Biomass productivity and water use relation in short rotation poplar coppice (Populus nigra x P. maximowiczii) in the conditions of Czech Moravian Highlands

Abstract

The plantations of short rotation coppice (SRC) usually based on poplar or willow species are promising source of biomass for energy use. To contribute to decision-making process where to establish the plantations we evaluated the water consumption and its relation to biomass yields of poplar hybrid clone J-105 (Populus nigra x P. maximowiczii) in representative conditions for Czech-Moravian Highlands. Water availability is usually considered as one of the main constraints of profitable SRC culture and therefore we focused on analyzing of the linkage between the aboveground biomass increments and the total stand actual evapotranspiration (ETa) and on water use efficiency of production (WUEP). During the seasons 2008 and 2009 the total stand ETa measured by Bowen ratio energy balance system constructed above poplar canopy and the stem diameter increments of randomly chosen sample trees were examined. The stem diameters were subsequently converted to total aboveground biomass (AB) by allometric equation obtained by destructive analysis at the beginning of 2010. The biomass volume and its increment of particular trees were subsequently converted to the whole canopy growth and correlated with the ETa values. Our results revealed that there was a statistically significant relation between water lost and biomass growth with coefficients of determination r2 0.96 and 0.51 in 2008 and 2009 respectively. By using multiple linear regression analysis additionally accounting for effect of precipitation events and thermal time (sums of effective temperatures above +5 °C) the AB growth was explained from 98 and 87% in 2008 and 2009, respectively. Therefore for further analysis the multiple linear regression model was applied. The dynamic of seasonal WUEP (expressed as gram of AB dry matter per thousand grams of water) reached up to 6.2 and 6.8 g kg−1 with means 3.13 and 3.54 g kg−1 in both executed years respectively. These values are situated in higher range comparing to the other broadleaved tree species of temperate climate zone and suggest that economically profitable plantation (defined by yield at least in the range of 10–12 Mg ha−1 year−1 of dry matter content) will consume more than 450–500 mm per growing season and thus will demand a locality with higher and adequately temporally distributed amount of precipitation especially in rain fed areas such as the discussed Czech-Moravian Highlands.