Agriculture Reference
In-Depth Information
Also important to consider is how factors beyond the field level affect the ability
of row-crop ecosystems to deliver these services. Watershed position and landscape
complexity can affect many aspects of ecological structure and function; examples
include the movement of organisms, nutrients, and water between and among eco-
systems, and the spatial patterns of soils and microclimates.
Organisms and Their Interactions
The main groups of organisms providing biological structure in cropping systems
include (1) plants as they consume resources both above and below ground (Gross
et al. 2015, Chapter 7 in this volume) and regulate the hydrologic cycle (Hamilton
2015, Chapter 11 in this volume); (2) microbes as they control organic matter turn-
over (Paul et al. 2015, Chapter 5 in this volume), nutrient availability (Millar and
Robertson 2015, Chapter 9 in this volume; Snapp et al. 2015, Chapter 15 in this
volume), and greenhouse gas fluxes (Schmidt and Waldron 2015, Chapter 6 in this
volume; Gelfand and Robertson 2015, Chapter 12 in this volume); (3) insects and
pathogens as they respond to changes in the plant community and affect plant pro-
ductivity (Landis and Gage 2015, Chapter 8 in this volume); and (4) humans as
they intentionally and unintentionally create biophysical and chemical disturbance
(Swinton et al. 2015a, Chapter 3 in this volume). Each of these groups is a focal
area of KBS LTER research and—together with research on watershed biogeo-
chemistry (Hamilton 2015, Chapter 11 in this volume) and regionalization (Gage
et al. 2015, Chapter 4 in this volume)—constitutes the core research areas of KBS
LTER. Understanding the interactions and integration among these core areas is
crucial for generating a comprehensive understanding of the drivers and dynamics
of the coupled human-natural system we call agriculture.
The KBS LTER Experimental Setting
Factorial field experiments, wherein different experimental treatments are estab-
lished in plots at a single geographic location, offer a powerful means for revealing
the influence of individual factors or groups of factors on ecological interactions
and agronomic performance. When treatments include a variety of cropping sys-
tems, the additional opportunity exists for identifying important interactions that
can then be further untangled with nested, single-factor experiments. Furthermore,
comparisons of cropping systems to unmanaged, reference plant communities at
different stages of secondary succession allow us (1) to gauge the extent to which
agriculture has produced long-term changes that may or may not be readily reversed
and (2) to understand how noncrop habitats may provide resources for beneficial
organisms and modify processes in a manner that might inform sustainable crop-
ping system management.
Plot-scale experimentation provides the basis for sound statistical inference and
its value cannot be overstated. But for many questions, the plots of such experiments
can be too small to capture important interactions or processes, or the phenomena
studied are significantly influenced by adjacent landscape elements. These include
