Dinâmica espaço-temporal de Melocactus ernestii subsp. ernestii (Cactaceae) no Nordeste do Brasil

Abstract

-(Spatio-temporal dynamics of Melocactus ernestii subsp. ernestii (Cactaceae) in northwestern Brazil): Melocactus ernestii Vaupel ssp. ernestii occurs in discontinuous outcrops in eastern Brazil. We investigated the spatio-temporal pattern of mortality events and survival of seedlings of M. ernestii relationship with plants and perennials, from the use of plots, assigned with the aid of measuring tapes, which were taken the Cartesian coordinates of the centroid of the stages of development, with subsequent analysis of point patterns based on Ripley's K function. Were mapped in plots 686 individuals of M. ernestii. The spatial pattern varied depending on the scale of the development stage and degree of weathering of the outcrops. The recruitment events and mortality were spatially structured and influenced by seasonal pulses of rainfall. Seedlings emerged ca. 50 cm from the centroid of adults. From the 136 seedlings monitored for 18 months, 84% died. The results showed that microsites initially effective in the maintenance of seed germination may not be effective in the establishment of seedlings. The magnitude of biotic interactions in stressful environments is species-specific and indicates that a positive association between adult plants and seedling survival is not consistent over time. This type of modeling population allows a better understanding of the role of positive and negative interactions as forces community structure, and may help to understand the complexity of biotic interactions in severe environmental gradients.Key words -independent labeling model, recruitment, Ripley's K function, spatial structure RESUMO -(Dinâmica espaço-temporal de Melocactus ernestii subsp. ernestii (Cactaceae) no Nordeste do Brasil) Melocactus ernestii Vaupel subsp. ernestii ocorre em afloramentos rochosos descontínuos no leste do Brasil. O presente estudo investigou o padrão espaço-temporal dos eventos de mortalidade e sobrevivência de plântulas da M. ernestii e a relação com as plantas perenes, a partir da utilização de parcelas, alocadas com auxílio de trenas, onde foram tomadas as coordenadas cartesianas do centróide dos estádios de desenvolvimento, com posterior análises de padrões de ponto baseado na função K de Ripley. Foram mapeados nas parcelas 686 indivíduos da M. ernestii. O padrão espacial variou em função da escala, do estádio de desenvolvimento e do grau de intemperização dos afloramentos. Os eventos de recrutamento e mortalidade foram espacialmente estruturados e influenciados por pulsos de precipitação sazonais. As plântulas emergiram a ca. 50 cm do centróide dos adultos. Das 136 plântulas monitoradas em 18 meses, 84% morreram. Os resultados mostraram que microsítios inicialmente eficazes na manutenção de sementes e promotores da germinação não necessariamente podem ser eficazes para o estabelecimento das plântulas. A magnitude das interações bióticas em ambientes estressantes é espécie-específica e indica que associação positiva entre plantas adultas e sobrevivência de plântulas não é consistente...

Survival dynamics of Melocactus conoideus Buining & Brederoo (Cactaceae), a threatened species endemic to northeastern Brazil

“…In addition, if we consider only the adult (G4 stage) individuals of M. conoideus, the rate of survival was high, which is in agreement with the patterns reported for other species in the family (Godínez-Álvarez et al 2003;Godínez-Álvarez & Valiente-Banuet 2004;Hughes et al 2011;Ferrer-Cervantes et al 2012). The decline of survival of Melocactus conoideus along of the months revealed a seasonal influence.…”

“…For Melocactus conoideus populations, the chances of survival were found to be similar for all age classes Mandujano et al 2007;Hughes et al 2011;Ferrer-Cervantes et al 2012). In addition, if we consider only the adult (G4 stage) individuals of M. conoideus, the rate of survival was high, which is in agreement with the patterns reported for other species in the family (Godínez-Álvarez et al 2003;Godínez-Álvarez & Valiente-Banuet 2004;Hughes et al 2011;Ferrer-Cervantes et al 2012).…”

“…The decline of survival of Melocactus conoideus along of the months revealed a seasonal influence. This was also observed by Hughes et al (2011) in Melocactus ernestii, which showed a high rate of mortality (90%) in seedlings, caused by seasonal droughts. This pattern is often observed in species living in environments with an unpredictable climate, such as the semi-arid region of Brazil (Figueroa & Castro 2000;Rojas et al 2005;Lima 2011).…”

“…Plant survival can be affected by various ecological factors, including temperature and rainfall, as well as the age structure and population density (Martinez et al 1994;Godínez-Álvarez et al 2003;Mandujano et al 2007;Hughes et al 2011). During periods of low rainfall, plants often show lower growth rates and increased mortality due to the decline in soil moisture (Godínez-Álvarez et al 2003;Hughes et al 2011).…”

“…During periods of low rainfall, plants often show lower growth rates and increased mortality due to the decline in soil moisture (Godínez-Álvarez et al 2003;Hughes et al 2011). Differences among age states could affect survival among cacti because younger individuals have a lower chance of survival (Godínez-Álvarez & ValienteBanuet 2004;Mandujano et al 2007;Hughes et al 2011).…”