Effects of reduced rainfall on coffee quality and volatile composition

BACKGROUND

For a significant subset of agricultural products, including coffee, wine and tea, sensory perceptions of terroir (i.e., characteristic flavors imparted by the growing environment) are tightly linked to the product's value. With increasing climate change, it is critical to understand how shifts in climate, such as changes in precipitation, may interact with management practices (e.g., cultivar selection) to impact sensory quality in terroir-driven crops, and what biochemical compounds may be associated with those impacts. Here, sensory quality and volatile profile composition were assessed for four Arabica coffee (Coffea arabica) cultivars grown in a field experiment where precipitation was reduced by rainout shelters, resulting in 14% lower soil moisture on average.

RESULTS

Our results indicate an overall increase in yield coincident with a moderate decrease in sensory quality in response to reduced precipitation. The presence and magnitude of the sensory quality shift varied by cultivar and sensory attribute, though the Acidity attribute was consistently negatively impacted across cultivars, albeit with a high degree of uncertainty. Additionally, 31 volatile compounds were identified across green coffee samples that were variably impacted by reduced precipitation. Hierarchical clustering analysis identified patterns in volatile clustering associated with sensory attributes suggesting that reduced precipitation effects on sensory attributes may depend on nonlinear combinations of secondary metabolites.

CONCLUSION

Ultimately, our results advance efforts to improve predictions of climate impacts on coffee-growing landscapes and communities and highlight the value of considering indicators of harvest value beyond yield to improve economic forecasts for agroecosystems under climate change.

Plant-microbial responses to reduced precipitation depend on tree species in a temperate forest

Given that global change is predicted to increase the frequency and severity of drought in temperate forests, it is critical to understand the degree to which plant belowground responses cascade through the soil system to drive ecosystem responses to water stress. While most research has focused on plant and microbial responses independently of each other, a gap in our understanding lies in the integrated response of plant-microbial interactions to water stress. We investigated the extent to which divergent belowground responses to reduced precipitation between sugar maple trees (Acer saccharum) versus oak trees (Oak spp.) may influence microbial activity via throughfall exclusion in the field. Evidence that oak trees send carbon belowground to prime microbial activity more than maples under ambient conditions and in response to water stress suggests there is the potential for corresponding impacts of reduced precipitation on microbial activity. As such, we tested the hypothesis that differences in belowground C allocation between oaks and maples would stimulate microbial activity in the oak treatment soils and reduce microbial activity in in the sugar maple treatment soils compared to their respective controls. We found that the treatment led to declines in N mineralization, soil respiration, and oxidative enzyme activity in the sugar maple treatment plot. These declines may be due to sugar maple trees reducing root C transfers to the soil. By contrast, the reduced precipitation treatment enhanced soil respiration, as well as rates of N mineralization and peroxidase activity in the oak rhizosphere. This enhanced activity suggests that oak roots provided optimal rhizosphere conditions during water stress to prime microbial activity to support net primary production. With future changes in precipitation predicted for forests in the Eastern US, we show that the strength of plant-microbial interactions drives the degree to which reduced precipitation impacts soil C and nutrient cycling.

[Nutrient and metabolic responses of the leaves of Cunninghamia lanceolata seedlings to warming and reduced precipitation in different season]

We examined the effects of warming (+5 ℃) and reduced natural precipitation (-50%) on nutrient status and physiological indices of Cunninghamia lanceolata seedlings during winter and summer in subtropical China. The results showed that seasonal changes in temperature and precipitation caused the seasonal differences in plant nutrient contents and metabolites levels. Contents of carbon, nitrogen, phosphorus, and potassium in leaves in winter were significantly higher than those in summer. In summer, reduced precipitation and warming had no significant effects on antioxidant enzyme activities in C. lanceolata leaves. In winter, superoxide dismutase and peroxidase activities in the leaves significantly decreased with reduced precipitation by 20.7% and 17.8%. Additionally, in winter, warming treatment significantly increased non-enzymatic ascorbic acid content by 132.5%. Carbon content decreased, whereas proline accumulation and nitrogen content increased under stress induced by combined warming and reduced precipitation in winter. However, carbon content increased by 3.3% under the treatment of simultaneous warming and reduced precipitation in summer. In addition, combined warming and reduced precipitation had no significant effects on the antioxidant system irrespective of the season. In conclusion, the adaptation mechanism of C. lanceolata to warming in summer might be different from that in winter. The changes in nutrient contents in C. lanceolata leaves were more sensitive to stress induced by combined warming and reduced precipitation. Nutrient demand and supply and seasonal changes in plant responses under climate change scenarios should be considered for better managing forest plantations and improving plant productivity.