Lengyel Attila kutatói blogja: 61. IAVS szimpózium Montanában

2018. augusztus 22., szerda

61. IAVS szimpózium Montanában

Egy hónapja az Egyesült Államokban, a Montana állambeli Bozemanban jártam, a boziták rendezték ugyanis a Nemzetközi Vegetációtudományi Szövetség (IAVS) éves találkozóját, szám szerint a 61.-et. A rendezvény az érdekes szakmai tematika mellett a közeli Sziklás-hegységbe szervezett kirándulások miatt is vonzó volt. A konferencia honlapja elérhető itt. Az alábbi három prezentációban szerepeltem:

A. Lengyel, G. Swacha, Z. Kącki: Preliminary results from the trait-based numerical classification of Molinio-Arrhenatheretea grasslands in Poland

Descriptive vegetation science has witnessed rapid progress in the last decades due to the improvement of broad-scale electronic databases. Most synthetic works aimed to delimit vegetation types on the basis of numerical analysis of species composition of sample plots. Such classifications are often used as multi-purpose references of habitat types, since the diversity and composition of natural communities are known to determine general ecosystem properties. However, it has been recognized that focusing on species composition may fail to reveal certain patterns of vegetation that are strongly linked with the functioning of ecosystems. Instead of the taxonomic identities of species, their functional traits could offer more relevant information. Functional classifications are expected to have more general validity than speciesbased classifications because often the same traits respond to the same environmental gradients in very different places of the world due to convergent evolution. In contrast, species are dispersal-limited, thus their local abundances are informative only within their respective distributional limits. Our aim was to classify managed herbaceous vegetation on deep soils and temperate climate of Molinio-Arrhenatheretea syntaxonomical class in Poland on the basis of phytosociological relevés, plant trait data, and using numerical methods. A total of 19,995 vegetation plots representing all major grassland types of Poland were retrieved from the Polish Vegetation Database, from which a narrower subset of ca. 6061 Molinio-Arrhenatheretea relevés were resampled. Records of specific leaf area, canopy height, seed mass, clonality and bud bank were obtained from the LEDA and CLOPLA databases. Gaps in the species by traits matrix were filled using Bayesian probabilistic matrix factorization, thus we had measurements or estimates for over 900 species. Several methods for expressing between-plot dissimilarities, noise elimination, and grouping plots were examined. The tested combinations of methods resulted in very different classifications in terms of biological interpretability. Among the several trials, Rao functional dissimilarity index with noise elimination by principal coordinate analysis and Ward’s agglomerative clustering provided the biologically most relevant results. Although, this classification did not reproduce the hierarchy of the syntaxonomical categories at a coarse scale, at finer resolutions the main subtypes of Molinio-Arrhenatheretea were differentiated: mesic and wet hay meadows and pastures, marshes and wet grasslands rich in sedges, herb-dominated tall-forb vegetation, trampled and grazed grasslands. After the first promising results, more specific differences between types in individual traits are subject to further research.

Z. Kącki, G. Swacha, A. Lengyel, M. Chytrý, L. Tichý, E. Stefańska-Krzaczek, M. Czarniecka, J. Korzeniak: Multilevel formalized classification of grasslands (Molino-Arrhenatheretea) in Poland

One of the most important goals of contemporary vegetation science is to create a universal and consistent classification system of vegetation at least at continental scale. This goal is becoming more and more realistic with the advent of new numerical methods and intensive development of vegetation-plot databases around the world. Formalized vegetation classification can be achieved by creating Cocktail definitions of vegetation units. Multi-level formalized classification approach has been proposed for the first time by Janišová and Dúbravková (2010) under the name Hierarchical Expert System. This approach has subsequently been used to create formal definitions of higher vegetation units at the level of alliances or classes. Formal definitions of vegetation units developed so far comprised at most two hierarchical levels, while theoretical basis of vegetation classification according to Braun-Blanquet approach requires development of complete hierarchical systems. The goal of our study was to create a multi-level and nested hierarchical classification system comprising associations, alliances, orders and classes. This system requires the assignment of a relevé to an association to be allowed on condition that this relevé was matched by the definition of alliance, order and class. In order to create formal definitions of vegetation units we used the Cocktail method and methodological achievements of Bruelheide (1997, 2000) and Landucci et. al (2015). Formal definitions were created using two types of groups: sociological species groups and functional species groups. A sociological species group is recorded in a relevé if the relevé contains at least a half of species from the group. Functional species group is recorded in a relevé if total cover of species from the group exceeds the arbitrarily set threshold. Functional species groups include species with a diagnostic value of particular vegetation unit from a hierarchical system. In order to create a functional species group we grouped species based on expert knowledge and extensive phytosociological literature surveys. Multi-level expert system was developed for grassland vegetation of the class Molinio-Arrhenatheretea. We used 85,000 relevés from the Polish Vegetation Database and 9 500 from Grasslands in the Polish Carpathians database. The main focus was on mesic grasslands. We created formal definitions for 17 associations and their superior syntaxonomical units (alliances: Arrhenatherion, Polygono-Trisetion, Cynosurion and Poion alpinae, order: Arrhenatheretalia, class: Molinio-Arrhenatheretea).

W. Willner, J. Roleček, J. Dengler, M. Chytrý, M. Janišová, A. Lengyel, O. Demina, Z. Kącki, A. Korolyuk, A. Kuzemko, U. Šilc, Z. Stančić, K. Vassilev, S. Yamalov: Formal definition of associations using diagnostic species: a case study of European meadow steppes

In 1910, the International Botanical Congress in Brussels defined the association as "plant community of definite floristic composition, uniform habitat conditions and uniform physiognomy". However, the question of what exactly is a "definite floristic composition" has puzzled vegetation scientists for almost a century. In recent decades, it has become clear that a floristic composition can only be considered "definite" if the membership of new plot records can be unambiguously determined on the basis of floristic assignment rules. In our case study, we aimed at establishing formal definitions for all associations of European meadow steppes, using a dataset of 34,173 plot records of dry and semi-dry grasslands of Central and Eastern Europe. Meadow steppes are semi-dry grasslands with a high portion of steppe species, i.e. of species with Siberian-Pontic-Pannonian distribution. In a first step, we classified the dataset into orders and alliances. As starting point, a TWINSPAN classification of the whole dataset was done and the diagnostic species of the main clusters were determined. The plots were re-assigned using formal definitions of the orders, and then the subset of the order Brometalia erecti, corresponding to all semi-dry grasslands of the study area, was again classified. On the basis of this second TWINSPAN classification, formal definitions of the alliances were established. Meadow steppes correspond to the alliance Cirsio-Brachypodion pinnati, which is distributed from Germany in the west to Russia in the East. Finally, we established formal definitions of all associations within this alliance. Associations were identified using (1) the TWINSPAN classification of the whole order, (2) TWINSPAN classifications of regionally restricted data sets (typically all Brometalia plots of one country) and (3) existing national classification schemes. All formal definitions were written in the expert system language of the JUICE program. Altogether, 6,742 plots were assigned to the Cirsio-Brachypodion pinnati. The expert system assigned 89% of these plots to one of 37 associations, while 11% of the plots remained unclassified. The formal definitions follow the logic of a determination key based on diagnostic species. Regional associations are particularly challenging since the constancy of geographical differential species is usually not high enough for them being present in all records of a region. Thus, a certain amount of miss-classified plots seems to be unavoidable unless associations are merged into rather heterogeneous units with very large distribution area. On the other hand, we suggest that sympatric associations should be clearly different in habitat conditions.

A kiránduláson a Yellowstone Nemzeti Park északi szomszédságában, a Yellowstone folyó völgyében jártunk, egy csapadékárnyékos területen, ahol a tengerszint feletti magasság (1000-2000 m) alapján várttól eltérően nem tűlevelű erdők, hanem Artemisia tridentata uralta préri a természetes növényzet. Persze, kicsit üdébb helyeken, illetve még magasabban azért előjön az erdő és a hegyi rétek zónája is. Néhány kép a kirándulásról.