Study on specifications of farmland shelterbelt net in Northeastern Plain of China

s: The farmland shelterbelts in Northeastern Plain of China have formed relatively complete net system. The func-tions of shelterbelt net in omnibearing wind check and prevention of frostbite as well as the field of integrated climate effect within shelterbelt net were analyzed, through located observation of meteorological factors. Within the shelterbelt net, the area with more than 10% efficiency of omnibearing wind check was determined as benefited area. The analysis of yield and quality of crops indicated that the sheltering range of shelterbelt net was 25 times tree height. The mature heights of the various varieties of poplar composed the shelterbelts were determined according to their height growth. Based on the comprehensive analysis above, the suitable size of farmland shelterbelt net in Northeastern Plain of China was decided to be 400 m×400 m.

A Method for Spatial Heterogeneity Evaluation on Landscape Pattern of Farmland Shelterbelt Networks:A Case Study in Midwest of Jilin Province,China

On the basis of landscape ecology, combining the Spot 5 high resolution satellite imagery with GIS, a method evaluating the spatial heterogeneity of shelterbelts distribution at landscape scale is put forward in this paper. The distance coefficients of reasonable and existing landscape indexes of farmland shelterbelt networks were com-puted, and then through the classification of the distance coefficients, and the establishment of evaluation rules, the spatial heterogeneity of farmland shelterbelts was evaluated. The method can improve the evaluating system of previ-ous studies on shelterbelts distribution, resolve the disadvantages of lacking spatiality of overall evaluation, and make the evaluation results have more directive significance for shelterbelt management. Based on this method, spatial het-erogeneity of shelterbelt networks was evaluated in the midwest of Jilin Province, China. The results show that the re-gions with fewer shelterbelts and no closed network account for 34.7% of the total area, but only 4.9% of the area has relative reasonable pattern of shelterbelt networks. Many problems exist in the distribution pattern of shelterbelts, therefore, much attention should be paid to construct farmland shelterbelts in the study area.

Effect of farmland shelterbelts on gully erosion in the black soil region of Northeast China

The black soil region of northeast China is one of the most important grain-producing areas in China. Increasingly severe gully erosion in this region has destroyed much farmland and reduced grain production. We analyzed SPOT5 imagery from 2007 and TM imagery from 2008 to describe the distributions of gullies and farmland shelterbelts in Kedong County and to assess the effect of farmland shelterbelts on gully erosion. The ima- gery revealed 2311 gullies with average density of 418.51 m km-2, indicating very serious gully erosion. With increasing slope gradient there was an inverse trend between gully density and shelterbelt density, indicating that farmland shelterbelts can prevent gully erosion. The defense effect of farmland shelterbelts against gullyerosion varied with distance： for distances 〈120 m, the defense effect was consistent and very strong; for distances of 120-240 m, a weak linear decrease was found in the defense effect; and for distances 〉240 m, the defense effect of the shelterbelts was significantly weaker. We recommend an optimal planting density of farmland shel- terbelts for the prevention of gully erosion at 1100-1300 m km-2.

Effects of Spatial Density of Farmland Shelterbelts on NDVI on the Northern Slope of Tianshan Mountains

[Objectives]To explore the effects of spatial density of farmland shelterbelts on NDVI on the northern slope of Tianshan Mountains.[Methods]Taking the economic belt of the northern slope of the Tianshan Mountains as the research area and using the grid method,the spatial density distribution of farmland shelterbelts can be known.Combining the grid method with NDVI data,the average value of normalized difference vegetation index(NDVI)during the growing period of crops can be obtained.In addition,the protection benefits of the shelterbelts on crops were analyzed through comparing the growth of crops within the protection zone with and without protection.[Results]The grids with shelterbelt distribution were better than the grids without shelterbelt distribution,and the shelterbelt played a great role in promoting crop growth.In the middle stage of crop growth,the protection benefit of shelterbelt was significant.The spatial density of shelterbelts was unevenly distributed in the range of 0.6 to 0.8,and the protection benefits were poor.[Conclusions]It is expected to explore the effects of shelterbelts on crop growth at a larger regional scale,so as to provide a basis for the management and design of shelterbelts in the future,and to provide a theoretical basis for studying the protective effect of farmland shelterbelts on crops.

豫东沙土农区杨树-农作物复合生态系统中温室气体排放的研究

为了探讨农林复合系统农田土壤温室气体排放的贡献率,在豫东沙区杨树—农作物复合生态系统中选取了2种典型的防护林网密度——大网格BT(防护林间距1000 m×1000 m)、小网格ST(防护林间距200 m×200 m),并用周边5~10年生的人工纯林地作对照,采用静态箱—气相色谱法对不同防护林网密度的杨树—农作物复合生态系统中土壤温室气体(CO_(2)、N_(2)O、CH_(4))季节排放通量进行田间原位测定。结果表明:豫东农区农田土壤是CO_(2)、N_(2)O的排放源、CH_(4)的吸收汇。不同农林复合模式对土壤温室气体的排放或吸收的强度都有不同的特征,大网格、小网格、林地土壤CO_(2)日排放通量均在7月达到最大值,分别为1163.17、1005.91、923.53 mg/(m^(2)·h);大网格的土壤N_(2)O日排放通量在7月达到最大值,小网格和林地则在8月达到最大值,土壤N_(2)O排放通量为4.29~313.28μg/(m^(2)·h);3种模式下土壤CH_(4)的吸收峰值均在7月达到最大值,其中大网格的吸收峰值最大,为4.41 mg/(m^(2)·h)。不同农林复合经营模式通过影响土壤、空气温度和湿度等来影响农田土壤温室气体排放,其中增温干燥强化了土壤CO_(2)和N_(2)O排放源的特征,但同时也增加了土壤作为大气CH_(4)吸收汇的功能,大网格、小网格、林地的全球增温潜势(GWP)分别为1.50×10^(5)、1.03×10^(5)、0.885×10^(5)kg C/hm^(2),单位面积GWP值以林地的最小、大网格的最大。总的来看,适当增加防护林网密度有利于减少农林系统的增温潜能。

农田防护林林网景观结构定量评价与分析

以东北地区的“三北”防护林工程重点建设区为研究对象,选取林网的带斑比、连接度、环度、优势度等作为评价指标,利用高分辨率的ZY-3影像,根据景观生态学原理及地理信息系统技术,对2021年实际林网和合理状态下林网的景观指标值进行定量评估及对比,并分析现有农田防护林景观结构参数的空间分布差异性。结果表明:该区域的防护林数量与面积基本达到优质林网的要求,并且分布较均匀,但是主副林带条数不足,成型状况较差,且形成的闭合网格太少,削弱了林网的防护功能。从林网数量、分布以及成型状况等方面对防护林工程进行了宏观评价,指明了下阶段建设工作方向,为该区域防护林的管理和更新提供参考。

绿洲农田防护林树干水分传输的方位差异

[目的]对栽植于渠道旁的绿洲农田防护林树干向、背渠两侧边材液流速率进行定位观测和比较,明确特殊立地条件下树干边材水分传输的方位差异,为提高利用液流估算树木蒸腾精度提供科学依据。[方法]以乌兰布和沙漠绿洲农田防护林的3种杨树(小美旱杨、新疆杨和北抗杨)为研究对象,采用有8个监测位点的热场变形液流测定技术同步监测和对比树干向渠和背渠2个方位的边材液流速率。[结果]边材液流速率在向渠侧(J_(Q-side))显著高于背渠侧(J_(NQ-side))(P<0.01),且3个树种表现一致。观测期内,小美旱杨、新疆杨和北抗杨的J_(Q-side)为J_(NQ-side)的1.83倍(R^(2)=0.90)、1.40倍(R^(2)=0.71)和3.55倍(R^(2)=0.71),典型晴天的J_(Q-side)日峰值平均值分别可达3.38、2.47和5.35 cm·h^(−1),午间前后,树干向、背渠两侧边材液流速率差异最大。J_(Q-side)和J_(NQ-side)均表现出随边材深度而递减的显著变化,其中向渠侧边材各位点(1.5~7.5 cm)的液流速率均显著高于背渠侧相应位点(P<0.01),该径向变化规律在每个树种不同方位均表现出一致性,可通过负指数函数较好拟合(R^(2)>0.98)。[结论]灌渠引起绿洲农田防护林树干向、背渠两侧边材的水分传输产生显著差异,但并不改变各方位的径向变化格局。

风沙区不同配置农田防护林防护效应及其对农田土壤水分的影响

[目的]明确风沙区不同配置农田防护林产生的防护效果差异以及影响田间土壤含水率的作用因子,为该地区水分管理和土地利用提供理论依据。[方法]选择南疆阿拉尔市十团3种典型配置的农田防护林,研究不同配置防护林内土壤含水率、风速、光照强度、空气温湿度等因素,综合分析土壤含水率变异性决定因子。[结果]疏透度为41%的5行新疆杨对田间小气候改善作用在0~1 H范围最显著,疏透度为47%的1行胡杨+2行新疆杨的林内有效防护距离最长,且田间土壤含水率显著大于5行新疆杨且大于4行新疆杨。5行新疆杨林内土壤含水率主要受空气温度、湿度、光照强度的影响,4行新疆杨和1行胡杨+2行新疆杨土壤含水率与防护林距离和土层深度有关。总体来看,林带疏透度对土壤含水率有直接负向作用,同时土壤容重随土层深度变化间接对含水率产生负向影响。[结论]合理调整农田防护林配置结构,能够提高防护林防护效益,为风沙区作物生长提供有利条件,同时促进当地水资源合理利用和可持续发展。

基于风洞试验的樟子松农田防护林防风效果研究

樟子松(Pinus sylvestris var. mongolica)是我国“三北”地区主要造林树种之一,樟子松防护林具有较强的防风固沙能力。本研究以樟子松防护林为研究对象,开展了5种行带式配置防护林防风效益风洞试验研究,测定了不同配置防护林防护区不同距离范围内风速及其流场特征,研究了樟子松防护林不同行带配置与防护效益关系,为常绿针叶树种农田防护林营造提供理论依据。结果表明:(1)防风效能随着林带行数的增加而增强,且林带后1 H~3 H内风速显著降低,形成风影区,风影区面积随着林带行数的增加而变大。(2)樟子松防护林带后风速流场发生显著变化,在12 m·s^(-1)风速条件下,1~5行1带的5种林带防风效能分别为15.1%、26.2%、37.5%、51.7%和51.9%,4行1带、5行1带结构配置防风效能均在50.0%以上。(3)樟子松防护林具有较强的防风效果,建议在干旱区农田防护林建设与更新中可采用樟子松造林,最适结构配置为4行1带。

农田防护林对库尔勒香梨火疫病影响的初步研究

为了解农田防护林对香梨火疫病的影响,对尉犁县6块农田库尔勒香梨树的感病情况进行调查,探究农田防护林对梨火疫病传播蔓延的限制作用。结果表明:靠近防护林带的香梨树感病率最低,具有一定规模、林相完整的防护林可以减少或隔绝园区梨火疫病原菌的传播,在一定程度上降低了病害发生;梨火疫病病情在农田内的发生并不均匀,呈现团块结构分布。在规划梨园防护林时,需要充分考虑主风向,特别是主要害风的方向。此外,在防治过程中应采取分区定点、强化防治的策略。

基于U-Net网络的高标准农田道路识别方法

高标准农田是国家粮食安全的重要保障,作为其中的重要工程,田间道路的快速准确获取可为高标准农田建设质量评估和效果评价提供基础数据支撑。针对传统方法对细窄田间道路识别精度低、泛化能力不强的问题,本文提出了基于U-Net网络的高标准农田道路识别方法。首先,在分析田间道路基本特征的基础上,选取GF-2影像作为试验数据,采用面向对象方法对影像进行分割并根据对象特征进行分类,剔除光谱特征与田间道路相似的建筑物等非道路要素,减少道路识别干扰;然后,对影像进行裁剪、标签制作和数据增强等操作,并使用U-Net网络挖掘影像的深浅层特征,通过不断调整参数对网络进行训练,实现田间道路的快速识别;最后,依据道路断点特征,采用局部连接法对道路断点进行修复,并以河北省定州市东亭镇为试验区进行方法测算与精度验证。结果表明:通过挖掘622幅田间道路样本的影像特征,U-Net网络可以有效识别各类场景下的高标准农田道路,通过对道路断点进行修复后,研究区田间道路识别精确率达96%,召回率和F1值分别为62%、75%,该识别精度能够满足高标准农田建设质量快速评估要求。相比传统识别方法,结合面向对象和深度学习的方法可以在减少建筑物干扰的基础上快速地识别出田间道路,能更好解决田间道路材质差异大、植被遮挡等造成识别结果噪声多、误识别问题,该方法可为细窄地物的识别提供方法参考。

河套灌区不同配置农田防护林对田间土壤水分和养分储量的影响

农田防护林作为提高生态环境效益的有效农业管理方式,对改善土壤理化性质、改善生态环境,提高作物产量具有重要意义。在河套灌区选择三种典型农田防护林(4行林带、5行林带和8行林带)测量了2019—2021年生长季农田内距防护林0.3 H、0.7 H、1 H、2 H、3 H和4 H处0~100 cm的土壤性质和防护林与农田的植被属性,测算了土壤水分储量(SMS)和土壤养分储量[碳储量(SCS)、氮储量(SNS)和磷储量(SPS)]。结果表明:(1)不同防护林系统水平方向上的土壤容重和土壤黏粒含量差异显著,在垂直方向上土壤属性均有显著差异。(2)防护林具有较好的保水性和养分供应功能,其中4行林带的土壤水分储量和养分储量高于其他林带,分别为SMS 237.44 mm、SCS 544.93 g·m^(-2)、SNS 953.72 g·m^(-2)和SPS 859.04 g·m^(-2)。(3)4行林带的整体长势比较好,其平均树高为30.06 m,胸径为0.41 m,且4行防护林的作物产量最高,为15.75 t·hm^(-2)。(4)冗余分析结果显示,不同防护林系统中,环境因子与生态系统功能之间存在密切关系,土壤特性与土壤水分和养分储量关系密切,另外,植被属性与SNS和SPS基本呈负相关。综上所述,4行林带的水分养分供给能力最强,本研究结果可为生态脆弱地区的防护林建设和生态修复提供有效的理论依据。

乌兰布和沙漠绿洲区典型农田防护林带风速流场数值模拟

研究不同结构配置林带前后流场分布和防护效应的差异,能够揭示林带的防风机理,为林带配置优化提供科学依据。以乌兰布和沙漠绿洲区4种配置林带(0.8 H宽度林带、0.2 H宽度林带、乔灌混交林带和无灌木对比林带,H代表林带高度)。对研究对象进行数值模拟,分析不同林带结构配置对林带风速流场特征、不同高度处的水平风速以及防护距离的影响。结果表明:气流在经过4条林带时均产生不同的速度分区,其中下部气流加速区和带后回流区受林带配置结构影响较大;在近地面0.1 H高度处,0.8 H宽度林带相较于0.2 H宽度林带在带后1 H范围内风速降低90.8%,带后回流强度增加55.2%,林带总体有效防护距离分别为17.8 H和15.5 H;乔灌混交林带相较于无灌木林带,带后1 H范围内风速降低122.4%,回流强度增加15.9%,林带有效防护距离分别为21.5 H和23.7 H,对比无灌木林带减少2.2 H。总之,较宽林带和乔灌混交林带能很好地改善林带后缘风速,抑制近地面气流加速作用,但也增强带后回流,缩短了林带有效防护距离,因此在林带配置中应根据不同位置合理规划。

不同农田防护林配置结构下玉米水分来源研究

由于气候条件干旱,合理平衡防护林与农田作物水分需求是河套灌区农田防护林林网体系建设的关键问题。为研究河套灌区典型农田防护林对农田作物水分来源的影响,选择河套灌区3种典型配置的防护林系统,测定并分析附近农田距农田边缘0.3,0.4,0.6,2 H处土壤含水率、土壤和作物茎秆水氢氧同位素值。结果表明:(1)7—9月各农田样地土壤含水率普遍较低,4,5行样地在近林端处土壤含水率均低于远林端处,8行样地各处土壤含水率没有明显差异。(2)各样地土壤水氢氧同位素随着土层深度的增加而贫化,其中,8行样地距农田边缘0.4~0.6 H处40—60 cm土层的土壤出现较大的同位素富集。(3)4行样地内距农田边缘0.3~0.4 H处玉米主要利用40—80 cm土层土壤水,0.6~2 H处玉米利用0—40 cm土层土壤水。5行样地0.3 H处玉米利用20—60 cm土层土壤水,0.4~2 H处玉米利用0—60 cm土层土壤水。8行0.3,2 H处玉米主要利用0—40 cm土层土壤水,0.4~0.6 H处玉米则更多地利用20—80 cm土层土壤水。研究认为,8行配置的防护林对农田作物水分利用范围影响更广,在不影响防护效果的前提下,4,5行防护林对农田作物生长用水影响范围更小。研究结果可为当地合理配置农田防护林体系提供理论参考。

中国农田防护林对作物产量影响的整合分析

【目的】系统评价中国农田防护林对作物产量的影响。【方法】在中国知网和Web of Science公开发表的文献中,通过检索关键词“农田防护林和产量”构建目标数据库,利用整合分析研究农田防护林对作物产量的影响及其在不同环境条件下的变化。【结果】1)中国农田防护林对作物的平均增产率为16.4%,考虑林带占地因素后为5.6%;2)不同作物的增产效应有显著差异(Q_(M)=8.55,p=0.02),玉米(22.02%)增产率最大,小麦(14.36%)和水稻(11.15%)较低;3)不同气候类型(Q_(M)=1.8,p=0.79)和不同林网规格(Q_(M)=3.25,p=0.16)条件下农田防护林对作物产量的影响无显著差异;4)作物的增产效应和背景产量呈负相关,在产量低于9727.5 kg·hm^(-2)时具有显著增产效应。【结论】农田防护林可有效提高作物产量,是保障粮食安全和应对气候变化的有效途径,未来研究应适当关注政策工具的制定和综合经济效益的提升。

宁夏中部干旱带农田防护林对西瓜叶片光合特性及产量的影响

以宁夏中部干旱带的旱柳防护林网为研究对象,测定0.5H(H为树高)、1H、2H、3H、5H与林网中心西瓜的光合生理特性及产量,分析防护林网对西瓜生长的影响。结果表明:林网内西瓜叶片的光合生理特性与其和林网的距离存在显著相关性,与林网中心相比,林网东侧2H、西侧1H、南侧1H与北侧0.5H范围内不同位置的光合有效辐射(PAR)日平均值减少30%以上,林网东侧受到的影响最大;林网内不同位置的净光合速率(Pn)与光合有效辐射间存在显著正相关关系,随着与防护林距离的增加,Pn与PAR呈相似的变化趋势;西瓜产量与气温和光合有效辐射间存在显著正相关关系,林网东侧2H、西侧1H、南侧1H与北侧0.5H范围内西瓜出现减产趋势,减产量为17.46%~38.08%,其余地方处于平产或增产区。综上,防护林通过遮阴影响了西瓜的光合特性,防护林附近区域西瓜减产严重;可在防护林影响范围内种植喜阴作物,增加经济效益。

Novel real-time safety algorithm for predicting multi-targets in the farmland road

The more information obtained about the driving environment,the more ensures driving safety.Due to the complex driving environment of farmland roads,targets beside the road sometimes have an important impact on driving safety.To achieve this goal,a novel real-time detection and prediction algorithm of targets was proposed.The whole image was divided into four parts by RCM:driving region,crossroad region,roadside region,and the other region.In addition,a safety policy for every part was enforced by the algorithm,which was based mainly on the combination of the YOLACT and GPM.On this basis,a self-collected data set of 5000 test samples is used for testing.The detection accuracy of the algorithm in the data set could reach up to 90%,and the processing speed to 30.4 fps.In addition,experiments were carried out on actual farmland roads,and the results showed that the proposed algorithm was able to detect,track,and predict targets on the farmland road,and alarm to driver in time before the targets rush into the road.This study provides an important reference for the safe driving of agricultural vehicles.

Extraction of straight field roads between farmlands based on agricultural vehicle-mounted LiDAR

The application of autonomous agricultural vehicles is gaining popularity as a way to increase production efficiency and lower operational costs.To achieve high performance,perception tasks(such as obstacle detection,road extraction,and drivable area extraction)are of great importance.Compared with structured roads,field roads between farmlands,including unstructured roads and semi-structured roads,are unfavorable for autonomous agricultural vehicle driving due to their bumpiness and unstructured nature.This study proposed an extraction method for the straight field roads between farmlands.The proposed method was based on the point cloud data acquired by LiDAR(Velodyne VLP-16)mounted on a John Deere 12046B-1204 tractor.The proposed method has three aspects:Euclidean Clustering-based extraction,boundary-based extraction,and road point cloud curve segment modification.Firstly,Euclidean Clustering with K-Dimensional(KD)-Tree data structure was adopted to extract the road curve segments close to the LiDAR composed of road points.Secondly,the boundary lines constraint was constructed to extract the distant road curve segments.Thirdly,the local distance ratio was used to modify the extracted road curve segments.The average extraction accuracy for both semi-structured and unstructured roads exceeded 98%,and the false positive rate(FPR)was less than 0.5%.These experimental findings demonstrated that the proposed road extraction method was precise and effective.The proposed method of this study can be applied to enhance the perception ability of autonomous agricultural vehicles thereby increasing the efficiency and safety of field road driving.

不同覆盖物对农田防护林防风效能影响

为揭示不同覆盖物对农田林网内风速分布及防风效能的影响,选取4种不同覆盖物和对照(无覆盖物)林网模型,对其防风效能进行了风洞模拟试验。结果表明:林网中防护林带高度范围内,覆盖物对林带前后的风速流场具有显著影响,尤其是高大果树类作物对风速削减程度较大。8m·s^(-1)风速条件下,各模式林网内平均风速排序为核桃+小麦间作模式<苹果+小麦间作模式<红枣+小麦间作模式<纯小麦模式<无覆盖物。林网中1cm和2cm高度处平均防效能分析表明,3种果树模式林网防风效能最佳,纯小麦模式防效虽弱于果树模式,但是较对照仍有一定的防效,表明林网内覆盖物(特别是果树类作物)对林带防风效能有明显增强作用。因此,随着集约化和精准农业推进,进行农田防护林网配置时,应充分考虑林网内作物本身的防风效能,尤其是高大果树类作物农田防护林网配置时,可适当调整林网大小,合理配置林带结构,提高经济效益。

河套灌区盐碱地主要造林技术与造林模式

河套灌区地处内陆半干旱区,交叉分布着大面积盐碱地。在长期的林业建设中,总结和研发出了以“两行一带”为基础的农田防护林模式和以延时造林、地形重塑造林、耐盐碱植物原土造林为代表的中重度盐碱地造林技术,为干旱、半干旱区盐碱地林业提供了成功范例。但是,现有技术与模式也存在基础理论支撑不足、应对新形势能力不足、生态功能不足等问题,需要从系统性理论基础、综合性技术体系和多样化、多功能模式等方面进行全面提升。