沙地樟子松人工林营林技术研究进展

人工林能否实现可持续经营与其营林技术息息相关。中国造林与世界各地一样,纯林多．树种单调．发生的问题也相似。自20世纪90年代以来,沙地樟子松人工林出现了不同程度的衰退现象．但目前在我国北方干旱、半干旱风沙地区樟子松人工造林仍在大面积推广．因此,为实现樟子松人工林的可持续经营,总结并探讨樟子松人工林营林技术显得尤为重要。本文在广泛收集国内外有关樟子松研究的基础上,综述了近20年来有关樟子松在造林和经营方面的研究进展,主要包括造成樟子松沙地造林成活率和保存率低的原因、提高造林成活率的技术方法、种子的生产、密度管理、栽培模式以及问伐与更新等,提出了在沙地樟子松造林与经营研究中亟待解决的一些问题和建议．对今后樟子松沙地人工林衰退研究及经营实践具有参考价值。     

沿海沙岸风蚀地黄泥客土和深埋造林效果分析

论述了广泛省汕头潮阳市田心镇华林管理区沙质海岸风蚀地试验示范林的造林存在蒸发量大于降水量,降水量过于集中,常年风大和冬连春旱等４个极为不利因素。试验采用黄泥客土和深埋造林可缓解这些不利因素,从而提高了造林成活率和保存率,是沙质海岸风蚀地造林的好方法。     

浅谈兴城地区荒山侧柏营养杯造林技术试验报告

从2006年至2013年,作者对兴城市地区侧柏营养杯进行造林技术研究结果表明,本地区在6-7月份造林成活率和保持率最高。本地区侧柏苗木选择3至5年生苗木,高度在70-150cm,地径在0.7至1.5cm为最好,应广泛推广应用,苗高小于70cm,虽然成活率高,但保存率低,而苗高大于150cm,成活率、保存率都低。     

浅析雷波县金沙江干热河谷造林初探

雷波县地处金沙江畔,气候干燥,土层潜薄,造林难度大,苗木成活率低。作者通过调查、实践,在雷波县造林难度极大的地带,根据自己的工作经验,提出在金沙江畔大力发展营器育苗,利用营器苗木推广营造混交林,提高造林成效,充分发挥林业的"三大效益"。     

提高杨树造林成活率的措施

在植树造林中,杨树以其适应性强,综合性好、经济价值高等优良特性,作为造林中的优选品种,应用最为广泛。本文针对提高杨树造林的成活率提出如何进行合理的规划以及如何选择合理的栽植杨树种的时间。     

广东番禺红树林造林研究

结合广东番禺红树林造林的现状,对影响红树林幼苗成活率和生长状况的因素进行初步分析,并据此提出提高造林保存率的措施等。影响红树林造林成活及生长的因素为①水深潮水越深,红树幼苗成活率越低,生长越差;②风浪海面风浪越大,红树幼苗受干扰越大,成活和生长越差;③人为活动干扰会严重影响红树幼苗的成活和生长;④造林地的杂草会影响某些红树植物幼苗的光照条件;⑤海滩垃圾废物会挂断和压倒大量红树幼苗;⑥海滩石油污染会阻止红树胚轴的萌发;⑦幼苗种植时越粗壮,种植得越精细,则种植后生长越好。并提出提高造林成效的措施①加强维护和管理包括护理受损伤的红树幼苗,清除塑料袋等垃圾物,制止在红树幼苗区的捕捞活动,造林前清除杂草和固定某些红树植物幼苗;②补植受破坏的红树幼苗和扩大种植。     

广东番禺红树林造林研究

结合广东番禺红树林造林的现状,对影响红树林幼苗成活率和生长状况的因素进行初步分析,并据此提出提高造林保存率的措施等。影响红树林造林成活及生长的因素为：①水深：潮水越深,红树幼苗成活率越低,生长越差;②风浪：海面风浪越大,红树幼苗受干扰越大,成活和生长越差;③人为活动干扰为严重影响红树幼苗的成活和生长;④造林地的杂草会影响某些红树植物幼苗的光照条件;⑤海滩垃圾废物会挂断和压倒大量红树幼苗;⑥海滩石油污染会阻止红树胚轴的萌发;⑦幼苗种植时越粗壮,种植得越精细,则种植后生长越好。并提出提高造林成效的措施：①加强维护和管理：包括护理受损伤的红树幼苗,清除塑料袋等垃圾物,罅在红树幼苗区的捕捞活动,造林前清除杂草和固定某些红树植物幼苗;②补植受破坏的红树幼苗和扩大种植。     

广东番禺红树林造林研究

结合广东番禺红树林造林的现状,对影响红树林幼苗成活率和生长状况的因素进行初步分析,并据此提出提高造林保存率的措施等。影响红树林造林成活及生长的因素为：①水深：潮水越深,红树幼苗成活率越低,生长越差;②风浪：海面风浪越大,红树幼苗受干扰越大,成活和生长越差;③人为活动干扰会严重影响红树幼苗的成活和生长;④造林地的杂草会影响某些红树植物幼苗的光照条件;⑤海滩垃圾废物会挂断和压倒大量红树幼苗;⑥海滩石油污染会阻止红树胚轴的萌发;⑦幼苗种植时越粗壮,种植得越精细,则种植后生长越好。并提出提高造林成效的措施：①加强维护和管理：包括护理受损伤的红树幼苗,清除塑料袋等垃圾物,制止在红树幼苗区的捕捞活动,造林前清除杂草和固定某些红树植物幼苗;②补植受破坏的红树幼苗和扩大种植。     

班克松苗木培育及造林技术初步研究

本文针对班克松引种栽培、结实后的苗木繁育和野外造林技术进行了研究。结果表明,种子通过低温催芽后,10±1g/m2播种量、0.5cm覆土厚度、湿润的床面可以提高种子的发芽率和存活率;叶面喷施磷钾肥对苗木后期生长和提高木质化程度具有促进作用。S1-1型的班克松苗木造林其缓苗时间、须根发育、地径、平均高生长、成活率和保存率等指标均优于S2-0型。改造后班克松种子千粒重达到3.65g,比改造前增加0.3g。     

造林成活率与造林技术造林季节的关系研究

随着人们生活水平的提高,对于生态环境保护有了更多的关注。森林作为生态环境保护中的重要内容,随着经济的发展它的数量正在逐渐减少,而现代森林大多属于是人工造林的形式,并且这种形式越来越普遍,在社会发展中发挥着重要作用。从人工造林的整个流程和作用来看,造林的成活率是关键性指标,它和造林技术以及造林季节都有密切的关系,必须要正确对待,本文就对造林成活率与造林技术和造林季节之间的关系进行了分析。     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.     

Composition and diversity of bird communities in Swedish farmland–forest mosaic landscapes

CapsuleThe amount of forest (at local and landscape scales) and occurrence of residual habitats at the local scale are shown to be the major factors influencing bird community composition in farmland–forest landscapes in central Sweden.

Aims To investigate the importance of local habitat and landscape structure for breeding birds in farmland–forest landscapes in central Sweden.

Methods Breeding birds were censused at 292 points. A detailed habitat mapping was made within 300 m of the points. Within a 300–600 m radius only two major habitats (forests and arable fields) were identified.

Results Cluster analyses of bird communities identified three site types that also differed in habitat composition: (i) partially forested sites in forested landscapes; (ii) heterogeneous sites with residual habitats in mosaic landscapes; and (iii) field-dominated farmland sites in open landscapes. A total of 19 of 25 farmland bird species (restricted to farmland or using both farmland and forest) had the highest abundance in farmland sites with mosaics of forest and farmland, while only six farmland species had the highest abundance in field-dominated sites. The bird community changed from being dominated by farmland species to being dominated by forest species (common in forest landscapes without farmland) at small proportions (10–20%) of forest at the local scale. A major difference in habitat composition between heterogeneous and field-dominated sites was the occurrence of different residual habitats (e.g. shrubby areas and seminatural grasslands). These habitats seemed to influence bird community composition more than land-use, despite covering <10% of the area. Seminatural grasslands were important for bird community composition and species-richness, but grazing seemed to be less important. Among different land-use types, cereal crops were the least preferred fields. Set-asides with tall vegetation and short rotation coppices were positively associated with species-richness of farmland birds.

Conclusion In general, the composition of the landscape was important for bird community composition, although amount and distribution of forests, occurrence of residual habitats and land-use of fields at the local scale had the strongest influence on bird community composition. The possible implications of these patterns for managing farmland–forest landscapes are discussed.     

Chemical constituents from the fruits of Rhus typhina L. and their chemotaxonomic significance

This work describes the isolation and characterization of twenty-nine compounds from the fruits of Rhus typhina L., including eleven flavonoids (1–11), eleven phenols (12–22), two pentacyclic triterpenes (23–24), two organic acids (25–26), one lumichrome (27), one courmarin (28) and one pyrimidine (29) on the basis of their spectroscopic data. Compounds apigenin (1), daidzein (4), orobol (5), 3′, 5, 5′, 7-tetrahydroxyflavanone (6), naringenin (7), butein (8), (-)-catechin (9), quercetin-3-O-α-L-(3″-O-galloyl)-rhamnoside (11), 2-hydroxybenzoic acid (13), 4-hydroxybenzaldehyde (14), vanillin (15), methyl 3,4-dihydroxybenzoate (16), 3,5-dihydroxybenzamide (18), tyrosol (19), caffeic acid (20), 3-(2,4,6-trihydroxyphenyl)-1-(4-hydroxyphenyl)-propan-1-one (21), phlorizin (22), friedelin (23), oleanolic acid (24), 4,4-dimethyl-heptanedioic acid (25), anthranilic acid (26), lumichrome (27), scoparone (28) and uracil (29) have not been recorded before in this plant. This is the first report on the occurrence of compounds 4–7, 9, 11, 13–14, 16, 18–21, 25–29 from the genus Rhus. Moreover, the chemotaxonomic significance of these isolated compounds was also summarized.