Functions for Biomass Estimation of Young Pinus sylvestris,Picea abies and Betula spp. from Stands in Northern Sweden with High Stand Densities

New silvicultural regimes with high within-stand competition require new functions for estimation of standing stock and growth of biomass components, since the allometry of trees is changed by light competition. This paper presents functions for estimation of the aboveground biomass dry weights for stem wood, stem bark, branches and leaves of young (diameter at breast height <10 cm) Scots pine (Pinus sylvestris L.), Norway spruce [Picea abies (L.) Karst.] and birch (Betula pendula Roth. and Betula pubescens Ehrh.) trees growing in dense mixed stands. The functions were derived from a sample consisting of 84 Scots pine, 43 Norway spruce and 66 birch trees from six stands in northern Sweden with high stand densities (>10000 st ha^-1). The logarithmically transformed power function displayed a good ability to stabilize the variance of dry weights and showed a good fit to the material (0.37< R ² <0.99). A comparison with the most commonly used biomass functions in Sweden today showed that they overestimated the weight of stem wood and branches, while the weight of foliage was underestimated. The nature of these discrepancies suggested that the precision of biomass estimations might also be improved for young trees at wider spacing.     

Effects of Seedbed Substrates on Regeneration of Picea abies from Seeds

The effects of seedbed substrates on the emergence and mortality of Norway spruce [ Picea abies (L.) Karst.] on clear-cuts were studied in a sowing experiment. Seven intact substrates as well as scarified plots on the same types of substrates were considered. The experiment took place at two locations in south-east Norway, during three consecutive years. Of intact substrates, Sphagnum spp. was found to be the best for emergence and litter was found to be the second best. Microhabitats dominated by feather mosses, Dicranum spp., Vaccinium myrtillus or Deschampsia flexuosa were poor environments for emergence. However, after two to three seasons, survival in per cent of emerged seedlings was more or less equal among all substrates. Emergence was higher on scarified plots than on intact substrates, and except for Sphagnum substrates, survival was equal or better. For scarified plots, the original substrate did not influence the emergence of seedlings, but mortality after the second summer differed owing to original substrate. The best substrates for scarification were V. myrtillus and D. flexuosa , while mortality was highest for plots that were originally dominated by Sphagnum . Weather conditions influenced the suitability of the substrates as seedbeds, as did the location of the plots.     

Risk of Snow Damage in Unmanaged and Managed Stands of Scots Pine,Norway Spruce and Birch

The aim of this study was to assess the risk of snow damage to trees in unmanaged and managed stands of Scots pine (Pinus sylvestris L.), Norway spruce [Picea abies (L.) Karst.] and birch (Betula spp.) over a rotation. The risk assessment was based on the prediction of critical snow loads in interaction with the windspeed at which trees can be expected to break or be uprooted, and on the frequency of long-term extremes of precipitation and of suitable temperature conditions for the accumulation of snow on the tree crowns. The Scots pine stands were found to be more susceptible to snow damage than the others, and an unmanaged stand of Scots pine to be more susceptible to break and uproot than a managed one. Correspondingly, an unmanaged stand of Norway spruce was more susceptible to stem breakage than a managed one, but less susceptible to uprooting. Neither unmanaged nor managed birch stands were likely to suffer any kind of snow damage. The susceptibility of unmanaged stands is caused by low tapering of the trees. Based on the frequency of long-term extremes in precipitation at the temperatures needed for snow accumulation on tree crowns, critical snow loads of 10-19, 20-29 and 30-39 kg m^-2 occurred 19.3, 3.3 and 1.3 times in a decade in southern Finland. Critical snow loads of 10-19, 20-29, 30-39 and 60-69 kg m^-2 occurred in northern Finland 17.0, 6.3, 1.7 and 0.3 times in a decade.     

Spatiotemporal Availability of Dead Wood in Protected Old-growth Forests: A Case Study from Boreal Forests in Eastern Finland

Spatiotemporal patterns of standing and fallen dead trees were examined in two protected Scots pine ( Pinus sylvestris L.)-Norway spruce ( Picea abies (L.) Karst.) forests in eastern Finland (Pahkavaara and Pönttövaara). In Pahkavaara the volume of standing dead trees was 10 m 3 ha -1 and the volume of fallen logs was 66 m 3 ha -1 , and in Pönttövaara the values were 48 m 3 ha -1 and 107 m 3 ha -1 , respectively. The areas differed with respect to the tree species composition, whereas the proportion of different decay stages was similar. Decay stage and dendrochronological analyses revealed the continuity of dead wood formation. The spatial pattern of standing dead trees was usually towards clustered. The volumes of fallen logs showed a spatial autocorrelation up to distances of 10-20 m. The results also suggest that the current amount and diversity of dead wood is rather high, but that forest succession is likely to lead to a less diverse state in the future.     

Survival and Growth of Picea abies Regeneration after Shelterwood Removal with Single- and Double-grip Harvester Systems

Three stands in Sweden were followed for 7 yrs to study the survival and growth of Norway spruce [Picea abies (L.) Karst.] regeneration after shelterwood removal with single- and double-grip harvester systems. The height of all seedlings within circular plots was recorded before and after final cutting. The tallest seedling and one randomly selected seedling on each circular plot were permanently marked and their annual height growth was measured each year during the period 1993-1999. No significant differences between single- and double-grip harvester systems were found with respect to their effects on regeneration density, survival or annual height growth. The annual height growth of the individual seedlings after shelterwood removal was significantly correlated with seedling height before shelterwood removal. Significant differences were found in annual height growth between seedlings with high and low vitality. Logging damage did not affect the annual height growth. Several practical conclusions were drawn. First, the choice of harvester system does not affect seedling height growth or survival after shelterwood removal. Secondly, the removal of a 200 m³ shelterwood with 200 stems ha^-1 does not seem to constitute a serious problem for seedling survival and growth. Finally, estimated vitality and seedling height both seem to be fairly good predictors of postrelease survival and growth.     

Scarification and Seedfall affects Natural Regeneration of Scots Pine Under Two Shelterwood Densities and a Clear-cut in Southern Sweden

A study was undertaken to evaluate the effect of Scots pine (Pinus sylvestris) shelterwood density and timing of removal on the regeneration of forests with improved wood quality. This paper focuses on the effect of scarification and seedfall on the success of natural regeneration of Scots pine under two shelterwood densities and in a clear-cut. Wood quality aspects will be addressed later in the study. After 4 yrs, natural regeneration of Scots pine under a 200 stems ha^-1 shelterwood reached 90000 seedlings ha^-1, 53000 under a 160 stems ha^-1 shelterwood and 3700 in a clear-cut. The high natural regeneration under the densest shelterwood resulted from a high seedfall, slower invasion by competing vegetation, consequent prolonged recruitment and low mortality. Since mortality largely decreased for both shelterwood densities and recruitment seems to continue, the success of regeneration should be maintained in the future if proper release operations are conducted. The latter could begin when seedlings reach a height of about 0.5 m and the cover should be maintained until they reach a height of about 6 m. Therefore, it may be possible to use 200 stems ha-1 Scots pine shelterwoods in southern Sweden to obtain dense stands and thus improve wood quality (stem taper, wood density, etc.).     

Browsing Damage on Pine (Pinus sylvestris and P. contorta) by a migrating moose (Alces alces) Population in Winter: Relation to Habitat Composition and Road Barriers

In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads.     

Responses of Pinus sylvestris and Picea abies Seedlings to Limited Phosphorus Fertilization and Treatment with Elevated Ozone Concentrations

Scots pine ( Pinus sylvestris L.) and Norway spruce [ Picea abies (L.) Karst.] seedlings were exposed to high phosphorus (HP) or low phosphorus (LP) availability for one growing season in the open field, and to combined P availability and elevated ozone (O 3 ) concentrations (0, 55, 110 and 210 ppb for Scots pine and 0, 40, 75 and 150 ppb for Norway spruce, respectively) for 28 days in controlled laboratory chambers. Compared with HP, the LP treatment reduced Scots pine current-year (C) shoot and root dry masses and Norway spruce total dry mass, whereas the highest O 3 concentrations increased the magnesium concentration of Scots pine C needles and P concentrations of the C needles of both tree species. Chlorophyll a, a+b and carotenoid concentrations of Scots pine C needles were significantly higher in the LP treatment compared with HP under the highest O 3 concentration (210 ppb). In the mesophyll tissue of C needles of both tree species, LP treatment increased the size of mitochondria and elevated O 3 -induced granulation of chloroplast stroma and disintegration of cytoplasm. Exposure to elevated O 3 concentrations increased swelling of chloroplast thylakoids and reduced the amount of vacuolar tannin in the LP Scots pine C needles. The results suggest disturbances in needle photosynthetic machinery due to acute exposure to the combination of elevated O 3 and low P availability. However, clear additive effects were found only in needle P concentrations < 1 mg g -1 in short-term O 3 exposure.     

Models for Predicting Wood Properties in Stems of Picea abies and Pinus sylvestris in Sweden

To study and model the variation of wood properties, sample trees were selected from 42 Norway spruce and 20 Scots pine stands covering a wide variation in climatic and site conditions, stand maturation and tree sizes. Plot and tree measurements were followed by sampling wood from different heights in each sample tree and laboratory measurements of wood properties. Mixed linear and non-linear prediction models were developed using diameters, number of annual rings and climatic indices as explanatory variables. The variation in spruce properties explained by these variables was: basic density 50%, latewood content 52%, juvenile wood diameter 85%, heartwood diameter 94% and bark thickness 76%. The corresponding values for pine were 59, 54, 79, 92 and 85%. Random among-tree variance was an important contributor to the remaining variation for density and latewood. In general, only a minor part of the random variation was related to variance between stands. Predictions derived from the models for density and juvenile wood in both species, and heartwood in pine showed good agreement when validated with data sets from two other studies. The resulting models may be used for predicting wood properties in forest planning and in bucking computers in harvesters, provided that the essential information is available.     

Diversity of higher plant in broad leaved Korean pine and secondary birch forests in Liangshui Natural Reserve

INTRoDUCTIoNBroad-lcavedKoreanpincforcstisthczonalclimaxecosystcminnortl1castmountainsofChina.Itisknot"nasdivcrscsPCCicsandsPCcialindicatorinthcnortl1cmtcmPCratcforcstty'PCsofthccarth.Bccauscthiski11dofforcstllashighproductivityandlargcasscss-ment,andiscomPoscdoflnany'\1aluabIccoIl1-mercialtI-eesPCcicssucl1asI,inuskoraicnsi3,Fraxinusman'I3huricactc.IthasbecncutoverinIargcarcasduringtl1clastscveraldcc-adcsandtl1coldforcstI1asbccndamagcdscri-ousIy.Noxt'n1ostoftl1cml1a\'cbcenreplacc…     

戴震公园不同群落类型物种多样性与更新调查分析

通过对黄山市城区戴震森林公园中森林群落进行调查,分析不同群落类型的物种多样性及更新情况。结果表明,不同优势树种组成的群落物种多样性存在一定差异,樟树-金钱松-椤木石楠所组成的群落,其丰富度和Shannon-Weine物种多样性指数高,分别为3.9712、2.2235;樟树-重阳木-水杉群落的Simpson指数和均匀度指数最高,分别为0.8869、2.1043;桂花群落相应指标最小,分别为0.3761、0.2782、0.1296、0.5831。更新特征是樟树-金钱松-椤木石楠群落最优,而桂花群落调查期间无更新。     

Effects of Partial Cutting and Scarification on Planted Picea abies at Mid-elevation Sites in South-east Norway

Mortality, injury and height growth of planted Picea abies (L.) Karst, were examined over a 6 yr period in eight stands at middle altitudes (430–620 m a.s.l.) in south-east Norway. There were four residual stand density treatments (shelterwoods of high, medium and low density, 25 × 25 m patch-cut) combined with three scarification treatments (unscarified, patch scarification, inverting) in a split-plot design. Mortality was very low during the experimental period, and did not differ significantly between the residual stand density treatments (mean = 11.1%). Both survival and plant height after 6 yrs were improved by inverting, while patch scarification was intermediate but not significantly different from the unscarified alternative. The patch-cutting resulted in the tallest plants, while only minor differences in height growth were found between the shelterwood treatments. The frequency of injured plants after 6 yrs was not significantly affected by the treatments (mean = 10.6%). The improved plant establishment at inverting is in agreement with previous studies on clear-cuts.     

Variation in Tree Size and Resistance to Ceratocystis polonica in a Monoclonal Stand of Picea abies

Tree resistance to the pathogenic blue-stain fungus Ceratocystis polonica was studied in a monoclonal stand of Norway spruce [ Picea abies (L.) Karst.] in relation to tree social status and diameter at breast height (DBH). The DBH distribution of the 33-yr-old stand ranged from 5 to 35 cm. There were clear differences in tree height between the suppressed (DBH 7.4-10.3 cm), codominant (DBH 11.8-17.4 cm) and dominant (DBH 18.6-23.9 cm) tree classes. The resistance was tested by mass inoculating trees with a low (400 inoculations m -2 , 60 cm inoculation belt) or high (400 inoculations m -2 , 120 cm inoculation belt) dosage. The small, suppressed trees were more susceptible to inoculation than the codominant and dominant trees, based on the amount of blue-stained and occluded sapwood, lesion length and dead cambium/phloem. A threshold in tree social status or tree size may be important in the overall resistance to fungal infection.     

长白山针阔混交林林木更新主要影响因素研究

基于14块针阔混交林固定样地的天然更新调查数据,针对影响天然更新效果的因素众多,仅用定性分析难以做出判断的特点,因此采用灰色系统中的关联度分析法,把影响天然更新的因素进行排序。排序结果依重要性分别是海拔高度、林木株数、郁闭度、腐殖质厚度、针叶树蓄积比重、蓄积量、针叶树株树、坡度。由于云冷杉等针叶树幼苗喜荫,不喜光,所以在采伐强度过大时将造成林内郁闭度降低,林内光照明显增强,进而严重影响云冷杉幼苗幼树的生长。因此,在实际生产中应慎重扩大采伐量,同时在采伐过程中尽可能减少对保留木的损伤,保证林分的天然更新。     

Regeneration of pitch pine (Pinus rigida) stands inhibited by fire suppression in Albany Pine Bush Preserve,New York

The Pine Barrens in New York State are dominated by pitch pine(Pinus ridgida) and scrub oaks(Quercus ilicifolia and Q. prinoides). With fire suppression over the last 90 years or so, P. rigida regeneration has become sparse, even in areas set aside to preserve this type of vegetation. We evaluated the effects of fire and an alternative disturbance(mechanical removal of vegetation)for increasing P. rigida regeneration in the Albany Pine Bush Preserve in eastern New York State. By comparing cover, diameter and height of P. rigida, Q. ilicifolia, Q.prinoides, and Vaccinium spp.(blueberry) growing on the sites with a known fire history, we documented structural and compositional changes in the vegetation since its establishment. We also compared sites on which Quercus sprouts were controlled through mechanical removal. In the years following a disturbance, height and cover of Q. ilicifolia increased continuously and the species became increasingly competitive. Both the density of P. rigida seedlings and Vaccinium cover decreased significantly as the diameter and height of Quercus increased. Our results confirmed that the dominance by P. rigida could be attributed to periodic fires at intervals of 20–25 years. We conclude that removing Q. ilicifolia can favor P. rigida dominance on the barren without fire by releasing pine seedlings from competition.     

Micromorphology and topochemistry of extractives in Scots pine and Norway spruce thermomechanical pulps: a cytochemical approach

Due to the increasing demand for Norway spruce as prime raw material for high-yield pulping, recent interest has focused on Scots pine as an alternative. However, the intrinsic properties of Scots pine, particularly the high amounts of extractives and the fiber properties, have been considered a disadvantage for thermomechanical pulping. A study was therefore conducted on the variations in the spatial distribution and redistribution of lipophilic extractives in spruce and pine wood and thermomechanical pulp (TMP) using cytochemical staining methods and chemical analysis. Chemical analyses showed chips from pine thinnings and sawmill slabs to contain three to five and two to three times, respectively, more extractives than found in spruce; in particular, the amount of triglycerides differed significantly. Results from staining techniques on the abundance and distribution of extractives (i.e., fats) between pine and spruce correlated with amounts detected by Fourier transform infrared spectroscopy and gel permeation chromatography. Cytochemical observations revealed information pertaining to species-specific distribution and redistribution of extractives among TMP fines and fibers and indicated the presence of a molecular film of extractives. Results indicate that the high concentrations of extractives in pine ray parenchyma are released during TMP processing and are redistributed onto the surfaces of the pulps, negatively affecting energy usage during primary refining.     

Patterns and factors in early-stage vegetation recovery at abandoned plantation clearcut sites in Oita, Japan: possible indicators for evaluating vegetation status

The abandonment of sites after clearcutting plantations is increasing rapidly in Japan. Although a few stand-level studies have been conducted, a broad-scale study is needed to understand the general tendency of vegetation recovery and to obtain information for the management of such extensively distributed abandoned clearcut sites. This study is a province-level study that aims to interpret the patterns and factors in early-stage vegetation recovery at abandoned plantation clearcut sites. We also discuss the potential indicators that may determine whether a certain site recovers towards evergreen broad-leaved forest consisting of Castanopsis cuspidata and Quercus glauca or towards deciduous broad-leaved forest comprising Q. serrata and Q. acutissima. A cluster analysis revealed that five types of vegetation (evergreen trees, evergreen trees–deciduous pioneer shrubs, pioneer species, deciduous trees, and deciduous shrubs) were observed from an early stage of succession. The first two vegetation types were considered to recover successfully to the target vegetation of evergreen broad-leaved forest, but the remaining three vegetation types did not show any tendency to recover to the target vegetations. According to the results of the detrended correspondence analysis, a smaller size of the abandoned site with adjacent evergreen broad-leaved forest and a longer time after clearcutting were identified as factors that enhance the invasion of evergreen tree species; these factors are also useful to predict the future successional tendency. In conjunction with these factors, the existence of regeneration sources (i.e., stumps) that allow sprouting appeared to be an important indicator for predicting the early-stage vegetation recovery.     

Effects of species and tree size diversity on recruitment in the Alaskan boreal forest: A geospatial approach

This study empirically evaluates and maps the relationships between recruitment and species and tree size diversity, as measured with the Shannon’s index, within mixed poplar/birch and mixed spruce stands across the boreal forest of Alaska. Data were collected from 438 permanent sample plots re-measured at a 5-year interval. Significant explanatory factors of recruitment, including species and tree size diversity were first identified using hierarchical partitioning. The effects of tree diversity on recruitment were then studied using generalized linear models and universal kriging to account for non-spatial factors and for spatial autocorrelation. We found a consistent positive relationship between recruitment and species diversity and a general negative relationship between recruitment and tree size diversity, indicating a tradeoff between species diversity and tree size diversity in affecting recruitment. These relationships however were not uniform across the landscape, presumably because they were subject to strong spatial autocorrelation attributable to natural disturbances and environmental stressors. In general, diversity had least effect on recruitment in stressful environments where stress, rather than competition, most likely governed recruitment.     

NP营养对杉木、湿地松、尾叶桉苗木干物质分配的影响

对酸性土壤上NP营养对杉木、湿地松、尾叶桉苗木根冠干物质分配的影响进行研究.结果表明:随着土壤NP营养亏缺的解除,尾叶桉苗叶片、根系干物质的累积随之下降,光合产物向茎部转移;湿地松根、茎干物质积累随NP营养水平的提高而下降,光合产物的累积向叶片转移;杉木根系干物质随NP营养亏缺的解除而下降,光合产物向叶片和茎部转移.3个树种的共同特点是:在营养亏缺状态下,苗木根冠比(R/S)的提高实际上反应了苗木对土壤NP营养亏缺的适应性特征.关于NP营养与根冠干物质分配的关系可以应用异速生长模型、Thornley模型、功能平衡模型来表示,3种模型均能良好反应出酸性土壤上NP营养对苗木干物质分配的影响,应用模型可对苗木根冠生长速率进行调控,这无疑对苗木的培育有重大的意义.异速生长模型中k=1可作为判别苗木营养最适平衡的一个标志.