Agriculture Reference
In-Depth Information
Treatment
Corn
Soybean
Winter wheat
Spring tillage
Fall tillage
Axis 1 (R
2
= 0.39)
Figure 7.3
. Weed species composition in response to agronomic and fallow treatments in
the Biodiversity Gradient Experiment. Plot scores are from non-metric multidimensional
scaling (NMDS) ordination of weed community composition and abundance in 2004 in rela-
tion to crop type (soybean, wheat, corn) and tillage time (spring, fall) for fallow treatments.
Ordination based on Bray-Curtis dissimilarity in species composition.
Temporal Dynamics and Community Assembly
The plant community that assembles in response to a particular disturbance regime,
whether in a row crop or an abandoned agricultural field, will depend on the nature
of the disturbance; the local and regional species pool; and climatic (e.g., tempera-
ture and precipitation), abiotic (soil fertility), and biotic factors (e.g., competitors,
mutualists, predators, and pathogens). Long-term KBS LTER studies allow us to
compare, in replicated plots, how different management practices (Table 7.1) affect
the colonization, establishment, persistence, and extinction of plant species in both
successional and row-crop communities. When chronic or repeated disturbances
cease, sites undergo a successional sequence of changes in both species composi-
tion and traits (Connell and Slatyer 1977). Long-term experiments within MCSE
plots allow us to examine how nutrient enrichment (fertilization) and climatic fac-
tors interact to affect these trajectories. We can also determine how variation in
chemical inputs to row crops affects the composition and diversity of weeds in
agronomic systems.
