A new iso-benzofuranone propanamide: 3-(3-oxo-1, 3-dihydroisobenzofuran-1-yl) propanamide (zenkeramide) (1) along with three known compounds: Trans-N-coumaroyltyramine (2), β-Sitosterol (3) and ...β-sitosterol-3-0-β-D-glucopyranoside (4) were isolated from the ethyl acetate fraction of the stem-bark of Celtis zenkeri Engl (Ulmaceae). The structure of the new compound was elucidated by extensive spectroscopic analysis. The compounds were examined for Urease Inhibitory Activity. Compounds 1 and 2 showed moderate activities (IC
50
values (μM) of 42.3 ± 0.19 and 45.2 ± 0.55, respectively), while compounds 3 and 4 were potent inhibitors of the Jack bean urease (IC
50
values (μM) of 20.3 ± 0.37and 27.6 ± 0.52, respectively), when compared to the standard inhibitor (thiourea- IC
50
21.5 ± 0.47). The isolation of all the compounds from C. zenkeri and the urease activity of compounds 1 and 2 are reported for the first time.
The direct removal of adult trees by logging affects tree recruitment in tropical rain forests. However, secondary effects of logging, such as loss of vertebrate seed dispersers may also affect tree ...recruitment. We studied the recruitment and spatial distribution of five tree species namely Balanites wilsoniana, Celtis zenkeri, Chrysophyllum albidum, Cordia millenii and Ricinodendron heudelotii in Kibale, Budongo and Mabira Forests in Uganda. These forests have been subjected to varying degrees of disturbance leading to changes in their vertebrate seed dispersers. Vertebrate frugivores of the five tree species were identified. Three 1-ha plots were established around adult trees of the same five species in each forest and the distance from the juveniles to the nearest adult conspecific was measured to generate a recruitment curve. Frugivore visitation rates were high in the less disturbed Budongo and Kibale (2.2 and 1.6 individuals h−1 respectively) compared with the highly disturbed Mabira (0.9 individuals h−1). In the frugivore-impoverished forest, 70–90% of juveniles established beneath adult conspecifics, whereas in the less-disturbed forests juveniles were established up to 80 m from adult conspecifics. Shade-tolerant species capable of recruiting beneath adult conspecifics appeared to maintain their populations without dispersal. Consequently, disturbances leading to significant loss of vertebrates may alter tree recruitment and spatial distribution with consequences for long-term population viability of shade-intolerant tropical trees.
Interspecific variation in water-induced fluctuations in stem girth demonstrates the mechanisms promoting coexistence in seasonally dry tropical forest. In addition, these fluctuations are a ...potential, but unevaluated, source of bias in measurements of annual tree growth rates. To examine diurnal and seasonal patterns of stem diameter change, tree girth was measured over 2 years (1997–1999), using dendrometer bands, for three species (
Celtis mildbraedii,
C. zenkeri and
Strombosia glaucescens) in semi-deciduous forest in Ghana. Soil matric potential was measured concurrently at 15
cm depth. In addition, measurements of all trees >20
cm dbh on three, 1
ha plots were made at the beginning and middle of the 1998/1999 dry season. During the severe 1997/1998 dry season, soil matric potential declined below −1.5
MPa and two species showed significant stem shrinkage. For the evergreen species,
C. mildbraedii, there was a significant positive effect of tree diameter on stem shrinkage, and shrinkage was greater in the second, compared to the first, half of the dry season. For the deciduous species,
C. zenkeri, shrinkage was reduced during the second half of the dry season, following leaf fall. During 1998/1999, soil matric potential, did not decline below −1.5
MPa, and rates of girth change remained positive for all species. There were no significant effects of size or phenology on the rate of girth change in the plot-based study. Deviations in annual increment calculated over successive monthly intervals indicate that a 10-fold difference in soil water availability between measurement occasions can lead to a 4% bias in estimates of annual growth. Measurements of forest plots should be made when inter-annual variation in soil water availability is low. In this forest, measurements should, therefore, be made during the wet season, contrary to published recommendations.
