Thinning Influences Wood Properties of Plantation-Grown Eucalyptus nitens at Three Sites in Tasmania

Thinning of forestry plantations is a common silviculture practice to increase growth rates and to produce larger dimension logs. The wood properties, basic density and stiffness, are key indicators of the suitability of timber for particular purposes and ultimately determine timber value. The impact of thinning operations on wood properties is, therefore, of considerable interest to forest growers and timber producers. To date, studies examining the impact of thinning on wood properties have produced variable results and understanding of the consistency of the effects of thinning treatments across various sites for important plantation species is limited. Two non-destructive assessment techniques, drilling resistance and acoustic wave velocity, were used to examine the impact of thinning on basic density and stiffness in 19–21-year-old plantation grown Eucalyptus nitens across three sites. Commercial thinning to 300 trees ha−1 decreased the stiffness of standing trees and this effect was consistent across the sites. Reduction in stiffness due to thinning ranged from 3.5% to 11.5%. There was no difference in wood properties between commercially and non-commercially thinned trees to 300 trees ha−1 and no difference in wood properties when thinned to 500 trees ha−1. Basic density was not affected by thinning. The site had significant effects on both basic density and stiffness, which were lowest at the highest precipitation and highest elevation site. The results indicate that wood properties are influenced both by silviculture and site environmental differences. This knowledge can be used for the better management of E. nitens resources for solid wood production.

Tabebuia rosea (pink poui).

T. rosea is a medium to large tree attaining a height of 28-37 m with a d.b.h. of 50-100 cm. It is widespread from Mexico to Peru, Venezuela and Ecuador. T. rosea is a very important species in these regions, its timber is valuable and of good quality, it is excellent to work and has an attractive finish. It shows good performance in forestry plantations and enrichment planting trials, and also has high potential to be used in afforestation projects. This species is also used in agroforestry (e.g. alley cropping), as a live fence, as a shade tree and as an ornamental. It is the national tree of El Salvador.

Chromolaena odorata (Siam weed).

C. odorata is a very widely distributed tropical shrub that is still expanding its range, and is considered one of the world's worst weeds. It continues to spread due to its effective short- and long-distance dispersal. It can form pure stands where established, often in disturbed areas, grasslands, fallow areas and forestry plantations, and is highly competitive. It is viewed as a major environmental weed, but is appreciated by some agriculturalists as it shortens fallow time in shifting cultivation.

Corchorus hirtus (Orinoco jute).

C. hirtus is a herb or subshrub found to be infesting wetlands in Minas Gerias, Brazil due to its high frequency and density (Mascarenhas et al., 1995). In Brazil, it is widely distributed and grows either as a ruderal or as an invading weed infesting pastures. It was listed as a weed in a checklist of invasive plants in forestry plantations in the Lower Amazon (Pires, 1992), but the paper states that the term 'invasive' is equated with 'weed' defined as any plant growing where it is not wanted, so its status as a true invasive is dubious. It is listed as a weed in several countries by Sinha et al. (2011). It often grows as a weed in grain fields in Central America (Standley and Steyermark, 1949).

The habitat diversity and its sosological evaluation of the Lviv museum of folk architecture as an example of previous analysis of anthropogenic landscape demutations

The habitats diversity of Lviv Skansen was researched and it sozological value was estimated. On the territory of Skansen, 19 types of habitats belonging to 12 groups of 7 classes have been identified and described. Among them, 14 types have an anthropogenic origin, 3 – semi-natural, and only one – natural. On the territory of the museum were found 2 species of vascular plants listed in the Red Book of Ukraine – Allium ursinum L. and Epipactis helleborine (L.) Crantz, as well as naturalized populations of cultural Crocus sp. and Leucojum vernum L. From the sozological point of view, tree habitats – highly artificial broadleaved deciduous forestry plantations, coniferous forestry plantations and hard water source settlements on tuff and travertine formations – are of the greatest importance. The last one is a new type of habitat for region, barely studied. Currently, only one location is known in the vicinity of Lviv (Bryukhovychi). On the territory of the European Union, this habitat is included in the list of particularly valuable habitats of the NATURA-2000 environmental network. Highly artificial broadleaved deciduous forestry plantations habitats, although formed by non-native species, are currently ongoing through demutation proces. During the years of absence any cuttings or other forms of management, the plantations of Robinia pseudoacacia L. and Aesculus hippocastanum L. were replaced by semi-natural forests from young undergrowth of Betula pendula Roth, Acer platanoides L. and Picea abies (L.) H.Karst. The grass layer in these forestry plantations is represented by fragments of typical nemoral species. Thus, despite the anthropogenic origin of the habitats formed in Lviv Skansen, they play an important role in the conservation and distribution of biodiversity and help maintain the stability of green corridors of sub- and urban areas.

Hibiscus elatus (blue mahoe).

Due to its rapid growth rate and valuable wood, H. elatus has been introduced and grown in experimental and forestry plantations. It has been also introduced in tropical and warm temperature areas to be used as an ornamental and shade tree (Weaver and Francis, 1989). This early successional tree has escaped from cultivation and can be found naturalized in disturbed sites, secondary montane forests and foothills (Francis and Liogier, 1991; Graveson, 2012). Currently, H. elatus is listed as invasive only in Trinidad and Tobago (Trinidad and Tobago Biodiversity, 2016), but it is spreading and becoming abundant on many Caribbean islands such as Puerto Rico, Virgin Islands, Grenada and St Lucia (Francis and Liogier, 1991; Kairo et al., 2000; Salazar and Soihet, 2001; Graveson, 2012). A risk assessment for Hawaii gave the species a low risk score of 5 (PIER, 2016).