河南天然林资源消长变化动态分析

通过对建国以来我省天然林资源的消长变化状况和天然林资源现状的论述 ,分析了我省天然林资源下降的主要原因 ,提出保护和恢复天然林必须要建立强有力的管理机构 ,全面禁止采伐天然林 ,并依造科学技术 ,保护天然林及其生物多样性     

滦河的水沙关系及水利工程对下游河道的影响

滦河径流年内分配极不均匀,有73％的输水量和96％的输沙量集中在汛期,大水挟大沙的特征明显.修建于干流上的潘家口水库、大黑汀水库和支流上的桃林口水库控制了流域89.9％的汇水面积,削减了滦河63％的径流量、99.3％的输沙量和汛期30％的径流峰值,引起了下游河道的快速响应,导致河床展宽变浅,出现衰亡迹象.     

Wood-inhabiting fungi in stems of Fraxinus excelsior in declining ash stands of northern Lithuania,with particular reference to Armillaria cepistipes

Abstract

Stem bases of 210 Fraxinus excelsior trees of three different health categories were sampled by the means of an increment borer in declining ash stands in northern Lithuania. From this number, 15 sound-looking, 132 declining and 63 dead trees from three discrete plots yielded 352 isolates, representing 75 fungal species. In addition, mycelial fans and rhizomorphs typical of Armillaria spp. from 205 and 20 trees, respectively, were sampled and subjected to fungal isolations. Species richness was similar in trees from each health category, but community structures differed, indicating that species composition of wood-inhabiting fungi in stems changes along with the changes in tree health condition. Armillaria cepistipes was the most common species (86 isolates from 210 wood samples, or 41.0%), isolated more frequently and consistently than any other potential tree pathogen. It also showed abundant occurrence on a majority of trees in the form of mycelial fans and rhizomorphs, from which 64 and 14 isolates of the fungus were obtained, respectively. The population structure of A. cepistipes revealed the presence of 53–93 genets per hectare, some of which extended up to 30–55?m.     

切花的衰败原因及保鲜措施

随着社会的进步和经济的发展,人们对切花的需求量越来越大,越来越受人们的重视。简单说明切花的分类和方法,主要介绍切花采后衰败的原因及保鲜措施,以达到提高切花品质,延长其插花寿命及观赏期的目的。     

Decreasing eel stocks: survival of the fattest?

Abstract –  Since the 1980s, the European eel Anguilla anguilla stock is in steep decline. Lipid reserves are essential to cover energetic requirements for silver eel migration and reproduction. Two large and independent data sets from Belgium and The Netherlands show an average one-third decrease in fat contents of yellow eels over the past 15 years. Also Le Cren's relative condition factor decreased. On the basis of the somatic energy reserves, reproductive potential of eels from various latitudes over Europe was estimated, assuming fat levels in yellow eel are indicative of those in silver eels. Only large individuals, females as well as males, with high lipid content seem to be able to contribute to the spawning stock. The decrease in fat content in yellow eels may be a key element in the stock decline and raises serious concerns about the chances of the stock to recover.     

Review on Causes of Forest Decline

Site degradation and yield decline of forest have attracted increasing attention from forest managers and scientists. Studies conducted by researchers from a variety of disciplines and perspectives have led to a variety of competing hypotheses concerning the causes of the problem. In this paper we review evidence of such a yield decline and examine the problem and its possible way to identify the individual contributions of the many determinants of yield decline, and their interactions.     

6HW-50型车载高射程喷雾机防治杨潜叶跳象试验

报道了使用6HW-50车载高射程喷雾机,采用1.2%苦烟乳油不同施药量进行杨潜叶跳象防治的对比试验的结果,旨在评估这一新药械防治杨潜叶跳象的效果.     

Crop residue destruction strategies that enhance rather than inhibit reproduction of Monosporascus cannonballus

Destruction of infected crop residue is a management strategy commonly recommended for the control of many plant diseases. Based upon knowledge of the biology of the root-infecting fungus Monosporascus cannonballus , this strategy is a likely candidate for use in the management of vine decline of melons caused by this pathogen. Specifically, ascospores, the primary survival structure and inoculum for root infection, are produced on infected melon roots primarily after crop termination. Thus, destruction of infected roots prior to reproduction would be a very practical method of preventing inoculum build-up in soil. Results from this study demonstrated that two plant residue destruction methods commonly used by growers at crop termination [i.e. foliar application of a herbicide (glyphosate) and mechanical destruction of vines] significantly enhanced, relative to untreated controls, the rapidity and extent of pathogen reproduction on infected roots left in field after harvest.     

Identification, occurrence and pathogenicity of Rhizopycnis vagum on muskmelon in Spain

Rhizopycnis vagum is a recently described coelomycetous fungus that contributes to vine decline of muskmelons in Honduras, Guatemala, Texas and California. This fungus has been associated with roots of muskmelon plants affected by vine decline in most Spanish muskmelon production areas. Isolates were collected from 1996 to 2000 and identified from their cultural and morphological characteristics and by sequencing the ITS region of the ribosomal coding nuclear DNA (rDNA) and phylogenetic analysis. A few isolates from muskmelon with growth characteristics similar to R. vagum were identified as Phoma terrestris . Watermelon, Cucurbita hybrids used as rootstocks for watermelon production, Amaranthus sp. and grapevine were also hosts for R. vagum . Based on disease reaction in muskmelon roots, the pathogenicity of 10 isolates of R. vagum from different hosts and geographical origins was verified. The fungus caused root discoloration, corky lesions, and eventually the presence of pink coloration on the roots. Rhizopycnis vagum appears to be a minor pathogen that contributes to muskmelon vine decline complex in Spain through infection of roots.     

Evaluation of root damage to English walnut caused by five Phytophthora species

The pathogenicity of five species of Phytophthora to English walnut was studied in a greenhouse experiment. Phytophthora cinnamomi was the most aggressive species, causing severe root rot and seedling mortality. The other species tested, P. cambivora , P. citricola , P. cactorum and P. cryptogea , did not induce visible crown symptoms on seedlings 2 months after inoculation. Some strains of P. cambivora and P. cactorum also caused taproot damage to seedlings. All except one of the tested isolates caused significant necrosis of fine roots and a significant reduction of root weight compared with noninoculated seedlings. Reduction of above-ground plant development was not statistically significant. While P. cinnamomi is well known as an aggressive primary pathogen of English walnut, the other species of Phytophthora may act as predisposing factors to walnut decline, affecting root system development and increasing host vulnerability to environmental stress.