Mapping the Abstractions of Forest Landscape Patterns

Abstract

The evaluation of landscape patterns is necessary to explain the relationships between ecological processes and spatial patterns and between the processes and patterns and the factors that control them or that they control. For decades, landscape metrics have been used to measure and abstract landscape patterns. Since the emergence of FRAGSTATS in 1993, the measures and methods incorporated in this software have become widely used and are now a de facto standard tool for calculating landscape metrics. However, there are no special metrics unique to forest landscapes. The selection of metrics depends on the purpose of the study rather than on the land use or cover type. However, some metrics are more often used for forested landscapes (e.g., core area metrics). Forest landscape patterns are changing fast due to both natural and human disturbances. Remote sensing offers a rapid method of acquiring up-to-date information over a large geographical area and is therefore widely used as a source of the data needed for pattern assessment and the calculation of landscape metrics. However, to obtain meaningful results, correct preparation of the data is essential. In this chapter, we review the various metrics used to measure forest landscapes for different purposes. We deal with five main issues from the perspective of forest landscape patterns: (1) data preparation before the calculation of metrics (e.g., vector vs. raster data, scale, classification) and the associated uncertainties, (2) measurements of a landscape’s configuration and composition using metrics, (3) interpretation of the results, (4) possible uses of the outcomes, and (5) future perspectives (e.g., 3D and 4D landscape metrics).

Appendix: Technical Terms

Categorical maps —Maps that define each unit of a landscape in terms of a descriptive category (e.g., forest vs. grassland) rather than quantitatively.

Central point method —A method used to convert vector data to raster data by assigning a value to a cell in a grid based on the value for the polygon that overlaps the center of the cell. See also majority rule method.

Fractal dimension —A ratio that provides a statistical index of the degree of complexity of a pattern by examining how the level of detail in a pattern changes in response to changes in the scale at which it is measured.

Free open-source software (FOSS) —Software whose source code is made available to anyone under a license in which the copyright holder provides the rights to study, change, and distribute the software to anyone and for any purpose.

Geographical information system (GIS) —A system designed to capture, store, manipulate, analyze, manage, and present all types of spatial or geographical data.

Graph theory —A mathematical description of the properties of graphs and, thus, of the pairwise relationships between variables or objects.

Image rectification—A transformation process used to project an image from a sensor’s coordinate system into a geographical coordinate system.

Landscape metrics—Algorithms that quantify specific spatial characteristics of patches, classes of patches, or entire landscape mosaics.

Leaf area index —A dimensionless quantity that characterizes plant canopies by dividing the total one-sided area of leaf tissue by the ground surface area covered by the canopy that contains those leaves.

LiDAR (light detection and ranging )—A remote sensing method that uses pulsed laser light to measure the distance between the sensor and a surface.

Majority rule method—A method used to convert vector data to raster data by using the feature that accounts for the largest area within a cell of a grid to define the attribute value assigned to the cell. See also central point method.

Map algebra—A set of primitive operations in a geographic information system (GIS) that allow two or more raster layers (“maps”) of similar dimensions to produce a new raster layer (map) using algebraic operations such as addition or subtraction.

Marxan algorithm —An algorithm used in conservation planning that aims to minimize the sum of the site-specific costs and connectivity costs for selected planning units, subject to the constraint that the conservation features in a reserve system must achieve predetermined targets.

Minimum mapping unit (MMU) —The size of the smallest feature that can be delineated within the boundaries of a map.

Modifiable areal unit problem—A challenge that occurs during the spatial analysis of aggregated data, in which the results differ when the same analysis is applied to the same data under different aggregation schemes.

Neutral landscape models —The minimum set of rules required to generate a pattern in the absence of a particular process; neutral models provide a means of testing the effect of the measured process on the patterns that are actually observed.

Open data—Data that can be freely used, reused, and redistributed by anyone, without restrictions from copyright, patents, or other mechanisms of control.

Red-edge chlorophyll index —A method used to estimate canopy chlorophyll and nitrogen contents based on remote sensing data.

SAR (synthetic aperture radar )—A form of radar that can be used to create images of objects, such as landscapes; the images can be two- or three-dimensional representations of the object.

Landscape metric scalograms—The response curves of landscape metrics to changing grain size that allow the detection of the most representative scales.