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1.
An experiment was carried out where sheep were grazed in temporary fenced paddocks at a stocking rate of 178 LSU ha−1 in a 5-year old broadleaf plantation of oak (Quercus spp.) and ash (Fraxinus excelsior) (1.5 m spacing) on fertile, former lowland pasture in Northern Ireland. The grazing regime was rotational and intensive,
with two grazing periods of 5 days in February and October 2001. Results showed that a significant proportion of the rank
herbage height was removed within the first 24 h of livestock introduction. Herbage biomass was reduced by approximately half
after 5 days. Sward height in grazed plots remained significantly lower than control plots for over 6 months after cessation
of grazing, whilst biomass remained significantly lower for over 4 months after cessation of grazing. No significant tree
damage to either oak or ash was measured during the February grazing trial, however significant damage to the lateral branches
of both oak and ash was observed in the October grazing trial. Leader damage did not occur on trees greater than 152 cm. Ash
was more commonly browsed than oak. Annual height increment of both tree species was unaffected by grazing, but annual stem
diameter increment was significantly reduced in both oak and ash in February grazed plots. Oak trees in both February and
October grazed plots were found to have a significantly smaller annual increase in canopy diameter than those in control plots.
Results are discussed with regard to practical implementation of controlled grazing in young broadleaf forestry plantations
on fertile, lowland soils. 相似文献
2.
A stand dynamic model was developed to predict the growth response in even-aged forest plantations of different initial planting
densities. The model is based on the integration of three subcomponents: height growth, self-thinning, and diameter increment.
The integrated model uses the height of dominant trees to simulate stand response to site quality and internal growth potential.
An extended self-thinning submodel is used to simulate mortality in stands due to crowding and inter-tree competition. A diameter
increment submodel is used to link the height growth and self-thinning submodels. The height growth submodel is based on an
application of the “Pipe Model” theory. The three-parameter self-thinning submodel is developed from an extended self-thinning
law that captures self-thinning in stands before they attain full stocking. The diameter increment model is based on the assumption
that diameter increment is related to height growth and available growing space described by stand density. The integrated
model is applied to data collected from a 45-year-old red pine (Pinus resinosa Ait.) plantation subsectioned with different initial planting densities. For the data used, only two parameters were required
to capture 99% of measured variation in height growth. Additional data from sites with different planting intensities are
required to formulate a more generalized height growth model. The slope of the linear self-thinning limit for red pine is
approximately −1.5. Model predictions are consistent with field measurements. 相似文献
3.
Giulia Attocchi 《Annals of Forest Science》2013,70(7):663-673
Context
Avoidance or control of epicormic shoots is among the major silvicultural challenges for the production of high-quality oak timber. In northern Europe, contemporary oak silviculture aims to produce valuable timber on a relatively short rotation, applying early, heavy thinning combined with artificial pruning.Aims
The aim of this study was to analyse the effects of pruning and stand density on the production of new epicormic shoots on young trees of pedunculate oak (Quercus robur L.).Methods
The study was based on two field experiments in even-aged stands of pedunculate oak subjected to different thinning practices and early selection of potential future crop trees. From ages 13 to 15 years, stem density was reduced to 300 trees ha?1, 1,000 ha?1 or stands remained unthinned. Pruning was conducted on selected trees at ages 22–24 years. At that age, the stem density in unthinned control plots ranged from 2,500 to 3,100 ha?1. All treatments were replicated twice within each experiment.Results
Pruning led to an overall increase in the total production of new epicormic shoots. More epicormic shoots were produced in the lower part of the stem (0–3 m in height) than in the upper part (3–6 m). The number of new epicormic shoots increased with increasing stand density.Conclusion
Early, heavy thinning combined with high pruning at regular intervals may help shorten the rotation length for pedunculate oak without further reduction in wood quality than that which is caused by wider annual growth rings. 相似文献4.
Faidherbia (Faidherbia albida) is being promoted widely in interventions for combating desertification, re-greening of the Sahel, carbon offset and various agroforestry projects. However, there is a dearth of information on its growth and canopy development. There are also no guidelines for optimum stocking densities for practitioners to follow. Therefore, the objective of this work was to evaluate scaling relationships between its growth in height, stem diameter and crown size and based on these relationships define stocking densities. In order to achieve this we: (1) modelled its growth in relation to plant density; (2) identified appropriate models for scaling stem height and diameter with crown size; (3) using information from step 2, we derived stocking densities under different scenarios. Crown diameter (CD) was found to scale with stem diameter (D) isometrically, while stem height scaled with CD allometrically. The scenarios derived using the CD–D scaling indicated that densities >50 plants ha?1 are untenable when DBH exceeds 40 cm. High initial densities (>625 plants ha?1) appear to lead to rapid self-thinning. Starting with low initial densities (<100 plants ha?1) was also expected to result in sub-optimal use of site resources and delayed net ecosystem production. As a compromise, we recommend establishment of stands at initial densities of about 625 trees ha?1 (or 4 m × 4 m spacing) and progressive thinning as stem diameter increases. The focus of this analysis has been on monoculture plantations of Faidherbia and the spacing may not be directly applicable where crops are integrated with trees. Therefore, we propose a follow-up study including modelling tree behaviour in mixed stands in order to refine recommendations. 相似文献
5.
Modelling self-pruning and branch attributes for young Quercus robur L. and Fagus sylvatica L. trees
The aim of this study was to develop statistical models for first order branchiness in young planted forest stands of pedunculate oak (Quercus robur L.) and European beech (Fagus sylvatica L.), and to give an ecological and silvicultural interpretation to these models. The reported models focus on the lower most-valuable stem part (i.e. until 6 m height), and cover different tree development classes to capture the development of branchiness over time. For each species 30 study plots were selected spread over two nearby forests in Flanders (northern Belgium), minimising site and genetic variability. Branches were counted on a total of 399 oak and 376 beech trees. On a subsample of 30 trees per species (one tree per plot), detailed non-destructive branch measurements were performed, yielding data for 555 oak and 438 beech branches. For both species, models for tree self-pruning (i.e. total branch number and dead branch portion), branch mortality and branch architecture (i.e. branch diameter and branch insertion angle) were built. A generalised linear mixed modelling approach was adopted. The models for total branch number and dead branch portion may be interpreted in terms of four processes contributing to self-pruning: (1) stand and tree development, (2) tree competitive status, (3) stand density and (4) site humidity. The reported models reveal similar self-pruning rates in oak and beech, but with different driving factors: early branch dying and slow shedding for oak and the other way around for beech. Mortality of individual branches is further determined by branch position and branch dimension. Branch diameter and branch insertion angle of both species are mainly related to branch cord length and relative branch position. All modelled effects are consistent with known ecological and ecophysiological processes. Silvicultural implications for stand establishment and early tree selection are discussed. The reported models can be used to fine-tune operational silvicultural choices for quality timber production. This is a first step towards the integration of branchiness models for oak and beech into forest growth simulators. 相似文献
6.
Density management is the usual method used by silviculturiststo achieve a desired future stand condition, and one of themost effective methods of design, display and evaluation ofalternative density management regimes in even-aged stands isthe use of stand density management diagrams. In the presentstudy, we describe a method for developing thinning schedulesfor even-aged pedunculate oak (Quercus robur L.) stands in Galicia(north-western Spain), using a density management diagram. Thediagram integrates the relationships among stand density, dominantheight, quadratic mean diameter and stand volume in a singlegraph. The data used in its construction were obtained from172 sample plots located throughout Galicia. The diagram isbasically composed of two equations: the first relates the quadraticmean diameter to the stand density and dominant height; thesecond relates the stand volume to the quadratic mean diameter,stand density and dominant height. These equations were fittedsimultaneously using full information maximum likelihood. Therelative spacing index is used to characterize the growing stockand the diagram provides isolines for dominant height, numberof trees per hectare, quadratic mean diameter and stand volume.Dominant height isolines together with the site index curvesallow specification of the timing of thinnings while intermediateand final harvest volumes are calculated using the stand volumesisolines. 相似文献
7.
We present management tools for growing four valuable broadleaved tree species, indigenous to subtropi.cal southern China. Crown diameter （CD） of the species studied can be predicted very well by using a model that is so e y a near funct on of d ameter at breast he ght （DBH）. The add t on of tree age （AGE） and yield class （YC） to this-nodel did not significantly improve its predictive capacity. We used species-specific crown diameter models to calcu- ate the amount of growing space and subsequently stand density that each species needs to achieve desired stem ＂adial growth rates. Furthermore we used this information to calculate a ＂distance factor＂, a rule of thumb that roughly ~stimates the distance between two neighboring trees needed to achieve a desired future target diameter. These tools ＇acilitate the planning of thinning regimes by using crown diameter models combined with annual radial growth rates to ;alculate the number of crop trees per hectare required to reach a desired target stem diameter. 相似文献
8.
Morio Imada Takashi Kunisaki Nobuya Mizoue Yukio Teraoka 《Journal of Forest Research》1997,2(2):89-93
A spacing experiment for Japanese oak (Quercus mongolica var.grosseserrata) with Nelder's design have been studied at the Kyushu University Forest in Hokkaido, since 1975. The oak seedlings were planted
according to systematic spacings which were 20 levels varying gradually from 40,816 to 1,086 seedlings per hectare with concentric
circular arcs (22 in number) and spokes (41 in number). In 1992 when the planted oak seedlings were 18-year-old, DBH, crown
diameter, total height and clear length of the survival trees were measured. Based on the results obtained from analyzing
the relationships between planting density and the mean values of each block, the optimum planting density should be 7,241
seedlings per hectare.
The title is tentative translation from the original Japanese title by the authors of this paper. 相似文献
9.
从美国东南部引进属于红栎组的纳塔栎、舒玛栎、水栎、柳叶栎和属于白栎组的弗栎,在我国长江三角洲平原地区多个地点和不同土壤类型条件下进行造林研究.采用1～2年生裸根苗经长途运输后进行栽种,纳塔栎、舒玛栎和水栎成活率达94％以上,柳叶栎为76％～81％,弗栎仅42％～50％.不同树种之间,幼年阶段的根系发育、枝梢生长习性、秋冬叶色变化和虫害状况存在明显差异.在3～6个地点水稻土上建立的前4种栎树人工林,8～10a后在保留密度900～1 500株·hm-2条件下,其年均径生长量和年均高生长量达到0.96～1.76 cm和0.8～1.33 m.在山坡红黄壤地上栽种的纳塔栎、舒玛栎和柳叶栎,其年均径生长量和年均高生长量分别为0.64～1.01cm和0.57～0.78 m.采用2～4年生带土弗栎苗在6个地点滨海盐土上造林的成活率达87％以上,在保留密度1 110～3 900株·hm-2条件下,其7～9 a林木年均径生长量和年均高生长量分别为0.78～1.13 cm和0.59～0.75 m.当树龄达6～9 a时,5种栎树均开始结实.研究表明,5种北美栎树在长江三角洲地区有较强的适应性,水栎、纳塔栎、舒玛栎、柳叶栎可以应用于平原地区生态景观林和城镇园林绿化建设,而弗栎在沿海防护林建设中具有推广前景. 相似文献
10.
11.
R. Geoff B. Smith Kevin Glencross J. Doland Nichols Graeme Palmer Rexon Viranamangga 《Small-Scale Forestry》2016,15(1):45-59
This paper investigates the products from first thinning at age 6 in Endospermum medullosum (whitewood) plantations in Vanuatu at three stocking densities, and the financial outcomes from several silvicultural thinning regimes based on these spacings. Whitewood plantings established at stockings rates of 417, 625 and 833 stems per hectare were thinned at age 6 to approximately 45 % retained basal area. The thinning products were measured during harvest and value was estimated based on costs of production and appropriate margins relative to radiata pine products already on the market. Financial modelling for the whole rotation was undertaken for each of the spacing and thinning scenarios in the trial. The volume and size of poles and posts at first thinning was related to spacing. Low stocking density produced smaller quantities of larger poles, whereas higher stocking densities produced larger quantities of smaller posts. However, the monetary value of larger products grown under lower stocking rates was less than the value of the greater volume of product at higher stocking rates. This greater volume at higher stockings resulted in higher NPV for regimes with higher initial stockings for modelled scenarios regardless of harvest age. An exception was a scenario where no market for thinnings is available. A direct silvicultural regime (i.e. one with low planting density and no thinnings) had the highest NPV due to the higher price per cubic metre of larger diameter logs, achieved more rapidly because thinning did not remove basal area. Where thinning products are marketable, higher initial planting densities provide higher returns. Where access to markets for thinning products is difficult or where infrastructure is expected to improve in the future, planting at low stocking and without any thinning provides a high return on investment. 相似文献
12.
13.
Free growth is a type of heavy thinning which aims to maximizediameter increment and produce valuable timber on a relativelyshort rotation. An experiment is described which investigatedthe application of free growth to a stand of oak {Quercus petraeaand Q. robur) planted in 1930. At age 58 free growth thinninghad resulted in a mean diameter at breast height of 39.0 cmwith an estimated mean tree volume of 0.98 m3, compared with29.3 cm and 0.52 m3 for equivalent crown thinned trees. Discountedcash flow calculations showed that free growth thinning of oakcould be justified using a 3 per cent discount rate assumingthat the increased intensity of pruning results in a large proportionof veneer quality timber; an independent assessment indicatedthis may be possible. Free growth thinning of oak is not a commonpractice in British broadleaved silviculture probably becauseof the cost of controlling epicormic shoots. It is suggestedthat it may be more appropriate to other species such as ash,sycamore and wild cherry. 相似文献
14.
P. M. McEvoy J. H. McAdam M. R. Mosquera-Losada A. Rigueiro-Rodríguez 《Agroforestry Systems》2006,66(2):85-92
Forest grazing has been recognised as being a useful tool in fire-risk reduction, in addition to having the potential to preserve
or enhance forest biodiversity if managed correctly. Concern for natural regeneration of forest trees in Europe has also prompted
interest in the effects of large herbivores on seedling and sapling growth and mortality. An investigation was carried out
into sapling damage and density of natural regeneration of oak (Quercus robur) in a mature, pony-grazed, Pinus radiata forest in Galicia, NW Spain under two different grazing regimes (continuous and rotational). In all treatments significantly
more oak seedlings and saplings were recorded in areas of grass sward than areas dominated by taller ground flora species.
Damage to oak saplings was assessed from the form (height and canopy) relative to stem diameter. The height and average canopy
diameter of similar-aged saplings were found to be significantly greater in ungrazed (control) than both continuous and rotationally
grazed treatments. Height and canopy diameters of similar-aged oak were not significantly different between the two grazing
treatments. Significant differences were observed in tree form, with unbrowsed saplings having the greatest height to canopy
width ratio and those in the continuously browsed plots having the smallest. An obvious decrease in the goodness of fit (R2) of regression analyses were found in continuously grazed areas compared to rotational and control plots for both height
and canopy data. The differences in damage observed were not significantly different enough to suggest one method of grazing
over the other as being better for minimising sapling damage. Management requirements are more likely to dictate grazing regime.
Overall, stock density is likely to have a more significant effect on damage than stocking system. 相似文献
15.
《Scandinavian Journal of Forest Research》2012,27(3):297-308
A study of 33 provenances in Danish field trials with Quercus robur and Q. petraea was made between 1993 and 1998. The trials include Danish, Dutch, German, Norwegian and Swedish provenances, and were established between 1900 and 1988. Growth, flushing, stem form and epicormic shoot formation were studied. There were strong geographical clines for growth; however, the variation within regions was considerable. Time of flushing followed a more complex clinal pattern and was related to both latitude and distance from the ocean. Stem form was highly variable within different geographical regions and it is suggested that this could be caused by different management regimes in the past. Oaks from some locations in Sweden and Norway seemed especially straight. Stem form is one of the most important parameters for commercial oak management and could be seriously improved through breeding, as it was under considerable genetic control. Epicormic shoot production was in part under genetic control, but no geographical patterns were found. Danish provenances of Q. petraea were growing more rapidly than similar Q. robur on sandy locations. Quercus petraea produced fewer epicormic branches and stem form was equal to or better than Q. robur. Quercus petraea should be recommended for landscape use on windy locations in Denmark. 相似文献
16.
Context
Cluster planting has become a conventional establishment method for oaks in Central Europe, where the spacing of seedlings within clusters varies between ‘nests’ (0.2?×?0.2 m) and ‘groups’ (1?×?1 m). Although the space between clusters is expected to fill with voluntary regeneration, its competitive effect on oak growth and quality had not been studied yet.Aims
The aim of the study was to analyse the effects of inter- and intraspecific interactions on growth and quality of oaks grown in cluster plantings by quantifying the influence of neighbouring trees. In addition, we analysed whether the spatial position of oaks within groups (inner section or periphery) influenced their quality development.Methods
Using Hegyi’s competition index, the influence of competition from intra- and interspecific trees from early, mid- and late-successional species, on diameter, height, slenderness and quality (length of branch-free bole) of 10- to 26-year-old oaks grown in cluster planting stands was quantified at seven sites in Baden-Württemberg and Hessen, Germany.Results
In general, mid- and late-successional trees exerted a stronger competitive influence on growth of target oaks in clusters than the conspecific oaks and pioneer tree species. Oak quality development benefited from intraspecific competition, but self-pruning was not further promoted through additional interspecific competition. Within groups, inner oaks had a higher probability of developing into potential future crop trees than outer oaks.Conclusion
Our study showed that intra- and interspecific competition had different effects on target oak trees and that these effect differed between nest and group plantings. The development of naturally regenerated and planted trainer trees in group plantings should be monitored carefully and if necessary be controlled through thinning or pollarding. 相似文献17.
Growth and branching habit of rooted cuttings collected from epicormic shoots of Betula pendula Roth
Patterns of shoot growth and branching were studied over two growing seasons in rooted cuttings collected from both epicormic shoots and seedlings of Betula pendula Roth. Epicormic shoots were induced to sprout on stumps and small logs of 5-, 10- and 30-year-old trees. The use of epicormic shoots enhanced the rooting capacity of stem cuttings collected from these shoots but did not appear to reverse the process of maturation. In this study, maturation was based on characteristics typical of mature trees but not necessarily those of the mother plant, because it was not possible to root cuttings, for comparison, from 5-, 10- and 30-year-old ortets, other than from epicormic shoots. There was evidence of the persistence of mature characteristics through an increase in shoot plagiotropism with increasing ortet age. Rooted cuttings from both seedlings and epicormic shoots, however, assumed an increasingly orthotropic habit with a smaller shoot angle at the end of the first growing season than at the beginning and this continued into the second growing season. Other indications of maturation, such as delayed bud flushing and the incidence of flowering with increasing ortet age, were also evident in rooted cuttings from epicormic shoots. There was a clear difference in branching habit depending on cutting source. Rooted cuttings derived from epicormic shoots produced nearly twice as many lateral branches compared with rooted cuttings collected from seedlings, but this was not an effect of maturation. There was some evidence that rooted cuttings derived from seedlings grew taller than rooted cuttings from epicormic shoots. 相似文献
18.
Thinning alters crown dynamics and biomass increment within aboveground tissues in young stands of Chamaecyparis obtusa 总被引：1，自引：0，他引：1
Qingmin Han Daisuke Kabeya Satoshi Saito Masatake G. Araki Tatsuro Kawasaki Chiharu Migita Yukihiro Chiba 《Journal of Forest Research》2014,19(1):184-193
The stand density of a forest affects the vertical distribution of foliage. Understanding the dynamics of this response is important for the study of crown structure and function, carbon-budget estimation, and forest management. We investigated the effect of tree density on the vertical distribution of foliage, branch, and stem growth, and ratio of biomass increment in aboveground tissues; by monitoring all first-order branches of five trees each from thinned and unthinned control stands of 10-year-old Chamaecyparis obtusa for four consecutive years. In the control stand, the foliage crown shifted upward with height growth but the foliage quantity of the whole crown did not increase. In addition, the vertical distribution of leaf mass shifted from lower-crown skewed to upper-crown skewed. In the thinned stand in contrast, the foliage quantity of individual crowns increased two-fold within 4 years, while the vertical distribution of leaf mass remained lower-crown skewed. The two stands had similar production rates, numbers of first-order branches per unit of tree height, and total lengths of first-order branches. However, the mortality rate of first-order branches and self-pruning within a first-order branch were significantly higher in the control stand than in the thinned stand, which resulted in a higher ratio of biomass increment in branch. Thinning induced a higher ratio of biomass increment in foliage and lower in branch. The increased foliage quantity and variation in ratio of biomass increment after thinning stimulated stem growth of residual trees. These results provide information that will be useful when considering thinning regimes and stand management. 相似文献
19.
INTRODUCTIoNTIle3/2powerlawofsellLthinnlngpro-posedbyYodaelal(l963)wasconsideredasthegeneralmodelwhichdescribedtherela-tionshipoftreesizcandmaximumpopulationdcnsity'fortl1e.plai1tpopulationundergoingself-thinning.Furtherresearch,however,re-vealedtheoreticalinconsistenciesandempiri-calinaccuracy'ofthelaw(Sprugel1984,Zeidc1()85,l987;Wellerl987).Theseresearchcrsconsideredtl1elaM'isathilure.Sincetl1en-asecondtideofsuppoltingappeared,theyinter-pretedandreflitcdtl1eopposingopinions(Osa`vaand… 相似文献
20.
Eucalyptus pilularis planted at three initial stocking densities of 833, 1111 and 1,667 stems ha?1 grown at either square or rectangular spacing was assessed for the effects of stocking and rectangularity on wood properties. Sample trees from each stocking and rectangularity combination were harvested at age 7 years and assessed for the commercially important wood properties of bow, as an indication of growth strain, shrinkage and basic density. Crown length ratio was used as an indicator of stand vigour and clear wood availability. Furthermore comment is made on the financial ramifications of wide inter-row spacing. Stocking and rectangularity significantly influenced bow but not shrinkage or basic density. Reducing within-row spacing to 2 m with a larger between-row-space of 6 m had minimal affect on wood properties. Reducing the number of rows, whilst still retaining a commercial stocking, reduces the establishment costs and increases the ease of mechanical harvesting without adversely affecting log value. 相似文献