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1.
Effects of Collembola (Heteromurus nitidus and Onychiurus scotarius) and earthworms (Aporrectodea caliginosa and Octolasion tyrtaeum) on the growth of two plant species from different functional groups (Poa annua and Trifolium repens), and on the development of aphids (Myzus persicae) were investigated in a laboratory experiment lasting 20 weeks. Using soil from a fallow site which had been set aside for
about 15 years, we expected that nitrogen would be of limited supply to plants and hypothesized that the soil animals studied,
particularly earthworms, would increase nutrient availability to plants and thereby also modify aphid reproduction and development.
Plant growth was modified strongly by the presence of soil animals. Earthworms caused a more than twofold increase in shoot
and root mass of P. annua but increased that of T. repens by only 18% and 6%, respectively. However, earthworms neither affected plant shoot/root ratio nor the nitrogen concentration
in plant tissue. In contrast, the presence of Collembola caused a reduction in plant biomass particularly that of P. annua roots, but plant tissue nitrogen concentration was increased, although only slightly. Aphid reproduction on T. repens was lowered in the presence of Collembola on average by 45% but on P. annua increased by a factor of about 3. It is concluded that Collembola decrease aphid reproduction on more palatable host plants
like T. repens but increase that on less palatable ones like P. annua. Earthworm presence also affected aphid reproduction but the effect was less consistent than that of Collembola. In the presence
of earthworms, aphid reproduction was in one experimental period increased by some 70%. Earthworms also modified the numbers
of Collembola and their vertical distribution in experimental chambers. Exploitation of deeper soil layers by H. nitidus was increased but, generally, O. scotarius numbers were reduced whereas those of H. nitidus increased in earthworm treatments. The presence of Collembola also influenced earthworm body mass during the experiment.
In general it declined, but in the presence of Collembola loss of body mass of A. caliginosa was more pronounced. We conclude that inhibiting effects between Collembola and earthworms resulted from the use of a common
resource, litter material rich in nitrogen. This is supported by the higher C/N ratio of the litter material in the presence
of earthworms and Collembola by the end of the experiment. Effects of soil invertebrates like Collembola and earthworms on
plant performance and aphid development are assumed to be modified by complex direct and indirect interactions among soil
animal groups.
Received: 6 July 1998 / Accepted: 1 March 1999 相似文献
2.
3.
Effects of Collembola (Protaphorura fimata) on the development of wheat (Triticum aestivum) and the reproduction of aphids (Rhopalosiphum padi) were investigated at different soil nutrient concentrations in a laboratory experiment. Fertilization with N and NPK increased biomass and nitrogen content of wheat, aphid reproduction and abundance of Collembola. Presence of Collembola tended to decrease biomass of leaves and ears, and caused a delayed ear production of the plants. Aphid reproduction was significantly reduced in the presence of Collembola (−14%) and most pronounced in fertilizer treatments. We suggest that the reduction of aphid reproduction is caused by Collembola-mediated changes in resource allocation and growth of wheat. 相似文献
4.
The ecological role of soil streptomycetes within the plant root environment is currently gaining increased attention. This review describes our recent advances in elucidating the complex interactions between streptomycetes, plants, pathogenic and symbiotic microorganisms. Streptomycetes play diverse roles in plant-associated microbial communities. Some act as biocontrol agents, inhibiting plant interactions with pathogenic organisms. Owing to the antagonistic properties of streptomycetes, they exert a selective pressure on soil microbes, which may not always be for plant benefit. Others promote the formation of symbioses between plant roots and microbes, and this is in part due to their direct positive influence on the symbiotic partner, expressed as, e.g., promotion of hyphal elongation of symbiotic fungi. Recently, streptomycetes have been identified as modulators of plant defence. By repressing plant responses to pathogens they facilitate root colonisation with pathogenic fungi. In contrast, other strains induce local and systemic resistance against pathogens or enhance plant growth. In conclusion, while streptomycetes have a clear potential of acting as biocontrol agents, care has to be taken to avoid strains that select for virulent pathogens or enhance disease development. We argue towards the use of an integrated screening approach in the search for efficient biocontrol agents, including assays on in vitro antagonism, plant growth, and disease suppression. 相似文献
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6.
Questions: How do arbuscular mycorrhiza and earthworms affect the structure and diversity of a ruderal plant community? Is the establishment success of newcomer plants enhanced by these soil organisms and their interactions? Methods: We grew a native ruderal plant community composed of different functional groups (grasses, legumes and forbs) in the presence and absence of arbuscular mycorrhizal fungi (AMF) and endogeic earthworms in mesocosms. We introduced seeds of five, mainly exotic, plant species from the same functional groups after a disturbance simulating mowing. The effects of the soil organisms on the native ruderal plant community and seedling establishment of the newcomer plants were assessed. Results: After disturbance, the total above‐ground regrowth of the native plant community was not affected by the soil organisms. However, AMF increased plant diversity and shoot biomass of forbs, but decreased shoot biomass of grasses of the native plant community. Earthworms led to a reduction in total root biomass. Establishment of the introduced newcomer plants increased in the presence of AMF and earthworms. Especially, seedling establishment of the introduced non‐native legume Lupinus polyphyllus and the native forb Plantago lanceolata was promoted in the presence of AMF and earthworms, respectively. The endogeic earthworms gained more weight in the presence of AMF and led to increased extraradical AMF hyphal length in soil. However, earthworms did not seem to modify the effect of AMF on the plant community. Conclusion: The present study shows the importance of mutualistic soil organisms in mediating the establishment success of newcomer plants in a native plant community. Mutualistic soil organisms lead to changes in the structure and diversity of the native plant community and might promote newcomer plants, including exotic species. 相似文献
7.
应用盆栽试验,通过调节不同光照强度并控制其它条件相互一致的条件下,研究了光照条件对土壤植物系统N素状况以及作物(莴笋)产量的影响.结果表明,光照强度的改变会引起作物生长状况的相应变化,同时也导致土壤N素(NH4+-N、NO3--N)状况、作物吸收N量以及作物对N素吸收速度等的改变.在试验所处的光照强度范围内,光照较强时,则作物吸收N素的速度较快、吸收N量增加,且产量高,但土壤中相应的N素含量(NH4+-N、NO3--N)则只能维持在相对较低的水平;光照较弱时,则出现与此相反的情况. 相似文献
8.
光照条件对土壤—植物系统氮素状况影响的研究 总被引:4,自引:0,他引:4
应用盆栽试验 ,通过调节不同光照强度并控制其它条件相互一致的条件下 ,研究了光照条件对土壤 植物系统N素状况以及作物 (莴笋 )产量的影响 .结果表明 ,光照强度的改变会引起作物生长状况的相应变化 ,同时也导致土壤N素 (NH 4 N、NO-3 N)状况、作物吸收N量以及作物对N素吸收速度等的改变 .在试验所处的光照强度范围内 ,光照较强时 ,则作物吸收N素的速度较快、吸收N量增加 ,且产量高 ,但土壤中相应的N素含量(NH 4 N、NO-3 N)则只能维持在相对较低的水平 ;光照较弱时 ,则出现与此相反的情况 . 相似文献
9.
Consequences of constitutive and induced variation in plant nutritional quality for immune defence of a herbivore against parasitism 总被引:1,自引:0,他引:1
Tibor Bukovinszky Erik H. Poelman Rieta Gols Georgios Prekatsakis Louise E. M. Vet Jeffrey A. Harvey Marcel Dicke 《Oecologia》2009,160(2):299-308
The mechanisms through which trophic interactions between species are indirectly mediated by distant members in a food web
have received increasing attention in the field of ecology of multitrophic interactions. Scarcely studied aspects include
the effects of varying plant chemistry on herbivore immune defences against parasitoids. We investigated the effects of constitutive
and herbivore-induced variation in the nutritional quality of wild and cultivated populations of cabbage (Brassica oleracea) on the ability of small cabbage white Pieris rapae (Lepidoptera, Pieridae) larvae to encapsulate eggs of the parasitoid Cotesia glomerata (Hymenoptera, Braconidae). Average encapsulation rates in caterpillars parasitised as first instars were low and did not
differ among plant populations, with caterpillar weight positively correlating with the rates of encapsulation. When caterpillars
were parasitised as second instar larvae, encapsulation of eggs increased. Caterpillars were larger on the cultivated Brussels
sprouts plants and exhibited higher levels of encapsulation compared with caterpillars on plants of either of the wild cabbage
populations. Observed differences in encapsulation rates between plant populations could not be explained exclusively by differences
in host growth on the different Brassica populations. Previous herbivore damage resulted in a reduction in the larval weight of subsequent herbivores with a concomitant
reduction in encapsulation responses on both Brussels sprouts and wild cabbage plants. To our knowledge this is the first
study demonstrating that constitutive and herbivore-induced changes in plant chemistry act in concert, affecting the immune
response of herbivores to parasitism. We argue that plant-mediated immune responses of herbivores may be important in the
evaluation of fitness costs and benefits of herbivore diet on the third trophic level. 相似文献
10.
The effect of litter type and macrofauna community on litter decomposition and organic matter accumulation in post-mining sites 总被引:1,自引:0,他引:1
Jan Frouz 《Biologia》2008,63(2):249-253
Field microcosms consisting of mineral soil (spoil substrate) and two types of litter taken either from an unreclaimed site
with spontaneously developed vegetation (mostly Salix caprea) or from an alder plantation (a mixture of Alnus glutinosa and A. incana) were exposed in spontaneously developed or reclaimed sites at a post-mining heap near Sokolov (Czech Republic) for one year.
The litter types differed remarkably in C:N ratio which was 29 for spontaneous litter and 14 for alder litter. The two microcosm
types were either accessible or not accessible to soil macrofauna. The effect of macrofauna exclusion on soil mixing was complex
and depended on litter quality and the site that determined soil fauna composition. In reclaimed sites where macrofauna was
dominated by saprophags, mainly earthworms, the macrofauna access increased soil mixing. In sites where predators dominated,
the macrofauna exclusion probably suppressed fragmentation and mixing activity of the mesofauna. 相似文献
11.
Accidental and deliberate introductions of earthworms into agricultural and reclaimed land are natural experiments that provide opportunities to understand the attributes of successful invaders and their impacts on local biota and ecosystem processes. We consider various case studies (e.g., earthworm invasions in agricultural soils in Australia and Brazil) and deliberate introductions of earthworms into reclaimed mine sites, landfills and cutaway peat in the U.K. and Ireland. Invasions of exotic earthworms, such as European Lumbricidae in Australia, have been geographically extensive, but remain very patchy at regional and field scales. Their impacts on soil properties, plant production and other biota are therefore also likely to be patchy. Various methods have been developed to deliberately inoculate exotic earthworms into disturbed lands, with varying degrees of success. The factors controlling success are, in general, poorly understood. A broad range of impacts of invasive earthworms on soil properties (e.g., soil structure, nutrient availability, burial of surface materials, incidence of root diseases) and plant yield and quality have been reported. Less is known of the impacts of invasive earthworms on other soil fauna, but they are likely to occur due to alterations in food availability and habitat structure. Influences on other biota are likely to extend to aboveground communities as well as those belowground. Introductions of earthworms to disturbed lands can yield substantial benefits in agricultural productivity and amelioration of soil degradation. However, the potential impact of the promotion or control of such introductions on non-target biota and ecosystem processes in pristine ecosystems nearby should be considered. 相似文献
12.
Links between plant community composition,soil organic matter quality and microbial communities in contrasting tundra habitats 总被引:6,自引:0,他引:6
Plant communities, soil organic matter and microbial communities are predicted to be interlinked and to exhibit concordant
patterns along major environmental gradients. We investigated the relationships between plant functional type composition,
soil organic matter quality and decomposer community composition, and how these are related to major environmental variation
in non-acid and acid soils derived from calcareous versus siliceous bedrocks, respectively. We analysed vegetation, organic
matter and microbial community compositions from five non-acidic and five acidic heath sites in alpine tundra in northern
Europe. Sequential organic matter fractionation was used to characterize organic matter quality and phospholipid fatty acid
analysis to detect major variation in decomposer communities. Non-acidic and acidic heaths differed substantially in vegetation
composition, and these disparities were associated with congruent shifts in soil organic matter and microbial communities.
A high proportion of forbs in the vegetation was positively associated with low C:N and high soluble N:phenolics ratios in
soil organic matter, and a high proportion of bacteria in the microbial community. On the contrary, dwarf shrub-rich vegetation
was associated with high C:N and low soluble N:phenolics ratios, and a high proportion of fungi in the microbial community.
Our study demonstrates a strong link between the plant community composition, soil organic matter quality, and microbial community
composition, and that differences in one compartment are paralleled by changes in others. Variation in the forb-shrub gradient
of vegetation may largely dictate variations in the chemical quality of organic matter and decomposer communities in tundra
ecosystems. Soil pH, through its direct and indirect effects on plant and microbial communities, seems to function as an ultimate
environmental driver that gives rise to and amplifies the interactions between above- and belowground systems.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
13.
Vegetation and soil development during succession in coastal dune slacks on Terschelling island, the Netherlands, was investigated, by comparing neighbouring ecosystems on similar substrates that had been developing for 1, 5, 35 and 76 years since the vegetation and organic soil layer had been removed. In this successional sequence, soil organic matter accumulated rapidly due to the production of litter and dead roots. N mineralization was extremely low, increasing from 0.2 g m-2 yr-1 after 5 years to 0.8 g m-2 yr-1 after 76 years. It was accompanied by a decline in the pH (KCl) in the upper 10 cm of the soil from 6.8 to 4.4. Most of the above-ground biomass accumulated in the shrub species Oxycoccus macrocarpos and Salix repens. The 5- year-old plots harboured many plant species (18 species per 0.25 m2), but plant species diversity was much lower in the older plots. It is concluded that most changes in species composition and the decline in diversity occurred because early successional plant species were gradually outshaded by the thick litter layer and the accumulated shrub biomass. 相似文献
14.
Plant litter may play an important role in herbaceous plant communities by limiting primary production and influencing plant
species richness. However, it is not known how the effect of litter interacts with fertilization. We tested for the role of
litter and fertilization in a large-scale experiment to investigate effects on diversity and biomass of plant species, growth
forms, native vs. non-native groups, and abiotic ecosystem components (e.g., soil moisture, PAR). We manipulated plant litter
(removed vs. left in situ) and nutrient availability (NPK-fertilized vs. unfertilized) for 4 years in 314-m2 plots, replicated six times, in an old-field grassland. While many of our species-level results supported previously published
studies and theory, our plant group results generally did not. Specifically, grass species richness and forb biomass was not
affected by either fertilization or plant litter. Moreover, plant litter removal significantly increased non-native plant
species richness. Relative to native plant species, all of our experimental manipulations significantly increased both the
biomass and the species richness of non-native plant species. Thus, this grassland system was sensitive to management treatments
through the facilitation of non-native plant species. We coupled biotic and abiotic components within a nonmetric multidimensional
scaling (NMS) analysis to investigate treatment effects, which revealed that specific treatments altered ecosystem development.
These results suggest that fertilization and plant litter may have larger impacts on plant communities and on ecosystem properties
than previously understood, underscoring the need for larger-scale and longer-term experiments. 相似文献
15.
BENOÎT GESLIN MATHILDE BAUDE FRANCOIS MALLARD ISABELLE DAJOZ 《Ecological Entomology》2014,39(3):334-342
1. Size variations in pollinator populations may modify competitive interactions among foragers. Competition among pollinators has been shown to lead to one of two contrasting behaviours: either specialisation to the most profitable plant species or generalisation to several species. When foraging, pollinators are also confronted with heterogeneity in the spatial distribution of plant resources. Because variations in both the forager density and plant spatial distribution can affect pollinator behaviour, focus was on the interactive effect of these two factors. 2. Bumble bee (Bombus terrestris L.) individuals were trained on a focal species (Lotus corniculatus L.) and experimentally tested whether variations in the forager density (two or six bumble bees foraging together), plant community spatial distribution (two plant species: L. corniculatus and Medicago sativa, which were either patchily or randomly distributed), and their interaction modified bumble bee foraging behaviour. 3. It was shown that when confronted with a high forager density, bumble bees focused their visits towards the most familiar species, especially when foraging under a random plant distribution. These modifications affected the fruiting of the focal plant species, with a significantly lower reproductive success under low density/patchy conditions. 4. This study demonstrates that the foraging decisions of bumble bees are influenced by variations in both the conspecific density and plant spatial distribution. Given the increasing impact of human activities on plant‐pollinator communities, this raises the question of the potential implications of these results for plant communities in natural conditions when confronted with variations in the pollinator density and spatial distribution of plants. 相似文献
16.
MARTINE KOS PATRICK KABOUW ROZEMARIJN NOORDAM KOEN HENDRIKS LOUISE E. M. VET JOOP J. A. VAN LOON MARCEL DICKE 《Ecological Entomology》2011,36(3):377-388
1. Plant resistance against herbivores can act directly (e.g. by producing toxins) and indirectly (e.g. by attracting natural enemies of herbivores). If plant secondary metabolites that cause direct resistance against herbivores, such as glucosinolates, negatively influence natural enemies, this may result in a conflict between direct and indirect plant resistance. 2. Our objectives were (i) to test herbivore‐mediated effects of glucosinolates on the performance of two generalist predators, the marmalade hoverfly (Episyrphus balteatus) and the common green lacewing (Chrysoperla carnea) and (ii) to test whether intraspecific plant variation affects predator performance. 3. Predators were fed either Brevicoryne brassicae, a glucosinolate‐sequestering specialist aphid that contains aphid‐specific myrosinases, or Myzus persicae, a non‐sequestering generalist aphid that excretes glucosinolates in the honeydew, reared on four different white cabbage cultivars. Predator performance and glucosinolate concentrations and profiles in B. brassicae and host‐plant phloem were measured, a novel approach as previous studies often measured glucosinolate concentrations only in total leaf material. 4. Interestingly, the specialist aphid B. brassicae selectively sequestered glucosinolates from its host plant. The performance of predators fed this aphid species was lower than when fed M. persicae. When fed B. brassicae reared on different cultivars, differences in predator performance matched differences in glucosinolate profiles among the aphids. 5. We show that not only the prey species, but also the plant cultivar can have an effect on the performance of predators. Our results suggest that in the tritrophic system tested, there might be a conflict between direct and indirect plant resistance. 相似文献
17.
Disparate effects of plant genotypic diversity on foliage and litter arthropod communities 总被引:1,自引:0,他引:1
Intraspecific diversity can influence the structure of associated communities, though whether litter-based and foliage-based
arthropod communities respond to intraspecific diversity in similar ways remains unclear. In this study, we compared the effects
of host-plant genotype and genotypic diversity of the perennial plant, Solidago altissima, on the arthropod community associated with living plant tissue (foliage-based community) and microarthropods associated with
leaf litter (litter-based community). We found that variation among host-plant genotypes had strong effects on the diversity
and composition of foliage-based arthropods, but only weak effects on litter-based microarthropods. Furthermore, host-plant
genotypic diversity was positively related to the abundance and diversity of foliage-based arthropods, and within the herbivore
and predator trophic levels. In contrast, there were minimal effects of plant genotypic diversity on litter-based microarthropods
in any trophic level. Our study illustrates that incorporating communities associated with living foliage and senesced litter
into studies of community genetics can lead to very different conclusions about the importance of intraspecific diversity
than when only foliage-based community responses are considered in isolation.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
18.
Agricultural intensification and climate change are expected to affect pest performance through excessive inputs of chemical fertilizers and increased probability of extreme drought events. Potential interactive effects of fertilization and water availability on aboveground pest performance may depend on soil fertility because of its effect on nutrient availability. In a greenhouse experiment, we examined the effects of inorganic fertilization on the performance of the grain aphid (Sitobion avenae, F.), an important pest of wheat, under different conditions of soil fertility and water availability. We found soil fertility and water availability to influence the positive effects of inorganic fertilizers on aphid growth, i.e. fertilization promoted faster aphid development time and higher fecundity and biomass under low fertility and under well-watered conditions. Moreover, although increased soil fertility favored aphid growth under well-watered conditions, it simultaneously sustained plant development. The current practices promoting soil fertility do not have direct negative consequence on crop protection under conventional cropping systems. 相似文献
19.
The population density of herbivores depends on the spatial scale as well as the temporal scale. In a small-scale, short-term
experiment, the number of individuals entering from the surrounding area will be most influential in determining the herbivore
density. In large-scale, long-term experiments, however, the density of herbivores will rather be influenced by the survival
rate of individuals inside the field because most of the herbivorous population derives from the parents that developed inside
the field. If we want to predict the large-scale long-term density of herbivores, therefore, emphasis should be placed on
the estimation of survival rate. To elucidate the effects of plant density on the large-scale long-term abundance of cabbage
pests, we examined the survival rates of three lepidopterous pests, the small white butterfly Pieris rapae crucivora Boisduval (Pieridae), the beet semi-looper Autographa nigrisigna (Walker) (Noctuidae), and the diamondback moth Plutella xylostella (Linnaeus) (Yponomeutidae) under two levels of plant spacing (sparse plot, 2 m × 2 m interval; dense plot, 0.5 m × 0.5 m
interval). The experiment with four blocks was repeated in two seasons. The number of eggs per plant was larger in the sparse
plots than in the dense plots for all species. The survival rate of eggs and larvae, on the contrary, was lower in the sparse
plots than in the dense plots. The lower survival rate of eggs in the sparse plots was mainly caused by the density dependency,
while the lower survival rate of larvae in the sparse plots was mainly caused by the direct effects of plant density. It was
thus suggested that the density of herbivores may become lower in the sparsely planted field in the long run because of the
higher mortality of larvae.
Received: September 16, 1998 / Accepted: March 22, 1999 相似文献
20.
Kareem M. Mousa Metwaly M.S. Metwaly Mohammed Ali Alshehri Samy M. Sayed Osama M. Rakha 《Saudi Journal of Biological Sciences》2022,29(4):2926
The biotic and abiotic factors including the agricultural implementation can modify soil acidification. We hypothesized that soil pH should as repercussion, alter the plant physiological and physical properties and eventually affect insect herbivores including agricultural pests. This study aimed to evaluate the impact of seven levels of soil pH on the performance of cowpea aphid Aphis craccivora on Vicia faba. Significant relationships between soil pH and growth of host bean seedlings or development and reproduction of the aphid were detected. Data demonstrated significant differences in the total longevity, the pre-reproductive, reproductive, post-reproductive and pre-viviparity periods. Within a suitable range of pH for bean growth between pH 5.3 and pH 7.2, the aphid performance was worse on seedlings growing better, however, under unfavorable extreme pH conditions, plant quality measured as height did not affect the aphids anymore and their performance was uniformly low except the case in pH 8.1 condition in which the best aphid reproduction was observed. The results confirm that soil pH affect the performance of cowpea aphid A. craccivora and also exhibited strong influence on the growth of broad bean plants. 相似文献