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1. chinaXiv:202112.00013 [pdf]

A new method of searching for concealed Au deposits by using the spectrum of arid desert plant species

CUI Shichao; ZHOU Kefa; ZHANG Guanbin; DING Rufu; WANG Jinlin; CHENG Yinyi; JIANG Guo
Subjects: Geosciences >> Geography

With the increase of exploration depth, it is more and more difficult to find Au deposits. Due to the limitation of time and cost, traditional geological exploration methods are becoming increasingly difficult to be effectively applied. Thus, new methods and ideas are urgently needed. This study assessed the feasibility and effectiveness of using hyperspectral technology to prospect for hidden Au deposits. For this purpose, 48 plant (Seriphidium terrae-albae) and soil (aeolian gravel desert soil) samples were first collected along a sampling line that traverses an Au mineralization alteration zone (Aketasi mining region in an arid region of China) and were used to obtain soil Au contents by a chemical analysis method and the reflectance spectra of plants obtained with an Analytical Spectral Device (ASD) FieldSpec3 spectrometer. Then, the corresponding relationship between the soil Au content anomaly and concealed Au deposits was investigated. Additionally, the characteristic bands were selected from plant spectra using four different methods, namely, genetic algorithm (GA), stepwise regression analysis (STE), competitive adaptive reweighted sampling (CARS), and correlation coefficient method (CC), and were then input into the partial least squares (PLS) method to construct a model for estimating the soil Au content. Finally, the quantitative relationship between the soil Au content and the 15 different plant transformation spectra was established using the PLS method. The results were compared with those of a model based on the full spectrum. The results obtained in this study indicate that the location of concealed Au deposits can be predicted based on soil geochemical anomaly information, and it is feasible and effective to use the full plant spectrum and PLS method to estimate the Au content in the soil. The cross-validated coefficient of determination (R2) and the ratio of the performance to deviation (RPD) between the predicted value and the measured value reached the maximum of 0.8218 and 2.37, respectively, with a minimum value of 6.56 μg/kg for the root-mean-squared error (RMSE) in the full spectrum model. However, in the process of modeling, it is crucial to select the appropriate transformation spectrum as the input parameter for the PLS method. Compared with the GA, STE, and CC methods, CARS was the superior characteristic band screening method based on the accuracy and complexity of the model. When modeling with characteristic bands, the highest accuracy, R2 of 0.8016, RMSE of 7.07 μg/kg, and RPD of 2.20 were obtained when 56 characteristic bands were selected from the transformed spectra (1/lnR)' (where it represents the first derivative of the reciprocal of the logarithmic spectrum) of sampled plants using the CARS method and were input into the PLS method to construct an inversion model of the Au content in the soil. Thus, characteristic bands can replace the full spectrum when constructing a model for estimating the soil Au content. Finally, this study proposes a method of using plant spectra to find concealed Au deposits, which may have promising application prospects because of its simplicity and rapidity.

submitted time 2021-12-03 From cooperative journals:《Journal of Arid Land》 Hits107Downloads48 Comment 0

2. chinaXiv:202112.00014 [pdf]

Elevated CO2 increases shoot growth but not root growth and C:N:P stoichiometry of Suaeda aralocaspica plants

WANG Lei; FAN Lianlian; JIANG Li; TIAN Changyan
Subjects: Geosciences >> Geography

The purpose of the current study was to investigate the eco-physiological responses, in terms of growth and C:N:P stoichiometry of plants cultured from dimorphic seeds of a single-cell C4 annual Suaeda aralocaspica (Bunge) Freitag and Schütze under elevated CO2. A climatic chamber experiment was conducted to examine the effects of ambient (720 μg/L) and CO2-enriched (1440 μg/L) treatments on these responses in S. aralocaspica at vegetative and reproductive stages in 2012. Result showed that elevated CO2 significantly increased shoot dry weight, but decreased N:P ratio at both growth stages. Plants grown from dimorphic seeds did not exhibit significant differences in growth and C:N:P stoichiometric characteristics. The transition from vegetation to reproductive stage significantly increased shoot:root ratio, N and P contents, but decreased C:N, C:P and N:P ratios, and did not affect shoot dry weight. Moreover, our results indicate that the changes in N:P and C:N ratios between ambient and elevated CO2 are mainly caused by the decrease of N content under elevated CO2. These results provide an insight into nutritional metabolism of single-cell C4 plants under climate change.

submitted time 2021-12-03 From cooperative journals:《Journal of Arid Land》 Hits118Downloads63 Comment 0

3. chinaXiv:202112.00016 [pdf]

Temporal and spatial variations of net primary productivity and its response to groundwater of a typical oasis in the Tarim Basin, China

SUN Lingxiao; YU Yang; GAO Yuting; ZHANG Haiyan; YU Xiang; HE Jing; WANG Dagang; Ireneusz MALIK; Malgorzata WISTUBA; YU Ruide
Subjects: Geosciences >> Geography

Net primary productivity (NPP) of the vegetation in an oasis can reflect the productivity capacity of a plant community under natural environmental conditions. Owing to the extreme arid climate conditions and scarce precipitation in the arid oasis regions, groundwater plays a key role in restricting the development of the vegetation. The Qira Oasis is located on the southern margin of the Taklimakan Desert (Tarim Basin, China) that is one of the most vulnerable regions regarding vegetation growth and water scarcity in the world. Based on remote sensing images of the Qira Oasis and daily meteorological data measured by the ground stations during the period 2006–2019, this study analyzed the temporal and spatial patterns of NPP in the oasis as well as its relation with the variation of groundwater depth using a modified Carnegie Ames Stanford Approach (CASA) model. At the spatial scale, NPP of the vegetation decreased from the interior of the Qira Oasis to the margin; at the temporal scale, NPP of the vegetation in the oasis fluctuated significantly (ranging from 29.80 to 50.07 g C/(m2?month)) but generally showed an increasing trend, with the average increase rate of 0.07 g C/(m2?month). The regions with decreasing NPP occupied 64% of the total area of the oasis. During the study period, NPP of both farmland and grassland showed an increasing trend, while that of forest showed a decreasing trend. The depth of groundwater was deep in the south of the oasis and shallow in the north, showing a gradual increasing trend from south to north. Groundwater, as one of the key factors in the surface change and evolution of the arid oasis, determines the succession direction of the vegetation in the Qira Oasis. With the increase of groundwater depth, grassland coverage and vegetation NPP decreased. During the period 2008–2015, with the recovery of groundwater level, NPP values of all types of vegetation with different coverages increased. This study will provide a scientific basis for the rational utilization and sustainable management of groundwater resources in the oasis.

submitted time 2021-12-03 From cooperative journals:《Journal of Arid Land》 Hits105Downloads51 Comment 0

4. chinaXiv:202112.00015 [pdf]

Using statistical models and GIS to delimit the groundwater recharge potential areas and to estimate the infiltration rate: A case study of Nadhour-Sisseb-El Alem Basin, Tunisia

Ali SOUEI; Taher ZOUAGHI
Subjects: Geosciences >> Geography

The water resources of the Nadhour-Sisseb-El Alem Basin in Tunisia exhibit semi-arid and arid climatic conditions. This induces an excessive pumping of groundwater, which creates drops in water level ranging about 1–2 m/a. Indeed, these unfavorable conditions require interventions to rationalize integrated management in decision making. The aim of this study is to determine a water recharge index (WRI), delineate the potential groundwater recharge area and estimate the potential groundwater recharge rate based on the integration of statistical models resulted from remote sensing imagery, GIS digital data (e.g., lithology, soil, runoff), measured artificial recharge data, fuzzy set theory and multi-criteria decision making (MCDM) using the analytical hierarchy process (AHP). Eight factors affecting potential groundwater recharge were determined, namely lithology, soil, slope, topography, land cover/use, runoff, drainage and lineaments. The WRI is between 1.2 and 3.1, which is classified into five classes as poor, weak, moderate, good and very good sites of potential groundwater recharge area. The very good and good classes occupied respectively 27% and 44% of the study area. The potential groundwater recharge rate was 43% of total precipitation. According to the results of the study, river beds are favorable sites for groundwater recharge.

submitted time 2021-12-03 From cooperative journals:《Journal of Arid Land》 Hits117Downloads59 Comment 0

5. chinaXiv:202112.00017 [pdf]

Predicting of dust storm source by combining remote sensing, statistic-based predictive models and game theory in the Sistan watershed, southwestern Asia

Mahdi BOROUGHANI; Sima POURHASHEMI; Hamid GHOLAMI; Dimitris G KASKAOUTIS
Subjects: Geosciences >> Geography

Dust storms in arid and desert areas affect radiation budget, air quality, visibility, enzymatic activities, agricultural products and human health. Due to increased drought and land use changes in recent years, the frequency of dust storms occurrence in Iran has been increased. This study aims to identify dust source areas in the Sistan watershed (Iran-Afghanistan borders)–an important regional source for dust storms in southwestern Asia, using remote sensing (RS) and bivariate statistical models. Furthermore, this study determines the relative importance of factors controlling dust emissions using frequency ratio (FR) and weights of evidence (WOE) models and interpretability of predictive models using game theory. For this purpose, we identified 211 dust sources in the study area and generated a dust source distribution map–inventory map–by dust source potential index based on RS data. In addition, spatial maps of topographic factors affecting dust source areas including soil, lithology, slope, Normalized difference vegetation index (NDVI), geomorphology and land use were prepared. The performance of two models (WOE and FR) was evaluated using the area under curve (AUC) of the receiver operating characteristic curve. The results showed that soil, geomorphology and slope exhibited the greatest influence in the dust source areas. The 55.3% (according to FR) and 62.6% (according to WOE) of the total area were classified as high and very high potential dust sources, while both models displayed acceptable accuracy with subsurface levels of 0.704 for FR and 0.751 for WOE, although they predict different fractions of dust potential classes. Based on Shapley additive explanations (SHAP), three factors, i.e., soil, slope and NDVI have the highest impact on the model's output. Overall, combination of statistic-based predictive models (or data mining models), RS and game theory techniques can provide accurate maps of dust source areas in arid and semi-arid regions, which can be helpful for mitigation of negative effects of dust storms.

submitted time 2021-12-03 From cooperative journals:《Journal of Arid Land》 Hits117Downloads58 Comment 0

6. chinaXiv:202112.00018 [pdf]

A bibliometric analysis of carbon exchange in global drylands

LIU Zhaogang; CHEN Zhi; YU Guirui; ZHANG Tianyou; YANG Meng
Subjects: Geosciences >> Geography

Drylands refer to regions with an aridity index lower than 0.65, and billions of people depend on services provided by the critically important ecosystems in these areas. How ecosystem carbon exchange in global drylands (CED) occurs and how climate change affects CED are critical to the global carbon cycle. Here, we performed a comprehensive bibliometric study on the fields of annual publications, marked journals, marked institutions, marked countries, popular keywords, and their temporal evolution to understand the temporal trends of CED research over the past 30 a (1991–2020). We found that the annual scientific publications on CED research increased significantly at an average growth rate of 7.93%. Agricultural Water Management ranked first among all journals and had the most citations. The ten most productive institutions were centered on drylands in America, China, and Australia that had the largest number and most citations of publications on CED research. "Climate change" and climate-related (such as "drought", "precipitation", "temperature", and "rainfall") research were found to be the most popular study areas. Keywords were classified into five clusters, indicating the five main research focuses on CED studies: hydrological cycle, effects of climate change, carbon and water balance, productivity, and carbon-nitrogen-phosphorous coupling cycles. The temporal evolution of keywords further showed that the areas of focus on CED studies were transformed from classical pedology and agricultural research to applied ecology and then to global change ecological research over the past 30 a. In future CED studies, basic themes (such as "water", "yield", and "salinity") and motor themes (such as "climate change", "sustainability", and "remote sensing") will be the focus of research on CED. In particular, multiple integrated methods to understand climate change and ecosystem sustainability are potential new research trends and hotspots.

submitted time 2021-12-03 From cooperative journals:《Journal of Arid Land》 Hits88Downloads45 Comment 0

7. chinaXiv:202111.00044 [pdf]

Response of ecosystem service value to land use/cover change in the northern slope economic belt of the Tianshan Mountains, Xinjiang, China

SUN Chen; MA Yonggang; GONG Lu
Subjects: Geosciences >> Geography

Land use/cover change (LUCC) is becoming more and more frequent and extensive as a result of human activities, and is expected to have a major impact on human welfare by altering ecosystem service value (ESV). In this study, we utilized remote sensing images and statistical data to explore the spatial-temporal changes of land use/cover types and ESV in the northern slope economic belt of the Tianshan Mountains in Xinjiang Uygur Autonomous Region, China from 1975 to 2018. During the study period, LUCC in the study region varied significantly. Except grassland and unused land, all the other land use/cover types (cultivated land, forestland, waterbody, and construction land) increased in areas. From 1975 to 2018, the spatial-temporal variations in ESV were also pronounced. The total ESV decreased by 4.00×108 CNY, which was primarily due to the reductions in the areas of grassland and unused land. Waterbody had a much higher ESV than the other land use/cover types. Ultimately, understanding the impact of LUCC on ESV and the interactions among ESV of different land use/cover types will help improve existing land use policies and provide scientific basis for developing new conservation strategies for ecologically fragile areas.

submitted time 2021-11-11 From cooperative journals:《Journal of Arid Land》 Hits90Downloads45 Comment 0

8. chinaXiv:202111.00045 [pdf]

Succession of soil bacterial and fungal communities of Caragana korshinskii plantation in a typical agro-pastoral ecotone in northern China over a 50-a period

MA Gailing; GOU Qianqian; WANG Guohua; QU Jianjun
Subjects: Geosciences >> Geography

Bacterial and fungal communities play critical roles in reestablishing vegetation structure, function and biodiversity in ecosystem restoration in arid and semi-arid areas. However, the long-term successional changes in bacterial and fungal communities that occur with artificial vegetation development are not fully understood. In this study, we investigated the successional changes in bacterial and fungal communities in Caragana korshinskii Kom. plantation over a period of 50 a (6, 12, 18, 40 and 50 a) and their relationships with key soil environmental factors in a typical agro-pastoral ecotone, northern China. The results showed that bacterial and fungal diversities (α- and β-diversity) were significantly affected by plantation age; moreover, the change in fungal community was more evident than that in bacterial community. Soil samples from 12 a plantation had the highest (P<0.05) bacterial and fungal α-diversity (i.e., abundance-based coverage estimator (ACE) and Chao1 index) at 0–10 cm depth compared with other samples. However, soil samples from plantation at the late recovery stage (40–50 a) had the highest α-diversity at 10–20 cm depth. Soil bacterial community was not significantly affected by plantation age at the genus level; but, soil fungal community was significantly affected at the genus level. Overall, Mortierella and Chaetomium were the dominant genera at natural recovery stage (0 a); Inocybe was the dominant genus at the early recovery stage (6–12 a); Inocybe and Mortierella were the dominant genera at the mid-recovery stage (12–40 a); And Mortierella, Cladosporium and Humicola were the dominant genera at the late recovery stage (40–50 a). Redundancy analysis (RDA) showed that β-glucosidase activity, total nitrogen and soil organic carbon were closely associated with bacterial community composition, while alkaline phosphatase, urease activity and total nitrogen were associated with fungal community composition, indicating that changes in enzyme activity and soil nutrients were the most important determinants of dominant genera. Furthermore, pathogenic microorganisms (Cladosporium and Humicola) were dominant in soils from 40–50 a plantation, which may affect plant growth, resulting in the decline of C. korshinskii plantation. Overall, the findings of this study improve the understanding of ecological patterns of bacterial and fungal communities in artificial vegetation and provide an important scientific basis for comprehensive ecological restoration management in arid and semi-arid areas.

submitted time 2021-11-10 From cooperative journals:《Journal of Arid Land》 Hits118Downloads67 Comment 0

9. chinaXiv:202112.00004 [pdf]

Disturbance of plateau zokor-made mound stimulates plant community regeneration in the Qinghai-Tibetan Plateau, China

XIANG Zeyu; Arvind BHATT; TANG Zhongbin; PENG Yansong; WU Weifeng; ZHANG Jiaxin; WANG Jingxuan; David GALLACHER; ZHOU Saixia
Subjects: Geosciences >> Geography

Mounds constructed by plateau zokors, which is widely distributed in alpine meadows significantly modified plant community structure. However, the variations of plant community structure under the disturbance of plateau zokor-made mound are less concerned. Therefore, we investigated the responses of plant community on zokor-made mound of different years (1 a and 3–4 a), and compared with undisturbed sites (no mound) in an alpine meadow in the eastern Qinghai-Tibetan Plateau (QTP), China. Species richness, coverage and Simpson diversity index were all significantly reduced by the presence of zokor-made mound, but plant heights were significantly increased, particularly in grasses and sedges. Several perennial forage species showed an increased importance value and niche breadth, including Koeleria macrantha, Elymus nutans and Poa pratensis. The effect of zokor-made mound on niche overlap showed that more intense interspecific competition produced a greater utilization of environmental resources. And this interspecific niche overlap was strengthened as succession progressed. The bare mound created by zokor burrowing activities provided a colonizing opportunity for non-dominant forage species, resulting in abundant plant species and plant diversity during the succession period. We concluded that presence of zokor-made mound was conducive to regeneration and vitality of plant community in alpine meadows, thus improving their resilience to anthropogenic stress.

submitted time 2021-11-10 From cooperative journals:《Journal of Arid Land》 Hits71Downloads21 Comment 0

10. chinaXiv:202112.00005 [pdf]

Effect of nitrogen and phosphorus addition on leaf nutrient concentrations and nutrient resorption efficiency of two dominant alpine grass species

LIU Yalan; LI Lei; LI Xiangyi; YUE Zewei; LIU Bo
Subjects: Geosciences >> Geography

Nitrogen (N) and phosphorus (P) are two essential nutrients that determine plant growth and many nutrient cycling processes. Increasing N and P deposition is an important driver of ecosystem changes. However, in contrast to numerous studies about the impacts of nutrient addition on forests and temperate grasslands, how plant foliar stoichiometry and nutrient resorption respond to N and P addition in alpine grasslands is poorly understood. Therefore, we conducted an N and P addition experiment (involving control, N addition, P addition, and N+P addition) in an alpine grassland on Kunlun Mountains (Xinjiang Uygur Autonomous Region, China) in 2016 and 2017 to investigate the changes in leaf nutrient concentrations (i.e., leaf N, Leaf P, and leaf N:P ratio) and nutrient resorption efficiency of Seriphidium rhodanthum and Stipa capillata, which are dominant species in this grassland. Results showed that N addition has significant effects on soil inorganic N (NO3–-N and NH4+-N) and leaf N of both species in the study periods. Compared with green leaves, leaf nutrient concentrations and nutrient resorption efficiency in senesced leaves of S. rhodanthum was more sensitive to N addition, whereas N addition influenced leaf N and leaf N:P ratio in green and senesced leaves of S. capillata. N addition did not influence N resorption efficiency of the two species. P addition and N+P addition significantly improved leaf P and had a negative effect on P resorption efficiency of the two species in the study period. These influences on plants can be explained by increasing P availability. The present results illustrated that the two species are more sensitive to P addition than N addition, which implies that P is the major limiting factor in the studied alpine grassland ecosystem. In addition, an interactive effect of N+P addition was only discernable with respect to soil availability, but did not affect plants. Therefore, exploring how nutrient characteristics and resorption response to N and P addition in the alpine grassland is important to understand nutrient use strategy of plants in terrestrial ecosystems.

submitted time 2021-11-10 From cooperative journals:《Journal of Arid Land》 Hits63Downloads26 Comment 0

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