Transplantation of organic surface horizons of boreal soils into warmer regions alters microbiology but not the temperature sensitivity of decomposition

Abstract

Pekka Vanhala, Kristiina Karhu, Mikko Tuomi, Katarina Bjorklof, Hannu Fritze, Hasse Hyvarinen, & Jari Liski, 'Transplantation of organic surface horizons of boreal soils into warmer regions alters microbiology but not the temperature sensitiviy of decomposition', Global Change Biology, Vol. 17 (1): 538-550, first published 16 December 2009. The version of record is available online at doi: 10.1111/j.1365-2486.2009.02154.x ?? 2010 Blackwell Publishing LtdChanges in soil carbon, the largest terrestrial carbon pool, are critical for the global carbon cycle, atmospheric CO2 levels and climate. Climate warming is predicted to be most pronounced in the northern regions and therefore the large soil carbon pool residing in boreal forests will be subject to larger global warming impact than soil carbon pools in the temperate or the tropical forest. A major uncertainty in current estimates of the terrestrial carbon balance is related to decomposition of soil organic matter (SOM). We hypothesized that when soils are exposed to warmer climate the structure of the ground vegetation will change much more rapidly than the dominant tree species. This change will alter the quality and amount of litter input to the soil and induce changes in microbial communities, thus possibly altering the temperature sensitivity of SOM decomposition. We transferred organic surface soil sections from the northern borders of the boreal forest zone to corresponding forest sites in the southern borders of the boreal forest zone and studied the effects of warmer climate after an adaptation period of 2 years. The results showed that initially ground vegetation and soil microbial community structure and community functions were different in northern and southern forest sites and that 2 years of exposure to warmer climate was long enough to cause changes in these ecological indicators. The rate of SOM decomposition was approximately equally sensitive to temperature irrespective of changes in vegetation or microbial communities in the studied forest sites. However, as temperature sensitivity of the decomposition increases with decreasing temperature regime, the proportional increase in the decomposition rate in northern latitudes could lead to significant carbon losses from the soils. ?? 2010 Blackwell Publishing Ltd

Microbial mediation of biogeochemical cycles revealed by simulation of global changes with soil transplant and cropping

“…The use of soil transplant as a proxy to study the effects of global changes has been successfully demonstrated in both plant biology and microbiology (Balser and Firestone, 2005;Breeuwer et al, 2010;De Frenne et al, 2011;Lazzaro et al, 2011;Vanhala et al, 2011). It was reported that soil microbial community structure and community functions were altered when soil was transplanted into warmer regions to simulate global warming (Vanhala et al, 2011), which was consistent with a number of studies showing that warming altered microbial community (Petchey et al, 1999;Rinnan et al, 2007;Zhou et al, 2012).…”

“…It was reported that soil microbial community structure and community functions were altered when soil was transplanted into warmer regions to simulate global warming (Vanhala et al, 2011), which was consistent with a number of studies showing that warming altered microbial community (Petchey et al, 1999;Rinnan et al, 2007;Zhou et al, 2012). Nevertheless, it remains unclear how microbial functional potentials, representing the underlying mechanisms of microbial community metabolism, are altered.…”

“…This observation may raise concerns for many climate change studies, which are often based on soil with vegetation (Balser and Firestone, 2005;Vanhala et al, 2011;Zhou et al, 2012), and underscores the importance of disentangling these effects. Indeed, the effects of soil transplant on microbial community were distinct between soils with and without vegetation.…”

“…We postulate that (i) southward soil transplant will result in an increase in microbial diversity, as community differentiation may be stimulated at warmer regions; (ii) changes of microbial functional potentials will affect processes such as nitrification and field CO 2 efflux; and (iii) cropping will alter the transplant effects on microbial community structure and metabolism, introducing complexity and imposing a challenge to climate change research, as most of the current studies were based on vegetated soil (Balser and Firestone, 2005;Vanhala et al, 2011;Zhou et al, 2012). Our test of these hypotheses may provide valuable insights to understand how these simulated global changes affect microbial community and soil functional processes.…”

Assessing the Relative Effects of Geographic Location and Soil Type on Microbial Communities Associated with Straw Decomposition

“…Methodologically, questions pertaining to the relative impacts of climate and soil can be most powerfully addressed through studies of reciprocal soil transplantation, whereby different types of soils are reciprocally transferred to different climate regions and subjected to parallel testing over a short or long period of time (28)(29)(30). To this end, we performed the first large-scale soil transplantation experiment under open field conditions.…”