Phytosociological databases are important data sources for a broad scale of ecological investigations. Vegetation samples are traditionally managed and published in tabular format, allowing for handling of the vegetation data in various combinations. Such tables usually comprise relevés originated from the same locality, vegetation type and collected by the same investigator. Nevertheless, these relevés are usually affected by the same bias. In this paper, we demonstrate the importance of the effects acting at the level of the table (i.e., ‘locally’), using the example of species removals from groups of relevés. We examine the effect of the removal of infrequent species on community classification in relation with several data set properties using simulated plot data sampled from simulated coenoclines. A data set comprised groups of relevés (‘tables’), within which relevés are sampled from the same point of the coenocline. Classifications obtained after the removal or permutation of infrequent species occurrences from these tables, after the removal of rare species from randomised tables and without any treatment were compared to a reference classification based on gradient positions of the relevés. The results show that the removal of locally infrequent species helps to recognise the gradient pattern incorporated in the tabular arrangement of relevés if the arrangement of relevés among tables is in accordance with their gradient position. In cases when the grouping of relevés is irrelevant regarding the real underlying pattern, the species removal is disadvantageous. Testing between-table heterogeneity within a data set is an especially successful way of examination of biological relevance of the arrangement of relevés. We conclude that influence of table-level effects is mainly dependent on the pattern which is in accordance with the grouping of plots.
Authors:K. Seis, S. Gärtner, P.J. Donoso, and A. Reif
Today, native vegetation in the Valdivian Coastal Range (VCR) is restricted to areas where small-scale land use dominates resulting in a vegetation mosaic. This study (1) provides a description of the vegetation types (VT) within the vegetation mosaic, (2) identifies land use drivers that lead to either degradation or recovery processes and, (3) attempts to provide an explanation for the vegetation mosaic with a conceptual model. In two regions of the VCR we sampled 102 plots for composition of vegetation and indicators of livestock browsing, timber cutting and coppice forestry. We classified the vegetation using a flexible beta method and Bray-Curtis distance. Diagnostic species were identified by an extended indicator species analysis. The clustering results were visualized in NMDS and recursive partitioning was used to explain variations in the VTs as a function of the land use variables. Differentiating effects were tested using PERMANOVA and a conceptual model for the vegetation dynamics was developed from the results. Four VTs such as (1) extensively grazed non-native grasslands (EGN); (2), closed and semi-closed grazed Ugni and Berberis shrublands; (3) severely impacted evergreen forests; and (4) sparsely disturbed evergreen forests were recognized. The browsing indicators were important for differentiating the VTs. The EGN grasslands were differentiated by having more than 0.075 dung piles/m2. Areas with fewer dung piles but direct browsing effects had the greatest impact on vegetation. Forests were preserved when the mean browsing index was equal to or lower than 0.5. The cutting frequency was significant in determining overall floristic composition. We showed that shrublands and evergreen forests within the vegetation mosaic and the result of small-scale farming led to high native forest species richness. This makes the vegetation mosaic especially valuable in a landscape dominated by exotic tree monocultures.
Relevé data (n = 216) from two-pairs of study areas located in the boreal forest of central and northern Alberta (Canada), with their centroids separated by 3.7° of latitude, were analyzed to determine if latitude-related species richness, composition, and abundance differences occurred in the understories of
forest stands. No difference in study area species richness (
= 0.248) occurred, which included 78 to 105 species (average 94). North compared to south areas had reduced relevé, forb, and graminoid richness; greater dominance concentration; and less total, vascular understory, herb, forb, and graminoid canopy cover (
<0.001). Nine herbs (
Calamagrostis canadensis, Cornus canadensis, Eurybia conspicua, Fragaria virginiana, Galium boreale, Lathyrus ochroleucus, Mertensia paniculata, Pedicularis labradorica
) and two shrubs (
) decreased in abundance (total ∼25% cover) from the south to north areas (
<0.001), and were associated ecologically with more open-growing forests and nontreed sites. Latitudinal differences were interpreted to be a response to cooler and slightly drier climatic conditions, and to reduced PAR availability caused by lower angles of solar incidence and the resulting more intensive shading by trees in northern areas. These factors in combination were estimated to reduce PAR to understory plants by at least 20%. Eight vegetation-types were recognized; each mostly limited to one study area. However, a
type occurred in both south and north areas. The northern variant contained less
(21%) and more (∼6%)
Leymus innovatus, Linnaea borealis
cover than southern stands.
Long term vegetation monitoring provides valuable information on spatio-temporal patterns in plant communities that could be analysed to detect spatial relationship changes among species and to interpret dynamic tendencies and assembly rules in non-equilibrium phytocoenoses. In studies of this kind, one should take into account recent ecological theories emphasizing the scale dependence of vegetation; in particular, fine-scale spatial patterns of vegetation are important constraints in the genesis and maintenance of diversity. The information theory models of Juhász-Nagy offer an appropriate tool for describing the relationship between diversity and multispecies spatial dependence in vegetation. Diversity (florula diversity) and spatial dependence (associatum) are calculated for a series of increasing plot sizes (spatial scaling). The plot sizes at which the two coenostate descriptors reach the maximum information represent the characteristic scales that should be considered as optimal plot sizes in monitoring data collection. Moreover, this methodology enables us to study non-equilibrium dynamics and assembly rules in a more effective way. Diversity and spatial dependence are related, but the power and direction of this relationship change according to environmental characteristics, vegetation type and successional context. The demonstrated correspondence between dominant pattern-generating mechanisms and the related trajectories in abstract coenostate spaces (florula diversity and associatum maximum values), obtained by exploratory simulation studies, can improve interpretation of dynamic state and vegetation tendencies and can support a better inference about the relative role of different background mechanisms. We present some results obtained using this methodology with field data from the forest of Bialowieza National Park (Poland). In particular, we compared the herb layer spatial patterns of dynamically contiguous regeneration phases of the same phytocoenosis. Sampling was performed by recording the presence of plant species in 10 cm x 10cm contiguous microquadrats arranged in 150 m long circular transects. Field data were analysed with the same information theory methods as the ones applied to simulated data. Results show that assemblages of plant individuals are less diverse and more associated in primary than in regenerating stands, suggesting, in both situations, competitive dominance and disturbance as the main ecological mechanisms. Thus, the method was proven effective in distinguishing slightly different dynamical processes.
We performed a gap analysis of protected area networks in Italy to assess the representativeness of potential natural vegetation (PNV) types of the European Natura 2000 network compared with the National Protected Area network. In this context, the PNV map, reflecting the diversity and spatial arrangement of the natural terrestrial ecosystems, can be considered as an appropriate proxy of environmental and biogeographical diversity of Italy. In this country, 775 protected areas are registered in the Official List of Protected Areas (OLPA), 2281 sites are listed as Sites of Community Interest and 590 as Special Protection Areas, constituting the Natura 2000 network. The adopted conservation target considered that any PNV type included for less than the 10% in the PAs network (OLPA, Natura 2000) was defined as a gap in the system. In particular we defined four categories of PNV protection: any PNV types with a representation of less than 10% in both the OLPA and N2000 was defined as a “total gap” (i.e., under-protected); any PNV type with a representation of less than 10% in either the OLPA or the N2000 was defined as a “partial gap”; any PNV type with a representation of between 10 and 50% in both the OLPA and N2000 was defined as “protected”; lastly, any PNV type with a representation of more than 50% in both the OLPA and N2000 was defined as “widely-protected”. Digital overlays of PNV and PAs networks were separately performed and statistics produced, indicating the current state of protection of Potential Natural Vegetation types in the two networks (OLPA and Natura 2000). We found that more than 59% of PNV types recognized on the Italian territory is not protected by the OLPA network. On the contrary, regarding Natura 2000 network, 68% of PNV types are protected, accounting for 27% more than OLPA. Compared to the National network of OLPA, the European network Natura 2000 is characterized by a larger percentage of territory in terms of area (18% of the Italian territory for Natura 2000 vs 10% of OLPA) but also by a smaller size of the sites, allowing for a more coherent distribution and efficiency in the protection of habitat remnants (68% PNV types protected by Natura 2000 vs 41% by OLPA). The proposed PNV approach can help guiding decisions on where and how to spend scarce conservation management resources.
. Changes in soil phosphorus fractions following positive and negative phosphorus balances for long periods. Plant and Soil. 254. 245–261.
1960. Experimentation en petit vases de végétationtypes d
Authors:Márton Mucsi, Péter Csontos, Andrea Borsodi, Gergely Krett, Orsolya Gazdag, and Tibor Szili-Kovács
A talajok hazai és nemzetközi kutatásában egyre nagyobb szerepet kap a talajok mikrobiótájának vizsgálata. Hazai viszonylatban szikes talajokon eddig kevés ilyen irányú kutatás történt. Kutatásunkban kiskunsági szikes talajok mikrobaközösségeinek katabolikus aktivitás mintázatát vizsgáltuk Apajpusztáról származó mintákon. A mintavételhez négy, a szikesedés különböző fázisaira jellemző növényzettel rendelkező területet választottunk ki (szoloncsák vaksziknövényzet, kiskunsági szikfoknövényzet, ürmös szikespuszta és füves szikespuszta), ezek területéről a talaj mikrobiológiai szempontból legaktívabbnak tekintett 0-10 cm-es rétegét mintáztuk.
A minták néhány fontosabb talajtani paraméterét meghatároztuk (szemcseösszetétel, pH, só-, humusz- és mésztartalom, valamint néhány fontosabb tápelem mennyisége). A négy eltérő növényzetű terület között a talajtani paramétereik alapján is jelentős különbségeket tapasztaltunk.
A minták mikrobiológiai aktivitását az itthon még kevéssé ismert mikrorespirációs (MicroRespTM) módszerrel vizsgáltuk. Ennek során a talajmintákhoz 23 különböző szerves szubsztrátot adtunk, és az általuk indukált légzési válaszon keresztül mértük, hogy az egyes talajminták mikrobaközösségei milyen mértékben képesek hasznosítani az egyes szubsztrátokat. Az így kapott, közösségre jellemző katabolikus aktivitás mintázatokat főkomponens elemzéssel és kanonikus korreszpondancia elemzéssel értékeltük.
Eredményeink alapján a mikrorespirációs módszer egyértelműen alkalmas az általunk vizsgált talajok mikrobiótájának elkülönítésére. Az egyes minták katabolikus aktivitás mintázatai közötti különbségek egybevágtak a minták közötti, talajfizikai és —kémiai tulajdonságban megfigyelt eltérésekkel.