Effect of clear-cutting on the diversity and distribution of Collembola in western Newfoundland balsam fir-Dryopteris and Equesetum-rubus forests

Arulnayagam, Daisy Chandrika (1995) Effect of clear-cutting on the diversity and distribution of Collembola in western Newfoundland balsam fir-Dryopteris and Equesetum-rubus forests. Masters thesis, Memorial University of Newfoundland.

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Abstract

The diversity and distribution of Collembola in western Newfoundland balsam Ill- forests were studied to determine if these forests return to their original conditions in respect to their biota, especially the collembolan community, when they regenerate after clear-cutting. The study was carried out in two different balsam fir forests of three different ages. They included balsam fir Dryopteris (FD) and balsam fir Equisetum-Rubus (FE) forest of 40 year old regrowth, 60 year old regrowth and old uncut forests. Within each type of forest two replicate sites of each of the three different ages were selected. Three types of samples, pitfall trap samples, microhabitat samples, and soil samples, were collected from the FI) forest. Soil samples were collected from the FE forest. -- Pitfall traps were used in the FD forest in summer 1992. Most of the species collected in pitfall traps were large, surface dwelling collembolans. Fifteen species were collected in the old forest and 14 and 19 species were collected in 40 and 60 year old forests, respectively. Tomocerus flavascens, T. minor, Entomobrya multifasciata, Orchesella cincta and Neanura muscorum were the dominant species in all sites. Pitfall traps did not reveal differences in collembolan communities between the different aged forests. -- Various microhabitats were sampled in the FD forest in summer 1993, including rotten wood, tree holes, deciduous leaves, moss from live and dead tree, lichen from live and dead tree, and bark from live and dead tree. Thirty-five species of Collembola were collected from all microhabitats in the old forest. Twenty-seven and 32 species were collected in 40 year and 60 year old forests respectively. Folsomia penicula and Isotomiella minor were the dominant species in the microhabitats on the ground. One species, Uzelia setifera, was collected only in the microhabitats on trees. -- Soil samples were collected in summers 1992, 1993 and June 1994 in the FD forest and in summer 1994 in the FE forest. Ten samples, each a cube of surface litter and soil, 10cm x 10cm x 10cm deep, were collected from each site on each sampling date. Each sample was cut into two horizontal halves, and each half was extracted separately in modified Berlese funnel. A total of 53 species representing 29 genera of Collembola were collected from the soil samples. The mean densities and diversity of the Collembola collected in the upper halves of the soil samples were higher than those of the lower halves on each sampling date, except Tullbergia granulata was more abundant in the lower halves. Mean densities of Collembola in the FD forest varied between 174.4 to 849.2/1000cm³ and in the FE forest 209.0 to 572.0/l000cm³. Seasonal patterns were observed in the proportion of Collembola occurring in the lower half of the samples and in the total number of Collembola collected in the FD forest. In the late summer the proportion of Collembola in the lower half of the samples was higher than that of the early summer, and the total abundance was higher in June and August than in July. -- In both FD and FE forests, old sites had the highest species diversity and abundance. In the FD forest, the 40 year old site had the lowest species diversity and the 60 year old forest had the lowest density. In the FE forest, 40 year old sites had both lowest species diversity and density. Two species, Folsomia penicula and Isotomiella minor were the dominant species in both forest types, comprising about 50-70% of the total number of Collembola. Tomocerus flavascens, Stenogastrura hiemalis and Isotoma (Desoria) beta were collected only in the old forest. T. minor and Willowsia buski were restricted to the regrowth forests, lsotomurus palustroides, Neelus minutus and Neelus incertus were collected only in the FE forest. -- This study indicates that clear-cutting does have a long term effect on the abundance and diversity of Collembola. Forty year old forests had the least diversity, and species diversity increased with forest age. Old forests contained three Collembola species that were not collected from regrowth forests.

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