Agriculture Reference
In-Depth Information
Depth distributions depend on the rooting strategies of individual species, soil physi-
cal conditions and nutrient status. However, the basic determinants are the vertical gra-
dients of nutrient availability and the simple fact that roots generally start growing from
close to the surface. As a result, root biomass is generally highest in the upper part of the
profile and diminishes with depth (Figure III.20). Departures from this general pattern
are due to the effects of four main factors
viz
., strategies of the individual plants, nutri-
ent availability, depth of the water table and the horizontal distributions of nutrient ele-
ments.
In the Banco tropical forest, coarse roots are evenly distributed in depth on the plateau
whereas they are concentrated in the upper 40 cm in the humid low lying areas of the
valley bottoms. Fine roots are more abundant close to the surface in both situations.
In a temperate forest at Ardennes (Belgium), fine roots have grown deeper than coarse
roots and the general pattern of rooting varies with tree species and the age of the stand
(van Praag
et al.,
1988) (Figure III.21).
