Slash Treatments Research Articles

Effects of site management treatments on growth of six-year-old, second-rotation Chinese fir (Cunninghamia lanceolata) plantations

The effects of five different site management treatments on the productivity of a six-year-old and secondrotation Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) plantations planted after harvesting a 29-year-old and first-rotation Chinese fir plantation in Xiayang State Forest Farm, Nanping, Fujian Province, were studied. Results showed that the Chinese fir grew best on plots treated with the double slash treatment (BL3), followed by the whole tree harvest (BL1) and the slash burning treatment (SB), and poorest on treatment BL2 (normal slash retention) and BL0 (removal of all organic matter aboveground). The site index of the second rotation Chinese fir plantations in BL3 and BL0 treatments increased by 0.56 and 0.27, respectively, compared with the first rotation, and decreased in the rest of the three treatments. Compared with the first rotation, the site index of the second rotation treated with BL1, SB and BL2 treatments decreased by 0.39, 0.45 and 0.63, respectively. Differences among the treatments were not statistically significant.

Effects of wildfire, salvage logging and slash treatments on soil degradation

AbstractThe effect of wildfire and the subsequent harvesting on soil degradation was evaluated in a burned Pinus pinaster stand in Galicia (NW Spain). During the first year following a fire of moderate intensity, burned trees were not harvested and soil erosion losses, measured by sediment collection at the bottom of bordered plots, were very low. An apparently limited impact of fire on soil and reduced rainfall erosivity for this period could be responsible for that result.Salvage logging took place 13 months after fire. Three post‐fire alternatives were compared: no harvesting (standing burned trees), harvesting + windrowed slash and harvesting + slash chopping. Soil losses were even lower during the 14 months after these treatments than for the previous pre‐harvesting period. Again, low mineral soil exposition and rainfall erosivity seemed to contribute to that result.Changes in soil bulk density and soil shear strength after clearcutting and slash manipulation were small and not enough to trigger sediment yield significantly.Harvesting and logging operations apparently increased soil inhomogeneities. This degree of variability was more adequately assessed by using micro‐plot fences instead of plot fences. The percentage of soil disturbed by machinery was the variable most related with the observed minor soil losses after harvesting, at micro‐plot level. This study indicated that the combined effect of wildfire and clearcutting caused only an acceleration of soil erosion when significant exposition of mineral soil occurred after these perturbations. However, these results must be taken with caution because rain erosivity during the study was low. To delay post‐fire clearcutting until several months after the fire could reduce the impact of this forestry operation on burned soils, taking advantage of the natural mulch created by scorched leaves fall, although other issues must be taken into account. Copyright © 2007 John Wiley & Sons, Ltd.

Commercial harvest of logging residue in clear-cuts affects the diversity and community composition of ground beetles (Coleoptera: Carabidae)

Structural complexity of the habitat is known to influence the diversity and abundance of arthropod populations. Earlier studies have shown that presence of logging residue (slash) on the ground contributes to microhabitat complexity and removal of slash for biofuel in clear-cuts can have short-term (∼1 year) effects on ground-active beetle populations. This study examines the consequences of slash removal on carabids (Coleoptera: Carabidae) 5–7 years after harvest. Sampling of beetles was done by pitfall trapping in three matched clear-cut pairs, in spruce forest in central Sweden. The number and diversity (Berger–Parker dominance index) of carabid species were significantly higher in clear-cuts with slash harvest than in sites where slash was left on the ground. No difference in the overall rank-abundance pattern was found between clear-cuts with different slash treatments, but for species with certain habitat preferences the community was significantly altered. In all clear-cuts, slash removal caused a shift in dominance with an increase in generalist species and a decline in forest species. The results show that removal of slash may have long-lasting effects on the carabid community composition and structure. Hence, in forest landscapes with large-scale biofuel harvest, generalist carabid species may increase their abundance. Following the precautionary principle, it is suggested that every fifth clear-cut should be free of slash harvest.

Effect of slash removal on Gremmeniella abietina incidence on Pinus sylvestris after clear-cutting in northern Sweden

The Gremmeniella abietina outbreak in Sweden in 2001-2003 forced forest owners to sanitary clear-cut large areas of middle-aged Pinus sylvestris stands. There is, however, little knowledge of effective reforestation of P. sylvestris on G. abietina-infected sites. Gremmeniella abietina disease incidence on P. sylvestris seedlings planted in 2003 was studied with and without (control) removal of infected P. sylvestris slash. Removed slash was piled in stacks around the regeneration plots. The seedlings were planted within 1 year after sanitation felling on three sites in northern Sweden. One year after planting, G. abietina pycnidia were found on 32% of the control seedlings and total infection, including stem cankers, reached 44%. Total and G. abietina-induced mortality was 15 and 10%, respectively. The method of removing and piling the infected slash reduced the number of infected seedlings by 50% and seedling mortality by 27% 1 year after planting, compared with control. Consequently, even if there is a clear sanitation effect of removing infected slash to the sides of the regeneration area, it does not eradicate the infection source from the stands. Postponed planting, slash burning or complete removal of the infected slash is needed to minimize the infection risk. The positive correlation found between slash coverage and infection rate indicates that clear-cuts with large amounts of infected slash should be given priority for slash treatment.

Species richness and biomass of understory vegetation in a Eucalyptus globulus Labill. coppice as affected by slash management

The aim of this study was to assess the effect of different slash management practices on understory biodiversity and biomass in Eucalyptus globulus coppices in Central Portugal. The experiment consisted of four treatments: (a) removal of slash (R), (b) broadcast over the soil (S), (c) as in S but concentrating woody residues between tree rows (W) and (d) incorporation of slash into soil by harrowing (I). Understory vegetation was surveyed during 1–6, 9, and 10 years, the proportion of soil cover by plant species estimated, and diversity and equitability indexes determined. Above ground understory biomass was sampled in years 2–6, 9, and 10. The highest number of species in most years occurred in plots where slash was removed. Differences between treatments in the proportion of plant soil cover were never significant, whereas differences in diversity index were only occasionally significant and apparently related to the number of species. Thus, differences in the equitability index were not significant. Understory biomass did not decrease during the rotation period, and was usually highest in R and I, and lowest in S, but not significantly different. At the end of the rotation period, understory biodiversity indices and biomass were apparently independent of slash treatment.

Soil Nutrient Dynamics after Harvesting and Slash Treatments in Boreal Aspen Stands

The effects of harvesting and slash treatments on soil nutrient dynamics were assessed in boreal aspen stands growing on mesic clayey sites. Stem‐only harvested stands were compared with unharvested controls according to a complete block design with three replications. Within harvested areas, four slash treatments (stem‐only harvesting [SOH], whole‐tree harvesting [WHT], wood chip application, and slash burns) were compared. Treatments created a gradient of slash that ranged from 52.3 Mg ha−1 in stem‐only to 13.8 Mg ha−1 in control stands. The amount of slash had no effect on wood decomposition rates but was strongly associated with higher forest floor organic C, Kjeldahl N and base cation concentrations (Cae and Mge), base saturation, pH, and effective cation exchange capacity (CEC) and lower microbial C/N when control stands were compared with stem‐only harvested stands. Slash burn severity was too low to significantly reduce slash loads and induce base cation release but severe enough to reduce forest floor microbial C and N concentrations (−48 and −55%, respectively) for at least one complete growing season. Slash burn also induced increases in forest floor available P (54%) concentration compared with other slash treatments. Chipping reduced forest floor microbial N concentration by 25% and increased microbial C/N by 28% but had no impact on nutrient availability. Differences between WTH and SOH were linked to the abundance of slash. Finally, the results illustrate that whatever the treatment, the amount of slash left on the ground is the main factor found to affect soil microbial community characteristics and soil nutrient availability.

The effects of slash and stump removal on productivity and quality of forest regeneration operations—preliminary results

Abstract The object of this study was to survey the effects of slash and stump removal on work productivity and work quality, as well as on the technology of forest regeneration operations. Site preparation and planting were studied in different conditions. Slash and stump treatments “removal” and “no removal” were established at each site. Time studies were made during site preparation and planting. The quality of mounding and planting was analysed by measurements of the seedlings. After slash removal, the increase of work productivity (E0) in mechanized planting was 18 per cent with a Bracke planting machine and 0 per cent with an Ecoplanter planting machine. The quality of mechanized planting was slightly improved by slash removal. After slash removal, the productivity (E0) of excavator-mounted mounders was 22 per cent higher with a mounding blade and 53 per cent higher with a ditching bucket. The quality of mounding was the same for both slash treatments. The productivity (E0) of three forwarder-mounted mounders was 5 per cent lower after slash removal, but at the same time the quality of the mounding was much better. In combined stump extraction and mounding, the time consumption of the mounding phase was about 40 per cent lower than for separate mounding after stump removal. The results show that slash and stump removal will improve work productivity and quality when using mechanized mounding and planting methods. In addition after slash and/or stump removal it may be possible and cost-effective to use new planting and site preparation methods based on forwarder-mounted mounders.

Slash Compression Treatment Reduced Tree Mortality from Prescribed Fire in Southwestern Ponderosa Pine

Abstract Intensive thinning prescriptions intended to restore historic forest structure have produced heavy broadcast slash fuel loads in northwestern Arizona, sometimes leading to high tree mortality following prescribed burning. Mechanical slash compression with a D-6 bulldozer to reduce the severity of fire effects on residual trees was evaluated. Ten of 42 measured trees (24%) died within 2 years after burning of broadcast slash, and crown scorch of trees without slash compression treatment averaged 26%. In contrast, no trees died after burning of compressed slash and crown scorch averaged <3%, even though the total fuel loading was indistinguishable from the broadcast slash treatment. The practice of raking fuels away from the boles of old-growth trees also contributed to reduced scorch as compared to younger, unraked trees. Slash compression is a viable method of reducing mortality, offering ecological and economical tradeoffs. Benefits include the ability to reduce large quantities of slash, safeguarding old-growth tree survival while rapidly achieving open forest structure. Costs include paying for equipment operation as well as the possibility of damage to soils or plants. West. J. Appl. For. 19(3):149–153.

Effects of Forest Postharvest Management Practices on Enzyme Activities in Decomposing Litter

Forest harvesting and site preparation alter many features of the soil environment affecting biological activity and litter decomposition. One aspect of biological activity, “lignocellulase” enzyme activity, has been found to be a good predictor of litter mass loss. We determined the effects of postharvest treatments (SLASH, BROADCAST BURN, and CHIP AND PILE treatments with the intact FOREST treatment as a control) on lignocellulose degrading and nutrient releasing enzyme activities (β-glucosidase, cellobiohydrolase, β-xylosidase, N-acetyl-glucosaminidase, phenol oxidase, and phosphatase) in decomposing pine litter in litterbags and in the forest floor and compared them with patterns of decomposition. In the forest floor, the SLASH treatment decreased phenol oxidase and phosphatase activities by half; the CHIP AND PILE treatment decreased β-glucosidase, cellobiohydrolase, phenol oxidase, and phosphatase activities by 50 to 75%; and the BROADCAST BURN treatment decreased N-acetyl-glucosaminidase, phenol oxidase, and phosphatase activities by 30 to 60%. In the litterbag litter, phenol oxidase activity, N-acetyl-glucosaminidase activity, and mass loss were lower in the BROADCAST BURN treatment than in the FOREST treatment. SLASH and CHIP AND PILE treatments did not affect enzyme activities or decomposition of the litterbag litter. The relationship between enzyme activities and incremental mass loss was significant in the FOREST and CHIP AND PILE treatments for β-glucosidase, cellobiohydrolase, and N-acetyl-glucosaminidase enzymes (r > 0.50, p < 0.05), but not significant in the BROADCAST BURN and SLASH treatments. Although reduced enzyme activities were accompanied by lower decomposition rates, enzyme activities were not always a dominant control of decomposition in certain highly disturbed treatments.

Rapidly eroding piñon-juniper woodlands in New Mexico: response to slash treatment.

The piñon (Pinus edulis Engelm.)-juniper [Juniperus monosperma (Engelm.) Sarg.] woodlands of Bandelier National Monument are experiencing accelerated erosion. Earlier studies suggest that causes of these rapidly eroding woodlands are related to an unprecedented rapid transition of ponderosa pine (Pinus ponderosa C. Lawson) savanna to piñon-juniper woodlands as a result of cumulative historical effects of overgrazing, fire suppression, and severe drought. To study the effectiveness of slash treatment in reducing accelerated erosion, we used sediment check dams to quantify sediment yield from twelve paired microwatersheds (300-1100 m2) within an existing paired water-shed study. Six of the twelve microwatersheds were located in a 41-ha (treatment) watershed with scattered slash treatment, whereas six microwatersheds were located in an adjacent 35-ha untreated (control) watershed. The primary purpose of our research was to quantify the rates of sediment yield between the treated and control microwatersheds. Sediment yield was measured from 15 individual storms during the months of June-September (2000 and 2001). In response to slash treatment, mean seasonal sediment yield for 2000 equaled 2.99 Mg/ha in the control vs. 0.03 Mg/ha in the treatment and 2.07 Mg/ha in the control vs. 0.07 Mg/ha in the treatment in 2001. The practice of slash treatment demonstrates efficacy in reducing erosion in degraded piñon-juniper woodlands by encouraging herbaceous recovery. Our data show that slash treatment increases total ground cover (slash and herbaceous growth) beyond a potential erosion threshold. Restored piñon-juniper woodlands, as the result of slash treatment, provide a forest structure similar to pre-grazing and pre-fire suppression conditions and decrease catastrophic fire hazard.

Understory plant species composition 30–50 years after clearcutting in southeastern Wyoming coniferous forests

To evaluate the long-term effects of clearcutting and slash treatment on understory plant species composition in Rocky Mountain coniferous forests, we collected comparable data from 30- to 50-year-old post-harvest stands and adjacent mature (>100-year-old) stands that originated after wildfire. In general, plant species richness was higher in the post-harvest stands than in adjacent mature stands, due in large part to the presence of species that benefit from disturbance. Species composition in post-harvest and mature stands was more similar in montane forests (2710–2805 m elevation) than in subalpine forests (2800–3164 m elevation), suggesting greater resilience of montane understories. Composition in post-harvest and mature stands was least similar when slash was piled and burned, and most similar when slash was lopped and scattered. Eighty-seven percent of the post-harvest stands had at least one exotic species, but total cover of exotic plant species in all post-harvest stands was ≤1%. Exotic species were largely absent from mature forests. Our results suggest that understory species of low-elevation montane forests recover more quickly from disturbance than do those of subalpine forests, with slash treatment and species life history traits strongly influencing this recovery.

Pine engraver (Ips pini) Colonization of Logging Residues Created Using Alternative Slash Management Systems in Western Montana

Abstract In this study, we observed effects of various slash treatments on pine engraver colonization. Five slash treatments (slash-free, chipped, small piles, large piles, scattered) were replicated five times at each of two sites, one consisting mainly of ponderosa pine and the other predominantly lodgepole pine. No pine engravers were found in slash-free or chipped slash treatments at either site. At the ponderosa pine site, significantly more pine engraver attacks and galleries were found in the scattered slash treatment than in small and large pile treatments. A significantly greater number of invertebrate natural enemies were also found in the scattered slash treatment, where they were approximately six to nine times as abundant as in the small pile and large pile treatments, respectively. No pine engravers were observed colonizing slash in the lodgepole pine treatments where slash was in an advanced stage of drying. At both sites, the use of a feller buncher–delimber during harvest increased the rate of drying of slash, reducing its suitability for pine engraver colonization. West. J. Appl. For. 17(2):96–100.

Restoring grassland savannas from degraded pinyon-juniper woodlands: effects of mechanical overstory reduction and slash treatment alternatives

Although the distribution and structure of pinyon-juniper woodlands in the southwestern United States are thought to be the result of historic fluctuations in regional climatic conditions, more recent increases in the areal extent, tree density, soil erosion rates and loss of understory plant diversity are attributed to heavy grazing by domestic livestock and interruption of the natural fire regime. Prior to 1850, many areas currently occupied by high-density pinyon-juniper woodlands, with their degraded soils and depauperate understories, were very likely savannas dominated by native grasses and forbs and containing sparse tree cover scattered across the landscape. The purpose of this study was to evaluate the effectiveness of mechanical overstory reduction and three slash treatment alternatives (removal, clustering and scattering) followed by prescribed fire as techniques for restoring grassland savannas from degraded woodlands. Plant cover, diversity, biomass and nutrient status, litter cover and soil chemistry and erosion rates were measured prior to and for two years following experimental treatment in a degraded pinyon-juniper woodland in central New Mexico. Treatment resulted in a significant increase in the cover of native grasses and, to a lesser degree, forbs and shrubs. Plant species richness and diversity increased most on sites where slash was either completely removed or scattered to serve as a mulch. Although no changes in soil chemistry or plant nutrient status were observed, understory biomass increased over 200% for all harvest treatments and was significantly greater than controls. While treatment increased litter cover and decreased soil exposure, this improvement did not significantly affect soil loss rates. Even though all slash treatment alternatives increased the cover and biomass of native grasses, scattering slash across the site to serve as a mulch appears most beneficial to improving plant species diversity and conserving site resources.

Temporal and spatial dynamics of coarse woody debris in harvested and unharvested lodgepole pine forests

Coarse woody debris (CWD) biomass was measured and mapped in burned, clearcut, and intact lodgepole pine forests in two areas of the Rocky Mountains of Wyoming: the Medicine Bow National Forest (MBNF) and Yellowstone National Park (YNP). In addition, the amount of CWD consumed or converted to charcoal by fire was estimated in a recently burned stand in YNP. A spatially explicit simulation model (DEADWOOD) was then created to simulate the effects of various clearcutting and fire regimes on CWD over a 1000-yr period. Approximately 8% of downed CWD were consumed during a single fire and an additional 8% was converted to charcoal. After 1000 yr of simulation, 100-yr fire-return intervals produced CWD that occupied more of the forest floor than did 200- or 300-yr intervals. The time required for 100% occupancy of the forest floor by CWD was 1125, 1350, and 1300 yr for 100-, 200-, and 300-yr fire-return intervals, respectively. Simulations suggest that current harvest and post-harvest slash treatment regimes will require at least four centuries longer for 100% of the forest floor to be occupied by CWD (1800–3600 yr) than under fire regimes. This may have important effects on soil characteristics. Only when post-harvest CWD slash was doubled over the current amounts did clearcutting leave sufficient CWD to maintain forest floor CWD within the historic range of variability for naturally developing post-fire stands.

Coarse Woody Debris following Fire and Logging in Wyoming Lodgepole Pine Forests

The accumulation and decomposition of coarse woody debris (CWD) are processes that affect habitat, soil structure and organic matter inputs, and energy and nutrient flows in forest ecosystems. Natural disturbances such as fires typically produce large quantities of CWD as trees fall and break, whereas human disturbances such as timber harvesting remove much of the CWD. Our objective was to compare the amount of CWD removed and left behind after clear-cutting to the amount consumed and left behind after natural fires in Rocky Mountain lodgepole pine. The masses of fallen logs, dead-standing trees, stumps, and root crowns more than 7.5 cm in diameter were estimated in clear-cut and intact lodgepole pine forests in Wyoming and compared to estimates made in burned and unburned stands in Yellowstone National Park (YNP), where no timber harvesting has occurred. Estimates of downed CWD consumed or converted to charcoal during an intense crown fire were also made in YNP. No significant differences in biomass of downed CWD more than 7.5 cm in diameter were detected between burned stands and those following a single clear-cut. However, the total mass of downed CWD plus the mass of snags that will become CWD was nearly twice as high in burned stands than in clear-cuts. In YNP, approximately 8% of the downed CWD was consumed by fire and an additional 8% was converted to charcoal, for an estimated loss of about 16%. In contrast, approximately four times more wood (70%) was removed by clear-cutting. Considering all CWD more than 7.5 cm in diameter that was either still present in the stand or removed by harvesting, slash treatment, or burning, clear-cut stands lost an average of 80 Mg ha−1 whereas stands that burned gained an average of 95 Mg ha−1. Some CWD remains as slash and stumps left behind after harvesting, but stands subjected to repeated harvesting will have forest floor and surface soil characteristics that are beyond the historic range of variability of naturally developing stands.

Timber harvesting residue treatment: Part 1. Responses of conifer seedlings, soils and microclimate

Timber harvesting residues have typically been burned within coniferous forest areas of the eastern Cascade Mountains of Washington State. Concerns about air pollution and quantities of coarse woody debris have generated interest in alternative residue treatments that will clear areas for planting and still reduce fire hazard. A total of six residue treatments were compared (three slash treatments where residues were burned (spring broadcast burning, fall broadcast burning, piling and burning) and three treatments where residues were not burned (clearing, chopping, pulling unmerchantable material)), along with no slash treatment to determine the effects of alternative approaches on soils and seedlings. Slash-treatment effects on soil bulk density and temperature, air temperature, and seedling growth and survival were examined at four different sites in the eastern Cascade Mountains. Results show that seedling performance was best with spring broadcast burning across all sites over five years of growth. Average height growth of Douglas-fir ( Pseudotsuga menziesii) and lodgepole pine ( Pinus contorta) over five years was 90 cm in the spring broadcast burn, with 75, 72, 71, 71, 66, and 61 cm for no slash treatment, piling and burning, pulling unmerchantable material, chopping, fall broadcast burn, and clearing, respectively. Seedling height growth may be related to soil temperatures that are closer to optimal for root and shoot growth when large quantities of slash were not insulating the soil. Soil bulk density did not appear to affect seedling growth (bulk density ranged from 0.7 to 1.15 g cm −3). None of the slash treatments that avoid burning increased growth relative to no slash treatment, and some may adversely affect survival. If slash burning can not be used to reduce quantities of timber harvesting residues, then leaving slash untreated appears to be the best alternative for seedling growth.

Timber harvesting residue treatment. Part II. Understory vegetation response

Foresters must have knowledge of understory vegetation responses to harvesting rehabilitation operations to manage competition effects on tree seedlings, protect species diversity, and reduce invasive weeds. Understory vegetation response to six post-harvest slash treatments, ranging from a high-intensity burn to mechanically chopped slash and untreated slash left in place, was documented for four eastern Washington mixed forest sites. We use species abundance graphs to show the relative effects of the six slash-treatment disturbances on vegetation dominance and diversity. Harvest substantially reduced understory cover, particularly among forbs. Shrub species persisted following harvest and in some treatments increased in cover. Slash treatments increased the abundance of weedy species that are not normally present in these forests. Treatments such as broadcast burning and pile/burn showed greater dominance by invader species. Overall, harvesting reduced species diversity but the response among slash treatments varied. After three growing seasons, species cover, richness, and diversity had no clear effect on seedling growth in slash-treatment plots.

Impact of Slash Burning on Nutrients in Industrial Plantations: A Conceptual Model for the Tsitsikamma, South Africa.

SYNOPSIS Slash treatment experiments were conducted after clearfelling of Pinus pinaster in the Tsitsikamma Forest Region, South Africa, to determine the effect of burning on pH, N and P budgets. pH(H2O) increased from an average of 4,49 to 4,78 and P-budgets in the topsoil increased by 60 % at the expense of a P-budget loss of 25 % in partly-consumed H (humus) layers, and a total loss of P in L and F-layers, which was completety consumed by the fire. N concentrations in the topsoil after burning ranged from 607 to 2 129 mg/kg. A volatilisation of 60 % of total N in forest floor layers, and 10 to 15 % of the total N-budget, is predicted. The increase in P and decrease in N budgets will act favourably to reduce high NP ratios, which will reduce the occurrence of Pinus radiata growth disorders experienced. The increase in P levels as a result of burning is inadequate for normal tree growth requirements, and fertiliser applications will still be needed to address the critical P shortages in the Tsitsikamma.

Experiments with upland rice in southern Belize: fertilizer application, weed control, plant spacing, sowing rate and variety

SUMMARYAgronomic research was carried out on upland rice in Toledo District, Belize, in 1979–86, with the objective of improving returns from the traditional system of shifting cultivation and of examining the potential for reducing the demand for new land by cropping for more than one season. The rice was grown in the wet season on land cleared from forest by slash and burn, using a traditional planting technique, placing seed in holes made with a pointed stick.In a series of fertilizer experiments, in which rice was grown for up to 7 consecutive years, urea and triple superphosphate both increased grain yield, whereas muriate of potash had no effect. Mean yield in the fifth year was 85 % of that in the first. Urea and triple superphosphate both increased the number of full grains/panicle.A slash and mulch weed control treatment before sowing resulted in low yields of grain in the third year; yield after the use of propanil and 2,4-D (after sowing) was, on average, 77% of the yield after hand weeding; omitting weed control after sowing led to very low yields, particularly in the second and third years.In the varieties Bluebonnet and C22, grain yield was increased by reducing the distance between stations, particularly where 6, rather than 15, seeds were sown per station. Reducing the distance between stations increased the leaf area index during crop development and the number of panicles/m2, which more than counterbalanced reductions in the number and area of leaf blades per plant, the number of panicles per plant and the number of full grains per panicle. However, the yield/kg of seed sown and per hour spent planting was greatest at the widest spacing. C22 produced more panicles per plant and a greater weight of grain per plant and per hectare than Bluebonnet.It was concluded that returns from the traditional system can be improved and the demand for new land reduced.

Acidity in four coniferous forest soils after different harvesting regimes of logging slash

The soil acidity of four coniferous sites, two in S Sweden and two in N Sweden, were studied 7–9 years after clear‐felling. Each site had three different slash treatments; (a) all slash harvested, (b) only needles remaining, and (c) all slash remaining. Our results verify that harvesting of slash after clear‐cutting means an acidification of the organic horizon in acid forest soils. On plots subjected to full slash harvest the pH‐value of the forest floor was 0.2–0.4 units lower than that of slash‐covered ones, and at three of the four study sites the exchangeable acidity was significantly higher on the slash‐cleared plots. Plots with only needles remaining were generally intermediate in acidity. The change in exchangeable acidity corresponded to approximately 10% of the theoretically estimated proton load caused by slash harvesting. The rate of proton flux associated with whole‐tree harvesting varied between 7–65 meq m‐3 yr‐1, which roughly corresponds to the amounts deposited in precipitation. Harvestin...