Invertebrate herbivory in the forest floor vegetation of virgin and managed forest sites in the Kibale Forest, western Uganda

Abstract

Summary Herbivory was studied in five different forest habitats (two virgin, two selectively felled and one exotic pine plantation) during 13 months by taking eight random samples of 50 living leaves from the forest floor vegetation per month. The leaves were classified in the field as untouched (0% consumed) or heavily damaged (over 25% consumed). The percentage of untouched leaves varied between 40 and 0·5% and of heavily damaged leaves between 25 and 0·2%. No clear seasonality in the amount of herbivory was detected. The exotic pine plantation had significantly fewer untouched leaves than two selectively felled forest sites, which differed significantly from each other in the percentage of heavily damaged leaves. Diurnal invertebrate herbivores from the same sites were collected by sweep netting. No clear correlations between leaf damage and the numbers of invertebrate herbivores were detected. Résumé On a étudié l'herbivorie dans cinq habitats forestiers différents‐deux intacts, deux où des arbres ont été sélectivement abattus et une plantation de pins exotiquesen récoltant par mois, pendant treize mois, huit échantillons de 50 feuilles vivantes prises au hasard dans la végétation forestière. Sur place, les feuilles étaient classées comme intactes (0% consommé) ou fortement abîmées (plus de 25% consommés). Le pourcentage de feuilles intactes variait entre 40 et 0,5% et celui des feuilles fortement abîmées, de 25 à 0,2%. La variation des pourcentages ne semble pas liée aux différentes saisons. La plantation de pins exotiques avait significativement moins de feuilles intactes que les deux endroits sélectivement exploités qui différaient significativement de chacun des deux autres en ce qui concerne le pourcentage de feuilles fortement abîmées. On a récolté au moyen d'un filet les invertébrés herbivores diurnes sur ces mêmes sites. On n'a détecté aucune corrélation claire entre les dommages causés aux feuilles et le nombre d'invertébrés herbivores.

Spatial variation of arthropod communities in virgin and managed sites in the Kibale Forest, western Uganda

“…It seems possible that as a result of a heavy selective logging as well as a clear-cut and planting pines, the arthropod community apparently is not returning towards to the virgin forest community in either site in Kibale forest, suggesting that new types of community equilibriums are developing in both managed sites differing from that of the adjacent virgin forest. Nummelin (1989Nummelin ( , 1996Nummelin ( , 2001 could not detect these trends in the arthropod communities in his study based on monthly samples taken in the very same sites during the proceeding 2 years of this study. This is apparently due the great seasonal variation, and the fact that the seasonal variation is not in phase in adjacent, but differently managed sites (Nummelin, 1996).…”

“…21 m 3 ha À1 timber removed) than another studied compartment (14 m 3 ha À1 ) (Skorupa and Kasenene, 1984). Both logged sites had denser forest floor vegetation than virgin sites, especially during the late rainy season (Nummelin, 1992).…”

“…In this study several samples were taken within the same habitat at the same time. Nummelin (1989Nummelin ( , 1992Nummelin ( , 1996Nummelin ( , 1998a give a closer description of each sampling habitats, their vegetation and arthropod communities.…”

“…The main focus of insect studies in tropical forests has been on forest plantations and pest species (e.g., Madoffe and Bakke, 1995 and references therein). The arthropods in clearcuts (Cambefort, 1984) as well as selectively logged sites have been studied to some degree (Howden and Nealis, 1975;Wolda et al, 1983;Holloway, 1987;Wolda, 1987;Nummelin, 1989Nummelin, , 1992Nummelin, , 1996Nummelin, , 1998aNummelin and Borowiec, 1991;Nummelin and Fürsch, 1992;Nummelin and Hanski, 1989;Hill et al, 1995;Ghazoul and Hill, 2001;Ghazoul, 2002).…”

“…Nummelin (1996) showed differences in the arthropod community between differently managed sites based on samples Forest Ecology and Management 195 (2004) [107][108][109][110][111][112][113][114] taken monthly from the same site within habitat having different management history (virgin, selectively logged, exotic pine). However, his results did not take into account the possible spatial variation within the visually uniform looking habitat.…”