丝栗栲林生长与生产力的研究

在福建省邵武市洪墩采育场，调查丝栗栲林标地１０块，做平均木、树干解析木９株，杉木人工林标地２块，研究丝栗栲的生长与生产力，结果表明：丝栗栲林的胸径、树高及单株材积总生长量，均随年龄的增加而增加；胸径２０ａ前生长最快；树高１６ａ前生长最快；材积３６ａ时尚未有下降的趋势。胸径、树高平均生长量，随年龄增加而增加，当生长量达高峰后，则随年龄的增加而下降；胸径生长高峰，好立地１２ａ，中、劣立地１５ａ；树高生长高峰，好立地１０ａ，中立地８ａ，劣立地１２ａ；材积平均生长量，随年龄增加而增加，好、劣立地３６ａ时仍未下降，中立地３４ａ时生长量最大。胸径、树高连年生长量随年龄增加而下降；材积连年生长量，随年龄增加而增加，当生长量达高峰后，则随年龄增加而下降，生长高峰出现的年龄，好立地２８ａ，中立地２２ａ，劣立地２６ａ。在相似的立地条件下，丝栗栲林的蓄积量比杉木人工林低，但乔木层总生物量比杉木林高。     

Seed production of western larch in seed-tree systems in the southern interior of British Columbia

A series of surveys and experiments were conducted on four sites to identify constraints to seed production and natural regeneration in western larch seed-tree systems in the southwestern interior of British Columbia, Canada. These surveys included pollen monitoring, a cone analysis to evaluate seed production potential, seed trapping to estimate seed rain and the installation of field germination trials to assess the effects of germination substrate and seed losses due to bird and rodent predators. Pollen shedding was found to be adequate for moderate seed production with filled seed counts ranging from 9 to 30 per cone (10–34% of all seeds/cone). No significant differences in seed yields per cone and cone characteristics were observed between uncut control stands and seed-tree stands. Seed rain was generally good in 1995, ranging from 70,000 to 4.6 million seed/ha. For the four seed-tree stands, the average filled seed percentage of the trapped seeds ranged from 9–30%. Seed rain and seed quality were much reduced in 1996. Field germination trials showed western larch seeds germinated and survived best (15–70%) on mineral soil but rodent and/or bird predation reduced germination success significantly. Germination/germinant survival on undisturbed forest floor, covered with predator exclusion screens, was intermediate.     

Growth and nut production of black walnut in relation to site, tree type and stand conditions in south-central United States

Black walnut (Juglans nigra) is a prime tree species for agroforestry practices in the United States providing highly prized wood and nuts for human consumption and wildlife. In 54 black walnut stands in south central United States, the site index (i.e., mean dominant height [DH], at age 25 years) ranged between 5.2 and 21.4 m, and was independent of stand density. There were no differences in height and stem diameter (DBH) growth rates between stands with improved varieties and native stock. Most stands were in a “free growth” stage because of either early age or wide spacing. Mean annual increments in DBH and height were positively related both for improved varieties and native stock. Understory competition had a substantial detrimental effect on DH. In a 26 year-old stand, trees growing within Kentucky blue grass (Poa pratensis) had a site index 5 m greater than trees growing within tall fescue (Festuca arundinacea). Predicted nut yields in 2002 varied between 0 and 1370 kg of hulled nuts per ha. Improved varieties had, in general, higher nut yields than predicted from a nut yield-DBH equation developed for individual trees. Nut yields were highly variable both within and among stands, and were related to DBH in native stock but not in improved varieties.     

Realized genetic gains observed in second generation seedling seed orchards of Eucalyptus pellita in Indonesia

The first generation genetic gains in four second-generation seedling seed orchards of Eucalyptus pellita established at two locations in Indonesia (Kalimantan and Sumatra) were examined by analyzing data on the height, diameter and stem form of the trees during years 1 to 3. The seed orchards each consisted of 60 open-pollinated families: 48–49 families from first-generation plus trees (improved population) and 11–12 families from natural forest (unimproved population). The realized gains for height and diameter were ca. 16 and 19%, respectively. These gains were highly significant and consistent, irrespective of age and location. However, the gains in stem form were much lower (4%) in Kalimantan than in Sumatra (21%) and only significant in the latter, possibly because of the more intensive silvicultural management regimes at the Sumatran sites. The results confirmed that the first-generation tree improvement program for E. pellita has been effective in Indonesia, and that it should provide improved seeds for operational plantation, thus raising their productivity.     

Influence of different forest conversion strategies on ground vegetation and tree regeneration in pine (<Emphasis Type="Italic">Pinus sylvestris</Emphasis> L.) stands: a case study in NE Germany

The conversion of anthropogenic into more natural, self-regenerating forests is one of the major objectives of forestry throughout Europe. In this study, we present investigations on permanent plots with different silvicultural treatment in NE German pine stands. Management of old-growth pine stands on acidic and nutrient-poor sandy sites differs in fencing, thinning, and planting of certain tree species. The investigations were carried out on the community, population, and individual level of the pine forest ecosystems. Thus, vegetation changes, size and height of tree populations, and height increment of tree individuals were observed over a time span of 6 years. Special attention was paid to short-lived tree species such as, e.g., Frangula alnus and Sorbus aucuparia, as well as to Fagus sylvatica as one of the most typical forest tree species of Central Europe. Vegetation changes are interpreted as a consequence of natural regeneration of formerly degraded forest sites, involving an increase in nutrient availability. High browsing pressure can be considered as a key factor for the inhibition of tree seedlings and growth of saplings. Some Sorbus aucuparia individuals, however, succeeded in growing out of the browsing height also in unfenced stands. Few found specimens of Fagus sylvatica proved that this species is able to establish spontaneously on these relatively dry, acidic sites under continental climate influence. Such natural regeneration processes, also including spontaneous rejuvenation of trees, can be integrated into silviculture as passive forest conversion management. An active management like thinning of stands, planting of trees, and fencing can accelerate forest conversion with regard to height growth and species number of trees.     

Natural Variation in Seed Characteristics of Eastern White Pine (Pinus strobus L.)

Natural variation in seed characteristics of eastern white pine (Pinus strobus L.) trees and its relationship with the size, form, and crown class of parent trees was examined in second-growth, white pine mixedwood stands in Ontario. Cones were collected prior to and following partial harvesting of two stands during 2 years of above-average seed production. Fully enlarged seed extracted from mature cones was X-rayed to determine seed yield per cone, the percentage of sound, partially filled, and empty seed, and the sound seed mass for each tree. Variation in seed yield per cone, the proportion of sound, partially filled, and empty seed, and seed mass was much greater among individuals than between stands or seed years. The strength and significance of the relationship of seed mass with sound seed yield differed with stand and seed year. In uncut stands, seed mass was higher for trees with dominant crown class, larger live crown ratios, and smaller height to diameter ratios, suggesting tree vigour and microsite quality influence seed mass. Proportion of partially filled seeds was significantly reduced in both stands in the second year likely due to increased growing degree days during female gametophyte development. The implications of these results to natural and artificial regeneration of white pine are discussed.     

Effects of crown-pruning on seed and pollen cone production in two lodgepole pine seed orchards in British Columbia

The effects of top pruning on subsequent seed and pollen cone production in lodgepole pine (Pinus contorta Dougl.) grafted clones in two seed orchards were evaluated. In the older orchard (14 years old), three pruning regimes were applied: an untreated control, a moderate pruning where 25% of the crown was removed and a severe pruning where 40% of the crown was removed. In the younger orchard (ten years old), only a control pruning and a severe pruning (50% of crown removed) were applied. Five-year seed cone production was lower in treated ramets compared to controls in both orchards. However, when cumulative seed cone yields were adjusted for reduced tree heights after pruning, differences were no longer significant in the older orchard. Strong clonal variation was observed in seed cone yields in both orchards. Pollen cone development was less variable among treatments in the older orchard. In the younger orchard, controls consistently produced heavier pollen crops. Pruning recommendations for similar orchards are made and results discussed for reducing the impacts of losses in seed cone yields.Deceased     

Effects of bamboo stands on seed rain and seed limitation in a rainforest

Bamboos often negatively affect tree recruitment, survival, and growth, leading to arrested tree regeneration in forested habitats. Studies so far have focused on the effects of bamboos on the performance of seedlings and saplings, but the influence of bamboos on forest dynamics may start very early in the forest regeneration process by altering seed rain patterns. We tested the prediction that the density and composition of the seed rain are altered and seed limitation is higher in stands of Guadua tagoara (B or bamboo stands), a large-sized woody bamboo native from the Brazilian Atlantic Forest, compared to forest patches without bamboos (NB or non-bamboo stands). Forty 1 m² seed traps were set in B and NB stands, and the seed rain was monitored monthly for 1 year. The seed rain was not greatly altered by the presence of bamboos: rarefied seed species richness was higher for B stands, patterns of dominance and density of seeds were similar between stands, and differences in overall composition were slight. Seed limitation, however, was greater at B stands, likely as a resulted of reduced tree density. Despite such reduced density, the presence of trees growing amidst and over the bamboos seems to play a key role in keeping the seeds falling in B stands because they serve as food sources for frugivores or simply as perches for them. The loss of such trees may lead to enhanced seed limitation, contributing ultimately to the self-perpetuating bamboo disturbance cycle.     

Spatial impacts of soil disturbance and residual overstory on density and growth of regenerating aspen

We examined spatial aspects of harvesting impacts on aspen regeneration at 25 sites in northern Minnesota. These sites had been clearcut or partially harvested 4–11 years ago. At each site, residual overstory, which was composed of trees other than aspen, soil disturbance, and tree regeneration were determined along transects leading away from skid trails into the neighboring stand. We characterized spatial extent of soil disturbance as soil strength using an Eijkelkamp soil cone penetrometer. Soil disturbance dropped off very quickly at the edge of skid trails, suggesting that the impact of harvesting traffic on areas adjacent to skid trails is minor. On skid trails, disturbance levels were higher on sites harvested in summer than on sites harvested in winter. Even after adjustment for differences in soil disturbance, stands harvested in winter had higher regeneration densities and greater aspen height growth than stands harvested in summer, suggesting that aspen regeneration was more sensitive to a given level of soil disturbance on summer-harvested sites versus on winter-harvested sites. Soil disturbance and residual overstory interactively reduced aspen regeneration densities and height growth, indicating that avoidance of soil disturbance is even more critical in partially harvested stands. Predictions based in the spatial patterns of impact found in this study indicated that harvesting conditions may have a great impact in future productivity of a site.     

Seedling growth and establishment in natural stands of yellow-cedar (Chamaecyparis nootkatensis) seedlings derived from the use of modified seed dormancy-breaking treatments

Following dispersal from the parent tree, seeds of yellow-cedar (Chamaecyparis nootkatensis[D. Don] Spach) exhibit low germination, primarily as a result of coat-imposed dormancy. Dormancy of the mature (intact) seed is effectively terminated by traditional warm/cold treatments. A chemical treatment using the anaesthetic 1-propanol combined with a three day warm water soak (30 °C), a two day GA₃ treatment and 60 d of moist chilling not only promotes high germinability of yellow-cedar seeds, but also elicits vigorous post-germinative growth following seedling emergence under nursery greenhouse conditions. Here we compare the effectiveness of the more traditional warm/cold treatments with the chemical treatment in terms of their capacity to elicit vigorous growth and establishment in natural stands following transplant of seedlings from a nursery greenhouse environment. Two seed lots (42313 and 43697) and open-pollinated seed from parent trees 13-6 and 19-8 showed equivalent seedling growth in natural stands following the chemical treatment and two traditional warm/cold treatments typically used for dormancy breakage by the forest industry and by the Ministry of Forests in British Columbia. The chemical protocol offers the advantage of reducing the time required to break seed dormancy. We have now demonstrated that it yields seedlings that exhibit vigorous growth and are capable of withstanding the vagaries of the environment.     

Effect of thinning intensity on tree growth and temporal variation of seed and cone production in a Pinus koraiensis plantation

Thinning of Korean pine (Pinus koraiensis Sieb. et Zucc.) is used to facilitate timber and cone production. The present study in Northeast China investigated the effects of thinning intensity on individual tree growth, temporal variation in cone yield, and seed quality in Korean pine plantation. In 2005, five thinning intensity levels (none, extreme, heavy, moderate and light) were set in 15 permanent plots in a 32-year-old Korean pine plantation at Mengjiagang Forest Farm, Jiamusi City, Heilongjiang Province. We recorded tree growth and seed cone production from 2013 to 2016, i.e., from 8 to 11 years after thinning. Except for height growth, thinning increased tree growth (diameter at breast height and crown size) and improved cone yield. The extreme thinning treatment (to 300 trees per hectare) resulted in the largest tree diameter, tree volume, crown size and 4-year cone production per tree. The highest cone yield per tree in the mast year (2014) was observed when stands were thinned to 500 trees per hectare (heavy thinning). Although the best cone and seed quality and the largest cone and seed mass per tree were recorded in the heavily thinned stand, no significant differences were found between heavy and moderate thinning stands (750 trees per hectare). At the stand level, the moderately thinned stand had the highest basal area, stock volume and seed cone production per stand. Our results suggest that thinning to 750 trees per hectare will improve timber and cone productivity in 40-year-old P. koraiensis stands.     

The effects of selective logging on stand structure and the regeneration of subboreal forests in Hokkaido, northern Japan

We investigated the effects of selective logging on stand structure and regeneration in selectively logged subboreal forests in Taisetsuzan National Park in Hokkaido in northern Japan. The basal area decreased and the size structure of trees altered in the stands studied due to repeated, intense selective logging, in which larger trees were cut down as a priority. Sapling density in the stands was much lower than that in primary forests. In the simple and multiple regression analyses that were used to estimate the effects of selective logging on sapling density, sapling density had a significant positive correlation with tree density and had little correlation with the density of logged stumps or the height ofSasa (dwarf bamboo) growing on the forest floor. These results suggest that the establishment sites around canopy trees influenced the establishment of saplings, rather than the gaps caused by selective logging. However, both the coefficient of determination and the standardized partial regression coefficient of multiple regression analysis were higher for the stand with a dense cover ofSasa than for the stand with a sparse cover ofSasa. Thus, the success of regenerating forests with selective logging depends on both the site of advanced regeneration and the light conditions that regulate growth.     

Germination traits and adaptive regeneration strategies of the threeCarpinus species

Germination tests in the three sympatricCarpinus species,C. laxiflora, C. tshonoskii, andC. cordata, were carried out to clarify their germination traits in relation to the regeneration strategies. Seeds did not germinate just after ripening under any conditions in the three species. After one or two rounds of cold stratification, however,C. laxiflora andC. tshonoskii showed high germination percentages (>80%) at alternating temperature in light whileC. cordata did not. After a long-term (10 months) cold stratification, about 100% ofC. cordata seeds germinated, although about 70% of these seeds were in “conditional dormancy” and cannot germinate in the dark. Seed germination in the threeCarpinus species was enhanced by alternating temperature, but not by light exposure. These results suggest that the seeds of the three species are dormant just after ripening and the dormancy is broken by cold stratification. with intra-generic variations in the breakage. Germination traits in each species may be closely related to the regeneration strategy;C. cordata maintains a persistent seed bank with seed dormancy and regenerates after disturbances as a seed bank strategist, whereas the other two species germinate in the next spring after seedfall and regenerate depending either on existing disturbed-sites or sites of recent disturbances after seedling establishment as a seed rain strategist (C. tschonoskii) or seedling bank strategist (C. laxiflora). This study was supported by grants from the Ministry of Agriculture, Forestry and Fisheries (BCP-97-III-A).     

Fruit production ofAcacia tortilis andA. nilotica in semi-arid Ethiopia

Dry, dehiscent fruits ofAcacia tortilis provide important fodder for pastoral livestock in dry seasons on the central Borana Plateau, fruits ofA. nilotica may also be useful during drought. Information was needed on fruit yield to assess what these species could contribute to improved calf feeding systems based on local resources. Fruit production of 10 mature trees per species was measured at five sites for seven months during 1988–9 (n=50 per species). Fruit yields varied according to site, season and species x site (each atP<0.001), but there was no main effect of species (P=0.13). Yields were not correlated with trunk diameter at breast height (DBH) or canopy area within or across species (P>0.05 in all cases). Yields ranged from 0 to 40 kg DM per tree overall, with an average of 5.3 kg DM per tree (or 65 g DM/m² of canopy area). This average tree had a DBH of 26 cm and a canopy area of 81 m². Low and highly variable fruit yields appear to constrain enhanced use of these species here. These species warrant further attention in research and development, however, given their strategic value as forage resources in pastoral systems and their ability to persist in variable environments.     

<Emphasis Type="Italic">Broussonetia papyrifera</Emphasis> (paper mulberry): its growth,yield and potential as a fallow crop in slash-and-burn upland rice system of northern Laos

In northern Laos, shortened fallows in the slash-and-burn upland rice system are not sustainable either from a production or economic standpoint. This paper evaluates the potential for using the indigenous fast-growing tree, Broussonetia papyrifera L. Vent. (paper mulberry) as an economic fallow crop. The objectives of this study are to assess the inner bark yield of paper mulberry, and to evaluate rice productivity following paper mulberry cultivation. In addition, allometric models for estimating the inner bark yield of paper mulberry are developed. Inner bark yield of paper mulberry stands ranging in age from 9 to 48 months ranged from 10 to 208 g m⁻², and increased with age. The models using diameter at breast height and stem height, or diameter at breast height only as independent variables explained well the variation in inner bark yield. When paper mulberry was completely removed during the rice growing season, rice yields in these areas were similar to those following weedy bush fallow. When paper mulberry was allowed to grow, rice yields were negatively correlated to paper mulberry stem density. When paper mulberry lateral branches were pruned back, rice yields could be maintained if the paper mulberry stem density was <0.22 stems m⁻², suggesting that if paper mulberry is managed properly, rice yields can be maintained at current levels. The paper mulberry-upland rice rotation system improves the productivity of a traditional slash-and-burn system through harvesting paper mulberry inner bark; however the long-term sustainability of such a system remains unclear and warrants further investigation.     

Cone and seed production from stone pine (<Emphasis Type="Italic">Pinus pinea</Emphasis> L.) stands in Central Range (Spain)

Natural regeneration of stone pine (Pinus pinea L.) stands in the Central Range of Spain can be difficult to attain. The success of this regeneration is affected by factors such as the total amount of seed available, the short dispersal ability of the pinyon, the conditions required for germination, specific problems associated with the establishment, early survival of the seedlings due to severe summer heat and drought, competition for water and mineral resources and grazing damage. This study focuses on seed availability. The amount of available seeds depends on the number and size of the cones and the number of viable pinyons within the cones. In stone pine stands, both variables show great year to year variability. Both cone and seed production, for a given year, are also conditioned by the vigour and health of the tree, its size, the condition and attributes of the stand and the loss of seed through pests or predation. In this study, the main factors which influence cone and pinyon production are identified and a multivariate model to predict annual cone and viable seed production is developed. To consider the correlation among observations coming from the same tree, stand or year, random components are included in the model. The multivariate random structure allows for future calibration of the model for a given year from a small additional sample of observations. It is important to know the total amount of viable seed produced in a stand for a given year since regeneration cuttings for Stone pine should be concentrated in high crop years.     

Phenology Differs among Norway Spruce Populations in Relation to Local Variation in Altitude of Maternal Stands in the Beskidy Mountains

An investigation of phenological and growth traits was conducted in a lowland plantation, comprised of 23 Norway spruce (Picea abies (L.) Karst.) seed stands from the Istebna region in the Beskidy Mountains of Poland. Significant differences were found among population in growth initiation, growth termination and the length of shoot elongation period. The two latter traits were highly correlated and were attributed to the altitude of the maternal stand. The tested populations were grouped based on phenology. Progeny of lower-alttitude stands ceased growth later, had a longer duration of shoot growth and greater current leader length compared to progeny of higher-altitude stands. Individual populations, however, did not differ in current-year growth and total tree height, implying higher within-population variation in growth traits than in phenology. The similar growth capacity of all tested populations suggests considerable gene flow between maternal stands, although differences in phenology imply the adaptation of progenies to the altitudinal environment of seed origin. These results suggest that within tested populations, selection is possible based on phenology alone, without considerable reduction of early height growth; final decisions, however, should be based on the environmental conditions of the planting site.     

Quantitative variation among Kenyan populations of Acacia senegal (L.) Willd. for gum production, seed and growth traits

Acacia senegal (L.) Willd. is an African leguminous multipurpose tree species belonging to subfamily Mimosoideae and subgenus Aculeiferum, highly valued for gum arabic production. This study estimated the genetic diversity within and among Kenyan populations of the species in the Bulla Sambul, Kutulo, Wamba and Meisori populations based on 12 quantitative traits, which included; tree height, diameter at breast height (DBH), number of branches, bark thickness, gum weight and various pod and seed traits on 20 randomly selected trees in every population. Duncan’s multiple range test (DMRT) and the dendrogram distinctively divided the populations into two groups; Wamba and Meisori in one group while Bulla Sambul and Kutulo in the other, indicating geographical structuring of the genetic variability. The trees were larger, taller with greater pod and seed traits in the Wamba and Meisori than the Bulla Sambul and Kutulo populations. Contrarily, trees had lighter seeds, more branches with higher gum weight in the Kutulo and Bulla Sambul than the Wamba and Meisori populations. The Shannon–Weaver diversity index (H), depicted 1,000-seed weight as the most varied trait across the populations. These findings provide essential information on the genetic diversity of the species, necessary for delineation of particular zones for seed sources for germplasm conservation, selection for domestication and improved gum arabic production.     

Growth and nutrition of young European ash (<Emphasis Type="Italic">Fraxinus excelsior</Emphasis> L.) and sycamore maple (<Emphasis Type="Italic">Acer pseudoplatanus</Emphasis> L.) on sites with different nutrient and water statuses

This study aimed to improve knowledge about the nutritional status, site requirements and site classification for European ash (Fraxinus excelsior L.) and sycamore maple (Acer pseudoplatanus L.) by reinvestigating young plantations from 1991/1992 on windfall-affected areas in Bavaria/Germany after another decade. Compared to the first survey in 1995, most stands improved their nutritional status until 2006. With the data set of element concentrations in leaves of ash and sycamore available, the range of adequate nutrition could be determined for these species in the pole stage phase. Both species show considerable height growth on a wide range of sites. Mean annual height growth of dominant sycamore trees increased with rising foliar N or P concentrations but not for Ca, Mg, K, Mn, Fe and Al. For ash, there was no relationship between the foliar nutrient level of any element and mean annual height growth. However, total height around age 20 was favourably influenced by high base saturation and a good water supply at well-drained sites. On acid soils, where nutrients are delivered by subsurface water flow, well-growing stands are found as well. Soil water status according to the state forest soil classification had no significant impact on mean annual height growth. Ash and sycamore show reduced productivity on some (moderately) dry soils and fail on poorly drained moist sites. Based on these results, the classification of forest sites suitable for ash and sycamore within the Bavarian study sites was revised. Dedicated to Professor Dr. Karl-Eugen Rehfuess on his 75th birthday.     

Adapting a growth equation to model tree regeneration in mountain forests

Management and risk analysis of protection forests depend on a reliable estimation of regeneration processes and tree growth under different site conditions. While the growth of forest stands and thus the average growth of larger trees is well studied and published in yield tables as well as embodied in numerous simulation models, there is still a lack of information about the crucial initial stages of tree growth. Thus, we evaluated juvenile tree growth for different site conditions in the Swiss Alps and developed an approach to model both the early and later stages of growth based on the Bertalanffy equation. This equation is physiologically well founded and requires only two parameter estimates: a maximum tree height and a growth parameter. Data for the parameter estimation were available from studies of tree regeneration at a range of sites in Switzerland: growth patterns of larch (Larix decidua) were available from a high-elevation afforestation experiment. For spruce (Picea abies), data were obtained from a blowdown area in the Alps. The growth equation was fitted to the observed data and we found a good correlation of the fitted curves with the observed data. The parameter estimates were validated with independent data sets. The extrapolated growth curves, calculated with the estimated growth rates, correspond well to the validation data. Thus, it is possible to use the Bertalanffy equation to model both the early and later stages of growth. With this approach, we provide a basis for modelling the growth of juvenile and mature trees of different tree species in mountain forests of the European Alps.