Modern pollen rain in humid tropical mountain forests from eastern Mexico: A patch-dynamics approach

Modern pollen rains have demonstrated that human legacies represent crucial information on the performance of strategies for biological conservation. However, the potential use of pollen rains in aspects related to human disturbance and other cultural processes remains scarcely explored in forest patches of tropical mountain environments. Our study offers an ecological model for stratifying management intensities using moss polster contents in three patches of humid tropical mountain forests from eastern Mexico. Moss polsters were collected at 48 sites between ca. 1600 and 2000 m asl in three Mexican tropical montane cloud forests. Beta diversity, Shannon, and Jaccard indices were calculated for each location. Deciphering palynological data, historical documents, and diversity indicators, we found that the most disturbed patches had the lowest values in the Shannon index (abundance data) and beta diversity (incidence and abundance data) due to intensive agriculture over the last 20 years at least. On the other hand, we found that lower-elevation gradients with a high degree of management intensity and geographical affinity expressed greater similarity according to the Jaccard index for unseen shared species. In contrast, shade-tolerant plants and some hygrophilous trees within the old-growth forest determined the species turnover among higher-elevation gradients in conserved areas. For these reasons, our findings suggest that moss polster contents capture reliable sources of pollen rains around 20 years, as it was once mentioned in the palynological literature. We conclude that pollen rains and management intensity are comparable between ecosystems in long-term approaches and historical legacies.