Home range and habitat use of feral cats in an urban mosaic in Pietermaritzburg,KwaZulu-Natal,South Africa

Feral cats (Felis catus) are one of the world’s worst invasive species with continuing expanding populations, particularly in urban areas. Effects of anthropogenic changing land-use, especially urbanisation, can alter distribution and behaviour of feral cats. Additionally, resource availability can influence home range and habitat use. Therefore, we investigated home range and habitat use of feral cats (n?=?11) in an urban mosaic with varying degrees of urbanisation and green spaces in Pietermaritzburg, KwaZulu-Natal, South Africa. Using global positioning cellular trackers, individual feral cats were followed for a minimum of six months. Minimum convex polygons (MCP) and kernel density estimates (KDE) were used to determine their home range, core area size, and habitat use. Mean home range (± SE) for feral cats was relatively small (95% MCP 6.2?±?4.52 ha) with no significant difference between male and female home ranges, nor core areas. There was individual variation in home ranges despite supplemental feeding in the urban mosaic. Generally supplemental resources were the primary driver of feral cat home ranges where these feeding sites were within the core areas of individuals. However, the ecological consequences of feeding feral cats can increase their survival, and reduce their home ranges and movement as found in other studies.     

Demography of a ground nesting bird in an urban system: are populations self-sustaining?

Urbanization poses threats to earth’s biota, and retention of remnant native habitat in protected areas within expanding urban boundaries may help alleviate threats to wildlife. However, it is unclear for nearly all nonsynanthropic (i.e., not benefiting from an association with humans) species whether vital rates in urban habitats can sustain populations or if populations persist only through immigration from outside the urban boundary. We conducted a three-year study of spotted towhees (Aves: Pipilo maculatus) breeding in four undeveloped parks in Portland, OR, USA, to measure park-specific seasonal reproductive output (F) and annual adult survival (S_A). We developed a stochastic model that combined F and S_A with an estimate of first-year survival to measure population growth rate (λ) in all parks assumed to be closed to immigration. F differed among parks but S_A did not. Relatively high F was possible because many pairs raised >1 brood/season. When combined with empirical estimates of survival through the 30-day period of post-fledging parental care (S_D = 0.645), only 2 of 4 parks were self-sustaining (i.e., λ > 1.0). However, S_D reflected substantial loss of fledglings to domestic cats (Felis catus). Assuming no loss to cats and either partial compensatory or additive mortality of fledglings substantially improved prospects of population persistence for declining (sink) populations. Moreover, allowing low levels of immigration to sinks reversed population declines in most parks even when vital rates were insufficient to maintain populations. Our results suggest that nonsynanthropic bird species can persist in urban landscapes, but also that offspring mortality in the post-fledging period may be a critical determinant of population viability.     

The roles of mosquito and bird communities on the prevalence of West Nile virus in urban wetland and residential habitats

This study investigated the impacts of urban wetlands and their adjacent residential environments on the transmission dynamics of West Nile virus (WNV) within the state of New Jersey (USA). A working hypothesis was that urban wetlands decrease the local prevalence of WNV through the dilution effect from increased bird diversity, and through relative reductions in the numbers of competent avian host and mosquito species commonly associated with WNV. Surveys of mosquito and bird communities were undertaken at six urban wetlands and their adjacent residential environments over two seasons (2009, 2010). The community compositions of both avian and mosquito species differed significantly across habitats, and over relatively short geographical distances. Residential areas contained significantly higher proportions of WNV-competent mosquito species (31.25?±?5.3?%; e.g. Culex pipiens and Culex restuans), and WNV-competent avian host species (62.8?±?2.3?%, e.g. House Sparrow and American Robin) when compared to adjacent urban wetlands (13.5?±?2.1?%; 35.4?±?2.1?% respectively). Correspondingly, WNV infection rates within local Culex spp. populations indicate that WNV was more prevalent within residential areas (28.53/1000) compared to wetlands (16.77/1000). Large urban wetlands (>100?ha) produced significantly lower weekly WNV infection rates in local Culex spp. (6.67?±?2.84/1000) compared to small (<15?ha) wetlands (22.57?±?6.23/1000). Avian species richness was also influenced by patch size. Large urban wetlands contained significantly more species than small wetland patches. These results confirm that the community compositions of mosquito and avian hosts are important drivers in WNV infections, and that the ecological conditions that favor transmission are more strongly associated with urban residential environments than with adjacent urban wetlands.     

Atmospheric carbon dioxide concentration variations in Rome: relationship with traffic level and urban park size

Carbon dioxide (CO₂) concentration variations in Rome in the period January 2009 to December 2010 was monitored. Five representative sites (T sites) in the city centre with different traffic levels and urbanistic characteristics, and four urban parks (P sites) of different sizes were selected. The regression analysis underlines the significant (p?≤?0.05) correlation between traffic levels and CO₂ concentration. Considering the daytime CO₂ concentration peak among T sites, Cerchi Street and Teatro Marcello Street, located in the city centre and closed by buildings, showed the highest traffic levels (85?±?3 and 63?±?2 cars min^?1, respectively) and the highest CO₂ concentration (512?±?11 and 488?±?8 ppm, respectively). With regards to the considered P sites, those extending over the largest surface areas (Villa Pamphilj Park and Villa Borghese Park, 180 and 80 ha, respectively) characterized by large tree coverage (81 ha and 60 ha, respectively) had a significant lower CO₂ concentration (404?±?9 ppm, mean value) than those extending over a small surface area (Villa Torlonia Park and Villa Celimontana Park, 14 ha and 11 ha, respectively). More efforts should be made to further reduce CO₂ concentration in the cities in order to ameliorate ecosystem services related to urban parks.     

Does urbanization affect the seasonal dynamics of bird communities in urban parks?

The environmental factors affecting the spatial dynamics of bird communities in urban parks are well understood, but much less attention has been paid to the seasonal dynamics of bird communities. Since migrant and resident human commensal birds might have contrasting responses to environmental factors of urban parks, we expected different seasonal dynamics among parks. On the other hand, because bird species can have different habitat relationships throughout the year, we also expected different responses of bird richness to environmental variables between breeding and non-breeding seasons. Bird surveys were conducted in 14 small urban parks (1–4 Ha) of Mar del Plata city (Argentina) for one full annual cycle. Bird richness changed between seasons, but bird abundance remained constant. Bird community composition did not vary between seasons, but urban parks near the urban center, with the highest pedestrian traffic and isolation to other green areas had the least seasonal change of composition. During the breeding season, bird richness was negatively affected by the percentage cover of high buildings surrounding the immediate limits of parks, whereas during the non-breeding season bird richness was not related with any environmental variable. Bird composition variation among parks was affected by the distance to the urban center during both seasons. Results showed that urbanization promotes a seasonal homogenization of bird communities in urban parks, probably by affecting the presence of migrant species and promoting the temporal stability of human commensal species.     

Drivers of soil carbon in residential ‘pure lawns’ in Auburn,Alabama

Urban land area is expanding worldwide and may contribute to long-term carbon (C) storage; however, little is known about potential drivers of soil C in urban areas. Residential areas are one of the largest urban land use zones and lawns can provide stable chronosequences for studying soil C dynamics. In residential lawns containing no trees (n?=?23), the relationships between soil C and four potential drivers [home age (1–51 years), yard maintenance practices (fertilization, irrigation, and bagging or mulching lawn clippings), soil nitrogen (N) and soil texture] were investigated. Soil C increased with home age at 0–15 cm depth by 0.026 kg C m^?2?yr^?1, declined by ?0.011 kg C m^?2?yr^?1 at 15–30 cm depth, and was stable at 30–50 cm depth. Soil C had a positive relationship with soil N (R ²?=?0.55) at the 0–15 cm depth. Soil C and N were not related to yard maintenance practices or soil texture. The low soil C sequestration rate and limited relationships between soil C and home age, yard maintenance, soil N and soil texture may have resulted from the positive influence of Auburn’s humid, subtropical climate on residue decomposition.     

Butterfly diversity,habitat and vegetation usage in Hong Kong urban parks

The conservation value of urban parks for butterfly communities remains poorly understood, particularly for tropical butterflies in Asia. We conducted point count and route transect butterfly surveys, and used them to sample four habitats located within 13 urban parks across Hong Kong. We found 1054 individuals and 58 species of butterflies recorded in 60 survey hours over 6 months. This represents approximately one quarter of the entire known Hong Kong butterfly species list. Over 30 % of the individuals counted were Catospilia sp. but six of the species identified are classified locally as rare or very rare. Tree-covered habitats and grasslands showed higher butterfly diversity than open areas. The most common butterfly behavior was “directed flight,” which we also found to be habitat-dependent and most common in ponds and open areas. We additionally observed the use of vegetation in urban parks, which included 40 species of nectar plant and four records of butterfly oviposition. The high butterfly diversity, presence of rare species and usage of vegetation (especially as a nectar resource) we documented in this study suggests that urban parks have some conservation value for Hong Kong. However, the use of pesticides and heavy vegetation clearing may limit significant butterfly reproduction and population growth. Altogether these results emphasize the diversity of uses of urban parks for butterflies in Hong Kong while also providing possible directions for improvement in habitat and vegetation management that could increase urban park value for biodiversity.     

Influence of human population size and the built environment on avian assemblages in urban green spaces

While studies of how habitat patch dynamics structures avian communities in urban environments has received some attention, there is considerably less known of how the built environment and human population size may influence the structuring of urban bird communities. We investigated bird populations in Pittsburgh, Pennsylvania (U.S.A.) through replicated point count surveys of breeding birds in 50 parks and cemeteries of varying sizes. We counted 4,435 individual birds in 441 counts. Of the 61 species detected, 27 were rare (detected at <8 points). Migratory species accounted for 46.1 % of all individuals, while 23.2 % of all individuals were of introduced species. Species richness increased significantly with green area size, as did the number of rare species. Species diversity decreased significantly with an increase in the proportion of individuals of introduced species; in particular, cavity nesters were less abundant when introduced species were present. Elements of the built urban environment including commercial development and transportation corridors were associated with significant reductions in park-wide species richness, mean number of species per point, and mean number of individual birds recorded per point. Human population size was positively related to increased numbers of individuals of introduced species, but a lower mean number of species per point. Ours is among the first to identify specific relationships between avian population characteristics and human population size, as few other studies have specifically incorporated human population size into a local, fine grain study design. Our data suggest that human population size is an important parameter that can be measured independently of characteristics of the built environment and the physical characteristics of the park itself as a correlate of avian diversity and abundance. Our study points to a variety of trade-offs needed to manage habitat for birds in urban settings.     

Basking habitat use and response of freshwater turtles to human presence in an urban canal of Central New Jersey

Pressures of rapid development continue to increase, and recreational activities are becoming a prominent driving force in many urban wildlife communities. Freshwater turtles live in many urban environments, yet little attention has been given to the impact of human recreation upon these communities. We examined the response of basking turtles to observer presence along the towpath of a recreational canal in central New Jersey. All species, except for turtles of the family Kinosternidae, were more frequently observed basking on substrate with less than 50 % canopy cover, log substrate was most preferred, and turtles on the towpath side basked an average of 3 m from the towpath. Turtles were vigilant and over 75 % of C. picta, T.S. elegans, and P. rubriventris responded to observer presence by retreating (swimming away). The distance from the towpath turtles were first seen basking by the observer (approach distance) was significantly correlated with the flight-initiation distance (distance of first respond to observer). Nearly 80 % of the variability in flight initiation distance for Kinosternidae was accounted for by the percent canopy cover, percent cloud cover, and height basking above the water. Researchers aiming to quantify and manage human recreational impact on turtles should examine flight-initiation distances. We encourage wildlife managers of urban parks to construct towpaths or recreational areas at a minimum of 7 m from the water’s edge, maintain moderate vegetation in basking areas, and construct additional basking platforms opposite from towpaths or at great distances from human recreational areas.     

Estimation of Feral Pigeon (Columba livia) population size using a novel Superimposed Urban Strata (SUS) method

A reference method to estimate Feral Pigeon (C. livia) population size in urban areas is missing: results of different surveys are difficult to compare due to the wide heterogeneity of approaches. A combined technique, the Superimposed Urban Strata (SUS) method, especially designed to estimate pigeon population size in urban areas, is proposed. SUS implements methods based on stratified sampling layers: its reliability was tested with a pilot study in Padua (Italy). The survey area was split into two superimposed strata and a different survey technique was applied to each stratum. The first stratum consisted of twelve topographic sampling units, identified as critical ornithic-density loci. The second stratum was obtained by selecting 10 % of the survey area with systematic sampling. In the estimate of the population size, different detection probabilities were assigned to the two strata. The SUS method was first applied in 2007, when three-year growth projections for the C. livia population were calculated, with a density-dependent model. In 2010, the survey was repeated to countercheck previous data. Estimated C. livia population size was of 2340 ±93 units in 2007, whereas in 2010 it was of 3679 ±161 units. The 2010 estimated population size resulted in fair accordance with the three-year projections, showing less than a 4 % mismatch. SUS proved to be an adequate estimate method for urban areas: so far it has been tested only in an average Italian urban area, but it could be easily adapted to other cities by calibrating parameters linked to the peculiar urban background.     

Understanding foraging flexibility in urban vervet monkeys,Chlorocebus pygerythrus,for the benefit of human-wildlife coexistence

Urban Ecosystems - Generalist wildlife species often thrive in urban environments because of increased anthropogenic resources. However, human-wildlife interactions, especially if negative, raise...     

Potential nitrogen mineralization responses of urban and rural forest soils to elevated temperature in Louisville,KY

Soil nitrogen (N) mineralization is an important process determining terrestrial N availability, and evidence suggests elevated temperatures will enhance N mineralization rates. Along a 40 km urban-rural gradient of chestnut oak forest stands in Louisville, KY, we expected N mineralization rates would be higher in urban than in rural forests in part due to increased temperatures caused by the urban heat island. However, a 12-month field study along this Louisville gradient showed that annual N mineralization rates were lower in urban than in rural stands. Since variation in precipitation inputs and other factors across this land-use gradient may be influencing soil N mineralization rates, we conducted a three-month soil incubation experiment in the lab to determine the extent to which a + 2 °C temperature difference could affect soil N mineralization in urban and rural soils. Across the range of temperatures tested, rural soils mineralized N at twice the rate of urban soils under base (7.86 vs. 3.65 mg N kg^?1 AFDW soil d^?1) and elevated (9.08 vs. 4.76 mg N kg^?1 AFDW soil d^?1) temperatures (p < 0.01). A 2 °C temperature difference, did not significantly alter total inorganic N production in urban (p = 0.272) or rural soils (p = 0.293). The proportion of nitrate produced was lower in the urban (15.1 %) than in the rural soils (72.3 %; p < 0.01). These results suggest that differences in soil organic matter quality and potentially decomposer community composition are the primary explanatory factors for forests along this Louisville gradient.     

Variability of bumblebee communities (Apidae,Bombini) in urban green areas

Based on current research the agglomerations are potentially desirable habitats for bumblebees. However, the relationship between the biodiversity of these bees and the green areas where they live is poorly understood. The aim of the study was to estimate the influence of green areas (ranging from 8 to 102 ha) of big cities on bumblebee species richness, composition, and the relative number of these insects. The studies were conducted within the administrative borders of the city of Wroc?aw (Poland) in 2011–2012 in 12 green areas such as parks, cemeteries and other places with trees and shrubs. Species richness and abundance of bumblebees was determined by direct observation during 30 min. The gathered materials were used to calculate how areas of urban green space affected qualitative and quantitative bumblebee community structure. In total, 13 species of bumblebees (Bombus Latr.) were recorded, of which 3 belonged to cuckoo bumblebees (Psithyrus subgenus). The share of the most similar groups was congregated in green areas not smaller than 30 ha. This was proved by analysis of qualitative structure (Sørensen index), quantitative structure (Renkonen index), and qualitative-quantitative structure (Cody’s index). The number of bumblebee species in the surveyed green areas (r = 0.7497) was decisive for the arrangement of the mutual similarity of group structure. Green urban areas should be created in a size of at least 30 ha. Such sites provide conditions for the most diversified bumblebee species communities. Sites smaller than 30 ha can play an important role as refuges, and allow migration to all pollinators.     

Coexisting with coyotes (<Emphasis Type="Italic">Canis latrans</Emphasis>) in an urban environment

The global spread of urban development and concomitant reduction in wilderness areas can both pressure and entice wild animals to adapt to the urban environment. As wildlife moves into metropolitan areas, however, they come into contact with residents who have become increasingly disconnected from natural environments and have little to no experience in dealing with wild animals. While many large carnivores actively avoid urban areas, North America’s coyote (Canis latrans) has proved remarkably adept at utilizing the highly altered habitat of the modern city. Yet while the coyote’s behavioural adaptations to urban areas have been relatively well researched, fewer studies have focused on human-coyote interactions in cities. Given that human attitudes, fears, knowledge and resulting behaviours often underpin human-wildlife conflicts, the following study investigates and compares the human aspects of coyote conflict in two cities with large populations of both people and coyotes: Chicago and Los Angeles. Data were collected via email surveys sent to residents of Cook and Los Angeles Counties. The survey instrument included questions on residents’ opinions, fears, knowledge, personal experiences with urban coyotes and behaviours affecting them. The general goal of the study was to investigate the potential for human-coyote coexistence in urban environments. The following research revealed great variation in attitudes towards coyotes, with animal lovers being as much a part of the problem as those with a paralyzing fear of wildlife. Consequently, finding acceptable solutions may pose a significant challenge to urban wildlife managers and reconciliation ecologists.     

Factors influencing expanded use of urban marine habitats by foraging wading birds

Urban marine habitats are often utilized by wildlife for foraging and other activities despite surrounding anthropogenic impact or disturbance. However little is known of the ecological factors that determine habitat value of these and other remnant natural habitats. We examined the preferential use of urban marine habitats in a northeast US estuary to try to elucidate the factors driving enhanced foraging activity at these sites. Using a bioenergetic model, we compared energy intake to energy expenditure and examined differences in behavior and foraging success of great egrets Ardea alba at three urban and three rural salt marshes in Narragansett Bay, Rhode Island USA. Mean per site available nekton energy averaged 4.44?±?0.97 GJ site^?1 and was significantly higher at urban than at rural sites. While energy expenditure by birds was similar across all sites, mean strike and prey capture rate were significantly greater at urban sites, and 70.1?±?12.2 % of strikes by egrets at urban sites were successful. Egrets foraging at urban sites consumed significantly more energy (23.2?±?6.62 W bird^?1) than those at rural sites. Model results indicated a net energy gain by egrets foraging at urban sites, versus a net energy loss at rural sites. Our results may help explain previously observed increases in the numbers of egrets foraging at urban marine habitats, and help provide input into decisions about the extent to which these areas should be considered for restoration or protection.     

Variations in carbon dioxide fluxes within a city landscape: Identifying a vehicular influence

To date, studies examining carbon dioxide (CO₂) fluxes in urban areas have been limited compared to those in rural environments. The objectives of our study were to examine the relationship between traffic volume and CO₂ fluxes. We demonstrated that CO₂ fluxes were strongly linked with surrounding land use, specifically impervious surfaces and traffic volume. A site near downtown Syracuse in New York State (USA) had relatively constant positive fluxes (source: +39 μmol CO₂ m^?2 s^?1) throughout the year as a result of strong vehicular traffic influence from two nearby interstate highways. There was a strong positive relationship between traffic and CO₂ fluxes (r²?=?0.93, p?<?0.0001) with marked differences between the weekend days versus the workweek days. In contrast, a residential site in Syracuse was dominated by vegetative influences during the leaf-on period due to CO₂ uptake by photosynthesis, reaching a maximum negative mean diurnal flux of ?11 μmol CO₂ m^?2 s^?1 around midday (sink). The spatial variations of CO₂ fluxes identify the critical role played by local traffic volumes in affecting the CO₂ dynamics of urban environments. Understanding the dynamic fluxes of CO₂ in urban environments has important implications for local, regional and global evaluations of CO₂ budgets and inventories, and carbon cycle and climate modeling.     

Seasonal comparisons of daily activity budgets of gray squirrels (Sciurus carolinensis) in urban areas

Gray squirrels (Sciurus carolinensis) use trees for various resource needs in urban and nonurban settings; particularly, mast producing trees which are the preferred and supplemental foods for the species. During periods of abundant mast availability, less time will be invested in foraging because of the higher success rate stemming from the increased ability to locate food items. Conversely, in periods of reduced mast availability, more time will be invested in foraging. However, correlations between food availability and foraging effort are only supported under the assumption that gray squirrels rely significantly on mast as a preferred or supplemental food source (Nixon et al, J Wildl Manag 39:1–25, 1975). Therefore, given the seasonal variation in the availability of mast, there should also be correlating seasonal variations in foraging effort. In this paper, we will examine daily and seasonal time-activity budgets of gray squirrels in urban areas. We studied the time-activity budgets of gray squirrels in six urban parks in Baltimore, MD. Seasonal frequencies of activities were expressed as percent occurrence and seasonal differences in activities were analyzed using a Tukey Studentized multiple range test for significance. We found that the activity with highest percent occurrence was forage (2003, summer: 23.8 %, fall: 25.9 %; 2004, summer: 23.1 %, fall: 25.2 %), followed by feed and store, all activities associated with food. Results of the Tukey Studentized multiple range test for seasonal differences of activities yielded significant results (P?P?=?0.003); fall 2003 and fall 2004 (P?=?0.048).     

Urban park area and age determine the richness of native and exotic plants in parks of a Latin American city: Santiago as a case study

Plant diversity and composition in urban parks is determined by socio-economics, environmental, and ecological drivers. These drivers give rise to urban spaces with unique compositions of flora, consisting of planted and spontaneous species. The present study aimed to determine the contribution of native and exotic species in urban parks of a Latin American city, and to assess the related role of park area, age and socio-economic status. We also evaluated administration type (public or private) and the effect of environmental factors on plant richness. We hypothesized that the composition of park vegetation differs according to urban-rural gradient. To determine flora composition, two transects (100 m long by 1–3 m wide) per park were selected in 49 parks. In each of these, we identified all the vascular plants found (woody and herbs, planted and spontaneous), which were then classified as native or exotic. We conducted ANCOVAs in order to determine the effect of five independent variables and one factor, on native and exotic plant richness. Of 550 recorded species, 16.2% were native and 83.8% exotic. Number of plant species per park varied between 42 and 146. The parks are known urban habitats containing the highest planted and spontaneously occurring exotic diversity in the city of Santiago, contrasting with other types of habitats. Likewise, parks in Santiago are habitats with low levels of planted and spontaneously occurring native diversity, compared to the parks of Europe, America North and Asia. Ours results show that park area and age affected native plant richness, while exotic plant richness was determined only by park age. We rejected all other possible drivers. Finally, according to the low frequency of native species, we propose that Santiago’s parks could be gradually reoriented towards ex-situ conservation of native plants.     

Drivers of biodiversity patterns in parks of a growing South American megacity

How urban habitats contribute to biodiversity conservation is a key challenge in a rapidly urbanising world. Urban parks can provide important habitats for native species, but previous studies are geographically biased; fast growing megacities, in particular in South America, are clearly understudied. To assess habitat functions and underlying drivers in parks of Santiago de Chile, we analysed the assemblages of wild growing plant species in two ubiquitous park habitat types (grasslands, wooded areas) in 15 parks (150 plots) along an urban-rural gradient. We first used linear contrasts to compare species richness, beta diversity and the proportion of introduced species. We then tested for the explanatory value of environmental variables operating at different spatial scales (plot, park, urban matrix). Unlike in most previous studies, biodiversity patterns were not related to the position of the parks on the urban-rural gradient. Introduced species, mostly from Europe, generally dominated both habitat types (>90 %). Socio-economic (population growth or density), but not spatial, variables were retained in most models. Maintenance intensity was most influential in predicting species assemblages, complemented by park age in wooded areas. A high proportion of European grassland species indicates a trend of homogenisation in park grassland at a cross-continental scale. We conclude that habitat functions of urban parks for native species that have been mainly demonstrated for Europe cannot be generalised to South American megacities. This highlights the need for innovative and locally appropriate conservation approaches (e.g., re-introduction of native species) to foster biodiversity functions in urban parks of South American megacities.     

Environmental and crown related factors affecting street tree transpiration in Helsinki,Finland

We investigated the drivers of street tree transpiration in boreal conditions, in order to better understand tree water use in the context of urban tree planning and stormwater management. Two streets built in Helsinki in 2002, hemiboreal zone that had been planted either with Tilia?×?vulgaris or Alnus glutinosa f. pyramidalis were used as the study sites. Tree water use was measured from sap flow over the 2008–2011 period by the heat dissipation method. Penman-Monteith based evapotranspiration models of increasing complexity were tested against the tree water use measurements to assess the role of environmental and tree related factors in tree transpiration. Alnus and Tilia respectively used 1.1 and 0.8 l of water per m² of leaf area per day under ample water conditions, but the annual variation was high. The Penman-Monteith evapotranspiration estimate and soil water status changes explained over 80 % of the variation in tree transpiration when the model was parameterized annually. The addition of tree crown surface area in the model improved its accuracy and diminished variation between years and sites. Using single parameterization over all four years instead of annually varying one did not produce reliable estimates of tree transpiration. Tree transpiration, scaled to different canopy cover percentages, implied that the columnar Alnus trees could transpire as much as all annual rainfall at or less than 50 % canopy cover.