Soil Ecological Properties Research Articles

Implementation of different forest management methods in a natural forest: Changes in soil microbial biomass and enzyme activities

Forest management measures have changed soil characteristics, and these changes vary with respect to different management methods. The purpose of our study was to determine the effects of forest management on the soil ecological properties, especially the microbial biomass and enzyme activity. A comprehensive soil quality assessment was used to implement the Soil Quality Index (SQI) Model. Soil samples were collected from a natural oak forest (Quercus aliena var. acuteserrata) after 6 years of different management methods. Three forest management methods were implemented: selective cutting to remove the trees affecting target trees (CNFM), selective cutting to optimizing the stand’s spatial structure (SBFM), selective cutting to harvest large-diameter timber and reduce the stand density (SFCS), using unmanaged plots as a reference (NT, control plots). Here, the results showed that microbial biomass C (MBC) and microbial entropy (Cmic/Corg) were both higher in the CNFM and SBFM compared to the NT. CNFM had larger the ratios for MBC and MBN than the NT, while a smaller content of microbial biomass P in the SBFM. Phosphatase and protease activities were impacted by forest management, which was manifested as decreases inprotease and increases in phosphatase. Changes in soil enzyme activity may have been caused by soil organic matter and total nitrogen (TN), and the soil microbial biomass was sensitive to changes in TN, available phosphorus, urease and catalase. SQI value decreased in the order: NT > SBFM > CNFM > SFCS, which demonstrate that SFCS had strongly negative effects on comprehensive soil quality compared to CNFM and SBFM. Our finding suggest that forest management strategies that optimizing the spatial structure of forests by selective logging increased efficiency of microbial C and phosphatase activity and had less intensely negative effects on soil quality.

Changes in Soil Health with Remediation of Petroleum Hydrocarbon Contaminated Soils Using Two Different Remediation Technologies

For sustainable soil management, there is an increasing demand for soil quality, resilience, and health assessment. After remediation of petroleum hydrocarbon (PHC)-contaminated soils, changes in the physicochemical and ecological characteristics of the soil were investigated. Two kinds of remediation technologies were applied to contaminated soils: land farming (LF) and high temperature thermal desorption (HTTD). As a result of total petroleum hydrocarbons (TPH), PHC-contaminated soils were efficiently remediated by LF and HTTD. The soil health could not be completely recovered after the removal of pollutants due to adverse changes in the soil properties, especially in soil enzyme activities. Therefore, monitoring is necessary for accurate estimation of soil ecotoxicity and effective remediation, and additional soil management, such as fertilizer application or organic amendments, is needed to restore soil heath. In the case of HTTD, soil ecological properties are severely changed during the remediation process. The decision to reuse or recycle remediated soils should reflect changes in soil quality. HTTD is a harsh remediation method that results in deterioration of soil fertility and ecological functions. Alternatives, such as low-temperature thermal desorption or additional soil management using fertilizer or organic amendments, for example, are needed.

Conifer tree plantations for land rehabilitation: an ecological‐functional evaluation

Plantations of exotic fast‐growing tree species have been widely used for maintaining or restoring ecosystem functions. Despite this, in tropical countries with high biodiversity, these plantations have been the subject of heated debate. We evaluated the long‐term effect of coniferous tree plantations (Cupressus lusitanica, Pinus patula, Pinus elliottii) on the ecological rehabilitation of the Andean highlands in Colombia. To determine degree of rehabilitation, we assessed whether there were differences in the structure or density of native understory vegetation or soil ecological properties between plots established within tree plantations and plots established within other vegetation cover types (secondary forests, ferns, pastures, and abandoned mining areas). Measured variables were combined to create an index of ecological rehabilitation (ERI). We found significant differences in the ERI values among vegetation cover types: secondary forest (11.78) > conifer plantations (P. elliottii: 6.23, P. patula: 5.33, C. lusitanica: 5.24) > ferns (4.16) > pasture (2.50) > abandoned mining areas (0.43). The results obtained showed that, from the structure of native understory vegetation and soil ecological properties, conifer plantations favored the rehabilitation process. However, among them, it was highlighted that the P. elliotii plantations showed significant differences in the density of native understory species, their values being 1.7 and 2.1 times higher than those corresponding to P. patula and C. lusitanica, respectively. Thus, unlike these plantations that could represent an ecological barrier over time, P. elliottii plantations have enabled the advancement of natural succession, showing a high diversity of native species.

Legume and Non-legume Trees Increase Soil Carbon Sequestration in Savanna

Savanna ecosystems are increasingly pressured by climate and land-use changes, especially around populous areas such as the Mt. Kilimanjaro region. Savanna vegetation consists of grassland with isolated trees or tree groups and is therefore characterized by high spatial variation and patchiness of canopy cover and aboveground biomass. Both are major regulators for soil ecological properties and soil-atmospheric trace gas exchange (CO2, N2O, CH4), especially in water-limited environments. Our objectives were to determine spatial trends in soil properties and trace gas fluxes during the dry season and to relate above- and belowground processes and attributes. We selected a Savanna plain with vertic soil properties, south east of Mt. Kilimanjaro. Three trees were chosen from each of the two most dominant species: the legume Acacia nilotica and the non-legume Balanites aegyptiaca. For each tree, we selected one transect with nine sampling points, up to a distance of 4 times the crown radius from the stem. At each sampling point, we measured carbon (C) and nitrogen (N) content, δ13C of soil (0–10, 10–30 cm depth) and in plant biomass, soil C and N pools, water content, available nutrients, cation exchange capacity (CEC), temperature, pH, as well as root biomass and greenhouse-gas exchange. Tree species had no effect on soil parameters and gas fluxes under the crown. CEC, C, and N pools decreased up to 50% outside the crown-covered area. Tree leaf litter had a far lower C:N ratio than litter of the C4 grasses. δ13C in soil under the crown shifted about 15% in the direction of tree leaf litter δ13C compared to soil in open area reflecting the tree litter contribution to soil organic matter. The microbial C:N ratio and CO2 efflux were about 30% higher in the open area and strongly dependent on mineral N availability. This indicates N limitation and low microbial C use efficiency in the soil of open grassland areas. We conclude that the spatial structure of aboveground biomass in savanna ecosystems leads to a spatial redistribution of nutrients and thus C mineralization and sequestration. Therefore, the capability of savanna ecosystems to act as C sinks is both directly and indirectly dependent on the abundance of trees, regardless of their N-fixing status.

Estimation of Nutrient Exports Resulting from Thinning and Intensive Biomass Extraction in Medium-Aged Spruce and Pine Stands in Saxony, Northeast Germany

A growing interest in using forest biomass for bioenergy generation may stimulate intensive harvesting scenarios in Germany. We calculated and compared nutrient exports of conventional stem only (SO), whole tree without needles (WT excl. needles), and whole tree (WT) harvesting in two medium aged Norway spruce (Picea abies L. Karst.) and Scots pine (Pinus sylvestris L.) stands differing in productivity, and related them to soil nutrient pools and fluxes at the study sites. We established allometric biomass functions for each aboveground tree compartment and analyzed their nutrient contents. We analyzed soil nutrient stocks, estimated weathering rates, and obtained deposition and seepage data from nearby Level II stations. WT (excl. needles) and WT treatments cause nutrient losses 1.5 to 3.6 times higher than SO, while the biomass gain is only 1.18 to 1.25 in case of WT (excl. needles) and 1.28 to 1.30 in case of WT in the pine and spruce stand, respectively. Within the investigated 25-year period, WT harvesting would cause exports of N, K+, Ca2+, and Mg2+ of 6.6, 8.8, 5.4, and 0.8 kg·ha−1 in the pine stand and 13.9, 7.0, 10.6, and 1.8 kg·ha−1 in the spruce stand annually. The relative impact of WT and WT (excl. needles) on the nutrient balance is similar in the pine and spruce stands, despite differences in stand productivities, and thus the absolute amount of nutrients removed. In addition to the impact of intensive harvesting, both sites are characterized by high seepage losses of base cations, further impairing the nutrient budget. While intensive biomass extraction causes detrimental effects on many key soil ecological properties, our calculations may serve to implement measures to improve the nutrient balance in forested ecosystems.

A review of the ecology, ecophysiology and biodiversity of microalgae in Arctic soil crusts

Biological soil crusts have been extensively studied in arid lands of temperate regions, particularly semi-arid steppes and warm deserts. Arctic soil crusts have received some attention, but they are far less studied than their temperate counterparts. While the tundra zone of Arctic regions has an abundant cover of lichens, mosses and low-growing vascular plants, the High Arctic semi-arid and arid deserts have a much reduced but still very significant cover of biological soil crust dominated by microalgae. This review discusses what is known about Arctic soil crusts with the intention of stimulating study of this sensitive ecosystem. Arctic soil crusts are considered to be one of the most extreme habitat types on earth. Low temperatures and lack of water associated with a wide spectrum of disturbances have a dramatic effect on chemical and physical soil ecological properties (salinity, pH, conductivity and gas content). Microalgae are the keystone microbial species in polar crusts, being significant primary producers, fixing atmospheric nitrogen and secreting polysaccharides that bind soil aggregates together, thereby reducing erosion and water runoff. The biological diversity of soil crust microalgae in the Arctic is high. Soil crusts of the Arctic semi-arid and arid deserts provide a special opportunity to study the environmental factors controlling the diversity, distribution and abundance of the microalgae in the absence of anthropogenic disturbance. However, anthropogenic disturbances and climate change are occurring in the Arctic, and even more transformations are expected in the near future. Therefore, the ecological study of Arctic ecosystems, including biological soil crusts, is a matter of urgency.

Reference bulk density and critical degree-of-compactness for no-till crop production in subtropical highly weathered soils

The concept of degree of compactness (DC), referred to as field bulk density (BD) as a percentage of a reference bulk density (BD ref), was developed to characterize compactness of soil frequently disturbed, but for undisturbed soil such as under no-tillage critical degree of compactness values have not been tested. The objective of this study was to compare methods to determine BD ref and limits of DC and BD for plant growth under no-tillage in subtropical soils. Data from the literature and other databases were used to establish relationships between BD and clay or clay plus silt content, and between DC and macroporosity and yield of crops under no-tillage in subtropical Brazil. Data of BD ref reached by the soil Proctor test on disturbed soil samples, by uniaxial compression with loads of 200 kPa on disturbed and undisturbed soil samples, and 400, 800 and 1600 kPa on undisturbed soil samples, were used. Also, comparisons were made with critical bulk density based on the least limiting water range (BDc LLWR) and on observed root and/or yield restriction in the field (BDc Rest). Using vertical uniaxial compression with a load of 200 kPa on disturbed or undisturbed samples generates low BD ref and high DC-values. The standard Proctor test generates higher BD ref-values, which are similar to those in a uniaxial test with a load of 1600 kPa for soils with low clay content but lower for soils with high clay content. The BDc LLWR does not necessarily restrict root growth or crop yield under no-tillage, since field investigations led to higher BDc Rest-values. A uniaxial load greater than 800 kPa is promising to determine BD ref for no-tillage soils. The BD ref is highly correlated to the clay content and thus pedotransfer functions may be established to estimate the former based on the latter. Soil ecological properties are affected before compaction restricts plant growth and yield. The DC is an efficient parameter to identify soil compaction affecting crops. The effect of compaction on ecological properties must also be further considered.

Reduced and Conservation Tillage Effects on Soil Ecological Properties in an Organic Farming System

ABSTRACT This study investigated the effects of reduced and conservation tillage, namely two-layer ploughing (LP) and layer-cultivating (LC) on soil ecological properties (physical, chemical, microbiological) in an organic farming system relative to ploughing (P). As a major trend, the amounts of soil organic C, microbial biomass C and N, the Cmic to Corg ratio, and microbial activity increased at 0–15 cm depth in the order?—LP—LC while they decreased at 15–25 cm depth in the same order, both in green fallow and winter rye plots. For example, at 0–15 cm depth, soil microbial biomass C concentration was significantly 25% (LP) and 30% (LC) greater in green fallow plots and 18 to 20% greater in winter rye plots than in P. This was highly correlated with an increase in aggregate stability at these sites. Non-ploughing also resulted in a significantly higher bulk density. In addition, the amounts of ergosterol were higher at 0–15 cm depth in LP and LC treatments than in P. Hence, it is indicated that the microbial community changed towards fungi at 0–15 cm depth in reduced and conservation tillage plots. It can be concluded that reduced or conservation tillage in organic farming systems has beneficial effects on soil organic matter, microbial biomass, and activity.

Soil microbiological monitoring of a pine forest after partial thinning for stand regeneration with beech seedlings

A 62 year old pine stand located in northeastern Germany (Brandenburg, Ost-Prignitz, Revier Beerenbusch) was studied with respect to a thinned vs. an unthinned variant. Samples of the litter layer and the top mineral horizon of an acid brown earth were collected from five plots at each variant in April and November during 3 years (2000–2002), respectively. Soil microbial biomass (Cmic and basal CO2 respiration were assayed using an infrared gas analysis system. Soil organic carbon (Core) and total nitrogen (Nt) contents were determined using a C/N elemental analyzer. In addition, cellulose decomposition in soil was assayed using a mini-container system. The contents of Corg, Nt, Cmic and basal respiration activity in the humus layer and in the mineral soil horizon did not differ significantly during 3 years shortly after thinning. Furthermore, no difference was detected comparing spring and autumn samplings of 3 years under study. On the other hand, cellulose decomposition in soil was slightly but not yet significantly increased in the thinned variant. Thus, 3 years after thinning no significant actual impacts on soil ecological properties were detected, but first evidence for increased soil biochemical activities in the thinned variant was found. Long-term monitoring and spatially more detailed analyzes are required to reveal lasting impacts of thinning. Special emphasis needs to be directed on the composition of soil microbial communities and on specific activities related to soil organic matter transformation.

The long-term fertilization experiments in Halle (Saale), Germany — Introduction and survey

Six of originally eight long-term trials in Halle (Saale), Germany. are still continuing. Five are situated at Julius-Kuhn-Feld, an experimental station launched by Julius Kuhn in Halle in 1866. Apart from the Eternal Rye trial established in 1878, those are phosphorus, potassium, lime, and organic fertilization long-term trials, all being launched by Karl Schmalfuss in 1949. Other long-term trials have been terminated, but data are available on the effects of nitrogen fertilization and the physiological reaction of fertilizers. Another long-term trial in Halle (Adam-Kuckhoff-Strasse 17b) investigates the influence of fertilization on soil formation from loess. Up to now, the major results are as follows: 1. Changes in soil-ecological properties due to fertilization and rotation were only evident after 30 years, and new steady states sometimes took 70 years to occur. 2. In the long term, the C- and N-contents of the soil largely depend on the amount of hardly decomposable organic matter applied with organic fertilization. High mineral-N doses, with consequent high crop and root residues, increased the humus content of the soil. 3. Mineral fertilization can replace organic fertilization in terms of sustainable yield capacity provided equal nutrient amounts were applied. 4 The high P-supply ability of the soil in Halle could not be explained by traditional soil analysis methods of calculating plant-available P. With some restrictions, the same is valid for K. 5. At the experimental site, soluble salts (nitrate, sulphate) accumulated in the subsoil. 6. A regular lime demand of central German chernozems could be proved, especially in case of low soil organic matter (SOM) and physiologically acid fertilization.