Forest Health Monitoring in the Ngangao Forest, Taita Hills, Kenya: A Five Year Assessment of Change

Forest Health Monitoring (FHM) provides a standardized detection-level survey of forest and tree characteristics for large forested areas. We have adopted FHM methods from this temperate-based program to tropical forests in the Eastern Arc Mountains (EAM) of Kenya and Tanzania. This paper reports the first assessment of trend data in the EAM over a period from 2001 to 2006. Growth and diversity statistics are presented for 11 forest plots in Ngangao Forest; only six (of 45) species constitute the predominance (68%) of basal area growth. Four endemic trees were tallied in our survey: Dasylepis integra, Leptonychia usambarensis, Macaranga conglomerata, and Polyscias stuhlmannii. We contrast diversity statistics with the nearby Chawia Forest and confirm the basic principal of species area relationships. Additionally, we examine visual crown assessments and tree damages. Tree crowns appeared healthy overall, although one species (Albizia gummifera) displayed increased dieback and foliage transparency and decreased crown density. Tree damages increased slightly over the survey period with stem decays constituting the most prominent symptom. Overall, we found no significant change in this first remeasurement of forest conditions at Ngangao Forest. The results reported here, however, may require more intense inspection of conditions. The Forest Health Monitoring approach constitutes a detection-level survey; it is dependent on follow-up by local experts to determine more precise causality where initial problems are found