Lachnicht, SL, PF Hendrix, and X. Zou. 2002. Interactive effects of native and exotic earthworms on resource use and nutrient mineralization in a tropical wet forest soil of puerto rico. Biology and Fertility of Soils 36 (1) (AUG): 43-52.
Investigation of single or mixed assemblages of
native Estherella sp. and exotic Pontoscolex corethrurus
from a rain forest in Puerto Rico was undertaken to understand
resource use patterns, and linkages with C and N
mineralization in a 19-day incubation. Resource use was
explored with addition of 15N-enriched leaf litter and 13Cenriched
glucose to reconstructed organic and mineral soil
horizons. Juvenile Estherella sp. became at least 6.06‰
more enriched in 13C than sub-adult Estherella sp. or adult
P. corethrurus. Sub-adult Estherella sp. became >3.6‰
enriched in 13C over P. corethrurus. δ15N acquired by P.
corethrurus was greater by 0.83–1.56‰ in the mixed-species
than the single-species assemblages. δ15N of subadult
Estherella sp. was enriched by 0.73–0.81‰ over juvenile
Estherella sp. in the single-species assemblage. Net
N immobilization occurred in the organic layer of all 15Nenriched
treatments. Net N mineralization in mineral soil
layers was significantly greater in microcosms with P.
corethrurus than in those containing only Estherella sp..
Cumulative respiration was greatest in P. corethrurus assemblages,
however, assemblages with only Estherella sp.
released more 13C in respiration. P. corethrurus assimilated
different N resources when incubated with, as compared
to without, native Estherella sp.. δ13C and δ15N signatures
acquired by assimilation of 13C and 15N differed
by species, developmental stage, and competitive interactions.
The results showed that alone, exotic P. corethrurus
induced higher mineralization rates than native Estherella
sp., but that the interaction of exotic and native species
impinged on resource use by P. corethrurus, reducing the
effect of the exotic species on C and N mineralization. Invasion
of exotic P. corethrurus may change the mineralization
potentials of C and N and their biogeochemical cycling