Making soil biodiversity matter for agriculture - Microbial Ecology in Sustainable Agroecosystems - page 269

et al., 2010; Wu et al., 2011). Nevertheless, there is sufficient evidence from microcosm and
field experiments to show that interactions between individual species can have major
consequences for ecosystem processes (Heemsbergen et al., 2004; Barrett et al., 2008). There
are also many reports showing that soil biodiversity is altered due to land-use change
(including intensification), climate change, and chemical inputs to soils (Wardle, Bardgett,
et al., 2004; Wardle, Brown, et al., 2004; Bardgett, 2005); that loss of symbionts (nitrogen-
fixing bacteria, mycorrhizae) in ecosystems has dramatic effects for nutrient cycling and
plant communities (van der Heijden and Horton, 2009); and that reduction of species num-
bers of mycorrhizal fungi in grasslands reduces primary production (van der Heijden et
al., 1998). Thus, loss of biodiversity in some natural soil systems can have a positive, nega-
tive, or no effect on ecosystem functioning, depending on the particular ecosystem and
type of disturbance (Nielsen et al., 2010).
In contrast, agriculture has a long history of evidence for the role of individual soil-
dwelling species in an ecosystem process (e.g., plant production). Pests, pathogens, or
herbivores of roots have long been known at the species level for their individual and char-
acteristic effect on plant physiology, metabolism, productivity, and crop yield. Also known
from years of greenhouse and field experiments is evidence of when control should be
initiated for species of root parasitic nematodes. This evidence includes an understand-
ing of the nematode biology (the plant host range, soil temperature and moisture range,
the feeding site preference [plant root tip, meristem, zone of elongation], life history) and,
for some species, the density of nematodes at which control should be initiated to pre-
vent increasing populations from causing plant economic damage (Bridge and Starr, 2007).
Agricultural evidence demonstrates that root parasitic nematode biodiversity at the indi-
vidual species or multiple species level can decrease an ecosystem process (e.g., net plant
productivity) and affect an ecosystem service (e.g., provision of food). Most agronomic
field research on target pests and pathogens, however, has not included multiple trophic
levels (van der Putten et al., 2010). There has been successful research based on including
an understanding of microbes, predators, and parasites into crop production as biocontrol
measures (e.g., Borneman and Becker, 2007; Gao et al., 2008).
The provision of ecosystem services provided by soils has been the subject of many
articles (Daily et al., 1997; Swift et al., 2004; van der Putten et al., 2004; Wardle, Brown, et
al., 2004; Lavelle et al., 2006; Barrios, 2007; Velasquez et al., 2007; Weber, 2007; Zhang et
al., 2007; Kibblewhite et al., 2008; Dominati et al., 2010; Nielsen et al., 2010; Sylvain and
Wall, 2011; Barrios et al., 2012). Among these studies is a new economic framework for
soil ecosystem services based on nonliving physical soil properties as the natural capi-
tal and soil biological activity as part of supporting services (Dominati et al., 2010). The
Dominati et al. article is a substantial departure from the MA (2005) that is based on bio-
diversity and nonliving resources—the ecosystem—that through functioning provide
ecosystem services for human well-being. Others noted a research need is quantifica-
tion of ecosystem services provided by soil biodiversity (Swift et al., 2004; Wall, 2004;
Barrios et al., 2012). Swift et al. (2004) questioned whether biodiversity and ecosystem
services in agricultural landscapes could be measured at field scales in industrialized
agriculture, particularly since an objective of agriculture was to reduce diversity and
to substitute fertilizer for the functions of soil biodiversity. Their article suggested that
biodiversity and ecosystem services could be maintained at landscape and farm scales
rather than the field scale, but this would require economic change and policies that
encouraged land-use diversity. Velasquez et al. (2007) tested a general indicator of soil
quality (GISQ), with macrofaunal biodiversity representing an integrating component