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1.
The authors tested two mini-yarders, one for uphill and the other for downhill extraction. The two machines were modern commercial
models, offering state-of-the-art yarding technology on a miniature scale and at a much lower cost than required for purchasing
a full-size tower yarder. The two units must not be regarded as alternative, but rather as complementary, since they offer
different capabilities and advantages. Both machines were tested while harvesting firewood from the thinning of young beech
stands in Central Italy. The tests indicated that both units can reach a productivity between 1.5 and 2.4 m3 SMH−1, including all delays, as well as set-up and dismantle time. Calculated extraction cost ranged between 24 and over 30€ m−3. The authors calculated a set of regression equations for estimating machine productivity as a function of the main work
conditions. The performance of the studied mini-yarders does not seem much inferior to that achieved by professional light
tower yarder under the same work conditions, but the lighter construction of the small-scale units may result in a lower resistance
to wear and abuse. In any case, mini-yarders seem ideal for deployment under the typical conditions of small-scale forestry,
offering a good solution to wood extraction on steep terrain, competitive with animal and winch logging in terms of productivity,
cost and operator comfort. 相似文献
2.
Further study is needed on loblolly pine (Pinus taeda L.) growth in a systematic array of plantation designs or stocking rates commonly used in temperate forestry and agroforestry
practices. Our objective was to determine loblolly pine growth responses and agroforestry implications of 13 plantation designs
(i.e., stocking rates in trees ha−1 [TPH]) at mid-rotation (14 years old). Survival, diameter at 1.3 m above soil surface (dbh), height, basal area (BA), and
volume (V) were measured in unthinned plantations ranging from 490 to 2,300 TPH. Stocking rate was positively correlated with
BA (r ≥ 0.67) and V (r ≥ 0.55) and negatively correlated with survival (r ≤ −0.83) and dbh (r ≤ −0.83). Plantations with ≥2,000 TPH had closed canopies and excessively high BA and V at mid-rotation. The 4- and 5-row
plantations (≥12 m alley spacing) had small dbh (≤17.5 cm). Single-row plantations with ≥3.6 m within row spacing and ≤700
TPH, and the 3-row multiple-row plantations (1,200 TPH), had acceptable BA (29.4–33.2 m2 ha−1) and V (127–136 m3 ha−1). Basal area was ≥30 m2 ha−1 in most plantations indicating thinning is needed to optimize individual tree growth. Besides timber, an array of design-dependent
agroforestry and forestry products should drive the selection of any one of these plantation designs: pine straw or biomass
production at ≥1,800 TPH, and alley cropping or silvopasture in single-row (≤1,000 TPH) and multiple-row plantations (<1,400
TPH). 相似文献
3.
A forest road network in northeastern Italy was explored by field investigations to evaluate the cost of covering annual demand
of woodchips according to three scenarios. The first scenario (A) considered the current extent of the forest road network
(mainly tractor road) and the associated qualitative characteristics; the second scenario (B) evaluated the possibility of
increasing the availability of the technical amount of forest biomass by extending the forest road network by three tractor
roads (3.9 km); the third scenario (C) considered the impact on woodchip supply of converting 9.3 km of tractor forest road
into truck forest road. At a woodchip price of 60 € t−1, the cost–supply curve of scenario C indicated a woodchip amount of 2886 t year−1, which was 561 t year−1 greater than scenario A and 161 t year−1 greater than scenario B. 相似文献
4.
Chloe Williams 《Southern Forests》2016,78(4):267-274
The South African forestry industry is experiencing an increase in the number of fully mechanised timber-harvesting systems. Understanding the productivity of these systems, for which data is currently limited for South Africa, is an important step to maximise the utilisation of machines being used. A time study of a mechanised cut-to-length system was conducted in Pinus elliottii sawtimber plantations in the Southern Cape forestry region of South Africa. A harvester and a forwarder were studied with the intention of analysing the division of work time amongst work elements, modelling each machine’s productivity and cost, and estimate fuel consumption. For the harvester’s productivity, a multiple regression model was developed using diameter at breast height (DBH), average distance moved per work cycle and slope class as predictors (adjusted R2? = 0.80). The harvester had a mean productivity of 33.6 m3 per productive machine hour (PMH0) under the current conditions with most of the productive time being used in the moving element. It consumed 25.5 L PMH0 ?1 of diesel on average. The forwarder’s fuel consumption was calculated as 16.8 L PMH0 ?1, while productivity was 46.8 m3 PMH0 ?1. The forwarder spent the longest portion of the work cycle in the loading and unloading phases. A productivity regression model was created that included load size and distance moved during the driving in the loaded phase (adjusted R?2 = 0.78). 相似文献
5.
J. V. N. S. Prasad G. R. Korwar K. V. Rao K. Srinivas Ch. Srinivasarao B. Pedababu B. Venkateswarlu S. N. Rao H. D. Kulkarni 《New Forests》2011,42(1):51-61
On-farm experiments were conducted in Khammam district of Andhra Pradesh from 2001 to 2006 to evaluate the biomass productivity,
intercrop yields and profitability of Eucalyptus tereticornis clonal and Leucaena leucocephala variety K-636 based systems. Trees were planted at a spacing of 3 × 2 m and evaluated at three locations. Height growth was
significantly higher in leucaena during the 4 year where as difference in diameter growth was not significant. Biomass partitioning to the bole was high in case of leucaena, ranged from 83% in 2.5–5 cm diameter at breast height (DBH)
trees to 89% in 12.5–15 cm DBH trees and in eucalyptus clones the corresponding values were 71% in 2.5–5 cm DBH trees and
83% in 12.5–15 cm DBH trees. Marketable biomass productivity was higher with leucaena (95 Mg ha−1) in comparison to eucalyptus (87 Mg ha−1). Competition effects of trees on intercrops were observed from the 2 year (2002 post-rainy season). Intercrop yields were
45% of the sole crop in eucalyptus system and 36% in leucaena system during the 2 year. Sole eucalyptus and leucaena plantations
and intercropping systems recorded higher gross and net returns over arable cropping. Therefore, it can be concluded that
leucaena variety K636 and eucalyptus clonal based agroforestry systems are profitable alternatives to arable cropping under
rainfed conditions. 相似文献
6.
The sustainability of cocoa growing systems in the humid tropics is debatable. Socio-economic and technical data were obtained
from 1,171 cocoa farmers and 1,638 cocoa plantations to assess the long-term dynamics of cocoa agroforests in central Cameroon
since the beginning of the twentieth century. On-site, we estimated the age of the cocoa trees and measured their density
in a sub-sample of 402 cocoa plantations. We inventoried associated woody species in 45 cocoa plantations from this sub-sample.
Our results revealed a high Shannon index for the cocoa plantations (2.6) and showed that an average of 25 tree species per
cocoa plantation had been planted with the cocoa trees at a density of 120 trees ha−1. Surveys indicated that there had been no mineral fertilization. Nearly 70% of the cocoa agroforests were over 40 years old,
and all farmers continuously regenerated their cocoa tree stands. Irrespective of the cocoa plantation age, the cocoa tree
density remained over 1,000 plants ha−1, and fermented dried cocoa yields were 255 kg ha−1 on average. Cocoa agroforests occupied 60% of the cultivated area on farms and cocoa sales accounted for 75% of total farm
income. Almost a third of the farmers were from the area and under 40 years old. In conclusion, our results show that the
farmers’ agroforestry practices, in addition to the fact that the cocoa tree stands were continuously regenerated and passed
down between generations of farmers, could explain the long-term dynamics of cocoa agroforests in central Cameroon. 相似文献
7.
Satish Chandra Garkoti 《Journal of Forest Research》2011,16(2):136-143
Fine root biomass, rates of dry matter production and nutrients dynamics were estimated for 1 year in three high elevation
forests of the Indian central Himalaya. Fine root biomass and productivity were higher in closed canopied cappadocian maple
forest (9.92 Mg ha−1 and 6.34 Mg ha−1 year−1, respectively), followed by Himalayan birch forest (6.35 Mg ha−1 and 4.44 Mg ha−1 year−1) and Bell rhododendron forest (6.23 Mg ha−1 and 2.94 Mg ha−1 year−1). Both fine root biomass and productivity declined with an increase in elevation. Across the sites, fine root biomass was
maximal in fall and minimal in summer. In all sites, maximum nutrient concentration in fine roots was in the rainy season
and minimum in winter. Fine root biomass per unit basal area was positively related with elevation, Bell rhododendron forest
having the largest fine root biomass per unit of basal area (0.53 Mg m−2) and cappadocian maple the least (0.18 Mg m−2). The production efficiency of fine roots per unit of leaf biomass also increased with elevation and ranged from 1.13 g g−1 leaf mass year−1 in cappadocian maple forest to 1.28 g g−1 leaf mass year−1 in Bell rhododendron forest. Present fine root turnover estimates showed a decline towards higher elevations (0.72 year−1 in cappadocian maple and 0.58 year−1 in Bell rhododendron forest) and are higher than global estimates (0.52). 相似文献
8.
Sebastian Derwisch Luitgard Schwendenmann Roland Olschewski Dirk Hölscher 《New Forests》2009,37(3):227-240
Tropical tree plantations may play an important role in mitigating CO2 emissions through their potential to capture and sequester carbon from the atmosphere. The Clean Development Mechanism (CDM)
as well as voluntary initiatives provide economic incentives for afforestation and reforestation efforts through the generation
and sale of carbon credits. The objectives of our study were to measure the carbon (C) storage potential of 1, 2 and 10-years
old Tectona grandis plantations in the province of Chiriquí, Western Panama and to calculate the monetary value of aboveground C storage if sold
as Certified Emission Reduction (CER) carbon credits. The average aboveground C storage ranged from 2.9 Mg C ha−1 in the 1-year-old plantations to 40.7 Mg C ha−1 in the 10-year-old plantations. Using regression analysis we estimated the potential aboveground C storage of the teak plantation
over a 20 year rotation period. The CO2-storage over this period amounted to 191.1 Mg CO2 ha−1. The discounted revenues that could be obtained by issuance of carbon credits during a 20 year rotation period were about
US$460 for temporary CER and US$560 for long-term CER, and thus, contribute to a minor extent (1%) to overall revenues, only. 相似文献
9.
《Southern Forests》2013,75(4):229-235
The cut-to-length method is a preferred method for harvest of pine plantations in Australia. The cut-to-length method studied in southern Tasmania consists of a feller-buncher, processor, forwarder, grapple loader and tractortrailers that were producing only pulp logs for the plantation owner Norske Skog. An elemental time study method was applied to evaluate the productivity of the machines within the flat terrain, Pinus radiata plantation. Multiple regression was used in SPSS to develop the productivity prediction models. The productivity of the feller-buncher and processor averaged 122.20 m3 per productive machine hours excluding all delays (PMH0) and 84.32 m3 PMH0 ?1, respectively. The average productivity for the forwarder, grapple loader and truck were 80.90 m3 PMH0 ?1, 100.80 m3 PMH0 ?1 and 27.40 m3 PMH0 ?1, respectively. The average fuel consumption of the feller-buncher, forwarder and processor were also documented. The trial assessed harvest residue left on the site and found 238.7 GMt ha?1 (31% of total biomass above the stump) was left of which 46% was stemwood. These research findings can be used for harvesting planning and improving logging efficiency. 相似文献
10.
Site productivity of the hybrid poplar clone Brooks6 was predicted using soil and site information from 6, 4-year-old plantations
in north-east Alberta. Predictions were made at both the local and microsite scales. Percent sand (R
2 = 0.352, P = 0.001) was the best single predictor of hybrid poplar productivity, showing a curved relationship. Soil pH also showed
a curved but weaker relationship with hybrid poplar productivity (R
2 = 0.133, P = 0.100). Maximum tree productivity occurred at sand contents between 55 and 70% and pH values near 6. Other variables, including
foliar nutrient concentrations, foliar δ13C, electrical conductivity, depth of the A horizon and total chemistry of the soil, were also related to hybrid poplar productivity
at the local and microsite scales. However, all of these variables were correlated to either soil texture (percent sand) or
pH. At the microsite scale within plantations, percent sand was the most important predictor of tree productivity and explained
more than 50% of the variability within plantations, although the relationship varied by plantation. In plantations with fine
textures, sandier microsites were associated with increased growth while in sandy plantations, finer textured microsites were
more productive. As a whole, the growth of the hybrid poplar clone Brooks6 appears to be mostly influenced by a combination
of soil water and nutrient availability, the former being impacted by soil texture and the latter being governed by soil pH. 相似文献
11.
From 2002 to 2003, based on the investigation of sample plots and stem analysis of remained plantation communities in the areas of returning farmland to forest in the 1980s in Datong County, Qinghai Province, this paper studies tree productivity and moisture potential productivity of six types of plantations on the land of returning farmland to forest, such as green poplar (Populus cathayana Rehd.) and shrub mixed forest, Asia white birch (Betula platyphylla) and China spruce (Picea asperata) mixed forest, Dahurian larch (Larix gmelinii) pure forest, China spruce pure forest and Asia white birch pure forest and so on. The results show that: in sub-humid region of Loess Plateau, 3 000 trees per hm2 is a proper standard of planting density. Under current condition, the productivity index of green poplar and shrub mixed forest, Asia white birch pure forest, China spruce pure forest, and Asia white birch and China spruce mixed forest with the density of 2 100–3 333 trees per hm2 can serve as potential productivity standard of actual biomass of arbor established forest. In sub-humid area, Thornthwaite Model is adopted to estimate plant climate potential productivity, which is about 8 462 kg8226;hm–28226;a–1. The actual potential water productive efficiency of Purplecone spruce (Picea purpurea) and Asia white birch pure established forest are 17.22 and 22.14 kg8226;mm–18226;hm–28226;a–1 respectively, and that of green poplar and shrub mixed established forest, and Asia white birch and China spruce mixed established forest are 21.14 and 19.09 kg8226;mm–18226;hm–28226;a–1 respectively. The potential productivity of green poplar and shrub mixed forest, Asia white birch and China spruce mixed forest, China spruce pure forest and Asia white birch pure forest which have grown into forest with the density of 3 000 trees per hm2 have attained or been close to that of local climax community, which is local maximum tree productivity at present. These types of forestation models are the developing direction of the returning farmland to forest project. 相似文献
12.
The importance of agroforestry systems in CO2 mitigation has become recognized worldwide in recent years. However, little is known about carbon (C) sequestered in poplar
intercropping systems. The main objective of this study is to compare the effects of three poplar intercropping designs (configuration
A: 250 trees ha−1; configuration B: 167 trees ha−1 and configuration C: 94 trees ha−1) and two intercropping systems (wheat–corn cropping system and wheat–soybean cropping system) on biomass production and C
stocks in poplar intercropping systems. The experiment was conducted at Suqian Ecological Demonstration Garden of fast-growing
poplar plantations in northwestern Jiangsu. A significant difference in C concentration was observed among the poplar biomass
components investigated (P ≤ 0.05), with the highest value in stemwood and the lowest in fine roots, ranging from 459.9 to 526.7 g kg−1. There was also a significant difference in C concentration among the different crop components (P ≤ 0.05), and the highest concentration was observed in the corn ear. Over the 5-year period, the total poplar biomass increased
with increasing tree density, ranging from 8.77 to 15.12 t ha−1, while annual biomass production among the crops ranged from 4.69 to 16.58 t ha−1 in the three configurations. Overall, total C stock in the poplar intercropping system was affected by configurations and
cropping systems, and configuration A obtained the largest total C stock, reaching 16.7 t C ha−1 for the wheat–soybean cropping system and 18.9 t C ha−1 for the wheat–corn cropping system. Results from this case study suggest that configuration A was a relative optimum poplar
intercropping system both for economic benefits and for C sequestration. 相似文献
13.
The responses of fine root mass, length, production and turnover to the increase in soil N availability are not well understood
in forest ecosystems. In this study, sequential soil core and ingrowth core methods were employed to examine the responses
of fine root (≤1 mm) standing biomass, root length density (RLD), specific root length (SRL), biomass production and turnover
rate to soil N fertilization (10 g N m−2 year−1) in Larix gmelinii (larch) and Fraxinus mandshurica (ash) plantations. N fertilization significantly reduced fine root standing biomass from 130.7 to 103.4 g m−2 in ash, but had no significant influence in larch (81.5 g m−2 in the control and 81.9 g m−2 in the fertilized plots). Similarly, N fertilization reduced mean RLD from 6,857 to 5,822 m m−2 in ash, but did not influence RLD in larch (1,875 m m−2 in the control and 1,858 m m−2 in the fertilized plots). In both species, N fertilization did not alter SRL. Additionally, N fertilization did not significantly
alter root production and turnover rate estimated from sequential soil cores, but did reduce root production and turnover
rate estimated from the ingrowth core method. These results suggested that N fertilization had a substantial influence on
fine root standing biomass, RLD, biomass production and turnover rate, but the direction and magnitude of the influence depended
on species and methods. 相似文献
14.
Tsutomu Enoki Takafumi Inoue Naoaki Tashiro Hiroaki Ishii 《Journal of Forest Research》2011,16(4):268-274
We measured the aboveground biomass, biomass increment and litterfall production of a 140-year-old, abandoned Cryptomeria japonica plantation in order to infer the effects of topography on biomass production. The plantation was unsuccessful and the naturally
regenerated broad-leaved trees contributed 93.4% (374.2 Mg ha−1) of the total aboveground biomass (400.2 Mg ha−1). Comparing between different slope positions, aboveground biomass decreased downslope corresponding to the decrease in broad-leaved
tree biomass. The biomass of C. japonica did not vary with slope position. Biomass increment and litterfall production of the broad-leaved trees also decreased downslope.
However, litterfall production per unit biomass and aboveground net primary production per unit biomass increased downslope.
Results of a path analysis showed that biomass increment of C. japonica decreased with increasing topographical convexity, whereas biomass and litterfall production of broad-leaved tree increased.
Litterfall production of broad-leaved tree decreased with increasing biomass of C. japonica, suggesting that, despite their small biomass, the presence of residual C. japonica may have negative effects on the distribution and productivity of the broad-leaved trees. Our results indicated that total
aboveground biomass of the study site was comparable to that of old-growth C. japonica plantations. We inferred that the variation in aboveground biomass of the broad-leaved trees was largely determined by the
topography, while their productivity was affected by interactions with planted C. japonica. 相似文献
15.
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
16.
A major limitation to efficient forage-based livestock production in Appalachia is asynchrony of forage availability and quality
with nutritional requirements of the grazer. Producers require dependable plant resources and management practices that improve
the seasonal distribution and persistence of high quality herbage, sustainability and environmental integrity of the agricultural
landscape. It was hypothesized that inorganic N and fecal coliform concentrations delivered in leachate to the soil/bedrock
interface would be lowest in deciduous forest (HF) and highest in pasture (CP) with HF converted to silvopasture (SP) between
the two. Piezometers were used to monitor water quality at the soil/bedrock interface under conventional pasture, SP, and
hardwood forest. The pasture and SP were rotationally grazed by sheep during the spring to fall grazing season (2004–2008).
Geometric mean fecal coliform bacteria concentrations (FC) were greatest in SP (18 FC 100 mL−1) with no difference between CP (7.5 FC 100 mL−1) and HF (5.6 FC 100 mL−1). Mean NO3-N concentration was lowest in SP (2.3 mg L−1) and greatest in CP (4.4 mg L−1) and HF (4.1 mg L−1), which were not significantly different. Mean NH4-N concentrations showed different trends with the lowest mean concentration in CP (0.5 mg L−1) and the greatest in SP (2.5 mg L−1) and HF (2.6 mg L−1), which were not significantly different. SP was shown to be a management option in the study area that reduces nitrate leaching,
but should be considered cautiously in near-stream areas and near wells where fecal bacteria pollution can be problematic.
This study makes an important contribution to our knowledge about interactions between landscape management and environmental
quality of the Appalachian region. A diversity of land and forage management options are needed to maximize forage and livestock
productivity while protecting surface and groundwater quality of the region. 相似文献
17.
Generic or default values to account for biomass and carbon accumulation in tropical forest ecosystems are generally recognized
as a major source of errors, making site and species specific data the best way to achieve precise and reliable estimates.
The objective of our study was to determine carbon in various components (leaves, branches, stems, structural roots and soil)
of single-species plantations of Vochysia guatemalensis and Hieronyma alchorneoides from 0 to 16 years of age. Carbon fraction in the biomass, mean (±standard deviation), for the different pools varied between
38.5 and 49.7% (±3 and 3.8). Accumulated carbon in the biomass increased with the plantation age, with mean annual increments
of 7.1 and 5.3 Mg ha−1 year−1 for forest plantations of V. guatemalensis and H. alchorneoides, respectively. At all ages, 66.3% (±10.6) of total biomass was found within the aboveground tree components, while 18.6%
(±20.9) was found in structural roots. The soil (0–30 cm) contained 62.2 (±13) and 71.5% (±17.1) of the total carbon (biomass
plus soil) under V. guatemalensis and H. alchorneoides, respectively. Mean annual increment for carbon in the soil was 1.7 and 1.3 Mg ha−1 year−1 in V. guatemalensis and H. alchorneoides. Allometric equations were constructed to estimate total biomass and carbon in the biomass which had an R
2aj (adjusted R square) greater than 94.5%. Finally, we compare our results to those that could have resulted from the use
of default values, showing how site and species specific data contribute to the overall goal of improving carbon estimates
and providing a more reliable account of the mitigation potential of forestry activities on climate change. 相似文献
18.
Jonathan C. Onyekwelu 《林业研究》2012,23(2):253-260
We investigated the Effects of plantation development, seasons, and soil depth on soil microbial indices in Gmelina arborea plantations in south-western Nigeria. Soil samples were obtained from the soil depths of 0-15 and 15-30 cm from plantations of six different ages during the rainy season, dry seasons, and their transitions. We used plate count and fumigation-extraction methods to determine microbe population and microbial biomass carbon (MB-C) and nitrogen (MB-N), respectively. Plantation age did not affect microbial indices, implying a non-significant effect of plantation development on microbial communities. It could also imply that soil microbial indices had already stabilized in the sampled plantations. Seasonal variation and soil depth had significant effects on microbial indices. At 0-15 cm soil depth, mean MB-C increased from 50.74 μg g-1 during the peak of the dry season (i.e. March) to 99.58 μg g-1 during the peak of the rainy season (i.e. September), while it increased from 36.22 μg g-1 to 75.31 μg g-1 at 15-30 cm soil depth between the same seasonal periods. Bacteria populations and MB-N showed similar increasing trends. Correlations between MB-C, MB-N, microbe populations, and rainfall were positive and linear. Significantly higher microbial activities took place in the plantations during the rainy season, increased with soil wetness, and decreased at greater soil depth. 相似文献
19.
Growth and yield of maize and timber trees in smallholder agroforestry systems in Claveria,northern Mindanao,Philippines 总被引:1,自引:1,他引:0
Manuel Bertomeu 《Agroforestry Systems》2012,84(1):73-87
On-farm experiments were conducted in the Philippines to study over a 4-year period the growth of two timber trees, gmelina
(Gmelina arborea R. Br.) and bagras (Eucalyptus deglupta Blume), and their impact on the grain yield of intercropped maize. The experiment consisted of maize monocropping plots (control)
and maize intercropped between trees planted in block (2 × 2.5 m), and hedgerow arrangement (1 × 10 m). Three maize crops
were planted in the block plots before canopy closure, and seven maize crops were planted in the hedgerow and monocropping
plots. Maize grain yield in the hedgerow and in the block arrangement with gmelina were respectively 37% (16.58 tons ha−1) and 68% (8.3 tons ha−1) lower than in monocropping (26.21 tons ha−1). In the plots with bagras, maize grain yield in hedgerow and in block arrangement were respectively 19% (24.8 tons ha−1) and 66% (10.4 tons ha−1) lower than in monocropping (30.6 tons ha−1). For both tree species, the diameter at breast height (dbh) was greater in hedgerow than in block arrangement, with the
difference being more pronounced with age. It was estimated that gmelina planted in hedgerows would produce 6–8 m3 ha−1 of merchantable volume more than if planted in block. The study verifies the hypothesis that intercropping between widely-spaced
trees rows (planted at 10 m or more) is more profitable and feasible to smallholders than either maize monocropping or woodlots,
and concludes with recommendations on how to further improve the productivity of tree-intercropping systems. 相似文献
20.
Jiaojun Zhu Kai Yang Qiaoling Yan Zugen Liu Lizhong Yu Hexin Wang 《Journal of Forest Research》2010,15(1):71-80
Thinning experiments were conducted in larch (Larix olgensis) plantations to assess the feasibility of converting even-aged plantation stands to uneven-aged forests with more complex
stand structures. Stands established in 1965 and 1960 were thinned in 2004 (Regime A, for determining the effect of recent
thinning on emergence of seedlings) and 1994 (Regime B, for examining the effects of the past thinning on establishments of
recruitments), respectively, at two intensities each. Natural regeneration, together with litter depth, canopy openness and
vegetation cover, was surveyed in the thinned plots. Results indicated that larch seedlings started to emerge in May, reached
a peak in June, decreased from June through September, and then disappeared in October. No larch seedlings exceeded 1 year
old in the thinned plots because of the low levels of light and dense litter and vegetation cover. However, there were many
naturally regenerated seedlings (5–50 cm in height) and saplings (50–500 cm in height) of broadleaved tree species such as
Acer spp., Fraxinus spp., Cornus controversa, Quercus mongolica, and even the climax tree species, Pinus koraiensis, in the thinned plots. The mean density of regenerated seedlings reached 6.7 and 4.5 stems m−2 in Regimes A and B, respectively, whilst the mean density of regenerated saplings reached 4,595 stems ha−1 in Regime B. These results suggest that it is impractical to turn even-aged larch plantations to uneven-aged larch forests,
but it may be feasible to develop uneven-aged larch-broadleaved forests from even-aged larch plantations through thinning. 相似文献