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1.
Health status of trees was studied in five types of native spruce forests in the Pechora-Ilych Nature Biosphere Reserve. The
study has shown that trees in the old-growth bilberry-spruce and fern-shamrock-spruce forests can be characterized as “healthy”,
with damage index varying from 0.03 to 0.5. The haircap-moss spruce forest with damage index 0.7 is categorized as a “weakened
stand”. Regeneration was pronounced in all forest types. Young growth (1500 to 4300 stems/ha) is mainly composed of conifers
and is classified as “healthy”. 相似文献
2.
Masahiro Ichikawa 《Ecological Research》2007,22(3):403-413
Swidden agriculture, commercial logging and plantation development have been considered to be the primary common causes of
degradation and loss of tropical rain forests in Southeast Asia. In this paper, I chose a part of northeastern Sarawak, East
Malaysia as my case study area to analyze the changes in its land-use characteristics. In the study area, as well as primeval
forests, we see that land use began about 100 years ago by a native group called the Iban; commercial logging began in the
1960s, and the development of oil palm plantations began recently. I describe the changes in land use as well as their social
and economic causes by referring to aerial photographs, literature surveys, interviews with government officers and the Iban,
and observation of land use. My analysis of land use demonstrates that on “state land”, where commercial logging and oil palm
plantation development are occurring, large areas of forest have been disturbed in a short period of time. The objective is
to benefit economically in response to the social and economic conditions surrounding the study area. On the other hand, in
the “Iban territory,” where the Iban practice their land use, land conversion has not occurred on a large scale and in a short
period of time, even though the forest has been cut and agricultural fields have been created in response to social and economic
conditions as well. They disperse small agricultural fields throughout their forest land. Therefore, the landscape of the
“Iban territory” is based on secondary forest, composed of patches of forest in various stages and with several types of agricultural
land. Today in Sarawak, monocrop plantations are rapidly expanding and little primeval forest remains. Given these conditions,
the land-use practices of natives such as the Iban will be evaluated from the viewpoint of ecosystem and biodiversity conservation.
It could play an important role in providing habitats for natural wildlife. 相似文献
3.
Dynamics of fine roots in five Chinese temperate forests 总被引:1,自引:0,他引:1
Xiankuai Quan Chuankuan Wang Quanzhi Zhang Xingchang Wang Yiqi Luo Ben Bond-Lamberty 《Journal of plant research》2010,123(4):497-507
We used a minirhizotron method to investigate spatial and temporal dynamics of fine roots (diameter ≤2 mm) in five Chinese
temperate forests: Mongolian oak forest, aspen-birch forest, hardwood forest, Korean pine plantation and Dahurian larch plantation.
Fine root dynamics were significantly influenced by forest type, soil layer, and sampling time. The grand mean values varied
from 1.99 to 3.21 mm cm−2 (root length per minirhizotron viewing area) for the fine root standing crop; from 6.7 to 11.6 μm cm−2 day−1 for the production; and from 3.2 to 6.1 μm cm−2 day−1 for the mortality. All forests had a similar seasonal “sinusoidal” pattern of standing crop, and a “unimodal” pattern of
production. However, the seasonal dynamics of the mortality were largely unsynchronized with those of the production. The
minimum values of standing crop, production and mortality occurred in March for all forests, whereas the maximum values and
occurrence time differed among forest types. The standing crop, production and mortality tended to decrease with soil depth.
The different spatiotemporal patterns of fine roots among the forests highlight the need for forest-specific measurements
and modeling of fine root dynamics and forest carbon allocation. 相似文献
4.
The conservation of Himalayan forests is big concern in view of global agenda. Many studies in this endeavor reported that
the rate of forests degradation is posing a severe threat to the landscape and existing biodiversity in the Himalayas. Currently
there many conservation approaches exists and of them four are widely recognized (1) Conservation through traditional religious
beliefs “traditional conserved forests” (TCF); (2) Conservation through governmental planning and schemes “government conserved
forests” (GCF); (3) Conservation through creation of protected areas (PAF); and (4) Conservation through community efforts
“community conserved forests” (CCF). Our hypothesis in this direction says that all the conservation approaches lead to same
results concerning to forest conservation. To testify our hypothesis we have studied the forests of each conservation regimes
and evaluated them based on the identified indicators. We have done empirical studies and following the cloud-free satellite
data were used for last three decades (such as Multi-Spectral Scanner, Linear Imaging and Self Scanning, and Enhanced Thematic
Mapper ) to study a change in vegetation dynamics of the mountain forests in multi-temporal dimension. Our research concluded
that community conservation approach have greater significance for biodiversity conservation and management in the Himalayan
region. Here we support the model of CCF for forest ecosystem conservation, alongside the sustainable livelihood of the mountain
societies. But every conservation regimes has its own importance in viewpoint of the particular objectives. Therefore, we
suggests advancement and revision of PAF and GCF however, some elements of CCF can be introduced in TCF for making up it more
sound in view of rapid socio-economic and cultural changes taking place in the communities.
An erratum to this article can be found at 相似文献
5.
Ana Hernando Rosario Tejera Javier Velázquez María Victoria Núñez 《Biodiversity and Conservation》2010,19(8):2221-2233
The main goal of Natura 2000 network is to guarantee the favourable conservation status of habitats and species ensuring European
biodiversity. As a result, certain forest areas have been included in this network listed as 9230-Quercus pyrenaica habitat
and 9340-Quercus ilex subsp. rotundifolia forest habitat. These areas were previously used for firewood extraction or livestock
grazing and browsing. Nowadays these habitats are coppice forests with asexual regeneration, which is far from the desired
conservation status. Traditional timber harvesting plans do not take account of the new objectives required for these Natura
sites, which attempt to ensure biodiversity and recreational uses instead of simply focusing on timber production. This paper
proposes a flexible methodology (applied to the study area “Dehesa Boyal” in ávila, Spain) for managing Natura 2000 forest
sites by stands for sustainable forest management and the new requirements. The methodology has two phases. The first, “Division
of the forest area into stands”, defines homogeneous patches of vegetation distinct in species composition, physiognomic structure
and future management. The second, “Conservation status assessment of stands”, quantifies the conservation status of each
previously classified stand considering a series of factors such as: functional health, restoration, floral richness and structure.
A total value integrating the conservation status of stands is then calculated for the habitat. Both phases use Geographic
Information System tools for managing information and visualizing results. The proposed methodology provides forest managers
with a good knowledge of the territory and subsequently enables them to take appropriate conservation measures to maintain
biodiversity. 相似文献
6.
Decomposition of soil organic matter from boreal black spruce forest: environmental and chemical controls 总被引:1,自引:0,他引:1
Black spruce forests are a dominant covertype in the boreal forest region, and they inhabit landscapes that span a wide range
of hydrologic and thermal conditions. These forests often have large stores of soil organic carbon. Recent increases in temperature
at northern latitudes may be stimulating decomposition rates of this soil carbon. It is unclear, however, how changes in environmental
conditions influence decomposition in these systems, and if substrate controls of decomposition vary with hydrologic and thermal
regime. We addressed these issues by investigating the effects of temperature, moisture, and organic matter chemical characteristics
on decomposition of fibric soil horizons from three black spruce forest sites. The sites varied in drainage and permafrost,
and included a “Well Drained” site where permafrost was absent, and “Moderately well Drained” and “Poorly Drained” sites where
permafrost was present at about 0.5 m depth. Samples collected from each site were incubated at five different moisture contents
(2, 25, 50, 75, and 100% saturation) and two different temperatures (10°C and 20°C) in a full factorial design for two months.
Organic matter chemistry was analyzed using pyrolysis gas chromatography-mass spectrometry prior to incubation, and after
incubation on soils held at 20°C, 50% saturation. Mean cumulative mineralization, normalized to initial carbon content, ranged
from 0.2% to 4.7%, and was dependent on temperature, moisture, and site. The effect of temperature on mineralization was significantly
influenced by moisture content, as mineralization was greatest at 20°C and 50–75% saturation. While the relative effects of
temperature and moisture were similar for all soils, mineralization rates were significantly greater for samples from the
“Well Drained” site compared to the other sites. Variations in the relative abundances of polysaccharide-derivatives and compounds
of undetermined source (such as toluene, phenol, 4-methyl phenol, and several unidentifiable compounds) could account for
approximately 44% of the variation in mineralization across all sites under ideal temperature and moisture conditions. Based
on our results, changes in temperature and moisture likely have similar, additive effects on in situ soil organic matter (SOM)
decomposition across a wide range of black spruce forest systems, while variations in SOM chemistry can lead to significant
differences in decomposition rates within and among forest sites. 相似文献
7.
Pedro Beja Carlos David Santos Joana Santana Maria João Pereira J. Tiago Marques Hélder Lima Queiroz Jorge M. Palmeirim 《Biodiversity and Conservation》2010,19(1):129-152
We examined seasonal patterns of spatial variation in understory bird assemblages across a mosaic of upland and floodplain
forests in central Amazonia, where variation in flooding patterns and floodwater nutrient load shapes a marked spatial heterogeneity
in forest structure and composition. Despite great differences in productivity due to flooding by either nutrient-rich “white
waters” (várzea) or nutrient-poor “black waters” (igapó), bird assemblages in the two floodplain forest types were relatively
similar, showing lower abundances than adjacent upland forests (terra firme) and sharing a set of species that were absent
or scarce elsewhere. Species that breed in pensile nests overhanging water were abundant in floodplain forests, whereas species
that feed on the ground were generally scarce. Flooding affected assemblage dynamics in floodplain forests, with some influx
of ground-dwelling species such as ant-following birds from adjacent upland during the low-water season, and the occupation
by riverine and aquatic species such as kingfishers during floods. Spatial configuration influenced the seasonal pattern of
assemblage structuring, with movements from terra firme occurring primarily to adjacent igapó forests. No such influx was
detected in várzea forests that were farther from terra firme and isolated by wide river channels. Results support the view
that habitat heterogeneity created by flooding strongly contributes to maintain diverse vertebrate assemblages in Amazonia
forest landscapes, even in the case of largely sedentary species such as understory forest birds. Including both upland and
floodplain forests in Amazonia reserves may thus be essential to preserve bird diversity at the landscape scale. 相似文献
8.
Peter Veen Josef Fanta Ivan Raev Iovu-Adrian Biriş Jacques de Smidt Bert Maes 《Biodiversity and Conservation》2010,19(6):1805-1819
Despite extensive forest destruction in the Middle Ages and later intensive commercial forest management, remnants of virgin
forests remained spared in some Central, Eastern and South-Eastern European countries. These virgin forests are the last examples
of original forests in this part of Europe. That is why their protection becomes an important issue of current European forestry
and nature protection policy. But the knowledge about the location and the area of virgin forests in these countries is incomplete
up till now. This article has the prime goal to present a conceptual framework what virgin forests might be (“A conceptual framework for defining of virgin forests” section). Based on this framework, a working methodology has been tested in Bulgaria and Romania (“Results of the two national projects in Romania and in Bulgaria” section and further). For this reason two projects have been carried out by the Royal Dutch Society of Nature Conservation
(KNNV) in close co-operation with the Forestry Institutes in Romania and in Bulgaria. The results of these projects are described
in general terms and further analysis in the future is necessary to describe specific features like forest structure and spatial
heterogeneity of these forests. Based on the results of the inventory, principles of sustainable protection and management
of the mapped virgin forests were defined and described in the research reports. The usefulness of the inventory became evident
already during the EU pre-accession period of both countries while preparing the NATURA 2000 network. The remaining virgin
forests of temperate Europe are an inexhaustible source of ecological information about biodiversity, structure, natural processes
and overall functioning of undisturbed forest ecosystems. Their research will reveal information which can be used for ecological
restoration of man-made forests which are degraded through intensive forestry practices over the last centuries. The last
virgin forests of temperate Europe represent an irreplaceable part of the natural capital of Europe and are worth to be protected
by law. Their last remnants in South-Eastern and Eastern Europe are endangered by commercial activities. A full inventory
of remaining virgin forests in all countries of temperate Europe is a matter of highest urgency. A representative selection
of virgin forest sites should be declared by UNESCO as World Heritage Sites. 相似文献
9.
Octavio Miramontes Og DeSouza Diego Hernández Eliane Ceccon 《Human ecology: an interdisciplinary journal》2012,40(2):167-174
We measured mobility patterns that describe walking trajectories of individual Me’Phaa peasants searching for and collecting
fuel wood in the forests of “La Monta?a de Guerrero” in Mexico. These 1-day excursions typically follow a mixed pattern of
nearly-constant steps when individuals displace from their homes towards potential collecting sites and a mixed pattern of
steps of different lengths when actually searching for fallen wood in the forest. Displacements in the searching phase seem
not to be compatible with Lévy flights described by power-laws with optimal scaling exponents. These findings, however, can
be interpreted in the light of deterministic searching on heavily degraded landscapes where the interaction of the individuals
with their fuel wood-scarce environment produces alternative searching strategies than the expected Lévy flights. These results
have important implications for future management and restoration of degraded forests and the improvement of the ecological
services they may provide to their inhabitants. 相似文献
10.
Edges resulting from forest clear-cutting and treefall gaps can affect plant populations and consequently the distribution
of species across landscapes. These two types of disturbance might interact to exacerbate or ameliorate “edge effects”, a
rarely tested possibility. We focused on the effects of distance from forest edge (0–10, 30–40, 60–70, and 190–200 m) and
habitat within forest fragments (treefall gaps and intact forest) on the early stages of development of Palicourea gibbosa and Faramea affinis, two common shrubs of montane forests in southwest Colombia. Seed germination and seedling growth did not change with distance
from forest edge. Within forest fragments, however, seed germination and seedling growth were higher in treefall gaps than
in intact forest understory for both species. In contrast, seed predation was influenced by distance from forest edge and
in P gibbosa it depended on habitat. Seed predation was highest in the forest interior (190–200 m from forest edge) and in P. gibbosa this was true only in treefall gap habitats. These results suggest that animal mediated processes such as post-dispersal
seed predation are more likely than physiological processes to be affected by anthropogenic edges. Our results provide some
evidence that treefall gaps may interact with “edge effects”, however, they are inconclusive as to whether they exacerbate
or ameliorate them.
Received: 31 August 1998 / Accepted: 18 February 1999 相似文献
11.
Yves Laumonier Yumiko Uryu Michael Stüwe Arif Budiman Budi Setiabudi Oki Hadian 《Biodiversity and Conservation》2010,19(4):1153-1174
Biogeographical studies are a necessary step in establishing conservation area networks. Determining the ecological factors
influencing vegetation is also a basic principle for hierarchical ecological classifications and a necessary prerequisite
for ecosystem-based land use planning. Eco-floristic sectors (EFS) have already been identified for the Indonesian island
of Sumatra, combining both approaches, dividing it into 38 EFSs representing unique ecosystems in terms of tree flora and
environment (Laumonier 1997). The impact of deforestation on individual EFSs has been highly varied and in some cases extreme. We assigned one of five
‘extinction risk categories’ to each EFS based on the percentage of forest lost between 1985 and 2007. Eighty-five percent
of all forest loss (10.2 million ha) occurred in the eastern peneplain, western lowland regions and swamps. In 2007, only
29% of forests were protected by conservation areas, only nine of the 38 EFS had more than 50% of their remaining forest cover
protected. 38% of remaining forest was “critically endangered”, “endangered” or “vulnerable” EFSs (5 million ha) but only
1 million ha (20%) were protected. Sumatra’s existing network of conservation areas does not adequately represent the island’s
ecosystems. Priorities for a new conservation area network can be formulated for integration into Sumatra’s new land use plans
at provincial and district level. Decision makers can now use EFSs to locate new conservation areas so they represent and
maintain the whole range of the island’s diversity. 相似文献
12.
Biotas from all ecosystems need to respond to factors that determine habitat suitability. These factors originate from different
scales. Effects can be assumed to be hierarchical in the order large-scale geographic > regional > local > small-scale in-habitat
factors. We aimed at the identification of general patterns by comparisons between ecosystems (forest floor snails, hololimnic
stream macroinvertebrates) and across scales, and include potential seasonal effects. Sampling sites displayed signs of naturalness,
such as high levels of deadwood accumulation in the forests, or a lack of artificial stream bed fixation plus a “good” to
“high” score for the assemblage-derived Multimetric Index (MMI) in the streams. Terrestrial and aquatic assemblages of non-emergent
taxa fluctuated independent of seasonal effects. They differed in their relative correlation with environmental matrices with
quasi-concentric effects in forests, and longitudinal effects in streams. Large-scale factors, namely geographic position,
strongly influenced assemblage turnover, but the effect is based on a high covariation between geographic position and environmental
factors. We thus extracted variables that best explained species turnover after correcting for spatio-temporal effects. The
terrestrial community assembling was habitat-based and mainly responded to soil acidification, distance to disturbances, and
regional scale deforestation and deciduous/mixed forest cover. The stream assemblages were structured by regional pasture
cover, organic pollution, regional deciduous forest cover and microlithal cover. Apparently, community assembly occurs along
with changes in regional forest cover and the transport of nutrients and matter that can originate from a distance, irrespective
of ecosystem and assumed “naturalness”. 相似文献
13.
Local Management of Mangrove Forests in the Philippines: Successful Conservation or Efficient Resource Exploitation? 总被引:1,自引:1,他引:1
Bradley B. Walters 《Human ecology: an interdisciplinary journal》2004,32(2):177-195
Recent environmental narratives suggest that local people are effective stewards of forest resources. Local restoration and management of mangrove forests, in particular, are now widely advocated as a solution to achieve both economic and environmental conservation goals. This paper presents findings from a study of 2 coastal sites in the Philippines that are renowned and often showcased as success stories in community-based, mangrove reforestation and management. These cases are especially intriguing because local tree planting and management emerged in both areas long before governments and nongovernment organizations began to promote such activities. These management systems are a successful economic innovation in that planted mangroves protect homes and fish pond dykes from wave and wind damage, and the production of high-value construction wood is dramatically enhanced through intensive plantation management. Mangrove plantations are an efficient alternative to harvesting from unplanted, natural mangroves and their spread may reduce harvesting pressures on existing forests. However, mangrove plantations are structurally and compositionaly very different from unplanted forests, a finding of particular concern given that such plantations are increasingly encroaching into and replacing natural forests. Furthermore, planted forests are not typically viewed by planters in terms of their environmental conservation values and are frequently cut and cleared to make space for alternative uses, especially fish farming and residential settlement. The suggestion that these local mangrove management systems are successful for conservation thus needs to be qualified. 相似文献
14.
J. Wilson White 《Theoretical Ecology》2011,4(3):357-370
All else being equal, inversely density-dependent (IDD) mortality destabilizes population dynamics. However, stability has
not been investigated for cases in which multiple types of density dependence act simultaneously. To determine whether IDD
mortality can destabilize populations that are otherwise regulated by directly density-dependent (DDD) mortality, I used scale
transition approximations to model populations with IDD mortality at smaller “aggregation” scales and DDD mortality at larger
“landscape” scales, a pattern observed in some reef fish and insect populations. I evaluated dynamic stability for a range
of demographic parameter values, including the degree of compensation in DDD mortality and the degree of spatial aggregation,
which together determine the relative importance of DDD and IDD processes. When aggregation-scale survival was a monotonically
increasing function of density (a “dilution” effect), dynamics were stable except for extremely high levels of aggregation
combined with either undercompensatory landscape-scale density dependence or certain values of adult fecundity. When aggregation-scale
survival was a unimodal function of density (representing both “dilution” and predator “detection” effects), instability occurred
with lower levels of aggregation and also depended on the values of fecundity, survivorship, detection effect, and DDD compensation
parameters. These results suggest that only in extreme circumstances will IDD mortality destabilize dynamics when DDD mortality
is also present, so IDD processes may not affect the stability of many populations in which they are observed. Model results
were evaluated in the context of reef fish, but a similar framework may be appropriate for a diverse range of species that
experience opposing patterns of density dependence across spatial scales. 相似文献
15.
Nuthatches (Sitta europaea: Aves) in forest fragments: demography of a patchy population 总被引:1,自引:0,他引:1
Erik Matthysen 《Oecologia》1999,119(4):501-509
Breeding density, local survival and summer recruitment of nuthatches were evaluated in a population scattered over many
small (1–30 ha) forest fragments, and compared with study plots inside larger forests. Since most young birds settle outside
the fragment in which they were born this population corresponds to the “patchy population” concept implying that patterns
in abundance may be better explained by processes at the population level than by metapopulation processes. Mean breeding
density was c. 50% lower in fragments and decreased with regional isolation (distance from larger forests) but not with local isolation
(distance to nearby fragments). Local survival of adults and established (i.e. territorial) 1st-year birds was not related
to forest size or isolation. However, fewer young birds settled in summer in the fragments compared with a large forest. This
difference probably reflects high mortality during the sensitive dispersal phase. Moreover, the observed number of recruits
and their estimated survival was insufficient to maintain the breeding population, suggesting significant net immigration
from larger forests. This “rescue effect” explains why densities are affected by regional, but not local isolation.
Received: 14 December 1998 / Accepted: 1 March 1999 相似文献
16.
17.
The effect of fire on nutrients in a pine forest soil 总被引:7,自引:0,他引:7
The effect of a hot summer fire on soil nutrient contents in the upper 2 cm of Aleppo pine forest with a dense woody understory
was studied from September 1985 to May 1986.
In comparison with the adjacent unburned forest, total nitrogen decreased by 25% but available forms of nitrogen were much
higher. In burned and unburned soils there was a similar trend to increase and decrease in NH
4
+
−N, However, while (NO
2
−
+NO
3
−
−N decreased in the unburned soil it rose rapidly in the burned ash soil. Total phosphorus increased by 300% after the fire
but decreased again 2 months later. Also water-soluble P increased up to November and then decreased to the levels of the
unburned soils. The same was true for electrical conductivity and pH, increasing immediately after the fire and then leveling
off again.
This increase in nutrient levels in the “ash soil” was reflected in the striking increase in shoot and root biomass and in
the content of N, P, Mg, K, Ca, Zn and Fe in wheat and clover plants grown in pots in these soils. These nutrient levels were
much higher in the wheat plants, which also produced 12 times more seeds in the “ash soil.”
It seems that fire in these pine forests causes a short-term flush of the mineral elements in the upper “ash soil” layer which
is reverted gradually via the herbaceous post-fire to the ecosystem. 相似文献
18.
Forestry is obliged to record as well as maintain and/or enhance biological diversity in forests due to national and international
agreements. Accordingly, it is necessary to work out methodological approaches for the assessment of biodiversity in forests.
In the study presented here, we focus on the total plant species pool (563 vascular plant and bryophyte species) of pine (Pinus sylvestris L.) forests in NE Germany to identify indicators for plant species richness. We distinguished several groups like “herb”,
“grass-like”, “woody”, “endangered”, and “exotic species”, for which we detected indicators for low (class #1), intermediate
(class #2), and high (class #3) species numbers. From a total of 84 species, which were identified by a three-step procedure,
most indicators were found for class #3. Only few indicators have been revealed for intermediate species numbers, i.e. class
#2. With help of Ellenberg’s ecological indicator values and information on the main occurrence in Central European vegetation
types and plant communities, respectively, we characterized the indicator species ecologically. The ecological site preferences
of the indicator species in general reflect the fact that species richness is highest in base-rich, light, and anthropogenically
disturbed pine forests. On the contrary, species-poor forests were revealed by indicators, which mainly occur on acidic sites.
It is concluded that a considerable set of indicators for species richness can help facilitate biodiversity assessments in
forestry and ecosystem restoration practice.
Electronic Supplementary Material The online version of this article (doi: ) contains supplementary material, which is available to authorized users. 相似文献
19.
F. Casas F. Mougeot I. Sánchez-Barbudo J. A. Dávila J. Vi?uela 《Biological invasions》2012,14(2):295-305
Hybridization is a widespread phenomenon, which plays crucial roles in the speciation of living beings. However, unnatural
mixing of historically isolated taxa due to human-related activities has increased in recent decades, favouring levels of
hybridization and introgression that can have important implications for conservation. The wild red-legged partridge (Alectoris rufa, Phasianidae) populations have recently declined and the releases of farm-reared partridges have become a widespread management
strategy. The native range of the red-legged is limited to the south-west of Europe (from Italy to Portugal). This species
does not breed in sympatry with the chukar partridge (A. chukar), whose range is Eurasian (from Turkey to China). However, red-legged partridges have often been hybridized with chukar partridges
to increase the productivity of farmed birds, and game releases may have spread hybrid birds into the wild. In this study,
we investigated the fitness (survival and breeding) differences between hybrid and “pure” red-legged partridges in a wild
population located in central Spain. Incubation probability was similar in hybrids and “pure” partridges. Hybrid females laid
larger clutches than “pure” ones, but hatching success did not differ between hybrid and “pure” partridges. Hybrid birds had
lower survival rate than “pure” ones, mainly because of higher predation rates. Our results show that, despite lower survival,
hybrid partridges breed in natural populations, so this could increase extinction risk of wild pure partridge populations,
through releases of farmed hybrid birds. The consequences of continued releases could be of vital importance for the long
term conservation of wild red-legged partridges. 相似文献
20.
James K. Wamsley 《Molecular neurobiology》1992,6(2-3):313-321
The axonal transport of neurotransmitter receptors is thought to be a common phenomenon in many neuronal systems. The “machinery”
for receptor (protein) “assembly” is found in the cell bodies of neurons and the “manufacture” of receptors takes place there.
These receptors are then “shipped” to their ultimate destinations by a transport process. This is an axonal transport mechanism
in the case of presynaptic receptors. Some form of transport process may also exist to send receptors out into the dendritic
arborizations of neurons, although the latter is more difficult to verify. Axonal transport has been demonstrated, in the
peripheral nervous systems, for many different neurotransmitter receptors. In the central nervous system, the results are
less clear, but indicate the presence of a transport mechanism for catecholamine, acetylcholine, and opiate sites. One important
component then, in the development of receptors, is the transportation to terminal membrane sites where they are ultimately
incorporated and available for interaction with neurotransmitters and drugs. 相似文献