黔东南林区宜杉的生态环境及其形成机理

在一定热量和土壤条件下,杉木生长受水分因素制约,黔东南林区的生态环境尤其是水环境特别适宜杉木生长。本文探讨其形成机理及开发利用前景。     

重点国有林区森林资源管理政策变革措施分析

重点国有林区天然林资源保护工程实施5年后,工程区内各级森林资源管理部门仍然沿用既往政策,已不适应新时期林业发展的趋势,更不利于森林资源的保护与利用。文中对尽快实施森林分类经营、规范林权流转、适度采伐人工商品林等森林资源管理政策提出了变革建议与对策。     

马尾松毛虫安全区划分的动物多样性指数指标研究

通过比较广西宾阳县、宁明县、陆川县、临桂县、全州县马尾松毛虫安全区春季与夏季松林群落中的害虫种数、天敌种数、中性动物种数和益害比、动物多样性指数,认为划分马尾松毛虫安全区动物多样性指数的具体数值为≥2.300,据此进一步将安全区划分为基本稳定区、中等稳定区和高度稳定区.     

白龙江、洮河水源涵养林区云杉落针病危险性分析评估

云杉落针病是白龙江、洮河水源涵养林区最为严重的林木叶部病害。为加强对该病的管理,有效控制其危害和在白龙江、洮河水源涵养林区乃至整个西北地区进一步扩散蔓延,参照有害生物危险性分析(Pest Risk Analysis)方法,结合该区森林资源状况和病虫害发生发展情况,对云杉落针病在白龙江、洮河水源涵养林区的潜在风险性进行了分析和评价。结果表明:云杉落针病为中度危险且接近高度危险性病害。并提出了相应的风险管理策略。     

北三局护林防火设施工程建设条件分析

文章通过对北部原始林区“北三局 (奇乾、乌玛、永安山 )”护林防火设施工程建设现状条件的分析 ,阐述进行护林防火设施建设的必要性     

干热河谷和干旱山地人工混播造林试验

干热河谷和干旱山地的人工混播造林试验，于１９９１～１９９２年在永胜大龙潭、猫猫山和水平水泄３个造林困难的地区进行。选用车桑子、山毛豆、银合欢、滇合欢、银荆、黑荆等树种进行人工混播造林试验。还分别进行了云南松与车桑子、银荆、黑荆、滇合欢、红木荷、金合欢的混播造林试验。经３、４年的试验，通过对各参试树种的种质评价，落种状况、出苗率、成苗率和各成苗期，苗木生长状况的观测。得出以车桑子、山毛豆、银合欢作为干热河谷和干旱山地的混播造林种较好。可在今后形成多树种，多层次的林分环境。     

Application of the pipe model theory to non-destructive estimation of leaf biomass and leaf area of pruned agroforestry trees

The relationship of branch cross sectional area (CS) to leaf biomass (LM) and leaf area (LA) was studied in three agroforestry tree species,Calliandra calothyrsus Maissn.,Erythrina berteroana Urban andErythrina poeppigiana (Walpers) O.F. Cook, to develop a non-destructive method for the estimation of LM and LA for trees managed with periodic pruning. Variation in these relationships was observed according to the bifurcation level and, in theErythrina spp., by clone. All the relationships were linear except the CS-LM relation in small branches ofE. poeppigiana, where it was initially exponential. At main branch level the relationship of CS to LM and LA was linear in all cases but the regression parameter values varied between species and clones, with determination coefficient (R²) 0.88–0.99. It was concluded that the ratio of main branch CS to LM and LA can be used for non-destructive estimation of the latter variables. The method has the additional benefit that the regression parameter value reflects the allocation of dry matter within a tree and, consequently, may give indications about its possible uses in different agroforestry systems.Work carried out at the Centro Agronómico Tropical de Investigación y Enseñanza (CATIE), Turrialba, Costa Rica.     

The impact of shade on morphology,growth and biomass allocation in <Emphasis Type="Italic">Picea sitchensis</Emphasis>, <Emphasis Type="Italic">Larix</Emphasis> × <Emphasis Type="Italic">eurolepis</Emphasis> and <Emphasis Type="Italic">Thuja plicata</Emphasis>

To determine the effect of shade on morphology, growth and biomass allocation in Picea sitchensis, Larix × eurolepis and Thuja plicata, seedlings were grown in the open or under shadehouses providing 25%, 50% and 75% reductions of full-light for two growing seasons. For most of the characteristics assessed there was no significant interaction between species and shade indicating that the morphological responses to changing shade treatments were not species-dependent. After two growing seasons the mean height increment for the three species was significantly greater in 25% (76.1 cm) and 50% shade (74.9 cm) than in the open (69.5 cm). Root collar diameter increment, shoot, root and total biomass declined significantly with increasing shade while the opposite was true for the height:diameter ratio. In both western red cedar and hybrid larch the shoot:root ratio was significantly greater in the shade while in Sitka spruce this characteristic was not influenced by shade. While all species had significantly greater specific shoot areas in 75% shade than in 0% shade, this trend was particularly pronounced in hybrid larch. In hybrid larch and western red cedar, the normalised specific projected shoot area increased significantly with increasing shade. The opposite trend was observed for Sitka spruce. We conclude that in the main the species studied demonstrated similar shade acclimation responses despite their reported differences in shade tolerance.     

Traditional agroforestry practices in Zimbabwe

Traditional agroforestry systems in the communal areas of Zimbabwe are described. There are systems centered on main fields, on home gardens, on homesites and on grazing areas. In the main fields, the major tree-related management practice is the conservation of preferred indigenous fruit trees. Fruit trees are also the focus of forestry activities around the gardens and the homesite; but here it is the planting of exotic species. In a localized area of Zimbabwe Acacia albida is important in fields. There is almost no use of tree fallows in Zimbabwe. Trees in grazing areas have numerous roles, but at present there is little knowledge about traditional management practices in these areas. In the development of agroforestry systems in Zimbabwe it is suggested that those systems designed to improve fodder production will make a significant contribution to farm productivity because of the importance of cattle in the farming system and the present fodder shortage. Interventions involving the planting of fruit trees are likely to be very successful, as there is much interest in such planting. Another area that needs to be developed is that of tree plantings to improve soil fertility.     

华北落叶松边材透水性与叶面积空间分布的相关性的探讨

对华北落叶松林单木累积叶面积、树干边材面积、树干边材透水率及透水量的垂直分布规律及其相互关系进行了探讨。研究表明，引入树干边材面积与边材透水率的积可明显提高估测树冠叶面积垂直分布的精度，进而为精确估测林分的叶面积空间分布提供了新途径。