首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
In the long term, defoliation of plants can be hypothesized to decrease plant carbon supply to soil decomposers and thus decrease decomposer abundance and nutrient mineralization in the soil. To test whether defoliation creates changes in soil that can feedback to plant growth, we collected soil from sub-arctic grassland plots that had been either defoliated or non-defoliated for three years and followed the growth of different plant species combinations in these soils in greenhouse conditions. Plant N acquisition and plant growth were lower in the soil collected from the defoliated field plots than in the soil collected from the non-defoliated plots. This response did not depend on the species composition or richness of the tested plant community. In the field, defoliation decreased net nitrogen mineralization. Despite the negative effect of decreased nutrient mineralization rate on plant growth and N accumulation in the greenhouse test, the aboveground abundance of most plant species was not affected by defoliation in the field. This indicates that plants in these sub-arctic grasslands can at least temporarily overcome defoliation-induced decrease in soil nutrient availability. To our knowledge, our results are the first direct evidence that defoliation can induce changes in the soil that negatively feedback to plant growth and N accumulation. This finding indicates that, especially in arctic and sub-arctic grasslands where nutrient mineralization rates are inherently low, soil feedbacks can have an important role in the outcome of herbivore–plant interactions.  相似文献   

2.
Defoliation-induced changes in grass growth and C allocation are known to affect soil organisms, but how much these effects in turn mediate grass responses to defoliation is not fully understood. Here, we present results from a microcosm study that assessed the role of arbuscular mycorrhizal (AM) fungi and soil decomposers in the response of a common forage grass, Phleum pratense L., to defoliation at two nutrient availabilities (added inorganic nutrients or no added nutrients). We measured the growth and C and N allocations of P. pratense plants as well as the abundance of soil organisms in the plant rhizosphere 5 and 19 d after defoliation. To examine whether defoliation affected the availability of organic N to plants, we added 15N-labelled root litter to the soil and tracked the movement of mineralized 15N from the litter to the plant shoots.When inorganic nutrients were not added, defoliation reduced P. pratense growth and root C allocation, but increased the shoot N concentration, shoot N yield (amount of N in clipped plus harvested shoot mass) and relative shoot N allocation. Defoliation also reduced N uptake from the litter but did not affect total plant N uptake. Among soil organisms, defoliation reduced the root colonization rates of AM fungi but did not affect soil microbial respiration or the abundance of microbe-grazing nematodes. These results indicate that interactions with soil organisms were not responsible for the increased shoot N concentration and shoot N yield of defoliated P. pratense plants. Instead, these effects apparently reflect a higher efficiency in N uptake per unit plant mass and increased relative allocation of N to shoots in defoliated plants. The role of soil organisms did not change when additional nutrients were available at the moment of defoliation, but the effects of defoliation on shoot N concentration and yield became negative, apparently due to the reduced ability of defoliated plants to compete for the pulse of inorganic nutrients added at the moment of defoliation.Our results show that the typical grass responses to defoliation—increased shoot N concentration and shoot N yield—are not necessarily mediated by soil organisms. We also found that these responses followed defoliation even when the ability of plants to utilize N from organic sources, such as plant litter, was diminished, because defoliated plants showed higher N-uptake efficiency per unit plant mass and allocated relatively more N to shoots than non-defoliated plants.  相似文献   

3.
To test a hypothesis that the effects of defoliation on plant ecophysiology and soil organisms depend on the timing of defoliation within a growing season, we established a greenhouse experiment using replicated grassland microcosms. Each microcosms was composed of three plant species, Trifolium repens, Plantago lanceolata and Phleum pratense, growing in grassland soil with a diverse soil community. The experiment consisted of two treatment factors—defoliation and plant growth phase (PGP)—in a fully factorial design. Defoliation had two categories, i.e. no trimming or trimming a total of four times at 2 week intervals. The PGP treatment had four categories, i.e. 1, 3, 7 or 13 weeks growth following planting before the first defoliation (subsequently referred to as PGP1, PGP2, PGP3 and PGP4, respectively). In each PGP treatment category, microcosms were harvested 1 week after the final defoliation. Harvested shoot and root mass and total shoot production (including trimmed and harvested shoot mass) increased with time and were lower in defoliated than in non-defoliated systems. The fraction of root biomass of harvested plant biomass decreased with time but was increased by defoliation at PGP3 and PGP4. The proportion of T. repens in total shoot production increased and those of P. lanceolata and P. pratense decreased with time. Defoliation increased the proportions of P. lanceolata and P. pratense in total shoot production at PGP3 and PGP4. Root N and C concentrations increased and root C-to-N ratio decreased with time in non-defoliated systems. Defoliation increased root N concentration by 38 and 33% at PGP1 and PGP2, respectively, but decreased the concentration by 22% at PGP4. In contrast, defoliation reduced root C concentration on average by 1.5% at each PGP. As with the effects on root N concentration, defoliation decreased the root C-to-N ratio at PGP1 and PGP2 but increased the ratio at PGP4. Among soil animal trophic groups, the abundance of herbivorous nematodes was higher at PGP4 than at PGP1-3 and that of predacious nematodes higher at PGP2-4 than at PGP1, while the abundance of bacterivorous, fungivorous and omnivorous nematodes and that of detritivorous enchytraeids did not differ between the PGP categories. Among bacterivorous nematodes, however, Acrobeloides, Chiloplacus and Protorhabditis species decreased and that of Plectus spp. increased with time. Defoliation did not affect the abundance of soil animal trophic groups, but reduced the abundance of herbivorous Coslenchus spp. at each PGP and raised the abundance of herbivorous Rotylenchus spp. and bacterivorous Eucephalobus spp. at PGP4. Confirming our hypothesis, the results suggest that the effects of defoliation on the attributes of grassland plants, such as biomass allocation between roots and shoots and root quality, may depend on the timing of defoliation within a growing season. However, contradicting our hypothesis, the results suggest that significant changes in plant attributes after defoliation may not always lead to substantial changes in the abundance of belowground organisms.  相似文献   

4.
Herbivores can indirectly affect ecosystem productivity by modifying feedbacks that occur between dominant plants and below-ground properties, especially through altering nutrient availability in soil. The aim of this study was to examine, under controlled conditions, the effect of simulated browsing by large herbivores on the growth characteristics of downy birch (Betula pubescens), a dominant tree species of native regenerating forests in northern Britain, and to determine how effects of browsing on tree growth cascaded through to soil microbial communities, thereby affecting nutrient availability in soil. Downy birch seedlings were grown in mesocosms for 2 years and subjected to simulated browsing in the form of defoliation and clipping treatments. Upon destructive harvest, a number of measures of both tree growth characteristics and soil biological and nutrient properties were made. Clipping of birch trees significantly reduced total root biomass (27%), fine root biomass (29%), coarse root biomass (27%) and above-ground biomass (18%), whereas defoliated trees were significantly shorter than non-defoliated trees. Despite these significant and negative effects of browsing on tree growth, soil biological properties remained largely unaffected, other than rates of N mineralisation, which were greater under defoliated trees. We conclude that other factors, such as herbivore effects on litter quantity and quality which feedback to soil biological properties in the longer-term are more important in determining ecosystem responses to browsing.  相似文献   

5.
Plant roots compete for nutrients mineralised by the decomposer community in soil. By affecting microbial biomass and activity Collembola influence the nutrient availability to plants. We investigated the effect of Collembola (Protaphorura fimata Gisin) on growth and competition between of two plant species, Cirsium arvense L (creeping thistle) and Epilobium adnatum Griseb. (square-stemmed willow herb), in a laboratory experiment. Two seedlings of each plant species were planted in rhizotrons either in combination or in monoculture (intra- and interspecific competition). Interspecific competition strongly reduced total biomass of C. arvense whereas E. adnatum suffered most from intraspecific competition. Collembola neither affected the competitive relationship of the two plant species nor shoot and root biomass. Although Collembola did not affect total root biomass they influenced root morphology of both plant species. Roots grew longer and thinner and had more root tips in presence of Collembola. Root elongation is generally ascribed to the exploitation of nutrient rich patches in soil. We hypothesise that changes in root morphology in presence of Collembola are due to Collembola-mediated changes in nutrient availability and distribution.  相似文献   

6.
The productivity and diversity of plant communities are affected by soil organisms such as arbuscular mycorrhizal fungi (AMF), root herbivores and decomposers. However, it is unknown how interactions between such functionally dissimilar soil organisms affect plant communities and whether the combined effects are additive or interactive. In a greenhouse experiment we investigated the individual and combined effects of AMF (five Glomus species), root herbivores (wireworms and nematodes) and decomposers (collembolans and enchytraeids) on the productivity and nutrient content of a model grassland plant community as well as on soil microbial biomass and community structure. The effects of the soil organisms on productivity (total plant biomass), total root biomass, grass and forb biomass, and nutrient uptake of the plant community were additive. AMF decreased, decomposers increased and root herbivores had no effect on productivity, but in combination the additive effects canceled each other out. AMF reduced total root biomass by 18%, but decomposers increased it by 25%, leading to no net effect on total root biomass in the combined treatments. Total shoot biomass was reduced by 14% by root herbivores and affected by an interaction between AMF and decomposers where decomposers had a positive impact on shoot growth only in presence of AMF. AMF increased the shoot biomass of forbs, but reduced the shoot biomass of grasses, while root herbivores only reduced the shoot biomass of grasses. Interactive effects of the soil organisms were detected on the shoot biomasses of Lotus corniculatus, Plantago lanceolata, and Agrostis capillaris. The C/N ratio of the plant community was affected by AMF.In soil, AMF promoted abundances of bacterial, actinomycete, saprophytic and AMF fatty acid markers. Decomposers alone decreased bacterial and actinomycete fatty acids abundances but when decomposers were interacting with herbivores those abundances were increased. Our results suggests that at higher resolutions, i.e. on the levels of individual plant species and the microbial community, interactive effects are common but do not affect the overall productivity and nutrient uptake of a grassland plant community, which is mainly affected by additive effects of functionally dissimilar soil organisms.  相似文献   

7.
Plants are often grazed resulting in a sudden and significant removal of shoot tissue, which decreases photosynthesis and changes C allocation between within the plant. From results obtained in percolated sand it is possible to demonstrate an increase of rhizodeposition within few days after defoliation followed by a decrease of rhizodeposition. The aim of our study was to test if this pattern can be also observed for plants grown in soil. We grew Plantago arenaria in microcosms and defoliated half of them after 45 d. Half of the defoliated and non-defoliated microcosms were harvested 1.5 d, and the other half 8.5 d, after defoliation. We observed an increase of microbial biomass 1.5 d after defoliation followed by a decrease assessed 8.5 d after the treatment. In parallel, soil soluble C and the metabolic quotient of the microbial biomass first decreased and then increased at the second harvest reaching values equivalent to those of the non-defoliated treatment. Based on these results together with results obtained in artificial soil, we conclude that the defoliation of P. arenaria grown in soil leads to a transient peak of root exudation.  相似文献   

8.
We performed a controlled experiment with rice seedlings (Oryza sativa L.) growing in Petri dishes on homogeneous nutrient agar containing a simple rhizosphere food web consisting of a diverse bacterial community and a common soil protozoa, Acanthamoeba castellanii, as bacterial grazer. Presence of amoebae increased bacterial activity and significantly changed the community composition and spatial distribution of bacteria in the rhizosphere. In particular, Betaproteobacteria did benefit from protozoan grazing. We hypothesize that the changes in bacterial community composition affected the root architecture of rice plants. These effects on root architecture affect a fundamental aspect of plant productivity. Root systems in presence of protozoa were characterized by high numbers of elongated (L-type) laterals, those laterals that are a prerequisite for the construction of branched root systems. This was in sharp contrast to root system development in absence of protozoa, where high numbers of lateral root primordia and short (S-type) laterals occurred which did not grow out of the rhizosphere region of the axile root. As a consequence of nutrient release from grazed bacteria and changes in root architecture, the nitrogen content of rice shoots increased by 45% in presence of protozoa. Our study illustrates that interactions over three trophic levels, i.e. between plants, bacteria and protozoa significantly modify root architecture and nutrient uptake by plants.  相似文献   

9.
The aim of this study was to test the relative importance of changes in density and species richness of soil mesofauna as determinants of nutrient mineralisation and plant growth. The experiment was carried out using microcosms containing a mixture of plant litter and soil in which seedlings of Lolium perenne were planted, and a range of combinations of levels of density and species richness of microarthropods added. Over the duration of the experiment, nutrient release, measured as concentrations of NO3 --N and total N in leachates, increased significantly with increasing microarthropod density, but decreased with increasing species richness. Leachate concentrations of NH4 +-N, dissolved organic N and C (DON and DOC) were not affected by the faunal treatments. Soil respiration, a measure of microbial activity, decreased with increasing density of microarthropods, whereas microbial biomass was not affected by microarthropods. Increasing density of soil animals had a negative effect on the shoot biomass of L. perenne while the effect of species richness was positive. Neither the species richness nor density of soil microarthropods was found to significantly influence root biomass. We conclude that variations in animal density had a greater influence on soil nutrient mineralisation processes than did species richness. Possible reasons for these opposing effects of animal density and diversity on soil N mobilization are discussed.  相似文献   

10.
The facilitating effect of the exudation of carbon (C) compounds from roots on rhizospheric processes has been shown in controlled experiments; however, it still remains unclear how important this pathway of C from plants to the soil may be in energy and nutrient processes in grazed grasslands under natural conditions. Root exudation may be a particularly important C pathway in grazed grasslands and help promote positive feedbacks between large herbivores and plants. In this study we performed a 13C pulse-chase experiment on plots that were clipped or left unclipped in a mesic grassland in Yellowstone National Park. The dominant grass species in the plots was Poa pratensis and it was used to measure the effect of defoliation on root C exudation, the rhizospheric microbial community, and feedbacks on plant nutrient uptake over a time period of 24–72 h. Defoliation stimulated C exudation from roots by 1.5-fold, which concomitantly increased rhizospheric microbial biomass by the same factor. The facilitating effects of defoliation on rhizospheric processes resulted in positive feedback on soil inorganic N pools and leaf N content, which increased by 1.2- and 1.5-fold respectively. Changes in soil inorganic N pools during the experiment indicated that the effect of the C flush on the rhizospheric decomposer community of defoliated plants resulted in a 5-fold increase in rhizospheric daily net N mineralization rate. These findings demonstrate that in a natural grassland community defoliation-induced stimulation of C exudation stimulates rhizospheric N-mineralization which ultimately benefits defoliated plants. The results also indicate the important role that short-term root–rhizospheric microbe interactions play in the C and N processes in grazed grasslands.  相似文献   

11.
A potassium-releasing bacterial strain Bacillus edaphicus NBT was examined for plant-growth-promoting effects and nutrient uptake on cotton and rape in K-deficient soil in pot experiments. Inoculation with bacterial strain B. edaphicus NBT was found to increase root and shoot growth of cotton and rape. Strain NBT was able to mobilize potassium efficiently in both plants when illite was added to the soil. In cotton and rape growing in soils treated with insoluble potassium and inoculated with strain NBT, the potassium content was increased by 30 and 26%, respectively. Bacterial inoculation also resulted in higher N and P contents of above ground plant components. The bacterial isolate was also able to colonize and develop in the rhizosphere soil of cotton and rape after root inoculation.  相似文献   

12.
The effects of calcium and humic acid on seed germination, growth and macro- and micro-nutrient contents of tomato (Lycopersicon esculentum L.) seedlings in saline soil conditions were evaluated. Different levels of humic acid (0, 500, 1000 and 2000 mg kg?1) and calcium (0, 100, 200 and 400 mg kg?1) were applied to growth media treated with 50 mg NaCl kg?1 before sowing seeds. Seed germination, hypocotyl length, cotyledon width and length, root size, shoot length, leaf number, shoot and root fresh weights, and shoot and root dry weights of the plant seedlings were determined. Macro- and micro-nutrient (N, P, K, Ca, Mg, S, Cu, Fe, Mn and Zn) contents of shoot and root of seedlings were also measured. Humic acid applied to the plant growth medium at 1000 mg kg?1 concentration increased seedling growth and nutrient contents of plants. Humic acid not only increased macro-nutrient contents, but also enhanced micro-nutrient contents of plant organs. However, high levels of humic acid arrested plant growth or decreased nutrient contents. Levels of 100 and 200 mg kg?1 Ca2+ application significantly increased N, Ca and S contents of shoot, and N and K contents of root.  相似文献   

13.
Interactions between the biocontrol fungus Clonostachys rosea IK 726 and a tomato/Glomus intraradices BEG87 symbiosis were examined with and without wheat bran, which served as a food base for C. rosea. In soil without wheat bran amendment, inoculation with C. rosea increased plant growth and altered shoot nutrient content resulting in an increase and decrease in P and N content, respectively. Inoculation with G. intraradices had no effect on plant growth, but increased the shoot P content. Dual inoculation with G. intraradices and C. rosea followed the pattern of C. rosea in terms of plant growth and nutrient content. Wheat bran amendment resulted in marked plant growth depressions, which were counteracted by both inoculants and dual inoculation increased plant growth synergistically. Amendment with wheat bran increased the population density of C. rosea and reduced mycorrhizal fungus colonisation of roots. The inoculants were mutually inhibitory, which was shown by a reduction in root colonisation with G. intraradices in treatments with C. rosea and a reduction in colony-forming units (cfu) of C. rosea in treatments with G. intraradices, irrespective of wheat bran amendment. Moreover, both inoculants markedly influenced soil microbial communities examined with biomarker fatty acids. Inoculation with G. intraradices increased most groups of microorganisms irrespective of wheat bran amendment, whereas the influence of C. rosea on other soil microorganisms was affected by wheat bran amendment. Overall, inoculation with C. rosea increased and decreased most groups of microorganisms without and with wheat bran amendment, respectively. In conclusion, despite mutual inhibition between the two inoculants this interaction did not impair their observed plant growth promotion. Both inoculants also markedly influenced other soil microorganisms, which should be further studied in relation to their plant growth-promoting features.  相似文献   

14.
Plant-growth-promoting bacteria isolated from the rhizosphere, phyllosphere and soil of the root zone in different climatic regions of Germany and Uzbekistan were analysed for plant-growth-promoting effects and nutrient uptake on winter wheat on different soils and under different temperature regimes. The investigations were carried out in pot experiments using loamy sand and sandy loam soils from Müncheberg, Germany and Calcisol soil from Tashkent, Uzbekistan. The temperature and soil types were found to influence growth-promoting effects. Inoculation with bacterial strains Pseudomonas fluorescens PsIA12, Pantoea agglomerans 050309 and Mycobacterium sp. 44 isolated from Müncheberg (semi-continental climate) was found to significantly increase the root and shoot growth of winter wheat at 16 °C compared to 26 °C in loamy sand. Mycobacterium phlei MbP18 and Mycoplana bullata MpB46 isolated from Tashkent (semi-arid climate) were found to significantly increase the root and shoot growth of winter wheat in nutrient-poor Calcisol at 38 °C as well as in nutrient-rich loamy sand at 16 °C. Bacterial inoculation also resulted in significantly higher N, P, and K contents of plant components. The bacteria isolates were able to survive in the rhizosphere and in the soil of winter wheat after root and shoot inoculation.  相似文献   

15.
Plants can mediate interactions between aboveground herbivores and belowground decomposers as both groups depend on plant-provided organic carbon. Most vascular plants also form symbiosis with arbuscular mycorrhizal fungi (AMF), which compete for plant carbon too. Our aim was to reveal how defoliation (trimming of plant leaves twice to 6 cm above the soil surface) and mycorrhizal infection (inoculation of the fungus Glomus claroideum BEG31), in nutrient poor and fertilized conditions, affect plant growth and resource allocation. We also tested how these effects can influence the abundance of microbial-feeding animals and nitrogen availability in the soil. We established a 12-wk microcosm study of Plantago lanceolata plants growing in autoclaved soil, into which we constructed a simplified microfood-web including saprotrophic bacteria and fungi and their nematode feeders. We found that fertilization, defoliation and inoculation of the mycorrhizal fungus all decreased P. lanceolata root growth and that fertilization increased leaf production. Plant inflorescence growth was decreased by defoliation and increased by fertilization and AMF inoculation. These results suggest a negative influence of the treatments on P. lanceolata belowground biomass allocation. Of the soil organisms, AMF root colonization decreased with fertilization and increased with defoliation. Fertilization decreased numbers of bacterial-feeding nematodes, probably because fertilized plants produced less root mass. On the other hand, bacterial feeders were more abundant when associated with defoliated than non-defoliated plants despite defoliated plants having less root mass. The AMF inoculation per se increased the abundance of fungal feeders, but the reduced and increased root AM colonization rates of fertilized and defoliated plants, respectively, were not reflected in the numbers of fungal feeders. We found no evidence of plant-mediated effects of the AM fungus on bacterial feeders, and against our prediction, soil inorganic nitrogen concentrations were not positively associated with the concomitant abundances of microbial-feeding animals. Altogether, our results suggest that (1) while defoliation, fertilization and AMF inoculation all affect plant resource allocation, (2) they do not greatly interact with each other. Moreover, it appears that (3) while changes in plant resource allocation due to fertilization and defoliation can influence numbers of bacterial feeders in the soil, (4) these effects may not significantly alter mineral N concentrations in the soil.  相似文献   

16.
  相似文献   

17.
The restoration of grassland and its dependence on the dispersal of characteristic plant species was analysed in the Saale River floodplain near Halle (Germany). Species composition and soil nutrient content were investigated in grassland converted to extensive management in 1989 (“restoration grassland”) and in adjacent grassland that had never been managed intensively (“old grassland”). In two experiments dispersal of Silaum silaus and Serratula tinctoria was studied following introduction of these species into “restoration grassland”. Seedling establishment was recorded and compared with the “old grassland”. Ten years after conversion to extensive management, characteristic floodplain grassland species had only reappeared in locations very close to “old grassland”. There were still differences in soil nutrient content of both grassland sites but a comparison of seedling survival provided evidence that conditions of establishment were similar. However, establishment rates appeared to be low in both grassland types indicating that a large initial input of seeds is required for re-establishment. Seeds of Silaum silaus and Serratula tinctoria were dispersed very short distances. About 75% of the seedlings were found within 1.5 m of parent plants. Management and flooding did not increase dispersal distances. The results strongly suggest that poor dispersal was the main limiting factor in determining the success of restoration. The implications of this result for nature conservation are discussed.  相似文献   

18.
  相似文献   

19.
In coastal foredunes, the grass Ammophila arenaria develops a soil community that contributes to die-back and replacement by later successional plant species. Root-feeding nematodes and pathogenic soil microorganisms are involved in this negative feedback. Regular burial by wind-blown beach sand results in vigorous growth of A. arenaria, probably because of enabling a temporary escape from negative soil feedback. Here, we examine the role of root-feeding nematodes as compared to the whole soil community in causing negative feedback to A. arenaria. We performed a 3-year sand burial experiment in the field and every year we determined the feedback of different soil communities to plant growth in growth chamber bioassays.In the field, we established A. arenaria in tubes with beach sand, added three endoparasitic root-feeding nematode species (Meloidogyne maritima, Heterodera arenaria and Pratylenchus penetrans) or root zone soil to the plants, and created series of ceased and continued sand burial. During three subsequent years, plant biomass was measured and numbers of nematodes were counted. Every year, bioassays were performed with the field soils and biomass of seed-grown A. arenaria plants was measured to determine the strength of feedback of the established soil communities to the plant.In the field, addition of root zone soil had a negative effect on biomass of buried plants. In the bioassays, addition of root zone soil also reduced the biomass of newly planted seedlings, however, only in the case when the field plants had not been buried with beach sand. Addition of the three endoparasitic root-feeding nematodes did not influence plant biomass in the field and in the bioassays. Our results strongly suggest that the negative feedback to A. arenaria is not due to the combination of the three endoparasitic nematodes, but to other components in the soil community, or their interactions with the nematodes.  相似文献   

20.
Intra-species variation in response to defoliation and soil amendment has been largely neglected in terms of the soil microbial community (SMC). The influence of defoliation and soil fertiliser amendment on the structure of the SMC was assessed with two Lolium perenne cultivars contrasting in ability to accumulate storage reserves. Plant response to defoliation was cultivar specific and depended on the nutrient amendment of the soil. Results suggested a greater ability to alter plant biomass allocation in the low carbohydrate accumulating cultivar (S23) compared to the high carbohydrate cultivar (AberDove) when grown in improved (IMP), but not in unimproved (UNI), soil. Although differences in plant growth parameters were evident, no treatment effects were detected in the size of the active microbial biomass (total phospholipid fatty acid (PLFA) 313.8 nmol g−1 soil±33.9) or proportions of PLFA signature groups. A lower average well colour development (AWCD) of Biolog sole carbon source utilisation profiles (SCSUPs) in defoliated (D) compared to non-defoliated (ND) treatments may be indicative of lower root exudation 1 week following defoliation, as a consequence of lower root non-structural carbohydrate (NSC) concentrations. Within the bacterial community the lower cyclopropyl-to-precursor ratio of PLFAs, and the trans/cis ratio of 16:1w7, in UNI relative to IMP soil treatments indicates lower physiological stress in UNI soils regardless of L. perenne cultivar. Discrimination of broad scale SMC structure, measured by PLFA analysis, revealed that soil treatment interacted strongly with cultivar and defoliation. In IMP soils the SMCs discriminated between cultivars while defoliation had little effect. Conversely, in UNI soils defoliation caused a common shift in the SMC associated with both cultivars, causing convergence of overall community structure. Separation of SMC structure along the primary canonical axis correlated most strongly (P<0.001) with root:shoot ratio (47.6%), confirming that differences in cultivar C-partitioning between treatments were influential in defining the rhizosphere microbial community.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号