Table_8_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范围内的粮食与饮料作物，进而对环境及人类福祉造成连带影响。尽管已有大量研究探讨了气候变化对作物产量的影响，但针对气候变化对作物品质（即养分、矿物质及次生代谢物（secondary metabolites）浓度）的相关研究仍相对匮乏。本系统综述（systematic review）以具有文化代表性的饮料作物——茶树（Camelia sinensis）为研究对象，聚焦气候变化相关环境因素对作物品质变化方向的影响。本系统综述共筛选出86篇符合综述研究主题的文献。研究结果表明，与气候变化相关的物候期变化、水分胁迫（water stress）、地理区位、光照条件、海拔、植食性生物与微生物、温度及土壤因子等因素，均可使次生代谢物浓度出现最高达50%的升降幅度。目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。尽管本系统综述证实多项环境参数会对茶叶品质产生影响，但这些影响的方向与强度尚未明确；不同研究间结论存在矛盾，这可能源于混杂变量的影响，包括茶树品种、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。本综述中证据最为一致的环境因素为物候期与水分胁迫：在18项相关研究中，有14项（78%）表明，当采摘季节从春季/首次采茶转为其他季节时，酚类化合物（phenolic compounds）浓度或其生物活性会出现下降；而在10项相关研究中，有7项（70%）显示干旱胁迫会提升酚类化合物水平或其生物活性。植食性作用与土壤肥力是对茶叶品质影响结论矛盾最为突出的两个变量。而这两个变量均为农户可进行有效调控的对象，这凸显了农业管理在气候减缓与适应中的重要性。未来亟需制定基于证据的管理策略，并培育具有气候韧性的作物品种，以减轻气候变化对作物品质的负面影响，以及降低农业与食品系统的整体风险。