Climate, sunlight, fire, soil and topography are some nonliving items in a rainforest. Named abiotic factors, these impact the health of the biotic factors, or living elements, of both tropical and temperate rainforests.
Climatic factors include temperature, rainfall, wind and storm patterns. Temperatures vary by whether a rainforest is temperate or tropical, with cooler temperatures in temperate rainforests. Research shows that numbers of large storm systems have a more significant impact on rainfall than warming temperatures. In particular, the El Ni?o Southern Oscillation is a pattern of decreased rain generated by fluctuations in ocean water temperature.
Sunlight is characteristically low in the rainforest understory. The vertical nature of the environment, where tall trees form a canopy, causes the blockage of most available light and leads to fewer undergrowth plants.
High winds change the sunlight available to the understory by opening up the canopy. Other disturbances include fire, floods and human interactions such as pollution and deforestation. The correlation of air pollution to plant health in temperate forests is unclear and requires additional research.
Soil composition refers to the minerals and nutrients available in the soil for plant growth. The pH of the soil also influences vegetation, with most rainforest soils being alkaline.
The topography of the rainforest includes the geologic formations that form its landscape features. Slopes direct rainwater to lower levels, creating water collection sites. Rocks prevent much plant growth due to unavailability of nutrients and soil. Aspect, or the direction faced by a slope, affects the daily duration of sunlight.