Extreme drought affects the productivity, but not the composition, of a desert plant community in Central Asia differentially across microtopographies.

Extreme climatic conditions are major drivers of ecosystem function and dynamics and their frequency is increasing under climate change. Climatic conditions interact with local microtopography, which might either buffer or exacerbate the degree of climatic stress. Here we sought to understand how extremely dry growing seasons affected the composition and productivity of desert ephemeral communities growing in sand dunes from the Gurbantunggut desert in Central Asia, and to which extent did microtopography modulate the response. We set up a rainfall manipulation study on four sand dune microtopographies and, during two consecutive years, we measured soil moisture, nutrients and texture, ephemeral layer composition, plant phenology, biomass accumulation and biomass allocation patterns for the dominant species. We observed significant biomass reductions during the extreme drought but plant community richness and composition were not affected, indicating that the composition of the ephemeral layer in this desert ecosystem may resist under extreme conditions. Additionally, extreme drought increased biomass allocation to reproductive organs of the dominant species. There were also significant microtopographic effects as the sensitivity of biomass to drought in western aspects was larger than in eastern aspects. Our results indicate that previously overlooked microtopographical differences may mediate the impact of climate change on plant communities.

Photosynthetic characteristics and water use efficiency of Tamarix ramosissima in shelterbelt and natural communities in south fringe of Taklamakan Desert, China.

The growth and reproduction of shelterbelt plants in arid regions is mainly limited by water availability, which can be alleviated by drip irrigation. We measured water use efficiency (WUE), leaf gas exchange and carbon isotope composition of Tamarix ramosissima in shelterbelt and natural communities in south fringe of Takelamakan Desert to investigate water use efficiency and photosynthetic properties of T. ramosissima differed in water sources. Compared to natural community, T. ramosissima in the drip irrigation community had low water potential due to irrigation and soil salinity. For natural community, T. ramosissima had lower predawn and midday water potential than other plants, indicating that T. ramosissima suffered serious water stress. The net photosynthe-tic rate (Pn), stomatal conductance (gs), intercellular carbon dioxide concentration (Ci) and maximum photosynthesis rate (Pn max) of T. ramosissima in the drip irrigation community were significantly lower than that in the natural community, indicating the photosynthesis of T. ramosissima in the drip irrigation community was weaker. Compared to the natural community, T. ramosissima in the drip irrigation community had higher long-term water use efficiency, which was related to salt stress caused by irrigation. We concluded that the current irrigation model could meet the water needs of shelterbelt plants. However, the technical defects and soil salt accumulation might affect long-term stability of the shelterbelt community.

[Effectiveness of Extracorporeal Shockwave Therapy in Treating Superior Lateral Brachial Cutaneous Nerve Compression Syndrome].

Objective To evaluate the effectiveness of radial extracorporeal shockwave therapy(rESWT) for the treatment of superior lateral brachial cutaneous nerve(SLBCN) compression syndrome.Methods A total of 40 patients with SLBCN compression syndrome who were treated in our department from March 2013 to October 2015 were equally randomized into two groups according to random number table:rESWT group(treated with rESWT for 1 cycle) and control group(treated with local hormone injection for 1 cycle). Visual analogue scale(VAS) and Constant-Murley scale(CMS) were applied to evaluate the shoulder joint function before treatment and 1 month and 1 year after treatment. Results The average CMS scores were(66.7±0.9) and(65.7±1.1)scores in rESWT group and control group,respectively,before treatment(t=0.67,P=0.510) and were(86.9±1.0) and(86.4±1.1)scores one month after treatment(t=0.35,P=0.730);it increased to(89.7±0.7) scores in rESWT group one year later,which was significantly higher than that in control group[(85.3±0.8)scores](t=3.56,P=0.002). The improvement rate was 95% in rESWT group and only 75% in control group. Before treatment,the median VAS score in rESWT group and control group were 5.00(5.00,6.00) and 5.00(4.00,5.75)scores(u=1.13,P=0.29);one month after treatment,the median VAS score in these two groups were 2(1.00,2.75) and 2.00(1.00,2.00)scores(u=0.04,P=0.85);one year later,it was 1.00(0.00,1.00) scores in rESWT group,significantly lower than that in [2.00(1.00,2.00)scores] control group(u=5.09,P=0.02). Conclusion Compared with local hormone injection,rESWT can remarkably alleviate pain and restore shoulder joint function in patients with SLBCN compression syndrome after one year of treatment.

Water use patterns of co-occurring C3 and C4 shrubs in the Gurbantonggut desert in northwestern China.

In water-limited ecosystems, spatial and temporal partitioning of water sources is an important mechanism that facilitates plant survival and lessens the competition intensity of co-existing plants. Insights into species-specific root functional plasticity and differences in the water sources of co-existing plants under changing water conditions can aid in accurate prediction of the response of desert ecosystems to future climate change. We used stable isotopes of soil water, groundwater and xylem water to determine the seasonal and inter- and intraspecific differences variations in the water sources of six C3 and C4 shrubs in the Gurbantonggut desert. We also measured the stem water potentials to determine the water stress levels of each species under varying water conditions. The studied shrubs exhibited similar seasonal water uptake patterns, i.e., all shrubs extracted shallow soil water recharged by snowmelt water during early spring and reverted to deeper water sources during dry summer periods, indicating that all of the studied shrubs have dimorphic root systems that enable them to obtain water sources that differ in space and time. Species in the C4 shrub community exhibited differences in seasonal water absorption and water status due to differences in topography and rooting depth, demonstrating divergent adaptations to water availability and water stress. Haloxylon ammodendron and T. ramosissima in the C3/C4 mixed community were similar in terms of seasonal water extraction but differed with respect to water potential, which indicated that plant water status is controlled by both root functioning and shoot eco-physiological traits. The two Tamarix species in the C3 shrub community were similar in terms of water uptake and water status, which suggests functional convergence of the root system and physiological performance under same soil water conditions. In different communities, Haloxylon ammodendron differed in terms of summer water extraction, which suggests that this species exhibits plasticity with respect to rooting depth under different soil water conditions. Shrubs in the Gurbantonggut desert displayed varying adaptations across species and communities through divergent root functioning and shoot eco-physiological traits.