Macroclimate, the larger-scale (10-1000km) atmospheric conditions that largely determine microclimate conditions, consists of solar radiation (sunshine), precipitation, wind speed, and the temperature and humidity of the overlying air mass.

Microclimate, is the small-scale climate that develops upwards and downwards from the ground surface, where radiant energy and precipitation are received and dissipated.   Micro climate fluctuates, more or less, greatly dependant on weather conditions, terrain, cover of vegetation, and soil properties.  Microclimate will certainly be influenced by site preparation.

Microtopography, the shape of the ground surface, is often characterized by small mounds and depressions.  Mounds and depressions influence the climatic regime owing to variations in their heights and frequencies, which, along with slope and aspect, tend to establish a mosaic of moisture, temperature, and nutrient conditions across a site.   For example a removal of insulating organic layer to expose the more conductive underlying mineral soil can significantly influence the daytime and nighttime soil temperature and nocturnal air temperature of the microclimate around the seedling.

Improving a forest environment by site preparation is accomplished be relieving the constraints to seedling establishment and/or performance.   Newly planted seedlings, for example, are vulnerable because the microclimate of the planted site is extreme.  Invading plant species may create severe competition for resources, and seedlings may not be completely acclimatized to site conditions and may also be stressed during the transplanting process.  Near surface moisture deficits, root zone moisture deficits, and low surface and soil subsurface temperatures are major constraints to seedlings on many cutovers.  Other stresses registered by seedlings reflects imbalances and/or extremes in light, nutrients, and soil or atmospheric chemistry.  Microclimatic components that can constrain seedling establishment and/or performance, and that can be influenced by or influence the choice of the site preparation method, are soil moisture and temperature, air temperature, and light. Other constrains are soil fertility, thickness of the unincorporated organic layer (humus, LFH, duff, or peat layer), and the biotic variables of harvesting residue and noncrop vegetative competition.  Soil temperature and moisture are two of the most important constraints to a tree seedling during the establishment phase and are highly interrelated: a change in one variable causes changes in the other.  Heat and moisture are coupled in terms of their effect on plant growth and their role in establishing the microclimate at a specific site; however, water is frequently the most important environmental factor that influences the day-to-day variation in tree growth.