不同密度华北落叶松林天然更新及其影响因子

以关帝山区8种林分密度(128、240、320、400、480、560、640和720株·hm^-2)华北落叶松纯林为研究对象,分析了不同密度下华北落叶松天然更新优劣及其影响因子。结果表明: 更新指数随林分密度增大先升高后降低,中密度(400～560株·hm^-2)林分更新效果明显优于过疏和过密林分;林下光环境、草本植物及凋落物对落叶松更新有双重作用,光照过强、草本植物盖度过大或凋落物过厚不利于林下更新,土壤有机质可使土壤质地松软、水分含量充足并形成低磷高氮环境促进林分更新;各因子对更新指数的影响依次为:土壤含水量(0.798)>全氮(0.621)>凋落物厚度(-0.597)>土壤孔隙度(0.504)>土壤有机质(0.493)>全磷(-0.404)>林下总光照(-0.274)>草本植物盖度(-0.021)。在后续森林经营中,可通过抚育间伐或补植将林分密度控制在480株·hm^-2左右,并适当清理林下凋落物,改善土壤条件,促进华北落叶松天然更新。     

华北落叶松—年生茎的电子显微镜研究

运用透射电子显微镜技术研究华北落叶松—年生枝条组织细胞的超微结构．皮层及韧皮部由大量簿壁细胞及少量重申胞组成．簿壁细胞中的前质体有分裂行为,叶绿体中含有体积大的淀粉粒及明显的基粒片层结构;有“Ｖ”形线粒体及链条状粗糙内质网,液泡多以次生溶酶体状态存在．筛胞处于解体状态,胞质位于管腔周围,具大量质体、胼胝体、Ｐ１－蛋白体．胞间连丝管状,大量贯穿于胞壁间．形成层带细胞壁凹凸不平,高度液泡化,内容物很少．本质部管胞腔中空,无内容物,壁厚,有初生壁及次生壁之分．对质体、筛胞、溶酶体、形成层等组织及结构进行了讨论．     

宁夏六盘山人工林和天然林生长季的蒸散特征

为了系统地认识森林生态系统结构对蒸散特征的影响,2009年5-10月,应用热扩散技术和传统水文学方法,对六盘山香水河小流域华北落叶松人工林和华山松天然林的蒸散及分量进行对比研究.结果表明: 华北落叶松人工林生长季总蒸散量为518.2 mm,是同期降雨量的104.6%,远高于天然林蒸散量420.5 mm.两种林分总蒸散量在其垂直层次上的分配比例相近,表现为冠层蒸腾量>草本+土壤层蒸散量>灌木蒸腾量,但林分各组成分量占总蒸散量的比例明显不同.其中,人工林冠层月均截留量和蒸腾量为19.6和25.2 mm,分别是天然林的1.2和1.9倍;人工林灌木层月均蒸腾量为 4.4 mm,占天然林的23.4%;人工林草本+土壤层月均蒸散量为37.1 mm,是天然林的1.8倍.采用Penman-Monteith方程对林分的实测蒸散量进行对比检验,两种方法对林分蒸散量的估计值基本接近.
     

Response of larch species to climate changes

Global warming has changed the distributions of forests of northeastern China. Larix are very important species in this area. Predicting the potential distributions of Larix species and their responses to climate change would attract more and more attention.This paper predicted the potential distributions of three Larix species based on 'climatic-topographic' relationships by logistic regression. The results showed that L. gmelinii is predicted to retreat northwestward by 220 km by 2050 and by 270 km more by 2100; L. olgensis var. changpaiensis is predicted to retreat northwestward by 200 km by 2050 and by 190 to 300 km more by 2100; L. principis-rupprechtii is predicted to retreat northeastward by 200 km by 2050 and by 250 to 400 km more by 2100. This indicated that L. gmelinii could have its optimum latitude moved into Russia, L. olgensis var. changpaiensis could move to the Small Xing'an Mountains and L. principis-rupprechtii would move to the middle part of the Great Xing'an Mountains.     

松墨天牛化学生态学

松墨天牛(Monoohamus alternatus)是危害针叶树的重要蛀干害虫,而且是松材线虫病(Bursaphelenchus xylophilus)的主要传播媒介昆虫.本文综述了松墨天牛与寄主植物之间、松墨天牛种内及松墨天牛与松材线虫之间的化学生态学研究进展.在松墨天牛与寄主植物相互关系中,寄主植物中的萜烯类挥发物在松墨天牛选择取食和产卵寄主时发挥重要的调节作用,这些挥发物常常因寄主危害与否而发生改变,并对天牛表现出性别差异;寄主中的化学物质如碳水化合物、氨基酸、甾醇、磷脂和黄酮等能够刺激或驱避天牛的取食和产卵行为.松墨天牛种内通讯过程中,两性天牛的吸引、求爱和交尾等生殖行为由性信息素所引起;雌天牛分泌的产卵忌避信息素能够调节产卵刻槽的空间分布,有助于卵的分散,避免下一代幼虫对生存空间和食物的竞争.松墨天牛与松材线虫之间化学生态关系的物质基础为寄主植物、天牛及线虫产生的单萜、CO2及不饱和脂肪酸,它们调控线虫向蛹室的聚集、进入虫体和脱离虫体等行为.最后,展望了松墨天牛化学生态学的研究方向.     

关帝山华北落叶松人工林细根生物量空间分布及季节变化

利用根钻法研究了山西关帝山华北落叶松（Larix principis—rupprechtii Mayr）人工林细根生物量的空间分布和季节变化特征。结果表明,华北落叶松不同径级细根生物量随土层深度的增加而逐渐减少,土壤表层（0—10cm）中各径级细根的生物量最高,Ⅰ级细根（根直径0～1mm）的生物量在不同土层深度间差异显著（P〈0．05）;距树干不同水平距离处各径级的细根生物量差异均未达到显著水平（P〉0．05）。在0～10cm土层中,各径级细根生物量的季节变化差异显著（P〈0．05）,均表现为单峰型,峰值出现在9月份;在10～20cm和20-30cm土层中,Ⅰ级和Ⅱ级（根直径1～2mm）细根生物量季节变化差异显著,Ⅲ级细根（根直径2～5mm）和Ⅰ级死根（根直径0～2mm）生物量季节变化差异不显著。     

Spatiotemporal variation and scale effect of canopy leaf area index of larch plantation on a slope of the semi-humid Liupan Mountains,Ningxia, China

Aims Leaf area index (LAI) is an important canopy structure parameter characterizing ecological and hydrological processes, such as forest growth, canopy interception and transpiration. Forest LAI is limited by both light and soil water availability, thus may vary with slope position and seasonality. This study is aimed at the spatiotemporal variation of LAI and its relationship with environmental variables. Methods A 34-years-old Larix gmelinii var. principis-rupprechtii planted forest situated on a typical slope located in a small watershed of Xiangshuihe within Liupan Mountains was selected for LAI observations. Sixteen plots along a 30 m wide transect along the slope was surveyed from May to October of 2015 to measure the monthly canopy LAI. Important findings It showed there was a remarkable difference of LAI among slope positions. The LAI in May decreased toward downslope direction with a scale effect of -0.02/100 m. Whereas for the period from June to August, LAI showed a nonlinear variation along slope positions: increasing from to top slope downward, reaching its maximum at the middle slope, and then decreasing to the slope foot. The scale effect of LAI was +0.15/100, +0.16/100, and +0.18/100 m in the slope range (downward positive) of 0-244.2 m, but -0.09/100, -0.08/100, and -0.07/100 m in the slope range of 244.2-425.1 m for June, July and August, respectively. The LAI increased toward downslope in September and October, with a slope scale effect of +0.03/100 m and +0.09/100 m, respectively. The seasonal variation of LAI-slope relationship showed a shift from the light and temperature control in the early growing season, to the soil water resources control in the mid growing season, and then to an integrated control of many factors in the late growing season. In the early growing season when soil moisture and nutrients were abundant, terrain shading limited the leaf growth in middle and downslope. From early to the mid growing season, the soil moisture on the slope was quickly depleted due to fast evapotranspiration and poor moisture retention of the coarse soil. On the other hand, average solar height increased, and allowed direct light radiation to penetrate to the middle then downslope. The result is that the leaf growth in the middle slope was the strongest in the mid growing season. During the late growing season, the temperature decreased fast in the mountain top to incur earlier leaf fall than the mountain foot. Thus the LAI exhibited the increasing trend toward the downslope.     

华北落叶松林细根生物量对土壤水分、氮营养空间异质性改变的响应

在华北落叶松(Larix principis-rupprechtii)林选取采伐干扰样地和未采伐干扰样地进行对比研究, 分析采伐干扰造成林下土壤水分和氮营养空间异质性的改变对细根生物量空间变异的影响。采用空间格局分析的小支撑、多样点的设计原则, 对每个样点的土壤分3层取样(0-10 cm、10-20 cm、20-30 cm)。进行细根(≤1 mm和1-2 mm)生物量与土壤含水量、全氮、硝态氮、铵态氮和土壤pH的偏相关分析, 以及细根生物量变异函数值和土壤各因子变异函数值的线性回归分析。研究结果表明, 在不同样地, 细根生物量与土壤各因子均表现为正相关关系, 不同土层相关性强弱表现各异, 其中土壤含水量与细根生物量的相关性显著。受采伐干扰后, 细根生物量与土壤含水量、全氮、土壤硝态氮空间变异的关联性更趋于明显。多元线性回归分析结果表明, 采伐干扰样地细根生物量的空间变异更多地受到土壤多因子的综合影响, 而未采伐干扰样地的细根生物量受土壤水分、全氮和硝态氮单独效应的影响更大。     

单株华北落叶松树冠穿透降雨的空间异质性

森林与水的关系是生态学和水文学研究的核心问题之一,为了研究降雨通过华北落叶松树木冠层后的空间分异规律,并合理确定准确测定穿透降雨所需的雨量筒数量及位置,2005年生长季在一株样树冠层下按离开树干的位置机械布置了32个雨量筒,测定了11场不同降雨事件的穿透降雨量,并利用传统统计学与地统计学方法分析了叶面积指数和穿透降雨的空间变异性规律.结果表明,树冠的叶面积指数在不同方向上具有空间变异性,随离开树干的距离增大而减小;穿透降雨率与叶面积指数呈负相关性,且随降雨量增大相关性减弱;穿透降雨率半方差函数分析结果表明,基台值C＋C0随降雨量增大而减小,C0/（C＋C0）随降雨量的增大而增大,分维数D随降雨量的增大而增大,随降雨强度的增大而先增大后减小,这说明较小降雨量时,冠层结构是引起穿透降雨率空间变异的主要因素;降雨量较大时,冠层结构的影响减弱,其空间分布差异主要受随机因素影响;通过Kriging插值法绘制的树冠下穿透降雨空间分布图表明,树冠下存在着穿透降雨的最小区域和有汇集降雨作用的＂漏斗＂区域,最小区域一般在树干偏东南或南方向,而降雨汇集区域多不固定.在比较了不同雨量筒布设方案的穿透降雨变化后发现,在距离树干1/2冠幅半径的同心环上至少布设内径不小于9cm的5个雨量筒时,测定的穿透降雨量可基本接近整个树冠下的穿透降雨量平均值.