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991.
The root parameters of forest trees can be indicators of a changing environment. We summarize the results of root studies
with regard to the effects of acidifying pollutants, especially soil acidification and aluminum toxicity, on various root
parameters of Japanese forest trees under experimentally controlled conditions. All root parameters such as biomass, morphology,
nutritional status, and physiology can be regarded as indicators, because, under laboratory conditions, root responses occur
prior to the responses in the aboveground parts. However, considering the conditions of forest sites, the nutritional status
and physiological changes are better indicators of soil acidification and Al stress than the biomass and morphological response.
The currently available data suggest that the most important indicator is the Ca/Al molar ratio in roots of Japanese tree
species. In order to predict and detect the initial effects of soil acidification, we postulate that the specific root response
to the Ca/Al molar ratio of tree roots should be considered as a parameter for use in long-term forest monitoring sites. 相似文献
992.
Comparing the model forms estimating generalised diameter-height relationships in Tecomella undulata plantations in hot arid region of India 总被引:1,自引:0,他引:1
Vindhya Prasad Tewari 《林业研究》2007,18(4):255-260
Four generalised diameter-height equations were developed and compared for pure and even-aged stands of Tecomella undulata in hot arid region of Rajasthan State in India. The data used to fit the equations consisted of 1 540 diameter-height observations collected from the plots laid out in uniformly stocked stands of varying age and density. The performance of four equations was tested by non-linear least squares regression and evaluated using different statistical criteria. Finally, these equations, with the same values of coefficients ob- tained during the fitting phase, were validated by an independent data set consisting of 854 diameter-height observations. Overall, equation (4) (Hui and Gadow function) was found to perform best for both the fitting data set as well as validation data set. 相似文献
993.
MA-SEBS as compatibilizer and impact modifier was incorporated into Polypropylene/Wood Fiber (PP/WF) to enhance interface adhesion and impact strength of the composite. The effect of MA-SEBS content on the impact fracture behavior of PP/WF composites was studied. The impact properties of composites with 8% MA-SEBS reached the maximum value. And further increasing of MA-SEBS content to 10% did not improve the fracture toughness, but improved the stiffness of composites by DMA analysis. This was attributed to the improved PP/WF adhesion. As the MA-SEBS content is more than 8%, the molecule interaction of PP and WF was expected to much stronger than lower MA-SEBS. Scanning electron microscopy (SEM) was performed to analyze the impact fracture surface and showed a stronger affinity for the wood surfaces. 相似文献
994.
文章在分析宁夏生态经济型林业发展现状的基础上,以生态学、恢复生态学和生态经济学为理论基础,围绕“生态”“经济”两条主线,以林业资源保育和增加植被盖度为切入点,由北向南将宁夏构建为3个林业生态功能区,即宁夏干旱带贺兰山及引黄灌溉绿洲生态网络体系建设区、宁夏中部干旱风沙带灌草配置区、宁夏南部半干旱带水土保持和水源涵养林区,实行多林种、树种,多序列的资源优化配置,以期形成产出效益的多样性和受益的社会性。 相似文献
995.
阐述了黑龙江省蜻蜓目药用昆虫褐顶赤蜻 ( Sympetrum inf uscatum Selys)的形态特征、生活习性、化学物质含量及药用价值 相似文献
996.
This paper describes the use by family forest landowners of educational programs provided by Washington State University Cooperative
Extension (WSUCE), and the associated use of technical assistance programs provided by state and federal agencies and the
private sector. Approximately 100,000 family forest owners controlled 19% or over 1.2 M ha of Washington’s forestland and
accounted for 29% of the timber harvested in the state on a volume basis in 1998. A variety of public and private assistance
and education programs are available to encourage and help family forest owners manage their forests. In 1999 a mail survey
was conducted to evaluate use and effectiveness of Washington’s family forest assistance and education programs. Over half
of the 872 responding family forest landowners had contact with an extension educator, program or educational material, and
about three quarters of these respondents gave an overall rating of the usefulness of extension programs and materials as
good or excellent. Respondents attending WSUCE forestry educational programs have larger median land ownership size, are older,
have owned their forests longer, have a higher rate of absentee ownership, and are better educated than non-users. They are
more likely to actively manage their forests for timber production and exhibit a clearer understanding of the multiple-use
capabilities of their forests. 相似文献
997.
998.
Barbara Moser Christoph Bachofen Jonathan D. Müller Marek Metslaid Thomas Wohlgemuth 《Annals of Forest Science》2016,73(4):959-970
Key message
Pinus sylvestris seedlings quickly expand their roots to deeper soil layers while Pseudotsuga menziesii concentrates its root system in the topsoil, thereby running the risk of desiccation during long dry spells, as indicated by lower survival after simulated summer drought.Context
Pseudotsuga menziesii (Douglas-fir) is regarded as a promising species to maintain the productivity of Central European lowland forests given the projected increase of long dry spells.Aims
Will the species be able to regenerate from seed and spread outside plantations in a drier temperate Europe?Methods
We measured the relative growth rate, biomass allocation, root architecture, and phenotypic plasticity of Pseudotsuga menziesii seedlings sown in a common garden and grown under current precipitation and prolonged drought, respectively. The species’ competitive ability with respect to Pinus sylvestris L., the most drought-tolerant native conifer in Central Europe, was assessed during three growing seasons.Results
Pinus sylvestris seedlings had higher relative growth rates than did Pseudotsuga menziesii seedlings, first in terms of aboveground biomass and later in terms of shoot height. This resulted in heavier and taller seedlings after three growing seasons under both moist and dry conditions. Shorter vertical roots corresponded with lower survival of Pseudotsuga menziesii seedlings under dry conditions.Conclusion
Fast root proliferation allows Pinus sylvestris seedlings to reach deeper water pools that are less rapidly depleted during transient drought. By contrast, the shallow root system might put Pseudotsuga menziesii seedlings at the risk of desiccation during prolonged dry spells.999.
1000.
中国葛藤叶蝉名录及新种、新记录描述(同翅目:叶蝉科) 总被引:3,自引:0,他引:3
本文系统报道我国葛藤上的叶蝉种类,共有11亚科40属50种,其中含3新种、1中国新记录属、5中国新记录种,建立1新组合种,并对折板叶蝉属Paradaevicephalus Ishilhara的属征进行了厘订。新种模式标本保存在安徽农业大学昆虫标本室。 相似文献