用多重马尔可夫链预测松毛虫发生面积的研究

该文以1998年建平县松毛虫发生面积预测为例,对应用多重马尔可夫链(MultiplcMarkovChin)进行松毛虫预测预报做了探讨,预测结果分析表明,利用多重马尔可夫链进行松毛虫发生面积预测较为准确.     

两种主要森林害虫发生面积预报的初步研究

应用马尔可夫链和灰色系统GM (1,1)预测模型对宁化县 2种主要森林害虫—马尾松毛虫和黄脊竹蝗的年度发生面积进行了分析和预测。结果表明 :马尔可夫链对马尾松毛虫和黄脊竹蝗发生面积预测效果较好 ,灰色系统GM (1,1)预测模型对马尾松毛虫发生面积预测效果较好 ,而对黄脊竹蝗发生面积预测效果较差     

应用马尔可夫链法预测松毛虫危害研究

应用马尔可夫链方法对马尾松毛虫的危害情况进行预测预报，简便可靠：     

马尾松毛虫危害预报的研究

文章对在马尾松毛虫危害预报中，应用马尔可夫链方法并结合Lotka-Volterra生态数学模型进行预测预报进行了论述。     

物流园区物流量灰色马尔可夫预测模型

物流量是物流园区规划、建设和管理的一项重要统计数据。结合灰色理论和马尔可夫链的特点,建立灰色马尔可夫预测模型,对某物流园区的物流量进行预测。首先,根据历史统计数据建立灰色预测模型,并对模型进行精度检验。再根据灰色模型预测误差将系统划分为3个状态,确定马尔可夫状态转移矩阵,建立灰色马尔可夫预测模型,并预测物流园区的物流量。将预测结果与灰色模型对比,结果表明,建立的灰色马尔可夫预测模型可用于物流园区物流量预测,且其预测精度较高。     

林地利用趋势的预测与控制的研究

林地利用状态的研究是林业发展规划的重要研究内容，根据森林资源连续清查的样地地类变化资料，应用马尔可夫链理论，建立预测模型，分析、预测林地利用的动态状况，为林地利用规划和林业生产决策提供科学的依据。     

利用马尔可夫链预测蜀柏毒蛾发生趋势

本文利用马尔可夫链，根据达县1990-2001年蜀柏毒蛾发生面积资料，采用概率转移矩阵预测2002年蜀柏毒蛾发生量和发生趋势，由此提供趋势预报方法。     

马尔可夫链在害虫测报应用中计算方法的简化

马尔可夫链在害虫测报上有不少应用的实例,它之所以应用如此广泛,是因为它只要利用害虫本身发生的历史状态的演变特点,就能预测未来的状况。有关马尔可夫链的原理可参阅[1]、[2]、[5]等文。这里     

森林采伐量的预测与调整决策的初步研究

文中运用马尔可夫链预测的理论,根据福建省森林资源连清资料,分析出该省1979—1983年间杉木林分经营的最薄弱环节,从中找出控制采伐量的关键所在,对杉木林分采伐量的预测和调整作出科学的决策。     

马尔可夫链在森林病虫害测报中的应用

马尔可夫链在当代统计数学上,占有相当重要的地位。利用马尔可夫链预测预报森林病虫害的发生发展,要利用害虫本身发生的历史状态、演变过程,计算其转移概率。通过外推法,就可以预测预报来年森林病虫害发生发展的趋势。也就是说,通过各阶转移概率后,从各状态之间的演变规律,确定来年害虫发生处在那个发生状态,就以那个状态范围的转移概率出现的最大值,作为来年森林病虫害预报的基础。     

西双版纳普文山地的秃杉引种试验初报

报道了在西双版纳普文热带林业研究所山地引种秃杉的试验情况。通过分析比较5~15年生引种林分林木的生长量与原产地天然秃杉林的生长量,发现秃杉在云南热区的生长量远高于其原产地,与当地速生树种相当,值得在云南广大热区推广种植。     

ENSO对黑龙江省森林火灾的影响

利用黑龙江省1980—1999年森林火灾数据,以及NINO3.4指数和SOI指数,分别对其进行谱分析,得出其波动周期分别为:火灾次数的周期为10.00年;火灾面积的周期为6.67年;La Nin~a和El Nin~o在这20年中的基本周期为5.00年。进而对其进行相关性分析,结果表明,La Nin~a和El Ni~no与森林火灾面积和次数的相关性极为显著,NI-NO3.4指数与森林火灾年发生面积与次数呈负相关,相关系数分别为-0.523 1和-0.659 4,SOI指数与森林火灾年发生次数与面积呈正相关,相关系数分别为0.525 4和0.536 3。La Ni~na对森林火灾的影响较El Nin~o的影响要小。由于受遥相关二次效应的影响,森林火灾的发生相对于El Nin~o事件的高峰有一定的滞后。在ENSO暖事件间期,通常火灾面积、次数会异常增高。     

杨树生长的密度效应与数量成熟研究

在洞庭湖平原区采用南抗杨树无性系进行的8种不同密度造林试验,试验结果显示胸径生长于5年生、树高生长于8年生以后在不同造林密度间均具显著差异,其变化规律是胸径、树高生长均随造林密度的增加而降低,表明林木此时的生长已开始受制于单株营养面积之不足。根据材积的连年生长量曲线和平均生长量曲线交汇情况,8种造林密度杨树林分的经营目标可分为两大类型:一是单株营养面积为8~16 m2造林密度的数量成熟为7~9年,所获材种为20 cm以下纸浆材、纤维板材等;二是单株营养面积为24~36 m2造林密度的数量成熟在10年以上,可培育26 cm以上大径材。     

Age-related trends in red spruce foliar plasticity in relation to declining productivity

Phenotypic plasticity in needle morphology with increasing tree size and age was investigated by comparing four age classes of red spruce (Picea rubens Sarg.) ranging from juvenile (3-12 years old) to mature (over 100 years old). With increase in tree age there were significant increases in leaf mass per unit area (LMA), mesophyll and vascular bundle area as a percentage of total needle cross-sectional area, and stomatal density. Within the vascular bundle, both xylem cross-sectional area and tracheid lumen area increased significantly, whereas air space as a percentage of total cross-sectional area decreased. These morphological changes were associated with a significant decrease in photosynthetic capacity and stomatal conductance, and an increase in (13)C enrichment. Although both photosynthetic capacity and whole-tree conductance decreased significantly between age classes 3 and 12 years, they did not differ between age classes 53 and 127 years, even though needle (13)C enrichment was significantly greater in the 127-year age class. Thus there appear to be compensatory mechanisms that maintain photosynthetic capacity as trees increase in size and vascular complexity, which in red spruce and other species, may affect leaf hydraulic conductance. Although increased LMA may contribute to reduced photosynthetic capacity in red spruce, similar relationships are not seen in other conifers.     

Crown structure and leaf area index development in thinned and unthinned Eucalyptus nitens plantations

The crown structure of Eucalyptus nitens (Deane & Maiden) Maiden 6 years after thinning, and the development of stand leaf area index both immediately and 6 years after thinning, were investigated. Thinning did not alter branch angle, branching density or the relationship between branch size and branch leaf area. However, larger branches were found in the lower crown of thinned trees and the increase in leaf area as a result of thinning occurred on the northern aspect of the crown. The vertical distribution of leaf area in unthinned trees was skewed toward the top of the crown and correlated with live crown ratio. The vertical distribution of leaf area in thinned trees tended to be less skewed and was unrelated to tree size or dominance. Leaf area index, as estimated from light interception measurements, increased at a constant rate soon after thinning regardless of residual stocking. In the longer term, residual stocking had a strong influence on leaf area increase per tree and was correlated with changes in crown length.     

平茬年限对沙冬青光合特性与比叶面积的影响

【目的】为在理论与技术上解决孑遗植物种质资源的保存与修复,探究沙冬青被平茬后更新恢复生长的机理和策略。【方法】利用Li-6400便携式光合仪测定了不同平茬年限沙冬青的光合生理特性,同时分析了不同平茬年限沙冬青比叶面积(SLA)与光合速率(Pn)、水分利用效率(WUE)的关系,从而更好地解释平茬复壮后植物补偿性生长机理与持续年限。【结果】平茬后沙冬青净光合速率(Pn)和蒸腾速率(Tr)显著提高,且日变化趋势一致,除平茬后恢复1 a的沙冬青为单峰型,其它平茬年限和未平茬(CK)均为双峰型,且均在11:00左右出现最大值,有第二峰值的出现在15:00左右,不同平茬年限沙冬青水分利用效率日变化趋势也呈单峰或者双峰型,但峰值出现的时间存在差异。随着平茬年限的增加,恢复生长的速度减慢,其净光合速率、蒸腾速率和水分利用效率也逐渐降低,日均值的大小顺序均为:平茬后恢复1 a>平茬后恢复3 a>平茬后恢复8 a>未平茬CK。不同平茬年限沙冬青的比叶面积差异性显著(P <0.05),且随着平茬年限的增加,比叶面积不断减小。不同平茬年限沙冬青比叶面积与净光合速率存在显著的正相关关系,与水分利用效率存在显著的负相关关系,随着平茬年限的增加,沙冬青比叶面积与净光合速率、水分利用效率的回归方程斜率均逐渐减小,即植株单位叶面积净光合速率和水分利用效率均逐渐降低。【结论】有必要通过对衰老、干枯的沙冬青进行合理平茬,以促进林分复壮和生长,同时提高生产力,有利于促进荒漠生态系统有效恢复。     

Productivity and growth efficiency in sugar maple forests

Sugar maple (Acer saccharum Marsh.)-dominated northern hardwood forests were examined at four locations along an acid deposition and climatic gradient in the Great Lakes region of the USA. The study sites were matched in terms of physiography, soils, stand history, and vegetative characteristics. Measurements of basal area and biomass growth were made for the 1988–1991 growing seasons. There were no significant differences in either basal area of biomass increment among the four sites over the 4 year period. There was a great deal of year-to-year variability with relative basal area growth rates ranging from as low as 0.2% to as high as 2.4% on a single site in successive years. Growth efficiency measures reflected this variability with as much as an 800% difference between successive years on a single site. When coupled with year-to-year variability of up to 34% in leaf area related to heavy seed years and defoliation, this indicates that growth efficiency and leaf area measures are not consistent indicators of aboveground productivity for tolerant deciduous species, especially if derived from short-term measurements or temporary plots.     

四翅滨藜造林试验

从青海引种四翅滨藜进行造林试验。通过4年的试验观测,取得以下结论：①宁夏南部山区特别年降水量300 mm以上的地方是四翅滨藜生长适宜的生态区域,而中北部年降水量200 mm以下的干旱区,发展四翅滨藜需要有补水条件;②容器苗造林是提高成活率的有效措施;③与豆科植物混交造林效果好。     

森林火灾重灾年现象与海温异常变化关系研究

根据黑龙江省林区 195 1～ 1990年的森林火灾统计数据和北太平洋海域 2 86个格点自 195 1～ 1991年历年逐月观测数据 ,运用异常度分析技术 ,研究了黑龙江林区森林火灾重灾年现象的当年及前后各 3a逐月北太平洋海温异常变化的基本规律和时相特点。研究发现 ,黑龙江林区的森林火灾重灾年与太平洋赤道附近海域 (10°S～ 10°N ,80°～ 180°W)海温 (seasurfacetemperature ,SST)持续正距平期显著正相关 ,两者基本同步 ,且以该海域 - 2aSST异常变冷为前期背景。对科学地预测该林区未来年、季森林火灾活动及林火致灾潜力具有重要参考价值     

Hydraulic conductance, light interception and needle nutrient concentration in Scots pine stands and their relations with net primary productivity

Aboveground xylem hydraulic conductance was determined in Scots pine (Pinus sylvestris L.) trees and stands from 7 to about 60 years of age. At the stand scale, leaf area index and net primary productivity (NPP, above- plus belowground) increased and reached a plateau at about 25-30 and 15-20 years, respectively; both parameters declined in mature stands. Stand hydraulic conductance followed a similar trend to NPP, with a maximum at about 15-20 years and a pronounced reduction in old stands. At the tree scale, annual biomass growth per unit of leaf area (growth efficiency) declined with tree age, whereas aboveground sapwood volume per unit leaf area, which is linearly related to maintenance respiration costs, steadily increased. Radiation interception per unit leaf area increased significantly with reduced leaf area index of mature stands, despite increased foliage clumping in the canopies of mature trees. Needle nutrient concentration did not change in the chronosequence. Tree hydraulic conductance per unit leaf area was strongly and positively correlated with growth efficiency. We discuss our findings in the context of growth reductions in mature and old trees, and suggest that increased hydraulic resistance and maintenance respiration costs may be the main causes of reduced carbon gain in mature and old trees.