Read the articles and learn more about carbon cycle, abiotic factors and interaction between climate and forests. You can pick the article from this sorted list or explore them through the menu on the right side.
The movements of Earth in relation to the Sun generate a strong annual cycle of radiation and temperature that further affects other environmental factors such. Environmental factors affect physiological processes and therefore, identification and understanding of their nature is needed in order to understand and predict the biological actions of a forest.
The water holding capacity of air depends sharply on the air's temperature i.e. the warmer the air is, the more water it can hold. At a given temperature, air is saturated when it reaches the maximum water holding capacity that is also known as the dew point. Relative humidity (RH) is the ratio between how much water vapour there is in the air and how much moisture the air can hold when it is saturated whereas vapour pressure deficit (VPD) is the difference between these two.
The diurnal and annual cycle in solar radiation is reflected into air temperature by the absorption of solar radiation. Soil temperature follows the changes in the air temperature with a time lag that increases with soil depth. Close to the soil surface, the variation in temperature is larger than, for example, half a meter deep in the soil. In summertime the soil surface warms up much more than the deeper soil layers. In summer the temperature in soil surface can reach 15 to 20 °C, while in deeper soil layers the temperature stays around 10°C. In midwinter, the temperature remains above zero in deeper soil layers, approximately at +1–2°C. The snow cover efficiently insulates the soil surface keeping the temperature close to zero.
Metsät yhteyttävät eli sitovat ilmakehän hiilidioksidia omaan biomassaansa ja metsämaahan samalla vapauttaen hiilidioksidia hengityksen kautta. Näiden sitovien ja vapauttavien prosessien nopeudet eri ajanhetkillä määräävät metsän hiilensidontakapasiteetin.
The current atmospheric CO2 concentration is around 385 ppm (0.0385 %). The concentration increases annually by approximately 2 ppm.
In the Northern Hemisphere, the CO2 rises in the winter and declines in the summer, mainly as a response to the seasonal activity of forests, other land vegetation and algae which all absorb atmospheric CO2 both in oceans and in terrestrial biospheres and release it by heterotrophic respiration. In addition, the house heating in winter contributes to the seasonal cycle of CO2 concentration.
A greenhouse gas is a gas in the atmosphere that absorbs and emits radiation within the thermal infrared range causing the greenhouse effect. Carbon dioxide (CO2) is one of the chief greenhouse gases. Its concentration has increased as a result from fossil fuel emissions (i.e. human activities). Plants absorb and release greenhouse gases and thus affect the atmospheric gas concentrations. The anthropogenic carbon dioxide in the atmosphere is partly absorbed by oceans and terrestrial biosphere such as forests.
There are plenty of methods available to measure photosynthesis. The method we use is actually a measurement of the carbon dioxide catch: We enclose a small part of the tree inside a chamber and follow the change of CO2 concentration in the air of this chamber. If the plant is taking in CO2, the concentration will decrease and if it is mostly releasing CO2, then the concentration will increase. From the difference in concentration in a given time, we can calculate the rate of CO2 exchange between the plant and the air.
The measuring concept is actually quite simple. We place a chamber on a small soil surface area and follow the change of CO2 concentration in the air of this chamber. The efflux of carbon dioxide from soil is usually higher than the photosynthetic uptake of ground vegetation and thus, the concentration of carbon dioxide starts to increase in the chamber. From the rate of the concentration change in a given time, we can calculate the rate of CO2 exchange between the soil surface and air.
Many years of measurements have provided a lot of information on the behaviour of the forest, how it photosynthesizes, transpires and respires. We know more or less what to expect the tree will do according to the time of the year, the available light, the air and soil temperature and the water availability in the soil. We can express this knowledge as mathematical models that can forecast the overall behaviour of the tree. Mathematical modelling is a typical tool to describe the phenomena in an exact and concise format. However, always bear in mind that the model reflects only such variables in the reality than exist in the model.
Years of measurements have produced a lot of information on soil respiration. We know more or less how the respiration rate is related to changing environmental conditions. As the plant respiration, soil respiration follows exponentially temperature. Approximately, respiration rates doubles for every 10°C increase in temperature. Soil water availability (REW) further regulates the respiration.
A greenhouse gas is a gas in the atmosphere that absorbs and emits radiation within the thermal infrared range causing the greenhouse effect. Carbon dioxide (CO2) is one of the chief greenhouse gases. Its concentration has increased as a result from fossil fuel emissions (i.e. human activities). Plants absorb and release greenhouse gases and thus affect the atmospheric gas concentrations. The anthropogenic carbon dioxide in the atmosphere is partly absorbed by oceans and terrestrial biosphere such as forests.