Age estimation of different tree species using a special kind of an electrically recording resistance drill

The determination of tree age is an important issue for urban green planning, forestry and dendrology; finding non-destructive and quasi-non-destructive methods for this purpose is of great theoretical and practical importance. The resistance drilling method is quasi-non-destructive because the average diameter of an opening that remains after drilling does not exceed 3 mm. Do electrically recording resistance drills allow precise assessment of tree age? The aim of this study is to assess the accuracy of determining the number of tree rings based on an examination of this special kind of drilling resistance profiles for three tree species, the pine Pinus sylvestris L., the oak Quercus robur L., and the birch Betula pendula ROTH. In 2015 and 2016, 15 pine trees, 15 oak trees, and 15 birch trees were randomly selected. For each studied tree, a measurement was conducted using the electrically recording resistance drill IML-Resi E400 with a flat-tipped 1.5/3 mm steel needle (research sample), and an increment core was taken (reference sample). The drill used was not a real Resistograph^®. The analysis of the E400-profiles underestimated the number of tree rings; the mean bias error (MBE) values were –6.5, –2.5, and –6.0 years for pine, oak, and birch, respectively. The proportion of investigated trees with less than five years difference between the research and reference samples varied from 38.4 (birch) to 66.7 (oak) percent. The accuracy of tree age determination was lowest for birch and highest for oak. The binomial generalised linear model (GLM) revealed that the most accurate tree age assessments were obtained from tree rings wider than 2 mm. The measurements clearly showed that the electrically recording resistance drill IML-Resi E400 enables a quick, although approximate, tree age assessment. Future research should concentrate on electronically regulating and recording drills, providing a higher spatial and signal resolution, and a stronger correlation to wood density.     

刺楸苗木繁育及栽植技术

针对刺楸种源稀少、繁殖困难、栽植不易成活等关键技术难题,进行了一系列的试验研究,总结出了刺楸苗木繁育及栽植的技术方法及措施,为刺楸的规模化栽培和开发利用奠定了技术基础。     

Impact of assessor on tree risk assessment ratings and prescribed mitigation measures

Tree risk assessment is an inherently human endeavor that can be influenced by risk perception, risk acceptance, and professional bias. Tree risk assessments from 296 arborists were evaluated to assess tree- and assessor-based factors that influenced ratings. Additionally, we investigated sources of variability associated with the main inputs of risk assessment – likelihood of impact ratings, likelihood of failure ratings, and consequences of failure ratings. Finally, we assessed the factors that influenced prescribed mitigation measures. Results indicate that professionals with training and industry credentials had lower risk ratings and were less likely to prescribe more active mitigation measures like tree removal. More notably, there was significant variability among raters, with the likelihood of impact and consequence of failure serving as the most variable factors in tree risk assessment.     

Installing cables did not affect annual radial increment in co-dominant stems of red oaks

Arborists install cables to support co-dominant stems. The adaptive growth hypothesis predicts that doing so will alter radial increments in the stems because their motion will have been restricted. To facilitate the wind-induced motion of cabled stems, cables made of more extensible material have been suggested as an alternative to systems made of steel. Cables made of steel and polypropylene were installed in red oaks (Quercus rubra L.). Trees were harvested after five years and annual radial increment was measured for the previous sixteen years in four directions (incident with and perpendicular to the direction of the cable) on five discs removed from two co-dominant stems that were cabled in each tree. Annual radial increment did not change in response to the installation of cables with one exception: in the three years following installation, it was greater incident with the cable on two discs immediately proximal and distal to the eyebolt in each co-dominant stem to which steel cables were attached. The exception appears to be due to the formation of wound wood. The results contradict the adaptive growth hypothesis, but this was likely due to cables not restricting wind-induced motion to the extent achieved in previous studies.     

Support for a new credential in urban forestry: Results from a survey of urban forest professionals

Urban forest professionals struggle with public recognition and a clear identity in spite of growing demand for their expertise. No single credential or professional support system defines or unites urban forest professionals, who instead rely on several closely allied professions for professional support. This reliance is thought to contribute to this lack of recognition and indistinct professional identity. Thus we asked urban forest professionals if they believed the urban forestry profession needs its own credential and, if such a credential were available, would they obtain it. An international survey resulted in 749 respondents from 13 countries, with the vast majority from the United States and Canada. On average, respondents believed a credential was needed and would obtain it if offered. Late-career professionals were less likely to say they would obtain such a credential, while there was some evidence that women and early-career respondents are more likely. Some groups, most notably the self-employed, were much less likely to think a credential was needed and even less likely to obtain it were it to be offered. Respondents already hold 2.38 credentials on average, the most commonly held credentials being from the closely allied professions of arboriculture and forestry. Without specifying the format or scope, the survey asked respondents for opinions about a hypothetical urban forestry credential. Respondents raised concerns related to whether a credential could embrace the full scope of urban forestry, whether there was overlap or redundancy among existing credentials, and the cost of obtaining additional credentials. In addition, respondents noted credentials may need to align with diverse regulatory and employment environments. Nonetheless, open-ended responses overwhelmingly noted that urban forestry has emerged as a distinct profession that merits a credential to support a unifying identity and recognize the specialized training required.