Agriculture Reference
In-Depth Information
services is rarely an explicit goal of intensive agriculture (Costanza et al. 1997,
Daily et al. 2000). An exception may be high value crops, such as fruits and veg-
etables, where management practices such as planting or maintaining diverse plant
communities along field edges have enhanced pollinators and fruit set (NRC 2007,
Ricketts et al. 2008, Garibaldi et al. 2011). Communities in the landscape surround-
ing crops are important for biological control services, especially for beneficial
insects that rely on the floral resources and habitat that plants provide (Landis et al.
2008, Meehan et al. 2011, Landis and Gage 2015, Chapter 8 in this volume). Thus,
both economic and environmental incentives exist for ecological research on the
functioning of row-crop systems and the contribution of plant diversity within and
surrounding row-crop fields to the ecosystem services from agricultural landscapes.
What are the ecological factors that control diversity and productivity in plant
communities, and how do they interact to affect the ecosystem services provided by
row crops? For plant communities in general, much evidence exists that disturbance
regimes (frequency, magnitude, and timing), soil fertility, and biotic interactions
(competitors and consumers; see Mittelbach 2012) influence local diversity, and
that these local factors interact with regional factors such as seed sources, landscape
connectivity, and climate to determine species composition and diversity (Davis
et al. 2000, Vellend 2010). But for weed communities, much less is known about
how these factors—both local and regional—interact to determine their diversity,
composition, and abundance in agricultural systems (Ryan et al. 2010, Egan and
Mortensen 2012).
In this chapter, we examine how disturbance and nutrient additions influence
plant species diversity, composition, and productivity of herbaceous plant commu-
nities typical of agricultural landscapes in the upper midwestern United States. We
focus primarily on studies at the Kellogg Biological Station Long-Term Ecological
Research site (KBS LTER) in successional fields and row crops. We compare results
from the Main Cropping System Experiment (MCSE, Table 7.1; details in Robertson
and Hamilton 2015, Chapter 1 in this volume) with smaller-scale experimental stud-
ies established within and adjacent to the MCSE. We also provide a broader context
for our research on fertilizer manipulations by summarizing results from cross-site
analyses of resource enrichments in herbaceous communities across a broad geo-
graphic gradient in North America, including a number of other LTER sites. We end
the chapter by discussing how interacting processes might shape the future of agri-
culture, particularly in the context of global climate change and grassland restoration
and management. Understanding how disturbance and nutrient availability interact
and affect herbaceous plant communities is fundamental to the development of bio-
logically based management of row crops and other agricultural systems.
Experimental Design and Research Approaches
The annual cropping systems of the MCSE provide us with the opportunity to com-
pare the effects of disturbance (tillage) and nutrient input (cover crops vs. inor-
ganic fertilizers), and their interaction, on weed communities and crop yield. Other
KBS LTER researchers have evaluated how these management practices affect
