Background:

The population structure is a demographic attribute that defines its viability and indicates the frequency of recruitment of new individuals. An approach to describe the population structure is by fitting a log-normal distribution of diametric sizes in columnar cacti, which indicates whether there is an adjust unimodal or multimodal distribution.

Question:

How is the distribution of diametric sizes and local spatial distribution pattern of the sympatric Pilosocereus palmeri and Cephalocereus scoparius columnar cacti in the tropical deciduous forest of Central Veracruz?

Study site and years of study:

The study was conducted in the tropical deciduous forest which is located 5 km from town of Cerro Gordo area, Veracruz, Mexico, during the 2013 rainy season.

Methods:

We measured the basal diameter of the individuals of the two columnar species in 20 rectangular plots of size 50 × 10 meters. We adjust the log-normal distribution to the diametric size model and obtained the population density and space distribution.

Results:

The population density is different more than double between the two columnar species. In addition, the frequency distribution of diametric sizes of P. palmeri adjusted a log-normal curve in contrast to that recorded in C. scoparius that was in pulse and both species have aggregate space distribution.

Conclusions:

The log-normal adjustment of the diametric sizes of P. palmeri is unimodal and indicates constant recruitment in the population, but C. scoparius has recruitment in pulses with multimodal type distribution. Also, both species have different population density but equal aggregate space distribution.