Electrostatics of the FeS clusters in respiratory complex I

Respiratory complex I couples the transfer of electrons from NADH to ubiquinone and the translocation of protons across the mitochondrial membrane. A detailed understanding of the midpoint reduction potentials (E_m) of each redox center and the factors which influence those potentials are critical in the elucidation of the mechanism of electron transfer in this enzyme. We present accurate electrostatic interaction energies for the iron-sulfur (FeS) clusters of complex I to facilitate the development of models and the interpretation of experiments in connection to electron transfer (ET) in this enzyme. To calculate redox titration curves for the FeS clusters it is necessary to include interactions between clusters, which in turn can be used to refine E_m values and validate spectroscopic assignments of each cluster. Calculated titration curves for clusters N4, N5, and N6a are discussed. Furthermore, we present some initial findings on the electrostatics of the redox centers of complex I under the influence of externally applied membrane potentials. A means of determining the location of the FeS cofactors within the holo-complex based on electrostatic arguments is proposed. A simple electrostatic model of the protein/membrane system is examined to illustrate the viability of our hypothesis.     

Modelling and analyzing density-dependent population processes: Comparison between wild and laboratory strains of the bean weevil,Callosobruchus chinensis (L.)

Three models were constructed for analyzing the population characteristics ofC. chinensis on stored beans; model A describing the whole reproductive process with a single equation, model B describing the three age-specific processes (oviposition, egg survival and larval survival) with separate equations, and model C which describes all these processes not for the whole habitat but for the individual beans comprizing it. The logit equation was employed here as a common basis to describe the density-response relationship involved. All three models showed very good fit to the experimental data obtained for both laboratory and wild strains of the weevil. The parameter values characterizing the population dynamics were, however, widely different between the two strains; the laboratory one which had been reared for some 500 generations showed significantly higher reproductive capacity, less sensitive and gentler response to crowding in both adult and egg stages, and more uniform egg distribution among individual beans, as compared with the wild strain newly introduced. Sensitivity analyses using these models suggested that these changes in population characteristics have been attained by the process of domestication or adaptation to stable laboratory conditions through a long period of time. This process seemed in effect to have optimized the population's performances in the laboratory environment. Evolutionary significance of such optimization was discussed with reference to the selection pressure which may have acted upon individuals.     

Complex Genetic Effects on Early Vegetative Development Shape Resource Allocation Differences Between Arabidopsis lyrata Populations

Costs of reproduction due to resource allocation trade-offs have long been recognized as key forces in life history evolution, but little is known about their functional or genetic basis. Arabidopsis lyrata, a perennial relative of the annual model plant A. thaliana with a wide climatic distribution, has populations that are strongly diverged in resource allocation. In this study, we evaluated the genetic and functional basis for variation in resource allocation in a reciprocal transplant experiment, using four A. lyrata populations and F₂ progeny from a cross between North Carolina (NC) and Norway parents, which had the most divergent resource allocation patterns. Local alleles at quantitative trait loci (QTL) at a North Carolina field site increased reproductive output while reducing vegetative growth. These QTL had little overlap with flowering date QTL. Structural equation models incorporating QTL genotypes and traits indicated that resource allocation differences result primarily from QTL effects on early vegetative growth patterns, with cascading effects on later vegetative and reproductive development. At a Norway field site, North Carolina alleles at some of the same QTL regions reduced survival and reproductive output components, but these effects were not associated with resource allocation trade-offs in the Norway environment. Our results indicate that resource allocation in perennial plants may involve important adaptive mechanisms largely independent of flowering time. Moreover, the contributions of resource allocation QTL to local adaptation appear to result from their effects on developmental timing and its interaction with environmental constraints, and not from simple models of reproductive costs.     

Evidence of non‐stationary relationships between climate and forest responses: Increased sensitivity to climate change in Iberian forests

Climate and forest structure are considered major drivers of forest demography and productivity. However, recent evidence suggests that the relationships between climate and tree growth are generally non‐stationary (i.e. non‐time stable), and it remains uncertain whether the relationships between climate, forest structure, demography and productivity are stationary or are being altered by recent climatic and structural changes. Here we analysed three surveys from the Spanish Forest Inventory covering c. 30 years of information and we applied mixed and structural equation models to assess temporal trends in forest structure (stand density, basal area, tree size and tree size inequality), forest demography (ingrowth, growth and mortality) and above‐ground forest productivity. We also quantified whether the interactive effects of climate and forest structure on forest demography and above‐ground forest productivity were stationary over two consecutive time periods. Since the 1980s, density, basal area and tree size increased in Iberian forests, and tree size inequality decreased. In addition, we observed reductions in ingrowth and growth, and increases in mortality. Initial forest structure and water availability mainly modulated the temporal trends in forest structure and demography. The magnitude and direction of the interactive effects of climate and forest structure on forest demography changed over the two time periods analysed indicating non‐stationary relationships between climate, forest structure and demography. Above‐ground forest productivity increased due to a positive balance between ingrowth, growth and mortality. Despite increasing productivity over time, we observed an aggravation of the negative effects of climate change and increased competition on forest demography, reducing ingrowth and growth, and increasing mortality. Interestingly, our results suggest that the negative effects of climate change on forest demography could be ameliorated through forest management, which has profound implications for forest adaptation to climate change.     

气候变化和经济发展对肾综合征出血热发生的影响

肾综合征出血热(hemorrhagic fever with renal syndrome, HFRS)是一种啮齿动物传播的自然疫源性疾病, 危害严重, 已成为全球重要的公共卫生问题。本研究采用数理统计模型及小波分析方法, 对陕西省西安市鄠邑区1984-2016年HFRS的发生与鼠类、气候和经济因素的关系进行分析, 探讨气候和经济因素对HFRS发生的影响。小波分析结果表明, 该地区的HFRS暴发史可能分为两个时期, 推测每个时期具有不同的主要宿主, 在2002年褐家鼠(Rattus norvegicus)可能取代黑线姬鼠(Apodemus agrarius)成为HFRS疫源地的主要宿主。广义可加模型模拟结果表明, HFRS的发生与1984-2001年黑线姬鼠密度间存在极显著非线性效应(F_2.06,9.02 = 102.415, P < 0.01), 两者间显现为正相关; 与2002-2016年的褐家鼠密度间呈正相关(F_1.67,9.02 = 73.929, P < 0.01); HFRS主要宿主的这种变化可能与当地气候变化和经济发展有关: HFRS的发生与年平均温度存在极显著的非线性效应(F_2.93,9.02 = 12.164, P < 0.01), 两者间呈负相关; 同样, HFRS的发生与上一年的国内生产总值(GDP)也存在显著非线性效应(F_1.70,9.02 = 2.917, P < 0.05), 两者间也呈负相关。结构方程模型通过直接和间接的影响途径证明了这种转移机制, 发现温度对HFRS发生有显著的直接负向影响以及通过褐家鼠的间接正向影响; GDP对HFRS发生有直接的负向影响。本研究表明HFRS的发生与气候变化和经济发展相关, 两者均能影响HFRS的暴发, 该结论有助于今后更好地对HFRS疾病进行预防和控制。     

基于中国生态系统研究网络的典型森林生态系统土壤保持功能分析

森林生态系统土壤保持功能在控制土壤侵蚀以及维持生态安全方面具有不可替代的作用。根据不同气候带降雨特征进行降雨侵蚀力参数校正,基于中国生态系统研究网络(CERN)的森林生态系统长期定位观测样地2005—2015年监测数据利用修正的通用土壤流失方程(RUSLE)定量分析了典型森林生态系统土壤保持功能的时空变化特征,并探讨了土壤保持功能的影响因素。研究结果表明:①日雨量侵蚀力模型在降雨丰富的热带模拟效果优于降雨相对较少的亚热带和温带,参数校正后模拟效果明显提升;②研究期内10个典型森林生态系统土壤保持量变化范围为4.44—891.67 t hm~(-2) a~(-1),呈现北低南高的空间格局(R~2=0.65~(***));土壤保持率均达到97%以上;③降雨、归一化植被指数、土壤质地和植被林龄是影响森林生态系统土壤保持功能的主要影响因素;降雨量与土壤保持量显著相关(R~2=0.52~*),NDVI和土壤质地与实际土壤侵蚀量显著相关(R~2=0.64~(**),R~2=0.41~*),植被林龄主要影响土壤保持率的变化速率。     

城市绿地对居民身心福祉的影响

城市绿地是人工与自然耦合的城市景观之一,是改善居民居住环境重要组成部分,更是提高居民身心健康的有效途径。以杭州主城区为研究对象,通过GIS技术对城市绿地遥感图像进行解译得到杭州主城区绿地空间布局图,同时,以人口密度为阻力要素,基于交通路网的500m网络距离可达范围内绿地数量和面积作为分类标准。通过对45个高、中、低不同档次的居民区进行问卷调查得到665份居民感知数据并进行统计整理。利用结构方程模型进行以绿地数量及游玩时间为标准的组间分析,区别不同组别的差异及其原因,分析城市绿地数量、面积,居民认知、动机,绿地吸引力等与居民身心健康福祉及满意度之间的关系。结果显示:城市绿地数量、居民游玩绿地次数时间等与居民福祉有显著的正向关系;居民对绿地作用的认知、去往绿地的动机进一步影响居民身心健康福祉;城市绿地的自身引力会激发居民去往绿地的积极性,从而增加去往绿地频次。另外,不同社会属性的个体对绿地需求不同,所产生的福祉效应及满意度也会有所差异。从增加居民区周围的街头绿地及邻里公园数量、提升绿地吸引力、提升居民对城市绿地作用的认知3个方面对城市绿地今后的发展规划提出建议。     

环渤海滨海湿地鸻鹬类水鸟多样性及其环境影响因子

环渤海湿地是水鸟南北迁徙的重要驿站,尤其对于该线路上的鸻鹬鸟类具有非常重要的意义。以环渤海地区12处典型滨海湿地为研究对象,于2016-2020年每年春季开展水鸟调查,明确了鸻鹬类水鸟群落组成及其时空变化,采用结构方程模型 （Structural Equation Modeling,SEM）分析了鸻鹬类水鸟多样性与环境因子的响应关系,评估了各环境因子的影响强度。结果表明：（1）共记录到鸻鹬类水鸟7科51种,几乎全部为旅鸟。全球极危物种1种,濒危物种3种,近危物种9种。国家一级保护鸟类2种,国家二级保护鸟类8种。黑腹滨鹬（Calidris alpina）、大滨鹬（Calidris tenuirostris）、黑尾塍鹬（Limosa limosa）、灰鸻（Pluvialis squatarola）、斑尾塍鹬（Limosa lapponica）个体数量最多。（2）山东黄河三角洲、辽宁辽河口、天津北大港等河口湿地,水鸟种类多,单位面积水鸟数量较少。（3）河北沧州沿海、山东滨州贝壳堤岛及其周边区域为环渤海地区湿地集中区,水鸟种类较多。（4）综合影响强度为保护强度>食物>气候,建立自然保护地是保护水鸟多样性的最有效措施。（5）建议将河北南大港湿地和鸟类省级自然保护区提升至国家级,扩大滨州贝壳堤岛与湿地国家级自然保护区面积,对山东黄河三角洲、辽宁辽河口覆盖的各级各类自然保护地进行优化整合。研究结果能为环渤海地区鸻鹬类水鸟保护策略的制定提供相关依据。     

吉林省天然阔叶混交林生态系统多功能性及驱动因素

量化天然林生态系统的多功能性,分析不同功能间的权衡-协同关系及驱动因子,对于天然林保护及修复具有重要的意义。基于吉林省第8次森林资源清查天然阔叶混交林固定样地调查数据、土壤及气候数据,选取土壤保持、涵养水源、碳储量、气候调节、土壤肥力维持、生物多样性、生产力和木材生产8个生态系统功能来表征生态系统多功能性。利用平均值法中的最大值转换法计算多功能性指数。结果表明：（1）8个功能间权衡、协同和中性关系均存在,但以协同关系为主。生物多样性除与气候调节为权衡关系外,与其他功能均为协同关系;碳储量-木材生产协同关系最强（r=0.960,P<0.01）,气候调节-涵养水源间权衡关系最强（r=-0.934,P<0.01）;（2）吉林省天然阔叶混交林的多功能性指数在0.31-0.89之间,且生物多样性和气候调节为主导功能;（3）多功能性与驱动因子的结构方程模型确定系数为R²=0.795,多功能性的驱动因子的总路径系数依次为：林分密度指数（0.752） > 平均年龄（0.375） > 年降雨量（0.365） > 树种丰富度（0.101） > 土壤pH（0.064） > 结构多样性（-0.037） > 年均温（-0.105）,林分密度是最重要的驱动因子。结果对理解天然阔叶混交林的多功能形成及经营调控有一定的意义。