| Ecosystems in East Africa are undergoing changes due to climatic and anthropogenic factors. Plant phenology, an important ecosystem property and among the first to respond to climate change, is the focus of this thesis. Recent studies have shown that plant phenology is changing; however, they have not addressed causes of the changes. The objectives of this thesis are to examine how plant phenology has changed from 1982 to 2006 in East Africa using remotely sensed data and to identify the possible drivers behind observed phenological changes. Information extracted from time series remotely sensed imagery revealed a great variability in phenological patterns over East Africa. It was found that the phenological patterns were highly correlated with precipitation patterns and land cover types. Temporal trends were computed using Mann-Kendall test and Sen's slope method, and the results indicated there were significant phenological changes from 1982 to 2006 (&agr; = 0.05). The start of the growing season has delayed in large parts of Tanzania while been earlier in parts of Uganda. The length of the growing season has reduced in parts of Tanzania while lengthened in parts of Uganda. Phenological driver analysis was conducted at two hot-spots with significant phenological changes, to determine the relative importance of climatic factors and land use/cover changes. The results suggested that climate change is a dominant factor at one hotspot (Tarangire National Park, Tanzania). However, anthropogenic factors were found to be dominant at another hotspot (Tabora District, Tanzania). In conclusion, climatic and anthropogenic factors are important contributors to phenological changes but their degrees of influence differ from place to place. |
