Agriculture Reference
In-Depth Information
many annual weed species varies with temperature and moisture (Baskin and
Baskin 1999), understanding how early season precipitation and temperature
interact with tillage (disturbance timing and frequency) is important for deter-
mining how climate change may affect the composition and abundance of weed
species in row crops.
Summary
Understanding the processes that determine the diversity and productivity of plant
communities remains an important challenge in plant community ecology, and is
fundamental to the sustainable management of agroecosystems. In this chapter, we
have focused primarily on comparisons of ecological processes in annual row crops
(corn, soybean, and wheat) and successional fields, which are important compo-
nents of the agricultural landscape of the upper U.S. Midwest.
Research at the KBS LTER has shown that agroecosystems and successional
grasslands generally conform to our understanding of how disturbance and nutri-
ent availability interact to determine productivity and species diversity in ter-
restrial plant communities. Disturbance, whether caused by tillage or herbicide
use, has a very strong effect on plant community composition in both the Early
Successional community and the weed communities of annual row crop systems.
Fertilization generally increases production and decreases species diversity in
grasslands (Gough et al. 2000, Clark et al. 2007), and while nutrient inputs cer-
tainly increase crop yield, the nutrient source (inorganic or legume-based) con-
founds our interpretation of the fertilizer effect of the abundance and composition
of weed communities. This constrains our ability to use results from unmanaged
successional grasslands to predict how crop grain yield or weed biomass will
respond to particular changes in agricultural management. However, research on
the ecology of weeds in agricultural ecosystems may provide insights into how
to manage invasive species in remnant, degraded, or restored ecosystems (Smith
et al. 2006).
Our experiments on row-crop and successional systems at the KBS LTER have
provided important insights into the mechanisms by which diversity may influence
crop yield. For example, studies of seed bank dynamics in the MCSE annual row-
crop systems have shown that disturbance and fertilization interact with soil biota
to influence seed mortality (Davis et al. 2005). Although this mechanism has not
been widely explored in natural plant communities, it may be among the plant-soil
feedbacks (Bever et al. 2010) that can be managed in reduced input or organic crop-
ping systems. Findings such as these can lead to the development of management
practices that rely less on chemical inputs and more on manipulation of ecosystem
processes. These insights inform future research on factors influencing plant com-
munities in sustainable agricultural systems, as well as natural systems. However,
while there is growing evidence of the importance of regional species pools and
other landscape factors to the composition and diversity of grassland communities,
considerably less is known about how these regional processes influence the com-
position of weed communities.
