Editorial: Tropical Montane Forests in a Changing Environment

Abstract

Tropical montane forests (TMFs) are found on most of Earth's continents along variable elevation ranges, whose potential upper limits are influenced by cloud condensation heights and minimum temperatures. They are most widespread in South America and in (semi-)humid mountain areas According to FAO and UNEP (2020), the area covered by tropical and subtropical montane forests is around 305 million hectares, about 13% of the area covered by tropical and subtropical forests. Their elevational limits are difficult to establish due to the interactions of the different factors that determine their characteristics. Among these, geomorphology plays a leading role in regulating TMF structure, and provides useful clues on the contributing mechanisms. Most TMFs occur under highly variable topography, including steep slopes Also, the latitudinal gradient, orography, and vertical thermal gradients have a direct influence on the fauna and flora of TMFs. The latitudinal pattern is not the same in all TMFs, the temperature and precipitation conditions occur due to seasonality in the climate and are unambiguously linked to species climatic affinity preferences Another factor is the annual precipitation that generally exceeds c. 1,000-1,200 mm and can be associated with low level cloud cover or mist, which results in a lower incidence of sunlight and lower primary productivity, suggesting that NPP for these forests is driven by changes in photosynthesis. This highlights the importance of variations in solar radiation. Despite this variability, TMFs store significant amounts of carbon in their soils. Lower temperatures also result in low nutrient inputs through slow mineralization of organic matter Declining temperature appears to be the principal rate-limiting factor for litter decay with increasing elevation on tropical mountains The low temperatures have also been linked to biogeochemical limitations, by reducing nitrogen availability However, biogeochemical cycling in TMFs is further affected-returning to our primary driver-by geomorphology via landslide activity and uplift, which increases the supply of rock-derived

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