Recruitment of tree species in mixed selection and irregular shelterwood forest stands

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.     

Productivity and optimal management of the uneven-aged hardwood forests of Hyrcania

Hyrcania is a productive region near the southern coast of Caspian Sea. Her forests are mostly uneven-aged beach-dominated hardwood mixtures. There is increasing willingness to treat these forests without clear-felling, following the ideas of continuous cover management. However, lack of growth and yield models have delayed this endeavor, and no instructions for uneven-aged management have been issued so far. This study developed a set of models that enable the simulation of stand development in alternative management schedules. The models were used to optimize stand structure and the way in which various initial stands should be converted to the optimal uneven-aged structure. The model set consists of individual-tree diameter increment model, individual-tree height model, survival model, and a model for ingrowth. The models indicate that the sustainable yield of the forests ranges from 2.2 to 7 m³ ha^?1 a^?1 in uneven-aged management, depending on species composition. Better ingrowth would substantially enhance productivity. The optimal stand structure for maximum sustained yield has a wide descending diameter distribution, the largest trees of the post-cutting stand being 80–100 cm in dbh. If cuttings are conducted at 30- or 40-year intervals, they should remove 20–40 largest trees per hectare. Despite moderate growth rate, uneven-aged management produces high incomes, 850–1,000 UDS ha^?1a^?1, because the timber assortments that are obtained from the removed large trees have very high selling prices. Optimal conversion to uneven-aged structure showed that the steady-state stand structure depends on initial stand condition and discount rate when the length of the conversion period is fixed. Discount rates higher than 1 % lead to reduced wood production, heavy cuttings, and low basal areas of the steady-state forest.     

Growth and productivity of black spruce in even- and uneven-aged stands at the limit of the closed boreal forest

The increasing commercial interest and advancing exploitation of new remote territories of the boreal forest require deeper knowledge of the productivity of these ecosystems. Canadian boreal forests are commonly assumed to be evenly aged, but recent studies show that frequent small-scale disturbances can lead to uneven-aged class distributions. However, how age distribution affects tree growth and stand productivity at high latitudes remains an unanswered question. Dynamics of tree growth in even- and uneven-aged stands at the limit of the closed black spruce (Picea mariana) forest in Quebec (Canada) were assessed on 18 plots with ages ranging from 77 to 340 years. Height, diameter and age of all trees were measured. Stem analysis was performed on the 10 dominant trees of each plot by measuring tree-ring widths on discs collected each meter from the stem, and the growth dynamics in height, diameter and volume were estimated according to tree age. Although growth followed a sigmoid pattern with similar shapes and asymptotes in even- and uneven-aged stands, trees in the latter showed curves more flattened and with increases delayed in time. Growth rates in even-aged plots were at least twice those of uneven-aged plots. The vigorous growth rates occurred earlier in trees of even-aged plots with a culmination of the mean annual increment in height, diameter and volume estimated at 40–80 years, 90–110 years earlier than in uneven-aged plots. Stand volume ranged between 30 and 238 m³ ha⁻¹ with 75% of stands showing values lower than 120 m³ ha⁻¹ and higher volumes occurring at greater dominant heights and stand densities. Results demonstrated the different growth dynamics of black spruce in single- and multi-cohort stands and suggested the need for information on the stand structure when estimating the effective or potential growth performance for forest management of this species.     

Forest management and carbon sequestration in wood products

Wood products are considered to contribute to the mitigation of carbon dioxide emissions. A critical gap in the life cycle of wood products is to transfer the raw timber from the forest to the processing wood industry and, thus, the primary wood products. Therefore, often rough estimates are used for this step to obtain total forestry carbon balances. The objectives of this study were (1) to examine the fate of timber harvested in Thuringian state forests (central Germany), representing a large, intensively managed forested region, and (2) to quantify carbon stocks and the lifetime of primary wood products made from this timber. The analyses were based on the amount and assortments of actually sold timber, and production parameters of the companies that bought and processed this timber. In addition, for coniferous stands of a selected Thuringian forest district, we calculated potential effects of management, as expressed by different thinning regimes on wood products and their lifetimes. Total annual timber sale of soft- and hardwoods from Thuringian state forests (195,000 ha) increased from about 136,893 t C (~0.7 t C ha⁻¹ year⁻¹) in 1996 to 280,194 t C (~1.4 t C ha⁻¹ year⁻¹) in 2005. About 47% of annual total timber harvest went into short-lived wood products with a mean residence time (MRT) < 25 years. Thirty-one per cent of the total harvest went into wood products with an MRT of 25–43 years, and only 22% was used as construction wood and glued wood, products with the longest MRT (50 years). The average MRT of carbon in harvested wood products was 20 years. Thinning from above throughout the rotation of spruce forests would lead to an average MRT in harvested wood products of about 23 years, thinning from below of about 18 years. A comparison of our calculations with estimates that resulted from the products module of the CO2FIX model (Nabuurs et al. 2001) demonstrates the influence of regional differences in forest management and wood processing industry on the lifetime of harvested wood products. To our knowledge, the present study provides for the first time real carbon inputs of a defined forest management unit to the wood product sector by linking data on raw timber production, timber sales and wood processing. With this new approach and using this data, it should be possible to substantially improve the net-carbon balance of the entire forestry sector.     

Accumulation of dead wood in abandoned beech (Fagus sylvatica L.) forests in northwestern Germany

Currently, there is much debate about what strategy is most suitable for increasing old-growth attributes in forests that have been managed intensively for wood production in the past. Passive restoration, i.e. cessation of forestry interventions, should be considered when the old-growth attributes desired can be restored within a feasible period of time.Our study focuses on standing and lying coarse dead wood (≥20 cm diameter) in beech-dominated forests in northwestern Germany. We analyzed monitoring data of 545 sample plots (sized 500-1000 m²) from 12 strict forest reserves (SFRs). The SFRs had been without forestry intervention for up to 28 years.Both, number of dead objects and volume of dead wood (m³ ha⁻¹) increased significantly with ongoing time since abandonment from forestry interventions. The mean amount doubled from 9 to 18 m³ ha⁻¹ within 10 years. The proportion of standing dead wood was about 40% of the total dead wood pool ≥20 cm diameter.With mixed linear modeling we showed that dead wood increased by a mean net rate of about 1 m³ ha⁻¹ a⁻¹. Therefore, after three decades critical values for restoring the dead wood pool could be reached. We hypothesized that the rate of dead wood input is mainly determined by disturbance driven tree mortality such as oak decline, bark beetle infestations and storms.A comparison with primeval forests or reserves abandoned more than 100 years ago showed that the SFRs studied are at the beginning of a long process of dead wood accumulation.Based on our results, the abandonment of forest activities in harvestable pure and mixed beech stands is an effective strategy for restoring the dead wood pool.     

Carbon stocks and productivity of mangrove forests in Tanzania

Mangroves offer a number of ecosystem goods and services, including carbon (C) storage. As a carbon pool, mangroves could be a source of CO₂ emissions as a result of human activities such as deforestation and forest degradation. Conversely, mangroves may act as a CO₂ sink through biomass accumulation. This study aimed to determine carbon stocks, harvest removals and productivity of mangrove forests of mainland Tanzania. Nine species were recorded in mainland Tanzania, among them Avicennia marina (Forssk.) Vierh., Rhizophora mucronata Lam. (31%) and Ceriops tagal (Perr.) C.B.Rob. (20%) were dominant. The aboveground, dead wood, belowground and total carbon were 33.5 ± 5.8 Mg C ha^?1, 1.2 ± 1.1 (2% of total carbon), 30.0 ± 4.5 Mg C ha^?1 (46% of total carbon) and 64.7 ± 8.4 Mg C ha^?1 at 95% confidence level, respectively. Carbon harvest removals accounted for loss of about 4% of standing total carbon stocks annually. Results on the productivity of mangrove forests (using data from permanent sample plots monitored for four years [1995-1998]) showed an overall carbon increment of 5.6 Mg C ha^?1 y^?1 (aboveground carbon), 4.1 C ha^?1 y^?1 (belowground carbon) and 9.7 C ha^?1 y^?1 (total carbon) at 23%, 32% and 27% levels of uncertainty, respectively. Both natural death and tree cutting/harvest removals resulted in significant decline of annual carbon productivity. Findings from this study demonstrate that mangroves store large quantities of carbon and are more productive than other dominant forest formations in southern Africa. Both their deforestation and forest degradation, therefore, is likely to contribute to large quantities of emission and loss of carbon sink functionality. Therefore, mangroves need to be managed sustainably.     

Carbon storage in old-growth and second growth fire-dependent western larch (Larix occidentalis Nutt.) forests of the Inland Northwest,USA

There is limited understanding of the carbon (C) storage capacity and overall ecological structure of old-growth forests of western Montana, leaving little ability to evaluate the role of old-growth forests in regional C cycles and ecosystem level C storage capacity. To investigate the difference in C storage between equivalent stands of contrasting age classes and management histories, we surveyed paired old-growth and second growth western larch (Larix occidentalis Nutt)–Douglas-fir (Pseudostuga menziesii var. glauca) stands in northwestern Montana. The specific objectives of this study were to: (1) estimate ecosystem C of old-growth and second growth western larch stands; (2) compare C storage of paired old-growth–second growth stands; and (3) assess differences in ecosystem function and structure between the two age classes, specifically measuring C associated with mineral soil, forest floor, coarse woody debris (CWD), understory, and overstory, as well as overall structure of vegetation. Stands were surveyed using a modified USFS FIA protocol, focusing on ecological components related to soil, forest floor, and overstory C. All downed wood, forest floor, and soil samples were then analyzed for total C and total nitrogen (N). Total ecosystem C in the old-growth forests was significantly greater than that in second growth forests, storing over 3 times the C. Average total mineral soil C was not significantly different in second growth stands compared to old-growth stands; however, total C of the forest floor was significantly greater in old-growth (23.8 Mg ha⁻¹) compared to second growth stands (4.9 Mg ha⁻¹). Overstory and coarse root biomass held the greatest differences in ecosystem C between the two stand types (old-growth, second growth), with nearly 7 times more C in old-growth trees than trees found on second growth stands (144.2 Mg ha⁻¹ vs. 23.8 Mg ha⁻¹). Total CWD on old-growth stands accounted for almost 19 times more C than CWD found in second growth stands. Soil bulk density was also significantly higher on second growth stands some 30+ years after harvest, demonstrating long-term impacts of harvest on soil. Results suggest ecological components specific to old-growth western larch forests, such as coarse root biomass, large amounts of CWD, and a thick forest floor layer are important contributors to long-term C storage within these ecosystems. This, combined with functional implications of contrasts in C distribution and dynamics, suggest that old-growth western larch/Douglas-fir forests are both functionally and structurally distinctive from their second growth counterparts.     

Dead wood in clearcuts of semi-natural forests in Estonia: site-type variation, degradation, and the influences of tree retention and slash harvest

Semi-natural forests, which naturally regenerate after timber harvesting, provide distinct opportunities for dead wood (DW) management for biodiversity. We described DW pool and sources of its variation during the first decade after final felling in Estonia, hemiboreal Europe. Depending on forest type, the mean post-harvest volumes of above-ground DW ranged from 70 to 119 m³ ha^?1. Final felling generally did not reduce downed coarse woody debris (CWD) because many sawn logs were left on-site, and soil scarification was rarely used. However, subsequent decay of downed CWD appears to be accelerated due to the increased ground contact of logs, so that even the relatively small inputs from live retention trees observed (5 m³ ha^?1 per decade) can be ecologically significant. While final felling greatly reduced snag abundance, the mortality of retained live trees generally balanced their later losses. The volumes of downed fine woody debris in conventional cutover sites were roughly double that of pre-harvest forests. Slash harvest caused an approximately twofold reduction in downed DW and resulted in CWD volumes that were below mature-forest levels. The results indicate that the habitat quality of cutovers critically depends both on the retention and on the post-harvest management of biological legacies. In Estonia, the necessary improvements include more careful retention of snags in final felling, selecting larger retention trees, focusing slash harvest on the fine debris of common tree species, and providing snags of late-successional tree species.     

How much carbon can the Siberian boreal taiga store: a case study of partitioning among the above-ground and soil pools

In the context of global carbon cycle management, accurate knowledge of carbon content in forests is a relevant issue in contemporary forest ecology. We measured the above-ground and soil carbon pools in the darkconiferous boreal taiga. We compared measured carbon pools to those calculated from the forest inventory records containing volume stock and species composition data. The inventory data heavily underestimated the pools in the study area(Stolby State Nature Reserve, central Krasnoyarsk Territory, Russian Federation). The carbon pool estimated from the forest inventory data varied from 25(t ha-1)(low-density stands) to 73(t ha-1)(highly stocked stands). Our estimates ranged from 59(t ha-1)(lowdensity stands) to 147(t ha-1)(highly stocked stands). Our values included living trees, standing deadwood, living cover, brushwood and litter. We found that the proportion of biomass carbon(living trees): soil carbon varied from99:1 to 8:2 for fully stocked and low-density forest stands,respectively. This contradicts the common understanding that the biomass in the boreal forests represents only16–20 % of the total carbon pool, with the balance being the soil carbon pool.     

Impacts of salvage-logging on the status of deadwood after windthrow in Swiss forests

Downed and standing deadwood (DW) is a key resource for maintaining forest biodiversity. Although extreme events such as windthrow and fires produce large quantities of DW, this substrate is often drastically reduced by logging activities. To elucidate the respecting consequences of salvage-logging, we assessed both quantity and quality of storm-derived DW (storms Vivian 1990 and Lothar 1999) in Swiss forests using a sample of 90 windthrow sites with ≥3 ha complete windthrow and at elevations ranging from 350 to 1,800 m a.s.l. The majority had been salvage-logged (SL) a few years after the windthrow. On each site, we recorded DW amount and quality on six circular sample plots 20 or 50 m² in size. DW volume on SL sites was surprisingly high, with 76.4 m³ ha^?1 on average 20 years after Vivian and 73.8 m³ ha^?1 10 years after Lothar. In comparison, DW volumes on unsalvaged sites, that is, with no post-windthrow intervention (NI), amounted to 270 m³ ha^?1. A wide variety of wood decay stages and diameter classes (10 to ≥70 cm) was found on both NI and SL sites, suggesting considerable habitat diversity for DW-associated species irrespective of the treatment. The considerable amounts of DW left after salvage-logging distinctly exceed the minimum DW volumes in forest stands proposed by Müller and Bütler (Eur J For Res 129: 981–992, 2010) in a conservation context, which demonstrates the importance of wind disturbance for biodiversity. Further studies should quantify DW of individual tree species, since habitat requirements are species-specific.     

Effects of management on coarse woody debris volume and composition in boreal forests in northern Sweden

Forest management practices have led to a reduction in the volume and a change in the composition of coarse woody debris (CWD) in many forest types. This study compared CWD volume and composition in reserves and two types of managed forest in the central boreal zone of Sweden. Ten areas were surveyed, each containing clear-cut, mature managed and old-growth stands, to determine the volume of standing and lying CWD in terms of species composition, decay class and size class. Volumes of CWD on clear-cuts and in mature managed forests were high compared with previous studies. Old-growth forests (72.6 m³ ha^?1) contained a greater volume of CWD than mature managed forests (23.3 m³ ha^?1) and clear-cuts (13.6 m³ ha^?1). Differences were greatest for the larger size classes and intermediate decay stages. Despite stand ages being up to 144 years, CWD volume and composition in managed forests was more similar to clear-cuts than to old-growth forests.     

Variation of stem density and vegetation carbon pool in subtropical forests of Northwestern Himalaya

The present study was conducted in five forest types of subtropical zone in the Northwestern Himalaya, India. Three forest stands of 0.1 ha were laid down in each forest type to study the variation in vegetation carbon pool, stem density, and ecosystem carbon density. The stem density in the present study ranged from (483 to 417 trees ha^?1) and stem biomass from (262.40 to 39.97 tha^?1). Highest carbon storage (209.95 t ha^?1) was recorded in dry Shiwalik sal forest followed by Himalayan chir forest > chir pine plantation > lower Shiwalik pine forest > northern mixed dry deciduous forest. Maximum tree above ground biomass is observed in dry Shiwalik sal forests (301.78 t ha^?1), followed by upper Himalayan chir pine forests (194 t ha^?1) and lower in Shiwalik pine forests (138.73 t ha^?1). The relationship with stem volume showed the maximum adjusted r² (0.873), followed by total density (0.55) and average DBH (0.528). The regression equation of different parameters with shrub biomass showed highest r² (0.812) and relationship between ecosystem carbon with other parameters of different forest types, where cubic function with stem volume showed highest r² value of 0.873 through cubic functions. Our results suggest that biomass and carbon stocks in these subtropical forests vary greatly with forest type and species density. This variation among forests can be used as a tool for carbon credit claims under ongoing international conventions and protocols.     

Stand characteristics of mixed oriental beech (<Emphasis Type="Italic">Fagus orientalis</Emphasis> Lipsky) stands in the stem exclusion phase,northern Iran

The structure of forest stands changes through developmental phases. This study is carried out in the unmanaged, oriental beech (Fagus orientalis Lipsky) stands in the north of Iran. The aim of this research was to quantify structural characteristics of stands in the stem exclusion phase using common structural indices, which include mingling, tree–tree distance, stem diameter, and tree height differentiation. According to our measurements from three stands, naturally regenerated stands tend to be mixed in species composition have slightly heterogeneous diameter distributions and uniform tree height. The average distance between trees was 3.3 m. Stocking volume of the stands had an average of 540 m³ ha^?1 and 412 stem ha^?1. Dead wood volume was 24 m³ ha^?1, and as a standing volume, the most frequent species in dead wood pool was oriental beech (F. orientalis) (48 %). The common form of dead trees was snag (41 %). The mean value of mingling and tree-to-tree interval indices revealed that beech was mixed intensively with hornbeam and appears to be a more successful competitor for space and light compared with hornbeam; moreover, we found relatively high evidence of inter-species competition in this phase. A better understanding of stand characteristics in the stem exclusion phase as a critical part of the natural dynamics of forest ecosystems could facilitate predictions about the future changes within the stand.     

Afforestation of savannah with cocoa agroforestry systems: a small-farmer innovation in central Cameroon

Cocoa cultivation is generally considered to foster deforestation. Contrary to this view, in the forest–savannah interface area in Cameroon, farmers have planted cocoa agroforestry systems on Imperata cylindrica grasslands, a soil-climate zone generally considered unsuitable for cocoa cultivation. We undertook a survey to understand the agricultural and ecological bases of this innovation. Age, cropping history and marketable cocoa yield were assessed in a sample of 157 cocoa plantations established on grasslands and 182 cocoa plantations established in gallery forests. In a sub-sample of 47 grassland cocoa plantations, we inventoried tree species associated with cocoa trees and measured soil organic matter levels. Marketable cocoa yields were similar for the two types of cocoa plantations, regardless of their age: 321?kg?ha^?1 in cocoa plantations on grasslands and 354?kg?ha^?1 in cocoa plantations in gallery forests. Two strategies were used by farmers to eliminate I. cylindrica prior to the establishment of cocoa plantations, i.e., cropping oil palms in dense stands and planting annual crops. Farmers then planted cocoa trees and fruit tree species, while preserving specific forest trees. The fruit tree and forest tree densities respectively averaged 223 and 68 trees?ha^?1 in plantations under 10?years old, and 44 and 27 trees?ha^?1 in plantations over 40?years old, whereas the cocoa tree density remained stable at 1,315 trees?ha^?1. The Shannon–Weaver index increased from 1.97 to 2.26 over the same period although the difference was not statistically significant. The soil organic matter level was 3.13?% in old cocoa plantations, as compared to 1.7?% in grasslands. In conclusion, our results show that the occupation of grasslands by cocoa agroforestry systems is both an important example of ecological intensification and a significant farmer innovation in the history of cocoa growing.     

The Lintula Larch Forest

The Lintula Larch Forest, also called the Raivola Larch Forest, is one of the most magnificent cultivated forests in northern Europe. It has had a major impact on the cultivation of larch throughout the world, and it became part of the Unesco's World Heritage list in 1991. This article summarizes for the first time to an international audience the establishment, administration and management, stand development and research carried out in Lintula Park. It is based on Russian and Finnish papers and earlier unpublished results. The forest is located 63 km north-west of St Petersburg in the Karelian Isthmus. It was established by order of Peter the Great to supply the Russian fleet with timber for shipbuilding. Ferdinand Gabriel Fockel, a German forest expert, established the oldest stands in 1738–1750 with seed from the Province of Arkhangelsk. Since then the area of the forest has expanded and now the total area of larch stands is 55.9 ha; 23.5 ha of the “old stands” established in 1738–1851 still remain. The Lintula larch stands were famous for their high yield, but part of the reputation was based on small sample plots that were not representative of the stands. However, the high volumes of different tree stands are impressive. For example, in a 255-year-old stand with 339 trees ha^?1 the volume of growing stock was 1284 m³ ha^?1. In small sample plots much higher volumes are found. The average annual growth of the oldest larch stands has never exceeded 6.2–7.2 m³ ha^?1. The volume increment was, however, long-lasting, and annual growth started to decrease only after 148–166 years. Some plots had an increase in yield even at the age of 257 years. The yield of the larches clearly surpassed that of Norway spruce and Scots pine in nearby stands. The Lintula Larch Forest has provided valuable experience on the cultivation of larch. The root system of larch is relatively weak, and it is therefore susceptible to wind damage and rot fungi. An important conclusion drawn from the development of the Lintula Larch Forest is that the cultivation of larch is worthwhile only when grown as pure stands using intensive growing techniques.     

Conversion of tropical moist forest into cacao agroforest: consequences for carbon pools and annual C sequestration

Tropical forests store a large part of the terrestrial carbon and play a key role in the global carbon (C) cycle. In parts of Southeast Asia, conversion of natural forest to cacao agroforestry systems is an important driver of deforestation, resulting in C losses from biomass and soil to the atmosphere. This case study from Sulawesi, Indonesia, compares natural forest with nearby shaded cacao agroforests for all major above and belowground biomass C pools (n = 6 plots) and net primary production (n = 3 plots). Total biomass (above- and belowground to 250 cm soil depth) in the forest (approx. 150 Mg C ha^?1) was more than eight times higher than in the agroforest (19 Mg C ha^?1). Total net primary production (NPP, above- and belowground) was larger in the forest than in the agroforest (approx. 29 vs. 20 Mg dry matter (DM) ha^?1 year^?1), while wood increment was twice as high in the forest (approx. 6 vs. 3 Mg DM ha^?1 year^?1). The SOC pools to 250 cm depth amounted to 134 and 78 Mg C ha^?1 in the forest and agroforest stands, respectively. Replacement of tropical moist forest by cacao agroforest reduces the biomass C pool by approximately 130 Mg C ha^?1; another 50 Mg C ha^?1 may be released from the soil. Further, the replacement of forest by cacao agroforest also results in a 70–80 % decrease of the annual C sequestration potential due to a significantly smaller stem increment.     

Structure of a Central-European mountain spruce old-growth forest with respect to historical development

This study examines the structural characteristics of the tree layer, dead wood, canopy openings, and regeneration patterns of a spruce old-growth forest in the Bohemian Forest, Czech Republic. An old-growth stand with minor human influence and a stand that was presumably logged about 200 years ago were analyzed and compared, as some forest managers considered the presumable human impact as a reason for salvage logging. Even though the stands differed in tree density, height and DBH structure, it was not possible to conclude whether it was due to management history or the environmental differences. The volume of dead wood also differed between the stands. There was about 142 and 83 m³ ha⁻¹ of dead wood in the old-growth stand and presumably logged stand, respectively. The amount of dead wood found in the old-growth stand was comparable with values reported from spruce old-growth stands across Central Europe. In both stands, many canopy trees were arranged in linear patterns, which was a result of spruce regeneration on nurse logs. This suggests that the origin and development of the stands were characterized by natural processes and during the past 200 years typical old-growth structural characteristics have already evolved.     

Ungulate-adapted forest management: effects of slash treatment at harvest on forage availability and use

Forest management strongly influences the interactions between ungulates and their food resources. Different ungulate-adapted measures have been proposed in forestry to improve forage availability or to reduce browsing damage. However, the potential and feasibility of such measures are inadequately known. We studied the effects of harvest timing and slash treatment in final felling and commercial thinning on the availability of Scots pine Pinus sylvestris forage and its use by ungulates during winter in the Swedish boreal forests. Pellet group counts showed that moose (Alces alces) was the dominating species using the post-harvest stands. Under conventional slash treatment, final felling stands held on average 226 kg pine forage ha^?1 after harvesting and commercial thinning stands 137 kg ha^?1. Ungulate-adapted slash treatment increased the available forage biomass by 20 %, but had no significant effect on consumption of forage by ungulates. Time since harvest had the strongest effect on forage consumption; for example, under conventional slash treatment, there was a tenfold increase in consumption (3 vs. 33 kg ha^?1) following final felling as exposure time increased from 2–3 to 4–5 months. Consumption was higher in thinned stands than in final felling stands for the first 3 months but not later. To increase ungulate use of the forage made available at harvest, pine-dominated stands should be harvested in the late autumn or early in the winter.     

Carbon stocks and net ecosystem production changes with time in two Italian forest chronosequences

Forest management influences several ecosystem processes, including carbon exchange between forest ecosystem and atmosphere. The aim of this paper was to study the carbon cycle over different age classes of two managed forests in the Italian Alps through direct measurements and modelling. For this purpose, ecosystem carbon dynamics of a beech forest (Fagus sylvatica L.) and of a spruce forest (Picea abies (L.) Karst.) were investigated using a chronosequence approach. In both forests, five forest development stages were identified (thicket, pole wood, young forest, mature forest and the regeneration phase) with an age spanning from 42 to 163?years for the beech forest and from 35 to 161?years for the spruce forest. Measured total ecosystem carbon stock increased up to 80–100?years, with a mean of 232?MgC?ha^?1 in the beech forest and of 299?MgC?ha^?1 in the spruce forest. Calculated net ecosystem production (NEP) was found to decrease linearly with age and had an average value of 2.2 and 4.4?MgC?ha^?1?year^?1 for beech and spruce forest, respectively. Model simulations reported an increase in NEP till 50–60?years followed by a decrease thereafter. The model also predicted a negative NEP for a short period (8–11?years) after the seed cut. Aboveground biomass was the main driver of carbon accumulation while soil carbon was not significantly influenced by both age and management system. Moreover, measured data and model showed that the applied shelterwood system allowed for a rapid recovery of the ecosystem after the disturbance (i.e. seed cut), bringing back forest to act as C sink in few years.     

Growth and thinning effects during a rotation period of hybrid aspen in southern Sweden

Hybrid aspen is an interesting tree species for wood production in northern Europe. In this study we examined growth dynamics over the whole rotation period. Height and diameter development, as well as annual growth of stem volume and stem biomass, were repeatedly recorded in 14 planted and 2 root sucker stands, aged up to 26 years, in southern Sweden. A main aim was to study the productivity level for hybrid aspen forestry with an expected rotation period of about 25 years. The study verified earlier prognoses, showing a mean annual increment (MAI) of 19.5 m³ of stem wood ha^?1 yr^?1 after 25 years. This corresponds to a dry weight of stem biomass of 7.2 tons dry matter (DM) ha^?1 yr^?1. Maximum MAI was still not reached after 25 years, although the growth curve was flattening out. If branch biomass is included, MAI is estimated to about 9 tons DM ha^?1 yr^?1 and further improvements in growth is expected by using the best genotypically selected clones available. Results from three different thinning regimens showed that thinning intensity provided significantly larger diameter growth, while no significant yield effects were seen among the thinning regimens.