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1.
Recovery of longleaf pine (Pinus palustris P. Mill.) is necessary to arrest the decline of many associated plants and animals, and the establishment of longleaf pine on much of its original range requires artificial regeneration and diligence. In central Louisiana, USA, two fertilization levels (No [NF] or Yes [F-36 kg/ha N and 40 kg/ha P]) in combination with three vegetation treatments (check, two prescribed fires [PF], or multi-year vegetation control by herbicidal and mechanical means [IVM]) were applied to container-grown longleaf pine plantings in two studies. In Study 1 (grass dominated), 6-year-old longleaf pine survival was 52% on the F–checks, 78% on the F–PF plots, and averaged 93% on the other four treatment combinations. Longleaf pine trees on the IVM plots (3.4 m) were significantly taller than on the other two vegetation treatments, and trees on the PF plots (1.8 m) were taller than trees on the check plots (1.2 m). In Study 2 (brush dominated), survival averaged 65% across the six-treatment combinations after 6 years. The longleaf pine trees were 4.7 m tall on the IVM plots and averaged 3.9 m tall on the check and PF plots. Fertilization increased P concentrations in the soil and longleaf pine foliage, while fertilization did not significantly affect longleaf pine height growth. Native fertility was not apparently limiting longleaf pine development contrary to prior research recommendations for these soils. In both studies, the IVM treatment reduced early herbaceous competition and the number and height of arborescent plants. The PF treatment reduced arborescent plant height on the grassy site where fires were more intense than on the brushy site.  相似文献   

2.
To compare release treatments, a randomized complete block study was established in a 7-year-old hardwood-loblolly pine (Pinus taeda L.) stand in central Louisiana established using chopping and burning. There were 5 blocks of 3 treatments each: (1) check, (2) hexazinone applied once, and (3) prescribed backfiring applied twice. The first burn in December 1985 (7 years after site preparation) had a fire intensity of 90 kJ/s/m. The hexazinone herbicide was applied in April 1986 (the 8th year after site preparation) with a metered spotgun applicator at a rate of 3.0 kg active ingredient/ha. The second burn in March 1989 (the 11th year after site preparation) had a fire intensity of 106 kJ/s/m.The two prescribed burns increased the number of stems less than 1.5 m tall from 1,380 to 2,960/ha red maple (Acer rubrum L.), blackgum (Nyssa sylvatica var. bifora), and sweetgum (Liquidambar styraciflua L.). Burning reduced the number of loblolly pines less than 2.0 m tall, which resulted in a significant increase in average loblolly pine height and diameter. Loblolly pine comprised 62 and 59% of the basal area on the check and burn treatments, respectively, 11 years after site preparation. Hexazinone reduced the number of blackgum, sweetgum, and oak (Quercus spp.) from 6,100 to 4,560 stems/ha and resulted in significantly less hardwood tree basal area than found on the check or burn treatments. Therefore, the herbicide treatment resulted in principally a loblolly pine stand (over 80% of the total tree basal area was pine) four years after hexazinone application.  相似文献   

3.
Historical land use and management practices in the southeastern United States have resulted in the dominance of loblolly pine (Pinus taeda L.) on many upland sites that historically were occupied by longleaf pine (Pinus palustris Mill.). There is currently much interest in restoring high quality longleaf pine habitats to such areas, but managers may also desire the retention of some existing canopy trees to meet current conservation objectives. However, fast-growing natural loblolly pine regeneration may threaten the success of artificially regenerated longleaf pine seedlings. We evaluated the establishment and growth of natural loblolly pine regeneration following different levels of timber harvest using single-tree selection (Control (uncut, residual basal area ∼16 m2/ha), MedBA (residual basal area of ∼9 m2/ha), LowBA (residual basal area of ∼6 m2/ha), and Clearcut (complete canopy removal)) and to different positions within canopy gaps (approximately 2800 m2) created by patch cutting at two ecologically distinct sites within the longleaf pine range: Fort Benning, GA in the Middle Coastal Plain and Camp Lejeune, NC in the Lower Coastal Plain. The density of loblolly pine seedlings was much higher at Camp Lejeune than at Fort Benning at the end of the first growing season after harvesting. Following two growing seasons, there were no significant effects of canopy density or gap position on the density of loblolly pine seedlings at either site, but loblolly pine seedlings were taller on treatments with greater canopy removal. Prescribed fires applied following the second growing season killed 70.6% of loblolly pine seedlings at Fort Benning and 64.3% of seedlings at Camp Lejeune. Loblolly pine seedlings were generally less than 2 m tall, and completeness of the prescribed burns appeared more important for determining seedling survival than seedling size. Silvicultural treatments that include canopy removal, such as patch cutting or clearcuts, will increase loblolly pine seedling growth and shorten the window of opportunity for control with prescribed fire. Therefore, application of prescribed fire every 2-3 years will be critical for control of loblolly pine regeneration during restoration of longleaf pine in existing loblolly pine stands.  相似文献   

4.
Woody plant encroachment is a threat to savanna ecosystems worldwide. By exploiting differences in the physiology and seasonality of herbaceous species and encroaching hardwoods, herbicides can be used to control woody shrubs in savannas without causing lasting harm to desirable vegetation. We applied three herbicides and one tank mix to control shrubs following removal of the slash pine (Pinus elliottii Engelm.) canopy and replanting with container-grown longleaf pine (Pinus palustris Mill.) seedlings in a mesic-wet savanna in the southeastern USA. The herbicides tested were imazapyr, sulfometuron methyl, hexazinone, and a hexazinone + sulfometuron methyl tank mix. 4 years after application, no negative effects on understory species richness, diversity, evenness, or community composition were evident in any of the herbicide treatments. Oaks (Quercus spp.), one of the dominant shrub genera on the study site, were resistant to sulfometuron methyl, and this herbicide was therefore ineffective both as a pine release treatment and for enhancing herbaceous species cover. Imazapyr was the most effective treatment overall, leading to significant improvements in longleaf pine seedling growth and also enhancing herbaceous species cover. Both hexazinone and the hexazinone + sulfometuron methyl tank mix provided some seedling growth and understory enhancement as well. In particular, the tank mix significantly increased wiregrass cover relative to the control. Shrubs resprouted quickly following a dormant-season prescribed fire in the fifth year after treatment, indicating that herbicide-related increases in herbaceous cover may be lost if an aggressive prescribed fire program is not implemented.  相似文献   

5.
The effects of j-rooting on water stress and growth of loblolly (Pious taeda L.) and eastern white pine (Pious strobus L.) were examined over three growing seasons in the field. Seedlings were planted in an area with severe herbaceous competition with either their roots planted straight or bent into a j shape. All seedlings were planted with their root collars placed at the soil surface. During the first year j-rooted seedlings consistently had lower water potentials but never statistically significant. Since both treatments were planted with the root collar at the soil surface, this trend was likely due to an initial shallower root system in j-rooted seedlings. In year three no differences in water potential were significant and no trends were evident. Growth did not differ significantly by treatment at any time but, by year three, j-rooted plants were consistently larger for both species.  相似文献   

6.
Pine plantations in the southeastern United States are often created using site preparation treatments to alleviate site conditions that may limit survival or growth of planted seedlings. However, little is understood about how site preparations affect longleaf pine (Pinus palustris P. Miller) seedlings planted on wet sites. In a 2-year study (2004 and 2005) on poorly drained, sandy soils of Onslow County, North Carolina, we examined the effects of common site preparation treatments on microsite conditions and quantified relationships between microsite conditions and longleaf pine seedling survival and growth. Treatments used in the study included site preparations designed to control competing vegetation (chopping and herbicide) combined with those that alter soil conditions (mounding and bedding). During both years, mounding and bedding treatments reduced the amount of moisture within the top 6 cm of soil and increased soil temperatures when compared to flat planting (p < 0.001). Soil moisture was inversely related to seedling mortality in 2004 (r2 = 0.405) and inversely related to root collar diameter in 2005 (r2 = 0.334), while light was positively related to root collar diameter in 2005 (r2 = 0.262). Light availability at the seedling level was highest on treatments that effectively reduced surrounding vegetation. Herbicides were more effective than chopping at controlling vegetation in 2004 (p < 0.001) and 2005 (p = 0.036). Controlling competing vegetation, especially shrubs, was critical for increasing early longleaf pine seedling growth.  相似文献   

7.
To study how fire or herbicide use influences longleaf pine (Pinus palustris Mill.) overstory and understory vegetation, five treatments were initiated in a 5–6-year-old longleaf pine stand: check, biennial arborescent plant control by directed herbicide application, and biennial burning in March, May, or July. The herbicide or prescribed fire treatments were applied in 1999, 2001, 2003, and 2005. All prescribed fires were intense and averaged 700 kJ/s/m of fire front across all 12 burns. Using pretreatment variables as covariates, longleaf pine survival and volume per hectare were significantly less on the three prescribed fire treatments than on checks. Least-square means in 2006 for survival were 70, 65, 64, 58, and 56% and volume per hectare was 129, 125, 65, 84, and 80 m3/ha on the check, herbicide, March-, May-, and July-burn treatments, respectively. A wildfire in March 2007 disproportionately killed pine trees on the study plots. In October 2007, pine volume per hectare was 85, 111, 68, 98, and 93 m3/ha and survival was 32, 41, 53, 57, and 55% on the check, herbicide, March-, May-, and July-burn treatments, respectively, after dropping trees that died through January 2009 from the database. Understory plant cover was also affected by treatment and the ensuing wildfire. In September 2006, herbaceous plant cover averaged 4% on the two unburned treatments and 42% on the three prescribed fire treatments. Seven months after the wildfire, herbaceous plant cover averaged 42% on the two previously unburned treatments and 50% on the three prescribed fire treatments. Before the wildfire, understory tree cover was significantly greater on checks (15%) than on the other four treatments (1.3%), but understory tree cover was similar across all five treatments 7 months after the wildfire averaging 1.1%. The greater apparent intensity of the wildfire on the previously unburned treatments most likely resulted from a greater accumulation of fuels on the check and herbicide plots that also collectively had a higher caloric content than fuels on the biennially prescribed burned plots. These results showed the destructive force of wildfire to overstory trees in unburned longleaf pine stands while also demonstrating the rejuvenating effects of wildfire within herbaceous plant communities. They caution for careful reintroduction of prescribed fire even if fire was excluded for less than a decade.  相似文献   

8.
A shortleaf pine (Pinus echinata Mill.) ripping study was established by the Missouri Department of Conservation in March 1988 at the Logan Creek Conservation Area, USA. The objective of the study was to evaluate the effects of ripping on soil chemical and physical properties, on free-to-grow status, and on survival and growth of planted shortleaf pine seedlings. After 16 years, ripping increased exchangeable calcium; however, it had no long-term effects on soil particle size, organic carbon, pH, exchangeable potassium and exchangeable magnesium. Ripping increased the percentage of free-to-grow saplings by 3.8% after two growing seasons. Ripping improved survival by 4% during the 1st three growing seasons and by 7.1% at age 16. After two growing seasons, ripping improved crown spread by 13.6%, height by 14.2%, diameter by 14%, and volume by 41.2%. At age 16, ripping no longer had an effect on shortleaf pine height and had reduced diameter by 5.3% and volume by 11.0%. Our results suggest that ripping 1) had no effect on long-term physical properties or chemical properties of the soil, 2) had no effect on the number of free-to-grow seedlings, and 3) produced short-term benefits on survival and growth of planted shortleaf pine.  相似文献   

9.
Conventional planted okra in Booneville, Arkansas and Lorman, Mississippi were mulched with loblolly pine straw (Pinus taeda L.) and longleaf pine straw (P. palustris Mill.), respectively, at a rate of 11 t/ha or left bare. At Booneville, plant stand, season yields (18.6 t/ha), pod weight (16.3 g), plant dry weight (2.3 kg), or stem diameter (3.5 cm) were not affected by the loblolly pine mulch. However, mulch application increased pod number (1.22 vs. 1.06×106/ha) and plant height (1.5 vs. 1.6 m), while reducing weed competition (0.05 vs. 0.40 t/ha) and visible plant stress, during periods of soil moisture deficits. Soil temperatures at 5 and 15 cm depth were reduced by mulch until mid-August when plant canopies covered the rows. Seasonal moisture at 30 and 45 cm depths was similar between mulched and bare soils, based upon unreplicated neutron probe measurements. At Lorman, season okra yield (29.8 vs. 24.6 t/ha), number of pods per ha (1.24 vs. 1.07×106) and weed competition were reduced and soil pH lowered 0.56 units by longleaf pine straw mulch. Mulch reduced early season yield at both locations.  相似文献   

10.
When combining pines and cattle on tame pasture, grazing is often delayed for several years until trees are large enough to resist injury. As an alternative approach to delayed or deferred grazing during the early years, this study in central Louisiana, USA, examined the effects of cattle grazing in subterranean clover (Trifolium subterraneum L.) pastures on slash (Pinus elliottii Engelm.) and loblolly pine (P. taeda L.) seeding survival and growth during the first 3 years of tree establishment. Pines were planted at about 1200 trees/ha in 3 rows on 0.4-ha subclover units with 1.3 m spacing within rows. Three grazing treatments included: (1) ungrazed pines, (2) limited grazing with a single-wire electric fence above the planted pines, and (3) grazed pines. Thirty Brahman crossbred cows with calves and a bull grazed the tame pasture on a controlled grazing, rotational basis from December through May each year, during the subterranean clover growing season. Pine trampling injury during the year was 8% on the grazed seedlings while essentially none occured under limited grazing. During the first 2 growing seasons, survival and height of the pines were significantly less on the grazed seedlings than on either the limited grazing or ungrazed seedlings. Pine heights from the limited grazing and ungrazed treatments were not different during the 3-year study; loblolly pine heights from the limited grazing treatment continued to be taller than the grazed treatment through the third year while the slash pine heights were similar for all treatments by the third year. Seedling mortality became more acute as severity of grazing injury increased; the greatest mortality occured when the terminal bud and needles were both browsed off.  相似文献   

11.
Abstract

The effect of different cleaning treatments on moose (Alces alces L.) damage to Scots pines (Pinus sylvestris L.) was examined using a generalized linear mixed model (GLMM) with a binomial response (logit-link function). The treatments were the following: no cleaning, point-cleaning of broadleaves (mainly birch, Betula pendula Roth and B. pubescens Ehrh.) within a radius of 1 m from the pine, point-cleaning delayed 2 years, topping of competing broadleaves (main stem cut at a height of 1.3 m) and total cleaning of broadleaves. A randomized complete block design with three replicates was established in three planted pine stands (mean height of pines 1.5 m). Measurements taken four growing seasons later (mean height of pines 3.5 m) showed that all cleaning treatments reduced moose damage, although the difference was not significant (p=0.078) in the case of topping. The proportion of damaged pines was predicted as a function of the characteristics of pines and broadleaves in two untreated, planted pine stands with a height of 3 m. Within these untreated stands the number of damaged pines increased in plots with a higher number of broadleaves and taller broadleaves. In conclusion, the results show that on relatively fertile growing sites of pine cleaning treatments reduced moose damage on pine. It is recommended that cleaning is performed before broadleaved trees occur as overgrowth above pines.  相似文献   

12.
Mature shrubs can provide microhabitats that are beneficial to tree seedling growth and development. Sugar pine trees (Pinus lambertiana) grow in a narrow zone on the eastern slope of the Carson Range in extreme western Nevada, whereas Jeffrey pine (Pinus jeffreyi) is the dominant tree species in the region, an area extensively disturbed by wild fire. This study compares seedling establishment of sugar pine and Jeffrey pine relative to mature shrubs. In the fall of 2002 (cohort 1) and 2003 (cohort 2), 13,600 seeds of both species were planted in wire mesh enclosures, at three sites, under a variety of microhabitat treatments: under shade and in the open, under two species of shrub cover, and with and without plant litter. Seedlings were monitored for survival through two growing seasons. Even though more sugar pine seedlings emerged, more Jeffrey pine seedlings survived, and Jeffrey pine was the more drought tolerant species, better suited for the xeric climate found in the Carson Range. Litter slightly hindered seedling emergence but had no effect on survival and there was no significant species × litter interaction. Supplemental water facilitated survival in all treatments with highest survival in shade treatments. Sugar pine seedlings showed a significant increase in survival over Jeffrey pine seedlings with the addition of water, particularly in open treatments and more of both species survived under manzanita shrubs with water. The highest seedling mortality occurred when shrub canopy was removed, and seedlings experienced the effect of full sun and competition for soil water. For either species, microhabitat is a significant factor in determining success or failure in rehabilitation efforts after disturbance.  相似文献   

13.
The effects of competing grasses on resource availability, growth and ecophysiological characteristics of 3-0 red pine (Pinus resinosa Ait.) seedlings were examined the first two years following outplanting in Anoka County, Minnesota, USA. Equal numbers of seedlings were planted into suppressed and undisturbed grass communities in a sandy soil. Grass suppression was maintained throughout the first growing season, but partially discontinued thereafter on the site. During the first field season interference from grass reduced pine seedling root collar diameter, needle length, number of new root tips, and lateral root length by over 40%. Mean pre-dawn needle water potential was 0.55 MPa lower in undisturbed grass plots during a brief drought in year one, but otherwise water stress was not significantly (p=0.05) influenced by grass interference. The presence of grass also reduced, up to 50%, the photosynthetically active radiation reaching the seedling canopy. At the end of year one, total biomass N, P, K, and Ca content were significantly (p=0.05) less in seedlings growing in the undisturbed grass community. Nitrogen was deficient in seedlings growing in grass. After two growing seasons, seedling shoot length (p=0.03), root collar diameter (p=0.001), and needle length (p=0.001) were significantly less (40, 54 and 20%, respectively) for seedlings growing in undisturbed grass. Seedling growth reductions induced by grass competition were associated with multiple environmental stressors in the field and not restricted to water stress as was observed in earlier studies with pine species at low and mid-latitude sites.  相似文献   

14.
After five years of growth at high-elevations (∼3000 m) in Utah, container lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) seedlings survived well (80–95%) and grew to similar heights regardless of nursery storage method and site preparation technique. Seedlings received one of three storage treatments: (1) spring-sown in the nursery, overwintered in cooler storage and outplanted in July; (2) spring-sown, overwintered in freezer storage, and outplanted in July; or (3) winter-sown, no storage, and hot-planted in late August. We outplanted seedlings at two locations that were clearcut and had received two treatments of surface organic matter (coarse wood, logging slash, and forest floor) removal: surface organic matter (OM) piled with a bulldozer and burned or surface OM remaining in situ. Compared to adjacent uncut stands, both site preparation treatments increased total soil bulk density, but retaining surface OM in situ maintained soil OM, carbon, and nitrogen levels. After one growing season, seedlings planted where surface OM had been bulldozed were taller and had more biomass, although survival was similar (≥96%) across site preparation treatments. The height growth advantage disappeared after five growing seasons and although overall survival was good, survival was highest where site preparation involved removal of surface OM and freezer-stored seedlings were planted. Total non-structural carbohydrates tended to be higher in roots than in shoots and were also higher in hot-planted seedlings than in stored seedlings. Our results indicate that nursery and forest managers have several options for successful nursery production and outplanting of container lodgepole pine seedlings in the central Rocky Mountains. Using hot-planted seedlings allows for a faster turnaround time (from seed to plantable seedling) and maintaining surface OM may be a cost-effective alternative to dozer piling and burning.  相似文献   

15.
A 17 acre (6.9?ha) agroforestry research and extension alley cropping trial was established at the Center for Environmental Farming Systems in Goldsboro, North Carolina in January 2007, with a randomized block design with five replications. Loblolly pine (Pinus taeda), longleaf pine (Pinus palustris) and cherrybark oak (Quercus pagoda) were planted in staggered rows, with each species planted for 140?ft (43?m) per replication. Crop land alleys of 40?ft or 80?ft (12.2–24.4?m) wide were left between the tree rows. Crops of soybeans (Glycine max) and corn (Zea mays) were planted in alternating years since establishment. As of 2011, survival rates were 93% for cherrybark oak, 88% for longleaf pine and 97% for loblolly pine. Average tree diameter at ground level was 1.0?in (2.5?cm) for cherrybark oak, 2.1?in (5.3?cm) for longleaf and 3.2?in (8.1?cm) for loblolly. Heights averaged 4.6?ft (1.4?m) for cherrybark oak, 5.2?ft (1.6?m) for longleaf pine and 10.4?ft (3.2?m) for loblolly pine. Growth, yield and economic projections for traditional timber production indicated that species volumes and values tracked the height and diameter relationships measured on the site. Loblolly pine had the largest projected internal rate of return, at 7.2%, followed by longleaf pine with pine straw harvests at 5.5%, longleaf without pine straw at 3.5% and cherrybark oak at 1.9%. There might be more loss in crop and silvopasture production with loblolly, however, and production of pine straw for longleaf or game mast for cherrybark oak may offer other benefits. Crop yields on the sandy soils on the site were very poor during the 4?years observed, which had a series of droughts and floods. These led to net financial losses in those years for the demonstration site, but state-wide average farm budget returns did show moderate profits. The results support the merits of agroforestry systems in the upper South to diversify income and reduce financial risks.  相似文献   

16.
Red pine and jack pine seedlings growing in styroblocks were inoculated 8 wk after sowing with mycelium/agar slurries of 3 mycorrhizal fungi (Laccaria bicolor, Scleroderma citrinum, and an unidentified basidiomycete), and one suspected mycorrhizal fungus (Cantharellula umbonata). Seedlings inoculated with L. bicolor developed mycorrhizae earlier and in greater numbers than the other inoculation treatments, with red pine out-performing jack pine in both respects. At 34 wk following sowing, seedlings were outplanted on a cleared xeric site in Baraga Co., in Michigan's Upper Peninsula. Seedlings inoculated with C. umbonata failed to form mycorrhizae and were not outplanted. Inoculation treatments did not affect shoot or root weight at outplanting. Red pine inoculated with L. bicolor averaged 21% and 19% greater survival compared with control seedlings after one and two years in the field, respectively. Other inoculation treatments failed to increase seedling survival for either tree species. Jack pine demonstrated higher overall survival than did red pine for both years in all corresponding inoculation treatments.  相似文献   

17.
On two silt loam flatwoods in Louisiana, use of mounds as planting sites for slash pine (Pinus elliottii Engelm. var. elliottii) was shown to be more effective than planting without mounds (untreated control) after six growing seasons in the field. Mounds formed were of two sizes: low mounds made of 550 dm3 of soil and high mounds made of 1,000 dm3 of soil. One site was in central Louisiana and had two drainage classes: a somewhat poorly drained Caddo-Messer complex and a poorly drained Caddo soil. On both drainage classes, pine survival was not affected by treatment, but the incidence of fusiform rust galls on the main stem (caused by Cronartium quercuum (Berk.) Miyabe ex Shirai f. sp. fusiforme Burdsall and Snow) was greater on trees planted on mounds. The second site was a poorly drained Caddo soil in southwestern Louisiana. At this site, there were fewer surviving pines on controls than on mounds, but the incidence of rust galls was not affected by treatment. At both sites, pines were taller and had a greater mean diameter at breast height on mounds than on controls. Mound size did not influence tree size at either site.  相似文献   

18.
We investigated the effects of herbaceous and woody vegetation control on the survival and growth of planted eastern white pine (Pinus strobus L.) seedlings through six growing seasons. Herbaceous vegetation control involved the suppression of grasses, forbs, ferns, and low-shrubs, and was maintained for 0, 2, or 4 years after white pine seedlings were planted. Woody control involved the removal of all tall-shrub and deciduous trees, and was conducted at the time of planting, at the end of the second or fifth growing seasons, or not at all. Seedling height and basal diameter responded positively and proportionally to duration of herbaceous vegetation control. Gains associated with woody control were generally not significant unless some degree of herbaceous vegetation control was also conducted. Only herbaceous control increased pine crown closure and rate of crown closure. Herbaceous control and the presence of 5000–15,000 stems per ha of young overtopping aspen were associated with reduced weevil (Pissodes strobi Peck.) injury and increased pine height growth. The study suggests that white pine restoration strategies on clearcut sites should focus on the proactive, early management of understory vegetation and the gradual reduction of overtopping cover from woody vegetation to create a seedling light environment that supports acceptable growth with minimal weevil damage.  相似文献   

19.
Abstract

The effects of soil scarification on reindeer lichen cover and re-establishment, reindeer foraging and damage possibly caused by reindeer to planted Scots pine seedlings were studied during six growing periods in a field experiment established in a reindeer lichen site that was grazed by a herd of 500–600 reindeer each winter. Seedlings (at a density equivalent to 2000 ha?1) were planted in mounds with mineral soil on top, in tracks with exposed mineral soil, in tracks with mixed organic material and mineral soil and in intact lichen mat (control) with no soil disturbance. The disturbed area varied from 0 to 28%. After six growing periods, the reindeer lichen cover and volume were 10–20% lower in the scarified plots than in the control plots. There was no clear evidence that the reindeer avoided foraging even in plots with the highest levels of soil disturbance. However, the behaviour of the reindeer during winter grazing seemed to be affected by both coverage of reindeer lichen (positively) and the proportion of exposed mineral soil (negatively). Damage possibly caused by reindeer trampling affected 8.2% of the living seedlings each year and approximately 50% of these seedlings were subsequently infected by fungal diseases (compared with 20% of viable undamaged seedlings). Scarification treatments that exposed mineral soil mildly resulted in higher survival and growth rates than the other treatments, especially the control.  相似文献   

20.
Effects of site preparation, shelterwood density and planting depth on the survival and growth of planted beech and oak seedlings were studied. Experiments were performed in one oak and one beech stand in southern Sweden. Two areas with different densities of shelterwood and one clearcut were established in each stand. Growth, damage and survival of the planted seedlings were observed for three years. Soil water potential was recorded weekly and radiation and soil temperatures were recorded continuously during the growing seasons.Neither site preparation methods nor planting depth affected oak seedling growth, when planting was carried out on fresh clearcuts or in shelterwoods, while growth of beech seedlings was positively affected by mounding. Growth of oak seedlings was inhibited by the shelterwood treatments. In beech seedlings, growth was lowest in dense shelterwood, while there was no difference in growth between seedlings on the clearcut area and in the shelterwood of low density. Differences in growth may be explained by differences in radiation and soil water potential.When planting was carried out on a one-year-old clearcut, site preparation improved the subsequent growth of oak and beech seedlings.  相似文献   

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