Mean Tree Volume Research Articles

Efficiency of a Woody 60 processor attached to a Mounty 4100 tower yarder when processing coniferous timber from thinning operations

Processor tower yarders (PTY) represent the current state of yard- ing technology being extensively used in mountainous conditions such as those from Central Europe where they were also developed and used for the first time. In proper technical conditions which are mostly related to forest road infrastructure such equipment may be introduced by technol- ogy transfer in other countries such as Romania where they could replace actual less-efficient forest equipment used in steep terrains. The aim of this study was to evaluate the efficiency of such equipment in conditions of thinning operations by adapting a time study to the general concepts and by using data collection techniques to suit the operational conditions im- posed by such equipment. In conditions of a mean tree volume of 0.21 m 3 × tree -1 , the results of our study indicate net production rates as high as 12.72 m 3 × h -1 when processing trees on landing, which could be also im- proved up to 17.52 m 3 × h -1 if the PTY have been be adequately installed on the forest road. Another key aspect which could improve the efficiency of such equipment performing landing operations is the number of planned and realized wood assortments since the time expenditure was affected by their number. Given the reduced impact on forest soils as well as the in- creased efficiency of tower yarders, our study concludes that there would be a lot of potential in actually using them in the Romanian forests lo- cated in steep terrain, if proper transportation infrastructure would exist. Keywords efficiency, time expenditure, productivity, processor tower yard- er, landing operations, traditional harvesting equipment

Operation times in John Deere 1110 E forwarders in regeneration felling

We calculated high-power forwarder productivity in regeneration felling with the objective to set long-term work plans. Based on the time studies of the forwarder operator’s work operation the operation time consumption was calculated and operation standards for the studied type of forwarder were designed. The standard values were determined based on the volume weight of harvested timber and the forwarding distance. The resulting time consumption required for forwarding 1 m<sup>3</sup> of timber, whose mean tree volume is <br /> 0.30–0.99 m<sup>3</sup>·stem<sup>–1</sup>, and upon forwarding distance of 100–1,000 m ranges from 0.05–0.09 Nh·m<sup>–3</sup>.    

English

Steep topography and thin native soils characterize the coal mining regions of southern West Virginia. State and federal regulations require replacement of native topsoil during reclamation for re-establishment of a vegetative cover. Due to hazards and expense associated with collecting this thin layer of soil before mining, regulators have allowed mine operators to use substitute topsoil materials, including weathered (brown) and unweathered (gray) geologic materials for growth media. For pasture and hayland post-mining land uses, substitute materials provide suitable physical and chemical properties for establishment and growth of forages with fertilization and liming. When reforestation is the post-mining land use, regulations in West Virginia require a 1.2 m layer of native topsoil and brown weathered sandstone, but unweathered materials may be used if native topsoil quantities are insufficient. This study examined tree growth on areas where brown and gray sandstone materials were applied to the surface as growth media at the Samples Mine in West Virginia. In a study already published at this site, we found significant differences in tree growth on brown and gray sandstone plots. For this study, we selected two additional gray sandstone plots for comparison to the original brown and gray plots. The two original sites were brown sandstone compacted and gray sandstone compacted, and we added nearby plots of gray sandstone slightly compacted and gray sandstone compacted and then ripped. Average pH ranged from 7.3 to 7.9 on the gray plots compared to 5.4 on the brown plot. Tree growth on brown sandstone was more than triple that of tree growth on all of the gray sandstone plots. Mean tree volume index on the brown compacted plot was 3108 cm 3 while mean tree volume index was significantly lower on the gray compacted plot (909 cm³), the gray slightly compacted plot (407 cm 3 ), and the gray ripped plot (885 cm³). Eight years after reclamation, the gray sandstone plots, whether slightly compacted, compacted, or ripped, showed poor tree growth compared to brown sandstone. Gray sandstone has proven to be an inferior topsoil substitute for reforestation on this site.

Norway spruce timber quality at different silvicultural measures and forest site types

The paper deals with a comparison of production quality of individual assortments of Norway spruce growing on different types of forest sites of the training forest enterprise of the Czech University of Life Sciences Prague in Kostelec nad Cernými lesy, Czech Republic. Two even-aged plots with different stand tending were compared: plot 1 – forest site type 4K (acidicbeechwood), plot 2 – forest site type 4P (acidic oak-firwood). The basic mensurational characteristics such as mean diameter, mean height, stand density, site index, mean tree volume, and stock volume were determined. The individual trees were divided into quality classes A, B, and C. From the statistical evaluation it is clear that the production potential is very similar on both plots. Lower stand density and higher light intensity affects differentiation of the diameter increment on both plots. The site type of plot 2 had a better effect on supply of ground water. The production of the individuals with high qualitative characteristics can be summarized into a few basic points for the maximum assortment yield. assortment classes; timber grading; wood quality; forest site types

Extracting structural attributes from IKONOS imagery for Eucalyptus plantation forests in KwaZulu-Natal, South Africa, using image texture analysis and artificial neural networks

The suitability of optical IKONOS satellite data (multispectral and panchromatic) for the estimation of forest structural attributes – for example, stems per hectare (SPHA), diameter at breast height (DBH), mean tree height (MTH), basal area (BA) and volume in plantation forest environments – was assessed in this study. The relationships of these forest structural attributes to statistical image texture from IKONOS imagery were analysed. The coefficients of determination (R 2) of multilinear regression models developed for the estimation of SPHA, DBH, MTH, BA and volume using statistical texture features from multispectral data were 0.63, 0.68, 0.81, 0.86 and 0.86, respectively. When the statistical texture features from panchromatic data were applied, the R 2 for the respective forest structural attributes increased by 25%, 31%, 6%, 0.2% and 0.2%, respectively. Artificial neural network (ANN) models produced strong and significant relationships between estimated and actual measures of SPHA, DBH, MTH, BA and volume with an R 2 of 0.83, 0.83, 0.90, 0.90 and 0.92, respectively, based on multispectral IKONOS data. Based on panchromatic IKONOS imagery, the R 2 for the respective forest structural attributes increased by 18%, 12%, 5%, 3% and 6%, respectively. Results such as these bode well for the application of high spatial resolution imagery to forest structural assessment.

Spatial and volume patterns of an unmanaged submontane mixed forest in Central Europe: 160 years of spontaneous dynamics

The long-term development of stand characteristics and tree spatial patterns (TSP), their mutual relation, and linkage to site and tree species were studied in the Boubín primeval forest (protected since 1858). Surveys were carried out in 1851, 1961/1964, 1972, 1984/1989, 1996 and 2010 on one to six research plots sized 0.58–1.00 ha. To see how results from these surveys could be generalized, results were also compared with whole-area data sets (46 ha) from 1972 to 2010. The proportion of Abies alba continually decreased, from 20% in 1851 to 2–3% in 2010. This decrease started no later than at the beginning of the 20th century. In contrast, the proportion of Fagus sylvatica slightly increased. The sum of dead and living wood volume was stable during the 159 year period, with deviations of only up to 5%. From 1961/64 to 2010, the number of living trees continually decreased, but the mean-tree volume and volume of dead wood increased. The distribution of dead wood always differed from the distribution of living trees. A random TSP was always most common, which seems to be typical for this type of forest. This was true even when A. alba was gradually forced out from the stand structure. Nevertheless, the pronounced decrease of A. alba found during the 1961/64 survey compared with 1851 was reflected in a tendency towards clustering, as gaps from A. alba dieback gradually closed. In these gaps, competitive pressure was lower, resulting in more clustered distributions. Regular distribution was recorded only rarely. F. sylvatica maintained a random or clustered TSP over long periods, depending on site conditions. On water-affected plots, it had a consistently higher tendency towards clustering. The only step change in TSP occurred due to Hurricane Emma in 2008. Otherwise, the most marked TSP changes over time were found for Picea abies, in which there was a gradual trend from clustered to random, connected with a decreasing number of individuals. The main reason for the decline of A. alba and the decreased number of living trees from 1961/64–2010 was the on-going effect of a high stock of red deer at the turn of the 19th and 20th centuries. The decreasing trend in the number of living trees showed no marked change, even 60 years after the game pressure was strongly reduced. However, the vertical structure became increasingly homogenized due to the long-term absence of severe abiotic and/or biotic disturbances.

Productivity of whole-tree bundler in energy wood and pulpwood harvesting from early thinnings

First thinnings have been neglected to great extent in Finland because of high harvesting costs. The whole-tree bundler (Fixteri) was developed in order to rationalize the integrated harvesting of small-diameter energy wood and pulpwood and to reduce transportation costs through load compaction. The operation of the whole-tree bundler is composed of cutting and compaction processes. In the present study, the productivity level and the performance characteristics of the second version of the whole-tree bundler (Fixteri II) in integrated energy wood and pulpwood harvesting from first thinnings were defined on the basis of a time study. When the mean volume of removed whole trees averaged 20 dm3 at the stand, the productivity of Fixteri II per effective working (E0 excluding delays) hour was 3.4 m3/(E0) and with an average removal of 75 dm3, it was 6.1 m3/(E0). When compared with the first prototype of the whole-tree bundler (Fixteri I), the productivity of Fixteri II was 38–77% higher, depending on the stand density and mean tree volume of the removal. The higher performance level of Fixteri II stemmed mainly from the increase in multi-tree cutting and from the introduction of grapple feeding of the bunches. Furthermore, the better hydraulic capacity of the base machine enabled a higher level of simultaneous working processes.

Estimating plot-level tree height and volume of Eucalyptus grandis plantations using small-footprint, discrete return lidar data

This study explores the utility of small-footprint, discrete return lidar data in deriving important forest structural attributes with the primary objective of estimating plot-level mean tree height, dominant height, and volume of Eucalyptus grandis plantations. The secondary objectives of the study were related to investigating the effect of lidar point densities (1 point/m2, 3 points/m2, and 5 points/m2) on height and volume estimates. Tree tops were located by applying local maxima (LM) filtering to canopy height surfaces created at each density level, followed by buffering using circular polygons. Maximum and mean height values of the original lidar points falling within each tree polygon were used to generate lidar mean and dominant heights. Lidar mean value was superior to the maximum lidar value approach in estimating mean plot height (R2∼0.95; RMSE∼7%), while the maximum height approach resulted in superior estimates for dominant plot height (R2 ∼0.95; RMSE∼5%). These observations were similar across all lidar point density levels. Plot-level volume was calculated using approaches based on lidar-derived height variables and stems per hectare, as well as stand age. The level of association between estimated and observed volume was relatively high (R2=0.82—0.94) with non-significant differences among estimates at high lidar point densities and field observation. Nearly all estimates, however, exhibited negative biases and RMSE ranging in the order of 20—43%. Overall, the results of the study demonstrate the potential of lidar-based approaches for forest structural assessment in commercial plantations, even though further research is required on improving stems per hectare (SPHA) estimation.

Using mixed estimation for combining airborne laser scanning data in two different forest areas

Airborne laser scanning (ALS) data have become the most accurate remote sensing technology for forest inventories. When planning new inventories the costs of fieldwork could be reduced if datasets of old inventory areas are effectively reused in the new area. The aim of this study was to apply mixed estimation using a combination of existing and new field datasets in area-based approach. Additionally, combining datasets with mixed estimation was compared with constructing new local models with smaller datasets. The two forest study areas were in Juuka and Matalansalo, which are located about 120 km apart in eastern Finland. ALS-based regression models were constructed using datasets of Matalansalo (472 reference plots) and Juuka (10–212 reference plots). Models were developed for the basal area median tree diameter and height, mean tree height, stem number, basal area and volume. The work was based on a simulation approach which involved five methods for approximating the regression coefficients. The first method merged the datasets using ordinary least squares (OLS) regression models, whereas the second and third methods combined datasets using mixed estimation on different weighting principles, and the final two estimated local models with predetermined and new independent variables. The results indicate that mixed estimation can improve the accuracy of derived stand variables compared with basic OLS models. Additionally, a sample of 40–50 plots was enough to build local models for basal area and volume and produce at least the equal accuracy of results than any other methods in this study.

Estimating plot-level forest structural attributes using high spectral resolution ASTER satellite data in even-aged Eucalyptus plantations in southern KwaZulu-Natal, South Africa

This study assessed the suitability of both visible and shortwave infrared of ASTER reflectance bands and various vegetation indices for estimating forest structural attributes of Eucalyptus species. The study was conducted in even-aged monoculture plantations of E. grandis and E. nitens in the southern KwaZulu-Natal Midlands of South Africa. Empirical relationships between forest structural attributes, i.e. stems per hectare (SPHA), diameter at breast height (DBH), mean tree height (MTH), basal area and volume, and ASTER data were derived using correlation and canonical correlation analysis (CCA). The results indicated weak relationships between the studied forest structural attributes and ASTER data. In the younger plantation stands (4–6 years) the adjusted R 2 values from CCA regression for SPHA, DBH, MTH, basal area and volume were 54.2, 63.5, 33.8, 25.4 and 30.3, respectively. The adjusted R 2 values in the mature stands (7–9 years) were distinctly weaker with values of 50.7, 55.8, 25.1, 20.2 and 27.3 for SPHA, DBH, MTH, basal area and volume, respectively. The results imply that ASTER satellite data are not applicable to forest structural attribute estimation in commercially managed forest stands.

Response of a rising 2-year-old natural Piedmont upland stand to fertilization

Hardwood stands in the southern U.S. are often regenerated naturally following clearcutting, with little or no silvicultural intervention in the early stages of stand development. Fertilizer was applied to a young naturally regenerating stand in order to evaluate the effectiveness of nutrient addition as a silvicultural tool in recently clearcut stands and to better understand the ecological relationships between site fertility and stand development. The study was installed on a rising 2-year-old naturally regenerated mixed pine-hardwood stand in the Hill Demonstration Forest in the Piedmont region (Durham County) of North Carolina. Fertilizer treatments were control, N, N + P, and N + P + K (at 200 kg N per ha, 50 kg P per ha and 100 kg K per ha). On a whole stand basis, increased growth rates were observed for trees on N + P and N + P + K plots. Fertilizer treatments did not affect total stand density, but the density of loblolly pine significantly decreased in N + P plots compared to the Control. The density of stems of stump origin also increased in plots receiving N + P. Density of sweetgum (Liquidambar styraciflua) significantly increased and hickory (Carya spp.) density decreased with the application of N + P. Dominant hardwood species with the exception of yellow-poplar (Liriodendron tulipifera) responded with an increase in height to only N + P fertilizer treatments. Yellow-poplar increased in groundline diameter, height and mean tree volume index with the application of N + P. Loblolly pine (Pinus taeda) responded to N + P + K fertilizer treatment with an increase in height, diameter and volume index over the Control. There was no growth response among treatments for the 16 largest trees per species per plot, with the exception of red oak (Quercus rubra) which responded with an increase in height in N + P plots. Projected growth responses were modeled on a whole stand level and indicate that the use of N + P fertilizer may be an effective silvicultural instrument to increase growth, accelerate stand development, and shorten rotation length.

Early development of tended mixtures of aspen and spruce in western Canadian boreal forests

In 1992, the Western Boreal Growth and Yield Association (WESBOGY) began a long-term study to evaluate the dynamics of regenerated aspen ( Populus tremuloides Michx.)—white spruce ( Picea glauca (Moench) Voss) mixedwood stands following manipulation of aspen to a range of densities. In this study six levels of aspen (0, 200, 500, 1500, 4000 stems ha −1 and natural) and three levels of spruce (0, 500 and 1000 stems ha −1) densities have been created. Data from four locations demonstrate substantial variation in initial aspen densities following clearcutting of aspen dominated stands. After 9 years densities begin to converge with the highest rates of mortality associated with high starting densities. A model was developed that shows a significant relationship between the proportion of trees surviving to the end of a year and the density at the beginning of the year. Size-density relationships based on quadratic mean root collar diameter, mean tree volume and mean tree height are presented. Three to four years following spacing of aspen to densities ranging from 200 to 4000 stems ha −1 there were no significant effects of density on aspen size. In addition, spacing of the aspen had no significant effect on spruce height at year 9 (3–4 years after spacing), but spruce root collar diameter (RCD) was significantly smaller in the unspaced compared to the spaced plots. The ratio of height to root collar diameter (HDR) for white spruce showed a significant and clear response to aspen density and increased with increasing aspen density.

Long-term responses of ecosystem components to stand thinning in young lodgepole pine forest: III. Growth of crop trees and coniferous stand structure

Enhanced growth of crop trees and development of late-seral structural characteristics in second-growth stands in temperate and boreal forest zones could be achieved by silvicultural practices such as pre-commercial thinning (PCT). This study was designed to test the hypotheses that large-scale stand thinning, at a 15-year period after PCT, would enhance: (i) productivity and structural features (crown volume, diameter, height, and volume growth of lodgepole pine ( Pinus contorta) crop trees); and (ii) coniferous stand structure (abundance, species diversity, and structural diversity of coniferous tree layers). Replicate study areas were located near Penticton, Kamloops, and Prince George in south-central British Columbia, Canada. Each study area had three stands thinned to densities of ∼500 stems/ha (low), ∼1000 stems/ha (medium), and ∼2000 stems/ha (high), with an unthinned young pine and old-growth pine stand for comparison. An overall analysis of tree growth in thinned stands, across these regional replicates, indicated that lodgepole pine grew significantly faster in mean diameter in the low- than either of the medium- or high-density stands. There was no difference in mean height growth among stand densities over the 15-year period since PCT. Mean tree volume increment was significantly higher in the low-density than in the high-density stands. Mean stand volume increment (m 3/ha) was similar in the medium-density (108.53) and high-density (132.51) stands, both of which were significantly higher than the low-density stands (72.88). Mean crown volume of crop trees was significantly greater in the low-density (52.8 m 3) and medium-density (42.9 m 3) stands than in the high-density (27.8 m 3), unthinned (11.7 m 3), or old-growth stands (30.9 m 3 pine only). This measure of crown size was similar among pine trees in the low-density, medium-density, and all conifers (43.2 m 3) in the old-growth stands. Other measurements of crown architecture followed this same pattern. Mean densities of understory trees were similar among stands for height classes up to 3 m. Mean species diversity and structural diversity of coniferous tree layers were highest in the low- and medium-density stands than in other treatment stands. Our results support the hypotheses that PCT enhances productivity (diameter and volume growth, but not height growth) and structural features (crown architecture) of young lodgepole pine, as well as diversity of coniferous tree layers in thinned stands. Accelerated development of some structural features of late-seral forest appeared in our young managed stands.

Estimating forest growth using canopy metrics derived from airborne laser scanner data

Canopy height distributions were created from small-footprint airborne laser scanner data with a sampling density of 0.9–1.2 m − 2 collected over 133 georeferenced field sample plots and 56 forest stands located in young and mature forest. The plot size was 300–400 m 2 and the average stand size was 1.7 ha. Spruce and pine were the dominant tree species. Canopy height distributions were created from both first and last pulse data. The laser data were acquired in 1999 and 2001. Height percentiles, mean and maximum height values, coefficients of variation of the heights, and canopy density at different height intervals above the ground were computed from the laser-derived canopy height distributions. Corresponding metrics derived from the 1999 and 2001 laser datasets were compared. Forty-five of 54 metrics derived from the first pulse data changed their values significantly due to forest growth. The upper height percentiles increased their values more than the field-based height growth estimates. The 50 and 90 height percentiles increased by 0.4–1.3 m whereas the field-estimated mean height increased by 0.2–0.9 m. Metrics derived from the last pulse data were less influenced by growth. Mean tree height ( h L), basal area ( G), and volume ( V) were regressed against the laser-derived variables to predict corresponding values of h L, G, and V based on the 1999 and 2001 laser data, respectively. Forest growth was estimated as the difference between the 2001 and 1999 estimates. Laser data were able to predict a significant growth in all the three biophysical variables over the 2-year period. However, the accuracy of the predictions was poor. In most cases the predictions were biased and the precision was low. Finally, several key issues of particular relevance to laser-based monitoring of forest growth are discussed.

Variation in insect damage and growth in Eucalyptus globulus

Abstract Objectives of this study were to examine (i) between‐provenance variation in susceptibility to insects in Eucalyptus globulus and (ii) relationships between insect damage and tree growth. We planted seedlings of 18 provenances of E. globulus from south‐east Australia in a field trial and measured tree growth and insect damage. Christmas beetles Anoplognathus spp. were the dominant herbivores during this experiment, and 99% of trees were affected by them. Defoliation of individual trees by Anoplognathus spp. ranged from 0% to 85%. The main results of this study were that: (i) provenances of E. globulus from Tasmania and the Bass Strait islands, which had previously shown resistance to autumn gum moth Mnesampela privata and leaf blister sawfly Phylacteophaga froggatti tended to be resistant to Anoplognathus spp.; (ii) mean tree volume was reduced by herbivory; and (iii) the volume‐based performance ranking of provenances changed depending on the probability of insect outbreaks. Fast‐growing provenances should be planted in optimal growing areas for E. globulus with low probability of insect outbreaks. However, in suboptimal growing areas, planting slightly slower growing but more resistant provenances is likely to result in greater output than planting fast‐growing provenances when the probability of insect outbreaks is high.

Economic consequences of three silvicultural methods in uneven-aged mature coastal spruce forests of central Norway

Summary Six experimental sites in the coastal spruce (Picea abies L. Karst.) forest of central Norway were used as the basis of an economic investigation of three silvicultural systems: a single tree selection system, a group system and clearcutting. The mean tree volume removed in the selection system was 0.6 m 3 , and ~0.3 m 3 for the other two methods. The harvesting cost was ~14 euro/m 3 for clearcutting, and about 10 per cent higher for the group and selection systems. In simulations of future revenues and expenses, the net present value (NPV) was approximately 15 per cent lower for the group and selection systems compared with clearcutting. Lower volume production in unevenaged stands and higher administration and harvesting costs had only a minor influence on the NPV. All calculations were carried out using a 2 per cent discount rate, a 3 per cent rate lowered the NPV of the group and selection systems to 75 per cent of the clearcutting method.

Fourteen-year growth response of young lodgepole pine to repeated fertilization

Four rates of N (0, 50, 100, and 150 kg·ha–1) with and without a fertilizer mix containing P, K, S, Ca, Mg, and micronutrients were applied to a stand of 8-year-old lodgepole pine (Pinus contorta var. latifolia Engelm.) in four applications during 7 years. Fourteen years after the first fertilization, mean tree basal area and volume were significantly increased in the treatments containing the two highest rates of N plus the fertilizer mix. Mean tree basal area was 38% greater and mean tree volume was 42% greater in the highest N (525 kg·ha–1) plus mix treatment than in the control treatment. Stand basal area increased 48% over the control in the highest N plus mix treatment. Mean tree basal area and volume were 27 and 25% greater than the control under the intermediate N rate (350 kg·ha–1) with mix, respectively. Height growth was not significantly increased by fertilization. Both higher rates of N (four applications of >100 kg·ha–1) and the fertilizer mix were required for significant growth responses to occur. Addition of N alone or mix alone had a negative effect on mean tree basal area and volume. Addition of higher N rates without the mix decreased foliar total S and SO4-S concentration and increased the N/S ratio. Addition of the higher rates of N without the mix aggravated slight K deficiencies. The responses to the higher N rates in combination with the fertilizer mix are mainly attributable to S.

Maximum size–density relationships for mixed softwoods in the northeastern USA

The maximum size–density relationships or self-thinning lines were developed for three mixed-softwood climax forest habitats (hemlock-red spruce, spruce-fir, and cedar-black spruce) in the northeastern USA. The plot data were collected from an extensive data base used in growth studies from 1950 to 1970, and represented a wide range of species compositions, sites, management options, and densities. Plots having late successional species compositions with relative density index higher than 0.7 were selected as the most fully-stocked plots for model development. Reduced major axis regression was used to fit the self-thinning lines to the data. The differences between the three forest habitats were tested using the 95% confidence intervals of the coefficients of the self-thinning lines. The results indicated that there were no differences between the hemlock-red spruce and spruce-fir habitats for both relationships of the mean tree volume versus number of trees, and the quadratic mean tree diameter versus number of trees. Thus, these two habitats were combined to develop a single self-thinning line. However, the cedar-black spruce forest habitat required a separate self-thinning line. These maximum size–density relationships can be readily used to construct stand density management diagrams.

Preparation of volume table of SAL (Shorea robusta) - an approach using satellite data

Sal (Shorea robusta) is an important forest tree species in north and north-eastern India. Large-scale plantations of this species have been raised there under taungya and coppice system of management. The conventional volume table prepared for high sal forest is referred to infer the volume of production of this species. Earlier workers have used aerial remote sensing data to develop volume tables of this species. In the present study a volume table for sal is developed based on remotely sensed satellite data using a regression technique. A two-step method was developed to estimate mean tree volume from satellite data. In step 1, mean crown diameter — an intermediate variable - was estimated from satellite data. In step 2, the estimated mean crown diameter was used to estimate the mean tree volume. Addition of age of the crop as an independent variable improved the predictive ability of the regression equation.

The effect of whole-tree harvesting on the growth of second rotation Sitka spruce

Summary Stem analysis has been used to examine the effects of two harvesting techniques upon growth of second rotation Sitka spruce planted in 1981 on a peaty gley site of low fertility in Kielder Forest, Northumberland. The effect of NPK fertilizer upon tree growth on conventionall y harvested plots was also determined. Weed competition was reduced by hand weeding and the application of herbicides. Repeated measures analysis was used to identify the time at which significant growth responses occurred. Whole-tree harvesting reduced mean tree volume from 1986 onwards while the addition of fertilizer to conventionall y harvested plots increased volume growth from 1990. By 1993, whole-tree harvesting had decreased mean tree volume by 32 per cent and the addition of fertilizer to conventionally harvested plots had increased mean tree volume by 13 per cent. Observed treatment effects are most likely due to the increased removal of nutrients during whole-tree harvesting. The release of nutrients from decomposing residues is expected to meet uptake requirements for approximately 7-9 years following replanting. Effects of shelter and weed competition should also be considered on sites where herbicides have not been used to control ground vegetation. Repeated measures analysis and the use of suitable growth functions provide powerful analytical tools to examine historical treatment effects derived from stem analysis.