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Jozani biodiversity inventory report 2002 - Coastal Forests of Kenya ...

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3.1.2 Vegetation data collection<br />

The classification and mapping <strong>of</strong> vegetation communities are the initial phases <strong>of</strong> ecological<br />

<strong>inventory</strong>. Sources <strong>of</strong> information include observations on, and measurements <strong>of</strong> species<br />

abundance, heights and diameter at breast height (DBH) for trees, how these attributes are<br />

influenced by the natural environment and by different types and intensities <strong>of</strong> land use practices.<br />

Eleven vegetation communities were recognized in this study area. Mangrove vegetation<br />

community was studied separately in another study.<br />

During sampling at least one transect line was established for each vegetation community that<br />

was identified during reconnaissance except for grassland, mangrove vegetation, shrubland and<br />

marine vegetation. Shrubland and grassland were not studied quantitatively but their species<br />

compositions were enumerated on various randomly selected sites. The mangrove vegetation and<br />

marine vegetation (algae and seagrasses) were not quantitatively assesed because they have<br />

already been separately studied in other studies (Shunula, 1997; Mohammed, 1999). The data<br />

were collected using a Nested Quadrat Method (Stohlgren et al, 1995; Crawley, 1997). Along<br />

each transect, sample plots were fixed at 100m intervals and each rectangular plot <strong>of</strong> 50m x 20m<br />

dimensions contained sub-plots for sampling shrubs and herbs as indicated below.<br />

Life Form Fixed plot area Length Width Definition<br />

Herbs 2.0m 2 2.0m 0.5m All forbs and grasses under 1.5m<br />

& all annuals<br />

Shrubs 10.0m 2 5.0m 2.0m Woody plants higher than 1.5m<br />

with dbh 10cm<br />

GPS readings were taken at each sample point but in the forest readings for some points could not<br />

be obtained due to forest shade and for such cases a gap or opening closest to the point was<br />

chosen where there was sufficient light.<br />

All herbs and shrubs that occur within the sub-plots were recorded and the number <strong>of</strong> individuals<br />

for each species was counted. Trees were recorded and measurements included height and DBH<br />

for each individual. Where individual trees were multi-stemmed from below the breast height,<br />

each stem was measured as a separate individual.<br />

15

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