Moss biocrust accelerates the recovery and resilience of soil microbial communities in fire-affected semi-arid Mediterranean soils.

After wildfires in Mediterranean ecosystems, ruderal mosses are pioneer species, stabilizing the soil surface previous to the establishment of vascular vegetation. However, little is known about the implication of pioneer moss biocrusts for the recovery and resilience of soils in early post-fire stages in semi-arid areas. Therefore, we studied the effects of the burgeoning biocrust on soil physicochemical and biochemical properties and the diversity and composition of microbial communities after a moderate-to-high wildfire severity. Seven months after the wildfire, the biocrust softened the strong impact of the fire in soils, affecting the diversity and composition of bacteria and fungi community compared to the uncrusted soils exposed to unfavourable environmental stress. Soil moisture, phosphorous, and enzyme activities representing the altered biogeochemical cycles after the fire, were the main explanatory variables for biocrust microbial community composition under the semi-arid conditions. High bacterial diversity was found in soils under mosses, while long-lasting legacies are expected in the fungal community, which showed greater sensitivity to the fire. The composition of bacterial and fungal communities at several taxonomical levels was profoundly altered by the presence of the moss biocrust, showing a rapid successional transition toward the unburned soil community. Pioneer moss biocrust play an important role improving the resilience of soil microbial communities. In the context of increasing fire intensity, studying the moss biocrust effects on the recovery of soils microbiome is essential to understanding the resistance and resilience of Mediterranean forests to wildfires.

The role of mosses in soil stability, fertility and microbiology six years after a post-fire salvage logging management.

After a wildfire, moss crust develops in early post-fire stages revealing important roles related to soil erosion prevention and increase of soil fertility. However, the post-fire management selected could determine the capacity of soil to recover and the active role of mosses in the ecosystem recovery. Salvage logging (SL) was performed in the wildfire that occurred in July 2012 in "Sierra de Mariola Natural Park" (E Spain), with detrimental consequences to soils in the short-term. The aim of the study is to assess if the presence of a biocrust dominated by mosses six years after the wildfire improved the soil quality and functions, and if the salvage logging management influenced the process. Our results showed that the SL management affected in a medium-term to the percentage of soil covered by mosses, reaching 78.4% in control soils compared to 56% in SL soils. Regarding the influence of mosses in soils, our results did not show greater differences in the physical parameters measured, hydraulic conductivity, water repellency and soil penetration resistance, possibly related to the lower developmental stages of the biocrust. However, it was observed that the presence of mosses played a significant role in both the soil fertility and the microbial activity. The improvement in soil fertility was registered mainly in the organic carbon, nitrogen, and phosphorous contents, and for the microbial parameters, for which higher values for the microbial biomass carbon and basal soil respiration were reached in soils under mosses. In conclusion, we can suggest that mosses had an important role in the functional recovery of degraded ecosystems after wildfires, and therefore we encourage considering the presence of mosses in the post-fire managements.

The role of organic amendment in soils affected by residual pollution of potentially harmful elements.

The addition of organic amendment in soils affected by residual pollution of potentially harmful elements (PHEs) is evaluated. The area was polluted twenty years ago and remediation actions were intensively applied, but evidence of pollution are still detected in some sectors. The amendment application produces significant changes in the main soil properties and modifies the mobility and availability of the pollutants. In general, Cu, Zn, Cd and Pb, showed a significant reduction in soluble and exchangeable forms after the vermicompost addition (percentage of reduction ranging from 59% for soluble Pb to 95% for exchangeable Zn), both in highly (UVS) as in moderately (VS1) polluted soils. This reduction is strongly related to the rise in OC content and pH. Arsenic presented no significant reduction or even an increase in soluble forms in moderately polluted soils (VS1), where the competing effects of OC and phosphorous could be responsible for this increase. Pb also showed an increase in availability after vermicompost application, probably related to the competing effect of Mg2+ coming from the organic amendment. The less mobile forms (those extracted with oxalic-oxalate, pyrophosphate and EDTA), indicate that vermicompost application reduce medium-long term mobility to similar values of those found in less polluted soils (VS2); anyway, an increase in available forms of Pb and As was detected in some cases, indicating a potential risk of toxicity that should be monitored over time.