Tillage intensity affects weed communities in agroecosystems - Invasive Plants: Ecological and Agricultural Aspects - page 186

Plant traits and functional groups
Plant communities do not conform strictly to any given set of constraints
because the 'filters' are not perfect and because species are not homogeneous
[19]. Thus, predictions on weed species response to changing agricultural
practices (including tillage intensity) have been difficult and prone to error.
Some researchers have suggested using plant traits, instead of species, as
the unit to examine constraints on community assembly [20, 43]. Traits are the
physical and physiological characteristics that determine the ecological func-
tion of a species. Dispersal and environmental filters plus internal mechanisms
remove species from an overall species pool that lack specific traits and thus
traits, rather than species, are filtered. Traits associated with both plant growth
and reproduction should be considered [44]. Booth et al. [19] suggest numer-
ous potential traits (e.g., plant morphology, growth rate, reproductive potential,
seed dormancy, life cycle) for consideration in trait-based analysis.
The trait-based approach may be further simplified by grouping a similar set
of traits into functional groups [20]. A functional group contains species with a
similar set of traits. They have similar ecological functions in a community and
therefore respond similarly to changing constraints. If sufficient information
exists, functional groups can be created by selecting important traits based on
ecological knowledge and experience, or by applying clustering techniques to
data sets with the goal of detecting correlations among traits across species. The
use of plant traits and functional groups may increase our understanding of
weed community development and allow better prediction of how weed com-
munities respond to changing agronomic practices (such as tillage) over time.
Approaches to studying tillage effects on agricultural weed communities
The following discussion presents examples from the Canadian Prairies on
how weed communities respond to tillage and attempts to determine what
traits respond to tillage and whether species can be grouped into functional
groups. It is recognized that these results are specific to the cropping systems
and environmental conditions of this region. Nevertheless, it is reasonable to
expect that some of the generalized results would be relevant to other agricul-
tural regions of the world.
Case 1 - A long-term study at one site
An 11-year field study was conducted at Lethbridge, Alberta, Canada, to deter-
mine the effect of various winter wheat ( Triticum aestivum L.) rotations and
tillage treatments on crop yield, soil quality and weed infestations [45, 46].
The crop rotation treatments were: 1) winter wheat-oilseed rape ( Brassica
rapa L.), 2) winter wheat-lentil ( Lens culinaris L.)/linseed ( Linum usitatissi-