The discontinuity of diurnal temperature range along the elevation: the role of fog

Abstract:

Mountains provide essential diverse habitats for the terrestrial ecosystem, and the elevational gradient of temperature enables the species an important way to respond to global warming. The near-surface air temperature can influence the land-atmosphere interaction, the photosynthesis rate, and the boundary layer stability. Besides the mean condition, the diurnal temperature range (DTR) determined species' elevational range size, which is affected remarkably by the hydro-climatological cycle. However, the lack of observational data makes it difficult to quantify the integrative effect of the hydro-climatological cycle on microclimate in montane regions, which is the environment the most animal experienced. We build up an integrative observation framework to explore the canopy effects on the microclimate along the elevation in the montane cloud forest (MCF), and the mechanisms behind. Previous studies have shown that radiation blocking is the main reason for the unique characteristics of the cloud-fog forest. Interestingly, in our result on the east side of the Central Cross-island Highway in Taiwan, we found that DTR linear increases with elevation in open sites as same as the past research mentioned. Nevertheless, the elevational trends of DTR are not significant under the canopy where is the main habitats for most species. Furthermore, the elevational trend of DTR is both discontinuous in open sites and under the canopy. The DTR get narrower between 1,500- 2,250m a.sl. where is the location of MCF. The blocking of solar radiation from the cloud-fog and the abundant interception on the trees and grassland might provide water sources for evaporation in the daytime, so the DTR is smaller in both MCF sites. The result implies that the species have to encounter a greater climate variability if they shift to a higher altitude under climate warming.