Many organisms respond to anthropogenic environmental change through shifts in their phenology. In plants, flowering is largely driven by temperature, and therefore affected by climate change. However, on smaller scales climatic conditions are also influenced by other factors, including habitat structure. A group of plants with a particularly distinct phenology are the understory herbs in temperate European forests. In these forests, management alters tree species composition (often replacing deciduous with coniferous species) and homogenizes stand structure, and as a consequence changes light conditions and microclimate. Forest management should thus also affect the phenology of understory herbs. To test this, we recorded the flowering phenology of 16 early-flowering herbs on 100 forest plots varying in management intensity, from near-natural to intensely managed forests, in central and southern Germany. We found that in forest stands with a high management intensity, such as Norway spruce plantations, the plants flowered on average about 2 weeks later than in unmanaged forests. This was largely because management also affected microclimate (e.g., spring temperatures of 5.9°C in managed coniferous, 6.7 in managed deciduous, and 7.0°C in unmanaged deciduous plots), which in turn affected phenology, with plants flowering later on colder and moister forest stands (+4.5 d per −1°C and 2.7 d per 10% humidity increase). Among forest characteristics, the percentage of conifers had the greatest influence on microclimate, but also the age, overall crown projection area, structural complexity and spatial distribution of the forest stands. Our study indicates that forest management alters plant phenology, with potential far-reaching consequences for the ecology and evolution of understorey communities. More generally, our study demonstrates that besides climate change other drivers of environmental change, too, can influence the phenology of organisms.

中文翻译：

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春季林下草本稍后在集约化管理的森林中开花

许多生物体通过物候变化来应对人为环境变化。在植物中，开花主要受温度驱动，因此受气候变化的影响。然而，在较小尺度上，气候条件也受到其他因素的影响，包括栖息地结构。一组具有特别独特物候的植物是欧洲温带森林中的林下草本植物。在这些森林中，管理改变了树种组成（通常用针叶树种代替落叶树）并使林分结构均质化，结果改变了光照条件和小气候。因此，森林管理也应影响林下草本植物的物候。为了测试这一点，我们在 100 个不同管理强度的林地中记录了 16 种早花草本植物的开花物候，从近乎自然的森林到集约化管理的森林，分布在德国中部和南部。我们发现，在管理强度高的林分中，例如挪威云杉人工林，植物开花平均比未管理的森林晚约 2 周。这主要是因为管理也影响了小气候（例如，管理的针叶地春季温度为 5.9°C，管理落叶地的春季温度为 6.7，未管理落叶地块的春季温度为 7.0°C），这反过来又影响了物候，植物在较冷和潮湿的环境中开花较晚林分（每 -1°C +4.5 天，每增加 10% 湿度增加 2.7 天）。在森林特征中，针叶树的百分比对小气候的影响最大，但对林分的年龄、总树冠投影面积、结构复杂性和空间分布也有影响。我们的研究表明，森林管理改变了植物物候，对林下群落的生态和进化具有潜在的深远影响。更一般地说，我们的研究表明，除了气候变化之外，环境变化的其他驱动因素也会影响生物的物候。