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They exhibit a host of biological features that make them potentially successful: 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.
In Mayall the sampled individuals at the two study sites were measured rosette diameter ddcreto their reproductive status was recorded. The two bottom lines refer to the size-specific mortality rate q x and sample size per category N.
We followed the fate of individuals in each category and estimated the probability of remaining in the same category, moving to a different one by growing to a larger size category, or regressing to a smaller size category due to a reduction in plant diameter after the loss of leaves, for instanceor dying, from the proportion of individuals following decrdto fate from May to May Part of the Tembembe site 97 ha was protected by a fence in ; thus, the fenced area has been free of cattle and the vegetation has been recovering since then.
Discussion Population growth rate did not vary significantly between the two sites, suggesting that the difference in disturbance level between sites does not have an important effect on the population dynamics of Agave angustifolia. Revista Chilena de Historia Natural The predominant soils are haplic feozems followed by pelic vertisols.
Their use with this aim has been considered an economic an ecological viable option, as it is presumed that they may effectively reduce soil erosion. Revista Mexicana de Biodiversidad And finally, the production of decreo rosettes was also incorporated in the matrices as the average contribution of adult individuals to the second size category.
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The ecotone vegetation includes some plant species in 98 genera and 42 families. Agave angustifolia Dw produces large rosettes with green-grayish narrow leaves cm longwhich are stiffly and erect and show moderately spaced lateral spines and a terminal dark spine.
In addition, we describe how we used our observations of the fate of juveniles and adults to estimate the relevant matrix entries.
Insurance against reproductive failure in a semelparous plant: In Xochicalco, individuals of 44476. Its lower part is slightly warmer and dryer that the higher one. How do plant ecologists use matrix population models?
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.
The observed and the stable size structure differed significantly in both sites Xochicalco: In Tembembe, the distribution of A. The relatively higher seed germination rates and seedling survival probabilities in Tembembe resulted in much higher fecundity values at this site decretoo to Xochicalco.
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Comparative demographic analysis of three Neobuxbaumia species Cactaceae with differing degree of rarity. In mast-seeding years the population growth rate should be considerably higher.
Thus, we had seedlings of two different ages three and five months oldwhich were introduced in Xochicalco and Tembembe in the same contrasting microsites considered in the germination experiment: In Xochicalco individuals in these three size categories were observed producing daughter rosettes of different sizes i. Restoration of degraded tropical forest landscapes. Yet, Tembembe and Xochicalco are not really semi-arid environments: A restoration program carried out in Tembembe, in central Mexico see Study Site below is considering the use of A.
The other important component of fecundity was seed production, which was quite low duringgiven that it was not a mast-seeding year. In our analyses, both stable size distributions were characterized by a very large proportion of size 1 individuals i.
We also wanted to gain a deeper understanding of the factors that affect these processes in natural conditions i. 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.
Análisis demográfico de Agave angustifolia (Agavaceae) con énfasis en la restauración ecológica
The simulated introduction of seedlings produced a substantial rise in lambda. To construct the Lefkovitch matrices, we subdivided the population in six size categories, according to rosette diameter Table 1. A wider use of Agave species would increase the diversity of plant species used for restoration of Mexican TDF, which is generally very low Bonfil and Trejo Annual Review of Ecology and Systematics The most endangered major tropical ecosystems.
Native agave plants, and even cacti, have been used for ecological restoration programs in other parts of Mexico Sinisterra et al.
The matrix for this site decreti modified to simulate the introduction of 10, 50,and 1, juveniles in the sample area. Thus, the studied populations are located in the central right-hand area of the demographic dexreto sensu Silvertown et al.
In addition, they perform an important role at the community level as nurse plants and as a food source for pollinators Gentry ; Nobel In Xochicalco, three-month old seedlings had a very high mortality rate during the first month in exposed microsites, and then they all died the following month Figure 3a. This allowed the partial recovery of the plant cover particularly of grasses and forbs and may have been an important factor determining the high seed germination and seedling establishment probabilities at this site.
In Mexico, of the ca. In Tembembe we collected 17 fruits from two individuals and in Xochicalco 29 fruits from three individuals. As this species is traditionally used for mezcal production mezcal is an alcoholic spirit similar to tequilait is frequently favored by local peasants, and in some areas – e. Plant propagation and the ecological restoration of Tropical Deciduous Forests. In the non-protected areas we have observed grazed A.
Thus, matrix analysis offers a description of the potential behavior of the studied population if the present demographic conditions were to remain constant over time i. All individuals – from all size categories – found in the expanded area were quantified. Comparative plant demography – relative importance of life-cycle components to the finite rate of increase in woody and herbaceous perennials.