Effect of grassland mosaic structure and dynamism on the reproductive habitat suitability for Alectoris graeca in central Apennines

Over the last several decades,the Mediterranean region has been subjected to mountain abandonment and farming cessation,leading to changes in vegetation and coenological features of grasslands,contextually to the strong decline of the rock partridge(Alectoris graeca).Our hypothesis was that the ongoing dynamic processes leading to the compositional changes of grasslands in central Apennines affect the habitat suitability for the singing male(territorial male defending its reproductive site).In 2015,we defined the presence/absence of spring territorial singing males in seven sites(1,250-2,400 m a.s.l.),by the census in 74 playback stations,distributed along 15 transects.We characterized the topography and the vegetation mosaic of such sites according to the collected topographic and vegetation cover data in 59 randomly selected plots(100 m×100 m)along the transects.To understand the relations among the environmental variables and the effect of the composition and dynamism of the vegetation mosaics on the presence/absence of the singing male,we used principal components analysis and generalized linear mixed-effect modelling.Our results emphasized the marked overlap between the general environmental conditions,which proved to define the habitat suitability for A.graeca,and the characteristics of the site chosen by the singing male for starting the reproductive activities.Moreover,we found that the site suitability for the singing male decreases when the vegetation recovery processes are ongoing,because of the spread of coarse tall grassesdominated communities and/or grassland types with dense turf.Tall grass-dominated communities and thick-turf grasslands exert their negative effect decreasing the habitat suitability for the singing male starting from low cover values.Therefore,it is conceivable that singing male’s suitable habitat will be dramatically restricted to the steepest south-facing slopes,where topographic and soil conditions do not allow the spread of grasslands with dense turf and of invasive/dominant tall grasses,increasing the threat to the species due to the effect of climate change on the vegetation features.

The interplay of nurse and target plant traits influences magnitude and direction of facilitative interactions under different combinations of stress and disturbance intensities in Andean dry grassland

Aims Facilitation is a key process in vegetation dynamics,driving the response to natural and anthropogenic pressures.In harsh-grazed systems,palatable plants mainly survive when nested under unpalatable tussocks and shrubs.The magnitude and direction of positive interactions are driven by resource availability,extent of herbivory and type of nurse species.We hypothesized that different combinations of disturbance and environmental stress affect community composition in the dry Puna(southern Peruvian Andes)by modifying nurse types and plant interactions in magnitude and specific associations.We investigated whether different combinations of stress and disturbance influence species richness,type and frequency of occurrence of nurse and beneficiary species and magnitude and patterns of plant interactions;whether nurse species influence these interactions and target species change their interactions under different combinations of stress and disturbance and whether plant functional traits differ in the studied communities and influence the pattern of spatial interactions.Methods We selected three plant communities subject to different precipitation and management regimes:in each we laid a number of transects proportional to its extension.Data collected include species presence/absence,type of spatial interactions with nurse species and functional traits.We calculated species richness and rarefaction patterns,described the patterns of plant-plant spatial interactions and investigated the associations between nurse and other species in the three communities using indicator species analysis(ISA).We performed ISA and correlation analysis to investigate whether plant functional traits influenced facilitative interactions.Important Findings We found that different combinations of stress and disturbance shaped a complex set of responses,including changes in the nurse species set.Nurse composition influenced magnitude and direction of plant interactions under different stress intensities.Heavy disturbance increased the relative importance of facilitation,even if the overall number of facilitated species decreased.Under equivalent disturbance regimes,increased abiotic stress led to a greater importance of facilitation.Different combinations of stress and disturbance affected the community assemblage also by changing the behaviour of some non-nurse species.Both heavy disturbance and strong stress led to a decrease of trait states;with certain combinations of stress and disturbance,preferential distribution of these states was observed.We also found that plant traits were of key importance in determining facilitative interactions.Some traits were mainly associated with one type of spatial interaction:plant architecture,life cycle and root type influenced the type of interaction between nurses and beneficiaries under different combinations of stress and disturbance.Our results also demonstrate that in plant interaction research the object of observations(species per se,species percentage,etc.)might influence outputs,and to effectively assess the impact of different stress and disturbance intensities on plant interactions it is necessary to work at the community level to consider the whole species pool.