Bioproductivity of black alder forests of Ukrainian Polissya

Abstract

Study of biological productivity of forest is crucial for estimation of
terrestrial ecosystems state and dynamics under global change. Models of
biological productivity represent dynamics of live biomass and Net Primary
Production of forest ecosystems. The assessment of dynamics of biological
productivity is an important part of the verified Full Carbon Account of forest.
Actual live biomass of a forest ecosystem is its maximal amount during the
growth period for an individual year and total production by live biomass by year
as the accumulated value of all phytomass produced by an ecosystem during its
life span up to year (Shvidenko et al., 2007).
The purpose of the study was to develop models of live biomass fractions
and to determine dynamics of bioproductivity of alder stands by site index in
Ukrainian Polissya.
Methodology developed at the International Institute for Applied Systems
Analysis (Shvidenko et al., 2007) was used. The algorithm combines growth
models, models of live biomass, and a number of parameters describing the
biological production of forest ecosystem (e.g. fine root turnover, foliage lifespan,
etc.). The models have been developed in two steps: (1) development of models
for estimation of live biomass dynamics, and (2) modeling of Net Primary
Production of forest ecosystems.
A special database of live biomass measurements by fractions of alder
forests in Ukrainian Polissya is used. The database also contains relevant
biometric characteristics of the stands in which the temporary sample plots were
established.
Live biomass is defined as organic matter of living plants of ecosystems.
Live biomass is not measured by forest inventory directly but is calculated by
models. We simulated the ratio (R ) of live biomass fractions (M ) to growing
fr fr

stock (GS) as a function of biometric characteristics of forests, which are defined
by forest inventory (age, site index and relative stocking):

where M live biomass fractions, t/ha; GS growing stock volume,
fr
m3/ha; A age, years; SI site index; RS relative stocking; and c c are
0 5
regression coefficients.
This equation was used for quantifying live biomass of four fractions (stem,
bark, branches, and foliage). Models of live biomass of roots, understory and
green forest floor was used from standard and reference materials (Tables and
models of growth and productivity of forests of major forest forming species of
Northern Eurasia, 2008).
The models are valid for ages from 5 to 100 years. It is shown that the
models developed are statistically significant at 0,05 level and adequately
describe the experimental data. The accuracy and adequacy with respect to all
variables included in equation were examined in the standard way, by calculating
multiple statistics of non-linear correlation and analysis of residuals.
Black alder stands stem density is increasing up to 55 years and then
decreases. By contrast biomass expansion factor of branches is constantly
decreasing. Biomass expansion factor of these fraction are higher in sparse and
low productive forests. Most of the forest biomass allocated in stem wood.
The models of live biomass fractions of alder stands (stem wood over bark,
bark, wood and bark of branches, foliage) were developed according to the
methodology of IIASA. Tables of bioproductivity of black alder forests in
Ukrainian Polissya were created based on the obtained models and yield tables
for modal alder stands of vegetative origin.
The research will help to reduce uncertainties of estimations of
greenhouse gas emissions in Ukraine. Tables and models of bioproductivity will
contribute to ecologization of forest management and creation of a solid
background for sustainable forest management.