Reconstructing historical forest fire risk in the non-satellite era using the improved forest fire danger index and long short-term memory deep learning-a case study in Sichuan Province,southwestern China

Historical forest fire risk databases are vital for evaluating the effectiveness of past forest management approaches,enhancing forest fire warnings and emergency response capabilities,and accurately budgeting potential carbon emissions resulting from fires.However,due to the unavailability of spatial information technology,such databases are extremely difficult to build reliably and completely in the non-satellite era.This study presented an improved forest fire risk reconstruction framework that integrates a deep learning-based time series prediction model and spatial interpolation to address the challenge in Sichuan Province,southwestern China.First,the forest fire danger index(FFDI)was improved by supplementing slope and aspect information.We compared the performances of three time series models,namely,the autoregressive integrated moving average(ARIMA),Prophet and long short-term memory(LSTM)in predicting the modified forest fire danger index(MFFDI).The bestperforming model was used to retrace the MFFDI of individual stations from 1941 to 1970.Following this,the Anusplin spatial interpolation method was used to map the distributions of the MFFDI at five-year intervals,which were then subjected to weighted overlay with the distance-to-river layer to generate forest fire risk maps for reconstructing the forest fire danger database.The results revealed LSTM as the most accurate in fitting and predicting the historical MFFDI,with a fitting determination coefficient(R^2)of 0.709,mean square error(MSE)of0.047,and validation R^2 and MSE of 0.508 and 0.11,respectively.Independent validation of the predicted forest fire risk maps indicated that 5 out of 7 historical forest fire events were located in forest fire-prone areas,which is higher than the results determined from the original FFDI(2 out of 7).This proves the effectiveness of the improved MFFDI and indicates a high level of reliability of the historical forest fire risk reconstruction method proposed in this study.

Multi-group pin power reconstruction method based on colorset form functions

A multi-group pin power reconstruction method that fully exploits nodal information obtained from global coarse mesh solution has been developed.It expands the intra-nodal flux distributions into nonseparable semi-analytic basis functions,and a colorset based form function generating method is proposed,which can accurately model the spectral interaction occurring at assembly interface.To demonstrate its accuracy and applicability to realistic problems, the new method is tested against two benchmark problems,including a mixed-oxide fuel problem.The results show that the new method is comparable in accuracy to fine-mesh methods.

Atmospheric nitrogen deposition affects forest plant and soil system carbon:nitrogen:phosphorus stoichiometric flexibility:A meta-analysis

Background:Nitrogen(N)deposition affects forest stoichiometric flexibility through changing soil nutrient availability to influence plant uptake.However,the effect of N deposition on the flexibility of carbon(C),N,and phosphorus(P)in forest plant-soil-microbe systems remains unclear.Methods:We conducted a meta-analysis based on 751 pairs of observations to evaluate the responses of plant,soil and microbial biomass C,N and P nutrients and stoichiometry to N addition in different N intensity(050,50–100,>100 kg·ha^(-1)·year^(-1)of N),duration(0–5,>5 year),method(understory,canopy),and matter(ammonium N,nitrate N,organic N,mixed N).Results:N addition significantly increased plant N:P(leaf:14.98%,root:13.29%),plant C:P(leaf:6.8%,root:25.44%),soil N:P(13.94%),soil C:P(10.86%),microbial biomass N:P(23.58%),microbial biomass C:P(12.62%),but reduced plant C:N(leaf:6.49%,root:9.02%).Furthermore,plant C:N:P stoichiometry changed significantly under short-term N inputs,while soil and microorganisms changed drastically under high N addition.Canopy N addition primarily affected plant C:N:P stoichiometry through altering plant N content,while understory N inputs altered more by influencing soil C and P content.Organic N significantly influenced plant and soil C:N and C:P,while ammonia N changed plant N:P.Plant C:P and soil C:N were strongly correlated with mean annual precipitation(MAT),and the C:N:P stoichiometric flexibility in soil and plant under N addition connected with soil depth.Besides,N addition decoupled the correlations between soil microorganisms and the plant.Conclusions:N addition significantly increased the C:P and N:P in soil,plant,and microbial biomass,reducing plant C:N,and aggravated forest P limitations.Significantly,these impacts were contingent on climate types,soil layers,and N input forms.The findings enhance our comprehension of the plant-soil system nutrient cycling mechanisms in forest ecosystems and plant strategy responses to N deposition.

FEM analysis of metal flowing behaviors in porthole die extrusion based on the mesh reconstruction technology of the welding process

A reconstruction technology of finite element meshes based on reversal engineering was applied to solve mesh penetration and separation in the finite element simulation for the divergent extrusion. The 3D numerical simulation of the divergent extrusion process in- cluding the welding stage for complicated hollow sections was conducted. Based on the analysis of flowing behaviors, the flowing velocities of the alloy in portholes and near the welding planes were properly controlled through optimizing the expansion angle as well as porthole ar- eas and positions. After the die structure optimization, defects such as warp, wrist, and the wavelike are eliminated, which improves the sec- tion-forming quality. Meanwhile, the temperature distribution in the cross section is uniform. Especially, the temperature of the C-shape notch with a larger thickness is lower than that of other regions in the cross section, which is beneficial for balancing the alloy flowing velocity.

Renovation of Forest Form of Nanjing Pearl Spring Scenic Area

Spontaneous mixed woods in Nanjing Pearl Spring Scenic Area are messy in structure and simple in form,lack of layer and seasonable change,and poor in ornamental effect;hence,four renovation methods have been proposed.First,it is the renovation of both sides of roads,that is,the renovation of roadside trees and ornamental shrubs and ground covers at both sides of roads;second,it is the plants disposition on waterfront forest lands,that is,the cultivation of wet tolerating and ornamental trees,wet tolerating native trees,flowering or leaf-viewing ground covers and ferns in waterfront areas;third,it is the renovation of forest form of the offshore area,that is,retaining original key tree species and conducting proper adjustment according to landscape requirement and trees' characters;forth,it is the renovation of distant forest form,that is,accelerating natural evolution by artificial measures based on current natural plants community.Finally,the development of Nanjing Pearl Spring Scenic Area has been predicted.

Meshless Surface Wind Speed Field Reconstruction Based on Machine Learning

We propose a novel machine learning approach to reconstruct meshless surface wind speed fields,i.e.,to reconstruct the surface wind speed at any location,based on meteorological background fields and geographical information.The random forest method is selected to develop the machine learning data reconstruction model(MLDRM-RF)for wind speeds over Beijing from 2015-19.We use temporal,geospatial attribute and meteorological background field features as inputs.The wind speed field can be reconstructed at any station in the region not used in the training process to cross-validate model performance.The evaluation considers the spatial distribution of and seasonal variations in the root mean squared error(RMSE)of the reconstructed wind speed field across Beijing.The average RMSE is 1.09 m s^(−1),considerably smaller than the result(1.29 m s^(−1))obtained with inverse distance weighting(IDW)interpolation.Finally,we extract the important feature permutations by the method of mean decrease in impurity(MDI)and discuss the reasonableness of the model prediction results.MLDRM-RF is a reasonable approach with excellent potential for the improved reconstruction of historical surface wind speed fields with arbitrary grid resolutions.Such a model is needed in many wind applications,such as wind energy and aviation safety assessments.

Under-forest Breeding Pattern and the Practice Form

Through the development in recent years, China's under-forest breeding pattern can be divided into four kinds of practice form of under-forest breeding pattern (the pattern of breeding driven by leading enterprises; the pattern of breeding driven by intermediary economic organizations; the pattern of breeding driven by the professional wholesale market; the pattern of breeding driven by the modern animal husbandry demonstration areas), according to difference in the main body participating in signing the operation contract in breeding pattern. In the production practice of under-forest breeding pattern, the most widely used and successful pattern is the pattern of breeding driven by leading enterprises and its derivative forms.

具备黑启动和构网能力的远海风电经DRU-MMC送出方案

由于具有成本低、体积重量小和可靠性高等特点,送端采用二极管整流器(DRU)、受端采用模块化多电平换流器(MMC)的送出方案在远海风电送出领域备受关注。鉴于DRU不能构建交流电网且无法倒送有功功率,文中提出一种具备黑启动和构网能力的远海风电经DRU-MMC送出方案。所提方案在DRU-MMC送出技术的基础上增加了常规小容量电压源型辅助换流器、耗能单元和必要的快速开关,通过直流海缆复用和快速开关倒闸重构拓扑,分别构建黑启动电源低压回路和风电传输高压回路,实现黑启动和功率传输2种工况在线切换;提出辅助换流器在不同运行阶段的构网控制策略,解决海上交流电网构建、DRU无功补偿和谐波抑制等问题,消除DRU-MMC送出方案对风电场类型的限制。最后,通过经济性分析和算例仿真,验证了所提方案的优越性和有效性。

中国传统地域建筑文化的当代重构议题——基于徽州合院形式的设计探索

徽州合院是特定地域内自然环境和社会文化在建筑形式上的重要表征。本文针对中国传统地域建筑文化的当代重构议题,立足于徽州合院形式的设计探索,从形式美学、空间组织、场所营造三个方面解析传统徽州合院地域特征,运用特征归纳、比较分析、案例解读等方法解读三个当代建筑案例,进而揭示出徽州合院在形式操作、空间组织、组群构建三个层级上转译与重构方法,阐释当今地域创作中对徽州合院形式的传承与变异,探索徽州合院形式对当代创作的潜能,并探讨建筑实践中传统与当代、地域与全球的关系。

基于风环境优化的岭南高校教学组团形态布局设计研究

校园形态与环境舒适性的关系是校园建设的热门议题。探讨高校公共教学组团布局类型及关键设计要素与风环境评价指标的关系,目的在于为风环境导向下的公共教学组团空间形态控制提供思考路径。选取岭南地区54所建成高校公共教学组团作为研究对象,归纳总结组团布局类型,分析风环境相关设计要素(包括建筑朝向、建筑间距与围合形式),抽象高校公共教学组团理想模型,运用Phoenics软件进行夏季风环境模拟;设计单因子变量实验,分析不同因素与室外风环境的关联关系;对3个设计要素进行关联分析,探讨不同设计制约条件下的最优因素水平组合。结果显示,行列式布局在4种布局类型中室外风环境表现最优;当建筑根据地形呈斜向行列式布局时,组团室外风环境舒适性和空间感受较好;建筑间距与组团室外风环境呈正相关关系,但差异性较小;呈E型或S型围合的组团布局模式,连接体采用架空、挖洞等手法进行通透性处理,是兼顾室外风环境舒适性与空间需求的较优组团形式。

基于数据集重构与Logistic回归的林火预测研究

以大兴安岭地区呼玛县为例,采用过采样、欠采样、混合采样以及人工合成等数据平衡方法对林火数据集进行重构,然后分别应用二项Logistic回归模型进行拟合。选择平均预测效果最佳的数据平衡方法,对全样本数据进行重构和建立模型,同时利用标准化回归系数法对各气象因子的相对重要性进行研究。结果显示,综合随机划分的10个样本共计40个平衡数据集,就拟合优度来说,过采样、混合采样和人工合成数据集差别不大,三者略大于欠采样数据集;就预测精度来说,过采样数据集﹥混合采样数据集﹥人工合成数据集﹥欠采样数据集,其中前三者差别不大,但明显大于欠采样数据集。计算各气象因子的标准化回归系数结果,FFMC、日最小相对湿度、DC绝对值最大,分别为0.771、0.720、0.527。本文通过过采样、混合采样及人工合成数据方法所得平衡数据集的拟合效果较好,其中以过采样数据集平均预测准确率最高,可用于该地区林火数据集重构及建立模型,各气象因子中,FFMC、日最小相对湿度、DC是影响研究区林火发生的主要驱动气象因子。

基于计算机模拟模型的林木冠层太阳短波辐射定量分析方法

【目的】定量模拟和刻画林木冠层太阳短波辐射的分布和截获情况,于时空变换下反演太阳短波辐射在不同林木冠层内的辐射通量变化,为林木培育经营和提质增效提供理论依据。【方法】首先,以公共数据集和真实扫描的校园内林木激光点云数据为例,结合设计的机器视觉算法,对林木激光点云进行枝叶分离和单叶分割,并用合适大小的椭圆形和圆柱体几何单元分别拟合每片叶片和骨架,开展林木真实模型重建;其次,运用计算机图形学方法,结合研究地点的经纬度和时刻,模拟太阳入射光线,并引入物理学的双向反射和透射分布函数及蒙特卡洛光线追踪算法,开展反射和透射光线与冠层内叶片的碰撞模拟;最后,根据仪器测量得到的不同树种叶片平均粗糙度和折射率,结合光线追踪算法,实现林木冠层内短波辐射分布计算和木林冠层光截获效率评估。【结果】利用本研究方法计算时空变换下不同树种(芒果、橡胶、紫薇、樱花)4株树冠及一片香樟树林的直射、反射和透射太阳辐射通量,其中直射辐射通量占比约86%、反射辐射通量占比约5%、透射辐射通量占比约9%。叶面积指数高的树冠会拦截更多直射和透射光线;在太阳高度角较小时刻(上午或下午),斜射的太阳光线反射后易与树冠中其他叶片发生二次求交,产生较多反射辐射通量。同时,由于林木的趋光性,中午树冠光线拦截率高于上午和下午10%左右。比对采用本研究方法计算的树冠辐射通量拦截比值和样地手持光电仪器实测结果,绝对误差小于6%。【结论】在测绘科学、计算机图形学及林学多学科视角融合下,本研究基于激光点云重建树木真实表观形态结构,并将蒙特卡洛光线追踪算法与物理学的双向反射和透射分布函数相融合,真实模拟光线在树冠中的传播过程,可准确获取林木冠层内太阳短波辐射分布与树冠辐射通量拦截值,对研究时空变换下林木太阳辐射吸收、光强与树冠形态结构的耦合关联及不同表型参数的林冠辐射传输模型均有重要启示意义。

基于激光点云的橡胶树参数反演与数字孪生构建

基于激光雷达(Light Detection And Ranging,LiDAR)数据重建树体三维模型并精准获取林木空间枝干结构参数对林木性状评价、森林动态经营管理与可视化研究具有重要意义。为此提出一种基于骨架细化提取的树木模型重建方法。首先,采用FocusS350/350 PLUS三维激光扫描仪获取3块不同树龄橡胶树的样地数据。然后,作为细化建模的重点,将枝干点云从原始树点中分离出来,再将其过度分割为若干点云簇,通过相邻点云簇判断是否有分枝以及动态确定骨架点间距,并将其运用在空间殖民算法以此来生成树的三维骨架点和骨架点连通性链表,根据连通链表结构自动识别树木中的主枝干和各个一级分枝,再通过广义圆柱体生成树干完成树木三维重建。最后,利用数字孪生技术对这3块不同树龄样地树木进行三维实景建模,使其穿越时空在同一空间中重现,以便更为直观地观察树木在生长过程中的形态变化。该算法得到的橡胶树胸径与实测值比对为,决定系数(R^(2))>0.91,均方根误差(root mean square Error,RMSE)<1.00 cm;主枝干与一级枝干的分枝角为,R^(2)>0.91,RMSE<2.93;一级枝干直径为,R^(2)>0.90,RMSE<1.41 cm;将3个树龄放在一起计算其生长参数,并与实测值进行对比,发现该算法同样适用于异龄林样地的各个生长参数计算。同时发现橡胶树的一级枝条的直径越大,其相对应的叶团簇体积就越大。运用人工智能的理论模型来处理林木的激光点云数据,旨在为森林的可视化以及树木骨架结构的智能化分析与处理等研究领域提供有价值的参考。

传统书院的精神传承与再利用——以天窝书院遗址为例

分析传统书院建筑和园林中蕴含的特征,将其运用到书院复建设计之中,有利于文教建筑的精神传承。基于精神传承和再利用理念,总结中国传统书院的精神属性、空间布局、建筑形制、园林营造等特征,以湖北五云山天窝书院为实践对象,探讨传统书院特征在现代书院中的再利用,营造既传承传统精神、又符合现代需求的现代书院。

文化转译视域下鄂伦春族萨满神话的文化IP设计研究

目的基于文化转译理念对萨满神话进行视觉元素重构,并形成创新型文化产业IP,进一步实现非物质文化遗产保护和地域性特色文化产业宣传。方法以黑龙江省鄂伦春族萨满神话中的萨满面具为研究对象,通过文化转译下语义学和语形学的研究来深入挖掘萨满神话的精神内核及萨满面具的物质文化资源。提取核心文化并有效组织内在文化逻辑结构,依此形成创新型视觉元素表达库。并运用语义学中的视觉修辞方法进行符号转译,通过视觉元素重构形成新型文化IP。结论将语言学中的文化转译理念引入设计学,能够更加精准地提取文化内核,并能有序的转译为视觉语言,从而促进龙江鄂伦春族萨满文化的视觉观感与文化保护,以及助力龙江萨满文化的创造性转化与创新型发展。

西北地区红桦天然次生林立地质量评价

在陕西、宁夏、甘肃、青海等地设置红桦天然次生林临时样地85块,以年龄-树高、胸径-树高数据为依据,选取常用的9个树木生长模型拟合导向曲线,采用相对优势高法编制立地指数表和立地形表,并采用2种方法对4个不同地区的立地质量进行比较,实现对西北地区红桦天然次生林立地质量的科学评价。结果表明,立地指数和立地形的最优导向曲线方程分别为H=18.073/{1+exp[-(A-22.571)/9.144]}、H=19.793/{1+exp[-(D-12.218)/6.588]};确定基准年龄为40 a,基准胸径为20 cm,指数级距为2 m,划定10~20 m共6个立地质量等级,编制立地指数表和立地形表。检验结果表明,两表的卡方值均小于临界值,落点检验精度分别为95%和97.5%,达到编表精度要求,均能够良好地反映红桦天然次生林立地质量。2种方法在对4个地区的立地质量评价中表现出较好的一致性,其中陕西火地塘林场立地质量最优,宁夏二龙河林场次之,青海北山林场和甘肃洮坪林场立地质量一般。

扬州市森林、湿地生态系统外来入侵植物调查分析与管理对策

通过线路踏查、资料分析,对扬州市森林、湿地生态系统外来入侵植物的种类组成、生活型、繁殖方式、原产地、入侵方式、生态系统类型及分布进行了研究。结果表明:扬州市外来入侵植物共有18种,隶属于9科15属,其中菊科种类最多(9种),占比50.00%;调查到的外来入侵植物均为草本植物,以一二年生草本植物最多(10种),占比55.56%;这些草本植物大多均依靠种子繁殖,仅有空心莲子草、大薸和凤眼蓝3种水生草本植物依靠营养繁殖;按原产地统计来看,原产于美洲的植物种类最多(15种),占83.33%;有50.00%(9种)入侵植物属于有意引入,44.44%(8种)属于无意引入,自然传入的仅有豚草1种。按生态系统来看,乔木林地和灌木林地中的外来入侵植物种类最多,有15和13种。就扬州市外来入侵植物发生情况进行了讨论分析,并提出相应的管理对策。

一类具时滞森林病虫害传染病模型

控制森林病虫害有利于增加森林碳汇量,对实现我国“双碳”战略具有重要意义。为了研究森林病虫害对林区的影响,建立了一个含饱和发生率的森林病虫害传播时滞微分方程模型,研究了平衡点的存在性与稳定性,以及平衡点处Hopf分支的存在性,同时利用多尺度方法推导出系统在Hopf分支临界点附近的规范型。结合全国森林清查报告等实际数据,对模型中的参数进行分析与预测,得出各参数的取值范围。选取合理参数进行数值模拟,并研究了部分参数变化对模型的影响。最后根据模拟结果,结合黑龙江省林区森林病虫害的防控现状给出结论和建议。

低产林改造措施对毛竹生长及其经济效益的影响

以怀化市具有典型代表性的低产毛竹林为研究对象,采用浅垦+林分结构调整(处理Ⅰ)、深垦+施肥+林分结构调整(处理Ⅱ)、带垦+压青+林分结构调整(处理Ⅲ)、撩壕+深施肥+林分结构调整(处理Ⅳ)等4种措施进行改造。2016—2020年连续监测毛竹林的发笋、成竹、秆质量、鲜笋质量、毛料质量、总产值、净产值以及新生鞭生长、新竹生长等因子。结果表明:不同低产林改造措施下毛竹的新生鞭长度、直径、分布深度以及单位面积鲜笋质量、壮芽数、新生竹净产值和增收、经济效益等均呈现为处理Ⅳ的>处理Ⅲ的>处理Ⅱ的>处理Ⅰ的。4种改造措施均可不同程度地提高毛竹低产林质量、产量和经济效益,其中处理Ⅳ的投入最高,增产幅度最大;新生鞭数量最多、质量最大、芽最多。低改4年后,处理Ⅳ的发笋数和成竹数均最多,分别达76725.0个·hm^(-2)和30780.0株·hm^(-2);新竹平均胸径、净产值、增收均最大,分别达12.13 cm、135701.0元·hm^(-2)、107420.0元·hm^(-2)。由此可见,毛竹林的经济效益与垦复深度和施肥量密切相关。本研究结果可为怀化市加强毛竹资源开发、提高林地产出、增加农民收入、助推乡村振兴等提供参考。

基于韧性视角下川西林盘活化建设实践路径启示——以成都大邑县南岸美村为例

随着近些年经济的快速发展、城镇化的快速推进的影响,川西林盘面临数量严重锐减、发展模式单一、生态环境破坏、林盘空心化严重、基础设施不足等种种困境。基于韧性视角,文章以成都大邑县南岸美村为例,在解析林盘韧性建设理念的基础上,分析林盘制度、经济、社会、生态、基础设施等多方面韧性建设,得出林盘活化利用启示,为传统林盘保护发展的实践提供参考。