Fern species composition, richness and selected traits in forest fragments around North East of Kibale National Park, Uganda

Abstract

Few studies have investigated how the effects of disturbance on ferns specifically on their traits vary with levels of forest disturbance even though such research could provide information necessary to stop further disturbance of already degraded forests. This research therefore investigated how fern species selected traits in addition to composition and richness vary with the level of forest disturbance (fragmentation and/or canopy opening).

Forest fragmentation level was obtained from a combination of area of the forest habitat and distance of the forest habitat from an intact forest (the control). Quadrats from which data on canopy closure obtained through hemispherical photography and selected traits of fern species (number of fronds and fertile fronds, length of the longest frond and width of the widest frond) was collected were set up along transects in study forest fragments and in the intact forest.

The unfragmented habitat had largely distinct fern species composition with 45.2% of the recorded species (42) associated with only it including Amauropelta bergiana (Schult.) Holttum, Asplenium dregeanum Kunze, Asplenium rutifolium (Bergius) Kunze, Asplenium erectum Willd. and Asplenium friesiorum C.Chr. among others. Fern species composition did not seem to largely vary between levels of forest fragmentation. However, there are species that were associated with only one level of fragmentation (light or moderate). Asplenium boltonii Schelpe and Asplenium mildbraedii Hieron were associated with only the lightly fragmented habitat while Asplenium hypomelas Kuhn, Blotiella currorii (Hook.) A.E. Tryon and Hypolepis goetzei Reimers were associated with only the moderately fragmented habitat. Similarly, there are species that were associated with only one level of canopy closure (high or medium). Asplenium boltonii Schelpe and Asplenium mildbraedii Hieron were associated with only high canopy closure levels while 26 species including Amauropelta bergiana (Schult.) Holttum, Asplenium dregeanum Kunze, Asplenium rutifolium (Bergius) Kunze, Asplenium erectum Willd. were associated with only medium canopy closure levels. Kruskal Wallis test revealed a statistically significant difference in the number of fern species in the study habitats with varying fragmentation levels. Fern species richness generally decreased with level of fragmentation. There were generally intra-specific variations in selected traits of selected fern species among forest habitats with different levels of canopy closure. However, the nature of variation in traits across forest habitats with differing canopy closure levels differed from species to species with the exception of length of the longest frond.

Lightly or moderately fragmented study habitats and those under medium or high canopy closure level should be sustainably managed. Fragmentation should be avoided where not avoidable, fragments should be sustainably managed by the owners and their management monitored. A study to investigate intra-specific variation of traits of fern species with canopy closure levels using traits and fern species other than those investigated in the current study is recommended.