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Effect of <i>Balanites glabra</i> canopy cover on grass production, organic matter and soil moisture in a southern Kenyan rangeland
Abstract
A
study was undertaken in Kenya's southern savanna rangelands
to determine the seasonal effect of Balanites glabra
canopy cover on aboveground grass biomass, grass species composition,
soil organic matter and soil moisture content. The study was
conducted during the period June to December 1999 in order to
capture both the dry and wet season effects. The grass biomass
in the sub-canopy zone (2–4m from tree trunk) was found to be
significantly higher than in the mid-canopy (0–2m from tree
trunk) and open grassland zones (4–6m from tree trunk) during
the dry season. However, the difference between the sub-canopy
and the open grassland was not significant during the wet season,
implying that the role of a tree canopy in enhancing grass biomass
is greater during the dry than the wet season. Variations in
percent grass species composition from the mid-canopy to the
adjacent open grassland were observed, indicating that while
B. glabra canopy cover favours certain grass species,
other species find the micro-climatic conditions under the canopy
unfavourable. Soil organic matter in the mid-canopy zone was
significantly higher than in the sub-canopy and adjacent open
zones during both dry and wet season. Although the sub-canopy
zone exhibited significantly higher soil moisture content than
the mid-canopy and open grassland zones during the dry season,
the difference between the sub-canopy and the adjacent open
grassland during the wet season was not significant, suggesting
that the tree canopy influence on soil moisture is more pronounced
in the dry than the wet season.
African Journal of Range & Forage Science 2003, 20(3): 259–264
study was undertaken in Kenya's southern savanna rangelands
to determine the seasonal effect of Balanites glabra
canopy cover on aboveground grass biomass, grass species composition,
soil organic matter and soil moisture content. The study was
conducted during the period June to December 1999 in order to
capture both the dry and wet season effects. The grass biomass
in the sub-canopy zone (2–4m from tree trunk) was found to be
significantly higher than in the mid-canopy (0–2m from tree
trunk) and open grassland zones (4–6m from tree trunk) during
the dry season. However, the difference between the sub-canopy
and the open grassland was not significant during the wet season,
implying that the role of a tree canopy in enhancing grass biomass
is greater during the dry than the wet season. Variations in
percent grass species composition from the mid-canopy to the
adjacent open grassland were observed, indicating that while
B. glabra canopy cover favours certain grass species,
other species find the micro-climatic conditions under the canopy
unfavourable. Soil organic matter in the mid-canopy zone was
significantly higher than in the sub-canopy and adjacent open
zones during both dry and wet season. Although the sub-canopy
zone exhibited significantly higher soil moisture content than
the mid-canopy and open grassland zones during the dry season,
the difference between the sub-canopy and the adjacent open
grassland during the wet season was not significant, suggesting
that the tree canopy influence on soil moisture is more pronounced
in the dry than the wet season.
African Journal of Range & Forage Science 2003, 20(3): 259–264
