Showing papers by "Martin Zobel published in 2004"
TL;DR: It is suggested that the presence of AM fungi that are more beneficial for the common species may be one factor behind the observed differential distribution and performance of the two plant species.
Abstract: Summary
1
An experiment was carried out to determine whether the community composition of root-colonizing arbuscular mycorrhizal fungi (AMF) influences the growth and nutrient status of two congeneric Pulsatilla species, one rare and one common in Estonia. We hypothesized that: (i) establishment and growth of plants is influenced by the composition of native AMF communities; (ii) growth of congeneric plant species with different abundances differs due to their response to specific AMF communities; and (iii) distribution of a plant species may depend on the composition of local root symbiotic AMF communities.
2
Rare Pulsatilla patens and common Pulsatilla pratensis were grown in pots, under homogeneous soil nutrient and microbial community conditions, containing either one from two (grassland and forest sites) of natural AMF soil inocula, or no AMF.
3
Lower establishment was observed in the non-mycorrhizal soil compared to AMF inoculated soils. Plant biomass, phosphorus concentration and root AMF colonization of both species were higher, and nitrogen concentration lower, in grassland as opposed to forest inoculum.
4
The common species displayed more vigorous growth than the rare counterpart in the presence of grassland inoculum. Conversely, slightly better growth of a rare species was recorded in the forest inoculum, in which plant biomass was an order of magnitude lower compared to the grassland inoculum.
5
As Pulsatilla spp. roots hosted site-characteristic AMF small-subunit rDNA sequence groupings, we suggest that the presence of AM fungi that are more beneficial for the common species may be one factor behind the observed differential distribution and performance of the two plant species.
126 citations
TL;DR: It is concluded that moisture conditions have a differential effect on the three fescue species mainly in the seedling establishment, not in the germination phase, and the coincidence of high rainfall and local disturbance, removing bryophytes, is required for the successful establishment of F. rubra and F. pratensis.
Abstract: Festuca ovina is the abundant matrix-forming species and F. rubra a subordinate species in shallow-soil calcareous grasslands. F. pratensis is a transient species, occurring sparsely in this community. We hypothesised that the different abundances of these three species are primarily due to the differential effect of moisture conditions on their germination and early establishment, and that the effect of the pattern of rainfall intensity depends on the presence or absence of a bryophyte layer. We studied the dependence of the germination and establishment of the three fescue species on the moisture conditions both in the laboratory and in the patches of intact grassland community (microcosms). In a laboratory germination experiment, F. pratensis showed the highest, F. rubra , the intermediate and F. ovina, the lowest drought tolerance. In microcosms, the establishment of F. ovina was the highest. At the same time, the annual mortality of seedlings of F. ovina was the lowest. All three species responded positively to an increasing irrigation level. Differently from F. ovina, F. rubra showed a positive response only in plots from which the bryophyte layer had been removed, while F. pratensis responded positively to both irrigation and bryophyte removal. We conclude that moisture conditions have a differential effect on the three fescue species mainly in the seedling establishment, not in the germination phase. For the successful establishment of F. rubra and F. pratensis, the coincidence of high rainfall and local disturbance, removing bryophytes, is required. The presence or absence of bryophytes had no effect on establishment in dry years, while in rainy years the removal of bryophytes has a clear positive effect.
45 citations
TL;DR: Lower vulnerability of D. carthusiana to competition, compared to D. expansa and D. dilatata, may explain the higher regional and local abundance of the former and the rarity of this species in Estonia could rather be explained by the impact of climatic factors.
Abstract: Question: Do different competitive abilities of three fern species explain their different regional abundances? Location: Estonia, Europe. Methods: The factorial pot experiment, in which single individuals of three fern species were grown in natural soil with 0, 2, 4, and 8 neighbouring individuals of Deschampsia flexuosa. Results: The response patterns of different biomass fractions and morphological parameters of fern species were similar to each other. The diploid D. expansa was the most vulnerable to competition, while tetraploid D. carthusiana and D. dilatata were more tolerant. D. carthusiana allocated relatively more to below-ground parts than the other two species and allocation to roots increased when neighbour density increased. For D. expansa and D. dilatata, allocation to below-ground parts decreased at high neighbour density, while in D. dilatata also the relative length of the stipe increased. Thus, the response of D. carthusiana corresponds to a ‘persistence type’ and that of D. di...
25 citations
TL;DR: It is concluded that stage structure of local populations can indicate the regional dynamics of a species and all local Diellia populations have to be considered as priority candi- dates for future conservation efforts.
Abstract: Single census data were used to investigate the stage structure within populations of the endemic fern genus Diellia in the Hawaiian Islands. Populations were classified as "dynamic" (sporelings predominate), "normal", or "regressive" (mature plants predominate). Six taxa were studied: Diellia erecta Brack., Diellia erecta f. alexandri (Hillebr.) W.H. Wagner, Diellia falcata Brack., Diellia mannii (D.C. Eaton) W.J. Rob., Diellia pallida W.H. Wagner, and Diellia unisora W.H. Wagner. There were significant differences between the population stage structures of differ- ent taxa. The populations of D. erecta f. alexandri, and D. unisora represented regressive cases. Diellia pallida was represented by two regressive and one dynamic local population. The status of local populations of D. erecta and D. falcata varied from dynamic to regressive. Diellia erecta f. alexandri, D. mannii, D. pallida, and D. unisora are probably near extinction. Variation in local population conditions of D. erecta, D. falcata, and D. pallida may represent the history of local colonization and subsequent extinction events. The regional dynamics of these taxa correspond with the metapopulation model, since pteridophytes have good dispersal ability, and recruitment of Diellia species takes place only in moist years and is influenced by local disturbances. We conclude that stage structure of local populations can indicate the regional dynamics of a species. All local Diellia populations have to be considered as priority candi- dates for future conservation efforts. Resume : Les auteurs ont utilise les donnees a simple consensus pour examiner la structure des stades des populations de fougeres endemiques appartenant au genre Diellia, aux iles Hawai. Ils ont classifie les populations en « dynami- ques » (ou predominent les plantules issues de spores), « normales » ou « regressives » (les plantes matures predomi- nent). Ils ont etudie six taxons : Diellia erecta Brack., Diellia erecta f. alexandri (Hillebr.) W.H. Wagner, Diellia falcata Brack., Diellia mannii (D.C. Eaton) W.J. Rob., Diellia pallida W.H. Wagner et Diellia unisora W.H. Wagner. On observe des differences significatives dans les structures des stades de population chez les differents taxons. Les po- pulations du D. erecta f. alexandri et du D. unisora montrent des structures regressives. Chez le D. pallida on trouve deux populations regressives et une population dynamique locales. Le statut des populations locales des D. erecta et D. falcata varient, de dynamiques a 'regressifs'. Les D. erecta f. alexandri, D. mannii, D. pallida et D. unisora sont probablement pres de l'extinction. La variation des conditions subies par les populations locales des D. erecta, D. fal- cata et D. pallida pourraient representer l'histoire de la colonisation locale et les evenements subsequents de l'extinc- tion. La dynamique regionale de ces taxons correspond au modele des metapopulations, puisque les pteridophytes possedent une bonne capacite de dispersion, et que le recrutement des especes de Diellia a lieu uniquement au cours des annees humides, tout en etant influencee par les perturbations locales. Les auteurs concluent que la structure des stades des populations locales peuvent indiquer la dynamique regionale d'une espece. Toutes les populations locales de Diellia doivent etre considerees comme candidates prioritaires pour les efforts de conservation a venir.
18 citations