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1.
Weeds in tropical agricultural systems can cause serious economic damage, and their control often requires the commitment of substantial resources in the way of labor, capital, or pesticides. Tropical shifting cultivation systems employ a fallow period to help overcome weed infestations in addition to improving soil productivity and reducing other pest populations. Short-term, intensive fallow systems that employ herbaceous and woody species to facilitate rapid restoration of soil productivity have evolved as an alternative to long-term fallows. Short-term fallows can impact weeds at all growth stages and play a role in the integrated management of weeds and crops. Fallow management that promotes vegetative soil cover may reduce weed recruitment due to attenuation of soil temperature and/or shift in light quality at the soil surface. Residues or litterfall from fallow species may alter the chemical and microbial ecology of the soil to favor losses from the weed seed bank due to germination, loss of seed vigor, or seed decay. In addition, fallow vegetation can influence weed seed predation. Enhancement of soil productivity should increase the vigor of crop growth and enable crops to better compete with weeds. The burning of fallow species residues may result in weed seed death due to extreme temperatures or may induce seed germination by the release of mechanical dormancy or chemical germination cues. Certain weeds may serve as improved fallow species due to their high nutrient scavenging efficiency in low-fertility environments and their ease of establishment. Short-term improved fallows can be an important component of integrated weed management, particularly by promoting the prevention and tolerance of weeds in crops.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
2.
Sovu Mulualem Tigabu Patrice Savadogo Per Christer Odén Lamphoune Xayvongsa 《Forest Ecology and Management》2009
Species composition, structure and diversity of secondary forests recovered on abandoned swidden cultivation fields in the lowland of Laos were studied in relation to distance from the natural forest, fallow age and crop-fallow rotation cycle. All woody species with stem diameter ≥1 cm were identified, counted and their diameter at breast height (1.3 m, dbh) measured on 290 plots in 162 swidden fallows. Distance from the forest edge related non-linearly and explained 46%, 54%, 63% and 52% of the variation in species richness, stem density, basal area and Simpson's index, respectively. The basal area of secondary forests increased significantly (p < 0.0001) while stem density tended to decrease (0.05 < p < 0.1) with increasing fallow age, whereas species richness and diversity measures remained insensitive. Species richness, stem density, basal area and Shannon-Wiener index were reduced by 28%, 35%, 72% and 23%, respectively while the number of bamboo clumps increased significantly by 45% as the crop-fallow rotation cycle increased from one to three. The occurrence of bamboo had a negative effect on most of the vegetation characteristics analyzed. From forest production and biodiversity conservation viewpoints, it is recommended that the natural regeneration in fallows with a history of previous severe land use intensity should be supplemented with enrichment planting irrespective of its distance from the natural forest. Although the management objectives for secondary forests on swidden fallows are not clearly set, promoting the development of bamboo forests in fallows would be one management option, given its importance in rural livelihood. 相似文献
3.
Jon D. Unruh 《Agroforestry Systems》1988,7(2):161-184
The ecological importance of fallowing to swidden (slash and burn) agriculture is well known. Cyclic agroforestry systems which emphasize utilization of the fallow cycle should, where appropriate, consider the ecologic processess of site recovery, so as not to impair the productivity of the subsequent swidden cycle. this artical discusses the ecologic ‘fit’ of a cyclic swidden-fallow management scheme into swidden cultivation and fallow succession. Such a fit suggests a reciprocally reinforcing situation between this agroforestry design and processes involved in site recovery. Observed among some indigenous and colonist inhabitants of the Peruvian Amazon, this system produces fallow crops and products, while enhancing site nutrient recovery. The economic benefits of this scheme have recently been reported (Denevan and Padoch, n.d.) while the ecologic attributes involved in promoting site recovery have not; primarily these include:
- Less destruction of the nutrient cycling root-mat in the swidden cycle, and its quicker re-formation in the fallow cycle.
- Discouraging the establishment of exotic, pantropical weeds and grasses such as imperata, while encouraging the colonization of local, early successional species.
- Encouraging the earlier establishment of woody plants in abandoned swiddens.
- A natural litterfall higher in nutrients than in unmanaged fallows.
- Additions of ‘slash’ litterfall higher in nutrient content than natural litterfall in the proximity of valuable managed plants.
- The increased capacity of the managed stand to scavenge limiting nutrients such as N and P from, and leach unneeded quantities of non-limiting nutrients such as K, Ca and Mg to, thoughfall.
- Increasing the alkalinity of throughfall, possibly resulting in less soil cation leaching in managed fallows.
- Staggering seed production, germination and maturation times of the rapid nutrient sycling softwood trees.
- Increasing the spontaneously occuring abundance of valuable fallow plants with management of successive fallow cycles, thereby possibly reducing the labor requirement, and increasing the value of this agroforestry scheme over time.
4.
The composition and pattern of weed flora in arable fields are determined by their seedbank structure; but the influence of
fallow management practices on weed seedbank structure is presently unknown. The objective of this study was to investigate
weed seedbank characteristics and weed population dynamics in arable fields in natural and planted-fallow systems. The study
plots were at Mbaise, a densely populated area of southeastern Nigeria, where farmers regenerate their exhausted soils by
maintaining planted fallows of Dactyladenia barteri (Hook. F. ex Oliv.) Prance & F. White, and at Umuahia, a less-densely populated area in the same region, where farmers depend
on natural bush fallow for soil regeneration. The effect of three years of fallow on the weed flora of arable fields in the
two fallow management systems differed remarkably. The first flush of weeds on fields that were cultivated after three years
of planted D. barteri fallow (Mbaise) consisted of 80% broadleaf weeds, 7% grass weeds and 13% sedges. On the other hand, the first flush of weeds
on the natural bush fallow fields (Umuahia) of the same fallow duration as the D. barteri fallow system consisted of 17% broadleaf weeds, 70% grasses and 13% sedges. Three years of planted fallow caused 36% decrease
in weed seedbank at Mbaise relative to the cropped field while the same duration of natural bush fallow caused a 31% increase
in weed seedbank at Umuahia. These results show that the planted D. barteri fallow system has a higher potential to reduce weed pressure in smallholder agriculture than the natural bush fallow system
and may explain in part why farmers in this humid forest zone have adopted the practice.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
5.
Chromolaena odorata, introduced to Laos in the 1930s, has become the most abundant weed and fallow species in slash-and-burn fields over a wide range of land use systems, elevation, and pH ranges. Regeneration from roots, high seed production and easy dispersal allow for the rapid colonization of fields in the initial fallow period. At rice harvest, after a 1-year and a 2-year fallow, the total aboverground biomass in monitoring plots was 1.4, 10, and 15.4 t ha–1, with 16, 48, and 29% contribution byC. odorata, respectively. With progressing fallow periodC. odorata is gradually replaced by tree and bamboo species. Slash-and-burn farmers preferredC. odorata over other fallow species common in their fields.Chromolaena odorata is an excellent fallow species considering its fast expansion after crop harvest, high biomass production, weed suppression, and fast decomposition rate. Some of these properties may, however, become a serious disadvantage when farmers gradually change to land use systems that integrate grazed fallow, crop rotation, and/or fruit and timber plantations. 相似文献
6.
在撒哈拉以南的非洲地区,黄独脚金寄生杂草（Strigahermonthica）侵扰是限制小农产自给性农业生产的主要因素之一。土壤肥力低加之总体环境退化是寄生杂草侵扰产生的重要原因。引入改良的耕作制度来解决寄生杂草侵扰和土壤肥力下降的问题势在必行。本文对肯尼亚西部双峰高原地区内,用豆科植物--印度田菁改良的休耕地对玉米产量和农田寄生杂草侵扰的作用进行了研究。实验处理分阶段进行,处理包括田菁改良6和18个月的休耕地、未经耕作自然植物再生6和18个月的休耕地、连续种植玉米未施肥的耕地和连续种植玉米同时施加氮和磷肥的耕地。结果表明,与未施肥玉米地相比,田菁改良休耕地明显（p〈0.5）增加玉米产量.除草管理降低了第一季度（428000±63000株·hm-2）、第二季度（51000±1500株·hm-2）玉米地寄生杂草植株种群。实验周期内,除草管理降低玉米地土壤中寄生杂草种子种群数。短期田菁改良休耕地对玉米产量的促进作用明显好于未施肥的玉米地,但是短期杂草休耕地对玉米产量无显著影响。种植玉米和除草控制寄生杂草效果要好于休耕。 相似文献
7.
Planted legume fallows reduce weeds and increase soil N and P contents but not upland rice yields 总被引：3，自引：1，他引：2
K. Saito B. Linquist D. E. Johnson S. Phengchanh T. Shiraiwa T. Horie 《Agroforestry Systems》2008,74(1):63-72
Shortened fallows have resulted in declining upland rice yields in slash-and-burn upland rice systems in northern Laos. We
studied the benefit of planted legume fallows for rice productivity, weeds, and soil nitrogen and phosphorus availability.
Four systems were evaluated over a 5-year period: 1-year fallow with native species, 1-year Cajanus cajan fallow, 1-year Leucaena leucocephala fallow, and continuous annual rice cropping. Rice was grown either once each year as continuous annual cropping or in alternate
years of 2001, 2003, and 2005. C. cajan and L. leucocephala were sown with rice during the 2001 growing season. In subsequent years, L. leucocephala regenerated from root stock and did not have to be resown, whereas C. cajan was resown in 2003. Establishment of either C. cajan or L. leucocephala had no significant effect on rice yield in 2001, and rice yields ranged from 2.0 to 2.3 t/ha. Rice yields declined rapidly
in succeeding years, and rice yields in the four systems ranged from 0.7 to 1.1 t/ha in 2003 and from 0.3 to 0.5 t/ha in 2005.
Although two planted fallow systems increased nitrogen input because of greater biomass accumulation in 2003 and 2005 and
soil phosphorus availability was higher following L. leucocephala fallow in 2005, there were no significant differences in rice yields among the four systems in either year. Weed biomass
during the rice growing season increased each year in all systems and increased more rapidly for continuous annual rice cropping,
in which the dominant weed species was Ageratum conyzoides L. Among the other three systems, there were no significant differences in the weed biomass in 2003 and 2005. We conclude
that C. cajan and L. leucocephala as 1-year fallows do not offset the negative effects of increased cropping intensity on rice yield in this region. 相似文献
8.
Prasit Wangpakapattanawong Nuttira Kavinchan Chawapich Vaidhayakarn Dietrich Schmidt-Vogt Stephen Elliott 《Forest Ecology and Management》2010
Rotational swidden cultivation systems, with fallow periods long enough for the regeneration of secondary forests are capable of maintaining forest cover and plant diversity in a dynamic balance in swidden cultivation landscapes. Regeneration of secondary forests through several successional stages and by a combination of coppicing and seedling development is still poorly understood, especially the influence of different swiddening practices and the role of animals as seed dispersers. Swidden cultivators possess a vast knowledge of plants growing in swidden fallows and of fallow dynamics as well. Forest restoration in Thailand has been carried out mainly on the basis of experimental research on the potential of indigenous tree species to promote natural forest regeneration and biodiversity recovery; the so-called framework species. Another viable source of knowledge for forest restoration can be the study of the semi-natural revegetation processes in fallows and the indigenous knowledge of swiddeners of these processes. The research presented here was carried out to attain a better understanding of forest regeneration on fallow swiddens under different swiddening regimes and how it may be applied to practical forest restoration, We investigated the vegetation characteristics of from various stages of secondary succession in fallow swiddens of the Karen and Lawa ethnic groups in the Mae Chaem watershed, Chiang Mai province, northern Thailand. Indigenous knowledge on the use of species and traditional ecological processes in swiddening was recorded by questioning key informants. The data were analyzed and discussed with respect to their application in forest restoration and participatory forest management. 相似文献
9.
Michael R. Dove 《Agroforestry Systems》1983,1(2):85-99
Swidden agriculture is today the focus of a great deal of debate in the context of agroforestry development in humid, tropical countries. This paper argues that much of this debate deals not with the empirical facts of swidden agriculture, however, but rather with widely-accepted myths, and that this explains the widespread failures of developmental schemes involving swidden agriculturalists. The paper examines three of these myths in some detail. One myth is that swidden agriculturalists own their land communally (or not at all), work it communally, and consume its yields communally. The truth is that their land (including land under secondary forest fallow) is typically owned by individual households, it is worked by individual household labor forces and/or by reciprocal but not communal work groups, and its yields are owned and consumed privately and individually by each household. A second myth is that swidden cultivation of forested land is destructive and wasteful, and in the worst cases results in barren, useless grassland successions. The truth is that swidden cultivation is a productive use of the forests, indeed more productive than commercial logging in terms of the size of the population supported, and forest-grassland successions are typically a function not of rapaciousness but of increasing population/land pressure and agricultural intensification — the grasses, including Imperata cylindrica, having value both as a fallow period soil-rebuilder and as cattle fodder. A third myth is that swidden agriculturalists have a totally subsistence economy, completely cut off from the rest of the world. The truth is that swidden agriculturalists, in addition to planting their subsistence food crops, typically plant market-oriented cash crops as well, and as a result they are actually more integrated into the world economy than many of the practitioners of more intensive forms of agriculture. In the conclusion to the paper, in a brief attempt to explain the genesis of these several myths, it is noted that they have generally facilitated the extension of external administration and exploitation into the territories of the swidden agriculturalists, and hence can perhaps best be explained as a reflection of the political economy of the greater societies in which they dwell. 相似文献
10.
对毛竹叶螨发生的竹林进行劈草和锄草抚育,通过1a观察发现,锄草的竹林中的毛竹叶螨的种群密度和危害高于劈草的竹林。建议竹林抚育要因地制宜,对杂灌不繁茂、土壤较疏松的竹林不劈草。对杂灌繁茂的竹林于8～9月份劈草,尽量不锄草。释放捕食螨防治毛竹叶螨结果表明,捕食螨防治效果留草竹林大于劈草竹林、大于锄草竹林,所以毛竹叶螨的防治要与竹林抚育管理相结合,竹林在释放捕食螨防治毛竹叶螨的当年林下要留草,禁止全垦全劈。 相似文献
11.
An experiment was carried out in a slash-and-burn production system in northern Laos to evaluate legume establishment methods
and effects of legume species on fallow vegetation, weeds, yield of upland rice, and soil parameters. Cajanus cajan, Calliandra
calothyrsus, Crotalaria anagyroides, Flemingia congesta, Leucaena leucocephala, and Sesbania sesban were dibbled separately
or mixed with rice. Legume and planting method had no effect on rice yield. Legume establishment was slightly improved and
vigor after rice harvest was higher when planted in separate hills. Compared to control (no legume), the above ground fallow
biomass observed 13 months after establishment, consisting mostly of Chromolaena odorata, was reduced by 68% with C. anagyroides
and by 40% with L. leucocephala, while other species had no effect. Most of the C. cajan and S. sesban plants died. In March
1995, 22 months after planting, the biomass was 0.21, 0.25, 1.62 and 2.56 kg m-2 for F. congesta, C. calothyrsus, C. anagyroides, and L. leucocephala, respectively. Legume species had no effect on rice
yield or weed biomass in the rice crop. The species tested can influence fallow vegetation but do not allow for field preparation
without burning. Compared to mulching, burning of residue reduced weed biomass by 42%, soil organic C by 9% and the C/N ratio
by 6% but increased extractable P by 90% and pH by 8%.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
12.
Advances in modelling and decision support systems for vegetation management in young forest plantations 总被引：1，自引：0，他引：1
The two most common forest vegetation management objectivesare to (1) minimize resource competition, and (2) to developmethods for managing specific weed species. This paper reviewsrelevant models and decision support systems for assisting inachieving these objectives. The aim of reducing resource competitionis to increase crop-tree growth and survival. Several modellingapproaches have been applied to this problem and these generallyestimate crop survival and growth benefits following some formof generalized weed control. Linkages with models of older treecrops are needed for comparing vegetation management strategiesin the context of complete silvicultural regimes. More refinedindividual tree models use competition indices to estimate thequantity of weed vegetation within the growing space aroundeach tree. The indices reflect resource use by the weeds andare sensitive to changes in weed growth over time and to theapplication of specific vegetation management treatments. Hybridand process-based models have the potential to provide moregeneralized models of inter-specific competition, but theirusefulness for forest practitioners has yet to be proven. Someforest vegetation management problems require a more detailedunderstanding of the biology and ecology of a specific species.In this case, different modelling approaches that consider overallweed population dynamics, distribution or spread may be appropriate. 相似文献
13.
Weed control may improve the growth of forest plantations by influencing soil water and nutrient availability, but our knowledge of leaf-level physiological responses to weed control at different within-canopy positions is limited for tropical and subtropical plantations. Foliar carbon (delta(13)C) and oxygen (delta(18)O) isotope compositions, gas exchange, and nitrogen (N(mass)) and phosphorus (P(mass)) concentrations at four canopy positions were assessed in a young spotted gum (Corymbia citriodora subsp. Variegata (F. Muell.) A.R. Bean & M.W. McDonald) plantation subjected to either weed control or no weed control treatment, to test if leaves at different positions within the tree canopy had the same physiological responses to the weed control treatment. Weed control increased foliar delta(13)C but lowered delta(18)O in the upper-outer and upper-inner canopy, indicating that weed control resulted in a higher foliar photosynthetic capacity at upper-canopy positions, a conclusion confirmed by gas exchange measurements. The increased photosynthetic capacity resulting from weed control can be explained by an increase in foliar N(mass). In the lower-outer canopy, weed control reduced foliar delta(13)C while lowering delta(18)O even more than in the upper-canopy, suggesting strong enhancement of the partial pressure of CO(2) in the leaf intercellular spaces and of foliar stomatal conductance in lower-canopy foliage. This conclusion was supported by gas exchange measurements. Foliar photosynthesis in the lower-inner canopy showed no significant response to weed control. The finding that leaves at different canopy positions differ in their physiological responses to weed control highlights the need to consider the canopy position effect when examining competition for soil nutrient and water resources between weeds and trees. 相似文献
14.
The effects of post-planting weed control intensity on the cover and composition of ground vegetation, and on growth, survival and foliar nutrient concentrations of 4-year old bare-rooted Scots pine (Pinus sylvestris L.) seedlings were studied over a 15-year period with experimentation on former arable land. Weed control treatments with terbuthylazine and glyphosate were carried out 1?C3 times during successive years, either as overall or as spot applications. The vegetation cover and the shading effect of vegetation decreased with increasing weed control intensity. The more intensive the weed control was, the better was the afforestation result in terms of tree seedling growth and survival. Overall application repeated three times increased seedling survival by 79 percentage points, and their final height, breast height, diameter, and stand volume after 15 years were increased by 183, 19, 15, and 822%, respectively. Weed control did not affect the foliage nutrient concentrations, except for magnesium. However, increase in weed control intensity was reflected in larger needle size 5 years after planting. 相似文献
15.
The adoption of planted fallow largely depends on the cost and feasibility of using the technology; easy, inexpensive and
simple fallow establishment methods are known to greatly enhance adoption. It was the objective of this study to assess the
effects of weeding regime on the establishment of Calliandra calothyrsus and Inga edulis on degraded acid soils in southern Cameroon. A combination of the two fallow species and two weeding regimes, weeding or
not weeding, were compared to a natural fallow. The trial was conducted in two sites of different base saturation levels with
four replications. The results indicate that differences between the two species and the two weeding regimes were statistically
significant (p 005) on both sites for all measured tree growth parameters, as well as the residual effects on subsequent maize grain yield.
Presence of weeds reduced stem diameter and height of C. calothyrsus and I. edulis at the early stage of their establishment. Weeding doubled the leaf biomass of both species. The highest woodmass was produced
by Inga in plots with weeding treatment, with 48 t/ha of dry material. Tree fallow improved the yield of succeeding crops by twofold
over the natural grass fallow. Weeding treatment improved maize yield, from 1.9t/ha to 2.8 t/ha after Calliandra fallow, and from 2.22 t/ha to 3.0 t/ha after Inga fallow. The significant effects of weeding treatments implies that fallow-improving tree species should be planted in relay
intercropping for trees to benefit from the weeding of crops, thus reducing the labour spent on fallow establishment.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
16.
17.
Charles Staver 《Agroforestry Systems》1989,8(2):173-196
In the Palcazu Valley alluvial Inceptisols are relay-cropped with maize-cassavaplantain in rotation with 2–5 years of tree
fallow. These lands, of limited extent, yet important for Yanesha Indian subsistence production, are being cropped even more
intensively as population increases and land is converted to other uses. The relay-planting of the tree-thicket combination
Inga edulis with Desmodium ovalifolium into the on-farm crop sequence was evaluated as a means to accelerate fallow recovery and thereby shorten fallow rotations.
Three experiments with Inga/Desmodium planted with cassava-plantain and one with rice under different weeding regimes after a Desmodium fallow were conducted. Inga and Desmodium were not chopped back or pruned during these experiments. Desmodium/Inga suppressed herbaceous weeds from one year after planting. Desmodium/Inga accumulated more woody biomass than natural fallows. Cassava yields were unaffected by the presence of Desmodium/Inga, while plantain yields were greater under Desmodium/Inga compared to natural weeds. Desmodium/Inga, while promising for shortening fallow rotations, demonstrated potential difficulties: increased labor for establishment,
tendency of Desmodium to weediness in later crop cycles, and suppression of the natural regeneration of trees and shrubs. 相似文献
18.
Striga hermonthica is a major constraint to smallholder subsistence agriculture production in the sub-Saharan African region. Low soil fertility
and overall environmental degradation has contributed to the build-up of the parasitic weed infestation. Improved cropping
systems have to be introduced to address the interrelated problems of S. hermonthica and soil fertility decline. Thus, the effects of improved fallow with leguminous shrub Sesbania sesban on maize yields and levels of S. hermonthica infestation on farm land in the bimodal highlands of western Kenya were investigated. The experimental treatments were arranged
in a phased entry, and randomized complete block scheme were six months Sesbania fallow, 18 months Sesbania fallow, six months natural fallow consisting of regrowth of natural vegetation without cultivation, 18 months natural fallow,
continuous maize cropping without fertilizer application, and continuous maize cropping with P and N fertilization. Results
show that Sesbania fallows significantly (p<0.05) increase maize yield relative to continuous unfertilized maize. S. hermonthica plant populations decrease in continuous maize between the first season (mean = 428 000 ± 63 000 ha−1) and second season (mean=51 000 ± 15 000 ha−1), presumably in response to good weed management. S. hermonthica seed populations in the soil decrease throughout the duration of the experiment in the continuous maize treatments. Short-duration
Sesbania fallows can provide modest yield improvements relative to continuous unfertilized maize, but short-duration weedy fallows
are ineffective. Continuous maize cultivation with good weed control may provide more effective S. hermonthica control than fallowing. 相似文献
19.
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
20.
《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