In the Amazonian rain forest, major parts of trees and shrubs are covered by epiphytic cryptogams of great taxonomic variety, but their relevance in biosphere–atmosphere exchange, climate processes, and nutrient cycling is largely unknown. As cryptogams are poikilohydric organisms, they are physiologically active only under moist conditions. Thus, information on their water content (WC) as well as temperature and light conditions experienced by them are essential to analyze their impact on local, regional, and even global biogeochemical processes. In this study, we present data on the microclimatic conditions, including water content, temperature, and light conditions experienced by epiphytic bryophytes along a vertical gradient, and combine these with above-canopy climate data collected at the Amazon Tall Tower Observatory (ATTO) in the Amazonian rain forest between October 2014 and December 2016. While the monthly average of above-canopy light intensities revealed only minor fluctuations over the course of the year, the light intensities experienced by the bryophytes varied depending on the location within the canopy, probably caused by individual shading by vegetation. In the understory (1.5 m), monthly average light intensities were similar throughout the year, and individual values were extremely low, remaining below 3 µmol m⁻² s⁻¹ photosynthetic photon flux density more than 84 % of the time. Temperatures showed only minor variations throughout the year, with higher values and larger height-dependent differences during the dry season. The indirectly assessed water content of bryophytes varied depending on precipitation, air humidity, dew condensation, and bryophyte type. Whereas bryophytes in the canopy were affected by diel fluctuations of the relative humidity and condensation, those close to the forest floor mainly responded to rainfall patterns. In general, bryophytes growing close to the forest floor were limited by light availability, while those growing in the canopy had to withstand larger variations in microclimatic conditions, especially during the dry season. For further research in this field, these data may be combined with CO₂ gas exchange measurements to investigate the role of bryophytes in various biosphere–atmosphere exchange processes, and could be a tool to understand the functioning of the epiphytic community in greater detail.

中文翻译：

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亚马逊雨林附生苔藓植物经历的小气候条件和水分波动

在亚马逊雨林中，树木和灌木丛的大部分被分类学上很丰富的附生隐孢子虫所覆盖，但是它们在生物圈-大气交换，气候过程和养分循环中的相关性却鲜为人知。由于隐球菌是多羟基生物，它们仅在潮湿条件下才具有生理活性。因此，有关其水分含量（WC）以及他们所经历的温度和光照条件的信息对于分析其对本地，区域乃至全球生物地球化学过程的影响至关重要。在这项研究中，我们介绍了附生苔藓植物沿垂直梯度经历的微气候条件的数据，包括水分，温度和光照条件，并将这些数据与2014年10月至2016年12月在亚马逊雨林的亚马逊高塔天文台（ATTO）收集的冠层以上气候数据相结合。尽管冠层以上光强度的月平均值在整个过程中显示出较小的波动。一年，苔藓植物所经历的光照强度根据树冠内的位置而变化，这可能是由于植被的单独遮蔽所致。在地下层（1.5 m）中，全年的月平均光强度相似，并且单个值极低，保持在3以下 苔藓植物所经历的光照强度根据树冠内的位置而变化，这可能是由植被的单个阴影所引起的。在地下层（1.5 m）中，全年的月平均光强度相似，并且单个值极低，保持在3以下 苔藓植物所经历的光照强度根据树冠内的位置而变化，这可能是由植被的单个阴影所引起的。在地下层（1.5 m）中，全年的月平均光强度相似，并且单个值极低，保持在3以下 µ mol m ^-2  s ^-1光合光子通量密度超过84％的时间。全年的温度变化很小，而在旱季则更高，且高度变化较大。苔藓植物的间接评估水含量因降水，空气湿度，结露和苔藓植物类型而异。冠层的苔藓植物受到相对湿度和凝结的diel波动的影响，而靠近森林地面的苔藓植物则主要对降雨模式作出响应。通常，生长在森林地面附近的苔藓植物受到光的供应的限制，而生长在树冠中的苔藓植物则必须承受微气候条件的较大变化，尤其是在干旱季节。为了进一步研究该领域，可以将这些数据与CO₂气体交换测量，以研究苔藓植物在各种生物圈-大气交换过程中的作用，并且可以成为更详细了解附生群落功能的工具。