A systematic quantitative review of urban tree benefits,costs, and assessment methods across cities in different climatic zones

Urban trees can potentially mitigate environmental degradation accompanying rapid urbanisation via a range of tree benefits and services. But uncertainty exists about the extent of tree benefits and services because urban trees also impose costs (e.g. asthma) and may create hazards (e.g. windthrow). Few researchers have systematically assessed how urban tree benefits and costs vary across different cities, geographic scales and climates. This paper provides a quantitative review of 115 original urban tree studies, examining: (i) research locations, (ii) research methods, and (iii) assessment techniques for tree services and disservices. Researchers published findings in 33 journals from diverse disciplines including: forestry, land use planning, ecology, and economics. Research has been geographically concentrated (64% of studies were conducted in North America). Nearly all studies (91.3%) used quantitative research, and most studies (60%) employed natural science methods. Demonstrated tree benefits include: economic, social, health, visual and aesthetic benefits; identified ecosystem services include: carbon sequestration, air quality improvement, storm water attenuation, and energy conservation. Disservices include: maintenance costs, light attenuation, infrastructure damage and health problems, among others. Additional research is required to better inform public policy, including comparative assessment of tree services and disservices, and assessment of urban residents and land managers’ understanding of tree benefits and costs.     

Spatial dynamics of the knob-tailed gecko Nephrurus stellatus in a fragmented agricultural landscape

In fragmented landscapes, a species?? dispersal ability and response to habitat condition are key determinants of persistence. To understand the relative importance of dispersal and condition for survival of Nephrurus stellatus (Gekkonidae) in southern Australia, we surveyed 92 woodland remnants three times. This gecko favours early post-fire succession conditions so may be at risk of extinction in the long-unburnt agricultural landscape. Using N-mixture models, we compared the influence of four measures of isolation, patch area and two habitat variables on the abundance and occurrence of N. stellatus, while taking into account detection probability. Patch occupancy was high, despite the long-term absence of fire from most remnants. Distance to the nearest occupied site was the most informative measure of patch isolation, exhibiting a negative relationship with occupancy. Distance to a nearby conservation park had little influence, suggesting that mainland?Cisland metapopulation dynamics are not important. Abundance and occurrence were positively related to ?%-cover of spinifex (Triodia), indicating that niche-related factors may also contribute to spatial dynamics. Patterns of patch occupancy imply that N. stellatus has a sequence of spatial dynamics across an isolation gradient, with patchy populations and source-sink dynamics when patches are within 300?m, metapopulations at intermediate isolation, and declining populations when patches are separated by >1?C2?km. Considering the conservation needs of the community, habitat condition and connectivity may need to be improved before fire can be reintroduced to the landscape. We speculate that fire may interact with habitat degradation and isolation, increasing the risk of local extinctions.     

Radio-telemetry as a tool to define protected areas for seabirds in the marine environment

Although most Manx shearwaters (Puffinus puffinus) in the UK are protected within Special Protection Areas (SPAs) at their breeding colonies, such site-based protection does not currently extend into the marine environment. Manx shearwaters form rafts (dense flocks of birds) on the sea adjacent to their breeding colony from late afternoon onwards, before coming ashore after nightfall. The ecological and protection requirements of Manx shearwaters in the UK would be more completely addressed if existing SPA boundaries were extended into adjacent marine areas to include those used for rafting behaviour. However the spatial extent of rafts has never been assessed accurately. Because rafting behaviour continues after nightfall, radio-telemetry was used to investigate rafting distributions of Manx shearwaters around the three largest UK colonies: Skomer (south-west Wales), Bardsey (north-west Wales) and Rum (north-west Scotland). Totals of 30, 28 and 30 birds were radio-tagged, with 174, 264 and 385 rafting locations estimated for Skomer, Rum and Bardsey, respectively. Kernel contour analysis was used to describe the ‘rafting range’ around each colony. The maximum extent of the 95% kernel contours was used to determine the area which would encompass most rafting birds. The maximum extents of rafting ranges were 4, 6 and 9 km, respectively for Skomer, Rum and Bardsey. We believe this is the first successful illustration of how radio-telemetry data can potentially be used to define protected areas for birds in the marine environment.     

Soil carbon saturation: Implications for measurable carbon pool dynamics in long-term incubations

The efficiency of agricultural management practices to store SOC depends on C input level and how far a soil is from its saturation level (i.e. saturation deficit). The C saturation hypothesis suggests an ultimate soil C stabilization capacity defined by four SOM pools capable of C saturation: (1) non-protected, (2) physically protected, (3) chemically protected and (4) biochemically protected. We tested if C saturation deficit and the amount of added C influenced SOC storage in measurable soil fractions corresponding to the conceptual chemical, physical, biochemical, and non-protected C pools. We added two levels of ¹³C-labeled residue to soil samples from seven agricultural sites that were either closer to (i.e., A-horizon) or further from (i.e., C-horizon) their C saturation level and incubated them for 2.5 years. Residue-derived C stabilization was, in most sites, directly related to C saturation deficit but mechanisms of C stabilization differed between the chemically and biochemically protected pools. The physically protected C pool showed a varied effect of C saturation deficit on ¹³C stabilization, due to opposite behavior of the POM and mineral fractions. We found distinct behavior between unaggregated and aggregated mineral-associated fractions emphasizing the mechanistic difference between the chemically and physically protected C-pools. To accurately predict SOC dynamics and stabilization, C saturation of soil C pools, particularly the chemically and biochemically protected pools, should be considered.     

Interactions between flavan-3-ols and poly(L-proline) studied by isothermal titration calorimetry: effect of the tannin structure

Interactions of proline-rich proteins (PRPs) with flavan-3-ols was studied using poly(L-proline) as a model protein by means of isothermal titration calorimetry (ITC). Several parameters were varied: (i) the galloylation and B-ring trihydroxylation of the flavan-3-ols (catechin, epicatechin, epicatechin gallate, and epigallocatechin gallate) and (ii) the degree of polymerization (monomers were compared to a mixture of oligomers with average degree of polymerization of 3.85). Large differences were observed between the flavan-3-ol monomers: no enthalpy change was measured when catechin and epicatechin were titrated by poly(L-proline), whereas thermodynamic parameters were determined in the case of galloylated monomers and mixture of oligomers. Stoichiometry ranged from 1 oligomer bound for each 12 proline units to 1 galloylated monomer for each 8 or 10 proline units. Association constants were in the range of 10(4)-10(5) M(-1), indicating a relatively high affinity of galloylated flavanols toward poly(L-proline), and the coexistence of both enthalpy- and entropy-driven phenomena was suggested. Finally, the binding of grape seed tannins to proteins was shown to be a cooperative process.     

Seed dispersal by weta

Weta are giant, flightless grasshoppers that are endemic to New Zealand. In the absence of native mammals, weta are thought to perform similar ecological functions. As such, they might be expected to be important seeds dispersers. However, insects are not known to consume fleshy fruits and to disperse seeds after gut passage. We conducted a series of observations and experiments to test whether weta form mutualistic partnerships with fleshy-fruited plants as seed dispersers, similar to small mammals elsewhere in the world. Results showed that weta are indeed effective seeds dispersers, providing an example of ecological convergence between unrelated organisms.     

A protein farnesyltransferase inhibitor ameliorates disease in a mouse model of progeria

Progerias are rare genetic diseases characterized by premature aging. Several progeroid disorders are caused by mutations that lead to the accumulation of a lipid-modified (farnesylated) form of prelamin A, a protein that contributes to the structural scaffolding for the cell nucleus. In progeria, the accumulation of farnesyl-prelamin A disrupts this scaffolding, leading to misshapen nuclei. Previous studies have shown that farnesyltransferase inhibitors (FTIs) reverse this cellular abnormality. We tested the efficacy of an FTI (ABT-100) in Zmpste24-deficient mice, a mouse model of progeria. The FTI-treated mice exhibited improved body weight, grip strength, bone integrity, and percent survival at 20 weeks of age. These results suggest that FTIs may have beneficial effects in humans with progeria.