Experimental evaluation shows limited influence of pine plantations on the connectivity of highly fragmented bird populations

Landscape and microhabitat features determine small mammal abundance in forest patches in agricultural landscapes

Intensification of agricultural landscapes represent a major threat for biodiversity conservation also affecting several ecosystem services. The natural and semi-natural remnants, available in the agricultural matrix, represent important sites for small mammals and rodents, which are fundamental for sustaining various ecosystem functions and trophic chains. We studied the populations of two small mammals (Apodemus agrarius, A. sylvaticus) to evaluate the effects of landscape and habitat features on species abundance along a gradient of agricultural landscape intensification. The study was performed in Friuli Venezia Giulia (north-eastern Italy) during 19 months, in 19 wood remnants. Species abundance was determined using Capture-Mark-Recapture (CMR) techniques. In the same plots, main ecological parameters of the habitat (at microhabitat and patch scale) and landscape were considered. Abundance of A. agrarius increased in landscapes with high extent of permanent crops (i.e., orchards and poplar plantations) and low content of undecomposed litter in the wood understory. Instead, A. sylvaticus, a more generalist species, showed an opposite, albeit less strong, relationship with the same variables. Both species were not affected by any landscape structural feature (e.g., patch shape, isolation). Our findings showed that microhabitat features and landscape composition rather than wood and landscape structure affect populations’ abundance and species interaction. The opposite response of the two study species was probably because of their specific ecological requirements. In this light, conservation management of agricultural landscapes should consider the ecological needs of species at both landscape and habitat levels, by rebalancing composition patterns in the context of ecological intensification, and promoting a sustainable forest patch management.

Effects of landscape transformation on bird colonization and extinction patterns in a large-scale, long-term natural experiment

Conversion of agricultural land to forest plantations is a major driver of global change. Studies on the impact of forest plantations on biodiversity in plantations and in the surrounding native vegetation have been inconclusive. Consequently, it is not known how to best manage the extensive areas of the planet currently covered by plantations. We used a novel, long-term (16 years) and large-scale (30,000 ha) landscape transformation natural experiment (the Nanangroe experiment, Australia) to test the effects of land conversion on population dynamics of 64 bird species associated with woodland and forest. A unique aspect of our study is that we focused on the effects of plantations on birds in habitat patches within plantations. Our study design included 56 treatment sites (Eucalyptus patches where the surrounding matrix was converted from grazed land to pine plantations), 55 control sites (Eucalyptus patches surrounded by grazed land), and 20 matrix sites (sites within the pine plantations and grazed land). Bird populations were studied through point counts, and colonization and extinction patterns were inferred through multiple season occupancy models. Large-scale pine plantation establishment affected the colonization or extinction patterns of 89% of studied species and thus led to a comprehensive turnover in bird communities inhabiting Eucalyptus patches embedded within the maturing plantations. Smaller bodied species appeared to respond positively to plantations (i.e., colonization increased and extirpation of these species decreased in patches surrounded by plantations) because they were able to use the newly created surrounding matrix. We found that the effects of forest plantations affected the majority of the bird community, and we believe these effects could lead to the artificial selection of one group of species at the expense of another.