Linking Land Surface Phenology and Growth Limiting Factor Shifts over the Past 30 Years

Abstract:

The study of global vegetation dynamics contributes to a better understanding of global change drivers and how these affect ecosystems and ecological diversity. Land-surface phenology (LSP) is a key response and feedback of vegetation to the climate system, and hence a parameter that needs to be accurately represented in terrestrial biosphere models [1]. However, the effects of climatic changes on LSP depend on the relative importance of climatic constraints in specific regions – which are not well understood at global scale.

In this study, we analyzed a Phenology Reanalysis dataset [2] to evaluate shifts in three climatic drivers of phenology at global scale and over the last 30 years (1982-2012): incoming radiation, evaporative demand and minimum temperature. As a first step, we compared LAI as modeled from these three factors (LAI_re) to remotely sensed observations of LSP (LAI_3g, [3]) over the same time period. As a second step, we examined temporal trends in the climatic constraints at Start- and End- of the Growing Season.

There was good agreement between phenology metrics as derived form LAI_3g and LAI_re over the last 30 years – thus providing confidence in the climatic constraints underlying the modeled data. Our analysis reveals inter-annual variation in the relative importance of the three climatic factors in limiting vegetation growth at Start- and End- of the Growing Season over the last 30 years. High northern latitudes, as well as northern Europe and central Asia, appear to have undergone significant changes in dominance between the three controls. We also find that evaporative demand has become increasingly limiting for growth in many parts of the world, in particular in South America and eastern Asia.

 [1] Richardson, A.D. et al. Global Change Biology 18, 566-584 (2012).

[2] Stöckli, R. et al. J. Geophys. Res 116, G03020 (2011).

[3] Zhu, Z. et al. Remote Sensing 5, 927-948 (2013).