基于SPAN与NDVI的全极化SAR数据喀斯特地区土地类型划分

地貌复杂性、地物多样性等特征使得全极化SAR（Synthetic Aperture Radar,SAR）数据的散射机制和散射强度相互交织,从而导致基于传统Wishart-H/α的全极化SAR数据难以实现喀斯特地区土地类型的有效划分。针对此问题,本文先用复Wishart距离测度对研究区土地类型样本进行聚类,同时利用H/α平面对研究区进行超盒聚类,然后根据超盒聚类结果平均相干矩阵与样本聚类结果平均相干矩阵间的复Wishart距离进行半监督分类,获得研究区土地类型划分的初步结果。在此基础上利用对建筑物与裸岩地敏感的极化总功率（Polarimetric-Total-Power,SPAN）和对林地、草地与耕地敏感的归一化植被指数（Normalized Differential Vegetation Index,NDVI）对初步结果继续进行划分,最终将研究区土地类型划分为水体、林地、草地、耕地、建筑地和裸岩地,总体分类精度为81.45%;采用另一地势相对平缓、地形相对单一的典型喀斯特地区全极化SAR数据进行验证,在实现该地区土地类型划分的同时总体分类精度为85.66%。说明gai该研究方法能够实现喀斯特地区土地类型的准确划分。     

基于Sentinel-1A影像和一维CNN的中国南方生长季早期作物种类识别

作物的早期识别对粮食安全至关重要。在以往的研究中,中国南方作物早期识别面临的主要挑战包括:1)云层覆盖时间长、地块尺寸小且作物类型丰富;2)缺少高时空分辨率合成孔径雷达(synthetic aperture radar,SAR)数据。欧洲航天局Sentinel-1A(S1A)卫星提供的SAR图像具有12 d的重访周期,空间分辨率达10 m,为中国南方作物早期识别提供了新的机遇。为在作物早期识别中充分利用S1A影像的时间特征,本研究提出一维卷积神经网络(one-dimensional convolutional neural network,1D CNN)的增量训练方法:首先利用生长季内全时间序列数据来训练1D CNN的超参数,称为分类器;然后从生长季内第一次S1A影像获取开始,在每个数据获取时间点输入该点之前(包括该点)生长季内所有数据训练分类器在该点的其他参数。以中国湛江地区2017年生长季为研究实例,分别基于VV、VH和VH+VV,评估不同极化数据在该地区的作物分类效果。为验证该方法的有效性,本研究同时应用经典的随机森林(random forest,RF)模型对研究区进行试验。结果表明:1)基于VH+VV、VH和VV极化数据的分类精度依次降低,其中,基于VH+VV后向散射系数时间序列1D CNN和RF测试结果的Kappa系数最大值分别为0.924和0.916,说明S1A时间序列数据在该地区作物分类任务中有效;2)在研究区域内2017年生长季早期,基于1D CNN和RF的5种作物的F-measure均达到0.85及以上,说明本文所构建的1D CNN在该地区主要作物早期分类任务中有效。研究结果证明,针对中国南方作物早期分类,本研究提出的1D CNN训练方案可行。研究结果可为深度学习在作物早期分类任务中的应用提供参考。     

双极化SAR影像的分类研究

合成孔径雷达(SAR)遥感数据的穿透性,可以反应亚表层的结构信息等特点,对地表景观分类有特殊的作用.通SAR究地物后向散射和极化等特性,可以反映地物的粗糙度、含水量等特点,用于土地利用调查有很好的效果.文章重点研究了双极化SAR数据特性与数据处理,利用决策树分类、K-means分类方法对吉林西部松原地区进行土地利用分类,并与Landsat 8数据的分类结果进行对比分析.结果表明,基于地物极化特性的双极化雷达数据分类结果明显优于光学遥感影像.     

Heat shock-induced resistance in strawberry against crown rot fungus Colletotrichum gloeosporioides

This present study investigated the effects of heat shock treatments in strawberry seedlings against crown rot caused by Colletotrichum gloeosporioides. Heat shock treatment at 50 °C for 20 s reduced the disease index of strawberry crown rot and increased chitinase 2-1 gene expression as well as free salycilic acid accumulation. Heat shock treatment did not reduce mycelial growth of C. gloeosporioides. BIT(2-benzisothiazol-3(2H)-one,1,1-dioxide) treatment could not protect strawberry seedlings against crown rot disease. This finding suggests that heat shock induces strawberry resistance against Colletotrichum crown rot and assumes that mechanisms other than SAR probably mediated the protective effect of heat shock-induced resistance.     

Influence of Long‐Term Sodic‐Water Irrigation,Gypsum, and Organic Amendments on Soil Properties and Nitrogen Mineralization Kinetics under Rice–Wheat System

Abstract

Influence of long‐term sodic‐water (SW) irrigation with or without gypsum and organic amendments [green manure (GM), farmyard manure (FYM), and rice straw (RS)] on soil properties and nitrogen (N) mineralization kinetics was studied after 12 years of rice–wheat cropping in a sandy loam soil in northwest India. Long‐term SW irrigation increased soil pH, exchangeable sodium percentage (ESP), and sodium adsorption ratio (SAR) and decreased organic carbon (OC) and total N content. On the other hand, application of gypsum and organic amendments resulted in significant improvement in all these soil properties. Mineralization of soil N ranged from 54 to 111 mg N kg^?1 soil in different treatments. Irrigation with SW depressed N mineralization. In SW‐irrigated plots, two flushes of N mineralization were observed; the first during 0 to 7 d and the second after 28 d. Amending SW irrigated plots with GM and FYM enhanced mineralization of soil N. Gypsum application along with SW irrigation reduced cumulative N mineralization at 56 days in RS‐amended plots but increased it under GM‐treated, FYM‐treated, or unamended plots. Nitrogen mineralization potential (N_o) ranged from 62 to 543 mg N kg^?1 soil. In the first‐order zero‐order model (FOZO), the easily decomposable fraction ranged from 5.4 to 42 mg N kg^?1 soil. Compared to the first‐order single compartment model, the FOZO model could better explain the variations in N mineralization in different treatments. Variations in N_o were influenced more by changes in pH, SAR, and ESP induced by long‐term SW irrigations and amendments rather than by soil OC.     

基于ARSIS策略的SAR影像与多光谱遥感小波融合

针对南方多云多雨、光学遥感数据不易获取的特点,在江苏省宝应县设置了区域试验,探索了ENVISAT/SAR影像与HJ-1A星多光谱遥感融合的模式与效果。基于ARSIS策略,利用Mallat小波变换和波段间交互构造模型IBSM,对SAR影像和HJ-1A/CCD影像进行小波分解与低频、高频系数重构,然后通过小波逆变换得到信息融合影像。针对低频与高频影像的不同区域特征使用不同的融合规则,以增强融合过程的自适应性。对融合影像进行了主观与相应的定量评价,并与PCA变换、IHS变换等传统方法进行比较。最后,利用GPS矢量样点提取了小波融合前后影像的波段值与NDVI信息,对融合效果做了进一步的分析与说明。结果表明,小波融合、IHS变换、PCA变换影像光谱扭曲度平均值分别为0.1016、0.3261、1.2772,其中小波融合方法的值最小。三者的信息熵平均值分别为14.7015、11.8993和13.2293,以小波融合方法的值最高。说明小波融合方法在提高空间分别率的同时,较好的增强了光谱保持能力,信息解译效果明显优于PCA变换和IHS变换2种方法。     

灌溉水质与灌溉沟坡度对华北土壤径流和侵蚀的影响

Irrigation-induced soil erosion seriously affects the sustainability of irrigated agriculture. The effects of irrigation water quality and furrow gradient on runoff and soil loss were studied under simulated furrow irrigation in laboratory using a soil collected from an experimental station of China Agricultural University, North China. The experimental treatments were different combinations of irrigation water salt concentrations of 5, 10, 20, and 30 mmol_c L^-1, sodium adsorption ratios (SAR) of 0.5, 5.0, and 10.0 (mmol_c L^-1)^0.5, and furrow gradients of 1%, 3%, and 5%, with distilled water for irrigation at 3 furrow gradients as controls. The experimental data indicated that total runoff amount, sediment concentration in runoff, and total soil loss amount generally decreased with increasing salt concentration in irrigation water but increased with its sodicity and furrow gradient. The effects of water quality and furrow gradient on soil loss were greater than those on runoff, and the increase of furrow gradient decreased the influence of water quality on soil loss. When the salt concentration increased from 5 to 30 mmol_c L^-1 at SAR of 10.0 (mmol_c L^-1)^0.5, total runoff amount, sediment concentration, and total soil loss amount decreased by 3.89%, 52.1%, and 53.92%, and 10.57%, 38.86%, and 42.03% at the furrow gradients of 1% and 5%, respectively. However, they respectively increased by 3.37%, 45.34%, and 55.36%, and 3.86%, 10.77%, and 13.91% when SAR increased from 0.5 to 10.0 (mmol_c L^-1)^0.5 at the salt concentration of 5 mmol_c L^-1. Irrigation water quality and furrow gradient should be comprehensively considered in the planning and management of furrow irrigation practices to decrease soil loss and improve water utilization efficiency.     

Effect of Foliar Applied Plant Elicitors on Microbial and Nematode Populations in the Root Zone of Potato

Abstract

Systemic acquired resistance (SAR) is a process whereby a plant that successfully resists a pathogen becomes highly resistant to subsequent infection not only by the original pathogen but also by a wide variety of pathogens. Most SAR research has focused on resistance in leaves, so much less is known about the effectiveness of foliar applications of SAR compounds in the protection of plant roots and associated microorganisms in soil. This study was conducted to determine if foliar SAR‐inducing applications (BTH or harpin) negatively impact the potato root system beneficial rhizosphere microbial populations and activity or influence pathogenic nematode populations. Foliar applications of benzo (1,2,3) thiadiazole‐7‐carbothioic acid S‐methyl ester (BTH) and the microbial protein harpin applied in various combinations, timings, and rates showed no effects on microbial biomass, culturable bacteria, Pseudomonas populations, or N‐mineralization potentials over 2 years. No stimulatory or inhibitory effects on major bacterial populations were observed, indicating that SAR induction does not have a negative effect on general microbial populations or activities. BTH and harpin both reduced the numbers of lesion nematodes (Pratylenchus spp.) by potato harvest. BTH reduced root knot nematodes, Meloidogyne chitwoodi at the end of the season. In addition, BTH and high‐dose harpin (applied at the 4× rate) reduced the nematode infection index in comparison to the control. The SAR elicitors increased the population densities of nontarget free‐living nematodes in the soil compared to the control. Potato yields were not affected by plant elicitors but BTH and harpin both reduced the number of culled potatoes 26% compared to the control. Future studies are designed to determine if these plant elicitors have any direct effect on rhizosphere diversity or if plants with active defense pathways alter carbon flow and root exudates into the soil.     

不同烟草品种感染TMV病程过程中CAT、PAL活力变化研究

对两个具有SAR特性和一个感病烟草资源进行接种TMV和SA处理,在不同时间测定CAT、PAL活力值,分析不同类型烟草资源病程过程中上述两个酶活力值的动态变化.结果表明:具有SAR特性的抗性品种资源对TMV和SA表现出较高的敏感性,PAL活力值在处理后明显地高于感病资源, CAT活力值在处理后低于感病资源;其中CAT活力值的变化早于PAL酶活力值的变化.两个具有SAR特性的烟草资源在总体趋势上相一致,但存在一定的差异性.这与克隆出的相应抗性基因片段序列结果相一致.     

合成孔径雷达数据估测森林生物量研究综述

合成孔径雷达（SAR）技术以其独特的成像机理及其全天候全天时成像能力,在森林生物量估测方面发挥着越来越重要的作用。首先对森林生物量SAR估算机理和方法进行介绍,然后分析主要的影响因素,最后指出今后的发展趋势。