共查询到20条相似文献,搜索用时 328 毫秒
1.
Fast-growing woody nurse crops planted among high value hardwoods can produce merchantable biomass early in the life of the
plantation. On a productive site in south-central Illinois (U.S.A.), experimental interplantings of European black alder (Alnus
glutinosa (L.) Gaertn.) and black walnut (Juglans nigra L.) were established and maintained under a factorial combination
of two initial densities and two thinning regimes. This study evaluated the growth response of the alder component of this
system. Although alder consistently overtopped walnut, alder mortality began to increase dramatically during the seventh growing
season and was nearly complete following the nineteenth growing season. Mean alder cumulative dry mass through year 14 ranged
from 19.05 to 58.62 Mg/ha among initial density and thinning treatments. Carbon sequestered in useable bolewood constituted
approximately 25 of total biomass. The productivity of the interplanted alder was comparable to that of native forests while
constituting only a portion of the stand and without negatively impacting walnut growth or bole quality. These results suggest
that, if marketed, alder has the potential to partially offset costs associated with walnut plantation establishment and maintenance. 相似文献
2.
《Scandinavian Journal of Forest Research》2012,27(1):69-77
Abstract This study compares two principally different harvesting systems used for the thinning of Norway spruce [Picea abies (L.) Karst.] plantations in the Alps. The first system was whole-tree harvesting (WTH), producing only whole-tree chips for energy purposes. This system minimizes the production costs by simplifying the harvesting process. The other system was cut-to-length (CTL) mechanical harvesting with an excavator-based harvester. This system maximizes value recovery by producing both short sawlogs and quality fuel chips. Trials were conducted on two similar sites in the Dolomites, in northern Italy, and demonstrated that the CTL system resulted in slightly higher harvesting costs, and also higher revenue. The price differences between the different products determine which system offers the best economic results. If the delivered price of sawlogs does not exceed [euro]25 t?1, WTH and CTL harvesting offer very similar economic performances, and become profitable only if the delivered price of raw chip wood exceeds [euro]40 t?1. If the delivered price of sawlogs increases to [euro]50 t?1, the mechanized CTL system always becomes preferable, and it will turn some profits when the price of raw biomass exceeds [euro]35 t?1. The CTL system is less sensitive to long extraction and transport distances than the WTH system. 相似文献
3.
Michael J. De Lasaux Raffaele Spinelli Bruce R. Hartsough Natascia Magagnotti 《Small-Scale Forestry》2009,8(3):367-379
The Authors tested a mobile small-log sawmill system that could produce cants and boards of variable size, according to the
needs and specifications of each property owner. The unit was deployed as part of a comprehensive mechanical fuel reduction
operation, aimed at thinning small properties around homesteads. Working on conifer small logs, the mill proved very efficient,
with a processing productivity between 0.3 and 2.8 m3 of lumber per working hour and a recovery rate of 50% for boards, and 67% for cants. The mill could be set up and dismantled
in a few hours and was easy to move around. However, the exceedingly small amount of logs available at each site entailed
a low utilization of the mill (about 25% of the time) and a consequently high processing cost. Under the conditions of the
study, milling cost can be contained below 150 US dollars per m3 of lumber only if the single site offers at least 50 m3 of logs, already sorted during harvesting. Hence the suggestion of pooling the wood obtained from small parcel fuel reduction
treatments in satellite yards and milling it only when a large enough amount has been accumulated. In turn, satellite yards
could be organized into an integrated network complementary—rather than alternative—to stationary mills. 相似文献
4.
We studied the effects of line thinning on stand structure, microclimate and understory species diversity of two Cryptomeria japonica D. Don plantations in south-central Japan. In each of two study sites we compared stand structure between the thinned stand
and an adjacent unthinned stand and found that line thinning increased the growth rate of residual trees such that stand basal
area may recover within 10 years after thinning. In the thinned stand, more open canopy conditions resulted in higher maximum
temperatures on the forest floor during the early growing season than in the unthinned stand. The thinned stand had greater
understory plant species richness and biomass than the unthinned stand. This study suggested that line thinning could potentially
enhance biodiversity while simultaneously increasing tree-growth rates in overstocked Cryptomeria japonica plantations. 相似文献
5.
Hiromi Yamagawa Satoshi Ito Yasushi Mitsuda Kazuro Fukuzato 《Journal of Forest Research》2006,11(2):99-106
We investigated factors limiting the recovery of natural forest in former large-scale conifer plantations abandoned after
clear-cutting in southwestern Japan. We analyzed forest recovery status (“recovered” sites covered by evergreen broad-leaved
trees, and “unrecovered” sites covered by pioneer community or nonvegetated sites) using aerial photographs and field survey.
We applied logistic regression analyses to evaluate the effects of topography, construction of harvesting roads, distance
from remnant forest, stand condition before clear-cutting, and prior land-use history on forest recovery. Human factors, i.e.,
land use and clear-cutting age, were found to affect to forest recovery more than environmental factors such as topography.
Harvesting roads had the strongest negative impact on forest recovery. Forest recovery after clear-cutting of young sugi plantations
also took longer than after clear-cutting of old sugi plantations or evergreen broad-leaved forests. Furthermore, areas formerly
utilized as meadows recovered less successfully than those that had been managed as coppices. The influences of these factors
were thought to be promoted by the advance reproduction as the regeneration sources for forest recovery. The influence of
stand age before logging suggested an effect of thinning, which might alter the abundance of advanced reproduction in the
understory. However, distance from remnant forest appeared to be less important. An influence of topography was also detected,
but this could be partly explained by the existence of advance reproduction in the understory in certain topographic positions.
Thus, our analysis suggests that regeneration sources originating from advanced reproduction in plantations play a significant
role for the recovery of natural forest after clear-cutting. 相似文献
6.
There is an urgent need for new, mechanized systems that may restitute some profitability to buffer strip harvesting and motivate regular maintenance. An opportunity for innovation is offered by the growing success of chip-fed boilers, since the production of chips is simpler than that of logs and has a higher potential for cost reduction. Within this context, a study was conducted in Italy with the goals of: (a) designing three alternative chip harvesting methods for buffer strips, (b) field-testing the performance of each alternative, and (c) developing a model for estimating the cost of these methods under varying operational and economic conditions. The three harvesting methods reflected different mechanization levels, with escalating investment requirements. Overall, the study demonstrated that frequent maintenance of young, single row buffer strips generates profits only when thoroughly mechanized. Using a dedicated feller-buncher, a front-end loader for extraction and an industrial truck-mounted chipper brought the delivered cost below the 14 €/m3 loose chips (approximately 4 €/GJ) presently paid by the district heating stations. However, the intermediate-mechanization system showed the highest potential for improvements. The␣study generated a spreadsheet-based model for predicting the effects of varying work conditions and cost hypotheses. 相似文献
7.
Whole-tree harvesting (WTH), where logging residues are removed in addition to stems, is widely practised in Fennoscandian boreal forests. WTH increases the export of nutrients from forest ecosystems. The extent of nutrient removals may depend on tree species, harvesting method, and the intensity of harvesting. We developed generalized nutrient equations for Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies Karsten), and birch (Betula pendula Roth and Betula pubescens Ehrh.) stands to be able to calculate the amounts of nitrogen, phosphorus, potassium, and calcium in stems and above-ground biomass (stem and crown) as a function of stand volume. The equations were based on Fennoscandian literature data from 34 pine, 26 spruce, and 5 birch stands, and they explained, depending on the tree species and nutrient, 61–99% and 56–87% of the variation in the nutrient amounts of stems and above-ground biomass, respectively. The calculations based on the equations showed that nutrient removals caused by stem-only harvesting (SOH) and WTH per harvested stem m3 were smaller in pine than in spruce and birch stands. If the same volume of stem is harvested, nutrient removals are, in general, nearly equal at thinnings and final cuttings in SOH, but larger in thinnings than final cuttings in WTH. If the principal aim is to minimize the nutrient removals per harvested stem m3, the harvesting should be done at mature pine stands. The effect of biomass removal on overall site nutrient status depends on site-specific factors such as atmospheric deposition, weathering of minerals, and the size of the nutrient pools in the soil. 相似文献
8.
《Forest Ecology and Management》2001,145(3):219-227
Long planning horizons generate substantial uncertainty in forest management, making management flexibility, the ability to choose between multiple options or opportunities, a desirable attribute of managed forests. Flexibility in forest management reflects both the relative rigidity of intervention requirements and the potential range of development pathways for a stand. The wind stability of Pacific Northwest Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) plantations is used to demonstrate the concept of management flexibility. Dense Douglas-fir plantations develop high height to diameter ratios (H/D same units) in the dominant trees making them unstable and prone to wind damage. The management of these plantations is inflexible, because without early and timely thinning, the stands do not contain stable trees that could be expected to survive long rotations or late thinnings. A combination of reduced planting densities and site-specific management reduces both the necessity and rigidity of intervention requirements (e.g., thinning) and expands the number of potential developmental pathways for these stands. The cost of greater management flexibility is reduced efficiency of wood volume production; however, greater adaptability to changing markets, labor conditions, and management objectives may be more important for many forest owners. While this approach to management is complex, it frees owners and managers from rigid management requirements and allows for a wider range of future stand conditions. 相似文献
9.
Jinghui Meng Yanfeng Bai Weisheng Zeng Wu Ma 《European Journal of Forest Research》2017,136(3):543-554
Coastal forests are normally established to mitigate coastal natural disasters instead of artificial barriers because of their low cost, ecological friendliness and economic benefits. The stand stability of coastal forests is of great importance to protect against coastal natural disasters. In the present study, we produced a stand density management diagram (SDMD) that can quantitatively guide the management of stand density to reduce the potential risk of windthrow in the coastal Casuarina equisetifolia L. plantations in southern China. The SDMD was developed using a relative spacing index (RS), average slenderness coefficient (SC) and a system of two equations as the basic components. The RS was used to characterize the growing stock, and the average SC was included to assess stand stability. Finally, we illustrated the application of the SDMD in formulating thinning schedules to secure stand stability. For comparison purposes, management options both with and without considering stand stability were produced and discussed. The study indicated that the SDMD produced here can provide detailed quantitative guidance of regulating stand density to secure stand stability for C. equisetifolia plantations. Additionally, this SDMD can be used to develop thinning schedules for a wide range of site qualities and management objectives for C. equisetifolia plantations. 相似文献
10.
M. Abdul Maleque Hiroaki T. Ishii Kaoru Maeto Shingo Taniguchi 《Journal of Forest Research》2007,12(1):14-23
We investigated the effects of line thinning on the abundance of Hymenoptera in two Japanese cedar plantations in northern
Hyogo Prefecture, central Japan, in order to evaluate the effectiveness of this silvicultural treatment for ecosystem management.
Line thinning is a silvicultural treatment practiced in Japan, where linear stand sections are cut (25%–35% of the total number
of trees) retaining one to two rows of trees. We used Malaise traps to capture Hymenoptera from the line-thinned stand (treatment
plot, including thinned and retained sections) and the unthinned stand (control plot). Overall, the total number of Hymenoptera
was greater in the treatment plot than in the control plot. The treatment plot hosted more functional groups and families
of Hymenoptera than the control plot in both plantations. In the Kuchiotani plantation (high-elevation site), the overall
abundance of Hymenoptera and of many Hymenopteran functional groups were positively correlated with both species richness
and biomass of understory plants. In the Sugi plantation (low-elevation site), understory vegetation was less developed and
there was no correlation with abundance of Hymenoptera. Our study indicates that line thinning is an effective silvicultural
treatment for future management of overstocked Japanese cedar plantations because it can fulfill biodiversity objectives,
but the effectiveness may depend on silvicultural and landscape factors. 相似文献
11.
Large areas of northern coniferous forests once naturally maintained by stand-replacing wildfires have shifted to an anthropogenic disturbance regime of clearcut harvesting followed by natural or artificial regeneration, with unknown consequences for soil biogeochemical processes. We used a comparative approach to investigate the effects of whole-tree harvesting (WTH) vs. stand-replacing wildfire (WF) on soil C and nutrient availability, and nutrition and growth of the succeeding stand, in jack pine (Pinus banksiana) forests of northern Lower Michigan. We compared total carbon (C), total nitrogen (N), potential N mineralization, and extractable phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) among stands regenerated via WTH or WF in two age classes (4–7 years and 12–18 years). We also measured jack pine foliar nutrition and height growth in these same stands, as well as estimating the contribution of legacy dead wood to ecosystem nutrient capital in young stands. We found some evidence in support of our hypothesis that WTH would leave behind greater pools of soil C and N, but lower pools of P and base cations. However, the differences we observed were confined entirely to surface organic horizons, with the two disturbance regimes indistinguishable when viewed cumulatively to our maximum sampling depth of 30 cm. Estimates of nutrient pools in legacy wood inherited by young jack pine stands were also small in comparison to total soil pools (ranging from 1 to 9% depending on the element), suggesting that decomposition and nutrient release from this material is not likely to result in noticeable differences in soil fertility later in stand development. Similar levels of soil nutrients between WTH- and WF-origin stands were reflected in our measures of jack pine foliar nutrition and height growth, which were both unaffected by mode of stand origin. Results from this study suggest that soil nutrient levels following WTH fall within the natural range of variation produced by WF in these jack pine forests; however, comparison with a similar study on boreal jack pine suggests that latitudinal effects on O-horizon nutrient capital may influence the degree to which WTH matches the effects of WF on soil nutrient availability. 相似文献
12.
人工林在保护香港自然环境起着重要作用,但绝大多数人工林为纯林,生态系统较为脆弱。人工林的改造对于增加林地生物多样性、提升人工林的生态服务功能具有重要意义。研究选取20 a 生的尾叶桉(Eucalyptus urophylla)林和马占相思(Acacia mangium)林进行间伐套种处理,套种密度为1665株/hm2;以不间伐林分为对照,比较间伐套种后林分的物种多样性及套种树种的生长表现。结果表明,间伐+套种3 a后,与未间伐林分相比,尾叶桉间伐林分植物的科、属和种数分别增加了78.6%、116.7%和100%,马占相思间伐林分相反。DCA 分析结果显示,群落中灌木层和草本层物种主要聚集在尾叶桉间伐林分,马占相思未间伐林分物种数次之。与未间伐相比,间伐+套种措施显著提高了尾叶桉林乔木层 Shannon-Wiener 指数和均匀度指数、灌木层的物种丰富度指数和均匀度指数及草本层的丰富度和 Shannon-Wiener 指数(P <0.05);但马占相思间伐+套种林分的乔木层、灌木层和草本层的 Shannon-Wiener 指数均显著低于未间伐林分(P <0.05);物种多样性指标总体表现为尾叶桉间伐林>未间伐林,马占相思未间伐林>间伐林。套种树种在尾叶桉和马占相思林分中的早期生长表现良好,树种间生长量没有明显差异。 相似文献
13.
Analyses of black walnut tree diameters 13 years after planting showed that interplanting autumn-olive, black locust, and European alder increased walnut tree growth, but only at certain locations. Interplanting autumn-olive resulted in increases of 56 to 351% at four of five locations and all species resulted in doubled walnut growth on an upland site. The interaction between treatment and location indicates that a fuller understanding of site and nurse species characteristics is needed to obtain the potential benefits of mixed plantings. 相似文献
14.
15.
Chen Hongji 《林业研究》1999,10(3):181-182
Different types of plantations were observed in Baishilazi National Nature Reserve, Liaoning Province, for 34 a. The environmental
quality ofAbies holophylla plantations was analyzed under different cutting systems. Analysis factors included soil erosion rate, humification degree
of litters, and water hold capacity. The surface soil loss of clear cutting area was 19000t·km−2·a−1 more than that of selective cutting area. The content of soil organic matter in board-leaved—Abies holophylla forest was 4.62% more than that in pure stand, and the water hold capacity of the mixed forest was 1.43 time of that of pure
stand. The mixed forest of board-leaved—Abies holophylla by selective cutting can upgrade the ecological environment quality.
This paper is a part of a key project from Liaoning Science Committee.
Responsible editor: Zhu Hong 相似文献
16.
17.
为了保持我国人工林的长期生产力和提高森林质量,达到可持续经营的目的。作者在以往研究工作的基础上,广泛收集了国内外有关成果与资料,概括论述了我国人工林森林生产力的现状、不能保持生产力的原因与机理以及长期保持人工林生产力的技术对策。按第八次清查的全国森林资源数据,每公顷蓄积量为89.79 m^3,其中天然林为104.6 m^3,人工林为52.76 m^3,人工林森林生产力明显低于天然林;我国优势树种人工林每公顷蓄积量也不高,如杉木为69.8 m^3,马尾松为56.2 m^3,落叶松为58.6 m^3,这些数据比日本2002年3月公布的人工林相似树种的数据低很多,如日本针叶树蓄积量为227.97 m^3·hm-2,柳杉为295.83 m^3·hm-2,落叶松为189.88 m^3·hm-2。关于年生长量,按全国第七次资源清查的中龄林与近熟林的数据做统计:杉木人工林5.2~4.2 m^3·hm-2,马尾松为3.2~1.8 m^3·hm-2,柏木为3.4~3.2 m^3·hm-2;但按作者掌握的我国重点或示范性、试验性小面积人工林生长量看,却很高,按我国编制的速生丰产林标准的生长量数据看比较高。我国大面积人工林生产力不高,短周期经营的杨树、桉树人工林也不高,主要原因是:(1)纯林化与针叶化严重。按第八次全国森林资源统计,纯林占人工林的85%,而且针叶化明显,人工乔木林10个优势树种中针叶林比例高达56.9%。人工纯林结构简单,生物多样性低,生物学上缺乏稳定性。人工纯林特别是针叶纯林,抗性低,抗自然灾害和大气污染能力均差,人工纯林维护地力的能力也弱。(2)集约育林的技术措施:立地控制技术未得到推广,适地适树适品种原则在育林中未能认真贯彻;密度、植被、地力控制技术也执行不力,大面积上的人工林仍属于粗放经营;连作引起林地土壤理、化、生物特性恶化,土壤质量衰退,导致林木生长不良,林分生产力逐代下降;造林作业造成水土流失,如杉木造林,传统的育林技术未得到明显改进,福建尤溪炼山后进行的3年观测结果表明,炼山和水土流失损失的有机质高达989.35 kg·hm-2,养分586.26 kg·hm-2。桉树在砖红壤进行的机耕整地,水土流失也很严重,不合理的造林作业,最终导致土壤质量与森林生产力下降。短周期培育人工林带来了2个重要问题,一是对林地肥力要求高,二是如何利用无性系才能保持长期生产力。短周期经营采用的无性系,生长速度快,生长量大,轮伐期短,养分需求量大,如刚果12号W5无性系,通常利用地上部分,以5~7 a的轮伐期计,消耗的养分达571.75 kg·hm-2,我国培养短周期人工林的土壤质量本底原本普遍不高,如果采取连作,土壤有机质养分会明显下降,土壤质量衰退,并对其功能产生危害。我国杨树、桉树等人工林要达到短周期持续经营,还需要实行多无性系造林。我国人工林长期生产力保持的技术对策,应采取先进的集约育林措施,包括遗传控制、立地控制、密度控制、植被控制与地力控制。 相似文献
18.
通过对马尾松4~20年生不同密度的人工同龄纯林生长资料的分析表明:第1次树高生长分化高峰期在4~7年生,第2次在11~14年生,幼林郁闭后林木直径分化状态比较稳定。中幼林期抚育间伐主要采伐劣等木,进入近熟林期后除采伐劣等木外,还可采伐一部分中等木。间伐施工应以留优去劣为主,适当照顾均匀。总稀疏强度与密度呈正相关性,出现稀疏的时间随密度增大而提前;连年稀疏强度高峰期出现在林分郁闭后的一段时间内。根据总稀疏强度与稀疏时间同密度的关系可确定不同密度林分的间伐强度与时间。利用马尾松人工林观测资料拟合出与立地条件、现存株数密度、林龄三因子相关的自然稀疏模型,从而可推算出不同立地条件的自然稀疏表,为马尾松人工林密度调控提供科学依据。 相似文献
19.
Kjersti Holt Hanssen Inger Sundheim Fløistad Aksel Granhus Gunnhild Søgaard 《Scandinavian Journal of Forest Research》2018,33(1):40-49
Removal of logging residues causes significant nutrient losses from the harvesting site. Furthermore, collection of residues into piles could lead to small-scale differences in establishment conditions for seedlings. We studied the effects of stem-only (SOH) and aboveground whole-tree harvesting (WTH) on Norway spruce (Picea abies) seedling growth and pine weevil (Hylobius abietis) damage at two sites (SE and W Norway). We also compared two planting environments within the WTH plots (WTH-0: areas with no residues, WTH-1: areas where residue piles had been placed and removed before planting). In practice, one-third of the residues were left on site after WTH. After three growing seasons there were no differences for height or diameter increment between SOH and WTH (WTH-1 and WTH-0 combined) treatments. However, relative diameter increment was largest for WTH-1 seedlings and lowest for WTH-0 seedlings. Few seedlings sustained pine weevil attacks at the W Norway site, with no differences among treatments. At the SE Norway site, the percent of seedlings damaged by pine weevils and average debarked area were significantly higher after WTH (82% and 3.3?cm2) compared to SOH (62% and 1.7?cm2). We conclude that WTH may lead to spatial differences in establishment conditions. 相似文献
20.
Guiding Principles for Small-Scale Forestry in a Watershed of the Venezuelan Andes: Constraints and Opportunities 总被引:1,自引:1,他引:0
In the Venezuelan Andes, some small-scale forest plantations have become an important resource basis for forest management.
In this paper, the forestry management progress in the Mucujún river watershed is analyzed. Constraints and opportunities
for sustainable management within national policies, local regulations, environmental features and social benefits are also
examined. Plantation assessment, and biophysical, legal and socioeconomics information, are used for guiding small-scale forestry
practices in this watershed, with emphasis on the main principles of landscape management. These plantations have become an
important part of the socio-ecological landscapes with potential for wood production—in the context of low intensity and low
environmental impact environmental services and amenity—because of the two protected areas within the watershed. Current forest
stand conditions, however, reflect that management requires improvement. Furthermore, the analysis suggests that improvement
of local livelihoods may be achieved with a small-scale forestry approach, taking properly into account the basic criteria
of social involvement and management of planted forests, while maintaining ecosystem services including biodiversity and water
supply. 相似文献