RCMAP - Time-Series - Cover

The RCMAP product suite includes eight fractional components: annual herbaceous, bare ground, herbaceous, litter, non-sagebrush shrub, perennial herbaceous, sagebrush, and shrub, rule-based error maps, and the temporal trends of each component. Data characterize the percentage of each 30-meter pixel in the Western United States covered by each component for each year from 1985-2020 - providing change information for 35 years (imagery for 2012 was unavailable). Because of file size limitations, individual component cover and error data are packaged in three time intervals including 1985-1995, 1996-2006, and 2007-2020. Perennial herb and non-sagebrush shrub are derivatives of herbaceous and annual herbaceous cover, and shrub and sagebrush cover, respectively, and do not have associated rule-based error maps.

We assess the temporal patterns in each RCMAP component with two approaches, 1) linear trends and 2) a breaks and stable states method with a temporal moving window based on structural change at the pixel level. Linear trend products include slope and p-value calculated from least squares linear regression. The slope represents the average percent cover change per year over the times-series and the p-value reflects the confidence of change in each pixel. The structural change method partitions the time-series into segments of similar slope values, with statistically significant break-points indicating perturbations to the prior trajectory. The break point trends analysis suite relies on structural break methods, resulting in the identification of the number and timing of breaks in the time-series, and the significance of each segment. We produce the following statistics: 1) for each component, each year, the presence/absence of breaks, 2) the slope, p-value, and standard error of the segment occurring in each year, 3) the overall model R2 (quality of model fit to the temporal profile), and 4) an index, Total Change Intensity. This index reflects the total amount of change occurring across components in that pixel.

 

Preferred citation: Rigge, M.B., Bunde, B., Shi, H., Postma, K., 2021, Rangeland Condition Monitoring Assessment and Projection (RCMAP) Fractional Component Time-Series Across the Western U.S. 1985-2020 (ver. 2.0, October 2021): U.S. Geological Survey data release, https://doi.org/10.5066/P95IQ4BT.

 

Related Publication

Rigge, M., Homer, C., Shi, H., Meyer, D., Bunde, B., Granneman, B., Postma, K., Danielson, P., Case, A., and Xian, G. 2021. Trends in rangelands fractional components across the western U.S. from 1985-2018. Remote Sensing, 13: 813.

Shi, H., M. Rigge, B. Bunde, D. Meyer, and K. Postma. In Preparation. Trends Analysis of 1985-2020 Rangeland Condition Monitoring Assessment and Projection (RCMAP) Fractional Component Time-Series.

Rigge, M., H. Shi, C. Homer, P. Danielson, and B. Granneman. 2019. Long-term trajectories of fractional component change in the Northern Great Basin, USA. Ecosphere: e02762

Shi, H., C. Homer, M. Rigge, K. Postma, and G. Xian. 2020. Analyzing change in a shrubland ecosystem with both long-term field observations and Landsat time-series in Wyoming, USA. Ecosphere: e03311.

Rigge, M., C. Homer, H. Shi, and D. Meyer. 2019. Validating a Landsat time-series of fractional component cover across western U.S. rangelands. Remote Sensing 11, 3009.

Rigge, M., Homer, C., Shi, H., Meyer, D., Bunde, B., Granneman, B., Postma, K., Danielson, P., Case, A., and Xian, G. 2021. Trends in rangelands fractional components across the western U.S. from 1985-2018. Remote Sensing, 13: 813.

Shi, H., M. Rigge, B. Bunde, D. Meyer, and K. Postma. In Preparation. Trends Analysis of 1985-2020 Rangeland Condition Monitoring Assessment and Projection (RCMAP) Fractional Component Time-Series.