1. Furthermore, the annual total CS was estimated to be 7.07 Tg carbon per year (Tg C yr−1) with high levels in 2002, 2008, and 2010, and the minimum appeared in 2011 with a slightly increasing trend of the total CS being observed with a rate of 0.06 Tg C yr−1. Tibet Autonomous Region was the administrative division with the largest total CS of limestone weathering (1.20 Tg C yr−1) in China, and karst zones in Southeastern China had the largest total CS (4.95 Tg C yr−1) which accounts for 70.01% of that in the three divided karst regions. On the basis of the diversity of rock chemical weathering carbon cycle mechanisms of different carbonate rock types, we estimated that the total CS of carbonate weathering in China may reach 11.37 Tg C yr−1 (the sink was approximately 5.02 t C km−2 yr−1), which amounts to 16.20% of the total biomass CS in China, furthermore, the CSF of carbonate weathering in China can reach 6.54 t C km−2 yr−1 if excluding the interference of the negative runoff. This finding indicates that CS of carbonate weathering is an indispensable part of China's terrestrial carbon sink system. The research pattern of this study was important for further improving the accuracy of the estimation for the global carbonate weathering carbon sink. [ABSTRACT FROM AUTHOR]

Abstract The magnitudes, spatial distributions and contributions to global carbon budget of the global carbonate carbon sink (CCS) still remain uncertain, allowing the problem of national measurement of CCS remain unresolved which will directly influence the fairness of global carbon markets and emission trading. Here, based on high spatiotemporal resolution ecological, meteorological raster data and chemical field monitoring data, combining highly reliable machine learning algorithm with the thermodynamic dissolution equilibrium model, we estimated the new CCS of 0.89 ± 0.23 petagrams of carbon per year (Pg C yr−1), amounting to 74.50% of global net forest sink and accounting for 28.75% of terrestrial sinks or 46.81% of the missing sink. Our measurement for 142 nations of CCS showed that Russia, Canada, China and the USA contribute over half of the global CCS. We also presented the first global fluxes maps of the CCS with spatial resolution of 0.05°, exhibiting two peaks in equatorial regions (10°S to 10°N) and low latitudes (10°N to 35°N) in Northern Hemisphere. By contrast, there are no peaks in Southern Hemisphere. The greatest average carbon sink flux (CCSF), i.e., 2.12 tC ha−1 yr−1, for 2000 to 2014 was contributed by tropical rainforest climate near the equator, and the smallest average CCSF was presented in tropical arid zones, showing a magnitude of 0.26 tC ha−1 yr−1. This research estimated the magnitudes, spatial distributions, variations and contributions to the global carbon budget of the CCS in a higher spatiotemporal representativeness and expandability way, which, via multiple mechanisms, introduced an important sink in the terrestrial carbon sink system and the global missing sink and that can help us further reveal and support our understanding of global rock weathering carbon sequestration, terrestrial carbon sink system and global carbon cycle dynamics which make our understanding of global change more comprehensive. Graphical abstract Unlabelled Image Highlights • Carbonate carbon sink is an important part of terrestrial sinks and missing sink. • CCS amounts to nearly 75% of net forest sink have huge contribution to carbon budget. • Tropical rainforest climate owns the greatest carbonate carbon sink flux. • Global new production of multi-years' CCFS maps in a spatial resolution of 0.05° • Separately carry out national measurement of 142 countries or regions for CCS [ABSTRACT FROM AUTHOR]

• The CUE in karst areas is higher than in non-karst areas, and the WUE is slightly lower than in non-karst areas. • The CUE exhibited an increasing trend, and grassland (7.2 × 10−3 yr−1) increase was the most obvious. • The WUE exhibited a downward trend, shrub land (−8.4 × 10−3 g C kg−1 H 2 O yr−1) decreased most significantly. • Precipitation contributed 57.21% of the increase of CUE and 33.1% of the decrease in the WUE. It is crucial to determine the factors affecting the carbon use efficiency (CUE) and water use efficiency (WUE) of vegetation in ecosystems. However, the relationships between climate changes and CUE and WUE by karst vegetation in China are still unclear. The response of the CUE and WUE to regional climate change was studied by using trend analysis and partial derivative method. In addition, the distribution characteristics of the CUE and WUE of different land use types were analyzed. The following results were found. (1). From 2000 to 2018, the average of CUE in karst areas of China was 0.557, and the average value of WUE was 1.237g C kg−1 H 2 O. (2) The CUE of grassland was higher than that of forest land (0.051), whereas the WUE value of grassland was far lower than that of forest land (1.415 g C kg−1 H 2 O). (3) CUE was affected by precipitation (P), exhibiting an increasing trend (5.5 × 10−3 yr−1), and the most obvious increase occurred in the grassland (7.2 × 10−3 yr−1). Under the influence of solar radiation (SR), the WUE decreased (−1.5 × 10−3 g C kg−1 H 2 O yr−1), and the largest decrease occurred in the shrub land (−8.4 × 10−3 g C kg−1 H 2 O yr−1). (4) 90.31 % CUE increase depended on P and SR, while 78.32 % of the decrease in the WUE was due to P and SR. This study makes important contributions to clarifying the responses of the CUE and WUE of ecosystems to climate changes in karst areas, optimizing the management of regional water and soil resources, and promoting healthy development of the ecological environment. [ABSTRACT FROM AUTHOR]

The chemical weathering of silicate rocks can yield bicarbonate which is transported via rivers to the ocean, followed by the deposition of carbonate, acting as a carbon sink on long time scales. The dissolution of carbonate minerals and the participation of exogenous acids (e.g., sulfuric acid and nitric acid) also affect the chemical weathering process. However, their effects have rarely been quantified at the global scale. Here, based on a compilation of time series datasets of hydro-chemistry samples from 3573 monitoring sites and high-resolution hydro-meteorological datasets, we quantified the effects of carbonate minerals and exogenous acids on the carbon fluxes from the chemical weathering of granite and basalt. The calculated true carbon fluxes of the chemical weathering of granite and basalt were approximately 28.72 Tg C/yr and 30.42 Tg C/yr on the global grid scale. Although the effects of exogenous acids to the true carbon fluxes of the chemical weathering from granite and basalt were similar, corresponding to 30% and 28% of the estimated cation fluxes, respectively, the effect of carbonate minerals on the chemical weathering of granite was approximately twice the effect on the chemical weathering of basalt. These discrepancies were caused by the differences in the chemical weathering characteristics and the laws that integrated the different effects of basalt and granite. Our results address the roles of carbonate minerals and exogenous acids in the global carbon cycle and their link to CO 2 consumption via the chemical weathering of silicate rocks. • Quantifying the effects of carbonate minerals and exogenous acids. • Reassessing magnitude and changes of the weathering carbon sink of granite and basalt. • Carbon fluxes of the chemical weathering of basalt were about twice that of granite. • Carbonate minerals have a more prominent effect on the chemical weathering of granite. [ABSTRACT FROM AUTHOR]

The global climate change situation partly depends on the climate change policies of countries around the world, including China. Therefore, it is necessary to reasonably reduce carbon emissions (CEs) and increase carbon sink in order to progressively achieve the carbon neutral (CN) goal. However, the capacity and the potential to achieve carbon neutral with the support of its ecosystem, that is to say the carbon neutral capacity (CNC) and potential, are still unclear. To this end, based on China's energy emissions data, meteorological and hydrological data, lithology data, and vegetation data, we used the GEM-CO 2 model, soil respiration model, spatial autocorrelation analysis method and other methods to establish the spatial information map of China city-scale CNC from 1997 to 2017. Furthermore, based on the future climate, vegetation data, CEs data and their influencing factors in 2025–2060, the Back Propagation neural network model was used to predict the CN potential of China's provinces. This study found during the study period, annual CEs of 5.63 Pg CO 2 were not absorbed, which is about 90% of the average annual CEs. And the carbon surplus regions were mainly concentrated in the less developed northeastern and southwestern border regions. Moreover, the change in the CNC in China from 1997 to 2017 was −13.37 Tg/yr, indicating that the CNC of China's terrestrial ecosystems overall reduced. It should be noted that most provinces are not highly polarized, that is, there is no significant differences in CNC between cities in the provinces. Moreover, the scenario simulation's method of IPCC provides a reference for this manuscript, so we set up two future scenarios (A2 and B1 scenarios). In the future, China is expected to achieve a carbon emission peak before 2030 under the B1 scenario while it will continue to grow under the A2 scenario. From 2017 to 2060, the CNC under the two scenarios (A2/B1) will decrease by 44.58% and increase by 15.54%. It follows then that the road to CN in China will be difficult without corresponding policy intervention. In short, this study has clarified China's CNC from the past to the future, as well as CNC's spatial distribution and changing trends. This provided theoretical and data support for China to introduce corresponding zero-carbon solutions based on its understanding of CNC. • The spatial information map of China city-scale carbon neutral capacity (CNC) was established. • Annual CEs of 5.63 Pg CO 2 were not absorbed, which is about 90% of the average annual CEs. • The carbon surplus regions were mainly concentrated in the less developed border regions. • From 2017 to 2060, the CNC under the two scenarios (A2/B1) will decrease by 44.58% and increase by 15.54%. [ABSTRACT FROM AUTHOR]

• The POC flux is approximately 0.12 –0.20 Pg C/yr from land to oceans. • Asia exports more POC than other continents (60.50–61.69%). • The Amazon basin contributes 53.30–58.68% of the POC to the Atlantic. • The POC flux has two key zones in the latitude zone along latitude bands. The transport of particulate organic carbon (POC) through rivers from land to sea affects the redistribution of global organic carbon. However, because of the limitation of the quantity and quality of monitoring data, the POC magnitude, scale and global distribution pattern of land-sea migration are still not well understood. Therefore, based on an updated GEMS-GLORI database and other reanalysis data, we use the soil erosion model (F erosion), total suspended solids model (F tss), and runoff model (F runoff) to re-analyze and generate the POC flux of major rivers in the world dataset. The major results are as follows: the POC flux from global terrestrial biosphere rivers exports approximately 0.12–0.20 Pg C to oceans every year, including 0.20 Pg F erosion , 0.17 Pg F tss , and 0.12 Pg F runoff. In contrast to earlier studies that the Pacific and Arctic Oceans are the main recipients of POC flux, we find that the Pacific and Atlantic received more POC flux and received 30.76%–62.51% and 26.77%–53.95%, respectively. This difference may be related to the combined effects of soil erosion, total suspended solids, and runoff. Asia exports more POC than other continents (60.50%–61.69%). The Amazon basin is the major contributor to the Atlantic POC, contributing 53.30%–58.68%. Furthermore, because of the intense human activities and the widespread distribution of many large watersheds in the highly eroded area, it was found that the POC flux has two key zones (25.75–41.5°N and 4.50°N–13.50°S) in the latitude zone. In summary, the above findings increase our understanding of the spatial redistribution of global organic carbon from land to sea. [ABSTRACT FROM AUTHOR]

• The POC flux is approximately 0.12 –0.20 Pg C/yr from land to oceans. • Asia exports more POC than other continents (60.50–61.69%). • The Amazon basin contributes 53.30–58.68% of the POC to the Atlantic. • The POC flux has two key zones in the latitude zone along latitude bands. The transport of particulate organic carbon (POC) through rivers from land to sea affects the redistribution of global organic carbon. However, because of the limitation of the quantity and quality of monitoring data, the POC magnitude, scale and global distribution pattern of land-sea migration are still not well understood. Therefore, based on an updated GEMS-GLORI database and other reanalysis data, we use the soil erosion model (F erosion), total suspended solids model (F tss), and runoff model (F runoff) to re-analyze and generate the POC flux of major rivers in the world dataset. The major results are as follows: the POC flux from global terrestrial biosphere rivers exports approximately 0.12–0.20 Pg C to oceans every year, including 0.20 Pg F erosion , 0.17 Pg F tss , and 0.12 Pg F runoff. In contrast to earlier studies that the Pacific and Arctic Oceans are the main recipients of POC flux, we find that the Pacific and Atlantic received more POC flux and received 30.76%–62.51% and 26.77%–53.95%, respectively. This difference may be related to the combined effects of soil erosion, total suspended solids, and runoff. Asia exports more POC than other continents (60.50%–61.69%). The Amazon basin is the major contributor to the Atlantic POC, contributing 53.30%–58.68%. Furthermore, because of the intense human activities and the widespread distribution of many large watersheds in the highly eroded area, it was found that the POC flux has two key zones (25.75–41.5°N and 4.50°N–13.50°S) in the latitude zone. In summary, the above findings increase our understanding of the spatial redistribution of global organic carbon from land to sea. [ABSTRACT FROM AUTHOR]

[Display omitted] • Produced a global 0.25° ×0.25° terrestrial GPP factor contribution dataset. • Soil drying contributes with 19% of the GPP change. • CO 2 concentration is the largest climate factors contributing to GPP (24%), main control area accounts for 9%. • GPP decrease zones, soil drying negative contribution exceeds 1.2 times of climate factors. • The negative contribution of soil drying to GPP offsets 35% of the positive contribution area of climate factors. Global warming and the fertilization effect of carbon dioxide (CO 2) have led to a general increase in gross primary production (GPP). Although soil drying (SD) may limit this increase, its limiting effect has not been confirmed and quantified. Hence, we evaluated the impact of SD and climate factors on GPP. From 1997 to 2017, GPP showed a slight downward trend but began to rise after 2011. In SD zones, 19% of the GPP change was attributed to SD, and CO 2 concentration in climate factors was the climate factor that contributed the most (24%) and accounted for the main control area (9%). Surprisingly, the negative contribution of SD to GPP offset 35% of the positive contribution area of the climate factors. In addition, SD and climate factors explained 1% and 23% of the GPP increase, respectively, but in areas where GPP decreased, the SD area exceeded that of climate factors by 1.2 times, further highlighting the importance of SD in the GPP drive mechanism. Compared with previous studies, we further quantified the contribution of SD and climate factors to GPP, which improved our understanding of the global pattern of total carbon absorption and its response to SD and climate factors. [ABSTRACT FROM AUTHOR]

The weathering carbon sink (CS) of rocks has a sensitive response to different influencing factors, and it is important to accurately distinguish this response in the global carbon cycle. However, no quantitative analysis of the response mechanism has been performed. In this study, the CS of the 12 types of terrestrial rocks in China from 2000 to 2014 is estimated using the GEM-CO 2 model. The relative contribution rates of climate change and ecological restoration to the CS are quantitatively evaluated using the Lindeman-Merenda-Gold model. Results showed that: (1) The CS of terrestrial rocks in China was 17.69 Tg C yr−1, and the CS flux (CSF) was 2.53 t C km−2 yr−1; mixed sedimentary rocks had the highest CS (6.89 Tg C yr−1), and carbonate rocks had the highest CSF (5.8 t C km−2 yr−1). (2) The average annual CSF slightly decreased at a rate of 5.4 kg C km−2 yr−1; the areas of the CSF that decreased in the south were the areas where water budget decreased significantly, and it was the areas with a reduced water budget and ecological deterioration in the north. (3) The relative contribution rates of water budget and precipitation reached 57% and 35%, respectively; the response of the CSF to temperature was evident in areas with low or decreasing temperatures, and the influence of fractional vegetation cover (FVC) on the CSF in low value area was evident. (4) Mixed sedimentary rocks and carbonate rocks displayed a more evident reduction trend in the CSF than other rocks. This research verified the applicability of the GEM-CO 2 model in China and presented a scientific basis for quantitative assessment of the impact of climate change and ecological restoration on the CSF. Unlabelled Image • High sensitivity of the CSF to climate change and ecological restoration. • Water budget and precipitation are the main factors affecting the change in the CSF. • The CSF in China showed a decreasing trend. • Mixed sedimentary rocks and the Pearl River Basin have the highest CSF, respectively. • Spatiotemporal distribution and dynamic change of the CSF. [ABSTRACT FROM AUTHOR]

• Soil in 65.87% of global vegetation greening areas dried, mainly from grasslands. • Vegetation negatively influenced the average SM of global greening and drying areas. • The enhanced soil-drying trend after vegetation increased was mainly in arid climate. • Vegetation growth in some drylands exacerbated the tendency of soil drying. Vegetation greening and soil drying, which are simultaneously observed, have brought controversy about whether vegetation greening leads to soil drying or wetting. Relevant conclusions from previous small-scale research are uncertain worldwide, and the indirect effects of climate via vegetation change on soil moisture (SM) are poorly understood. Here, to explore the effects of vegetation greening on SM change, the patterns of SM trends (wetting to more wetting (W to W), wetting to drying (W to D), drying to wetting (D to W) and drying to more drying (D to D)) were identified in the global vegetation greening (GVG) areas from 1982 to 2015 by using the turning years in the quantity of vegetation greenness and then validated by structural equation model (SEM) and 400 ground stations. The main results are as follows: 1) In the study period, 65.87% (33.57%, Sig.) of the GVG areas featured soil drying including the southeast of the United States, Africa north of the equator, the inland of Europe, the south of China and the inland of Australia, which were mainly from grasslands, barren, savannas, open shrublands, woody savannas and croplands. 2) Vegetation significantly and negatively influenced the average SM of global greening and drying areas, and their climate was arider than that in global greening and wetting areas. 3) Soil in over half of the GVG areas was toward drying after vegetation greenness increased but only the D to D pattern was mainly distributed in drylands (Semi-arid, Arid and Hyper-arid areas) such as the Loess Plateau of China and eastern Australia. The W to W and W to D patterns were remarkably observed in the in-situ SM. 4) SEM showed that the direct effects of vegetation increase on W to W and D to D patterns were stronger than those of temperature and precipitation, especially that the indirect effect of temperature on D to D pattern via promoting vegetation greening outweighed the direct effect of temperature. Overall, the increase in vegetation mainly caused by climate warming has exacerbated the tendency of soil drying in some drylands. Therefore, vegetation restoration or forestry management requires the consideration of local SM-carrying capacity for plants, especially in Semi-arid and Arid ecosystems. [ABSTRACT FROM AUTHOR]

• We found the ESV increased by US$ 23.42 billion from 1992 to 2015 in karst areas. • The contribution rate of regulating service function was 69%. • The implementation of ecological project has a positive impact on ESV in karst areas. • The ESV appeared to be more sensitive to bidirectional land transfer. Karst ecosystem services (ESs), the key components of global terrestrial ESs, play a crucial role in human welfare and livelihood. However, the spatiotemporal changes of ecosystem service values (ESVs) in the karst areas of China remain unclear. In this paper, land use/land cover (LULC) data were used to estimate the ESVs changes during 1992–2015 by the benefit transfer method, to reveal its spatial heterogeneity and to explain the sensitivity of ESVs to land use change. The results indicated that the ESVs were increased by US$ 23.42 billion at 0.10%·yr−1 due to the LULC changes in over 15% of the total karst areas in China, while those in the non-karst areas were reduced by US$ 32.87 billion at 0.14%·yr−1. In particular, the value of the regulation services contributed 69.05% to the total ESVs in the karst area, followed by support services (18.23%), provision services (8.54%), and cultural services (4.15%). The net change of ESVs showed a spatial heterogeneity, i.e. ESVs in the Northwest and North part of southwest increased, but that in the northeast and eastern part of southwest decreased. The ESVs were more sensitive to the bidirectional land conversion than the unidirectional conversion. These results provide an important scientific basis for ecological restoration and reconstruction of karst areas. [ABSTRACT FROM AUTHOR]

• ERA-Interim SM well reflected the interannual change of observational SM. • SM in the karst areas of China declined in 1982–2015. • Precipitation is more important for SM changes in the karst areas than temperature. • SM may be affected on a macro-scale by exposed rocks redistributing rainfall. Soil moisture is one of the restricting factors in a fragile karst ecological environment. However, its spatiotemporal evolution characteristics in the karst areas of China remain poorly understood. Thus, based on soil moisture from reanalysis (ERA-Interim product) and ground stations, this study used the Mann-Kendall test, the Theil-Sen slope estimator, sensitivity analysis and stepwise regression and obtained the following results: 1) ERA-Interim soil moisture well reflected the interannual change of observational soil moisture at 0–7, 7–28 and 28–100 cm. 2) The reanalysis and station data showed that soil at various depths in the karst areas was dominated by a drying trend in 1982–2015. 3) Soil moisture in karst areas of southern China was high but decreased fastest. In the karst areas of northern China, soil moisture was low and declined quickly. Nevertheless, soil wetting was observed in the central karst areas of Qinghai-Tibet Plateau. 4) Changes of soil moisture throughout the karst region of China and its subareas were mainly affected by precipitation, followed by temperature. 5) In Qinghai-Tibet Plateau and southern China, soil moisture in karst areas is overall higher than that in non-karst areas when under low vegetation coverage levels (NDVI ≤ 0.3) of some climate zones, possibly caused by the centralized allocation of precipitation in karst areas due to exposed rocks. In conclusion, climate, vegetation, and geological background make the spatiotemporal distributions of soil moisture differ within the karst region, while the soil drying trend in recent decades and global climate change are not conducive to the ecological restoration of vulnerable karst areas. [ABSTRACT FROM AUTHOR]

• The drying trend of the global soil accelerated in 2001–2017. • The global soil moisture in the future will be dominated by decreasing trend. • 65.1% of the global soil drying trend was induced by temperature rising. • The soil wetting was affected by the action of temperature, precipitation and NDVI. Soil moisture (SM) is a comprehensive variable of terrestrial ecosystems. However, the global SM trend in recent decades and the future is uncertain, and the main factors causing soil drying and wetting are not fully understood. This study using Extended Triple Collation, Mann-Kendall test, Theil-Sen estimate, Hurst exponent, Ensemble Empirical Mode Decomposition and pertinent methods found that 1) at the pixel scale, the long-term daily SM data from ERA-Interim was closest to the true SM compared with ESA CCI and GLDAS; 2) the global average SM in 1979–2017 decreased remarkably and the declining trend accelerated in 2001–2017; 3) soil drying was observed in seven major land covers; among which, urban area has the largest area proportion of soil drying, about 80%; 4) the strong persistence of SM trend indicates that the global future soil will continuously be dominated by a drying trend; 5) overall, 65.1% of the global soil drying trend was attributed to temperature rising, whereas 82% of the wetting trend was affected by the combined action of temperature, precipitation, and NDVI. Under global warming, the soil drying area expanded at a rate of 1% yr−1 in 1979–2017 and the global SM will keep diminishing in the next years, which may increase the risks of extreme heatwaves, water resources shortage, land degradation, and other eco-environmental problems. [ABSTRACT FROM AUTHOR]