Basal Area Removal Research Articles

Effects of forest harvesting on summer stream temperatures in New Brunswick, Canada: an inter-catchment, multiple-year comparison

Abstract. This paper presents a pre- and post-harvest comparison of stream temperatures collected in five neighbouring streams (sub-catchments) over a period of five years (1994-1998). The aim of the study was to determine whether land cover changes from clear cutting in areas outside forest buffer zones (applied to streams >0.5 m wide) might contribute to an increase in summer mean stream temperatures in buffered streams downslope by infusion of warmed surface and sub-surface water into the streams. Specific relationships were observed in all five forest streams investigated. To assist in the analysis, several spatially-relevant variables, such as land cover change, mid-summer potential solar radiation, flow accumulation, stream location and slope of the land were determined, in part, from existing aerial photographs, GIS-archived forest inventory data and a digital terrain model of the study area. Spatial calculations of insolation levels for July 15th were used as an index of mid-summer solar heating across sub-catchments. Analysis indicated that prior to the 1995 harvest, differences in stream temperature could be attributed to (i) topographic position and catchment-to-sun orientation, (ii) the level of cutting that occurred in the upper catchment prior to the start of the study, and (iii) the average slope within harvested areas. Compared to the pre-harvest mean stream temperatures in 1994, mean temperatures in the three streams downslope from the 1995 harvest areas increased by 0.3 to 0.7°C (representing a 4-8% increase; p-value of normalised temperatures <<0.05). The greatest temperature change occurred in the stream that had the greatest proportion of its upper catchment harvested (16.8%), which also had the highest calculated potential solar loading ( ~2749 MJ per stream cell). From the analysis it was determined that the thinning applied to the forest buffer of that stream, with a basal area removal of ~28%, was insufficient to cause significant change in the observed stream temperature. Similar effects were observed following a second harvest in 1997. In general, increases in mean stream temperature coincided with forest harvesting activities outside forest buffers, where conditions promoting stream warming were greatest. In this study, no clear relationship existed between forest buffer strip width (ranging from 30-60 m) and the level of stream warming observed at the monitoring stations. Keywords: terrain attributes, solar radiation, land cover, forest buffers, New Brunswick regulations, spatial modelling, DEM, forest covertypes

Transition matrix for modeling the dynamics of a subtropical seminatural forest in southern Brazil

Transformation into seminatural managed forests and sustained use of wood is a major goal to maintain nature-oriented forest ecosystems in the tropics and subtropics. In the present study a transition matrix was used to model the development of an uneven-aged subtropical humid forest of Rio Grande do Sul (Brazil) which was remeasured three times. The approach consists of an estimation of the probability matrix of diameter classes and the incorporation of recruitment and mortality from this forest. Different harvest strategies are elaborated within a sustainable management approach with the objective of sawtimber production (goal-diameters of 60 and 80 cm of the valuable species, respectively). The application of a 15-year cutting cycle with a basal area removal of 7 m 2 (or ∼14 m 2 in a 30-year cutting cycle) could be proven to be a sustainable intervention strategy.

Nutrient status of Norway spruce stands subjected to different levels of overstorey removal

Foliage nutrient concentrations of overstorey and understorey Norway spruce [Picea abies (L.) Karst.], and height growth and needle weights of understorey saplings, were studied in a 7-year period after harvest. The following treatments were applied on each of three sites 5 years prior to needle sampling: control with no cutting, partial cutting with 50–60% removal of basal area, and patch cut (25×25 m – 0.063 ha clear-cut). Saplings on control plots had higher concentrations of K and Cu in current-year needles (C) than overstorey trees. Increased harvest intensity led to a reduction of K in C needles and Mg in (C+1) needles of saplings, and of B in both saplings (C, C+1) and overstorey trees (C+1). Sapling needle weights generally increased with harvest intensity, whereas no effect of foliage N status on needle weights could be detected. The growth response of saplings was explained by the interaction between foliage N status, quantified as average N concentration in C and (C+1) needles, and harvest intensity. The results illustrate that sufficient N supply is a key factor for the ability of advance regeneration to utilise the improved light condition associated with overstorey removal.

Streamflow response of mixed-species eucalypt forests to patch cutting and thinning treatments

An 11-year paired-catchment study was implemented to assess the effect of differing logging practices on streamflow in mixed-species eucalypt forest at Tantawangalo Creek, southeastern Australia. Following a 3-year calibration period, Ceb catchment was retained as a control, Wicksend catchment was patch-cut to remove 22% of basal area, and Willbob catchment was thinned to remove 12% of basal area. The treatments resulted in an initial increase in monthly total streamflow and baseflow at both treated catchments. In annual terms, total streamflow increased by 10% in the first 3 years after logging at Wicksend, and by 31% for the first 4 years at Willbob, despite the difference in basal area removed. Streamflow then returned to pre-treatment levels for 1 year and subsequently declined by 20% below pre-treatment levels over the next 4 years at Wicksend. Willbob displayed a return to, but not below, pre-treatment levels over the same period. Although there were some large post-treatment stormflows, changes in baseflows were largely responsible for the streamflow increases, and at Wicksend, explained the streamflow decreases in the latter observation period. Differences in regeneration densities between the treated catchments indicate the greater magnitude and persistence of flow increases at Willbob were due to poor regeneration following the thinning treatment, while dense and vigorous under- and overstorey regeneration dampened initial flow increases and facilitated significant decreases at Wicksend. Significant streamflow decreases after disturbance have not been widely reported for mixed-species eucalypt forests, and the magnitude of streamflow increases after only 12% basal area removal at Willbob is unusual.

New management options in chestnut coppices: an evaluation on ecological bases

The effects of long rotation periods and heavy low thinning on chestnut ( Castanea sativa Mill.) coppices have been evaluated from a bio-ecological point of view. Aboveground tree biomass and its partitioning, bio-ecological indexes such as litter production, leaf area index (LAI), radiation regime, and growth efficiency have been analyzed for 4 years in thinned and unthinned permanent plots established in a coppice stand aged 11 years under normal rotation (NR) and in a coppice stand aged 35 years under long rotation (LR). A decrease in LAI, litter production and growth rate with the age was observed. LR showed high current annual increments (>16.0 m 3 ha −1 per year and 8.0 Mg ha −1 per year for volume and aboveground biomass, respectively). Only slight differences in growth efficiency were observed. The adoption of heavy thinning (one third of basal area removal) affected stocking and determined significant differences in the light regime below the canopy, amount of gaps in canopy cover and LAI values, particularly in the years immediately after thinning, whereas slight differences were observed in growth efficiency. Nevertheless, chestnut showed a good aptitude, more evident in the younger stand, to re-build a homogeneous canopy cover: only a few years after thinning, canopy cover characteristics of thinned plots were similar to those of control plots and differences were not significant. Growth and increments in thinned plots were practically the same as in control plots, a consequence of consistently higher performances of released trees in the thinned plots. The results concur to a positive evaluation of a cultivation system based on long rotation periods and heavy thinnings, not only for the obtainable revenue, but especially from a bio-ecological point of view and make it a valid alternative either to abandonment or traditional over-exploitation of chestnut coppice stands.

Demographic response of tree juveniles to reduced-impact logging in a Costa Rican montane forest

We assessed diameter and height growth, and mortality in seedlings (individuals ≥0.3, but <1.5 m tall) and saplings (individuals ≥1.5 m tall, but <10 cm DBH) of five common canopy tree species in an oak–bamboo forest in the Costa Rican highlands (2600–2800 m elevation) 5 years after a controlled logging operation under two harvesting intensities (20 and 30% basal area removal of stems ≥10 cm DBH, respectively). The species were Quercus costaricensis, Q. copeyensis, Drymis granadensis, Ocotea austinii, and Weinmania pinnata. For seedlings, the overall 5-year mortality rate (exponential model) was significantly higher under the lightest harvest intensity while for saplings, no significant differences in mortality were detected among harvesting intensities. Also for all species combined, annual 5-year diameter and height growth rates did not differ significantly among harvesting intensities for seedlings, although saplings grew significantly better under the higher harvest intensity. Our results suggest that, as a whole, saplings of the study species were more responsive to overstory removal than seedlings. At the species level, however, Quercus showed the largest significant differences in growth rates across harvest intensities and also with respect to the other studied species in both size classes. Based on our findings, and given the high abundance of advance regeneration at the study site (especially for Quercus), we propose that Costa Rican oak–bamboo forests show promising silvicultural potential for timber management under low-impact logging prescriptions.

Shelterwood harvesting in root-disease infected stands — post-harvest soil disturbance and compaction

Soil disturbance and compaction are described for an integrated project, testing the use of shelterwood harvesting and root removal treatments. Sites were winter harvested and assessed the following summer using criteria from the Forest Practices Code (FPC) of British Columbia. At two installations, pushover harvesting caused a significantly greater level of counted soil disturbance and forest floor displacement than hand felling combined with ground skidding. Disturbance levels increased with basal area removal on pushover harvested treatment units. The highest disturbance was on the clearcut–pushover treatment at the Golden site, where levels averaged 36% for both variables. Soil disturbance on the Nakusp site was lower for a number of reasons. Pushover harvesting at the Golden site also resulted in over 25% of the sample points becoming calcareous at the surface, due to exposure and deposit of calcareous subsoil; as opposed to less than 5% on the hand felled treatment units. Pushover harvesting at Golden, compared to the Nakusp site, also yielded a greater proportion of the treatment units occupied by stump holes, because of larger tree size and finer soil textures. Soil compaction significantly increased total bulk density at Golden and decreased total porosity and two measures of aeration porosity at both sites. Machine disturbance not meeting the disturbance survey criteria of the FPC occupied up to 16% of treatment units at the Golden site. This uncounted disturbance was not significantly different from countable compaction for five physical properties. Compaction impacts were usually significant, irrespective of the harvesting method or basal area retention on a treatment unit. Aeration porosities for some compacted samples were at or below ‘critical’ values of 15% on both sites. Tree growth at Golden is expected to be reduced because compaction has reduced aeration porosity and push felling exposed greater levels of free lime. Site sensitivity guidelines for pushover harvesting are exceeded for the soil conditions at Golden. More recent harvesting on other sites has resulted in less disturbance than reported here. It appears that countable soil disturbance can be limited to 15% for pushover harvesting under operational conditions.

Relative Abundance and Species Richness of Herpetofauna in Forest Stands in Pennsylvania

Abstract The relative abundance and species richness of herpetofauna was investigated to assess the impact of recent logging operations in 47 forest stands in northeastern Pennsylvania during 1996 and 1997. Stands including nonindustrial private forestlands and public lands that have received some type of harvesting within the last 8 yr ranged from near complete overstory tree cover to complete removal of overstory cover. Stands included the two dominant forest types in the region: northern hardwood (Betula, Fagus, Prunus, Acer, and Tsuga spp.) and oak-hickory/(Quercus and Carya spp.). A total of 8,181 individuals of 26 species (12 salamander, 7 snake, 6 frog, and 1 toad species) were observed in the study stands. The relative abundance and species richness of salamanders increased significantly with increasing retention of tree basal area. Forest stands containing &amp;gt; 15 m²/ha live tree basal area appeared to be a threshold level for high salamander abundance. Snake species abundance and richness increased significantly with increasing removal of tree basal area. The abundance of anuran species showed no significant relationship with amount of tree basal area removal, but the relative abundance and species richness of anurans depended on the presence of water within or bordering the stands. Forest type did not change the overall response of herpetofauna community composition to forest harvesting, although salamanders were more abundant in northern hardwood stands, and snakes were more abundant in oak-hickory stands. Patterns and threshold levels of abundance and species richness of herpetofauna determined in this study may be used to maintain the abundance and richness of selected species when harvesting forest stands. For. Sci. 46(1):139-146.

Biomass, litterfall and productivity in chestnut coppices of various age at Monte Amiata (Central Italy)

The effects of longer rotation periods and thinning practice on bio-ecological processes and indexes such as biomass, litterfall, leaf area index (LAI) and productivity have been analysed in thinned and unthinned permanent plots in a chestnut (Castanea sativa Mill.) coppices under traditional system (11 yrs.) and under long rotation (35 yrs.). Plots were established in a large chestnut vegetation area (Monte Amiata -Tuscany) in order to evaluate the sustainability of management options alternative to the traditional intensive exploitation. Both traditional and long rotation coppices showed high productivity (aboveground biomass 108.4 Mg ha'1 and 239.5 Mg ha'1 respectively), high LAI (6.5 nr m"2 and 5.1 m2 m'2) and annual litterfall values (6.28 Mg ha'1 and 5.60 Mg ha'1). The applied thinning (one third of basal area removal) affected stocking, stand growth and efficiency. Chestnut coppices, namely those under traditional rotation, showed however a good aptitude to re-build an homogeneous canopy cover a few years after thinning occurrence. Results concur to positively evaluate, not only from an economic point of view but also from a bio-ecological one, the adoption of management systems based upon long rotation period and on a less intensive exploitation of chestnut coppice.

Effect of partial cutting on predation risk to artificial bird nests

Based on relative abundance data, partial cutting has been suggested as a technique to maintain habitat for birds associated with late-seral forests, but there has been little study of partial cutting effects on nesting success. One of the primary limitations to nesting success is nest predation. We compared predation rates (proportion of nests disturbed in a 14-day period) in partially cut (30 or 60% basal area removal), clearcut, and uncut forests in northwestern British Columbia, in two experiments using ground-placed (1993) and shrub-placed (1998) artificial nests. In the ground-nest experiment there was a very low predation rate (0.06) and no detectable difference among treatments (p = 0.403). In the shrub-nest experiment, there was a 0.36 predation rate and little evidence of treatment differences (p = 0.295). Based on 90% confidence intervals for differences in observed predation rate, the 30% removal clearly did not increase predation risk relative to uncut forest. With the 60% removal, however, we cannot rule out a possible increase in predation risk compared with either uncut forest or clearcuts.

Simulation Study of a Single-grip Harvester in Thinning from Below and Thinning from Above

The time consumption and productivity of a single-grip harvester were studied, using a simulation model, when thinning from below and above in eight randomly selected stands. The model estimated the time required for each work element, given machine and tree positions, and tree size. A 2×5 factorial design was used with factors thinning type [from below (Tb) and above (Ta)] and tree size. Trees were subjectively selected for harvest according to thinning type. Total basal area removal was 30% plot−1. Approximately 50% more trees were harvested in Tb than in Ta Time consumption tree−1 was higher for Ta than Tb. Time consumption for machine and boom movements decreased with increasing number of harvested trees, and time for felling and processing of trees increased with harvested mean stem volume. Harvester productivity was 36% higher for Ta, since the increase in harvested mean stem volume was higher than the increase in time consumption tree−1.

Simulation Study of a Single-grip Harvester in Thinning from Below and Thinning from Above

Abstract The time consumption and productivity of a single-grip harvester were studied, using a simulation model, when thinning from below and above in eight randomly selected stands. The model estimated the time required for each work element, given machine and tree positions, and tree size. A 2×5 factorial design was used with factors thinning type [from below (Tb) and above (Ta)] and tree size. Trees were subjectively selected for harvest according to thinning type. Total basal area removal was 30% plot−1. Approximately 50% more trees were harvested in Tb than in Ta Time consumption tree−1 was higher for Ta than Tb. Time consumption for machine and boom movements decreased with increasing number of harvested trees, and time for felling and processing of trees increased with harvested mean stem volume. Harvester productivity was 36% higher for Ta, since the increase in harvested mean stem volume was higher than the increase in time consumption tree−1.

Adequacy of Natural Hardwood Regeneration on Forestlands in Northeastern Pennsylvania

Abstract The density of established and newly germinated commercial tree regeneration was assessed on 33 stands in northeastern Pennsylvania representing both northern hardwood and oak-hickory forest types. The purpose of the study was to determine the amount of regeneration on stands with differing amounts of residual basal area after harvest. Most stands were on nonindustrial private lands that had been harvested between 2-8 yr ago. The density of new germinants decreased while the density of seedling and sapling regeneration greater than 3 ft tall increased with increasing basal area removal. This result suggests that recruitment of taller seedlings and saplings improves with increasing intensity of harvests. Evidence of browsing by white-tailed deer (Odocoileus virginianus Zimmermann) was observed on nearly all species and was 50% or higher for seven species. High fern cover was most evident in heavily browsed areas. Neither slash cover nor height of slash was related to the density of any of the regeneration classes. This suggests that slash may not always afford adequate protection from deer. As in other parts of the state, a relative scarcity of sapling regeneration and high browsing incidence on many commercially valuable species indicates that problems with deer and competing species, like fern, need to be addressed in order to achieve sustainable forest management in northeastern Pennsylvania. North. J. Appl. For. 15(3):130-134.

Relations of Small Mammal Populations to Even-Aged Shelterwood Systems in Sub-Boreal Spruce Forest

Natural regeneration of cutover forest lands and integration of nontimber resources into forest management have generated investigation of alternative silvicultural systems to clearcutting. An overstory canopy, or shelterwood, may reduce the frequent frost problems observed in interior Douglas-fir (Pseudotsuga menziesii var. glauca) plantations and improve the success of natural regeneration, if seed predation by small mammals does not threaten the survival of the seed supply. We tested the hypothesis that a shelterwood silvicultural system would adversely affect dynamics of small mammal populations in 30% and 50% basal area (BA) removal stands, and we evaluated natural seed production, predation, and germination under a shelterwood canopy in the southcentral interior of British Columbia. Deer mice (Peromyscus maniculatus) and southern red-backed voles (Clethrionomys gapperi) were the most common small mammal species prior to harvest, and both species continued to be dominant in the first and second year postharvest. Abundance (P = 0.007) and recruitment (P = 0.015) of red-backed voles was 50% higher in shelterwood (treatment) than unharvested (control) stands. The shelterwood harvest did not affect abundance (P = 0.42) or recruitment (P = 0.47) of deer mice. There were no differences in average survival of deer mice and red-backed voles between control and treatment stands (P > 0.05). Mean body mass of adult male deer mice was similar in control and treatment stands (P = 0.27) but was lower for red-backed voles in the 50% BA removal than control stands (P = 0.05). Seedfall crops in the second year postharvest were 7.4-29.6 times larger than in the first year on treatment and control units, but there was no difference between units in either year (1992: P = 0.24; 1993: P = 0.93). Seed predation seemed to fluctuate with seasonal levels of small mammal populations (lower in spring and higher in fall) but not with the amount of seed crop available. Germination occurred in 62% of the seeds that survived overwinter on the seedbeds created during harvesting. Thus, regeneration success, as measured by seed survival and establishment, did not seem affected by the small mammal communities in 30% and 50% BA removal stands.

Wind and snow damage in a thinning and fertilization experiment in Picea abies in southern Sweden

Summary Changes in susceptibilit y to wind and snow damage due to thinning and fertilization were examined in even aged Norway spruce (Picea abies (L.) Karst.) stands in southern Sweden. The stands are part of a nationwide experiment to investigate growth and yield following different thinning and fertilization regimes established between 1966 and 1983. The material used in this study included 16 replications of seven treatments. The treatments were: three levels of thinning from below (20-70 per cent); 20 per cent thinning from above; thinning from below in combination with N and NP fertilization (thinning percentage 25—28 per cent); and unthinned control. The stands have been censused twice for damage during an average period of 12 years. The degree of wind and snow induced damage varied between 9 and 20 per cent of the basal area increment produced during the observation period. For treatments with high basal area removal, the highest relative number of trees damaged by wind occured during the first period after thinning. The densest stands (i.e. unthinned controls and stands thinned from above) showed a high proportion of snow damage throughout the observation period. The block effect was in general more significant than the effect of treatments on damage level. When analysing the influence of the block effect (i.e. of site and stand characteristics) on damage level, wind damage was best predicted by stand basal area left after thinning and stand age, while snow damage was best predicted by latitude, altitude, site index, and stand age. On average the tested site and stand characteristics explained 17 per cent of the variation in wind damage and 36 per cent in snow damage.

Interspecific variation in tree seedling establishment in canopy gaps in relation to tree density

Abstract. We tested whether interspecific variation in tree seedling establishment in canopy gaps was significantly related to interspecific variation in tree density, for seven deciduous forest tree species (Quercus alba, Hamamelis virginiana, Acer rubrum, Sassafras albidum, Quercus rubra, Prunus serotina, Ostrya virginiana). For each species, seedling establishment was calculated as the difference in seedling density before experimental gap creation versus three years after gap creation. In each of the six experimentally‐created gap types (33 % or 66 % removal of tree basal area from 0.01‐ha, 0.05‐ha or 0.20‐ha patches), differences in seedling establishment among species were significantly related to differences in their density in the tree canopy. A regression model with loge tree density as the independent variable accounted for between 93 % and 98 % of interspecific variation in seedling establishment.Our results provide empirical support for models of tree dynamics in gaps that assume seedling establishment depends on canopy tree density.

Interactive, multiobjective programming for forest resources management

Forest resources management is approached by a visual “free search” type of interactive procedure for multiple objective linear programming, which accounts for imprecision in the model by use of fuzziness. Specifically, a ponderosa pine forest resources management problem is examined. The problem is concerned with performing on given subwatersheds six different levels of vegetation treatment strategies ranging between 0 and 100% tree basal area cut in the forest. This problem is evaluated to “satisfice” six multiple and usually conflicting objective functions, namely, water yield, herbage production, sediment yield, recreational use, economicbenefit, and cost. The problem is subject to physical constraints, some of which, such as the total area that may be subjected to high percentage tree basal area removal, are not precisely defined and may be taken as fuzzy. Further, one objective, recreational use level, is defined as a fuzzy goal. The problem is formulated as a multiple objective linear programming model, in which fuzzy set membership value is also considered as an objective to be optimized. The effects of the fuzziness on the trade-offs between the conflicting objectives is examined using a visual interactive system called PARETO RACE. The system enables a decision-maker to search freely any part of the efficient frontier by controlling the speed and direction of motion. By using PARETO RACE, the decision-maker is also able to analyze relationships between the objective function values and visualize interactively how fuzziness in resources and objectives is reflected in objective functions. The model appears to lead to compromise policies acceptable to the decision-maker.

Barriers to Establishment of Invading, Non-forest Plants in Deciduous Forest Nature Reserves

A field experiment was conducted to define minimum values of irradiance (i.e. light reaching the forest floor) and exposed mineral soil required for non-forest species to become established in deciduous forest in Southern Canada. Three logging intensities (0%, 33%, and 66%, of tree basal-area removed) were combined with three plot sizes (0.01, 0.05, and 0.20 ha) to create a range of values of irradiance and exposed mineral soil. The total number of non-forest species that became established during the first three years after logging was recorded.Non-forest species invaded experimental plots only when irradiance was at least 8% of incident light. There was no single minimum area of exposed mineral soil required for invasion. A few non-forest species became established even in the absence of exposed mineral soil where penetrating irradiance was 8% or greater. More non-forest species became established as irradiance and the amount of exposed mineral soil increased.Logging increased both irradiance and the amount of exposed mineral soil. Only a small amount of logging (e.g. 33% removal of tree basal-area from a 0.01 ha plot) would be compatible with the conservation objective of preventing invasion by undesirable non-forest species.

Initial growth of Pinus sylvestris advance reproduction following varying degrees of release

Initial growth of released Scots pine (Pinus sylvestris L.) advance reproduction in nine stands dominated by Scots pine was studied in north Sweden. In each stand, one 40 × 40 m plot was established for each of four different intensities of overstorey removal: 0% (control), 60%, 85%, and 100%. Seedings were monitored on one 18 × 8 m sub‐plot at the centre of each plot for two growing seasons following overstorey treatment. Only undeformed seedlings, uninjured before treatment and during the study period, were considered. In the second growing season, needle lengths and number of laterals increased or tended to increase compared to the control for all treatments. Compared to the control, leading annual shoot lengths for all treatments initially tended to decrease (seedlings > 10.0 cm), but increased or tended to increase (all seedlings) during the second growing season. It is concluded that seedling performance generally improved with increasing basal area removal.

Extent and causes of mortality in Pinus sylvestris advance growth in northern Sweden following overstorey removal

Mortality of Scots pine (Pinus sylvestris L.) advance growth seedlings following overstorey removal was studied in nine stands in north Sweden. In each stand, one 40 × 40 m plot was established for each of four different intensities of overstorey removal: 0% (control), 60%, 85% and 100%. Seedlings were monitored on one 18 × 18 m sub‐plot at the centre of each plot for two or three growing seasons following overstorey removal. For seedlings taller than 100 mm, mortality and number of injured seedlings after two growing seasons increased significantly with increasing basal area removal. Seedlings ≤ 100 mm showed the same trend, though not statistically significant. For the height interval > 100 ≤ 500 mm, mortality was not significantly influenced by seedling height. Most of the mortality and the injuries to seedlings were caused by Hylobius abietis (L.) and Pissodes spp. It is concluded that insect damage to released Scots pine advance growth in northern Sweden is a common problem.