Browsing by Author "Stepp, John Richard"

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Beyond Yields: Climate Effects on Specialty Crop Quality and Agroecological Management
(2016-03) Ahmed, Selena; Stepp, John Richard
Climate change is impacting the sustainability of food systems through shifts in natural and human dimensions of agroecosystems that influence farmer livelihoods, consumer choices, and food security. This paper highlights the need for climate studies on specialty crops to focus not only on yields, but also on quality, as well as the ability of agroecological management to buffer climate effects on quality parameters. Crop quality refers to phytonutrient and secondary metabolite profiles and associated health and sensory properties that influence consumer buying decisions. Through two literature reviews, we provide examples of specialty crops that are vulnerable to climate effects on quality and examples of climate-resilient agroecological strategies. A range of specialty crops including fruits, vegetables, tree nuts, stimulants, and herbs were identified to respond to climate variables with changes in quality. The review on climate-resilient strategies to mitigate effects on crop quality highlighted a major gap in the literature. However, agricultural diversification emerged as a promising strategy for climate resilience more broadly and highlights the need for future research to assess the potential of diversified agroecosystems to buffer climate effects on crop quality. We integrate the concepts from our literature review within a socio-ecological systems framework that takes into account feedbacks between crop quality, consumer responses, and agroecosystem management. The presented framework is especially useful for two themes in agricultural development and marketing, nutrition-sensitive agriculture and terroir, for informing the design of climate-change resilient specialty crop systems focused on management of quality and other ecosystem services towards promoting environmental and human wellbeing.
Effects of Extreme Climate Events on Tea (Camellia sinensis) Functional Quality Validate Indigenous Farmer Knowledge and Sensory Preferences in Tropical China
(2014-10) Ahmed, Selena; Stepp, John Richard; Orians, Colin M.; Griffin, Timothy S.; Matyas, Corene; Robbat, Albert Jr.; Cash, Sean; Xue, Dayuan; Long, Chunlin; Unachukwu, Uchenna J.; Buckley, Sarabeth; Small, David; Kennelly, Edward
Climate change is impacting agro-ecosystems, crops, and farmer livelihoods in communities worldwide. While it is well understood that more frequent and intense climate events in many areas are resulting in a decline in crop yields, the impact on crop quality is less acknowledged, yet it is critical for food systems that benefit both farmers and consumers through high-quality products. This study examines tea (Camellia sinensis; Theaceae), the world's most widely consumed beverage after water, as a study system to measure effects of seasonal precipitation variability on crop functional quality and associated farmer knowledge, preferences, and livelihoods. Sampling was conducted in a major tea producing area of China during an extreme drought through the onset of the East Asian Monsoon in order to capture effects of extreme climate events that are likely to become more frequent with climate change. Compared to the spring drought, tea growth during the monsoon period was up to 50% higher. Concurrently, concentrations of catechin and methylxanthine secondary metabolites, major compounds that determine tea functional quality, were up to 50% lower during the monsoon while total phenolic concentrations and antioxidant activity increased. The inverse relationship between tea growth and concentrations of individual secondary metabolites suggests a dilution effect of precipitation on tea quality. The decrease in concentrations of tea secondary metabolites was accompanied by reduced farmer preference on the basis of sensory characteristics as well as a decline of up to 50% in household income from tea sales. Farmer surveys indicate a high degree of agreement regarding climate patterns and the effects of precipitation on tea yields and quality. Extrapolating findings from this seasonal study to long-term climate scenario projections suggests that farmers and consumers face variable implications with forecasted precipitation scenarios and calls for research on management practices to facilitate climate adaptation for sustainable crop production.
Effects of water availability and pest pressures on tea (Camellia sinensis) growth and functional quality
(2014-01) Ahmed, Selena; Orians, Colin M.; Griffin, Timothy S.; Buckley, Sarabeth; Unachukwu, Uchenna J.; Stratton, Anne E.; Stepp, John Richard; Robbat, Albert Jr.; Cash, Sean; Kennelly, Edward J.
Extreme shifts in water availability linked to global climate change are impacting crops worldwide. The present study examines the direct and interactive effects of water availability and pest pressures on tea (Camellia sinensis; Theaceae) growth and functional quality. Manipulative greenhouse experiments were used to measure the effects of variable water availability and pest pressures simulated by jasmonic acid (JA) on tea leaf growth and secondary metabolites that determine tea quality. Water treatments were simulated to replicate ideal tea growing conditions and extreme precipitation events in tropical southwestern China, a major centre of tea production. Results show that higher water availability and JA significantly increased the growth of new leaves while their interactive effect was not significant. The effect of water availability and JA on tea quality varied with individual secondary metabolites. Higher water availability significantly increased total methylxanthine concentrations of tea leaves but there was no significant effect of JA treatments or the interaction of water and JA. Water availability, JA treatments or their interactive effects had no effect on the concentrations of epigallocatechin 3-gallate. In contrast, increased water availability resulted in significantly lower concentrations of epicatechin 3-gallate but the effect of JA and the interactive effects of water and JA were not significant. Lastly, higher water availability resulted in significantly higher total phenolic concentrations but there was no significant impact of JA and their interaction. These findings point to the fascinating dynamics of climate change effects on tea plants with offsetting interactions between precipitation and pest pressures within agro-ecosystems, and the need for future climate studies to examine interactive biotic and abiotic effects.
Plant-Climate Interaction Effects: Changes in the Relative Distribution and Concentration of the Volatile Tea Leaf Metabolome in 2014–2016
(2019-11) Kfoury, Nicole; Scott, Eric R.; Orians, Colin M.; Ahmed, Selena; Cash, Sean B.; Griffin, Timothy; Matyas, Corene; Stepp, John Richard; Han, Wenyan Han; Xue, Dayuan; Long, Chunlin; Robbat Jr., Albert
Climatic conditions affect the chemical composition of edible crops, which can impact flavor, nutrition and overall consumer preferences. To understand these effects, we sampled tea (Camellia sinensis (L.) Kuntze) grown in different environmental conditions. Using a target/nontarget data analysis approach, we detected 564 metabolites from tea grown at two elevations in spring and summer over 3 years in two major tea-producing areas of China. Principal component analysis and partial least squares-discriminant analysis show seasonal, elevational, and yearly differences in tea from Yunnan and Fujian provinces. Independent of location, higher concentrations of compounds with aromas characteristic of farmers’ perceptions of high-quality tea were found in spring and high elevation teas. Yunnan teas were distinct from Fujian teas, but the effects of elevation and season were different for the two locations. Elevation was the largest source of metabolite variation in Yunnan yet had no effect in Fujian. In contrast seasonal differences were strong in both locations. Importantly, the year-to-year variation in chemistry at both locations emphasizes the importance of doing multi-year studies, and further highlights the challenge farmers face when trying to produce teas with specific flavor/health (metabolite) profiles.