Temperature

Temperature can be measured in any environment by using a thermometer. Certain species have different tolerance to different ranges of temperatures. In certain conditions, temperature may determine the range of distribution of some species, since (among other effects) it can slow down or speed up enzymatic processes.

Some animal and plant species can use different strategies to acclimate themselves to extreme temperatures. For low temperatures, the presence of thick layers of fur or fat on animals will help them stay warm, while the use of CAM photosynthesis (Crassulacean Acid Metabolism) in plants allows them to retain water in the tissues on arid conditions.

Salinity

Salinity is defined as the amount of salts dissolved in the water or contained in the soil/sediment. Salinity is usually caused by cations and anions such as Ca2+, K+, Mg2+ and Cl-. The salinity of certain areas can increase due to the proximity to the sea, where water can percolate through the terrain, but it can also be the effect of dissolved minerals in the substrate. High level of salinity can be toxic for organisms that are not adapted to it, since it can decrease the ability of the organisms to maintain homeostasis and retain water. Salinity can be measured by using a conductometer or a refractometer. Conductometers typically use the resistance to an electric current to estimate the salinity, for this reason, the unit of measurement of salinity is micro-Siemens per meter.

Water content

Water content is the quantity of water that is contained in a certain material, in this case, substrate. Water is a required element for life and low levels of water content are harmful for species that not have the right adaptations. Water content may be measured by the difference in weight between wet substrate (without any treatment) and dry substrate (after drying for 48 hours in an oven). For that reason one of the most common units to measure the water content of a soil is the % in volume, or cubic centimeters of water per cubic centimeter of soil.