Detecting Climate Effects on Vegetation in Northern Mixed Prairie Using NOAA AVHRR 1-km Time-Series NDVI Data

Zhaoqin Li,Xulin Guo

doi:10.3390/rs4010120

Abstract

Grasslands hold varied grazing capacity, provide multiple habitats for diverse wildlife, and are a key component of carbon stock. Research has indicated that grasslands are experiencing effects related to recent climate trends. Understanding how grasslands respond to climate variation thus is essential. However, it is difficult to separate the effects of climate variation from grazing. This study aims to document vegetation condition under climate variation in Grasslands National Park (GNP) of Canada, a grassland ecosystem without grazing for over 20 years, using Normalized Difference Vegetation Index (NDVI) data to establish vegetation baselines. The main findings are (1) precipitation has more effects than temperature on vegetation; (2) the growing season of vegetation had an expanding trend indicated by earlier green-up and later senescence; (3) phenologically-tuned annual NDVI had an increasing trend from 1985 to 2007; and (4) the baselines of annual NDVI range from 0.13 to 0.32, and only the NDVI in 1999 is beyond the upper bound of the baseline. Our results indicate that vegetation phenology and condition have slightly changed in GNP since 1985, although vegetation condition in most years was still within the baselines.

Highlights

Grasslands are economically essential for achieving higher agricultural productivity as they hold the largest grazing capacity in the world [1]
It is essential to understand how vegetation in Canadian prairie responds to climate variation in order to come up with adaptations to deal with climatic variation
In this paper we examine the impacts of climatic variation on vegetation productivity in Grasslands National Park (GNP), quantified using Normalized Difference Vegetation Index (NDVI), and establish the NDVI baselines

Summary

Introduction

Grasslands are economically essential for achieving higher agricultural productivity as they hold the largest grazing capacity in the world [1]. Research has indicated climate impacts on grasslands (e.g., [4,5]), which affect agricultural productivity, wildlife habitats, and carbon stocks. Climate modeling projects that the precipitation pattern in Canadian prairie may be subject to change in the future [7]. Under such circumstances, the grazing capacity and carbon stock capacity of Canadian prairie may be subjected to change, and wildlife may have to undergo migration, adaptation, or even extinction. It is essential to understand how vegetation in Canadian prairie responds to climate variation in order to come up with adaptations to deal with climatic variation

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