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1.

? Context

Copaifera species produce an oleoresin of commercial importance that is widely extracted in Amazon communities.

? Aims

This paper addresses two questions. (1) What are the morphological characteristics of Copaifera species that influence oleoresin production? (2) How do different Copaifera species respond to repeated harvests?

? Methods

We performed a large-scale experiment in the Brazilian Amazon. We tapped 110 Copaifera trees belonging to four species, and several morphological tree characteristics were measured to determine their effect on oleoresin production.

? Results

The proportion of Copaifera reticulata and Copaifera paupera trees that yielded more than 1 ml oleoresin was higher than the other species. The oleoresin volumes from yielding Copaifera pubiflora trees were significantly higher than those from C. reticulata and C. paupera, with Copaifera multijuga yielding intermediate values. Interestingly, none of the studied morphological tree characteristics had a significant effect on the proportion of yielding trees. Hollowed trees yielded significantly smaller volumes than non-hollowed trees. Both the proportion of yielding trees and oleoresin volumes decreased from the first to the second harvests for C. reticulata and C. paupera; however, the opposite pattern was observed for C. pubiflora.

? Conclusions

Oleoresin production capacity varies by species, and management protocols should account for these differences.  相似文献   

2.
The long-term success of forest management depends primarily on the sustainability of timber production. In this study we analyse the population structure, tree age and wood increment of Malouetia tamaquarina (Aubl.) (Apocynaceae) to define a species-specific minimum logging diameter (MLD) and felling cycle by modelling volume growth. Contrary to other timber species in the nutrient-rich white-water floodplains forests (várzea), M. tamaquarina grows in the subcanopy of old-growth várzea forests. The wood of this species is utilized by local inhabitants in the floodplains for handicraft. In 35 plots of 25 m × 50 m we measured diameter at breast height (DBH) and tree height of all trees taller than 150 cm height. From 37 individuals with DBH > 15 cm we sampled two cores by increment borers to determine the wood density, tree age and diameter increment rates. In the management area of a várzea settlement with about 150 ha recently harvested trees of M. tamaquarina have been recorded and DBH was measured. The species presents an inverse J-shaped diameter distribution indicating that the species is obviously regenerating in the old-growth forests. Tree-ring analysis indicates a mean age of 74.5 years for a DBH of 22.7 cm for a studied population comprising 37 trees with maximum ages of up to 141 years for an individual with a DBH of 45.7 cm. The tree species has low annual diameter increment rates (3.16 ± 0.6 mm) despite a low wood density (0.36 ± 0.05 g cm−3). The volume growth model indicates a MLD of 25 cm and a felling cycle of 32.4 years. In the management area 35 trees with a mean DBH of 24 cm were recorded, similar to the defined MLD. The abundance of trees above the MLD is 2.7 trees ha−1, or 405 trees, when extrapolated to the whole management area. Considering a felling cycle of 32.4 years (annual production unit of 4.63 ha) this results in total of 12.5 harvestable trees, almost three times less than actually harvested. The actual practice of harvesting M. tamaquarina risks the overexploitation of this slow-growing species.  相似文献   

3.
Tropical forests are characterized by diverse assemblages of plant and animal species compared to temperate forests. Corollary to this general rule is that most tree species, whether valued for timber or not, occur at low densities (<1 adult tree ha−1) or may be locally rare. In the Brazilian Amazon, many of the most highly valued timber species occur at extremely low densities yet are intensively harvested with little regard for impacts on population structures and dynamics. These include big-leaf mahogany (Swietenia macrophylla), ipê (Tabebuia serratifolia and Tabebuia impetiginosa), jatobá (Hymenaea courbaril), and freijó cinza (Cordia goeldiana). Brazilian forest regulations prohibit harvests of species that meet the legal definition of rare – fewer than three trees per 100 ha – but treat all species populations exceeding this density threshold equally. In this paper we simulate logging impacts on a group of timber species occurring at low densities that are widely distributed across eastern and southern Amazonia, based on field data collected at four research sites since 1997, asking: under current Brazilian forest legislation, what are the prospects for second harvests on 30-year cutting cycles given observed population structures, growth, and mortality rates? Ecologically ‘rare’ species constitute majorities in commercial species assemblages in all but one of the seven large-scale inventories we analyzed from sites spanning the Amazon (range 49–100% of total commercial species). Although densities of only six of 37 study species populations met the Brazilian legal definition of a rare species, timber stocks of five of the six timber species declined substantially at all sites between first and second harvests in simulations based on legally allowable harvest intensities. Reducing species-level harvest intensity by increasing minimum felling diameters or increasing seed tree retention levels improved prospects for second harvests of those populations with a relatively high proportion of submerchantable stems, but did not dramatically improve projections for populations with relatively flat diameter distributions. We argue that restrictions on logging very low-density timber tree populations, such as the current Brazilian standard, provide inadequate minimum protection for vulnerable species. Population declines, even if reduced-impact logging (RIL) is eventually adopted uniformly, can be anticipated for a large pool of high-value timber species unless harvest intensities are adapted to timber species population ecology, and silvicultural treatments are adopted to remedy poor natural stocking in logged stands.  相似文献   

4.
Boreal species that are dependent on old forests, such as many cavity-using birds and mammals, are at high risk from conventional harvest practices. These species may benefit from ecologically sustainable forest management practices that increase heterogeneity within stands and across landscapes. Structural retention within cutblocks and spatial aggregation of cutblocks into large (1000s ha) harvest units are two such management practices being implemented by forestry companies in the boreal plains of Alberta and Saskatchewan. However, little is known about the implications of these practices for old forest species. The goal of our study was to determine if the cavity-using assemblage associated with old upland forest in this region is retained within aggregated harvests with structural retention. We used a cavity web approach to describe and contrast interactions among cavity excavators (woodpeckers, chickadees, and nuthatches) and the secondary (i.e. non-excavating) species reusing their cavities. We described the cavity web for two intact landscapes of old upland forest and for two aggregated harvest landscapes. We identified four key excavators of intact forest: yellow-bellied sapsucker (Sphyrapicus varius), hairy woodpecker (Picoides villosus), northern flicker (Colaptes auratus), and pileated woodpecker (Dryocopus pileatus). These woodpeckers should be considered key excavators primarily of mature and old aspen forest, which dominated the study landscapes. Each woodpecker filled a unique role in the cavity web and all are important for conservation of two mammal and three bird species that used their cavities. In the short term (i.e. within four years post-harvest), the key cavity excavators and many secondary cavity-using species associated with intact forest were retained in the harvested landscapes. One secondary species (American kestrel (Falco sparverius)) was unique in the harvest cavity web. Compared to the intact cavity web, the harvest web had lower abundance of sapsuckers, greater abundance of flickers, and high reuse of flicker cavities by kestrels. These differences were associated with the shift from intact forest to a landscape characterized by patches of old forest surrounded by early-successional habitat. Abundances of hairy and pileated woodpeckers were too low to detect differences between intact and harvested landscapes. The key excavators primarily used trembling aspen (Populus tremuloides) for cavity trees and thus aspen should be targeted for retention in harvested landscapes. A more detailed examination of the habitat requirements of the key excavators is needed to develop best practices for tree and patch retention and ensure conservation of the cavity-using assemblage in aggregated harvests.  相似文献   

5.
We monitored the decomposition of mixed leaf litter (Quercus spp., Carya spp., and Pinusechinata) in a Missouri Ozark forest eight years after experimental harvest. Leaf litter mass losses and changes in carbon chemistry (extractive, acid soluble, and acid insoluble fractions) were measured over 32 months in field incubations to determine the effects of litter composition and stand manipulation on decomposition and nitrogen (N) concentration in the remaining litter. The decay (k) rate over this period ranged between 0.39 (±0.010) and 0.51 (±0.002) year−1 for oak, oak–hickory, and oak–pine litter. There were significant main effects of stand manipulation (p = 0.03) and litter type (p < 0.01) on decay. Mass losses of oak and oak–hickory litter were 7% (p = 0.02) and 4% (p = 0.04) higher on harvested stands than controls, respectively. Mass loss of oak–hickory litter was 3% faster than oak–pine (p = 0.03) and 6% faster than oak (p = 0.02) litter on control stands, whereas the oak–hickory litter mass loss was 5% higher than oak litter on harvested stands (p = 0.01). The decay (k) rate had a linear relationship with initial leaf litter nitrogen content and lignin-to-N ratio. The nitrogen concentration in remaining litter had a nonlinear relationship to cumulative mass loss suggesting an exogenous source of N. In summary, this study demonstrated significant effects of timber harvest and litter mixtures on decomposition and N dynamics in a managed Missouri Ozark forest.  相似文献   

6.
Lianas are often overlooked in temperate ecological studies even though they are important components of forest communities. While lianas have been shown to damage tropical canopy trees and reduce the growth of juvenile trees, the impact of lianas on canopy tree growth in temperate systems is largely unknown. Growth of trees ≥8 cm dbh was examined over a 9-year period within 50-year old post-agricultural secondary forests in the Piedmont region of New Jersey, USA. Five lianas, Celastrus orbiculatus, Lonicera japonica, Parthenocissus quinquefolia, Toxicodendron radicans, and Vitis species, occurred throughout the forest. Total liana basal area, number of stems, and percent cover within host trees were evaluated to assess liana burdens on 606 previously censused trees. These data were related to tree growth to assess liana impacts. Forest trees were separated based on their dominance in the canopy to determine whether lianas had the potential to influence forest composition. In general, lianas in the forests were fairly abundant, with 68% of the trees having at least one liana present. On average, each tree supported 9.7 cm2 of liana basal area and 23% of the canopy was covered by lianas. Most of the variation in tree growth was related to the dominance of trees within the canopy, with canopy dominant and co-dominant trees growing 2.5× more than suppressed trees. Liana basal area and number of lianas stems were not related to tree growth, but liana canopy cover decreased tree growth. However, not all trees were equally affected as canopy cover of lianas only reduced growth in dominant and co-dominant trees. Lianas were most influential on host tree growth in unsuppressed trees when occupying a majority of the canopy, only a minority of forest trees. This suppression was not related to differential liana colonization of canopy trees as all canopy classes supported equivalent liana burdens. Though lianas impacted only a minority of the trees in this system, some liana species, C. orbiculatus and Vitis spp., are still increasing and may pose future risks to forest growth and development.  相似文献   

7.
Agave cupreata is harvested from tropical dry forests, oak forests, and other habitats by rural communities in the Chilapa region of Guerrero, Mexico to make mescal, a traditional and culturally important liquor. Local management systems use various techniques to regulate Agave harvest and encourage regeneration, including the exclusion of cattle. This study examines the impacts of cattle exclusion and of the different habitat types on the population structure and density of A. cupreata. Sampling was conducted in pastures, oak forest, tropical dry forest, and mixed oak-tropical dry forest using 54 transects of 1000 m2, where Agave was counted by size-class and measurements were taken of the vegetation and physical environment. Transects were divided between areas with cattle present and cattle excluded in all four habitats except for oak forest, where all areas were open to cattle. Agave density per 1000 m2 was highest in pasture (148 ± 5, mean ± SE), followed by oak forest (100 ± 4), tropical dry forest (88 ± 5) and mixed oak-dry forest (81 ± 2). The size-class structures of Agave populations were also significantly different between vegetation types, with oak forest supporting higher seedling densities but lower numbers of juveniles. A regression subset selection algorithm showed that one of the most important factors influencing Agave populations was the presence of cattle, which can reduce densities by trampling and grazing on seedlings and floral stalks. Cattle presence significantly lowered Agave densities in the smaller size classes in all vegetation types but did not significantly alter size-class structure. Total Agave density per 1000 m2 was significantly higher in transects where cattle were absent (148 ± 4) than where cattle were present (81 ± 1). In all areas sampled, the high number of juveniles relative to other size-classes suggests that Agave populations are successfully regenerating in the Chilapa region, and the higher Agave densities in fenced areas suggest that local management techniques are effectively increasing Agave yields. These results highlight the potential for sustainable management of Agave to conserve forest habitats while also providing important income from mescal to local communities in the region.  相似文献   

8.
Wild pistachio (Pistacia atlantica Desf.) is the most economically important tree species in many rural areas in the west of Iran. The species produces resin used for a wide variety of traditional uses. Because the resin can be harvested non-destructively, the trees are maintained until mortality occurs from natural causes. The result is that natural, managed stands include a variety of age classes. In recent years, a lack of smaller size classes has been observed in the Qalajeh forest, which is located in the Zagros Mountain region of western Iran. We established a series of plots in an area typical of Qalajeh forest to characterize the diameter distribution of the wild pistachio component. We confirmed a deficit of stems <30 cm dbh, based in the expectation that the landscape-level diameter distribution should be characterized by a negative exponential curve. For trees ≥30 cm dbh, de Liocourt's equation closely fit the diameter distribution (r2 = 0.93), translating to a q-factor of 1.34. We used this curve to estimate the deficit number of stems in diameter classes <30 cm. We estimate that this forest should have 19–24 wild pistachio trees/ha in the 5–25 cm classes, as compared to about 5 trees/ha found currently. Based on local conditions, we recommend that at least 30 seedlings/ha should be planted to allow 6–8 trees to reach to the 5 cm class.  相似文献   

9.
It has long been established that mature forests are mosaics of patches in different development phases but it has seldom explicitly been taken into account in ecological studies. We demonstrate here that these development phases, which are related to the population dynamics of trees, play an important role in the distribution of fauna based on observations on frugivorous birds. In an area close to the Calakmul Biosphere Reserve in Mexico, we studied the abundance of large forest bird species in relation to forest development phases, with a methodology that seems promising for ecological diagnosis and prognosis in forest management planning. Fine-scale forest mapping and bird counts were carried out in two block-transects of 40 m × 3000 m. Tree sampling in a sub-transect was used to generate population characteristics of trees. Large bird species preferred mature or senescent forest patches, whereas relatively young, growing forest patches were avoided. Important large tree species such as Manilkara zapota, Thouinia paucidentata, Guaiacum sanctum and Esenbeckia pentaphylla, characteristic of older forest patches, showed skewed size distributions indicating stress or overexploitation. The population of M. zapota, a key fruiting species that accounted for 26.5% of the total woody biomass, was most heavily affected by stress. A future collapse in the population of M. zapota, a decrease of the total area of older forest, and a decline in the abundance of large birds is likely if stress on the system continues at this level.  相似文献   

10.
We compared avian communities among three timber harvesting treatments in 45-m wide even-age riparian management zones (RMZs) placed between upland clearcuts and along one side of first- or second-order streams in northern Minnesota, USA. The RMZs had three treatments: (1) unharvested, (2) intermediate residual basal area (RBA) (targeted goal 11.5 m2/ha, realized 16.0 m2/ha), and (3) low RBA (targeted goal 5.7 m2/ha, realized 8.7 m2/ha). Surveys were conducted one year pre-harvest and three consecutive years post-harvest. There was no change in species richness, diversity, or total abundance associated with harvest but there were shifts in the types of birds within the community. In particular, White-throated Sparrows (Zonotrichia albicollis) and Chestnut-sided Warblers (Dendroica pensylvanica) increased while Ovenbirds (Seiurus aurocapilla) and Red-eyed Vireos (Vireo olivaceus) decreased. The decline of avian species associated with mature forest in the partially harvested treatments relative to controls indicates that maintaining an unharvested RMZ adjacent to an upland harvest may aid in maintaining avian species associated mature forest in Minnesota for at least three years post-harvest. However, our observations do not reflect reproductive success, which is an area for future research.  相似文献   

11.
Information on roosting requirements and responses to forest management is integral to effectively conserve and manage bat populations. Tree hollows are especially important for roosting bats given the long time taken for hollows to form. We used radiotelemetry to compare roost site selection in two species, Vespadelus regulus and Nyctophilus gouldi, in logged jarrah forests of south-western Australia. We compared characteristics of roost trees and forest structure around roost trees (n = 48) with randomly located plots at a local roost tree level (n = 90) in February and March 2009. For landscape features, we compared roost trees with randomly selected trees in the broader landscape that had cavities or exfoliating bark (n = 204). V. regulus roosted solely in hollows that were located predominantly in contemporarily unlogged buffers and mature forest while N. gouldi used a broader range of roost types, located in contemporarily unlogged buffers and mature forest and in retained habitat trees in gap release and shelterwood creation silvicultural treatments. In contrast with N. gouldi, which selected hollows or crevices under bark near the ground and close to vegetation, V. regulus used hollows that were high above ground and had little surrounding vegetation. Both species preferred large trees, in intermediate or advanced stages of decay and crown senescence. Bats changed roosts frequently, with short distances between subsequent roosts, suggesting a degree of spatial fidelity. Contemporarily unlogged buffers and mature forest contained higher densities of trees with hollows than gap release and shelterwood creation areas, potentially providing more alternate bat roosts. Our results demonstrate the importance of mature forest and unlogged buffers as bat roost sites in logged jarrah forests of south-western Australia, but the area of old forest required by these and co-occurring bat species remains to be determined.  相似文献   

12.
The aim was to study the potential for using natural regeneration as a basis for transformation of simply structured conifer plantations into mixed Mediterranean forests. We studied the variation along a rainfall gradient, in the natural regeneration of tree species in the understory of planted 40- to 50-year-old Aleppo pine (Pinus halepensis) forests. The study was conducted within the Mediterranean zone of Israel, which extends from the semiarid northern Negev desert (rainfall ca. 300 mm yr−1) in the south to the humid Upper Galilee in the north (ca 900 mm yr−1). Cover and height, density, and species composition of regenerating trees were measured on south- and north-facing slopes in forest sites of comparable silvicultural history (site preparation methodology, planting density and thinning regime) distributed along the rainfall gradient. Altogether, 12 species of regenerating native broadleaved trees were found in the understory of the various forest sites. Surface cover, density and species richness increased linearly along the entire rainfall gradient, on both north- and south-facing slopes, ranging from zero in the driest forest sites up to 85% cover, 7980 trees ha−1 and 4.5 species per 200 m2, respectively, in the most humid ones. Species composition of regenerating trees was also related to rainfall amount, through changes in the relative importance of species along the rainfall gradient. The effect of topographic aspect on tree regeneration was inconsistent, i.e., the interaction Rainfall × Aspect was significant. Nevertheless, the general trend showed better regeneration on north-facing slopes. Most of the regenerating trees in the understory were small, i.e., less than 100 cm in height, with no clear effect of rainfall amount and topographic aspect on the relative abundance of height classes. Regeneration by Aleppo pine was highly variable among and within the different forest sites and ranged from 0 to 1565 trees ha−1, with no clear relationships with rainfall amount and topographic aspect. In light of our results we propose that the future structure of forests should vary with respect to annual rainfall amount within possible silvicultural scenarios.  相似文献   

13.
A high incidence of Diplodia shoot blight (site means ranging 85-100%) was observed on recently planted red pine (Pinus resinosa) seedlings where mature red pine stands previously had been clearcut. An investigation of the potential of harvest debris as a source of inoculum of Diplodia pathogens then was conducted. Cones, bark, needles, stems from shoots bearing needles, and stems from shoots not bearing needles (both suspended above the soil and in soil contact) were collected from harvest debris left at sites where clearcutting occurred. Conidia were quantified, and their germination rate was assessed, and Diplodia species were identified using PCR. Conidia of Diplodia species were found at all study sites and conidia counts increased from samples collected from 6 to 18 months after harvest. Germinable conidia were obtained from debris collected 6 months to 5 years after harvest. Fewer conidia were obtained from debris collected at intervals of up to 4-5 years after harvest and the percentage of germinable conidia was lower after longer intervals following harvest. More conidia were obtained and a greater percentage germinated from debris collected above the soil than from debris in soil contact. The host substrate also influenced the number of conidia and the percentage that germinated. Planting red pine seedlings next to debris infested with Diplodia pathogens could provide a persistent source of inoculum. Results should prompt further consideration by land managers and researchers of the potential forest health risks, in addition to benefits, that may be associated with harvest debris.  相似文献   

14.
Leaves of the long-lived Dioon merolae have been harvested intensively for decades (possibly for centuries) for ceremonial purposes by Zoque and mestizo groups inhabiting the Central Depression of Chiapas, Mexico. Over a period of four years, we evaluated vital rates (stem growth, leaf production, reproductive performance, and survival) and projected population growth rates in three populations (250 plants each, divided into eight size classes: new germinants, seedlings, saplings (S1, S2), and adults, A1-A4) with different leaf harvesting histories: non-defoliated by humans for at least 55 years (or very old harvest), defoliated annually until 15 years ago (recovering from harvest), and defoliated annually for at least the past 25 years (currently being harvested intensely). Population structure was affected by leaf harvest history. Stem growth was negatively affected by the annual harvest of leaves in size classes from seedlings up to A4 (ANOVA, P < 0.003); fewer leaves were produced by seedlings, saplings and adults at the annually harvested site (ANOVA, P < 0.027). Survival was high at all sites across all size classes; in the annually harvested site, A4 plants showed a decrease in survival (one dead out of four plants). Sex ratio of adults that produced cones during the four years of study was 61% males to 39% females. At the non-defoliated site, adult classes A2 and A4 produced >80% of the cones; no cones were produced by the A3 and A4 adult size classes at the annually harvested site. Asymptotic estimates of population growth indicated growing populations (λ ≥ 1); the highest mean values of finite population growth rate were obtained in the non-harvested site (λ = 1.0202). Elasticity analysis with population projection matrices indicated that stasis (L, 9-38%) was the component that most contributed to λ, followed by growth (G, 1.2-2.9%), and fecundity (F, 0.2-1.1%). We observed detrimental effects on several vital rates due to continued long-term defoliation, although population growth parameters do not currently suggest a decreased trend as a result of the annual harvest of leaves. The duration of this study of a very long-lived plant species suggests caution when setting levels and frequency of leaf harvest. The results help pinpoint practical recommendations that could be implemented in a sustainable management plan for this species, particularly to increase seed production in the annually harvested site, and recruitment of new germinants and seedlings at all sites. However, sound practices will need to consider the interests of involved stakeholders (landowners, pilgrims, conservation organizations and authorities) to effectively reduce anthropogenic pressure on this endangered species.  相似文献   

15.
There is limited understanding of the carbon (C) storage capacity and overall ecological structure of old-growth forests of western Montana, leaving little ability to evaluate the role of old-growth forests in regional C cycles and ecosystem level C storage capacity. To investigate the difference in C storage between equivalent stands of contrasting age classes and management histories, we surveyed paired old-growth and second growth western larch (Larix occidentalis Nutt)–Douglas-fir (Pseudostuga menziesii var. glauca) stands in northwestern Montana. The specific objectives of this study were to: (1) estimate ecosystem C of old-growth and second growth western larch stands; (2) compare C storage of paired old-growth–second growth stands; and (3) assess differences in ecosystem function and structure between the two age classes, specifically measuring C associated with mineral soil, forest floor, coarse woody debris (CWD), understory, and overstory, as well as overall structure of vegetation. Stands were surveyed using a modified USFS FIA protocol, focusing on ecological components related to soil, forest floor, and overstory C. All downed wood, forest floor, and soil samples were then analyzed for total C and total nitrogen (N). Total ecosystem C in the old-growth forests was significantly greater than that in second growth forests, storing over 3 times the C. Average total mineral soil C was not significantly different in second growth stands compared to old-growth stands; however, total C of the forest floor was significantly greater in old-growth (23.8 Mg ha−1) compared to second growth stands (4.9 Mg ha−1). Overstory and coarse root biomass held the greatest differences in ecosystem C between the two stand types (old-growth, second growth), with nearly 7 times more C in old-growth trees than trees found on second growth stands (144.2 Mg ha−1 vs. 23.8 Mg ha−1). Total CWD on old-growth stands accounted for almost 19 times more C than CWD found in second growth stands. Soil bulk density was also significantly higher on second growth stands some 30+ years after harvest, demonstrating long-term impacts of harvest on soil. Results suggest ecological components specific to old-growth western larch forests, such as coarse root biomass, large amounts of CWD, and a thick forest floor layer are important contributors to long-term C storage within these ecosystems. This, combined with functional implications of contrasts in C distribution and dynamics, suggest that old-growth western larch/Douglas-fir forests are both functionally and structurally distinctive from their second growth counterparts.  相似文献   

16.
The efficiency with which trees convert photosynthetically active radiation (PAR) to biomass has been shown to be consistent within stands of an individual species, which is useful for estimating biomass production and carbon accumulation. However, radiation use efficiency (?) has rarely been measured in mixed-species forests, and it is unclear how species diversity may affect the consistency of ?, particularly across environmental gradients. We compared aboveground net primary productivity (ANPP), intercepted photosynthetically active solar radiation (IPAR), and radiation use efficiency (? = ANPP/IPAR) between a mixed deciduous forest and a 50-year-old white pine (Pinus strobus L.) plantation in the southern Appalachian Mountains. Average ANPP was similar in the deciduous forest (11.5 Mg ha−1 y−1) and pine plantation (10.2 Mg ha−1 y−1), while ? was significantly greater in the deciduous forest (1.25 g MJ−1) than in the white pine plantation (0.63 g MJ−1). Our results demonstrate that late-secondary hardwood forests can attain similar ANPP as mature P. strobus plantations in the southern Appalachians, despite substantially less annual IPAR and mineral-nitrogen availability, suggesting greater resource-use efficiency and potential for long-term carbon accumulation in biomass. Along a 260 m elevation gradient within each forest there was not significant variation in ?. Radiation use efficiency may be stable for specific forest types across a range of environmental conditions in the southern Appalachian Mountains, and thus useful for generating estimates of ANPP at the scale of individual watersheds.  相似文献   

17.
We studied the carbon density and accumulation in trees at five sites in a tropical dry forest (TDF) to address the questions: how is the TDF structured in terms of tree and carbon density in different DBH (diameter at breast height) classes? What are the levels of carbon density and accumulation in the woody species of TDF? Is the vegetation carbon density evenly distributed across the forest? Does carbon stored in the soil reflect the pattern of aboveground vegetation carbon density? Which species in the forest have a high potential for carbon accumulation? The WSG among species ranged from 0.39 to 0.78 g cm−3. Our study indicated that most of the carbon resides in the old-growth (high DBH) trees; 88-97% carbon occurred in individuals ?19.1 cm DBH, and therefore extra care is required to protect such trees in the dry forest. Acacia catechu, Buchanania lanzan, Hardwickia binata, Shorea robusta and Terminalia tomentosa accounted for more than 10 t ha−1 carbon density, warranting extra efforts for their protection. Species also differed in their capacity to accumulate carbon indicating variable suitability for afforestation. Annually, the forest accumulated 5.3 t-C ha−1 yr−1 on the most productive, wettest Hathinala site to 0.05 t-C ha−1 yr−1 on the least productive, driest Kotwa site. This study indicated a marked patchy distribution of carbon density (151 t-C ha−1 on the Hathinala site to 15.6 t-C ha−1 on the Kotwa site); the maximum value was more than nine times the minimum value. These findings suggest that there is a substantial scope to increase the carbon density and accumulation in this forest through management strategies focused on the protection, from deforestation and fire, of the high carbon density sites and the old-growth trees, and increasing the stocking density of the forest by planting species with high potential for carbon accumulation.  相似文献   

18.
As part of an assessment of sustainability for the strip clear-cutting system (or Palcazú Forest Management System), we determined whether commercial tree species regenerating in two strips (30 m × 150 m) clear-cut in the Peruvian Amazon in 1989 would reach commercial size (≥30 cm diameter at breast height (dbh)) 40 years after the initial cutting, the expected harvesting cycle. We projected the growth of six common commercial species (Eschweilera bracteosa, Guarea cinnamomea, Micropholis guyanensis, Pouteria guianensis, Qualea paraensis, and Cedrelinga catenaeformis) and two pioneer species (Alchornea triplinervia and Miconia phaeophylla) using bootstrapping techniques (the Lieberman model), based on 2-year diameter increments (2004–2006) and mortality rates obtained from 1630 trees growing in secondary forest sites including the regenerating strips. These demographic data were further used to project the growth of all trees ≥6.5 cm dbh of commercial (sawnwood value) species from each strip, and from a deferment-cut treatment applied to half of one of the strips. Three models were used for growth projections: (1) using all diameter increments to simulate average growing conditions, (2) using diameter increments of trees exposed to high light to simulate growing conditions under intensive forest management with low mortality rates and (3) using diameter increments of the fastest growing individuals. Roundwood volume was calculated using allometric equations for emergent, canopy, and subcanopy species.  相似文献   

19.
Allometric equations have been developed for various different vegetation types but have rarely been validated in the field and never for dry tropical forest such as caatinga. In three areas of semi-arid Brazil, with regenerating caatinga vegetation, we measured and weighed twelve hundred individuals of four tree species and used the data to validate equations previously determined in mature caatinga. They and several other equations developed for tropical vegetations overestimate the biomass (B) of trees from the regeneration areas by more than 20%, possibly because these trees have reduced crowns, with lower branch masses. We then determined new allometric equations for them, validating equations for one site against data of the others and pooling the data if they were cross-validated. The best equations were power ones, based on diameter at breast height (D), with little improvement by including height, crown area and/or wood density (Caesalpinia pyramidalis, B = 0.3129D1.8838; Croton sonderianus, B = 0.4171D1.5601; Mimosa ophthalmocentra, B = 0.4369D1.8493; and Mimosa tenuiflora, B = 0.3344D1.9648 and 0.4138D1.7718).  相似文献   

20.
We examined the regeneration and structure of mixed conifer forests under single-tree harvest management in western Bhutan. Sixteen 900 m2 (30 m × 30 m) plots were sampled at four Forest Management Units (FMUs; Chamgang, Gidakom, Paro-Zonglela, and Haa-East) representing the forest type, including half the plots in single-tree harvest stands and half in unlogged stands. In addition, we solicited information on traditional forest management practices from informants using survey questionnaires and collected tree species data from felling records from respective local forest offices. Rural timber demand is concentrated on the removal of straight and well-formed bluepine trees for beams, planks, and scaffolding. Single-tree harvest, however, has not significantly altered stand structures from unlogged stands. Similarly, tree regeneration is not different when comparing single-tree harvest and unlogged stands, except at Chamgang FMU, where seedling densities were generally higher in harvested stands than in unlogged stands. These results indicate that single-tree harvest is not detrimental to regeneration and utilization of mixed conifer forests in western Bhutan.  相似文献   

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