Anthropogenic modifications to water regimes are one of the main factors threatening the stability and existence of floodplain forests. This study presents an analysis of topsoil biogeochemistry within three floodplain forest stands with different levels of human alteration. Decreasing contents of soil organic carbon (OC) and microbial biomass were observed along the gradient from natural to plantation forest. High annual variations were observed in soil N contents and in microbial biomass, while comparable spatial variations were observed within the natural forest. High ground-water levels resulted in increased accumulation of available Na⁺ and SO₄²⁻ in the natural forest soil, yet the concentrations of ions were at sub-saline levels. The increasing contents of available Mn, SO₄²⁻ or Cl⁻ had mostly positive effects on soil microbial activity across the sites, though the results indicate the existence of a certain ecological limit for soil microorganisms. Reintroduction of surface-water flooding should be considered in future forest and water management to promote the dilution of ions accumulated in soils and natural deposition of sediments rich in organic matter (OM) at the sites.

Plant distribution is most closely associated with the abiotic environment. The abiotic environment affects plant species’ abundancy unevenly. The asymmetry is further deviated by human interventions. Contrarily, soil properties preserve environmental influences from the anthropogenic perturbations. The study examined the supra-regional similarities of soil effects on plant species’ abundance in temperate forests to determine: (i) spatial relationships between soil property and forest-plant diversity among geographical regions; (ii) whether the spatial dependencies among compared forest-diversity components are influenced by natural forest representation. The spatial dependence was assessed using geographically weighted regression (GWR) of soil properties and plant species abundance from forest stands among 91 biogeographical regions in the Czech Republic (Central Europe). Regional soil properties and plant species abundance were acquired from 7550 national forest inventory plots positioned in a 4 × 4 km grid. The effect of natural forests was assessed using linear regression between the sums of squared GWR residues and protected forest distribution in the regions. Total diversity of forest plants is significantly dependent on soil-group representation. The soil-group effect is more significant than that of bedrock bodies, most of all in biogeographical regions with protected forest representation >50%. Effects of soil chemical properties were not affected by protected forest distribution. Spatial dependency analysis separated biogeographical regions of optimal forest plant diversity from those where inadequate forest-ecosystem diversity should be increased alongside soil diversity.

Natural pine site differentiation is instrumental in the modification of Scots pine cultivation to environmental change. The aim of this study was to distinguish azonal pine sites in prevailing beechwood conditions by the means of soil property interrelationships. The study aimed at verifying assumptions (i) that intrinsic soil properties suggest differences at naturalness among various communities in the same mesoclimate, relief or on same soil group and (ii) whether pines differ from beechwoods uniformly or unevenly among different regional population areas. The verification was carried out by discrimination analysis of the H- and A-horizon forest soil properties at selected pine and beech stands in the Czech Republic between 2006 and 2015. Homogeneous pines were confirmed either on poorly developed or very infertile soils. Mixed pines were found on Cambisols. Complete separability was found between pines and beechwoods on Podzols due to inverse proportions of correlations among acid phosphomonoesterase (APMEA) and urease (UA) activities, C _org , C _mic , base saturation, bulk density and aeration. The inverse proportions among UA, N _tot , C _mic and soil hydrophysical properties conditioned the separability of pines on different soil groups than beechwoods. Soil indications of natural pines are related to phosphorus release by APMEA and site resistance to drought due to soil organic matter and water-holding capacity.

Long-term human activities substantially altered floodplain regions of temperate Europe. Forest management and extensive changes in hydrology greatly affected natural floodplain soil properties, in which microbes play key roles. This study aims to assess the effects of human activities through a gradient of forest management intensity on soil microbial community (SMC), its biomass, activity, and structure. Soil chemical and physical-chemical properties were used to explain the general associations and within-site variation using principal component analysis (PCA), linear regression (LR) and linear mixed-effect regression (LMER) models. It was found that forest management application, regardless of its intensity, led to significant microbial biomass reduction. PCA revealed that microbial biomass, expressed as a sum of phospholipid fatty acids along with recalcitrant carbon fraction (ROC) best explained the variability in data. LR and LMER highlighted that bacteria are affected by floodplain forest management more than fungi, and that bacterial response to pH was highly diversified. Also, pH was identified as the best predictor of SMC structure and activity but not of its size. The study calls for further investigation in SMC interactions with ROC, soil-available Fe and Mn, and the role of redox-active metals in soil organic carbon degradation.

Soil proteases are involved in organic matter transformation processes and, thus, influence ecosystem nutrient turnovers. Phytohormones, similarly to proteases, are synthesized and secreted into soil by fungi and microorganisms, and regulate plant rhizosphere activity. The aim of this study was to determine the effect of auxins, cytokinins, ethephon, and chlorocholine chloride on spruce forest floor protease activity. It was concluded that the presence of auxins stimulated native proteolytic activity, specifically synthetic auxin 2-naphthoxyacetic acid (16% increase at added quantity of 5 μg) and naturally occurring indole-3-acetic acid (18%, 5 μg). On the contrary, cytokinins, ethephon and chlorocholine chloride inhibited native soil protease activity, where ethephon (36% decrease at 50 μg) and chlorocholine chloride (34%, 100 μg) showed the highest inhibitory effects. It was concluded that negative phytohormonal effects on native proteolytic activity may slow down organic matter decomposition rates and hence complicate plant nutrition. The study enhances the understanding of rhizosphere exudate effects on soil microbial activity and soil nitrogen cycle.