Productivity of coffee plantations is threatened by both climate change and decreasing revenues of coffee growers. Using shade trees might protect against temperature variability, erosion and excessive radiation but there may be trade-offs in productivity and quality. While impacts of shade trees on arabica (Coffea arabica) have been reviewed, a global synthesis on robusta (Coffea canephora) coffee is lacking. We assessed how shade affects robusta growth and productivity, and what are the interactions and trade-offs. We conducted a systematic literature search in Web of Science and CAB Abstracts on 16 December 2019. Thirty papers fulfilled our inclusion criteria of being experimental studies on the impact of overstory trees with approximately half being from Brazil or India. Shade improved robusta tree growth and yield with some contrasting effects on physicochemical and biochemical properties. Shade (> 30%) was associated with reduced beverage quality. Significant interactions between shade and location, rainfall level and robusta clone were found. Among the clones tested, 06V, C153, LB1, GG229 and JM2 showed a higher productivity and growth (from + 17 to + 280%) under moderate shade (41–65%). This is the first meta-analysis of the effects of shade on robusta coffee. By synthesizing data from different studies, we highlight for the first time that the effect of shade on robusta coffee depends on tree age. Shade had positive impacts on older robusta trees (mean of 16 years), while the impact of shade on younger trees was either insignificant or negative. We highlight the importance of both clone type and tree ages. Research gaps included a lack of knowledge on the effects of shade with respect to coffee and shade tree age as well as interactive effects. More in-depth studies are needed to understand the mechanisms of how shade trees affect robusta coffee.

气候变化和咖啡种植者收入的下降都威胁着咖啡种植园的生产力。使用遮荫树可能会防止温度变化，侵蚀和过度辐射，但在生产率和质量上可能会有所取舍。虽然已经审查了遮荫树对阿拉伯咖啡（Coffea arabica）的影响，但有关罗布斯塔（Coffea canephora）的全球综合）咖啡不足。我们评估了阴影如何影响罗布斯塔的生长和生产力，以及相互作用和权衡因素是什么。我们于2019年12月16日在Web of Science和CAB Abstracts中进行了系统的文献检索。有30篇论文符合我们的纳入标准，是关于过高树木影响的实验研究，其中约一半来自巴西或印度。遮荫改善了罗布斯塔树的生长和产量，对理化和生化特性产生了一些相反的影响。阴影（> 30％）与饮料质量下降有关。发现阴影和位置，降雨水平和罗布斯塔克隆之间存在重要的相互作用。在测试的克隆中，在中等阴影（41–65％）下，06V，C153，LB1，GG229和JM2显示出更高的生产率和生长（从+ 17到+ 280％）。这是首次对阴影对罗布斯塔咖啡的影响进行荟萃分析。通过综合来自不同研究的数据，我们首次强调了阴影对罗布斯塔咖啡的影响取决于树龄。阴影对年长的罗布斯塔树（平均16年）产生积极影响，而阴影对年幼的树树的影响则微不足道或消极。我们强调克隆类型和树龄的重要性。研究空白包括对与咖啡和树荫年龄有关的阴影影响以及交互作用的知识缺乏。需要进行更深入的研究，以了解遮荫树如何影响罗布斯塔咖啡。阴影对年长的罗布斯塔树（平均16年）产生积极影响，而阴影对年幼的树树的影响则微不足道或消极。我们强调克隆类型和树龄的重要性。研究空白包括对与咖啡和树荫年龄有关的阴影影响以及交互作用的知识缺乏。需要进行更深入的研究，以了解遮荫树如何影响罗布斯塔咖啡。遮荫对老龄罗布斯塔树（平均16年）产生积极影响，而遮荫对幼树的影响则微不足道或消极。我们强调克隆类型和树龄的重要性。研究空白包括对与咖啡和树荫年龄有关的阴影影响以及交互作用的知识缺乏。需要进行更深入的研究，以了解遮荫树如何影响罗布斯塔咖啡。