Identification of the main site factors and management intensity affecting the establishment of Short-Rotation-Coppices (SRC) in Northern Italy through stepwise regression analysis

Abstract Data collected from 183 poplar and 102 willow SRC experimental plots, located in Central-North Italy, were subjected to stepwise regression analysis to acquire information on the environmental factors affecting plant survival and productivity in the first two-year rotation cycle. Nine Populus ×canadensis Mönch, eight P. deltoids Bartr. clones and four hybrids of Sali× matsudana Koidz were included in analysis. Independent variables were: annual and seasonal water availability (rainfall and irrigation), annual mean air temperature, soil texture, pH, N and organic matter content, planting density and management intensity. Dependent variables were: a) mean annual yield during the first two-year rotation cycle in tons per hectare per year of dry matter (Odt·ha−1·y−1); b) plant survival at the end of the second year from planting (%). Water availability resulted the main variable driving plant survival and biomass production in both poplar and willow clones. Water availability appeared to be the principal factor affecting the establishment of poplar and willow energy plantations in the Po valley. Possible variations in the rainfall regime consequent to climate changes could seriously influence land suitability to SRC. Experimental data also indicate that choice of planting density may increase the biomass yield during the first two-year especially with P. deltoides clones

Growth dynamics of ‘Imola’ poplar clone (Populus ×canadensis Mönch) under different cultivation inputs

The influence of environmental drivers and management strategies on crops growth is a focal point to deal with the potential impact of the climate changes on forest yields. The main aim of this study was to evaluate the effect of irrigation and fertilization on growth dynamics of ‘Imola’ clone, an elite poplar crossed from Populus deltoides Bartr. and Populus nigra L. for short rotation coppice purposes. Using a split-plot design with three replications, two treatments were applied (irrigation and fertilization) with two levels each one: ‘no’ and ‘yes’; 4 theses were considered: irrigation-only (IRR), fertilization-only (FRT) and the irrigation with fertilization (IRF) and control (CRT). At the end of the first 5-year cycle the average yield, in dry matter, was 36.8 Mg ha-1 for non-irrigated plots and 80.8 Mg ha-1 for irrigated plots. While no statistical evidence was detectable for fertilization treatment, a Linear Mixed Model analysis applied to data highlighted the Summer (June-August) as key season for the irrigation of trees. Conversely, interaction between irrigation and fertilization negatively affected growth in the same period. Overall, this trial demonstrated a low impact of fertilization on growth dynamics. Water availability was confirmed as the most important factor for poplar growth, in such site, focusing on the importance of studying alternative, less impacting methods for irrigating such crops

Low cost poplar inventory in the plain of Piemonte (Italy)

The forest inventory is an important tool to know the current and to estimate the future wood availability for industry. Generally it request high economic and time costs if based on direct sampling on the areas or on classification of aerial photo or satellite images.  The paper shows a methodology based on open source software (QGIS®) and images free available on the web (trough ‘Google EarthTM’ software) to carry out a forest inventory particularly regarding poplar stands surface. This cultivation in Italy is characterized by short rotation, about ten years, and the wood is a row material very important for the industry, particularly for plywood. The results of an experimental survey located in the plain of Piemonte Region (north-west Italy) are presented in order to evaluate the timing of completion and the efficiency of the methodology. Data of land cover, divided by poplars, other forest plantations, and natural forests are showed and compared with old inventories, carried out with traditional methods. The evidence of reduction of costs in term of man involved, time, and materials is counterbalanced by some problems due to different age of the web images; however, this alternative methodology, applied by an experienced operator can ensure a good level of precision for the purposes required, with very low costs

The Suitability of Short Rotation Coppice Crops for Phytoremediation of Urban Soils

This experiment was aimed at verifying the usefulness of phytoremediation using Short Rotation Coppice (SRC) in an urban Zn-contaminated site. Besides elemental uptake and reclamation, the SRC method was applied to evaluate the additional benefits of a green infrastructure. Nine different plants with rapid growth and large biomass production were selected: three Populus clones, three Salix hybrids, and three Robinia genotypes. Annual and biennial coppicing were evaluated. Poplar clones were more productive using annual coppicing, while Salix and Robinia produced higher biomass in blocks not coppiced. Poplar had the highest phytoextraction rate during the second year, with 1077 g/ha. Salix clones S1 and S3 extracted similar quantities using biennial coppicing. After two years, the bioavailable fraction of Zn decreased significantly using all species, from the 26% decrease of Robinia to the 36% decrease of Salix. The short rotation coppice method proved to be useful in an urban context, for both landscape and limiting the access to the contaminated area. Improving the biomass yield through the phytomanagement options (fertilization, irrigation, coppicing, etc.) could make SRC phytoremediation an economic and effective solution to manage urban contaminated areas, coupling the added values of biomass production to the landscape benefits

Common walnut (Juglans regia L.) wood characteristics in two Italian plantations

The Woodnat project (H2020) has the goal of identifying the problems that led to poor yields in walnut plantations established under the financial support of EU 2080/92 Regulation and Rural Development Programme, and of improving the market demand for smaller assortments. Some of the plantations monitored in the framework of the project needed thinning: one,  an experimental stand with 5 plots with different layouts and species established in 1994, was thinned in spring 2018; in a second one, a polycyclic plantation established in 1996 with common walnut, hybrid poplar and nurse trees, the walnut was thinned in spring 2017.  At thinning, sample disks were taken at the base of 5 trees randomly selected at each site for the determination of density and shrinkage in the radial, tangential and longitudinal direction. The average density was 0.52g/cm3; the average tangential shrinkage was 12%, while the average radial shrinkage was 6.7%. There were differences in behaviour between the samples from the two sites, probably due to different vegetal materials, age of the plantations and cultivation models

Climate-wise models of biomass productivity for hybrid poplar clones in Europe

Renewable bioenergy has the potential to contribute sustainably to the energy sector. Forestry is the main source of biomass for energy in Europe, and poplar (genus Populus) is widely used for short rotation coppice (SRC). Many studies have assessed poplar clones’ productivity but there is a lack of regional studies and links with the climate. We investigated the biomass productivity of twenty hybrid poplar clones for SRC. Clones were planted in sixteen locations across nine countries in Europe, although not all clones were replicated in all locations. In each location, clones were planted in three replicated plots. All plots were harvested after four years, and the aboveground dry biomass estimated. We fitted clone-specific linear mixed models of total aboveground dry biomass production at plot level as function of climatic variables. For many clones (eight) only annual heat moisture deficit negatively affected productivity, in few cases (3) together with a quadratic term for a smoother relationship. In some other clones (five) only the mean summer precipitation positively and linearly affected productivity. On average, the variance explained by the fixed effects in those models was 56%. For the remaining clones (seven), no climate variables resulted significant. Our study explicitly investigated the quantitative link between water availability and poplar SRC productivity, one of the most important known factors but not often studied with a modelling approach. Further, we show the most productive clones in dried conditions. We also highlight the need to larger scale regional experiments to produce models that can be used in climate change scenarios