Search Results - (Author, Cooperation:M. O. Gessner)

2014-05-09

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Arctic Regions ; *Biodiversity ; Carbon/metabolism ; *Carbon Cycle ; *Ecosystem ; Nitrogen/metabolism ; Nitrogen Cycle ; Plants/metabolism ; Tropical Climate

2012-06-16

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Animals ; Biodiversity ; Biomass ; *Ecosystem ; Europe ; Eutrophication ; Ilex ; Invertebrates/*metabolism ; *Plant Leaves ; Quercus ; *Rivers/microbiology ; *Water Pollution, Chemical

1365-2427

Blackwell Publishing Journal Backfiles 1879-2005

Biology

1. Breakdown of four leaf species (Platanus orientalis, Populus nigra, Salix atrocinerea, Rubus ulmifolius) was studied in a Mediterranean second-order stream characterised by abundant travertine precipitation, a history of fire in its catchment, and a recently revegetated alluvial corridor.2. Compared to breakdown rates reported in the literature for congeneric species, breakdown of the four species was slow (k = 0.0024–0.0069 day−1 for the tree species, and 0.0103 and 0.0111 day−1 for Rubus), in spite of high water temperatures, indicating that the travertine layer that quickly covered submerged leaves impeded decomposer activity and physical fragmentation losses.3. Breakdown rates nevertheless differed between leaf species in a predictable manner, suggesting that the observed mass loss was largely due to biological processes.4. The observed tendency towards increasing leaf nitrogen and phosphorus concentrations during breakdown suggests that microorganisms were actively involved in leaf breakdown; however, this interpretation must be viewed with caution because of potentially confounding effects by nutrients contained in the travertine layer.5. Leaf breakdown of the three indigenous species was faster than that of the exotic species P. orientalis. Due to the recalcitrance of its leaves, the frequent use of Platanus in revegetation schemes following the destruction of indigenous vegetation by fire, exacerbates the negative effect of travertine precipitation on leaf breakdown and, by extension, energy flow in Mediterranean karst streams.

Electronic Resource

1432-1939

Key words Alpine springbrook ; Leaf breakdown ; Nutrient addition ; Aquatic hyphomycetes ; Macroinvertebrates

Springer Online Journal Archives 1860-2000

Biology

Abstract  This study assessed the effect of nutrient enrichment on organic matter breakdown in an alpine springbrook, using alder leaf packs to which phosphorus and nitrogen were added in the form of slow-release fertilizer briquettes. The breakdown of leaf packs with nutrients added (k=0.0284 day–1) was significantly faster than that of unfertilized packs (k=0.0137 day–1), resulting in a 30% higher mass loss after 42 days. Unfertilized leaves enclosed in fine-mesh bags broke down at an even slower rate (k=0.0062 day–1). Phosphorus and nitrogen concentrations were initially higher in leaf packs with nutrients added, but this difference disappeared within 3 weeks. Fungal biomass developing in decomposing leaves was substantial (c. 55 mg dry mass per 1 g leaf dry mass) although similar between fertilized and unfertilized packs, as was the sporulation activity of aquatic hyphomycetes. There was a significantly greater number and higher biomass of macroinvertebrates (shredding nemourid stoneflies in particular) on the fertilized packs, suggesting that the increased leaf mass loss was brought about by shredder feeding.

Electronic Resource

1432-1939

Aquatic Hyphomycetes ; Ergosterol ; Fungal biomass ; Leaf decomposition ; Stream

Springer Online Journal Archives 1860-2000

Biology

Summary Fungal biomass, measured as ergosterol content, was determined on alder leaf litter incubated during autumn in a softwater Pyrenean stream. The ergosterol content of the leaf litter increased rapidly to a maximum of 462 μg/g detrital dry mass. Ergosterol contents of aquatic Hyphomycetes grown in shake culture were typically ≤5 mg/g mycelial dry mass. Using the corresponding ergosterol-to-biomass conversion factor of 200, peak fungal mass accounted for 9.2% of total system mass, or 10.2% of leaf dry mass. For the period of highest activity (incubation days 7–28), net fungal production on leaf litter was estimated as 2.3 mg d−1 g−1 leaf mass. A conservative estimate of the growth efficiency for the same period was 105 mg mycelial mass per gram leaf mass degraded, assuming that non-leaf organic matter did not constitute an important carbon source supporting fungal production.

Electronic Resource