Сибирский лесной журнал (Aug 2016)
Specific net primary production of the Eurasia forest-forming species in transcontinental gradients: methods and uncertainties
Abstract
The paper is devoted to a new aspect in the study of biological productivity of forest ecosystems on a geographical basis, expressed indirectly by climate parameters. Some features of change of specific net primary production (SNPP) of forest–forming species in Eurasia in the transcontinental gradients are shown for the first time using the voluminous factual material. SNPP represents the ratio of net primary production (NPP) to biomass and is expressed in relative units or percentage (by analogy with the percentage of the current stem volume increment that is used in traditional forest mensuration). An overview of methods and results of studying the percentage of the current stem volume increment and relationships between NPP and biomass involving into SNPP as the numerator and the denominator correspondingly is given. The database on biomass and NPP of forest ecosystems (t/ha) in a number of 920 definitions for 2-needled pines (subgenus Pinus), 116 – for larches (Larix Mill.), 480 – for spruce-fir forests (Picea Dietr., and Abies Mill.) and 230 definitions for birch forests (Betula L.) on the territory from Britain to South China is compiled. Using multiple regression analysis technique, the statistically significant changes in SNPP of aboveground, underground and understorey biomass according to two transcontinental gradients, namely by zonal belts and continentality of climate, are stated. The age dynamics of different species SNPP has a common pattern of decline with the age of a tree stand, but various quantitative parameters. Regularities of SNPP change according to zonal belts and in relation to the index of climate continentality are statistically significant, but substantial differences between woody species are found, to explain that is not possible yet. Because the term SNPP means «the rate of the transformation of organic substances» or, in other terms, the intensity of nutrient cycling, one apparently must include into the formula for SNPP the current biomass quantity plus all its litter, timber and root falls during the given time period, instead of biomass stock taken from the database formed. However, information on the forest detritus pool is on the level of expert evaluations yet.
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