生长季修剪对库尔勒香梨生长的影响     

张琦  蒋学玮  冯建菊  王大伟 《塔里木大学学报》1999,(4)

库尔勒香梨3年生幼树在5月12日、6月8日、7月6日三个时期进行生长季修剪能够开张枝条角度,降低树冠高度,扩大树冠,缓和树势,促进花芽分化,以7月6日进行修剪效果最好,发育枝生长量、背上枝生长量最短,干径和花芽量最大都达到显著水平,为早期丰产奠定基础。  相似文献   

大面积低产油桐林改良配套技术   总被引：1，自引：0，他引：1  

戴益源 《西北林学院学报》1999,14(3):45-51

通过14.2 hm2高产试验和335.73 hm2示范推广,将先进的科学技术与当地的生产力水平相结合,使低产油桐林改良技术进行了检验.高产试验经过4 a的科学管理,油桐林状况得到了较好的改善,桐籽产量由原来每公顷637.5 kg,增加到1 608.6 kg,平均每公顷增产971.1 kg;示范推广由每公顷375 kg,提高到1 166.25 kg,平均每公顷增加791.25 kg;并对不同的管理和施肥方式,进行了较系统的研究,为更大面积的油桐低产林改良提供了可靠的技术依据.  相似文献   

祁连山东端封山育林效果初步分析   总被引：1，自引：0，他引：1  

李耀山  张有万  杜长有 《西北林学院学报》1999,14(2):29-32

通过对祁连山东端17块具有代表性的封育地与封育前及对照区的天然更新、幼树高生长、灌木高度、盖度进行对比分析,得出了封山育林效果显著的结论,并运用森林群落演替理论对试验结果进行了论证,从而说明封山育林是发展祁连山水源涵养林的一项重要而有效的措施.  相似文献   

The anaesthetic‐like effect of tea tree oil in common carp Cyprinus carpio L.     

Grzegorz Jan Hajek 《Aquaculture Research》2011,42(2):296-300

This study investigated the efficacy of tea tree oil (TTO) as an anaesthetic for common carp, Cyprinus carpio L., by estimation of behaviour changes and responsiveness to being taken out of the water. All applied concentrations (from 0.2 to 0.6 mL L⁻¹) resulted in sedation and immobilization. The lowest effective concentration (induction time ≤3 min, recovery time ≤10 min after 15 min of exposure) was 0.5 mL L⁻¹. Exposure in excess of 30 min at a concentration of 0.5 mL L⁻¹ caused mortality. TTO displayed distinct general anaesthetic‐like properties, fulfilling the basic requirements for a potent fish anaesthetic.  相似文献   

牡丹红斑病的研究   总被引：3，自引：0，他引：3       下载免费PDF全文

吴玉柱  季延平  刘慇  赵桂华  牛迎福  王海明  赵海军 《林业科学研究》2005,18(6):711-716

牡丹红斑病在山东菏泽牡丹栽培区的发病率达50％左右,病重的牡丹园可达90％以上。从8批次384个样品中分离获得512个分离株,经筛选、纯化、回接试验,依其培养性状和形态特征,病原菌鉴定为牡丹枝孢Cladosporium paeoniae Pass。病害发生与牡丹不同品种、初侵染源等因子密切相关。筛选出了50％多菌灵、70％甲基托布津等防治红斑病的有效药剂,应用800倍液从3月中旬牡丹展叶前至7月中旬防治4次,效果达90％以上,感病指数可控制在5以下。  相似文献   

Evaluating the quality of street trees in Washington,D.C.: Implications for environmental justice     

《Urban Forestry & Urban Greening》2023

Urban street trees are part of the bundle of environmental amenities that support healthy social, economic, and environmental functions. In this study, we systematically evaluate the quality of 196,825 street trees at the US. Census tract level in Washington D.C., as well as related impacts from socioeconomic, landscape patterns and environmental factors using Ordinary least-squares (OLS) regression, geographically weighted regression (GWR) and structural equation modeling (SEM). Our results reveal that environmental and socioeconomic factors can explain most of the spatial variation of street tree quality in Washington, D.C. There is a substantial statistical negative relationship between median household income and the percent of street trees under stress, which provided the evidence of the inequities of street tree quality in Washington D.C. Higher-income neighborhoods exhibited a lower proportion of street trees under stress. In addition, the extreme summer temperature is positively associated with the proportion of street trees under stress. The quality of street trees is directly impacted by environmental and landscape pattern factors. There is also an indirect impact from socioeconomic factor toward quality of street trees. Our findings suggest that multiple variables, related to income, age, education, landscape pattern, and environment contribute to the quality of street trees in D.C. Based upon our findings, we identify strategies and insights for urban street tree management in DC to not only address environmental inequity and injustice, but also promote a more inclusive and resilient urban greenery system.  相似文献   

Tree species-rich open oak woodlands within scattered urban landscapes promote biodiversity     

《Urban Forestry & Urban Greening》2023

It is becoming increasingly evident that cities are important places for biodiversity. Biodiverse urban forests are vital green areas within cities and have favorable impacts on the citizens, including their health. We focused on the effect of the urban forest environment on biodiversity in Prague, the capital of the Czech Republic. We used a multi-taxon approach with five taxa of different ecological demands: butterflies, bees and wasps, vascular plants, mosses, and lichens. We modeled their responses to the various urban forest attributes at four hierarchical levels – plot, permeability, forest, and landscape. Our results revealed that temporally continuous forests dominated by native oaks with open canopies, a high number of admixed and interspersed tree species and shrubs, together with scattered trees in the surrounding landscape, were optimal biodiverse forest environments. The most influential parameter that positively influenced bees and wasps, plants, and lichens at the plot level was canopy openness. We found that the permeability was suitable mainly on 20 m surroundings and increasing coverage of native oaks and tree species richness were the most important parameters. Continuity was the only found parameter that influenced mosses at the forest level. Scattered tree vegetation was the most important landscape parameter and positively drove the species richness of bees and wasps. Forest management methods can relatively easily solve the improvement of the scattered light gap structure within urban forests. Applying traditional forest management (pasture management, controlled burning and/or coppicing) is also an option but requires sensitive communication with the public. The canopy cover has been used as an indicator of urban forest health conditions, now indicating that artificial disturbances could be important issues for urban forest management and planning in the future. Therefore, active forest management is an essential method for biodiversity maintenance. We conclude that urban forests have a high potential for increasing native biodiversity. The response of the studied groups in urban forests was complementary. The resulting biodiverse stages of urban forests are akin to the established idea of the open temperate deciduous woodlands.  相似文献   

果树施药仿形喷雾神经网络模型及其应用   总被引：4，自引：2，他引：2  

林惠强  肖磊  刘才兴  洪添胜 《农业工程学报》2005,21(10):95-99

在试验的基础上,建立了反映果树施药仿形喷雾过程参量与分布质量系数之间映射关系的BP神经网络模型,在建模中运用了正交试验设计、交叉评价网络训练法、样本标准化处理和主元分析等技术,对网络结构及其参数进行了优选。结果显示,网络模型输出同试验结果相关系数R达到0.99,表明具有广泛的适应性。同时,该网络可以实现各种定量分析计算,例如：预测在特定过程参量下的分布质量系数,或者根据指定的效果目标,确定合适的喷雾参量等。  相似文献   

一种基于小波变换的图像过渡区提取及分割方法   总被引：8，自引：3，他引：5  

赵茂程  郑加强  凌小静 《农业工程学报》2005,21(11):103-107

具有复杂背景的树木图像的分割对于精确对靶施药及智能化植保机械的设计具有重要意义。为实现树木图像的精确分割,针对该类图像的特点,该文提出了一种基于小波变换的过渡区提取树木图像分割方法。通过对比小波变换系数、小波变换系数聚类以及小波包系数,最终选取了同时能够分解出更多高频、低频信息的小波包变换系数提取特征,根据小波包变换系数定义了小波能量比参数,将小波能量比参数值归一化为图像灰度值,采用自适应阈值和神经网络两种方法提取了过渡区,实现了具有复杂背景树木图像的分割。试验表明,该方法分割精度高,对于分割复杂背景的树木图像具有特别意义。  相似文献   

Modeling spatio-temporal crop allocation patterns by a stochastic decision tree method, considering agronomic driving factors     

Luc Sorel  Patrick Durand  Christian Walter 《Agricultural Systems》2010,103(9):647-655

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