Agriculture Reference
In-Depth Information
sulfate or ammonium nitrate in Ýeld plots with different populations of earthworms. To examine how
earthworms inÞuence the redistribution and lability of surface and soil organic matter, double labeling
of plants with
N holds much promise. Over time, the soil could be analyzed for organic
fractions with different mineralization kinetics. Estimates of surface casting by earthworms are not
difÝcult to make, but creative methodologies need to be developed to quantify amounts of belowground
cast production in the Ýeld. The use of Þuorescent dyes may be suitable. Equally important is assessment
of the length of time over which casts maintain their structural integrity and how C and N cycling
processes change as casts age. Finally, more information is required on how earthworms contribute to
gaseous, leaching, and overland Þow Þuxes of nutrients.
C and
13
15
A HIERARCHICAL APPROACH
Determining the role of earthworms in nutrient cycling processes can unify many different aspects
of the biology and ecology of earthworms. Studies at all levels of the ecological hierarchy can
provide information that will contribute to a better understanding of how earthworms inÞuence
biogeochemical cycles at larger spatial and temporal scales (Figure 9.5).
I
E
NDIVIDUAL
ARTHWORMS
Information on the physiological ecology of earthworms can help in understanding the type and
amounts of organic matter that earthworms consume and assimilate. Fundamental to an understand-
ing of the biology of any soil-inhabiting organism is knowledge of its C and N assimilation
efÝciency. QuantiÝcation of C and N assimilation efÝciencies is important because these could
Spatial Patterns
Source-Sink Relationships
Landscape
Ecosystem
Storage vs. Loss of C and N
C and N Flux
Ecological Groups
Community
Biomass and Growth
Reproduction and Mortality
Population
Assimilation and Excretion
Gut Microbiology
Individual
FIGURE 9.5
Diagram showing a hierarchical approach for investigating the effects of earthworms on nutrient
cycling processes.
