Dynamics of above- and below-ground biomass and nutrient accumulation in an age sequence of Nothofagus antarctica forest of Southern Patagonia

Nothofagus antarctica (Forster f.) Oersted is a deciduous tree species, which naturally grows on poorly drained or drier eastern sites in the Andes Mountain near Patagonian steppe. Above- and below-ground biomass and nutrients pools were measured in pure even-aged stands at different ages (5–220 years) and crown classes. Functions were fitted for total biomass and nutrients accumulation, and root/shoot ratio of individual trees against age. Total biomass accumulated for mature dominant trees was eight times greater than mature suppressed trees. Biomass root/shoot ratio decreased with age from 1.8 to a steady-state of 0.5. All nutrients concentration (except Ca) decreased with age and varied according to the degree of crown suppression classes. Nutrient concentrations varied between biomass pool components following the order leaves > bark > small branches > fine roots > medium roots > rooten wood > coarse roots > sapwood > heartwood. Total nutrient accumulation followed the order dominant > codominant > intermediate > suppressed trees and its accumulation rate varied over time, e.g. P accumulation rate of dominant trees increased from 0.17 g tree⁻¹ year⁻¹ during regeneration to 1.39 g tree⁻¹ year⁻¹ in mature trees. Nutrients uptake reached a peak during the period of maximum biomass production, and root/shoot ratio of nutrients decreased from its maximum value at 5 years of age (0.6, 4.0, 0.9, 1.5, 1.0 and 2.6 for N, P, K, Ca, S and Mg, respectively) to a steady-state asymptote beyond 50 years of age. Thus, accumulation of nutrients in roots was greater during the regeneration phase of stand development, and nutrient accumulation increased in above-ground over time. Also, nutrient use efficiency increased in mature trees (111–220 years) and decreased in suppressed crown classes. The equations developed for individual trees have been used to estimate stand biomass and nutrient accumulation from forest inventories data. Total stand biomass varied from 62.5 to 133.4 t ha⁻¹ and total nutrients accumulation ranged from 3 kg Mg ha⁻¹ to 1235 kg Ca ha⁻¹. Proposed equations can be used for practical purposes such as to estimate pasture nutrients requirement in a silvopastoral system based on nutrients supply from leaf litter returns, or to determine amelioration practices like debarking stems before harvesting.     

Wood volume yield and stand structure in Norway spruce understorey depending on birch shelterwood density

Wood volume yield and stand structure were investigated for Norway spruce understorey growing at 1500 trees ha⁻¹ under birch shelters of two different densities, 300 and 600 trees ha⁻¹, and Norway spruce growing without shelter, in a field trial in the boreal coniferous forest, 56 years after the establishment of the stand and 19 years after establishment of the trial.Wood volume yield in sheltered spruce (mean annual increments of 1.87 and 1.78 m³ ha⁻¹ year⁻¹ under the dense and sparse shelterwoods, respectively) was significantly lower than that of unsheltered spruce (mean annual increment 2.43 m³ ha⁻¹ year⁻¹). The loss in wood volume yield for sheltered spruce was more than compensated for by the additional wood volume yield in the shelterwoods (mean annual increments 3.26 and 1.88 m³ ha⁻¹ year⁻¹ for the dense and sparse shelterwood respectively).Shelterwood density did not produce any significant differences in inequality of the understorey stands, measured as skewness and the Gini coefficient for the wood volume distributions. This implies that two-sided competition for nutrients and water was more significant than competition for light.Immediately after trial establishment, trees in the no shelterwood treatment (i.e. where all overstory trees had been removed) showed a marked increase in diameter growth. Over time, the growth rate of unsheltered Norway spruce was reduced to a level comparable to that of sheltered spruce. The difference in average diameter has persisted during the trial period. There was no similar effect on height growth, resulting in an increased slenderness index (h/d) with increased shelterwood density for the understorey trees.     

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.     

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.     

A financial analysis of rain forest silviculture in southwestern Sri Lanka

We examine the financial aspects of three silvicultural systems to encourage the sustainability of valuable hardwood species in mixed-dipterocarp forests of southwest Sri Lanka. We compare the net present value (NPV) of the current forest management approach (diameter limit harvests) with shelterwood harvests that promote light hardwood timber species. In this analysis, we also consider the potential of enrichment planting various precious timber (Diospyros quaesita — calamander), and non-timber forest product (NTFP) species (Caryota urens — fishtail palm; Elettaria cardamomum var. major — cardamom; Calamus zeylanicus — rattan) in conjunction with timber harvests. Two real (inflation adjusted) discount rates were used, 4 and 6%, respectively. Results show that when real discount rates are low (4%), and advance regeneration is present, NPV is highest for the one-cut shelterwood (US $9983 ha⁻¹). At a high discount rate (6%), reflecting the current short-term concession system and unstable rights to harvest, and where no advance regeneration was present, the diameter limit system (US $7173 ha⁻¹) was the optimum. On sites with advanced regeneration, the one-cut shelterwood system is clearly preferable. For all but rattan, shelterwood treatments provide higher NPVs for NTFPs than diameter limit cuttings primarily because of the higher light regimes and more growing space made available early in the rotation. The value for tea cultivation (US $26,000 ha⁻¹) far exceeds the value of managing these lands for timber alone, explaining the dramatic expansion in tea plantations on private lands. However, our results suggest that managing these lands for a combination of timber and enrichment plantings of NTFPs (US $23,000 ha⁻¹) can be comparable to tea plantations. By managing for NTFPs and timber, forest managers have new opportunities to solve the old problems of high-grading and land-use conversion.     

Long-term growth and ecophysiological responses of a southeastern Oklahoma loblolly pine plantation to early rotation thinning

A thinning levels study was initiated in a 9-year-old loblolly pine (Pinus taeda L.) plantation containing 26.6 m² ha⁻¹ basal area during the spring of 1984 in southeastern Oklahoma. Thinning treatments consisted of (1) three control plots (BA100), (2) three plots thinned to approximately 50% of the original basal area (BA50) and (3) three plots that were thinned to 25% of the original basal area (BA25). In 1987 the BA50 and BA25 plots were both rethinned to a basal area of 12 m² ha⁻¹. No other thinnings were done through age 24.The control plots have attained a basal area of 45.3 m² ha⁻¹ and basal area is now starting to decline. The BA25 and BA50 plots have basal areas between 34 and 35 m² ha⁻¹. Mortality has averaged about 90 trees ha⁻¹ per year from age 10 to age 24 on the control plot, declining from 2078 trees ha⁻¹ at age 10 to 827 trees ha⁻¹ at age 24. Mortality losses in the BA25 and BA50 plots have been only 3.2–7.7 trees ha⁻¹ per year over the entire study period. Cumulative stem biomass lost to mortality was 10.5, 16.0 and 61 Mg ha⁻¹, respectively, for the BA25, BA50 and BA100 treatments. Cumulative standing live biomass at age 24 in the BA100 treatment is 132 Mg ha⁻¹. Cumulative standing live biomass in the BA25 and BA50 treatments at age 24 is 86 and 79%, respectively, of that observed in the BA100 treatment. These results suggest wide ranges of residual stand densities left after an early thinning will produce a high percentage of the potential total maximum standing stem biomass. Diameter distributions at age 24 show only 33% of the trees in the BA100 treatments have the dimensions to be sawtimber (≥30 cm) but 92 and 95% of the trees in the BA25 and BA50, respectively, are sawtimber dimension or larger. Mean annual stem biomass production (MAI) of the BA100 treatment is 7.5 Mg ha⁻¹ per year at age 24. MAI of the thinned treatments is about 5.1 Mg ha⁻¹ per year and is converging to that of the BA100 treatment. The basis for this convergence is not that the live trees in the BA100 treatment are producing live biomass less rapidly than the thinned plots, but that mortality losses in the BA100 plot are much higher. Current annual stemwood production in all treatments is often limited by the severe summer droughts that occur in this region. The wide variations in weather experienced at this site also result in variations in earlywood:latewood ratio and ring specific gravity.     

Modelling coarse woody debris dynamics in even-aged Scots pine forests

Coarse woody debris (CWD) has become an important component in the study of forest ecosystems, being a key factor in the nutrient cycle as well as a habitat for many species. CWD dynamics varies greatly from primeval to managed forests. To assess the CWD dynamics, a chronosequence trial was established in two Scots pine forests in the Central mountain range in Spain. Although, the shelterwood system has been applied in both forests, one has received more intensive silviculture, whereas in the other, regeneration has been much more gradual and the thinning regime has not been so intensive. In order to inventory CWD, five decay classes and four categories according to size and CWD type (stumps and fallen logs or branches) were defined. The volume of branches and logs (estimated from length and mean diameter) and the number of stumps by size class and decay class are used to characterise the CWD. The most notable differences between the two silvicultural systems can be appreciated in the graph as peaks for temporary distribution of larger logs and stumps when intensive silviculture is applied. The CWD observed in the forests studied is mainly produced by logging. The maximum volume of logs and branches above 5 cm in diameter is 43.25 m³/ha after regeneration felling in the first forest, whereas in the other, a maximum of 16.30 m³/ha is reached at 60 years, just after thinning. Large stumps (diameter equal or greater than 30 cm) make up an important part of CWD biomass in these forests just after the regeneration felling. A model was developed to predict the changes in CWD quantity and quality distribution over time as well as predicting the effect of different silviculture options on CWD dynamics. The model integrates two different processes: the CWD inputs (which may be continuous or instant), and the decay process, modelled through a Richards–Chapman function. The average lifetime of CWD obtained ranges from 30 years for stumps over 30 cm in diameter to 8 years for logs with a diameter less than 10 cm.     

Effects of experimental acidification,nitrogen addition and liming on ground vegetation in a mature stand of Norway spruce (Picea abies (L.) Karst.) in SE Sweden

During the period 1976–1991, a combined experiment of acidification, liming and nitrogen addition in a mature spruce stand was conducted at Farabol in south-east Sweden. The aim of this study was to investigate the effects of these treatments on the ground vegetation 0, 1, 5 and 15 years after experimental establishment. The treatment regimes were nitrogen (200 kg N ha⁻¹, repeated three times at 4–5-year intervals, totally 600 kg N ha⁻¹), sulphur powder (50 and 100 kg S ha⁻¹ a⁻¹, totally 600 and 1200 kg ha⁻¹), sulphur plus nitrogen (600+600 kg ha⁻¹) and limestone (500 kg ha⁻¹ a⁻¹, i.e. totally 6000 kg ha⁻¹). The results showed that nitrogen addition and liming promoted the abundance of the grass Deschampsia flexuosa, while acidification had a negative effect on D. flexuosa and herbs in the field layer. There was a negative reaction giving immediate damage to the bryophytes in connection with additions of nitrogen, sulphur powder and lime. The magnitude of damage and the capacity to recover varied among species as well as among treatments. The recovery from immediate damage after liming was much faster than after the treatments with sulphur powder and/or nitrogen. A negative interaction between sulphur powder and nitrogen was found for herbs and mosses where the combined effects were stronger than the effects of a single treatment alone. Acidification also had a negative effect on the total number of species. The results of this study showed that acidification and nitrogen deposition could negatively influence forest vegetation by changing the nutrient availability in the soils. Liming led to an improved growth of the forest ground vegetation and the flora changed towards a more nitrophilic species composition.     

Stand development and production dynamics of loblolly pine under a range of cultural treatments in north-central Florida USA

The objectives of this study were to examine the effects of stand development and soil nutrient supply on processes affecting the productivity of loblolly pine (Pinus taeda L.) over a period approximately equal to a pulpwood rotation (18 years). The experiment consisted of a 2×2 factorial combination of complete and sustained weed control and annual fertilization treatments (C: control treatment, F: fertilization, W: weed control, FW: combined fertilization and weed control), located on a Spodosol in north-central Florida, USA. The reduction of soil nutrient limitations through fertilization or control of competing vegetation resulted in dramatic increases in almost every measure of productivity investigated, including height (19.7 m in the FW treatment versus 12.5 m in the C treatment at age 18 years), basal area (FW=44.2 m² ha⁻¹, F=39.6 m² ha⁻¹, W=36.6 m² ha⁻¹, C=19.9 m² ha⁻¹ at age 16 years), stemwood biomass accumulation (114 Mg ha⁻¹ in FW versus 42.8 Mg ha⁻¹ in C at age 18 years), foliar nitrogen concentration (1.53% in plots receiving fertilization versus 1.06% in unfertilized plots at age 17 years) and leaf area index (age 16-year peak projected of approximately 3.3 at age 9–10 years in F and FW plots, 2.5 in the W treatment and 1.5 in the C plots). Cultural treatments also decreased the growth ring earlywood/latewood ratio, and accelerated the juvenile wood to mature wood transition. While soil nutrient supply was a major determinant of productivity, production changes that occurred within treatments over the course of stand development were equally dramatic. For example, between age 8 and 15 years, stemwood PAI in the FW treatment declined by 275%; similarly large reductions occurred in the F and W treatments over the same time period. The reductions in PAI in the treated plots were linearly related to stand BA, suggesting the decline in productivity was associated with the onset of inter-tree competition. Responses of stemwood PAI to re-fertilization treatments at age 15 years suggests that the declines in growth and growth efficiency with time were partially attributable to nutrient limitations.     

Carbon sources and sinks in high-elevation spruce–fir forests of the Southeastern US

This paper examines carbon (C) pools, fluxes, and net ecosystem balance for a high-elevation red spruce–Fraser fir forest [Picea rubens Sarg./Abies fraseri (Pursh.) Poir.] in the Great Smoky Mountains National Park (GSMNP), based on measurements in fifty-four 20 m × 20 m permanent plots located between 1525 and 1970 m elevation. Forest floor and mineral soil C was determined from destructive sampling of the O horizon and incremental soil cores (to a depth of 50 cm) in each plot. Overstory C pools and net C sequestration in live trees was estimated from periodic inventories between 1993 and 2003. The CO₂ release from standing and downed wood was based on biomass and C concentration estimates and published decomposition constants by decay class and species. Soil respiration was measured in situ between 2002 and 2004 in a subset of eight plots along an elevation gradient. Litterfall was collected from a total of 16 plots over a 2–5-year period.The forest contained on average 403 Mg C ha⁻¹, almost half of which stored belowground. Live trees, predominantly spruce, represented a large but highly variable C pool (mean: 126 Mg C ha⁻¹, CV = 39%); while dead wood (61 Mg C ha⁻¹), mostly fir, accounted for as much as 15% of total ecosystem C. The 10-year mean C sequestration in living trees was 2700 kg C ha⁻¹ year⁻¹, but increased from 2180 kg C ha⁻¹ year⁻¹ in 1993–1998 to 3110 kg C ha⁻¹ year⁻¹ in 1998–2003, especially at higher elevations. Dead wood also increased during that period, releasing on average 1600 kg C ha⁻¹ year⁻¹. Estimated net soil C efflux ranged between 1000 and 1450 kg C ha⁻¹ year⁻¹, depending on the calculation of total belowground C allocation. Based on current flux estimates, this old-growth system was close to C neutral.     

Effects of enhanced nitrogen deposition on foliar chemistry and physiological processes of forest trees at the Bear Brook Watershed in Maine

Effects of enhanced nitrogen deposition on nutrient foliar concentrations and net photosynthesis of sugar maple (Acer saccharum Marsh.), American beech (Fagus grandifolia Ehrh) and red spruce (Picea rubens Sarg.) were evaluated at the Bear Brook Watershed in Maine (BBWM). The BBWM is a paired-watershed forest ecosystem study with one watershed treated since 1989 with bimonthly dry ammonium sulfate ((NH₄)₂SO₄) additions at a rate of 25.2 kg N ha⁻¹ year⁻¹, while the other watershed serves as a reference. The (NH₄)₂SO₄ treatment resulted in significant increases in foliar N concentrations for all three species and significant reductions in foliar Ca, Mg and Zn concentrations for American beech and red spruce. Treatment effects on foliar concentrations of other nutrients were not significant in any species. Despite higher N concentrations in all species, only treated sugar maple showed significantly higher photosynthetic rates. The non-response in net photosynthesis to higher foliar N in American beech and red spruce might be attributed to their low foliar Ca and/or Mg concentrations. Higher net photosynthetic rates in sugar maple might be explained by the higher foliar N and by the ability of this species to maintain an adequate Ca and Mg supply. Results suggested that nutrient imbalances due to inadequate supply of Ca and Mg might have counteracted a potential increase in net photosynthesis induced by higher N concentrations in American beech and red spruce.     

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.     

Managing forests infested by spruce beetles in south-central Alaska: Effects on nitrogen availability,understory biomass,and spruce regeneration

In Alaska, an outbreak of spruce beetles (Dendroctonus rufipennis) recently infested over one million hectares of spruce (Picea spp.) forest. As a result, land management agencies have applied different treatments to infested forests to minimize fire hazard and economic loss and facilitate forest regeneration. In this study we investigated the effects of high-intensity burning, whole-tree harvest, whole-tree harvest with nitrogen (N) fertilization, and conventional harvest of beetle-killed stands 4 years after treatment, as well as clear-cut salvage harvest 6 years after treatment. We measured available soil ammonium and nitrate and estimated N loss from leaching using in situ cation and anion resin exchange capsules. We also assessed spruce regeneration and responses of understory plant species. Availability and losses of N did not differ among any of the management treatments. Even a substantial application of N fertilizer had no effect on N availability. Spruce regeneration significantly increased after high-intensity prescribed burning, with the number of seedlings averaging 8.9 m⁻² in burn plots, as compared to 0.1 m⁻² in plots that did not receive treatment. Biomass of the pervasive grass bluejoint (Calamagrostis canadensis) was significantly reduced by burning, with burn plots having 9.5% of the C. canadensis biomass of plots that did not receive treatment. N fertilization doubled C. canadensis biomass, suggesting that N fertilization without accompanying measures to control C. canadensis is the least viable method for promoting rapid spruce regeneration.     

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.     

Nutrient uptake and growth of young trees in a P-deficient soil: Tree species and phosphorus effects

Phosphorus deficiency is widespread in the subhumid highlands of eastern Africa but there are few data on the effect of P deficiency on the growth of agroforestry tree species. We studied the effect of P application on growth, nutrient uptake and dry matter partitioning in young trees of Calliandra calothyrsus, Cedrela serrulata, Eucalyptus grandis, Grevillea robusta, Markhamia lutea, Senna spectabilis, and Sesbania sesban on a P-deficient soil (Kandiudalfic Eutrudox, bicarbonate-EDTA extractable P = 1 mg kg⁻¹) in western Kenya. The trees were grown at two P levels (control and 500 kg added P ha⁻¹) at 1 m² spacing in a randomized complete block design with three replications. Leaf K concentrations were in the low range for all species (5–9 mg g⁻¹) and K deficiency may have limited responses to P. Averaged over species, P addition increased aboveground shoot dry matter by a factor of 2.6 at 62 and 124 days, but the response decreased to 1.3 at 325 days. The increases at 62 days were large in sesbania (5.4) and eucalyptus (3.2) but small in calliandra (1.4) and markhamia (1.1). Relative response to P was more strongly correlated with shoot growth rate per unit root length among species than with shoot growth rate alone. Calliandra, which had high early growth rate but low response to added P, had an exceptionally high root length (6.0 km m⁻²) compared with the other species (0.3–2.1 km m⁻²). P addition increased N and P content but decreased final shoot K content in sesbania and calliandra, and had little effect on K content in the other species. The high-yielding species (eucalyptus, sesbania and calliandra) accumulated more than 30 g N and 2 g P m⁻² in shoots in 325 days of growth. The proportion of total shoot N in wood (branch + stem) was in a higher range (67–75%) in the shrubby species (sesbania, calliandra, senna) than in the upperstorey tree species (38–43%). Slow early shoot growth relative to total root length, and high specific root length (root length per unit root mass) are proposed as criteria for the selection of species and provenances that are well adapted to P deficient soils.     

A comparison of harvesting productivity and costs in thinning operations with and without midfield

Mechanised thinning operations can be carried out in the forest where skid roads are provided on which harvesters and forwarders can move. In the transition to continuous cover forestry (CCF) it is better to keep a thinner network of skid roads in the forest. Instead of tracks for harvesters and forwarders, these areas can be used for younger generations of trees. Moreover, fewer skid roads in the forest environment make the stand more natural. Fewer skid roads were introduced in this research as an alternative thinning operation with midfield¹ (MF) to the most popular mechanised thinning operation with skid roads² (SR). The aim of this paper is to analyse the productivity and economic aspects of thinning operations based on harvesters and forwarders, where there are different distances between skid roads. In both of the operations, harvesters and forwarders were used, but in the MF operation a chainsaw was additionally used to cut trees beyond the reach of the harvester boom. The distances between skid roads in the MF operation were 35–38 m, while in the other they were 18–20 m. The research was carried out in premature pine stands in a flat terrain in Poland. Bigger productivity and lower costs were found in the MF thinning operations. In the younger 44-year-old stand, the average harvester (Timberjack 770) productivity (in operational time) in the MF operation was 5.87 m³h⁻¹ and in the SR operation 4.52 m³h⁻¹; forwarding provided by the Vimek 606 6WD achieved a productivity of 5.03 and 4.52 m³h⁻¹, respectively. In the older 72-year-old stand, the Timberjack 1270B productivity was 11.53 m³h⁻¹ in MF and 8.70 m³h⁻¹ in SR; the Timberjack 1010B forwarder achieved 11.22 m³h⁻¹ (MF) and 8.84 m³h⁻¹(SR).The costs of harvesting and forwarding 1 m³ of wood were lower in the MF operations. In the younger stand, harvesting costs were 5.78 €/m³ (MF) and 6.72 €/m³ (SR) while forwarding costs were 1.94 and 2.18 €/m³ respectively. In the older stand, harvesting costs were 5.58 €/m³ (MF) and 6.78 €/m³ (SR); the forwarding costs were 2.65 €/m³ (MF) and 3.41 €/m³ (SR).     

Biomass,harvestable area,and forest structure estimated from commercial timber inventories and remotely sensed imagery in southern Amazonia

The purpose of this study was to determine if spatially-explicit commercial timber inventories (CTI) could be used in conjunction with satellite imagery to improve timber assessments and forest biomass estimates in Amazonia. As part of a CTI, all commercial trees ≥45 cm DBH were measured and georeferenced in 3500 ha of a logging concession in NW Mato Grosso, Brazil. A scientific inventory was conducted of all trees and palms ≥10 cm DBH in 11.1 ha of this area. A total of >20,000 trees were sampled for both inventories. To characterize vegetation radiance and topographic features, regional LANDSAT TM and ASTER images were obtained. Using a stream network derived from the ASTER-based 30 m digital elevation model (DEM), a procedure was developed to predict areas excluded from logging based on reduced impact logging (RIL) criteria. A topographic index (TI) computed from the DEM was used to identify areas with similar hydrologic regimes and to distinguish upland and lowland areas. Some timber species were associated with convergent landscape positions (i.e., higher TI values). There were significant differences in timber density and aboveground biomass (AGB) in upland (6.0 stems ha⁻¹, 33 Mg ha⁻¹) versus lowland (5.4 stems ha⁻¹, 29 Mg ha⁻¹) areas. Upland and lowland, and timber and non-timber areas could be distinguished through single and principal component analysis of LANDSAT bands. However, radiance differences between areas with and without commercial timber on a sub-hectare scale were small, indicating LANDSAT images would have limited utility for assessing commercial timber distribution at this scale. Assuming a 50 m stream buffer, areas protected from logging ranged from 7% (third order streams and above) to 28% (first order and above) of the total area. There was a strong positive relationship between AGB based on the scientific inventory of all trees and from the commercial timber, indicating that the CTI could be used in conjunction with limited additional sampling to predict total AGB (276 Mg ha⁻¹). The methods developed in this study could be useful for facilitating commercial inventory practices, understanding the relationship of tree species distribution to landscape features, and improving the novel use of CTIs to estimate AGB.     

Nitrogen budgets for Scots pine and Norway spruce ecosystems 12 and 7 years after the end of long-term fertilisation

The magnitude of nitrogen storage and its temporal change in forest ecosystems are important when analysing global change. For example, the accelerated growth of European forests has been linked to increased nitrogen deposition, but the changes in the N inputs that cause long-term changes in ecosystems have not yet been identified. We used two Swedish forest optimum nutrition experiments with Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) to study the long-term fate of N applied to these forest ecosystems. In the pine experiment, in addition to fertiliser (NPK) application, soil acidity was manipulated by application of lime and dilute sulphuric acid. From the spruce experiment, we selected treatments with similar fertiliser doses as in the pine experiment and with and without lime addition.We quantified various terms in the N budget 12 years (pine) and 7 years (spruce) after the last N addition. In the pine stand the NPK-treatment was the only treatment to produce a significant increase in N in the tree biomass (97% above control), whereas in the spruce stand the N additions increased tree N in all treatment combinations (207% above control). In the pine stand the relative distribution of nitrogen between trees and soil did not vary across treatments, with trees containing around 12% of ecosystem N and humus containing around 44% of soil N. The increases in N stocks in the pine stands were mainly in the soil. In contrast, in the spruce ecosystem trees accumulated most of the added N and the increase in the soil was restricted to the humus layer.In the pine ecosystem, large losses of added N (between 254 and 738 kg ha⁻¹ out of 1040 kg ha⁻¹ added as fertiliser) occurred, whereas in the spruce ecosystem we recovered more N than could be accounted for by inputs (between 250 and 591 kg ha⁻¹). There was no clear pattern in the interaction between acidification/liming and N additions.     

Changes in soil,seepage water and needle chemistry between 1984 and 2004 after liming an N-saturated Norway spruce stand at the Höglwald,Germany

In 1984, a liming experiment with a surface application of 4 t ha⁻¹ of dolomitic limestone was started at the acidic N-saturated Norway spruce forest “Höglwald” in southern Germany and monitored until 2004. The decay of surface humus due to the accelerated mineralisation accounted for 18.5 ± 2.7 t ha⁻¹ C or 50% of the initial pool and 721.6 ± 115.0 kg ha⁻¹ N or 46% for N. Due to some translocation of organic material to the mineral soil the values to 40 cm depth are slightly lower (13.5 ± 4.4 t ha⁻¹ C or 15% of the initial pool and 631.6 ± 192.8 kg ha⁻¹ N or 13% for N). In the control plot NO₃⁻ concentrations at 40 cm depth were above the European level of drinking water (0.8 mmolc l⁻¹ or 50 mg NO₃⁻ l⁻¹) for nearly the whole investigation period. Liming increased NO₃⁻ concentrations in seepage water for approximately 15 years, and accelerated leaching losses by 396.2 NO₃⁻–N kg ha⁻¹ from 1984 to 2003. The increase in pH of the soil matrix was more or less restricted to the humus layer and the upper 5 cm of the mineral soil during the whole time span, while the base cations Ca and Mg reached deeper horizons with seepage water. From 1984 to 2003, an amount that nearly equalled the applied Mg, was leached out of the main rooting zone, while most of the applied Ca was retained. The time series of the elemental concentrations in needles showed minor changes. Ca concentrations in needles increased with liming, while Mg remained nearly unchanged, and P decreased in older needles.     

Stand development after different thinnings in two uneven-aged Picea abies forests in Sweden

Two field experiments, located in Central and Northern Sweden, were used to study the influence of standing volume on volume increment and ingrowth in uneven-aged Norway spruce (Picea abies (L.) Karst.) stands subjected to different thinnings. Each experiment had a 3 × 2 factorial block design with two replications. Treatments were thinning grade, removing about 45, 65, and 85% of pre-thinning basal area, and thinning type, removing the larger or the smaller trees, respectively. Each site also had two untreated control plots. Plot size was 0.25 ha. Volume increment was 0.5–6.8 m³ ha⁻¹ year⁻¹ for the plots, and significantly positively (p < 0.01) correlated with standing volume. Within treatment pairs, plots thinned from Above had consistently higher volume increment than plots thinned from Below. Ingrowth ranged from 3 to 33 stems ha⁻¹ year⁻¹, with an average of 14 and 21 stems ha⁻¹ year⁻¹ at the northern and southern site, respectively. At the southern site ingrowth was significantly negatively (p < 0.01) correlated with standing volume, but not at the northern site. Mean annual mortality after thinning was 2 and 7 stems ha⁻¹ year⁻¹at the northern and southern site, respectively.