MULTISCALE SAMPLING OF PLANT DIVERSITY: EFFECTS OF MINIMUM MAPPING UNIT SIZE

MULTISCALE SAMPLING OF PLANT DIVERSITY: EFFECTS OF MINIMUM MAPPING UNIT SIZE Only a small portion of any landscape can be sampled for vascular plant diversity because of constraints of cost (salaries, travel time between sites, etc.). Often, the investigator decides to reduce the cost of creating a vegetation map by increasing the minimum mapping unit (MMU), and//or by reducing the number of vegetation classes to be considered. Questions arise about what information is sacrificed when map resolution is decreased. We compared plant diversity patterns from vegetation maps made with 100-ha, 50-ha, 2-ha, and 0.02-ha MMUs in a 754-ha study area in Rocky Mountain National Park, Colorado, United States, using four 0.025-ha and 21 0.1-ha multiscale vegetation plots. We developed and tested species––log(area) curves, correcting the curves for within-vegetation type heterogeneity with Jaccard’’s coefficients. Total species richness in the study area was estimated from vegetation maps at each resolution (MMU), based on the corrected species––area curves, total area of the vegetation type, and species overlap among vegetation types. With the 0.02-ha MMU, six vegetation types were recovered, resulting in an estimated 552 species (95%% ci == 520––583 species) in the 754-ha study area (330 plant species were observed in the 25 plots). With the 2-ha MMU, five vegetation types were recognized, resulting in an estimated 473 species for the study area. With the 50-ha MMU, 439 plant species were estimated for the four vegetation types recognized in the study area. With the 100-ha MMU, only three vegetation types were recognized, resulting in an estimated 341 plant species for the study area. Locally rare species and keystone ecosystems (areas of high or unique plant diversity) were missed at the 2-ha, 50-ha, and 100-ha scales. To evaluate the effects of minimum mapping unit size requires: (1) an initial stratification of homogeneous, heterogeneous, and rare habitat types; and (2) an evaluation of within-type and between-type heterogeneity generated by environmental gradients and other factors. We suggest that at least some portions of vegetation maps created at a coarser level of resolution be validated at a higher level of resolution. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Ecological Applications Ecological Society of America

MULTISCALE SAMPLING OF PLANT DIVERSITY: EFFECTS OF MINIMUM MAPPING UNIT SIZE

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Publisher
Ecological Society of America
Copyright
Copyright © 1997 by the Ecological Society of America
Subject
Articles
ISSN
1051-0761
D.O.I.
10.1890/1051-0761%281997%29007%5B1064:MSOPDE%5D2.0.CO%3B2
Publisher site
See Article on Publisher Site

Abstract

Only a small portion of any landscape can be sampled for vascular plant diversity because of constraints of cost (salaries, travel time between sites, etc.). Often, the investigator decides to reduce the cost of creating a vegetation map by increasing the minimum mapping unit (MMU), and//or by reducing the number of vegetation classes to be considered. Questions arise about what information is sacrificed when map resolution is decreased. We compared plant diversity patterns from vegetation maps made with 100-ha, 50-ha, 2-ha, and 0.02-ha MMUs in a 754-ha study area in Rocky Mountain National Park, Colorado, United States, using four 0.025-ha and 21 0.1-ha multiscale vegetation plots. We developed and tested species––log(area) curves, correcting the curves for within-vegetation type heterogeneity with Jaccard’’s coefficients. Total species richness in the study area was estimated from vegetation maps at each resolution (MMU), based on the corrected species––area curves, total area of the vegetation type, and species overlap among vegetation types. With the 0.02-ha MMU, six vegetation types were recovered, resulting in an estimated 552 species (95%% ci == 520––583 species) in the 754-ha study area (330 plant species were observed in the 25 plots). With the 2-ha MMU, five vegetation types were recognized, resulting in an estimated 473 species for the study area. With the 50-ha MMU, 439 plant species were estimated for the four vegetation types recognized in the study area. With the 100-ha MMU, only three vegetation types were recognized, resulting in an estimated 341 plant species for the study area. Locally rare species and keystone ecosystems (areas of high or unique plant diversity) were missed at the 2-ha, 50-ha, and 100-ha scales. To evaluate the effects of minimum mapping unit size requires: (1) an initial stratification of homogeneous, heterogeneous, and rare habitat types; and (2) an evaluation of within-type and between-type heterogeneity generated by environmental gradients and other factors. We suggest that at least some portions of vegetation maps created at a coarser level of resolution be validated at a higher level of resolution.

Journal

Ecological ApplicationsEcological Society of America

Published: Aug 1, 1997

Keywords: Jaccard’’s coefficients ; keystone ecosystems ; minimum mapping unit ; modified-Whittaker plot ; species––area curves ; species overlap ; vascular plant diversity

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