Raster Visualization in R: Vegetation productivity in the Yuba River Watershed

Below is a brief example of raster visualization in R. It is a more thorough explanation of an example of rasterVIS that I used in a recent lecture I gave in the Department of Geography and Environment at San Francisco State University. The goal is to gain a brief understanding on vegetation productivity dynamics in the Yuba River Watershed (where the SFSU Sierra Nevada Field Campus is located) and quickly display the data using Oscar Perpiñán’s excellent R package rasterVis.

I used eMODIS (EROS Moderate Resolution Imaging Spectroradiometer) data to characterize the NDVI derived productivity of the Yuba River Basin during the month of August. eMODIS is a standardized product which uses MODIS surface reflectance from a 7-day composite period (Brown et al. 2015). I used all eMODIS images from August during the period 2000 through 2016 to calculate the 17-year August mean. I then calculated August productivity anomalies for a dry year (2014) and an average year (2006) to identify the spatial and temporal variability in productivity within the watershed (based on regional data; Malone et al. 2016).

To execute the example below, please download the data here. I have not included the base data or code to calculate the global mean and anomalies.

Load the required packages in R (note: the Rcolorbrewer library is loaded with the rasterVis library).

Load the required data:

Plot the mean productivity for August (2000-2016):

Note: the NDVI values are scaled by a value of 10000. The gray graphics along the top and left axes represent the mean of the row (right) and column (top) values.

Plot the 2014 and 2006 August productivity anomalies:

Compare dry-year anomalies (top) with average-year anomalies (bottom). The anomalies are analogous to Z-scores and were calculated as the deviation from mean, normalized by the standard deviation.

Literature Cited

Brown, J. F., D. Howard, B. Wylie, A. Frieze, L. Ji, and C. Gacke. 2015. Application-ready expedited MODIS data for operational land surface monitoring of vegetation condition. Remote Sensing 7:16226–16240.

Malone, S. L., M. G. Tulbure, A. J. Pérez-luque, T. J. Assal, L. L. Bremer, D. P. Drucker, V. Hillis, S. Varela, and M. L. Goulden. 2016. Drought resistance across California ecosystems : evaluating changes in carbon dynamics using satellite imagery. Ecosphere 7:1–19.

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