Study on the oasification process and its effects on soil particle distribution in the south rim of the Tarim Basin, China in recent 30 years

AbstractOasification is an important geography process in arid areas, although little research attention has been paid to the process compared to desertification. In fact, studying oasification not only directly reveals its effects on the environment, but can also uncover causes of desertification through examination of oasification causes and processes. In this study, oases located on the south rim of Tarim Basin in Xinjiang, China, were selected as a regional study area. For assessing changes in oases area over the past 30years, four images taken in September in 1977, 1992, 2000 and 2010 were used. To further investigate the effects of oasification on the environment, the Cele Oasis was specifically selected as a representative study area, and soil particle-size distributions (PSD) were analyzed. The results indicated that the oasification process was unmistakable and should receive more attention in the southern marginal zone of the Tarim Basin. In addition, the results also revealed that oasification can have positive effects on the soil environment. In terms of management implications, it is essential that farmland remain in continuous use after reclamation; otherwise, reclamation will weaken oasification and intensify desertification

Computation on the Optimal Control of Networked Control Systems with Multiple Switching Modes Over High Speed Local Area Networks

The optimal control problem for the networked control system with multiple switching modes over high speed local area networks is addressed, where an initial state is a parametric vector. Because in the general case, the time delay is much less than the sampling period and the possibility of the packets collision is much lower, it can be assumed that the influence of the time delay and the packets loss on the optimal controller design can be ignored. On the basis of the assumption, the networked control systems with multiple switching modes are modeled as a hybrid system. Moreover, based on the Bellman type inequality for the hybrid systems, a dynamic program to solve the optimal control with a parameter vector is proposed, in every step of the technique, the feasible region is divided into evenly distributed grid points, and then, the optimal control law is transformed into maximizing the lower bound of the cost to go function in grid points. Finally, an experiment setup of the networked control system with multiple switching modes is constructed and a simulation example is given to illustrate the optimal control computation results

Stoichiometry of C:N:P in the Roots of Alhagi sparsifolia Is More Sensitive to Soil Nutrients Than Aboveground Organs

The stoichiometry of carbon, nitrogen, and phosphorus (C:N:P) among leaves, stems, and roots reflects trade-offs in plants for acquiring resources and their growth strategy. The widely distributed plant Alhagi sparsifolia is an ideal species to study the ecological stoichiometry in different organs in response to the availability of nutrients and water in the desert ecosystem. However, which response of organs is most sensitive to environmental conditions is still unclear. To answer this question, we collected samples of plants and soils including not only aboveground leaves and stems, but also underground roots and soils from a wide range of arid areas during the growing season. The C, N, P, C:N, C:P, and N:P ratios in leaves, thorns, stems, and roots were derived to explore their relationship as well as their response mechanisms to nutrients and water spanning 1 m deep in the soil. The results showed that the order of N concentration was leaves > thorns > stems > roots, that the concentration of P in the leaves, thorns, and stems was similar, and that their values were higher than those in the roots. First, the C:N ratios in the leaves and stems were significantly positively correlated with the ratio in roots. The C:N ratios in each organ showed a significant relationship with the soil alkali hydrolyzable nitrogen (SAN) above a depth of 60 cm. In addition to SAN, soil available phosphorus (SAP) and soil organic carbon (SOC) affect the C:N ratio in the roots. Second, the C:P and N:P ratios in aboveground organs showed no correlations with the ratios in roots. The C:P and N:P ratios in the leaves and thorns have no relationship with soil nutrients, while the C:P ratio in roots was influenced by SAN and SOC in all soil layers. Finally, the N:P ratios in roots were also affected by nutrients in different soil depths at 0–20 and 60–80 cm. These results illustrate that the roots were more sensitive to soil nutrients than the aboveground parts. Our study of ecological stoichiometry also suggests a novel systematic approach for analyzing the sensitivity of responses of an organ to environmental conditions.Fil: Yin, Hui. Xinjiang University; China. Chinese Academy of Sciences; República de ChinaFil: Zheng, Hongwei. Chinese Academy of Sciences; República de ChinaFil: Zhang, Bo. Chinese Academy of Sciences; República de ChinaFil: Tariq, Akash. Chinese Academy of Sciences; República de ChinaFil: Lv, Guanghui. Xinjiang University; ChinaFil: Zeng, Fanjiang. Chinese Academy of Sciences; República de ChinaFil: Graciano, Corina. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Fisiología Vegetal. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Fisiología Vegetal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Exogenous γ-aminobutyric acid (GABA) mitigated salinity-induced impairments in mungbean plants by regulating their nitrogen metabolism and antioxidant potential

BackgroundIncreasing soil salinization has a detrimental effect on agricultural productivity.Therefore, strategies are needed to induce salinity-tolerance in crop species for sustainable foodproduction. γ-aminobutyric acid (GABA) plays a key role in regulating plant salinity stresstolerance. However, it remains largely unknown how mungbean plants (Vigna radiata L.) respondto exogenous GABA under salinity stress.MethodsThus, we evaluated the effect of exogenous GABA (1.5 mM) on the growth and physiobiochemicalresponse mechanism of mungbean plants to saline stress (0-, 50-, and 100 mM [NaCland Na2SO4, at a 1:1 molar ratio]).ResultsIncreased saline stress adversely affected mungbean plants' growth and metabolism. Forinstance, leaf-stem-root biomass (34- and 56%, 31- and 53%, and 27- and 56% under 50- and 100mM, respectively]) and chlorophyll concentrations declined. The carotenoid level increased (10%)at 50 mM and remained unaffected at 100 mM. Hydrogen peroxide (H2O2), malondialdehyde(MDA), osmolytes (soluble sugars, soluble proteins, proline), total phenolic content, andenzymatic activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), peroxidase(POD), glutathione reductase (GTR), and polyphenol oxidation (PPO) were significantlyincreased. In leaves, salinity caused a significant increase in Na+ concentration but a decrease inK+ concentration, resulting in a low K+/Na+ concentration (51- and 71% under 50- and 100- mMstress). Additionally, nitrogen concentration and the activities of nitrate reductase (NR) andglutamine synthetase (GS) decreased significantly. The reduction in glutamate synthase (GOGAT)activity was only significant (65%) at 100 mM stress. Exogenous GABA decreased Na+, H2O2,and MDA concentrations but enhanced photosynthetic pigments, K+ and K+/Na+ ratio, Nmetabolism, osmolytes, and enzymatic antioxidant activities, thus reducing salinity-associatedstress damages, resulting in improved growth and biomass.ConclusionExogenous GABA may have improved the salinity tolerance of mungbean plants by maintaining their morpho-physiological responses and reducing the accumulation of harmfulsubstances under salinity. Future molecular studies can contribute to a better understanding of themolecular mechanisms by which GABA regulates mungbean salinity tolerance

Coordinated Patterns in the Allocation, Composition, and Variability of Multiple Elements Among Organs of Two Desert Shrubs Under Nitrogen Addition and Drought

Nutrient allocation closely correlates plant functional traits and development to ecosystem supply services. Desert shrubs maintain the stability of desert ecosystems, whereas the knowledge of how they coordinate nutrients among organs is still limited when responding to differing nitrogen (N) and water regimes. Here we investigated the allocation, composition, and variability of nine elements within organs of Alhagi sparsifolia and Calligonum caput-medusae seedlings under various N addition (0, 3, 6, and 9 gN m−2 year−1) and water regimes (drought versus well-watered). Results showed that plant species identity, organ type, and nitrogen and water treatments significantly affected the concentrations of nine elements independently and interactively (P < 0.05). N addition significantly improved elemental allocation to roots of drought-stressed A. sparsifolia seedlings, whereas N addition of 9.0 gN m−2 year−1 exerted adverse influence on C. caput-medusae. Photosynthetic organs contained more macronutrients, such as N and potassium (K), whereas trace metals accumulated in roots, such as iron (Fe) and manganese (Mn). Soil elemental concentrations were weakly correlated with those in plants. Macroelements in all organs show less variability (coefficient of variation). Coarse root Fe and stem K contents constituted hub traits in plant element networks (PENs) of A. sparsifolia and C. caput-medusae seedlings, respectively, and may play a key role in plant adaptation in desert environments. The looser PEN of A. sparsifolia implied its stronger adaptability than C. caput-medusae. Desert shrubs can coordinate the allocation of multiple elements within and among organs in response to changes in water and N in the environment.Fil: Zhang, Zhihao. Cele National Station Of Observation And Research For Desert-grassland Ecosystems; China. Chinese Academy of Sciences; República de ChinaFil: Chai, Xutian. Chinese Academy of Sciences; República de China. Cele National Station Of Observation And Research For Desert-grassland Ecosystems; ChinaFil: Tariq, Akash. Cele National Station Of Observation And Research For Desert-grassland Ecosystems; China. Chinese Academy of Sciences; República de ChinaFil: Zeng, Fanjiang. Chinese Academy of Sciences; República de China. Cele National Station Of Observation And Research For Desert-grassland Ecosystems; ChinaFil: Graciano, Corina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Fisiología Vegetal. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Fisiología Vegetal; ArgentinaFil: Li, Xiangyi. Cele National Station Of Observation And Research For Desert-grassland Ecosystems; China. Chinese Academy of Sciences; República de ChinaFil: Gao, Yanju. Cele National Station Of Observation And Research For Desert-grassland Ecosystems; China. Chinese Academy of Sciences; República de ChinaFil: Ullah, Abd. Cele National Station Of Observation And Research For Desert-grassland Ecosystems; China. Chinese Academy of Sciences; República de Chin

Influence of floodwater irrigation on vegetation composition and vegetation regeneration in a Taklimakan desert oasis

Naturally occurring floods in the summer months are the main source of surface water application in the foreland of Qira oasis, which is characterized by a hyperarid climate and is located at the southern fringe of the Taklimakan Desert. We investigated the impact of repeated artificial flood irrigation on seedling recruitment and growth of Alhagi sparsifolia and Karelinia caspica plant communities which are part of the dominant vegetation in Qira oasis. Flood irrigation was applied three times during the growing season and we studied the effect of irrigation on species recruitment, vegetation growth, species composition, and changes in soil water and nutrient concentrations in the soil profile. Results show that (1) repeated flood irrigation had a positive effect on seedling recruitment of the two species, with vegetative recruitment via root tillers being more important than seed recruitment for both species. (2) Irrigation promoted the germination and establishment of herbaceous weed species, which increased species diversity as well as ground coverage. (3) Irrigation also increased soil water and soil nutrient concentrations in the upper soil layer and changed the soil nutrients in the vertical profile. Available N, P, K and the total P and K increased in the soil profile. Our study demonstrates that naturally occurring flood irrigation has significant ecological benefits and plays an important role in promoting the renewal of desert vegetation and a short-term increase of soil nutrients. Our study also highlights the potential negative consequences for vegetation composition and rejuvenation if naturally occurring floods in the study area are diminished by either the effects of climate change or human management

Growth, physiological characteristics and ion distribution of NaCl stressed Alhagi sparsifolia seedlings

Alhagi sparsifolia is a leguminous perennial desert species that is plays an important role in dune stabilization and revegetation of degraded desert ecosystems. We investigated the effects of three different levels of salinity (50, 150, 250 mmol/L NaCl) on the growth, shoot photosynthetic parameters and salt distribution amongst different plant organs in one-year-old A. sparsifolia seedlings in a pot experiment over a 50 d period. The minimum (predawn) and maximum (midday) water potentials of A. sparsifolia seedlings decreased with the increase of external NaCl concentrations as a consequence of the osmotic or water deficit effect of saline solutions outside the roots. Salinity also reduced gas exchange parameters in A. sparsifolia, with seedlings subjected to salinity having lower photosynthesis rates and reduced stomatal conductances compared to the control. The reductions in photosynthetic rates in high salinity treatments of the A. sparsifolia seedlings were mainly caused by stomatal limitation. Consequently plants growing at greater external NaCl concentrations had significantly lower biomass accumulation compared to the control grown at 50 mmol/L. However, plants exposed to higher salinity were able to maintain growth throughout the experiment but allocated a greater proportion of biomass belowground. Plants exposed to higher external salinity levels had increased concentrations of Na+ and Cl- ions in shoots and roots, suggesting that A. sparsifolia seedlings were utilizing Na+ and Cl- as osmolytes to increase the cellular osmolality and decrease their water potential. We observed the greatest NaCl concentrations in the plants treated with 150 mmol/L NaCl indicating that there may be a threshold level of NaCl that can be tolerated by the plants. In conclusion our results indicate that A. sparsifolia seedlings are moderately salt tolerant. Photosynthetic gas exchange parameters were reduced by greater external salinity but the seedlings maintained substantial photosynthetic rates even under high salinity stress, were able to maintain growth over the 50 d experimental period and showed no signs of salinity toxicity or damage

Leaf and whole tree adaptations to mild salinity in field grown Populus euphratica

Populus euphratica Oliv. is a highly salt tolerant tree species, and this study represents the first comprehensive investigation of salt tolerance mechanisms of mature trees of P. euphratica in the field. We measured NaCl concentration in xylem sap, NaCl accumulation in leaves, the effect of NaCl on leaf physiological parameters and osmotic adjustment and the allocation and distribution of NaCl between different plant organs on a whole plant level in trees exposed to mild saline groundwater (around 30 mM) in China. Populus euphratica showed three key mechanisms of salt tolerance. The primary mechanism had a strong control over Na+ and Cl- uptake with effective exclusion mechanisms for Cl- with up to 99% of the external NaCl being excluded from the xylem. Secondly, the trees allocated large proportions of NaCl into the leaves, which served as a salt elimination mechanism as the leaves are ultimately shed at the end of the growing season. Thirdly, the trees tolerated high foliar Na+ concentrations through a combination of osmotic adjustment using sucrose and probable sequestering of Na+ in the apoplast. Our results indicate that the control of Na+ and Cl- uptake and the regulation of Na+ and Cl- delivery to the shoot are key to salt tolerance of P. euphratica in the field with tolerance of high Na+ concentrations in leaves being a critical component

Coupling relationship of leaf economic and hydraulic traits of alhagi sparsifolia shap. In a hyper-arid desert ecosystem

In this study, Alhagi sparsifolia Shap. was used to test the hypothesis that leaf economic and hydraulic traits are coupled in plants in a hyper-arid region. Five economic traits and six hydraulic traits were examined to explore the relationship. Results showed that the stomatal density (SD) on both surfaces was coupled with maximum stomatal conductance to water vapor (gwmax) and leaf tissue density (TD). SD on adaxial surface (SDaba) was significantly positively related to vein density (VD) but negatively related to leaf thickness (LT) and stomatal length on adaxial surface (SLada). Nitrogen concentration based on mass (Nmass) was significantly negatively correlated with leaf mass per area (LMA), LT, and VD, whereas nitrogen concentration based on area (Narea) was significantly positively related to LMA and TD. Mean annual precipitation (MAP) contributed the most to the changes in LT and stomatal length (SL). Soil salt contributed the most to TD, SD, and gwmax. Soli nutrients influenced the most of LMA and VD. Mean annual temperature contributed the most to Nmass and Narea. In conclusion, the economics of leaves coupled with their hydraulic traits provides an economical and efficient strategy to adapt to the harsh environment in hyper-arid regions.Fil: Yin, Hui. University Of Chinese Academy Of Sciences; China. Xinjiang University; China. Xinjiang Institute Of Ecology And Geography Chinese Academy Of Sciences; China. Cele National Station Of Observation And Research For Desert-grassland Ecosystems; ChinaFil: Tariq, Akash. University Of Chinese Academy Of Sciences; China. Cele National Station Of Observation And Research For Desert-grassland Ecosystems; China. Xinjiang Institute Of Ecology And Geography Chinese Academy Of Sciences; ChinaFil: Zhang, Bo. University Of Chinese Academy Of Sciences; China. Cele National Station Of Observation And Research For Desert-grassland Ecosystems; China. Xinjiang Institute Of Ecology And Geography Chinese Academy Of Sciences; ChinaFil: Lv, Guanghui. Xinjiang University; ChinaFil: Zeng, Fanjiang. Cele National Station Of Observation And Research For Desert-grassland Ecosystems; China. Xinjiang Institute Of Ecology And Geography Chinese Academy Of Sciences; China. University Of Chinese Academy Of Sciences; ChinaFil: Graciano, Corina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Fisiología Vegetal. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Fisiología Vegetal; ArgentinaFil: Santos, Mauro. Universidade Federal de Pernambuco; BrasilFil: Zhang, Zhihao. University Of Chinese Academy Of Sciences; China. Xinjiang Institute Of Ecology And Geography Chinese Academy Of Sciences; China. Cele National Station Of Observation And Research For Desert-grassland Ecosystems; ChinaFil: Wang, Peng. Cele National Station Of Observation And Research For Desert-grassland Ecosystems; China. Xinjiang Institute Of Ecology And Geography Chinese Academy Of Sciences; ChinaFil: Mu, Shuyong. Xinjiang Institute Of Ecology And Geography Chinese Academy Of Sciences; Chin

Alhagi sparsifolia acclimatizes to saline stress by regulating its osmotic, antioxidant, and nitrogen assimilation potential

Alhagi sparsifolia (Camelthorn) is a leguminous shrub species that dominates the Taklimakan desert's salty, hyperarid, and infertile landscapes in northwest China. Although this plant can colonize and spread in very saline soils, how it adapts to saline stress in the seedling stage remains unclear so a pot-based experiment was carried out to evaluate the effects of four different saline stress levels (0, 50, 150, and 300 mM) on the morphological and physio-biochemical responses in A. sparsifolia seedlings. Our results revealed that N-fixing A. sparsifolia has a variety of physio-biochemical anti-saline stress acclimations, including osmotic adjustments, enzymatic mechanisms, and the allocation of metabolic resources. Shoot-root growth and chlorophyll pigments significantly decreased under intermediate and high saline stress. Additionally, increasing levels of saline stress significantly increased Na + but decreased K + concentrations in roots and leaves, resulting in a decreased K + /Na + ratio and leaves accumulated more Na + and K + ions than roots, highlighting their ability to increase cellular osmolarity, favouring water fluxes from soil to leaves. Salt-induced higher lipid peroxidation significantly triggered antioxidant enzymes, both for mass-scavenging (catalase) and cytosolic fine-regulation (superoxide dismutase and peroxidase) of HO. Nitrate reductase and glutamine synthetase/glutamate synthase also increased at low and intermediate saline stress levels but decreased under higher stress levels. Soluble proteins and proline rose at all salt levels, whereas soluble sugars increased only at low and medium stress. The results show that when under low-to-intermediate saline stress, seedlings invest more energy in osmotic adjustments but shift their investment towards antioxidant defense mechanisms under high levels of saline stress. Overall, our results suggest that A. sparsifolia seedlings tolerate low, intermediate, and high salt stress by promoting high antioxidant mechanisms, osmolytes accumulations, and the maintenance of mineral N assimilation. However, a gradual decline in growth with increasing salt levels could be attributed to the diversion of energy from growth to maintain salinity homeostasis and anti-stress oxidative mechanisms