AGR 2050 Lecture Notes - Lecture 5: Intermediate Disturbance Hypothesis, Minor Disturbance, Species Richness

• School: University of Guelph
• Department: Agriculture
• Course: AGR 2050
• Professor: Clarence J Swanton

Document Summary

Species richness: the number if species present in a community. Evenness: compares the abundances of each species (informs whether a community is composed of many rare species and a few common ones or if they are equally represented) Large scale historical and climate factors are important determinates of diversity: time since glaciation, speciation, dispersal. Smaller scale local factors moderate species richness patterns: topography, spe(cid:272)ies(cid:859) i(cid:374)tera(cid:272)tio(cid:374)s, distur(cid:271)a(cid:374)(cid:272)e. Disturbance: any event that disrupts the existing structure or function of the environment (temporal scale; periodic or continual, spatial scale; small or large, intensity; low, moderate or high) Assumes a trade-off (cid:271)et(cid:449)ee(cid:374) a pla(cid:374)t(cid:859)s a(cid:271)ility to (cid:272)o(cid:373)pete a(cid:374)d its a(cid:271)ility to (cid:449)ithsta(cid:374)d disturbances. Predicts that diversity will be higher at intermediate levels of disturbance: high level: long-lived, late successional species will be eliminated and only colonizers will do well, low level: a few well-adapted species dominate and exclude colonizers. The main limitation of the hypothesis is defining high, intermediate and, low disturbances.