Validating a Time Series of Annual Grass Percent Cover in the Sagebrush Ecosystem     

Stephen P. Boyte  Bruce K. Wylie  Donald J. Major 《Strength and Conditioning Journal》2019,72(2):347-359

We mapped yearly (2000–2016) estimates of annual grass percent cover for much of the sagebrush ecosystem of the western United States using remotely sensed, climate, and geophysical data in regression-tree models. Annual grasses senesce and cure by early summer and then become beds of fine fuel that easily ignite and spread fire through rangeland systems. Our annual maps estimate the extent of these fuels and can serve as a tool to assist land managers and scientists in understanding the ecosystem’s response to weather variations, disturbances, and management. Validating the time series of annual maps is important for determining the usefulness of the data. To validate these maps, we compare Bureau of Land Management Assessment Inventory and Monitoring (AIM) data to mapped estimates and use a leave-one-out spatial assessment technique that is effective for validating maps that cover broad geographical extents. We hypothesize that the time series of annual maps exhibits high spatiotemporal variability because precipitation is highly variable in arid and semiarid environments where sagebrush is native, and invasive annual grasses respond to precipitation. The remotely sensed data that help drive our regression-tree model effectively measures annual grasses’ response to precipitation. The mean absolute error (MAE) rate varied depending on the validation data and technique used for comparison. The AIM plot data and our maps had substantial spatial incongruence, but despite this, the MAE rate for the assessment equaled 12.62%. The leave-one-out accuracy assessment had an MAE of 8.43%. We quantified bias, and bias was more substantial at higher percent cover. These annual maps can help management identify actions that may alleviate the current cycle of invasive grasses because it enables the assessment of the variability of annual grass ? percent cover distribution through space and time, as part of dynamic systems rather than static systems.  相似文献   

陆生野生动物栖息地分类体系研究     

田家龙  钟立成  吕忠海 《野生动物学报》2019,(1):209-216

在分析研究国际野生动物栖息地分类体系,归纳总结我国野生动物栖息地分类方法基础上,结合我国实际情况及适应野生动物栖息地保护管理及科学研究需求,提出了陆生野生动物栖息地分类体系。该系统分为三级,包括一级12个栖息地类,二级66个栖息地型,三级218个基本类型。构建野生动物栖息地分类体系,能够更好地从多层次、空间立体格局上实施野生动物及栖息地保护、恢复和改善野生动物生存环境,维系野生动物种群健康发展。该体系建立与实施对国家生态安全维护,实现全国野生动物保护多层次化和多元化具有重要意义。  相似文献   

玛曲县天然草原资源及分布研究     

娘毛加  俞联平  杨林平  俞慧云  李新媛  陈兴荣  李昀 《中国草食动物科学》2019,(6):39-42

甘肃省玛曲县作为黄河源区重要的水涵养区和生态脆弱区,其天然草原对涵养水源、保护黄河源区生态安全、确保当地草地畜牧业生产的健康发展具有十分重要的意义。为摸清玛曲县草原资源现状,将遥感与地面调查相结合,选择决策树分类等方法对玛曲县天然草原的分布、分类和面积进行研究与评价。结果表明:玛曲县有低地草甸、高寒草甸、山地草甸和高寒草原4个草原类,总草原总面积93.13万hm2,其中高寒和低地草甸分别占全县草原面积的82.37%和11.62%,山地草甸和高寒草原仅占4.23%和1.78%;各乡镇分类草原面积均以高寒草甸所占比例最大,其中阿万仓镇、木西合乡、欧拉镇和欧拉秀玛乡高寒草甸所占比例均在90%以上,尼玛镇、阿孜站和西科河羊场占比在80%以上,仅齐哈玛镇占比在50%以下(47.02%);低地草甸占比较大的乡镇有曼日玛镇(40.68%)、齐哈玛镇(26.21%)、采日玛镇(24.30%)和河曲马场(30.84%)。  相似文献   

农业大数据助力现代农业高质量发展     

林羽  刘斌琼 《福建畜牧兽医》2019,(4):32-33

农业大数据对推动我国现代化农业强国建设具有重要的意义,本文较为细致地梳理了农业大数据的发展意义和存在的问题,并对其未来的发展趋势进行讨论。  相似文献   

基于SNP标记的玉米自交系S155、PHA458和A01的遗传多样性分析     

孙佩  张培风  张玉红  周联东  王蕊  王文洁  张瑞平  李祥  马朝阳  李合顺  王学军 《陕西农业科学》2023,69(9):1-7

为了分析玉米品种新科891的遗传结构和遗传多样性,本研究利用Affymetrix Axiom 10K SNP芯片对玉米品种新科891的双亲自交系（母本S155、父本PHA458）及自交系A01进行全基因组扫描,获得多态性标记4 926个。结果表明,群体聚类分析和群体遗传结构分析的杂种优势类群划分结果基本一致。母本S155为SS类种质,父本PHA458含有NSS和塘四平头类血缘,自交系A01为塘四平头类血缘,新科891的杂种优势模式为SS×NSS,这为新科891双亲的后续改良与创新奠定基础,并为杂交组配的育种工作提供依据。  相似文献   

基于形态数据的大白菜核心种质构建方法的研究   总被引：4，自引：0，他引：4  

李国强  李锡香  沈镝  王海平  宋江萍  邱杨 《园艺学报》2008,35(12):1759-1766

 以国家蔬菜种质资源中期库收集保存的1 651份大白菜种质为试材,按照大白菜分类系统和生态型,采用分层分组法,将所有种质分为6组。基于43个形态性状的数据,比较了4种组内取样比例法、6种总体取样规模和2种取样方法在构建大白菜核心种质中的作用和效果。结果表明：组内以多样性比例法更能使各组的取样份数或比例趋于平衡,并较好地保持原始收集品的变异度。当总体取样规模为15%时,多样性比例法所构建的核心种质的遗传多样性指数达到最大,表型保留比例亦能达到98％左右;而当总体取样规模增加到20%以上时,虽然表型保留比例接近100％,但核心种质遗传多样性指数迅速降低。因此,认为15%总体取样规模较为合适。在一定的组内取样比例法和总体取样规模下,聚类取样构建的核心种质的遗传多样性指数（I）、表型保留比例（RPR）和变异系数（CV）均比随机取样的高。根据获得的优化方案最终在表型水平建立了包含248份种质的中国大白菜核心种质。  相似文献   

不同播期对黄秋葵生长及发育的影响   总被引：2，自引：0，他引：2  

LI Chunmei AO Yi 《长江蔬菜》2008,(6)

研究了6个不同播期对黄秋葵生长发育的影响。结果表明,播期在3月24～31日,对黄秋葵株高、茎粗、叶面积、折算产量、果形和品质均有明显的促进作用;播期在3月11～18日,对黄秋葵茎粗、分枝数和折算产量也有作用,并降低第一果节位,但果实畸形率高;播期在4月7～14日,对黄秋葵株高和果实品质有作用,但折算产量明显较低。  相似文献   

海棠品种分类研究进展   总被引：4，自引：0，他引：4  

周婷  沈星诚  周道建  范俊俊  赵明明  张往祥  曹福亮 《园艺学报》2018,45(2):380-384

海棠集观花、观叶、观果于一身,为北温带重要的观赏花木。对海棠品种分类研究进展进行了系统回顾,包括品种溯源与器官演化、品种分类简史及研究现状,同时指出存在的问题,并予以建议,以期为海棠种质鉴定、良种选育、遗传多样性研究、亲缘关系探讨及产业化发展提供理论依据。  相似文献   

Modelling the Phenological Relationships of Questing Immature Ixodes Ricinus (Ixodidae) Using Temperature and NDVI Data          下载免费PDF全文

J. Alonso‐Carné  A. García‐Martín  A. Estrada‐Peña 《Zoonoses and public health》2016,63(1):40-52

All active stages of the tick Ixodes ricinus were collected monthly at two sites in northern Spain between the years 2000 and 2007. We used percentile accumulation of the active stage in the environment to evaluate simple and coherent correlations between accumulation of the active stages of larvae and nymphs and medium‐resolution MODIS satellite‐derived information on the climate, including monthly and accumulated temperature and the Normalized Difference Vegetation Index (NDVI). This framework is not intended to predict the actual abundance of ticks in the field as a measure of the hazard to humans, but to provide a basic structure for addressing the phenology of the tick in its geographic range. We demonstrated that the accumulation of larval ticks in the active stage is a sigmoid function of the accumulated temperature from the beginning of the calendar year. We also demonstrated that the accumulated temperature necessary to recruit nymphs from the questing larval stage is a function of the changes in accumulated larvae and nymphs and the accumulated temperature and NDVI recorded by the Aqua sensor. The low p‐values obtained in the regressions confirmed that such recruitment can be calculated using time intervals to estimate, for example, the beginning of the questing period or the time of the year when a population peak can be expected. The comparison among predicted and actual accumulated temperatures between larvae and nymph recruitment had an averaged error of ±20 days in one complete year. The use of accumulated temperature and NDVI proposed in this study opens up the re‐evaluation of reports on the phenology of the tick in Europe. This framework is intended to evaluate the same correlations along the tick's range and predict its phenological patterns in areas of pathogen transmission risk for humans.  相似文献   

基于MODIS数据的伊犁河谷植被指数变化及其对气候的响应     

陈爱京  肖继东  曹孟磊 《草业科学》2016,33(8):1502-1508

利用2006-2014年主要生长季(5-9月)的MODIS遥感数据,分析了2006-2014年的年平均NDVI和生长季月NDVI变化规律。同时,收集整理同期伊犁河谷地区的气温与降水资料,并对NDVI与当月、2个月滑动、3个月滑动和5个月滑动的平均气温、降水值进行了相关性分析。结果表明,NDVI与气温、降水都存在一定的相关性,NDVI受当月平均气温的影响最大;NDVI与当月降水和滑动平均降水的相关性都很好,但3个月滑动平均降水对NDVI的影响最大,并且通过了0.01的极显著性检验。  相似文献