Barbara Mariotti

Container effects on growth and biomass allocation in Quercus robur and Juglans regia seedlings

Container size and shape impacts biomass allocation of nursery seedlings. Effects of different pot types on shoot and root growth and biomass allocation were evaluated in nursery cultivation of Quercus robur L. and Juglans regia L. We compared two containers currently used in Italian forest nurseries (ISSA-pot®; Plastecnic®) and two alternative types (Superoots Air-pot®; Tubex®); different pot sizes were also included: two for ISSA-pot and Plastecnic; four for Air-pot. Seedlings were evaluated during 1-year nursery growth and biomass allocation was determined on a sub-sample at the end of the growing season. For both species, seedlings grown in larger containers generally grew more and containers >4.5 l produced the largest seedlings. Root biomass was >50% of total biomass in all containers with the tap-root comprising the major root system component. Air pruning in the Air-pots inhibited seedling growth of both species in narrow deep pots, while in bigger sizes (wide and deep) it produced positive responses, especially for walnut. Container configuration differentially affected the studied species: shoot and root system development of walnut seedlings was more limited by pot diameter than depth. Q. robur had improved shoot and root system development when grown in Tubex.

Relation of Fraxinus excelsior seedling morphology to growth and root proliferation during field establishment

Abstract The demand for hardwood seedlings has increased in recent years in Italy, particularly for tree farming programmes oriented towards quality wood production; the availability of high-quality seedlings is a crucial step towards being successful in establishing such productive plantations. The aim of this work was to identify the most important morphological seedling quality attributes. Nursery stock consisting of 1-year-old bareroot Fraxinus excelsior seedlings was evaluated for field performance at the end of the first growing season on a plantation site in the Po Valley, northern Italy, in relation to the objective of producing high-quality timber plantations. The approach consisted of (1) morphological characterization (i.e. stem height, root collar diameter, shoot and root architecture) of the seedlings before outplanting; (2) morphological assessment (including root excavations) of the plants after the first year of field growth; (3) relating attributes observed during phases (1) and (2); and (4) identifying those morphological characteristics that effectively predict outplanting success. The results indicate that the highest quality seedlings are best selected on the basis of initial shoot height and root system morphological type (i.e. stem heights 40–50 cm with a fasciculate root system of at least 40 cm length and rich in fine roots). Planting these seedling morphological types may dramatically improve field performance (i.e. more than 100% increase of height increment in this case), which will help to promote the development of afforestation plantations oriented towards high-quality wood production.

A tree from waste: Decontaminated dredged sediments for growing forest tree seedlings

The sediments dredged from a waterway and decontaminated through a phytoremediation process have been used as substrates alternatively to the traditional forest nursery substrate for pot productions of holm oak (Quercus ilex L.) planting stocks. The substrates, made by mixing decontaminated sediments to agricultural soil at different degrees, were tested in order to evaluate their suitability as growth substrates. The experiment was carried out at the nursery of the Department of Agricultural, Food and Forestry Systems of the University of Florence (Italy). The experimental design consisted of four randomized blocks with six pots as replicates for each of the following treatments: 100% sediments, 66% sediments, 33% sediments, 100% agronomic soil and 100% traditional peat based substrate. In each pot, one holm oak acorn was seeded. Germination and both physiological and morphological traits of the seedlings were analysed during and at the end of the first growing season. Holm oak grown in phytoremediated sediments at higher concentrations showed germination levels comparable to those in the traditional substrate, and survival capacity (especially in 66% sediments) slightly higher than in 100% soil. Physiological performance of seedlings resembled that on the traditional substrate which required the addition of fertilizer, at least for the first growing season. Seedlings grown in mixed substrates with higher sediment concentrations occasionally showed better photosynthetic capacity with improved connectivity between the units of the photosystem II. At the end of the first growing season, height as well as the number of growth flushes of the seedlings grown in sole sediment or soil-sediment substrates were similar to what generally is observed for forest nursery stock of Quercus spp.. Regarding the root-system articulation and growth in depth, results in the mixed substrates were comparable to those for seedlings grown in the traditional forest nursery media, and higher than seedlings grown in 100% agronomic soil. According to our results, the reclamation of dredged sediments can provide appropriate nursery substrate for germination beds for forestry species.

Beech coppice conversion to high forest: results from a 31-year experiment in Eastern Pre-Alps

Key messageSelective thinning is a more viable method for beech coppice conversion to high forest when compared with thinning from below as it enhances tree growth, reduces mortality of the remaining trees, and allows to obtain stands with a higher mechanical stability and larger crowns.ContextBeech forests in North-East Italy have been largely managed as coppice. Due to socio-economic changes, a large conversion to high forests program started in the second half of the past century.AimsA long-term experiment testing the effects on tree growth and stability of two different conversion methods (thinning from below—method A; selective thinning—method B) was implemented.MethodsBoth silvicultural treatments started in 1979 with a first thinning followed by a second one in 1997. All trees were periodically measured in order to assess mortality, stability, and growth during the period 1979–2010. In 2010, an assessment of stem quality and crown size was also performed.ResultsBoth methods were economically viable, but method B acted with a higher intensity both in 1979 and in 1997, thus making the harvest more profitable for the owners. Moreover, method B enhanced tree growth, especially in the period after the first thinning, reduced mortality, and allowed to obtain stands with a higher mechanical stability and with larger crowns.ConclusionIt would be possible to adopt some of the criteria prescribed with method B in future thinnings over the large areas actually managed with method A, as prescribed by the law.