Seasonal and long‐term soil water regime in West African tropical forest

Abstract

Abstract. Variation of soil matric potential of a Wet Evergreen and a Moist Semi‐deciduous West African forest were compared. The two forest types differed strongly in their soil water regime. Wet Evergreen forest experienced matric potentials below −100 kPa only occasionally, while in Moist Semi‐deciduous forest matric potentials were less than −2.5 MPa for periods of several weeks or more each season. A water balance equation was used to simulate the soil water regime at both sites and predict severity and length of the dry period. The predictions showed good agreement with the field measurements of soil water potential over a 2‐yr period. The methodology was used to estimate the occurrence and severity of droughts over longer periods at the two sites. The balance calculations suggest that droughts occur occasionally in the Wet Evergreen forest under study. The potential impact of droughts on species distribution and vegetation disturbance in tropical forests is discussed.

Effects of drought on isolates of Bradyrhizobium elkanii cultured from Albizia adianthifolia seedlings of different provenances

“…Also, for Bonsa River and Bobiri isolates, -0.03 MPa permitted the most growth, whereas the growth of the Tinte Bepo isolate at this osmotic potential was less than at -0.1 and -0.2 MPa. It is not uncommon for isolates of the same inoculation group to show different growth responses (Issa and Wood 1995), and it is possible that as Tinte Bepo soils experience regular seasonal droughts (Veenendaal et al 1996), its isolate has been selected for these conditions rather than for conditions of no moisture limitation. The antithesis is true of the other two isolates, for which drought conditions are rare.…”

“…1300 mm yr -1 ) (Swaine 1996). Soils in Tinte Bepo Forest Reserve annually experience periods of several weeks when soil matric potential is less than -1.5 MPa whilst in evergreen forests such droughts are rare, with soil matric potential typically above -0.5 MPa throughout the year (Veenendaal et al 1996).…”

Microhabitat associations and seedling bank dynamics in a neotropical forest

“…Temporal variability in several of the parameters we measured has been observed, particularly in seasonal tropical forests (Wright 1992;Roy and Singh 1995;Veenendaal et al 1996). For example, litter that had begun to decompose at the time of this survey at the onset of the rainy season, may vary seasonally in a given site depending on inputs and decomposition rates, which also vary with precipitation (Puig et al 1990).…”

Quantifying the deciduousness of tropical forest canopies under varying climates

“…African forests (Hall & Swaine 1981;Veenendaal et al 1996). Kikuzawa (1991Kikuzawa ( , 1995 showed how a simple model of leaf value predicts increasing deciduousness in forests with longer periods unfavorable for growth.…”