Evaluation of Alnus subcordata for urban environments through assessment of drought and flooding tolerance

The urban environment is stressful and trees experience multiple stresses, including drought, flooding, and extreme heat, all of which are likely to increase under future climate warming and increasing urbanisation. In the selection of tree species to maximise ecosystem services, tolerance to site characteristics such as flooding and severe drought is of critical importance. This study evaluated the suitability of a rare species, Alnus subcordata C.A. Mey (Caucasian alder) from the Hyrcanian forests of southern Azerbaijan,for its functionality as an urban tree. A total of 48 pot-grown, two-year-old saplings of A. subcordata were tested in a greenhouse experiment using a complete randomised block design. Each block contained four replicates of three treatments (waterlogging, drought, control), with 16 plants per treatment. Height differences between treatments were measured, and water status was estimated by determination of midday leaf water potential (ΨL) and stomatal conductance (gs). To estimate drought tolerance reaction in the treatments, leaf water potential at turgor loss (ΨP0) was used together with broken-stick modelling of water status over time. There was a significant difference in tree height between the different treatments. In the drought treatment, A. subcordata plants showed no height increase, while plants in both the waterlogged and control treatments increased in height during the nine-week experiment. Over 63 days of flooding, plant water status was slightly more negative in the waterlogging treatment, but did not deviate essentially from the control. In the drought treatment, plant water status rapidly deviated from the control. There was a significant differencein ΨP0 between treatments, with drought-treated plants showing the lowest value (−2.31 MPa).This study demonstrated that A. subcordata has limited tolerance to drought and seems to rely more on waterloss-avoiding strategies. However, the species may be usable at periodically waterlogged sites, due to its high tolerance to flooding. It could therefore be recommended for wet urban environments and stormwater management facilities, for which reliable guidance on suitable trees is currently lacking.

Logging damage to residual trees during sustainable harvesting of uneven-age stands in the Hyrcanian forests of Iran

Background: The frequency of wounded trees and intensity of wounds during logging operations can have serious impacts on stand growth and forest sustainability. The aims of the study were to evaluate and compare stand (tree and regeneration) damage level, wound characteristics, and damage types occurring when using a cable skidder in salvage logging and selection cutting. Methods: This study was conducted on four sites of mixed uneven-aged hardwood stands in the Hyrcanian forests of Iran. At two sites, salvage logging was applied (SL1 and SL2), and low-intensity selection cutting (SC1 and SC2) was applied at the other two. A systematic plot sampling design was used on the study area for damage assessment. Results: The percentage of regenerating trees damaged was 2.8, 2.1, 4.3, 1.4 %, in SL1, SL2, SC1, and SC2, respectively. The corresponding percentage of damaged trees was 4.3, 3.7, 4.9, 1.7 %. Most of the damage (48–79%) to the stand occurred during the winching stage at all the sites. Most of the wounds were located on the bole (51–78%). The average wound height and wound size at selection cutting sites were significantly higher than at the salvage logging sites. The incidence of high-intensity wounds at the salvage logging sites (55% at SL1 and 57% at SL2) was higher than at the selection cutting sites (24% in SC1 and 30% in SC2). Regenerating beech (Fagus orienalis Lipsky) and alder (Alnus subcordata C.A.Mey) had the highest incidence of damage. The number of damaged trees increased with increasing winching distance. Conclusion: Damage levels in stands during salvage logging and low-intensity selection cutting are lower (about a quarter) than the damage level to residual trees (12–23%) and regeneration (5–11%) from conventional selection cutting in uneven-aged mixed hardwood stands in the Hyrcanian forests. Because of the ecological and conservation value of deadwood, if the incidence of wind-fallen trees is low, the wood should be left in forest stands due to the high cost of salvage logging and the damage caused to residual and regenerating trees.

The Research of the Radial Growth of the Flora Species Which Do Not Have Special Protection on the South Hillsides of Greater Caucasus

The radial growth of the trunks of the following flora species which do not have special protection on the southern hillsides of Greater Caucasus was studied in the article: Georgioan oak- Quercus iberica M.Bieb Common hornbeam - Caprinus betulus L. Common chestnut - Castanea sativa Mill. Black walnut - Juglans nigra L., Heart leaved alder - Alnus subcordata C.A.Mey. During the dendrochronological analyses, the dynamics of growth over the years were analysed based on the distances between the tree rings. The impact of the climatic factors on the growth of the trees was analysed and the ages of tree species were investigated. Based on the dendrochronological historical application, according to the numbers of tree rings, the ages of the trees were defined in the studied species. According to the numbers of tree rings, the oldest type of the rare and scanty flora types which have no special protection was identified as Caprinus betulus L. in the Zagatala region. The tree was taken from Zagatala district, planted in 1944, was 75 years old and had 330 cm diameter. The observation of dendrochronological researches indicates the formation of a new microclimate. It was observed that in the investigated species, radial growth was more intense during matureness, then it was weakened with age. In the comparative analysis, it was observed that the minimum radial growth was in 2010 and 2015, and the maximum growth was between 1973 and 1985 in the Zagatala region

Effect of the root biotechnical characteristics of Alnus subcordata, Paulownia fortunei and Populus deltoides on the soil mechanics

The effect of root reinforcement depends on the biotechnical characteristics of the root system including the tensile strength of individual roots, the root density and the distribution of the root system in the soil. This research was conducted in the Hyrcanian forest in Iran, where shallow landslides are frequent due to road construction. The effect of the root biotechnical characteristics of Alnus subcordata, Paulownia fortunei and Populus deltoides each one in 2-, 10- and 15-year-old plantations was assessed. The profile trenching method was used in this study to obtain the root area ratio of individual species by counting the number of roots and measuring the root diameter. For each species, single root specimens were sampled and tested for tensile tests in the laboratory using the standard Instron apparatus. The natural moisture content (two weeks after rainfall), Atterberg limits, shear strength of the soil were determined for plantations, stable and unstable sites. Results of this study indicated that plastic index and internal friction angle decreased with increasing root diameter rate. Moreover, internal friction angle and cohesion increased with increasing root area ratio and root diameter and density index. Tensile strength of roots decreased with increasing stand age. The highest and the lowest tensile strengths among species were observed for Paulownia fortunei and Populus deltoides, respectively. The findings of this research contribute to expanding the knowledge of root biotechnical properties of some tree species and to the choice of the most appropriate species for improving plastic index and shear strength in landslide prone areas.

Chemical analysis and antioxidant activities of bark extracts from four endemic species of Hyrcanian forests in Iran

Chemical analysis of the bark from four Hyrcanian forest species,Pterocarya fraxinifolia,Alnus subcordata,Gleditsia caspicaandParrotia persicawere performed, and their total phenol contents, and antioxidant and chelating activities were evaluated. The greatest total phenol content (TPhC), 54.3% in dry extract, was detected inP. fraxinifoliabark and the lowest one inG. caspicabark with 4.5%. The 50% inhibitory concentrations (IC50) in the radical-scavenging assay against DPPH radicals in bark acetone extracts ofP. fraxinifolia,A. subcordata,G. caspicaandP. persicawere 0.17, 0.21, 13.35, 0.19 mg ml−1, respectively. In the metal-chelating activity system,G. caspicaextract demonstrated significant activity.Pterocarya fraxinifolia,A. subcordataandP. persicabark acetone extracts revealed a high potential for inhibition of DPPH radicals due to high amounts of phenolics. Superior health benefits can be expected from the compounds syringol, 4-vinylguaiacol, tyrosol, chavicol, resorcinol, hydroquinone, vanillin, rheosmin and acetophenone.Gleditsia caspicawas found to have significant chelating activity due to isoeugenol.

Two new Diptacus species (Acari: Trombidiformes: Diptilomiopidae) from Iran

Two new Diptacus species (Diptilomiopidae: Diptilomiopinae) including D. genusetosus sp. nov. and D. longiscatuber sp. nov. were collected from Alnus subcordata C. A. Meyer (Betulaceae) and Cornus sanguinea L. (Cornaceae), respectively, in Aliabad-e-Katul, Iran. They are described and illustrated. The new species appear to be vagrants on the leaf underside, they are white wax producers and no damage was observed on the infested plants. This is the first record of an eriophyoid mite on Cornaceae in Iran.