Influence of surface water and groundwater on functional traits and trade-off strategies of oasis communities at the end of the Keriya River, China.

Plant functional traits reflect the capacity of plants to adapt to their environment and the underlying optimization mechanisms. However, few studies have investigated trade-off strategies for functional traits in desert-wetland ecosystems, the mechanisms by which surface water disturbance and groundwater depth drive functional trait variation at the community scale, and the roles of intraspecific and interspecific variation. Therefore, this study analyzed specific differences in community-weighted mean traits among habitat types and obtained the relative contribution of intraspecific and interspecific variation by decomposing community-weighted mean traits, focusing on the Daliyabuyi Oasis in the hinterland of the Taklamakan Desert. We also explored the mechanisms by which surface water and groundwater influence different sources of variability specifically. The results showed that plant height, relative chlorophyll content, leaf thickness, leaf nitrogen content, and nitrogen-phosphorus ratio were the key traits reflecting habitat differences. As the groundwater depth becomes shallower and surface water disturbance intensifies, plant communities tend to have higher leaf nitrogen content, nitrogen-phosphorus ratio, and relative chlorophyll content and lower height. Surface water, groundwater, soil water content, and total soil nitrogen can influence interspecific and intraspecific variation in these traits through direct and indirect effects. As arid to wet habitats change, plant trade-off strategies for resources will shift from conservative to acquisitive. The study concluded that community functional traits are mainly contributed by interspecific variation, but consideration of intraspecific variation and the covariation effects that exist between it and interspecific variation can help to further enhance the understanding of the response of community traits in desert-wetland ecosystems to environmental change. Surface water disturbance has a non-negligible contribution to this adaptation process and plays a higher role than groundwater depth.

Effects of meteorological factors and groundwater depths on sap flow density of Populus euphratica in a desert oasis, Taklamakan Desert, China.

Accurate estimation of desert vegetation transpiration is key to regulating desert water resources of desert ecosystems. Sap flow density (SFD) can indirectly reflect a tree's transpiration consumption, and it has been affected by climate warming and groundwater depths in desert ecosystems. Sap flow responses to meteorological conditions and groundwater depths are further affected by tree of different sizes. However, how meteorological factors and groundwater depths affects tree sap flow among tree sizes remains poorly understand. In this study, a 50 × 50 m P. euphratica stand was selected as a sample plot in the hinterland of the Taklamakan Desert, and the SFD of P. euphratica of different sizes was measured continuously using the thermal diffusion technique from May to October of 2021 and 2022. The results showed that SFD of large P. euphratica was consistently higher than that of small P. euphratica in 2021 and 2022. and the SFD of P. euphratica was significantly and positively correlated with solar radiation (Rad) and vapor pressure deficit (VPD), and the correlation was higher than that of the air temperature (Ta) and relative humidity (RH), and also showed a strong non-linear relationship. Analysis of the hour-by-hour relationship between P. euphratica SFD and VPD and Rad showed a strong hysteresis. Throughout the growing season, there was no significant relationship between SFD of P. euphratica and groundwater depth, VPD and Rad were still the main controlling factors of SFD in different groundwater depths. However, during the period of relative groundwater deficit, the effect of groundwater depth on the SFD of P. euphratica increased, and the small P. euphratica was more sensitive, indicating that the small P. euphratica was more susceptible to groundwater changes. This study emphasized that Rad and VPD were the main drivers of SFD during the growing season, as well as differences in the response of different sizes of P. euphratica to groundwater changes. The results of the study provide a scientific basis for future modeling of transpiration consumption in P. euphratica forests in desert oases, as well as the regulation and allocation of water resources.

Understanding Acute Respiratory Distress Syndrome in High-Altitude Environments: A Comprehensive Review of Diagnosis and Treatment.

Approximately 2% of the global population lives above 1500 m, where low atmospheric pressure, decreased oxygen levels, harsh cold and dry conditions, strong radiation, and the effects of climate change present significant health challenges. Residents of these high-altitude areas display physiological adaptions, including smaller body size, enlarged ribs, improved oxygen delivery in hypoxic conditions, and adjustments in oxygen utilization and metabolism. Both acute and chronic hypoxia prevalent in such regions can trigger various diseases by stimulating hypoxia-inducible factors, boosting inflammatory responses, and impairing mitochondrial function.Acute Respiratory Distress Syndrome (ARDS) - a critical respiratory condition associated with high morbidity and mortality - occurs more frequently among the health risks in these environments. Hypoxia is a critical predisposing and aggravating factor for high-altitude ARDS. Despite similarities with its low-altitude counterpart, ARDS in high-altitude areas displays unique pathophysiology and clinical manifestations due to the specific environmental conditions.This review aims to shed light on how high-altitude environments influence the diagnosis and treatment of ARDS, providing a comprehensive understanding of the distinct challenges inherent to these regions.

Machine-learning analysis to predict the fluorescence quantum yield of carbon quantum dots in biochar.

Biochar nanoparticles have recently attracted attention, owing to their environmental behavior and ecological effects. However, biochar has not been shown to contain carbon quantum dots (< 10 nm) with unique photovoltaic properties. Therefore, this study utilized several characterization techniques to demonstrate the generation of carbon quantum dots in biochar produced from 10 types of farm waste. The generated carbon quantum dots had a quasi-spherical morphology and high-resolution lattice stripes with lattice spacings of 0.20-0.23 nm. Moreover, they contained functional groups with good hydrophilic properties, such as amino and hydroxyl groups, and elemental O, C, and N on the surface. A crucial determinant of the photoluminescence properties of carbon quantum dots is their fluorescence quantum yield. Therefore, the relationship between the biochar preparation parameters and the fluorescence quantum yield was investigated using six machine learning analytical models based on 480 samples. Among the models, the gradient-boosting decision-tree regression model exhibited the best predictive performance (R2 > 0.9, RMSE <0.02, and MAPE <3), and was used for the analysis of feature importance; compared to the properties of the raw material, the production parameters had a greater effect on the fluorescence quantum yield. Additionally, four key features were identified: pyrolysis temperature, residence time, N content, and C/N ratio, which were independent of farm waste type. These features can be used to accurately predict the fluorescence quantum yield of carbon quantum dots in biochar. The relative error range between the predicted and the experimental value of fluorescence quantum yield is 0.00-4.60 %. Thus, the prediction model has the potential to predict the fluorescence quantum yield of carbon quantum dots in other types of farm waste biochar, and provides fundamental information for the study of biochar nanoparticles.

Cellular absorption of polystyrene nanoplastics with different surface functionalization and the toxicity to RAW264.7 macrophage cells.

Nanoplastics (NPs) are a matter of widespread concern, as they are easily absorbed by a wide variety of organisms and accumulate in biological tissues. While there is evidence that nanoplastics are toxic to various organisms, few studies have investigated the mechanisms underlying the toxicities of NPs with different surface functionalizations to macrophage cells. In this study, mouse mononuclear macrophage (RAW264.7) cells were exposed to polystyrene nanoplastics (PS-NPs) with three different surface functionalizations, namely pristine polystyrene (PS), carboxyl-functionalized polystyrene (PS-COOH), and amino-functionalized polystyrene (PS-NH2), to evaluate the cellular endocytosis, lactate dehydrogenase (LDH) release, cell viability, reactive oxygen species (ROS), mitochondrial membrane potential, apoptosis, and related gene expression. Results showed that all three PS-NPs were endocytosed into cells. However, in the concentration range of 0-100 µg/mL, PS had no effect on cell viability or apoptosis, but it slightly increased cellular ROS and decreased mitochondrial membrane potential. PS-NH2 exhibited the highest cytotoxicity. PS-COOH and PS-NH2 induced ROS production, altered the mitochondrial membrane potential, and caused cell apoptosis regulated by the mitochondrial apoptosis pathway. Results also showed that cell membrane damage induced by PS-NH2 is one of the primary mechanisms of its cytotoxicity to RAW264.7 cells. The results of this study clarify the toxicities of PS-NPs with different surface functionalizations to macrophages, thereby improving the identification of immune system risks related to nanoplastics.

The combined effect of surface water and groundwater on environmental heterogeneity reveals the basis of beta diversity pattern in desert oasis communities.

Beta diversity indicates the species turnover with respect to a particular environmental gradient. It is crucial for understanding biodiversity maintenance mechanisms and for prescribing conservation measures. In this study, we aimed to reveal the drivers of beta diversity patterns in desert hinterland oasis communities by establishing three types of surface water disturbance and groundwater depth gradients. The results indicated that the dominant factor driving the beta diversity pattern within the same gradient shifted from soil organic matter to pH, as groundwater depth became shallower and surface water disturbance increased. Among the different gradients, surface water disturbance can have important effects on communities where original water resource conditions are extremely scarce. Under the premise that all habitats are disturbed by low surface water, differences in groundwater depth dominated the shifts in the community species composition. However, when groundwater depth in each habitat was shallow, surface water disturbance had little effect on the change in species composition. For the two components of beta diversity, the main drivers of species turnover pattern was the unique effects of surface water disturbance and soil environmental differences, and the main driver of species nestedness pattern was the common effect of multiple environmental pressures. The results of this study suggest that increasing the disturbance of surface water in dry areas with the help of river flooding will help in promoting vegetation restoration and alleviating the degradation of oases. They also confirm that surface water and groundwater mutually drive the establishment of desert oasis communities. Equal focus on both factors can contribute to the rational ecological recovery of dryland oases and prevent biodiversity loss.

Rhamnolipid-Enhanced ZVI-Activated Sodium Persulfate Remediation of Pyrene-Contaminated Soil.

In soil, polycyclic aromatic hydrocarbons (PAHs) are tightly bound to organic components, but surfactants can effectively transform them from a solid to a liquid phase. In this study, the biosurfactant rhamnolipid (RL) was selected as the eluent; shaking elution in a thermostatic oscillator improved the elution rate of pyrene, and the effects of RL concentration, temperature, and elution time on the elution effect were compared. After four repeated washings, the maximum elution rate was 75.6% at a rhamnolipid concentration of 20 g/L and a temperature of 45 °C. We found that 38 µm Zero-Valent Iron (ZVI) had a higher primary reaction rate (0.042 h-1), with a degradation rate of 94.5% when 3 g/L ZVI was added to 21 mM Na2S2O8 at 60 °C. Finally, electron paramagnetic resonance (EPR) detected DMPO-OH and DMPO-SO4 signals, which played a major role in the degradation of pyrene. Overall, these results show that the combination of rhamnolipid elution and persulfate oxidation system effectively remediated pyrene-contaminated soil and provides some implications for the combined remediation with biosurfactants and chemical oxidation.

Photocatalytic materials modified with carbon quantum dots for the degradation of organic pollutants under visible light: A review.

In recent years, carbon quantum dots (CQDs) have received widespread attention owing to their non-toxicity, sustainability, excellent photostability, and intrinsic photoluminescence properties. In particular, CQDs have attracted considerable interest for visible-light-driven photocatalysis because of their excellent electron transfer characteristics and high light capture efficiency. Many studies have reported CQDs/photocatalyst composite systems constructed to make full use of the solar spectrum, improving the ability of photocatalytic materials to degrade organic pollutants. Here, we review the recent research on CQDs-based photocatalysts, and their ability to remove environmental pollutants, with a special emphasis on degradation mechanisms. Several improvements in the catalytic response of CQDs to visible light are also included. In addition, we discuss the aspects that should be considered to construct composite materials based on CQD characteristics and the potential applications of CQD-based photocatalysts for efficient utilization of visible light.

Influence of natural and anthropogenic controls on runoff in the Keriya River, central Tarim Basin, China.

The potential impact of natural factors on the runoff of intermittent rivers and ephemeral streams (IRES) has been largely ignored in the Tarim Basin, China. A representative example is the Keriya River. To quantify the long-term dynamic variations in lower reach surface runoff of IRES, river length, defined as the distance between a selected fix point along the perennial river segment to its dynamic, ephemeral end, was used as an indicator. Using a total of 272 remote sensing images, we digitized and measured the distance (river length) between the center of Yutian County and the river's end point on each image, and then calculated monthly inter-annual and intra-annual variations in length of the lower Keriya River from 2000 to 2019. Hydrometeorological data were combined with descriptors of anthropogenic disturbances to assess the relative influence of natural factors and anthropogenic disturbances on lower reach river runoff. The results showed that intra-annual variations in river length fluctuated seasonally, with the minimum value occurring in June; two main peaks occurred in March and August. The minimum June value in river length was closely linked to an increase in agricultural water demand and a decrease in upper reach runoff. The August peak in river length was related to the peak values in upper reach runoff and agricultural water demand; upper reach runoff made a significant contribution because the former was about 20% more than the latter in summer. The March peak corresponded to elevated lower reach groundwater levels and to the melting of ice along river channels. Inter-annual variations in river length were due to inter-annual variations in upper reach runoff and middle reach agricultural water use which increased slightly during the study period. Inter-annual variations in frequency and amplitude of the fluctuations in river length were mainly controlled by changes in upper reach runoff. The minimum in river length in 2009 was consistent with the low in upper reach runoff of the Keriya River and other rivers in the Tarim Basin. The most significant factors controlling variations in river length are natural in origin.

Microplastics in arid soils: Impact of different cropping systems (Altay, Xinjiang).

Although microplastic pollution in the soil environment is currently an important research topic, few studies have focused on farmland soil in arid regions. This study investigated the abundances, sizes, polymer compositions, and forms of microplastics across nine agricultural plots cultivated with maize, sunflower, and potato (three of each crop) plants to determine the influences of different cropping characteristics and agricultural practices. The study area was within the arid region of the Ulungur River basin in Qinghe County, Altay, Xinjiang, China. The main forms of microplastics were fragments and fibers, and polyethylene was the dominant polymer (91.6%). The microplastic abundance ranged from 11 347 items/kgdw to 78 061 items/kgdw (mean of 52 081.7 items/kgdw). The abundance and proportion of microplastics with a diameter of <0.2 mm were significantly higher in the sunflower and maize plots (i.e., tall crops) than in the potato plots (i.e., short crops) (p < 0.05). This is due to straw residues affecting the migration and recovery of the mulch. The abundance and fragmentation of microplastics were significantly higher in the sunflower and maize plots where plastic mulch was extensively used because these tall crops anchored the mulch near their stem-root systems. The mulch was then slowly aged (e.g., via wind erosion) before being fragmented due to agricultural practices (e.g., mechanical plowing and residue retention). Although microplastics sourced from mulch are probably immobilized by straw residues in the short term, fragile and easily broken pieces of mulch are eventually released into the soil due to agricultural practices. The findings suggest that different cropping characteristics can affect the abundance and fragmentation of microplastics in agricultural soils, even within the same region, and thus the level and type of microplastic pollution. Traditional plastic mulch should be replaced with biodegradable mulch to reduce microplastic pollution in agricultural fields.

[Water sources of Populus euphratica with different tree ages in the oasis of desert hinterland.] / æ²™æ¼ è ¹åœ°å¤©ç„¶ç»¿æ´²ä¸åŒæž—é¾„èƒ¡æ¨æ°´åˆ†åˆ©ç”¨æ¥æº.

Understanding vegetation water utilization can provide scientific basis for vegetation protection and rational distribution of water resources in arid desert oasis area. In this study, sapling (DBH≤10 cm), mature (10 cm40 cm) Populus euphratica were chosen as sample trees in natural oasis of Dariaboui. We measured oxygen isotopes of xylem water and potential water sources (surface water, soil water in 0-3 m soil layer and groundwater) of P. euphratica with different tree ages. The IsoSource model was used to study water sources of P. euphratica. The results showed that soil water content increased with increasing soil depth, while the δ18O value of soil water decreased firstly and then stabilized. When groundwater depth was 2 m, the δ18O value of xylem water increased with increasing tree ages. When the depths of groundwater were 4.2 and 8 m, the δ18O values of xylem water decreased with increasing tree ages. Water sources of P. euphratica varied across tree age. When the depth of underground water was 2 m, the main water source for young trees was surface water, and the contribution proportion was 64.7%. For mature and overmature trees, it was deep soil water and ground-water, with a contribution of about 30%. When the depth of groundwater was 4.2 m, the main water sources of P. euphratica of different tree ages were deep soil water and groundwater, and the contribution proportion was about 30%. The lowest contribution of P. euphratica of different tree ages was shallow soil water, accounting for about 10%.

Distinct leaf functional traits of Tamarix chinensis at different habitats in the hinterland of the Taklimakan desert.

Leaf functional traits reflect plant adaptive strategies towards environmental heterogeneity. However, which factor play the key role of plasticity of leaf functional traits among various variable environmental factors remains unclear in desert hinterland oasis area. Here, we analyzed variations in leaf water content (LWC), δ 13C values of leaves (δ 13C), specific leaf area (SLA), leaf organic carbon concentration (LOC), leaf total nitrogen concentration (LTN), leaf total phosphorus concentration (LTP), and leaf C: N: P stoichiometry in Tamarix chinensis growing in five habitats at the Daliyabuyi, a natural pristine oasis in northwestern China, that differ abiotically and biotically. The spatial heterogeneity of leaf functional traits was evident. Abiotic factors vitally influence leaf functional traits, of which groundwater depth (GWD) and soil C: N stoichiometry (SOC: STN) are crucial. GWD exhibited close relationships with LWC (P < 0.05) and LOC: LTP (P < 0.01), but not δ 13C. Soil water content (SWC) and SOC: STN were negatively related to SLA (P < 0.01; P < 0.05). While, SOC: STN showed positive relationships with LOC: LTN (P < 0.05). As for biological factors, we found T. chinensis in habitat with Sophora alopecuroidies had the highest LTN, possibly as a result of N fixation of leguminous plants (S. alopecuroidies) promotes the N concentration of T. chinensis. Close relationships also existed between leaf functional traits, LWC showed significantly negatively relatd to δ 13C, LOC: LTN and LOC: LTP (P < 0.05), whereas δ 13C had positively correlated with LOC: LTN (P < 0.01) but negatively correlated with LTN (P < 0.05). T. chinensis had relative higher LWC couple with lower δ 13C, and exhibiting lower C, N, P in leaves and their stoichiometric ratios, and also lower SLA which compared with other terrestrial plant. Such coordinations suggesting that T. chinensis develops a suite of trait combinations mainly tends to more conservative to response local habitats in Daliyabuyi, which is contribute to understand desert plant resource acquisition and utilization mechanisms in extremely arid and barren environments.

Responses of two dominant desert plant species to the changes in groundwater depth in hinterland natural oasis, Tarim Basin.

Groundwater is increasingly becoming a permanent and steady water source for the growth and reproduction of desert plant species due to the frequent channel cutoff events in arid inland river basins. Although it is widely acknowledged that the accessibility of groundwater has a significant impact on plant species maintaining their ecological function, little is known about the water use strategies of desert plant species to the groundwater availability in Daryaboyi Oasis, Central Tarim Basin. This study initially determined the desirable and stressing groundwater depths based on ecological and morphological parameters including UAV-based fractional vegetation cover (FVC) images and plant growth status. Then, leaf δ13C values of small- and big-sized plants were analyzed to reveal the water use strategies of two dominant woody species (Populus euphratica and Tamarix ramosissima) in response to the groundwater depth gradient. The changes in FVC and growth status of plants suggested that the actual groundwater depth should be kept at an appropriate range of about 2.1-4.3 m, and the minimum groundwater depth should be less than 7 m. This will ensure the protection of riparian woody plants at a normal growth state and guarantee the coexistence of both plant types. Under a desirable groundwater condition, water alternation (i.e., flooding and rising groundwater depth) was the main factor influencing the variation of plant water use efficiency. The obtained results indicated that big-sized plants are more salt-tolerant than small ones, and T. ramosissima has strong salt palatability than P. euphratica. With increasing groundwater depth, P. euphratica continuously decreases its growth status to maintain hydraulic efficiency in drought condition, while T. ramosissima mainly increases its water use efficiency first and decreases its growth status after then. Besides, in a drought condition, T. ramosissima has strong adaptability than P. euphratica. This study will be informative for ecological restoration and sustainable management of Daryaboyi Oasis and provides reference materials for future research programs.

[Response of foliar δ13C in Populus euphratica and Tamarix sp. to different groundwater depths in the oasis of desert hinterland]. / æ²™æ¼ è ¹åœ°å¤©ç„¶ç»¿æ´²èƒ¡æ¨å’ŒæŸ½æŸ³å¶ç‰‡Î´13C值对不同地下水埋深的响应.

Water use efficiency of plants in arid regions plays a key role in affecting the distribution and water use of plants. We analyzed the responses of water use efficiency of Populus euphratica and Tamarix sp. to different groundwater depths by measuring foliar δ13C of the two dominant species in a desert hinterland. The results showed that as the groundwater depth increased from 2.1 m to 4.3 m, foliar δ13C of Tamarix sp. increased slightly and remained relatively stable. Tamarix sp. had a more stable water use efficiency to adapt to the arid environment. Foliar δ13C of P. euphratica first slightly decreased and then increased. P. euphratica improved its water use efficiency to adapt to drought stress. At the same groundwater depth, foliar δ13C of Tamarix sp. was higher than that of P. euphratica, indicating that water use efficiency of Tamarix sp. was higher than that of P. euphratica.

The competition-dispersal trade-off exists in forbs but not in graminoids: A case study from multispecies alpine grassland communities.

Much theoretical evidence has demonstrated that a trade-off between competitive and dispersal ability plays an important role in facilitating species coexistence. However, experimental evidence from natural communities is still rare. Here, we tested the competition-dispersal trade-off hypothesis in an alpine grassland in the Tianshan Mountains, Xinjiang, China, by quantifying competitive and dispersal ability using a combination of 4 plant traits (seed mass, ramet mass, height, and dispersal mode). Our results show that the competition-dispersal trade-off exists in the alpine grassland community and that this pattern was primarily demonstrated by forbs. The results suggest that most forb species are constrained to be either good competitors or good dispersers but not both, while there was no significant trade-off between competitive and dispersal ability for most graminoids. This might occur because graminoids undergo clonal reproduction, which allows them to find more benign microenvironments, forage for nutrients across a large area and store resources in clonal structures, and they are thus not strictly limited by the particular resources at our study site. To the best of our knowledge, this is the first time the CD trade-off has been tested for plants across the whole life cycle in a natural multispecies plant community, and more comprehensive studies are still needed to explore the underlying mechanisms and the linkage between the CD trade-off and community composition.

Vasoactive intestinal peptide administration after stroke in rats enhances neurogenesis and improves neurological function.

The aim of this study was to investigate the effects of vasoactive intestinal peptide (VIP) on neurogenesis and neurological function after cerebral ischemia. Rats were intracerebroventricular administered with VIP after a 2h middle cerebral artery occlusion (MCAO) and sacrificed at 7, 14 and 28 days after MCAO. Functional outcome was studied with the modified neurological severity score. The infarct volume was evaluated via histology. Neurogenesis, angiogenesis and the protein expression of vascular endothelial growth factor (VEGF) were measured by immunohistochemistry and Western blotting analysis, respectively. The treatment with VIP significantly reduced the neurological severity score and the infarc volume, and increased the numbers of bromodeoxyuridine (BrdU) immunoreactive cells and doublecortin immunoreactive area in the subventricular zone (SVZ) at 7, 14 and 28 days after ischemia. The cerebral protein levels of VEGF and VEGF expression in the SVZ were also enhanced in VIP-treated rats at 7 days after stroke. VIP treatment obviously increased the number of BrdU positive endothelial cells in the SVZ and density of cerebral microvessels in the ischemic boundary at 28 days after ischemia. Our study suggests that in the ischemic rat brain VIP reduces brain damage and promotes neurogenesis by increasing VEGF. VIP-enhanced neurogenesis is associated with angiogenesis. These changes may contribute to improvement in functional outcome.

Vasoactive intestinal peptide increases VEGF expression to promote proliferation of brain vascular endothelial cells via the cAMP/PKA pathway after ischemic insult in vitro.

Vasoactive intestinal peptide (VIP) enhances angiogenesis in rats with focal cerebral ischemia. In the present study, we investigated the molecular mechanism of the proangiogenic action of VIP using an in vitro ischemic model, in which rat brain microvascular endothelial cells (RBMECs) are subjected to oxygen and glucose deprivation (OGD). Western blotting and immunocytochemistry were carried out to examine the expression of VIP receptors and vascular endothelial growth factor (VEGF) in cultured RBMECs. The cell proliferation was assessed by the MTT assay. Cyclic adenosine monophosphate (cAMP) and VEGF levels were measured by using the enzyme-linked immunosorbent assay. The cultured RBMECs expressed VPAC1, VPAC2 and PAC1 receptors. Treatment with VIP significantly promoted the proliferation of RBMECs and increased OGD-induced expression of VEGF, and this effect was antagonized by the VPAC receptor antagonist VIP6-28 and VEGF antibody. VIP significantly increased contents of cAMP in RBMECs and VEGF in the culture medium. The VIP-induced VEGF production was blocked by H89, a protein kinase A (PKA) inhibitor. These data suggest that treatment with VIP promotes VEGF-mediated endothelial cell proliferation after ischemic insult in vitro, and this effect appears to be initiated by the VPAC receptors leading to activation of the cAMP/PKA pathway.

[Markov process of vegetation cover change in arid area of northwest China based on FVC index].

Based on the fractional vegetation cover (FVC) data of 1982-2000 NOAA/AVHRR (National Oceanic and Atmospheric Administration/ the Advanced Very High Resolution Radiometer) images, the whole arid area of Northwest China was divided into three sub-areas, and then, the vegetation cover in each sub-area was classified by altitude. Furthermore, the Markov process of vegetation cover change was analyzed and tested through calculating the limit probability of any two years and the continuous and interval mean transition matrixes of vegetation cover change with 8 km x 8 km spatial resolution. By this method, the Markov process of vegetation cover change and its indicative significance were approached. The results showed that the vegetation cover change in the study area was controlled by some random processes and affected by long-term stable driving factors, and the transitional change of vegetation cover was a multiple Markov process. Therefore, only using two term image data, no matter they were successive or intervallic, Markov process could not accurately estimate the trend of vegetation cover change. As for the arid area of Northwest China, more than 10 years successive data could basically reflect all the factors affecting regional vegetation cover change, and using long term average transition matrix data could reliably simulate and predict the vegetation cover change. Vegetation cover change was a long term dynamic balance. Once the balance was broken down, it should be a long time process to establish a new balance.