Resumo Biological soil crusts (biocrusts) são componentes importantes em regiões áridas e semiáridas, comumente associados à facilitação da flora vascular. Os biocrusts em afloramentos rochosos da Caatinga, no semiárido nordestino, são representados principalmente por populações do musgo pioneiro Campylopus lamellatus. Entretanto, a Caatinga está sob progressivo processo de desertificação, que deve se prolongar pelos próximos 100 anos. Assim, entender a resposta fisiológica de C. lamellatus sob um cenário de mudanças climáticas, deve basear previsões sobre o rumo da flora de ambientes rochosos em cenário futuro. Aqui, nós avaliamos uma população do musgo C. lamellatus durante o efeito prolongado de seca, causado pelo El Niño, e durante a primeira estação chuvosa após o fenômeno. Nós utilizamos a biomassa (massa seca) e proporção de clorofilas como medidas de vigor. Nós identificamos a diminuição do investimento em alocação de biomassa e a degradação dos pigmentos fotossintéticos durante o evento de seca. Em contrapartida, constatamos o rápido aumento das clorofilas durante a estação chuvosa, i.e., investimento em biomassa via regeneração de clorofilas. Desse modo, nós concluímos que a resiliência do C. lamellatus é rápida até mesmo para uma planta fotófila, o que deve assegurar sua função facilitadora em condições de saturação ambiental.

Abstract Biological soil crusts (biocrusts) are important biological components in arid and semi-arid regions because they can serve as ecological facilitators for the vascular flora. Biocrusts of rocky outcrops of the Caatinga biome in the semiarid region of Northeast Brazil are comprised mainly of populations of the pioneer moss Campylopus lamellatus. Meanwhile, the Caatinga is undergoing progressive desertification, which is likely to continue for the next 100 years. Therefore, the physiological responses of C. lamellatus to climate change should be included in predictions regarding the future of the flora of these rocky environments. We evaluated a population of C. lamellatus during a prolonged drought brought about by El Niño, and during the first subsequent rainy season. We used biomass (dry mass) and proportion of chlorophyll as measures of tolerance. We identified decreased investment in biomass allocation and the degradation of photosynthetic pigments during the drought event. In contrast, we observed a rapid increase of chlorophyll during the rainy season, which represents biomass investment via chlorophyll regeneration. We conclude that the resilience of C. lamellatus is rapid, even for a photophilic plant, and should ensure its facilitative function under conditions of water saturation of the environment.

ABSTRACT The species-area relationship (SAR) is one of the oldest and most studied ecological models, having even served as the foundation of the Theory of Island Biogeography. Nevertheless, the relative importance of habitat heterogeneity to SAR remains poorly understood. Our aim was to test the relative importance of habitat heterogeneity to the SAR of bryophyte assemblages of soil islands of rocky outcrops in the semi-arid region of Brazil. We randomly selected 15 to 20 soil islands on each of four outcrops for a total of 59 soil islands, and calculated the area, mean depth, and number of substrates for each. We used Generalized Linear Models (GLM) to test the SAR with two models, one using species richness and another using life-form richness as the dependent variables. We found no positive relationship between area and habitat heterogeneity, nor any evidence of a SAR, such as a positive relationship between area and species or life-form richness neither between habitat heterogeneity and species richness. However, our findings did show that life-form richness is related to bryophyte species richness on the soil islands. We conclude by suggesting that not only can microclimate influence bryophyte richness, but opportunistic colonization by bryophytes is also important.

In the state of Paraíba, Brazil, there is an abundance of rocky outcrops, which are typical elements of the semi-arid landscape. Those outcrops provide refuge to species with morphological adaptations to stressful climates and to rare communities of plants, including bryophytes. Nevertheless, there have been no studies of bryophytes in such habitats in the state. Therefore, this work aimed to inventory bryophytes on two outcrops in the municipality of Puxinanã, in Paraíba, addressing some of the ecological aspects of survival in xerophytic environments. Samples were collected once every two weeks from February 2010 to May 2011. The usual techniques of bryophyte sampling and herbarium preservation were employed. We recorded 21 bryophyte species (six liverworts and 15 mosses), some of which are rare for Brazil. We performed cluster analysis, using the unweighted pair group method with arithmetic mean, based on the Sørensen similarity index. We thus defined three clusters among the studied outcrops and similar areas recorded in the literature. The rocky outcrops proved to be singular in terms of bryophyte species composition, which, as in most xerophytic environments, included light-demanding and generalist species, featuring various morphological adaptations to resist water stress, primarily in terms of their leaf structure. Our results demonstrate the urgent need for additional studies in the state of Paraíba, including floristic, conservation, evolutionary and biogeographic studies.