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1.
When combining pine and cattle production on improved pastures, grazing may have to be delayed for several years until trees
are large enough to resist injury. During this period forage would be lost unless harvested for hay. This study in south Georgia,
USA, examined hay production during the first 3 years, cattle production during the next 3 years, and effects of this management
system on survival and growth of slash pine(Pinus elliottii) planted in widely-spaced rows within the pastures.
Pines were planted at 225 trees/ha in configurations of 3.0 x 14.6 or 4.9 x 9.1 m in pastures recently sprigged or seeded
with Coastal bermudagrass (Cynodon dactylon) or Pensacola bahiagrass(Paspalum notatum). Pastures were fertilized annually and cut for hay four or five times each year.
Wide-row spacings permitted haying operations, but tree rows and turning areas removed 5 to 8 percent of the area from production.
However, hay yields and liveweight gains by yearling cattle were near normal for this locale.
Slash pine planted in these fertilized pastures survived well, grew rapidly, and only a few trees were killed during haying
operations. After 6 years, 83 percent of the trees survived and averaged 6.5 m in height and 13.2 cm in diameter. Cattle killed
a few trees by rubbing during the 4th year.
Wide-row spacing of pines permits harvesting forage for hay while waiting for the trees to become large enough to permit grazing.
This approach to agroforestry produces annual returns to the landowner while awaiting maturity of the pines. 相似文献
2.
H. R. Powers 《Forest Pathology》1984,14(7):426-431
Control of fusiform rust in southern pines has improved significantly over the last 10 years. The new systemic fungicide Bayleton provides excellent control in forest tree nurseries with 3 to 5 sprays per season. The topical fungicides previously used had to be applied 35 or more times per season to obtain equivalent control. Disease resistant seedlings have also become available to forest land managers for use in the reforestation programs. The first such seedlings, loblolly pines from specific geographic areas, have reduced the incidence of fusiform rust in young plantations by one-half. Both loblolly and slash pine seedlings from rust-resistant seed orchards are also now becoming available, and they should reduce disease levels significantly. New approaches, such as the development of seedling seed orchards from survivors of artificial inoculation tests should further improve the levels of rust resistance. Current research on the reduction of inoculum on both die pine and oak hosts may provide new management techniques for disease control. 相似文献
3.
Pastures store over 90% of their carbon and nitrogen below-ground as soil organic matter. In contrast, temperate conifer forests
often store large amounts of organic matter above-ground in woody plant tissue and fibrous litter. Silvopastures, which combine
managed pastures with forest trees, should accrete more carbon and nitrogen than pastures or timber plantations because they
may produce more total annual biomass and have both forest and grassland nutrient cycling patterns active. This hypothesis
was investigated by conducting carbon and nitrogen inventories on three replications of 11 year-old Douglas-fir (Pseudotsuga menziesii)/perennial ryegrass (Lolium perenne)/subclover (Trifolium subterraneum) agroforests, ryegrasss/subclover pastures, and Douglas-fir timber plantations near Corvallis, Oregon in August 2000. Over
the 11 years since planting, agroforests accumulated approximately 740 kg ha–1 year –1 more C than forests and 520 kg ha–1 year–1 more C than pastures. Agroforests stored approximately 12% of C and 2% of N aboveground compared to 9% of C and 1% of N above
ground in plantations and less than 1% of N and C aboveground in pastures. Total N content of agroforests and pastures, both
of which included a nitrogen-fixing legume, were approximately 530 and 1200 kg ha–1 greater than plantations, respectively. These results support the proposition that agroforests, such as silvopastures, may
be more efficient at accreting C than plantations or pasture monocultures. However, pastures may accrete more N than agroforests
or plantations. This apparent separation of response in obviously interrelated agroecosystem processes, points out the difficulty
in using forest plantation or pasture research results to predict outcomes for mixed systems such as agroforests.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
4.
On highly-weathered Ultisols of the Georgia (USA) Piedmont, a combination of no-till agriculture and alley cropping presents
an option for rapidly increasing soil nitrogen availability while restoring long-term soil fertility. Three years after the
establishment of Albizia julibrissin hedgerows and no-till agriculture trials, we measured inorganic soil nitrogen (NO3
-–N and NH4
-–N) and net nitrogen mineralization during a 4-month field study and a 14-day laboratory study . We also measured the influence
of tree leaf amendments on grain sorghum production and N uptake. Soil nitrate increased four-fold within two weeks of adding
Albizia leaf mulch. Soil ammonium did not increase as rapidly nor to the same extent after tree mulch addition. Averaged over
the 4-month study, soil nitrate and ammonium were 2.8 and 1.4 times higher in the alley-cropped than in the treeless no-till
plots. Net nitrification and mineralization were no higher in the alley cropping plots, during either field or laboratory
incubations. Tree mulch additions enhanced crop biomass production and N uptake 2 to 3.5 times under both high and low soil
moisture conditions. Our study demonstrates the dramatic short-term impacts of Albizia mulch addition on plant available nitrogen.
Combined with no-till practices, alley cropping with Albizia hedges offers Piedmont farmers an option for reducing reliance
upon chemical N fertilizer while improving soil organic matter levels.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
5.
For 3 years following a severe, November 1992 tornado, abundance and growth of tree regeneration in intact forest-floor and windthrow-pit microsites were studied in three mixed pine and hardwood stands in the Georgia Piedmont, USA. The research had two objectives: (1) determine if performance of tree regeneration differed between microsite types and between pre- and post-tornado cohorts on intact forest-floor microsites, and (2) determine if variation in light and soil water availability from the disturbance affected performance of eight species artificially seeded into intact forest-floor microsites. Near each of the 42 sample points (12–20 per site) spaced on 15 m grids, species and height of tree seedlings were recorded within a 1 m radius plot of intact forest floor and the nearest windthrow pit. Intact forest-floor microsites were dominated by two late-successional species, Acer rubrum (3.5 pre-tornado stems per m2 and 1.8 post-tornado stems per m2) and Ostrya virginiana (2.6 post-tornado stems per m2), while windthrow pits were dominated by an early successional species, Liriodendron tulipifera (1.7 stems per m2). Although seedling survival did not vary significantly among species or microsite types, first-year height of seedlings in intact forest-floor microsites (24 cm) was significantly greater than those in windthrow-pit microsites (19 cm). Second-year height growth of new seedlings of Cornus florida in intact forest-floor microsites (52 cm) significantly exceeded that of many other combinations of species and microsite type. Species artificially-seeded into intact forest-floor microsites in 1994 and 1995 varied considerably in emergence (<1–24%), survival (<1–16%), and height (5–15 cm), and those with the heaviest seed survived best. From 1994 to 1995, average gap fraction, an index of light availability, decreased 17% from 0.23 to 0.19. Soil water content in 1995 under gap fractions of greater than 0.3 (21%) averaged significantly less than under gap fractions of either 0.1–0.3 (24%) or less than 0.1 (26%). Significant positive correlations were detected for relationships of emergence and survival of several species to soil water content. Overall rankings of seedling performance between microsites (intact forest floor>windthrow pits), between cohorts (pre-tornado>post-tornado origin), and among species (mid- to late->early-successional species) indicate that advanced regeneration and new seedlings of A. rubrum, O. virginiana, and C. florida will be long-term dominants of the understory because of their high abundance, initial growth responses, and shade tolerance. 相似文献
6.
William L. Gaines Richy J. Harrod James Dickinson Andrea L. Lyons Karl Halupka 《Forest Ecology and Management》2010
The restoration of natural fire regimes has emerged as a primary management objective within fire-prone forests in the interior western US. However, this objective becomes contentious when perceived to be in conflict with the conservation of rare wildlife species. For example, the integration of fire ecology in disturbance-prone forests of eastern Washington with the recovery of the Northern spotted owl has been described as a management dilemma. We intersected modeled spotted owl habitat with mapped priority fuels treatment areas in order to determine the magnitude of the potential conflict between fuels management and owl conservation. Our results show that there is considerable overlap within dry forests between high suitability spotted owl habitat and moderate-high priority fuels treatment areas (34% overlap). However, there is also considerable overlap of lower suitability spotted owl habitat with moderate-high priority fuels treatment areas (35% overlap) providing opportunities to accomplish multiple management objectives if one considers a landscape perspective. We propose that a conservation strategy for the Northern spotted owl in the eastern Cascades consider the following: emphasize landscape restoration of dry forests within which spotted owl habitat is embedded; landscapes considered for restoration need to be large enough to accomodate the effects of fire disturbances and still retain sufficient habitat to support spotted owl populations; and include adaptive management allowing for adequate monitoring and feedback for managers to make needed adjustments. 相似文献
7.
8.
Maintenance of biodiversity is becoming a goal of forest management. This study determined effects of broadcast pine release herbicide treatments on plant species richness, diversity, and structural proportions seven years after treatment. Three study blocks were established in central Georgia. Plots 0.6–0.8 ha in size were planted to loblolly pine (Pinus taeda L.) in the Winter of 1982–83 and then treated with imazapyr (Arsenal), glyphosate (Roundup), and hexazinone (Velpar L. and Pronone 10G) in 1985. In 1992, overstory and understory (<1.5 m height) layers were examined utilizing stem and rootstock counts and basal area of overstory species and cover of understory species. ANOVA's were used to test for significance using a randomized complete block model. We found no effect of treatments on species richness. Diversity, measured separately for overstory and understory layers by Shannon-Wiener and Simpson indices, also was not influenced significantly by treatments. Arsenal significantly decreased Diospyros virginiana L. and increased Rubus argutus Link and legumes. Hexazinone treatments generally decreased Quercus nigra L., and Roundup significantly reduced Vaccinium spp. compared to the Check. We concluded that herbicide release treatments did not decrease overstory or understory plant species richness and diversity seven years post-treatment. 相似文献
9.
Panos V. Petrakis Vassilios Roussis Constantinos Vagias Maria Tsoukatou 《European Journal of Forest Research》2010,129(6):1047-1056
The pine scale (Marchalina hellenica) has been introduced to Attica and reached unprecedented population densities. Using a randomised transect-based sampling
design in eight sites, we sampled the insect in random 10 cm squares on the trunk and main branches of pine trees. The insect
did not show any clumping other than a micro-site preference for fissures and cracks. Canonical discriminant analysis and
generalised multinomial logit regression modelling were used to determine the most important ecological variables which were
the following: the population density of the insects; crown transparency; mean distance between trees; and the quality of
the habitat. The site and the distance from the line transect were insignificant. The interaction of crown transparency with
the abundance of the insect, the mean distance between trees and the quality of each site were important in configuring the
level of damage sustained by the pine tree. 相似文献
10.
Min B. Rayamajhi Paul D. Pratt Ted D. Center Thai K. Van 《European Journal of Forest Research》2010,129(6):1155-1168
The exotic tree Melaleuca quinquenervia (melaleuca) forms dense forests usually characterized by low plant diversities and dense litter biomass accumulations on
forest floors of ecologically sensitive ecosystems, including portions of the Florida Everglades. We quantified litter accumulation
in mature melaleuca stands and compared decomposition rates of melaleuca leaves with a sympatric native plant, either Cladium jamaicense (sawgrass) in sawgrass marshes or Pinus
elliottii (slash pine) in pine flatwoods habitats that varied in soil types. Total litter accumulation in mature melaleuca forests
prior to June 1997 ranged from 12.27 to 25.63 Mg ha−1. Overall, melaleuca leaves decomposed faster in organically rich versus arenaceous soils. Decomposition rates were lower
for melaleuca leaves than for sawgrass in both melaleuca-invaded and uninvaded sawgrass marshes. In arenaceous soils of pine
flatwoods, melaleuca leaf and pine needle decomposition rates were similar. Complete mineralization of sawgrass leaves occurred
after 258 weeks, whereas melaleuca leaves had up to 14% and pine foliage had up to 19% of the original biomass remaining after
322 weeks. Total carbon (C) in intact decomposing leaves varied slightly, but total nitrogen (N) steadily increased for all
three species; the greatest being a fourfold in sawgrass. Increases in N concentrations caused decreases in the C/N ratios
of all species but remained within an optimal range (20–30) in sawgrass resulting in higher decomposition rates compared to
melaleuca leaves and pine needles (C/N ratio >30). Slower decomposition of melaleuca leaves results in denser litter layers
that may negatively affect recruitment of other plant species and impede their establishment in invaded communities. 相似文献
11.
Eucalypt plantations are expanding rapidly in Australia, and their value for native fauna requires investigation. The relative conservation value of young eucalypt plantations was investigated through assessment of avifauna richness, abundance and composition using transect surveys incorporating point counts in five broad habitat types—dryland forests, riparian forests, dryland plantations, riparian plantations, and riparian pastures (strips of riparian vegetation surrounded by pastures). A total of 73 species were recorded during formal surveys. Species richness and abundance were comparable among all habitat types except dryland plantations, which supported fewer species and in lower numbers. The avifauna assemblage differed according to broad habitat types. Forest habitats (dryland and riparian) harboured more forest- and woodland-dependent species, and a greater abundance of nectarivores and insectivores. Riparian plantations supported a similar number of forest- and woodland-dependent species to forest habitats, but also retained some open-country species. Riparian pastures had the highest cumulative species richness, reflecting a diverse mix of forest- and woodland-dependent birds and open-country species. It was the preferred habitat type for granivores and vertebrate eaters. Dryland plantations were dominated by common species and omnivores, and supported fewer forest- and woodland-dependent birds, insectivores and frugivores compared with other habitat types. The presence of riparian strips increased avifauna diversity and abundance in plantations and pastures to a greater extent than predicted by the proportional area of riparian habitat. The importance of riparian habitats needs to be recognised and incorporated into management policies if biodiversity conservation is to be an objective of plantation establishment. 相似文献
12.
I. A. S. Gibson 《Forest Pathology》1974,4(2):89-100
The incidence of dothistroma blight [Dothistroma septospora (Doroguin) Morelet] throughout the world during the last fifteen years is reviewed with particular reference to its economic effects. Impact of the disease has been generally slight in the northern hemisphere, with most severe effects localised in nursery and ornamental stocks in parts of the USA and Canada. In Central and East Africa and New Zealand chronic defoliation has caused serious loss of increment in young Pinus radiata; in Chile outbreaks have been acute and of short duration, causing only slight yield loss. Economic control has been obtained by a well organised copper fungicide spray programme in New Zealand, but this means has proved impracticable in Africa. Experience gained in New Zealand will be valuable when similar problems arise in industrial forest plantations in the future. 相似文献
13.
Keisuke Sakata 《Journal of Forest Research》2005,10(5):385-390
In this study, a forestry profit model for carbon dioxide (CO2) emission trading was constructed using southeast Georgia, USA, as the model area. The value of CO2 credits regarding forest stores of carbon was calculated using the stock changing method, the average storing method, the ton-year method, and the returning CO2 credit method. Based on this model, the CO2 price at which an afforestation interest rate reaches its maximum in each 5-year interval at a cutting age of 10–50 years was calculated, considering the influence on the cutting age by introducing emission trading. The cutting age at which an afforestation interest rate reaches its maximum was 32 years. The cutting age shortened with the rise of CO2 price in all four accounting methods. Assuming the dealing CO2 price, we can forecast what the present cutting age will be according to the stock changing method and the average storing method in regard to this model. Assuming this CO2 price and using the ton-year method and the returning CO2 credit method, we can forecast that the present cutting age is not going to change. 相似文献
14.
Using a retrospective approach, based on historical needle cast disease and insect pest records, data series of needle losses (reconstructed by the use of the needle trace method), tree growth parameters and meteorological data were studied to determine the impact of the appropriate pointer (epidemic or calamity) years on the annual radial and height increment of 46 sample trees in six Scots pine (Pinus sylvestris) stands in Estonia from 1887 to 2006. First, the needle cast epidemics during the last 120 years were retrospectively determined, with resulting 4.6 epidemics per decade as a mean frequency. If the sum of precipitation from May to August reached 300 mm (the mean of 12 epidemic years studied: 361 ± 15 mm), an epidemic of needle cast caused by Lophodermium seditiosum might follow the next year in young plantations. For insect defoliators, similarly clear triggering threshold values of precipitation or temperature could not be determined, although dry and warm summers and mild winters supported the calamities. We separately detected that both larger needle losses and growth reductions in trees related to Lophodermium needle cast epidemic years lasted until the same age of pines, 22–24 years, but for insect pest (diprinoid sawflies) calamity years the growth reduction lasted longer. The relevance of these findings for the prediction of Lophodermium needle cast epidemics is briefly discussed. 相似文献
15.
16.
We used geographic information system applications and statistical analyses to classify young, premature forest areas in southeastern Georgia using combined data from Landsat TM 5 satellite imagery and ground inventory data. We defined premature stands as forests with trees up to 15 years old. We estimated the premature forest areas using three methods: maximum likelihood classification (MLC), regression analysis, and k-nearest neighbor (kNN) modeling. Overall accuracy (OA) of classifying the premature forest using MLC was 82% and the Kappa coefficient of agreement was 0.63, which was the highest among the methods that we have tested. The kNN approach ranked second in accuracy with OA of 61% and a Kappa coefficient of agreement of 0.22. Regression analysis yielded an OA of 57% and a Kappa coefficient of 0.14. We conclude that Landsat imagery can be effectively used for estimating premature forest areas in combination with image processing classifiers such as MLC. 相似文献
17.
Due to the lack of knowledge about ponderosa pine performance under silvopastoral systems (SPS) conditions, the objective
of this study was to determine the effect of stand density and pruning on the growth magnitude of ponderosa pines growing
in NW Patagonia (SPS with 350 and 500 pines ha−1 vs. commercial densities of 1,300 trees ha−1, HPP). Individual growth rate was higher in SPS 350 trees than in SPS 500 trees, being both higher than in HPP plots, indicating
a higher sensitivity of this drought resistance species to relative water availability. The higher individual growth compensated
the lower amount of trees per land unit, being the whole stand growth similar or even higher in both SPS treatments than in
the HPP stand. Pruning reduced diameter growth in both SPS treatments, at least until 2 years after pruning, with a more marked
effect in the pruning treatment with the higher amount of extracted foliage. Carbon fixation reduction in addition to changes
in carbon allocation within different plant parts after pruning could be the responsible of observed stem growth reductions.
We suggest that higher growth rates in combination with frequent pruning in low density plantations can be applied to shorten
the rotation period producing high quality timber in comparison with plantations managed under conventional conditions in
Patagonia. Additional advantages could be associated to the lower environmental impact of low canopy cover plantations compared
to high density stands. 相似文献
18.
19.
Timing of shedding seeds and cones, and production in different stands of Scots pines at Abernethy Forest, Scotland 总被引:1,自引:0,他引:1
A study was carried out over 11 seed years on the timing ofshedding of seeds and cones, and annual seed fall and cone productionin three stands of native Scots pinewood and a Scots pine plantationin Abernethy Forest, Scotland. Peaks in seed fall took placemainly in May, and cones were shed mainly between June and August.There were few residual seeds remaining in shed cones. Synchronizedpeaks in seed fall and cone production (mast years) took placeat 3-year intervals across the different stands. The differencebetween cohorts of high and low cone production ranged fromfactors of 5 to 20 among sites. Coefficients of variation forcone production ranged from 62 to 84 per cent among sites. Therewere no significant differences in cone production among sites,but there were site-related differences in seed fall. The largercanopy cover in the plantation probably accounted for the higherseed fall per square metre there, though variations in the amountof seed eaten by birds and mammals may also have been important.Canopy cover needs to be considered when converting cone densitiesunder crowns to cone density per unit of woodland area. A similarcalculation is difficult for seeds because they are lighterthan cones and many fall outside the area under the crowns.The results are discussed in relation to the potential for treeregeneration and the availability of food for birds and mammalsprior to seed dispersal. 相似文献
20.
油松移栽防治病虫害的几点意见 总被引:1,自引:0,他引:1
通过对本溪市峪明路油松在移植过程中由于多种原因造成病虫害侵染、生长不良和生理原因大量枯黄落叶等现象进行调查分析 ,总结出行道树移栽中把握好选苗、栽植和养护等环节 ,减少病虫害发生的几项措施 ,为今后城市行道树栽植提供切实可行的理论和实践依据 相似文献