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71.
Trade-offs among wood production, wood quality and ecological characteristics in the management of harvested forest stands are explored through model simulation of various silvicultural regimes. Long-term production of merchantable wood, production of various types of high-quality wood, and the level of certain quantitative ecological indicators are projected for coniferous forests of Pacific Northwestern USA. The set of ecological indicators used is based on the species composition and physical structure of old, unlogged forest stands. Simulations are performed with an ecological model of forest stand dynamics that tracks the fate of live and dead trees. Short rotations (<50 years) produce the least amount of high-quality wood over the multi-century simulation period. They also fail to generate ecological attributes resembling those of old forest stands. Production of high-quality wood is moderate to high under all rotations of 80 years or more; however, most ecological indicators require longer rotations unless alternatives to clearcutting are applied. Alternatives examined include retention of 15% cover of live tree canopy at each harvest in combination with artificial thinning between harvests. Thinning from below can expedite the development of large live and dead trees, and canopy height diversity without greatly diminishing wood quantity or quality. Proportional thinning retains understory stems, thereby expediting the recruitment of shade-tolerant trees. A possible drawback to thinning, particularly proportional thinning, is the diminished production of clean-bole wood at rotations of 150 and 260 years. It is concluded that most wood quantity, wood quality and ecological objectives can be met with long rotations (ca. 260 years). Certain objectives can be met with shorter rotations (80–150 years) when treatments of thinning and canopy tree retention are applied. 相似文献
72.
The ecological effects of planting exotic Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] in Central Europe are still poorly understood. The aim of this study was to answer the question of whether Douglas-fir affects tree specific arthropod communities in different mature forest types (Douglas-fir, spruce and beech dominated) in Southern Germany. Therefore, arthropod communities of stem and tree crown strata of Douglas-fir and spruce (Picea abies L.) were sampled in the years 1999–2001 using arboreal photo-eclectors and flight interception traps. Statistical analysis was conducted for all species and focused on conifer specialists at three levels: (1) species diversity, (2) guild structure and (3) community structure. Within the stem stratum, species diversity was significantly higher on spruce than on Douglas-fir independent of year and stand composition. This could not be explained by a single feeding guild, rather by species changing strata during the vegetation period. In contrast, species diversity in tree crowns was approximately the same for both conifer species. However, communities in Douglas-fir crowns were conspicuously different from those in spruce crowns, especially in the Douglas-fir dominated stand type. While zoophagous insects exhibited higher activity on Douglas-fir in 2000, xylophagous beetles were more abundant on spruce in 2001. In European beech stands with widely spaced Douglas-fir trees, the site specific and broad-leaved tree related fauna might be maintained. In addition, Douglas-fir with its resource of Adelges cooleyi and crowns that overtop the broad-leaved tree canopy, offer additional resources for several aphidophagous and thermophile species. 相似文献
73.
74.
Determination of a common forest life cycle assessment method for biodiversity evaluation 总被引:1,自引:0,他引:1
Forest biodiversity is highly linked with the occurrence of certain forest development phases (fdp) within the forest life cycle. Generally, the disintegration phase provides the highest biodiversity. The objective of the study was to test different existing forest life cycle assessment approaches aiming at developing a common reliable fdp assessment method. We tested and compared three approaches to record fdp in beech, mixed beech and spruce forests, in managed and unmanaged forests, and in four different plot sizes ranging from 125 to 2000 m2. The main results of the fdp comparison are as follows:
- (1)
- In approximately two thirds of the cases the three considered methods did not yield a corresponding fdp record.
- (2)
- Generally, the larger the plot sizes, the larger the average fdp deviation in forest reserves.
- (3)
- The fdp deviation is stronger in beech or spruce dominated forest reserves than in mixed beech forest reserves.
- (4)
- Plots of 500 m2 show most distinct numbers of microhabitats corresponding to the fdp sequence within the forest life cycle.
- (5)
- Furthermore, the managed forests mostly show lower fdp deviation than the forest reserves.
75.
辐射松(PinusradiataD.Don)原产于加利弗尼亚海岸,被引种到世界各地,现在是南半球主要的人工林造林树种。1990年以来辐射松被引种到长江上游四川省阿坝州的干旱河谷地区,幼树的成活和早期生长表现良好。本文的主要内容包括:辐射松在原产地和引种地的生长情况,种源和遗传上的差异,环境限制因子和辐射松的气候生境,病虫害,引种不成功的经验教训以及辐射松在生态恢复中的应用。文中还简述了辐射松在阿坝干旱河谷地区的早期生长情况,列举了在长江上游干旱河谷地区引种辐射松可能遇到的问题以及所需开展的研究。图4表5参90。 相似文献
76.
尼泊尔安纳布尔纳保护区的建设简单朴实,尽可能地减少了对环境的破坏,原汁原味的自然和人文景观吸引了越来越多的旅游徒步者。借鉴其保护方法,我国风景名胜区还应在立法、管理体制和规划上更加完善。 相似文献
77.
人工林害虫的生态控制策略 总被引:1,自引:0,他引:1
森林害虫的科学管理必须考虑长远的经济效益和社会效益问题,只有对森林害虫进行生态控制才能达到森林可持续经营的目的。在人工林构建中,只有模拟天然林结构,从害虫栖息地抗虫林分结构出发,才能从根本上解决猖獗成灾问题。在对黑龙江省主要造林树种的天然抗虫结构、人工混交林和人工纯林的结构及害虫发生情况进行对比分析的基础上,提出了人工林害虫生态控制策略。 相似文献
78.
浅析生态园林建设与城市可持续发展 总被引:4,自引:0,他引:4
如何利用园林植物的生态效应为城市可持续发展服务是每一个城市规划工作者共同面临的问题。文章分析了生态园林建设与城市可持续发展的关系,发展现状与前景,并对其未来可能的发展方向与思路提出了见解。 相似文献
79.
80.
用可持续发展观对建设生态园林城市工作进行分析,探讨我省创建园林城市和生态园林城市的思路和方法。 相似文献