Correlations between productivity and phytomass identified in the TEEB-Russia project (2013-2022)

Negative relationships were found between phytomass and productivity of natural ecosystems within European Russia for 50 х 50 km squares.

Correlations between phytomass and productivity for 50-km squares: a) for indicators of natural ecosystems; b) for indicators adjusted considering the degree of territory transformation

Phytomass and productivity are key factors in fulfillment of ecosystem services (ES). For some ES, phytomass is primarily important (for example, for carbon storage, regulating the water cycle, purifying runoff, preventing soil erosion), and for others, productivity is primarily important (provisioning ES, carbon sequestration). Should the negative correlation between phytomass and productivity be considered the basis for a trade-off between these ES? Our analysis says no.
The relationships between productivity and phytomass are different for three groups of flat ecoregions (mountain ecoregions are excluded from this analysis):
1) northern and forest ecoregions (green in below Figure);
2) steppe and semi-desert (orange in Figure);
3) forest-steppe (yellow in Figure).
Within groups “1” and “2” positive dependencies were revealed. For northern and forest ecoregions, the angle of inclination of the dependence is steeper than for steppe and semi-desert. This difference reflects the fundamental differences in the structure and functioning of forest and grassy ecosystems, which must be considered when assessing ES and ecosystem assets. The values of indicators for the ecoregions of the Arctic deserts and tundra (indicated by a blue circle in Figure) in further analyzes can be assigned both to the group of northern and forest ecoregions, and to the group of grassy ecoregions. For the forest-steppe ecoregion, a negative relationship between phytomass and productivity indicators was revealed, which forms the third side of the triangle (yellow in Figure). The formation of an almost straight outer side of this triangle for indicators of natural ecosystems (Figure a) can be explained by the fact that the forest-steppe ecoregion is a mosaic of forest and steppe plots and includes both almost completely forest squares (90% of the forest area) and completely treeless squares, as well as numerous intermediate variants. The values of indicators in forest squares are close to those in mixed forests, and the values in treeless squares are close to those in the steppe ecoregion. Squares with different ratios of forest and treeless areas are located on the line connecting these extreme values. The relationships for the adjusted indicators are similar, but the values for the forest-steppe and steppe ecoregions are significantly shifted towards lower values of productivity and phytomass due to the strong transformation of these ecoregions.

Correlations between phytomass and productivity for 50 km squares: a) for natural ecosystems; b) for indicators, adjusted considering the degree of territory transformation. The values for the group of northern and forest ecoregions are shown in green, the values for the steppe and semi-desert ecoregions are shown in orange, and for the forest-steppe ecoregion are shown in yellow. Blue circles highlight values for the Arctic deserts and tundra.

Thus, the negative relationship between phytomass and productivity, revealed for the whole European Russia, does not reflect causal relationships, but is the result of a combination of data related to different groups of ecoregions. Within each of these groups, as mentioned above, the dependencies are positive, and a negative dependence is detected for the forest-steppe ecoregion for the above reasons. This pattern indicates that approaches to ecosystem management in forest and grassy ecoregions should be different. In the forest-steppe ecoregion, management approaches should be developed taking into account the spatial distribution and proportion of forest and treeless areas in target areas. If squares transformed by man are dropped from the general sample for European Russia, the relationship between phytomass and productivity changes from negative to positive (Figure below). The squares of the forest-steppe and steppe ecoregions disappear from the samples, where squares with 90-100% of the area of natural ecosystems are represented.

Change in the sign of the correlations between phytomass and productivity with the consecutive exclusion from the analysis of squares transformed by humans.

Current values of phytomass of natural forest ecosystems are many times lower than values of climax communities (Figure below). The farther south the type of forest ecosystems is widespread, the more pronounced this difference. Obviously, before the transformation of territories by humans, not all communities were climax due to natural ecosystem disturbances, that is, the average phytomass values were lower than those characteristic of climax communities. However, the role of anthropogenic changes in ecosystems in the decrease in phytomass observed today is obvious. For taiga ecoregions, this is the result primarily of forest clearing for logging (i.e., the use of the provisioning ES of timber production). Due to forest felling, primary climax forests over most of these ecoregions have been replaced by secondary small-leaved forests, as is shown on the forest map (light blue on Figure). The main factor of territory transformation in mixed forest ecoregion, and especially in forest steppe, is agriculture leading to replacement of forests by farmlands. Gray color on the forest map indicates the zone where forests can grow, but today are absent. Anthropogenic transformation therefore substantially lowered phytomass and productivity of forest ecosystems. It can be assumed that these changes have led to a decrease in some important regulating ES.

Current values of phytomass and productivity within European Russia and values for climax communities. Circles denote mean values for the ecoregions. Contour polygons show phytomass and productivity values for climax communities.

For details and references see here: Bukvareva, E.N., Sviridova, T. V. (Eds.). (2020). Ecosystem services of Russia: prototype of national report. Volume 2. Biodiversity and ecosystem services: accounting principles in Russia. Moscow: Publishing House of Biodiversity Conservation Center.