Kitaibelia vol. 3 – no. 2. (1998) p.315-316.
Funkciós csoportok térbeli szerveződése löszgyepekben
Bartha Sándor – Fekete Gábor – Molnár Edit – Virágh Klára – Oborny Beáta – Mucina, Ladislav
Sessile plant species express considerable variation in population level attributes that influence their occupation of space and time in a community. Longevity, mode of reproduction, growth forms, and dynamical morphology are examples for characters that influence the way how species compete and exploit resources. Recent non-equilibrium theories of species diversity recognized the importance of that variation in the spatial and temporal dynamics of species and applied it to explain species coexistence. However, few case studies have analysed multispecies patterns within this context. We studied the spatial organization of functional groups in Hungarian loess grasslands at two scales (landscape scale a nd the scale of plant individuals) using spatial statistics. Species were classified into the following functional groups: annual semelparous forbs vs. grasses, perennial soliter semelparous forbs, nonclonal vs. clonal iteroparous perennial forbs, non-clonal vs. clonal dwarf shrubs, perennial grasses, sedges and cryptogams. Some of these groups were further divided into mesic and xeric variants according to the morphology and the ecophysiology of species, and based on their regional coenological preferences. Data about landscape scale variation were collected near Isaszeg estimating the cover of species in ten 2x2m quadrats in each vegetation types, i.e. in stands dominated by Stipa capillata, Bothriochloa ishaemum, Chrysopogon gryllus, Festuca rupicola, Bromus erectus and Brachypodium pinnatum, respectively. Finescale patterns were sampled near Albertirsa in nine 3x5m grids recording presence of plant species in 10x10 cm contiguous quadrats. The nine grids represented different disturbance regimes and successional stages of Festuca and Bothriochloa types of loess vegetation. Fine-scale spatial dependence of functional groups were analysed using information theoretic models across a range of scales from 0.1 to 1.5 m. We found considerable differentiation and significant spatial dependence of functional groups at scales of the landscape and the individuals. Some groups showed similar patterns at both scales, e.g., the mesic versus xeric variants, that were negatively associated. Considering subordinated gap-exploiter groups, annual forbs and short- lived semelparous perennial forbs were positively associated to each other but negatively to soliter perennial forbs at finer scales. At landscape scale, annuals were rare and showed no preference, while the other two groups were positively associated and preferred a mesic, transitional vegetation state, the Bromus erectus type. These results suggest that gap structre is scale dependent and different gap-exploiter groups can utilize these habitats with different strategies. Dominant or co-dominant functional groups (perennial grasses, perennial clonal forbs and dwarf shrubs) showed landscape-scale differentiation along a mesic-xeric gradient but we did not found consistent patterns at fine scales. The pairwise spatial relations of matrix-forming species might be masked by textural and dynamical constraints, and by the indirect effects of other species.