Cd、水分单一及复合胁迫对异叶天南星叶片抗氧化酶的活性影响

为探讨Cd、水分单一及复合胁迫条件下对异叶天南星叶片伤害及其抗氧化酶活性的响应,研究并比较了不同浓度Cd (200、400、800 mmol/L)和水分胁迫（PEG6000模拟,浓度分别为10%、20%、40%）条件下异叶天南星叶片的丙二醛(MDA)和超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)等抗氧化酶活性的影响。结果表明：在单一、复合胁迫条件下,相对于对照来说,MDA含量呈上升趋势,SOD、POD、CAT整体呈现先升高后降低趋势。同时,对于比较同水平浓度下单一因子胁迫而言,复合胁迫MDA含量体现出协同效应,SOD、POD、CAT则体现协同或拮抗效应。     

Cumulative impacts of fisheries in the California Current

Ecosystem‐based fisheries management calls for the consideration of the indirect and cumulative effects of fishing, in addition to estimating direct fishing mortality. Here, we quantify such effects of fishing fleets, and their interactions, using a spatially explicit Atlantis simulation model of the food web and fisheries in the California Current. Simulations testing the effects of single fleets suggested that bottom trawl, fixed gear, and hake (Merluccius productus) trawl primarily have direct impacts on their target and bycatch species. Few indirect effects from these three fleets extended through predator–prey links to other parts of the food web. In contrast, effects of the purse seine fleet extended beyond the three groups it harvested, strongly altering the abundance of predators, planktonic prey, and benthos. In terms of nine ecosystem attributes, our experiments involving single fleets identified six fleets that caused the bulk of negative impacts. Specific fleets impacted different aspects of the ecosystem, for instance with groundfish gears causing reductions in piscivore abundance, and hake trawl and purse seine increasing krill through reducing abundance of planktivores. In terms of interactions among fleets' effects, the vast majority of effects were simply additive – the combined effect of two fleets was simply the sum of the individual fleets' effects. The analyses offer one way to sharpen the focus of ecosystem‐based fisheries management in the California Current, emphasizing impacts and interactions of particular stressors.     

水氮互作对石羊河流域春小麦群体产量和水氮利用的影响

【目的】探讨西北旱区春小麦最佳的水氮耦合形式。【方法】在甘肃石羊河流域绿洲区采用田间试验,研究不同生育阶段的水量分配以及氮肥处理对春小麦群体产量和水氮利用的影响。【结果】施氮量、拔节期和抽穗期灌水对干旱区春小麦的产量影响显著;施氮量168 kg/hm2,并于拔节期灌水90 mm、抽穗期灌水70 mm,小麦可获得较高的籽粒产量。水氮对小麦地上干物质累积量的影响与对籽粒产量的影响相似,但抽穗期灌水对地上干物质累积量影响不显著。在施氮量224 kg/hm2、抽穗期和灌浆期灌水均为50 mm的条件下,小麦可获得较高的收获指数。在生产中考虑提高小麦收获指数时,首先应保证较高的籽粒产量。分蘖期和灌浆期灌水均为30 mm时,小麦的水分利用效率高达2.424 kg/m3,但产量降低约45%。施氮量对小麦地上干物质和籽粒氮素累积量影响显著;拔节期灌水90 mm、施氮量168 kg/hm2时,小麦籽粒的氮素累积量最大。【结论】石羊河流域春小麦最优灌水施氮模式为:施氮量168 kg/hm2,全生育期灌水4次,拔节期灌水90 mm,分蘖期、抽穗期、灌浆期均灌水60 mm。     

Forest landscape models: Definitions,characterization, and classification

Previous model classification efforts have led to a broad group of models from site-scale (non-spatial) gap models to continental-scale biogeographical models due to a lack of definition of landscape models. Such classifications become inefficient to compare approaches and techniques that are specifically associated with forest landscape modeling. This paper provides definitions of key terminologies commonly used in forest landscape modeling to classify forest landscape models. It presents a set of qualitative criteria for model classification. These criteria represent model definitions and key model implementation decisions, including the temporal resolution, number of spatial processes simulated, and approaches to simulate site-level succession. Four approaches of simulating site level succession are summarized: (1) no site-level succession (spatial processes as surrogates), (2) successional pathway, (3) vital attribute, and (4) model coupling. Computational load for the first three approaches is calculated using the Big O Notation, a standard method. Classification criteria are organized in a hierarchical order that creates a dichotomous tree with each end node representing a group of models with similar traits. The classified models fall into various groups ranging from theoretical and empirical to strategic and tactical. The paper summarizes the applications of forest landscape models into three categories: (1) spatiotemporal patterns of model objects, (2) sensitivities of model object to input parameters, and (3) scenario analyses. Finally, the paper discusses two dilemmas related to the use of forest landscape models: result validation and circular reasoning.     

交互式双分支特征融合的草莓病害程度快速诊断方法

针对现有草莓病害程度诊断方法存在识别精度低、参数量大、推理时间长等问题，提出了一种基于交互式双分支特征融合的草莓病害程度快速诊断方法。该方法首先以短程密集连接模块为基础，构建一种轻量化的交互式双分支特征融合网络(Interactive bilateral feature fusion network, IBFFNet),用于提取图像的语义特征和细节特征。然后，通过注意力简化的金字塔池化模块获取上下文分支中的多尺度语义特征，利用边缘增强模块丰富空间分支中的边缘细节特征。最后，融合多尺度语义特征和空间细节特征，实现病斑和叶片区域的精确分割。在草莓叶部病害程度数据集上的实验结果显示，IBFFNet2＿Seg的平均交并比达到77.8%,在单张NVIDIA GTX1050显卡上处理速度可达40.6 f/s,满足实际应用中对算法实时性和分割精度的要求。此外，在测试集上IBFFNet2＿Seg预测病害程度与真实程度的决定系数R²为0.98,说明该模型可以准确预测草莓病害严重程度。本研究可为草莓病害精准防治提供可靠的技术支撑。     

基于交互式骨架模型的玉米根系三维可视化研究

植物根系可视化交互设计对于提高虚拟植物生长研究整体水平意义重大。该文提出一种植物根系逐部位交互式精确设计方法，并在玉米根系建模中予以应用。通过分析玉米根系结构特征并建立其拓扑结构，采用交互式骨架模型确定其整体结构，设计密度函数确定分支数量和分布，利用模板技术衍生相似部位，利用带参数随机L系统产生一级侧根及根毛，对玉米根系各组成部位逐个精确建模，然后拼接形成完整的玉米根系。本系统综合可视化设计多种方法，交互性、真实感都比较好，既可展现玉米根系各组成部分细微特征，又可表现玉米根系整体特征。本系统研究和设计方法具有一定通用性，对其它可用轴线表示其拓扑结构的相似植物可视化建模也有一定借鉴意义。