GENETIC ADAPTATION AND ACCLIMATION OF PHYTOPLANKTON ALONG A STRESS GRADIENT IN THE EXTREME WATERS OF THE AGRIO RIVER–CAVIAHUE LAKE (ARGENTINA)1

We tested if different adaptation strategies were linked to a stress gradient in phytoplankton cells. For this purpose, we studied the adaptation and acclimation of Dictyosphaerium chlorelloides (Naumann) Komárek et Perman (Chlorophyta) and Microcystis aeruginosa (Kütz.) Kütz. (Cyanobacteria) to different water samples (from extremely acid, metal‐rich water to moderate stressful conditions) of the Agrio River–Caviahue Lake system (Neuquén, Argentina). Both experimental strains were isolated from pristine, slightly alkaline waters. To distinguish between physiological acclimation and genetic adaptation (an adaptive evolution event), a modified Luria‐Delbrück fluctuation analysis was carried out with both species by using as selective agent sample waters from different points along the stress gradient. M. aeruginosa did not acclimate to any of the waters tested from different points along the stress gradient nor did D. chlorelloides to the two most acidic and metal‐rich waters. However, D. chlorelloides proliferated by rapid genetic adaptation, as the consequence of a single mutation (5.4 × 10^?7 resistant mutants per cell per division) at one locus, in less extreme water and also by acclimation in the least extreme water. It is hypothesized that the stress gradient resulted in different strategies of adaptation in phytoplankton cells from nonextreme waters. Thus, very extreme conditions were lethal for both organisms, but as stressful conditions decreased, adaptation of D. chlorelloides cells was possible by the selection of resistant mutants, and in less extreme conditions, by acclimation.     

Climate change increases risk of fusarium ear blight on wheat in central China

To estimate potential impact of climate change on wheat fusarium ear blight (FEB), simulated weather for the A1B climate change scenario was input into a model for estimating FEB in central China. In this article, a logistic weather‐based regression model for estimating incidence of wheat FEB in central China was developed, using up to 10 years (2001–2010) of disease, anthesis date and weather data available for 10 locations in Anhui and Hubei provinces. In the model, the weather variables were defined with respect to the anthesis date for each location in each year. The model suggested that incidence of FEB is related to number of days of rainfall in a 30‐day period after anthesis and that high temperatures before anthesis increase the incidence of disease. Validation was done to test whether this relationship was satisfied for another five locations in Anhui province with FEB data for 4–5 years but no nearby weather data, using simulated weather data obtained employing the regional climate modelling system PRECIS. How climate change may affect wheat anthesis date and FEB in central China was investigated for period 2020–2050 using wheat growth model Sirius and climate data simulated using PRECIS. The projection suggested that wheat anthesis dates will generally be earlier and FEB incidence will increase substantially for most locations.     

Growth and water relations of Tamarix ramosissima and Populus euphratica on Taklamakan desert dunes in relation to depth to a permanent water table

The hypothesis that water relations and growth of phreatophytic Tamarix ramosissima Ledeb. and Populus euphratica Oliv. on dunes of varying height in an extremely arid Chinese desert depend on vertical distance to a permanent water table was tested. Shoot diameter growth of P. euphratica was inversely correlated with groundwater depth (GD) of 7 to 23 m (adj. R² = 0.69, P = 0.025); growth of T. ramosissima varied independent of GD between 5 and 24 m (P = 0.385). Pre‐dawn (pd) and midday (md) water potentials were lower in T. ramosissima (minimum pd ?1.25 MPa, md ?3.6 MPa at 24 m GD) than in P. euphratica (minimum pd ?0.9 MPa, md ?3.05 MPa at 23 m GD) and did not indicate physiologically significant drought stress for either species. Midday water potentials of P. euphratica closely corresponded to GD throughout the growing season, but those of T. ramosissima did not. In both species, stomatal conductance was significantly correlated with leaf water potential (P. euphratica: adj. R² = 0.84, P < 0.0001; T. ramosissima: adj. R² = 0.64, P = 0.011) and with leaf‐specific hydraulic conductance (P. euphratica: adj. R² = 0.79, P = 0.001; T. ramosissima: adj. R² = 0.56, P = 0.019); the three variables decreased with increasing GD in P. euphratica. Stomatal conductance of P. euphratica was more strongly reduced (> 50% between ?2 and ?3 MPa) in response to decreasing leaf water potential than that of T. ramosissima (30% between ?2 and ?3 MPa). Tolerance of lower leaf water potentials due to higher concentrations of leaf osmotically active substances partially explains why leaf conductance, and probably leaf carbon gain and growth, of T. ramosissima was less severely affected by GD. Additionally, the complex below‐ground structure of large clonal T. ramosissima shrub systems probably introduces variability into the assumed relationship of xylem path length with GD.     

新疆两盐湖可培养极端嗜盐菌组成及功能多样性研究

【目的】通过分析不同成盐类型盐湖中的极端嗜盐菌群落组成差异,探究可培养极端嗜盐菌的功能特性。【方法】采集新疆硫酸盐型盐湖七角井和碳酸盐型盐湖南湖的土壤样品,通过平板稀释涂布法分离极端嗜盐菌,经过形态学观察、特征分析获取代表菌株,通过耐盐性测定和16S rRNA基因序列测序等对代表菌株进行鉴定,并对极端嗜盐菌的蛋白酶、淀粉酶、纤维素酶和酯酶活性进行筛选,同时检测苯酚降解能力。【结果】本研究共获得1 679株极端嗜盐菌,代表菌株45株,隶属于5门14个属,古菌数量(70.58%)明显多于细菌,最优盐浓度生长范围为18.4%–20.0%。在属水平上,盐湖中优势类群为古菌的Haloterrigena属(32.94%)和Natrialba属(26.03%),以及细菌的Aquisalimonas属(9.85%)和Aliifodinibius属(8.10%)。两盐湖中,盐度较低的南湖物种丰富度高于七角井盐湖,古菌物种组成相似,均以Haloterrigena属为主;细菌群落组成有差异,南湖以Aquisalimonas属为主,而七角井以Aliifodinibius属为主。功能筛选表明,盐湖中80%的嗜盐...     

Max试验验证症状限制心肺运动试验为最大极限运动进一步临床研究*

目的: 验证临床受试者所完成的心肺运动试验（CPET）为最大极限运动,进一步设计完善Max试验验证CPET结果客观定量功能评估的准确性及以某特定指标的特定数值作为停止运动的标准是否可行。方法: 选择2017年9月至2019年1月在阜外医院签署知情同意书后进行CPET和Max试验受试者216例。其中正常受试者41例,因CPET峰值呼吸交换率（RER）≤1.10,或运动中心率和血压不上升,对CPET极限运动结果存在质疑的临床患者175例进行研究。其中60例已初步报告,本研究进一步扩大研究。Max试验方法：完成CPET测试后,先蹬车≥60 r/min,再施加130%峰值功率的恒定功率,鼓励受试者运动至不能坚持的极限状态。计算分析Max试验30 s的最大心率和最大摄氧量、及其与峰值心率和峰值摄氧量之间的差值和百分差值。百分差值=（Max值-峰值值）/Max值× 100%。评测标准：①若心率和摄氧量任一指标的差值百分比≤-10%（Max测试的数值低于CPET峰值数据）则定义Max试验操作失败,否则为成功;2若心率和摄氧量的差值百分比均在-10%~10%,则Max试验操作成功,证明CPET数据为极限运动,CPET 峰值相关数据较为准确;③若心率和摄氧量差值任一指标差值百分比≥10%时,则Max试验操作成功,证明CPET结果为非极限运动。结果: 病例组峰值摄氧量（L/min、ml/（min·kg）、%pred）、无氧阈（L/min、ml/（min·kg）、%pred）、峰值氧脉搏（ml/beat、%pred）、峰值RER、峰值收缩压（mmHg）、峰值运动负荷（W/min）、峰值心率（bpm）、摄氧有效性峰值平台（OUEP）（比值、%pred）低于正常组,二氧化碳通气有效性平均90 s最低值（Lowest Ve/VCO₂）（比值、%pred）、二氧化碳通气效率斜率（Ve/VCO₂ Slope）（比值、%pred）高于正常组（P<0.05）。所有正常组与病例组均安全无任何事件完成CPET和Max试验。216例受试者中,Max试验成功198例（91.7%）,其中证明CPET为极限运动182例,为非极限运动16例;失败18例（8.3%）。结论: 在临床检查中,若对CPET结果是否为最大极限存在质疑,利用Max试验可验证CPET是否为极限运动。Max试验方法安全可行,值得进一步深入研究和临床推广应用。     

基于地理和气象要素的春玉米生育期栅格化方法

本文以黄河流域春玉米生育期和气象站点气象数据为主要数据源,采用多元逐步回归法分析了各生育期和经度、纬度、海拔高度、降水、年均温、≥10℃积温和日照时数等影响因子的关系,建立逐步回归方程,对各生育期空间栅格化方法进行了探讨,结果表明：（1）生育期空间拟合插值的统计检验说明春玉米“播种期”、“抽雄期”和“收获期”三个时期模拟效果最好,“拔节期”效果精度相对较好;（2）播种期基本满足从西南到东北延后的变化趋势,而拔节期、抽雄期和收获期基本上表现了从南北向中部、中部向东西两侧延后的现象。本研究得到的生育期与地理和气象要素之间的逐步回归方程,可为气候条件变化下作物生育期栅格化模拟试验以及农业生产应该采取的适应机制研究提供一定的依据。     

天气变化对人口死亡率的影响——以广州市和上海市为例

人口死亡率与天气有一定的关系,以广州、上海两市１０个冬季和夏季的逐日死亡资料和气象资料,利用统计学和天气学方法得出,在最高温度达３４℃的“热日”,各类死亡数明显增多;而冬季死亡数随最低温度的下降而略有增加;广州夏季最大死亡率出现在“阴凉型”天气,而上海则是在“晴热型”天气,且上海死亡率受最高温度的影响大于广州;广州和上海冬季死亡率最大的天气均是“严寒型”,但广州死亡率受低温的影响要比上海大．在其他气象要素相似的情况下,风速对死亡率有一定的影响．     

Assessing the response of forest productivity to climate extremes in Switzerland using model–data fusion

The response of forest productivity to climate extremes strongly depends on ambient environmental and site conditions. To better understand these relationships at a regional scale, we used nearly 800 observation years from 271 permanent long‐term forest monitoring plots across Switzerland, obtained between 1980 and 2017. We assimilated these data into the 3‐PG forest ecosystem model using Bayesian inference, reducing the bias of model predictions from 14% to 5% for forest stem carbon stocks and from 45% to 9% for stem carbon stock changes. We then estimated the productivity of forests dominated by Picea abies and Fagus sylvatica for the period of 1960–2018, and tested for productivity shifts in response to climate along elevational gradient and in extreme years. Simulated net primary productivity (NPP) decreased with elevation (2.86 ± 0.006 Mg C ha^?1 year^?1 km^?1 for P. abies and 0.93 ± 0.010 Mg C ha^?1 year^?1 km^?1 for F. sylvatica). During warm–dry extremes, simulated NPP for both species increased at higher and decreased at lower elevations, with reductions in NPP of more than 25% for up to 21% of the potential species distribution range in Switzerland. Reduced plant water availability had a stronger effect on NPP than temperature during warm‐dry extremes. Importantly, cold–dry extremes had negative impacts on regional forest NPP comparable to warm–dry extremes. Overall, our calibrated model suggests that the response of forest productivity to climate extremes is more complex than simple shift toward higher elevation. Such robust estimates of NPP are key for increasing our understanding of forests ecosystems carbon dynamics under climate extremes.     

River ecosystem resilience to extreme flood events

Floods have a major influence in structuring river ecosystems. Considering projected increases in high‐magnitude rainfall events with climate change, major flooding events are expected to increase in many regions of the world. However, there is uncertainty about the effect of different flooding regimes and the importance of flood timing in structuring riverine habitats and their associated biotic communities. In addition, our understanding of community response is hindered by a lack of long‐term datasets to evaluate river ecosystem resilience to flooding. Here we show that in a river ecosystem studied for 30 years, a major winter flood reset the invertebrate community to a community similar to one that existed 15 years earlier. The community had not recovered to the preflood state when recurrent summer flooding 9 years later reset the ecosystem back to an even earlier community. Total macroinvertebrate density was reduced in the winter flood by an order of magnitude more than the summer flood. Meiofaunal invertebrates were more resilient to the flooding than macroinvertebrates, possibly due to their smaller body size facilitating greater access to in‐stream refugia. Pacific pink salmon escapement was markedly affected by the winter flood when eggs were developing in redds, compared to summer flooding, which occurred before the majority of eggs were laid. Our findings inform a proposed conceptual model of three possible responses to flooding by the invertebrate community in terms of switching to different states and effects on resilience to future flooding events. In a changing climate, understanding these responses is important for river managers to mitigate the biological impacts of extreme flooding effects.