摘要
The relationship of plant species diversity to cultural eutrophy in tropical wetlands was studied in Puerto Rico with experimental plots, a survey of 25 eutrophic sites developing from the wastes of society, and a simulation mini-model. The model is a quantitative hypothesis which contains the mechanisms to maximize empower (gross production) by reinforcing low diversity, net production overgrowth when resources are in excess, but switches to high diversity efficiency and recycle to maximize gross production when excess resources are absent. To study self-organization with eutrophy, six wetland plots (3×2 m) were seeded with many plant species and treated for five months with pig wastewaters and control plots with groundwater. Vegetation was seeded: (1) with seed bank; (2) with ten species of local rainforest and wetland trees (60 individuals in each plot); and (3) with weedy species invading from fertile surroundings. The fertilized waste plots filled in with vegetation in less than half the time (9 weeks) required for the clear water control plots (21 weeks). Vegetative diversity in both waste and control plots was maximum (2.73–3.34 bits per individual) shortly before 100 % cover was reached, and then declined with the competitive overgrowth of a few species (mixed grasses and Commelina diffusa). Of the planted seedlings, there was little growth, and individuals of only four species survived. Survival of Andira inermis and Cyrilla racemiflora was 42 and 53 % , respectively. Dominants of oligotrophic wetlands (Pterocarpus officinalis and Prestoea montana) were displaced. A survey of 25 other wetland sites, receiving high nutrient waters from developments, found low diversity overgrowth, but different species prevailing. Eighty-five species were involved in wetland self-organizational processes and ecological engineering management. Eutrophic wetlands, such as those released from sugar cane closure in Puerto Rico and elsewhere, may be in a state of marshy, arrested succession because there may not be a forest species already adapted for rapid reforestation of the excess nutrient habitat. The study provides evidence of the overgrowth principle as the natural means for ecological engineering of eutrophic interfaces between the current civilization and environment.