Plant biodiversity

At community and larger scales, vegetative structural diversity provides an important regulatory function in agricultural landscapes¹. The presence of trees and shrubs as boundary plantings and hedges with multiple plant species provide barriers to runoff, increases capture of water and soil resources, and provides important habitats for beneficial insects that often require a high boundary-to-field ratio².

Mosiacs of different plant life forms across an area are also associated with other important regulatory services; however, metrics at these larger scales are beyond the scope of this framework. However, we recommend using transects (2 m by 50m) across the farm landscape for characterizing tree diversity.  We recommend 2 to 3 transects per hectare. The species and number of individuals (as well as tree height and diameter at breast height, or 1.3 m) is recorded.  The landscape herbaceous diversity (crops, weeds, invasives, rare species, etc) can also be assessed at the landscape level by placing one of the 1m by 1 m quadrants at the 0m, 25m and 50m positions along the transect. 

Diversification of crops grown, as well as associated plants, involves choices made by a household at the farm level, and at the field level. For a given field, crops can be grown in mixed intercropped systems, or as sole crops. Non-crop species are sometimes considered weeds and are removed, as possible, but often several species are left in the field along with the crops.  These non-crop species are also important and should be noted.

¹Newton et al., 2008

²Andow, 1991