Lt. Szott et al., BIOMASS AND LITTER ACCUMULATION UNDER MANAGED AND NATURAL TROPICAL FALLOWS, Forest ecology and management, 67(1-3), 1994, pp. 177-190
The accumulation of biomass and litter and changes in vegetation struc
ture by six managed leguminous fallows, planted in a previously cultiv
ated Ultisol (Acrisol) in the Peruvian Amazon, were compared with that
of naturally established secondary vegetation. The planted fallows in
cluded: Centrosema macrocarpum (CM), Pueraria phaseoloides (PP), Stylo
santhes guianensis (SG), Desmodium ovalifolium (DO), Cajanus cajan (CC
), and Inga edulis (IE). The aboveground mass of planted legumes, tree
s, herbaceous vegetation, and litter and root mass were measured at 4,
8, 17, 29, 41, and 53 months after fallow initiation; leaf area index
(LAI) and leaf area density (LAD) were measured at 4, 8, and 17 month
s. After 8 months, total mass in the IE, CC, and DO treatments was sig
nificantly greater than in the CM and PP treatments; total mass in the
natural fallow (NF) treatment was similar to that in the IE, CC, and
DO treatments after 29 months. Aboveground biomass contributed about 7
5-85% of total mass and was greater when trees were present. Abovegrou
nd biomass ranged from 8 (CM) to 63 t ha-1 (IE) at 53 months. Planted
legume biomass in most treatments increased until 17 or 29 months, but
later declined when many of the legumes were replaced by invading tre
es. By 53 months, planted legume biomass represented less than 10% of
aboveground mass in all treatments except CM and IE. The LAI increased
from 4 to 17 months, but there were few differences among treatments
at any date; LAD greatly decreased with time in the treatments with tr
ees. The formation and maintenance of dense vegetation canopies with h
igh LAD in the CM, SC, and PP treatments inhibited the invasion and gr
owth of trees. Biomass data at 53 months suggest that the IE and DO tr
eatments accumulated similar amounts of biomass and litter as the NF t
reatment because of the rapid establishment of planted legumes and the
successful invasion of trees and that the CM, SC, and PP treatments p
erformed poorly because of the exclusion of trees. Further research co
mbining trees and other leguminous or non-leguminous vegetation is req
uired to develop management practices that maximize biomass accumulati
on during managed fallows.