Gotsch Sybil G, Davidson Kenneth, Murray Jessica G, Duarte Vanessa J, Draguljić Danel
Franklin and Marshall College, Department of Biology, Lancaster, Pennsylvania 17603 USA
Franklin and Marshall College, Department of Biology, Lancaster, Pennsylvania 17603 USA.
Am J Bot. 2017 Dec;104(12):1790-1801. doi: 10.3732/ajb.1700247. Epub 2017 Dec 1.
Tropical Montane Cloud Forests (TMCFs) are important ecosystems to study and preserve because of their high biodiversity and critical roles in local and regional ecosystem processes. TMCFs may be particularly affected by changes in climate because of the narrow bands of microclimate they occupy and the vulnerability of TMCF species to projected increases in cloud base heights and drought. A comprehensive understanding of the structure and function of TMCFs is lacking and difficult to attain because of variation in topography within and across TMCF sites. This causes large differences in microclimate and forest structure at both large and small scales.
In this study, we estimated the abundance of the entire epiphyte community in the canopy (bryophytes, herbaceous vascular plants, woody epiphytes, and canopy dead organic matter) in six sites. In each of the sites we installed a complete canopy weather station to link epiphyte abundance to a number of microclimatic parameters.
We found significant differences in epiphyte abundance across the sites; epiphyte abundance increased with elevation and leaf wetness, but decreased as vapor pressure deficit (VPD) increased. Epiphyte abundance had the strongest relationship with VPD; there were differences in VPD that could not be explained by elevation alone.
By measuring this proxy of canopy VPD, TMCF researchers will better understand differences in microclimate and plant community composition across TMCF sites. Incorporating such information in comparative studies will allow for more meaningful comparisons across TMCFs and will further conservation and management efforts in this ecosystem.
热带山地云雾森林（TMCFs）是重要的生态系统，因其具有高度的生物多样性以及在当地和区域生态系统过程中发挥的关键作用而值得研究和保护。由于TMCFs所占据的微气候带狭窄，且TMCF物种易受云底高度预计增加和干旱的影响，它们可能特别容易受到气候变化的影响。由于TMCF站点内部和站点之间地形的变化，目前缺乏对TMCFs结构和功能的全面理解，且难以实现。这导致了在大尺度和小尺度上微气候和森林结构的巨大差异。
在本研究中，我们估算了六个站点树冠层（苔藓植物、草本维管植物、木本附生植物和树冠层死亡有机物质）中整个附生植物群落的丰度。在每个站点，我们都安装了一个完整的树冠层气象站，以将附生植物丰度与多个微气候参数联系起来。
我们发现不同站点的附生植物丰度存在显著差异；附生植物丰度随海拔和叶片湿度的增加而增加，但随水汽压亏缺（VPD）的增加而降低。附生植物丰度与VPD的关系最为密切；VPD存在差异，仅靠海拔无法解释这些差异。
通过测量树冠层VPD这一指标，TMCF研究人员将能更好地理解不同TMCF站点微气候和植物群落组成的差异。将这些信息纳入比较研究将使跨TMCFs的比较更有意义，并将进一步推动该生态系统的保护和管理工作。
