Does Earlier and Increased Spring Plant Growth Lead to Reduced Summer Soil Moisture and Plant Growth on Landscapes Typical of Tundra-Taiga Interface?

Alemu Gonsamo,Jing M Chen,Michael T Ter-Mikaelian,Jiaxin Chen

doi:10.3390/rs11171989

Abstract

Over the past four decades, satellite observations have shown intensified global greening. At the same time, widespread browning and reversal of or stalled greening have been reported at high latitudes. One of the main reasons for this browning/lack of greening is thought to be warming-induced water stress, i.e., soil moisture depletion caused by earlier spring growth and increased summer evapotranspiration. To investigate these phenomena, we use MODIS collection 6, Global Inventory Modeling and Mapping Studies third-generation (GIMMS) normalized difference vegetation index (NDVI3g), and Global Land Evaporation Amsterdam Model (GLEAM) satellite-based root-zone soil moisture data. The study area was the Far North of Ontario (FNO), 453,788 km2 of heterogeneous landscape typical of the tundra-taiga interface, consisting of unmanaged boreal forests growing on mineral and peat soils, wetlands, and the most southerly area of tundra. The results indicate that the increased plant growth in spring leads to decreased summer growth. Lower summer soil moisture is related to increased spring plant growth in areas with lower soil moisture content. We also found that earlier start of growing season leads to decreased summer and peak season maximum plant growth. In conclusion, increased spring plant growth and earlier start of growing season deplete summer soil moisture and decrease the overall summer plant growth even in temperature-limited high latitude ecosystems. Our findings contribute to evolving understanding of changes in vegetation dynamics in relation to climate in northern high latitude terrestrial ecosystems.

Highlights

High latitude ecosystems are responding more rapidly [1,2] and consistently [3] to climate warming than other terrestrial ecosystems
We focused on the influence of spring plant growth on summer soil moisture content and plant growth in Far North of Ontario (FNO) ecosystems, comprising boreal forest, wetlands, and the most southerly area of tundra
We study the FNO, which has heterogeneous landscapes typical of the tundra-taiga interface consisting of unmanaged boreal forests in the south and southwest, the world’s third largest area of wetlands (281,439 km2), and the most southerly area of tundra (Figure 1)

Summary

Introduction

High latitude ecosystems are responding more rapidly [1,2] and consistently [3] to climate warming than other terrestrial ecosystems. We use satellite observations independently recorded by multiple sensors to study the relationships among spring and summer plant growth and soil moisture status on heterogeneous landscapes typical of the tundra-taiga interface. In order to assess the impact of average plant available soil water on the relationship between spring and summer vegetation activity, we separately analysed the statistical strength of the observed relationships per long-term average soil moisture classes.

Results

Conclusion