STUDY ON RELATIONS BETWEEN HEAVY-DISASTER-PERIOD OF FOREST FIRE ACTIVITY AND SUNSPOT ACTIVITY, SSTA

The HDPFF (heavy-disaster-period of forest fire) takes up 1 / 4-1 / 3 of all observation years, but the loss takes up 80-90% of all. The author studied the relations between forest fire activity in Heilongiiang Province from 1950 to 1989 and activity of sunspot, SSTA (sea surface temperature abnormality) of the North Pacific Ocean. The study discovered that : (1 )there was a negative correlation between forest fire condition in Heilongjiang Province and annual average of sunspot relative numbers, furthermore, the heavy-disaster-period was prone to occur in valley year and the next year; (2) SSTA in the North Pacific Ocean markedly influenced the forest fire activity and the level of its conditions in Heilongjiang province.

Application of optimal harvesting decision model to the analysis of Chinese forestry economic policy

This paper firstly extends the single period forest optimal harvesting decision model to infinite periods,in order to indicate how to determine the optimal rotation period aimed at maximizing forest revenue in all directions when repeat planting and harvesting trees on the same plot of earth till infinite future.The study also analyzes the influence of discounted rates,timber price,harvesting costs,planting costs,and tax on the determination of optimal rotation period;and how the optimal rotation period will change when we introduce the factors of continuously rising timber price and ecological revenue.Secondly,the authors introduce the intergenerational equity principle into the above model to design a resource-exploiting mode which satisfies bom the dynamic efficiency principle and the intergenerational equity principle.Last but not least,the research applies the above model to the analysis of Chinese forestry economic policy and explains the economic theory of institutions such as Government Purchasing Ecological Forest,Tree Compensation,and Forestry Subsidization,which provides a necessary theoretical foundation for future application of these new institutions.Besides,in regard to mis theoretical framework,the authors analyze the necessity of the Natural Forest Protection and Grain for Green projects which are currently being implemented in China.We also point out the emphasis of work to insure the project sustainable and successful.Finally,the research discusses the enterprise's incentive to over-the-quota harvesting and the government's means of restricting such behavior,which highlights the fact mat improved supervision and higher penalties are helpful in restricting over-the-quota harvesting.

Use of tree species by three species of Magicicada(Hemiptera:Cicadidae)in an Appalachian forest

Periodical cicadas(Magicicada spp.)are endemic to deciduous forests in the eastern United States.In successional forests,they must partition resources such as host trees to coexist.We measured tree size,emergence holes,oviposition scar bundles,and chorusing center abundances of Magicicada species on 12 common tree species in a deciduous forest to understand host-tree use.We predicted that the abundance of periodical cicadas and use of specific host-tree species would change depending on the Magicicada species and tree life stage.We considered the size of the tree(diameter at breast height)as a covariate to control for tree size and collected eggs for a greenhouse experiment to assess whether nymphs prefer to feed on Quercus rubra or Acer saccharum.More emergence holes were found below Quercus species than any other tree species.The abundance of periodical cicadas on host trees used for chorusing centers varied depending on the Magicicada species,but were most abundant on Quercus species.Oviposition scar bundles were also more frequent on Quercus.More nymphs were found on Quercus than Acer in the nymph preference study.Though periodical cicadas used Quercus hosts more than other tree species,their abundances on different host tree sizes and species differed significantly.Periodical cicada species may use specific host species and life stages as a way to partition resources and minimize competition among the Magicicada species during emergence years.

Estimation of Relative Ecological Value of Returning Farmland to Forest & Mountain Enclosure for Grazing Prohibition——A case study in Yongxing Township of Jingyuan County,Gansu Province

[Objective]Returning farmland to forest and mountain enclosure for grazing prohibition ecological effect and economy rationality were explored.[Methods]A case study of returning farmland to forest and barren hills grazing prohibition in Yongxing Township of Jingyuan County was used to discuss and estimate the relative ecological function and relative ecological value.[Results]1）The ecological value of the forest of returning farmland was far more than the sum of the ecological value of farm crops and the agricultural output,and also more than the national subsidy standard.So the state policy of returning farmland to forests is not only favorable to local eco-environment restoration,but also reasonable in economic development.2）The ecological value of mountain enclosure for grazing prohibition was less than the opportunity cost of prohibiting grazing,also less than the national subsidy standard.The sum of the relative ecological value of prohibiting grazing and the state subsidies was more than the opportunity cost of prohibiting grazing.However,the ecological value of new vegetation through returning farmland to forest project was greater than the China＇s average ecological value of grassland.[Conclusion]The relative ecological value can be used to solve the problems in the equivalent conversion among various ecological indexes and between ecological indexes and economic indexes.

陆浑灌区实际蒸散发影响因素分析

实际蒸散发是水文循环的关键环节,分析灌区实际蒸散发及其影响因素对灌区水资源的高效利用和农业高质量发展具有重要意义。然而,目前蒸散发的影响因素研究在确定主要因素时往往采用解释力较差的传统统计学方法,在相关性分析时忽略了蒸散发与其影响因素在空间上的相关性。因此利用改进的随机森林模型确定实际蒸散发的主要影响因素,并通过岭回归模型和地理加权回归模型探究实际蒸散发与其影响因素的时空相关关系。结果表明:(1)在灌溉期,地表净辐射、平均气温、叶面积指数和实际水汽压是实际蒸散发的主要影响因素;在非灌溉期,地表净辐射、平均气温、风速和日照时间是实际蒸散发的主要影响因素。实际蒸散发在一定程度上代表了灌区的作物耗水量。因此,灌区作物耗水在灌溉期和非灌溉期的影响作用有一定的差异。(2)在时间上,风速与实际蒸散发为负相关关系且呈显著负相关(P<0.05),其余影响因素与实际蒸散发均为正相关关系且呈显著正相关(P<0.05);在空间上,除风速与实际蒸散发在大部分区域呈负相关关系,其余影响因素都与实际蒸散发在大部分区域呈正相关关系。因此,除风速外,其余影响因素对灌区作物耗水在大部分区域都为正向促进作用。

广西暴雨集中度智能气候预测方法研究

利用1961—2023年广西79个气象观测站逐日降水和国家气候中心大气环流、海温指数资料,构建广西暴雨集中度计算方法,基于逐步回归方法、粒子群-神经网络、随机森林算法,建立暴雨集中度气候预测模型。结果表明,广西存在以桂林和柳州两市北部为中心的桂东北地区、以“东兰、巴马、凤山”为中心的桂西山区和沿海地区三个暴雨集中度高值区,暴雨集中度异常大小基本反映发生洪涝和干旱灾害的严重程度。经过2020—2023年气候预测试验,粒子群-神经网络算法预测效果最好,其次为随机森林算法,第三是逐步回归方法。

周期性羽化昆虫形成机制

当昆虫类群表现为长生命周期k(k>1)年时,成虫的羽化表现为非周期性、周期性和过渡周期性3种形式。非周期性即为成虫每年均羽化,周期性即为成虫每k年才羽化1次,过渡周期性为非周期昆虫逐渐进化为羽化周期性的必经阶段,不同年份羽化的同生群在密度上产生了显著差异,形成了小同生群和优势同生群。自然界中表现出完全羽化周期性的昆虫种类是较少的,但由于其高种群密度的成虫同步性羽化现象,对比非周期性昆虫更易暴发成灾。为明确周期性昆虫演化进程并为林区虫害防控提供理论指导,总结了周期性昆虫的种类和生活特性,不同年间的气候异质性、自然灾害、扩散到未分布区域、天敌、种间和种内竞争等因素均有可能成为过渡周期现象形成的最初驱动力,生活史延长、寄主-天敌互作、低温驱动效应、天敌不敏感-捕食者饱足效应、种间和种内竞争等是促使昆虫羽化周期性形成的可能机制。在林区管理实践中,应提前评估害虫羽化周期性产生的趋势和程度。当成虫表现出完全羽化周期性,应在集中羽化年份内采取见效快的综合防控策略,降低唯一同生群密度至经济阈值以下。当成虫表现出过渡周期性,应加大优势同生群防治力度、降低小同生群防治频率,以及采取天敌林间释放和保育技术以平衡天敌对目标害虫的不同发育阶段种群的控制作用大小,遏制或减缓天敌-寄主互作驱动下的周期性演化进程,逐渐实现由过渡周期阶段向非周期性的逆转。当成虫表现出非周期性,应减少专化性天敌的释放和针对害虫特定阶段的防治措施使用频率,优先选择作用于所有发育阶段且致死率不存在显著差异的防治手段,避免因人为干扰产生的周期性演化和进一步的成灾。

黑水县彩林观赏期预报模型构建及时空变化研究

利用黑水县2008—2020年彩林物候期观测和同步气象资料,筛选影响彩林变色日序的关键气象因子,通过多元回归等数理方法建立月尺度的彩林观赏期短期气候预测模型和未来10 d的彩林观赏期中期气象预报模型并进行检验,依托GIS平台及多年平均气象数据模拟黑水县彩林变色日序时空分布。结果表明:黑水县彩林平均于9月28日、10月16日分别进入始红、盛红状态;彩林始红日序与7月的月平均气温、月平均最高气温显著正相关,与7月累计降水量显著负相关;彩林盛红日序与7月累计降水量显著负相关,与8月平均最低气温显著正相关;彩林进入始红及盛红状态日序与前10 d各气象要素均不显著相关;彩林观赏指数与前10 d平均气温、平均最高气温、平均最低气温、平均相对湿度、累计降水量呈显著负相关,与平均气温日较差、累计日照时数呈显著正相关;彩林观赏期日序整体随海拔高度由东南向西北倾斜攀升而提前,在10月10日前全县彩林均进入始红状态。本研究通过相关气象因子建立黑水县彩林短期气候预测模型及中期气象预报模型,检验认为彩林观赏期短期气候预测模型在彩林始红及盛红状态预测中具有较高准确性和可操作性,中期气象预报模型仅适用于彩林始红状态的预测。

内蒙古大兴安岭林火时空动态的变化特征

内蒙古大兴安岭森林火灾频发,研究其季节性变化趋势及空间动态分布特征,对今后该地区森林防火期划分和防火资源的合理分配具有重要意义。利用Mann-Kendall趋势检验法、滑动t检验法对1981—2018年内蒙古大兴安岭森林火灾数据进行趋势和突变分析,使用分位数回归法研究影响森林火灾过火面积的时间与空间因素,得出内蒙古大兴安岭森林火灾在时间和空间上的动态变化特征。结果表明:内蒙古大兴安岭森林火灾整体呈先下降(1981—1999年)再上升(2000—2007年)又下降(2008—2018年)的趋势。森林火灾主要发生在春、夏、秋三季,春季森林火灾变化较复杂,波动明显,在1991年发生突变;秋季森林火灾波动较平缓,但在1994年发生突变;2004—2011年期间夏季森林火灾明显增长,火险期向夏季发生偏移和延长;冬季发生火灾较少。森林火灾过火面积与火灾持续时间呈正相关,尤其在高分位点处,正相关性更加显著。内蒙古大兴安岭森林火灾主要发生在鄂伦春自治旗等地,从空间横向动态变化来看,整体呈现由西南向东北递增的趋势;从空间纵向动态变化来看,海拔对森林火灾过火面积的影响并不显著。建议应加强内蒙古大兴安岭东北地区及春、夏两季的林火监测和防火宣传,适当调整森林防火期和防火资源时空分配,将有助于减少内蒙古大兴安岭森林火灾的发生。

基于Sentinel-1和Sentinel-2的不同物候期农作物识别研究

为减少农作物提取过程中受光学数据成像质量的影响,基于Google Earth Engine平台,采用Sentinel-1和Sentinel-2数据,分别对小麦越冬期、返青期、孕穗期、成熟期四个物候期进行小麦和油菜的识别。使用随机森林方法对构建的光谱特征、植被指数特征、红边指数特征、纹理特征和极化特征共34个特征进行优选,构建特征集;并对比最小距离、决策树、支持向量机、随机森林四种分类器在四个物候期的识别结果,确定最优的分类器;同时还验证了极化特征在四个物候期对识别结果的影响。研究结果表明,在四个物候期中最优的分类器均为随机森林,其中识别精度从高到低的物候期分别为小麦的孕穗期、成熟期、返青期、越冬期,总体精度(OA)分别为92.91%、91.93%、90.24%、87.69%,Kappa系数分别为91.00%、89.92%、87.61%、84.53%。在四个物候期中加入极化特征均能提高识别的精度,其中在小麦的返青期和成熟期更为明显。

An approach to spatially explicit reconstruction of historical forest in Northeast China

The spatially explicit reconstruction of historical land-cover datasets plays an important role in studying the climatic and ecological effects of land-use and land-cover change（LUCC）. Using potential natural vegetation（PNV） and satellite-based land use data, we determined the possible maximum distribution extent of forest cover in the absence of human disturbance. Subsequently, topography and climate factors were selected to assess the suitability of land for cultivation. Finally, a historical forest area allocation model was devised on the basis of the suitability of land for cultivation. As a case study, we used the historical forest area allocation model to reconstruct forest cover for 1780 and 1940 in Northeast China with a 10-km resolution. To validate the model, we compared satellite-based forest cover data with our reconstruction for 2000. A one-sample t-test of absolute bias showed that the two-tailed significance was 0.12, larger than the significant level 0.05, suggesting that the model has strong ability to capture the spatial distribution of forests. In addition, we calculated the relative difference of our reconstruction at the county scale for 1780 in Northeast China. The number of counties whose relative difference ranged from-30% to 30% is 99, accounting for 74.44% of all counties. These findings demonstrated that the provincial forest area could be transformed into forest cover maps well using the model.

Global periodic attractor for a model of forest with diffusion and seasonal effects

where γ（v） = a（v- b）2 + c with positive a, b, c. As a simple mathematical model ofmono-species forest with two age classes it takes account of seed production and dispersal,where u denotes the density of "young" tree, v denotes the density of "old" tree, and ω de-notes the density of air-borne seeds; α,β,δ and d are seed production, deposition, establish-ment and diffusion rates respectively; f and h are coefficients of aging and mortality of "old"tree respectively. （1）p（t）≡0 was first presented and was then reduced to a lower-dimensionalreaction-cross-diffusion model to study travelling wave solutions in ref. [1]. We assume herethat p （t） is a periodic function of period T and 0≤p（t）≤pM, considering the seasonal ef-fects of winds, weather conditions, temperature, etc.. We consider （1） under the initial con-

新时期如何做好森林抚育管理工作

森林产业关乎着生态平衡,是自然生态资源的重要组成部分。但就我国森林资源的占有量来看,还有待提升,且部分森林资源在经济建设中遭到破坏,可见加强森林抚育管理工作具有重要意义。通过新时期森林抚育管理,能够满足生态平衡需求,同时也能够有效提高我国绿化覆盖面积,保护林业资源。但当前森林抚育管理工作仍然存在一定的不足,作为林业部门,根据森林抚育管理的基本内容,制定相应的抚育管理策略,以此做好生态资源保护工作。

基于随机森林和逻辑回归的舟山梅雨期暴雨关键指标研究

本文分析了2010—2020年舟山梅雨期(6—7月)暴雨的时空分布特征和天气形势特征。利用ERA5再分析资料和随机森林算法分析了700 hPa风速和风向、850 hPa风速和风向、850 hPa的温度和露点温度、500 hPa温度以及强天气威胁指数等共8个物理量与舟山梅雨期暴雨序列的相关性,计算得到各物理量相关性,筛选出前6个物理量建立预报方程,通过逻辑回归方法可得舟山梅雨期暴雨预报模型,用来判断暴雨是否发生,对舟山梅雨期发生暴雨的概率可提供参考依据。

基于随机森林模型的高龄产妇产褥期疲乏现状及影响因素分析

目的 探讨高龄产妇产褥期疲乏现状并分析影响因素,为采取针对性干预措施提供参考。方法 便利选取唐山市3所医院产后6周复查的353名高龄产妇,采用产后疲乏量表、积极心理资本问卷、家庭关怀度指数、匹兹堡睡眠质量指数进行调查。基于随机森林模型与LASSO回归探讨产褥期疲乏的影响因素。结果 高龄产妇产褥期疲乏总分为(15.29±2.81)分,疲乏发生率为90.9%。积极心理资本、产后出血量、BMI、妊娠并发症、睡眠质量是高龄产妇产褥期疲乏的影响因素(均P<0.05),共解释44.7%的变异量。结论 高龄产妇产褥期疲乏水平较高,需重点关注BMI较高及有妊娠并发症的产妇,可通过提高心理资本水平,减少产后出血量,改善睡眠质量,减轻高龄产妇产褥期疲乏。

施肥时期对毛竹林出笋成竹及新竹生长的影响

为探究施肥时期对毛竹林出笋成竹及新竹生长的影响,2019—2022年在福建省永安市进行了不同施肥时期试验,设置3种施肥时期处理:5月份施肥1次+挖冬笋前1个月施肥1次(处理A),5月份施肥1次+边挖冬笋边施肥1次(处理B),5月份施肥1次+挖冬笋后1个月施肥1次(处理C),以不施肥作为对照(CK),分析比较不同施肥时期对毛竹林春笋出笋量、成竹量及新竹生长量的影响。结果表明,以处理B对毛竹林出笋成竹及新竹生长的促进作用最好,平均春笋出笋量达939个/hm^(2),平均成竹量达883株/hm^(2),新竹平均胸径达10.9 cm,平均竹高达12.3 m,分别较对照提高28.10%、32.38%、14.74%、14.95%。研究结果可为笋竹两用毛竹林施肥时期选择提供技术参考。

江西九连山森林水果和野生蔬菜初探

【目的】森林水果和野生蔬菜是森林大食物观中粮食的重要组成部分,为了调查统计江西九连山分布的森林水果和野生蔬菜资源组成和种数。【方法】采用路线调查法对公路两侧、常绿阔叶林和针叶林等各种林分中的森林水果和野生蔬菜进行摄影、采集标本,记录其地理位置、种群数量和生境信息。【结果】建立了九连山森林水果和野生蔬菜名录;分析了江西九连山森林水果和野生蔬菜的科属结构、地理区系、生活型、营养和药用价值,并统计了九连山地区森林水果的果期,同时提出了九连山森林水果和野生蔬菜的开发建议。【结论】江西九连山森林水果资源和野生蔬菜资源丰富,营养药用价值高,开发潜力大,可为保障粮食安全提供数据支撑和实践指导。

6种针叶树活枝叶在森林防火戒严期的燃烧性比较

在森林防火戒严期内,用自行设计的燃烧试验装置对云南松Pinus yunnanensis Franch.,华山松Pinusarmandii Franch.,地盘松Pinus yunnanensis Franch. var. pygmaea(Hseh)Hseh,杉木Cunninghamia lanceolata(Lamb.)Hook.,藏柏Cupressus torulosaD.Don和柳杉Cryptomeria fortunei Hooibrenk ex Otto et Dietr.6种针叶树的活枝叶进行9次燃烧试验和无样品的对照试验。在测定和分析样品含水率、引燃时间、有焰燃烧时间、试验过程中烟气温度和质量损失变化等基础上,提出了燃烧性参数,即单位质量可燃物在有焰燃烧阶段相对于对照试验的烟气净积温与引燃时间之比。根据该参数计算6种针叶树9次燃烧试验的燃烧性参数,并根据9次试验燃烧性参数的平均值对6种针叶树的燃烧性进行了综合排序,即柳杉>藏柏>杉木>地盘松>华山松>云南松。研究结果还表明,6种针叶树的燃烧性在防火戒严期呈动态变化,并在总体上呈下降趋势。

落叶灌木南烛在防火戒严期的燃烧性动态

在森林防火戒严期内,用自行设计的燃烧试验装置对落叶树种南烛(Lyonia ovalifolia)的活枝条进行了8次燃烧试验,在测定和分析样品引燃时间、试验过程中烟气温度变化和质量损失过程等基础上,提出了燃烧特征参数,即单位质量可燃物在试验过程中相对于无样品的对照试验的烟气净积温与引燃时间之比,根据该参数计算了8次燃烧试验的特征参数。研究结果表明,南烛的燃烧性在森林防火戒严期内呈动态变化,并呈逐渐下降趋势。

返青期休牧对退化高寒草甸植被的影响

该项研究试图通过返青期休牧达到快速恢复退化高寒草甸植被的目的,于2015年5-7月在青海省祁连县默勒镇春季草场上进行返青期休牧试验。通过调查3个休牧样地和3个放牧样地,研究草地主要植被的株高、盖度和地上生物量等植被状况和高原鼠兔有效洞口的数量,从而评估返青期休牧对退化草地植被的影响。结果表明:返青期休牧时,草地的牧草高度、群落盖度和地上总生物量相对于放牧草地分别提高了165%,4%和77%,毒草生长明显受到了抑制,且其生物量下降了50%,高原鼠兔有效洞口数下降了72%。因此,我们认为在高寒草地过牧的关键时期实施返青期休牧可快速恢复退化草地植被,为高寒草地的合理利用提供了有效措施。