Co-Cultivation of Grapevines and Transgenic American Chestnuts: Improving Water Relations through Niche Facilitation

The purpose of this project is to investigate how co-cultivating grapevines and transgenic American chestnuts in an agroforestry setting can promote sustainable agricultural practices that enhance ecological resilience and economic viability in the Northeast region. Transgenic ‘Darling’ trees have been engineered with an oxalate oxidase (OxO) gene from wheat, thereby expressing an enzyme that confers a degree of tolerance to the fungal pathogen Cryphonectria parasitica (Newhouse et al., 2021). American chestnuts and grapes were selected as the focus organisms of this research, given the major ecological, social, and economic role chestnuts served prior to their decline from chestnut blight; the present-day high commodity value of grapes; and the fact that species of the genus Vitis are often lianas that naturally grow on trees (Keller, 2020). Moreover, there is an established agroforestry tradition of using hardwood trees as tutors for grapevines in Mediterranean and tropical climates (Altieri and Nicholls, 2002; Dupraz and Liagre 2019; Paris et al. 2019; Oliva Oller et al., 2022), though the viability of this system within a mesic environment, characteristic of our Central New York study site, has not been fully examined. The potential of mixed-species agroforestry to enhance growth and physiological performance of co-cultivated organisms and drive economic diversification in agricultural landscapes underscores the motivation for this research.

Co-cultivation of grapevines and American chestnuts may address several key issues in sustainable agriculture. First, growing grapevines on chestnut trees may yield savings on infrastructure. Chestnut trees require modest inputs, such that their maintenance may offset the costs of building and maintaining traditional grape trellis systems. Secondly, this project promotes the diversification of land use and income sources, potentially improving farm resilience to climate change driven market fluctuations. For instance, vignerons–i.e. farmers who cultivate a vineyard for winemaking–could receive supplementary income from the co-cultivated transgenic chestnut trees, which reliably mast if they can adequately tolerate chestnut blight. Further, this form of multilayer farming optimizes and increases the productivity of a plot, as the vertical scaffolding of the trees allows more crop to be grown on a given piece of land. Lastly, this agricultural framework can contribute to the restoration and conservation of the American chestnut, a species of substantial historical, ecological, and economic importance in the Northeast. 

I propose to utilize a pre-existing unique experimental platform to test the relative benefits of co-cultivation relative to traditional monoculture in field conditions. Species interactions in co-cultivated settings can result in benefits to one or both species via facilitation or reductions in performance via competition. The degree of facilitation versus competition is likely to be density-dependent. The SUNY ESF Grape and Chestnut Co-Cultivation study, established in 2020, allows for testing of these interactions through a traditional agroforestry vineyard schema in which three plots, each containing nine trees trellised with varying densities of grapes, border a square crop field. Transgenic American chestnuts are planted alongside grapevines at densities of one, three, and five vines per tree, with nearby, non-paired chestnuts and grapes serving as monoculture controls (Figure 1 in Media). The physiological assessment of the chestnut trees will include LI-COR LI-6800 system measurements of light saturated photosynthetic rates, stomatal conductance, and leaf water potential across each grape planting density. A complementary growth assessment within this experiment will measure grape harvest yield and tree basal diameter and height to determine how the measured physiological processes may be influencing biomass acquisition and allocation, and whether co-cultivated crops may be facilitating or impeding the productivity of the other compared to monoculture plantings. We will not measure chestnut harvest yield, as the four-year-old chestnuts are unlikely to reach reproductive maturity by the conclusion of this study.

This project aligns with Northeast SARE's outcome statement by contributing to the goal of promoting sustainable agriculture practices that enhance environmental stewardship, farm profitability, and rural community vitality. This research honors the holistic connections among land, water, air, and all living beings through its consideration of plant-soil feedbacks, interspecies water relations, chestnut's pronounced carbon sequestration potential, and the ample socio-economic benefits that pairing chestnut trees with grapes may have for farmers and rural community members. By demonstrating the potential of mixed-species agroforestry to address complex agricultural challenges while also fostering ecological resilience and economic viability, our research will support the overall objectives of sustainable agriculture initiatives in the Northeast region. Moreover, by providing evidence of the benefits and challenges associated with this framework, our research will inform land managers and other agricultural stakeholders, and serve as a proof of concept toward promoting the adoption of these sustainable agroforestry practices.