Abstract

It is well known that forest microclimates contrast strongly with the climate outside forests. We studied microclimate (air temperature, air humidity, soil temperature and soil moisture) beneath the forest canopies of four dominant forest types along an altitudinal gradient (300-2200masl) in Central Himalaya. Microclimatic conditions across the under canopy of the four forests varied significantly. In the study area May was the warmest month (mean across the under canopy of four study sites=29.1 °C) and January was the coldest month (mean=11.0 °C), with mean annual temperature of 22.9 °C. The under-canopy temperature was found to be about 4 °C lower than the mean atmospheric temperature (27.0 °C) reported in the study area. With respect to air temperature the south aspects were slightly warmer than the north aspects. The mean annual soil temperature (18.0 °C) was found to be about 5 °C lower than the mean annual air temperature (22.9 °C) across the forest under canopies. The RH was recorded in a narrow range of 72-75% across the forests that decreased with altitude significantly. The N aspects recorded markedly higher RH than the S aspects. The soil moisture was recorded maximum during rainy season (mean=16.4%) and minimum during summer (mean=11.7%). Both air temperature, soil temperature and RH decreased significantly with increasing altitude. ANOVA indicates that both air temperature (p<0.026) and soil temperature (p<0.001) were significantly different across the forests and sampling months. These existed a significant negative relationship between air temperature and altitude (r=0.996; p<0.004) and between relative humidity and altitude (r=-0.993; p<0.007). The soil temperature and altitude were negatively correlated (r=0.975; p<0.025). The dampening of air temperature, higher humidity and soil moisture under the canopy of these forests has several advantages to the plants and the fauna dependent upon them. These forests with distinct microclimate may act as a micro-refugia to provide congenial habitat and conserve rich biodiversity in the face of global warming in this region.

Keywords:Forest microclimate; Altitudinal gradient; Global warming; Biodiversity; Microrefugia; Central himalayan forests