Modelling agroforestry systems of cacao (Theobroma cacao) with laurel (Cordia alliodora) and poro (Erythrina poeppigiana) in Costa Rica III. Cycles of organic matter and nutrients

Models for cycles for organic matter and nutrients element (N, P, K, Ca and Mg) are presented for the agroforestry systems of cacao (Theobroma cacao) withCordia alliodora orErythrina poeppigiana in Turrialba, Costa Rica.For the models, system reserves (soil, humus, vegetation divided into leaves, branches, stems, fine roots, fruits) and transference between compartments (production and decomposition of litter residues) inputs (fertilizer, rainfall) and outputs (harvests) of the system are considered.The implications of the models are discussed in detail.Aspects of net primary production in the systems studied are considered.N fixation is calculated on the basis of balances. Analysis of soil water showed high variations that coincided with rainfall patterns and pruning of theE. poeppigiana.For part I see Vol. 4, No. 3, 1986 For part II see this issueAgroforestry Project, CATIE/GTZ (Tropical Agricultural Research and Training Center/Gesellschaft für Technische Zusammenarbeit), Turrialba, Costa Rica     

梅州市城区行道树的结构特征

采用抽样调查方法对梅州市城区20条主要道路的行道树进行调查,分析梅州城区行道树的组成特征、结构特征,探讨多样性指数和物种重要值.结果表明:1)梅州城区行道树共有13科18属23种7 133株,其平均胸径、平均冠幅、平均树高分别为27.59 cm,4.10 m,6.94 m,总体上看,平均冠幅偏小;2)物种丰富度指数S、ShannonWiener指数H和Simpson指数D偏小且各道路问差异明显,说明各道路行道树存在一定程度的物种单一性、层次的单调性;3)梅州市城区行道树优势树种是大叶榕、垂榕、大王椰子,次优势种为海南榄仁、阿珍榄仁、阴香,它们是梅州城市街道绿化的好树种.基于南亚热带植物区系的特点,提出了梅州城区行道树的骨干树种、一般树种、试用树种名单,共计50种.     

城市旱垂柳平头后的腐朽规律与防控技术研究

研究牡丹江市城市旱垂柳立木腐朽菌种群的分布规律,发生发展状况及其对城市旱垂柳（Salix matsudana var．pseudo-matsudana y．l．Z）材的分解能力进行测定;对城市旱垂柳林的立木腐朽防治技术进行对比分析。研究结果表明：城市旱垂柳具有发达的愈伤组织系统、树皮保护系统,萌芽能力和生根能力特别强,根系发达等许多优良品质,因而其生命力特别顽强,抵御病虫害毁灭性打击的能力很强,它是城市森林的优质高效树种;城市旱垂柳林容易遭受人工整枝、整形、平头、机械伤害等强烈的干扰,导致17种以上木材腐朽菌的侵入,腐生率与林龄（胸径）呈正相关,随林龄的增大腐生真菌的种类相应增多,但死亡率较低;测定的毛革盖（Coriolus hirsutus（Wulf．：Fr．）Quél．）等8种旱垂柳木材腐朽菌的降解能力排序为：毛革盖,云芝,香栓,多毛盖菌,单色下皮黑,桦革裥,树舌,黑管菌。对旱垂柳林施行的一切园林技术措施都必须有利于其愈伤组织的快速愈合,以及树皮系统的尽力保护。     

退耕还林工程可持续发展问题研究

简要总结了我国自2002年全面启动退耕还林（草）工程以来所取得的成果．分析了还存在的工程规划不尽合理;没有建立起有效的产权制度;劣质种苗造林;未能适地适树等现象屡见不鲜;后续产业发展步履艰难等问题．为了巩固成果实现该工程的可持续发展,应采取保持政策的可持续性;政府进行宏观调控,刺激农民的参与意愿;征收生态环境补偿税;适地适树（草）提高工程质量等应对措施．     

华山古树名木衰败死亡原因及保护措施初探

通过对华山古树名木的调查,特别是对死亡古树名木的调查分析,阐明了影响华山古树名木衰弱死亡的原因是干旱、雷击及病虫危害,并提出了加强华山古树名木保护管理的对策和措施。     

Formal Address

Summary

A combination of social, economic and physical factors contribute to a decision to migrate for a peasant farmer. Seventy percent of Panamanian land comprises steep topography with low soil fertility. Campesinos (peasant farmers) must perpetually migrate when the land they have settled in the forest loses fertility. This process of continual migration results in deforestation and conversion of forest land to pasture land, which then becomes degraded and subsequently abandoned. Also, government policy has not favored the activities of small land owners, but loans from national banks have financed the promotion of large-scale cattle ranches.

Migration patterns consist of moving to a forested area, clearing it for agriculture for one to three years, and thereafter sowing it for pasture. These conditions eventually result in low agricultural and cattle production. Campesinos therefore sell the land to cattle ranchers who can afford to invest in better management practices. Deforestation in the Canal Watershed, therefore, has left a pattern of land ownership comprising a matrix of a few large landowners, within which remain numerous but small peasant land holdings.

A program for small land owners in and around the Watershed region that promotes social, cultural, and economic stability of land use is needed. Supporting and promoting agroforestry with uses of native tree species associated with subsistence and market crops is an alternative for slowing deforestation and promoting sedentary land use.     

A comparison between excavator-based harvester productivity in coppiced and planted Eucalyptus grandis compartments in KwaZulu-Natal,South Africa

Due to the labour challenges in South Africa, mechanised forestry equipment has increasingly been required to operate in complex forest conditions – such as coppiced Eucalyptus compartments – where they have not operated before. For this reason, harvesters are either used in certain coppiced compartments with uncertain productivity expectations, or harvesters are not used in these compartments due to a lack of productivity knowledge. This research aimed to determine the influence of tree volume and tree form on the productivity of an excavator-based harvester in coppiced regrowth – with either double or single stems, or planted single stems – in Eucalyptus grandis pulpwood compartments. In addition, the stem felled first and the distance between stems were investigated for coppiced double stems. The stem felled first is whichever stem between the two coppiced double stems the harvester grabbed, felled and processed first. The tree volume was determined; thereafter the trees were classified into different form classes. The tree volume and the cycle time were used to determine productivity. The research results showed that planted trees had the highest productivity across all tree sizes, followed by coppiced single stems and then coppiced double stems. When harvesting a 0.2 m³ tree, the mean harvester productivity was 8.7 m³ per productive machine hour (PMH₀) in coppiced double stems, 13.8 m³ per PMH₀ in coppiced single stems and 16.1 m³ per PMH₀ in planted trees. In coppiced double stems the productivity was significantly influenced by the size of the stem felled first. In coppiced double stems the productivity was not significantly influenced by the distance between stems. The productivity for both coppiced single stems and coppiced double stems was significantly influenced by stem form. The poorly formed trees had lower productivity compared to the trees with good form.     

贵州省古银杏资源的分布及生长特征研究

2011年8月通过访谈、查阅文献资料与实地调查,对贵州省古银杏资源的分布及生长特征进行分析。结果表明,贵州省100～4000年生古银杏共有1969株,主要分布于遵义市和六盘水市;垂直分布海拔为300～1700m,集中分布800—1100m。其中75．96％为雌株,24．04％为雄株,雌雄比为3．16：1;树高最高为50．0m,最矮为2．0m;树龄最大为4000年,最小为100年;胸径最大为479cm,最小为26cm;其平均冠幅最大为40．0m,最小为1．0m。垂乳银杏有88株,复干银杏有35株,雌雄同株仅1株。     

外来树种在城市园林绿化中的应用研究概况

指出了生物地理学是对地球表面物种分布寻求解释的科学,其研究领域涉及生物学和地理学两个方面。在长期的自然进化历史中,动植物在地球表面的分布形成了一定的格局,这种格局尽管随着时期的变化而发生着变化,但是在特定的历史时期是相对稳定的。在今天就能看到每个树种有着其一定的自然分布区。中国幅员辽阔,具备多种气候带和气候类型,立地备件复杂多样,形成多种多样的生态气候区,为许多引种树种的生长提供了优越条件和场所。近几十年来,中国林木引种取得巨大成就。外采树种越来越成为城市绿化的重要组成部分。总结了外来树种的特点和弊端,提出了对加强外来树种应用的几点对策。     

石梓栽培技术的研究

本文报道了石梓栽培技术研究结果：23°N以南为石梓适生地区，其年均温20．5－24．5℃，极端低温＞－1．5℃，年降雨量1200－2000mm，年平均风速＜2．5m/s。适宜立地为地形开阔，阳光充足，土壤疏松，表土层含有机质＞2％，全氮＞0．1％，速效磷＞0．025mg/100g土，PH4．5－6．9，土壤含水率10％－24％，种子贮存以干燥器最好，贮存一芽率87．4％，催芽用浸晒和浸沤处理，比不处理提前10天发芽，发芽率提高9％－12％，不同子叶类型的芽苗分别移植，较混合移植的苗木合格率提高20．6％；评定了种子主要质量指标和效果良好的育苗，造林方法。技术综合指标；材积年均生长量＞12m^3/ha。