Data from: Checkerboard score-area relationships reveal spatial scales of plant community structure

Identifying the spatial scale at which particular mechanisms influence
plant community assembly is crucial to understanding the mechanisms
structuring communities. It has long been recognized that many elements of
community structure are sensitive to area; however the majority of studies
examining patterns of community structure use a single relatively small
sampling area. As different assembly mechanisms likely cause patterns at
different scales we investigate how plant species co-occurrence patterns
change with sampling unit scale. We use the checkerboard score as an index
of species segregation, and examine species C-score-sampling area patterns
in two ways. First, we show via numerical simulation that the C-score-area
relationship is necessarily hump shaped with respect to sample plot area.
Second we examine empirical C-score-area relationships in arctic tundra,
grassland, boreal forest, and tropical forest communities. The minimum
sampling scale where species co-occurrence patterns were significantly
different from the null model expectation was at 0.1 m2 in the tundra, 0.2
m2 in grassland, and 0.2 Ha in both the boreal and tropical forests.
Species were most segregated in their co-occurrence (maximum C-score) at
0.3 m2 in the tundra (0.54 m by 0.54 m quadrats), 1.5 m2 in the grassland
(1.2 by 1.2 m quadrats), 0.26 Ha in the tropical forest (71 m by 71 m
quadrats), and a maximum was not reached at the largest sampling scale of
1.4 Ha in the boreal forest. The most important finding is that the
dominant scales of community structure in these systems are large relative
to plant body size, and hence we infer that the dominant mechanisms
structuring these communities must be at similarly large scales. This
provides a method for identifying the spatial scales at which communities
are maximally structured; ecologists can use this information to develop
hypotheses and experiments to test scale-specific mechanisms that
structure communities.