Zur Ökologie von Thekamöben (Protozoa: Rhizopoda) in süddeutschen Wäldern

Abstract

Summary Investigations were conducted in spruce stands (U1-southeast of the Schwabische Alb nearby Ulm, Ux - Oberschwaben, Fg - Fichtelgebirge, Ed - Welzheimer Wald, Ks - Sudschwarzwald), deciduous forests (V2 - Luzulo-Fagetum, EF - Melico-Fagetum, Au - meadow, Fraxino-Ulmetum) and an orchard (Ow), all sites nearby Ulm. Species spectra, abundances, biomasses, relative abundances, and diversity of the coenoses were compared. Additionaly, in some spruce stands (VI, Ux) impacts of liming and fertilization, artificial rain and contaminations of the soil layer with diluted sulphuric acid and sodium chloride, and with Nexit and Ripcord (substances used against bark beetles) on coenoses of testate amoebae were tested. Ratios of full and empty shells were comparedunder different points of view. The colonizationof the lower trunk region was observed. 62 species were found; 41 in spruce stands, 55 in deciduousforests and the orchard. 9 species were euconstant in spruce stands, 8 in deciduous forests and the orchard. The investigated spruce stands showed a very uniform species range and species identities. In contrast, the deciduous forests and the orchard showed only little correlations. Soil treatments in spruce stands caused only little effects on species of the coenoses. All investigated sites and subsites showed, as a rule, Soerensen-indices above 70%. Samples were often sorted by time and not by test site or the treatment. During the investigated time, considerable fluctuations of abundances and biomasses occurred. Abundances (means) of testate amoebae in spruce stands varied between 7,000 and 23,000 individuals per gram dry mass substratum (gTM). In the deciduous forests and orchard abundances were ten times lower. In Au only 140 individuals/gTM were found. Under consideration of the different masses of the substratum, all investigated sites except Au showed populations of 50-200 mio. indo per square meter. The testate amoebae coenoses of the spruce stands reacted quite different to liming and fertilization. Lime caused a significant increase in abundances, while fertilizers and lime together caused a not significant decrease in abundances. A decrease of the fertilization effect may have happened at the end of the investigation time. Total biomass correlated, as a rule, with abundances. In spruce stands, biomass varied from 0.07 to 0.35 mg live weight/gTMand 0.8 to 5.0 grams per square meter, respectively. In deciduous forests and the orchard biomass varied from 0.002 to 0.04 mg live weighUgTM and 0.1 to 0.7 gram per square meter, respectively. In untreated spruce stands the following species occurred frequently (with regard to individuals): Phryganella acropodia (Hertwig & Lesser), Trinema complanatum Penard, Trinema lineare Penard, Schoenbornia humicola (Schonborn) and Corythion dubium Taranek. Also occurred frequently at times: Plagiopyxis declivis Thomas, Euglypha laevis (Ehrenberg), Schoenbomia viscicula Schonborn, Cyclopyxis ambigua Bonnet & Thomas and Hyalosphenia subflava Cash. In the deciduous forests and orchard the composition of frequency was quite different. Only Trinema lineare and Euglypha laevis were frequent on all sites. In untreated spruce stands, the following species occurred frequently (with regard to biomasses): Plagiopyxis declivis Thomas, Centropyxis sylvatica(Deflandre), Trinema complanatum Penard, Schoenbornia humicola (Schonborn), Trigonopyxis arcula (Leidy), Hyalosphenia subflava Cash and Nebela parvula Cash/Nebela tincta (Leidy). For the deciduous forests and orchard, the same differences occurred as mentioned above. The following species were found frequently: Plagiopyxis declivis Thomas, Plagiopyxis parvoblonga Bonnet, Centropyxis aerophila var. sphagnicola Deflandre, Centropyxis elongata (Penard)/Centropyxis cassis (Wallich), Trinema complanatum Penard and Trinema enchelys (Ehrenberg). Diversity and evenness of the coenoses in the spruce forests came to 2.2 (Hs) and 0.8 (D and E), these indices are quite uniform. The treated sites showed, as a rule, a decrease in diversity. In V2, EF and Ow diversity was higher, in Au diversity was lower than in the spruce forests. The ratio empty: full shells of testate amoebae was clearly determined by the kind of humus layer. In spruce stands, the ratio empty: full shells (means) was 2.5 to 4.5, in the deciduous forests and the orchard the ratio was often lower than 1.0. Relationships between these ratios and the soil-pHor the soil-moisture (all data) were not detected. In VI and Ux the full shells increased during the investigated time. The ratios regarding single species increased on fertilized sites and decreased on the irrigated site. Only a few species colonized, especially in the deciduous forests, with few individuals the lower trunk region. There, Corythion dubiumwas more frequent than other species. Because of its shell construction (small pseudostome, flattened shell) this species is well adapted to dryness.