Table_4_Environmental Factors Variably Impact Tea Secondary Metabolites in the Context of Climate Change.docx

Climate change is impacting food and beverage crops around the world with implications for environmental and human well-being. While numerous studies have examined climate change effects on crop yields, relatively few studies have examined effects on crop quality (concentrations of nutrients, minerals, and secondary metabolites). This review article employs a culturally relevant beverage crop, tea (Camelia sinensis), as a lens to examine environmental effects linked to climate change on the directionality of crop quality. Our systematic review identified 86 articles as relevant to the review question. Findings provide evidence that shifts in seasonality, water stress, geography, light factors, altitude, herbivory and microbes, temperature, and soil factors that are linked to climate change can result in both increases and decreases up to 50% in secondary metabolites. A gap was found regarding evidence on the direct effects of carbon dioxide on tea quality, highlighting a critical research area for future study. While this systematic review provides evidence that multiple environmental parameters are impacting tea quality, the directionality and magnitude of these impacts is not clear with contradictory evidence between studies likely due to confounding factors including variation in tea variety, cultivar, specific environmental and agricultural management conditions, and differences in research methods. The environmental factors with the most consistent evidence in this systematic review were seasonality and water stress with 14 out of 18 studies (78%) demonstrating a decrease in concentrations of phenolic compounds or their bioactivity with a seasonal shift from the spring and /or first tea harvest to other seasons and seven out of 10 studies (70%) showing an increase in levels of phenolic compounds or their bioactivity with drought stress. Herbivory and soil fertility were two of the variables that showed the greatest contradictory evidence on tea quality. Both herbivory and soil fertility are variables which farmers have the greatest control over, pointing to the importance of agricultural management for climate mitigation and adaptation. The development of evidence-based management strategies and crop breeding programs for resilient cultivars are called for to mitigate climate impacts on crop quality and overall risk in agricultural and food systems.

气候变化正影响全球食用与饮料作物，进而对环境及人类福祉产生连锁效应。尽管已有大量研究探讨了气候变化对作物产量的影响，但针对气候变化如何作用于作物品质——即营养物质、矿物质及次生代谢物的浓度——的相关研究仍相对匮乏。本综述以具有文化代表性的饮料作物茶树（Camelia sinensis）为研究载体，探讨气候变化关联的环境因素对作物品质变化方向的影响。本次系统综述共筛选出86篇与本综述研究主题相关的文献。研究结果表明，与气候变化相关的物候期变化、水分胁迫、地理区位、光照条件、海拔、植食性生物与微生物、温度及土壤因子的改变，均可使次生代谢物浓度出现最高达50%的升降幅度。当前仍缺乏二氧化碳对茶叶品质直接影响的相关研究证据，这指明了未来值得重点探索的研究方向。尽管本次系统综述证实多项环境参数均会对茶叶品质产生影响，但这些影响的方向与强度尚无定论；不同研究间的结论存在矛盾，这可能源于混杂变量的干扰，例如茶树品种、栽培品系、特定环境与农业管理条件的差异，以及研究方法的不同。本次综述中证据最为一致的环境因素为物候期与水分胁迫：18项相关研究中有14项（占比78%）表明，当采摘季从春季或首次采茶季转向其他季节时，酚类物质浓度或其生物活性会出现下降；而10项研究中有7项（占比70%）显示，干旱胁迫会提升酚类物质的含量或其生物活性。植食性影响与土壤肥力是两类对茶叶品质的研究结论矛盾最为突出的变量。而这两类变量均为农户可施加较强管控的因素，这凸显了农业管理在气候变化减缓与适应中的重要意义。亟需制定基于证据的管理策略与抗逆品种培育计划，以减轻气候变化对作物品质的影响，并降低农业与食品系统的整体风险。