Dissolved organic carbon affects soil microbial activity and nitrogen dynamics in a Mexican tropical deciduous forest

Abstract

Seasonal variation of dissolved organic C (DOC) and its effects on microbial activity and N dynamics were studied during two consecutive years in soils with different organic C concentrations (hilltop and hillslope) in a tropical deciduous forest of Mexico. We found that DOC concentrations were higher at the hilltop than at the hillslope soils, and in both soils generally decreased from the dry to the rainy season during the two study years. Microbial biomass and potential C mineralization rates, as well as dissolved organic N (DON) and NH 4 + concentrations and net N immobilization were higher in soils with higher DOC than in soils with lower DOC. In contrast, net N immobilization and NH 4 + concentration were depleted in the soil with lowest DOC, whereas NO 3 À concentrations and net nitrification increased. Negative correlations between net nitrification and DOC concentration suggested that NH 4 + was transformed to NO 3 À by nitrifiers when the C availability was depleted. Taken together, our results suggest that available C appears to control soil microbial activity and N dynamics, and that microbial N immobilization is facilitated by active heterotrophic microorganisms stimulated by high C availability. Soil autotrophic nitrification is magnified by decreases in C availability for heterotrophic microbial activity. This study provides an experimental data set that supports the conceptual model to show and highlight that microbial dynamics and N transformations could be functionally coupled with DOC availability in the tropical deciduous forest soils.

The aggregates stability indicator <ASItest&gt; to evaluate soil spatiotemporal change in a tropical dry ecosystem

“…The greater stability of aggregates and total porosity at the upper position of the hillslope could be due to the organic carbon content, although there were no significant differences in the organic carbon content in both hillslope positions (Table 4). Montaño et al (2007) found that organic carbon concentrations were higher at the hilltop than at the hillslope soils, which is in line with a higher organic material accumulation.…”

“…García-Oliva et al (2003) There are different studies disclosing that in dry season, greater contents of total carbon are acquired, decreasing of this property from dry to wet season suggests a rapid decomposition and mineralization of litter-derived organic materials during the wet season (Montaño et al, 2007;Yamashita et al, 2011). These soil processes could be positively influencing the stabilization of soil aggregates.…”

Dissolved soil organic carbon and nitrogen were affected by conversion of native forests to plantations in subtropical China

“…The enhanced supply of heat and water in the summer might have affected WSOC and WSON concentrations through changing the soil microbial activities (Michalzik . Previous research found that lower WSOC in the rainy season was accompanied by lower microbial biomass in tropical rainforests (Garcı´a-Oliva et al 2003;Montan˜o et al 2007). Because WSOC could be both a product of and substrate for soil microbes, the lower WSOC in the rainy season could have been caused by the extensive consumption of WSOC at the early-rainy season or the low microbial production of WSOC (Montan˜o et al 2007).…”

Nutrient addition effects on tropical dry forests: a mini-review from microbial to ecosystem scales

“…Arrows represent hypothesized direction of change in pool or process under N deposition. (Montano et al, 2007), N, and P (Galicia and Garcia-Oliva, 2004) are dependent upon season and the intensity of plant-microbe competition.…”