Variability and heterogeneity of humus forms at stand level: Comparison between pure beech and mixed beech-hornbeam forest

Abstract

-We investigate the influence of tree canopy composition on humus form variability and heterogeneity by comparing a pure beech stand and a mixed beech-hornbeam one (70% beech and 30% hornbeam). Macro-morphological humus form descriptors were recorded using a spatially explicit sample design at stand level. Leaf litter composition and light intensity accounting for stand management as well as bulk density for harvesting practices (soil compaction) were also recorded. A multiple correspondence analysis (MCA) and geostatistics were used to assess humus form variability and heterogeneity, as well as the spatial correlation between stand characteristics and humus forms. Humus form variability and activity were greater under the mixed stand than under the pure one. Geostatistics revealed that humus form patchiness was greater under the mixed stand than under the pure one and the improvement in decomposition processes seemed to be confined to spatial distribution of hornbeam litterfall. From a practical viewpoint, these results could provide ideas on the way of mixing tree species at stand level. We assume that with a given percentage of mull-forming tree species, a dispersed tree mixture provides a more extensive improvement than a clumped mixture.

Evaluating humus forms variation in an unmanaged mixed beech forest using two different classification methods

“…The presence of Mull-forming tree species like hornbeam (Carpinus betulus) within a stand dominated by Moder-forming species such as beech (Fagus orientalis) has probably a positive impact on the forest floor decomposition rate and can facilitate the building of a Mull form. A similar impact of mixed canopies has already been observed by Brandtberg et al (2000) and Aubert et al (2006).…”

“…The presence of Mull-forming tree species like hornbeam (Carpinus betulus) within a stand dominated by Moder-forming species such as beech (Fagus orientalis) has probably a positive impact on the forest floor decomposition rate and can facilitate the building of a Mull form. A similar impact of mixed canopies has already been observed by Brandtberg et al (2000) and Aubert et al (2006).According to Green et al (1993), Mull is a humus form in which organic matter is combined with the upper mineral soil instead of being accumulated on its surface as in Mor and Moder humus forms. Actually, the most common Mull subunit in the study site is vermimull, resulting from a high activity of large earthworms, which are able to incorporate organic matter and mineral particles, forming the topsoil crumby structure of Mull.…”

Aboveground–belowground relationships in temperate forests: Plant litter composes and microbiota orchestrates

“…Both stands are situated on a flat topographic site (plateau) and grow on an endogleyic dystric Luvisol (FAO, 1998) that has developed on the same parental material: more than 80 cm of loess (lamellated silts) lying on the same type of clay with flints according to studies previously conducted in the region (Lautridou, 1985;Laignel et al, 1998). For more details on physical and chemical soil properties, see Aubert et al (2006).…”

Structural relationships among vegetation, soil fauna and humus form in a subalpine forest ecosystem: a Hierarchical Multiple Factor Analysis (HMFA)

“…A similar small-scale pattern was already found in mountain and subalpine forests (Bernier and Ponge 1994;Sagot et al 1999) and also to a lesser extent in temperate forests (Ponge and Delhaye 1995;Aubert et al 2006;Chauvat et al 2007). We confirm the finding of Kallimanis et al (2002), which shows that forest regional biodiversity stems largely from mechanisms of patch coexistence.…”