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1.
Christian Temperli Golo Stadelmann Esther Thürig Peter Brang 《European Journal of Forest Research》2017,136(3):493-509
The demand for wood as construction material, renewable source for energy and feedstock for chemicals is expected to increase. However, timber increments are currently only partly harvested in many European mountain regions, which may lead to supply shortages for local timber industries, decreases in forest resistance to disturbances and functioning as protection from gravitational hazards. Using an inventory-based forest simulator, we evaluated scenarios to increase wood mobilization in the 7105-km2 Swiss canton of Grisons for the period 2007–2106. Scenarios varied with respect to landscape-scale harvesting amounts and silvicultural strategies (low vs. high stand-scale treatment intensity) and accounted for regulations and incentives for protection forest management. With 50 and 100% increases of harvests, the current average growing stock of 319 m3 ha?1 was simulated to be reduced by 12 and 33%, respectively, until 2106 in protection forests of Northern Grisons, where management is prioritized due to subsidies. Outside protection forests and in Southern Grisons, growing stock was simulated to continually increase, which led to divergent developments in forest structure in- and outside protection forests and in the Northern and Southern Grisons. The effect of silvicultural strategies on simulated forest structure was small compared to the effect of future harvesting levels. We discuss opportunities and threats of decreasing management activities outside protection forests and advocate for incentives to promote natural regeneration also outside protection forests to safeguard long-term forest stability. 相似文献
2.
Current silvicultural treatments in beech forests are aimed at achieving thick logs without discoloured hardwood. Therefore
intensive thinning is applied already in younger stands with the objective of large-sized trunks at an age of 100 years. However,
this approach bears the risk that dead wood structures and broken trees are completely removed from the forest. The impact
of three different silvicultural management intensity levels on wood-inhabiting fungi over decades was investigated in a large
beech forest (>10,000 ha) in southern Germany in 69 sampling plots: A Intensive Thinning and Logging with high-value trees,
B Conservation-Oriented Logging with integration of special structures such as dead wood and broken trees and C Strict Forest
Reserves with no logging for 30 years. The analysis of community showed marked differences in the fungus species composition
of the three treatments, independent of stand age. The relative frequencies of species between treatments were statistically
different. Indicator species for naturalness were more abundant at sites with low silvicultural management intensity. Fomes fomentarius, the most common fungus in virgin forests and strict forest reserves, is almost missing in forests with high-management intensity.
The species richness seemed to be lower where intensive thinning was applied (P = 0.051). Species characteristic for coarse woody debris were associated to low management intensity, whereas species with
a significant preference for stumps became more frequent with increasing management intensity. A total amount of dead wood
higher than 60 m3/ha was found to enable significantly higher numbers of species indicators of naturalness (P = 0.013). In conclusion, when applying intensive silvicultural treatment, the role of dead wood needs to be actively considered
in order to maintain the natural biocoenosis of beech forests. 相似文献
3.
The strategy for implementing silvicultural practices in Japanese plantation forests was examined to achieve a carbon uptake of 13.0 Mt-C year–1, which was capped by the Marrakesh Accords, during the first commitment period, 2008–2012. The plantation forests that implemented silvicultural practices in the period 1990–2012 (FM plantation forests) were identified in compliance with the hypothesized identification rules, and carbon uptake in the forests was estimated using a simple model composed of simulation and optimization components on the assumption that whole plantation forest is classified into only two groups. Furthermore, parametric analysis was conducted to investigate the relationships among three factors: (1) the average annual harvesting volume (including thinning) in plantation forests during the first commitment period, (2) the total area of FM plantation forests in 2012, and (3) the average annual amount of carbon to be sequestered in FM plantation forests during the first commitment period. The results imply that young stands have to be prioritized in implementing silvicultural practices under any harvesting plan and carbon sequestration goal, and that FM plantation forests sequestered 8.0–10.5 (Mt-C year–1) carbon in inverse proportion to the harvesting volume of 21.0–14.0 million m3 year–1 (log volume), assuming that most of the plantation forests were incorporated into them. 相似文献
4.
Context
Recruitment is an important process in forest stand dynamics, especially in uneven-aged stands. Continuous recruitment is a prerequisite for diverse, uneven-aged silvicultural systems, but patterns may vary significantly.Aims
The main goals of the study were to examine the recruitment of the main tree species in selection and irregular shelterwood stands in silver fir?CEuropean beech?CNorway spruce forests and to determine the main predictors of the recruitment occurrence.Methods
Data from 5,486 permanent inventory plots were used to study recruitment of saplings into the tree layer (diameter at breast height ??10?cm).Results
Recruitment rate differed significantly between selection (7.6?trees?ha?1?year?1) and irregular shelterwood (26.1?trees?ha?1?year?1) stands. Shade-tolerant fir and beech recruited with higher probability in selection stands, while light-dependent sycamore recruited with higher probability in irregular stands. In addition, forest types, soil pH, stand basal area, mean diameter, and the basal area of the same tree species with respect to recruitment were found to be important predictors of recruitment occurrence.Conclusions
The application of different uneven-aged silvicultural systems and their forms makes it possible to considerably influence the future tree species composition of uneven-aged forests. 相似文献5.
Goddert von Oheimb Christina Westphal Werner Härdtle 《European Journal of Forest Research》2007,126(3):359-370
The diversity, spatial patterns and temporal dynamics of dead wood were examined within the near-natural beech forests (Fagus sylvatica) of Serrahn (North-eastern Germany). Data were collected in an 8 ha sample plot and in two permanent plots (0.36 and 0.25 ha)
that had been established at the end of the 1960s. The mean volume of dead wood was 94 m3 ha−1, amounting to 14% of the total volume of all trees. The dead wood displayed a large variation in dead wood type, tree size
and decay class. Standing dead wood accounted for about one-third of the total dead wood volume. The densities of standing
dead trees were about 10% of the densities of the living trees over a wide range of diameters. The overall spatial distribution
of dead trees exhibited a random pattern. Among the different dead wood types, standing entire dead trees and uprooted trees
deviated from this pattern by displaying a significantly aggregated pattern. In the permanent plots a high mortality of overstorey
trees was observed (1.3% year−1) and the average amount of dead wood increased greatly from 2.9 to 111.6 m3 ha−1 over the 35-year observation period. The near-natural beech forests of Serrahn have experienced a long period of low human
interference. Nevertheless, our results suggest that the structure and dynamics of dead wood are strongly affected by the
last major disturbance events that took place at the end of the Middle Ages. Information about the forest history is therefore
a basic requirement when interpreting the results obtained in near-natural forests. 相似文献
6.
《Forest Policy and Economics》2003,5(2):141-155
Analysis of the impacts of forest management and climate change on the European forest sector carbon budget between 1990 and 2050 are presented in this article. Forest inventory based carbon budgeting with large scale scenario modelling was used. Altogether 27 countries and 128.5 million hectare of forests are included in the analysis. Two forest management and climate scenarios were applied. In Business as Usual (BaU) scenario national fellings remained at the 1990 level while in Multifunctional (MultiF) scenario fellings increased 0.5–1% per year until 2020, 4 million hectare afforestation program took place between 1990 and 2020 and forest management paid more attention to current trends towards more nature oriented management. Mean annual temperature increased 2.5 °C and annual precipitation 5–15% between 1990 and 2050 in changing climate scenario. Total amount of carbon in 1990 was 12 869 Tg, of which 94% in tree biomass and forest soil, and 6% in wood products in use. In 1995–2000, when BaU scenario was applied under current climatic conditions, net primary production was 409 Tg C year−1, net ecosystem production 164 Tg C year−1, net biome production 84.5 Tg C year−1, and net sequestration of the whole system 87.4 Tg C year−1 which was equal to 7–8% of carbon emissions from fossil fuel combustion in 1990. Carbon stocks in tree biomass, soil and wood products increased in all applied management and climate scenarios, but slower after 2010–2020 than that before. This was due to ageing of forests and higher carbon densities per unit of forest land. Differences in carbon sequestration were very small between applied management scenarios, implying that forest management should be changed more than in this study if aim is to influence carbon sequestration. Applied climate scenarios increased carbon stocks and net carbon sequestration compared to current climatic conditions. 相似文献
7.
The purpose of this study was to predict the likely amounts of carbon sequestration on a national scale for Japan in the Article-3.4
private planted forests of the Kyoto Protocol during the first commitment period. We regarded the planted forests that had
undergone silvicultural practices such as weeding, pruning, and thinning since 1990 as Article-3.4 planted forests in accordance
with the definition given by the Forestry Agency of Japan. Regression models were developed to predict the forest areas that
had undergone silvicultural practices, employing silvicultural subsidies and forest workers' wages as predictor variables.
Then the time series changes in the predictor variables were provided by extending their recent trends, with the result being
that the forest areas that have undergone silvicultural practices were predicted on the basis of the three scenarios of the
variables. Thus, the Article-3.4 forest area was calculated considering overlaps of silvicultural practices over fixed stands,
and the area was converted into the amount of carbon sequestration by multiplying it by coefficients such as a volume table,
biomass expansion factor, and others. The result implied that Article-3.4 private planted forests were expected to sequester
8.16–8.87 Mt-C year−1 during the first commitment period. These amounts cover 63%–68% of the carbon sequestration goal by land-use change and forestry
activities capped under the Marrakesh Accords. To realize this prediction, it is important to provide a sufficient silvicultural
subsidy to last until the end of the first commitment period and to implement silvicultural practices on the forest stands
that have not undergone such practices since 1990. 相似文献
8.
D. Hessenmöller O. Bouriaud D. Fritzlar A.S. Elsenhans 《Scandinavian Journal of Forest Research》2018,33(7):668-680
Maintaining a permanent forest canopy cover and eventually harvesting wood in a final harvest according to predefined dimensions is often considered as prototype for future management of deciduous forests. An uneven-aged structure is considered by the public to resemble “natural” conditions, and by forest engineers it is considered as being more resilient to disturbances. In the Hainich-Dün region of Thuringia, Germany, beech-dominated selection forests covering about 10,000?ha have been managed for almost 1000 years, initially by irregular use, but as regular selection system since about 200 years. Managing these stands remains difficult, due to the lack of yield tables and a quantification of harvest of uneven-aged stands considering differences in site conditions and handling of over-sized trees. It is the objective of the present study to develop tables of target stand volumes, increments, and harvest for different diameter ranges of uneven-aged stands according to site conditions. The present study is based on repeated grid-based inventories of about 2150 plots, which were partly re-inventoried 3 times over the past 20 years. The recommended target wood volumes vary between 296 and 388 m3 ha?1. Stand growth rates of different yield classes were estimated to range between 6.7 and 7.7 m3 ha?1 yr?1 which is 30% lower than for age class forest. Nevertheless, the economic returns are higher. Thus, selective cutting with single tree selection remains a viable silvicultural system, but it may change over time into small-scale shelter-woods for improving growth of regeneration. 相似文献
9.
Kelly Ann Bona Magdalena S. Burgess James W. Fyles Claude Camiré Pierre Dutilleul 《Forest Ecology and Management》2008
Fast-growing trees such as hybrid poplars (Populus) have the potential to decrease rotation length (time to harvest) and thus produce wood products more quickly from smaller areas of land. Several forest companies in Quebec currently plant hybrid poplar on formerly logged forest sites, rather than on agricultural land as is more common elsewhere. The forest sites often have acidic soils, and lime addition has been proposed to improve hybrid poplar growth. In addition, forest sites present challenges with regard to control of competitive vegetation, particularly in jurisdictions such as Quebec where use of herbicides in forests is banned or restricted. 相似文献
10.
We compared the dead wood (DW) conditions of Cheshmeh-sar forest and Sardab forest with different management history,including reserve forest and harvested forest. The First forest took 100% inventory from all the available DW. Also dead trees were compared interms of species, shape, location and quality of fracture in both forests.Volumes of dead wood in Cheshmeh-sar and Sardab forests were 207.47and 142.74 m3, respectively. Due to this significant difference, impact onthe management level was determined. In Cheshmeh-sar forest, 42% ofdead trees were standing and 58% were fallen type while in Sardab forest 38.6% were standing and 61.4% fallen. But the difference was not statistically significant between them (p = 0.0587). In terms of quality, dead trees of hard, soft and hollow had the highest frequency, respectively.However, 71.5% of DW was seen as hard dead in Cheshmeh-sar forestwhile hard dead trees in Sardab forests were 54.2%. Soft quality degree ofdead trees which formed in Cheshmeh-sar and Sardab forest were calculated as 26.6% and 43.4% respectively. Also 30% of the dead trees of Sardab forest were eradicated while in Cheshmeh-sar this amount was reduced to 12%. Due to this significant difference ((Р=0/018), it is concluded that the type of management and human interference are affecting the quality of dead trees and makes us to think the human interferences could effect on the ecosystem of touched forests. 相似文献
11.
To understand the influence of disturbance, age–class structure, and land use on landscape-level carbon (C) budgets during conversion of old-growth forests to managed forests, a spatially explicit, retrospective C budget from 1920 through 2005 was developed for the 2500 ha Oyster River area of Fluxnet-Canada's coastal BC Station. We used the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3), an inventory-based model, to simulate forest C dynamics. A current (circa 1999) forest inventory for the area was compiled, then overlaid with digitized historic disturbance maps, a 1919 timber cruise map, and a series of historic orthophotographs to generate a GIS coverage of forest cover polygons with unique disturbance histories dating back to 1920. We used the combined data from the historic and current inventory and forest change data to first estimate initial ecosystem C stocks and then to simulate forest dynamics and C budgets for the 86-year period. In 1920, old-growth forest dominated the area and the long-term landscape-level net ecosystem C balance (net biome productivity, NBP) was a small sink (NBP 0.2 Mg C ha−1 year−1). From 1930 to 1945 fires, logging, and slash burning resulted in large losses of biomass C, emissions of C to the atmosphere, and transfers of C from biomass to detritus and wood products (NBP ranged from −3 to −56 Mg C ha−1 year−1). Live biomass C stocks slowly recovered following this period of high disturbance but the area remained a C source until the mid 1950s. From 1960 to 1987 disturbance was minimal and the area was a C sink (NBP ranged from 3 to 6 Mg C ha−1 year−1). As harvest of second-growth forest began in late 1980s, disturbances again dominated the area's C budget, partially offset by ongoing C uptake by biomass in recovering young forests such that the C balance varied from positive to negative depending upon the area disturbed that year (NBP from 6 to −15 Mg C ha−1 year−1). Despite their high productivity, the area's forests are not likely to attain C densities of the landscape prior to industrial logging because the stands will not reach pre-logging ages. Additional work is underway to examine the relative role historic climate variability has had on the landscape-level C budget. 相似文献
12.
Scattered trees and woodlots are a prominent feature of agricultural landscapes of Rwanda. However, little is known about their characteristics and their contribution to farmers’ wood needs. Here, we present the results of a survey of (a) the abundance, composition, and size of trees and woodlots in the low, medium and high altitude regions of Rwanda, (b) total woody biomass and biomass for fuelwood at farm and landscape levels, and (c) opportunities for their sustainable use. Scattered trees occurred in all landscapes at minimum densities ranging from 20 to 167 trees ha?1. Of the 56 tree genera recorded, a handful of tree species dominated, with the ten most common species accounting for over 70 % of all trees recorded. Most of them provided fuelwood, fruit and timber to farm owners. Woodlots occurred on about 40 % of the survey farms and consisted for 90 % of eucalyptus coppice. Woody biomass dry weight of scattered trees on agricultural landscape was 0.7 t ha?1 in low altitude region (LAR), 3 t ha?1 in medium altitude region (MAR), and 1 t ha?1 in high altitude region (HAR). Dry weight woody biomass in woodlots (<0.5 ha) was the highest in MAR (221 t ha?1), followed by that in HAR (205 t ha?1) and least in LAR (96 t ha?1). About 80 % of total woody biomass in trees and woodlots on farmland was useable biomass for fuelwood, indicating that the production of fuelwood on agricultural land was important. Woody biomass on agricultural land was higher than that in forest plantations, and was potentially sufficient to reduce the gap between fuelwood supply and demand when the entire agricultural area was taken into account. In order to achieve this on agricultural land, while contributing to food security and environmental conservation as well, smallholder farmers must be provided with incentives to grow woodlots and to adopt agroforestry systems, thereby considering the trade-offs with agricultural production. Strategies to encourage smallholder farmers to increase the use of agroforestry have to account for the farmers’ ecological and socioeconomic conditions. 相似文献
13.
Analyses of land snails and habitat factors in acid beech forests were conducted in southern Germany (northern Bavaria). The
objectives were to study the effects of habitat characteristics on snail density and species richness. Habitat structures
were determined for 37 plots in one big forest. We found a significant relationship between the number of snail species and
individuals and the following set of habitat factors coverage of herbaceous layer, growing stock, mean diameter at breast
height of the three largest trees (DBHmax), stand age, total dead wood volume per ha, and advanced decomposed dead wood volume
per ha. We use maximally selected rank statistics to estimate cutpoints separating stands with low densities, from stands
with high snail densities. Here, we define cutpoints for a significant higher snail density at a stand age of 187 years, 57 m3/ha dead wood, 40 m3/ha advanced decomposed dead wood, 63 cm DBHmax and more than 1% herbaceous layer. For species richness, cutpoints are estimated
at 338 m3/ha stand volume, 170 years stand age, 50 m3/ha total dead wood amount, 15 m3/ha advanced decomposed dead wood and 56 cm DBHmax. The microhabitat analysis shows a higher pH value and a higher Calcium
content at the bottom of large snags and under large lying dead wood pieces in comparison to litter, upper mineral soil and
at the bottom of vital living trees. Snail species and individual density are significantly linked to these patterns of chemical
parameters. The identified cutpoints are a good base for ecological management decisions in forest management. 相似文献
14.
We developed a computer model to simulate carbon storage in managed slash pine plantations in Florida. The model is based on ecosystem level carbon dynamics and land use data structured by age class of planted trees. Based on a scenario of constant planting at the average level (1952–1979), Florida slash pine forests would store carbon at the rate of 2.81 × 106 t year?1. However, simulated carbon storage is sensitive to the age class distribution of the forests. There will be a 106 t year?1 decrease in carbon storage between 1980 and 1987, due to reduced levels of planting during the past decade. This trend is relatively independent of current planting levels. 相似文献
15.
Forest carbon storage in the northeastern United States: Net effects of harvesting frequency,post-harvest retention,and wood products 总被引：1，自引：0，他引：1
Temperate forests are an important carbon sink, yet there is debate regarding the net effect of forest management practices on carbon storage. Few studies have investigated the effects of different silvicultural systems on forest carbon stocks, and the relative strength of in situ forest carbon versus wood products pools remains in question. Our research describes (1) the impact of harvesting frequency and proportion of post-harvest structural retention on carbon storage in northern hardwood-conifer forests, and (2) tests the significance of including harvested wood products in carbon accounting at the stand scale. We stratified Forest Inventory and Analysis (FIA) plots to control for environmental, forest structural and compositional variables, resulting in 32 FIA plots distributed throughout the northeastern U.S. We used the USDA Forest Service's Forest Vegetation Simulator to project stand development over a 160 year period under nine different forest management scenarios. Simulated treatments represented a gradient of increasing structural retention and decreasing harvesting frequencies, including a “no harvest” scenario. The simulations incorporated carbon flux between aboveground forest biomass (dead and live pools) and harvested wood products. Mean carbon storage over the simulation period was calculated for each silvicultural scenario. We investigated tradeoffs among scenarios using a factorial treatment design and two-way ANOVA. Mean carbon sequestration was significantly (α = 0.05) greater for “no management” compared to any of the active management scenarios. Of the harvest treatments, those favoring high levels of structural retention and decreased harvesting frequency stored the greatest amounts of carbon. Classification and regression tree analysis showed that management scenario was the strongest predictor of total carbon storage, though site-specific variables were important secondary predictors. In order to isolate the effect of in situ forest carbon storage and harvested wood products, we did not include the emissions benefits associated with substituting wood fiber for other construction materials or energy sources. Modeling results from this study show that harvesting frequency and structural retention significantly affect mean carbon storage. Our results illustrate the importance of both post-harvest forest structure and harvesting frequency in carbon storage, and are valuable to land owners interested in managing forests for carbon sequestration. 相似文献
16.
《Forest Ecology and Management》2005,219(1):13-28
Carbon budgets are developed to understand ecosystem dynamics and are increasingly being used to develop global change policy. Traditionally, forest carbon budgets have focused on the biological carbon cycle; however, it is important to include the industrial forest carbon cycle as well. The overall objective of this study was to quantify the major carbon fluxes associated with the production of Wisconsin's industrial roundwood, by using life cycle inventory (LCI) methodology to produce an industrial forest carbon budget. To achieve this objective we (1) developed carbon LCIs for the harvest process for three major forest ownerships (state, national, and private non-industrial), (2) developed carbon LCIs for a dimensional lumber and two oriented strand board (OSB) mills and (3) completed a scaled version of 1 and 2 to include more Wisconsin forestlands and to incorporate the other major processes within the industrial forest carbon cycle (e.g. primary mill, secondary mill, product use and product disposal processes of the industrial forest carbon cycle). The carbon budgets for the harvesting process of the Chequamegon-Nicolet National Forest (CNNF), the Northern Highland American Legion State Forest (NHAL), and the non-industrial private forests that participated in the managed forest laws of Wisconsin (MFL-NIPF) were 0.10, 0.18 and 0.11 tonnes C ha−1 year−1), respectively. The dimensional lumber and OSB products were both net carbon sources, and released 0.05–0.09 tonnes C/tonnes C processed). More carbon is sequestered than released within the industrial forest carbon cycle of Wisconsin's national (6 g C m−2 year−1), state (12 g C m−2 year−1) and non-industrial private forests (7 g C m−2 year−1). Using published net ecosystem production data we estimate that the net forest carbon cycle budget (sum of the biological and industrial C cycle, [Gower, S.T., 2003. Patterns and mechanisms of the forest carbon cycle. Ann. Rev. Environ. Resour. 28, 169–204]) for the CNNF ranges between −897 and 348 g C m−2 year−1. Life cycle inventories of wood and paper products should be clear and explicitly state what processes are included, so that results can be used by policy makers and future researchers. 相似文献
17.
This paper examines the situation of private woodlands in Turkey, which are referred to as ‘non-forest private woodlands’ (NFPWs). The questions addressed by this study are ‘Why are NFPWs not defined as forest?’, ‘Is the exclusion of NFPWs from forests reasonable?’ and ‘What are the consequences of excluding NFPWs from the forest regime?’. It is found that the criteria used to define a forest in Turkey, and hence to exclude NFPWs from forests, do not have a rational basis. Moreover, the threshold level of area, the most decisive criterion, is far beyond comparable international values and cannot be explained by country peculiarities. Also, NFPWs are more likely to be granted tree cutting approval if they have some type of official cadastre or if they harvest trees for domestic use. Commercial-use NFPWs make tree cuttings in higher quantities than domestic harvesters. NFPWs in general can be perceived as fuelwood harvesters as opposed to industrial wood suppliers. NFPWs with forest or land cadastre tend to harvest at higher levels compared to those without a cadastral survey. In the 8-year period 1993 and 2000, approximately 2.5 M m3 of wood was harvested on NFPWs across Turkey. The annual wood production on NFPWs throughout the country decreased drastically during that period, from about 700,000 m3 down to about 150,000 m3. This may be an alarming sign for environmental and socio-economic sustainability involving these lands. Forest management of these lands can be improved if the forestry administration authority implements planned environment-related regulative criteria as well as sound channels of communication, designed to lead the landowners towards best ‘forest’ management practices and hence to guarantee the sustainability of the communities and the natural resource base of the country. 相似文献
18.
Paulo Marcelo Paiva Marcelino Carneiro Guedes Claudia Funi 《Forest Ecology and Management》2011,261(3):508-514
The regeneration of Brazil nut trees depends on tree-fall gaps in the forest. However, shifting cultivation fallows also create comparable biotic and abiotic opportunities for the dispersion and establishment of this gap-loving species. At the same time, the ability of Brazil nut trees to resprout enables fallow individuals to survive successive slash-and-burn cycles. Recognizing the importance of shifting cultivation for the food security of forest dwellers, we investigated whether the high level of Brazil nut regeneration found in cultivation fallows could be explained by the resprouting capability of Brazil nut trees, the number of cultivation cycles, past agricultural use and distance to the nearest conspecific productive adults. We found that the Brazil nut tree population density increased from 8.86 trees ha−1 to 13.69 trees ha−1 and 27.09 trees ha−1 at sites after one, two and three or more shifting cultivation cycles, respectively. As a consequence of resprouting, after a certain number of shifting cultivation cycles, the fallows become dominated by Brazil nut trees, and the landholders may decide to preserve them and to exclude enriched sites from future agricultural use. Protected for their extractive value, the secondary forests spontaneously enriched with Brazil nut trees are allowed to develop into nut-producing forests that have reduced chances of conversion into crops or pastures, thus reversing the classical process of Amazon forest degradation. 相似文献
19.
20.
We focused our attention on quantifying the factor complex of forest regeneration in 423 mature and old stands with contrasting
environmental conditions. We recorded the microhabitat selection of tree recruits, the frequency of tree seedlings, and evaluated
the drivers of sapling abundance and diversity. The majority of forest regeneration was established on undisturbed forest
floor. Dead wood was a frequent substrate in spruce-(co)dominated forests. Seedling frequency within a stand was related to
the site-type specific productivity gradient of stands—pine seedlings were common in low-productivity and spruce in high-productivity
boreal forests. Seedlings of temperate broad-leaved trees dominated in productive boreonemoral forests, except for oak, which
showed a uniform distribution of abundance in all forest site-types. Sapling abundance was dictated by forest site-type, and
facilitated by stand diversity, variability in stand closure, lying dead wood, abundant moss, and a thick organic layer. Only
in boreal forests was sapling abundance suppressed by the abundant spruce and younger trees. Upon considering the relationship
between sapling abundance and species richness, sapling diversity was dependent on forest site-type, suppressed by stand density
and dead wood (old gap) abundance, and facilitated by stand diversity. In addition, boreonemoral stands, competition from
herbs, and facilitation by mosses occurred. The observed pattern of tree recruitment points to the importance of top-down
effects of the overstory, competing or facilitating interactions with forest floor vegetation, and availability of regeneration
microhabitats, which in complex make their ecology comparable with forest herbs. Natural forest regeneration can be enhanced
if silvicultural methods support mixed stands and enhance field layer diversity. Oak can provide the universal tree species
to improve stand structure over a wide range of habitats. 相似文献