• Energy Research

Radiation use efficiency values estimation based on the biomass increment (one approach) and on NPP from eddy covariance (two approaches) estimation of NPP brings the values of 0.13, 0.40, and 0.47 g (C) MJ −1 , respectively. The productivity of terrestrial ecosystems is primarily reliant on the absorption of solar radiation energy and its conversion into biomass. Monteith (1977) first introduced the concept of radiation use efficiency (RUE), which expresses the effectiveness of a plant stand to use solar radiation for the formation of new biomass and to maintain existing biomass. The presented paper uses a long-term, decadal, time series of biomass data, which is based on forest inventory data and an allometric relation, and on the application of eddy covariance (EC) estimation of Net Primary Production (NPP). These approaches provide different values of light use efficiency (LUE). LUE is based on direct carbon exchange estimation, LUE i , which denotes instantaneous efficiency based on the relationship between the daily sum of incident global radiation (GR i ) and NPP and LUES, calculated as the ratio between the sum of NPP and the sum of GR i per growing season. RUE is based on direct yearly biomass increment expressed in carbon units (carbon = 0.5 × biomass) divided by the sum of GR i per year. The obtained values amount to 0.13, 0.40, and 0.47 g(C) MJ−1 for RUE, LUES, and LUE i , respectively. The higher value of LUE i reflects a direct relation with the efficiency of photosynthetic carbon pumping. In contrast, the RUE value, based on biomass inventories, is the result of woody mass formation that is caused by several mutually related physiological processes and “wastages” of radiation utilization.

Radiation use efficiency values estimation based on the biomass increment (one approach) and on NPP from eddy covariance (two approaches) estimation of NPP brings the values of 0.13, 0.40, and 0.47 g (C) MJ −1 , respectively. The productivity of terrestrial ecosystems is primarily reliant on the absorption of solar radiation energy and its conversion into biomass. Monteith (1977) first introduced the concept of radiation use efficiency (RUE), which expresses the effectiveness of a plant stand to use solar radiation for the formation of new biomass and to maintain existing biomass. The presented paper uses a long-term, decadal, time series of biomass data, which is based on forest inventory data and an allometric relation, and on the application of eddy covariance (EC) estimation of Net Primary Production (NPP). These approaches provide different values of light use efficiency (LUE). LUE is based on direct carbon exchange estimation, LUE i , which denotes instantaneous efficiency based on the relationship between the daily sum of incident global radiation (GR i ) and NPP and LUES, calculated as the ratio between the sum of NPP and the sum of GR i per growing season. RUE is based on direct yearly biomass increment expressed in carbon units (carbon = 0.5 × biomass) divided by the sum of GR i per year. The obtained values amount to 0.13, 0.40, and 0.47 g(C) MJ−1 for RUE, LUES, and LUE i , respectively. The higher value of LUE i reflects a direct relation with the efficiency of photosynthetic carbon pumping. In contrast, the RUE value, based on biomass inventories, is the result of woody mass formation that is caused by several mutually related physiological processes and “wastages” of radiation utilization.

This study falls into site-specific studies (here in the Drahanská vrchovina Highland) focusing on the determination of allometric relationships between the stem dendrometric and biomass parameters in young Norway spruce stands. The total aboveground biomass (TB) of a sampled tree with 14.9 m in height and 15.5 cm in stem diameter at 1.3 m (DBH) averaged to 110.3 kg. The stem biomass participated on average by 54 %, branch biomass by 24 % and needle biomass by 22 % on the TB of the sampled spruce tree. TB of the tree and the biomass of individual aboveground tree organs were predicted with the highest accuracy (over 91 %) from DBH or a stem diameter at the one tenth of the tree height using allometric-power functions. The stem diameters up to 70 % of the relative tree height predicted TB accurately (over 95 %) as well. The biomass expansion factors based on the stem volume expansion to TB of the tree, as well as the biomass of each of the aboveground tree organs did not show functional dependency on DBH.

This study falls into site-specific studies (here in the Drahanská vrchovina Highland) focusing on the determination of allometric relationships between the stem dendrometric and biomass parameters in young Norway spruce stands. The total aboveground biomass (TB) of a sampled tree with 14.9 m in height and 15.5 cm in stem diameter at 1.3 m (DBH) averaged to 110.3 kg. The stem biomass participated on average by 54 %, branch biomass by 24 % and needle biomass by 22 % on the TB of the sampled spruce tree. TB of the tree and the biomass of individual aboveground tree organs were predicted with the highest accuracy (over 91 %) from DBH or a stem diameter at the one tenth of the tree height using allometric-power functions. The stem diameters up to 70 % of the relative tree height predicted TB accurately (over 95 %) as well. The biomass expansion factors based on the stem volume expansion to TB of the tree, as well as the biomass of each of the aboveground tree organs did not show functional dependency on DBH.