Agriculture Reference
In-Depth Information
biodiversity questions when taxa are mobile or are influenced by other habitats in
the landscape. For example, herbivorous insects and their predators as well as birds
and other vertebrates typically respond to landscape structure at scales larger than
can be accommodated in replicated field plots (Landis 1994, Landis and Marino
1999, Landis and Gage 2015, Chapter 8 in this volume). In some cases, noncrop
habitats in the landscape can serve as metapopulation sources and sinks. Likewise,
many biogeochemical questions depend on interactions that include landscape
position and the presence and location of disproportionalities (Nowak et al. 2006),
that is, hotspots of biogeochemical transformations such as high-phosphorus soils,
or shallow streams and wetlands through which water flows on its way to larger
rivers or lakes (Hamilton 2015, Chapter 11 in this volume).
Addressing these sorts of questions requires a landscape approach, rarely ame-
nable to exact replication and instead more often dependent on regression and other
inferential approaches (Robertson et al. 2007). Landscapes are often delineated
hydrologically as watersheds or drainage basins, which are hierarchical by nature
and can be grouped as needed to ask questions at larger scales. They can also be
defined on the basis of other properties or processes—airsheds for questions related
to nitrogen deposition or ozone impacts (e.g., Scheffe and Morris 1993), or food-
sheds for questions related to the movement of nutrients and other materials related
to food products (e.g., Peters et al. 2009).
An understanding of the roles of the social system (Fig. 1.4) requires expanding
study boundaries to include pertinent drivers of change and human behaviors that
respond to these drivers. In some cases, this might require regional surveys of farm-
ers to understand the factors they weigh when making tillage or crop choices (e.g.,
Swinton et al. 2015b, Chapter 13 in this volume); in other cases this might require
knowledge of the regional economy to understand land-use patterns and decisions
(e.g., Feng and Babcock 2010). Where findings can be related back to the systems
deployed in our field experiments, they will have the greatest power to contribute to
our understanding of the interconnections between socioecological and biophysical
realms in our conceptual model (Fig. 1.4).
The KBS LTER Main Cropping System Experiment
The KBS LTER Main Cropping System Experiment (MCSE) is an intensively stud-
ied factorial experiment that is the focus of much of the biophysical research at
KBS LTER (Figs. 1.2 and 1.3). As mentioned earlier, it includes four annual and
three perennial cropping systems plus four replicated reference communities in dif-
ferent stages of ecological succession, including an unmanaged late successional
forest (Table 1.1). Seven systems were established and first sampled in 1989; the
other four were already established and first sampled as noted below.
Each cropping system is intended to represent a model ecosystem relevant to
agricultural landscapes of the region (Gage et al. 2015, Chapter 4 in this volume).
They are not intended to represent all major crop × management combinations—to
do this would require scores of additional experimental systems. Model systems
are arranged along a gradient of decreasing chemical and management inputs. And
differences that occur along this management intensity gradient can be understood,
