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Vegetation restoration in dryland regions may be a powerful way to control desertification and promote local habitat recovery. In these artificial revegetation systems, ecosystem processes and functioning are strongly determined by nitrogen (N) availability, while soil inorganic N (SIN) is the major available N form and is absorbed as a main N source for plants. However, SIN dynamics, their influencing factors, and their relative importance to the ecosystem of these N‐limited systems are not well understood. A field investigation was conducted to examine the monthly variations in SIN and its response to planting age and vegetation type in a typical artificial sand‐fixing system in northwestern China. The SIN content in topsoil (0–20 cm) during the growing season ranged from 7.10 to 95.65 mg kg−1, with a mean value of 27.14 mg kg−1. Soil nitrate N had a dominant role in determining SIN monthly dynamics, which showed a fluctuating trend with two peak values in early July and late August. SIN showed a significant increasing trend with the planting age of sand‐fixing vegetation, and it was highest for Nitraria sphaerocarpa (55.66 ± 5.76 mg kg−1), followed by Haloxylon ammodendron (29.81 ± 3.47 mg kg−1) and interspace (11.39 ± 1.13 mg kg−1). SIN displayed a hump‐shaped relationship with air temperature (R2 = 0.96, p < 0.01) and had a maximum at 19.88°C. The change rate of SIN was positively correlated with accumulated precipitation (R2 = 0.99, p < 0.05). SIN was correlated significantly with soil organic carbon (SOC), total nitrogen (TN), and soil clay content. Our results revealed that climatic (air temperature and precipitation), abiotic (soil texture), plant (planting age and vegetation type), and nutrient‐related (SOC and TN) factors regulate SIN dynamics in artificial sand‐fixing vegetation systems. Climate was the predominant factor affecting soil ammonium N, and soil nutrients (SOC and TN) were the predominant factor affecting soil nitrate N. Therefore, these factors should be integrated into optimizing regional vegetation establishment and improving ecosystem management practices in sand‐fixing lands. [ABSTRACT FROM AUTHOR]

Vegetation on dunes regulates the water supply from the dunes to the inter-dune lowland, which is a crucial factor affecting lake water dynamics in the inter-dune lowland. Previous researchers have paid insufficient attention to the water regulation function of dunes on a landscape- and regional scale. To fill this gap, both remote sensing technology and field observations were used to analyze the variations in the lake area and their influence factors, such as vegetation coverage and precipitation in the lake watershed, on a multi-year scale (2000–2020) and one-year scale (2021), respectively. The results showed that precipitation is the main factor influencing the changes in lake water, and artificial sand vegetation can regulate the changes in lake water. On the multi-year scale, with the coverage of artificial sand-fixing vegetation increasing on sand dunes in the lake watershed, the areas of the lakes were gradually decreasing. On the one-year scale, with dune vegetation coverage increased, the water supply from dunes to lakes showed a decreasing trend. This model can provide a possibility for estimating and predicting the influence of water supply from dunes to lakes that is affected by sand-fixing vegetation. The findings have significant theoretical and practical utility for the rational utilization of water resources in sandy land, as well as for assisting in the selection of an optimized construction mode for desert control projects. [ABSTRACT FROM AUTHOR]

Abstract Vegetation restoration in dryland regions may be a powerful way to control desertification and promote local habitat recovery. In these artificial revegetation systems, ecosystem processes and functioning are strongly determined by nitrogen (N) availability, while soil inorganic N (SIN) is the major available N form and is absorbed as a main N source for plants. However, SIN dynamics, their influencing factors, and their relative importance to the ecosystem of these N‐limited systems are not well understood. A field investigation was conducted to examine the monthly variations in SIN and its response to planting age and vegetation type in a typical artificial sand‐fixing system in northwestern China. The SIN content in topsoil (0–20 cm) during the growing season ranged from 7.10 to 95.65 mg kg−1, with a mean value of 27.14 mg kg−1. Soil nitrate N had a dominant role in determining SIN monthly dynamics, which showed a fluctuating trend with two peak values in early July and late August. SIN showed a significant increasing trend with the planting age of sand‐fixing vegetation, and it was highest for Nitraria sphaerocarpa (55.66 ± 5.76 mg kg−1), followed by Haloxylon ammodendron (29.81 ± 3.47 mg kg−1) and interspace (11.39 ± 1.13 mg kg−1). SIN displayed a hump‐shaped relationship with air temperature (R2 = 0.96, p

Summer rain is changeable in the semi-arid climate and is the limiting factor to the survival and growth of sand-fixing vegetation, especially in the Tibetan Plateau. Caragana intermedia is the dominant sand-binding shrub on a sand dune in the northeast Tibetan Plateau. Stable hydrogen and oxygen isotopes of xylem water, soil water, and groundwater were examined to study the rainwater uptake process by C. intermedia in mid-summer. Soil water content was monitored continuously before and after a 13.9-mm rain. Contribution of each water source was analyzed by the MixSIAR model. The results showed that the surface soil water (0−10 cm) was replenished by rainwater through increasing soil water content and reducing its stable isotope. Caragana intermedia mainly used surface soil water (0−10 cm) replenished by rainwater one day after the rain, accounting for about 60% of its total water source. As water availability decreased in upper soil layers, it used soil water at deeper levels (10−150 cm), the same water source as that one day before the rain. The rapid and efficient uptake of rainwater by C. intermedia reflected its response to summer rain, which is an adaptive strategy to the semi-arid environment. Therefore, C. intermedia could survive on a sand dune by shallow soil water replenished from rainwater in the Tibetan Plateau.

• In-situ tests in five sands with different vegetation coverages and types. • Deep percolation (DP) directly measured by a DP recorder. • DP in mobile sand more sensitive to rainfalls of > 10 mm and high-intensity. • Increases in vegetation coverages and forest selection reduced DP and soil water. Deep percolation (DP) determines the sustainable utilization of regional groundwater resources and provides large hydrological benefits to ecosystems in semiarid sandy regions. However, studies involving DP variability have rarely conducted in-situ tests with different vegetation coverages (VC) and vegetation types using direct measurements. This study measured soil moisture and DP for four years in five plots, with DP measured using a deep percolation recorder: mobile sand (MS) as the control group; Artemisia ordosica semifixed (AOSF) with VC of 30%–35% and Artemisia ordosica fixed (AOF) with VC of 70%–75% (AOSF and AOF stand ages: 30–40 years), representing different vegetation coverages; and Salix psammophila fixed (SPF) and Pinus sylvestrix var. Mongolica fixed (PSMF) with the same VC of 45%–50% (SPF and PSMF stand ages: 30 years), representing different vegetation types. The effects of sand-fixing vegetation on DP and soil water were evaluated using the relative extractable soil water (RESW) and soil water storage deficit metrics. DP occurrence in MS was closely related to rainfall amounts of > 10 mm and high-intensity rainfall rather than the total annual rainfall. Increases in vegetation coverages and forest selection significantly reduced DP and RESW compared with MS. DP in the shrub plot (SPF) was significantly higher than that in the forest plot (PSMF). Plants utilized water from different sources among the sandy land types: the shallow (0–80 cm) and deep layers (80–200 cm) in PSMF and AOF, and only from the shallow layer in AOSF and SPF. However, compared with MS, soil water storage deficit occurred to varying degrees in each plot. This study can provide a scientific reference for the restoration of the ecology and water cycle in sandy regions. [ABSTRACT FROM AUTHOR]

Planting vegetation to restore the soil environment is one of the most important methods for combating desertification. Reasonable vegetation type and vegetation coverage has an important role in sand control and the regional ecological security. The objective of this study is to clarify the appropriate type and coverage of sand-fixing vegetation in the Mu Us Desert. We identified changes in the topsoil properties as affected by different types and coverage of sand-fixing vegetation, and assessed the relationship between the soil fractal dimension (D) and major soil properties. Our results showed that: (1) with increasing cover of sand-fixing vegetation, fine soil material and soil nutrient content increased, indicating that the soil environment could accelerate restoration after planting or recovery of sand-fixing vegetation; (2) there were significant positive relationships between D and soil properties, which indicated that D was a sensitive and useful index for evaluating the influence of sand-fixing vegetation on soil physicochemical properties; and (3) recovery of natural vegetation using fencing should be given priority in areas where the soil matrix is not completely destroyed, and plant cover should be maintained at approximately 40% to 60%. We suggest that native shrubs, rather than trees, should be considered when choosing a sand-fixing vegetation. [ABSTRACT FROM AUTHOR]

The stability and sustainability of revegetated ecosystems is a central topic in ecological research. In this study, long-term monitoring and focused research on vegetation, soil and soil moisture from 2006 to 2012 were used to develop a model for evaluating indices of ecosystem stability using the analytical hierarchy process method. The results demonstrated that rainfall (R), vegetation coverage (C), and surface soil moisture (S) were the three most influential factors among the 14 indicators considered in a revegetated desert area in the Tengger Desert, China. A stability index (SI) was defined as SI = VAR (R) × VAR (C)/VAR (S), and a comparative study was conducted to examine the stability index of the natural vegetation community. The SI was divided into three regimes: SI < 0.006 was stable, 0.006 ≤ SI < 0.015 was semi-stable, and 0.015 ≤ SI was unstable. The stable, semi-stable and unstable periods of revegetated ecosystems in our simulations were 191, 17 and 11 years, respectively, within the total modeling period of 219 years. These results indicated that the revegetated desert ecosystem would be stable in most years during the vegetation succession, and this study presents new ideas for future artificial vegetation management in arid desert regions. [ABSTRACT FROM AUTHOR]