A global synthesis of the effects of diversified farming systems on arthropod diversity within fields and across agricultural landscapes

Agricultural intensification is a leading cause of global biodiversity loss, which can reduce the provisioning of ecosystem services in managed ecosystems. Organic farming and plant diversification are farm management schemes that may mitigate potential ecological harm by increasing species richness and boosting related ecosystem services to agroecosystems. What remains unclear is the extent to which farm management schemes affect biodiversity components other than species richness, and whether impacts differ across spatial scales and landscape contexts. Using a global metadataset, we quantified the effects of organic farming and plant diversification on abundance, local diversity (communities within fields), and regional diversity (communities across fields) of arthropod pollinators, predators, herbivores, and detritivores. Both organic farming and higher in‐field plant diversity enhanced arthropod abundance, particularly for rare taxa. This resulted in increased richness but decreased evenness. While these responses were stronger at local relative to regional scales, richness and abundance increased at both scales, and richness on farms embedded in complex relative to simple landscapes. Overall, both organic farming and in‐field plant diversification exerted the strongest effects on pollinators and predators, suggesting these management schemes can facilitate ecosystem service providers without augmenting herbivore (pest) populations. Our results suggest that organic farming and plant diversification promote diverse arthropod metacommunities that may provide temporal and spatial stability of ecosystem service provisioning. Conserving diverse plant and arthropod communities in farming systems therefore requires sustainable practices that operate both within fields and across landscapes.     

基于多尺度协同的长沙市生态网络构建与层级优化

城市化背景下人类与自然环境的矛盾呈现出多尺度、层级化特征，而传统生态网络的构建方式较少考虑不同尺度下生态要素的关系，无法从区域落实到中心城区，难以形成系统性的解决方案。研究在综合梳理各尺度生态网络构建方法的基础上，以长沙市为例，基于形态学空间格局分析（Morphological Spatial Pattern Analysis，MSPA）、景观连通性原理和生态斑块重要性评价识别生态源地，并通过多层级生态阻力面的确定，综合运用最小费用路径（Least-cost path method，LCP）、电路理论、层级传导理论、尺度嵌套等方法对市域、都市区、中心城区的生态网络进行了协同构建和层级优化，最后基于不同尺度生态网络的特点应用并落实到多层级的国土空间规划体系中。研究结果表明：（1）长沙市域生态网络和都市区生态网络具有较好的层级嵌套特征；共识别两尺度生态叠合源地14个、生态叠合廊道15条，主要通过中心城区内的湘江、浏阳河和捞刀河部分河段与外围生态绿圈相衔接，形成"外环内楔"的空间格局。（2）确定市域重要廊道、市域潜在廊道、生态叠合廊道、都市区重要廊道、都市区潜在廊道的核心保护面积共501.14 km²，并提取位于生态廊道核心保护区范围内的生态夹点和生态障碍点，以进一步落实生态保护修复策略。（3）得到具有重要生态连通功能的中心城区生态绿道长度441.2 km，生态修复单元56个，并结合生态阻力值划分为5级进行针对性修复。（4）基于不同尺度生态网络的衔接、嵌套，最终构建"市域总体生态安全格局-都市区城市生态空间发展格局-以城市绿道为基础的中心城区生态修复单元"，并与不同层级的国土空间规划体系相对应。研究结果将为以大城市为中心的跨尺度生态系统修复和生态安全格局构建提供科学参考。     

Gene expression kinetics in individual plasmodial cells reveal alternative programs of differential regulation during commitment and differentiation

During its life cycle, the amoebozoon Physarum polycephalum forms multinucleate plasmodial cells that can grow to macroscopic size while maintaining a naturally synchronous population of nuclei. Sporulation‐competent plasmodia were stimulated through photoactivation of the phytochrome photoreceptor and the expression of sporulation marker genes was analyzed quantitatively by repeatedly taking samples of the same plasmodial cell at successive time points after the stimulus pulse. Principal component analysis of the gene expression data revealed that plasmodial cells take different trajectories leading to cell fate decision and differentiation and suggested that averaging over individual cells is inappropriate. Queries for genes with pairwise correlated expression kinetics revealed qualitatively different patterns of co‐regulation, indicating that alternative programs of differential regulation are operational in individual plasmodial cells. At the single cell level, the response to stimulation of a non‐sporulating mutant was qualitatively different as compared to the wild type with respect to the differentially regulated genes and their patterns of co‐regulation. The observation of individual differences during commitment and differentiation supports the concept of a Waddington‐type quasipotential landscape for the regulatory control of cell differentiation. Comparison of wild type and sporulation mutant data further supports the idea that mutations may impact the topology of this landscape.     

The dynamics of freshwater phytoplankton stability in the Naroch Lakes (Belarus)

The phytoplankton community of the Belarus Lakes Naroch, Myastro and Batorino, which have a Trophic State Index of 42.3, 60.7 and 66.8, respectively, underwent drastic changes to their structure during the period between 1968 and 2012. Thanks to an extensive monitoring program, these changes were well-documented and were qualitatively interpreted as signs of the community destabilization. The main objective of this study was the quantification of the ecological stability of the phytoplankton community in the Naroch Lakes. The approach to the quantification of ecological stability was based on defining the stability index as an inverse of the Euclidean Distance between the current and the reference states of the algal community (EuD-approach). The stability of the phytoplankton community was characterized by two indices: a “combined” index (SI[Comb]), and a “total community” index (SI[TotB]). SI[Comb] was calculated based on the individual taxonomic group biomasses and thus characterizes the stability of a community structure. SI[TotB] was calculated based on the values of the total algal biomass. Analyses of the results of this study extended the plausibility of the EuD-approach for the quantification of lake phytoplankton stability and allowed us to identify the dynamics of the stability of the Naroch Lakes phytoplankton. For the Naroch Lakes, we observed relatively larger SI[TotB] values in comparison with the SI[Comb] values. The results enabled us to examine the relationship between the lake trophic status and the stability of the phytoplankton community.     

The lifetime of molecular (Davydov) solitons

The lifetime of Davydov solitons in a one-dimensional system is studied theoretically. The process of thermalization and the properties of solitons at finite temperature are investigated and the processes of soliton creation and disintegration are discussed.     

城市扩张过程中建设用地景观格局演变特征及其驱动力

剖析城市扩张过程中建设用地景观格局演变特征及其驱动力,不仅有助于城市生态环境问题的解决,而且为城市用地结构优化、城市景观规划等工作提供科学依据。以快速城市化的中型城市—扬州市为例,利用多期(1995、2000、2005、2010年和2015年)Landsat卫星影像、乡镇水平的扬州统计年鉴等数据,运用景观格局分析、增强回归树(Boosted regression trees)等方法,研究建设用地的扩张模式、形态及景观格局,定量探究地理、社会和经济因子对景观格局的影响机制,从而明晰景观格局演变特征及其驱动力。结果表明,1995—2015年,建设用地面积持续增加,填充式(Infilling)、边缘式(Edge-expansion)和跳跃式(Leapfrog)3种扩张模式在各时段均有出现,但其优势度随着城市发展而改变。建设用地的形态在城市扩张的过程中经历着"集聚"和"扩散"的交替变化过程,景观格局则出现了同质化倾向,景观破碎化下降、聚合度增加。地理因子(海拔和到县市中心的距离)对景观格局的综合影响虽然高于社会经济,但它的影响力却随着城市发展呈现出下降趋势,社会经济的作用则逐渐增强。海拔和人口密度的增加会促进景观的破碎化、抑制景观的集聚;人口数量的增加会促进景观的集聚、降低景观的破碎化;其余因子(到县市中心的距离、人均GDP和第二产业占比)的作用则随城市的发展而发生转变,如人均GDP对景观破碎化的作用表现为"促进→抑制"的转变、第二产业则为"抑制→促进"。