Dead trees and protected polypores in unmanaged north-temperate forest stands of Lithuania

The availability of coarse woody debris (CWD) and distribution of dead trees into categories of mortality (dead standing, broken and uprooted) were investigated in north-temperate forests of central Europe (Lithuania). The studied area comprised 188.7 ha and included 18 different stands 40–130 years of age with a variety of tree species (spruce (Picea abies (L.) Karst.), pine (Pinus sylvestris L.), alder (Alnus glutinosa (L.) Gaertn.), birch (Betula pendula Roth and B. pubescens Ehrh.), aspen (Populus tremula L.), oak (Quercus robur L.), forest types (caricus-sphagnum, vaccinium-myrtillus, oxalis, myrtillus-oxalis, caricus-calamagrostis) and edaphic conditions (peaty, sandy, loamy soils of different moisture). The stands were excluded from wood harvesting for at least 30 years. A total of 11 365 dead trees (over 10 cm in DBH) or 6160.7 m³ of dead wood was found (60.2 trees/ha and 32.6 m³/ha). The volume of CWD per hectare was larger in older stands (r_S=0.78, P<0.01). Tree mortality during the last 2 years consisted of 482 trees and 381 m³, or 1.28 trees/ha×year and 1.01 m³/ha×year. In 25–33% of cases it was wind-related. Uprooted and broken trees were of larger DBH than dead standing. The distribution into the categories of mortality was strongly dependent on tree species (chi-square test, d.f.=10,P=0). Dead standing dominated in CWD of pine and alder. Broken trees comprised almost a half in CWD of aspen, and about one-third in birch, alder and oak. Uprooting most often occurred in spruce, aspen and birch. Edaphic conditions and stand age had a pronounced impact on distribution into mortality categories for spruce (chi-square test, d.f.=20, P<0.00001) and pine (d.f.=8, P≤0.0003). On peat soil, only a minority of trees of both pine and spruce was uprooted, and standing dead prevailed. In CWD of spruce and pine, the proportions of both dead standing and broken decreased and that of uprooted trees increased on mineral soils of higher moisture and bulk density in older stands. By contrast, uprooting in birch and alder occurred less often on more wet sites, where the proportions of standing snags were higher. A total of 41 species of wood-decomposing polypores were found in the study area. Among those, 10 (24%) were of conservation value.     

Initial impact of supervised logging and pre-logging climber cutting compared with conventional logging in a dipterocarp rainforest in Sabah,Malaysia

Pre-marked skid trails, directional felling and climber cutting when logging in tropical rainforests may be important ways of reducing damage to the forest, thus creating a healthier stand and improving future yields.This study, carried out in a virgin dipterocarp rainforest in the south of Sabah, Malaysia, compared two types of logging (both with and without pre-cutting climbers): conventional selective logging (CL) and supervised logging (SL). The latter is a selective logging system in which both pre-marked skid trails and directional felling were implemented. The pre-marked skid trails were aligned parallel to each other, spaced 62 m apart. A randomised complete block 2 × 2 factorial design was used in the experiment, consisting of 16 gross treatment plots, each of 5.76 ha with a 1 ha net plot in the centre.Fewer trees tended (0.050 < P ≤ 0.100) to be logged in SL plots than in CL plots (on average 9.4 and 13.0 trees ≥60 cm diameter breast height ha⁻¹). Pre-felling of climbers resulted in four more dipterocarp trees being logged ha⁻¹, compared with no climber cutting: a statistically significant difference (P ≤ 0.050). The basal areas lost of both large trees (≥ 60 cm dbh) and small dipterocarp trees (10–29 cm dbh) tended to differ between the logging systems, with CL leading to greater losses.There were significant differences in the residual stands left by the logging systems, with respect to the number of dipterocarps and their basal area in the diameter class 10–29 cm; ca 30% more stems being found after SL. No significant differences (or tendencies) in these variables were found in the residual stands in other diameter classes, or when trees of all species were considered.     

Tree cavities in riverine forests: What determines their occurrence and use by hole-nesting passerines?

We assessed: (1) the relative importance of different macro- and microhabitat characteristics for explaining the occurrence of tree cavities and their occupancy by hole-nesting passerines and (2) the role of woodpeckers as keystone species in riverine aspen and birch stands in central Estonia. In 1999–2003, multiple surveys were carried out in 16 stands with a total area of 104 ha. Of the 713 tree-holes found, 483 were considered suitable for secondary cavity-nesters. The mean density was 4.1 ± 3.0 (S.D.) suitable cavities ha⁻¹ (including 2.0 ± 1.3 suitable for hole-nesting passerines). Woodpeckers had excavated 88% of suitable cavities. The density of breeding woodpeckers explained 78% of variance in the density of woodpecker-excavated cavities (mean = 28 holes per pair) and 51% of natural cavities. Woodpecker-excavated and natural cavities occurred in very similar conditions, determined mostly by tree species, decay and size, stand type, as well as the vicinity of other cavities. Ninety-six of 161 occupancy cases of cavities were by passerines, which – probably to reduce the risk of nest predation or physical destruction – preferred small natural cavities in live trees. We conclude that riverine areas are important centres of cavity supply in forested regions and the value of woodpeckers as keystone species comes mostly from the large quantity, but not quality, of the cavities they provide. The results imply that: (1) for cavity-nesters, large (DBH > 30 cm) broadleaved trees, both live and dead, are the most important to retain during forestry operations in hemiboreal riverine forests and (2) woodpecker censuses may indicate cavity abundance, particularly if woodpecker-holes dominate among all cavities.     

Effect of spacing and water availability on root:shoot ratio in Eucalyptus camaldulensis

Our limited understanding of the processes that control the allocation of biomass in trees is one of the factors that hinders our ability to develop mechanistic models of tree growth. Furthermore, accurate assessment of carbon sequestration by forests is hampered by lack of information regarding below-ground biomass. Below-ground to above-ground biomass ratios (BGB:AGB) are known to vary with a number of environmental factors, tending to increase in drier, harsher conditions. However, there are few, good datasets of BGB:AGB ratios of large trees, especially native Australian species. We aimed to investigate the response of BGB:AGB to water availability and tree spacing in 10-year-old Eucalyptus camaldulensis growing in a plantation in a low rainfall area.We carefully harvested 16 trees, ranging in diameter at breast height (DBH) from 7.6 to 25 cm, from a research trial near Deniliquin, NSW. Four replicates of each treatment from a factorial design with wide (3 m × 6 m) and narrow (3 m × 1.5 m) spaced trees and with natural rainfall (408 mm/year) (control) or irrigated plots (flooded six times per year) were selected. Above-ground tree parts were harvested separating stem, branch and foliage. Soil cores to 1 m depth were taken to sample small roots (<15 mm diameter) within each plot, then all roots >15 mm belonging to each tree were excavated using compressed air and an excavator. Roots were separated into six size classes within the range from <2 to >50 mm.Both water and spacing treatments influenced tree growth with trees being larger in irrigated, wide spaced plots. The BGB:AGB ratio was strongly influenced by irrigation (0.68 control, 0.34 irrigated) but not spacing. Allometric analysis of above- and below-ground biomass as a function of DBH showed that the relationship between DBH and above-ground biomass was conserved across treatments.By contrast, the relationship between DBH and below-ground biomass was influenced by water availability, commensurate with the large differences in BGB:AGB ratio. The BGB:AGB ratio increased with tree size largely due to an increase in small roots.The proportion of total root mass in the small roots (<15 mm) obtained through coring was 25–48% with 18–30% of total root biomass in the <5 mm diameter class.     

Stand and landscape level effects of a major outbreak of spruce beetles on forest vegetation in the Copper River Basin,Alaska

From 1989 to 2003, a widespread outbreak of spruce beetles (Dendroctonus rufipennis) in the Copper River Basin, Alaska, infested over 275,000 ha of forests in the region. During 1997 and 1998, we measured forest vegetation structure and composition on one hundred and thirty-six 20-m × 20-m plots to assess both the immediate stand and landscape level effects of the spruce beetle infestation. A photo-interpreted vegetation and infestation map was produced using color-infrared aerial photography at a scale of 1:40,000. We used linear regression to quantify the effects of the outbreak on forest structure and composition. White spruce (Picea glauca) canopy cover and basal area of medium-to-large trees [≥15 cm diameter-at-breast height (1.3 m, dbh)] were reduced linearly as the number of trees attacked by spruce beetles increased. Black spruce (Picea mariana) and small diameter white spruce (<15 cm dbh) were infrequently attacked and killed by spruce beetles. This selective attack of mature white spruce reduced structural complexity of stands to earlier stages of succession and caused mixed tree species stands to lose their white spruce and become more homogeneous in overstory composition. Using the resulting regressions, we developed a transition matrix to describe changes in vegetation types under varying levels of spruce beetle infestations, and applied the model to the vegetation map. Prior to the outbreak, our study area was composed primarily of stands of mixed white and black spruce (29% of area) and pure white spruce (25%). However, the selective attack on white spruce caused many of these stands to transition to black spruce dominated stands (73% increase in area) or shrublands (26% increase in area). The post-infestation landscape was thereby composed of more even distributions of shrubland and white, black, and mixed spruce communities (17–22% of study area). Changes in the cover and composition of understory vegetation were less evident in this study. However, stands with the highest mortality due to spruce beetles had the lowest densities of white spruce seedlings suggesting a longer forest regeneration time without an increase in seedling germination, growth, or survival.     

Harvesting intensity versus sustainability in Indonesia

In East Kalimantan (Indonesia), impacts of conventional (CNV) and reduced-impact logging (RIL) on forest ecosystems were compared on the basis of pre- and post-harvesting stand inventories. There was a positive and significant correlation between the proportion of trees damaged by felling and the density of trees felled. Logging intensity ranged from 1 to 17 trees ha⁻¹(9–247 m³ ha⁻¹) and averaged 9 trees ha⁻¹ (86.9 m³ ha⁻¹). The study has shown that with RIL techniques, logging damage on the original stand can be significantly reduced by 50% compared with conventional logging. However, this 50% reduction in logging damage, was dependent on the felling intensity. With a felling intensity of 8 stems ha⁻¹ or less, RIL techniques only damaged 25% of the original tree population whereas 48% were damaged with conventional techniques. Above this felling intensity (i.e. 8 stems ha⁻¹), the effectiveness of RIL in limiting forest damage was significantly reduced, mainly because of the increasing felling damage. Moreover, the removal of all harvestable timber trees, leaving only few potential crop trees, will result in a seriously depleted residual stand. Because of the high damage involved by high felling intensity, leaving few potential crop trees, and the yield capacity of the remaining stand, acceptable harvesting volume will not be reached within the felling rotation of 35 years. It is concluded that silvicultural system based on diameter limit alone, as is the Indonesian system (TPTI), cannot be compatible with sustainability and more sophisticated harvested-selection rules are needed.     

Logging activity and tree regeneration in an Amazonian forest

We studied the effect of experimental logging of 4 ha plots on the regeneration of tree species in a forest 90 km north of Manaus, Amazonas, Brazil. Logging resulted in a total reduction in live wood volume of 44–107 m³ ha⁻¹, although only 63% of this volume was felled, and only 43% removed from the plots. The density of established regeneration (trees and shrubs with diameter at breast height ≤10 cm, and height ≥200 cm) was greater in logged plots than in control plots when measured 3 and 7–8 years after logging. Species richness was also significantly higher in logged plots than in controls. We registered 139 species per 1000 stems, 7–8 years after logging, 143 species per 1000 stems, 3 years after logging, and 136 species per 1000 stems in control plots. Overall species composition was significantly affected by the intensity of logging damage in the plots after 7–8 years, and control plots were significantly different from plots logged 3 years previously. However, changes were not great in relation to natural variation within the forest. Most species increased in density after logging (mean=17%), and the number of individuals belonging to species with commercial value on the local market was 15% greater in logged plots than in control plots. The total potential value of the regeneration, based on the value of wood per m³ (when adult) of the individuals, was 23% higher in logged plots than in control plots, though this difference was not statistically significant. Therefore, enrichment planting is not necessary to maintain either the biodiversity, or potential economic value for wood production, of this forest.     

Structure of Quercus gambelii communities in the Lincoln National Forest,New Mexico,USA

The structure of eight Quercus gambelii (Gambel's oak) communities in the Lincoln National Forest, New Mexico, USA were examined. Belt transects were used to estimate the density and basal area of the trees and the density of juvenile woody plants. In addition, diameter size-class distributions of Q. gambelii were examined to determine community development. The communities were estimated to be 109–137 years old and mid to late-successional. Total tree density was 3586–6480 plants/ha, with Q. gambelii having a relative density of 94–100%. Total basal area was 20.1–42.0 m²/ha, with Q. gambelii relative basal area 82–100%. The density and basal area of all other species present was low. Quercus gambelii juvenile density ranged from 1760 to 9160 plants/ha. Juveniles of all other species found were zero to 847 plants/ha. Based on Weibull analyses, all of the diameter size-class distributions of Q. gambelii were unimodal. There were few or no individuals in the smallest (1–5 cm) diameter size-classes, suggesting that recruitment of small Q. gambelii plants into the adult population may be below the replacement rate for these stands. Pooled size-class distributions for the other species were non-normal with most individuals in the smallest diameter size-classes. Low light levels below the canopy, a lack of canopy gaps, or browsing by Cervus elaphus (elk = red deer) may be the primary causes of poor recruitment because there were large numbers of Q. gambelii juveniles, but these individuals are not entering the small-tree size-class in any of the communities.     

Necromass in undisturbed and logged forests in the Brazilian Amazon

Necromass is an important stock of carbon in tropical forests. We estimated volume, density, and mass of fallen and standing necromass in undisturbed and selectively logged forests at Juruena, Mato Grosso, Brazil (10.48°S, 58.47°W). We also measured standing dead trees at the Tapajos National Forest, Para, Brazil (3.08°S, 54.94°W) complementing our earlier study there on fallen necromass. We compared forest that was selectively logged using reduced-impact logging methods and undisturbed forest. We estimated necromass density accounting for void volume for necromass greater than 10 cm diameter at Juruena for five decay classes that ranged from freshly fallen (class 1) to highly decayed material (class 5). Average necromass density adjusted for void space (±S.E.) was 0.71 (0.02), 0.69 (0.04), 0.60 (0.04), 0.59 (0.06), and 0.33 (0.05) Mg m⁻³ for classes 1 through 5, respectively. Small (2–5 cm) and medium (5–10 cm) size classes had densities of 0.52 (0.02) and 0.50 (0.04) Mg m⁻³, respectively. The average dry mass (±S.E.) of fallen necromass at Juruena was 44.9 (0.2) and 67.0 (10.1) Mg ha⁻¹ for duplicate undisturbed and reduced impact logging sites, respectively. Small and medium sized material together accounted for 12–21% of the total fallen necromass at Juruena. At Juruena, the average mass of standing dead was 5.3 (1.0) Mg ha⁻¹ for undisturbed forest and 8.8 (2.3) Mg ha⁻¹ for forest logged with reduced impact methods. At Tapajos, standing dead average mass was 7.7 (2.0) Mg ha⁻¹ for undisturbed forest and 12.9 (4.6) Mg ha⁻¹ for logged forest. The proportion of standing dead to total fallen necromass was 12–17%. Even with reduced impact harvest management, logged forests had approximately 50% more total necromass than undisturbed forests.     

Effects of uneven-aged management on diameter distribution and species composition of northern hardwoods in Upper Michigan

Uneven-aged management using single-tree or group selection has been in practice for many decades, especially in northern hardwood forests. Use of stocking regulation tools is thought to produce and maintain specific stand structures that upon regulation, are sustainable over time. We evaluated stand structures in northern hardwoods in Upper Michigan across three ownerships that practice different approaches toward uneven-aged management. Industry land (MeadWestvaco—MWV) uses primarily diameter limit cutting combined with a sawyer-select harvest method, retaining a maximum diameter of 45.7 cm (18 in.) with a residual basal area of 16.1 m²/ha (70 ft²/ac) and a cutting cycle of 10 years. The Michigan Department of Natural Resources (DNR) uses a crop tree release technique with a residual basal area of 18.4 m²/ha (80 ft²/ac) and a cutting cycle of 20 years. Both ownerships view regeneration of new cohorts as inevitable given the intensity of disturbance and the forest type. The third ownership (the Ford Forestry Center School Forest at Michigan Technological University—FFC) employs strict stocking regulation using the BDq method (residual basal area of 16.1 m²/ha (70 ft²/ac), maximum diameter of 50.8–55.9 cm (20–22 in.), and a q-ratio of 1.3) with a cutting cycle ranging from 12 to 15 years.Stand structure on a total of 25 stands was characterized for these ownerships to assess the impact of management strategy on stand structure and species composition. Differences in species composition and lower diversity indices were found where increasing sugar maple dominance was an objective (FFC ownership). All ownerships showed reduced relative importance values of mid-tolerant species such as yellow birch in their stands as compared to values reported for old-growth or unmanaged stands. Diameter distributions were classified into one of three shape categories (negative exponential, increasing q-ratio, and rotated sigmoid) using the regression of DBH, DBH², and DBH³ on the log₁₀ of trees per hectare. The best model in terms of adjusted-R² and root mean square error (RMSE) was selected for each stand. All management strategies resulted in similar occurrences of distribution shapes, despite some evidence of a trend toward a rotated sigmoid distribution. These trends suggest that several different diameter distribution shapes in uneven-aged northern hardwoods in the Lake States are possible following a variety of management approaches, with sugar maple increasing in dominance with strict adherence to certain stocking regulation guidelines.     

Harvesting intensity affects forest structure and composition in an upland Amazonian forest

Forest structure and floristic composition were studied in a series of 0.5 ha natural forest plots at four sites near Porto Trombetas in Pará State, Brazil, 11–12 years after being subjected to differing levels of above-ground biomass harvest and removal. In addition to undisturbed control plots, experimental treatments included: removal of most trees ≥45 cm DBH (low intensity harvest); removal of trees <20 and ≥60 cm DBH (moderate intensity harvest); clear-cutting (100% above-ground biomass removal). Post-harvest basal area growth generally increased with harvest intensity, and total basal areas for trees ≥5 cm DBH were, at the time of our study, 60% (in the clear-cut) to about 80% of those in the control plots. Biomass harvests stimulated recruitment and growth of residual trees, particularly in the smaller diameter classes, but had little effect on species richness for small trees, seedlings, vine, herbs, and grasses. Species richness for trees ≥15 cm DBH was greater in the control and low-intensity (74–75 species) than in the moderate intensity (47 species) and clear-cut (26 species) treatment plots. While the tree flora within all harvest treatments was broadly similar to the undisturbed (control) plots and included similar numbers of species of the major plant families typical of the surrounding forests, the more intensive harvest treatments, especially the clear-cut, were dominated by a higher proportion of short-lived, early successional tree species.     

Biomass and nutrient accumulation in pure and mixed plantations of indigenous tree species grown on poor soils in the humid tropics of Costa Rica

Aboveground biomass and nutrients and soil chemical characteristics were examined in young plantations of four indigenous tree species: Hieronyma alchorneoides, Vochysia ferruginea, Pithecellobium elegans, and Genipa americana, growing in mixed and pure stands at La Selva Biological Station, Costa Rica. Total tree biomass production rates ranged from about 5.2 Mg ha⁻¹ year⁻¹ for G. americana to 10.3 Mg ha⁻¹ year⁻¹ for H. alchorneoides pure stands, and for the species mixture it was about 8.9 Mg ha⁻¹ year⁻¹. Branches and foliage formed 25–35% of total tree biomass but they represented about 50% of total tree nutrients. H. alchorneoides, the four species mixture, and P. elegans had the greatest accumulations of total aboveground nutrients per hectare. The importance of the plantation floor as a nutrient compartment varied temporally. When forest floor litter biomass was at its peak, plantation floor litter N, Ca, and Mg were roughly equal to, or greater than stem nutrients for all species except for P. elegans. For P. elegans, the plantation floor consistently represented a very low proportion of total aboveground nutrients. G. americana and V. ferruginea trees showed 55–60% less biomass accumulation in mixed than in pure stands while H. alchorneoides and P. elegans trees grew 40–50% more rapidly in mixture. P. elegans foliage had 60% lower Ca but higher P concentrations in mixed than in pure stands, and G. americana had higher foliar Mg in mixed than in pure stands. V. ferruginea stands had the highest concentrations of soil Ca, Mg, and organic matter, particularly in the top layers. Relative to pure plantations, soil nutrient concentrations in mixed plantations were intermediate for N, P, and K, but lower for Ca and Mg. The results of this study can be used in the selection of tree species and harvest designs to favor productivity and nutrient conservation.     

Population structure and nut yield of a Bertholletia excelsa stand in Southwestern Amazonia

Although Brazil nut (B. excelsa) is often touted as one of the most economically successful NTFPs, little is known about the population structure of this species within its natural range in Southwestern Amazonia or ecological factors that affect fruit production. Since these are considered fundamental for sustainable resource management, we examined a natural Brazil nut stand in an extractive reserve in Acre, Brazil, posing the following questions: (1) What is the spatial distribution, species density, and size–class structure of B. excelsa? and (2) What tree-level factors influence Brazil nut production? In a 420 ha census, 568 trees ≥10 cm diameter at breast height (dbh) were counted, resulting in a density of 1.35 trees ha⁻¹. Based on the nearest-neighbor method, an index of aggregation (R) of 0.77 indicated a rejection of the null hypothesis of a strictly random distribution pattern. Yet, this value suggests a much greater tendency toward randomness than either clumping or uniformity. Our data do not show the commonly reported existence of groves, referring to clearly defined clusters of 50 to several hundred trees separated from similar clusters by great distances. Almost 1/4 of the population (23%) was composed of non-reproductive juveniles. Maximum R² improvement analysis applied to four distinct diameter classes provided insight into the dynamics of production-related variables over the species life cycle. While dbh explained 1/3 of production variance (R² = 0.3360) in the smallest diameter class (10 cm ≤ dbh < 50 cm), which included those in the process of reaching reproductive maturity, crown form best explained production variance of very large trees (dbh ≥ 100 cm). Results also demonstrated a significant negative correlation between crown vine load and production of trees ≥ 50 cm dbh (r = −0.13, P = 0.008), suggesting the need for further study on vine cutting as a possible silvicultural treatment for enhancing nut yields.     

Growth and carbon stocks of a spruce forest chronosequence in central Europe

Human induced changes in global environmental conditions are expected to influence or, as it is hypothesised in this study, have already influenced the biomass and growth of forest ecosystems. In this study, we reconstruct the history of tree growth and quantify the standing biomass along a chronosequence of six Norway spruce stands (Picea abies [L.] Karst; 16–142 years old) on acid soils in a mountainous region with high nitrogen deposition. The inventories of the study sites, as well as the historical stem growth of the sample trees were compared with common yield tables, representing growing conditions before 1960, to find out if and when significant changes in growth of trees had occurred. The growth at tree level (0.003–0.030 m³ yr⁻¹) was about 150–350% higher than predicted by the yield tables, independent of tree age. Because of low stand densities due to early thinning, the increase of stem growth at stand level (90% higher than yield table predictions) and the stand volume (35% higher than yield table predictions) were not as high as the increase of growth at tree level. Total biomass at stand level (including stems, branches, twigs, needles and roots) ranged between 35 and 180 t C ha⁻¹. Net primary productivity varied between 6 and 13 t C ha⁻¹ yr⁻¹. Intensive tree thinning activities probably stimulated growth of remaining trees, but the observed growth rates were beyond what would be expected from these activities exclusively. Thus it is assumed that the fertilisation effects of increased nitrogen deposition and CO₂ concentration, and improved climatic conditions due to ongoing climate change, have contributed to the observed changes in stem growth and that the thinning activities were synergetic with changing environmental conditions. The implications for carbon sinks as accountable under the Kyoto Protocol are probably small, because changes in environmental conditions are not accountable under the Kyoto Protocol and most of the observed changes in growth took place before 1990, the baseline for the Kyoto Protocol. Additionally, it is assumed that impacts on the carbon balance of forest stands due to changes in the thinning regime after 1990, which would be accountable according to article 3.4 of the Kyoto Protocol, are very small without any synergetic changes in environmental conditions.     

Effects of post-fire salvage logging on boreal mixed-wood ground beetle assemblages (Coleoptera,Carabidae)

The frequency and intensity of salvage logging has recently increased in burned forests of the Canadian boreal so that post-fire areas make up a significant annual share of all harvested forest land in some years. However, little is known about how this practice affects re-establishment of animal and plant communities that already have been strongly altered by the fire. We pitfall-trapped carabid beetles (Coleoptera, Carabidae) for two consecutive years following a large-scale boreal wildfire (276,000 ha) in burned mixed-wood forests of 12 landscape units (2.5 km × 2.5 km each). These units included four salvage treatments, each replicated three times: control (no salvaging), low (ca. 20–30% of merchantable mixed-wood removed), moderate (40–50%) and high salvage intensity (60–70%). We established 16 sampling sites in each unit: on the control landscapes, all 16 sites were in un-logged stands; in low-salvage units, 4 out of 16 sites were in salvaged areas; in moderate- and high-salvage units, 8 and 12 out of 16 sites, respectively, were in salvaged areas. Salvage logging positively affected carabid species richness. However, there was an overall salvage-caused decrease in the abundance of many common forest-dwelling carabids, and an increase in the abundance of disturbance or open-habitat specialists. Interestingly, the effects of salvage logging on the total catch and several abundant forest species (e.g., Calosoma frigidum, Harpalus laevipes, Pterostichus punctatissimus, P. adstrictus and Platynus decentis) appeared to be more important at the landscape level (the four landscape treatments) than at the level of sampling sites (site logged versus not). We suggest that this observation resulted from ambiguous site-level responses to salvage that collectively contributed to the (mostly negative) significant responses at the landscape level. Effects of fire severity (estimates based on tree survival) on carabids were species-specific; however, the impact of this measure was most often significant at the site, and not at the landscape, level. A Multivariate Regression Tree revealed that fire severity and the overall (pre-fire) amount of mixed-wood forest on the landscape were significant determinants of assemblage structure, with the local effects of fire severity being strongest.     

Effects of wood-ash on the tree growth,vegetation and substrate quality of a drained mire: a case study

The effects of wood-ash fertilisation on tree stands, soil characteristics and ground vegetation were studied on a drained pine mire in Finland (64°51′N, 26°04′E, 62 m a.s.l.). The original site type was a treeless, mesotrophic Sphagnum papillosum fen. The site was drained in 1933 and the wood-ash fertilisation experiment was started in 1947. The treatments were: (i) unfertilised, (ii) wood-ash 8 t ha⁻¹, and (iii) wood-ash 16 t ha⁻¹.Drainage and ash application had radical and long-lasting consequences on the biological activity on the site and the vegetation compartments studied. The understorey vegetation had been profoundly affected by the ash with almost complete transformation of the species and other life forms. Even 50 years after the ash treatment the changes in vegetation/site type and the tree stand were clearly visible. On the unfertilised plot, the biomass of ground vegetation consisted mostly of mosses and dwarf shrubs, but on the ash-treated plots it consisted mostly of herbs and grasses typical of upland forests.Ash treatment had promoted stem volume growth of Scots pine (Pinus sylvestris L.) substantially and for a long time. The total wood production on the ash plots during 1947–1994 was 13 and 17 times over that of the control plot. Unfertilised pine trees suffered from P and K deficiency throughout the study period. The concentrations of some plant nutrients (P, K) decreased during the past years on Ash8. No nutrient shortage afflicting the tree stand was observed on Ash16 during the study period.Ash application has also led to increased concentration of nutrients in the peat. A sizeable proportion of the mineral nutrients applied were still in the 0–20 cm peat layer. On the ash-treated plots the amount of soil nitrogen (0–20 cm) was 18 and 29 times and the amount of soil phosphorus 9 and 13 times over the amount bound by the tree stand and the ground vegetation (Ash8 and Ash16, respectively). The stock of potassium was generally small in the surface peat—only 60–90% of the amount of potassium bound in the tree stand and the ground vegetation.It was concluded that wood-ash had powerfully influenced the biological processes in surface peat. The decomposition of cellulose was significantly accelerated by both ash treatments. Ash fertilisation also increased the emissions of CO₂. The intensified decomposition rate in the litter, vegetation and peat explained to a large extent the accelerated growth of the Scots pine stands studied.     

Development of equations for predicting Puerto Rican subtropical dry forest biomass and volume

Carbon accounting, forest health monitoring and sustainable management of the subtropical dry forests of Puerto Rico and other Caribbean Islands require an accurate assessment of forest aboveground biomass (AGB) and stem volume. One means of improving assessment accuracy is the development of predictive equations derived from locally collected data. Forest inventory and analysis (FIA) measured tree diameter and height, and then destructively sampled 30 trees from 6 species at an upland deciduous dry forest site near Ponce, Puerto Rico. This data was used to develop best parsimonious equations fit with ordinary least squares procedures and additive models fit with nonlinear seemingly unrelated regressions that estimate subtropical dry forest leaf, woody, and total AGB for Bucida buceras and mixed dry forest species. We also fit equations for estimating inside and outside bark total and merchantable stem volume using both diameter at breast height (d.b.h.) and total height, and diameter at breast height alone for B. buceras and Bursera simaruba. Model fits for total and woody biomass were generally good, while leaf biomass showed more variation, possibly due to seasonal leaf loss at the time of sampling. While the distribution of total AGB into components appeared to remain relatively constant across diameter classes, AGB variability increased and B. simaruba and B. buceras allocated more carbon into branch biomass than the other species. When comparing our observed and predicted values to other published dry forest AGB equations, the equation developed in Mexico and recommended for areas with rainfall >900 mm/year gave estimates substantially lower than our observed values, while equations developed using dry forest data from forest in Australia, India and Mexico were lower than our observed values for trees with d.b.h. <25 cm and slightly higher for trees with d.b.h. >30 cm. Although our ability to accurately estimate merchantable stem volume and live tree AGB for subtropical dry forests in Puerto Rico and other Caribbean islands has been improved, much work remains to be done to sample a wider range of species and tree sizes.     

A non-invasive method for reconstructing the relative mortality rates of trees in mixed-age,mixed-species forests

The death of overstory trees drives changes throughout forest ecosystems. Knowledge of mortality rates for these larger trees provides a long-term perspective on forest development and forest health. Tree mortality rates are typically determined by repeated censusing of trees over extended time intervals. We describe a method of reconstructing relative mortality rates that does not require injuring live trees on the study plots. To determine when trees died, we used cross-dating (matching tree-ring patterns of dead and live trees), identification of sapling releases, and assessment of tree decomposition. Dead trees were identified to genus or sub-genus by microscopic examination of wood. We reconstructed live tree community structure so that mortality could be relativized on a taxonomic-group- and tree-size-specific basis by the tree densities existing when mortality occurred. We modified a forest development model to operate backwards in time and validated this model by comparing past tree stem diameters predicted by the model with past stem diameters known from tree-ring measurements. All tree-ring measurements from live trees were obtained off the study plots. We report data for all trees ≥20 cm diameter at breast height (DBH) from seven oak-hickory forest sites in Arkansas, Illinois, Indiana, and Ohio, USA. Total plot area was 6.7 ha. Mortality rates were determined for the past 20 years by genus or sub-genus, DBH, and decade. The average mortality rate was 0.60% per year. The accuracy of the reconstructed mortality rates approaches that of mortality rates obtained by repeated censusing. While this mortality reconstruction method does not yield data for individual species, and may involve some compromise in accuracy, the method offers substantial benefits: long-term mortality data may be obtained from a short-term study, mortality rates may be obtained for the past, and because this reconstruction method is non-invasive, future mortality rates can be measured on the same plots.     

Diameter increment patterns among 106 tree species in a logged and silviculturally treated Costa Rican rain forest

Studies of growth rates of trees in managed neotropical forests have rarely employed complete botanical identification of all species, while published information for Central American lowland rain forests largely concerns forests free of recent disturbance. We studied diameter increments of trees in a managed Costa Rican rain forest. The Pentaclethra macroloba-dominated forest was located on low hills with Ultisols in Holdridge's Tropical Wet Forest life zone. The 540 m × 540 m (29.2 ha) experimental area was lightly logged during 1989–1990. The 180 m × 180 m (3.24 ha) experimental plots comprised a 100 m × 100 m (1.0 ha) central permanent sample plot (PSP) with a 40-m wide buffer strip. Post-harvest silvicultural treatments were liberation/refinement (in 1991) and shelterwood (in 1992), applied under a complete randomized block design with three replicates, using logged but untreated plots as controls. All live trees ≥10 cm DBH in the PSPs, were identified to species; data reported are for 1993–1996. Cluster analysis was used to group species on the basis of the median and quartiles of their diameter increment distributions, separating data by silvicultural treatments; five diameter increment groups were established and subdivided on the basis of the adult height of each species (four categories), giving 17 species groups in the final classification. Adult height and silvicultural treatment made a significant contribution to growth rate variation. Median annual increments of the slowest-growing species groups, which featured many under- and middle story species, were ca. 1 mm; those for the fastest growing species, which were mainly canopy and emergents, were ca. 16 mm. All species in the groups of very fast growth were pioneers, whether short or long-lived, though many other pioneer species did not show fast growth. The proportions of species found in groups of moderate, fast or very fast growth were greater in the silviculturally treated plots than in the controls, and one complete diameter increment group, of fast growth, was only represented in the treated plots. Crown form, crown illumination and presence of lianas in the crown, showed significant correlations with diameter increments, though the importance of these latter two variables varied with silvicultural treatment. The very fast growth groups differed from the others in having higher proportions of trees with well-formed, well-illuminated crowns and an irregular diameter distribution with relatively few individuals in the smallest DBH class. Comparison with data from other neotropical forest sites shows that long-lived pioneers such as Vochysia ferruginea and Jacaranda copaia grow fast or very fast at all sites, while non-commercial canopy and emergent species of Chrysobalanaceae and Sapotaceae appear to be uniformly slow-growing. Growth data for the majority of species are, however, published for the first time.