Tree regeneration under high levels of wild ungulates: The use of chemically vs. physically-defended shrubs

摘要: Abstract Wild ungulate populations have increased dramatically in the last decades, limiting tree regeneration. However, how different types of shrubs (chemically vs. physically-defended) act as seedlings facilitators under damage (browsing or rooting) remains largely unknown. Here, we integrate both biotic and abiotic stress to assess seedling survival three microsites [open, chemically-defended (aromatic) physically-defended (spiny) shrubs]. We studied a Mediterranean oak (Quercus pyrenaica) for two contrasting levels (dry wet growing seasons) environments where deer (Cervidae) wild boar (Sus scrofa) are abundant. After first summer 24.7% were still alive year whereas only 9.0% survived dry year. Seedling was higher shrub cover, independently annual weather conditions type. Shrubs, on average, reduced mortality by ungulates approximately 75% 50% due greater earlier impact browsers (deer) drier years, when preferred food (green grass) is scarce. Physically-defended prevent better than other microsites, reducing 35–59% comparison 70–77% open and, therefore, serve good nurse also worked well defense against at low (wet years) but diminished its efficiency high browsing activity spiny years. Thus, recommend use protectors browsers. Restoration efforts (e.g. reforestation) level should take into account type predominant mechanism herbivores (chemical physical) cover more efficiently future restoration practices.