蒙古栎次生林林木竞争对不同抚育间伐方式的响应

[目的]以长白山林区蒙古栎次生林为研究对象,分析其林木竞争关系及对不同抚育间伐方式的响应,为了解此类群落的生态适应机理及制定合理的经营措施提供依据。[方法]2013年在吉林汪清设置12块样地,开展传统经营(T1)、目标树经营密度1和密度2(T2,T3)以及对照试验(T0),2018年进行了复测。通过有序样本聚类的方法确定Hegyi指数竞争木数量并分析了蒙古栎次生林的竞争关系以及各林层、优势树种及目标树的竞争关系对不同抚育间伐方式的响应。[结果](1)蒙古栎次生林样地的优势树种为:蒙古栎、红松和白桦,Hegyi指数最佳相邻竞争木个数为8。(2)样地内主要树种的总竞争排序为:蒙古栎红松色木槭糠椴白桦大青杨落叶松水曲柳黑桦;主要树种的平均种间竞争略高于平均种内竞争。(3)T2,T3上林层竞争明显降低;4种抚育间伐方式均降低了白桦和蒙古栎的竞争强度,其中T3下降的幅度最大;红松的竞争强度仅在T0升高;对于优势树种来说,T2,T3来自糠椴和色木槭的种间竞争增大,而来自大青杨的种间竞争减小;T2和T3对目标树竞争的减缓作用明显优于T0和T1。[结论]基于目标树经营的抚育间伐能够有效降低蒙古栎次生林上林层及优势树种的竞争,从而可针对性培育目标树种,引导林分的正向演替,进一步验证了目标树经营的可行性和合理性。     

兴安落叶松天然林种内和种间关系研究

通过对大兴安岭北部兴安落叶松原始林公顷样地的调查,利用Hegyi单木竞争模型分析了兴安落叶松天然林的种内、种间竞争强度。研究结果表明:兴安落叶松天然林的种内、种间竞争强度分别占竞争强度的56%和44%,说明兴安落叶松种间竞争较小,主要竞争来自种内。兴安落叶松伴生树种种类较少,种内与主要伴生树种种间的竞争顺序为:兴安落叶松种内>兴安落叶松种间>白桦种内>白桦种间。兴安落叶松种内竞争强度及白桦种内竞争强度与对象木的胸径大小之间呈指数函数关系,而兴安落叶松种间竞争强度及白桦种间竞争强度与对象木的胸径大小之间呈幂函数关系。随着兴安落叶松胸径的增大,受到的竞争强度逐渐减小。     

天然红松林空间竞争研究

本研究基于黑龙江省五营林业局红松天然林标准地调查数据,研究红松天然林内种内和种间竞争关系。研究结果表明,红松的种内和种间竞争强度分别占总竞争强度的17.0%和83.0%,说明红松天然林种内竞争小,主要竞争来自种间。     

近天然落叶松-云冷杉林树种竞争关系的变化

以4块落叶松-云冷杉间伐实验样地为对象,采用6个与距离无关的竞争指标,研究林木竞争状态在20年间(1986～2006年)的变化及间伐的影响。结果表明,落叶松为主要树种,竞争能力最强,其竞争压力主要来自种内,红松和其他阔叶树的竞争能力有逐渐增强的趋势,因此,随着林分生长,落叶松的竞争主体地位受到了来自其他针叶树云冷杉、红松及阔叶树种的威胁。该林分竞争关系近期相对稳定,但有从落叶松-云冷杉林向阔叶树及红松林发展的趋势。间伐影响种间竞争关系和林分平均竞争水平,影响程度与间伐对象的选择与间伐强度有关。林分竞争水平随间伐强度的增加而降低,但会逐渐恢复。     

哈尔滨市6种绿化树种生理特性比较

为了全面了解各绿化树种的生理生态特性,增加哈尔滨市园林绿化树种及其生态功能的多样性,为绿化树种的选择提供理论依据。对东北乡土树种白桦、蒙古栎、糠椴、紫椴、茶条槭和黄檗二年生幼苗的生理指标进行测定,通过这6种树种生理指标的研究,对各树种的适宜应用作综合的评价分析,结果表明：这6树种最大光合速率分别为：茶条槭9.70μmolCO2/m^2·s,白桦7.67μmolCO2/m^2·s,黄檗5.88μmolCO2/m^2·s,紫椴5.51μmolCO2/m^2·s,糠椴5.20μmolCO2/m^2·s和蒙古栎4.04μmolCO2/m^2·s。6树种之间呼吸速率的差异不显著,平均为1.01μmolCO2/m^2·s。水分利用效率的种间差异较大,茶条槭、糠椴和蒙古栎高于黄檗、紫椴和白桦。所以从生态园林的角度,在水分短缺的地点,选择绿化树时应先考虑水分利用效率高的茶条槭、糠椴和蒙古栎,而在土壤水分条件较好的可适当优先考虑净光合能力强的树种。     

云南松天然林的种内和种间竞争

[目的]通过对云南松天然林内云南松种内和种间竞争强度的测定,分析揭示竞争强度在云南松群落内的动态变化规律及云南松种群的生态适应机制.[方法]在云龙天池自然保护区云南松天然林设置样方进行群落学调查的基础上,采用Hegyi单木竞争指数模型,以云南松为对象木,定量分析林分、对象木、竞争木的竞争强度,采用回归分析方法建立对象木胸径与林分、种内、种间竞争强度的函数模型.[结果]天池自然保护区云南松天然林的种内和种间竞争强度分别为80.16%和19.84%;云南松种内与主要伴生树种种间竞争强度大小顺序为:云南松种内> 水红木> 华山松> 米饭花> 大白花杜鹃> 槲栎> 马缨花> 旱冬瓜;云南松与整个林分、伴生树种以及种内的竞争强度与对象木胸径之间存在显著负相关关系,对象木胸径越大,其竞争能力越强.[结论]云南松天然林内云南松的竞争压力主要来自种内竞争;林分种内及种间竞争强度与对象木胸径间存在CI=AD^-B形式的幂函数关系;胸径20 cm以上云南松的竞争压力变化趋于平缓,胸径20 cm以下的云南松中、幼林是抚育管理的重点林分.     

哈尔滨市3种阔叶树树干钠镁钙铝纵向变化特征

以东北林业大学城市林业示范研究基地内生长的黄波罗、蒙古栎和白桦为研究对象,分析不同阔叶树树干不同高度Na、Mg、Ca、Al元素纵向变化特征,探讨3树种对以上元素的运移速率。结果表明,在1958年前和1959—1962年间,除了Mg元素,黄波罗树干其他3种元素纵向格局为根茎含量大于胸径。3树种在1963—2007年间各时间段,以上元素纵向变化呈现出在胸径或1/2树高为最低的凹形曲线,或为最高值的凸形曲线,或纵向变化较为平缓等多种形式。同一时期,各树种树干Al纵向变幅最高;其他树种其余3种元素纵向变幅较低且值相当。树干中4种元素纵向运移速率由易到难排序分别为:黄波罗Mg>Ca>Na>Al;蒙古栎Ca>Na>Al>Mg;白桦Mg>Al>Ca>Na。蒙古栎对Na、黄波罗和白桦对Mg、蒙古栎和白桦对Al、Ca元素的迁移能力较强。     

帽儿山地区山杨次生林林木竞争关系的研究

基于山杨（Poptdus davidianaD．）次生林固定标准地M712、M720的每木检尺数据,采用Hegyi单木竞争指数对帽儿山林场天然山杨次生林的种内、种间竞争强度进行定量分析。研究结果表明：山杨次生林林木所受到的竞争强度随着林木径级的增大而逐渐减小。山杨次生林种内竞争较与伴生树种枫桦的种间竞争弱。山杨次生林种内和种间竞争强度的顺序为：枫桦〉白桦〉蒙古栎〉杏树〉黄菠萝〉山杨〉胡桃楸〉槭树〉榆树〉水曲柳〉椴树〉暴马丁香〉桦树〉花楸〉花曲柳〉色木。     

小兴安岭红松针阔混交林林分空间结构分析

用角尺度、混交度、大小比数3个空间结构参数对黑龙江省凉水自然保护区的红松针阔混交林进行分析,用Hegyi竞争指数分析种内种间竞争关系,为制定合理的森林保护措施提供依据。分析结果表明:林木分布格局为随机分布;总体来看该林分处于强度混交向极强度混交过渡的状态,单一树种聚集在一起的情况较少,大多与其它不同树种混交;各树种在林木大小分化程度上存在很大差异,针叶树种较占优势,阔叶树种则分化严重,既有占优势树种又有受压树种;林分的种内竞争大于种间竞争。     

几种防火树种的水分特性与防火性能分析

测定了山杨、大青杨等8个阔叶树种树皮和枯落物绝对含水率和相对含水率,依据含水率做了防火性能的排序,分析和评价了各树种的防火特性。结果表明,各树种枯落物的含水率由高至低的排序为山杨大青杨水曲柳胡桃楸蒙古栎黄波椤色木槭白桦;不同树种树皮含水率由高至低的排序为大青杨山杨胡桃楸水曲柳色木槭黄波椤蒙古栎白桦。     

Site Quality Evaluation for Mixed, Uneven-aged, Natural Forest Dominatedby Korean Pine in Northeast China

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Evaluation of competition and light estimation indices for predicting diameter growth in mature boreal mixed forests

A series of conventional distance-independent and distance-dependent competition indices, a highly flexible distance-dependent crowding index, and two light resource estimation indices were compared to predict individual tree diameter growth of five species of mature trees from natural-origin boreal mixed forests. The crowding index was the superior index for most species and ecosites. However, distance-independent indices, such as basal area of competing trees, were also effective. Distance-dependent light estimation indices, which estimate the fraction of seasonal photosynthetically-active radiation available to each tree, ranked intermediate to low. Determining separate competition indices for each competitor species accounted for more variation than ignoring species or classifying by ecological groups. Species’ competitive ability ranked (most competitive to least): paper birch ≈ white spruce ≈> trembling aspen > lodgepole pine > balsam poplar. Stratification by ecosite further improved model performance. However, the overall impact of competition on mature trees in these forests appears to be small.     

Growth of planted seedlings inside protective sleeves under strip openings of different widths in a post-agricultural forest

Many second growth forests have poor regeneration and in some spatial and economic context, such as post-agricultural forests, it may be beneficial to increase tree diversity. We planted seedlings of yellow birch (Betula alleghaniensis) and bur oak (Quercus macrocarpa) in strip openings of 3, 6 and 9 m width to control light. Individual mesh sleeves were used to reduce browsing pressure but they also reduced available light for seedlings: a large mesh and a small mesh sleeves were tested in each opening. Available light for seedlings ranged from 5 to 46% of full sunlight. First year growth was almost non-responsive to all treatments for both species, but birch showed strong responses during second year. Birches in the large mesh sleeve and the 9 m opening had the largest height and diameter increments, while those in the small mesh sleeve and the 3 m opening had the smallest increments. Small mesh sleeves increased the height over stem diameter ratio for both species. Treatments affected several other morphometric variables of birch but none of the oak. More time is needed to assert if bur oak can be a candidate species for enrichment planting. We recommend strip openings of 9 m width and large mesh sleeves, for protection against deer browsing, while controlling neighbouring competition, to promote artificial regeneration of hardwood species.     

采伐对柞桦林水文效应的影响

通过对柞桦林与其采伐迹地小区径流对比试验表明:柞桦林采伐后,林冠层截留功能丧失,灌草层、枯枝落叶层截留有所增大,地表径流系数增大73.3%,说明采伐对林地的产流有一定的影响;观测结果表明,柞桦林比采伐迹地产生的地表径流、壤中流少;在降水量少于50mm的情况下,柞桦林地一般不出现壤中流。     

塞罕坝地区针阔混交林空间结构特征研究

为探究塞罕坝地区针阔混交林空间结构,利用针阔混交林径级分布与空间结构相关指数对林分进行分析,结果表明:针阔混交林中阔叶树种生长速度要比针叶快,而且占优势,白桦、山杨径级比例分布趋势接近正态分布;华北落叶松、山杨,属于随机分布,分布的比较均匀,白桦、五角枫与蒙古栎分布不均匀,处于聚集分布的状态;华北落叶松、白桦与山杨处于优势地位,五角枫与蒙古栎大部分都是处于劣势地位,生长空间很小;华北落叶松、白桦、山杨混交程度不高,处于中度混交状态,五角枫与蒙古栎数量少,并且分布的较散,因此多为强度混交。     

Species-specific spatial structure,species coexistence and mortality pattern in natural,uneven-aged Scots pine (<Emphasis Type="Italic">Pinus sylvestris</Emphasis> L.)-dominated forest

Complexity of uneven-aged forests results from the heterogeneity of their structure reflected among others by the spatial pattern of their components. Forest structure is usually modified by various processes operating at different scales and time. Structure and processes are not independent, and both are important drivers of forest dynamics. The impact of natural processes on forest structure manifested in the specific spatial pattern of trees can be quantified by point pattern analysis applied to long-term repeatedly measured stem-mapped plots. Such studies are relatively scarce in the literature although they provide better insight into the mechanisms affecting forest dynamics. Our study is focused on the spatiotemporal analysis of the structure of mixed uneven-aged Scots pine-dominated forest located at the Kampinoski National Park (Poland). Univariate analysis showed that the initial pattern of all live trees was initially random and it shifted toward more uniform with forest aging. Spatial patterns of individual tree species varied from that stated for all forest community. We observed changes in spatial pattern of Scots pine and common oak from random toward more clumped (pine) or uniform (oak) pattern. In case of black alder and common birch, the initial aggregated pattern was maintained over the examined 14-year period of the forest succession. Bivariate analysis showed that the most common interspecific association between pairs of tree species was spatial segregation (pine vs. alder, alder vs. birch and oak vs. birch) followed by spatial independence (pine vs. oak and oak vs. alder). The positive association was stated only for pine and birch and only for certain spatial scales (> 5 m). Simultaneously, at small distances they showed reciprocal repulsion. Changes in spatial relationships between tree species were negligible over 14-year period of forest succession. Our results confirmed the density-dependent mortality process in the uneven-aged Scots pine-dominated forest over 14-year period of forest development. Our study showed that spatial interactions between individuals along with species-specific ecological requirements should be incorporated into realistic models of forest development, helping to manage the forest ecosystems toward their greater structural complexity.     

Forest regeneration composition and development in upland, mixed-oak forests

Advance regeneration in 52 mature mixed-oak stands was analyzed and described. Red maple (Acer rubrum L.) was the most abundant species in the study area. Among oak (Quercus) species, northern red oak (Q. rubra L.) was the most abundant within the Allegheny Plateau physiographic province, whereas chestnut oak (Q. montana L.) was the most abundant within the Ridge and Valley physiographic province. Sixteen stands, for which data are available through the fourth growing season following harvest, were used to describe stand development. Cumulative height, a composite measure of size and density, was used to describe early stand development. Black gum (Nyssa sylvatica Marsh.) and black birch (Betula lenta L.) had dramatic increases in stand density and cumulative height after overstory removal. Cumulative height of northern red oak and chestnut oak showed a faster positive response to overstory removal than red maple. Oak retained its dominance in cumulative height for at least 4 years after harvest. Red maple nevertheless remained the most abundant tree species after overstory removal. Our results suggest that the principal advantage of red maple regeneration is its ability to accumulate in large numbers prior to harvest.     

Using a retrospective dynamic competition index to reconstruct forest succession

Understanding forest dynamics and stand structures is crucial for predicting forest succession. However, many forests have been altered due to century-long land-use practices, which complicates the reconstruction of past and current successional trajectories. For a better understanding of successional processes, we suggest studying the intra- and interspecific competition among single trees across time. We introduce a tree-ring based competition index to reconstruct the competitive dynamics of individual trees over time. This new retrospective dynamic competition index combines a temporal and a spatial component by calculating the yearly ratio between the basal area increments (bai) of the neighbouring trees and the subject tree. The new index is applied to mixed Scots pine (Pinus sylvestris L.) and pubescent oak (Quercus pubescens Willd.) stands in the inner-Alpine dry-valley Valais, for which a change in species composition is hypothesised. The aim is to analyse current stand structures in terms of recent changes in the competitive interactions at the single tree level and to relate these competitive dynamics to land-use change and increasing drought due to climate change. On five plots, the positions of 456 trees were recorded and increment cores were taken to derive bai data. The individual dynamic competition index curves were aggregated in clusters, which define typical patterns of competitive dynamics in both tree species. A large percentage of the trees (87% in oak, 70% in pine) were clustered into a group of trees with constant competition at a relatively low level. However, a smaller group of pines (20%) had recently faced increasing competition. In addition, stand structure analyses indicated a change towards a higher proportion of oak. This change in the competitive ability between oak and pine was found to be related to drought, in that oak had a competitive advantage in dry years. Furthermore, the high proportion of dead branches in pines with decreasing competitive abilities indicated increasing competition for light as a consequence of natural development towards a later successional stage that favours the more shade-tolerant oak. The new retrospective dynamic competition index proved to be promising in studying forest succession. The tree-ring based method allows us to identify changes in the competitive ability of single trees with a high temporal resolution and without repeated assessments.     

Effect of spacing on growth and quality parameters in sessile oak (Quercus petraea) stands in central Poland: results 7 years after planting

We examined the growth and quality of young oaks in stands established at three different spacings. The three densities were the traditional level, that is, 8000?seedlings?ha^?1 (1.5?×?0.85?m) plus two where the initial density was decreased by 50% and 70%, achieved by increasing the distance between the rows from 1.5 to 3 or 4.5?m. The experiment was located in central Poland on a moderately fertile site. In the two wider spacings, the intention was to use natural regeneration occurring between oak rows as a replacement of intraspecific competition for oaks. The mean height was only affected in the third and the fourth year after establishment. Subsequently, the differences between spacings with respect to both growth and quality traits were insignificant and small. At lower densities, natural regeneration of willow and aspen was abundant and inter-species competition replaced intra-species competition, thus explaining the absence of a spacing effect on growth and quality properties. In the study period, the wider spacings were economically beneficial compared to traditional densities. A strong competition affecting height growth caused by natural regeneration necessitated extensive tendings. More tendings are likely to be needed in the future and they might reduce the initial economical superiority of wider spacing. The study indicates that it is possible to decrease the initial spacing in oak plantations and simultaneously support good growing conditions by means of natural processes, for example, natural regeneration. However, economic efficiency of the method has to be studied in a longer perspective.     

Structure of pollarded oak forest in relation to aspect in Northern Zagros,Iran

We analyzed the structure of pollarded oak forest and biometric indices of pollarded oak species in relation to aspect in northern Zagros forests, western Iran. A number of 319 circular plots (0.1 ha) were established using a systematic random method over the study area. In each plot, for all trees (diameter at breast height ≥5 cm) diameter was measured and tree species was recorded. Total height, trunk height, and major and minor diameter axis of the crown of two trees in each plot (nearest tree to the center of the plot and the largest tree in term of diameter) were measured. As the dispersion of slope and altitude classes in the study area were identical, the effect of these factors was assumed to be constant. To evaluate the effect of aspect on biometric indices of oak trees a comparison was used for each oak species separately. The results indicated that the forest species composition differed statistically significant in main aspects except for easterly and westerly aspects (P < 0.01). The diameter of similar oak trees was significantly different except for Lebanon oak in northerly and southerly and Gall oak in easterly and westerly aspects (P < 0.01), but there was no significant difference between the total height and crown area of similar oak species in different aspects. Differences in diameter, height, and crown area distributions showed a significant difference in main aspects. The basal area and tree density in northerly and southerly aspects were significantly different (P < 0.05).