Breeding success of tree swallows along a gradient of agricultural intensification

The intensification of agricultural practices has been identified as the main cause of population decline in farmland birds since the 1960s in both Europe and North America. Although the links between species richness or abundance and various components of agricultural intensification are well established, the mechanisms underlying these trends have rarely been addressed along a gradient of intensification or have been quantified at only one spatial scale. Here we quantified the influence of landscape structure on the nest box occupancy and breeding success of Tree Swallows (Tachycineta bicolor) at seven spatial scales (1, 2, 3, 4, 5, 10, and 20 km radii) over a 10 200-km2 gradient of agricultural intensification in southern Québec, Canada. A network of 400 nest boxes distributed among 40 farms was visited every two days over three breeding seasons, 2004-2006. Nest box occupancy decreased with the proportion of intensive cultures (maize, cereals, and soybeans) in the landscape, especially when manure heaps and tanks were abundant, and was also determined by local variables (i.e., nest box clearance, interspecific competition) and by previous-year fledging success. Clutch size decreased as the breeding season progressed and with the proportion of intensive cultures in the landscape, with no consistent variation across spatial scales. Hatching success was not related to any landscape variables but increased with clutch size. Both the number of fledglings and fledging probability increased with the proportion of extensive cultures (hayfields, pastures, and fallows). These effects increased with spatial scale and reached a plateau at the 5 km radius: the maximum distance from the nest reached by foraging Tree Swallows. Our results can likely be attributed to lower food availability in intensive cultures compared to extensive ones. This study suggests that several components of breeding that impact on population structure and dynamics of insectivorous birds will be negatively affected by agricultural intensification.     

Competition-colonization trade-offs and disturbance effects at multiple scales

The competition-colonization trade-off has long been a mechanism explaining patterns of species coexistence and diversity in nonequilibrium systems. It forms one explanation of the intermediate disturbance hypothesis (IDH) for local communities--specifically that diversity should be maximized at intermediate disturbance frequencies, yet only a fraction of empirical studies support IDH predictions. Similarly, this trade-off is also a powerful explanation of coexistence at larger spatial scales. I show, with a microbial experimental system, that the diversity-disturbance relationship is dependent on the relative distribution of species along this trade-off. Here I show that, when species are skewed toward late-successional habits, local diversity declines with disturbance. Yet, despite this trait skew, diversity at scales larger than the patch appears insensitive to the trade-off distribution. Intermediate disturbance frequencies produce the greatest diversity in patch successional stage, thus benefiting the maximum number of species at larger scales.     

Future Trends and Mitigation Options for Energy Consumption and Greenhouse Gas Emissions in a Developing Country of the Middle East Region: a Case Study of Lebanon’s Road Transport Sector

The road transport system in Lebanon is one of the most unsustainable in the Middle East region due to, in large part, the absence of a national transportation strategy. This study proposes mitigation measures based on Lebanon’s commitments for reducing fossil fuel use and CO₂ emissions from road transport by increasing the share of fuel-efficient and hybrid electric vehicles and increasing the utilization of the existing bus service. Results show that increasing the market share of fuel-efficient vehicles to 35% in 2040 stabilizes energy use and emissions. The addition of hybrid vehicles to the first strategy, with a target of 10% market share by 2040, leads to 11% additional savings. Increasing the share of bus passenger kilometers traveled to 45% in 2040 leads to a reversal of adverse impacts. A combined strategy of all three measures leads to 63% reductions in 2040 compared to 2010, which is even superior to their cumulative savings.     

The composition,leaching, and sorption behavior of some alternative sources of phosphorus for soils

Concerns about the sustainability of inorganic fertilizers necessitate the characterization of alternative P source materials for agronomic P-efficiencies and P losses via leaching. Firstly, this study examined nutrient compositions including P speciation of seven soil amendments: sewage sludge (SS), anaerobic digestate (AD), green compost (GC), food waste compost (FWC), chicken manure (CM), biochar, and seaweed. Secondly, soil P leaching and availability was studied on a subset of four materials (SS, AD, GC, and CM). Sorption of extracts onto columns of a test soil showed strong P retention for SS and compost, but weak P sorption for CM and especially AD, suggesting short-term leaching risks for soil applied AD. Limited P desorption with water or citrate indicated sorbed P was strongly fixed, potentially limiting crop availability. These data indicate that variation in P forms and environmental behavior should be understood to maximize P usage, but minimize leaching and soil P accumulation. Hence, different alternative P source materials need differing recommendations for their agronomic management.     

Risk Tradeoffs in Adaptive Ecosystem Management: The Case of the U.S. Forest Service

Natural resource planning processes on public lands in the United States are driven in large part by the requirements of the National Environmental Policy Act (NEPA), which dictates general processes for analyzing and disclosing the likely impacts of proposed actions. The outcomes of these processes are the result of multiple factors, many related to the manifold smaller incremental decisions made by agency personnel directing the processes. Through interviews with decision makers, team leaders, and team members on five NEPA processes within the U.S. Forest Service, this study examines those incremental decisions. Risk, in particular external relationship risk, emerged as a dominant lens through which agency personnel weigh and make process-related decisions. We discuss the tradeoffs associated with agency actors’ emphasis on this form of risk and their potential implications for adaptive ecosystem management and organizational performance.