Sand Grassland Research Articles

Detection of fine-scale relationships between species composition and biomass in grassland

We elaborated and tested a novel operative framework for sampling and analysing fine-scale pattern of plant composition and biomass. We combined presence/absence sampling of plant species with non-destructive biomass estimation. In an open perennial sand grassland, we used 46 m long circular transects consisting of 0. 05 m by 0. 05 m adjoining elementary sampling units. This arrangement allows us to scale across a range of 0. 05 to 20 m. For measuring aboveground green biomass, we applied digital camera sensitive to red and near infrared parts of light spectrum, and we calculated normalised differential vegetation index (NDVI). We used information statistics proposed by Juhász-Nagy to study the association between spatial patterns of production and species composition. Since information statistical functions applied require binary data, we transformed NDVI data into one or several binary variables. We found that not only dominant species but subordinate gap species were also associated to high biomass, although the strength of association varied across scales. Most of the significant associations were detected at fine scales, from 0. 05 to 0. 25 m. At the scales commensurable with quadrat sizes usually applied in grasslands, i. e., from 0. 5 to 2. 0 m, we could hardly find any significant associations between species composition and biomass. We concluded that the novel methods applied proved reliable for studying fine-scale relationships between species composition and biomass.

Juniper Shade Enables Terricolous Lichens and Mosses to Maintain High Photochemical Efficiency in a Semiarid Temperate Sand Grassland

On a semiarid sand grassland (Festucetum vaginatae) colonised by juniper (Juniperus communis L.) shrubs terricolous lichens and mosses segregate strongly between microhabitats: certain species grow in the open grassland, others almost exclusively in the shade of junipers. The contrasting irradiances of these microhabitats influence much the metabolism of these organisms, and thus affect their small-scale distribution. This was confirmed by determining the efficiency of photochemical energy conversion by measuring chlorophyll a fluorescence parameters. In the open grassland maximum photochemical efficiency of photosystem 2 (PS2, Fv/Fm) declined from the humid spring to the hot and dry summer in all species, and this was caused by an increase in base fluorescence (F0), but not by the decrease in fluorescence maximum (Fm). In summer, mosses and lichens growing in the open grassland generally possessed lower Fv/Fm than cryptogams growing in the shade cast by juniper shrubs. Thus mosses and lichens in the open grassland suffer lasting reduction in photochemical efficiency in summer, which is avoided in the shade of junipers. Juniper shrubs indeed influence the composition and small-scale spatial pattern of sympatric terricolous lichen and moss communities by—among others—providing a shelter against high light in summer.

Possible role of the seed bank in the restoration of open sand grassland in old fields

The species composition of the seed bank and aboveground vegetation of an old field was compared to a reference grassland stand. The relative importance of dispersal and recruitment as limiting factors was analysed, and measures for appropriate restoration are proposed. Grassland species were able to re-establish in the old field soon after abandonment of cultivation, with Stipa borysthenica as the dominant species. Five years after abandonment of cultivation, the seed bank was still dominated by weedy annuals while grassland species made a relatively high contribution to the seed bank in the reference site. The results do not support recruitment to be the limiting factor in recently abandoned fields, because grassland species that occurred in the seed bank were also present in the vegetation. A rapid regeneration of the matrix species is predicted due to their good dispersal capacity and the vicinity of the open sand grassland. However, the introduction of subordinate species and the control of invasive plants might require human intervention.

Changes in the composition of sand grasslands along a climatic gradient in Hungary and implications for climate change

Changes in the composition of sand grasslands along a climatic gradient in Hungary and implications for climate change

DISPERSAL PATTERNS OF TERRICOLOUS LICHENS BY THALLUS FRAGMENTS

Dispersal patterns from seven terricolous lichen species, with a high capacity for asexual reproduction by fragmentation (Cetraria muricata, Cladonia species), were studied in differing vegetation types in north-eastern Germany. Marked lichen thalli were fragmented by trampling. After 15 days the spread of thallus fragments was monitored. Whereas most of the fragments that were dispersed by wind remained within a 20-cm radius from the source, the maximal dispersal distance was 57cm in a dry sand grassland and 68cm in an open pioneer pine forest. Dispersal was negligible in a closed old-growth pine forest. Several fragmented lichen cushions were disturbed and removed by animals, and led to a maximal dispersal distance of 9·70m. These results suggest that: (a) thallus fragments provide good short-distance dispersal in open vegetation, but are inefficient for long-distance dispersal, and (b) wind and animals are important factors for the dispersal of thallus fragments. For restoration management of man-made substrata, artificial introduction of lichen thalli is proposed.

Atmospheric deposition to grassland canopies: Lysimeter budgets discriminating between interception deposition, mineral weathering and mineralization

Lysimeter experiments were used to determine atmospheric input to grassland canopies. The combined effect of interception deposition + mineral weathering + mineralization was calculated from input/output budgets. Four types of lysimeters were used, either filled with very pure quartz sand or chalk grassland soil, and either without vegetation or planted with Brachypodium pinnatum (L.) Beauv., Combination of budgets for these four types of lysimeters yielded separate estimates of interception deposition and mineral weathering + mineralization. Ratios between total deposition and bulk deposition were 1.74 and 1.93 for N and S, respectively. Sources and sinks of H+ for lysimeters with chalk grassland soil and planted with Brachypodium (abbrev. CP-lysimeters) were about 10 times larger than for lysimeters without plants and filled with quartz sand. The contribution of atmospheric input to total H+-sources was 80% for bare lysimeters filled with quartz sand, and only 12% for CP-lysimeters. Bulk deposition and total atmospheric deposition of N was 1.25 and 2.18 kmol ha−1 yr−1, respectively, whereas N mineralization of chalk grassland soil yielded 1.62 kmol ha−1 yr−1, ‘Acid rain’ has only a minor influence on H+-transformations within a chalk grassland ecosystem, but N cycling is seriously affected by atmospheric input.

Habitats, food resources, and natural enemies of a community of larval Cicindela in southeastern Arizona (Coleoptera: Cicindelidae)

This study examines food resources, natural enemies, and natural history of three cohorts of larvae of eight Cicindela species from seven habitats in southeastern Arizona. Larvae of most species occurred with adults in the same habitats. Pond and ditch edge habitats had low soil desiccation, no parasitism, and significantly more food than other habitats. Playa species were heavily parasitized (24.1–44.2%) by a bombyliid fly (Anthrax). Sand ridge, saltbush flat, and grassland species experienced little food, moderate to heavy parasitism by a tiphiid wasp, Pterombrus rufiventris, and occasional soil desiccation. Pond and ditch edges had much higher larval densities than other habitats. However, relative to adults, few species were present. Survivorship (first instar to adult) was low for all species [Formula: see text]. Reduced activity during midday was correlated with high burrow surface temperatures. Seasonal activity varied from 8 to nearly 12 months. Life cycles ranged from 1 to 4 years with 2 years most common. Food is an apparent limiting resource for most species. Larval habitat, life cycle, and size all may influence rates of parasitism.