Maria L. Arosa

Throwing the baby out with the bathwater: does laurel forest restoration remove a critical winter food supply for the critically endangered Azores bullfinch?

The invasive Clethra arborea has a dual-role in the diet of the Azores bullfinch, a critically endangered bird species endemic to the island of São Miguel (Azores, Portugal). This is a crucial winter food resource but it lowers the availability of native laurel forest species that compose most of the bird’s diet throughout the year. The removal of this and other invasive alien species is part of current laurel forest habitat restoration programmes, disregarding the impact on the Azores bullfinch population. In order to evaluate the first responses of the Azores bullfinch to habitat restoration, we studied bird diet, foraging behaviour, food availability and habitat occupancy in managed (without C. arborea) and control areas. Significant increases in the availability of native food resources in managed areas were noticeable in the diet, particularly the intake of Ilex perado ssp. azorica and Prunus lusitanica ssp. azorica flower buds. In most of the studied months birds heavily used and foraged in managed over control areas. The one exception was in December, when a resource-gap occurred in managed areas, which may be overcome in the short-term due to re-establishment of native plants following removal of invasive aliens.

Spore Maturation and Release of Two Evergreen Macaronesian Ferns, Culcita macrocarpa and Woodwardia radicans, along an Altitudinal Gradient

Abstract The variables affecting spore phenology have been poorly studied in contrast with the abundant literature on leaf phenology. This paper deals with the influence of altitude and canopy cover on spore maturation and release of Culcita macrocarpa and Woodwardia radicans in the island of São Miguel, Azores. The study was conducted during one sporing season at three altitudes (400, 600, and 800 m). In both species spore maturation occurred in autumn and may be controlled by the previous accumulation of photosynthates. Spores were not released until late winter owing to a requirement for dry weather conditions. Dispersal took place later at higher altitude, due to lower temperature and higher humidity. This gradual liberation of spores along an altitudinal gradient is important for the endemic Azores bullfinch Pyrrhula murina (a bird that feeds on spores in winter), providing food over an extended period.

Factors affecting cork oak (Quercus suber) regeneration: acorn sowing success and seedling survival under field conditions

Background: The lack of regeneration of cork oak (Quercus suber) is putting at risk the conservation of the montado. Biotic and abiotic factors as well as management are thought to constrain regeneration. Aims: Identify limitations to regeneration during the early stages and relate them to management practices. Methods: Experimental burying of acorns was carried out at three distinctly managed montados. Cache predation, seedling emergence, survival and resprouting were monitored during the first year. Regeneration was evaluated by testing the effect of biotic and abiotic factors in each stage. Results: Regeneration was determined by temperature and relative humidity. Early emerged seedlings showed higher drought tolerance and resprouting ability. Bigger acorns and higher plant cover significantly assisted emergence, survival and resprouting. Mortality causes were drought (38%) and mechanical ploughing (33%), while cache predation and browsing on seedlings were low (1.7%, when excluding tag effect on cache predation, and 0.6%, respectively). Seedling emergence and survival of drought were significantly lower in the most disturbed site than in the other two sites. Conclusions: Abiotic factors restrain regeneration while acorn size and plant cover are key factors determining seedling emergence and survival. The lack of regeneration may be overcome in the short term by preserving the shrub layer. Moreover, reforestation by direct sowing should be also considered.

Leaf decomposition of cork oak under three different land uses within a montado of southern Portugal

This study compared litter decomposition dynamics of cork oak at three sites under different land-uses (grassland, shrubland and woodland), in a montado ecosystem in Southern Portugal. The montado is a protected habitat within the EU Habitats Directive, but the long-term persistence of cork oak is endangered in these ecosystems, with health of poor cork oak and low natural regeneration rates being the main causes of degradation. Moreover, human management has resulted in the conversion of woodlands to grasslands and may have long-term effects on soil nutrient availability, eventually modifying soil nutrient budgets. Knowledge of the ecological processes is therefore relevant for ecosystem management and species conservation. In the study, the estimated amount of leaf fall from cork oak showed no significant differences between land uses, despite the positive influence of tree crown size on leaf fall. Decomposition was affected by season, vegetation cover, leaf thickness and litter quality. Differences in land use that exposed soil to harsh climate conditions negatively affected soil microbial dynamics, resulting in lower decomposition rates in the more disturbed sites with lower canopy cover.

Temporal effects dominate land use as factors affecting soil nematode communities in Mediterranean oak woodlands

We analysed the soil nematode community within three different montados (agricultural, pastoral and forestry uses), focusing on temporal variation. Nematodes were classified into trophic groups (bacterivores, fungivores, omnivores, predators and plant-parasitic nematodes (PPN)) and we calculated the maturity index for free-living taxa (MI), maturity index for plant-parasitic taxa (PPI) and the nematode channel ratio (NCR). Temporal variations were most evident during winter when there was a rise in the abundance of the five functional groups. Concordantly, there was a simultaneous increase of soil moisture and organic matter, due to litter decomposition. Fungivore abundance was highest in the forest and the temporal occurrence and abundance of many PPN genera was largely determined by land use. Land management was responsible for differences in plant community structure and composition, thus plant diversity increased from the agricultural to the forestry use. Because the montado shows great temporal variability in vegetation structure our results of MI, PPI and PPI/MI ratio explain the significant changes in the nutritional status over time, with the highest values recorded in the spring. NCR is a good indicator of energy efficiency in the soil decomposition process. Its lowest values were attained in the forest, where the slow-growing plant species favoured a lower activity of the bacterial energy channel and a prevalence of the fungal-based decomposition energy channel. Nematode composition reflected plant succession, changes in decomposition in the soil food web and temporal variations in the structure of soil.