Agriculture Reference
In-Depth Information
Table 7.2. Species composition and rotational diversity treatments of the KBS
biodiversity gradient experiment. a
Treatment
Description b
Number of
Treatments c
Crops per
Year
Cover
Crops per
Year
Total
Species per
Year
Crops over
Rotation
Cover
Crops over
Rotation
Total
Species over
Rotation
Spring or fall
plowed fallow d
2
0
0
10-12
0
0
20+
C-S-W with 2
cover crops
3
1
1-2
2-3
3
3
6
C-S-W with 1
cover crop
3
1
1
2
3
2
5
C-S-W
rotation
3
1
0
1
3
0
3
C-S, S-C,
W-S rotations
3
1
0
1
2
0
2
C, S, or W
with 1 cover
crop
3
1
1
2
1
1
2
C, S, or W
monoculture
3
1
0
1
1
0
1
Bare soil e
1
0
0
0
0
0
0
a All treatments replicated in each of four blocks; see Smith et al. (2008) for a detailed description of treatments and
rotations.
b Crops planted in rotations are Corn = C, Soybean = S, and Wheat = W and, when included, either 1(legume) or 2 (legume
and small grain) cover crops. Rotations are indicated by a hyphen; all entry points of rotations are planted each year.
c Number of treatments = number of entry points.
d Fallow treatments are tilled once a year (spring or fall), allowing weeds to establish.
e Bare soil treatment is repeatedly tilled to prevent weed establishment and to serve as a “no plant” reference for soil
and microbial studies.
production (Grman et  al. 2010), and (3)  successional trajectories (Huberty et  al.
1998). This experiment has shown the influence of landscape position or initial
colonization events on successional trajectories (Foster and Gross 1999) and how
these factors can constrain the restoration of native grasslands (Gross and Emery
2007, Suding and Gross 2006a, b; Suding et al. 2004). Participation in cross-site
synthesis projects across the LTER Network has allowed us to compare results from
the KBS LTER to those observed in other grasslands and has broadened our under-
standing of the response of herbaceous plant communities across North America
to increases in N deposition and why these responses may differ across sites (e.g.,
Gough et al. 2000, 2012; Suding et al. 2005; Clark et al. 2007; Cleland et al. 2013).
Disturbance as a Driver of Plant Community Diversity
Disturbance, particularly fire and grazing, has been shown to be important in
determining the composition and diversity of a variety of grasslands (Huston
1979, Miller 1982, Pickett and White 1985). Fire frequency (Collins 1992,
 
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