Date of Award

Spring 5-3-2024

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Plant, Soil, and Environmental Sciences

Advisor

Rachel E. Schattman

Second Committee Member

Bruce E. Hall

Third Committee Member

Sean Birkel

Additional Committee Members

Yongjiang Zhang

Abstract

Wild blueberries (Vaccinium angustifolium Ait. and V. myrtilloides Mitchx.) are now under increasing variations in climate conditions (Chen et al., 2022; Fernandez et al., 2020; Tasnim et al., 2021). High temperature and changes in rainfall patterns associated with climate change have direct effects on soil moisture regimes, and therefore wild blueberry crops. Over the last century, climate change in Maine (U.S.A) has been characterized by less frequent and more intense precipitation and warming temperatures. Extreme rainfall events are increasingly affecting the structure and functions of wild blueberries. Changes in precipitation patterns are influencing plant growth, physiology and edaphic conditions of wild blueberries. Rising temperatures increase the risks of drought by increasing the rate of evaporation which reduces the soil water content. However, the future influence of these changes on Maine wild blueberries remains unknown. In 2022 and 2023, two experiments were conducted. The first assessed the impacts of probable future precipitation conditions on wild blueberries, while the second established the irrigation strategies for climate change risk mitigation. The experiments were conducted in a greenhouse over a period of two years (from May 2022 to October 2023). Three precipitation scenario treatments were tested on six different “parent plants” (which are likely to be different genotypes) of wild blueberries using a factorial design (2x3). This study utilized historically dry and wet years to develop a plausible future precipitation scenario. Leaf and stem morphological and functional traits, along with edaphic conditions were used to assess the performance of wild blueberries. We found that, compared to a historically dry year, the plausible future scenario increases the leaf production. However, no significant differences were observed among other treatments in 2022. In 2023, the historically wet treatment was significantly higher than the historically dry treatment, highlighting the importance of both rainfall amount and distribution in the leaf production of wild blueberries. Furthermore, when compared to the treatment designed to simulate the future conditions, plants grown under the historically wet year treatment had significantly higher soil water content (%vwc) and soil electrical conductivity. The rainfall pattern in the historically wet treatment was more evenly distributed across the study periods compared to the historic dry and probable future conditions treatment. This suggests that the distribution of rainfall is more important than the total annual amounts. The purpose of the second experiment is to establish the optimal amount and frequency of irrigation for wild blueberries, and to explore the effects of dry periods between precipitation or irrigation events. As wild blueberries are a biennial crop, this assessment was made to include both harvest and non-harvest years. Three different irrigation amounts and frequencies were tested, including: (a) 1-inch (2.5cm) of water per week (high irrigation frequency, or HIF), (b) 2-inch (5cm) of water every second week (medium irrigation frequency, or MIF), and (c) 3-inch (7.5cm) of water every third week (low irrigation frequency, or LIF). The effects of each treatment on crop development and soil conditions were tested at the leaf development, flowering, green fruit, and fruit ripening stages. The results show that the HIF treatment significantly increased the stem length, leaf chlorophyll concentration, soil water content, and soil electrical conductivity compared to the MIF and HIF treatments. Reduced stem length, low photosynthetic rate and soil water content were observed in plants that received the LIF treatment compared to the HIF and MIF treatments. In conclusion, our results indicate that the LIF significantly reduces the number of flowers, while the MIF produces as much flowers as HIF.

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