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1.
《Forest Ecology and Management》2001,140(1):39-50
Recent studies point to the promise of rain forest extraction for more sustainable rural development in Amazonia but often overlook important differences within traditional communities in terms of relative economic reliance upon specific forest resources. This paper reports on a study of charcoal production among forest peasants in an Amazonian river community, near Iquitos, Peru. In-depth household interviews (n=36) provided information on household economic activity, demographic composition, and access to land, labor and capital as well as on the nature, role and economic importance of charcoal in the household economy. Our results indicate that peasant charcoal production — often cast as a rapacious, wasteful use of the forest — can provide significant cash income for forest peoples and high returns per hectare, particularly when integrated into swidden-fallow agroforestry systems, without causing notable forest destruction. Low returns to labor, however, limit prospects for peasants to prosper by charcoal production. Variations in household output of charcoal are explained by differential access to intra- and extra-household labor. Among those households most reliant upon charcoal, two subgroups are found — ‘charcoal-dependent’ households and ‘charcoal-specialized’ households — both of which rely on charcoal production, but for different reasons and with distinct outcomes. These two sub-groups are divided by differences in non-market mediated access to local land and labor. Clearly, to be successful, initiatives aimed at promoting rain forest conservation and management among ‘resource-reliant’ households must be informed by careful attention to the underlying conditions that give rise to differential rain forest reliance. 相似文献
2.
Agroforestry is a new name for a rather old practice. From a historical point of view, various agroforestry systems existed in Europe, of which the wood pastures (Neolithicum), the Dehesas in Spain (~4,500 years old) and the Hauberg of the Siegerland (established in the Middle Age) are the most prominent. Other widespread systems in Europe were hedgerows, windbreaks and Streuobst (orchard intercropping). Due to mechanisation and intensification of agriculture, trees have been progressively removed from agricultural fields and traditional agroforestry systems slowly disappeared. Today, agroforestry systems are again increasing in interest as they offer the potential to solve important ecological and, especially, biodiversity problems, while at the same time enabling the production of food, wood products and fodder for cattle. Although agroforestry systems offer many advantages, many farmers are sceptical of these systems and are critical and risk-averse with regard to adopting new practices. However, in comparison to traditional systems, modern agroforestry systems can be adapted to current farming practices. By selecting suitable trees and appropriate tree management, high-quality timber can be produced without influencing agricultural crops excessively. In future, agroforestry systems will become increasingly important as they offer the prospect of producing woody perennials for bioenergy on the same land area as food and/or fodder plants, while enhancing overall biodiversity. 相似文献
3.
Biologically mediated soil processes rely on soil biota to provide vital ecosystem services in natural and managed ecosystems. However, land use changes continue to impact on assemblages of soil biota and the ecosystem services they provide. The objective of the present study was to assess the effect of land use intensification on the distribution and abundance of soil invertebrate communities in the Nilgiri, a human-dominated biosphere reserve of international importance. Soil invertebrates were sampled in 15 land use practices ranging from simple and intensively managed annual crop fields and monoculture tree plantations through less intensively managed agroforestry and pristine forest ecosystems. The lowest taxonomic richness was found in annual crops and coconut monoculture plantations, while the highest was in moist-deciduous and semi-evergreen forests. With 21 ant species, agroforestry systems had the highest diversity of ants followed by forest ecosystems (12 species). Earthworms and millipedes were significantly more abundant in agroforestry systems, plantations and forest ecosystems than in annual crop fields. Ants, termites, beetles, centipedes, crickets and spiders were more abundant in forest ecosystems than in other ecosystems. It is concluded that annual cropping systems have lower diversity and abundance of soil invertebrates than agroforestry and natural forest ecosystems. These results and the literature from other regions highlight the potential role that agroforestry practices can play in biodiversity conservation in an era of ever-increasing land use intensification and habitat loss. 相似文献
4.
This paper examines how agroforestry-based farming systems evolved in the Dhanusha district of Nepal following the conversion of forest into agriculture during the early 1950s. Some data are from two focus group discussions with agroforestry farmers and one meeting with agroforestry experts. The farmers?? discussion traced the development of farming practices from 1950 to 2010 to identify the drivers of land use change. The experts?? discussion resulted in a scale to differentiate the prevailing farming systems in the study area considering five key components of agroforestry: agricultural crops, livestock, forest tree crops, fruit tree crops and vegetable crops. Data related to the system components were collected from the randomly selected households. The study reveals that land use had generally changed from very simple agriculture to agroforestry, triggered by infrastructure development, technological innovations, institutional support (subsidies and buy-back guarantees) and extension programs. A range of farming systems with varying degrees of integration was evident in the study area: simple agriculture; less integrated agroforestry; semi-integrated agroforestry and highly integrated agroforestry. The three types of agroforestry systems, which are the focus of this study, varied significantly in terms of farm size, cropping intensity, use of farm inputs, tree species diversity, tree density, home to forest distance and agricultural labour force. 相似文献
5.
The role of different agroforestry systems in the conservation of plant diversity and forest structure has not been directly
compared in many agricultural dominated landscapes. In this study, we investigated tree diversity and forest structure in
a complex agroforestry landscape traditionally grown for cocoa and mixed food crops and compared these to the natural forest
in southeastern Ghana. The study was carried out using 36 25 m × 25 m plots. There was significant difference [95% Confidence
Interval (95% CI)] in the native forest/non-crop tree species richness between the natural forest and the agroforest farmlands
but species richness was similar between the cocoa and mixed food crops agroforests. The density of native forest/non-crop
trees was significantly higher (P < 0.05) in the natural forest but similar between cocoa and mixed food crops agroforest. Similarly, the basal area of native
forest/non-crop trees was significantly higher (P < 0.05) in the natural forest but comparable between cocoa and food crops agroforest. Of the 20 most abundant native forest/non-crop
trees recorded, 12 of them showed significant responses (P < 0.05) to land use change with nine of the species significantly abundant in the natural forest relative to the agroforest
systems. Eighteen native forest/non-crop trees species in the agroforestry systems were commonly recorded as being used; 100%
of them being used as fuel wood with 83.3 and 77.8%, respectively, used as medicines and materials. The findings of this study
suggests that although complex agroforestry systems are a poor substitute for the natural forest the heterogeneous mosaic
landscape in which complex agroforestry forms part can be strategically managed to maximize the benefits of both sustainable
agriculture production and conservation of plant diversity by acting as buffer between protected areas and intensively managed
areas. 相似文献
6.
Seasonal variation of soil respiration rates in a secondary forest and agroforestry systems 总被引：2，自引：0，他引：2
Kikang Bae Don Koo Lee Timothy J. Fahey Soo Young Woo Amos K. Quaye Yong-Kwon Lee 《Agroforestry Systems》2013,87(1):131-139
Agroforestry systems are widely practiced in tropical forests to recover degraded and deforested areas and also to balance the global carbon budget. However, our understanding of difference in soil respiration rates between agroforestry and natural forest systems is very limited. This study compared the seasonal variations in soil respiration rates in relation to fine root biomass, microbial biomass, and soil organic carbon between a secondary forest and two agroforestry systems dominated by Gmelina arborea and Dipterocarps in the Philippines during the dry and the wet seasons. The secondary forest had significantly higher (p < 0.05) soil respiration rate, fine root biomass and soil organic matter than the agroforestry systems in the dry season. However, in the wet season, soil respiration and soil organic matter in the G. arborea dominated agroforestry system were as high as in the secondary forest. Whereas soil respiration was generally higher in the wet than in the dry season, there were no differences in fine root biomass, microbial biomass and soil organic matter between the two seasons. Soil respiration rate correlated positively and significantly with fine root biomass, microbial biomass, and soil organic C in all three sites. The results of this study indicate, to some degree, that different land use management practices have different effects on fine root biomass, microbial biomass and soil organic C which may affect soil respiration as well. Therefore, when introducing agroforestry system, a proper choice of species and management techniques which are similar to natural forest is recommended. 相似文献
7.
Indigenous fruit trees of Madagascar: potential components of agroforestry systems to improve human nutrition and restore biological diversity 总被引：3，自引：0，他引：3
E. Styger J. E. M. Rakotoarimanana R. Rabevohitra E. C. M. Fernandes 《Agroforestry Systems》1999,46(3):289-310
Biodiversity in Eastern Madagascar is threatened by slash and burn agriculture, which is resulting in species extinction,
land and soil degradation and rural impoverishment. An ethnobotanical study was undertaken to determine the domestication
potential of indigenous fruit tree species as components of agroforestry systems. Four major selection criteria were used:
nutritional and income needs of the population, diversification of the agroecosystem, and protection of plant and animal diversity.
At three sites, Andasibe, Masoala and Ranomafana, in the humid primary forest region of Eastern Madagascar, a total of 150
wild fruit species from 82 genera and 42 families, of which 85% were indigenous and 92% of woody habit, were identified. In
contrast to most of the deforested areas in Madagascar, the rural population in these areas possess an intimate knowledge
of indigenous plant resources. Most of the indigenous fruits are collected from the forest but for a few species, domestication
is initiated by managing naturally established species or by planting individual trees in agricultural fields. Wild fruits
supplement the daily diet, substitute for exotic fruits, gain importance during periods of food shortage and are most appreciated
by children. Commercialization of wild fruits is mainly undertaken by the poorer section of the population. Gender related
differences in knowledge and preferences on species were identified and related to the respective household responsibilities.
A list of the 26 priority species was established based on the preferences of children, women and men at the three sites.
Local, fruit-eating lemur species are also highly dependent on indigenous fruit trees and are crucial for successful regeneration
of forest vegetation.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
8.
Diane Saint-Laurent Jean-Sébastien Berthelot Vernhar Gervais-Beaulac 《Agroforestry Systems》2018,92(6):1517-1534
A number of forests in agroforestry environments are at risk due to urban development or agricultural expansion. These forests often consist of patches of wooded areas scattered in the agricultural and urban grid, and often constitute green corridors that enable a flow between animal and plant species (migration corridors). This study evaluates the composition and structure of riparian forests in agroforestry areas that are subject to various natural and anthropogenic disturbances. This study aims to understand the dynamics of these riparian forest populations and evaluate the effects of the disturbances on the tree stands (e.g. floods, partial cutting), while taking into account their development over space and time based on a diachronic assessment from 1945 to 2010. Although these woodlands are subject to various disturbances, a fairly large diversity of tree species can be noted, and the regeneration of the saplings and small trees follows a normal growth curve (asymmetric) with a high contingency of young tree population comparable to a typical reverse-J distribution. However, lower densities are observed for riparian stands subject to frequent flooding, which could over time compromise recruitment and forest regeneration for some tree species (e.g. woody plants with weak adaptive strategies). The multivariate analyses (Redundancy Analysis and Canonical Correspondence Analysis) conducted over all the soil, environmental and forest data reveal that some variables are more strongly related to the composition of the forest populations, including pH, ground litter and soil drainage. However, these variables must still be considered as being part of a set of interacting soil conditions. Lastly, the future of these woodlands may appear uncertain because there are no government policies or measures to ensure their protection and preservation. 相似文献
9.
Traditional agroforestry systems and biodiversity conservation in Benin (West Africa) 总被引：1，自引：1，他引：0
Vodouhe G. Fifanou Coulibaly Ousmane Biaou Gauthier Sinsin Brice 《Agroforestry Systems》2011,82(1):1-13
In the past, the conservation of biodiversity has been mostly understood in terms of the management of protected areas and
natural forests, ignoring the possible role of farm areas and the ways through which rural communities have promoted biodiversity
in their subsistence agricultural production systems. The present study focused on the floristic diversity within traditional
agroforestry parkland systems around the Pendjari Biosphere Reserve in Benin and showed the diversity of tree species in the
area as well as socio-economic factors which affect the practice of this farming system. We used questionnaires and interviewed
a total of 118 households to collect data. Respondents were interviewed on their farms and during the interview; we inventoried
the number of tree on the farm and determined the farm size. Twenty-one tree species belonging to 14 botanical families were
recorded during the surveys and the average stand density of the woody component of farmlands was 7.97 ± 5.43 stems/ha. A
number of both native and exotic tree species occurred in the parkland agroforestry systems with dominance of indigenous tree
species. Species richness varied with the size of household where households with small land holding conserve more tree species
in their field than households with large land holdings. 64% of households surveyed were making deliberate efforts to plant
tree species on their farmlands. The most important reasons which determined household ambitions to conserve woody species
on farmland were tree products contribution to food and medicine. Results also showed that respondents who noticed that trees
were decreasing in the wild conserve more tree species on their farmlands. This research highlights the role of traditional
agroforestry practices to support tree species richness and provides evidence of the farms’ role as biodiversity reservoirs. 相似文献
10.
The role of disturbance in structuring vegetation is widely recognized; however, we are only beginning to understand the effects of multiple interacting disturbances on ecosystem recovery and development. Of particular interest is the impact of post-disturbance management interventions, particularly in light of the global controversy surrounding the effects of salvage logging on forest ecosystem recovery. Studies of salvage logging impacts have focused on the effects of post-disturbance salvage logging within the context of a single natural disturbance event. There have been no formal evaluations of how these effects may differ when followed in short sequence by a second, high severity natural disturbance. To evaluate the impact of this management practice within the context of multiple disturbances, we examined the structural and woody plant community responses of sub-boreal Pinus banksiana systems to a rapid sequence of disturbances. Specifically, we compared responses to Blowdown (B), Fire (F), Blowdown-Fire, and Blowdown-Salvage-Fire (BSF) and compared these to undisturbed control (C) stands. Comparisons between BF and BSF indicated that the primary effect of salvage logging was a decrease in the abundance of structural legacies, such as downed woody debris and snags. Both of these compound disturbance sequences (BF and BSF), resulted in similar woody plant communities, largely dominated by Populus tremuloides; however, there was greater homogeneity in community composition in salvage logged areas. Areas experiencing solely fire (F stands) were dominated by P. banksiana regeneration, and blowdown areas (B stands) were largely characterized by regeneration from shade tolerant conifer species. Our results suggest that salvage logging impacts on woody plant communities are diminished when followed by a second high severity disturbance; however, impacts on structural legacies persist. Provisions for the retention of snags, downed logs, and surviving trees as part of salvage logging operations will minimize these structural impacts and may allow for greater ecosystem recovery following these disturbance combinations. 相似文献
11.
Staline Kibet 《Forest Ecology and Management》2011,261(6):949-957
The Kenyan coastal forests make up one of the World 25 Biodiversity Hotspots. They consist of over 140 fragments (the majority with areas less than 0.5 km2) of the once extensive Zanzibar-Inhambane lowland moist forest. The over 60 known Mijikenda sacred Kaya forests and groves scattered along the coastal hinterland form the greater part of this ecosystem. The forests are of biological and cultural significance, and this has been recognized nationally and internationally, with some now listed as World Heritage Sites. The forests are protected by councils of Kaya elders who regulate use of their resources. Increasing human population and subsequent rise in demand for forest products and land for settlement has put a strain on these relic forests. Farm encroachment and extraction of forest products in different Kaya forests have affected the vegetation ecology at varying levels. This study investigated the spatial species distribution, association and regeneration potential of commonly utilized plants in one of these traditionally managed ecosystems. A modified nested plot method was used to collect data in the field.Using TWINSPAN multivariate, and indicator species analysis, two plant communities (Asteranthe and Bridelia) and an undifferentiated vegetation type were identified. Species association in Asteranthe consisted largely of forest dependant species, with a significant presence of woody climbers. It was comprised of two sub-communities namely Manilkara and Scorodophloeos. In contrast the second plant community, Bridelia, was dominated by light demanding species. It comprised one sub-community (Catunaregam) and a seral stage (Keetia). The species diversity and richness was higher in the Asteranthe community compared to Bridelia. Some of the forest species commonly utilized by the local people were observed to regenerate both in open and closed forest habitats while others had seedling recruitment confined to closed forest.Despite some coastal forests showing physiognomic similarity, detailed study shows intra-variation linked to topography, exposition, type and intensity of human perturbation both currently and in the distant past. Clearly, vegetation patterns of coastal forests of eastern Africa change at fairly short intervals.Recruitment of forest specialists is likely to decline if closed forests are opened up by farm encroachment, however their less specialized counterparts can pioneer in re-colonization of disturbed sites if conservation is strengthened. There is need to invigorate traditional management systems of forests with cultural significance by recognizing and giving increased legal mandates to the local custodians. 相似文献
12.
A general classification of agroforestry practice 总被引：1，自引：0，他引：1
Fergus L. Sinclair 《Agroforestry Systems》1999,46(2):161-180
Present classification schemes confuse agroforestry practices, where trees are intimately associated with agricultural components
at a field scale, with the whole farm and forest systems of which they form a part. In fact, it is common for farming systems
to involve the integration of several reasonably discrete agroforestry practices, on different types of land. The purpose
of a general classification is to identify different types of agroforestry and to group those that are similar, thereby facilitating
communication and the organized storage of information. A new scheme is proposed that uses the ‘practice’ rather than the
‘system’ as the unit of classification. This allows an efficient grouping of practices that have a similar underlying ecology
and prospects for management. A two stage definition of agroforestry is proposed that distinguishes an interdisciplinary approach
to land use from a set of integrated land use practices. Four levels of organization are recognized through analysis of the
role of trees in agricultural landscapes: the land use system, categories of land use within systems, discrete groups of components
(trees, crops, animals) managed together, and functionally connected groups of such discrete practices in time and space.
Precedents for this form of analysis are found in the literature and it conforms with generally accepted methods of systems
analysis. Classification of major types of agroforestry practice proceeds primarily according to the components involved and
the predominant usage of land. A secondary scheme further classifies these in terms of the arrangement, density and diversity
of the tree components involved.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
13.
In tropical regions where agricultural activities are limited, agroforestry is an alternative for both economic development and for the management and conservation of biodiversity. The potential role of different types of land use as reservoirs of dung beetle diversity in the wet tropical forest of the Pacific lowlands of Colombia is evaluated in three agroforestry systems that differ in canopy cover and the sowing density of Borojoa patinoi crops associated with timber forest. Although total species richness was similar among land use types, differences related to the decrease in the abundance and biomass of the species were remarkable, and reflected in turn by the diversity and structure of the guilds. The general pattern observed was one in which the structure of the dung beetle assemblage of B. patinoi growing below a diversified and permanent tree cover was similar to that of the primary and secondary forest. Beetle diversity in management systems with less tree cover or a high sowing density of B. patinoi was lower and very similar to that of abandoned agricultural fields. This suggests that B. patinoi agroforestry systems can be viewed as valuable instruments for biodiversity management and conservation in the wet tropical forests of the Pacific lowlands and not just as substitutes for forest, though we must be aware that structural changes in the beetle community may in turn affect the ecological processes regulated by these insects in the agrosystems under study. 相似文献
14.
Walmir Ribeiro de Carvalho Steel Silva Vasconcelos Osvaldo Ryohei Kato Carlos José Bispo Capela Débora Cristina Castellani 《Agroforestry Systems》2014,88(2):357-368
The current expansion of the oil palm (Elaeis guineensis Jacq.) in the Brazilian Amazon has mainly occurred within smallholder agricultural and degraded areas. Under the social and environmental scenarios associated with these areas, oil palm-based agroforestry systems represent a potentially sustainable method of expanding the crop. The capacity of such systems to store carbon (C) in the soil is an important ecosystem service that is currently not well understood. Here, we quantified the spatial variation of soil C stocks in young (2.5-year-old) oil palm-based agroforestry systems with contrasting species diversity (high vs. low); both systems were compared with a ~10-year-old forest regrowth site and a 9-year-old traditional agroforestry system. The oil palm-based agroforestry system consisted of series of double rows of oil palm and strips of various herbaceous, shrub, and tree species. The mean (±standard error) soil C stocks at 0–50 cm depth were significantly higher in the low (91.8 ± 3.1 Mg C ha?1) and high (87.6 ± 3.3 Mg C ha?1) species diversity oil palm-based agroforestry systems than in the forest regrowth (71.0 ± 2.4 Mg C ha?1) and traditional agroforestry (68.4 ± 4.9 Mg C ha?1) sites. In general, no clear spatial pattern of soil C stocks could be identified in the oil palm-based agroforestry systems. The significant difference in soil carbon between the oil palm area (under oil palm: 12.7 ± 2.3 Mg C ha?1 and between oil palm: 10.6 ± 0.5 Mg C ha?1) and the strip area (17.0 ± 1.4 Mg C ha?1) at 0–5 cm depth very likely reflects the high input of organic fertilizer in the strip area of the high species diversity oil palm-based agroforestry system treatment. Overall, our results indicate a high level of early net accumulation of soil C in the oil palm-based agroforestry systems (6.6–8.3 Mg C ha?1 year?1) that likely reflects the combination of fire-free land preparation, organic fertilization, and the input of plant residues from pruning and weeding. 相似文献
15.
E. Somarriba 《Agroforestry Systems》1992,19(3):233-240
Concepts used by various authors are analyzed in order to define agroforestry and discuss, in detail, some ambiguous terms often encountered (biological and economic interactions, time sequences, etc.). Only those concepts which differentiate agroforestry from other non-agroforestry forms of land use are retained as part of the definition, which is: agroforestry is a form of multiple cropping under which three fundamental conditions are met: 1) there e exist at least two plant species that interact biologically; 2) at least one of the plant species is a woody perennial; and 3) at least one of the plant species is managed for forage, annual or perennial crop production. 相似文献
16.
《Journal of Sustainable Forestry》2013,32(4):11-28
Abstract We present an initial assessment of a community forestry program in the Bethel Cooperative in Northern Guatemala, which is located within the Mayan Biosphere Reserve, part of the Man in the Biosphere Program. Implementing the polycyclic felling system, 20 forest plots will be harvested in succession, one every 20 years. Within the harvest areas and at control sites, permanent monitoring plots have been established to study tree growth and natural regeneration. An average incremental growth rate was determined to be 0.68 cm/yr and was independent of whether or not harvest occurred, but was not independent of the commercial classification of the trees. Size class structure revealed a mixed-aged stand for all commercial categories that was minimally impacted by harvest. Natural regeneration of saplings and small trees may be affected by harvest and could impose long-term limits on the production of marketable trees. However, current cutting practices, size class structure, and conservative estimates of tree growth indicate that consistent harvests can be sustained well into the future. Community income from and participation in forestry-related activities were significant. Finding new markets, enhancing the marketability of new species, and developing non-timber forest resource trade and related activities will be crucial for the success of this program. 相似文献
17.
Differences in transpiration between a forest and an agroforestry tree species in the Sudanian belt 总被引：1，自引：1，他引：0
Kohomlan G. Beranger Awessou Christophe Peugeot Alain Rocheteau Luc Seguis Frédéric C. Do Sylvie Galle Marie Bellanger Euloge Agbossou Josiane Seghieri 《Agroforestry Systems》2017,91(3):403-413
Average population growth in the African Sudanian belt is 3 % per year. This leads to a significant increase in cultivated areas at the expense of fallows and forests. For centuries, rural populations have been practicing agroforestry dominated by Vitellaria paradoxa parklands. We wanted to know whether agroforestry can improve local rainfall recycling as well as forest. We compared transpiration and its seasonal variations between Vitellaria paradoxa, the dominant species in fallows, and Isoberlinia doka, the dominant species in dry forests in the Sudanian belt. The fallow and dry forest we studied are located in northwestern Benin, where average annual rainfall is 1200 mm. Sap flow density (SFD) was measured by transient thermal dissipation, from which tree transpiration was deduced. Transpiration of five trees per species was estimated by taking into account the radial profile of SFD. The effect of the species and of the season on transpiration was tested with a generalized linear mixed model. Over the three-year study period, daily transpiration of the agroforestry trees, V. paradoxa (diameters 8–38 cm) ranged between 4.4 and 26.8 L day?1 while that of the forest trees, I. doka, (diameters 20–38 cm) ranged from 9.8 to 92.6 L day?1. Daily transpiration of V. paradoxa was significantly lower (15 %) in the dry season than in the rainy season, whereas daily transpiration by I. doka was significantly higher (13 %) in the dry season than in the rainy season. Our results indicate that the woody cover of agroforestry systems is less efficient in recycling local rainfall than forest cover, not only due to lower tree density but also to species composition. 相似文献
18.
19.
Effects of gaps on regeneration of woody plants: a meta-analysis 总被引：1，自引：0，他引：1
Forest gaps, openings in the canopy caused by death of one or more trees, have a profound effect on forest regeneration and drive the forest growth cycle. It is therefore necessary to understand the effects of forest gaps on regeneration for modern forest management. In order to provide a quantitative assessment of the effects of forest gaps on regen-eration of woody plants, we conducted this review of gap effects on woody plant regeneration on the basis of 527 observations from 42 indi-vidual papers, and reported the results of these data in a meta-analysis. Overall, densities of regenerated woody plants were significantly greater （359%） in forest gaps than on the closed-canopy forest floor. The regen-eration density in gaps of plantation forests was significantly greater （P＆lt;0.05） than that of natural forest because the regeneration in gaps of plan-tation forests was improved by both gap effects and experimental meas-ures. Similarly, in comparison to natural gaps, regeneration was better enhanced in artificial gaps. Regeneration density exhibited a significantly positive correlation with gap size, but a negative correlation with gap age because the gap size decreased with increasing gap age. Shade tolerance of woody plants affected regeneration density in gaps and understory. Average regeneration density of shade-tolerant species exhibited a sig-nificantly positive response to gaps but densities remained lower in total than those of intermediate and shade-intolerant species. Gap effects on regeneration decreased in response to increasing temperature and pre-cipitation because of the limiting effects of lower temperature and moisture on woody plant regeneration. In summary, forest gaps enhance woody plant regeneration, and the effects of gaps varied by forest type, gap characteristics, environmental factors and plant traits. The results of this meta-analysis are useful for better understanding the effects and roles of gaps on forest regeneration and forest management. 相似文献
20.
A mail survey was conducted to gain understanding of the agroforestry practices of non-industrial private forest landowners (NIPF) in Washington State, located in the north-western USA. Although NIPF owners control 1.5 million hectares of the state's commercial forestland base, their diversity of forestland uses, land management practices and objectives as land managers are not well understood. Past NIPF surveys and anecdotal information suggest agroforestry is a major use of NIPF lands. We defined agroforestry as a potentially sustainable land use practice combining the deliberate growing of woody perennials with agricultural crops and/or animals. Objectives of this study were to:
- determine the extent that agroforestry is used by Washington's NIPF owners,
- develop insight into NIPF owners' motivations for practicing agroforestry,
- describe the agroforestry practices within three distinct physiographic and agroecological zones in Washington, and
- determine the agroforestry information needs of NIPF owners.