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Progress in study on irrigation practice with saline groundwater on sandlands of Taklimakan Desert Hinterland
Abstract
The study on the distribution and dynamic changes of soil moistures and salts under different irrigating methods and managements
of using saline groundwater on the sand lands of the hinterland of the Taklimakan Desert, started in 1997. The results show
that drip irrigation can be applied to seedlings (furrow irrigation can be applied to level lands) using saline groundwater
in the process of constructing the biological shifting sand control system along the desert highway in the hinterland of the
Taklimakan Desert; an irrigation frequency of 20 days and an irrigation amount of 30 kg/m2·time are suitable to the shifting sand control forest belts at the same year as they were afforested. Along with the increase
of forest age, the irrigation norm can be properly increased, the irrigation interval can be prolonged.
... Thus, saline water is widely used to drip irrigate crops [21]. Xu et al. [22] showed that drip irrigation was the optimal method for low-cost and water-saving irrigation for shelterbelt construction in the Taklimakan Desert. All plants of the TDHS are drip-irrigated with highsalinity (2.82-29.70 ...
... Plants are drip-irrigated with highly saline groundwater (salinity: 2.82-29.87 g/L) pumped from local wells [13,22]. On both sides of the highway the topography is heterogeneous and complex [27]. ...
... The irrigation systems used in the TDHS and the TDRS (Fig 2) are mainly drip irrigation, which was shown to be the best irrigation method [22]. After groundwater being pumped from the well (Fig 2B), it is imported to water valves ( Fig 2G) through main pipes ( Fig 2F) and control valve wells ( Fig 2C). ...
Freshwater resources are scarce in desert regions. Highly saline groundwater of different salinity is being used to drip irrigate the Taklimakan Desert Highway Shelterbelt with a double-branch-pipe system controlling the irrigation cycles. In this study, to evaluate the dynamics of soil moisture and salinity under the current irrigation system, soil samples were collected to a 2-m depth in the shelterbelt planted for different years and irrigated with different groundwater salinities, and soil moisture and salinity were analyzed. The results showed that both depletion of soil moisture and increase of topsoil salinity occurred simultaneously during one irrigation cycle. Soil moisture decreased from 27.4% to 2.4% for a 15-day irrigation cycle and from 26.4% to 2.7% for a 10-day-cycle, respectively. Topsoil electrical conductivity (EC) increased from 0.64 to 3.32 dS/m and 0.70 to 3.99 dS/m for these two irrigation cycles. With increased shelterbelt age, profiled average soil moisture (0–200 cm) reduced from 12.8% (1-year) to 7.1% (10-year); however, soil moisture in 0–20-cm increased, while topsoil salinity decreased. In addition, irrigation salinity mainly affected soil salinity in the 0–20-cm range. We conclude that water supply with the double-branch-pipe is a feasible irrigation method for the Taklimakan Desert Highway Shelterbelt, and our findings provide a model for shelterbelt construction and sustainable management when using highly saline water for irrigation in analogous habitats.
... Over the last 20 years, a great "green wall" of 436 km has been gradually erected in the center of the Taklimakan Desert, and has helped transform the desert into an oasis [1]. People could not travel very far into the desert in previous decades and centuries because of its hyper-arid environment, known as the "sea of death" in China. ...
... At present, a 72-78-meter-wide tree belt has been built along the 436 km of the highway, with a green area of 3128 ha. Despite groundwater with a high saline content, the greenbelt has been most successful, with a 90% plant survival rate [1]. Furthermore, its establishment has improved the biological diversity and soil fauna activity, e.g., 13 herb species have been found since the construction of the TDHS [9]. ...
Building highway and its biological protection system in a drought-affected shifting-sand desert is a great challenge. This challenge was completed by the construction of the Taklimakan Desert Highway Shelterbelt (TDHS)—the longest of its kind in the world (436 km). The TDHS can serve as a model for highway construction and desertification control using eco-friendly and cost-effective approaches in other desert regions. Notably, we proved that local saline groundwater irrigation offers potential advantages and opportunities for the growth of halophytes and sandy soil development in hyper-arid desert environments. Here, we systematically (1) summarize the project, its results, and vital technical issues of saline water irrigation; (2) address soil hydrological processes that play a crucial role in maintaining those systems; and (3) highlight useful insights for soil development, plant survival, and soil–plant–water–biota synergy mechanisms. Indeed, the TDHS project has provided a proof of concept for restoration and desert greening initiatives.
... As groundwater in the region is high in salinities (2.58-29.70 g/L), plants grown in the TDHS are typically drip-irrigated with local saline groundwater (Xu et al. 2006). Risks associated in using highly saline water as a plant water source include poor seed germination, reduced seedling growth, and reduced plant vigor (Sairam and Tyagi 2004, Paz et al. 2012, Riccardi et al. 2014, Sperling et al. 2014, Zhao et al. 2014. ...
... The irrigation interval is typically 15 d in March, April, May, September, and October and 10 d in June, July, and August. The irrigation application rate is typically 30 L per plant per irrigation event (Xu et al. 2006). Shifting sand was stabilized after the construction of the TDHS and the long-term drip irrigation resulted in the formation of a salt crust that is widely distributed at the soil surface within the shelterbelt (Zhang et al. 2008a). ...
Afforestation of shelterbelts is a sustainable practice to protect highways from shifting sand dunes in desert areas. The Taklimakan Desert Highway Shelterbelt (TDHS) in China is known as "the Great Green Wall of Taklimakan Desert" and borders a 436-km distance along the highway. This study assessed the early survival, above-ground growth, and root growth of three salt-and drought-tolerant plant species (Calligonum aborescens Litv., Tamarix ramosissima Ledeb., and Haloxylon ammodendron (C. A. Mey.) Bunge) in TDHS; those were drip-irrigated with local high saline groundwater. The results demonstrated that more than 80% of Haloxylon ammodendron seedlings could survive regardless of irrigation water salinities ranging from 2.82 to 29.70 g/L. In contrast, survival rates of Calligonum aborescens seedlings were greater than 65% when using irrigation water salinities ≤13.99 g/L and less than 50% when irrigated with water having salinities of 20.99-29.70 g/L, respectively. However, plant survival rates of Tamarix ramosissima were much lower than 50% when irrigated with water having salinities >4.82 g/L. Furthermore, under the same salinity, the height, crown width, and maximum width of basal stems were the greatest for Calligonum aborescens plants and the lowest for Tamarix ramosissima plants. Root length varied among the species depending on tree age and the applied water characteristics. We conclude that afforestation is feasible with saline water in this extreme arid shifting desert, particularly Calligonum aborescens plants should be grown at the outer margin of the shelterbelt due to its faster growth to more quickly stabilize the shifting sand. Our study may provide a good resolution for afforestation and marginal saline water utility in most arid and semiarid regions.
... There were significant differences of the average height between species by LSD method (p = 0.013 < 0.05 In most cases of arid and semi-arid regions, water supply is restricted in plants growth and survival as a dominant factor (Wang, 2004). Generally, if only the soil volume moisture is above 2%, there will be no water limit to the desert plants which commonly grow on sand dunes (Xu et al., 2006). According to this view, there was no water stress to the desert plants whether the IA was Table 2 The orthogonal experiment table OA9(3 4 ) and Significant effects for analyzing the influence factors, such as species (SP), irrigation amount (IA, mm) and irrigation frequency (IF, days) to average soil moisture (SM, %, n = 6, at the end of irrigation every time), average soil electrical conductive (EC, dS m −1 , n = 6, at the end of irrigation every time) and the shelterbelt shrubs height (SH, cm) of the current year. ...
... Under such natural conditions, soil moisture evaporates strongly and soil salt accumulates easily at soil surface and forms salt crust to restrict the shelterbelt plants development. But after the construction of shelterbelt project, shifting sandy soil was fixed, the soil environment became better, the salt crust development were under control and did not show too much stress to the plants under the current irrigation management (Xu et al., 2006;Zhang et al., 2008). In this study, salt accumulation occurred at the soil surface in 15 mm treatment and decreased with the shortened interval and the increasing IA. ...
In order to determine the best combination of the most adaptable shrub, the irrigation frequency (IF) and irrigation amount (IA) in the Tarim Desert Highway Ecological Shelterbelt Project, we investigated the soil moisture (SM), soil electrical conductivity (EC) and shelterbelt shrubs height (SH) where the plants were irrigated with the saline groundwater (5 g L−1) bumped from the local wells. And an orthogonal array experiment was set to test the effects of the species, IF and IA on the plants height. When the different irrigation ways were used to irrigate the shelterbelt plants, significant differences in plant species heights, soil moisture, and salt accumulation on the surface were found. All of these findings suggested that the IF 20-day with IA 30 mm every time was the better choice in which the soil moisture was above 2%, little salt accumulated on the dune surface and the most plants’ height occurred. Our results indicated that species was the more important factor to concern than IF and IA when the IA was above 15 mm with the IF less 30-day. The shrub traits determined greatly the growth status. And Haloxylon ammodendron was the best species selected among the three main shelterbelt shrubs, Tamarix taklamakanensis, H. ammodendron and Calligonum caput-medusae in the ecological shelterbelt project. Multivariate orthogonal array designs provided an effective strategy to determine the optimum irrigation management of individual additive components to the shelterbelt shrubs in the Tarim Desert Highway Ecological Shelterbelt Project.
... The groundwater was pumped for drip irrigation to water shrubs in the vegetation. The drip irrigation pipes run along the rows of shrubs, and the vegetation was irrigated twice per month from March to May and from September to October, and three times per month from June to August with ~ 30 litres of water per plant per irrigation event (Xu et al. 2006). ...
A fundamental challenge in soil macroecology is to understand how microbial community structure shapes ecosystem function along environmental gradients of the land surface at broad spatial scales (i.e. the horizontal dimension). However, little is known about microbial community structure–function relationships in extreme environments along environmental gradients of soil depth at finer spatial scales (i.e. the vertical dimension). Here, we propose a general spatial dimension partitioning approach for assessing the patterns and drivers of soil microbial community structure–function relationships across horizontal and vertical spatial gradients simultaneously. We leveraged a 200‐km desert soil salinity gradient created by a 12‐year saline‐water irrigation in the Tarim basin of Taklamakan Desert. Specifically, using a general linear model, hierarchical variance partitioning, and a path model, we assessed the patterns and key ecological processes controlling spatial turnover in microbial community structure (i.e. β‐diversity) and enzymatic activity relevant to carbon, nitrogen, and phosphorus cycling along soil salinity gradients across study sites (horizontal dimension) and soil depths (vertical dimension). We found a decoupled relationship between soil microbial β‐diversity and enzymatic activity. Differences in soil depth (on the scale of meters) were as important as geographic distance (on the scale of kilometers) in shaping bacterial and fungal β‐diversity. However, the vertical and horizontal turnover in enzymatic activity was largely attributed to an increase in the heterogeneity of soil properties, such as soil texture, water content, and pH. Our findings suggest that dispersal limitation controls microbial community β‐diversity and that environmental heterogeneity, rather than soil salinization, controls enzymatic activity. Taken together, this work highlights that in the face of ongoing environmental alterations, soil depth is an under‐explored spatial dimension that must be considered in soil conservation efforts as a critical factor in determining microbial community structure and function in extreme environments.
... Due to less rainfall in arid desert regions, water scarcity has become a worldwide issue of increasing severity [1,5]. The lower-quality saline-alkaline groundwater is widely applied [6][7][8]. Unfortunately, saline water irrigation normally leads to greater salinity hazards to plant growth and survival in groundwater extraction [9,10]. Therefore, establishing a suitable irrigation regime for artificial vegetation growth and survival is crucial to saving groundwater utilization and reducing the salinity hazards. ...
Freshwater resources are in a shortage in arid regions worldwide, especially in extremely arid desert areas. To solve this problem, highly saline groundwater is used for drip irrigation of desert plants. Since more irrigation infiltrating into the deep soil cannot be absorbed and utilized by desert plants, it is crucial to determine optimal water-saving irrigation regimes. In this study, we examined the effects of irrigation regimes on the soil water dynamics of two typical woody halophyte species (Haloxylon and Calligonum), and quantified the irrigation intervals and periods based on a field test of precision irrigation control in the Taklimakan Desert Highway shelterbelt. Results showed that the change in soil moisture of two species in the shallow 0–60 cm layer could be divided into a rapid decline period (1–9 d), a slow decline period (9–19 d), and a relatively stable period (19–39 d) after irrigation. The decrease rate of soil moisture at the 0–60 cm depth was significantly higher than that at the 60–200 cm depth. The irrigation regime combining 35 mm irrigation with 10 days was beneficial to soil water storage and plant use with respect to Calligonum, while the irrigation regime combining 35 mm irrigation with 40 days was best for Haloxylon. Increasing the single irrigation amount and prolonging the irrigation period can further enable the more effective use of irrigation water. This study highlights that saline groundwater irrigation provides potential advantages for desert plants’ survival under reasonable irrigation regimes.
... Establishing vegetation is an important tool for controlling desertification and reducing erosion in desert ecosystems [2][3][4]. Irrigation is the primary intervention to improve the success of vegetation establishment in desert ecosystems with low precipitation and high evapotranspiration rates [5,6]. For example, shrub planting has been a crucial strategy in the Taklimakan desert highway shelterbelt project, which crosses the largest mobile desert in China and uses drip irrigation to support vegetation to reduce wind-blown sand that blocks the road [7]. ...
Irrigation is the main strategy deployed to improve vegetation establishment, but the effects of increasing water availability on N use strategies in desert shrub species have received little attention. Pot experiments with drought-tolerant shrub Calligonum caput-medusae supplied with water at five field capacities in the range of 30-85% were conducted using local soil at the southern margin of the Taklimakan Desert. We examined the changes in plant biomass, soil N status, and plant N traits, and addressed the relationships between them in four-and seven-month-old saplings and mature shrubs after 28 months. Results showed that the growth of C. caput-medusae was highly responsive to increased soil moisture supply, and strongly depleted the soil available inorganic N pools from 16.7 mg kg −1 to an average of 1.9 mg kg −1 , although the total soil N pool increased in all treatments. Enhancement of biomass production by increasing water supply was closely linked to increasing total plant N pool, N use efficiency (NUE), N resorption efficiency (NRE), and proficiency (NRP) in four-month saplings, but that to total plant N pool, NRE, and NRP after 28 months. The well-watered plants had lower N concentrations in senesced branches compared to their counterparts experiencing the two lowest water inputs. The mature shrubs had higher NRE and NRP than saplings and the world mean levels, suggesting a higher N conservation. Structural equation models showed that NRE was largely controlled by senesced branch N concentrations, and indirectly affected by water supply, whereas NRP was mainly determined by water supply. Our results indicated that increasing water availability increased the total N uptake and N resorption from old branches to satisfy the N requirement of C. caput-medusae. The findings lay important groundwork for vegetation establishment in desert ecosystems.
... The volume of irrigation water and the salt distribution in soil profile can affect the salt leaching process (Swarajyalakshmi, Gurumurthy, & Subbaiah, 2003), so the soil salt dynamics has been extensively explored (Xu, Li, & Wang, 2006;Zhou, Xu, Lei, & Li, 2006;Miyamoto, Chacon, Hossain, & Martinez, 2005;Mousavi, Soltani-Gerdefaramarzi, & Mostafazadeh-Fard, 2010). However, most of the laboratory studies were focused on the effect of water and soil properties on the response to irrigation, while there is scarce information on the impact of drip irrigation with saline water on the growth, soil, and groundwater of Tamarixramosissima and Haloxylonammodendron forests under desert environment. ...
Fan, J., Wei, Y., Xinwen, W., & Yang, X. (March-April, 2017). Effect of drip irrigation with saline water on the construction of shelterbelts for soil and groundwater protection in the hinterland of the Taklimakan Desert, China. Water Technology and Sciences (in Spanish), 8(2), 19-30.
In order to perceive the effect of drip irrigation with saline water in the desert hinterland on plant growth of shelterbelts and underground environment (vadose zone and groundwater), by developing water-saving irrigation technology to ensure the scientifically substantiated utilization of water resources, four different irrigation cycle experiments (difference in irrigation period I: 12d; IV: 25d; II & III: 25d in the summer and the respective spring and autumn periods, which were the same: 15d and 20d, respectively) were carried out during the irrigation season in four different regions of well irrigation area. In this paper, regular on-site investigation was adopted to observe soil, water, and salt. Single-factor analysis of variance and least significant difference (LSD) are used to analyze the data acquired by the survey method and for measuring plant growth, complemented with the comparison of groundwater level and chemical index before and after irrigation. The results showed that the reduction of annual irrigation volume from 420 mm to 201.6 mm had almost no effect on plant growth and could save more than 50% of the water as compared to treatment I. Considering the impact on the height-growth of Tamarix, treatment II could be optimized, so that more than 30% of the water could be saved as compared to treatment I. Three days after irrigation, the salt was leached through the soil body into the groundwater. The groundwater level in the shelterbelt area, total dissolved solids (TDS), and total hardness exhibited an upward trend. Six days after irrigation, the high salt concentration region was found at a depth of 0–30 cm.
... The irrigation rate is 30 L tree -1 per application. The irrigation schedule was determined by Xu et al. (2006) based on the dual K c method (Allen et al. 1998) after field experiments conducted for several years and is applied to the entire TDHS. ...
It is a serious threat for the sustainable protection of the Taklimakan Desert Highway Shelterbelt (TDHS) from shifting sand burial. To explore the effects of shifting sand burial on soil evaporation, salt accumulation and their distribution, Micro-lysimeters were used under sand burial of different thickness (1, 3 and 5 cm) and particle size (<0.063, 0.063–0.20 and 0.20–2.00 mm). The results demonstrated that: (1) soil daily evaporation and accumulative evaporation decreased with the sand burial thickness, and thus evaporative inhibiting efficiency increased. Consequently, the soil water content increased with sand burial thickness (1.48–12.70%) than the control; (2) finer-textured (<0.063 mm) sand burial (0–2 cm depth) promoted soil evaporation and salt accumulation at topsoil, accumulative evaporation increased 5.1 mm and electrical conductivity (EC) of topsoil increased 13.30 dS m⁻¹ compared with the control; and (3) while topsoil EC decreased 1.65–6.46 dS m⁻¹ with the increase in sand burial thickness, soil EC beneath the sand burial interface showed a reverse trend. We concluded that shifting sand burial has obvious effects on soil water evaporation, salt accumulation and water-salt redistribution, and it could be considered to save water and reduce salt accumulation in arid desert areas like the TDHS with saline irrigation.
... Drip irrigation and high-pressure irrigation methods proved to be the most suitable irrigation methods in the construction of the ecological shelterbelt along the Taklimakan Desert Highway (Xu et al. 2006). Drip irrigation, also known as trickle irrigation or micro irrigation, is a water-saving irrigation method. ...
In a desert ecosystem, water plays a very important role in most ecological properties and processes. Located in the hinterland of the Eurasian continent, Xinjiang is covered by the sandy Gobi Desert, which is dotted with patchy oases. Land desertification is becoming a serious problem as the rapid growth in population and increased exploitation of water and soil resources increases. However, water that could be used to combat desertification is relatively scarce. Most of the conventional water resources are used in industry, agriculture and for social and economic development. Therefore, we need to develop non-conventional water (NWRU) for biological sand control. After 30 years of research, four types of NWRU technologies have been developed. (1) Non-irrigation afforestation technology using moisture, stored in the humid sandy subsurface, is applicable in the regions where precipitation is more than 100 mm per annum, of which most is snow fall; (2) water harvesting afforestation technology that collects snowmelt water and rainfall has been developed in the regions where precipitation is more than 100 mm and where the land is overlain by a low-permeability soil; (3) flood water irrigation afforestation technology, using summer floods, is feasible in regions with abundant flood water and where their occurrence coincides with the vegetation growing season; and (4) drip irrigation afforestation technology, using underground brackish water, has been developed in regions where abundant underground brackish water can be supplied through irrigation systems. This paper reviews the four types of NWRU technologies for biological sand control in Xinjiang and provides some technical references for combating desertification in similar areas around the world.
... The total salt contents were much higher in the salt-encrusted soils than in the shifting sandy soils, but the difference diminished as the age of the shelterbelt increased. This finding is consistent with previous results from the same study area (Xu et al., 2006). The soluble salt content of soil is one of the important indicators for determining the degree of soil salinization. ...
Understanding soil evaporation in reforestation processes in an area of extreme drought is important. We examined the effects of drip-irrigated, high-salinity groundwater on the formation of soil salt crusts and subsequent soil evaporation in the Taklimakan Desert Highway Shelterbelt. Soil evaporation was measured using micro-lysimeters (MLS, 20 cm in length x 10 cm in diameter), and chemical characteristics, including SOM, total salts, ion composition and pH, were analyzed. The results showed that the inhibition efficiency of salt crusts on soil evaporation decreased from the surface to the lower soil layers. Following irrigation, the inhibition efficiency was 33.0% in the shelterbelt, which was much higher than the 13.8% observed for the bare soil. Total salt content and ion contents (ClÖ¾, Na+, and SO42Ö¾) were much higher for the soil salt crusts than for shifting sandy soils, while the contents of other ions (Mg2+, K+, Ca2+, HCO3Ö¾, and CO32Ö¾) were very similar. The total salt content and ion composition of the salt crusts increased during the first 2 years of shelterbelt age, and decreased from 2 to 5 years. With the increasing age of the shelterbelts, the SOM of the salt crusts increased, whereas the total salts and pH decreased. We concluded that the formation of soil salt crusts results in reduced soil evaporation and the soil chemical condition functioned better for growth of the Taklimakan Desert Highway Shelterbelt.
... Mineralization of irrigation water in study area is 4.04 g/L. Figure 3 showed that salt contents of soil salt crusts in shelterbelt with salinity water drip-irrigation change much, and was much higher than shifting sandy land, but reduced gradually with the forest ages. This conclusion is consistent to the conclusions of Zhou's and Xu's [16,17]. Salt contents of soil salt crusts in shelterbelt irrigated for two years, five years, eight years and 11 years increased 317.15 times, 111.19 times, 108.96 times and 95.65 times than shifting sandy land. ...
Soil salt crusts are special layers at soil surface which are widely distributed in the Trim Desert Highway Shelterbelt under drip-irrigation with high salinity groundwater. In order to reveal annual variation of their chemical characteristics, soil salt crusts in shelterbelt of different ages in hinterland of the Taklimakan Desert were sampled. SOM, total salt, inions and pH were analyzed. Following results were obtained. SOM of salt crusts increased with the shelterbelt ages, but increasing trend became lower gradually. Total salt, ions, and pH of salt crusts reduced gradually with the shelterbelt ages. Total salt of salt crusts in shelterbelt of different ages was much higher than shifting sandy land. Ions were higher than shifting sandy land, Cl(-), Na(+), and SO4 (2-) increased more obvious, then Mg(2+), K(+), Ca(2+) and HCO3 (-), CO3 (2-) was little and nearly had no change. pH was all alkaline, pH of salt crusts in shelterbelt of 11 years was even lower than shifting sandy land. We can include that the quality of shallow soil (0~30 cm) in the Trim Desert Highway Shelterbelt becomes better gradually.
... In order to obtain simplified and reasonable statistics for modeling uncertainty, and satisfy the actual needs of hydrogeological workers, more and more researchers, e.g. [3,6,[15][16][17][18][19][20][21], accepted to use a framework to analyze groundwater modeling uncertainty. In general, according to the logical process of groundwater modeling, the uncertainty stems from three sources which are model parameter, conceptual model (or model structure) and observation data, respectively. ...
Groundwater system is a complex and open system, which is affected by natural conditions and human activities. Natural hydrological processes is conceptualized through relatively simple flow governing equations in groundwater models. Moreover, observation data is always limited in field hydrogeological conditions. Therefore, the predictive results of groundwater simulation often deviate from true values, which is attribute to the uncertainty of groundwater numerical simulation. According to the process of system simulation, the uncertainty sources of groundwater numerical simulation can be divided into model parameters, conceptual model and observation data uncertainties. In addition, the uncertainty stemmed from boundary conditions is sometimes refered as scenario uncertainty. In this paper, the origination and category of groundwater modeling uncertainty are analyzed. The recent progresses on the methods of groundwater modeling uncertainty analysis are reivewed. Furthermore, the researches on the comprehensive analysis of uncertainty sources, and the predictive uncertainty of model outputs are discussed. Finally, several prospects on the deveolpment of groundwater modeling uncetainty analysis are proposed.
Soil microbes have a major impact on microbial function in extreme environments, such as deserts, where environmental factors such as salinity and soil water act as strong filters to community structure. In fact, environmental filtering in these extreme environments can occur over even small gradients in soil depth, which is often overlooked, but important in the functioning of these systems. We leveraged a 200-km desert soil salinity gradient to test the relationships between microbial community structure and function (i.e., enzymatic activity) at different soil depths. Surprisingly, differences in soil bacterial and fungal community structure were not linked to differences in enzymatic activity, implying that soil microbial communities have a high degree of functional redundancy among soil depths. However, we found that the effects of soil depth (at the scale of meters) were just as important as the effects of geographic distance (on the scale of kilometers) on soil bacterial and fungal community structure, while the vertical variability in enzymatic activity along soil depth was largely attributed to the increase in heterogeneity of soil properties (i.e., soil texture, water content, and pH). Although contrasting assembly processes determine community structure and function, these findings suggest that soil depth restructures microbial community structure and function in extreme environments. Our data highlight that soil conservation efforts in arid ecosystems should consider soil depth as a key attribute in the face of ongoing desertification in many ecosystems.
Significance
Soil microbes mediate many ecosystem functions in extreme environments, where environmental factors act as strong filters to community structure. Environmental filtering can occur over even the small scale along soil depth profiles, which is often overlooked, but important in regulating ecosystem functioning. Here, we investigate the structure-function relationships of soil microbial communities along soil-depth profiles in the Taklamakan desert. We show that soil depth restructures soil microbial community structure and function. This work highlights that soil conservation efforts in arid ecosystems should consider soil depth as a key attribute in the face of ongoing desertification in many ecosystems.
The longest artificial highway shelterbelt flowing across the Taklamakan desert was conducted in 2005. To ensure the sustainable development of the highway and shelterbelts, scholars have carried out a large number of studies on the shelterbelt since 1991. This review is based on a 30-year monitoring program from 1991 to 2021. We find that, with the increase of shelterbelt age, some ecological and economic benefits gradually appear, such as saving transportation cost, promoting economic development in Southern Xinjiang, improving the sandy soil and microenvironment, and increasing the biodiversity. In the meanwhile, some adverse phenomena also exist, such as high maintenance costs, decrease in water tables because of irrigation, threats of the protected species, pollution from pumping oil wells, and the potential damage from highway burying as sand dunes move forward. In view of these problems, some suggestions are as follows. First, the science-policy sections of both the UNFCCC and the UNCCD should pay special attention to providing research-based guidance for the international cooperation and coordination. Second, China government should provide the necessary funding to establish the 27th China desert observation and research station to ensure long-term monitoring and slow down the pace of construction on the desert highway to allow time to develop strategies that minimize the impact on wild animals. Third, it is necessary to apply solar photovoltaic power in well irrigation and sand industry development. Fourth, the sand-blocking belt of 10 m width and 10 m away from the outside of the upwind shelterbelt can be laid every five years in view of sand-buried roads. In short, the inter-agency collaboration and coordination are both essential to ensuring the success of sustainable development and management of the Taklamakan Desert man-made ecosystem.
Desertification is one of the most serious environmental problems in the world, especially in the arid desert regions. Combating desertification, therefore, is an urgent task on a regional or even global scale. The Taklimakan Desert in China is the second largest mobile desert in the world and has been called the “Dead Sea” due to few organisms can exist in such a harsh environment. The Taklimakan Desert Highway, the longest desert highway (a total length of 446 km) across the mobile desert in the world, was built in the 1990s within the Taklimakan Desert. It has an important strategic significance regarding oil and gas resources exploration and plays a vital role in the socio-economic development of southern Xinjiang, China. However, wind-blow sand seriously damages the smoothness of the desert highway and, in this case, mechanical sand control system (including sand barrier fences and straw checkerboards) was used early in the life of the desert highway to protect the road. Unfortunately, more than 70% of the sand barrier fences and straw checkerboards have lost their functions, and the desert highway has often been buried and frequently blocked since 1999. To solve this problem, a long artificial shelterbelt with the length of 437 km was built along the desert highway since 2000. However, some potential problems still exist for the sustainable development of the desert highway, such as water shortage, strong sandstorms, extreme environmental characteristics and large maintenance costs. The study aims to provide an overview of the damages caused by wind-blown sand and the effects of sand control measures along the Taklimakan Desert Highway. Ultimately, we provide some suggestions for the biological sand control system to ensure the sustainable development of the Taklimakan Desert Highway, such as screening drought-resistant species to reduce the irrigation requirement and ensure the sound development of groundwater, screening halophytes to restore vegetation in the case of soil salinization, and planting cash crops, such as Cistanche, Wolfberry, Apocynum and other cash crops to decrease the high cost of maintenance on highways and shelterbelts.
In order to clarify the influence of saline water irrigation to plant growth and distribution ofsoil water-salt, and providing theoretical basis for sustainable water supply of ecological constructionin desert area, the data of soil water-salt and plant growth was observed at Tarim Desert HighwayShelter-forest Ecological Project No. 17 well. The law of soil water and salt spatial distribution wasanalyzed, and the responses of plant growth to 4 different irrigation amounts were studied by singleelement variance analysis. The results were as follows: the soil water content reaches or is close tosaturation in layer of 100~120cm under the 420mm irrigation water condition; The soil water contentreaches or is close to saturation in layer of 160~180cm under the 233.1mm irrigation water condition;The soil water content reaches or is close to saturation in layer of 180~200cm under the 285.6mm irrigation water condition; The soil water content reaches or is close to saturation in layer of160~180cm under the 201.6mm irrigation water condition. The vertical distribution law of soilssalinity is that the soil salt can enter groundwater after 3 days of irrigation, and be gathered in 0~30cmsoil layer. There were no significant differences except the Tamarix plant height in plant growthindexes among 4 different irrigation quantities treatments.
We explored the unique environmental conditions and management model of the Tarim Desert Highway shelter forest as well as the important roles of such shelter forest in development of the socio-economy of South Xinjiang. Experiments were conducted in the shelter forest lands drip-irrigated with underground saline water. Our results indicated that there are canonical correlations among soil nutrients, microbial amount and enzyme activity. The correlation between soil nutrients and soil microbial biomass was mainly attributed to total nitrogen, organic matter, total phosphate of nutrient factors, and amount of actinomycetes, carbon and phosphate content in microbe. The correlation between soil nutrients and soil enzyme activity was due to organic carbon, available potassium in soil and soil enzyme activities such as catalase activity and phosphatase activity. The correlation between soil microbial mass and activities of soil enzymes was due to phosphate and nitrogen contents in microbe and soil enzymes invertase and phosphatase activities. In addition to the correlations of soil nutrients and soil bio-activities, there is a vertical difference between these three factors in soil. We concluded that irrigation with saline groundwater had major effects on soil mineralization process. The release of soil nutrients in the process supported microbial mass colonization and soil enzyme activities in the Tarim Desert Highway shelter forest land. However, high level of salt in ground water adversely affected soil nutrient accumulation and microbe survival.
Phreatic evaporation is a great lose for shallow groundwater in the Taklimakan Desert. Given soil type and groundwater table,
the limiting rate of phreatic evaporation is defined as the maximum of water transferred from groundwater to soil surface
per unit time, which is a key parameter and control condition for phreatic evaporation model developing. The soil water characteristic
curve for the aeolian sandy soil in the Taklimakan Desert was fitted with the least square method based on the formula of
soil moisture characteristics curve proposed by Van Genuchten, using observed soil moisture and soil water suction data. The
unsaturated hydraulic conductivity was determined by the instantaneous profile method in situ and the calculation formula for unsaturated hydraulic conductivity was established. According to the steady flow theory,
the quasi-analytical solution of limiting rate of phreatic evaporation was derived on the basis of generalization of the formula
of unsaturated hydraulic conductivity. The results show that the soil moisture characteristics in the Taklimakan Desert can
be well described by Van Genuchten’s formula, and the limiting rate of phreatic evaporation declines by power function with
the descending of groundwater table.
We studied the variation of soil moisture as well as its regularity over the irrigation cycle at shelterbelts along the Tarim
Desert Highway at different site types and different planting years. The results show that: (1) There is an obvious temporal
variation of soil moisture within a typical irrigation period in shelterbelts along the Tarim Desert Highway, and the soil
water storage varied linearly with the number of days after irrigation. Along the direction perpendicular to the soil top,
the soil profile can be divided into four layers and each shows different dynamics of soil moisture variation, including the
quickly changing layer (0–20 cm), the active layer (20–60 cm), the weakly layer (60–100 cm), and the regulated layer (under
100 cm). (2) Both the soil moisture and soil water content decreased gradually with the number of planting year, while the
soil water deficit increased. It indicates that shelterbelts along the Tarim Desert Highway can retain the water accumulated
from previous years. (3) The soil water storage of harden sand is the maximum among all types of sites. Specifically, it is
about 1.58 times higher than that of longitudinal dune, 1.15 times higher than clay, and 1.43 times higher than flat sand.
Its soil water deficit was over 900 mm.
Technological demonstration of the biological shifting sand control along the roads in a desert oilfield base in the Tazhong region: An experimental study on the irrigation systems with saline groundwater on sandlands
- X Xu
- X. Xu
Xu X. Technological demonstration of the biological shifting sand
control along the roads in a desert oilfield base in the Tazhong region: An experimental study on the irrigation systems with saline
groundwater on sandlands. Pedology Bulletin (in Chinese), 2001,
32: 112-114
Analysis on the feasibility of constructing the biological shifting sand control systems along the roads in a desert oilfield base in the Tazhong region
- S Sun
- X Xu
- L Zhu
- S. Sun
Sun S, Xu X, Zhu L, et al. Analysis on the feasibility of constructing the biological shifting sand control systems along the roads in a
desert oilfield base in the Tazhong region. Arid Zone Research (in
Chinese), 2002, 19(4): 21-23
Soils and Land Resources in the Taklimakan Desert
- X Xu
Xu X. Soils and Land Resources in the Taklimakan Desert (in Chinese). Beijing: Science Press, 1994. 36-38
Soils and Land Resources in the Taklimakan Desert (in Chinese)
- X Xu
- X. Xu