Replication data for: Implications of shifts in coffee production on tree species richness, composition and structure on small farms around Mount Kenya

Small coffee farms around Mount Kenya in Kenya contain many planted and remnant tree species but little is known in the region about the relationship between trees on farms and the methods and dynamics of coffee production. Shifts in production may alter tree diversity and potentially impact on future biodiversity conservation efforts by affecting niches available for indigenous trees on farms. Here, knowledge was gathered on how changes in coffee production on 180 small farms around Mount Kenya may affect tree diversity, categorizing farms according to coffee yield levels over a period of five years as increasing, decreasing or stable production. Tree species richness, abundance and composition were analyzed using species accumulation curves, Rènyi diversity profiles, rank abundance and ecological distance ordinations, and the effects of coffee production examined using quasi-Poisson generalized linear regressions. Species richness were positively correlated with tr ee basal area but negatively related to coffee, banana and maize yields value. A difference in average tree species richness, abundance and basal area on increasing farms was observed compared to the decreasing and stable farms, even though formal tests on richness and densities differences were inconclusive. These dynamics do not significantly influence vegetation structure but seem to have a bearing on species composition on farms of different coffee production. The overall low abundance (23 % of trees) but high richness (78 % of species) of indigenous trees on coffee farms could change markedly if the dynamics observed in the current study persist, indicating the need for the development of intensified multi-species cropping systems.肯尼亚山周边的小型咖啡农场内，人工栽植与原生留存的树种种类繁多，但该区域内关于农场树木与咖啡生产方式、生产动态之间的关联仍有待阐明。生产模式的转变可能会改变树木多样性，并通过影响农场乡土树木可利用的生态位，进而对未来的生物多样性保护工作产生潜在影响。本研究针对肯尼亚山周边180家小型咖啡农场，采集了咖啡生产变化对树木多样性影响的相关数据，并以五年期内的咖啡产量水平为依据，将农场划分为产量递增、递减与稳定三类。研究采用物种累积曲线、雷尼（Rènyi）多样性剖面、秩多度分析及生态距离排序法，对树木物种丰富度、多度与群落组成进行了分析；同时借助准泊松广义线性回归模型，检验了咖啡生产的相关影响效应。结果显示，树木物种丰富度与树木基面积呈正相关，却与咖啡、香蕉及玉米的产值呈负相关。尽管针对物种丰富度与密度差异的正式检验结果尚未明确，但相较于产量递减与稳定的农场，产量递增的农场在平均树木物种丰富度、多度及基面积方面均存在差异。这些动态变化未对植被结构产生显著影响，但似乎会对不同咖啡生产模式的农场的物种组成产生影响。咖啡农场中乡土树木的总体多度较低（仅占树木总量的23%）但物种丰富度较高（占物种总数的78%），若本研究观测到的动态趋势持续存在，这一格局或将发生显著改变，这表明亟需发展集约化多物种种植系统。