Non-climatic causes for low productivity of Siberian tundra ecosystems

Abstract

Tundras are low-productivity communities. If it is only a consequence of unfavourable climate, then how could herb communities that fed numerous large herbivores (mammoth fauna) exist during more severe periods of the late Pleistocene in the same latitude? There is an imbalance between climatic potential and real productivity of tundras. It is associated with an extremely low content of plant nutrients in soils. The imbalance occurred after late Pleistocene pastoral ecosystems had alternated with modern tundras. The disappearance of large herbivores, a keystone species of Pleistocene ecosystems of Siberia, was one of the reasons for this. In Pleistocene landscapes, there were two mechanisms for recycling nutrients. The first one was a biological rotation related to plants’ taking nutrients that had been released in the process of mortmass mineralisation. It still exists in tundra though now it is less effective. The second mechanism was animals’ returning nutrients from low relief parts to higher surfaces. It practically does not work now. Zoogenic mechanisms to maintain high nutrient status of Pleistocene soils compensated for the unfavourable climate. An essential condition for the formation of tundras, along with climatic factors, was the disappearance of large herbivores. The ecosystem in the Holocene developed under the conditions of total disappearance of mineral elements accompanied by productivity loss. Tundra ecosystems may have higher productivity, which is an important conclusion for regulation of natural processes.