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排序方式: 共有232条查询结果,搜索用时 15 毫秒
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2.
Thomas Thomidis 《Phytoparasitica》2002,30(2):191-193
The virulence ofPhytophthora citrophthora isolated from various host-plants on three peach rootstocks (GF677, PR204, KID I) was examined. There was no significant
difference among the rootstocks with respect to their susceptibility to testedP. citrophthora isolates. The most virulent isolate originated from sycamore (Acer pseudoplatanus); isolates from pistachio trees (Pistacia vera) also showed high virulence but were significantly less virulent than the sycamore isolate. Isolates originating from plum
(Prunus domestica), almond (Prunus amygdalus) and lemon (Citrus limon) trees were moderately virulent on peach rootstocks; those from cyclamen (Cyclamen persicum) showed the lowest virulence of those tested. There was thus great variation in virulence among the testedP. citrophthora isolates. It is possible that the isolates ofP. citrophthora from sycamore, pistachio, plum, almond and lemon trees are a threat to peach trees, whereas the low virulence of the isolates
from cyclamen hosts suggests that these pathogens are not a serious threat to peach trees.
http://www.phytoparasitica.org posting Jan. 3, 2002. 相似文献
3.
落叶松人工林树冠形状的预估 总被引:5,自引:0,他引:5
以长白落叶松(Larix algernsis Henry)人工林为研究对象,利用松江河林业局设置的8块团状枝解析标准地作为基础数据,采用树干一致性削度方程垢研究方法,建立了能预估任意部位的树冠体积(Cv(h),树冠横断面面积Ca(h)及树冠表面各Cs(h)的一致性树冠体积/冠形方程系统。由217株伐倒木树冠资料采用非线性一回归方法建立了预估全树冠方程,某一指定高度以上的树冠体积,某一指定高度处的累 相似文献
4.
Sabine Augustin Jan Evers Hans-Peter Dietrich Johannes Eichhorn Thomas Haussmann Regina Icke Ansgar Isenberg Wolfgang Lux Monica Musio Hans Pretzsch Winfried Riek Thomas Rötzer Bernd Schultze Andreas Schulze Jörg Schröder Walter Seidling Nicole Wellbrock Klaus von Wilpert Barbara Wolff 《European Journal of Forest Research》2005,124(4):251-260
In the 1970s unexpected forest damages, called “new type of forest damage” or “forest decline”, were observed in Germany and
other European countries. The Federal Republic of Germany and the German Federal States implemented a forest monitoring system
in the early 1980s, in order to monitor and assess the forest condition. Due to the growing public awareness of possible adverse
effects of air pollution on forests, in 1985 the ICP Forests was launched under the convention on long-range transboundary
air pollution (CLRTAP) of the United Nations Economic Commission for Europe (UN-ECE). The German experience in forest monitoring
was a base for the implementation of the European monitoring system. In 2001 the interdisciplinary case study “concept and
feasibility study for the integrated evaluation of environmental monitoring data in forests”, funded by the German Federal
Ministry of Education and Research, concentrated on in-depths evaluations of the German data of forest monitoring. The objectives
of the study were: (a) a reliable assessment of the vitality and functioning of forest ecosystems, (b) the identification
and quantification of factors influencing forest vitality, and (c) the clarification of cause-effect-relationships leading
to leaf/needle loss. For these purposes additional data from external sources were acquired: climate and deposition, for selected
level I plots tree growth data, as well as data on groundwater quality. The results show that in particular time series analysis
(crown condition, tree growth, and tree ring analysis), in combination with climate and deposition are valuable and informative,
as well as integrated evaluation of soil, tree nutrition and crown condition data. Methods to combine information from the
extensive and the intensive monitoring, and to transfer process information to the large scale should be elaborated in future.
相似文献
Sabine AugustinEmail: |
5.
大比例尺航片正射影像中的树冠提取 总被引:1,自引:0,他引:1
为使森林航片的分类精度达到单株林木提取水平,以凉水国家级自然保护区1:8000正射影像、DEM及红松(Pinus koraiensis)生境、立地条件特征为基础,对航片进行了传统的非监督分类、监督分类和专家分类,并对其分类机理进行了分析,提取了红松树冠光谱特征、纹理特征。在构建的红松树冠识别模型基础上,执行分类,并运用混淆矩阵分析法对分类结果进行了精度检验。结果表明:将纹理信息、DEM信息、红松生境及立地条件特征信息作为专家知识,构建红松树冠识别模型进行分类的方法,能有效地降低地物分类中"同物异谱"和"同谱异物"现象,使分类的总体精度达到96%,比监督分类提高了10%,从而使大比例尺森林航片分类精度达到了单株林木提取水平。 相似文献
6.
为更好地保护宁夏湖泊湿地资源,采用生态浮床技术,在实验室内自配富营养化水,模拟宁夏灌区农田退水的基本特征,探讨水芹、生菜、油菜3种水耕蔬菜对宁夏灌区富营养化农田退水中氮、磷的净化能力。结果表明:水芹、生菜及油菜3种水耕蔬菜对水体中氮、磷的吸收效果均较好,能显著降低农田退水中氮、磷的浓度。对总氮的去除率为水芹(79.01%)油菜(70.03%)生菜(67.66%)对照(20.07%);对总磷的去除率为水芹(95.66%)油菜(91.04%)生菜(86.32%)对照(21.70%);对氨氮的去除率为水芹(84.77%)生菜(83.15%)油菜(73.12%)对照(33.51%)。综合来看,水芹的净化能力强于生菜及油菜,在开展宁夏灌区水生植物净化工程中可以着重考虑水芹的应用。 相似文献
7.
Thomas Thomidis 《Phytoparasitica》2001,29(1):47-49
The relative virulence ofPhytophthora cactorum andP. syringae originating from almond trees, and ofP. citrophthora originating from citrus, to apple, pear, peach, cherry and plum rootstocks, was studiedin vivo andin vitro. Results of the different experiments were in good agreement. All testedPhytophthora isolates showed little virulence to pear rootstocks-causing only minor crown rot symptoms - and no virulence at all to apple
rootstocks. In contrast, they were highly virulent to stone fruit rootstocks, causing crown rot disease. The non-pathogenicity
of these isolates to pome rootstocks could be interpreted as strict host specificity. 相似文献
8.
《Plant Production Science》2013,16(2):186-191
AbstractAnatomical observations were conducted to clarify some characteristics of the crown root primordia (CRP) formation in wheat stems. Unelongated portions of main stems were sampled from the plant at 3.2 and 7.2 plant age in leaf number, which were adopted as indexes because of the similarity to rice plants. Then, serial cross sections were made to investigate the position of CRP in the unelongated stem taking into consideration the running of vascular bundles in the stem. CRP were formed just outside tissues of the peripheral cylinder of longitudinal vascular bundles. The positions of CRP were not successive along the stem axis. They showed no definite relation to the running of vascular bundles. Diameters of CRP at the upper portion of the stems were larger than those at the lower portion. The positions of CRP along the stem axis were not distinguishable into nodal and internodal position. CRP and emerged CRs were not classified by the well-known ‘nodal root’ or ‘shoot unit root’, or the ‘unit’, which have been applied recently to rice plants. Further studies are necessary to clarify the factors controlling CRP formation anatomically and quantitatively. 相似文献
9.
10.
Branch mortality and potential litterfall from Douglas-fir trees in stands of varying density 总被引:5,自引:0,他引:5
Douglas A. Maguire 《Forest Ecology and Management》1994,70(1-3):41-53
Forest floor characteristics influence nutrient cycling and energy flow properties of forest ecosystems, and determine quality of habitat for many forest plants and animals. Differential crown recession and crown development among stands of differing density suggest that an opportunity may exist to control the input of fine woody litter into the system by manipulating stand density. The objective was to measure the rate of branch mortality among stands of differing density and to estimate the range in total per hectare necromass inputs. Although litter traps are reliable for estimating per hectare rates of litterfall, branch mortality dating on sectioned stems uniquely allows assessment of several other litterfall components: (1) individual tree contributions to total litterfall; (2) the amount of branch material released by mortality, regardless of whether the branches are shed to the forest floor; (3) the distribution of basal diameters characterizing the litterfall from a given tree and stand. Twenty-four trees were felled and sectioned on permanent plots that were part of a silvicultural study of stand density regimes in Douglas-fir (Pseudotsuga menziesii (Mirbel) Franco.). Whorl branches were dissected out of bole sections to determine the dates of mortality, and a branch biomass equation was applied to estimate potential rate of litterfall. Periodic annual rates were expressed in four ways: (1) number of branches per tree; (2) mass of branches per tree; (3) mass of branches per unit of crown projection area; (4) mass of branches per hectare. For the growth periods investigated, larger trees and trees growing on denser plots tended to release a greater necromass through branch mortality. Average branch basal diameter generally decreased with increasing stand density. Annual branch mortality ranged from 33 to 430 g m−2 crown projection area for individual trees, and from 236 to 1035 kg ha−1 for individual plots. These rates approached the low end of the range of previously published fine litterfall rates for Douglas-fir. Rates on these plots were relatively low owing to the temporary delay in crown recession imposed by artificial thinning. A conceptual model of branch litter dynamics is presented to depict consistencies with crown development among stands managed under different density regimes. 相似文献