Canu A.,University of Sassari |
Scandura M.,University of Sassari |
Merli E.,Wildlife Service |
Chirichella R.,University of Sassari |
And 4 more authors.
Hystrix | Year: 2015
Reproductive synchrony among gregarious mammals has a strong adaptive value and may lead to cooperative behaviors aimed at maximizing offspring survival. Additionally, temporal clustering of estrus has important implications on individual mating tactics and ultimately affects the degree of polygamy in a population. Although several studies have examined the reproductive biology of wild boar (Sus scrofa), much remains to be understood about the patterns of timing and synchrony of reproduction in natural populations. We analyzed the spatiotemporal distribution of conception dates in an Italian wild boar population taking into account the effects of environmental and individual factors, in order to determine the main variables influencing the timing of reproduction and to detect the signs of a socially-driven reproductive synchrony. Specifically, for each litter belonging to 354 pregnant sows culled between 2006 and 2013 in a mountain area of Tuscany, we determined the conception date (CD) from an estimate of the mean fetal age and the culling date. We then investigated which factors drove the variation in CD, by implementing linear mixed models, Mantel tests and spatial autocorrelation analyses. The selected model showed significant effects of rainfall, temperatures, and previous and current productivity on CD, as well as a strong correlation of CDs among sows culled in close spatial and temporal proximity (i.e., in the same hunting ground and hunting season). Likewise, autocorrelation analyses and Mantel tests consistently indicated that closer sows had similar conception dates. Overall, our results confirm the effect of resource availability and climate on wild boar reproductive phenology, and suggest socially-driven reproductive patterns, in spite of a high turn-over in social groups due to hunting. Finally, possible advantages and evolutionary implications of reproductive synchrony in wild boar are discussed. © 2015 Associazione Teriologica Italiana.
Chianucci F.,Research Center for Silviculture |
Chianucci F.,University of Tuscia |
Cutini A.,Research Center for Silviculture
Agricultural and Forest Meteorology | Year: 2013
Rapid, reliable and meaningful estimates of forest canopy are essential to the characterization of forest ecosystems. In this paper the accuracy of digital hemispherical (DHP) and cover (DCP) photography for the estimation of canopy properties in deciduous forests was evaluated. Leaf area index (LAI) estimated from both these photographic methods and from light transmittance data derived from DHP were compared with direct measurements obtained by litter traps (LAILT) and an AccuPAR ceptometer. Also, comparison with different gap fraction methods used to calculate LAI in DHP and LAI-2000 PCA were performed.We applied these methods in four forest stands of Quercus cerris, two stands of Castanea sativa and four stands of Fagus sylvatica, the most common deciduous species in Italy, where LAILT ranged from 3.9 to 7.3. Both photographic methods provided good indirect estimates of LAILT. The DCP method provided estimates of crown porosity, crown cover, foliage cover and the clumping index at the zenith, but required assumptions about the light extinction coefficient at the zenith (k), to accurately estimate LAI. Cover photography provided good indirect estimates of LAI assuming a spherical leaf angle distribution, even though k appeared to decrease as LAI increased, thus affecting the accuracy of LAI estimates in DCP. In contrast, the accuracy of LAI estimates in DHP appeared insensitive to LAILT values, but the method was sensitive to photographic exposure and more time-consuming than DCP.The studied stands were characterized by higher within-crown clumping than between-crowns clumping; only the segmented analysis of gap fraction for each ring of the fisheye images was found to provide reliable and useful clumping index in DHP. The 1-azimuth segment method employed in PCA poorly detected clumping in dense canopies.The correlation between transmittance estimates by DHP with values measured at noon with the AccuPAR ceptometer was linear and significant, although the variability observed in reference measures suggested that results obtained with the ceptometer should be treated with caution.We conclude both photographic methods are suitable for dense deciduous forests. Cover photography holds great promise as a means to quickly obtain inexpensive estimates of LAI over large areas. However, in situations where no direct reference measurements of . k are available, we recommend using both DHP and DCP, in order to cross-calibrate the two methods; DCP could then be used for more routinely indirect measurement and monitoring of LAI. © 2012 Elsevier B.V.
Mazza G.,Research Center for Silviculture |
Mazza G.,University of Tuscia |
Amorini E.,Research Center for Silviculture |
Cutini A.,Research Center for Silviculture |
Manetti M.C.,Research Center for Silviculture
Annals of Forest Science | Year: 2011
Context: This research was conducted in a 62-year-old stone pine (Pinus pinea L.) forest within the National Natural Reserve of the Roman Coast, Italy. Net undercanopy precipitation was measured between September 2004 and December 2008 in a unthinned and a thinned area of about 1 ha each. Aims: The goals were to document and compare net under-canopy rainfall (throughfall and stemflow) in thinned and unthinned stands, and evaluate how the re-growth of tree crowns following thinning influences canopy interception. Methods:Thinning was carried out during the winter of 2002 and reduced the number of trees by 56% and leaf area index (LAI) by 63%. Rainfall, throughfall, and stemflow were measured and analysed.Results: Interception loss averaged 23% and 40% in the thinned and unthinned areas respectively, but difference decreased during larger rainfall events. Net under-canopy precipitation was always higher (P<0.001) in the thinned area, and showed a significant (P=0.041) relationship with LAI. Stemflow was very low. Conclusion: These results highlight the positive effect of thinning, which reduces water loss from precipitation caused by interception of rainfall in Mediterranean forests that have never been thinned. Thinning guarantees a greater flow of water under the canopy, particularly in the driest months and for lower amounts of rainfall, and improves stand growth rates. © 2011 INRA and Springer Science+Business Media B.V.