According to Richard 1963 as cited in zahari haji ismail 1994 said that in the highland tropic, there is a steady decrease in ambient temperature with the increase in altitude. In the tropics, temperature decrease at the rate of 0.4 degree to 0.7 degree celcius per 100 meter increase in altitude. said However it varies with some factors which include the locality, season and air humidity refered to Dale 1963 as cited in zahari haji ismail 1994. Above 2500 meter , the rate decreases to 1.2 degree celcius per 300 meter rise. Temperature affects plant due to its influence on their growth processes and distribution.
According to burgess 1975 as cited in zahari haji ismail said that the native mountain plant may die when transferred to the lowlands. The optimal temperature for photosynthesis for such plants are lower than for respiration, as such the highl lowland ambient temperature which wxceeds optimal for photosynthesis, increases respiratiob rate, leading to wet depletion
According to wyatt-smith 1963 as cited in zahari haji ismail 1994 said that the topography plays an important role in determining the rainfall of an area. According to Richard 1964 as cited in zahari haji ismail 1994 said that maximum rainfall in tropical highlands occurs at altitudes where temperature is cold enough to the high mountains.
According to smith 1963 as cited in zahari haji ismail 1994 said that the rainfall reaches its maximum at the altitudes of 300 meter a.s.l. and betond this it decreases. As cited in Zahari ismail There must been some moisture stress occured on the ridges. Thus it is very difficult to find meranti seraya on the foot of hills due to the occurance of heavy rainfall and lacvk of regular drought.
Light and radiation
According to grubb and hitemore 1969 as cited in zahari haji smail 1994 said that the frequency of fog or cloud in the rainforest is the most vital factor determining the distribution of the formation of vegetation types in the mountains.
The light intensity at 180 meter a.s.l in coastal hill rainforest measured at the forest floor is around 2 percent (whitemore and wong 1969) as cited in zahari haji ismail 1994. While in kand hill forest is measured abaout 10 percent less sunshine than the plains (Burgess 1969). The increasing fog frequency decreases light inthesity, dampens the range of light intensities and generally exerts a moderating influence on the annual variation pattern of light intensity (Brown 1919) as cited in Zahari ismail 1994.
According to robinwith 1951 as cited in zahari haji ismail 1994 said that the most important use of light by plant is for photosynthesis, and the average actively growing land plant use only about 1 percent of visible emission for photosynthesis.
As cited in zahari haji ismail 1994 said that light intensity available in the forest floor around highland rainforest stand is adequate for the growth of herbs.
As cited in zahari haji ismail 1994 mention that the humidity increase with altitude up to the fog belt regions (Burgess, 1969). According to Richard 1964 as cited in zahari haji ismail 1994 said that the condition on the mountain rain forest, has found the zone of maximum humidity and highly evaporation increases.
As cited in zahari haji ismail 1994 said that the amount of air movement affects the rate of evaporation and thus minimizing the temperature in the forest stand (Burgess 1969). Expected an increase in wind speed with elevation (Burgess, 1975). According to smith 1965 as cited in zahari haji ismail 1994 said that the highly wind speed occurs at the highly altitudes.
According to Richards 1964 as cited in zahari haji ismail 1994 said that the both structure and floristic composition of the highland forests are partly determined by the wind speed and he suggested that wind may be one of the factors that cause the maximum drawfing of the vegetation on isolated peaks and ridges on highland and mountain forest.
a. Soil physical condition.
As cited in zahari haji ismail 1994 have written that there is a significantly relationship between plant composition and soil characteristics (Burgess 1975).
According to Richards 1964 as cited in Zahari haji ismail 1994 said that the soil at higher altitudes tend to be very shallow with thicker litter accumulation and contain bigger size rock due to the decrease of temperature and intense erosion which often result in very immature soils, especially on the steep slopes