Successional traits mediate germination responses to grazing: Implications for restoration

Abstract

Understanding how native flora germination responds to disturbances is critical for successful ecological restoration. Germinative traits shared by some species can facilitate their establishment during ecological succession, a process that disturbances, such as grazing can significantly alter. This study explored the mechanisms by which grazing affects the germination features of successional species in Monte Desert, with implications for restoration efforts. We hypothesized that grazing-induced damage to parental plants would decrease germination capacity by limiting reproductive effort and resource allocation to seeds, resulting in lower germination percentage, slower germination, and reduced synchrony with increasing grazing. This hypothesis was tested using both experimental data and a hypothetical causal model. Moreover, life-history traits enable successional species to respond differently to grazing, resulting in different impacts on their germination capacity. Seeds from ten species were collected along a grazing gradient and sown under greenhouse conditions. Overall, grazing had no significant effect neither on germination percentage nor synchrony but increased germination time. The causal model revealed that grazing reduces plant reproduction triggering cascading effects on seed set, seed weight, germination, and germination timing. Grazing delayed germination in early species but accelerated it in intermediate species, while germination synchrony remained unaffected in early and intermediate species, suggesting differential adaptive responses. This study revealed that grazing can indirectly influence desert plant fitness when direct effects seem absent. Understanding these indirect mechanisms is essential to predict dryland vegetation dynamics under grazing pressure and optimizing species selection in restoration and conservation programs.