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Finally, the effect of microsite and seedling age were marginally significant: To evaluate the differences between the stable and the observed population structures, and between the observed population structure in andpaired chi-square tests were run.
The survival of these seedlings was recorded monthly for a year. Considering all of the above, some species in the Agave L. In our study, the slight differences in the demography of the two populations cannot be accounted for only as a result of disturbance level, as the two sites also vary in relation to climate and soil.
Análisis demográfico de Agave angustifolia (Agavaceae) con énfasis en la restauración ecológica
Materials and methods Study species. They exhibit a host of biological features that make them potentially successful: In Mayall the sampled individuals at the two study sites were measured rosette diameter and their reproductive status was recorded.
Evaluation of the conservation status of a rare cactus Mammillaria crucigera through the analysis of its population dynamics. The size-specific reproductive values showed a similar behavior in both populations, with low values in the first category and increasing towards larger categories Table 2a and b. Fruits ripen between May and July; they are brownish ovoid capsules, ca.
Exotic plant species as problems and solutions in ecological restoration: The other important component of fecundity was seed production, which was quite low duringgiven that it was not a mast-seeding year.
Therefore, it is not surprising that the relatively milder conditions allow for growth to become an important process for population dynamics.
In contrast, the rest of the size categories had a much lower mortality rate, decret tended to be higher in Tembembe than in Xochicalco.
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Large-scale ecological restoration of degraded tropical forest lands: At the end of Mayjust before the onset of the rainy season, we carried out a germination experiment to evaluate the probability of germination under natural conditions. We followed the fate of individuals from one year to the next and built two Lefkovitch matrices.
The seeds of all the fruits collected in each area were devreto and groups of 50 seeds were scattered on the bare soil in exposed microsites five replicates and protected microsites five replicates; under the crown of a nurse plant, mainly Acacia spp. Chapman and Hall, New York. However, the performance of its populations at the site must first be examined to evaluate the potential success of such restoration efforts.
To explore the effect of recreto extractive management in the Tembembe population which is where extraction takes placenumerical simulations were performed on the population projection matrix for this site.
The proportion of reproductive individuals was quite low in both populations. Revista Mexicana de Biodiversidad These were used to project the numerical behavior of the populations through time and calculate the finite population growth rate to which they would converge.
A global overview of the conservation status of tropical dry forests. Variation in the populations dynamics of the palm Sabal yapa in a landscape shaped by shifting cultivation in the Yucatan peninsula, Mexico. The two bottom lines refer to the size-specific mortality rate q x and sample size per category N.
Also in the cacti Coryphantha werdermannii and Mammillaria magnimamma populations were negatively affected by disturbance Valverde et al.
In this section we describe the different experiments performed to obtain the main demographic data needed to build the population projection matrices for each site, in particular for the individuals in the early life-cycle stages, which are generally scarce in the field. In our analyses, both stable size distributions were characterized by a very large proportion of size 1 individuals i.
When categories are expressed in terms of plant size, the resulting matrix is called a Lefkovitch matrix Lefkovitch The results of our study suggest that Agave angustifolia could successfully be used for the ecological restoration of disturbed fields in the Tembembe area.
It involves building a contribution matrix in which each entry represents the contribution of its respective a i,j to an increase or a decrease i. The entries of the elasticity matrices were obtained as described in de Kroon et al. A two-way ANOVA was used to test the effect of site Xochicalco and Tembembe and microsite exposed and protected on seed germination percentage at the end of the rainy season arcsine transformed for normality.
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Environmental Biology of Agaves and Cacti. Also, a seedling establishment experiment was performed. With full awareness of these limitations, projection matrix results may be properly interpreted and used as an aid for the management and conservation of natural populations Crone et al. In mast-seeding years the population growth rate should be considerably higher. The stable size structure vector w and the size-specific reproductive values vector v are reported.
These were the variations in the fecundity entries as discussed belowwhich were in turn determined by a higher seed germination and seedling establishment probability in Tembembe compared to Xochicalco, probably due to the higher altitude and thus lower temperatures that prevail at Tembembe. Thus, the fecundity values Ddecreto x incorporated in the Lefkovitch matrices were given as:. The mean number of fruits per reproductive plant was Tembembein which the three main demographic process fe represented.
Therefore, in some natural populations, the flowering stalks are severed during their early developmental 4467, and entire plants are later extracted, which results in a decrease in fecundity.
The relatively higher seed germination rates and seedling survival probabilities in Tembembe resulted in much higher fecundity values at this site compared to Xochicalco. Similarly, most of the contributions referring to vegetative spread were positive in Xochicalco, and negative in Tembembe, except for a 4,5 Figure 6. In addition, retrospective and prospective analyses elasticity matrices and Life-Table Response Experiments – LTRE as well as numerical simulations were used to evaluate the potential results of different management practices at the restoration site Illsley et al.
Another important result of matrix analysis is the stable size distribution to which the population would converge if the current demographic behavior remained constant over time i. In addition, demographic variation through time in Agave populations may also reflect variation in inflorescence removal for mezcal production.