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1.
Tree regeneration and future stand development after bark beetle infestation and harvesting in Colorado lodgepole pine stands 总被引：1，自引：0，他引：1
Byron J. CollinsCharles C. Rhoades Robert M. HubbardMichael A. Battaglia 《Forest Ecology and Management》2011,261(11):2168-2175
In the southern Rocky Mountains, current mountain pine beetle (Dendroctonus ponderosae Hopkins) outbreaks and associated harvesting have set millions of hectares of lodgepole pine (Pinus contorta var. latifolia Engelm. ex Wats.) forest onto new stand development trajectories. Information about immediate, post-disturbance tree regeneration will provide insight on dynamics of future stand composition and structure. We compared tree regeneration in eight paired harvested and untreated lodgepole pine stands in the Fraser Experimental Forest that experienced more than 70% overstory mortality due to beetles. New seedlings colonized both harvested and untreated stands in the first years after the beetle outbreak. In harvested areas the density of new seedlings, predominantly lodgepole pine and aspen, was four times higher than in untreated stands. Annual height growth of pine and fir advance regeneration (e.g., trees established prior to the onset of the outbreak) has doubled following overstory mortality in untreated stands. Growth simulations based on our regeneration data suggest that stand basal area and stem density will return to pre-beetle levels in untreated and harvested stands within 80-105 years. Furthermore, lodgepole pine will remain the dominant species in harvested stands over the next century, but subalpine fir will become the most abundant species in untreated areas. Owing to terrain, economic and administrative limitations, active management will treat a small fraction (<15%) of the forests killed by pine beetle. Our findings suggest that the long-term consequences of the outbreak will be most dramatic in untreated forests where the shift in tree species composition will influence timber and water production, wildfire behavior, wildlife habitat and other forest attributes. 相似文献
2.
福建柏、杉木及其混交林生长与生态效应研究 总被引：66，自引：1，他引：66
本文从林分生长、空间分布格局、生物量及其与生态环境的相互作用等方面对14年生福建柏、杉木纯林及其混交林作了对比研究。结果表明,在南方丘陵营造福建柏、杉木混交林有利于维护地力和形成稳定的人工林生态系统,在经济、生态和美学方面均优于杉木纯林。混交林生物量比杉木、福建柏纯林高22.9％和4.7％,达79.58 t/ha,福建柏纯林比杉木纯林高17.4％。补植福建柏是改造杉木中低产林的有效措施之一。 相似文献
3.
This study examined topsoil samples from the humic mineral horizon in four pure silver fir (Abies alba Mill.) and five mixed stands with beech (Fagus sylvatica L.), spruce (Picea abies L.; Karst.) and pine (Pinus sylvestris L.). In every stand, 60–70 sampling locations were chosen using a stratified random scheme that represented a gradient in local stand density and local species composition. One working hypothesis was that stand density and species composition affect the content of nutrients in the mineral humic soil horizon. Specifically, the analysis statistically tested for relationships between general and species-specific local stand density measures (basal area, sum of tree diameters weighted by distance, canopy openness) and the contents of total C, total N (in four stands), base cations (Ca2+, Mg2+, K+, Na+) and Mn2+ (in nine stands). A considerable variation in nutrient concentrations was observed; the coefficients of variation ranged from 0.21 to 0.38 for N, from 0.20 to 0.94 for the sum of base cations and from 0.56 to 0.95 for Mn. However, no clear relationship emerged between local stand density and the concentration of N and base cations; in five stands, manganese showed a negative correlation with local stand density. In the mixed fir-beech stand, significantly higher concentrations of Ca, K and Mn were found in the vicinity of beeches, and species-specific stand density explained up to 15, 29 and 34% of total variation in the content of these elements, respectively. Similar tendencies also appeared in the mixed stands with pine, although the relationships were weak. The results obtained for two fir-spruce stands were ambiguous. In sum, in the stands studied, small canopy gaps and inter-crown openings might not be considered ‘‘nutrient hot spots’’, and the admixed species, except for beech, had an insignificant effect on nutrient content in the humic mineral horizon. 相似文献
4.
对竹林及其它6种林分在鸟类生存活动空间中的地位进行比较研究,结果表明:在鸟类种类和数量上,竹林与其它类型林分间无显著差异;各乡镇间,鸟类种类和数量的分布均比较均衡。 相似文献
5.
选择福建省建阳范桥国有林场16年生杉木×闽粤栲混交林与杉木纯林为研究对象,对不同坡位不同林分养分积累量进行分析对比。结果表明:上坡立地条件下,杉木纯林乔木层N、P、K养分积累量均大于杉木×闽粤栲混交林。中坡和下坡林分乔木层养分积累量则表现为混交林大于杉木纯林。不同林分乔木层养分积累量均占整个林分养分积累总量的90%以上,且表现为N>K>P和下坡>中坡>上坡。上坡杉木纯林的灌木层和草本层N、P积累量均大于混交林,下坡林分的灌木层N、P、K养分积累量均表现为杉木×闽粤栲混交林大于杉木纯林。不同林分凋落物的N和P的积累量均大大超过草本层和灌木层的积累量。 相似文献
6.
《Forest Ecology and Management》2005,219(1):29-42
The influence of stand composition and age on forest floor chemical properties, nitrogen availability, and microbial activity was examined in mixed and pure stands of Douglas-fir (Pseudotsuga menziesii) and paper birch (Betula papyrifera). Decomposition of Douglas-fir and birch litter over two years as well as annual litter input was also measured. Mixed and pure stands of each species aged 10–25, 50–65 and >85 years old were selected in the Interior Cedar Hemlock (ICH) zone of southern interior British Columbia. Significantly more total N was mineralized in the forest floor of pure birch compare to that of pure Douglas-fir stands while forest floor of mixed species stands had intermediate N mineralization values. When sampling times were pooled forest floor N mineralization was lowest in the young stands compared to the older stands. Stand composition did not significantly affect litter decomposition were found in litter decomposition, microbial respiration and biomass. Stand age, however, did affect these parameters significantly. More birch litter mass was lost in young stands than in their older counterparts while the opposite trend was observed for fir litter. Generally, lower basal respiration, microbial biomass and Cmic/Corg was found in young compared to older stands. Concentrations and contents of forest floor total N and exchangeable K and Mg, and pH under pure birch were consistently higher compared to pure Douglas-fir. While forest floor total C, available P contents, exchangeable K and Mg concentrations were lowest in young stands, no differences were observed for total N and exchangeable Ca. All litter nutrient concentrations and contents were highest in pure birch stands. No clear trends could be discerned in litter nutrient concentration data among stand ages, although when converted to nutrient contents, there was a general increase with stand age. Both stand type and age had significant effects on forest floor properties and processes suggesting that stand age is another factor to evaluate when assessing the influence of forest composition on forest floor processes and chemistry. In terms of the effect of mixture, the data indicated that the maintenance of paper birch in mixed stands in these forest may have some effect on nutrient availability and status. 相似文献
7.
Many boreal tree stands are neither clearly even-aged nor clearly uneven-aged. The stands may undergo a series of stages, during which an even-aged stand is transformed into two-storied mixed stand, and finally to multistoried or uneven-aged stand structure. The species composition often changes during the succession of stand stages. This study developed models for stand dynamics that can be used in different stand structures and species compositions. The model set consists of species-specific individual-tree diameter increment and survival models, and models for ingrowth. Separate models were developed for Scots pine, Norway spruce, and hardwood species. The models were used in a growth simulator, to give illustrative examples on species influences and stand dynamics. Methods to simulate residual variation around diameter increment and ingrowth models are also presented. The results suggest that mixed stands are more productive than one-species stands. Spruce in particular benefits from an admixture of other species. Mixed species improve diameter increment, decrease mortality, and increase ingrowth. Pine is a more beneficial admixture than birch. Simulations showed that uneven-aged management of spruce forests is sustainable and productive, and even-aged conifer stands growing on medium sites can be converted into uneven-aged mixed stands by a series of strong high thinnings. 相似文献
8.
To test the direct regeneration hypothesis and support natural disturbance-based forest management we characterized the structure and composition of boreal mixedwood forests regenerating after large wildfires and examined the influence of pre-fire stand composition and post-fire competing vegetation. In stands which had been deciduous (Populus sp.)-dominated, conifer (white spruce)-dominated, or mixed pre-fire we measured regeneration stocking (presence in 10 m2 plots), density and height 10–20 years post-burn in five wildfires in Alberta, Canada. Most plots regenerated to the deciduous or mixed stocking types; plots in the older fire and in stands that were pure conifer pre-fire had higher amounts of conifer regeneration. Surprisingly, regeneration in pre-fire ‘pure’ white spruce stands was most often to pine, although these had not been recorded in the pre-fire inventory. Pre-fire deciduous stands were the most resilient in that poplar species dominated their post-fire regeneration in terms of stocking, density and height. These stands also had the highest diversity of regenerating tree species and the most unstocked plots. High grass cover negatively affected regeneration density of both deciduous and conifer trees. Our results demonstrate the natural occurrence of regeneration gaps, pre- to post-fire changes in forest composition, and high variation in post-fire regeneration composition. These should be taken into consideration when developing goals for post-harvest regeneration mimicking natural disturbance. 相似文献
9.
《Forest Ecology and Management》1988,25(2):123-138
This study describes and compares (i) the diameter distribution of black spruce (Picea mariana (Mill.) B.S.P.) and balsam fir (Abies balsamea (L.) Mill.) within mixed black-spruce/balsam-fir stands, and (ii) the diamter distribution of black spruce within pure stands, at various stages of stand development. Employing relative-frequency diameter-class data from 128 0.081-ha semi-permanent sample plots located in natural mixed (57 plots) and pure (71 plots) stand types of central insular Newfoundland, 1st, 2nd, 3rd and 4th-order polynomial functions were used to describe stand structure at various species heights. The Chi-square statistic was used to compare distributions within and between stand types by height class. Results indicated that both species within mixed stands, and black spruce within both stand types, had similar distribution trends, i.e., initially reverse J-shaped or positively-skewed unimodal distributions progressing to a semi-bimodal or positively skewed mound-shaped distribution. Black spruce occupied a slightly greater proportion of the larger diameter classes, whereas balsam fir occupied a slightly greater proportion of the smaller diameter classes, indicating a semi-stratified structure. 相似文献
10.
Hedi Kebli Gavin Kernaghan Pascal Drouin Suzanne Brais 《European Journal of Forest Research》2014,133(5):905-918
Limited scientific information is currently available regarding saproxylic fungal communities in the boreal forest of North America. We aimed to characterize the community development, richness and activity of saproxylic fungi on fresh wood in harvested and unmanaged boreal mixedwood stands of northwestern Québec (Canada). Fresh wood blocks (n = 480) of balsam fir (Abies balsamea (L.) Mill.) and trembling aspen (Populus tremuloides Michx.) were placed on the forest floor in a range of stand conditions (n = 24). Blocks were harvested every 6 months for up to 30 months and characterized for species composition and richness (PCR–DGGE, DNA sequencing), respiration, wood density and lignin and cellulose content. Colonization by a wide range of functional groups proceeded rapidly under different stand conditions. We detected a total of 35 different fungal operational taxonomic units, with the highest species richness at the wood block level being observed within the first 12 months. No differences in community composition were found between wood host species or among stand conditions. However, the variability in fungal communities among blocks (β diversity) was lower on trembling aspen wood compared with balsam fir and decreased over time on trembling aspen wood. Also, fungal activity (respiration and wood decomposition) increased on trembling aspen wood blocks and species richness decreased on balsam fir wood over time in partial-cut sites. The overlap in tree composition among stands, the high volume of logs and the recent management history of these stands may have contributed to the similarity of the saproxylic fungal community among stand types and disturbances. 相似文献
11.
Understory plants are important components of forests because they are responsible for the majority of the vascular plant diversity of forest ecosystems. The richness and composition of understory communities are closely related to the tree layer diversity, structure and composition. The aim of this study was to examine the understory diversity of Anatolian black pine (Pinus nigra Arnold subsp. pallasiana (Lamb.) Holmboe)-dominated forests on the Kazda?? Mountains of West Turkey. To describe the overstory structure and composition in a numerically and quantitatively well-defined manner, cumulative abundance profiles (CAPs) of the tree species were used. The resemblance of the sampling plots was classified into five stand types assessing the CAP through the Fuzzy C-Means clustering method. A permutational multivariate analysis of variance (PERMANOVA) was performed to test the variance of the community ecological distance between the five stand types, and the results showed significant differences in these clusters. Many shade-tolerant plants were associated with the mixed stands of Anatolian black pine–Kazda?? fir. The composition of the herb and shrub layer could not be explained by the environmental variables but by differences in the overstory structure of the stands. Pure or nearly pure Anatolian Black pine stands were more diverse than mixed oak–Anatolian black pine and Kazda?? fir–Anatolian black pine stands. However, although dense and young pure Anatolian black pine stands had the most diverse plant species in the shrub layer, they were ranked third in terms of the herb layer diversity. The Anatolian black pine–Kazda?? fir mixed stands had the lowest herb and shrub layer diversity. These results allow us to comprehend the relationship between the overstory structure and composition, and the understory diversity. Understanding this relationship is important for the conservation of understory plant diversity in the management of forest ecosystems. 相似文献
12.
Tree plantations can be an important tool for restoration of abandoned pasturelands in the tropics. Plantations can help speed up secondary forest succession by improving soil conditions, attracting seed-dispersal agents, and providing shade necessary for understory growth. In this study, abundance and richness of understory regeneration was measured in three native tree plantations 15–16 years of age at La Selva Biological Station in the Costa Rican Caribbean lowlands. Each plantation contained tree species in pure plots, a mixture of the species, and natural regeneration plots (no trees planted). The greatest abundance of regeneration was found in the understory of pure plots of Jacaranda copaia (Aubl.) D.Don., Vochysia guatemalensis Donn.Sm., Dipteryx panamensis Benth, Vochysia ferruginea Mart., and in two mixed stands, while the lowest was found in the natural regeneration treatments with about half the values as in the plantation stands. There was a significant negative correlation between percent canopy openness and abundance of regeneration in the understory. Two distinctive clusters separated the regeneration treatments from the mixed and pure plantations at a very low Bray–Curtis similarity value. The natural regeneration treatments are separated from mixed and pure plantations in the two-dimensional ordination. The lack of difference between the understory make-up of pure and mixed plantations in abundance, species richness, and seed-dispersal syndromes of understory species suggests that planting mixed stands is not necessarily superior to planting pure stands for promoting understory diversity of woody species. While regeneration of woody species can be faster under pure- or mixed-species plantations than in open pastures, the abundance, richness and species composition depends on each plantation species, or species assemblages in case of the mixtures. 相似文献
13.
Growth of regenerating trees in different light environments was studied for the mountainous, mixed-species forests in the Carpathian Mountains of Romania. The primary species in these mixtures were silver fir (Abies alba Mill.), European beech (Fagus sylvatica L.) and Norway spruce (Picea abies (L.) Karst). Seedlings/saplings of these species were selected and measured in different stands from two different geographical locations. Regenerating trees were measured for height and diameter growth during the summer of 2002. For each seedling/sapling, percentage of above canopy light (PACL) and stand basal area (BA) were used to assess available and occupied growing space respectively. Regeneration growth was compared against these two variables and regression relationships were developed. Using these models, we predicted the dynamics of regeneration as both growth and species composition. Our results showed that in low-light environments (PACL<20–35%; BA>30 m2/ha), shade tolerant fir and beech clearly outcompeted the spruce. Therefore, in dense stands, spruce could be eliminated by the shade tolerant species. For intermediate levels of cover (PACL=35–70%; BA=15–35 m2/ha) the spruce grew at comparable rates as the beech and fir. All three species showed similar growth rates in open conditions (PACL>80–90%; BA<15–20 m2/ha) with the spruce having a tendency to outgrow the others. However, in terms of establishment, such conditions favor spruce and inhibit fir and beech. 相似文献
14.
《Forest Ecology and Management》2002,159(3):173-186
The effects of partial cutting on species composition, new and residual-tree cohorts, tree size distribution, and tree growth was evaluated on 73 plots in 18 stands throughout southeast Alaska. These partially cut stands were harvested 12–96 years ago, when 16–96% of the former stand basal area was removed.Partial cutting maintained stand structures similar to uncut old-growth stands, and the cutting had no significant effects on tree species composition. The establishment of new-tree cohorts was positively related to the proportion of basal-area cut. The current stand basal area, tree species composition, and stand growth were significantly related to trees left after harvest (p<0.001). Trees that were 20–80 cm dbh at the time of cutting had the greatest tree-diameter and basal-area growth and contributed the most to stand growth. Diameter growth of Sitka spruce and western hemlock was similar, and the proportion of stand basal-area growth between species was consistent for different cutting intensities.Concerns about changing tree species composition, lack of spruce regeneration, and greatly reduced stand growth and vigor with partial cuts were largely unsubstantiated. Silvicultural systems based on partial cutting can provide rapidly growing trees for timber production while maintaining complex stand structures with mixtures of spruce and hemlock trees similar to old-growth stands. 相似文献
15.
以福建省顺昌县的杉木纯林、毛竹纯林、杉木马尾松混交林、杉木阔叶混交林、阔叶林等5块样地为对象,从结构性、功能性和抗干扰性等3个方面出发,筛选出15个指标,并利用主成分分析（PCA）实现了研究区森林健康评价。结果显示：福建省顺昌县杉木纯林、毛竹纯林、杉木马尾松混交林、杉木阔叶混交林、阔叶林等5块样地的森林健康综合指数值依次为-0．27、-0．25、0．35、0．53和-0．01,从优到次的排名为：杉木阔叶混交林、杉木马尾松混交林、阔叶林、毛竹纯林、杉木纯林。 相似文献
16.
6种杉阔混交林造林效果的调查研究 总被引：2，自引：0，他引：2
对6种杉阔混交林的调查研究结果表明:6种混交林均取得良好混交效果,促进了杉木树高、直径生长,提高了林分蓄积量,混交林分蓄积量比杉木纯林大4.3%~27.9%.鄂西红豆树、红锥、格氏栲在速生杉木的促进和竞争下,顶端优势明显,分叉少,干形通直,可培育大径材.观光木、乳源木莲分别与杉木混交,种间关系协调,生长稳定.杉檫混交林有利于檫树生长稳定,培育大径材,但应对檫树混交比例加以控制,不宜过大.6种阔叶树均为杉木优良的伴生树种,可大力推广. 相似文献
17.
Matija Klopcic Klemen Jerina Andrej Boncina 《European Journal of Forest Research》2010,129(3):277-288
Uneven-aged silver fir-European beech forest stands were studied to (1) analyse the dynamics of diameter structure and tree
species composition in the past two centuries and (2) determine the impact of red deer on the regeneration and recruitment
of silver fir. The study used current data on forest stands, archival data from old forest management plans for the period
1789–2004, and red deer harvesting records for the period 1907–2006. During the observation period, the silver fir population
aged and silver fir and European beech alternated in dominance. The study revealed a strong impact of red deer on the composition
and recruitment of tree regeneration, especially on silver fir regeneration. The drastic changes in red deer density (from
extermination up to 5.8 animals km−2) and past forest management practices were apparently the main factors driving the population dynamics of silver fir (regeneration,
recruitment, and diameter structure) in the study area during the past two centuries. 相似文献
18.
江西德兴天然次生林林下幼苗更新特征 总被引：1，自引：0，他引：1
为了解实生和萌生幼苗个体数量及比例在各类植被中的变化情况,本文以江西德兴常绿阔叶林不同林分为研究对象,对各林型中幼苗的种类组成、数量、多样性与更新方式进行调查研究。结果表明：7种林分类型的乔木更新情况不同,德兴常绿阔叶林更新幼苗共35种,分属17科23属。更新苗数量最低的是拟赤杨＋马尾松林,仅为1 250株/hm^2,更新苗最多的林分类型为米槠＋甜槠林,为6 500株/hm^2;甜槠＋木荷林更新幼苗种类高达25种,居7种林分之首,马尾松＋木荷林下幼苗仅有10种;从演替更新年龄结构来看,马尾松＋木荷林和丝栗栲＋木荷林所在的群落,林下更新苗属于增长型锥体。其它5种林型属于下降型锥体。 相似文献
19.
Mani Ram Moktan Georg Gratzer William H. Richards Tek Bahadur Rai Dawa Dukpa Kinley Tenzin 《Forest Ecology and Management》2009
Group selection tree harvest has been proposed as an ecologically sustainable silvicultural technique in mixed conifer forests of the western Bhutan Himalayas. To evaluate this silvicultural technique, we studied the ecological consequences of a group selection tree harvest in mixed conifer forests by assessing 127 circular plots (71 in logged and 56 in unlogged stands) in two forest management units (FMUs). Tree species composition and diversity were similar between logged and unlogged stands. Seedling density and height growth vary by species and were influenced by logging and microsites, with generally taller seedlings found in the logged versus unlogged stands. Early successional shade-intolerant species colonized logged stands. Seedlings growing on bare soil scarified by harvesting had medium vigour while seedlings growing on bryophyte mats showed good vigour in both logged and unlogged stands. Moist sites with a northerly aspect supported profuse conifer seedling regeneration, compared to sites with a dry southerly aspect. Damage to conifer seedlings from herbivore browsing was minimal. Conifer seedling density and height growth was negatively affected by competition from herbaceous vegetation, most notably Salvia officinalis. Group selection tree harvest in southern dry exposures in spruce-dominated stands is silviculturally unsuitable because it alters tree succession. 相似文献
20.
通过对不同结构青海云杉林天然更新情况的调查分析,结果表明:不同生境条件下青海云杉林的树种组成、林分结构、生长状况和更新状况都有较大的差别;青海云杉的径级和高度决定着青海云杉林内不同树木个体间的竞争和分异状况,决定着不同高度级内的株数分布比例;青海云杉纯林中林分结构单一,更新良好;青海云杉+白桦混交林林分结构复杂,更新不良;青海云杉纯林下,拥有丰富的云杉种源,云杉种子饱满,保存云杉幼树数量多且生长状况好,能维持云杉种群的更新连续性和相对稳定性;林冠郁闭度为0.4时,更新情况最好;当郁闭度为0.7时,更新情况差。 相似文献