Rapid plant movement slower "growth-movements" of plants, called tropisms. Tropisms encompass movements that lead to physical, permanent alterations of the plant while rapid plant movements are usually reversible or occur at over a shorter span of time. A variety of mechanisms are utilized by plants in order to achieve these fast movements. Extremely fast movements such as the explosive spore dispersal techniques of "Sphagnum" mosses may involve increasing internal pressure via dehydration, causing a sudden propulsion of spores up or through the rapid opening of the "flower" opening triggered by insect pollination. Fast movement can also be expressed in predatory plants, where the
Plant functional type key parameters are defined, such as fecundity, competitiveness, resorption (rate at which plant decays and returns nutrients to the soil after death), etc.; the value of each parameter is determined or inferred from observable characteristics such as plant height, leaf area, etc. Climatologists and ecologists struggle to determine which minimal set of plant characteristics best model the actual responses of the biosphere in response to climate changes. Plant functional type Plant functional types (PFTs) is a system used by climatologists to classify plants according to their physical, phylogenetic and phenological characteristics as part of an overall effort to develop a