Many
numerical tools exist for describing community structure and how that structure
changes over time. Many of these approaches are univariate (species richness)
or have questionable underlying ecological meaning (rank-abundance curves). In
addition, patterns of aggregate structure may mask lower order dynamics in
species abundances at a site over time. Rank clocks and rank abundance
statistics provide a rich graphical and analytical framework for displaying and
quantifying community dynamics. We used rank clocks, in which the rank order
abundance for each species is plotted at each sample date in temporal clockwise
direction, to display changes in species abundances and richness over time. We
used mean rank shift per time and proportional species persistence to quantify
changes in community structure under different experimental or empirical
treatments. Rank clocks and analyses were performed on long-term data from
three LTERs: fertilized and control plots at Cedar Creek, annually burned and
unburned grasslands at Konza Prairie, and grassland and shrubland communities
at Sevilleta. Rank clocks show that relatively constant species richness masks
considerable temporal dynamics in relative species abundances. At Cedar Creek, fertilized
plots initially experienced high mean rank shifts and then stabilized rapidly
below those of unfertilized plots. Rank shifts were higher in unburned vs.
annually burned grassland at Konza Prairie and throughout time in grassland
compared to shrubland at Sevilleta. Proportional persistence showed that arid
grasslands were more dynamic than mesic grasslands. We conclude that rank
clocks and rank abundance statistics provide important insights into community
dynamics that are hidden in traditional univariate or curve-fitting approaches.