000			029430000a22004690004500
911			_aXL1996502633
901			_aF40
903			_aE
903			_aV
904			_aBCO
905			_aC
906			_a19960101
908			_aJ
909			_aAS
912			_aEn
912			_aEn
914			_aBCO1
914			_aINFOR
914			_aBN
082	0	4	_a24731
100	1		_962177 _aDenslow, J.S.
260			_c1995
041	0		_aEn
500			_aIlus. Tab. 37 ref. Sum. (En)
520			_aA null model for the effects of treefall gaps on tree species diversity of tropical rain forests is based on the well-known relationship between abundance and diversity: habitats supporting larger numbers of individuals can support more populations and more species than habitats supporting small numbers of individuals. Because seedling establishment and sapling density increase following canopy opening, gaps are often also sites of high species diversity. Both tree density and diversity are likely to be greater in areas of high stand-turnover rates. Thinning and non-catastrophic mortality reduce both density and diversity in areas of low gap frequency. Nevertheless, natural and anthropogenic disturbances, such as logging, have been hypothesized to both enhance and limit species diversity through changes in habitat heterogeneity, shifts in competitive balances among species, and creation of otherwise-rare habitats. Species-accumulation curves can be used to evaluate these alternatives by comparing observed species-abundance patterns with expected changes in diversity due to density effects alone. Topographic variation in density and diversity of shrubs and small saplings at the La Selva (Costa Rica) Biological Station preserve was analyzed as an example. The total number of species for each of 18 sites was estimated by fitting a two-parameter hyperbola (similar to the Michaelis-Menten equation) to sample data using a maximum-likelihood method. Although both density and diversity were higher on slopes than on ridges, total species richness was nevertheless higher on slopes than is predictable from density effects alone. High stand-turnover rates on slopes may enhance tree species diversity through increases in tree density and in habitat heterogeneity.
650	1	4	_96 _aBIODIVERSIDAD
650	1	4	_9140644 _aCLAROS
650	1	4	_9143732 _aDENSIDAD DE LA POBLACION
650	1	0	_aDAÑOS _9143455
650	1	4	_9138301 _aBOSQUE TROPICAL HUMEDO
691			_9137891 _aBIODIVERSITY
691			_9332806 _aPOPULATION DENSITY
691			_9341808 _aTROPICAL RAIN FORESTS
692			_aBIODIVERSITE
692			_aDENSITE DE POPULATION
692			_aFORET TROPICALE HUMIDE
773	0		_tEcological Applications (EUA) _d1995 _gv. 5(4) p. 962-968
040			_aCR-TuBCO _cCR-TuBCO _bEs
245	1	0	_aDisturbance and diversity in tropical rain forests: the density effect
942			_cANA
003			CR-TuBCO
999			_c58199 _d58199