Fine-root rhizosphere and morphological adaptations to site conditions in interaction with tree mineral nutrition in young silver birch (Betula pendula Roth.) stands

Abstract

Limited nutrient acquisition from soil is a key process limiting productivity in boreal forest. We investigated short-root morphological adaptations and rhizosphere effect in relation to site conditions in interaction with tree mineral nutrition. We studied seven young (8-to 14-yearold) silver birch (Betula pendula Roth.) stands on abandoned agricultural land in Estonia. Soil pH varied from 3.8 to 7.0, and soil N % from 0.07 to 0.26%. Tree nutrient (NPK) status was expressed by leaf nutrient concentrations. Leaf N correlated negatively with short-root specific length and area. Summed activity (SA) and metabolic diversity of bacteria (by BIOLOG Ecoplate TM ), bacterial community diversity (by DGGE) and pH KCl were determined for rhizosphere (R) and bulk soil (S) to reveal the extent of the rhizosphere effect. Bacterial activity in rhizosphere was 1.4-4.7 times higher than in bulk soil. Ratio SA R /SA S indicating root support to the rhizosphere bacterial communities decreased with increasing bulk soil pH; however, when bulk soil pH was C5, the decrease in SA R /SA S was insignificant, i.e. the rhizosphere effect stayed at a stable level. Diversity of bacterial community was 6% higher in bulk soil than in rhizosphere. Rhizosphere acidification occurred in studied stands when bulk soil pH KCl C 5. Short-root N % correlated positively with SA R /SA S . We concluded that tree N-nutritional status was related to short-root morphological parameters but not to studied microbiological characteristics in the soil of young silver birch stands.

Morphological plasticity of ectomycorrhizal short roots in Betula sp and Picea abies forests across climate and forest succession gradients: its role in changing environments

“…The biggest part of the morphological variation of birch EcM roots was described by SRL, which has been used as an indicator of environmental change, characterizing also the economic aspects of the root system and being sensitive to nutrient availability of trees (Ostonen et al, 2007a,b; Rosenvald et al, 2011b). Morphological plasticity includes the possibility to induce changes in physiology or activity (e.g., the metabolism) of root tips (Useche and Shipley, 2010; Makita et al, 2011).…”

“…However, mean SRL values of EcM roots of silver birch in native forest and in mine forest are more similar in older stands. As EcM root SRL of silver birch is related to soil fertility (Rosenvald et al, 2011b), more similar soil conditions in older stands determine also more similar SRL values there. Majority of the studied native birch forests still form a separate group from mine site forests in the ordination plot based on all EcM root traits probably because of the differences in soil, as the soil formation in mining areas has just started.…”

Carbon budgets in fertile silver birch (Betula pendula Roth) chronosequence stands

“…(Nadelhoffer and Raich, 1992;Eissenstat and Yanai, 1997;Jackson et al, 2000;Makkonen and Helmisaari, 2001;Block et al, 2006;Jones et al, 2009;Hodge et al, 2009;Rosenvald et al, 2011;Finér et al, 2011;Yuan and Chen, 2012).…”

The relationship between soil bacteria substrate utilisation patterns and the vegetation structure in temperate forests

“…Priha and Smolander (1999) showed clear separation of CLPP between the rhizosphere bacteria of coniferous and deciduous tree seedlings cultivated in organic soils, but not in mineral soil. However, these authors examined different tree species than those examined in the present study: pine, spruce and birch; the latter tree species have extraordinary high soil biological activity (Rosenvald et al 2011;Chodak et al 2015). Fang et al (2014) observed that pine forest soil bacteria were characterised by a lower functional diversity H 0 Shannon index for Biolog Ò ECO than mixed and broadleaved forests in the subtropical monsoon climate in South China.…”

“…Next to DNA-and RNA-based methods, the functional diversity approaches remain the most comprehensive strategies. One of the common methods to study soil bacteria functional diversity is community-level physiological profiling (CLPP) using Biolog Ò plates, based on colorimetric measurements of utilisation of various carbon substrates through microorganisms on microtitre plates (Preston-Mafham et al 2002;Classen et al 2003;Rosenvald et al 2011).…”