Replication Data for: Opportunities for sustainable intensification of coffee agro-ecosystems along an altitudinal gradient on Mt. Elgon, Uganda

During the months of April and May 2014, vegetation structure was measured on the 150 selected plots. The altitude and plot boundary coordinates were recorded using Garmin eTrex GPS. Plot size was calculated based on plot boundary coordinates in R Statistics (R Core Team, 2014) using the sp package (Pebesma and Bivand 2005). The number of coffee trees, banana mats and stems, and shade trees were counted on the entire plot and densities (in number per ha) were calculated. Shade tree species were identified and the number of species per plot recorded. The canopy closure as an indicator for average plot- level shade was estimated using a Forestry Suppliers spherical crown densiometer (convex model A) according to Lemmon (1957) at four positions within the plot. Coffee yields were obtained through farmer recall per plot of the various harvests of the year and provided as coffee cherries or parchment, which was then converted into green been. The cumulative annual production was divided by the plot size and number of coffee trees to obtain green bean yield per hectare and green bean yield per coffee tree, respectively. The recall data was obtained using triangulation questions by an experienced local team, which proved to be successful in previous studies (Van Asten et al., 2011a; Wang et al., 2015). This allows a wide coverage of yield data. Data on age of the coffee trees, coffee management, and livelihood characteristics were obtained through structured farmer interviews during farm visits.2014年4至5月，研究人员对选定的150个样地开展植被结构测定工作。采用佳明eTrex全球定位系统（Garmin eTrex GPS）记录样地海拔与边界坐标。基于样地边界坐标，借助R统计软件（R Core Team, 2014）中的sp包（sp package, Pebesma & Bivand, 2005）计算样地面积。在全样地范围内统计咖啡树、香蕉丛（banana mats）与茎秆以及遮荫树的数量，并计算单位公顷密度（单位：株/ha）。完成遮荫树物种鉴定，并记录每个样地的物种数。参照Lemmon（1957）的方法，使用林业供应商公司生产的凸面A型球形冠层密度仪（Forestry Suppliers spherical crown densiometer, convex model A），在样地内4个测点估算林冠郁闭度，以此作为样地水平平均遮荫程度的表征指标。咖啡产量数据通过农户回忆获取各样地当年度多批次收获量，原始数据以咖啡鲜果或带壳咖啡豆形式提供，随后统一转换为绿咖啡豆。将年度累计总产量分别除以样地面积与咖啡树总数量，最终得到单位公顷绿咖啡豆产量与单株咖啡树绿咖啡豆产量。本次回忆数据由经验丰富的本地团队采用三角验证法提问收集，该方法在既往研究（Van Asten et al., 2011a; Wang et al., 2015）中已被证实可行，可实现产量数据的大范围覆盖。通过田间走访开展的结构化农户访谈，获取了咖啡树树龄、咖啡种植管理措施以及农户生计特征相关数据。