Articles | Volume 13, issue 1
Research article
14 Jan 2016
Research article |  | 14 Jan 2016

Environmental controls on the increasing GPP of terrestrial vegetation across northern Eurasia

P. Dass, M. A. Rawlins, J. S. Kimball, and Y. Kim

Abstract. Terrestrial ecosystems of northern Eurasia are demonstrating an increasing gross primary productivity (GPP), yet few studies have provided definitive attribution for the changes. While prior studies point to increasing temperatures as the principle environmental control, influences from moisture and other factors are less clear. We assess how changes in temperature, precipitation, cloudiness, and forest fires individually contribute to changes in GPP derived from satellite data across northern Eurasia using a light-use- efficiency-based model, for the period 1982–2010. We find that annual satellite-derived GPP is most sensitive to the temperature, precipitation and cloudiness of summer, which is the peak of the growing season and also the period of the year when the GPP trend is maximum. Considering the regional median, the summer temperature explains as much as 37.7 % of the variation in annual GPP, while precipitation and cloudiness explain 20.7 and 19.3 %. Warming over the period analysed, even without a sustained increase in precipitation, led to a significant positive impact on GPP for 61.7 % of the region. However, a significant negative impact on GPP was also found, for 2.4 % of the region, primarily the dryer grasslands in the south-west of the study area. For this region, precipitation positively correlates with GPP, as does cloudiness. This shows that the south-western part of northern Eurasia is relatively more vulnerable to drought than other areas. While our results further advance the notion that air temperature is the dominant environmental control for recent GPP increases across northern Eurasia, the role of precipitation and cloudiness can not be ignored.

Short summary
Productivity of the vegetation of northern Eurasia has been found to be increasing over the last few decades. Using statistical tools we investigate major factors driving the increase in photosynthetic activity. Most of this change is explained by rising temperatures, which drive an increase in productivity. However, the contribution of changing patterns of rainfall and cloudiness is also significant, especially in the southern parts of the region which exhibit higher drought vulnerability.
Final-revised paper