Variations in soil chemical properties and microbial biomass in artificial gaps in silver fir stands

Abstract

Changes in soil chemical and microbiological parameters in small (185 m 2 ) and medium (410 m 2 ) gaps, created in mature silver fir (Abies alba Mill) stands (mean height 30 m) in the Calabrian Apennines (Southern Italy), were studied over 2 years. Medium gaps had high soil temperature and photosynthetically active radiation (PAR) transmittance and low soil moisture. Within small gaps we detected a greater amount of organic matter, with respect to under canopy cover sites and medium gaps. Moreover, a different trend of the organic matter between small and medium gaps was observed. In the medium gaps, with respect to under canopy cover sites and small gaps, we found a relatively low content of organic matter, associated to a lower amount of humic acid, which suggested that the organic substrate undergoes a mineralization rather than a humification process. An opposite trend was observed in small gaps, where the increase of organic matter content, associated to an increase of humic acid and microbial biomass, suggested a better humification process. Moreover, in small gaps the highest level of urease and the greatest fluorescein diacetate (FDA) hydrolysis were observed. The different trend of organic matter observed in small and medium gaps may be related to changes in the environmental conditions. PAR transmittance, significantly higher in medium gaps, contributed to increase soil temperature and decrease soil moisture, affecting soil microbial populations and organic matter trend. These results suggest that the creation of small gaps represents the silvicultural practice with minor environmental impact.

Responses of Abies alba seedlings to different site conditions in Picea abies plantations

“…In a large gap, the adaptability of fir natural regeneration is limited and it may be suppressed by more adaptable tree species such as the spruce (Stancioiu and O'Hara 2006c). Muscolo et al 2010, determined the optimum gap size to 185 m 2 to meet the ecological requirements of silver fir natural regeneration (Phillips and Shure 1990;Muscolo et al 2007). It is also recommended to regenerate fir under a shelterwood (Grassi and Bagnaresi 2001;Kantor 2001;Musil 2003).…”

Use of canopy gap openings to restore coniferous stands in Mediterranean environment

“…The silvicultural treatment fostered natural regeneration of silver fir, enhancing the development of a multi-layered forest structure and fulfilling timber production objectives without compromising ecosystem management principles. Subsequently, in the same experimental area, Muscolo et al (2007a) investigated the changes in soil chemical and microbiological parameters over 2 years in the same small (185 m 2 ) and medium (410 m 2 ) gaps. Medium gaps had higher soil temperature, PAR transmittance and low soil moisture than small gaps.…”

Mikroklima i prirodno pomlađivanje šumskih progala nastalih odumiranjem stabala obične jele (Abies alba Mill.)

“…Gaps in the stand, which are the result of disappearance of trees, create conditions different from those in the neighbouring canopy-covered stand (Hubbell andFoster 1986, Muscolo et al 2007), and this affects regeneration (Brown 1993). The removal of trees result in a change of the microclimate (Aussenac 2000, Ritter et al 2005, Vilhar et al 2005, Muscolo et al 2007, Albanesi et al 2008. Microclimate conditions have an important role for the processes in the forest ecosystem.…”

“…Temporal and spatial variations of microclimate conditions in and around forest gaps have rarely been investigated in managed or natural fir forests with varying climates and species compositions (Vilhar et al 2005, Muscolo et al 2007, Rozenberger at al. 2007, Albanesi et al 2008, Muscolo et al 2010.…”

“…Gaps can also be created artificially, by human activities such as silvicultural practices (Muscolo et al 2007, Albanesi et al 2008.…”