Tree Morphometric Relationships and Dynamic Elasticity Properties in Tropical Rain Tree (Samanea saman Jacq. Merr)

Rain tree (Samanea saman) is a dominant species commonly planted as a shade tree in urban landscapes in the tropics, including in Indonesia. This species is also targeted for routine inspection and monitoring within tree management systems. Management should particularly focus on tree health through assessment of tree growth conditions as well as tree stability. However, baseline information on the relationships of many key characteristics for the rain tree (e.g., growth, morphometrics, and biomechanics) is lacking. Therefore, an investigation was carried out to determine the relationship of morphometric parameters to tree growth, which included use of an acoustic tool to assess the elasticity of the tree stem. Fifty rain trees were selected for data collection and evaluated using stress wave velocity tools and visual morphometrics assessment. The results demonstrated that, in general, the trees had good vigor and stability. Statistical analysis showed a strong relationship between tree growth parameters and selected morphometric characteristics. The use of a nondestructive acoustic-based instrument enabled determining the modulus of elasticity, which provided equivalent results with the elasticity value obtained through a common method for determining tree stability. Only live crown ratio and tree slenderness parameters had a relationship with the dynamic modulus of elasticity. These results offer a means of measurement that is simpler, less expensive, and faster than current methods, although further testing is needed for different tree species and growth sites.

Coarse root distribution of Vatica pauciflora (Korth.) Blume in different soil slopes as revealed by root detector

Tree roots have an essential role in absorbing water and nutrients from the soil and supporting tree stability. As an anchor for the tree, the environment can significantly affect root structure but it is rarely investigated due to below ground distribution. The study was aimed to determine the distribution of coarse roots of Vatica trees (Vatica pauciflora) which grows in different soil slopes. Six mature Vatica trees at Bogor Botanical Garden were selected in this study. Root detector as the main tool based on acoustic method was used to evaluate the root distribution. Analysis photogrammetry was carried out to complement the root detector results. The results found that the root detector only can evaluate the radial distribution of coarse root, while root distribution on downward soil cannot be detected. The condition of the site with different slope categories (e.g., flat to steep) affected root distribution patterns. A study on root distribution was useful to assist the evaluation of tree stability and to support arboriculture study.

Tree slenderness coefficient at Bali Botanic Garden

Standing trees has a higher risk regarding structural damage that can cause trees or parts of trees to fail. Meanwhile, Bali Botanic Garden is located in a highland area that periodically gets natural disasters such as heavy wind. However, the information on tree stability is little known. Therefore, tree stability at Bali Botanic Garden was assessed using tree slenderness coefficient (SC) as an indicator. Purposive sampling technique was adopted for locations which highly visited. A total of 624 trees with dbh>40 cm were examined as samples. Trees were classified based on their SC as high (>80), moderate (SC:70-80), low (SC<70). Data were analyzed using descriptive and correlation analysis. Tree slenderness coefficient at Bali Botanic Garden classified as low (609 specimens), medium (11 specimens), and high (4 specimens). Trees with the high category were three individuals of Bischofia javanica Blume (SC=82.76, 83.69, and 89.63) and a Syzygium polyanthum (Wight) Walp. (SC=116.13). Trees with high SC had a higher susceptibility to wind-induced damage. There was a negative correlation between SC and others tree parameters except for tree height (r=0.44). Hence appropriate silvicultural treatment like thinning is recommended to enhance better tree development and minimize tree risk.

Impact of heavy pruning on development and photosynthesis of Tilia cordata Mill. trees

Tree pruning is carried out to reduce conflict with infrastructure, buildings, and any other human activity. However, heavy pruning may result in a diminished tree crown capacity for sugar production and exposure to fungal infection. This risk leads to a decrease in tree stability or vigour. In this work, we analysed the effect of heavy pruning of roadside trees on the photosynthetic performance process compared to neighbouring unpruned trees. Four years of tree crown growth was studied by terrestrial imaging. Tree vitality (Roloff’s classification) and risk (Visual Tree Assessment) were evaluated. Over-pruned trees showed intensified photosynthetic efficiency during the growing season following pruning. Particularly ET0/TR0 and PIABS tended to increase in pruned trees while higher Fv/Fm was noted only in late October, suggesting delayed leaf senescence. After four years, pruned trees rebuilt their crowns, however not in their entirety. Results obtained from biometric, vitality, and risk assessment showed high differentiation in pruned tree crown recovery. Our results revealed that despite the intensified efforts of trees to recover from wounding effects, severe pruning evokes dieback occurrence and a higher risk of failure in mature trees.

The Clade Displacement Index: how to detect hotizontal gene transfers in unrooted gene trees

While most genes of any organism are inherited vertically - i.e. from its parent organisms - sometimes they can be exchanged between unrelated species in a process known as the horizontal gene transfer (HGT). Studies of HGT contribute to our knowledge about the mechanisms of evolution, including the emergence of new pathogens, and a great deal of effort has been put into different methods of finding transferred genes. The golden standard of HGT detection is the analysis of the incongruence between the gene and the species trees. Those methods typically require rooted trees, in which the direction of evolution is known. Gene trees are typically unrooted, and rooting them is yet another step in HGT analysis, prone to errors which may lead to wrong conclusions. A natural question arises: can HGTs be detected in gene trees without rooting them at all? It turns out that, for a particular, yet broad, class of transfers, the answer to this question is: yes. It also turns out that the same methodology can be applied to complement the bootstrap support in assessing the stability of gene tree topology. In this article, we present the Clade Displacement Index, a measure of shift of a given clade's location between two trees. We derive algorithms to compute it and give several examples of its applications to HGT detection and gene tree stability analysis. We finish by pointing out directions for further studies and an example that shows that not all HGTs are detectable without knowing the location of the root of the gene tree. A Jupyter Notebook with the implementation and applications of CDI described in this paper is available at \url{https://github.com/mciach/CDI}

Norway spruce production and static stability in IUFRO thinning experiments in the Czech Republic

Despite recent issues, Norway spruce remains the most important commercial tree species which might be demanded henceforth for its broadly utilizable wood. Even before foresters faced both the bark beetle outbreaks and spruce decline, spruce monospecific stands were known to be prone also to other damage due to snow and wind. On this basis, measures that help prevent such failures were looked for, which resulted in the establishment of international IUFRO experimental series focused on impacts of different thinning regimes on stability and production of spruce stands. The thinning treatments differed in numbers of trees removed and retained on the site when dominant height of crop trees was reached or allowable cut in non-crop trees was accumulated. Also effects of different width of skid trails were tested. The study summarizes the results from the two IUFRO experiments in the Czech Republic. Effects of thinning regimes on spruce were found positive though thinning reduced the total volume production of wood while improving crop-tree stability which enhanced production safety. Different widths of skid trails had no effect on wood increment. Early thinning of spruce can be used to prevent their damage. No such measure, however, can alleviate the spruce decline.

Comparison of variability in results of acoustic tomographs in pedunculate oak (Quercus robur L.)

Tree acoustic tomography is a widely used device supported method for tree stability assessment. In this work, the results of the three most commonly used devices for acoustic tomography of standing trees (ARBOTOM®, ArborSonic®, and PiCUS®) were compared on selected individuals of sessile oak in Brno, Czech Republic. According to the statistical analysis, there was a significant difference between values measured by the PiCUS® acoustic tomograph and those measured by both the ARBOTOM and ArborSonic® acoustic tomographs. Based on the measured data, velocities measured by PiCUS® were considerably lower than those recorded by the other acoustic tomographs (ARBOTOM® and ARBORSONIC®). Measured radial and tangential velocities differed from each other. In data obtained from the defective cross-sections, this difference was attenuated. Image reconstructions (tomograms) from the acoustic tomographs differed from each other. Complex shapes of defects in standing trees can significantly influence acoustic tomography results. According to the statistical analysis, there was no significant relationship between sound velocity and density, while there was a relatively strong positive correlation between sound velocity and moisture content.

Impacts of Wire Basket Retention and Removal on Whole Tree Stability and Long-term Growth1

When balled-and-burlapped trees are planted, a decision must be made regarding whether the wire basket, burlap, and other packing materials should be removed (completely or partially) or retained. While past research has failed to show a significant impact of either approach with regard to initial growth and establishment, many professionals still question whether a decision to leave the wire basket intact at planting will have longer-term impacts to tree health and stability. In this study, we revisit two nursery trials first initiated in 2011 and 2012 to assess the impact of burlap folding, and full wire basket removal, partial removal, or retention on tree growth and root anchorage five to six growing years after planting. We found that neither stem caliper (min P = 0.249) nor twig elongation (min P = 0.297) differed among removal treatments with the Norway maple (Acer platanoides L.) and ‘Skycole' honeylocust (Gleditsia triacanthos L. var. inermis) trees used in this study. Similarly, we were unable to detect any differences in rooting strength among the removal treatments tested (min P = 0.154). These results serve as further evidence that wire baskets are not a cause of early tree mortality or instability. Index words: Arboriculture, biomechanics, growth and longevity, nursery production, static-pull test, transplanting, transplant shock. Species used in this study: Norway maple (Acer platanoides L.); ‘Skycole' honeylocust (Gleditsia triacanthos L. var. inermis).