Is size structure a good measure of future trends of plant populations? an empirical approach using five woody species from the Cerrado (Brazilian savanna)

Abstract

Is size structure a good measure of future trends of plant populations? An empirical approach using fi ve woody species from the Cerrado (Brazilian savanna) RESUMO (A estrutura de tamanho é uma boa medida de tendências futuras em populações de plantas? Uma abordagem empírica com cinco espécies lenhosas de Cerrado). As estruturas de tamanho de populações têm sido frequentemente usadas para inferir sobre a capacidade de regeneração de uma população, assumindo que as estruturas de tamanho com formato "J-invertido" representam populações estáveis. Nós apresentamos uma abordagem empírica desta questão com cinco espécies lenhosas de Cerrado. Usando dados de contagem de todas as plantas destas cinco espécies por um período de doze anos, nós analisamos a distribuição de tamanho dos indivíduos de duas maneiras: a) por meio de histogramas de frequência em classes de tamanho, e seu ajuste a uma curva exponencial negativa; b) calculando o coeficiente de Gini. Para verificar a existência de uma relação entre a estrutura de tamanho e as tendências futuras em número, consideramos a estrutura de tamanho no ano do primeiro censo. ABSTRACT(Is size structure a good measure of future trends in plant populations? An empirical approach using fi ve woody species from the Cerrado (Brazilian savanna)). Size distributions in woody plant populations have been used to assess their regeneration status, assuming that size structures with "reverse-J" shapes represent stable populations. We present an empirical approach of this issue using fi ve woody species from the Cerrado. Considering count data for all plants of these fi ve species over a 12-year period, we analyzed size distribution by: a) plotting frequency distributions and their adjustment to the negative exponential curve and b) calculating the Gini coeffi cient. To look for a relationship between size structure and future trends, we considered the size structures from the fi rst census year. We analyzed changes in number over time and performed a simple population viability analysis, which gives the mean population growth rate, its variance and the probability of extinction in a given time period. Frequency distributions and the Gini coeffi cient were not able to predict future trends in population numbers. We recommend that managers should not use measures of size structure as a basis for management decisions without applying more appropriate demographic studies.

Diversity, Population Structure, and Above Ground Biomass in Woody Species on Ngomakurira Mountain, Domboshawa, Zimbabwe

“…Recent studies have questioned reliance on inverse J distributions in forest management as they are based on a biologically unrealistic assumption of equal mortality among size classes [49]. Declining populations may also show the classic "inverse J" shape and some stable populations may not show this shape due to differences in growth rates among size classes [50]. Most of the common miombo woody species reach much larger DBH sizes in mature forests [26].…”

Estrutura diamétrica da vegetação arbustivo-arbórea no entorno de nascentes da bacia hidrográfica do rio Piauitinga, Salgado – SE, Brasil

“…Entretanto, Virillo et al (2011), após analisarem dados sobre a estrutura de cinco espécies lenhosas de Cerrado, por um período de doze anos afirmaram que medidas de estrutura de tamanho não devem ser usadas como base para decisões de manejo sem que análises demográficas mais apropriadas sejam realizadas.…”

Population Structure and Fruit Productivity Analyses in Support of the Use of Caryocar brasiliense

“…The structure of a managed population may indicate its conservation state. Additionally, the factors that may affect a species' productivity can be better understood when fruit production is associated with the species' demographic parameters, thereby allowing the establishment of management strategies that do not affect long-term species persistence (Leite et al, 2006;Zardo & Henriques, 2011;Virillo et al, 2011). Studies of C. brasiliense extraction in yet unmanaged Cerrado areas enable us to assess other factors that may affect the population structure and productivity of this species (Giroldo & Scariot, 2015), and consequently to propose conservation measures considering the current scenario and extraction as an income source.…”