Submitted to: Biodiversity of Soil International Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 9/24/2007
Publication Date: 9/29/2007
Citation: Arevalo, G.E., Zuniga, C.L., Baligar, V.C., Canto, S.M. 2007. Population dynamics of funga, nematode, bacteria and algal population in a soil of mazon region of peru. Biodiversity of Soil International Conference Proceedings. 9.29.2007. Interpretive Summary:
Technical Abstract: Soil microbes are mainly responsible for litter decomposition and nutrient cycling in the forest ecosystems. Population dynamics of soil microbes (fungus, bacteria, nematodes, algae) under secondary forest in tropical region is not well understood. An experiment was implemented at Tropical Crop Research (ICT) station, Tarapoto, San Martin-Peru, in a secondary forested area. Five blocks of 1 ha each were selected at random over an area of 8.64 ha. In each block 10 sites were selected for soil sampling. The soil samples were collected from four depths (0-20, 20-40, 40-60, 60-80 cm). In any given block samples collected from 10 sites were combined based on the depth of sampling and a composite sample was obtained for each depth for microbial analysis. The microorganisms (fungus, nematodes, bacteria and algae) were determined in the Phytopathology and Soils laboratory of ICT. For mycological analysis the soil samples were processed by serial dilutions of a mother solution, and also by cultures from supernatant and precipitates. For this test, three culture media were adapted: Potato Dextrose Agar (PSA), Corn Meal Agar (CFA) and V8 juice-Maltose -Agar (V8MA). For fungus determinations, samples were incubated at 25°C until the formation of identifiable structures; and the number of colony forming units per gram of soil were registered. For the bacterial determination a serial dilutions and growing in a nutritive agar method was used. Bacteria were divided into aerobic and anaerobic, and the colony forming units per gram of soil were recorded. Modified Cobb’s method was used in extraction of nematodes and algae from obtained soil samples. The nematodes were identified and classified as nonparasitic and parasitic nematodes, and registering nematode number per gram of soil. For algae, the total population per gram of soil was recorded. In this study, 48 fungi genera were identified; the major populations were located in the first 20 cm of soil depth and the population decreased with increasing soil depth (1.22 x 108, 6.44 x 107, 5.88 x 107 and 4.66 x 107 cfu/g soil for 0-20, 20-40, 40-60 and 60-60 cm respectively). The best culture media that expresses the major population of fungi was CFA followed by PSA and V8MA (1.07 x 108, 9.95 x 107 and 8.56 x 107 cfu/g soil, respectively). The anaerobic bacteria were dominant at all soil depths. Ten nematode genera were identified and predominant were: Helicotylenchus as parasitic and Dorylaimida and Rhabditida as nonparasitic. The nematode population was highest in the first 20 cm of soil depth and decreased with soil depth similar to fungal population. However, the nonparasitic nematodes were present in all soil depths. In all, 21 alga genera were identified, and predominantly higher populations were observed in the surface soil layer.