Responses to nitrogen pulses and growth under low nitrogen availability in invasive and native tree species with differing successional status.

Invasive species are frequently found in recently disturbed sites. To examine how these disturbance-dependent invasive species exploit resource pulses resulting from disturbance, twelve physiological and morphological traits, including age-dependent responsiveness in leaf traits to nitrogen pulse, were compared between Bischofia javanica, an invasive tree species in Ogasawara islands, and three native Ogasawara species, each having a different successional status. When exposed to a nitrogen pulse, invasive B. javanica showed higher increases in photosynthetic capacity, leaf area, epidermal cell number and cell size in leaves of broad age classes, and root nitrogen absorption ability than two native mid-/late or late-successional species, but showed no particular superiority to a native pioneer species in these responses. Under low nitrogen, however, it showed the largest relative growth rate among the four species, while the native pioneer showed the lowest growth. From these results, we concluded that the combination of moderately high responsiveness to resource pulses and the ability to maintain steady growth under resource limitations may give B. javanica a competitive advantage over a series of native species with different successional status from early to late-successional stages.

Differences on post-fire regeneration of the pioneer trees Cecropia glazioui and Trema micrantha in a lowland Atlantic Forest

A study of natural post-fire succession was carried out in a disturbed vegetation around fragments of the Atlantic Rain Forest (National Biological Reserve of Poço das Antas (22° 30’- 22° 33’S, 42° 15’- 42° 19’ W), Rio de Janeiro State). All the pre-fire individuals of Cecropia and Trema in the area were numbered with plastic labels.In order to check for the presence of new sprouts and mortality, two other censuses were carried out, at 3 and 12 months after the fire.The dominant species were:Pteridium aquilinum,Panicum maximum,Trema micrantha and Cecropia glazioui. Few days after the passage of fire, grasses and ferns spread their area,while the stands of Trema and Cecropia were completely burned. Most of individuals of Cecropia produced some sprouts while most of individuals of Trema died.However,a great number of seedlings of Trema were recruited while only one single seedling of Cecropia were observed during a period of one year.Most of these seedlings died through the year while the sprouts were already reproducing.The uses of Cecropia in places where fire is recurrent could be more appropriate because of its higher chance of survival and faster recovering ability after fire

Se realizó un estudio sobre la sucesión natural después del fuego en una vegetación alrededor de fragmentos de la selva lluviosa atlántica (Reserva Biológica Nacional de Poço das Antas (22° 30’-22° 33’ S, 42° 15’- 42° 19’ W), Estado de Río de Janeiro).Todos los individuos de Cecropia y Trema previos del fuego en el área fueron numerados con marcas plásticas. Se realizaron otros dos censos, 3 y 12 meses después del fuego con el objetivo de detectar mortalidad y buscar la presencia de nuevos brotes. Las especies dominantes fueron: Pteridium aquilinum, Panicum maximum, Trema micrantha y Cecropia glazioui. Pocos días después del paso del fuego,los pastos y helechos se dispersaron por el área, mientras que los troncos de Trema y Cecropia estaban completamente quemados. La mayoría de los individuos de Cecropia produjeron algunos rebrotes mientras que la mayoría de los individuos de Trema murieron. Sin embargo, un gran número de plántulas de Trema fueron reclutadas mientras que únicamente una plántula de Cecropia fue observada durante el período de un año. La mayoría de estos plántulas murieron a lo largo del año, mientras que los brotes se estan ya reproduciendo. Los usos de Cecropia en lugares donde el fuego es recurrente puede ser más apropiado debido a su mayor chance de sobrevivir y a su habilidad de recuperarse más rápido después del fuego

Differences on post-fire regeneration of the pioneer trees Cecropia glazioui and Trema micrantha in a lowland Brazilian Atlantic forest.

A study of natural post-fire succession was carried out in a disturbed vegetation around fragments of the Atlantic Rain Forest (National Biological Reserve of Poço das Antas (22 degrees 30'-22 degrees 33'S. 42 degrees 15'-42 degrees 19'W), Rio de Janeiro State). All the pre-fire individuals of Cecropia and Trema in the area were numbered with plastic labels. In order to check for the presence of new sprouts and mortality, two other censuses were carried out, at 3 and 12 months after the fire. The dominant species were: Pteridium aquilinum, Panicum maximum. Trema micrantha and Cecropia glazioui. Few days after the passage of fire, grasses and ferns spread their area, while the stands of Trema and Cecropia were completely burned. Most of individuals of Cecropia produced some sprouts while most of individuals of Trema died. However, a great number of seedlings of Trema were recruited while only one single seedling of Cecropia were observed during a period of one year. Most of these seedlings died through the year while the sprouts were already reproducing. The uses of Cecropia in places where fire is recurrent could be more appropriate because of its higher chance of survival and faster recovering ability after fire.