Allometry and rainfall interception of Cordyla pinnata in a semi-arid agroforestry parkland, Senegal

Abstract

Allometric relations and rainfall interception of widely spaced Cordyla pinnata [(A. Rich.) Milne-Redh] trees were studied in a traditional agroforestry parkland in the semi-arid peanut basin of Senegal. Leaf biomass and leaf area were most strongly correlated to diameter at crown base ( R 2=0.99 and 0.97, respectively), but were also strongly correlated with diameter at breast height, tree height, crown diameter, crown length, and crown volume. Average foliar biomass was 82 kg per tree and 33.7 g m −2 for the parkland, while leaf area indices averaged 3.7 for individual trees and 0.16 for the parkland. The influence of crown size, pruning intensity and distance from the tree on rainfall interception was examined during 40 rainfall events totaling 714 mm, averaging 17.8 mm and ranging from 2 to 40 mm. Interception was 22% at a distance of one-half the crown radius from the tree trunk ( 1 2 R ) and 9% at one crown radius (1 R). Such horizontal variations in interception may be important to crop growth and yield. A power model of the relationship between gross precipitation and rainfall interception was developed and yielded R 2 values of 0.85 and 0.53 at distances 1 2 R and 1 R, respectively. Interception at 1 2 R decreased linearly with pruning intensity, was greater for the larger crown lengths, and was not affected by crown diameter. Canopy storage capacity estimated by three different methods ranged from 4.8 to 5.0 mm. Relative light intensity under the tree crowns was correlated with throughfall ( R 2=0.62) and was increased by pruning for the largest crown volume class.