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1.
Linking habitat suitability and seed dispersal models in order to analyse the effectiveness of hydrological fen restoration strategies 总被引：1，自引：0，他引：1
A.H. van Loon H. Soomers P.P. Schot M.F.P. Bierkens J. Griffioen M.J. Wassen 《Biological conservation》2011,(3):1025-1035
The effectiveness of measures targeted at the restoration of populations of endangered species in anthropogenically dominated regions is often limited by a combination of insufficient restoration of habitat quality and dispersal failure. Therefore, the joint prediction of suitable habitat and seed dispersal in dependency of management actions is required for effective nature management. Here we demonstrate an approach, which links a habitat suitability and a seed dispersal model. The linked model describes potential species distribution as a function of current species distribution, species-specific dispersal traits, the number of successful dispersal events, dispersal infrastructure and habitat configuration. The last two variables were related to water management actions. We demonstrate the applicability of the model in a strategy analysis of hydrological restoration measures for a large fen area in which still numerous endangered plant species grow.With the aid of the linked model, we were able to optimise the spatial planning of restoration measures, taking into account both the constraints of water management practices on abiotic restoration and the effects of habitat fragmentation on dispersal. Moreover, we could demonstrate that stand-alone habitat suitability models, which assume unlimited dispersal, may considerably overestimate restoration prospects. For these reasons, we conclude that linked habitat suitability and dispersal models can provide useful insights into spatially differentiated potentials and constraints of nature restoration measures targeted at the sustainable conservation of endangered plant populations whose habitats have been deteriorated due to undesirable effects of land and water management on abiotic conditions. These insights may contribute to the design of cost-effective nature restoration and conservation measures. 相似文献
2.
《国际水土保持研究(英文)》2022,10(3):414-421
Desertification in degraded grasslands is manifested through the development of bare sandy patches, which eventually lead to habitat fragmentation. The ability of these bare sandy patches to regenerate naturally through in-situ soil seed banks is not well understood. To fill this knowledge gap, we randomly selected 24 bare sandy patches with areas ranging from 19 to 898 m2 in a desertified grassland of the Horqin sandy land, Northern China to determine whether soil seed bank can be used for natural regeneration of bare sandy patches. Species composition and density of soil seed bank as well as aboveground vegetation composition, abundance and coverage were investigated. We then determined their relationships with in-situ habitat characteristics. Our observations showed that the studied area had low soil seed bank density and species richness, as well as depauperate soil seed bank communities. Consequently, local soil seed bank was not able to provide sufficient seed source for natural regeneration. This was indicated by the relationships between aboveground vegetation, soil seed bank and the in-situ habitat characteristics. For bare patches with an area between 300 m2 and 900 m2, increase the soil seed bank density and species richness should be the main restoration measures. For bare patches with a small area of less than 50 m2, restoration of vegetation density should be the main measure. Our data highlighted that different extents of desertification, indicated by different bare patches, are requiring distinct restoration measures. 相似文献
3.
About twenty-five percent of all southern African Oxalis species are rare/endangered and highly localized, making them especially vulnerable to extinction through inbreeding, low genetic variation, disrupted biological interactions and stochastic events; all consequences of small population sizes. Moreover, Oxalis displays tristyly, which is a rare and specialized sexual system that includes a strong self-incompatibility component between three floral morphs to promote out-crossing within populations. As tristyly requires the availability of plants with different floral morphs as well as effective pollinators for seed production, this breeding system can affect small populations when fully expressed. Factors that may have an effect on rarity in Oxalis were investigated by focusing on the expression of tristyly, levels of natural seed production, clonality and the ecology of eight rare/highly localized Oxalis species. Field experiments revealed that the reproductive success of some Oxalis species may be hampered by tristyly, resulting in extremely low levels of natural seed production. Other species display a more relaxed expression of self-incompatibility, which in combination with the possibility of cross-pollinations provides reproductive assurance regardless of population structure and pollinator availability. Others are rare and endangered, but appear not to be negatively affected by the tristylous breeding system. Most species are limited by their highly specific habitat requirements and are particularly vulnerable to variation in rainfall patterns. 相似文献
4.
In the Pantanal wetlands of Central Brazil, the endangered hyacinth macaw (Anodorhynchus hyacinthinus), the largest psitacid in the world, makes its nest almost exclusively in natural hollows found in the manduvi tree (Sterculia apetala). The recruitment of manduvis greatly depends on the seed dispersal services provided by the toco toucan (Ramphastos toco), responsible for 83.3% of the seed dispersal. The toco toucan, however, is responsible for about 53% of the preyed eggs, resulting in a case of conflicting ecological pressures in which the reproduction of the hyacinth macaw is indirectly dependent on the seed dispersal services of its nest predator. The case illustrates the intricacies of biotic interactions in species-rich environments where species may be tied by indirect, subtle ecological links which conservationists should be aware of. 相似文献
5.
The impact of clonality on an endangered tree (Elaeocarpus williamsianus) in a fragmented rainforest
The occurrence and distribution of clonality in the endangered rainforest tree Elaeocarpus williamsianus (Elaeocarpaceae) was investigated using SSR and RAPD analyses for 170 apparent individual trees found across seven sites. The results obtained with the two molecular techniques were in complete agreement in showing that single clones are present in most of the E. williamsianus sites with two genets occurring at the largest and most adequately protected site. In addition, seed production, viability and germinability were determined for four of these populations. Fruit were produced in all four populations tested although sterile fruit were very common. Only two E. williamsianus trees representing different genets within the same site produced viable seed. The overall genetic diversity within E. williamsianus is much lower than expected and thus the potential for sexual reproduction has been significantly diminished. It is concluded that habitat fragmentation removed an existing balance between vegetative and sexual reproduction in this species. Such findings have added urgency to the management of this species which could include a reintroduction program incorporating the collation of all clones within selected sites. 相似文献
6.
An endemic dwarf birch, Betula apoiensis, is critically endangered, and two populations of this species are restricted to the ridges of Mt. Apoi in Hokkaido, Japan. We observed the flowering phenology, pollen dispersal, and viable seed production and conducted pollination experiments in order to examine pollen limitation and hybridization with a sympatric congener, B. ermanii. B. apoiensis flowered earlier than B. ermanii but had a more variable flowering time among trees than B. ermanii. The female flowering of B. apoiensis temporally overlapped with the male flowering of B. ermanii as well as with that of B. apoiensis. Pollination experiments demonstrated that seed set and seed germination were higher in female flowers outcrossed than in those that were non-pollinated, selfed, hybridized with B. ermanii pollen, or pollinated naturally. A few selfed or hybrid seeds were filled and germinated, which indicates that self-incompatibility and reproductive barriers are not complete. Logistic regressions of local density of conspecific trees on natural seed set and seed germination were significantly positive. These results suggest that B. apoiensis is pollen-limited. 相似文献
7.
This study investigates the dynamics and viability of a marsh fritillary butterfly Euphydryas aurinia metapopulation in a Belgian successional landscape. Based on capture-mark-recapture and winter nest census data, we first estimated demography (survival and recruitment rates, population size, density dependence) and dispersal parameters (emigration rate, effect of patch connectivity on dispersal, mortality during dispersal). Then using RAMAS/GIS platform, we parameterised a population viability analysis (PVA) model with these parameters to simulate the future of this metapopulation under different scenarios.The metapopulation does not seem viable even if natural reforestation is controlled by adequate management. In its present state, the patch system is not able to sustain enough individuals: due to the large temporal fluctuations in demographic parameters, a carrying capacity far higher than currently would be necessary to limit extinction risk to 1%, suggesting the existence of an extinction debt for the species in Belgium. The situation of E. aurinia appears much worse compared to two other fritillary species threatened in Belgium, for which similar PVA are available. It is therefore urgent to increase the carrying capacity of the patch system. How and where it is achieved are of secondary importance for the gain in viability: improvement of habitat quality through restoration, or increase of habitat quantity via enlargement of existing patches and/or creation of new habitat in the matrix. A regime of management based on regular re-opening and maintenance of habitat patches may be the only guarantee of long-term persistence for this critically endangered species in Belgium. 相似文献
8.
H. Gibb J. Hjältén John P. Ball R.B. Pettersson J. Landin O. Alvini K. Danell 《Biological conservation》2006,132(2):250-260
Traits such as poor dispersal ability and high habitat specificity are thought to predispose some species to a greater risk of extinction than others. Habitat preferences and morphological features associated with dispersal ability were compared between red-listed species and common congenerics co-occurring in boreal forests in northern Sweden. Measurements of body size, wing loading and wing aspect ratio were used to compare dispersal abilities, while catches from experimental treatments of dead wood were used to compare habitat preferences. We also compared how restricted red-listed species were to particular sites or habitats relative to common species. The red-listed Epuraea longipennis was longer and wider, while Epuraea. deubeli weighed less than common Epuraea species. In contrast to expectations, these red-listed species had a larger wing area (relative to their body mass) and thus a lower wing-loading than congeneric species, suggesting superior dispersal abilities. The red-listed Tachinus elegans possessed intermediate morphological characteristics, compared with common congenerics. However, the relationships between the risk of extinction in fragmented habitats and size and dispersal ability are likely to be scale-dependent, so intermediate or superior dispersal abilities may increase extinction risk at some scales. Red-listed species were not found in fewer sites or habitat types than congenerics so were not more likely to be habitat specialists. However, some red-listed species preferred deeply shaded and Fomitopsis pinicola-inoculated logs, relative to congenerics, suggesting that specificity to these particular microhabitats may be connected with extinction risk. 相似文献
9.
Terrestrial orchids typically produce numerous small seeds that contain very small nutrient reserves. The seeds are structurally adapted for wind dispersal but little is known about their fate after dispersal. Some studies of seed viability in situ indicate survival for up to two years in temperate orchid species. Seeds stored in the laboratory may last much longer. We investigated seed viability of seven North American orchid species with seed packets buried in a range of soil and wood substrates within their natural habitats. In Goodyera pubescens most seeds germinated within one year. Four other species continued to germinate sparsely during the observation period, but after almost seven years many seeds were still viable. In one species, Liparis liliifolia, seeds that had been in situ for four years had germination rates as high as 68% when sown in vitro with a compatible fungus. The remaining two species did not germinate during the observation period but the seeds were judged to be intact and tested positively for viability after four years in the ground. These observations are interpreted as different species-specific strategies for in situ germination and their seed bank potential is discussed. 相似文献
10.
11.
Habitat fragmentation is a major threat to species survival worldwide due to genetic isolation, inbreeding depression, genetic drift and loss of adaptive potential. However the data on how gene-flow changes following habitat fragmentation is contradictory. If there is significant gene-flow between spatially isolated populations then limited conservation resources could be directed away from projects to ‘establish genetic connectivity’ and used to address other consequences of habitat fragmentation.This research focused on an endangered tree species Gomortega keule (Gomortegaceae) in a fragmented landscape in the Central Chile Biodiversity Hotspot and addressed three questions: (1) How far does pollen move between pollen donors and seed trees and what is the shape of the dispersal curve? (2) Do insect pollinators travel outside of forest patches? (3) Do small populations and single trees contribute to genetic connectivity across the landscape?Paternity analysis results show that G. keule’s insect pollinators travel outside of forest patches, over distances of 6 km, beyond the scale of population fragmentation or genetic structure. Pollen moved from small sites and single trees into large sites, as well as in the other direction, indicating these sites play a key role as functioning elements of the wider population and as stepping stones between sites. Fragmentation at the scale investigated has not led to genetic isolation, thus genetic connectivity per se is not a conservation priority. Other consequences of land-use change, specifically continuing habitat loss and population reduction, still threaten the survival of the species. 相似文献
12.
We examined germination and seedling survival of Petrocoptis grandiflora and Petrocoptis viscosa (Caryophyllaceae), two narrow endemic species from the northwest Iberian Peninsula. The experiments were carried out with seeds of three of eight populations of P. grandiflora and one of the three sole populations of P. viscosa. Under natural conditions, both P. grandiflora and P. viscosa produce very large numbers of seeds. However, the specific microhabitat of these species (cracks and crevices of limestone rockfaces) has very marked effects on seed germination, and subsequent seedling survival. In the present study, we examined the effects of light, cold treatment and seed weight on germination capacity. In the case of P. grandiflora, we also compared the germination of seeds of the different populations. In addition, we assessed seedling survival over a 1-year period. Seeds maintained in darkness showed higher germination percentages than seeds maintained with a 12:12 h photoperiod. The application of a short period of cold prior to germination had no significant effect in either species. In the case of P. grandiflora, population of origin had a significant effect on germination percentage. Of all the factors considered, seed weight was the most important source of variability, both in seed germination and subsequent seedling survival. In both species in the natural habitat, less than 10% of germinated seeds survived by the end of the year. Seedling survival was affected by microhabitat. Seedlings in non-rockface soil microhabitats were more likely to suffer herbivory or interspecific competition than seedlings in crevices in the rockface. 相似文献
13.
Paul Severns 《Biological conservation》2003,110(2):221-229
Willamette Valley upland prairie in western Oregon, USA, has been reduced to less than 1% of its original historic range following European settlement in the 1850s. Lupinus sulphureus ssp. kincaidii (Kincaid's lupine), a threatened species and the primary larval host plant of the endangered Icaricia icarioides fenderi (Fender's blue butterfly), was historically a panmictic metapopulation. Habitat fragmentation may be causing many of the Kincaid's lupine colonies to display typical symptoms of inbreeding depression, such as low seed production. Hand outcrosses on bagged inflorescences significantly increased seed set and seed fitness compared to open pollination and within-colony pollen treatments. Natural seed set was positively correlated with an increase in the number of Kincaid's lupine patches, suggesting that population size limits seed set. An increase in fruit set was positively correlated with Kincaid's lupine raceme number, raceme density, and the number of lupine patches, demonstrating that floral display and population size increase pollinator service. Restoration of Kincaid's lupine populations should consider measures that lessen the effects of inbreeding depression, especially in small, isolated populations, for the long-term persistence of the species. 相似文献
14.
Grevillea caleyi is an endangered plant species with a restricted range lying partly within Ku-ring-gai Chase and Garigal National Parks in NSW, Australia. The principle threatening processes affecting G. caleyi are habitat destruction and adverse fire regimes combined with high levels of seed predation. A stochastic, spatially explicit, individual-based model was constructed to investigate the population dynamics of small populations of the species and to determine the impact of a variety of management strategies. Results of model simulations indicate there is a high risk of population decline and local extinction in remnant sites with small populations under current management regimes. The most effective fire management strategy is to schedule fires that burn 20-100% of sub-populations every 5-15 years, in combination with reduced predation rates. When predation management strategies are employed in conjunction with a structured fire regime, then a 20-30% reduction in predation rates can improve the chance of long-term persistence substantially. 相似文献
15.
Joanne C. Chee-Sanford 《Biology and Fertility of Soils》2008,44(5):763-771
Current interest in biological-based management of weed seed banks in agriculture furthers the need to understand how microorganisms
affect seed fate in soil. Many annual weeds produce seeds in high abundance; their dispersal presenting ready opportunity
for interactions with soil-borne microorganisms. In this study, we investigated seeds of four common broadleaf weeds, velvetleaf
(Abutilon theophrasti), woolly cupgrass (Eriochloa villosa), Pennsylvania smartweed (Polygonum pensylvanicum), and giant ragweed (Ambrosia trifida), for potential as sources of carbon nutrition for soil fungi. Seeds, as the major source of carbon in an agar matrix, were
exposed to microbial populations derived from four different soils for 2 months. Most seeds were heavily colonized, and the
predominant 18S rRNA gene sequences cloned from these assemblages were primarily affiliated with Ascomycota. Further, certain fungi corresponded to weed species, regardless of soil population. Relatives of Chaetomium globosum (98–99% sequence identity) and Cordyceps sinensis (99%) were found to be associated with seeds of woolly cupgrass and Pennsylvania smartweed, respectively. More diverse fungi
were associated with velvetleaf seeds, which were highly susceptible to decay. The velvetleaf seed associations were dominated
by relatives of Cephaliophora tropica (98–99%). In contrast to the other species, only few giant ragweed seeds were heavily colonized, but those that were colonized
resulted in seed decay. The results showed that seeds could provide significant nutritional resources for saprophytic microbes,
given the extant populations can overcome intrinsic seed defenses against microbial antagonism. Further, weed species-specific
associations may occur with certain fungi, with nutritional benefits conferred to microorganisms that may not always result
in seed biodeterioration. 相似文献
16.
Dorte Friis Nyhagen 《Biological conservation》2005,122(3):491-497
This study was conducted over a 7-month period in the south-west of Mauritius and investigates the diet of the endemic flying fox Pteropus niger and its potential role as pollinator and seed disperser. The identification of food plants and seed dispersal events were made by direct observations of bats or indirectly by the analysis of ejecta found on the ground. P. niger was observed to visit 22 plant species for food of which 20 were visited for fruit, two for floral resources, and one for foliage (one species was visited for both fruit and floral resources). Two thousand thirty-two P. niger fruit ejecta from 16 species were collected containing 2460 seeds. Ejecta from eight of these species (including five endemic to Mauritius) contained seeds, all of which were mature and intact (with one possible exception) and some were germinating. Forty-seven observations were made of the dispersal of seeds in fruit, ejecta and faeces, including seeds from three endemic and one native plant species. All seeds in dispersed ejecta were found to be mature and undamaged by bats. Pollen smears from the lips of six dead and 12 captured bats showed that these animals carried a minimum of 18 pollen species. Each smear had an average of 2.2 pollen species and a pollen load of 17.7 grains. Our results suggest that P. niger plays an important role in maintaining plant diversity in the heavily fragmented landscape of Mauritius. 相似文献
17.
Muhammad Ather Nadeem Asif Tanveer Rizwan Maqbool Ali Zohaib Muhammad Asif Shehzad 《Archives of Agronomy and Soil Science》2017,63(3):344-351
Little is known of glyphosate-induced hormesis in weeds and how this might influence weed management. To test the hormetic effect of low doses of glyphosate on broad-leaved weeds, two experiments were conducted, in the laboratory and the screenhouse. The hormetic effects of glyphosate solution in growth media (0, 65, 130, 250, and 500 g acid equivalent (a.e) ha?1) and foliar spray (0, 4, 8, 16, 32, and 64 g a.e. ha?1) were tested on four broad-leaved weeds (Coronopus didymus, Chenopodium album, Rumex dentatus, and Lathyrus aphaca). Glyphosate solution in the range 65–250 g a.e. ha?1 stimulated the germination and seedling growth of all tested weeds. However, at 500 g a.e. ha?1 inhibition of germination and growth was observed. Foliarly applied glyphosate in the range 4–32 g a.e. ha?1 increased root and shoot length, dry biomass, and seed production ability of all four weeds species; however, the stimulatory response was species dependent. These results indicate that glyphosate hormesis could play a significant role in altering crop/weed competition and might influence weed management. 相似文献
18.
The southern Iberian Peninsula is one of the most important refugia of Tertiary relict plant taxa in Europe. Under the present summer-dry climate, relict populations may experience a severely reduced regeneration. We studied the demographic structure, seed set and initial recruitment in relict populations of the endangered tree Frangula alnus subsp. baetica (Rhamnaceae) to evaluate its regeneration potential under the present environmental conditions. Populations are restricted to small riparian forests of Southwest Spanish and North Moroccan mountain ranges. The distribution of fruit crop sizes was highly left-skewed, and a few old trees produced the large bulk of the population seed pool. Bird-mediated seed dispersal appeared inefficient and post-dispersal seed predation by mice was high. Secondary seed transport by elevated creek water flow after winter rains modified the primary seed dispersal, but in consequence most seeds germinated on recently formed sandbanks where seedlings experienced reduced initial growth and survival. The most important mortality factor was desiccation, followed by herbivory. None of 1144 monitored seedlings survived for 2 years. The demographic survey through five populations indicates that drought periods may cause temporal regeneration bottlenecks. Moreover, over the last two decades populations have experienced increasing regeneration problems. Two causes are suggested: (1) browsing pressure from introduced game animals, and (2) the impact of torrential water flow peaks after heavy winter rains, exacerbated by large-scale vegetation slashing in surrounding cork oak forests. We discuss conservation strategies for this and other relict tree species that account for the pecularities of their habitat within the Mediterranean. 相似文献
19.
Species can become regionally rare when limited by the availability of suitable habitats or by limited dispersal ability. We tested if the presence of a rare bryophyte species (Sphagnum angermanicum) was dispersal or habitat limited and at the same time investigated the possibility of establishing new populations of this rare species. Further, we tested how propagule (fragment) size and small scale disturbances affected establishment success. All field experiments were performed by artificially transporting propagules (of various sizes) to new and old sites for the species in Sweden.We show that S. angermanicum is dispersal limited on a regional scale, as no significant differences in establishment success were found between new suitable sites and old occupied sites. The larger the propagule the better was the establishment success; the best establishment success was found when transplanting whole shoots. Disturbances did not increase establishment success, in contrary, when compared to controls success was reduced by the more intensive disturbance treatments. We suggest that disturbance maybe more important for increasing direct dispersal than for making the microhabitat more advantageous for establishment. However, an intermediate disturbance, which slightly reduces the Sphagnum-community length increment, might also be beneficial for the establishment success of S. angermanicum propagules.The reasonably high establishment success of S. angermanicum propagules in new suitable sites suggests that artificial introductions of fragments could be considered as an active management regime for the species if the number of localities continues to decrease. 相似文献
20.
Oil prospecting and its impact on large rainforest mammals in Loango National Park, Gabon 总被引：1，自引：0，他引：1
Resource extraction is increasingly affecting protected areas worldwide. However, aside from studies on logging, limited information is available about the effect this has on wildlife, which may be of great consequence, especially when endangered species could be affected. Specifically, the effect of intense human-induced noise during oil exploration on wildlife is poorly understood. We explore the effect of seismic oil exploration on large mammal distribution in an 80 km2 area of Loango National Park, Gabon. Following the ecological theory of habitat disturbance, we predicted that changes in habitat use in response to noise disturbance would scale with the body/home range size of each species examined. Our study was conducted over six months before, during and after low-impact seismic operations. We recorded counts along transects of indirect signs of elephants (Loxondota africana cyclotis), chimpanzees (Pan troglodytes troglodytes), gorillas (Gorilla gorilla gorilla), duikers (Cephalophus spp.), and the vocalizations of five monkey species (Cercocebus torquatus,Cercopithecus cephus, C. nictitans, C. pogonias and Lophocebusalbigena) and modeled seismic impact over different spatial scales (small, intermediate and large). We found that elephants avoided seismic activity on all three spatial scales, apes avoided on the intermediate and small scales, and there was no effect for duikers and monkeys. We conclude that low-impact seismic operations can cause considerable temporary habitat loss for species with large ranges and suggest that the impact on those endangered species can be minimized by adequately spacing seismic lines and activity in space and time to enable species to move away from the progressive noise disruption. 相似文献