Deadwood moisture affects multiple functions of downed logs in forest ecosystems. They include provision of habitats for xylobionts, additional water stores and organic carbon stocks. In contrast to Northern American forests, little is known about moisture variability in downed logs of important tree species within the Temperate Zone of Europe. Therefore, our study aimed at elucidating this variability according to species, site and decay class (DC). Measurements were taken by TDR during two vegetation periods in eight Carpathian natural forests representing distinct site conditions, ranging from xerothermophilous to subalpine. Downed logs of Quercus spp., Abies alba Mill., Fagus sylvatica L., and Picea abies L., belonging to various DCs, were selected and instrumented with TDR probes. Species and DC‐specific TDR calibration showed the importance of intrinsic wood porosity. The course of deadwood moisture consisted of drying during the early decay stage, except for A. alba and F. sylvatica, and an intense water reabsorption at later decay stages. Average moisture for all species and sites displayed seasonal trends, reflecting the occurrence of precipitation clusters and dry periods, as well as short‐term fluctuations. Cross‐spectral analysis revealed that both sapwood and heartwood participated in wetting and drying processes, but only after reaching an advanced stage of decay. New findings can be applied in interpreting, modelling and predicting deadwood water stores, habitat properties and respiration. Copyright © 2011 John Wiley & Sons, Ltd.
Little is known on soil organic carbon (SOC) stocks in karst areas worldwide, although many of them have seen long-term application of agroforestry systems with a potential for carbon sequestration. Therefore, our study aimed to assess landscape-level SOC concentration and stock in the Silica Plateau, a part of the Slovak Karst Biosphere Reserve located in the Western Carpathians (Slovakia) with a centuries-long agroforestry record. The most represented local soil units are Chromi-Rendzic Leptosols and Chromic Cambisols with clayey loam texture, C/N ratio 9-12, and pH H 2 O 6.6-6.2 in their organo-mineral surface horizons. Mull surface humus form prevails under mixed forest stands dominated by hornbeam (Carpinus betulus L.), oak (Quercus petraea L.), and beech (Fagus sylvatica L.). A total of 2,700 soil samples were collected from 150 soil pits. Both SOC concentrations and stocks were determined for the 0-60 cm mineral soil layer. Soil stoniness was accounted for by means of electrical resistivity tomography. According to the analysis of covariance, cropland SOC concentration (0.026 g g -1 ) is significantly lower compared to forestland (0.040 g g -1 ) and pastureland (0.041 g g -1 ) (P \ 0.01). During the period of 130 years after forest clearing, cropland SOC stock has been reduced at an exponential decay rate of ca 0.002 year -1 , while the SOC stock in pastureland has increased following land use change from cropland by approximately 30% during the same period of time. Irrespective of land use history, overall SOC stock is high reaching on average 207.4 Mg ha -1 , out of which 66% are stored within 0-30 cm and 34% within 30-60 cm soil layers.
To characterize the spatial heterogeneity of selected soil microbiological characteristics in relation to soil moisture content within a natural beech stand, we collected soil samples at 50 m intervals along a 1,500 m long transect in a beech primeval forest at Vtáčnik mountains (Slovakia) from organic layers (OL and OF horizons) and the mineral A horizon (depth 0-10 cm) in July 2004 and June 2005. Gravimetric soil moisture, basal and substrate-induced respiration, respiration in situ and soil catalase activity were measured. Statistically significant differences in soil variables were found among horizons and partially among sampling dates. Soil microbial activity was closely correlated with soil moisture, especially in the OL horizon. No clear spatial autocorrelation of the assessed soil variables was found, but a significant correlation between years occurred. Moisture and microbial activity parameters were positively correlated with canopy openness in the A horizon, whereas no or negative correlations were observed in the overlying organic horizons.
Measurement of soil hydraulic conductivity requires considerable time and effort, which makes it difficult to characterize this important parameter across larger areas, especially remote forest regions. Forest soils are frequently texturally coarser than those in agricultural areas, making them more probable candidates for applications building on the stochastic‐convective hypothesis. We developed a method for measuring unsaturated soil hydraulic conductivity based on the analysis of a dye tracer resident concentration profile. In the experiment, partially saturated, steady‐state water flow was established in a forest allophanic soil by a sprinkler operating at 50 mm h−1, after which the water application was switched to a 10 mg L−1 Brilliant Blue FCF solution. The tracer was applied continuously until its cumulative infiltration reached 125 mm, after which the stained soil profile was exposed and photographed. The picture was subjected to an image analysis procedure designed to obtain the resident concentration profile of the tracer. The concentration was fitted to the solution of the convective lognormal transfer function, whose parameters were used in further calculations using functional relationships derived from the stochastic‐convective framework. The resulting hydraulic conductivity as a function of soil water content agreed within an order of magnitude with the relationship obtained by the instantaneous profile method. While the Mualem–van Genuchten model better reproduced the shape of that relationship, it strongly underestimated the hydraulic conductivity across the soil water content interval of interest (0.1–0.4). Finally, ways to improve the predictive capacity of the stochastic‐convective approach in terms of the general trends of the functional relationship were proposed.
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