Old-growth tropical forests harbor an immense diversity of tree species but are rapidly being cleared, while secondary forests that regrow on abandoned agricultural lands increase in extent. We assess how tree species richness and composition recover during secondary succession across gradients in environmental conditions and anthropogenic disturbance in an unprecedented multisite analysis for the Neotropics. Secondary forests recover remarkably fast in species richness but slowly in species composition. Secondary forests take a median time of five decades to recover the species richness of old-growth forest (80% recovery after 20 years) based on rarefaction analysis. Full recovery of species composition takes centuries (only 34% recovery after 20 years). A dual strategy that maintains both old-growth forests and species-rich secondary forests is therefore crucial for biodiversity conservation in human-modified tropical landscapes.

The nutrient demands of regrowing tropical forests are partly satisfied by nitrogen-fixing legume trees, but our understanding of the abundance of those species is biased towards wet tropical regions. Here we show how the abundance of Leguminosae is affected by both recovery from disturbance and large-scale rainfall gradients through a synthesis of forest inventory plots from a network of 42 Neotropical forest chronosequences. During the first three decades of natural forest regeneration, legume basal area is twice as high in dry compared with wet secondary forests. The tremendous ecological success of legumes in recently disturbed, water-limited forests is likely to be related to both their reduced leaflet size and ability to fix N, which together enhance legume drought tolerance and water-use efficiency. Earth system models should incorporate these large-scale successional and climatic patterns of legume dominance to provide more accurate estimates of the maximum potential for natural nitrogen fixation across tropical forests.

Diversity of gall-inducing insects in the tropical dry forest (caatinga) of Pernambuco. We report on the richness of galling insects in the vegetation of caatinga of Pernambuco state, Brazil. We recorded 64 different types of galls collected primarily from leaves and stems of 48 species of host plants belonging to 17 families and 31 genera. The most common gall morphological types were spheroid and discoid, glabrous, predominantly green and with one chamber. The main gall inducing taxon was the Cecidomyiidae (Diptera). The results of this study contribute to existing knowledge of galling insect and host-plant diversity in caatinga.
Diversidade de insetos indutores de galhas na floresta tropical seca (caatinga) de Pernambuco. Este artigo reporta sobre a riqueza de insetos galhadores na vegetação de caatinga de Pernambuco, Brasil. Foram registrados 64 diferentes tipos de galhas coletadas principalmente em folhas e caules de 48 espécies de plantas hospedeiras pertencentes a 17 famílias e 31 gêneros. Os tipos morfológicos de galhas mais comuns foram esferóide e discóides, glabro, predominantemente verde e com uma câmara. O principal táxon indutor de galhas foi Cecidomyiidae (Diptera). Os resultados deste estudo contribuem para o conhecimento da diversidade de insetos galhadores e planta-hospedeira na caatinga

Biodiesel is an alternative to petroleum diesel fuel. It is a renewable, biodegradable, and nontoxic biofuel. Interest in the production of biodiesel from Jatropha curcas L. seeds has increased in recent years, but the ability of J. curcas to grow in salt-prone areas, such as the Caatinga semiarid region, has received considerably meager attention. The aim of this study was to identify the main physiological processes that can elucidate the pattern of responses of J. curcas irrigated with saline water, which commonly occurs in the semiarid Caatinga region. This study measured the activity of the antioxidant enzymes involved in the scavenging of reactive oxygen species, which include catalase (CAT) and ascorbate peroxidase (APX), as well as malondialdehyde (MDA) levels. The levels of chlorophyll (Chl), carotenoids, amino acids, proline, and soluble proteins were also analyzed. The net carbon assimilation rate (P N ), stomata conductance (g s ), and transpiration rate (E) decreased with salt stress. The activities of CAT and APX were decreased, while H 2 O 2 and MDA levels as well as electrolyte leakage were significantly increased in salt-stressed plants compared to the untreated ones. These observations suggest that the ability of J. curcas plants resist to salt stress is associated with the activities of protective enzymes and their defensive functions. However, our results indicate that the reactive oxygen species scavenging system is not sufficient to protect J. curcas leaves against oxidative damage caused by salt stress, and, therefore, it cannot be treated as a salt tolerant plant species.

No abstract

The effects of osmolytes, osmotic potential (Ψs), temperature, and their interactions on the germinability, germination rate, and other germination parameters of the invasive shrub Prosopis juliflora, which grows in the semiarid environmental conditions of the Caatinga in northeast Brazil, were evaluated. To study the effects of polyethylene glycol (PEG) and NaCl stress and temperature on germination, two separate experiments were carried out at the Plant Ecophysiology Laboratory of the Federal University of Pernambuco in 2011. The overall germinability decreased significantly with increases in both PEG (one-way ANOVA, F4,75 = 111.21, P ≤ 0.001) and NaCl (one-way ANOVA, F4,75 = 12.82, P ≤ 0.001); however, the effects were more accentuated with PEG than NaCl. The PEGtreated seeds maintained their germinability, even when they were subjected to a Ψs = −1 MPa after being rinsed and allowed to germinate on deionized water. In contrast, NaCl-treated seeds usually lost their ability to germinate; this fact was possibly linked to the accumulation of Na + and Cl − in the cells, which may have contributed to a loss of membrane function that led to the death of the embryos. Although numerous studies describing seed germination in the presence of osmolytes have been conducted, studies that show the interactions between osmolytes, osmotic potentials, and temperature are scarce. The present study is the first to describe these interactions for P. juliflora seeds.

RESUMO -Insetos indutores de galhas, também denominados cecidógenos, são considerados mais especializados por possuírem interação direta com tecidos internos da planta, modificando-os em seu benefício e tornando-se mais dependentes da espécie hospedeira. Este estudo investigou a fauna de insetos galhadores em espécies hospedeiras da Caatinga, em ambientes com diferentes intensidades de ação antrópica. As áreas foram selecionadas de acordo com uma escala de sucessão ecológica (preservadas, intermediárias e antropizadas), sendo três réplicas de cada, totalizando nove áreas. Em cada área foram amostradas oito parcelas de 10 m 2 cada, distanciadas 10 m entre si. Foram encontrados 25 morfotipos de galhas distribuídos em 18 espécies hospedeiras pertencentes a oito famílias vegetais. Fabaceae foi a família com maior riqueza de galhas, com seis morfotipos, sendo Caesalpinia pyramidalis Tul. a espécie com maior número de galhas, com quatro morfotipos. Em relação aos órgãos atacados, 68% das galhas ocorreram em folhas, 28% em ramos e 4% em botões florais. A maioria das galhas encontradas ocorreu isoladamente (84%), glabra (56%) e de formas esféricas (32%), amorfas (28%), discoides (12%) e globoides (12%). No estrato arbóreo foi encontrada a maior riqueza de galhas, com 16 morfotipos, seguido do estrato arbustivo e herbáceo, respectivamente com sete e dois morfotipos. A riqueza de galhas sofreu influência do grau de conservação das áreas, e houve diferenças entre os ambientes preservados e antropizados.Palavras-chave: Impacto ambiental, Bioindicadores e Herbivoria. (12%). The greatest richness of galls was found in the tree layer, with sixteen morphotypes followed by shrub (7) and herbaceous (2). The richness of galls was influenced by the degree of conservation of the studies areas. There were differences between the preserved and anthropic areas. THE INSECT GALL RICHNESS IN PRESERVED AND ANTHROPIC AREAS OF CAATINGA

An inventory of gall inducing insects and their host plants in the Atlantic forest of Pernambuco, northeastern Brazil is presented. Samples of galls and their host plants were taken in six fragments of Atlantic forest. One hundred thirty-six different morphotypes of insect galls on 79 host plant species belonging to 35 plant families and 53 genera were recorded. The host plant families most attacked by galling insects were: Lecythidaceae, Myrtaceae, and Nyctaginaceae. The most frequent galling taxa were Diptera of the Cecidomyiidae family (95%), followed by Lepidoptera and Coleoptera. Galls occurred most frequently on leaves and stems, had globoid and elliptical shapes, green color and absence of trichomes on the external walls. The data indicate an intermediary richness of gall inducing insects when compared to other Brazilian Atlantic forests.