Alterações morfológicas e fenológicas em gramíneas (Poaceae) do semiárido brasileiro em resposta a mudança climática

Abstract

In recent decades, global warming has raised the temperature of the Earth's surface and oceans by an average of 0.2°C per decade. Between 2006-2015, the global average temperature increased by 1°C compared to 1850-1900, indicating a concerning trend of global warming. Risks associated with climate change are more pronounced with a 1.5°C increase in global temperature. Consequences encompass areas such as human health, food security, water supply, and biodiversity. Anthropogenic climate changes have been linked to a reduction in plant vegetative organs and alterations in flowering times. In semi-arid regions, considered the most vulnerable to climate change, aridity may intensify due to global warming. Grasses in these environments are adapted to stressful conditions like water deficit and droughts. Increased aridity may lead to greater expansion and invasion of grasses in these areas. However, specific morphological responses of grasses to anthropogenic climate changes have not been studied. Consequently, several hypotheses were formulated: (1) grasses in the Brazilian Semi-Arid are adjusting their vegetative and reproductive organs to adapt to climate changes; (2) precipitation plays a central role in morphological changes of annual grasses in the semi-arid region; (3) climate change influences the flowering time of annual grasses in the semi-arid region. To test these hypotheses, 591 specimens of annual grasses from the Brazilian Semi-Arid of four species (Enteropogon mollis, Panicum trichoides, Paspalum fimbriatum, and Paspalum scutatum) were selected from herbaria and digital collections. The average temperature in the Brazilian Semi-Arid increased by 1.89°C between 1960 and 2021. Three species showed a reduction in plant height over the years, while Enteropogon mollis exhibited no continuous directional change. Most species also responded to climate and geographic variables, particularly by increasing reproductive organs as temperature rises, indicating a plastic strategy adapted to semi-arid environments. In phenological analysis, temperature played a crucial role in the flowering time of some grasses. Enteropogon mollis and Paspalum fimbriatum delayed flowering in higher temperatures. Morphological and phenological changes in grasses, crucial as forage species, have the potential to trigger a significant cascading effect. This may impact the availability of resources for herbivores, resulting in substantial ecological imbalance.