Charcoal as a habitat for microbes and its effect on the microbial community of the underlying humus

Abstract

Pietikäinen, J., Kiikkilä, O. and Fritze, H. 2000. Charcoal as a habitat for microbes and its effect on the microbial community of the underlying humus. -Oikos 89: 231-242.Wildfires produce a charcoal layer, which has an adsorbing capacity resembling activated carbon. After the fire a new litter layer starts to accumulate on top of the charcoal layer, which liberates water-soluble compounds that percolate through the charcoal and the unburned humus layer. We first hypothesized that since charcoal has the capacity to adsorb organic compounds it may form a new habitat for microbes, which decompose the adsorbed compounds. Secondly, we hypothesized that the charcoal may cause depletion of decomposable organic carbon in the underlying humus and thus reduce the microbial biomass. To test our hypotheses we prepared microcosms, where we placed non-heated humus and on top one of the adsorbents: non-adsorptive pumice (Pum), charcoal from Empetrum nigrum (Em-pCh), charcoal from humus (HuCh) or activated carbon (ActC). We watered them with birch leaf litter extract. The adsorbing capacity increased in the order Pum B HuChB EmpChBActC, the adsorbents being capable of removing 0%, 26%, 42% and 51% of the dissolved C org in the litter extract, respectively. After one month, all adsorbents harboured microbes, but their amount and basal respiration was largest in EmpCh and HuCh, and smallest in Pum. In addition, different kinds of microbial communities with respect to their phospholipid fatty acid and substrate utilization patterns were formed in the adsorbents. The amount of microbial biomass and number of bacteria did not differ between humus under different adsorbents, although different microbial communities developed in humus under EmpCh compared with Pum, which is obviously related to the increased pH of the humus under EmpCh, and also ActC. We suggest that charcoal from burning can support microbial communities, which are small in size but have a higher specific growth rate than those of the humus. Although the charcoal layer induces changes in the microbial community of the humus, it does not reduce the amount of humus microbes.

Biochar affects soil organic matter cycling and microbial functions but does not alter microbial community structure in a paddy soil

“…This was evidently because the complexity of the substrate directly correlates with the number of enzymes required for its degradation. Therefore, the utilization of the complex BC substrate required more N. Similar to our observations, the substrate use pattern of microorganisms changed after BC addition in a forest organic soil horizon (Pietikäinen et al, 2000), and these changes were attributed to the microbial community structure and enzyme activities. The latter is supported by our results because the altered substrate utilization pattern after BC amendment was mainly due to changes in the soil peptidase activity (LAP).…”

“…3A, and Table 1). Previous studies reported an increase in bacterial abundance and altered microbial communities after BC addition under controlled laboratory conditions, which was attributed to the physic-chemical properties of BC (e.g., sorption, pH, chemical properties, habitats) (Anderson et al, 2011;Hale et al, 2015;Pietikäinen et al, 2000). However, such short-term positive effects of the physico-chemical properties of BC on microorganisms under controlled laboratory conditions were not as notable in our long-term field study.…”

“…On the other hand, BC addition suppressed SOC decomposition with altered microbial community structure by increasing Grampositive bacteria in a 30-day incubation study (Lu et al, 2014). The addition of BC altered C sources use patterns of microorganisms, perhaps via changes in the microbial population (Pietikäinen et al, 2000). All these studies suggested that SOM cycling might be influenced via microorganisms after BC addition.…”

“…However, information on microbial communities associated with soil SOM dynamics related to BC amendment is particularly limited (Gul et al, 2015). Furthermore, the majority of BC studies have relied on short-time incubation experiments (Farrell et al, 2013;Pietikäinen et al, 2000;Xu et al, 2014). Long-term field trials examining organic C-and N-related effects of BC on microorganisms still remain to be studied.…”

Impact of fire on the macrofungal diversity in scrub jungles of south-west India

“…However, low-intense pre-monsoon showers likely help selected macrofungal growth, sequester nutrients and restore soil qualities. As porous charcoal adsorb water similar to soil strata (Pietikainen et al 2000), those fungi hidden within partially charred woody litter will be benefitted. During postfire conditions, significant decrease in mycorrhizal species was seen in Cistus and Pinus plots of Spain (Martín-Pinto et al 2006), corroborating with the present study.…”