This study compared the utility of three sampling methods for ecological monitoring based on: interchangeability of data (rank correlations), precision (coefficient of variation), cost (minutes/transect), and potential of each method to generate multiple indicators. Species richness and foliar cover by species were measured for each method on four transects (70 m) in 15 sites (three in each of five plant communities) in the northern Chihuahuan Desert. Randomized species accumulation curves and rank correlations of the three methods were conducted with these data.

Results/Conclusions

Line- (17 ± 2) and grid-point intercepts (16 ± 2) provide lower estimates of species richness than ocular estimates (21 ± 2). There were no differences in precision and number of species detected per unit of sampling effort. Estimates of foliar cover with line- and grid-point intercepts were similar and highly correlated between them (r=0.96, p<0.0001). Ocular estimates were different and poorly correlated with estimates of other methods (line-point: r=0.62, p=0.007; grid-point: r=0.70, p=0.002). Ocular estimates further varied with plant community. Precision of estimates with line-point intercepts was higher than ocular estimates. Cost was similar (line-point: 23 ± 2, ocular estimates: 27 ± 4 minutes/transect), except for grid-point intercepts which take longer (31 ± 3). Results suggest that point based methods provide interchangeable data with higher precision than ocular estimates. Moreover these methods are potentially able to provide data on 12 additional indicators.