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1.
Many plants release allelopathic chemicals that can inhibit germination, growth, and/or survival in neighboring plants. These impacts appear magnified with the invasion of some non-native plants which may produce allelochemicals against which native fauna have not co-evolved resistance. Our objective was to examine the potential allelopathic impact of an invasive non-native shrub/tree on multiple plant species using field observation and experimental allelopathy studies. We surveyed and collected an invasive, non-native tree/shrub (Rhamnus cathartica) at Tifft Nature Preserve (a 107-ha urban natural area near Lake Erie in Buffalo, NY). We also surveyed understory plant communities in the urban forest to examine correlations between R. cathartica abundance and local plant community abundance and richness. We then used experimental mesocosms to test if patterns observed in the field could be explained by adding increased dosages of R. cathartica to soils containing five plant species, including native and non-native woody and herbaceous species. In the highly invaded urban forest, we found that herbaceous cover, shrubs and woody seedlings negatively covaried with R. cathartica basal area and seedlings density. In the mesocosm experiments, R. cathartica resulted in significant decreases in plant community species richness, abundance, and shifted biomass allocation from roots. Our results provide evidence that R. cathartica is highly allelopathic in its invaded range, that R. cathartica roots have an allelopathic effect and that some plant species appear immune. We suggest that these effects may explain the plant’s ability to form dense monocultures and resist competitors, as well as shift community composition with species-specific impacts. 相似文献
2.
Utilization of the extrafloral nectaries (EFNs) and fruits of Canavalia lineata and C. cathartica by ants was investigated at 30 sites in Japan. The fruits of C. lineata and C. cathartica were inhabited by five and eight ant species, respectively. Ant nesting periods and their utilization of EFNs differed between
C. lineata and C. cathartica. Canavalia lineata flowers once a year, and periods of EFN-utilization and fruit-nesting by ants do not overlap. The fruit-nesting ants on C. lineata seem to invade the plant from the holes made by moth larvae or breaches made by decay. The ants nesting on the fruits of
C. lineata may defend the plant against seed herbivores because they feed on moth larvae. Canavalia cathartica flowers several times over a year, and fruits are found throughout the year; therefore, periods of EFN-utilization and fruit-nesting
by ants are overlapped. Canavalia cathartica offers year-round nesting sites and food for ants, and therefore may receive a higher defensive effect from ants than C. lineata.
Handling editor: Graham Stone. 相似文献
3.
Katherine G. Rascher André Große-Stoltenberg Cristina Máguas Christiane Werner 《Ecosystems》2011,14(6):904-919
In water-limited ecosystems, where potential evapotranspiration exceeds precipitation, it is often assumed that plant invasions
will not increase total ecosystem water use, because all available water is evaporated or transpired regardless of vegetation
type. However, invasion by exotic species, with high water use rates, may potentially alter ecosystem water balance by reducing
water available to native species, which may in turn impact carbon assimilation and productivity of co-occurring species.
Here, we document the impact of invasion by an understory exotic woody species (Acacia longifolia) in a semi-arid Mediterranean dune pine forest. To quantify the effects of this understory leguminous tree on the water use
and carbon fixation rates of Pinus pinaster we compare an invaded and a non-invaded stand. A. longifolia significantly altered forest structure by increasing plant density and leaf area index in the mid-stratum of the invaded
forest. A. longifolia contributed significantly to transpiration in the invaded forest (up to 42%) resulting in a slight increase in stand transpiration
in the invaded relative to non-invaded forest. More importantly, both water use and carbon assimilation rates of P. pinaster were significantly reduced in the invaded relative to non-invaded stand. Therefore, this study shows that exotic plant invasions
can have significant impacts on hydrological and carbon cycling even in water-limited semi-arid ecosystems through a repartitioning
of water resources between the native and the invasive species. 相似文献
4.
Geoffrey R. Smith Kathleen G. Temple Haley A. Dingfelder David A. Vaala 《Aquatic Ecology》2006,40(1):125-130
Nitrogen pollution as a result of agricultural runoff and atmospheric deposition is a major challenge to aquatic ecosystems,
and is likely to increase in the future. Nitrogenous pollutants are potential stressors of amphibian larvae through their
toxicological impacts on individuals; however, they may also increase primary productivity. We examined how such an anthropogenic
stressor could influence the interactions between two potentially competing species of tadpoles (Rana clamitans and R. catesbeiana). In a 42 d mesocosm experiment, R. catesbeiana survival, but not final mass, was reduced by nitrate addition. Rana catesbeiana survival was lower when in competition with R. clamitans than when only experiencing intraspecific competition. For R. clamitans, survival was not affected by nitrate addition or competition type. Rana clamitans in nitrate addition mesocosms were heavier than tadpoles from no nitrate mesocosms, and were heavier in intraspecific than
in interspecific mesocosms. Our results suggest that nitrate can influence the performance of amphibian larvae, and that its
effects could have complex effects on aquatic ecosystems. 相似文献
5.
While a plant’s capacity to tolerate damage by herbivores can be studied as a single trait, it is important to recognize that
tolerance is generally a result of the combined action of several different traits. Here, we report on a pair of experiments
to identify mechanisms for tolerating floral herbivory in Solanum carolinense, an andromonoecious perennial herb that regularly suffers from high levels of florivory. We measured the effect of actual
and simulated florivory on host-plant fitness and assessed which plant traits exhibited plasticity in response to florivory.
In addition, for each of nine plant genets, we calculated tolerance indices and determined which traits were genetically correlated
with tolerance. Traits that served to help S. carolinense tolerate florivory in terms of sexual reproduction included initiating more inflorescences, aborting fewer buds prior to
anthesis and fewer ovaries after fertilization, and increasing the ratio of perfect:male flowers. In addition, the greater
the levels of florivory, the more the plants allocated to root growth, which may promote tolerance through greater potential
future reproduction. The plant population contained significant genetic variation for tolerance itself and for nearly all
of the putative tolerance mechanisms, which suggests that S. carolinense has the potential to evolve greater tolerance through a variety of different routes in response to natural selection. 相似文献
6.
Daniel Simberloff 《Biological invasions》2009,11(7):1735-1742
In addition to rats, nutria (Myocastor coypus) and the North American beaver (Castor canadensis) have certainly caused damage at an ecosystem level when introduced to islands, in both cases primarily by ecosystem engineering.
Of other introduced rodents successfully established on islands, the gray squirrel (Sciurus carolinensis) may be in the process of damaging entire forest ecosystems, particularly by bark-stripping. Though introduced muskrats (Ondatra zibethicus) have had ecosystem-level impacts in continental Europe, their impact on islands worldwide to which they have been introduced
has been very limited. The North American red squirrel (Tamiasciurus hudsonicus) and Barbary ground squirrel (Atlantoxerus getulus) have each had substantial impacts when introduced to particular islands, but for neither species have these impacts yet
been demonstrated to spread through an entire ecosystem. Introduced house mice (Mus musculus) may well generate ecosystem impacts on remote islands lacking rats, and it is possible that explosions of house mice on
islands after rat eradication, a common occurrence, will lead in some instances to ecosystem impacts. 相似文献
7.
Ecophysiology of exotic and native shrubs in Southern Wisconsin 总被引:14,自引:0,他引:14
Summary We compared seasonal trends in photosynthesis of two naturalized exotic shrubs (Rhamnus cathartica and Lonicera X bella) and two native shrubs (Cornus racemosa and Prunus serotina) in open and understory habitats in southern Wisconsin. We examined the relationships between resource availability and leaf photosynthetic performance in these four species. All four species had similar relationships between leaf nitrogen (N) content and photosynthetic rate, but the species differed in absolute leaf N content and therefore in photosynthetic rates. Maximum daily photosynthetic rates of all species were significantly correlated with leaf N content in the open habitat, but not in the understory, where low light availability was the major limitation to photosynthesis. Extended leaf longevity was important in the forest understory because it allowed shrubs to take advantage of high light availability at times when the overstory canopy was leafless. Early leaf emergence was more important than late senescence: from 27% to 35% of the annual carbon gain of P. serotina, R. cathartica, and L. X bella occurred prior to leaf emergence of C. racemosa, the species with the shortest leaf life span. Extended leaf longevity of exotic shrubs may help explain their persistence in the understory habitat, but it contributed relatively less to their annual carbon gain in the open habitat. 相似文献
8.
Effect of lead on the reaction of O-demethylase in p-nitro anisole in the cladoceran Moina macrocopa
L. Martinez-Tabche N. E. Morales M. B. Ramirez C. I. Galar G. H. Cardona 《Journal of Aquatic Ecosystem Stress and Recovery (Formerly Journal of Aquatic Ecosystem Health)》1994,3(4):255-258
The presence of the Mixed-Function Oxydase (MFO) system, in Moina macrocopa was detected through the transformation of p-nitroanisole to para-nitrophenol. The presence of this enzymatic system suggested that this cladoceran participates in the biotransformation of xenobiotics in aquatic ecosystems. This capacity, in conjunction with the aquatic flea's high tolerance to environmental stress, suggested that M. macrocopa could be used in bioremediation efforts to increase ecosystem health. The effects of lead on the MFO system in M. macrocopa, were also studied. Lead acted as an inhibitor of the enzymatic complex. Therefore, induction of MFO-activity as an early warning may not work in waterbodies affected by both inducers of MFO and inhibitors like lead. 相似文献
9.
Pamela Z. Kamya Symon A. Dworjanyn Natasha Hardy Benjamin Mos Sven Uthicke Maria Byrne 《Global Change Biology》2014,20(11):3365-3376
Outbreaks of crown‐of‐thorns starfish (COTS), Acanthaster planci, contribute to major declines of coral reef ecosystems throughout the Indo‐Pacific. As the oceans warm and decrease in pH due to increased anthropogenic CO2 production, coral reefs are also susceptible to bleaching, disease and reduced calcification. The impacts of ocean acidification and warming may be exacerbated by COTS predation, but it is not known how this major predator will fare in a changing ocean. Because larval success is a key driver of population outbreaks, we investigated the sensitivities of larval A. planci to increased temperature (2–4 °C above ambient) and acidification (0.3–0.5 pH units below ambient) in flow‐through cross‐factorial experiments (3 temperature × 3 pH/pCO2 levels). There was no effect of increased temperature or acidification on fertilization or very early development. Larvae reared in the optimal temperature (28 °C) were the largest across all pH treatments. Development to advanced larva was negatively affected by the high temperature treatment (30 °C) and by both experimental pH levels (pH 7.6, 7.8). Thus, planktonic life stages of A. planci may be negatively impacted by near‐future global change. Increased temperature and reduced pH had an additive negative effect on reducing larval size. The 30 °C treatment exceeded larval tolerance regardless of pH. As 30 °C sea surface temperatures may become the norm in low latitude tropical regions, poleward migration of A. planci may be expected as they follow optimal isotherms. In the absence of acclimation or adaptation, declines in low latitude populations may occur. Poleward migration will be facilitated by strong western boundary currents, with possible negative flow‐on effects on high latitude coral reefs. The contrasting responses of the larvae of A. planci and those of its coral prey to ocean acidification and warming are considered in context with potential future change in tropical reef ecosystems. 相似文献
10.
Luciana Helena T. Freitas João Luiz H. Faccini Marcelo B. Labruna 《Experimental & applied acarology》2009,47(4):321-345
The present study consisted of two experiments that evaluated experimental infections of Haemaphysalis leporispalustris ticks by a Brazilian strain of Rickettsia rickettsii, and their effect on tick biology. In experiment I, ticks were exposed to R. rickettsii during the larval, nymphal or adult stages by feeding on rabbits (Oryctolagus cuniculus) needle-inoculated with R. rickettsii, and thereafter reared on uninfected rabbits for the entire next tick generation. Regardless of the tick stage that acquired
the infection, all subsequent tick stages were shown to be infected by PCR (infection rates varying from 1.3 to 41.7%), and
were able to transmit R. rickettsii to uninfected rabbits, as demonstrated by rabbit seroconversion, guinea pig inoculation with rabbit blood, and PCR on rabbit
blood. In Experiment II, ticks were exposed to R. rickettsii during the larval stage by feeding on rabbits co-infested with R. rickettsii-infected adult ticks, and thereafter reared on uninfected rabbits until the next generation of larvae. Again, all subsequent
tick stages were shown to be infected by PCR (infection rates varying from 3.0 to 40.0%), and were able to transmit R. rickettsii to uninfected rabbits. Thus, it was demonstrated that larvae, nymphs, and adults of H. leporispalustris were able to acquire and maintain the R. rickettsii infection by transstadial and transovarial transmissions within the tick population, with active transmission of the bacterium
to susceptible rabbits by all parasitic stages. Analyses of biological parameters of uninfected and R. rickettsii-infected tick lineages were performed in order to evaluate possible deleterious effects of R. rickettsii to the infected tick lineages. Surprisingly, all but one of the four R. rickettsii-experimental groups of the present study showed overall better biological performance than their sibling uninfected control
ticks. Results of the present study showed that H. leporispalustris could support infection by a high virulent strain of R. rickettsii for at least two generations, in which infected tick lineages tended to have better performance than uninfected ticks. Our
results support a possible role of H. leporispalustris in the enzootic maintenance of R. rickettsii in Latin America, as previously suggested by earlier works. 相似文献
11.
Sand dune ecosystems have a high conservation value worldwide, but they are highly threatened by exotic plant invasion. We
investigated the impacts of the exotic invasive species Carpobrotus edulis on the composition and structure (spatial pattern, total cover, species diversity and species co-occurrence) of native sand
dune communities in the western coast of Portugal. We studied eight sites following a north-south gradient; in each site we
established 8–10 transects of 25 contiguous quadrats of one square meter. C. edulis had a significantly clumped pattern in five of the study sites, which, however, was not related to the spatial pattern of
native species. The effects of climate on the community structure variables were on average three times stronger than those
of C. edulis. This species also had small effects on the floristic composition of native species. Our results indicate that the success
and impacts of C. edulis are habitat-dependent and context-specific. They also provide evidence of a strong resilience to the impacts of invasion
in the studied sand dune ecosystems: C. edulis did not reach large abundances or exert negative impacts on native communities to the extent expected. These ecosystems provide
a unique opportunity to increase our understanding on the origin of impacts by invasive species, and on how particular communities
resist the impacts of an invader. 相似文献
12.
When sex is not enough: ecological correlates of resprouting capacity in congeneric tropical forest shrubs 总被引:1,自引:0,他引:1
In moist tropical forests resprouting may be an important component of life history, contributing to asexual reproduction
through the clonal spread of individuals derived from shoot fragments. However, in contrast to other ecosystems where resprouting
is common, the ecological correlates of resprouting capacity in tropical forests remain largely unexplored. In this study
we characterized shade tolerance, resprouting capacity and sexual reproductive success of eight co-occurring Piper species from lowland forests of Panama. In field experiments we found that shade-tolerant Piper species had a higher capacity to regenerate from excised or pinned stem fragments than light-demanding species in both gap
and understory light conditions. In contrast, shade-tolerant species had lower recruitment probabilities from seeds, as a
consequence of lower initial seed viability, and lower seedling emergence rates. All Piper species needed gap conditions for successful seedling establishment. Of 8,000 seeds sown in the understory only 0.2% emerged.
In gaps, seed germination of light-demanding species was between 10 and 50%, whereas for shade-tolerant species it was 0.5–9.8%.
We propose that the capacity to reproduce asexually from resprouts could be adaptive for shade-tolerant species that are constantly
exposed to damage from falling litter in the understory. Resprouting may allow Piper populations to persist and spread despite the high rate of pre-dispersal seed predation and low seed emergence rates. Across
Piper species, we detected a trade-off between resprouting capacity and the annual viable seed production per plant but not with
annual seed mass produced per plant. This suggests that species differences in sexual reproductive success may not necessarily
result from differential resource allocation. Instead we suggest that low sexual reproductive success in the understory may
in part reflect reduced genetic diversity in populations undergoing clonal growth, resulting in self-fertilization and in-breeding
depression. 相似文献
13.
Eastern and Western Gambusia (i.e., Gambusia holbrooki and G. affinis, respectively) are considered together here because these two fish species are very closely related, similar in appearance,
similar in biology and often confused. Widely divergent attitudes have developed with regard to these fish with some viewing
them as being highly beneficial to humans through controlling mosquitoes and the diseases they harbor, and others expressing
concern about the negative impacts that these fish may have on other species with which they interact. Because of the widespread
distribution, high levels of abundance, ease of capture and captive maintenance, and divergent attitudes, a very large and
diffuse literature has developed with regard to these species. In fact, few fish species have been studied as much as or more
than these two species combined. There has, however, been no comprehensive review of their biology published to date. As it
is not possible to provide a comprehensive review of Gambusia biology in one reasonably sized document, I provide here a review of aspects of their biology at the level of species and
individual. In another review I focused instead on the levels of population and species communities and consider the impacts
that these fish have on mosquitoes and other organisms (Pyke, unpublished). As would be expected of such widespread and abundant
species, Gambusia affinis and G. holbrooki are clearly very tolerant, adaptable and variable in their biology, at both an individual and population level. Both individuals
and populations can tolerate, and often thrive within, a wide range of conditions and the abilities of individuals to do this
are enhanced if they have time to acclimate to any changes. Populations can adapt through genetic or evolutionary changes
in response to conditions that vary in space or time, and there is significant genetic variation within and between populations. 相似文献
14.
Invasive species are a leading threat to native ecosystems, and research regarding their effective control is at the forefront
of applied ecology. Exotic facilitation has been credited with advancing the success of several aggressive invasive species.
Here, we suggest using the knowledge of exotic facilitations to control invasive earthworm populations. In northern hardwood
forests, the invasive shrubs Rhamnus cathartica (buckthorn) and Lonicera x bella (honeysuckle) produce high quality leaf litter, and their abundance is positively correlated with exotic earthworms, which
increase nutrient cycling rates. We performed an invasive plant removal experiment in two northern hardwood forest stands,
one dominated by buckthorn and the other by honeysuckle. Removal of invasive shrubs reduced exotic earthworm populations by
roughly 50% for the following 3 years. By targeting invasive species that are part of positive feedback loops, land managers
can multiply the positive effects of invasive species removal. 相似文献
15.
One of the last primitive island ecosystems in the Indian Ocean has been invaded since 1969 by the Sri Lankan privet, Ligustrum robustum. L. robustum is still spreading in the forests of La Réunion Island, where only 30% of the original vegetation remains, but where 98%
of the primary native vegetation of the Mascarene Islands still exists. On Mauritius, where L. robustum was introduced about 1895, it now forms dense, impenetrable thickets, and its presence has been correlated with the inability
of native vegetation to re-establish. We assessed the potential impacts of L. robustum invasion on the native ecosystems of La Réunion and identified the factors of invasibility. We determined the degree of invasion
in 12 plots of 156 m2 and followed native flora and privet recruitment for 3 years in 12 seedling plots of 39 m2. The data show that monocultural L. robustum stands now exist in human-disturbed primary forest patches (3.3 individuals/m2 and 80% of total individuals) and high seedling densities (0.3–0.6/m2) occur in the least disturbed patches. L. robustum's rapid growth, high shade tolerance and seed production, bird-assisted seed dispersal and high seedling recruitment contribute
to its invasiveness in intact forests. The conservation of the original ecosystems of La Réunion depends on the setting up
of a long-term and immediate global control strategy.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
16.
Biological invasions can vary in the extent of their effects on indigenous communities but predicting impacts for particular
systems remains difficult. In coastal marine ecosystems, the green seaweed Codium fragile ssp. fragile is a notorious invader with its reputation based on studies conducted largely on rocky shores. The green seaweed has recently
invaded soft-bottom eelgrass communities by attaching epiphytically to eelgrass (Zostera marina) rhizomes, thereby creating the potential for disruption of these coastal habitats through competition or disturbance. We
investigated the effect of this invader on various aspects of eelgrass performance (shoot density and length, shoot growth,
above- and below-ground biomass, carbohydrate storage) using both small-scale manipulative and large-scale observational experiments.
Manipulative experiments that varied Codium abundance demonstrated clear negative effects over a 4-month period on shoot density and carbohydrate reserves, but only
for high, but realistic, Codium biomass levels. Light levels were much lower under canopies for high and medium density Codium treatments relative to low and control Codium cover treatments, suggesting that shading may influence eelgrass growing under the algal cover. In contrast, these effects
were either not detectable or very weak when examined correlatively with field surveys conducted at larger spatial scales,
even for sites that had been invaded for over 4 years. It is premature to extend generalizations of Codium’s impact derived from studies in other systems to eelgrass communities; further efforts are required to assess the long-term
threats that the alga poses to this ecosystem. This study demonstrates the need to investigate impacts of invasions over multiple
scales, especially those that incorporate the temporal and spatial heterogeneity of the invader’s abundance. 相似文献
17.
Primate social grouping is understood as an adaptive strategy for mitigating environmental selection pressures, but the relative importance of various pressures may vary. Physiological measures of well-being can show their short-term impacts and suggest their relative importance and capacity to provide ultimate or proximate control of group size. I examined correlations between pressures commonly proposed as causes of social grouping (foraging success, intergroup and intragroup agonism, and predation risk) and individual levels of fecal cortisol, a hormonal stress measure, in a free-ranging population of Lemur catta. I collected behavioral data on 45 female Lemur catta at Berenty Reserve, Madagascar, over 3 seasons (August 1999-July 2000) and determined individual cortisol levels from 474 fecal samples. Neither predator alarm rates nor intragroup agonism rates correlated with cortisol levels in any season. However, females with low daily food intake and high rates of escalated intergroup defense exhibited higher cortisol levels. The data suggest that acquisition and defense of food resources are principal challenges in Lemur catta, and may be important factors determining social grouping and other behavioral or life history adaptations. 相似文献
18.
Donna B. Harris 《Biological invasions》2009,11(7):1611-1630
In this first comprehensive review of negative effects of introduced rodents on insular small mammals, the focal species Rattus rattus, R. norvegicus, R. exulans and Mus musculus are implicated in at least 11 extinctions. Furthermore, removal experiments, eradication campaigns and control programmes
provide evidence for negative effects on extant populations. While data are currently insufficient for meaningful generalisation
with regard to the most threatening rodents, the most threatened small mammals, and the true extent of the problem, it is
interesting that R. rattus is implicated in the majority of impacts. This may be explained by its extensive distribution and ecological plasticity.
I conclude with methodological recommendations to guide data collection for impact quantification and the study of impact
mechanism. This information should facilitate the prioritisation and justification of eradication campaigns, control programmes
and biosecurity measures while ensuring that much-needed attention is paid to the conservation of insular small mammals. 相似文献
19.
Rhamnus cathartica (common buckthorn) is a shrub (or small tree) of Eurasian origin, which has become invasive in North America. Internal feeders and sap suckers were prioritized for biological control from over 30 specialized insects identified from the target plant in its native European range. Five leaf‐feeding moths were also considered for further investigations. Field observations and preliminary host range tests with the stem‐boring beetle Oberea pedemontana, the root‐boring moth Synanthedon stomoxiformis, the shoot‐tip‐boring moth Sorhagenia janiszewskae and the leaf‐feeding moths Ancylis apicella, A. unculana, Triphosa dubitata, Philereme transversata and P. vetulata confirmed that all of these species were lacking host specificity in no‐choice conditions. Choice oviposition tests carried out with most of the prioritized species to assess their ecological host range yielded unreliable results. Three psyllids, Trichochermes walkeri, Cacopsylla rhamnicolla and Trioza rhamni are promising in terms of host specificity, but are infected with the plant disease ‘Candidatus Phytoplasma rhamni’. Fruit‐ or seed‐feeding insects may present the best potential for biological control of buckthorn in directly reducing seed set and thus seedling establishment. However, it was not possible to obtain adult fruiting trees of native North American Rhamnus species for testing. It is concluded that there are no promising arthropod agents based on what is known to date. Pathogens could offer new opportunities for biological control of R. cathartica in North America. 相似文献
20.
Duñabeitia MK Hormilla S Garcia-Plazaola JI Txarterina K Arteche U Becerril JM 《Mycorrhiza》2004,14(1):11-18
Three ectomycorrhizal (ECM) isolates of Rhizopogon luteolus, R. roseolus and Scleroderma citrinum were found to differ markedly in their in vitro tolerance to adverse conditions limiting fungal growth, i.e. water availability, pH and heavy metal pollution. S. citrinum was the most sensitive, R. luteolus intermediate and R. roseolus the most tolerant species. Pinus radiata D. Don seedlings were inoculated in the laboratory and in a containerised seedling nursery with spore suspensions of the three ECM species. Colonisation percentage was considerably lower under nursery conditions, probably due to competition by native fungi. The effects of nursery ECM inoculation on seedling growth depended on the fungal species. Only R. roseolus-colonised plants showed a significantly higher shoot growth than non-mycorrhizal plants. All three fungi induced significantly higher root dry weights relative to control plants. Despite the low mycorrhizal colonisation, mycorrhization with all three species improved the physiological status of nursery-grown seedlings, e.g. enhanced root enzyme activity, shoot nutrient and pigment content, net photosynthesis rate and water use efficiency. Of the three fungal species, R. roseolus was the most effective; this species was also the most adaptable and showed the greatest range of tolerance to adverse environmental conditions in pure culture. It is, therefore, proposed as a promising fungal species for ECM inoculation of P. radiata in the nursery. 相似文献