Environmental Engineering Reference
In-Depth Information
CHAPTER
2
Primary Production: The Foundation
of Ecosystems
Michael L. Pace
1
and Gary M. Lovett
2
1
University of Virginia, Charlottesville
2
Cary Institute of Ecosystem Studies, Millbrook, NY
INTRODUCTION
Primary production is the storage of energy through the formation of organic matter
from inorganic carbon compounds. Primary production is carried out by autotrophic
organisms. The term
autotrophic
is derived from the Greek words
autos
, meaning self, and
trophikos
, meaning pertaining to food. Autotrophs are “self-feeders.” Higher plants as well
as some microbes (e.g., algae) are autotrophs. Plants and algae conduct the most familiar
form of primary production—photosynthesis—where carbon dioxide is incorporated into
organic matter using energy from sunlight. In most ecosystems primary production is car-
ried out by a variety of species and the diversity of autotrophs influences primary produc-
tion (e.g.,
Tilman et al. 2006
). The accrual of organic matter by primary producers
represents the first step in the capture, storage, and transfer of energy in most ecosystems.
There are several reasons why ecologists consider primary production a fundamental
ecosystem process. The ecosystem carbon cycle begins with the fixation of carbon
(i.e., incorporation of CO
2
into organic matter). Herbivores consume this organic carbon
produced by autotrophs to support their growth and metabolism. Other components of
the food web such as detritivores and predators also depend directly or indirectly on pri-
mary production for their energy supply. Primary producers require nutrients such as
nitrogen and phosphorus to build biomolecules such as proteins and nucleic acids. The
uptake and cycling of nitrogen, phosphorus, and other elements accompanies primary
production, and the ratio of elements that ultimately comprises primary producers influ-
ences many ecological processes (
Sterner and Elser 2002
). The formation of organic matter
