Blossom software was used to help determine the influence of periodic
emergency haying on the composition and structure of grassland vegetation
on Conservation Reserve Program lands. This study provided information
on the long-term effects of emergency haying on wildlife habitat that
could then be used to refine management guidelines.
Because there was no reason to believe vegetation changes would occur
as simple shifts in means or variances, the researchers desired a test
that was capable of detecting any form of distributional difference. Consequently,
they used the Multi-Response Permutation Procedures (MRPP) to compare
measures of vegetation height, density, and composition among fields hayed
for different numbers of years. Selected regression quantiles (0.9, 0.75,
0.5, 0.25, and 0.1) were used to estimate the complex distributional changes
that were detected with the MRPP comparisons.
The following figures from Allen et al. (2001) illustrate the use and
results of the multi-response permutation procedures and regression quantile
estimates (solid black lines are 10th, 25th, 50th, 75th and 90th percentiles
for linear model that included just years hayed and dotted red lines are
for model that also adjusts for years since last hayed). Study results
showed that legumes increased (MRPP, P < 0.001)and grass cover remained
fairly constant (MRPP, P = 0.731) with increasing number of years that
fields were hayed.
U.S. Department of the Interior | U.S. Geological Survey
URL: http://www.fort.usgs.gov/resources/spotlight/blossom/blossom_haying.asp
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