Evaluating the Impact of Grazing Cessation and Reintroduction in Mixed Prairie Using Raster Time Series Analysis of Landsat Data

Dandan Xu,Weixin Xu,Jeff K Harder,Xulin Guo

doi:10.3390/rs13173397

Abstract

Great efforts have been made to manage and restore native prairies to protect native species, enrich biodiversity, protect ecological resilience, and maintain ecosystem services. Much of this has been focused on preventing degradation from overgrazing and crop conversion. Understanding the consequences of management polices is important to identify best practices. Previous research has compared restoration outcomes from variable intensity grazing, prescribed fire, and grazing removal. However, few studies have explored the optimal durations of management practices and variation in restoration outcomes among vegetation communities. This study evaluates whether the impact of grazing cessation and reintroduction varies among native vegetation communities and measures the effective time periods of grazing cessation and reintroduction. Restoration outcomes were evaluated using four biophysical indicators (fresh biomass, soil organic matter, green cover, and litter cover) and two vegetation indices (normalized difference vegetation index (NDVI) and normalized difference water index (NDWI)) measured from Landsat images using seasonal Kalman filter and raster time series analysis. The results show that: (i) Grazing cessation increased soil organic matter and green cover while decreasing fresh biomass compared to moderate grazing management, while grazing reintroduction influences those indicators in an opposite direction; (ii) The effective time period for prairie conservation is about 11–14 years and varies among vegetation communities and biophysical indicators; (iii) The effective intensity of grazing cessation is highest in valley grassland, moderate in upland grassland, and mildest in sloped grassland; (iv) Grazing reintroduction returned the three native vegetation communities to the initial condition (i.e., the stage in 1985 before large grazers were removed), with less time than the time consumed for grazing cessation to restore the prairie ecosystem to the maximum changes; (v) Grazing reintroduction effectively influences upland and valley grasslands for 7 to 9 years, varying from different indicators, while it continuously affected sloped grassland with no clear time lag; (vi) The intensity of grazing reintroduction was strongest in sloped grassland, moderate in upland grassland, and mildest in valley grassland. The results of this study suggest expected time periods for prairie management methods to achieve results.

Highlights

Temporal Trends of the Difference in NIR, SWIR1, SWIR2, and land surface temperature (LST) between GNP and NIR reflectance of upland, sloped, and valley grasslands in GNP was higher than that of surrounding pastures in 1985, based on the temporal trend of the difference in NIR reflectance between GNP sites and the surrounding pastures (Figure 3a–c)
During the effective time periods, valley grassland had the strongest response to grazing cessation, while upland grassland and sloped grassland had a milder response to grazing cessation based on the temporal dynamics of the difference in NIR reflectance
Grazing cessation has been suggested as a superior prairie management policy to Grazing cessation has been suggested asorganic a superior prairie management long-term moderate grazing for enhancing soil matter and increasing greenpolicy cover. to

Summary

Introduction

Native prairies in the Great Plains of North America provide diverse habitats and quality forage for livestock and wildlife [1], and maintain a variety of ecological functions including carbon storage, water conservation, soil stability, low-input grazing, Remote Sens. The provision of these services in native prairies is highly impacted by climate change, in particular precipitation, a strong regulator of grassland productivity [4]. Grassland managers have tried numerous methods to preserve and restore native prairies for the purpose of enriching biodiversity, preserving native species, enhancing ecological connectivity and habitat heterogeneity, increasing ecological resilience, and maintaining ecosystem services [5,6,10,11,12]. Appropriate prairie management has been shown to mitigate greenhouse gas emissions [13], enhancing carbon sequestration [1], and modulating the impact of climate change [4]

Methods

Results

Conclusion