Impact of elevation on tree community structure in cedrela odorata invaded forest: a case of Kalinzu Central Forest Reserve, Bushenyi, Uganda

Abstract

Invasive species are a current focus of interest of ecologists, biological conservationists and natural resources managers due to their rapid spread, threat to biodiversity and damage to ecosystems. In the past, tropical forests have long been regarded as highly resistant to invasive species though it is now known that disturbances, including anthropogenic and natural ones, can play a catalytic role in invasion of tropical ecosystems. Part of the Kalinzu forests has disappeared or has been deeply fragmented. This deforestation dynamic is still ongoing under a strong demographic pressure, forests being mostly cut for timber, charcoal, poles and stakes. On the other hand, some reforestation projects were also undertaken, in particular by planting non-native species like Cedrela odorata. The deliberate or accidental introductions of nonnative species are an underestimated anthropogenic impact in Kalinzu CFR. The spread of invasive alien species in the area is expected to further change the native community composition, reduce species diversity, retard ecosystem process, and cause ecological imbalance in the fragile Kalinzu CFR, Despite this observation no study has been carried out on Cedrela odorata invasion in tropical forests in Uganda. More so, research on the effect of elevation on the species density, diversity and richness in areas with Cedrela odorata invasion is still limited. This study aimed at determining the tree community structure in compartment 7 of Kalinzu CFR which is characterized by Cedrela odorata invasion. At different elevation, 90 plots in total were established along transects and all individual plants enumerated, tree species abundance and relative abundance were analyzed, Anova was used to compare the differences in species richness and diversity for the uphill, mid-hill and valley. The study reveal the abundance and distribution of Cedrela odorata in KCFR and provide a basis for an enabling policy and institutional environment that provides a coherent framework for the sustainable prevention and management of IAS in Kalinzu CFR. A total of 53 tree species were encountered in the 90 plots in compartment 7 of KCFR. Margalef species richness was significantly higher in mid-hill but did not vary significantly among the three elevations (uphill, mid-hill and valley). Shannon-Weiner diversity was highest in mid-hill and lowest in the valley but also did not vary significantly among the three elevations (uphill, mid-hill and valley). The management of Kalinzu CFR should apply integrated practices to reduce the rate of invasion of Cedrela by cutting or uprooting since these methods cause limited environmental impacts.