Abstract

Productivity of northern latitude forests is an important driver of the terrestrial carbon cycle and is already responding to climate change. Studies of the satellite-derived Normalized Difference Vegetation Index (NDVI) for northern latitudes indicate recent changes in plant productivity. These detected greening and browning trends are often attributed to a lengthening of the growing season from warming temperatures. Yet, disturbance-recovery dynamics are strong drivers of productivity and can mask direct effects of climate change. Here, we analyze 1-km resolution NDVI data from 1989 to 2014 for the northern latitude forests of the Greater Yellowstone Ecosystem for changes in plant productivity to address the following questions: (1) To what degree has greening taken place in the GYE over the past three decades? and (2) What is the relative importance of disturbance and climate in explaining NDVI trends? We found that the spatial extents of statistically significant productivity trends were limited to local greening and browning areas. Disturbance history, predominately fire disturbance, was a major driver of these detected NDVI trends. After accounting for fire-, insect-, and human-caused disturbances, increasing productivity trends remained. Productivity of northern latitude forests is generally considered temperature-limited; yet, we found that precipitation was a key driver of greening in the GYE.

Highlights

  • Increases in photosynthetic activity detected in northern latitudes are often attributed to a lengthening of the growing season from warming temperatures (Myneni and others 1997; Tucker and others 2001; Nemani and others 2003; Zhu and others 2013)

  • What is the relative importance of disturbance and climate in explaining Normalized Difference Vegetation Index (NDVI) trends? We found that the spatial extents of statistically significant productivity trends were limited to local greening and browning areas

  • The order of magnitude difference between the regional average NDVI trend (+ 0.0004 NDVI/yr) and the greening/browning localized trends (+ 0.0033 NDVI/yr, - 0.0035 NDVI/yr, respectively) highlights the importance of analyzing plant productivity at finer spatial resolutions that otherwise are aggregated in coarse scale analyses

Read more

Summary

Introduction

Increases in photosynthetic activity detected in northern latitudes are often attributed to a lengthening of the growing season from warming temperatures (Myneni and others 1997; Tucker and others 2001; Nemani and others 2003; Zhu and others 2013). To isolate the influence of human land use and disturbance, individual pixel NDVI trends were summarized for the GYE before and after filtering out pixels that had land cover layers that were not natural vegetation (using NLCD data), burned since 1984 (using MTBS data), areas affected by bark beetles (using ADS data), and logged stands (using NAFD data) using functions from the ‘‘raster’’ R package (Hijmans 2015).

Results
Conclusion
Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call