Agriculture Reference
In-Depth Information
with biodiversity questions for different taxa—for example, seed banks and
noncrop plant diversity would not be well represented in 0.01-ha or smaller
plots commonly studied in agricultural research, although even 1-ha plots are
insufficient for research on more mobile taxa such as vertebrates and many
arthropods.
In each MCSE replicate is a permanent set of five sampling stations near which
most within-plot sampling is performed. Additionally, replicate plots typically host
microplot experiments that focus on testing specific mechanistic hypotheses, such
as N-addition plots to test the relationship between nutrient availability and plant
diversity and predator-exclusion plots to examine the role of predators in control-
ling invasive insects. Some microplot experiments are permanent, such as annually
tilled × N fertilized microplots within the Early Successional community (Gross et
al. 2015, Chapter 7 in this volume); many have been shorter term.
Regular measurements for all 11 systems and communities in the MCSE include
(1) plant species composition, above-ground net primary productivity, litter fall,
and crop yield; (2) predaceous insects, in particular, coccinellids (ladybird bee-
tles); (3) microbial biomass and abundance; (4) soil moisture, pH, bulk density,
carbon, inorganic nitrogen, and nitrogen mineralization; (5) NO
3
−
concentrations
in low-tension lysimeters installed at a 1.2-m depth (Bt2/C horizon) in replicate
plots of all systems; and (6) a number of weather variables measured at a weather
station on the MCSE. Precipitation chemistry is monitored as part of the National
Atmospheric Deposition Program/National Trends Network at another weather sta-
tion 2 km away to avoid contamination by agricultural activities on site. Soil carbon
is measured to 1-m depth at decadal intervals in all systems. The soil seed bank is
sampled on a 6-year cycle.
Ancillary Experiments
In addition to the MCSE, several long- and shorter-term ancillary experiments
address specific questions. In some cases these are located in subplots nested within
the plots of the MCSE, and in others they are at independent locations. Here, we
describe the most important.
The MCSE Scale-Up Experiment
The need to understand how findings from our 1-ha MCSE cropping systems scale
up to commercially sized fields motivated the establishment of the MCSE Scale-Up
Experiment (Fig. 1.5). Although larger than most agronomic research plots, the
1-ha MCSE plots may still suffer from artifacts related to plot size. For example,
because plots are managed for research, agronomic operations may not be as influ-
enced by labor issues as they might be on a commercial farm. The frequency and
timing of operations such as mechanical weed control and planting date may affect
weed densities and yields, and a commercial operator will have less flexibility for
optimal scheduling due to labor constraints.
Additionally, our 1-ha plots are embedded in a matrix of other plots with differ-
ent plant communities that could provide insect refugia or seed sources not typically
