Clearcutting forestry and Eurasian boreal forest grouse: Long-term monitoring of sympatric capercaillie Tetrao urogallus and black grouse T. tetrix reveals unexpected effects on their population performances

Along the succession gradient of the boreal forest ecosystem, black grouse Tetrao tetrix inhabits the early and capercaillie Tetrao urogallus the latest stages. When converting old forest to clearcuts and plantations, commercial forestry has therefore been assumed to affect capercaillie negatively and to be favourable to black grouse. During a 30-year period (1979-2008) we monitored sympatric populations of the two species in a forest in southeast Norway based on annual spring and autumn censuses and radio-marked birds. During this period, the proportion of old, semi-natural forest was halved and clearcuts and young plantations increased accordingly. The grouse populations did not change as predicted. While the trend in August numbers of adult black grouse declined, males more than females, abundance of adult capercaillie remained unchanged. Number of males at leks showed similar patterns. Equally surprising, breeding success (number of chicks per female in August) of both species increased, thus indicating that the populations were regulated more by variation in adult survivorship than by recruitment of young birds. No correlations were found with changing climatic factors (precipitation and temperatures in winter and spring, snow depth and time of snow melt), except that year-to-year breeding success was positively correlated with minimum temperatures during 2 weeks posthatch. The results are explained by a combination of more flexible habitat selection than previously assumed and a changing predator regime: In the early period, nearly all capercaillie leks were located in old, semi-natural forest, but as plantations grew older (>30 years), new leks were established there. Similarly, while young capercaillie broods used old semi-natural forest almost exclusively when the study started, they frequently used middle-aged plantations, especially those with a ground cover of bilberry Vaccinium myrtillus, when these became common in later years. The increasing breeding success could largely be explained by more females rearing chicks successfully, presumably due to a marked decline in the main nest predator, the red fox Vulpes vulpes. A practice of thinning of the old, semi-natural forest some years prior to final harvesting probably facilitated predation of black grouse by goshawks Accipiter gentilis. Contrary to many beliefs, our results indicate that both capercaillie and black grouse are quite tolerant to changes in forest management regimes. In our study, numerical and functional responses of predators (mainly red fox and goshawk) apparently played a more important role in regulating grouse numbers than habitat factors per se.     

Burning and mowing as habitat management for capercaillie Tetrao urogallus: An experimental test

In Scots pine Pinus sylvestris forests, the important ecological effects of natural fires could be emulated using prescribed fire. Species that may benefit from fire effects include capercaillie Tetrao urogallus, a large forest grouse. A key component of forest habitats for capercaillie is the ericaceous shrub, bilberry Vaccinium myrtillus, which is eaten by capercaillie, and supports abundant arthropods, taken by young chicks. We carried out an experiment testing whether prescribed burning would be a valuable technique for capercaillie habitat management. The study took place at Abernethy Forest, the largest ancient native pinewood in Britain, and a key capercaillie site, holding c 8-20% of the British population. Prescribed fire in woodland is highly novel in Britain. We therefore also tested mowing, which might replicate some fire effects more cheaply and safely. Twenty-five experimental blocks were established within open pine stands with ground vegetation including bilberry, but dominated by heather Calluna vulgaris. Each block held three 700 m² plots, randomly assigned to control, mow and burn. Vegetation, arthropods and capercaillie dung were monitored over a 7-year period, including 1 year prior to treatment. Mean bilberry cover, initially around 12%, increased in mown and burnt areas, but there were also increases in controls, following unusual natural die-back of heather. By the sixth season after treatment, bilberry cover was significantly higher in burnt and mown areas than controls, averaging 27% (95% confidence intervals 24-30), compared to 20% (19-21) in controls. Biomass of spiders, an important dietary group for capercaillie chicks, as measured by pitfall trapping, was significantly higher in burnt and mown plots than controls, by about 56% (38-76). However, biomass of caterpillars, often considered a more important dietary group, did not show clear differences between treatments. An alternative analysis was used to ‘statistically remove’ natural heather die-back; this enhanced the treatment differences in bilberry cover and spider biomass. Capercaillie dung counts suggested that burnt, and especially mown areas, had more summer capercaillie usage than controls. Capercaillie conservation at sites similar to Abernethy is likely to benefit from either prescribed fire or mowing, because these techniques increase bilberry and spider abundance. This study illustrates the value of collaboration between researchers and land-managers, in developing and testing novel management techniques. We support the idea that ‘dominance reduction’, delivered through managed disturbance, offers a general principle to guide land-managers wishing to maintain biodiversity, particularly where key species, like capercaillie, are strongly associated with sub-dominant plant species like bilberry.     

Using ecological forest site mapping for long-term habitat suitability assessments in wildlife conservation—Demonstrated for capercaillie (Tetrao urogallus)

Although key factors for vegetation composition and structure, site and soil condition have received little attention as predictors of habitat suitability in wildlife ecology to date. Using the example of capercaillie (Tetrao urogallus), an indicator species for open, well-structured forest habitats, we evaluated the potential use of ecological forest site mapping for the identification of areas where the preferred vegetation structures are supported by the prevailing soil conditions. These are sites that we, therefore, expected to be of long-term relevance to the species.     

Comparing different forest zoning options for landscape-scale management of the boreal forest: Possible benefits of the TRIAD

Forest management has been criticised in the last 20 years for its negative impact on the native species, structures and functions of the forest. Of many possible alternatives proposed to minimize these effects, the functional zoning (or TRIAD) approach is gaining popularity in North America. The goal of this approach is to minimize the negative environmental impacts of forestry while maintain timber supply by dividing the forest into three broad land-use zones: (1) conservation, (2) ecosystem management, and (3) wood production. In this study, we used a spatially explicit landscape model to simulate the effects of fire and six different forest management scenarios on a boreal mixedwood forest management unit in central Quebec. The management scenarios examined included the current practices scenario, a scenario proposed by the provincial government, and four TRIAD scenarios varying in the amount of forest allocated to each of the three zones. For each scenario, we examined the harvest volume, percentage old-growth forest or old forest managed to favour old-growth attributes, and effective mesh size of forest patches by 20-year age classes. With more area set aside for conservation and high-retention partial cut harvesting techniques designed to maintain the attributes of old-growth stands, all TRIAD scenarios resulted in higher percentages of stands with old-growth attributes than the current practices scenario and the government proposed scenario, and two of the four TRIAD scenarios also resulted in higher harvest volume over the long term. All forest management scenarios resulted in significantly lower effective mesh size than the fire-only scenario, but this difference was not as pronounced for the four TRIAD scenarios as for the current practice and government proposed scenarios. We conclude that the TRIAD approach has the potential to minimize some of the negative impacts of forestry on the landscape, while maintaining timber supply over the long term.     

Looking deeper: An investigation of soil carbon losses following harvesting from a managed northeastern red spruce (Picea rubens Sarg.) forest chronosequence

Forest harvesting in eastern North America has been occurring for centuries but its effect on soil carbon storage and dynamics below 20 cm is not well known. This paper investigates age-related variations in carbon storage and dynamics in the organic layer and 6 depth strata in the top 50 cm of the mineral soil during ecologically important stages of post-harvest succession in a first rotation red spruce forest chronosequence that includes one of the largest old growth reference stands in northeastern North America. Storage of carbon reached a minimum 32 years post-harvest, at which time stores were approximately 50% of the intact forest. However, storage approached the range of the intact forest approximately 100 years post-harvest. Examination of age-related variations with depth revealed that concentrations of carbon below 20 cm may be driving the temporal trends in whole soil storage in these forests. Corresponding carbon isotope data were consistent with increased isotopic fractionation attributable to increased rates of mineralization post-harvest. Based on these results, we suggest that a greater emphasis should be placed upon examining storage of carbon below 20 cm in the mineral soil when evaluating the sequestration potential of intensive forest management, specifically rotation length.     

The response of the pseudoannual species Trientalis europaea L. to forest gap dynamics in a near-natural spruce forest

The objective of this study was to test relationships between gap size, gap age and performance of the pseudoannual forest herb layer species Trientalis europaea. We also tested for a potential covariation of performance variables with light as the putative driving factor of gap size and gap age effects. The study took place in the core zone of the Harz National Park in a near-natural spruce forest at Mt. Brocken, Germany. We established 70 randomly distributed plots of three different gap age classes (<15 years, >15 and <60 years, >60 years) and undisturbed forest stands. We recorded growth variables of Trientalis (e.g. height of ramets, number of flowers and fruits per ramet and number of daughter tubers per ramet) and measured PPFD (photosynthetic photon flux density). Gap sizes were assessed with GPS, ranged from 131 m² to 16400 m² and were independent from gap age. Population density of T. europaea was neither affected by gap size nor by gap age. However, gap age had an effect on the fitness of Trientalis ramets. In gaps, the species produced a higher number of flowers and fruits. In general, the average proportion of flowering and fruiting was very low, with 13% and 4%, respectively. In contrast, light intensity had a significant positive effect on ramet density, while the number of daughter tubers differed between 0.8 and 0.5 tubers per individual under lowest light and full light intensity, respectively. The general conclusion is that gap size had no effects on the performance of T. europaea, while gap age had both direct effects and indirect effects mediated by light.     

Oak (Quercus robur L.) regeneration in early successional woodlands grazed by wild ungulates in the absence of livestock

Wooded pastures grazed by livestock are believed to be landscapes that provide favourable conditions for spontaneous regeneration of oaks, including Quercus robur. A key mechanism for oak regeneration in these systems is ‘associational resistance’, spatial association with unpalatable plants which offer protection against herbivory. There is little knowledge on how oak regenerates without livestock grazing and in the presence of only wild large herbivores. We studied this in an area (114 ha) abandoned from agricultural use and in the early 1980s incorporated into the Bia?owie?a National Park, Poland. Its ungulate community consists of native red deer, European bison, roe deer, moose and wild boar. Secondary succession has led to the development of a mosaic habitat including tree and tall shrub groves (29% of the area), open meadow communities (60%), and edge, transitory zone between groves and meadows (11%). Our systematic inventory assigned oaks to height classes (0-0.2, 0.2-0.5, 0.5-1.3, 1.3-2.5, 2.5-5.0, >5.0 m), dichotomous shape characteristic (regular vs. “bonsai” sapling), as well as a habitat definition, in particular the characteristics of woody vegetation in the immediate surroundings of oaks. A selection of 17 oaks was subject to coring for the comparison of growth dynamics. Oak density was highest inside groves, with 504 oaks ha⁻¹, and in the edge zone (493 oaks ha⁻¹) and lowest in meadows (47 oaks ha⁻¹). Most of the 0-5-m oaks (62%) grew without another woody plant species within 1 m radius. The remaining oaks (38%) were associated mainly with Rubus idaeus and saplings of Carpinus betulus and Populus tremula - all highly ungulate-preferred species. The age (0.5 m above ground) of cored oaks in grove and edge habitats varied from 11 to 37 years, indicating continuous recruitment since agricultural abandonment. The initial growth dynamics of the more mature oaks did not differ from that of present “bonsais,” supporting the idea that browsing is not an unconditional impediment and that “bonsai” can be a temporary stage of successful oak development. In contrast to other studies, we found that associational resistance from unpalatable plants is not necessary to secure successful oak regeneration in woodlands subject to browsing by wild ungulates. This might have been possible because of the abundance of highly attractive vegetation making oak relatively unpreferred by ungulates. We suggest that the observed secondary succession provides a contemporary analogy of historic processes that resulted in the establishment of broadleaf forests with a substantial proportion of oak.     

Designing old forest for the future: Old trees as habitat for birds in forests of Mountain Ash Eucalyptus regnans

Old trees are one of many habitat attributes associated with old forests. They are known to be required by many wildlife species including cavity-dependent birds. Forest managers need to select strategies for retaining and regrowing old trees to maintain suitable numbers over time at appropriate configurations in the forest landscape. This paper presents data from wet forests in south-eastern Australia to help elucidate the effects of different strategies on forest birds as one element of biodiversity that needs to be conserved in these forests.     

Natural and human disturbances affect natural regeneration of Swietenia macrophylla: Implications for rainforest management

In this paper we document how changes in forest structure mediated by natural (hurricane) and human (logging) disturbances affect natural regeneration of Swietenia macrophylla via its effects on seed predation, germination, and early recruitment. Work was carried out in two ejidos within the Mayan zone of Quintana Roo, differing with regard to their exposure to the effect of the hurricane Dean 2008 (Naranjal Poniente; high hurricane impact) and Señor (with no evidence of hurricane effects). We experimentally set S. macrophylla seeds in both hurricane conditions and contrasting logging effects, in three treatments: (1) open access, (2) rodent and insect access and (3) rodent and insect exclusion. We measured three dependent variables: (i) number of seeds predated, (ii) number of seeds germinated and (iii) number of seedlings established. We found that the three variables measured were differentially affected by logging and hurricane Dean. Seed predation was higher in areas with hurricane effects; germination showed no differences, but early recruitment was differentially affected by the two conditions, via an increasing of herbivory and sun exposition. Both types of disturbances studied occurred periodically in Yucatan Peninsula and elsewhere in tropics, so it is necessary to implement specific actions in order to face changes in mahogany natural regeneration stocks, and supporting the future management of tropical forests.     

Climate and recent fire history affect fuel loads in Eucalyptus forests: Implications for fire management in a changing climate

Predicted changes to global climates are expected to affect natural fire regimes. Many studies suggest that the impact of these effects could be minimised by reducing fuel loads through prescribed burning. Fuel loads are dynamic and are affected by a range of factors including fire and climate. In this study, we use a 22-year dataset to examine the relative influence of climate and fire history on rates of litterfall and decomposition, and hence fuel loads, in a coastal Eucalypt forest in south-eastern Australia. Litterfall and decomposition were both affected by temperature, recent rainfall and fire history variables. Over the study period prescribed burning immediately reduced fuel loads, with fuel loads reaching pre-burn levels within 3 years of a fire. Modelling fuel loads under predicted climate change scenarios for 2070 suggests that while fuel loads are reduced, the levels are not significantly lower than those recorded in the study. Based on these predictions it is unlikely that the role or value of prescribed burning in these forests will change under the scenarios tested in this study.     

Utilization of non-timber forest products in humid tropics: Implications for management and livelihood

Community dependence on forest resources for diverse needs has high implications for long term management of forests. Sustainable extraction of non-timber forest products (NTFPs) is considered best feasible strategy for forest conservation in biodiversity rich areas. This paper examines the heterogeneity of NTFPs use by tribal communities in northeast India, a global hot spot by examining diversity of NTFPs at-large, its consumption pattern, and contribution to rural income and forest revenue. A total of 343 NTFPs recorded used for diverse purposes by tribal communities. When species choice grouped as per use category, utilization for medicinal (163 species), edible fruits (75 species) and vegetables (65 species) purposes was reasonably high. Community dependence on forest resources was 100% for firewood and house construction material. 76 plant species were sold in three major local markets while an additional 22 species traded at commercial scale mainly outside the state. NTFPs contributed 19-32% of total household income for different tribal communities, which was significant. Illicium griffithii, Rubia cordifolia, Oroxylum indicum, Swertia chirayita, Litsea sebifera, Taxus wallichiana, Valeriana jatamansii, Thalictrum foliolosum, Picrorhiza kurrooa, Everniastrum cirrhatum, Cordyceps sinensis, Aconitum fletcherianum, Nardostachys jatamansi, Picrorhiza kurrooa, Gymnadenia orchidis, Calamus, Quercus and Pinus roxbughii were important commercial species. NTFPs also generated substantial revenue to the State government, though it is falling year after year, which is alarming. To meet community livelihoods, income and forest revenue from NTFPs, it desires a thorough management plan and policy guidelines for these resources from all line departments. The knowledge on diversity, its consumption pattern, and contribution to rural income and forest revenue may enable planners to accurately plan sustainable management of NTFP resources and community development in near future.     

The influence of gap creation on the regeneration of Pinus tabuliformis planted forest and its role in the near-natural cultivation strategy for planted forest management

It remains unclear whether or not creating gaps in planted forests can increase the plant species composition, structure, and biodiversity, and also whether it can be helpful for restoring planted forests (to a more natural state). Based on a comparison of species composition and structure among forest patches, small gaps (4-25 m²), medium gaps (25-150 m²) and large gaps (150-450 m²), we found that (1) creating gaps enhanced vascular plant diversity. Both the species richness and Shannon diversity indices of small, medium and large gaps were significantly higher than in the understory. The pattern of increasing diversity of vascular plants with gap creation could be partly attributed to the emergence of novel shade intolerant species in gaps. (2) Creating gaps favored the colonization and regeneration of native species. Gap size influenced not only the emergence and density of individuals of different species, but also the emergence of different life form types. Small gaps promoted the regeneration of some shrub species, such as Ostryopsis davidiana, Rosa hugonis, and Forsythia suspense, leading to these species becoming canopy dominants early on in succession. The medium and large gaps favored the growth of tree species, such as Populus davidiana and Betula platyphylla (early successional stage), and Quercus liaotungensis and Pinus tabulaeformis (later successional phase). (3) The canonical correspondence analysis showed that plant species composition and distribution were mainly influenced by gap size and slope aspect, and that the recorded plant species could be divided into three life forms (trees, shrubs and herbs) on the biplot diagram. (4) Finally, creating gaps provided opportunities not only for native pioneer species in the early successional stage, but also for climatic climax species to grow to canopy dominants in later successional phases, suggesting that a more natural forest will develop with plant succession. Gap size plays an important role in plant regeneration, and it could be used to produce desired successional communities in near natural management for planted forests.     

Post-logging regeneration and recruitment of shihuahuaco (Dipteryx spp.) in Peruvian Amazonia: Implications for management

Over the past decade, shihuahuaco timber - comprising several species of Dipteryx (Fabaceae) traded internationally as “cumarú” or “Brazilian teak” - has become one of the most highly demanded types of hardwood from Peruvian Amazonia, particularly in the Chinese market. Dipteryx is an ecologically important canopy-emergent genus with widespread distribution in neotropical forests. To assess the response of Dipteryx to logging, we conducted inventories in three logging areas in the Regions of Ucayali and Loreto, Peru. The size-class distributions of Dipteryx populations in recently logged sites showed that initial post-logging conditions enhance recruitment of residual seedlings. These conditions are created by a combination of logging gaps and the activities of farmers migrating into logged lands. Through protection and liberation of shihuahuaco seedlings in post-logged forest as well as within and around agricultural fields, local residents and timber companies could favor the recovery of this valued resource. However, as logged land is increasingly converted to agriculture and pastureland, the reestablishment of mature seed trees is not assured.     

Availability of standing trees for large cavity-nesting birds in the eastern boreal forest of Québec,Canada

Large cavity-nesting birds depend on large-diameter trees for suitable nest sites. The increased spatial extent of commercial timber harvesting is modifying forest structure across the land base and may thus compromise the availability of large trees at the landscape scale. In this study, our objectives were to (1) characterize the availability of large living and dead trees in old-growth stands dominated by different tree species and surficial deposits that encompass the range of natural cover types of eastern Québec's boreal forest; (2) analyze the distribution of trees among decay-classes; and (3) compare the availability of large trees in unharvested, remnant, and harvested stands for the entire range of decay-classes. A total of 116 line transects were distributed across unharvested forests, remnant linear forests, and cutblocks in cutover areas. Unharvested forest stands (black spruce [Picea mariana], balsam fir [Abies balsamea]–black spruce, balsam fir–white spruce [Picea glauca] and balsam fir) reflected a gradient of balsam fir dominance. The remnant forests selected were isolated for 5–15 years. Analyses were performed at two diameter cut-off values. Trees with DBH ≥20 cm were considered for availability of total trees whereas trees with DBH ≥30 cm were considered for availability of large trees. Forest stands comprised high proportions of standing dead trees (33% of all stems, 8% were large dead stems). Availability of total and large standing trees increased with the dominance of balsam fir in stands. Forest stands located on thick surficial deposits showed higher densities of large dead trees for every stand type suggesting a higher productivity on those sites. Availability of stems according to decay-classes showed a dome-shaped distribution with higher densities of snags in intermediate decay stages. However, for large stems, black spruce stands showed a significantly lower availability that was consistent across all decay-classes. In linear remnant forests, pure balsam fir stands were absent. Remnant stands thus showed a much lower availability in large trees when compared with unharvested balsam fir stands. Clearcuts had the lowest densities of dead trees across sampled stands. Current even-aged management practices clearly affect availability and recruitment of large trees, therefore forest-dwelling wildlife relying on these structures for breeding is likely to be affected by large-scale harvesting in coniferous boreal forests.     

Recent changes in forest productivity: An analysis of national forest inventory data for common beech (Fagus sylvatica L.) in north-eastern France

Changes in forest growth have been found in European forests and worldwide. However most observations have been derived from samples of restricted size, whose representativeness at a regional forest scale is questionable. National forest inventories provide an interesting perspective for both regional scale assessment of these trends and the investigation of their variations over environmental gradients, but have been little used.     

Seed and seedling survival of African mahogany (Entandrophragma spp.) in the Central African Republic: Implications for forest management

African mahoganies of the genus Entandrophragma are among the most valuable and important timber species harvested in Central Africa, representing more than 70% of total export volume from many areas. In spite of the importance of these species, relatively little is known about their regeneration ecology and little effort has gone into understanding the reasons for the consistently reported regeneration failures after logging. I assessed seed survival to germination (Entandrophragma angolense) and seedling survivorship (E. cylindricum) in three different forest types – monodominant Gilbertiodendron, mixed species, and fallow forest – under three different treatments – control, small mesh chicken wire, and large mesh chicken wire – to evaluate the relative importance of different causes of mortality. All seeds were eaten in controls and in both exclosure treatments within Gilbertiodendron forest in a matter of days. Seed survivorship to germination within exclosures in mixed species and fallow forest increased by approximately 10 and 25%, respectively, compared to Gilbertiodendron forest. Six-month seedling survivorship in controls was 37, 12, and 9% in Gilbertiodendron, mixed species and fallow forest, respectively. Seedling mortality was due to different causes in each forest type. In Gilbertiodendron forest controls, an equivalent percentage of seedlings died due to fungal and insect attack (27 and 28%, respectively), while in mixed species forest controls 28 and 55% of seedlings died of these causes, respectively. In fallow forest controls, 48% of seedlings died from predation and/or uprooting by small mammals, all in the first few weeks post-sowing; insect attack (26%) and drought (13%) were other important causes of seedling deaths. Protecting seedlings with exclosures had a dramatic effect on seedling survivorship within the fallow forest, increasing to over 50%.     

Population viability risk management (PVRM) for in situ management of endangered tree species—A case study on a Taxus baccata L. population

Population viability risk management (PVRM) provides a framework for explicitly including qualitative information about the possible outcomes of a management decision with regard to the viability of an endangered population in conservation management. Multi-criteria decision-making (MCDM) techniques enables managers to select the most preferred choice of action in a context where several criteria apply simultaneously. In that context a combined approach of the PVRM concept and a MCDM technique is presented for the development, evaluation and finally ranking of the in situ conservation strategies. We discuss the concept based on a case study for the maintenance of a gene conservation forest of an English yew population (Taxus baccata L.) in Styria, Austria. As part of the PVRM the analytic hierarchy process (AHP) is used to evaluate six conservation strategies with regard to the viability of the yew population. The viability of the population is evaluated based on the results of an analysis of the current environmental, social and economical state and a characterization of the ecological parameters of its population. The most significant risk factors (illegal cutting, browsing by game, tree competition, light availability and genetic sustainability) are structured and prioritised according to their impact on the viability of the yew population applying the AHP. Effects of the six conservation strategies on the viability of the yew population are determined through a qualitative assessment of the probability of a decrease of the population along with four different environmental scenarios. In this context strategy IV combining selective thinning, protection measures, game control with public relation activities seems to be the most effective alternative. The benefits of the combined approach of the PVRM concept with the AHP for the rational analysis of conservation strategies for this endangered tree species are discussed.     

Understorey condition scoring of Ghanaian lowland tropical moist forest during stock survey: a technique for regulating the allowable cut in ecologically and structurally degraded production forest

Understorey condition scoring is a rapid assessment field technique for appraising and delimiting the various stages of ecological and structural decline in fire-degraded, lowland, tropical moist forest. The scoring system is designed to be incorporated into stock survey. It is simple and consistent, with only minimal time and labour requirements. The degree of degradation is assessed from the vegetation structure contained within the first 2 m of the stand's vertical profile and is assigned to one of six categories. Sample plots of 20 m radius are used to distinguish localised, degraded areas from natural forest chablis and a high sampling intensity is employed to enable accurate mapping of the forest condition. Establishing the spatial extent and degree of degradation facilitates a more appropriate determination of the allowable cut at the sub-compartmental level, thereby affording protection to affected areas of forest against further ecological and structural deterioration. In addition, the system can be used for long-term condition monitoring and targeting dry-season fire-control operations.