Do not log-transform count data

1. Ecological count data (e.g., number of individuals or species) are often log-transformed to satisfy parametric test assumptions.
2. Apart from the fact that generalized linear models are better suited in dealing with count data, a log-transformation of counts has the additional quandary in how to deal with zero observations. With just one zero observation (if this observation represents a sampling unit), the whole dataset needs to be fudged by adding a value (usually 1) before transformation. 
3. Simulating data from a negative binomial distribution, we compared the outcome of fitting models that were transformed in various ways (log, square-root) with results from fitting models using Poisson and negative binomial models to untransformed count data. 
4. We found that the transformations performed poorly, except when the dispersion was small and the mean counts were large.  The Poisson and negative binomial models consistently performed well, with little bias

Insurance spares, safety equipment and spare parts on ships

This paper deals with the treatment of spare parts on ships, in accordance with the Income Tax Act, No. 58 of 1962 (as amended), (hereafter 'the Act'). The question that is central to this issue is specifically when a spare part is brought into use. Flowing from this is the question of the purpose of a spare part. In summary the issues are as follow: What expenditure should properly be regarded as forming part of the cost of a ship? The expenditure envisaged here comprises essential safety equipment and spares included in a ship at the time of its construction prior to commissioning and its maiden voyage. If such expenditure is considered not to form part of the cost of a ship, should it in the alternative be deducted as operating expenditure? Should it then be included in trading stock as 'consumable stores and spare parts ... used or consumed' by virtue of having been brought into use or consumed when added to the ship? Should the cost of the subsequent replacement of the above items properly be regarded as operating expenditure? Apparently an airline received a written ruling from the Commissioner for the South African Revenue Services that if an aircraft is acquired with a spare engine, it will be regarded as part and parcel of the plane. It will be regarded as one asset for taxation purposes on which wear and tear is permitted. The airline is not required to include this 'spare' engine as a spare part for trading stock purposes

Tennis racket performance studies and the design of a novel test machine

The investigation was instigated by a growing concern from the International Tennis Federation (ITF) that the contribution of racket technology in the modem game of tennis might be changing the nature of the game by making it too fast. The serve was earmarked as the most critical stroke influencing the speed of the game, resulting in the decision to build a test machine, which would investigate racket performance under realistic serve conditions. In order to determine the design specifications for the machine the following studies were performed. [Continues.

Soil sealing causes substantial losses in C and N storage in urban soils under cool climate

Urban soil can store large amounts of carbon (C) and nitrogen (N). To accurately estimate C and N storage in urban soils, C and N contents underneath impervious surfaces - the most prevalent land cover type in cities - should be taken into account. To date, however, only few studies have reported urban soil C and N content underneath impervious surfaces, and no data exist for cities under cold/cool climates, such as the Boreal zone. Here, we studied, for the first time, the effects of sealing on soil C and N storage in a Boreal city. Sealed soils were sampled for physico-chemical and biological parameters from 13 sites in the city of Lahti, Finland, at three depths (0–10 and 45–55 cm, representing the construction layer composed of gravel, other moraine material and crushed rock, and the native soil layer beneath the ca. 1 m thick construction layer). Our results show that urban soils underneath impervious surfaces in Finland contain 11 and 31 times less C and N content, respectively, compared with warmer regions. This is due to a deep C and N deficient construction layer below sealed surfaces. Even though impervious surfaces cover ca. twice the area of pervious surfaces in the centre of Lahti, we estimate that only 6% and 4% of urban soil C and N, respectively, are stored underneath them. Furthermore, we found very little C and N accumulation underneath the sealed surfaces via root growth and/or leakage through ageing asphalt. Our results show that soil sealing, in concert with a massive top soil removal typical to cold climates, induces a considerable loss of C and N in Boreal urban areas.Peer reviewe

The delivery of Cultural Ecosystem Services in urban forests of different landscape features and land use contexts

Urban greenspace provides citizens with important cultural ecosystem services (CES). Identifying landscape features and land use contexts that facilitate CES delivery is critical for guiding urban greenspace management. However, how landscape features and urban context interact with each other in influencing the CES of greenspaces remains unclear. Studies on the CES of patchy urban forests are needed as they are essential urban CES providers, but vulnerable under urban land use pressure. To address these concerns, we compared the CES of 20 urban forest patches in Helsinki, Finland, with five different combinations of landscape features (i.e. size and connectivity) and land use contexts (i.e. surrounding construction density). CES were assessed through an on-site survey on visitors' use, perceptions of CES experience and overall satisfaction, to capture the possible disparities among CES measurements. In larger (>20 ha) forests, visitors were highly satisfied with CES, particularly appreciating the experience of physical health improvement and inspiration through longer and more intense physical uses. Visitors of urban forests in a low construction density context appreciated experiences of cultural heritage, psychological restoration and physical health improvement. Urban forests deliver unique CES characterised by physical use and the benefit of restoration, aesthetics and contact with nature. We suggest that maintaining large urban forests is more effective in promoting CES in high-density areas. In low-density areas, maintaining small forests with open greenspace in the surroundings can also promote CES experiences. We identify management gaps caused by a mismatch between use intensity and CES experiences of urban forests, while both are important in determining people's overall satisfaction. Read the free Plain Language Summary for this article on the Journal blog.Peer reviewe

Landscape context and substrate characteristics shape fungal communities of dead spruce in urban and semi-natural forests

Urban green areas are becoming increasingly recognized for their biodiversity potential. However, little is known about how urbanization shapes cryptic species communities, such as those residing in deadwood. In this study, we investigated downed Norway spruce trunks at intermediate stages of decay, in urban and semi-natural forests in southern Finland. To understand the interconnections between landscape context, deadwood characteristics and wood-inhabiting fungal communities, we studied structural characteristics, surface epiphyte cover and internal moisture and temperature conditions of the tree trunks, and fungal communities residing in the wood. Our findings showed that urban tree trunks had less epiphyte cover and lower moisture than trunks in semi-natural forests. Overall, urban forests provide less favourable habitats for a majority of the dominant wood-inhabiting fungal species and for red-listed species as a group. Yet, 33% of urban trunks hosted at least one red-listed species. While these landscape-scale effects may be driven by local climatic conditions as well as contingencies related to available species pools, our results also highlight the significance of substrate-scale variability of deadwood in shaping wood-inhabiting fungal communities. We show that epiphyte cover is a significant driver or indicator of these small-scale dynamic processes in deadwood.Peer reviewe

Dog Urine Has Acute Impacts on Soil Chemistry in Urban Greenspaces

Urban residents and their pets utilize urban greenspaces daily. As urban dog ownership rates increase globally, urban greenspaces are under mounting pressure even as the benefits and services they provide become more important. The urine of dogs is high in nitrogen (N) and may represent a significant portion of the annual urban N load. We examined the spatial distribution and impact of N deposition from dog urine on soils in three urban greenspace typologies in Finland: Parks, Tree Alleys, and Remnant Forests. We analyzed soil from around trees, lampposts and lawn areas near walking paths, and compared these to soils from lawn areas 8 m away from pathways. Soil nitrate, ammonium, total N concentrations, and electrical conductivity were significantly higher and soil pH significantly lower near path-side trees and poles relative to the 8 m lawn plots. Also, stable isotope analysis indicates that the primary source of path-side N are distinct from those of the 8 m lawn plots, supporting our hypothesis that dogs are a significant source of N in urban greenspaces, but that this deposition occurs in a restricted zone associated with walking paths. Additionally, we found that Remnant Forests were the least impacted of the three typologies analyzed. We recommend that landscape planners acknowledge this impact, and design parks to reduce or isolate this source of N from the wider environment.Peer reviewe

Plant functional type affects nitrogen dynamics in urban park soils similarly to boreal forest soils

Purpose Although plant functional type can modulate soils and their processes in natural, nitrogen (N)-limited ecosystems, little is known about their ability to influence soil N dynamics in urban ecosystems that have high excess N input. We investigated whether i) plant functional type effects on soil N dynamics in urban parks follow the same pattern as those in undisturbed natural/semi-natural forests, and ii) park age influences plant functional type effects on soil N dynamics under boreal climate. Methods We selected 13 urban parks of varying ages (young: 10 to 15, old: > 70 years), and 5 undisturbed natural/semi-natural forests (> 80 years) in southern Finland. In these parks and forests, we measured soil total N concentration, availability of inorganic N, nitrous oxide (N2O) flux and earthworm biomass under three plant functional types (evergreen tree, deciduous tree, lawn). Results Our results showed that plant functional type influenced N dynamics also in urban greenspace soils, which may relate to the clear effect of plant functional type on earthworm biomass. Evergreen trees tended to have the highest ability to foster N accumulation and reduce N2O emissions in urban parks. Moreover, with increasing park age, N accumulation increased under trees but decreased under lawns, further emphasising the role of vegetation in affecting soil N dynamics in urban greenspaces. Conclusions Our results show that, similar to natural/semi-natural forests, plant functional type, irrespective of park age, can influence soil N dynamics in urban parks.Peer reviewe

Pitfall trap efficiency: do trap size, collecting fluid and vegetation structure matter?

Apart from experimental design, the selection of pitfall trap size, collecting fluid and habitat type sampled may also influence the capture efficiency of the method. We combined three field studies from two very different geographic areas, in which the efficiency of pitfall traps, using carabid beetles (Coleoptera: Carabidae), is evaluated. First, we showed that ethylene-glycol is a more efficient collecting fluid compared to commercial anti-freeze, paraffin and salt water in collecting beetles in a forest patch in South Africa. Second, we showed that larger traps (90 mm mouth diameter) are more efficient in collecting carabids than small traps (65 mm) in a meadow in Finland. We also showed that for these large traps, commercial vinegar was a better collecting fluid than propylene-glycol, but that for small traps, propylene-glycol was superior to vinegar in collecting carabids. Finally, we showed that the trappability of Pterostichus oblongopunctatus and Carabus hortensis differed in enclosures placed into two different habitat types (a forest and a clear-cut in Finland), while trappability did not differ significantly for two other species (Calathus micropterus and Pterostichus niger) in these habitat types. However, for the two Pterostichus species studied, the catches in traps placed in the centre of the enclosures were slightly higher in the clear-cut, compared to the forest, and catches were higher in enclosures with rich field-layer vegetation, compared to enclosures with poor vegetation. The three studies re-emphasise the uncertainties of using pitfall traps in ecological studies. However, with careful planning and standardisation to help avoid erroneous interpretations, pitfall trapping is an invaluable method for the field ecologist

Carabid beetles of tropical dry forests display traits that cope with a harsh environment

The tropical dry forest (TDF) ecosystem is characterised by strong seasonality exasperated periodically by the El Nino/southern oscillation (ENSO). The environment produced by this event could constrain the survival of small organisms, such as insects. Carabid beetles were collected in a TDF in Armero, Colombia, during wet and dry seasons in both El Nino and non-El Nino periods. A series of traits linked to desiccation resistance were measured to characterise their adaptation to the TDF environment and to investigate changes experienced by carabid beetles during both episodes in quantitative (assemblage) and qualitative (traits) parameters. We found no difference in the presence of traits between El Nino and non-El Nino episodes, but carabid assemblages changed significantly in composition and assemblage structure between these episodes. During both periods, small-sized and nocturnal species dominated the assemblages, but in terms of number of individuals, medium and large-sized, and visual hunter species dominated. Calosoma alternans and Megacephala affinis were the most abundant species with high dispersal capacity. Carabid beetles exhibited morphological traits well-adapted to drought experienced in TDF, including when it is exasperated by ENSO. However, long-term studies can help to elucidate the real effects of ENSO and to confirm the adaptation of carabid beetles to cope with this extreme environment.Peer reviewe