Bader Maaike Y, Moureau Elodie, Nikolić Nada, Madena Thomas, Koehn Nils, Zotz Gerhard
Faculty of Geography Ecological Plant Geography University of Marburg Marburg Germany.
Institute for Biology and Environmental Sciences Functional Ecology of Plants University of Oldenburg Oldenburg Germany.
Ecol Evol. 2022 Jan 24;12(1):e8406. doi: 10.1002/ece3.8406. eCollection 2022 Jan.
Future climate-change effects on plant growth are most effectively studied using microclimate-manipulation experiments, the design of which has seen much advance in recent years. For tropical forests, however, such experiments are particularly hard to install and have hence not been widely used. We present a system of active heating and CO fertilization for use in tropical forest understoreys, where passive heating is not possible. The system was run for 2 years to study climate-change effects on epiphytic bryophytes, but is also deemed suitable to study other understorey plants. Warm air and CO addition were applied in 1.6-m-tall, 1.2-m-diameter hexagonal open-top chambers and the microclimate in the chambers compared to outside air. Warming was regulated with a feedback system while CO addition was fixed. The setup successfully heated the air by 2.8 K and increased CO by 250 ppm on average, with +3 K and +300 ppm as the targets. Variation was high, especially due to technical breakdowns, but not biased to times of the day or year. In the warming treatment, absolute humidity slightly increased but relative humidity dropped by between 6% and 15% (and the vapor pressure deficit increased) compared to ambient, depending on the level of warming achieved in each chamber. Compared to other heating systems, the chambers provide a realistic warming and CO treatment, but moistening the incoming air would be needed to avoid drying as a confounding factor. The method is preferable over infrared heating in the radiation-poor forest understorey, particularly when combined with CO fertilization. It is suitable for plant-level studies, but ecosystem-level studies in forests may require chamber-less approaches like infrared heating and free-air CO enrichment. By presenting the advantages and limitations of our approach, we aim to facilitate further climate-change experiments in tropical forests, which are urgently needed to understand the processes determining future element fluxes and biodiversity changes in these ecosystems.
利用微气候操纵实验能最有效地研究未来气候变化对植物生长的影响，近年来这类实验的设计有了很大进展。然而，对于热带森林而言，此类实验特别难以设置，因此尚未得到广泛应用。我们提出了一种用于热带森林林下的主动加热和二氧化碳施肥系统，因为在林下无法进行被动加热。该系统运行了两年，以研究气候变化对附生苔藓植物的影响，但也被认为适用于研究其他林下植物。在1.6米高、直径1.2米的六边形开顶箱中进行暖空气和二氧化碳添加，并将箱内微气候与外界空气进行比较。通过反馈系统调节升温，而二氧化碳添加量是固定的。该装置成功地将空气加热了2.8K，平均使二氧化碳浓度增加了250ppm，目标是升温3K和增加300ppm。变化幅度很大，尤其是由于技术故障，但不存在一天中或一年中特定时间的偏差。在升温处理中，绝对湿度略有增加，但与环境相比，相对湿度下降了6%至15%（水汽压差增加），这取决于每个箱内实现的升温水平。与其他加热系统相比，这些箱子提供了逼真的升温和二氧化碳处理，但需要对进入的空气进行加湿，以避免干燥成为一个混杂因素。在光照不足的森林林下，该方法比红外加热更可取，特别是与二氧化碳施肥相结合时。它适用于植物水平的研究，但森林生态系统水平的研究可能需要无箱方法，如红外加热和自由空气二氧化碳富集。通过阐述我们方法的优点和局限性，我们旨在促进热带森林中进一步的气候变化实验，这对于理解这些生态系统中决定未来元素通量和生物多样性变化的过程来说是迫切需要的。
