Climate Change Patterns of Wild Blueberry Fields in Downeast, Maine over the Past 40 Years

Rafa Tasnim,Yong-Jiang Zhang,Francis Drummond

doi:10.3390/w13050594

Abstract

Maine, USA is the largest producer of wild blueberries (Vaccinium angustifolium Aiton), an important native North American fruit crop. Blueberry fields are mainly distributed in coastal glacial outwash plains which might not experience the same climate change patterns as the whole region. It is important to analyze the climate change patterns of wild blueberry fields and determine how they affect crop health so fields can be managed more efficiently under climate change. Trends in the maximum (Tmax), minimum (Tmin) and average (Tavg) temperatures, total precipitation (Ptotal), and potential evapotranspiration (PET) were evaluated for 26 wild blueberry fields in Downeast Maine during the growing season (May–September) over the past 40 years. The effects of these climate variables on the Maximum Enhanced Vegetation Index (EVImax) were evaluated using Remote Sensing products and Geographic Information System (GIS) tools. We found differences in the increase in growing season Tmax, Tmin, Tavg, and Ptotal between those fields and the overall spatial average for the region (state of Maine), as well as among the blueberry fields. The maximum, minimum, and average temperatures of the studied 26 wild blueberry fields in Downeast, Maine showed higher rates of increase than those of the entire region during the last 40 years. Fields closer to the coast showed higher rates of warming compared with the fields more distant from the coast. Consequently, PET has been also increasing in wild blueberry fields, with those at higher elevations showing lower increasing rates. Optimum climatic conditions (threshold values) during the growing season were explored based on observed significant quadratic relationships between the climate variables (Tmax and Ptotal), PET, and EVImax for those fields. An optimum Tmax and PET for EVImax at 22.4 °C and 145 mm/month suggest potential negative effects of further warming and increasing PET on crop health and productivity. These climate change patterns and associated physiological relationships, as well as threshold values, could provide important information for the planning and development of optimal management techniques for wild blueberry fields experiencing climate change.

Highlights

Changing temperature and precipitation patterns due to global climate change are threatening crops all over the world [1,2,3]
The threshold air temperature for maximum photosynthesis of wheat (Triticum spp.) is 33 ◦ C [7,8] whereas a recent study on wild blueberry (Vaccinium angustifolium Aiton) physiology showed that photosynthesis declined from the maximum when air temperature increased above 25 ◦ C [9]
The maximum temperature during the growing season increased by 1.2 ± 0.05 ◦ C over the last 40 years in the wild blueberry fields compared to 0.9 ± 0.06 ◦ C in Maine (Figure 2a)

Summary

Introduction

Changing temperature and precipitation patterns due to global climate change are threatening crops all over the world [1,2,3]. Maine has three climate zones: Northern, Interior and Coastal, where long-term annual average temperatures from 1895 to 2018 are 3.4, 5.8 and 6.6 ◦ C, respectively [5,6]. Such temperature variation across Maine might not affect different plant and crop species located at different climate zones in similar ways. This is because plant species often have different optimal and threshold values for atmospheric temperature or precipitation, beyond which their physiological performance and growth deteriorate. The threshold air temperature for maximum photosynthesis of wheat (Triticum spp.) is 33 ◦ C [7,8] whereas a recent study on wild blueberry (Vaccinium angustifolium Aiton) physiology showed that photosynthesis declined from the maximum when air temperature increased above 25 ◦ C [9]

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