Relação entre deciduidade e concentrações foliares de nutrientes em espécies lenhosas do cerrado

Abstract

-(Correlation between deciduousness and foliar nutrient concentrations in the woody species of "cerrado"). The main objective of the present study was to compare the variations in leaf nutrient concentrations among 15 woody species of a "cerrado" sensu stricto belonging to different phenological groups to determine the influence of deciduousness on mineral nutrition. The main hypothesis was that evergreen species would present lower foliar concentrations, less specific leaf area, and smaller seasonal variations than deciduous species, because their leaves would persist beyond one annual cycle of dry and wet season. The study was conducted in a "cerrado" sensu stricto at the "Reserva Ecológica do IBGE" in the Federal District of Brazil. Fully expanded leaves collected from three individuals of each species at two-month intervals for a year were analyzed. Specific leaf area was also determined. The concentrations of N, P, K, Ca and Mg and seasonal variation were lower in the evergreen species than in the deciduous species. Deciduous species showed higher concentrations of N, P and K at the beginning of the rainy season when leaves were recently formed and their concentrations decreased toward the beginning of the next dry season. Concentrations of Ca increased toward the end of the rainy season. Brevideciduous species had lower concentrations of N and P than deciduous species and higher concentrations of N, P and Ca than evergreens. Mean specific leaf area of evergreen species (54.0 cm 2 g -1 ) was smaller than that of deciduous (67.0 cm 2 g -1 ) and brevideciduous species (83.5 cm 2 g -1 ). Specific leaf area was correlated with N and P. Thus there were significant differences not only between evergreen and deciduous species but also between deciduous and brevideciduous species.Key words -"cerrado", mineral nutrition, specific leaf area RESUMO -(Relação entre deciduidade e concentrações foliares de nutrientes em espécies lenhosas do cerrado). O principal objetivo deste estudo foi comparar as variações nas concentrações foliares de nutrientes de 15 espécies lenhosas do cerrado sensu stricto pertencentes a diferentes grupos fenológicos para determinar a influência da deciduidade na nutrição mineral. As principais hipóteses foram que espécies sempre-verdes apresentariam menores concentrações de nutrientes foliares, menor área foliar específica e menor variação sazonal que espécies decíduas porque suas folhas persistem por mais de um ciclo anual de estações seca e chuvosa. O estudo foi realizado em um cerrado sensu stricto na Reserva Ecológica do IBGE no Distrito Federal. Folhas completamente expandidas coletadas de três indivíduos de cada espécie, em intervalos de dois meses durante um ano, foram analisadas. A área foliar específica também foi determinada. A concentração de N, P, K, Ca e Mg e a variação sazonal foram menores nas espécies sempre-verdes do que nas decíduas. Espécies decíduas mostraram as maiores concentrações de N, P e K no inicio da estação chuvosa, época em que as folhas encontram-se recent...

<b>Nutrient retranslocation in forest species in the Brazilian Amazon

“…However, this pattern is not a definite rule because a global analysis of the data from 92 studies conducted in different ecosystems indicated that there are no significant differences between deciduous and non-deciduous species regarding the N and P contents in green and senescent leaves (Kobe et al, 2005). This result may be expected due to the influence of different factors, such as variations even between species from the same phenological group (Wright & Westoby, 2003), phylogeny (plant family) (Villar, Robleto, Jong, & Poorter, 2006) and environment conditions (Franco et al, 2005;Araújo & Haridasan, 2007).…”

“…This is a consequence of some strategies that minimize the nutritional demand and increase nutrient conservation by non-deciduous species, such as low growth rates and higher leaf longevity, allowing them to colonize low-fertility soils (Chapin, 1980;Araújo & Haridasan, 2007). However, this pattern is not a definite rule because a global analysis of the data from 92 studies conducted in different ecosystems indicated that there are no significant differences between deciduous and non-deciduous species regarding the N and P contents in green and senescent leaves (Kobe et al, 2005).…”

“…Therefore, the evaluation of foliar nutrient content is one of the most widely used techniques in forest nutrition research (Araújo & Haridasan, 2007) as leaves are considered the most active and representative organs for plant nutritional status (Malavolta, 2006). Furthermore, foliar nutrient contents are influenced by their availability in the soil (Aerts, 1996).…”

“…Therefore, pioneer tree species present lower nutrient contents in both green and senescent leaves (leaf litter) than the non-pioneer species (Boeger, Wisniewski, & Reissmann, 2005;Pinto, Martins, Barros, & Dias, 2009). Regarding plant phenology, it is known that deciduous or semideciduous plants generally have higher foliar nutrient contents because senescent leaves are lost before the internal retranslocation of nutrients compared with the nondeciduous phenological group in tropical or temperate forests (Aerts, 1996;Aerts & Chapin, 2000;Franco et al, 2005;Araújo & Haridasan, 2007). However, few studies have focused on nutritional retranslocation monitoring in forest plantations in the Amazon, especially related to native species (Magalhães & Blum, 1999).…”

Fenologia da Siparuna guianensis Aublet em dois bosques de preservação ambiental em Cuiabá-MT

“…Uma característica marcante da vegetação lenhosa do Cerrado é a ocorrência de diferentes grupos fenológicos em relação à produção e queda de folhas (ARAUJO; HARIDASAN, 2007;FRANCO et al, 2005;LENZA;KLINK, 2006). Tem sido encontrado que, com o aumento da severidade da estação seca, ocorre maior proporção de espécies decíduas, sendo que a queda foliar ocorre durante essa estação (BATALHA; MANTOVANI, 2000;MIRANDA, 1995;OLIVEIRA, 1998;REICH, 1995;WILLIAMS et al, 1997) e o brotamento, florescimento e frutificação podem ocorrer de maneira menos sazonal, tanto na estação seca como na chuvosa (BATALHA; MANTOVANI, 2000;GOUVEIA;FELFILI, 1998).…”