Opposite responses of vascular plant and moss communities to changes in humus form, as expressed by the Humus Index

Abstract

Question: Does the distribution of plant species found in forests correlate with variation in the Humus Index (based on a ranking of humus forms) and, if so, do the species exhibit different responses according to phyletic lineages? Location: Paris Basin, France, with a temperate Atlantic climate Methods: Mosses and vascular plants (herbs, ferns) were inventoried in two broad-leaved forests with contrasting soil conditions, where 15 and 16 sites were investigated, respectively. Variety of stand age and prevailing soil conditions were analysed in 5 plots and 20 sub-plots in a grid at each site. Mantel tests were used to estimate correlations between the Humus Index and plant species richness, taking into account spatial autocorrelation. Results: The local (plot, sub-plot) species richness of moss communities increased with the Humus Index, i.e. when humus forms shifted from mull to moder. The reverse phenomenon was observed in vascular communities. The opposite response of these two plant groups could be explained by opposite strategies for nutrient capture which developed in the course of their evolutionary history. Conclusions: Although not necessarily causative, the Humus Index predict fairly well changes in species richness which occur in forest vegetation, provided that phyletic lineages and geographical position are taken into consideration.

Local and regional trends in the ground vegetation of beech forests

“…Over a large set of beech stands, belonging to two common habitats, Endymio-Fagetum (EF) and Ilici-Fagetum (IF), our study confirmed the opposite trends in vascular and moss species richness which had been shown in Brotonne and Saint-Palais IF beech stands (Lalanne et al, 2008): at the sampling plot level, when the Humus Index increases, passing from mull (Humus Index 1-4) to moder (Humus Index 5-7) then to mor (Humus Index 8), moss species richness increases and vascular species richness decreases, thereby reinforcing the view of phylogenetic conservatism of the ecological niche (Prinzing et al, 2001). This observation is in agreement with Brunet et al (1997) and Roem and Berendse (2000) who showed that at local level vascular plant species richness decreases when soil acidity increases in woodland and grassland, respectively.…”

“…At each site five plots 20 Â 20 m, four at angles of a 1 ha square and one at its centre (Lalanne et al, 2008) were surveyed for ground vegetation and environmental factors. In each plot vascular plants (herbs, ferns) and mosses were identified at the species level (Appendix 1) and quantified according to the BraunBlanquet method.…”

“…Indirect (PCA) and direct (RDA) gradient analysis were used to discern main local and regional ecological factors, which could explain the observed variation in species composition. Particular attention will be given to the humus type, which is both a cause and a consequence of vegetation development (Ponge, 2003;Godefroid et al, 2005) and to which beech forest plant species are highly sensitive (Le Tacon and Timbal, 1973;Falkengren-Grerup and Tyler, 1993;Lalanne et al, 2008).…”

Drivers of bryophyte diversity allow implications for forest management with a focus on climate change

“…We also described the characteristics of the humus layer (e.g., humus type) and the mineral soil (e.g., soil texture) in the field. From these descriptions, we selected the humus form (according to Arbeitskreis Standortkartierung, 1996) known to be important for bryophytes (Lalanne et al, 2008;Startsev et al, 2008). Furthermore, on the basis of this on-site diagnosis, we calculated the soil's water-storage capacity (according to Arbeitskreis Standortkartierung, 1996) and assigned the samples to ten moisture index classes according to Ewald et al (2000).…”

The impact of parent material, climate, soil type and vegetation on Venetian forest humus forms: A direct gradient approach

“…Humus forms, patterning the way organic matter is distributed and transformed within the forest soil profile (Bal, 1970;Klinka et al, 1990;Kindel and Garay, 2002), and known as key components of plant-soil relationships (Ponge, 2003(Ponge, , 2013, are easy to identify directly on the field without expensive laboratory analyses. They also could be mapped with the aid of digital mapping techniques (Aberegg et al, 2009), taking into account their local variability by standardized protocols (Ponge et al, 2002;Lalanne et al, 2008). The systematic census of humus forms could allow in a near future a clearer assessment of the amount and distribution of fast-recycling (organic horizons) and stable (organo-mineral horizons) carbon at scales varying from local to regional then to global levels (Thornley and Cannell, 2001;Hedde et al, 2008;Andreetta et al, 2011).…”