Tree phenology and abiotic variables 1998-2017 at Ngogo, Kibale National Park, Uganda

Fruit production in tropical forests varies considerably in space and time, with important implications for frugivorous consumers. Characterizing temporal variation in forest productivity is thus critical for understanding adaptations of tropical forest frugivores, yet long-term phenology data from the tropics, in particular from African forests, are still scarce. Similarly, as the abiotic factors driving phenology in the tropics are predicted to change with a warming climate, studies documenting the relationship between climatic variables and fruit production are increasingly important.  Here we present data from 19 years of monitoring the phenology of 20 tree species at Ngogo in Kibale National Park, Uganda. Our aims were to characterize short- and long-term trends in productivity and to understand the abiotic factors driving temporal variability in fruit production. Short-term (month-to-month) variability in fruiting was relatively low at Ngogo, and overall fruit production increased significantly through the first half of the study. Among the abiotic variables we expected to influence phenology patterns (including rainfall, solar irradiance, and average temperature), only average temperature was a significant predictor of monthly fruit production. We discuss these findings as they relate to the resource base of the frugivorous vertebrate community inhabiting Ngogo.

Methods
Fruit presence was monitored monthly between 1998 and 2017 in 717 trees located along a permanent phenology trail. 400 of these trees belonging to species of importance in the diet of chimpanzees and other frugivores were analyzed in this study. We calculated, for each month of the study, a ripe fruit score (RFS), based on a combination of the percentage of stems of species X fruiting in month i and the density of species X in the habitat. Details of this methodology can be found in the accompanying paper. We gathered rainfall and temperature data directly in the research camp during each morning of the study period. We obtained irradiance data for the Ngogo research site from the Helio-Clim3 Database of Daily Solar Irradiance (maintained by MINES ParisTech-Armines; http://www.soda-is.com).

热带森林的果实生产在空间与时间维度上均存在显著差异，对食果消费者具有重要生态意义。因此，表征森林生产力的时间变异特征，是理解热带森林食果动物适应性的关键所在。然而，热带地区（尤其是非洲森林）的长期物候数据仍较为稀缺。同理，随着气候变暖，驱动热带物候的非生物因子预计将发生改变，故而记录气候变量与果实生产之间关联的研究愈发重要。

本研究展示了乌干达基巴莱国家公园恩戈戈（Ngogo）区域20种树木为期19年的物候监测数据。本研究的目标在于二点：一是刻画果实生产力的短期与长期变化趋势，二是阐明驱动果实生产时间变异的非生物因子。恩戈戈区域的结实月际短期变异相对较低，且在研究前半段，整体果实产量呈现显著上升趋势。在我们预期会影响物候模式的非生物变量（包括降雨量、太阳辐照度与平均气温）中，仅平均气温能够显著预测月度果实产量。我们还探讨了本研究发现与栖息于恩戈戈区域的食果脊椎动物群落的资源基础之间的关联。

方法
1998年至2017年间，研究人员每月对沿永久物候样带分布的717棵树木的果实存在情况开展监测。本研究选取其中400棵属于黑猩猩及其他食果动物食谱中重要物种的树木进行分析。我们基于研究期内每个月的物种X结实茎秆占比，与物种X在栖息地内的种群密度，计算得到成熟果实得分（Ripe Fruit Score, RFS）。该方法的详细细节可参见随附论文。研究期间，我们每日清晨在研究营地直接收集降雨量与气温数据。我们从由巴黎矿业学院-阿尔米讷（MINES ParisTech-Armines）维护的《每日太阳辐照度Helio-Clim3数据库》（http://www.soda-is.com）获取恩戈戈研究站点的辐照度数据。