Reforestation in Monroe County, 1939-1998

Tom Evans

Introduction

Researchers at the Center for the Study of Institutions, Population and Environmental Change (CIPEC) are using GIS and remote sensing techniques to understand what factors contribute to forest cover change in Indiana. GIS methods are used to identify land cover changes occurring on individual private landholdings. Spatial partitions based on parcel boundaries allow researchers to see which parcels have increased or decreased in forest cover. A multi-layer framework integrates multi-temporal land cover data interpreted from historical aerial photography from 1939-present. The current research is focused on Monroe County, Indiana with initial data development occurring in Indian Creek and Van Buren Townships.

Figure 1. Indian Creek and Van Buren Townships, Monroe County, Indiana

Methods

A time series of aerial photography was scanned and registered to a common map projection. These photos were then visually inspected and forest vs. non-forest land cover was interpreted and digitized. Minimum mapping unit used in the digitizing process was ~ 20 x 20 meters. An estimated forest cover of 50% or higher was used for an area to be interpreted and classified as forest. Land cover changes derived from these air photo products are integrated with other data including parcel boundaries, surface topography, soils and transportation to explore the relationship between land cover change and various social and biophysical factors. This research provides empirical data to inform a multi-disciplinary land cover change modeling effort (see http://www.cipec.org/research/biocomplexity/ for more details and list of project members). Some results from this analysis are shown in the figures below.

Figure 2. Land Cover Change in Indian Creek Township, 1939 to 1998

Figure 3. Land Cover Change in Van Buren Township, 1939 to 1998

Indian Creek Township has changed from ~43% forest cover in 1939 to ~60% forest cover in 1998. Van Buren Township has changed from ~30% forest cover in 1939 to ~48% forest cover in 1998. Overall, both townships have changed from ~37% forest cover in 1939 to ~54% forest cover in 1998. Deforestation has also occurred during this period but was outpaced by afforestation.

Figure 4. Percent Forest Land Cover by Year, 1939 to 1998

Spatial metrics (descriptors of land cover composition and pattern) are used to characterize the nature of forests over time. Land cover has become less fragmented and less patchy between 1939 and 1998. This decreased patchiness is in part because forest succession is occurring proximal to areas already forested, increasing the mean patch size of existing forests. Afforestation has occurred in areas of moderate surface topography (5-20% surface slope).

Figure 5. Mean Forest Patch Area, Indian Creek and Van Buren Townships

Figure 6. Number of Forest Patches, Indian Creek and Van Buren Townships

Indian Creek and Van Buren Townships are now under increasing development pressure from urban expansion around the city of Bloomington. These findings present land cover changes for both townships. Subsequent research is integrating land cover change datasets with multi-temporal property boundary data to explore how parcelization and land fragmentation are related to land cover change. The agent-based land cover model is fit to the spatial metrics derived from the historical land cover data at the parcel level. The model now reproduces the process of afforestation and explores agent characteristics and dynamics that have contributed to it.

Acknowledgements

This research is supported by NSF research grant SES-0083511. Acknowledgements to Rich Caldanaro for digitizing the land cover data sets and preparing the figures shown above. Shanon Donnelly and Chuck Winkle have contributed to this research and are working on complementary research (see http://www.indiana.edu/~geog). The authors acknowledge the Monroe County Assessor's office for the provision of digital parcel boundary data from 1998. Acknowledgements to Laura Carlson for digitizing and attributing parcel boundary data for these townships for years 1928, 1957, 1967, 1971, 1980, 1990, and 1997. For more information contact Tom Evans, Department of Geography and Center for the Study of Institutions, Population and Environmental Change - evans@indiana.edu

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Last Updated: May 11, 2005
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