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Quantitative identification of water utilization characteristics of xerophytic shrubs is an important prerequisite for the selection and optimization of a regional artificial sand-fixing vegetation system. In this study, a hydrogen (dD) stable isotope technique was used to study the changes in water use characteristics of four typical xerophytic shrubs, Caragana korshinskii, Salix psammophila, Artemisia ordosica, and Sabina vulgaris in the Hobq Desert under light (4.8 mm after 1 and 5 days) and heavy (22.4 mm after 1 and 8 days) rainfall events. Under light rainfall, C. korshinskii and S. psammophila primarily used the 80-140 cm layer of soil water (37-70%) and groundwater (13-29%), and the water use characteristics did not change significantly after the light rainfall event. However, the utilization ratio of A. ordosica to soil water in the 0-40 cm layer increased from less than 10% on the first day after rain to more than 97% on the fifth day after rain, whereas the utilization ratio of S. vulgaris to soil water in the 0-40 cm layer also increased from 43% to nearly 60%. Under heavy rainfall, C. korshinskii and S. psammophila still used the 60-140 cm layer (56- 99%) and groundwater (~15%), while the main water utilization depth of A. ordosica and S. vulgaris expanded to 0-100 cm. Based on the above results, C. korshinskii and S. psammophila primarily use the soil moisture of the 80-140 cm layer and groundwater, while A. ordosica and S. vulgaris use the soil moisture of the 0-100 cm layer. Therefore, the co-existence of A. ordosica and S. vulgaris will increase the competition between artificial sand-fixing plants, while the combination of the two plants with C. korshinskii and S. psammophila will avoid competition between artificial sand-fixing plants to some extent. This study provides important guidance for regional vegetation construction and sustainable management of an artificial vegetation system. [ABSTRACT FROM AUTHOR]

Trade‐offs exist for xerophytic shrubs between functional traits, involving in water loss and assimilate accumulation, can contribute to its survival and growth rate regulation in arid environments. However, growth analysis based on plant functional traits has been focused on the study of herbs and woody species. It is still unclear how the functional traits of xerophytic shrubs regulate their growth rate.In this study, we selectedeight xerophytic shrubs as samples to analyze the regulation process of the functional traits of shrubs on growth rate. Plants were cultivated for three years, and three harvests (every one year) were carried out. Factors explaining between‐species differences in relative growth rate (RGR) varied, depending on whether different ages were considered.The results showed that RGR was positively correlated with net assimilation rate, but there was a significant negative correlation with leaf area ration (LAR), specific leaf area (SLA), and leaf biomass ratio in the age 1. However, in the age 2, RGR showed a significant positive correlation with the morphological traits (i.e., leaf area ration and specific leaf area), but not with physiological traits (i.e., net assimilation rate) and leaf biomass allocation.Our results suggested that the fluctuation of environmental factors affects the regulation path of the plant functional traits on RGR of xerophytic shrubs. However, the analysis of causality model showed that no matter in which age, net assimilation rate and leaf area ration principally drive the variation in RGR among xerophytic shrubs. [ABSTRACT FROM AUTHOR]

The effects of rainfall intensity on stemflow production as described in the literature are quite inconsistent (increase, decrease, or no clear relationship) due to complex interactions between rainfall characteristics, and the effect of raindrop size on stemflow production has rarely been explored. Here we conducted field rainfall simulation experiments on two dominant xerophytic shrubs (Caragana korshinskii and Artemisia ordosica) in northwesten China to quantitatively examine the relationship between rainfall intensity and stemflow production, and to test whether larger raindrops result in a decrease in stemflow production. We found that (1) stemflow production increased with rainfall intensity until reaching a threshold value and then began to decrease, and (2) stemflow showed a significant (P <.01) linear decrease with increasing raindrop size. Our study is useful to reconcile the disputed relationships between rainfall intensity and stemflow production, and provides a basis for a quantitative evaluation to fill the knowledge gap regarding how raindrop size determines stemflow production. [ABSTRACT FROM AUTHOR]

To investigate the effects of increasing drought on the photosynthesis of xerophytic shrubs, a watercontrolled pot culture of Hedysarum mongolicum and Caragana korshinskii, two commonly planted shrubs in the arid regions in northwest China, was conducted. The shrubs were planted in light, moderate and serious drought treated soils (LD, MD and SD, the soil moistures are 65%, 50% and 30% of the field capacity, while the common soil moisture is 75% of that). The responses of the chloroplastic antioxidant system, photosynthetic response parameters and the relationships among them were detected. The results indicated that (1) the chloroplastic ascorbate peroxidase (APX) and dehydroascorbic acid reductase (DHAR) activities of H. mongolicum significantly increased in LD conditions, while the glutathione reductase (GR) activity significantly decreased. Chloroplastic superoxide dismutase (SOD), DHAR and GR activities of C. korshinskii and antioxidants contents (ascorbic acid, glutathione and carotenoids) significantly increased in LD conditions. Along with the increasing drought stress, chloroplastic antioxidase activities and antioxidants contents in both shrubs exhibited increasing tendencies, except for the APX and GR activities of C. korshinskii and the DHAR activities of both the shrubs, which exhibited significant decreases after temporary increasing. Significant chloroplastic membrane lipid peroxidationstarted to be observed in SD and LD conditions for the 2 species, respectively. (2) the maximum net photosynthetic rate (Pnmax), light saturation point (LSP), the maximum carboxylation rate was (kcmax), the maximum electron transfer rate (Tmav) and the utilization rate of triose phosphate (TPU) of H. mongolicum and the Pnmax, apparent quantum efficiency (AQY), Jmax and TPU of C. korshinskii significantly decreased in LD conditions. Along with the increasing drought stress, all the photosynthetic response parameters except dark respiration rate (Rd) and light compensation point (LCP) exhibited decreasing tendencies. (3) there were significant negative relationships among parts of the chloroplastic antioxidant indices and photosynthetic response parameters, however, the oxidative damage of chloroplasts is not the only dominant limiting factor of the photosynthesis under drought stress. (4) H. mongolicum was more suitable for the revegetation of arid regions in LD and MD conditions than C. korshinskii considering their abilities of chloroplastic antioxidation and maintaining photosynthesis. [ABSTRACT FROM AUTHOR]

Isotopic composition of gross rainfall has been extensively used as a conservative tracer to track water movement and other hydrological processes in vegetated ecosystems. Recent studies from forest ecosystems, however, demonstrated that vegetation canopies can alter the isotopic composition of rainwater during rainfall partitioning into throughfall and stemflow, likely leading to errors and biases in aforementioned studies. No known studies, to date, had investigated this topic in shrub-dominated arid and semi-arid ecosystems where water is typically the driving factor in ecological, hydrological and biogeochemical processes. In this study, event-based gross rainfall, the throughfall and stemflow induced by shrubs of Caragana korshinskii were measured and samples were collected within a water-limited arid desert ecosystem of northern China, and their water stable isotopes (18O and 2H) were also analyzed in the laboratory. We mainly aimed to investigate whether there is an isotopic enrichment or depletion in stemflow and throughfall in comparison to gross rainfall, and to evaluate the possible underlying mechanisms. Our results indicated an enrichment of both isotopes in stemflow, while a general more depletion in throughfall than in gross rainfall, which is presumably affected by a combinative effects of canopy evaporation, isotopic exchange, and selective canopy storage. Deuterium excess of stemflow were found to be significantly higher (P < 0.05) than that of gross rainfall and throughfall. Moreover, we detected the pronounced "amount effect", with a significant (P < 0.05) negative relationship between isotopic composition and the amount of gross rainfall, throughfall, and stemflow, respectively. Our study is expected to contribute to an improved understanding of physical processes and water routing in shrub canopies within vast arid desert ecosystems. Unlabelled Image • We found a general isotopic enrichment in stemflow than in gross rainfall. • We found a general isotopic depletion in throughfall than in gross rainfall. • We detected the pronounced "amount effect". • Mechanisms affecting alteration in isotopic composition were discussed. • Factors reflecting evaporative demand were well related to isotopic composition. [ABSTRACT FROM AUTHOR]

Quantitative identification of water utilization characteristics of xerophytic shrubs is an important prerequisite for the selection and optimization of a regional artificial sand-fixing vegetation system. In this study, a hydrogen (δD) stable isotope technique was used to study the changes in water use characteristics of four typical xerophytic shrubs, Caragana korshinskii , Salix psammophila , Artemisia ordosica , and Sabina vulgaris in the Hobq Desert under light (4.8 mm after 1 and 5 days) and heavy (22.4 mm after 1 and 8 days) rainfall events. Under light rainfall, C. korshinskii and S. psammophila primarily used the 80-140 cm layer of soil water (37-70%) and groundwater (13-29%), and the water use characteristics did not change significantly after the light rainfall event. However, the utilization ratio of A. ordosica to soil water in the 0-40 cm layer increased from less than 10% on the first day after rain to more than 97% on the fifth day after rain, whereas the utilization ratio of S. vulgaris to soil water in the 0-40 cm layer also increased from 43% to nearly 60%. Under heavy rainfall, C. korshinskii and S. psammophila still used the 60-140 cm layer (56-99%) and groundwater (~15%), while the main water utilization depth of A. ordosica and S. vulgaris expanded to 0-100 cm. Based on the above results, C. korshinskii and S. psammophila primarily use the soil moisture of the 80-140 cm layer and groundwater, while A. ordosica and S. vulgaris use the soil moisture of the 0-100 cm layer. Therefore, the co-existence of A. ordosica and S. vulgaris will increase the competition between artificial sand-fixing plants, while the combination of the two plants with C. korshinskii and S. psammophila will avoid competition between artificial sand-fixing plants to some extent. This study provides important guidance for regional vegetation construction and sustainable management of an artificial vegetation system., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Yongsheng, Zilong, Xiangqian, Qiang, Hui and Li.)

Summary Throughfall is known to be a critical component of the hydrological and biogeochemical cycles of forested ecosystems with inherently temporal and spatial variability. Yet little is understood concerning the throughfall variability of shrubs and the associated controlling factors in arid desert ecosystems. Here we systematically investigated the variability of throughfall of two morphological distinct xerophytic shrubs ( Caragana korshinskii and Artemisia ordosica ) within a re-vegetated arid desert ecosystem, and evaluated the effects of shrub structure and rainfall characteristics on throughfall based on heavily gauged throughfall measurements at the event scale. We found that morphological differences were not sufficient to generate significant difference ( P < 0.05) in throughfall between two studied shrub species under the same rainfall and meteorological conditions in our study area, with a throughfall percentage of 69.7% for C. korshinskii and 64.3% for A. ordosica . We also observed a highly variable patchy pattern of throughfall beneath individual shrub canopies, but the spatial patterns appeared to be stable among rainfall events based on time stability analysis. Throughfall linearly increased with the increasing distance from the shrub base for both shrubs, and radial direction beneath shrub canopies had a pronounced impact on throughfall. Throughfall variability, expressed as the coefficient of variation (CV) of throughfall, tended to decline with the increase in rainfall amount, intensity and duration, and stabilized passing a certain threshold. Our findings highlight the great variability of throughfall beneath the canopies of xerophytic shrubs and the time stability of throughfall pattern among rainfall events. The spatially heterogeneous and temporally stable throughfall is expected to generate a dynamic patchy distribution of soil moisture beneath shrub canopies within arid desert ecosystems. [ABSTRACT FROM AUTHOR]

Summary: The capacity of shrub canopy water storage is a key factor in controlling the rainfall interception. Thus, it affects a variety of hydrological processes in water-limited arid desert ecosystems. Vast areas of revegetated desert ecosystems in Northwestern China are occupied by shrub and dwarf shrub communities. Yet, data are still scarce regarding their rainwater storage capacity. In this study, simulated rainfall tests were conducted in controlled conditions for three dominant xerophytic shrub types in the arid Tengger Desert. Eight rainfall intensities varying from 1.15 to 11.53mmh−1 were used to determine the canopy water storage capacity. The simulated rainfall intensities were selected according to the long-term rainfall records in the study area. The results indicate that canopy storage capacity (expressed in water storage per leaf area, canopy projection area, biomass, and volume of shrub respectively) increased exponentially with increase in rainfall intensity for the selected shrubs. Linear relationships were found between canopy storage capacity and leaf area (LA) or leaf area index (LAI), although there was a striking difference in correlation between storage capacity and LA or LAI of Artemisia ordosica compared to Caragana korshinskii and Hedysarum scoparium. This is a result of differences in biometric characteristics, especially canopy morphology between the shrub species. Pearson correlation coefficient indicated that LA and dry biomass are better predictors as compared to canopy projection area and volume of samples for precise estimation of canopy water storage capacity. In terms of unit leaf area, mean storage capacity was 0.39mm (range of 0.24–0.53mm), 0.43mm (range of 0.28–0.60mm), and 0.61mm (range of 0.29–0.89mm) for C. korshinskii, H. scoparium, and A. ordosica, respectively. Correspondingly, divided per unit dry biomass, mean storage capacity was 0.51gg−1 (range of 0.30–0.70gg−1), 0.41gg−1 (range of 0.26–0.57gg−1), and 0.73gg−1 (range of 0.38–1.05gg−1) for C. korshinskii, H. scoparium, and A. ordosica, respectively, when the rainfall intensities ranged from 1.15, 2.31, 3.46, 4.61, 6.92, 9.23 to 11.53mmh−1. The needle-leaved species A. ordosica had a higher canopy water storage capacity than the ovate-leaved species C. korshinskii and H. scoparium at the same magnitude of rainfall intensity, except for C. korshinskii when it was expressed in unit of canopy projection area. Consequently, A. ordosica will generate higher interception losses as compared to C. korshinskii and H. scoparium. This is especially the case as it often forms dense dwarf shrub communities despite its small size. [Copyright &y& Elsevier]