Aridity mediates the effect of wood extraction on the reproductive output of an endemic disturbance‐adapted woody species (Cenostigma microphyllum, Leguminosae) in the Caatinga dry forest

Abstract

Chronic anthropogenic disturbances and climate change have been recognized as drivers of biological reorganization across human‐modified tropical landscapes, also negatively affecting the reproductive output of some plant species. Here, we investigated to what extent these drivers affect the reproductive output of Cenostigma microphyllum, a disturbance‐adapted tree species endemic to the Caatinga dry forest. The production of flowers/inflorescence, fruits and seeds was estimated for 105 plants (≥3 cm diameter at soil height) across 11 forest stands (20 × 50 m each), covering gradients of chronic disturbances (e.g. goat and livestock herbivory; wood extraction; and removal of non‐timber forest products) and aridity at the Catimbau National Park. We documented that when the drivers were analysed in isolation, the fruit‐set was positively associated with increased wood extraction, and the fruit‐set and total number of seeds/plots were reduced under increasing aridity. We also verified a complex interaction between wood extraction and aridity emerged. In forest stands, the combination of high levels of aridity and wood extraction leads to a decrease in the fruit‐set and total number of seeds/plots. Conversely, the fruit‐set and total number of seeds/plots increased in stands exposed to lower aridity but high levels of wood extraction. Our results suggest that chronic disturbances and aridity affect plant fitness in a complex way including both negative and positive effects on attributes related to plant reproductive performance, which could result in both proliferation and population decline in the same landscape. Although C. microphyllum benefits from anthropogenic disturbances and is considered a disturbance‐adapted species, it apparently does not benefit from increases in aridity, which is an expected future scenario for the Caatinga dry forest.

Divergent effects of leaf‐cutting ant herbivory and soil engineering on the reproductive success of plants in a Caatinga dry forest

“…Limited water availability, as observed during the study period, may thus result in flower and fruit production of plants with ant herbivory not differing from control plants. Although C. pyramidale can tolerate water stress (Ribeiro et al, 2021) and is even recognised as a disturbance‐adapted species (Ribeiro et al, 2015; Ribeiro‐Neto et al, 2016), it has been observed that open and desiccated conditions due to increased aridity combined with human disturbance negatively affect the reproduction of the closely related and co‐occurring species Cenostigma microphyllum (Oliveira et al, 2022). Thus, it seems that even disturbance‐adapted species can have their reproductive success negatively affected in scenarios of very severe environmental conditions.…”