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Cotton is a revenue source for cotton-producing countries; as the second-largest crop in Pakistan, it significantly contributes to its economy. Over the past few decades, cotton productivity has become unstable in Pakistan, and climate change is one of the main factors that impact cotton yield. Due to climate change, it becomes very important to understand the change trend and its impact on cotton yield at the regional level. Here, we investigate the relationship of standardized cotton yield variability with the variability of climate factors using a 15-yr moving window. The piecewise regression was fitted to obtain the trend-shifting point of climate factors. The results show that precipitation has experienced an overall decreasing trend of −0.64 mm/yr during the study period, with opposing trends of −1.39 mm/yr and 1.52 mm/yr before and after the trend-shifting point, respectively. We found that cotton yield variability increased at a rate of 0.17%/yr, and this trend was highly correlated with the variability of climate factors. The multiple regression analysis explains that climate variability is a dominant factor and controlled 81% of the cotton production in the study area from 1990 to 2019, while it controlled 73% of the production from 1990 to 2002 and 84% from 2002 to 2019. These findings reveal that climate factors affact the distinct spatial pattern of changes in cotton yield variability at the tehsil level. [ABSTRACT FROM AUTHOR]

Human activities in a transborder watershed are complex under the influence of domestic policies, international relations, and global events. Understanding the forces driving human activity change is important for the development of transborder watershed. In this study, we used global historical land cover data, the hemeroby index model, and synthesized major historical events to analyze how human activity intensity changed in the Heilongjiang River (Amur River in Russia) watershed (HLRW). The results showed that there was a strong spatial heterogeneity in the variation of human activity intensity in the HLRW over the past century (1900—2016). On the Chinese side, the human activity intensity change shifted from the plain areas for agricultural reclamation to the mountainous areas for timber extraction. On the Russian side, human activity intensity changes mostly concentrated along the Trans-Siberian Railway and the Baikal-Amur Mainline. Localized variation of human activity intensity tended to respond to regional events while regionalized variation tends to reflect national policy change or broad international events. The similarities and differences between China and Russia in policies and positions in international events resulted in synchronous and asynchronous changes in human activity intensity. Meanwhile, policy shifts were often confined by the natural features of the watershed. These results reveal the historical origins and fundamental connotations of watershed development and contribute to formulating regional management policies that coordinate population, economic, social, and environmental activities. [ABSTRACT FROM AUTHOR]

The vegetation of alpine tundra in the Changbai Mountains has experienced great changes in recent decades. Narrowleaf small reed ( Deyeuxia angustifolia), a perennial herb from the birch forest zone had crossed the tree line and invaded into the alpine tundra zone. To reveal the driven mechanism of D. angustifolia invasion, there is an urgent need to figure out the effective seed distribution pattern, which could tell us where the potential risk regions are and help us to interpret the invasion process. In this study, we focus on the locations of the seeds in the soil layer and mean to characterize the effective seed distribution pattern of D. angustifolia. The relationship between the environmental variables and the effective seed distribution pattern was also assessed by redundancy analysis. Results showed that seeds of D. angustifolia spread in the alpine tundra with a considerable number (mean value of 322 per m). They were mainly distributed in the low elevation areas with no significant differences in different slope positions. Effective seed number (ESN) occurrences of D. angustifolia were different in various plant communities. Plant communities with lower canopy cover tended to have more seeds of D. angustifolia. Our research indicated reliable quantitative information on the extent to which habitats are susceptible to invasion. [ABSTRACT FROM AUTHOR]

The simulation optimization (S/O) method is widely used in the identification of groundwater contamination sources (IGCSs). However, in most cases, the IGCSs has the characteristics of many variables to be identified and a high degree of nonlinearity. When the grey wolf optimization algorithm (GWO) is used to solve the optimization model for this kind of problem, due to the relatively weak local search ability it has the disadvantage of premature convergence. To improve the GWO, the GWO and gradient descent algorithm were integrated to construct a hybrid grey wolf gradient optimization algorithm (HGWGO) with little dependence on the initial value and a strong local search ability. The HGWGO was then applied to solve the optimization model and improve the accuracy of the IGCSs results. In addition, when solving the optimization model, calling the simulation model hundreds of times will generate a large calculation load and consume a massive amount of computing time, which would seriously hinder the IGCSs. Thus, a surrogate model of the simulation model was established by applying a deep belief neural network (DBNN) to participate in the iterative calculation. The results showed that compared with the simulated annealing algorithm and GWO, the HGWGO had a higher calculation accuracy and could improve the accuracy of IGCSs. Although the HGWGO requires a high computational cost, the improvement in solution accuracy was sufficient to compensate for this shortcoming. The DBNN surrogate model had a high accuracy and could save 99% of the computing time by participating in the iterative calculation instead of the simulation model. [ABSTRACT FROM AUTHOR]

Korean pine ( Pinus koraiensis ) is an important species of forests in Northeast China and the Russian Far East. In recent years, human disturbances have increasingly threatened the long-term population sustainability of Korean pine in Northeast China. Though the Chinese government has implemented various programs to restore and protect Korean pine, results have not been satisfactory. Economic income often conflicts with ecosystem function, so figuring out ways to balance ecologic and economic values is important for Korean pine sustainability and management. The effects of humans on Korean pine forest are complex and interact in ways that are difficult to predict at the landscape scale. In this paper, we used a simulation approach to examine multiple intensities of timber harvest and seed harvest on landscape-scale Korean pine coverage and age structure. We found that the influences of seed harvest became increasingly important over the simulation period. Seed harvest noticeably influenced the percent coverage of young (<60 yr) Korean pine. Young age classes of Korean pine disappeared when seed harvest intensity was high, even with a low timber harvest intensity. Except during high timber harvest intensities, Korean pine maintained its coverage and age structure to a certain extent under a medium seed harvest level. When seed harvest was prohibited, Korean pine coverage remained steady compared to initial conditions, regardless of the timber harvest intensity. Percent coverage of young and middle age (60–120 yr) Korean pine increased late in the simulation period. Our study showed that some level of seed harvest intensity combined with medium and low timber harvest intensities may be optimal for managers to maintain a viable economy together with ecosystem sustainability. [ABSTRACT FROM AUTHOR]

Northwest China (NW China) falls within Arid Central Asia (ACA) and has a climate dominated by westerly winds, a fragile ecosystem, and a high sensitivity to climate change. Paleoenvironmental reconstructions of this region can assist in understanding the general processes contributing to environmental variation in such arid areas. This study examined a dated sedimentary core containing both peat and lacustrine deposits obtained from the shore of the Bosten Lake, NW China. The study aimed to reconstruct paleoenvironmental variations over the last 3,000 years and to explore the possible drivers of peatland development over the last millennium. An examination of grain size and δ13C was conducted to investigate lake level variation. The results showed that the lake level of the Bosten Lake declined gradually between 2,905 and 480 cal yr BP and increased thereafter, consistent with other records of the Bosten Lake. At a centennial timescale, the lake level was high under a wet climate during the Dark Age Cold Period (DACP), whereas it decreased significantly during the Medieval Warm Period (MWP). The inferred "cold and wet" and "warm and dry" patterns indicated climatic characteristics of a "westerlies-dominated climatic regime". In addition, the persistent decreasing lake level during the MWP resulted in Phragmites peatland initiation and development along the shores of the Bosten Lake. [ABSTRACT FROM AUTHOR]

BACKGROUND: Drought affects the characteristics of water use during crop production and so quantitatively evaluating the impacts is important. However, it remains unclear how crop water use responds to drought. To address this gap, water footprint (WF) and standardized precipitation evapotranspiration index (SPEI) were calculated by remote sensing approaches to assess the effects of drought on crop water use. Rainfed maize is the most important crop in Jilin Province, and its growth and water use are more susceptible to drought. The present study explored not only the impact of growing season drought on the maize WF values in Jilin Province, but also the response of WF values to drought at different time scales. RESULTS: Spatially, 72.94% of the WFblue pixels showed a non‐significant increase, and the WFgreen in 68% pixels decreased significantly, being mainly concentrated in the middle region. Furthermore, the pixels affected by monthly time scale drought were mainly in the middle region, whereas the pixels affected by annual time scale drought were mainly in the western region. CONCLUSION: Drought not only affected on the source and structure of agricultural water consumption, but also had different effects on WF values at different time scale. These effects had obvious spatial differences. The present study systematically explored the effects of drought on the WF values for rainfed maize in different climate regions and a consideration of these effects could provide valuable information on rainfed maize growth and the agricultural water use response to a changing climate. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Vegetation is the main component of the terrestrial ecosystem and plays a key role in global climate change. Remotely sensed vegetation indices are widely used to detect vegetation trends at large scales. To understand the trends of vegetation cover, this research examined the spatial-temporal trends of global vegetation by employing the normalized difference vegetation index (NDVI) from the Advanced Very High Resolution Radiometer (AVHRR) Global Inventory Modeling and Mapping Studies (GIMMS) time series (1982-2015). Ten samples were selected to test the temporal trend of NDVI, and the results show that in arid and semi-arid regions, NDVI showed a deceasing trend, while it showed a growing trend in other regions. Mann-Kendal (MK) trend test results indicate that 83.37% of NDVI pixels exhibited positive trends and that only 16.63% showed negative trends (P < 0.05) during the period from 1982 to 2015. The increasing NDVI trends primarily occurred in tree-covered regions because of forest growth and re-growth and also because of vegetation succession after a forest disturbance. The increasing trend of the NDVI in cropland regions was primarily because of the increasing cropland area and the improvement in planting techniques. This research describes the spatial vegetation trends at a global scale over the past 30+ years, especially for different land cover types. [ABSTRACT FROM AUTHOR]

Rapid changes in soil temperature are unequivocal under global change, especially in mid-high latitudes. Studies on the relationships between soil temperature and climate system are lacking at regional climatic scale. Here, changes in shallow soil temperature (0, 5, 10, 15, 20 cm), both in the cold temperate zone (CTZ) and the mid-temperate zone (MTZ) in Northeast China, were compared and analyzed using daily data from growing seasons (May to September) from 1964 to 2011. The influences of air temperature and precipitation on soil temperature were analyzed. The results showed that for nearly half a century, the increasing trend of surface soil temperature in the CTZ was lower than that in the MTZ, with + 0.17 and + 0.54 °C/decade, respectively. Air temperature increased faster for the MTZ than the CTZ. Precipitation increased in the CTZ but decreased in the MTZ. Since 1996, the temperature increase and precipitation decrease were more obvious in the MTZ. In summary, given the complex effects of temperature and precipitation, the response of soil temperature was more significant in the MTZ than in the CTZ. These results emphasize the importance of independently researching soil temperature of different climate zones. Susceptibility of soil temperature to global warming will advance our understanding on utilization of climatic resources in the development of agricultural production. [ABSTRACT FROM AUTHOR]

Abstract: BACKGROUND: Rice is a special crop, and its production differs from that of other crops because it requires a thin layer of water coverage for a long period. The calculation of the water footprint of rice production should differ from that of other crops owing to the rice growing process. This study improved the calculation of blue and grey water footprints of rice production and analyzed the variations in the water footprints for rice production under different rainfall years in Jilin Province. RESULTS: In the drought year, the green water footprint was the lowest and the blue water footprint was the highest among the three years, while in the humid year, the green water footprint was the highest and the blue water footprint was not the lowest. The areas with higher water footprints were found in the east and west regions of Jilin Province, while the areas with lower water footprints were found in the middle east and middle regions of Jilin Province. CONCLUSION: Blue water was the primary water resource for rice production, although more precipitation provided the highest green water in the humid year; also, the spatial distributions of water footprints were not the same under different rainfall years. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

ABSTRACT: Using the daily precipitation records during 1961–2013 from 686 meteorological stations across China and the atmospheric circulation indexes, this study investigates the spatio‐temporal changes in the occurrence time and length of the extreme precipitation period (EPP), as well as their influencing factors. The results show the following aspects: (1) In the last 53 years, the start dates of the extreme precipitation period (EPPS) generally advanced. The end dates of the extreme precipitation period (EPPE) are delayed, which show an increasing trend. The lengths of the extreme precipitation period (EPPL) in most of the China meteorological stations increased. (2) The spatial patterns of the trends in the occurrence time and length of the extreme precipitation period are similar and show obvious clustering. The occurrence time and length of the extreme precipitation period have obvious spatial gradient differences in their average values. In southeastern China, the average EPPS is earlier, EPPE is later than those in other regions, and their EPPL is prolonged. The EPP in northeastern China begins later and ends earlier, and its EPPL is shorter than that in other regions. (3) The western Pacific subtropical high, Northern Hemisphere polar vortex, Antarctic Oscillation, and western Pacific warm pool have significant effects on the occurrence time and length of EPP over China, and different regions show different effects. [ABSTRACT FROM AUTHOR]

The soil fauna communities were studied in the Songnen Grassland, which is located at the easternmost Eurasian steppe of northeast China. We sampled sites from May to October with different alkaline contents to investigate the salinization process on soil fauna. We found that the dominant groups were Prostigmata, Oribatida, and Gamasina mites and the collembolan families Isotomidae and Entomobryidae. Results showed that the composition of the soil fauna communities differed significantly among the habitats with different salinity. Number and density of taxa were lower in communities with high salinity. The highest number of taxa (66) was found on the Artemisia anethifolia sites, the lowest number (47) on the Alkali patches. The Shannon-Wiener index was the lowest on the Alkali patches, whereas the Simpson-dominance index was the highest in these habitats. The number and density of taxa changed during the seasons. The soil fauna tended to gather on soil’s surface. According to the Redundancy analysis, the soil organic matter positively affected the density of the soil fauna and soil fauna decreased with increasing degree of salinization in Songnen Grasslands. [ABSTRACT FROM AUTHOR]

ABSTRACT On the basis of the daily minimum temperature, records of 109 meteorological stations over Northeastern China ( NEC) from 1961 to 2013 and the output data of eight models from CMIP5, this study investigates the recent and future spatiotemporal changes of the frost-free season. The results show that the date of last spring frost ( LSFD) has a significant decreasing trend. Stations exhibiting significant negative trends are mostly distributed in the eastern Jilin Province and the Midwest of Heilongjiang Province. The date of first fall frost ( FFFD) and length of frost-free season ( LFFS) both show significant increasing trends. The spatial patterns of stations showing significant positive trends in the FFFD and LFFS are similar, which are mainly located in the middle part of Eastern Inner Mongolia and the south and middle parts of Changbai Mountains. The LFFSs have significant increasing trends with the magnitudes of 0.49 days/decade for RCP2.6, 1.62 days/decade for RCP4.5, and 3.85 days/decade for RCP8.5 during 2006-2100. The southern Liaoning Province and the northwestern NEC will experience the longer LFFS under each scenario between 2071 and 2100. The frost-free season indices have significant correlations with the Northern Hemisphere Polar Vortex Area index. The atmospheric circulation patterns of an anticyclonic circulation anomaly prevailed over the Lake Baikal region and a cyclonic circulation anomaly located in the northwest Pacific Ocean in springs and an anticyclonic circulation anomaly prevailed over the south part of the Russian Far East in falls block more cold air flowing into NEC, which result in the earlier LSFD and later FFFD. The adverse patterns in springs and in falls could bring out the later LSFD and earlier LSFD, respectively. Our results could benefit the prevention and reduction of frost disaster and provide a reference for the policy-making of future crop production. [ABSTRACT FROM AUTHOR]

Peatlands are some of the largest carbon reservoirs in terrestrial ecosystems and play a key role in the global carbon cycle. Understanding peatland development, carbon accumulation processes, and the peatland response to varying forcing factors over different temporal and spatial scales helps reveal the underlying processes and general patterns of these ecosystems. To assess the role of climate and local conditions in peatland development, the basal samples from 23 peat cores and three well dated long peat cores were used to explore peatland initiation, lateral expansion, and carbon accumulation rate in the Baijianghe peatland located in the Changbai Mountains, Northeast China. Our results reveal that the Baijianghe peatland was initiated from forest conditions at 7.9 cal. kyr BP and then expanded laterally by paludification. The rapid expansion between 5 and 4 cal. kyr BP likely resulted from high precipitation and gentle topography. The mean carbon accumulation rates of the three long peat cores were 36.3, 39.1 and 48.4 g C m−2 yr−1, respectively, which are higher than rates from the northern peatlands. Both climate and local conditions have exerted an important influence on carbon accumulation rates in the Baijianghe peatland since the middle Holocene. The carbon accumulation patterns between 5 and 1.5 cal. kyr BP were probably linked to local conditions rather than climatic settings, including topography, hydrological conditions, and plant composition. The consistently decreasing carbon accumulation rate values at all locations within the BJH peatland over the last 1.5 cal. kyr BP suggests that climate is the primary control. This study highlights the varying primary controls on the process of peatland development and reveals the important role of local conditions in carbon accumulation. [ABSTRACT FROM AUTHOR]

ABSTRACT On the basis of the daily precipitation records of 442 meteorological stations throughout Northeast Asia ( NEA) from 1961 to 2009, this study investigates spatiotemporal changes in summer extreme precipitation ( SEP) and the relationship between SEP and East Asia summer monsoon ( EASM) in NEA. The results show that the spatial patterns of the trends in SEP indices are similar, with obvious clustering, except for the consecutive dry days ( CDD) index. Stations exhibiting increasing trends are mainly located in Eastern China ( EC) and the western part of Western Japan ( WJ). Stations with decreasing trends are mostly distributed in Northern China ( NC) and the southern region of Eastern Japan ( EJ). The spatial patterns of the correlations between the EASM index EASMI and the SEP indices are similar, except for the CDD index. Stations that show decreasing trends mostly exhibit positive correlations between SEP indices and the EASMI, and vice versa. The spatial patterns of trends (increasing trends in EC, decreasing trends in NC and Northeast China) in SEP indices between 1961 and 2009 have a correlation with a weakening EASM. This study demonstrates that the mechanism dominating the mean state change of the EASM also applies to SEP. A strong mid-latitude cyclone could result in a regional SEP (R99p occurred in more than 20 stations over a subregion in 1 day) in EC and Japan in weak EASM years, and could result in a regional SEP in NC in strong EASM years. [ABSTRACT FROM AUTHOR]

• CEEMD was applied to the joint identification of simulation model parameters and GCSs information. • CEEMD had a significant noise reduction effect when used to denoise the observed concentrations. • The accuracy of the identification results improved when the noise-reduced observed concentrations were applied. Identification of groundwater contaminant sources (GCSs) relies on actual observed data, and the observed data directly affects the accuracy of the identification results. However, the observed data inevitably contains noise due to accidental and systematic errors, and the identification results of GCSs based on the observed data containing noise are usually not reliable. This seriously restricts the rational design of contamination remediation plans and contamination risk assessment. To solve this problem, complementary ensemble empirical mode decomposition (CEEMD) was applied to the joint identification of simulation model parameters and GCSs information in this study for the first time. The wavelet analysis and CEEMD methods were used to reduce the noise in observed concentrations respectively, and the noise reduction effect of the two methods was compared and analyzed. Then the simulated concentrations, observed concentrations and noise-reduced observed concentrations with the best noise reduction effect were then applied to identify simulation model parameters and GCSs information, respectively, after which the corresponding identification results were compared and analyzed. The results showed that CEEMD could reduce the noise contained in the observed concentrations more effectively and make it closer to the actual values when compared with the wavelet analysis method. The accuracy of identification results based on the noise-reduced observed concentrations by was improved. As the noise contained in the observed concentrations increased, the noise reduction effect of the CEEMD decreased. Nevertheless, the accuracy of the identification results based on the noise-reduced observed concentrations was still higher than that of those based on the observed concentrations with the same intensity noise without denoising. [ABSTRACT FROM AUTHOR]

• CEEMD was applied to the joint identification of simulation model parameters and GCSs information. • CEEMD had a significant noise reduction effect when used to denoise the observed concentrations. • The accuracy of the identification results improved when the noise-reduced observed concentrations were applied. Identification of groundwater contaminant sources (GCSs) relies on actual observed data, and the observed data directly affects the accuracy of the identification results. However, the observed data inevitably contains noise due to accidental and systematic errors, and the identification results of GCSs based on the observed data containing noise are usually not reliable. This seriously restricts the rational design of contamination remediation plans and contamination risk assessment. To solve this problem, complementary ensemble empirical mode decomposition (CEEMD) was applied to the joint identification of simulation model parameters and GCSs information in this study for the first time. The wavelet analysis and CEEMD methods were used to reduce the noise in observed concentrations respectively, and the noise reduction effect of the two methods was compared and analyzed. Then the simulated concentrations, observed concentrations and noise-reduced observed concentrations with the best noise reduction effect were then applied to identify simulation model parameters and GCSs information, respectively, after which the corresponding identification results were compared and analyzed. The results showed that CEEMD could reduce the noise contained in the observed concentrations more effectively and make it closer to the actual values when compared with the wavelet analysis method. The accuracy of identification results based on the noise-reduced observed concentrations by was improved. As the noise contained in the observed concentrations increased, the noise reduction effect of the CEEMD decreased. Nevertheless, the accuracy of the identification results based on the noise-reduced observed concentrations was still higher than that of those based on the observed concentrations with the same intensity noise without denoising. [ABSTRACT FROM AUTHOR]

The identification of groundwater contamination sources (IGCSs) is an important requirement for the remediation and treatment of groundwater contamination. The data assimilation methods such as ensemble Kalman filter (EnKF) and ensemble smoother (ES) have been applied to IGCSs in recent years and obtained good identification results. The unscented kalman filter (UKF) is also a data assimilation method with the potential to simultaneously identify hydraulic conductivity and GCSs. However, when UKF is applied to identify hydraulic conductivity and GCSs, it is necessary to use the observed data at different times separately, which increases the complexity of the update process and this may result in low identification accuracy. ES is a variant of EnKF that updates the system parameters with all observed data in all time periods, which makes ES faster and easier to implement than EnKF. Therefore, inspired by the ES, an unscented kalman smoother (UKS) based on UKF was proposed for simultaneously identifying the hydraulic conductivity and GCSs in this study. The UKS can use the data observed in all time periods simultaneously, while it is also simpler to operate and the calculation speed is faster. Present studies have shown that ES can solve IGCS problems. Thus, ES was also applied to identify the hydraulic conductivity and GCSs in this study, and its identification performance was compared with UKS. In contrast to previous applications of ES to IGCSs, both UKS and ES were set up with stop iteration conditions instead of only performing one update process, and thus both methods applied multiple update processes. The results showed that compared with ES, the identification results obtained by UKS were characterized by greater stability, higher accuracy, and the iterative process required less iteration process and computational time. [ABSTRACT FROM AUTHOR]

Land use and its environmental effects can be quantitatively expressed with land-use intensity. In this study, a land-use intensity metric was improved using a geographic mapping method. The relationships between observed rapid changes in land use and temperature in the Dongting Lake area from 2001 to 2010 were examined. The results revealed the following features: (1) The temperature increased when the land-use intensity increased via a hierarchical transition owing to grass and forest land reductions of 26.25% and 11.74%, respectively; built-up land increased by 48.45%. (2) The temperature increase was driven more by the external environment than by land-use intensity changes. Human activities produced larger effects in the western region than in the eastern or central region of the study area, according to the observed variations in the centres of gravity for temperature and land-use intensity. (3) The temperature response to land-use intensity changes was more sensitive in low-altitude areas than in high-altitude areas; the response presented a north-south gradient, possibly due to socioeconomic and urbanisation differences. [ABSTRACT FROM AUTHOR]

Accelerated tree growth in the alpine treeline ecotone (ATE) has been linked to the recent rapid climate warming. However, the role of tree age and elevation in the growth response of trees to climate change remains unclear. Here, we developed basal area increment chronologies of Betula ermanii from the closed forest belt (CFB) at lower elevation to the ATE of Changbai Mountain with three tree age classes (young: 0–60 years, middle-aged: 60–120 years, and old: > 120 years). In ATE, all age classes of B. ermanii have been experiencing dramatic growth acceleration since 1981. Young trees, with higher temperature sensitivity, exhibited the most prominent warming-induced growth enhancement relative to middle and old-aged trees. In CFB, young and middle-aged trees exhibited similar sensitivity to the temperature increase during the warm period relative to the cold period, with strikingly accelerated growth enhancement trends. In contrast, old trees did not show any significant growth trend. Moreover, young trees in ATE showed significantly (p < 0.01) higher growth rates than those in CFB, whereas middle-aged trees in ATE showed significantly (p < 0.05) lower growth rates than those in CFB. Our results reveal that the response of tree growth to climate change varies with tree age and elevation. Therefore, these factors should be considered to avoid overestimation or underestimation of tree growth trends and bias in estimating potential forest production. [ABSTRACT FROM AUTHOR]

Traditionally, patch-based analysis at the landscape scale fragmentation has been used in the study of landscape ecology while the study of boundary and node has not been considered as much detail until recently. This study investigated the possibility of applying boundary- and node-based methods in landscape pattern analysis to the upper reaches of the Minjiang River in the southwestern China. Boundary-based and node-based landscape indices were selected to be used in analyzing changes in landscape patterns, and the results were compared with analysis using traditional pattern indices. We compared the responses of patch-area-based, boundary-length-based and node-number-based indices, and concluded that boundary-based and node-based indices are more sensitive to disturbance than patch-based indices with various patterns, and node-based indices are even more sensitive than boundary-based ones. Thus, the results suggest that boundary-based and node-based pattern analysis methods provide helpful supplementary information to traditional patch-based pattern analysis methods. The results about pattern dynamics of landscapes in the upper reaches of the Minjiang River based on boundaries and nodes showed that with human disturbance, the dominance of forest landscape was weakened by other landscape types; thus the landscape pattern of the study area became more homogeneous and the boundary network became more complex. These changes further augmented disturbance interfaces in the landscape and increased the possibilities of further landscape fragmentation. [ABSTRACT FROM AUTHOR]

Peatlands are one of the most significant carbon reservoirs in the terrestrial ecosystem. Understanding past peatland carbon accumulation processes and their responses to varying external and internal forcing factors would help reveal the general development patterns of peatland ecosystems and provide useful insights into projecting the fate of carbon reservoirs into the future. In this paper, the basal ages of 17 peat cores were used to explore the lateral expansion processes of the Laolike peatland, northeast China. Two cores were selected to calculate carbon accumulation rates (CAR) and reconstruct moisture/precipitation records based on δ13C and grain size analyses. The basal ages show that the peatland was initiated at 12.1 cal kyr BP, then laterally expanded with its fastest rate occurring during the early Holocene, and reached its largest area around 6 cal kyr BP. The time-weighted mean CAR in the Laolike peatland ranged from 31.1 to 52.9 g C/m2/yr (with an average of 42 g C/m2/yr) during the Holocene. The peatland experienced a high CAR of 52.5 g C/m2/yr from 11.7 to 5 cal kyr BP, followed by a low CAR of 35.1 g C/m2/yr after 5 cal kyr BP. Both lateral expansion and vertical accretion are consistent with the summer insolation, climate seasonality, and the strength of the East Asia summer monsoon (EASM) over multi-millennium timescales, where the CAR correlated well with δ13C and grain size, implying moisture/precipitation might be the primary factors controlling carbon accumulation over millennium timescales. Local conditions, such as topography and hydrology, also played an important role in the process of peatland initiation and lateral expansion, as well as the discrepant CAR within the peatland. This study reveals the roles of climate and local conditions in peatland initiation, expansion, and CAR during the Holocene. In addition, we provide a window for a better understanding of the driving factors of peatland development in the temperate zones of the Northern Hemisphere. • Climate conditions are the primary control on the lateral expansion and vertical accretion of Laolike peatland over multi-millennium timescales. • Moisture/precipitation affects carbon accumulation of Laolike peatland over millennium timescales. • Local conditions play an important role in the lateral expansion and the internal differences of carbon accumulation rate. [ABSTRACT FROM AUTHOR]

Interday temperature fluctuations (ITFs) have a series of direct and visible impacts on human productivity, daily life, and some rapidly occurring processes in the Earth's critical zones. The Loess Plateau of China (LPC) is characterized by Chinese continental monsoon climate and fragile ecological environment, and thus, is sensitive to ITFs. To evaluate the spatiotemporal distribution of the ITF frequency and level, and the related large‐scale circulation background, we collected daily temperature data from 53 meteorological stations in the LPC for 1961–2015, and calculated the number of days per year in which the average ITF was greater than 1°C (ITFD) and the corresponding variance of the ITF (ITFL). The annual average ITFs were mostly warming; the first half of the year experienced mainly warming, while the second half underwent cooling. The level and frequency of the interday maximum temperature fluctuation contributed greatly to increases in the interday mean temperature fluctuation level and frequency. The spatial distributions of ITFD and ITFL were related to their latitude and longitude. Stations with positive ITFD indicator trends were mostly concentrated in the southwestern LPC, while stations with negative ITFL indicator trends mainly occurred in the northwestern LPC. At an 850 hPa geopotential height, the stronger ITFs in spring more strongly correlated with the Mongolian high and Aleutian low. While at a 500 hPa geopotential height, the ITF were more strongly correlated with the Mongolian high. These results suggest that ITFs are more complex than previously reported and may need to be considered in future climate change assessments. [ABSTRACT FROM AUTHOR]

As one of the most sensitive regions to global climate change, alpine tundra in many places around the world has been undergoing dramatic changes in vegetation communities over the past few decades. Herbaceous plant species in the Changbai Mountains area have significantly expanded into tundra shrub communities over the past 30 yr. Soil microbial communities, enzyme activities, and soil nutrients are intertwined with this expansion process. In order to understand the responses of the soil microbial communities to such an expansion, we analyzed soil microbial community structures and enzyme activities in shrub tundra as well as areas with three different levels of herbaceous plant expansion. Our investigation was based on phospholipid fatty acid (PLFA) analysis and 96-well microtiter plates. The results showed that herbs have expanded greatly in the tundra, and they have become the dominant species in herbaceous plant expansion areas. There were differences for community composition and appearance among the shrub tundra and the mild expansion, moderate expansion, and severe expansion areas. Except for soil organic matter, soil nutrients were increased in herbaceous plant expansion areas, and the total nitrogen (TN), total phosphorus (TP), available nitrogen (AN), and available phosphorus (AP) were greatest in moderate expansion areas (MOE), while soil organic matter levels were highest in the non-expanded areas (CK). The total soil PLFAs in the three levels of herbaceous plant expansion areas were significantly higher than those in the non-expanded areas, and total soil PLFAs were highest in the moderately expanded area and lowest in the severely expanded area (SEE). Bacteria increased significantly more than fungi and actinomycetes with herbaceous plant expansion. Soil hydrolase activities (β-1,4-glucosidase (βG) activity, β-1, 4-N-acetylglucosaminidase (NAG) activity, and acid phosphatase (aP) activity) were highest in MOE and lowest in the CK treatment. Soil oxidase activities (polyphenol oxidase (PPO) activities and peroxidase (PER) activities) were also highest in MOE, but they were lowest in the SEE treatment. The variations in total soil PLFAs with herbaceous plant expansion were mostly correlated with soil organic matter and available phosphorus concentrations, while soil enzyme activities were mostly correlated with the total soil nitrogen concentration. Our results suggest that herbaceous plant expansion increase the total soil PLFAs and soil enzyme activities and improved soil nutrients. However, soil microorganisms, enzyme activity, and nutrients responded differently to levels of herbaceous plant expansion. The soil conditions in mild and moderate expansion areas are more favorable than those in severe expansion areas. [ABSTRACT FROM AUTHOR]

Vegetation in high altitude areas normally exhibits the strongest response to global warming. We investigated the tundra vegetation on the Changbai Mountains and revealed the similarities and differences between the north and the southwest slopes of the Changbai Mountains in response to global warming. Our results were as follows: 1) The average temperatures in the growing season have increased from 1981 to 2015, the climate tendency rate was 0.38°C/10yr, and there was no obvious change in precipitation observed. 2) The tundra vegetation of the Changbai Mountains has changed significantly over the last 30 years. Specifically, herbaceous plants have invaded into the tundra zone, and the proportion of herbaceous plants was larger than that of shrubs. Shrub tundra was transforming into shrub-grass tundra. 3) The tundra vegetation in the north and southwest slopes of the Changbai Mountains responded differently to global warming. The southwest slope showed a significantly higher degree of invasion from herbaceous plants and exhibited greater vegetation change than the north slope. 4) The species diversity of plant communities on the tundra zone of the north slope changed unimodally with altitude, while that on the tundra zone of the southwest slope decreased monotonously with altitude. Differences in the degree of invasion from herbaceous plants resulted in differences in species diversity patterns between the north and southwest slopes. Differences in local microclimate, plant community successional stage and soil fertility resulted in differential responses of tundra vegetation to global warming. [ABSTRACT FROM AUTHOR]

• Specify the fire occurrence characteristics in mainland China. • Address the significance of weather elements causing fire occurrence. • Recognize the impact of fire prevention on fire occurrence. Understanding the degree to which weather factors influence fire occurrence is crucial for managing wildfires because China's recent rigorous fire prevention measures have made fire occurrence drivers distinct from those in other nations. This study first examined the features of mainland China wildfires in order to provide an explanation. We used 38,158 confirmed wildfires from 2005 to 2021 and used a partial least squares (PLS) regression model and partial correlation analysis (PCA) to investigate which weather element is more important in driving wildfire occurrence in each of the twelve ecoregions in mainland China. According to the findings, there were less wildfires in mainland China reduced significantly from 2005 to 2021 (R2 = 0.78, P < 0.01), and the fire seasons were varied according to the ecoregions. We discovered using Pearson correlation that weather factors had a significant correlation with the occurrence of wildfires in the majority of locations of mainland China, but at a lower decision level. From the Variable Importance in Projection (VIP) scores of each weather element, we found that humidity and diurnal temperature range (DTR) were more significant than other weather factors in influencing the occurrence of wildfires, especially in southern China. The partial correlation coefficients (P cor) between weather elements and fire occurrence draw the same conclusion that the driver strength of weather elements is different in different ecoregions. The findings also demonstrated that, on a monthly time frame, weather elements had no delay effect in driving fire occurrence. The impact of forest management laws and fire suppression measures on the frequency of wildfires in mainland China was examined. Instead of focusing on the forecast of fire occurrence, this study investigated which weather factors were more relevant in fire occurrence against the backdrop of tight forest fire prevention and control in China and presented a new perspective on wildfire research and management. This study also will be use as a reference for the nations interested in managing wildfires and emphasizes the significance of human actions in causing wildfires, particularly China's fire suppression practices. [ABSTRACT FROM AUTHOR]

BACKGROUND Field-scale changes in the water footprint during crop growth play an important role in formulating sustainable water utilisation strategies. This study aimed to explore field-scale variation in the water footprint of growing sunflowers in the western Jilin Province, China, during a 3-year field experiment. The goals of this study were to (1) determine the components of the 'blue' and 'green' water footprints for sunflowers sown with water, and (2) analyse variations in water footprints and soil water balance under different combinations of temperature and precipitation. Specific actions could be adopted to maintain sustainable agricultural water utilisation in the semi-arid region based on this study. RESULTS The green, blue, and grey water footprints accounted for 93.7-94.7%, 0.4-0.5%, and 4.9-5.8%, respectively, of the water footprint of growing sunflowers. The green water footprint for effective precipitation during the growing season accounted for 58.8% in a normal drought year but 48.2% in an extreme drought year. When the effective precipitation during the growing season could not meet the green water use, a moisture deficit arose. This increase in the moisture deficit can have a significant impact on soil water balance. CONCLUSION Green water was the primary water source for sunflower growth in the study area, where a scarcity of irrigation water during sunflower growth damaged the soil water balance, particularly in years with continuous drought. The combination of temperature and precipitation effected the growing environment, leading to differences in yield and water footprint. The field experiments in this area may benefit from further water footprint studies at the global, national and regional scale. © 2016 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Vegetation in the alpine tundra area of the Changbai Mountains, one of two alpine tundra areas in China, has undergone great changes in recent decades. The aggressive herb species Deyeuxia angustifolia (Komarov) Y. L. Chang, a narrow-leaf small reed, was currently encroaching upon the alpine landscape and threatening tundra biota. The alpine tundra of the Changbai Mountains has been experiencing a warmer climate and receiving a high load of atmospheric nitrogen deposition. In this study, we aimed to assess the respective roles of climate warming and atmospheric nitrogen deposition in promoting the upward encroachment of D. angustifolia . We conducted experiments for three years to examine the response of D. angustifolia and a native alpine shrub, Rhododendron chrysanthum , to the conditions in which temperature and nitrogen were increased. Treatments consisting of temperature increase, nitrogen addition, temperature increase combined with nitrogen addition, and controls were conducted on the D. angustifolia communities with three encroachment levels (low, medium, and high levels). Results showed that 1) D. angustifolia grew in response to added nutrients but did not grow well when temperature increased. R. chrysanthum showed negligible responses to the simulated environmental changes. 2) Compared to R. chrysanthum , D. angustifolia could effectively occupy the above-ground space by increasing tillers and growing rapidly by efficiently using nitrogen. The difference in nitrogen uptake abilities between the two species contributed to expansion of D. angustifolia . 3) D. angustifolia encroachment could deeply change the biodiversity of tundra vegetation and may eventually result in the replacement of native biota, especially with nitrogen addition. Our research indicated that nutrient perturbation may be more important than temperature perturbation in promoting D. angustifolia encroachment upon the nutrient- and species-poor alpine tundra ecosystem in the Changbai Mountains. [ABSTRACT FROM AUTHOR]

BACKGROUND Water footprint ( WF) methodology is essential for quantifying total water consumption of crop production and making efficient water management policies. This study calculated the green, blue, grey and total WFs of maize production in Northeast China from 1998 to 2012 and compared the values of the provinces. This study also analyzed the spatial variation and structure characteristics of the WFs at the prefecture level. RESULTS The annual average WF of maize production was 1029 m3 per ton, which was 51% green, 21% blue and 28% grey. The WF of maize production was highest in Liaoning Province, moderate in Heilongjiang Province and lowest in Jilin Province. The spatial differences of the WFs calculated for the 36 major maize production prefectures were significant in Northeast China. There was a moderate positive spatial autocorrelation among prefectures that had similar WFs. Local indicator of spatial autocorrelation index ( LISA) analysis identified prefectures with higher WFs in the southeast region of Liaoning Province and the southwest region of Heilongjiang Province and prefectures with lower WFs in the middle of Jilin Province. CONCLUSION Spatial differences in the WF of maize production were caused mainly by variations in climate conditions, soil quality, irrigation facilities and maize yield. The spatial distribution of WFs can help provide a scientific basis for optimizing maize production distribution and then formulate strategies to reduce the WF of maize production. © 2015 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Because of the limited number of observation stations and the short time series of orbiting carbon satellite data, it is difficult to monitor CO2concentrations (XCO2) at broad spatial scales for long time spans. Therefore, we are limited in accurately forecasting change in XCO2. Studies based on the approach of using satellite sensor-derived data as independent variables to model CO2exchange show promising results for closed forest stands. There is a need to extend this approach to other land-cover types to monitor XCO2at large spatial scales. In this study, Moderate Resolution Imaging Spectroradiometer (MODIS)-derived indices were used to model XCO2. Greenhouse Gases Observing Satellite (GOSAT) data and MODIS-derived indices in 2010 and 2011 were selected to construct XCO2models during the growing season (May–October). We selected three ground stations to assess the accuracy of the modelled XCO2for each month from 2011 to 2013. The accuracy of the results indicates that the average bias was 2.25, 4.53, and 4.43 ppm at the three ground stations, respectively, although the largest bias was 10.03 ppm (at Shangdianzi Station in June 2013). We also used GOSAT Thermal and Near Infrared Sensor for Carbon Observation (TANSO) point data in 2012 and 2013 as the observed data to assess the accuracy of the XCO2models, and achieved a slightly favourable result for each month, except June. The overall conclusion of this study is that the proposed new approach to obtaining XCO2at the regional scale needs to be perfected in the future. [ABSTRACT FROM PUBLISHER]

Tree line ecotone in the Changbai Mountains has undergone large changes in the past decades. Tree locations show variations on the four sides of the mountains, especially on the northern and western sides, which has not been fully explained. Previous studies attributed such variations to the variations in temperature. However, in this study, we hypothesized that topographic controls were responsible for causing the variations in the tree locations in tree line ecotone of the Changbai Mountains. To test the hypothesis, we used IKONOS images and WorldView-1 image to identify the tree locations and developed a logistic regression model using topographical variables to identify the dominant controls of the tree locations. The results showed that aspect, wetness, and slope were dominant controls for tree locations on western side of the mountains, whereas altitude, SPI, and aspect were the dominant factors on northern side. The upmost altitude a tree can currently reach was 2140 m asl on the northern side and 2060 m asl on western side. The model predicted results showed that habitats above the current tree line on the both sides were available for trees. Tree recruitments under the current tree line may take advantage of the available habitats at higher elevations based on the current tree location. Our research confirmed the controlling effects of topography on the tree locations in the tree line ecotone of Changbai Mountains and suggested that it was essential to assess the tree response to topography in the research of tree line ecotone. [ABSTRACT FROM AUTHOR]

Rain-fed crops are a major crop type, and their water use is extremely vulnerable to climate change. Studying the water requirement characteristics of rain-fed crops in different growth stages and associated climatic driving factors is of great significance for sustainable crop production. The water footprint (WF) of crops can comprehensively reflect the type and quantity of water consumption during the crop growth period. Previous studies have focused on quantifying the crop WF throughout the growth period, and less attention has been given to quantifying the crop WF in different growth stages. This study quantified the WFs of rain-fed maize and associated climatic driving factors in five growth stages from 1996 to 2018 in Northeast China. The results show that (1) the WF of rain-fed maize in each growth stage showed distinct differences. The highest WF occurred in the tasseling-milky growth stage, whereas the lowest WF occurred in the sowing-emergence growth stage. (2) The variation trends of maize WF in different growth stages were heterogeneous across Northeast China. The declining trends were mainly distributed in the southwest, while increasing trends were mainly distributed in the east in most growth stages. (3) Sunshine hours and temperature had a greater impact on the maize WF in most growth stages. The impacts of other climatic factors on the WF of rain-fed maize differed among different growth stages. Precipitation contributed much more to the variation in maize WF in early growth stages, relative humidity had the greatest impact on the WF of maize in the jointing-tasseling growth stage, and wind speed played a major role in the variation in the maize WF at the milky-mature growth stage. Management measures should be adjusted to alleviate the impact of climatic conditions on crop water consumption in different growth stages according to the results. • Water footprint (WF) of rain-fed maize in different growth stages was analyzed. • The highest WF was in tasseling-milky stage and the lowest in sowing-seeding stage. • Sunshine hours and temperatures had a greater impact on WF in most growth stages. • Feasible measures to reduce the impact of climatic factors on WF were discussed. [ABSTRACT FROM AUTHOR]

Grey water footprints (GWFs) can be used as an indicator to describe the influence of diffuse pollution on water environments and identify major contaminants. To improve the calculation of GWF, we conducted a field experiment with combinations of different slopes and fertilizer types on maize production in the black soil region of China. The goals of this study were to determine the actual amount of water used to dilute the pollutants; to explore the changes in the GWF under different slopes and fertilization types; and to identify the most critical pollutants and determine if they are consistent with those identified in previous studies. The results showed that the average GWFs of maize production were much different in 2016 and 2017. The GWFs of the 5° plots were much larger than those of the 1° plots and 3° plots, and the GWFs of the mineral fertilizer plots were larger than those of the organic manure plots in most cases. The loss rates of total nitrogen (TN) in the mineral fertilizer plots and the organic manure plots were all 0.2% in 2016 and 2.7% and 3.1% in 2017, respectively, which was much lower than 10% as reported in most articles. The most frequent critical pollutant was total nitrogen (TN), while total phosphorus (TP) and chemical oxygen demand (COD) were also critical pollutants in some cases, which differed somewhat from the results of previous studies. The uneven annual distribution of rainfall led to large interannual differences in the size of the GWFs. Therefore, using field observations, pollutant loss from agricultural ecosystems could be determined in line with local conditions, which should provide a reference for relevant measures to control diffuse pollution. [ABSTRACT FROM AUTHOR]