Otindag Sandy Land Research Articles

Azimuthal and radial variations in sap flow and its effects on the estimation of transpiration for Picea mongolica.

In this study, we applied thermal dissipation probe technology to examine sap flow in various directions (east, south, west, and north) and at different depths (0-2, 2-4, 4-6 cm) within the stem of natural Picea mongolica trees in the eastern of Otindag Sandy Land to provide a scientific basis for accurately quantifying water consumption of P. mongolica forests through transpiration and to enhance the understanding of water relations. The results showed that the diurnal variation of sap flow in different directions displayed a unimodal curve, with the sap flow sequence being south>east>west>north. The sap flow at different sapwood depths exhibited an obvious unimodal curve, with a significant decrease as sapwood depth increased. Compared with that calculated from the mean sap flux density in four directions (23.57 kg·d-1), water consumption calculated using the mean value in south-east, east-west, south-west, north-east, north-south, and north-west was overestimated by 10.2%, 5.5%, 14.5%, and underestimated by 12.3%, 8.2%, 9.8%, respectively. The water consumption calculated using the values from the east, south, and west was overestimated by 6.1%, 14.4%, and 15.4%, respectively, and underestimated by 30.7% in the north. In addition, compared with the water consumption calculated from the mean value in three sapwood depths (48.51 kg·d-1), that calculated using sap flux density at sapwood depths of 0-2, 2-4, and 4-6 cm were overestimated by 18.8%, underestimated by 1.7%, and underestimated by 62.9%, respectively. These results indicated that sap flow of P. mongolica had significant azimuthal and radial variations, which considerably influence the estimation of tree water consumption. Installing probes at 0-2 cm simultaneously in both the north and east of the trunk could effectively reduce the estimation error of whole-tree water consumption by 4.2%. This approach enabled the accurate quantification of water consumption of individual P. mongolica trees in sandy areas, thereby improving the precision of transpiration water consumption estimates scaling up from individual level to stand level.

East Asian summer monsoon and early anthropogenic impacts on the lacustrine carbon cycle in the Otindag Sandy Land since the middle Holocene

Lake systems play a pivotal role in the global carbon cycle, yet the biogeochemical processes in alkaline and saline lakes have received little attention. In this study, we present a comprehensive analysis of δ13Ccarb and δ18Ocarb records from Lake Chagan in the Otindag Sandy Land, located in North China, spanning approximately 7000 years. Our aim is to explore how the lacustrine inorganic carbon cycle responded to both climate change and human activity. The findings reveal a notable highstand in Lake Chagan around 6.9–6.0 cal kyr BP, followed by a gradual regression leading to an unstable state over the past 1.6 cal kyr BP. The hydroclimate variations inferred from Lake Chagan align with other regional records, suggesting that long-term East Asian summer monsoon (EASM) precipitation trends were influenced by decreasing insolation and variations in solar irradiance on a centennial timescale. The sources of dissolved inorganic carbon (DIC) in lake water generally mirrored regional hydroclimate changes since the middle Holocene. Our evidence indicates that during periods of strong EASM activity, more allochthonous organic matter was converted to lake water DIC, coinciding with high vegetation cover and intense soil erosion. While hydroclimatic changes significantly impacted the lacustrine carbon cycle, the isotopic evidence also suggests substantial anthropogenic influences post-1.6 cal kyr BP, particularly in terms of the input of allochthonous organic matter into the lakes of the Otindag Sandy Land. These findings underscore the potential for anthropogenic-driven terrestrial carbon cycle feedback to global climate change over millennia.

Evaluation of the Groundwater Ecological Water Requirement in the Southeast Margin of Otindag Sandy Land Based on Allowable Groundwater Depth Drawdown

Water resources in arid and semi-arid areas are limiting factors for ecosystem health and economic development. Therefore, an accurate and reasonable assessment of ecological water demand is crucial for efficient water resource utilization. In this study, we used vegetation coverage and groundwater depth to assess the state of vegetation growth in the Zhenglanqi, located at the southeastern edge of Otindag Sandy Land. Our results indicate the existence of a statistical power index function between vegetation coverage and groundwater depth scatter plots, where even minor changes in groundwater depth can have a significant impact on vegetation growth. In order to quantitatively assess the impact of subsidence on vegetation ecology, we propose a maximum allowable subsidence level under conditions that maintain normal ecological conditions, based on the initial subsidence depth and ecological guarantee rate. Our findings suggest that regions with shallower initial groundwater depths are more sensitive to changes in their environment than regions with deeper groundwater depths. The total groundwater consumption in the study area was 83 million cubic meters while maintaining an ecological guarantee rate of 80%; thus, while ensuring normal environmental conditions, human exploitation of shallow groundwater accounts for only 16 percent.

Quantifying the contributions of natural and anthropogenic dust sources in Shanxi Province, northern China

Dust storms have direct or indirect impacts on climate change and human health. Identifying and quantifying natural/anthropogenic dust sources can facilitate effective prevention and control of dust events. Based on surface real-time PM10 monitoring data, satellite remote sensing and the HYSPLIT model, this study determined the specific timing, coverage and sources of dust events in Shanxi Province, Northern China. Thus, a composite fingerprinting technique was established to quantify potential dust sources and dust contributions of single dust events. The dust oxidation model was validated, indicating that the composite fingerprinting technique was well suited to the study region. The results show that natural dust sources (67%) contributed more to the study region than anthropogenic dust sources. They were mainly from the northwest and north of the study region. Particularly, the contributions of Taiyuan (TY) and Linfen (LF) accounted for the largest (82%) and smallest (55%) proportions, respectively, both exceeding 50%. Anthropogenic dust sources contributed 33%, mainly from the east and south of the study region. The contribution of anthropogenic dust sources increased in the study region from north to south. In terms of potential dust sources, the Tengger Desert and Badain Jaran Desert (TDBD) contributed the most (26%), followed by the Otindag Sandy Land (OL) (22%). The Taklimakan Desert (TD) contributed the least (2%). The Middle Farmland region of the Hexi Corridor (HMF) in the west (15%) had the largest proportion of anthropogenic dust sources. Differences in the regional contribution of potential dust sources mainly resulted from winter winds, surface drought severity and particle size. At an insignificant distance from the study region, the contribution of potential dust sources was larger in the west than in the east and increased from south to north overall. These methods and findings can contribute to improving the ecological environment in Northern China.

Sustainable restoration in sandy lands is challenged by the divergent responses of grassland functional types to disturbance

The effective management of regional grassland degradation requires a deep understanding of how different grassland types respond to climate change and human disturbance over different spatial and temporal scales. This study examined the dynamics and underlying driving mechanisms of various grassland types in the Otindag Sandy Land over 36 years (1986–2021) by integrating time-series Landsat images and extensive climate and socio-environmental data. We found that the dynamics and driving factors of different grassland types varied significantly. In low-cover grasslands, the area of desert grassland fluctuated with a decreasing trend after the breakpoint, while that of sandy grassland increased continuously without any breakpoints. In high-cover grasslands, the area of typical grassland only increased after the breakpoint, whereas that of temperate savanna grasslands first decreased and then increased insignificantly. Additionally, the desert grassland area was significantly negatively correlated with annual precipitation (AP), whereas the sandy grassland area was negatively correlated with annual mean wind speed (AMWS). The dynamics of typical grasslands were jointly influenced by climate and human factors, with temperate savannas mainly driven by the AP and AMWS. Moreover, high-cover grasslands were more sensitive to human activities than low-cover grasslands, and the most significant driving factors changed before and after the breakpoint in the area dynamics. These findings provide valuable insights into the monitoring and conservation of sandy land ecosystems.

Spatiotemporal variations in ecological quality of Otindag Sandy Land based on a new modified remote sensing ecological index

Spatiotemporal variations in ecological quality of Otindag Sandy Land based on a new modified remote sensing ecological index

Heterogeneity, marginality, stagementation and driving forces in the Otindag Sandy Land and its ecotones based on GIMMS NDVI3g v1.0

Due to differences in spatial and temporal scales and perspectives, there are academic debates about the understanding of the ecological evolution in Otindag Sandy Land. How vegetation in the sandy hinterland and marginal intersects interacts with the regional climate system and how it responds to human activities remain to be addressed. The motivation for this study is to try to clarify the abovementioned geographical misunderstandings. By setting up a core area (CA), a check area (CK) and four ecotones, various datasets such as the remote sensing vegetation index products GIMMS NDVI3g v1.0 (1982–2015), meteorological data (1982–2015), night-time lighting data (1984–2020), population data (1986–2016) and livestock data (1986–2016) were adopted; and maximum value composite (MVC), average value composites (AVC), linear regression analysis (θslope), phenology analysis (SOS, LOS, and EOS), coefficient of variation (Cov) analysis.and Hurst index (H) prediction were performed; and partial data consistency was validated by MODIS NDVI (2000–2015) dataset. The study found that: (1) vegetation coverage had spatial heterogeneity; (2) vegetation phenology exhibited a spatial differentiation; (3) vegetation growth rate had spatial differences; (4) vegetation response to climate change was regional and significant; (5) the coefficient of variation (Cov) of vegetation was segmental and regional; and(6) the response of vegetation to human activities was not significant. The results demonstrate that the NDVI development in the Otindag Sandy Land and its ecoregions is spatially heterogeneous, regional, marginal and temporally segmental and is more sensitive to climate change than to human activities.

The largest deflation basin in Asia reveals that the Miocene basin-filling sediments in the eastern Gobi Desert are an important dust source

Deflation is one of the most important exogenic forces in arid and semiarid regions. It not only shapes various wind erosion landforms but also releases a large amount of dust into the atmosphere. The Sunite Steppe in the eastern Gobi Desert is located in arid areas, where Neogene strata are widely distributed. However, the deflation process and its impact on landforms in this area are still unclear. We conducted comprehensive research on stratigraphy, sedimentology and geomorphology and found that there is a giant deflation basin (Sunite Deflation Basin) located to the west of the Otindag Sandy Land and to the east of the Tunggur Platform (Tamuqintala High Platform). With an area of over 8000 km2 and a volume of ∼393 km3, that deflation basin ranks second only to the Qattara Depression in North Africa and is much larger than Big Hollow in the United States; it is the second largest deflation basin in the world and the largest in Asia. Unlike the Qattara Depression (comma-like) and Big Hollow (rod-like), the Sunite Deflation Basin is shell-like in planform. The western edge of the basin is well defined with steep basin walls, indicating that the basin was developed on the ground represented by the Tunggur Platform. The basin bottom gradually becomes shallower from west to east, which is consistent with the prevailing westerly. Subordinate deflation basins, deflation mounds and blowouts are widely distributed in the Sunite Deflation Basin. The basement of the basin is mainly composed of Miocene alluvium and red clay, i.e., basin-filling sediments. The amount of dust (<20 μm) released from the basin that can be transported over long distances is preliminarily estimated to be as high as 216 km3. If all dust is deposited in the downwind loess area (∼37,200 km2) near Chifeng in Northeast China, the deposition thickness can reach ∼5.8 m. Nd isotope and U–Pb detrital zircon data suggest that the Miocene basin-filling sediments comprise aeolian deposits derived from the Gobi Desert and fluvial deposits derived from the Yinshan-Yanshan Orogenic Belt. The Sunite Deflation Basin must have begun forming after the deposition of basin-filling sediments (∼7.5 Ma) and most likely began to develop at ∼3.6 Ma as a result of the strengthened East Asian winter monsoon due to global cooling.

Tracking the Provenance of Aeolian Loess in Northeastern China by Uranium Isotopes

AbstractThe aeolian loess deposits in northeastern China have substantial potential for reconstructing the paleoclimate in the East Asian monsoon boundary zone. Identifying the source of the aeolian dust is crucial to interpret the paleo‐proxies recorded in the loess deposits in northeastern China; however, traditional geochemical tracers such as Nd and Sr isotopes cannot discriminate between the potential source areas, that is, the Otindag Sandy Land, Horqin Sandy Land, and Hulun Buir Sandy Land regions. In this study, the (234U/238U) activity ratio is used to constrain the provenance of the loess deposits in northeastern China. The (234U/238U) of the studied loess‐paleosol sequences (from 0.935 to 0.910) decreases with increasing depositional age (from 10 to ∼1,000 ka), which is consistent with predictions from uranium isotope comminution age model. A derived (234U/238U) of 0.935 ± 0.003 for the newly deposited loess (zero depositional age) is most similar to that of the Otindag Sandy Land positioned at a proximal upwind direction, suggesting that the Otindag Sandy Land is the most likely source of the aeolian dust that formed the loess deposits in northeastern China. A transportation time of 432 ± 65 ka was calculated for these deposits, indicating extensive mixing of the fine dust in the source regions, which could partially explain the relative homogeneity of loess deposits in northeastern China. The transportation time longer than several glacial‐interglacial cycles suggests that reconstructions of regional paleoclimate on orbital timescales should be viewed with caution because the potential influence of climatic changes could largely be buffered.

Spatio-Temporal Patterns and Driving Forces of Desertification in Otindag Sandy Land, Inner Mongolia, China, in Recent 30 Years

Background: Desertification is one of the main obstacles to global sustainable development. Monitoring, evaluating and mastering its driving factors are very important for the prevention and control of desertification. As one of the largest deserts in China, the development of desertification in Otindag Sandy Land (OSL) resulted in the reduction in land productivity and serious ecological/environmental consequences. Although many ecological restoration projects have been carried out, the vegetation restoration of OSL and the impact mechanism of climate and human activities on desertification remain unclear. Methods: Taking OSL as the research area, this paper constructs the desertification index by using the remote sensing images and meteorological and socio-economic data, between 1986 and 2016, and analyzes the spatio-temporal evolution process and driving factors of desertification by using trend analysis and spearman rank correlation. Results: The results showed that: (1) Desertification in the OSL has fluctuated greatly during the past 30 years. Desertification recovered between 1986 and 1990, expanded and increased between 1990 and 2000, reduced between 2000 and 2004, developed rapidly between 2004 and 2007, and recovered again between 2007 and 2016; (2) The desertification of OSL is dominated by a non-significant change trend, accounting for 73.27%. In the significant change trend, the area of desertification rising trend is 20.32%, which is mainly located in the north and east, and the area of declining trend is 6.41%, which is mainly located in the southwest; (3) Desertification is the result of the superposition of climate and human activities. Climate change is the main influencing factor, followed by human activities, and the superposition effects of the two are spatio-temporal differences. Conclusions: These results shed light on the development of desertification in OSL and the relative importance and complex interrelationship between human activities and climate in regulating the process of desertification. Based on this, we suggest continuing to implement the ecological restoration policy and avoid the destruction of vegetation by large-scale animal husbandry in order to improve the situation of desertification.

Morphological dynamics of a trough-shaped blowout on a fixed dune in China

• There is a strong link between blowout morphology and the pattern of airflow. • The pattern of airflow within blowout is related to the regional wind direction. • Airflow undergoes separation and deflection in the leeward of the deflation basin. • Corkscrew vortices are the determinant of upwind expansion of the deflation basin. The formation and development of blowouts is an important surface indication of sand drift activity in semiarid grassland areas; thus, an accurate understanding of their morphological evolution characteristics and dynamic processes is of significance for grassland desertification control. This study analyzed the long-term topographic change of a trough blowout developed on a fixed sand dune in the Otindag sandy land of China via ground measurements from 2011 to 2020 and examined the short-term airflow structure through field observations. The results indicated that the area of the deflation basin shows a state of continuous growth. The expansion of the deflation basin was most obvious on the western, southwestern and southern slopes, which is contrary to the regional prevailing wind direction. As airflow passes over the blowout, there is significant airflow steering with the change in topography, and the degrees of airflow steering and acceleration are determined by the direction of the approaching wind. Airflow expands and decelerates on the leeward side of the deflation basin, causing flow separation and producing a recirculation zone on the sheltered lee slopes. Based on a detailed analysis of the results, we suggest that the soil collapse and sand avalanches caused by vortices are the main reasons for the upwind expansion of the deflation basin. Collectively, these findings reveal a strong link between the blowout morphology and the airflow pattern.

Grain-size composition of the surface sediments in Chinese deserts and the associated dust emission

Chinese deserts are one of the essential source areas for global dust emission, and the intensity of dust emissions varies significantly depending on the grain-size composition of sediments, wind force, and vegetation coverage. To obtain complete and accurate information on the grain-size compositions of the surface sediments in these deserts and to assess the contribution of Chinese deserts to Asian dust emission, we systematically collected surface sediments from 12 deserts in northern China, and analyzed their grain-size composition. We also calculated dust emissions from 2010 to 2019 based on the sand transport rate and clay content. The mean grain-size of surface sediments was 2.34Φ, and the clay and silt contents were only 0.6 and 6.7%, respectively. The Taklimakan Desert had the finest surface sediment, with a mean grain-size of 2.75Φ, whereas the Kumtag Desert had the coarsest sediment, with a mean grain-size of 2.00Φ. The total annual dust emission of the Chinese deserts from 2010 to 2019 was 70.6 Tg y-1. The Taklimakan Desert in the western region, the Badain Jaran Desert and the adjacent Tengger and Ulan Buh deserts in the central region, and the Otindag Sandy Land in the eastern region were the greatest contributors to dust emission. These core areas of dust emission are also the regions with the highest dust storm frequency, indicating that the deserts are significant regions for dust storms in northern China and an important surface type for dust emission in China. We found a significant positive correlation between dust emission and dust storm frequency.

Assessment of the effects of ecological restoration projects on soil wind erosion in northern China in the past two decades

Wind erosion is a typical natural hazard in arid and semiarid regions. In recent decades, China has shown significant changes of greening trend due to a range of several ecological restoration projects (ERPs), Meanwhile, the wind erosion in northern China changed significantly. The debate about whether climatic change or ERPs dominated the variations in wind erosion was never truly resolved, which seriously affect the deployment of ERPs in the future, and it is a concerns of both academia and the Chinese government. To address this debate, we distinguished the ERPs’ effects on wind erosion from the climate change background by modeling the wind erosion under the different surface vegetation scenarios with the revised wind erosion equation (RWEQ) that was validated by our field observations. The simulated results shown that relative to the benchmark year (2000), the ERPs caused a rate of decrease of 17.77% of wind erosion modulus (WEM) in northern China during the period of 2001 to 2019, which occupied approximately 61% of the total decrease of WEM by ERPs and climatic fluctuations. This result means that the ERPs played the dominant role in wind erosion decreasing overall. Considering the effects of ERPs to wind erosion, the wind erosion intensity, the climatic fluctuation, and vegetation carrying capacity, this study concluded that the Gurbantunggut Desert, the Otindag Sandy Land, the Lop Nor, the Gashun Gobi Desert, the Mongolia Gobi Desert and the Hexi Corridor are the potential regions for ERP deployment in the future. We believe this study should provide robust evidence to resolve the debate on what dominates the variations in wind erosion processes in northern China, and give the valuable suggestions for ecological restoration project deployment in the future.

A new scientific framework of dryland ecological quality assessment based on 1OAO principle

Human disturbance and climate change can easily lead to the shift of dryland ecological quality. However, how to comprehensively assess the shift of dryland ecological quality remains challenging. The ecological quality of specific dryland ecosystem in Northern China is less investigated following the launch of long-term large-scale national ecological restoration projects. This study established a dryland ecological quality assessment framework by the “One-out, all-out (1OAO)” principle. The ecological quality dynamics of Otindag sandy land in Northern China was evaluated by choosing 16 years (2000–2015) ecological quality as a baseline and comparing it to the report period (2005–2020). Three indicators, normalized difference vegetation index (NDVI), soil organic carbon (SOC) and dust sandstorm (DSS) was used to represent vegetation, soil and atmosphere quality, respectively. Our results showed that the vegetation quality kept stable in most areas, improved area of vegetation quality accounted for 30% of Otindag sandy land. The soil quality improved and degraded area accounted for 10% and 83%, respectively. The atmosphere quality increased in 98% area of Otindag sandy land. Overall, the ecological quality of Otindag sandy land improved in one fifth but degraded in four fifth following the launch of the national ecology restoration projects. Both degradation area is persistent since 2000 and no recent degradation found compared baseline to report period. The improvement was mainly in the southeastern part and the degradation was in western part of Otindag sandy land. This study provides practical basis for the scientific evaluation of dryland ecological quality dynamics and will facilitate the regional ecosystem management.

Variation in fractional vegetation cover and its attribution analysis of different regions of Beijing-Tianjin Sand Source Region, China

Based on the MODIS NDVI data from 2000 to 2018, we estimated the fractional vegetation cover (FVC) using the dimidiate pixel model and analyzed the spatiotemporal characteristics of FVC in the Beijing-Tianjin sand source region (BTSSR). The geographical detector model was used to estimate the impacts of natural and human factors on FVC spatial distribution at the regional scale. The results showed that the FVC of the BBTSR showed an increasing trend from 2000 to 2018, with an annual growth rate of 0.013·(10 a)-1 and a vegetation increase rate of 8.2%. The area with high FVC was concentrated in the Yanshan Mountain water source protection area, followed by the pastoral transitional zone desertified land control area and the Otindag sandy land area. The area with poor FVC was concentrated in the northern arid grassland area. The explanatory power of driving factors to FVC varied across different regions. Among the natural factors, annual precipitation was the main driving factor for the spatial distribution of FVC in the northern arid grassland area, the Otindag sandy land area and the Yanshan Mountain water source protection area. Slope was the main driving factor for the spatial distribution of FVC in the pastoral transitional zone desertified land control area. Among different human activities, the number of large livestock at the year-end was the main driving factor controlling the spatial distribution of FVC in the northern arid grassland area and the pastoral transitional zone desertified land control area, while population density was the main driving factor controlling the spatial distribution of FVC in the Otindag sandy land area and the Yanshan Mountain water source protection area. There were regional differences in the influen-ce of other factors on FVC spatial distribution. The results of the interaction detector showed that the two-factor interactions were mainly the double-synergy and nonlinear synergy. The interaction of human activities with annual precipitation and slope could more fully explain the spatial variations of FVC. The range of suitable vegetation growth identified by the risk detector was the area with annual precipitation of 316.4-486.0 mm, average relative humidity of 48.4%-57.6%, and average annual temperature of 2.5-7.9 ℃, while other driving factors were different in different zones.

Simulations of spatial patterns and species distributions in sandy land using unmanned aerial vehicle images

The spatial distribution of vegetation in sandy lands is closely related to micro-topography. Point pattern analysis of vegetation distribution from ground surveys and satellite images is a commonly used method but does not capture the influence of spatial heterogeneity at small scales. This study examined long-term ecological observation sites of elm (Ulmus pumila) sparse forest in the Otindag Sandy Land, China. Elevation models from unmanned aerial vehicles (UAVs) and ground survey data on vegetation structure from 3768 elms were used to classify the terrain of sampled sites using a decision tree classification. It combined terrain factors, including slope, aspect, and small-scale altitude differences. Plots were divided into five topographic types: sand flat (53%), sand lowland (17%), sunny slope (13%), shady slope (10%), and sandy ridges (7%). Elm densities varied from 141.7 trees hm−2 on shady slopes to 17.0 trees hm−2 on sand lowland. A 2D Poisson fitting method was applied to the diameter at breast height, crown width, and other vegetation growth characteristics to simulate and verify the distribution of elms in the plots. Multivariate analysis was undertaken to confirm the effect of topographic factors on variation of tree characteristics. The integrated terrain approach could better characterize the spatial distribution of sparse forests. This research demonstrated that UAVs were a useful tool to measure spatial heterogeneity of sand micro-topography. Simulations of the distribution of plant characteristics indicated that the terrain classification matched the spatial pattern analysis of elms in semi-arid regions. Simulation of vegetation distribution is a useful technique for analyzing arid regions. This study will assist with further research on ecological restoration and vegetation protection in semi-arid areas.

Does Shrub Encroachment Indicate Ecosystem Degradation? A Perspective Based on the Spatial Patterns of Woody Plants in a Temperate Savanna-Like Ecosystem of Inner Mongolia, China

Shrub encroachment, i.e., shrub emergence or an increase in woody plant cover, has been widely observed in arid and semiarid grasslands and savannas worldwide since the 2000s. However, until now, there has been a clear division of opinion regarding its ecological implications. One view is that shrub encroachment is an indicator of ecological degradation, and the other is that shrub encroachment is a sign of the restoration of degraded ecosystems. This division leads to completely different judgments about the states and transition phases of shrub-encroached ecosystems, which further affects decisions about their conservation and management. To determine whether ecosystems experiencing shrub encroachment are degrading or are in a postdegraded restoration stage, the spatial distributions and interactions of woody plants after shrub encroachment were investigated in this study. An Ulmus pumila-dominated temperate savanna-like ecosystem with significant shrub encroachment in the Otindag Sandy Land, Inner Mongolia, China, was selected as the research area, and woody plants were surveyed within a 25-hectare (500 × 500 m) plot. Spatial point pattern analysis was employed to analyze the distribution patterns of the woody plants. The results indicated different patterns for U. pumila trees, i.e., a random distribution pattern for old trees (with a diameter at breast height (DBH) of more than 20 cm) and aggregated distribution patterns for medium (5 cm ≤ DBH &lt; 20 cm) and juvenile trees (DBH &lt; 5 cm) at scales of 0–9 and 0–12 m, respectively. For most shrubs, there was significant aggregation at a scale of 0–6 m. However, there were significant negative relationships between old U. pumila trees (DBH ≥ 20 cm) and most shrub species, such as Caragana microphylla and Spiraea aquilegifolia. In contrast, there were positive relationships between juvenile trees (DBH &lt; 5 cm) and most shrub species. These results suggest that, to some extent, shrub encroachment may have disrupted the normal succession pattern in the U. pumila community in this area, and without conservation, the original tree-dominated temperate savanna-like ecosystem may continue to deteriorate and eventually become a shrub-dominated temperate savanna-like ecosystem.

Spatiotemporal Variation of Vegetation Coverage and Its Response to Climate Factors and Human Activities in Arid and Semi-Arid Areas: Case Study of the Otindag Sandy Land in China

Vegetation coverage is a key variable in terrestrial ecosystem monitoring and climate change research and is closely related to soil erosion and land desertification. In this article, we aimed to resolve two key scientific issues: (1) quantifying the spatial-temporal vegetation dynamics in the Otindag Sandy Land (OSL); and (2) identifying the relative importance of climate factors and human activities in impacting vegetation dynamics. Based on correlation analysis, simple regression analysis, and the partial derivative formula method, we examined the spatiotemporal variation of vegetation coverage in the OSL, belonging to the arid and semiarid region of northern China, and their interaction with climate-human factors. The results showed that the vegetation coverage of the area showed a downward trend with a rate of −0.0006/a during 2001–2017, and gradually decreased from east to west. Precipitation was the main climate factor controlling the overall distribution pattern of vegetation coverage, while the human factors had a more severe impact on the vegetation coverage than the climate factors in such a short period, and the overall impact was negative. Among the human factors, population pressure, urbanization, industrialization, pastoral production activities, and residents’ lifestyles had a negative impact. However, ecological restoration polices alleviated the contradiction between human development and vegetation deterioration. The results of this article provide a scientific basis for restoring grassland systems in arid and semi-arid areas

Ecological and environmental consequences of ecological projects in the Beijing–Tianjin sand source region

Abstract Evaluation of influences of the Beijing–Tianjin Sand Source Control Project on soil wind erosion and ecosystem services is imperative for mastering the benefits and drawbacks of the program, as well as for distinguishing more reasonable estimations to evaluate regional sustainable development. Within the Beijing–Tianjin Sand Source Region, we quantified the spatiotemporal patterns of land use/cover changes (LUCCs), soil wind erosion modulus (SWEM), and essential ecosystem services throughout 2000–2015 by utilizing field investigations, remotely sensed data, meteorological data, and modeling. The influences of ecological projects on wind erosion and ecosystem services has been subsequently assessed by using those modifications brought on via the LUCCs (e.g., conversion from cropland to grassland/woodland) during the ecological construction. The results indicated that the SWEM showed a decline and ecosystem services which included carbon storage, water retention, and air quality regulation exhibited growth driven by using both local climate exchanges and human activities such as ecological projects. Excluding the effects of climate factors, the LUCCs stemming from ecological projects caused a total SWEM decrease of 3.77 million tons during 2000–2015, of which approximately 70% was prompted by the way of the transition from desert to sparse grassland. And from this transition, ecosystem services including both water retention and aboveground net primary productivity manifest a general increase. The sub-regions of desert grassland in Bayannur, Ordos Sandy Land, and Otindag Sandy Land were hot spots for wind erosion declines and ecosystem service enhancements induced by the ecological projects. We recommend that endeavors be coordinated toward the scientific management of the degraded lands and distribution of the local populace, as well as the implementation of diverse measures in the expected hotter and drier future.

Spatiotemporal variations and driving factors of dust storm events in northern China based on high-temporal-resolution analysis of meteorological data (1960–2007)

Northern China is a significant source of dust source in Central Asia. Thus, high-resolution analysis of dust storms and comparison of dust sources in different regions of northern China are important to clarify the formation mechanism of East Asian dust storms and predict or even prevent such storms. Here, we analyzed spatiotemporal trends in dust storms that occurred in three main dust source regions during 1960–2007: Taklimakan Desert (western region [WR]), Badain Jaran and Tengger Deserts (middle region [MR]), and Otindag Sandy Land (eastern region [ER]). We analyzed daily dust storm frequency (DSF) at the 10-day scale (first [FTDM], middle [MTDM], and last [LTDM] 10 days of a month), and investigated the association of dust storm occurrences with meteorological factors. The 10-day DSF was greatest in the FTDM (accounting for 77.14% of monthly occurrences) in the WR, MTDM (45.85%) in the MR, and LTDM (72.12%) in the ER, showing a clear trend of movement from the WR to the ER. Temporal analysis of DSF revealed trend changes over time at annual and 10-day scales, with mutation points at 1985 and 2000. We applied single-factor and multiple-factor analyses to explore the driving mechanisms of DSF at the 10-day scale. Among single factors, a low wind-speed threshold, high solar radiation, and high evaporation were correlated with a high DSF, effectively explaining the variations in DSF at the 10-day scale; however, temperature, relative humidity, and precipitation poorly explained variations in DSF. Similarly, multiple-factor analysis using a classification and regression tree revealed that maximum wind speed was a major influencing factor of dust storm occurrence at the 10-day scale, followed by relative humidity, evaporation, and solar radiation; temperature and precipitation had weak influences. These findings help clarify the mechanisms of dust storm occurrence in East Asia.