Effect of inter‐annual meteorological fluctuations and wild boar disturbance on the vegetation of Mediterranean temporary ponds

Abstract

Questions Which are the effects of inter‐annual meteorological fluctuations on plant species richness and vegetation dynamics in Mediterranean temporary ponds, shallow wetlands characterized by alternating phases of drought and flooding? Which are the effects of wild boar disturbance? How do the responses of specialist or non‐specialist species of the habitat differ? Location NW Sardinia Island (Italy). Methods We assessed plant cover during six years within one 60 cm × 60 cm quadrat in each of five areas. To measure the effect of inter‐annual meteorological fluctuations on vegetation, we used two indices: the evapotranspiration and the synthetic agrometeorological indicator. To quantify the effect of disturbance by boars, we compared two treatments: disturbed and non‐disturbed (located outside and inside 1.5 m × 1.5 m exclosures respectively). As a whole, we monitored 60 plots (6 years × 2 treatments × 5 replications). We analyzed data using ANOVA, PERMANOVA and BIO‐ENV. Results Plant species richness and composition showed significant differences between years and treatments. Species composition was correlated with the evapotranspiration before the vegetative peak during the last period and with the agrometeorological indicator during the whole vegetative period. Specialist species showed much weaker growth, quantified as cover, in the drier years. Starting from the third survey year, plant richness and cover of specialist species were significantly higher in disturbed than in not‐disturbed plots. The extent of bare soil generally was not affected by the treatment. Conclusions Meteorological fluctuations affect plant species composition and vegetation dynamics in Mediterranean temporary ponds. The sensitivity of specialist species could make them particularly vulnerable to climate change. Nevertheless, they are resilient to unpredictable disturbances such as burrowing by wild boar. However, our results concerning the positive impact of wild boar disturbance on the vegetation cannot be generalized. Elsewhere, the lack of hunting activity could also be a problem for these habitats.

Impact of Horse Grazing on Floristic Diversity in Mediterranean Small Standing-Water Ecosystems (SWEs)

“…Generalist species are the ecological types that dominated in large SWEs, whereas, in small and undisturbed SWEs, generalist and specialist species achieved the same average coverage values. This finding differs from that reported in Caria et al [18], which showed that specialist species had the highest overall cover, in addition to being significantly higher in disturbed than in not-disturbed areas. It is noteworthy that, despite such differences in the coverage, specialist species recorded similar values in both different sizes and treatments of SWEs.…”

“…Overall, the main biological form recorded in both large and small SWEs was therophytes, in agreement with previous studies [43]. In these environments, in fact, the cover of therophytes is linked to their very short life cycles, which are considered an adaptation to survive fluctuations in water availability [18,44,45]. Conversely, differences in coverage of biological form were found based on the level of disturbance; in undisturbed areas, the therophytes dominated, whereas, in disturbed and over-disturbed situations, hemicryptophytes reached the main cover percentage, slightly exceeding the value of therophytes.…”

“…It is noteworthy that, despite such differences in the coverage, specialist species recorded similar values in both different sizes and treatments of SWEs. Consistent with results achieved by Deil [49] and Caria et al [18], such relative stability of specialist species seems to be related to their adaptation (short life cycle, large perennial seedbanks, phenotypic plasticity) to the harsh conditions encountered in the temporary ponds. A similar trend in cover percentage was detected for the three ecological types of species in small and in undisturbed SWEs.…”

“…In this study, the floristic diversity of SWEs and the impact of the disturbance associated with the presence of wild horses on floristic diversity in small standing-water ecosystems was analyzed. Although some studies indicated a positive effect of traditional grazing on plant diversity [27,35,40] and species richness [18] in Mediterranean SWEs, in this study, a greater species richness was found in small and undisturbed SWEs, and the same pattern was also recorded for mean values of floristic richness. This result suggests horse grazing has a negative impact on the richness of plant species in this type of habitat.…”

“…Such phenomenon may cause irreparable damage to the hydrologic cycle of Mediterranean SWEs [13][14][15][16]. Nevertheless, some studies highlighted that the intensity and frequency of the disturbances generated by alternative phases of flooding and dry stages allow the presence and stable growth of plant species in many Mediterranean SWEs [17,18], indicating a certain resilience to these changes [10,19]. The interaction of all these threats has a general negative effect on freshwater habitats [10], and on the specialized vascular flora that colonizes SWEs.…”