Gap size effects on above- and below-ground processes in a silver fir stand

Abstract

Changes in soil properties related to natural regeneration of silver fir (Abies alba, Mill.) in small (185 m 2 ) and medium (410 m 2 ) gaps, in the Calabria Apennines (Southern Italy), were studied 2 years after gap creation. The organic matter within the medium gaps decayed more rapidly than those in the small gaps. Among the microenvironmental variables and soil properties, soil temperature was most strongly positively related to organic matter decomposition rates. Medium gaps had high soil temperature and photosynthetically active radiation (PAR) transmittance, and low soil moisture. Within medium gaps, we found a great amount of phenolic compounds and a low content of organic matter and humic acids. These results indicate that in the medium gaps mineralization of organic matter was more important than humification. In contrast, in small gaps, the great amount of organic matter, the high content of humic acid and the values of humification index suggested that in these gaps the humification process of organic matter prevailed. Within small gaps, we observed more silver fir regeneration than medium gaps. Difference in organic matter content, particularly in the amount of phenolic compounds, may account for differences observed in natural regeneration of silver fir between small and medium gaps.

Effect of size and surrounding forest vegetation on chemical properties of soil in forest gaps

“…Although soil OM is the main source of total N +3 and other nutrients, OM content and soil chemical parameters did not show a similar trend, except for N +3 and EC. The 5-15 ha gaps both in the beech and mixed forests had significantly lower OM than the large gaps, as found by Muscolo et al (2010), Haghverdi et al (2012), and Kooch et al (2010). At the same time, Muscolo et al (2007) and Arunachalam & Arunachalam (2000) reported lower OM content for soils in large gaps compared to small openings.…”

“…Our results are not always in agreement with those of earlier studies, though similar findings for soil pH are reported by Muscolo et al (2007) and Ritter et al (2005). On the contrary, Muscolo et al (2010) and Arunachalam & Arunachalam (2000) found that soil pH was slightly higher in small gaps, while Kooch et al (2010) and Haghverdi et al (2012) reported higher pH values for large openings as compared to medium gaps. In addition, Chunyu & Xiuhai (2007) found a positive correlation between soil pH and gap size.…”

“…Soil moisture and temperature affect not only litter decomposition but also other processes occurring in the soil. Muscolo et al (2010) found that medium-sized gaps had a higher soil temperature and photosynthetically active radiation transmittance, and lower soil moisture than small-sized gaps and organic matter (OM) decayed more rapidly in the medium gap than in the small gap. Indeed, higher soil moisture and temperature conditions can favor the rapid decomposition of litter materials and, hence, the nutrient cycling in the openings.…”

“…In fact, different tree species in the surrounding canopy have been reported to differently affect the soil chemical characteristics in the gaps (Augusto et al 1998, Hagen-Thorn et al 2004, Sariyildiz et al 2005, Wang & Wang 2007, Vesterdal et al 2008 (Ritter 2005, Muscolo et al 2007, 2010 have demonstrated that the soil compaction due to harvesting activities (e.g., logging machines) may affect the hydrological, physical and chemical properties of the soil, as well as the decomposition and mineralization processes, determining an increase in the surface runoff and nutrient leaching, poor aeration, and low moisture capacity and porosity in the soil (Muscolo et al 2010). Finally, Bartsch (2000) and Scharenbroch & Bockheim (2007) found that gaps had less cations as compared to the surrounding forest stands due to nutrient leaching.…”

“…Forest openings are special habitats differing from the surrounding forest environment and having a significant effect on forage production (Frost & Edinger 1991, Fernald et al 2009), plant diversity and species composition (Rhoades et al 2004, Galhidy et al 2006, Chunyu & Xiuhai 2007, seedling establishment and growth (Muscolo et al 2010), climatic parameters , and soil chemical properties (Chunyu & Xiuhai 2007, Scharenbroch & Bockheim 2007, Thiel & Perakis 2009). Gap size influences especially ambient and soil temperatures, solar radiation, wind speed, and soil moisture.…”