Soil Microorganisms and Phenolics: Their Implication in Spruce Natural Regeneration Failure

Allelopathy in Northern Temperate and Boreal Semi-Natural Woodland

“…They showed that phenolics issued from mulch straws significantly inhibited NH 4 + oxidizers, and thus available N for R. idaeus, a notoriously nitrophilous species. However, surely the addition of mulch (which was high C:N) would also promote the growth of microorganisms, which would then compete for soil N. Based on this finding, we studied the phenolics-soil microorganisms interactions in a subAlpine spruce forest (Souto et al, 1998b) and showed that fungi and bacteria populations increased as phenolics content drastically decreased. Thus, research is underway to use soil microorganisms as allelochemicals regulators (by means of C and N control).…”

“…Souto et al (1994 and found that soil microorganisms mediate long-term allelopathic effects in forest soils. Some fungi were negatively affected by allelochemicals from soil extracts (Zhang, 1997), whereas other compounds, like some phenolics, had stimulatory effects (Black and Dix, 1976;Lindeberg et al, 1980;Souto et al, 1998b). In any case, chemical compounds present in forest litter probably determine to a great extent the distribution and activity of different litter-decomposing fungi (Lindeberg et al, 1980), which may explain substrate preference often found among litter-decomposing saprotrophs.…”

“…Further, some experiments were done in sterile conditions, when most of them were not. This induces important differences in results because microorganisms are able to metabolize very rapidly compounds such as phenolics (Lockwood and Filonow, 1981) and in very large amounts (Souto et al, 1998b). A second criticism about such investigations concerns the absence of identification of allelochemicals.…”

“…Thus, tannins acted as a general microbial inhibitor, whereas phenolics acted as growth substrate. Souto et al (1998b) studied the effects of some phenolic compounds present in Norway Spruce (Picea abies) forests soils. They found that fungi and cellulose hydrolyzers were positively affected by this kind of compounds, whereas heterotrophic bacteria were inhibited.…”

The Allelopathic Potential of <i>Conocarpus lancifolius</i> (Engl.) Leaves on Dicot (<i>Vigna sinensis</i> L.), Monocot (<i>Zea mays</i> L.) and Soil-Borne Pathogenic Fungi

“…Tannins are reported to be microbial inhibitors while phenolics were growth substrates [11]. Some phenolics in forests soils were used by fungi and cellulose hydrolyzers whereas growth of heterotrophic bacteria was inhibited [12]. Thus alleloochemicals do not only affect changes in plant communities but also microbial populations in the soil.…”