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Trees are living elements interspersed throughout our cities, and are considered by economists to be "fixed assets". Though they form part of our cities they do not have a set price as normally understood and calculated within the framework of a perfectly competitive market. The main aim of this article was to compare the main methods developed in the USA (North American) and Europe (Finnish, Swiss, French and Capitalisation methods) for determining the monetary value of urban trees in the town of Santiago del Estero, northeastern Argentina. The values of eight specimens of the most abundant species in the city (Brachychiton populneum, Citrus auriantum, Grevillea robusta, Jacaranda mimosifolia, Sapindus saponaria, Tabebuia impetiginosa, Thevetia peruviana, and Tipuana tipu) were calculated using all five methods mentioned above and the mean values returned compared by ANOVA. The results suggest a methodology combining both capitalisation and parametric indices might be the most useful way of determining the value of city trees.

Keywords: small area estimation; EBLUP; MSE estimator; LiDAR; estimation of natural resources SMALL AREA ESTIMATION OF FOREST ATTRIBUTESForest management involves decision-making problems and, to evaluate the different management alternatives, up-to-date information about wood stocking, structure, and health status is needed. Decisions may affect the whole forest, and also subdivisions of the forest called stands or management units (MUs) (Packalen et al., 2011;Finley et al., 2014), sub-stands, or even smaller parts such as treatment units or harvest areas. Thus, information needs to be provided at all these divisions of the forest to assist with its management.Forest areas are typically so large that obtaining field measurement of the variables of interest over all the forest is impossible in practice. Thus, information to aid decision-making processes is typically based on descriptive statistics for each area of interest (AOI). Different authors have recognized the importance of incorporating the uncertainty or lack of knowledge in forest planning decision processes (e.g., Pasalodos et al., 2013) by supplementing the estimates associated to each AOI with suitable reliability measures. Furthermore, forest inventories are sometimes enforced, either by law (Spanish Ministry of Agriculture 1971, Castilla y Leon Regional Goverment 1999) or by contractual agreements, to provide estimates for certain MUs with relative errors below specific thresholds.Traditional forest inventories rely on probability-based sampling designs to estimate means or totals for different variables of interest. During the last decades, remotely sensed auxiliary information has been included in forest inventories to increase their efficiency. The most extended methodology for this purpose is the area-based approach (ABA) (Naesset, 2002). In this methodology, remotely sensed covariate grids covering the whole study area are typically regarded as a census, and pixels play the role of population units for which auxiliary information is available. Field measurements are also conducted in a number of plots of size similar to pixels. Each field plot is also considered as a population unit, and measurements of the variables of interest as well as auxiliary information are available for them.Design-based direct estimators such as regression estimators (Cochran, 1977) or generalized regression estimators (Deville and Sarndal, 1992) make use of highly correlated auxiliary information and have been used under the ABA setup with remotely sensed auxiliary information to increase the efficiency of forest inventories (Breidenbach and Astrup, 2012). But field surveys are expensive, and the number of field plots (or sample units) that can be allocated within a specific AOI decreases with its area. Thus, for AOIs of reduced

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Urban trees perform a number of basic functions related to the environment and the welfare of city dwellers (ecological, recreational, psychological), although their benefits are not readily quantifiable. However, in certain situations, it is essential to assign an economic value to the trees. There are currently various methods for valuing the benefits of trees and greenspaces in human settlements, including statistical methods, the travel cost method, contingent valuation, the hedonic pricing method, and integrated methods. However, these methods are not used in official valuations of urban trees; in these cases, appraisal methods are used. The aim of this paper is to study the appraisal methods used for their detailed features and the possibilities of their application. The main conclusion of this review is that there are a number of methods with different types of application. The best method is selected according to tree location, type of land ownership, and the availability of data. Methods with a higher degree of applicability are CTLA, a parametric method of low difficulty, and Contato, a mixed method of medium difficulty. In any case, it is advisable to increase efforts to objectify the correction index in the case of parametric and mixed methods.

It is important today to take account of the opinions of both experts and stakeholders in the sustainable management of forests. SILVANET (Universidad Politécnica de Madrid, Madrid, Spain) is a software package that offers a useful methodology for assessing the preferences of individuals or groups, and applying them to the design of a sustainable forest management plan. The program starts by identifying the personal preferences of the evaluators based on information provided individually when comparing and selecting sustainability options from a series of site pairs. The evaluator is given information on certain sustainability indicators obtained in the area to be assessed. The scope of the evaluator's knowledge of sustainable forest management and the consistency of his/her decisions is assessed, and he/she is then included in a group of people with similar systems of preferences to encourage interaction between evaluators in the same group. The preferences are characterized by matrices that encode individual assessments, the maximization of their utility and the analysis of past decisions. Finally, by identifying preferences, we are able to design the forest management system that maximizes the concept of sustainability for each individual or group of individuals. In this paper, we present the results of its application to mono-specific conifer forest stands, although it can be adapted to other forest types. The forestry management experts classify its usability as good, although non-expert users give it a lower rating.

Several studies show that the interaction between airborne pollutants and pollen grains can lead to greater pollen allergenicity, and thus increase and exacerbate the incidence of pollinosis, all of which represents a major public health problem. This article analyses the possible influence of various airborne pollutants (O3, PM10 and PM2.5, NO2, CO and SO2) on the tree-type pollen grains of Cupressaceae, Olea, Platanus, Pinus, Ulmus and Populus. The 11 areas around the stations in the Madrid Region’s pollen monitoring network (Red Palinocam) were taken as a geographic reference for this study. The degree of interaction between airborne pollutants and pollen types was explored using the rank correlation analysis. O3 and NO2 are the pollutants with the highest rate of significant correlations with pollen types. Olea, Cupressaceae and Platanus—the most highly allergenic in this study—are among the pollen types with the greatest number of significant correlations with almost all the air pollutants in the different areas. This could point to a potential associative effect between both variables which would exacerbate the negative effects on public health.

Urban trees are generally considered to be a public asset and are an important part of a city's heritage. The aim of this work is to analyse the influence of season on the economic appraisal of various trees in Madrid. Photographs were taken of 43 individual tree specimens in summer and winter. The survey was designed to compare differences of opinion in the economic assessment of trees. The trees were assessed by eight valuation methods used worldwide. A total of 78 agroforestry engineering students answered a written survey, and the variables considered were: percentage of students who always evaluated the tree equally (%0), percentage of students who assigned more value to the summer photograph (%S), and percentage of students who assigned more value to the winter photograph (%W). The results were analysed by the statistical test of equal proportions and ANOVA to detect differences according to tree type (evergreen or deciduous), species, and other groupings made by the authors in previous works. W and S percentages are similar. The ANOVA analysis rejects the equality of percentages of S and W between groups. The Welch test rejects the equality of the percentage of S, W, and O between species.