Long-Term Post-Disturbance Forest Recovery in the Greater Yellowstone Ecosystem Analyzed Using Landsat Time Series Stack

Feng Zhao,Chengquan Huang,Ran Meng,Maosheng Zhao,Zhiliang Zhu,Peng Gong,Le Yu

doi:10.3390/rs8110898

Abstract

Forest recovery from past disturbance is an integral process of ecosystem carbon cycles, and remote sensing provides an effective tool for tracking forest disturbance and recovery over large areas. Although the disturbance products (tracking the conversion from forest to non-forest type) derived using the Landsat Time Series Stack-Vegetation Change Tracker (LTSS-VCT) algorithm have been validated extensively for mapping forest disturbances across the United States, the ability of this approach to characterize long-term post-disturbance recovery (the conversion from non-forest to forest) has yet to be assessed. In this study, the LTSS-VCT approach was applied to examine long-term (up to 24 years) post-disturbance forest spectral recovery following stand-clearing disturbances (fire and harvests) in the Greater Yellowstone Ecosystem (GYE). Using high spatial resolution images from Google Earth, we validated the detectable forest recovery status mapped by VCT by year 2011. Validation results show that the VCT was able to map long-term post-disturbance forest recovery with overall accuracy of ~80% for different disturbance types and forest types in the GYE. Harvested areas in the GYE have higher percentages of forest recovery than burned areas by year 2011, and National Forests land generally has higher recovery rates compared with National Parks. The results also indicate that forest recovery is highly related with forest type, elevation and environmental variables such as soil type. Findings from this study can provide valuable insights for ecosystem modeling that aim to predict future carbon dynamics by integrating fine scale forest recovery conditions in GYE, in the face of climate change. With the availability of the VCT product nationwide, this approach can also be applied to examine long-term post-disturbance forest recovery in other study regions across the U.S.

Highlights

Forests in the Greater Yellowstone Ecosystem (GYE) experience frequent natural and anthropogenic disturbance events [1,2]
We examined the spatial patterns of post-disturbance forest recovery in the GYE by calculating the number of years until a disturbed pixel spectrally recovered to forest
The Vegetation Change Tracker (VCT) RNR maps had overall accuracies of ~80% for different disturbance and forest types. These accuracies were consistent among different disturbance types (Table 1) and forest types (Table 2), recovery detection over harvested areas was slightly more accurate than over burned areas

Summary

Introduction

Forests in the Greater Yellowstone Ecosystem (GYE) experience frequent natural (e.g., wildfires, insect and disease outbreaks, and snow and wind damage) and anthropogenic (e.g., land use changes and timber harvesting) disturbance events [1,2]. Recovery from past disturbance is an integral process of carbon cycles [3,4]. Inclusion of the forest recovery process following disturbance is Remote Sens. 2016, 8, 898 critical to calculating regional carbon fluxes and can better inform policy makers on both the importance and uncertainty of disturbances in the regulation of the regional and global carbon cycles [5]. Many ecosystem models assume post-disturbance forest recovery occurs immediately or homogenously across the landscape. This modeling hypothesis, has not been supported by ground observations [6]. There is an urgent need to efficiently examine forest recovery conditions at large scales

Methods

Results

Discussion

Conclusion