THE RECIPROCAL RELATIONSHIPS BETWEEN HIGH LATITUDE CLIMATE CHANGES AND THE ECOLOGY OF TERRESTRIAL MICROBIOTA: EMERGING THEORIES, MODELS, AND EMPIRICAL EVIDENCE, ESPECIALLY RELATED TO GLOBAL WARMING
Authors: O. Roger Anderson
Abstract: High-latitude, moss-rich tundra communities (e.g., Sphagnum and Hylocomium spp.) are circumpolar in distribution, including conifer forests and tundra ecosystems that occupy millions of square kilometers. The sheer geographic scale of these high latitude biomes is sufficient to warrant scientific interest. However, it is becoming increasingly clear that major changes in high latitude climate patterns may have significant affects on the ecology of these communities. In turn, changes in the life histories, physiology, and productivity of the biota may also directly, or indirectly, influence local to global climate patterns; especially the balance of atmospheric carbon dioxide that is sequestered by primary production versus that released by respiratory activity – thus, potentially influencing global warming. Substantial attention has been given to aboveground biota, particularly the role of plants in this biotic-climatic reciprocal relationship, notably in relation to global warming and likely changes in annual mean temperature and precipitation patterns across vast geographic regimes at high latitudes. However, belowground processes also are likely to be substantially affected, especially the response of microbiota. Changes in the biology of terrestrial microbial communities may be directly affected by local meteorological factors, but also indirectly by effects of above- and belowground coupling. This coupling includes the effects of climate variables on plant physiology, especially the degree of primary productivity, release of organic compounds into the soil and their influences on the productivity and respiratory activity of associated belowground microbiota (e.g., bacteria, fungi and eukaryotic microbes, including protozoa). The major groups of protozoa include heterotrophic flagellates, naked amoebae (lacking a shell) and testate amoebae (enclosed in an organic or mineralized shell). With increasing evidence that the tundra permafrost is incurring prolonged seasonal warming and thawing to greater depths, there is an increased probability that associated microbial communities, that are normally more dormant during much of each annual climatic cycle, may become increasingly metabolically active. Given the enormous stores of plant-derived organic matter that have accumulated and remained frozen during millennia, there is substantial potential for enhanced terrestrial microbial respiration and significant release of atmospheric carbon dioxide. Nearly one-third of the global terrestrial carbon is stored in these high latitude environments. Currently, there is increasing interest in the complexities of the responses of terrestrial microbial communities to high-latitude climatic changes and the likelihood that they could have a significant effect on global warming through elevated respiratory activity. Some of the current emerging theories, models, and recent empirical evidence for the dynamics of these reciprocal interactions between climate and terrestrial microbial communities are reviewed, with particular attention to biogeochemical and ecological perspectives.
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