辽东山区落叶松林近自然化改造短期效果分析

在辽宁清原县选择25年生落叶松人工林进行近自然化改造,以不间伐林分作为对照,研究近自然化改造对林分生长和林下草本层植物多样性的影响。结果表明:间伐1年后,间伐林分平均胸径和林分材积生长量及生长率均高于对照,差异显著(p0.05)。在间伐林分中,目标树的胸径生长量显著高于一般林木的胸径生长量。近自然化改造显著地提高了林下草本层植物多样性,间伐林分林下草本层丰富度指数和Shannon-Wiener多样性指数高于对照。因此,近自然化改造促进了人工落叶松林的林分生长,提高了林下草本层植物多样性,有利于目标树的持续快速生长。今后经营落叶松中龄人工林时,应多关注目标树的生长。     

徐州市侧柏人工林的群落结构特征

依据群落学的调查资料,利用TWINSPAN分类法对徐州市近50年生的34个侧柏人工林群落进行了分类;并运用频度、重要值和径级分析法,分析群落的树种组成和径级结构,探讨人工林的自然化发展趋势和近自然化改造途径。结果表明:现有侧柏人工林内已不同程度地侵入了一些阔叶树种,表现出了自然化的发展趋势;不同的立地条件下侧柏人工林的自然化发展速度不同;现有人工林内各树种的径级分布均有间断,树种自身的天然更新困难。侧柏人工林的近自然化改造应重视对林冠下侧柏及其它阔叶树种的培育,按照"侧柏人工林→针阔混交林→阔叶林"的模式,因地制宜地分阶段进行。     

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。     

古永林区云南松采伐跡地的天然更新

云南松是我省的主要用材树种之一。目前我省采伐利用的森林资源也大部份是云南松。随着我国社会主义建设事业的发展,对木材需要量的增长,采伐迹地逐年扩大,因而对云南松迹地更新问题已引起了生产单位和科研部门的重视,曾进行过不少调查研究工作。为此,我们在腾冲县     

学术活动

中国林学会云南省分会举行云南松采伐更新学术讨论会 1965年10月11日至18日,中国林学会云南省分会在昆明召开了“云南松采伐更新学术讨论会”。出席这次会议的代表共52人,包括云南省林业厅,云南省云南松主要分布地区的林业局、林场,云南省林业科学研究及教学部门,广西、四川、贵州三省(区)的科研教学单位,以及林业部和     

海南省岛东林场木麻黄退化人工林补植模式研究

以海南省岛东林场木麻黄退化人工林补植乡土树种和珍贵树种为研究对象,提出近自然化改造经营模式。在岛东林场木麻黄林下补植乡土树种和珍贵树种的3种改造模式进行比较。结果表明,以模式2林木生长的效果较好,能够有效地改善林分的水平和垂直结构,调节林冠下光环境,增大林冠下散射光比例,为下层植被生长提供有效光照条件;增加树种多样性和森林的近自然程度,为退化森林恢复经营提供模式和范例。     

云南松林试行采伐方式的建议

一、决定云南松林采伐方式的根据森林的采伐方式,一方面与林区的营林方向、主要树种的更新有关,另一方面与木材生产及水土保持有密切的关系。在权衡各方面的关系的基础上才能决定森林的采伐方式。1.云南松的更新情况及其与采伐方式的关系云南松是一个容易更新的树种。而天     

兴安落叶松林天然更新苗生长观察一例

利用兴安落叶松幼苗解析木资料,对原始兴安落叶松在林冠下、采伐道、次生裸地进行苗木生长分析。调查后表明,采伐道上天然更新落叶松苗生长发育最好,次生裸地次之,林冠下最差。     

山西省关帝林局双家寨林场华北落叶松近自然采伐技术

笔者介绍了山西省关帝林局双家寨林场概况,根据树种组成,将采伐对象划分为华北落叶松纯林、轻度混交的华北落叶松林和华北落叶松混交林。根据不同类型的华北落叶松林分,制定了不同的采伐策略,确定采伐目标树种、采伐株数和强度。采伐后,林分结构趋于合理,混交比例适宜,林冠透光性明显提高,林下光照充足,有利于林下更新和植被多样性保护。     

云南松天然更新调查报告

一、调查的目的及地区调查的目的是了解云南松天然更新与环境条件的关系,及过去执行的各种采伐方式和更新措施对云南松天然更新的影响,为制定云南松采伐方式和更新措施提供依据。调查地区有:拉祜林区的仁和和长箐林场;楚雄林区的新村林场和南盘江林区的一场和五场。这些地方大体上代表了云南省云南松主要分布区的情况。拉祜林区在云南省北部金沙江中游,是海拔高度1000—2500米的中山。山体由花岗岩(仁和)及砂岩(长箐)构成。山     

长白山林区次生阔叶林冠下红松人工更新与培育技术

通过对长白山林区林隙环境、林隙对红松生长的影响及肛伐强度对阔叶树生长、红松更新的研究,为科学地确定上红松更佳的最佳上层郁闭度,提高林分生长量,确定红松采伐年龄,促进天然林保护工程的发展提供科学的依据和技术。     

Comparison of stand dynamics after dieback caused by pine wilt disease among pine forests with different management regimes in western Japan

In pine forests damaged by pine wilt disease, in western Japan, the effect of protection regimes of pine trees on the stand dynamics were examined in the following four stands: (1) lightly damaged stand (age 30–40 years) with no procedure in operation for protecting pine trees; (2) severely damaged stand (age 30–40 years) with no procedure in place for protecting pine trees; (3) severely damaged stand (age 50 years) with a selective cutting of infected trees; (4) severely damaged stand (age 30–40 years) with a selective cutting of infected trees. All the stands had been abandoned before the pine wilt disease damage. The understory structure of the severely damaged stand with no protection procedure was similar to that of the lightly damaged stand. Frequent invasion by tree species and acceleration in the growth of understory trees occurred after the dieback in the selective cutting stand. These results suggest that a deficiency in the canopy layer caused by the dieback resulted in low disturbance intensity in the early stages after the dieback, but the selective cutting increased the intensity by the reduction in the understory as well as the canopy layer. The intensity of the disturbance in the selective cutting stands was larger in the younger stand because it had a higher density of selectively cut pine trees. The different stand structure of pine forests occurred after the dieback because the intensity of the disturbance varied as a result of the selective cutting operation and the stand age.     

Restoring longleaf pine (Pinus palustris Mill.) in loblolly pine (Pinus taeda L.) stands: Effects of restoration treatments on natural loblolly pine regeneration

Historical land use and management practices in the southeastern United States have resulted in the dominance of loblolly pine (Pinus taeda L.) on many upland sites that historically were occupied by longleaf pine (Pinus palustris Mill.). There is currently much interest in restoring high quality longleaf pine habitats to such areas, but managers may also desire the retention of some existing canopy trees to meet current conservation objectives. However, fast-growing natural loblolly pine regeneration may threaten the success of artificially regenerated longleaf pine seedlings. We evaluated the establishment and growth of natural loblolly pine regeneration following different levels of timber harvest using single-tree selection (Control (uncut, residual basal area ∼16 m²/ha), MedBA (residual basal area of ∼9 m²/ha), LowBA (residual basal area of ∼6 m²/ha), and Clearcut (complete canopy removal)) and to different positions within canopy gaps (approximately 2800 m²) created by patch cutting at two ecologically distinct sites within the longleaf pine range: Fort Benning, GA in the Middle Coastal Plain and Camp Lejeune, NC in the Lower Coastal Plain. The density of loblolly pine seedlings was much higher at Camp Lejeune than at Fort Benning at the end of the first growing season after harvesting. Following two growing seasons, there were no significant effects of canopy density or gap position on the density of loblolly pine seedlings at either site, but loblolly pine seedlings were taller on treatments with greater canopy removal. Prescribed fires applied following the second growing season killed 70.6% of loblolly pine seedlings at Fort Benning and 64.3% of seedlings at Camp Lejeune. Loblolly pine seedlings were generally less than 2 m tall, and completeness of the prescribed burns appeared more important for determining seedling survival than seedling size. Silvicultural treatments that include canopy removal, such as patch cutting or clearcuts, will increase loblolly pine seedling growth and shorten the window of opportunity for control with prescribed fire. Therefore, application of prescribed fire every 2-3 years will be critical for control of loblolly pine regeneration during restoration of longleaf pine in existing loblolly pine stands.     

不同间伐强度对人工阔叶红松林生长的影响

文章针对不同间伐强度对人工阔叶红松林生长的影响进行了调查研究。结果表明:阔叶树胸径生长和蓄积增长率随间伐强度加大而增加,但对树高的影响较小;间伐强度的增大会明显促进红松胸径和树高的生长,但是首次抚育间伐会使当年的树高生长量显著降低,以后随林龄的增加树高生长量会逐渐恢复正常生长;中度间伐措施对阔叶树和红松的生长均比较有利,10a生的阔叶红松林实施上层抚育的适宜间伐强度为45%左右;中度间伐的林分由于资源水平适中(主要是光资源),因而有利于林下植被均匀度和多样性的提高。     

天然林冠下红松被压木极限生长形态学指标的研究

通过研究１００株原始红松林内树高小于１４ｍ的红松解析木，分析了林下红松生长类型，林下红松生长与上层结构因子的关系，林下红松的形态特征及生理特性，结果表明，林下红松生长可划分为恒定型、下降型和上升型。被自然淘汰的林下红松皆属于恒定型和下降型。林下红松的生长受上层林冠结构因子的制约，没有合适的结构条件，林下红松很难存活。研究得出了天然林冠下红松被压木能够上升到上层林冠所需胸径、树高、树冠面积、边材宽、冠长／树高等形态学指标的最低极限值。     

Multipurpose conversion management of Scots pine towards mixed oak–birch stands—A long-term simulation approach

The forest growth model 4C was used to investigate how conversion management of a Scots pine (Pinus sylvestris L.) stand towards a mixed oak–birch stand would affect stand structural development – and hence biodiversity and productivity – in the long term. For this purpose the 4C model was parameterised for natural regeneration of light demanding species and extended for management of multi-layered stands. A series of structural indicators was selected to describe key factors of forest biodiversity at the stand scale. Two consecutive aspects of Scots pine conversion were tested: (1) the choice of conversion strategy between thinning and gap creation and (2) the choice of conversion regime in terms of cutting cycle, thinning type and pine tree retention. Three simulated conversion strategies aim at the gradual removal of the pine canopy but differ in the spatial organisation of pine cuttings and hence result in different light conditions for regeneration. Only the directed gap creation strategy was able to maintain and increase birch admixture to the stand and to approach natural stand structural development. Simulation of 12 conversion regimes for the directed gap creation strategy indicated that thinning type (from above or from below), pine tree retention at final felling (50% of the standing volume or none) and cutting cycle (6, 9 or 12 years) all significantly influence stand structural development. These effects were clearest for oak development. Birch occurred in a few mixed clusters, but tended to disappear when longer cutting cycles were used. Based on a multi-criteria analysis we conclude that the optimal conversion regime – in which both stand productivity and biodiversity objectives can be combined – implies thinning from above, pine tree retention, and cutting cycles of 6 years. The conceptual validity of the model as well as the applicability of the results are discussed.     

Photosynthetic utilization efficiency of absorbed photosynthetically active radiation by Scots pine and birch forest stands in the southern Taiga

Absorption and utilization of photosynthetically active radiation (PAR) were investigated in Scots pine (Pinus sylvestris L.) and birch (Betula pendula Roth.) stands that were 41 years old at the end of the experimental period. Canopy depth of the Scots pine stand was about half that of the birch stand (6.5 versus 11.0 m), but absorption of PAR was similar in the two stands. The Scots pine forest canopy, with a leaf area index of 8.9, absorbed 90% of the incoming PAR (APAR), whereas the birch forest canopy, with a leaf area index of 5.9, absorbed 92% of APAR. During maximum foliage development, the upper Scots pine canopy absorbed more PAR than the upper birch canopy (75 versus 66%). The upper, middle and lower layers of the Scots pine canopy contained 37, 48 and 15% of the total needle surface area, respectively. The corresponding distribution of foliage surface area in the three layers of the birch canopy was 50, 30 and 20%, respectively. Measurements of photosynthetic rate were combined with estimates of leaf area index and stand phytomass to determine rates of primary production on a sunny day, a cloudy day, and on an annual basis. The energy equivalents of short- and long-term carbon gain were used with determinations of APAR to calculate photosynthetic utilization efficiency. Throughout the growing season, photosynthetic utilization efficiency of APAR in the upper canopy layer of the Scots pine forest was almost twice that in the lower canopy layer. In the birch forest, photosynthetic utilization efficiency was greater in the lower canopy layer than in the upper canopy layer. In all cases, utilization efficiency was higher in the birch stand than in the Scots pine stand (52 versus 29 J kJ(-1)). Taking account of respiration of the non-photosynthetic parts of each stand (night respiration of needles or leaves; respiration of branches, trunk and roots), estimated utilization efficiency of APAR for net primary production was 11 J kJ(-1) for Scots pine and 19 J kJ(-1) for birch. Solar conversion ratios, expressed as whole-plant net primary productivity per unit of APAR for the growing season, were 0.81 g MJ(-1) for Scots pine and 0.93 g MJ(-1) for birch.     

Effects of thinning and canopy type on growth dynamics of Pinus sylvestris: inter-annual variations and intra-annual interactions with microclimate

We assessed the effects of thinning (0, 20 and 30 % extraction of basal area) and canopy type (pine–beech vs. pine plots, beech accounting for 12 % of total basal area) on radial growth of dominant and codominant Scots pine at inter-annual scale and on microclimatic conditions, radial growth and xylogenesis 9 years after thinning at intra-annual scale. Thinning weakly affected pine growth, which was enhanced 3 years after harvesting. Over time, a gradual reduction in pine growth in mixed canopy relative to pure canopy occurred only in unthinned plots apparently due to beech expansion. Indeed, 9 years after thinning, a higher seasonal radial increment and a greater number of tracheids were produced under pine canopy in the unthinned plots, whereas no differences between canopy types were observed in the thinned plots. Radial increment and tracheid production were mainly affected by tree water status (air and soil humidity, throughfall). The differences of tree water status caused by treatments, and plausibly disparities in tree size and tree-to-tree competition, were the main drivers explaining the patterns observed for radial increment and xylogenesis. Our results suggest that the negative effects of beech competition on Scots pine growth in similar mixed forest may be controlled to some extent by thinning.     

Canopy cover effects on mass loss, and nitrogen and phosphorus dynamics from decomposing litter in oak and pine stands in northern Lower Michigan

Patterns of litter decomposition and nitrogen (N) and phosphorus (P) release in relation to various levels of canopy cover were examined using litterbags placed on the forest floor of northern red oak (Quercus rubra L.) and red pine (Pinus resinosa Ait.) stands in northern Lower Michigan, USA. A series of experimental plots consisted of four levels of canopy cover treatments, i.e. clearcut, 25% (50% during first sampling year), 75%, and uncut. Mass loss from decomposing leaves was higher for oak leaves in red oak stands (approximately 60% loss of the original mass) than for pine needles in red pine stands (approximately 40% loss of the original mass) during the 2 year study period. Leaf mass loss in the clearcut red oak treatment was significantly higher than in the uncut red oak treatment. In contrast, no canopy cover effects on litter mass loss were found in red pine stands. Nitrogen concentrations in decomposing litter increased during the 2 year period in all canopy cover treatments in both stand types, but they did not differ significantly among canopy cover treatments. These results indicate that various levels of red oak and red pine canopy removal generally have a minor impact on litter decomposition and nutrient (N and P) release during the first 2 years following canopy manipulation, except in red oak clearcuts.     

Inter-specific competition and management modify the morphology, nutrient content and resorption in Scots pine needles

Influence of tree-to-tree competition on nutrient resorption is still not well understood. To contribute filling this gap, we assessed the effects of thinning (0, 20 and 30 % extraction of basal area) and canopy type (beech–pine vs. pine subplots) on needle dry weight, needle length, nutrient content and nutrient resorption (N, P and K) in Scots pine (Pinus sylvestris) needles of different cohorts, 8–9 years after thinning. Thinning and canopy type often concurrently affected needle morphology (e.g. lighter and shorter needles in 30 % thinning, heavier and longer needles in pine canopy on the first year of study) and nutrient content (e.g. decrease in N, P and K in 30 %; N, P and K higher in pine canopy on the first year of study). However, effects of thinning appeared only in older cohorts for N and P but were found in old and new cohorts for needle dry weight, needle length and K, indicating that some thinning effects remained after 8–9 years. Canopy effects on morphology and nutrient content were more frequent in recent cohorts, in relation to an increase in beech cover over time. While no clear effects of thinning on the nutrient resorption were observed, higher values were observed in the pine than in the mixed canopy, which could be related to a higher Scots pine stem growth in those patches. The observed differences between treatments will likely increase as the stand develops, probably leading to beech trees being dominant, and as future thinnings are carried out.