Weighted mean patch size: A robust index for quantifying landscape structure

Bai Lian Li, Steve Archer

Research output: Contribution to journalArticle

39 Citations (Scopus)

Abstract

Variables such as number of patches and mean patch size have been widely used to describe landscape structure. However, these simple, independent measurements often fail to adequately represent or track offsetting or reinforcing changes that occur from interactions between patch number, size and shape. Here, we present a synthetic 'weighted mean patch size' (WMPS) index which combines information represented in patch size and number. The utility of the WMPS index, which was based on percolation theory, is demonstrated using two data sets. The first data set consisted of output from a cellular automata-based simulation of landscape response to disturbance that varied in intensity and scale. Unlike simple estimates of mean patch size, the WMPS index was highly sensitive to disturbance and varied in a consistent fashion with both intensity and scale of disturbance. The second application involved the use of historical aerial photography to compare the dynamics of tree/shrub clusters (= patches) in a subtropical savanna parkland during a period of drought (1941-1960) and a period of normal to above-normal annual rainfall (1960-1983). Contrary to expectations, mean cluster (= patch) size increased in both periods. In addition, greatest increases in mean patch size occurred during the drought period, apparently the result of higher mortality among small clusters relative to large clusters. In contrast, climate-induced vegetation dynamics indicated by the WMPS index (decrease during drought period; increase in subsequent pluvial period) tracked those of other structural measurements (cluster density, total cover, cluster growth rate) and appeared to reflect dynamic, rainfall-induced changes in patch structure associated with changes in tree and shrub canopy area and plant numbers. These examples suggest the WMPS index, by combining information on patch size and number, can preserve process-level ecological information and provide robust, functionally relevant numerical representations of landscape structure over time and in response to disturbance.

Original languageEnglish (US)
Pages (from-to)353-361
Number of pages9
JournalEcological Modelling
Volume102
Issue number2-3
DOIs
StatePublished - Oct 29 1997
Externally publishedYes

Fingerprint

patch size
landscape structure
drought
shrubs
rain
aerial photography
savannas
preserves
disturbance
canopy
climate
vegetation
index
shrub
rainfall
cellular automaton
vegetation dynamics
savanna
mortality

Keywords

  • Cellular automata
  • Disturbance
  • Landscape response
  • Patch size
  • Savanna
  • Spatial patterns
  • Vegetation dynamics

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Ecological Modeling
  • Ecology

Cite this

Weighted mean patch size : A robust index for quantifying landscape structure. / Li, Bai Lian; Archer, Steve.

In: Ecological Modelling, Vol. 102, No. 2-3, 29.10.1997, p. 353-361.

Research output: Contribution to journalArticle

@article{f8236e5c59ca401a8a19d2dc480c931e,
title = "Weighted mean patch size: A robust index for quantifying landscape structure",
abstract = "Variables such as number of patches and mean patch size have been widely used to describe landscape structure. However, these simple, independent measurements often fail to adequately represent or track offsetting or reinforcing changes that occur from interactions between patch number, size and shape. Here, we present a synthetic 'weighted mean patch size' (WMPS) index which combines information represented in patch size and number. The utility of the WMPS index, which was based on percolation theory, is demonstrated using two data sets. The first data set consisted of output from a cellular automata-based simulation of landscape response to disturbance that varied in intensity and scale. Unlike simple estimates of mean patch size, the WMPS index was highly sensitive to disturbance and varied in a consistent fashion with both intensity and scale of disturbance. The second application involved the use of historical aerial photography to compare the dynamics of tree/shrub clusters (= patches) in a subtropical savanna parkland during a period of drought (1941-1960) and a period of normal to above-normal annual rainfall (1960-1983). Contrary to expectations, mean cluster (= patch) size increased in both periods. In addition, greatest increases in mean patch size occurred during the drought period, apparently the result of higher mortality among small clusters relative to large clusters. In contrast, climate-induced vegetation dynamics indicated by the WMPS index (decrease during drought period; increase in subsequent pluvial period) tracked those of other structural measurements (cluster density, total cover, cluster growth rate) and appeared to reflect dynamic, rainfall-induced changes in patch structure associated with changes in tree and shrub canopy area and plant numbers. These examples suggest the WMPS index, by combining information on patch size and number, can preserve process-level ecological information and provide robust, functionally relevant numerical representations of landscape structure over time and in response to disturbance.",
keywords = "Cellular automata, Disturbance, Landscape response, Patch size, Savanna, Spatial patterns, Vegetation dynamics",
author = "Li, {Bai Lian} and Steve Archer",
year = "1997",
month = "10",
day = "29",
doi = "10.1016/S0304-3800(97)00071-9",
language = "English (US)",
volume = "102",
pages = "353--361",
journal = "Ecological Modelling",
issn = "0304-3800",
publisher = "Elsevier",
number = "2-3",

}

TY - JOUR

T1 - Weighted mean patch size

T2 - A robust index for quantifying landscape structure

AU - Li, Bai Lian

AU - Archer, Steve

PY - 1997/10/29

Y1 - 1997/10/29

N2 - Variables such as number of patches and mean patch size have been widely used to describe landscape structure. However, these simple, independent measurements often fail to adequately represent or track offsetting or reinforcing changes that occur from interactions between patch number, size and shape. Here, we present a synthetic 'weighted mean patch size' (WMPS) index which combines information represented in patch size and number. The utility of the WMPS index, which was based on percolation theory, is demonstrated using two data sets. The first data set consisted of output from a cellular automata-based simulation of landscape response to disturbance that varied in intensity and scale. Unlike simple estimates of mean patch size, the WMPS index was highly sensitive to disturbance and varied in a consistent fashion with both intensity and scale of disturbance. The second application involved the use of historical aerial photography to compare the dynamics of tree/shrub clusters (= patches) in a subtropical savanna parkland during a period of drought (1941-1960) and a period of normal to above-normal annual rainfall (1960-1983). Contrary to expectations, mean cluster (= patch) size increased in both periods. In addition, greatest increases in mean patch size occurred during the drought period, apparently the result of higher mortality among small clusters relative to large clusters. In contrast, climate-induced vegetation dynamics indicated by the WMPS index (decrease during drought period; increase in subsequent pluvial period) tracked those of other structural measurements (cluster density, total cover, cluster growth rate) and appeared to reflect dynamic, rainfall-induced changes in patch structure associated with changes in tree and shrub canopy area and plant numbers. These examples suggest the WMPS index, by combining information on patch size and number, can preserve process-level ecological information and provide robust, functionally relevant numerical representations of landscape structure over time and in response to disturbance.

AB - Variables such as number of patches and mean patch size have been widely used to describe landscape structure. However, these simple, independent measurements often fail to adequately represent or track offsetting or reinforcing changes that occur from interactions between patch number, size and shape. Here, we present a synthetic 'weighted mean patch size' (WMPS) index which combines information represented in patch size and number. The utility of the WMPS index, which was based on percolation theory, is demonstrated using two data sets. The first data set consisted of output from a cellular automata-based simulation of landscape response to disturbance that varied in intensity and scale. Unlike simple estimates of mean patch size, the WMPS index was highly sensitive to disturbance and varied in a consistent fashion with both intensity and scale of disturbance. The second application involved the use of historical aerial photography to compare the dynamics of tree/shrub clusters (= patches) in a subtropical savanna parkland during a period of drought (1941-1960) and a period of normal to above-normal annual rainfall (1960-1983). Contrary to expectations, mean cluster (= patch) size increased in both periods. In addition, greatest increases in mean patch size occurred during the drought period, apparently the result of higher mortality among small clusters relative to large clusters. In contrast, climate-induced vegetation dynamics indicated by the WMPS index (decrease during drought period; increase in subsequent pluvial period) tracked those of other structural measurements (cluster density, total cover, cluster growth rate) and appeared to reflect dynamic, rainfall-induced changes in patch structure associated with changes in tree and shrub canopy area and plant numbers. These examples suggest the WMPS index, by combining information on patch size and number, can preserve process-level ecological information and provide robust, functionally relevant numerical representations of landscape structure over time and in response to disturbance.

KW - Cellular automata

KW - Disturbance

KW - Landscape response

KW - Patch size

KW - Savanna

KW - Spatial patterns

KW - Vegetation dynamics

UR - http://www.scopus.com/inward/record.url?scp=0030713277&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0030713277&partnerID=8YFLogxK

U2 - 10.1016/S0304-3800(97)00071-9

DO - 10.1016/S0304-3800(97)00071-9

M3 - Article

AN - SCOPUS:0030713277

VL - 102

SP - 353

EP - 361

JO - Ecological Modelling

JF - Ecological Modelling

SN - 0304-3800

IS - 2-3

ER -