Water-use efficiency in response to simulated increasing precipitation in a temperate desert ecosystem of Xinjiang, China

Water-use efficiency（WUE） is a key plant functional trait that plays a central role in the global cycles of water and carbon. Although increasing precipitation may cause vegetation changes, few studies have explored the linkage between alteration in vegetation and WUE. Here, we analyzed the responses of leaf WUE, ecosystem carbon and water exchanges, ecosystem WUE, and plant community composition changes under normal conditions and also under extra 15% or 30% increases in annual precipitation in a temperate desert ecosystem of Xinjiang, China. We found that leaf WUE and ecosystem WUE showed inconsistent responses to increasing precipitation. Leaf WUE consistently decreased as precipitation increased. By contrast, the responses of the ecosystem WUE to increasing precipitation are different in different precipitation regimes： increasing by 33.9% in the wet year（i.e., the normal precipitation years）and decreasing by 4.1% in the dry year when the precipitation was about 30% less than that in the wet year.We systematically assessed the herbaceous community dynamics, community composition, and vegetation coverage to explain the responses of ecosystem WUE, and found that the between-year discrepancy in ecosystem WUE was consistent with the extent to which plant biomass was stimulated by the increase in precipitation. Although there was no change in the relative significance of ephemerals in the plant community, its greater overall plant biomass drove an increased ecosystem WUE under the conditions of increasing precipitation in 2011. However, the slight increase in plant biomass exerted no significant effect on ecosystem WUE in 2012. Our findings suggest that an alteration in the dominant species in this plant community can induce a shift in the carbon-and water-based economics of desert ecosystems.

Amphipods fail to suppress the accumulation of Ulva lactuca biomass in eutrophic Yundang Lagoon

The Gross growth efficiency （GGE） is defined as the amount of consumer carbon produced relative to the amount of prey ingested in a given time interval. In population ecology, it can be considered as an index for the ability of a consumer to convert the biomass of food into its population production. In this study, it was firstly applied to estimate the role of amphipods grazing in the biomass dynamics of macroalgae （Ulva lactuca） in Yundang Lagoon （a subtropical eutrophic coastal lagoon, Xiamen City, China）. It was found that amphipods were the dominant group （82.2%-98.7%） in the benthic assemblage, in which five amphipod species （Corophium uenoi, Ampithoe valida, Grandidierella japonica, Grammaropsis laevipalmata andCa-prella panantis） were observed in the lagoon. However, onlyA. valida significantly consumedU. lactuca among these amphipod species. A series of experiments were conducted to estimate the consumption of U. lactuca byA. valida. It was suggested that the monthly secondary production （P） ofA. valida using size frequency method ranged from 2.39 to 13.68 g/m2.GGEofA. valida exponentially reduced with body size and was closely associated with water temperature. Therefore,GGE equation for different months using the temperature recorded during the field investigation was fitted. The monthly consumption ofU. lactuca was figured out to be 86.7-1 549.0 g/m2 by the sum of consumption （P/GGE） byA. valida at different size, ac-counting for 2.0%-37.5% ofU. lactucaproduction. It indicates that the grazing effect ofA. valida did play a role in reducingthe accumulation ofU. lactucabiomass whenA. valida was abundant, but it finally fails to limit the U. lactucagrowth in Yundang Lagoon. Low abundance of A. valida and high nutrient loading may be two major reasons for the outbreak ofU. lactuca bloom in the lagoon.

Water, land, and energy use efficiencies and financial evaluation of air conditioner cooled greenhouses based on field experiments

High temperature and humidity can be controlled in greenhouses by using mechanical refrigeration cooling system such as air conditioner(AC)in warm and humid regions.This study aims to evaluate the techno-financial aspects of the AC-cooled greenhouse as compared to the evaporative cooled(EV-cooled)greenhouse in winter and summer seasons.Two quonset single-span prototype greenhouses were built in the Agriculture Experiment Station of Sultan Qaboos University,Oman,with dimensions of 6.0 m long and 3.0 m wide.The AC-cooled greenhouse was covered by a rockwool insulated polyethylene plastic sheet and light emitting diodes(LED)lights were used as a source of light,while the EV-cooled greenhouse was covered by a transparent polyethylene sheet and sunlight was used as light source.Three cultivars of high-value lettuce were grown for experimentation.To evaluate the technical efficiency of greenhouse performance,we conducted measures on land use efficiency(LUE),water use efficiency(WUE),gross water use efficiency(GWUE)and energy use efficiency(EUE).Financial analysis was conducted to compare the profitability of both greenhouses.The results showed that the LUE in winter were 10.10 and 14.50 kg/m^(2) for the AC-and EV-cooled greenhouses,respectively.However,the values reduced near to 6.80 kg/m^(2) in both greenhouses in summer.The WUE of the AC-cooled greenhouse was higher than that of the EV-cooled greenhouse by 3.8%in winter and 26.8%in summer.The GWUE was used to measure the total yield to the total greenhouse water consumption including irrigation and cooling water;it was higher in the AC-cooled greenhouse than in the EV-cooled greenhouse in both summer and winter seasons by almost 98.0%–99.4%.The EUE in the EV-cooled greenhouse was higher in both seasons.Financial analysis showed that in winter,gross return,net return and benefit-to-cost ratio were better in the EVcooled greenhouse,while in summer,those were higher in the AC-cooled greenhouse.The values of internal rate of return in the AC-and EV-cooled greenhouses were 63.4%and 129.3%,respectively.In both greenhouses,lettuce investment was highly sensitive to changes in price,yield and energy cost.The financial performance of the AC-cooled greenhouse in summer was better than that of the EV-cooled greenhouse and the pattern was opposite in winter.Finally,more studies on the optimum LED light intensity for any particular crop have to be conducted over different growing seasons in order to enhance the yield quantity and quality of crop.

Effects of Additional Rifle-Carriage Training on Physiological Markers and Roller-Skiing Performance in Well-Trained Biathletes

Purpose The purpose was to investigate whether an increased amount of training while carrying the rifle affects skiing in well-trained biathletes at submaximal and maximal workloads during a pre-season period lasting a minimum of 12 weeks.Methods Seventeen well-trained biathletes(9 females,8 males)were assigned to an intervention(IG,n=10)or control(CG,n=7)group.Before(T1)and after(T2)the training intervention all participants performed,using treadmill roller-skiing,a submaximal test without the rifle on one day and two submaximal workloads and a maximal time trial(TT)with the rifle on a subsequent day.Between T1 and T2 all participants performed a minimum of 12 weeks of normal training,the only difference between groups being that IG performed more of their training sessions carrying the rifle.Results IG performed more training compared to CG(15.4±1.1 vs.11.2±2.6 h/week,P<0.05),including a higher amount of training with the rifle(3.1±0.6 vs.1.1±0.3 h/week,P<0.001).Speed at 4 mmol/L of blood lactate increased significantly for CG from T1 to T2(P=0.028),while only tended to increase for IG(P=0.058).Performance during the TT,VO2max and the aerobic metabolic rate increased significantly from T1 to T2,although the differences disappeared when including the speed at baseline as a covariate.Conclusion According to the present results,increasing training while carrying the rifle by 2 h/week does not appear to improve skiing performance in well-trained biathletes.In addition,physiological markers at submaximal and maximal intensities while carrying the rifle were not affected after the training intervention.