Dangerous life at the edge: Implications of seed predation for roadside revegetation

Question

Anthropogenic edges caused by transport infrastructure such as dirt roads and trails (also known as Soft Linear Developments; SLD) are pervasive in almost every terrestrial ecosystem. Revegetating these edges may reduce some of their negative effects, such as their permeability to biological invasions and detrimental effects on wildlife, potentially becoming suitable habitat for a broad range of species. Selecting species with low post‐dispersal seed predation rates may improve the effectiveness of revegetation programmes.

Location

Mediterranean scrublands in SW Spain.

Methods

We made offerings of a total of 16,000 seeds of eight species of fleshy‐fruit shrubs both along SLD edges and scrubland interiors in two independent blocks in each of three distant locations. Using four types of selective enclosure, we assessed the relative contribution of three seed predator guilds (ants, rodents and birds) to seed predation rates both along SLD edges and scrubland interiors.

Results

The effects of anthropogenic edges on seed predation rates were species‐specific. The large and hard‐seeded species Chamaerops humilis was not predated at all. Juniperus phoenicea and Corema album seeds had higher predation rates in scrubland interiors than in edges. The small‐seeded Rubus ulmifolius experienced relatively low seed predation rates compared to the other species. Predation rates for this species were higher along SLD edges than in scrubland interiors. Ants were the main seed predators in the area, and showed marked preferences for J. macrocarpa and C. album seeds at both SLD edges and scrubland interiors.

Conclusions

Our results show the strong context‐dependency of seed predation rates in both SLD edges and scrubland interiors, and thus the importance of well spatially and temporally replicated studies. Species with large and hard seeds may be good candidates for roadside revegetation programmes. However, the relative suitability of plant species would depend on the seed predator community. Our findings confirm that studies on seed predation may help planning cost‐effective species selection for edge revegetation efforts worldwide.     

Characterization,source apportionment,and human health risk assessment of polycyclic aromatic hydrocarbons (PAHs) in road dust of a small island state in the Caribbean

Sixty-four and fifty-six road dust samples were collected over two seasons from various locations throughout the island of Trinidad and analyzed for the 16 priority PAHs. Total PAH concentrations ranged from 21 ng g^?1 to 4723 ng g^?1 (d.w.) for the rainy season and 36 ng g^?1 to 2428 ng g^?1 (d.w.) for the dry season. The Σ4–6 ring PAHs accounted for 88% and 63% of the 16 PAHs in road dust samples for the rainy and dry seasons, respectively. PAH diagnostic ratios, principal component analysis, and cluster analysis revealed both pyrogenic and petrogenic sources in road dust for the two seasons, with major contributions from vehicular emissions. Contributions from incomplete combustion and petroleum sources were also identified. The estimated Incremental Lifetime Cancer Risk (ILCR) associated with exposure to road dust PAHs in Trinidad for the rainy and dry seasons indicated no potential risk for both children and adults, as denoted by ILCR values lower than 10^?6.     

Infrastructure features outperform environmental variables explaining rabbit abundance around motorways

Human disturbance is widespread across landscapes in the form of roads that alter wildlife populations. Knowing which road features are responsible for the species response and their relevance in comparison with environmental variables will provide useful information for effective conservation measures. We sampled relative abundance of European rabbits, a very widespread species, in motorway verges at regional scale, in an area with large variability in environmental and infrastructure conditions. Environmental variables included vegetation structure, plant productivity, distance to water sources, and altitude. Infrastructure characteristics were the type of vegetation in verges, verge width, traffic volume, and the presence of embankments. We performed a variance partitioning analysis to determine the relative importance of two sets of variables on rabbit abundance. Additionally, we identified the most important variables and their effects model averaging after model selection by AICc on hypothesis‐based models. As a group, infrastructure features explained four times more variability in rabbit abundance than environmental variables, being the effects of the former critical in motorway stretches located in altered landscapes with no available habitat for rabbits, such as agricultural fields. Model selection and Akaike weights showed that verge width and traffic volume are the most important variables explaining rabbit abundance index, with positive and negative effects, respectively. In the light of these results, the response of species to the infrastructure can be modulated through the modification of motorway features, being some of them manageable in the design phase. The identification of such features leads to suggestions for improvement through low‐cost corrective measures and conservation plans. As a general indication, keeping motorway verges less than 10 m wide will prevent high densities of rabbits and avoid the unwanted effects that rabbit populations can generate in some areas.     

城市道路绿化带"微峡谷效应"及其对非机动车道污染物浓度的影响

研究不同绿化带结构对非机动车道污染物浓度的影响,将为城市道路绿化带格局提供依据。利用遮荫网模拟10、20、30 m隔离的道路绿化带,并模拟了3种不同结构的绿化带,分别对各类道路微气候条件(风)及SO₂、NO_x、NH₃、总悬浮颗粒物(TSP)和可吸入颗粒物(PM10)等5种主要污染物浓度进行了观测。结果表明:风速小于2 m/s时,10 m和20 m间隔的道路绿化带会产生"微峡谷效应",使绿化带间隔内风速增加。10 m间隔的绿化带较其它两种绿化带对各种污染物的净化百分率更明显,且污染物净化百分率与风速大多正相关显著。12.5 m的模拟绿化带与10 m的间隔交替的绿化带可以更有效地降低非机动车道的污染物浓度,污染物净化百分率与风速也大多正相关显著。不同结构道路绿化带会影响道路微气候条件,从而影响非机动车道污染物浓度。城市道路绿带存在合理的绿带结构,可以通过设计更合理的城市道路绿带模式有效改善城市非机动车道空气质量。     

Characteristics of trajectory in the migration of Amoeba proteus

Summary. We investigated the behavior of migration of Amoeba proteus in an isotropic environment. We found that the trajectory in the migration of A. proteus is smooth in the observation time of 500-1000 s, but its migration every second (the cell velocity) on the trajectory randomly changes. Stochastic analysis of the cell velocity and the turn angle of the trajectory has shown that the histograms of the both variables well fit to Gaussian curves. Supposing a simple model equation for the cell motion, we have estimated the motive force of the migrating cell, which is of the order of piconewton. Furthermore, we have found that the cell velocity and the turn angle have a negative cross-correlation coefficient, which suggests that the amoeba explores better environment by changing frequently its migrating direction at a low speed and it moves rectilinearly to the best environment at a high speed. On the other hand, the model equation has simulated the negative correlation between the cell velocity and the turn angle. This indicates that the apparently rational behavior comes from intrinsic characteristics in the dynamical system where the motive force is not torquelike.     

道路建设对西南地区景观格局的影响

为揭示西南地区道路建设对景观格局的影响,基于2015年土地覆被和道路数据,计算了研究区道路核密度与景观指数,在此基础上分析了道路建设的直接、间接和综合影响,探讨了影响的空间异质性和对不同土地覆被影响的特点,指出了各景观指数的适用性。结果表明：(1)道路建设使斑块密度增加,斑块离散化加剧,发生明显的破碎化趋势,同时道路核密度与PD、SHDI、SPLIT变化百分比呈显著正相关,与COHESION、CONTAG、PAFRAC呈显著负相关;(2)道路建设对景观指数的影响程度由大到小依次表现在：破碎化、斑块空间分布形态、聚集连通性,其中PD能很好的表征道路建设对景观破碎化的作用程度,SPLIT在识别破碎化程度高的区域更具优势;(3)不同景观指数具有不同适用性,PAFRAC适用于道路不发达区域,CONTAG适用于道路分布异质性较高的区域,DIVISION适用于人类活动强度不大的区域,COHESION、SPLIT适用于探究道路及伴随的人类活动共同作用的区域,PD、SHDI在探究道路的直接作用时适用性广泛;(4)探究不同土地覆被类型受道路建设的影响,林地优先选取PD、DIVISION;草地优先选取DI...     

The combined effect of heat and carbon monoxide on the performance of motorsport athletes

Two of the major stressors endured by a motorsport athlete (MSA) during a racing event are the effects of heat and carbon monoxide. To date, there has been little research into their combined effect on driving performance. Using an interactive racecar simulator located within an environmental chamber, subjects drove a simulated race (60 min) in environmental conditions similar to those that develop during a NASCAR Winston Cup oval track race (50 degrees C ambient temperature and 10-12% carboxyhaemoglobin levels). Subjects also completed cool (20 degrees C) and heat only (50 degrees C) race simulations. During the simulations, oxygen consumption, heart rate, core and skin temperatures and psychomotor performance were measured. The results demonstrated that exposure to a racecar micro-environment combining both heat and CO produced significantly greater (P<0.05) sweat loss and core temperature change (1.53 kg; 1.06 degrees C) when compared to the heat only (1.14 kg; 0.73 degrees C) and cool conditions (0.35 kg; 0.09 degrees C). Furthermore, a significant decrease (P<0.05) in psychomotor performance was also shown between the heat/CO condition (contact points=38), and both the heat only (25 points) and cool conditions (22 points). It follows that lengthy exposure to these two stressors could produce a substantial decrement in driving performance, thereby endangering the MSA and other race competitors.     

Behavioral Adaptations of Moose to Roadside Salt Pools

Abstract: Sodium has many fundamental physiological functions in animals but is rare in boreal ecosystems where moose (Alces alces) thrive. In Québec (Canada), sodium is readily available in aquatic vegetation and in salt pools that form along highways. We do not know if moose are adopting specific behaviors to access sodium sources or if they simply use the sodium sources they encounter during their movements. We tested the hypothesis that moose modify both space and habitat use to gather sodium from salt pools. We expected moose to use salt pools mostly in spring and early summer, when needs are greatest and before aquatic vegetation has fully developed. We fitted 47 moose with Global Positioning System telemetry collars and collected data for 2 to 36 months between 2003 and 2006. We rarely located moose at salt pools (0.12% among the 95,007 locations collected). As we expected, use of salt pools was highest in late spring and in early summer, and we observed a time lag between peak use of salt pools compared to use of lakes and waterways, indicating moose fulfilled their sodium requirements in salt pools before aquatic vegetation was available. Moose selected salt pools over lakes and waterways when these 2 sodium sources were present in their home range and moved rapidly over large distances to reach them. Our results were consistent with moose using salt pools when they are likely to be sodium deficient. Salt pools were less accessible, required long-distance movements, and were located in habitually avoided areas along highways. Elimination of roadside salt pools should be considered among strategies to reduce cervid-vehicle collision risks in boreal environments.