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1.
The removal or maintenance of harvest residues in eucalypt plantations may influence site quality and productivity. Removal of slash from the site may facilitate further management operations and provide a valuable energy resource, but effects on site productivity and sustainability for a rotation time span were not yet assessed under Mediterranean conditions. Therefore, a study was carried out to assess the effects of slash (harvest residues plus forest floor litter) management and soil preparation options on stand productivity and understory vegetation dynamics, hypothesizing that those options influence tree growth, forest floor dynamics and understory biomass and diversity. An experiment was installed in West Central Portugal, consisting on: removal of slash without soil preparation (R); broadcast of harvest residues on the soil surface without soil disturbance (S); as in S, but concentrating the woody debris between tree rows (W); incorporation of slash into the soil by harrowing (I); removal of slash followed by harrowing (RH); and as in I followed by ripping (IS). The experiment was monitored for a rotation time span (140 months). Maintenance of slash followed by deep soil disturbance led to the highest wood production, but differences between treatments were not significant (p > 0.05). Forest floor load and understory biomass were also similar between treatments. Ground vegetation played an important role on nutrient cycling in early rotation stages, such effect being irrespective on slash management options. Incorporation of slash into the soil followed by ripping is probably the best option to match production and environmental sustainability of eucalypt plantations in Mediterranean conditions. 相似文献
2.
为探索板栗幼林抚育对生长的影响,通过板栗幼林中耕除草、间作与未间作对比试验。研究结果表明:中耕除草同龄的成活率以及树高、地径生长都比未中耕除草栗林有所增加,1次中耕除草效果差,中耕除草2~3次效果最好。间作薯类、豆类及谷类的板栗生长量比未间作的都有所增加,以间作薯类和豆类效果最明显。 相似文献
3.
A study was initiated in 1994 to evaluate the effects of bedding timing and frequency and pre-plant herbicide application, with and without post-plant herbaceous weed control, on growth of three slash pine (Pinus elliottii Engelm.) plantations and one loblolly pine (Pinus taeda L.) plantation on flatwoods sites. Site preparation treatments included early bedding alone, late bedding alone, double bedding, early bedding plus banded pre-plant herbicide, and early bedding plus broadcast pre-plant herbicide. Each site preparation treatment was tested with and without a first-year post-plant herbicide application for herbaceous weed control (HC). Results ranging from age 5 to 11 are reported, depending on installation. Pine growth following late bedding alone was similar or greater than that with early bedding alone. Double bedding did not consistently increase pine growth as compared with single bedding alone. Early bedding plus either broadcast or banded pre-plant herbicide application generally exhibited greater pine growth than did bedding alone treatments or bedding plus post-plant herbaceous weed control treatments. Broadcast pre-plant herbicide application resulted in similar or greater growth than banded pre-plant herbicide application. Post-plant herbaceous weed control improved loblolly pine growth across all site preparation regimes on the one test location. For slash pine plantations evaluated, post-plant herbaceous weed control resulted in significant growth increases on some but not all sites. The differences in growth response to bedding and pre- and post-plant herbicide applications are discussed in relation to treatment efficacy in controlling woody shrub and herbaceous competing vegetation. Effective bedding and chemical site preparation reduces the need for post-plant herbicide applications for slash pine on certain sites. Good site preparation, including the application of herbicides for competition control, is essential for fast growing slash and loblolly pine plantations in the flatwoods. 相似文献
4.
F. Vargas R. Rubilar C. A. Gonzalez-Benecke M. Sanchez-Olate Pablo Aracena 《New Forests》2018,49(3):383-398
Numerous studies have quantified the responses to vegetation management in Eucalyptus plantations but most publications have reported early responses in tree growth and a gap in knowledge exist about the magnitude and duration of growth responses throughout the whole rotation. We evaluated the long-term response (9 years-old) of E. globulus across a gradient of sites to different intensity levels of free area of competing vegetation around individual tree seedlings. Competing vegetation intensity levels considered free areas ranging between 0 (control) to 2.54 m2 plus a treatment with total weed control. Competing vegetation biomass production during the first growing season was 2.9, 6.5, 2.2 and 12.9 Mg ha?1, for sites ranging from low to high annual rainfall. Across sites, maximum response in stand volume ranged between 58 and 262 m3 ha?1 at age 9 years and was proportional to the amount of competing biomass controlled during the first growing season. Total competing vegetation control showed the largest response in stand volume at sites with 2.9 and 12.9 Mg ha?1 of competing vegetation. However, the 2.54 m2 vegetation control treatment showed the maximum response for sites with 2.2 and 6.5 Mg ha?1 of competing vegetation. The duration of response for vegetation control treatments ranged between 5 and 9 years. However, at the site with the largest accumulation of competing vegetation biomass the response to vegetation control showed a sustained and divergent response. Our results suggest that vegetation control improved site resources acquisition increasing long-term stand productivity by reducing environmental limitations to tree growth differentially at each site. 相似文献
5.
6.
A Eyles D Worledge P Sands ML Ottenschlaeger SC Paterson D Mendham AP O'Grady 《Tree physiology》2012,32(8):1008-1020
Early weed control may improve the growth of forest plantations by influencing soil water and nutrient availability. To understand eucalypt growth responses to weed control, we examined the temporal responses of leaf gas-exchange, leaf nitrogen concentration (N) and water status of 7-month-old Eucalyptus globulus L. trees in a paired-plot field trial. In addition, we monitored the growth, leaf N and water status of the competing vegetation in the weed treatment. By the end of the 11-month experiment, complete weed control (WF treatment) of largely woody competitors increased the basal diameter of E. globulus by 14%. As indicated by pre-dawn water potentials of >?-?0.05 MPa, interspecies competition for water resources was minimal at this site. In contrast, competition for N appeared to be the major factor limiting growth. Estimations of total plot leaf N (g m(-2) ground) showed that competing vegetation accounted for up to 70% of the total leaf N at the start of the trial. This value fell to 15% by the end of the trial. Despite increased leaf N(area) in WF trees 5 months after imposition of weed control, the photosynthetic capacity (A(1500)) of E. globulus was unaffected by treatment suggesting that the growth gains from weed control were largely unrelated to changes in leaf-level photosynthesis. Increased nutrient availability brought about by weed control enabled trees to increase investment into leaf-area production. Estimates of whole-tree carbon budget based on direct measurements of dark respiration and A(1500) allowed us to clearly demonstrate the importance of leaf area driving greater productivity following early weed control in a nutrient-limited site. 相似文献
7.
Herbicides are more cost-effective than alternative weed control methods for increasing early growth of Eucalyptus dunnii and Eucalyptus saligna 总被引：1，自引：0，他引：1
Effective weed control is an essential management task in establishing commercial tree plantations. Much of the current weed control strategies employed in Australian forestry relies on the use of available herbicides. However, given community concern regarding the use of herbicides, investigation of alternative weed control methods is warranted. We tested the ability and cost-effectiveness of mechanical (hand weeding and inter-row slashing), mulching (sawdust over newsprint, woodchips and jute), cover crops and herbicide applications for weed control in establishing eucalypt plantations. Jute matting and herbicide treatments reduced weed competition and increased seedling growth to age 2 years in plantations of Eucalyptus dunnii and Eucalyptus saligna in northern NSW, Australia. Growth increased by 269 % (Experiment 1) and 196 % (Experiment 2) in the Jute and by 216 % (Experiment 2) in the Herbicide treatments when compared to the control (no weed control) at 2 years age. As the Jute material deteriorated, after nearly 2 years, weed cover increased and there were significantly more weeds present in the Jute treatment compared to the Herbicide treatment. Jute matting costs approximately 15 times more than the herbicide regime used and, therefore, could not presently be considered a viable option for weed control in commercial eucalypt plantations. Other weed control treatments, including hand weeding, sawdust and woodchip mulches, slashing and sowing cover crops did not effectively control weeds and did not improve survival or increase seedling growth to age 2 relative to the control. We conclude that herbicides remain the most cost-effective weed control option available to commercial growers of eucalypt plantations. 相似文献
8.
Intensively managed loblolly pine (Pinus taeda) forests are common in the southeastern United States and offer opportunities for conservation of biologic diversity. Within intensively managed landscapes, stand establishment relies on combinations of mechanical and chemical site preparation and herbaceous weed control (HWC) to manage competing vegetation and increase pine production. However, few long-term studies have described relationships between intensity of stand establishment and effects on plant communities. Therefore, we examined effects of 6 treatments that varied in intensity via combinations of mechanical (wide spacing and strip shear or narrow spacing and roller chop) and chemical (application or no application) site preparation treatments with HWC (broadcast or banded) from 1 to 8 years after site preparation on plant communities in loblolly pine plantations (n = 6) in the Coastal Plain of North Carolina, USA. All treatments resulted in abundant and diverse plant communities. Chemical site preparation had short lived (?4 year) effects on the herbaceous community but long-term effects on woody plants and pine cover. Increasing management intensity by including broadcast HWC or roller chop/narrow spacing did not additively reduce woody vegetation cover or species richness. However, broadcast HWC reduced grass, vine, and forb cover in the first year post-treatment. Average Morista community similarity values ranged from 0.69 to 0.89 among treatments and plots receiving the same chemical site preparation contained the most similar plant communities. Banded HWC can be paired with wide spacing to maximize herbaceous plant growth important for many wildlife species, particularly in the first few years after site preparation. Site preparation techniques should be tailored to local site conditions, plant communities, and management objectives. 相似文献
9.
Masahiko Nakagawa 《林业研究》2013,24(1):131-136
I developed a weeding-duration model for Sakhalin fir (Abies sachalinensis (Fr. Schmidt) Masters) plantations that employs a generalized linear model. The number of years following planting that weeding is necessary is the response variable, and elevation, slope steepness, maximum snow depth, annual precipitation, geology, soil, site index, slope aspect, and vegetation type are explanatory variables. Among the explanatory variables, geology, soil, slope aspect, and vegetation type are categorical data. A Poisson distribution is assumed for the response variable, with a log-link function. Elevation, slope steepness, maximum snow depth, annual precipitation, site index, and vegetation type had a significant effect on weeding duration. Among the eight models with the smallest Akaike information criterion (AIC), I chose the model with no multicollinearity among the explanatory variables. The weeding-duration model includes site index, maximum snow depth, slope steepness (angle) and vegetation type as explanatory variables; elevation and annual precipitation were not included in the selected model because of multicol- linearity with maximum snow depth. This model is useful for cost-benefit analyses of afforestation or reforestation with Abies sachalinensis. 相似文献
10.
In this study, a weeding-duration model for Larix kaempferi plantations was developed that employs a generalized linear model. The number of years that weeding is necessary is the response
variable, and elevation, slope, maximum snow depth, annual precipitation, geological type, soil type, site index, slope aspect,
and vegetation type are explanatory variables. Among the explanatory variables, geological type, soil type, slope aspect,
and vegetation type are categorical data. We assumed a Poisson distribution for the response variable. The link function was
log. Among the models that could be developed from these variables, we chose the model with the smallest Akaike’s information
criterion (AIC). The weeding-duration model can be written as follows: years that weeding is necessary = Exp (−0.0172833 × site
index + 0.0014053 × maximum snow depth (cm) + 1.7417731). The results of this study imply that weeding of Larix kaempferi plantations is needed for more years as the maximum snow depth increases and fewer years as the site index increases. This
model is useful for cost–benefit analyses of afforestation or reforestation with Larix kaempferi. 相似文献
11.
P. K. Chandrasekhara Pillai R. C. Pandalai T. K. Dhamodaran K. V. Sankaran 《New Forests》2013,44(4):521-532
The effect of nitrogen addition and weed management on fibre properties of wood from 6.5-year-old Eucalyptus grandis and E. tereticornis from intensively managed short-rotation plantations were investigated. Trees for analyses were sampled from plots with zero nitrogen input (n = 4), plots with high level (187 kg N ha?1) nitrogen input (n = 4), plots from which weed growth was not removed throughout the rotation (n = 4) and plots from which weeds were removed periodically (n = 4). Fibre characteristics were evaluated on wood samples collected from base, breast height, 50, 75 and 100 % of merchantable bole height of trees. Though N input and weed management improved tree growth significantly irrespective of species, the treatment effects did not cause any significant change in fibre characteristics such as fibre length, fibre diameter, lumen width and wall thickness. Longest and widest fibres were observed at the outer most radial portion of wood in all cases. In general, within tree fibre length varied significantly along the radial direction of wood. Fibre diameter, lumen width and wall thickness lacked any specific pattern between species and treatments. Runkel ratio and felting and flexibility coefficients values showed high pulping quality of wood irrespective of species and treatments. The study concluded that the fibre properties that influence pulpwood quality of Eucalyptus have not been affected by silvicultural practices, like fertilizer input and weed management, aimed at improving productivity of short-rotation eucalypt plantations. 相似文献
12.
《Journal of Sustainable Forestry》2013,32(2-3):109-121
Summary Eucalypt plantations in India are an important source of fiber for paper making and fuel for local villagers. Large areas of land have supported eucalypt plantations for several rotations, and productivity has generally been declining through successive rotations. In 1997, we initiated a project to examine site management options as a way to improve the productivity of these sites. We established a large experimental infrastructure at each of four sites in Kerala, consisting of up to five separate fully randomized block experiments at each site, examining interrotation management options (organic matter manipulation, N and P fertilizer input, legume cover cropping, weed control). Two of the sites were typical lowland plantations with Eucalytus tereticornis, and the other two sites were typical upland plantations with Eucalytus grandis. Following treatments, we monitored plantation productivity and impacts on soil and nutrient cycling for one full rotation (6.5 years). We found it is possible to increase the volume growth of E. grandis by up to 48%, and E. tereticornis by up to 268% through a combination of optimum site practices (mostly weed control and nutrient addition), but productivity responses are dependent on site-specific factors. Key outcomes of this research are presented, with special reference to application in the broader context of tropical eucalypt plantations. 相似文献
13.
Forest tree species in the eastern US such as American chestnut (Castanea dentata (Marsh.) Borkh) and oaks (Quercus spp.) have been negatively impacted by forest changes over the past century. Many mature, introduced pine (Pinus spp.) plantations exist in the Midwest US following establishment 50–60 years ago yet have little economic and ecological value. As oak and chestnut have similar site preferences to pines, these stands may be ideal sites for hardwood restoration plantings. We sought to determine optimal management strategies for converting pine plantations by manipulating their canopies. We underplanted hybrid American chestnut and northern red oak (Quercus rubra L.) seedlings into three canopy treatments (control, shelterwood, clearcut) and included an open field treatment. For each of two growing seasons, 0, 30, or 60 g 19N–6P–12K of controlled-release fertilizer (CRF) were also applied to seedlings. Soil chemical parameters and leaf nutrients were analyzed throughout the study. Chestnut and oak seedlings had significantly greater height after two growing seasons in the clearcut and shelterwood than the control and open field, and chestnut had significantly greater diameter as well. Chestnut height and RCD growth were threefold that of oak after two growing seasons. In general, fertilization increased seedling growth more in the clearcut and open field than shelterwood and control for both species. Soils had significantly higher pH, K, and S in the open field than in pine stands. Results suggest that pine plantations may serve as target sites for restoration of these hardwood species. Shelterwoods and clearcuts are both favorable conversion options for oak and chestnut, and addition of CRF may augment further growth increase, especially in open environments. 相似文献
14.
To improve the productivity and wood quality of poplar plantations, effects of four planting spacing on canopy characteristics, biomass production and stem roundness in poplar plantations were evaluated over 8 years. Planting spacing influenced canopy characteristics of the plantations, and further affected the understory vegetation and plantation productivity. Understory vegetation biomass and Shannon-Wiener index were negatively correlated with leaf area index, but both diversity indexes and aboveground biomass of understory vegetation were higher in stands with a wider spacing. Tree diameter growth increased with increasing planting spacing, while the increment in plantations of square configurations (5?×?5 m and 6?×?6 m) was higher than those with rectangular configurations (3?×?8 m, 4.5?×?8 m). The highest poplar biomass production was achieved in the plantation with 5?×?5 m spacing at age 8. Moreover, poplar trees showed a tendency with better stem roundness in a square configuration. The results suggest that planting spacing not only affect canopy characteristics, understory vegetation and tree growth but also wood quality, and square configurations (5?×?5 m and 6?×?6 m) could be a better option for poplar plywood timber production at similar sites. 相似文献
15.
S. E. Williams M. van Noordwijk E. Penot J. R. Healey F. L. Sinclair G. Wibawa 《Agroforestry Systems》2001,53(2):227-237
Perennial tree crops are often grown in complex multistrata systems that incorporate natural vegetation. These systems contribute
simultaneously to sustaining rural livelihoods and to the conservation of biodiversity, but their productivity is usually
low. Introduction of high yielding germplasm, usually selected in monocultural plantations, is a potential way to increase
productivity, but a critical requirement is that such plants can be established in a competitive multispecies environment.
The establishment of clonal planting stock in the jungle rubber agroforests of Indonesia was explored through participatory
on-farm research. The trial involved four farmers who grew clonal rubber trees in a total of 20 plots, constituting five replicate
experimental blocks spread across four farms. Unexpectedly, vertebrate pest damage by monkeys (Presbytis melalophos nobilis) and wild pigs (Sus scrofa) was the most important influence on establishment, explaining almost 70% of the variation in rubber tree growth. The amount
of labour invested in weeding was also positively correlated with rubber tree growth. Farmers generally decided to completely
cut back vegetation between rows of rubber trees, including potentially valuable trees, rather than weeding within the rows
and selectively pruning trees in the inter-row. Farmers thought that the inter-row vegetation would harbour vertebrate pests
and compete with the clonal rubber, and they had access to fruits, firewood and other non-timber forest products from other
land. Thus, contrary to expectations, when offered clonal germplasm, farmers opted to use plantation monoculture methods to
protect what they considered a valuable asset, rather than maintain the traditional multispecies strategy they use with local
germplasm.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
16.
Arne Sæbø Inger Sundheim Fløistad Jan Netland Brynjar Skúlason Øyvind Meland Edvardsen 《New Forests》2009,38(2):143-156
Abies nordmanniana and Abies lasiocarpa, established for Christmas tree production in southwestern Norway (58°44′N, 5°38′E), were treated with different weed control
methods, including chemicals, use of black plastic mulch, grass or clover as ground cover, living mulch and mechanical hoeing.
Ground cover with black plastic mulching resulted in the best growth and quality in A. lasiocarpa; the least favourable treatment was when grasses were allowed to grow close to the trees. Unless measures were taken to remove
this competing vegetation, the ground cover grew over the trees, smothering 94% of them. A. nordmanniana plants grew to the same height on plots with no weed control as on plots with thorough weed eradication. Stem diameter decreased
on plots with ground vegetation compared to seedlings grown in the weed-free environment. The use of Trifolium repens as ground cover decreased height growth by 30% compared to thorough weed control. Both grasses and clover sown as living
mulch, damaged the trees more than did natural weed vegetation. 相似文献
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18.
Weed suppression is an important reason for fallowing in swidden systems. Recently, in Laos, an increase in weeds and resulting increase in labor input has become a problem; however, causal factors influencing weed growth and weeding labor other than fallow period have yet to be fully examined. Therefore, an experimental research on swidden weeds, combining a forest survey and interviews with local farmers, was conducted in a mountain village in northern Laos where swidden agriculture is practiced as a major means of livelihood. Weed amount, weed composition and time required for weeding were found to be more influenced by fallow vegetation than fallow period. Bushy vegetation in a short fallow field was shown to lead to abundance of herbaceous weeds, resulting in higher labor input. There was a possibility that increases in some bamboo species were a cause of recent weed increases. Based on the results, we suggest that maintaining a minimum fallow period of forest fallowing, with fallow management to suppress bamboo and promote tree growth may be effective in reducing labor input in swidden agriculture. 相似文献
19.
《Southern Forests》2013,75(3):187-199
During the 1990s a number of trials were implemented in the summer rainfall region of South Africa to determine both the short- and long-term impacts of competing vegetation on pine growth. Trial sites were selected across different physiographic regions such that a range of altitudinal, climatic and environmental gradients were represented. Although the understanding gained from these trials allowed for the development of vegetation management standards, their operational and economic viability need to be tested on a commercial basis. Four pine trials were thus initiated to test the applicability of these standards when utilised on a commercial scale. Two of the trials were situated at lower-altitude sites (900 m and 1 000 m above sea level [asl]), one at a mid-altitude site (1 267 m asl), and one at a higher-altitude site (1 650 m asl). Several vegetation management treatments developed to suit the predicted vegetation load at each site were implemented and varied according to either weeding intensity (high, moderate and minimal), or the area around the tree that was kept free of vegetation (no vegetation control, a ring/row weeding and complete vegetation control). Tree growth up to 3.5 years was linked to the level of vegetation management in each treatment and its associated total cost for that time period, allowing for the development of different cost-benefit comparisons. The intensity of vegetation management required to produce significant growth benefits decreased with increasing altitude, as did the area that needed to be kept free from competing vegetation. In contrast to the higher-altitude site, where tree growth did not benefit from vegetation management, there was a 18, 25 and 112% increase in diameter growth for the high-intensity vegetation management operations relative to minimal or no vegetation control at the three mid- and lower-altitude sites. Besides demonstrating the commercial applicability of research results, this series of trials has shown that site-dependent vegetation management is viable on a commercial scale and will allow the South African forest industry to adjust their weed control budgets on a regional scale (linked to altitude). 相似文献
20.
Long-term effects of nitrogen fertilization on the productivity of subsequent stands of Douglas-fir in the Pacific Northwest 总被引：1，自引：0，他引：1
The carryover effects of N fertilization on five coastal Pacific Northwest Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) plantations were studied. “Carryover” is defined as the long-term impact of N fertilizer added to a previous stand on the growth of a subsequent stand. Average height and diameter at 1.3 m above-ground (DBH) of 7–9-year-old Douglas-fir trees and biomass and N-content of understory vegetation were assessed on paired control (untreated) and urea-N-fertilized plots that had received cumulative additions of 810–1120 kg N ha−1 to a previous stand. Overall productivity was significantly greater in the fertilized stands compared to the controls. In 2006, the last growth measurement year, mean seedling height was 15% greater (p = 0.06) and mean DBH was 29% greater (p = 0.04) on previously fertilized plots compared to control plots. Understory vegetation biomass of fertilized plots was 73% greater (p = 0.005), and N-content was 97% greater (p = 0.004) compared to control plots. These results show that past N fertilization markedly increased seedling growth in these plantations as well as biomass and N-content of understory vegetation in a subsequent rotation. These findings suggest that N fertilization could potentially increase site productivity of young Douglas-fir stands found on low quality sites in the Pacific Northwest 15–22 years after application by a carryover effect. These plantations have not yet reached the age where marketable materials can be harvested from them, and the growth of trees should be monitored over a longer time period before potential impacts on older stands, if any, can be determined. 相似文献