Endozoochory of a dry fruited tree aids quarry passive restoration and seed soaking further increases seedling emergence

Abstract

As more work assert passive restoration as a complementary approach to technical reclamation, it is imperative to know its drivers. Although the consequences of endozoochory are crucial to predict passive restoration success, few experimental studies assess the use of heavily disturbed sites by seed dispersers such as carnivores and how the seeds they bring in emerge and survive. Using an indoor sowing experiment conducted in situ, we examined for the first time how carnivore endozoochorous seeds collected in a quarry potentially influence its passive restoration, through effects on plant emergence and survival. Also, we tested whether sowing date and water soaking, relevant factors when sowings are to be carried out, would affect seedling emergence and survival rates when compared with the effect of endozoochory. Most interesting in our analysis were the results for Carob tree (Ceratonia siliqua), a dry-fruited species being used in an ongoing action of artificial revegetation of this quarry located within a natural park in Portugal. Irrespective of the carnivore species, endozoochorous carob seeds collected in the quarry performed similarly to untreated seeds regarding emergence rates. Endozoochorous carob seedlings showed greater mortality rates but the net result for the plant can still be the colonization of recently vacant habitats by a large proportion of viable seeds. The later carob seeds were sown, the faster seedlings emerged, including endozoochorous seedlings. As expected, water soaking implied faster emergences. Broadly, plantings, sowings with previous soaking, and carnivore-mediated seed dispersal of this dry-fruited tree can jointly enhance quarry restoration. Implications for practiceO_LIRestorers can undertake pilot sowing experiments similar to ours prior to large scale revegetation campaigns to identify which species can benefit the most from endozoochory. C_LIO_LICarnivores in the surroundings of a quarry contribute a large proportion of viable seeds, likely assisting quarry passive restoration. C_LIO_LICarnivores ingesting carob seeds later in the fruiting season may assist quarry passive revegetation more readily as seeds ingested around that time emerge earlier. C_LIO_LIImmersion in tap water seems to be a simple, inexpensive, and a highly efficient method to break physical dormancy when carob seed sowings are to be carried out in degraded sites. C_LI