Biological changes in northern spruce forest soil after clear-cutting

In northern Finland, reforestation has frequently failed in clear-cut areas of coniferous forests. These failures prompted an investigation of the changes in the invertebrate fauna and in the bacterial populations of such forest soils after clear-cutting. Clear-cut areas in four neighbouring sites of various ages were sampled monthly, and the results were compared with those for samples taken simultaneously from a control site in an untreated spruce stand. After clear-cutting, the total biomass of the invertebrate fauna showed a strong increase, mainly due to an increase of the Enchytraeidae populations. The biomass reached its maximum after 7 yr and returned to the original level by year 13 after clear-cutting. Bacterial counts showed the same pattern as the faunal biomass; the numbers at first increased after clear-cutting, then regressed, and approached the control value after 13 yr. Cellulose degradation and soil respiration behaved in the same way. Bacterial numbers showed a significant seasonal variation at all sites, including the control; counts were maximal after the snow melt in June and decreased during the growing season.     

Positive relationship between herbaceous layer diversity and the performance of soil biota in a temperate forest

The current decline in biodiversity is particularly pronounced in the herbaceous layer of forest ecosystems. We explored the relationship between a naturally occurring plant diversity gradient in the understory vegetation of a deciduous forest and several above-and belowground ecosystem processes. We show that particularly soil microbial parameters and microarthropod densities are positively correlated with plant species richness. These results confirm recent findings in grassland ecosystems and highlight the intimate interconnectance between the diversity and functioning of above-and belowground compartments. We conclude that irrespective of a potential causal relationship between plant species richness and belowground processes, it is essential to consider the performance of soil biota in order to understand the relationship between herbaceous layer composition and ecosystem function.     

Bioactivity in limed soil of a spruce forest

Summary The stimulative effect of lime on the bioactivity of various soil horizons was demonstrated by the ATP test, and respiration and microcalorimetric measurements, but not by FDA hydrolysis or the iron reduction test. The latter showed clear inhibition. When the natural structure of layers was saved while sampling, a smaller stimulation of bioactivity was observed than in the case of mixing natural layers. No stimulation was recorded when the lime layer was removed.     

Biomass distribution of a microarthropod community in spruce forest soil

It has been previously demonstrated that fractal habitat features, combined with the allometric relationship between body size and metabolic rate, can sufficiently predict the biomass distribution in arthropod communities. This study shows that the relationship between biomass B and abundance N in a community of soil microarthropods is flatter than might be predicted by a combination of hypotheses concerning the (1) fractal dimension of pore surface, (2) metabolic rate, and (3) accessibility of soil pores. The relationship between B and N is N B ^-0.80 for the size classes to the right of the mode of the biomass distribution. Since the relationship between B and metabolic rate M is M B ^0.81, the energy use per size class is independent of size (B ^-0.80×B ^0.81 B ⁰) for a broad range of size classes with the exception of very small microarthropods.     

Leaching of metals from the A-horizon of a spruce forest soil

The study quantifies the amount of metals (Na, K, Mg, Ca, Al, Fe, Mn, Ni, Cr, V, Cu, Zn, Cd, Pb) leached from the A-horizon of a podzolic spruce forest soil in southern Sweden during 2.5 yr, and offers statistical evidence of environmental conditions of importance to metal release. Considerable losses of Pb, Cr, Ni and V may occur from the A-horizon of forest soils under conditions favoring leaching of organic matter, Fe, and Al, i.e. during periods of comparably high soil temperature and moisture. Metals with a larger fraction present in exchangeable form (Na, Mg, Ca, Zn, Cd) are more susceptible to minor pH changes. An accelerated deposition or internal production of acidic matter therefore will reduce the retention times of these elements particularly.     

Methane consumption in a frequently nitrogen-fertilized and limed spruce forest soil after clear-cutting

Abstract. The effects of especially frequent nitrogen (N) additions (from 1959 to 1986, totalling 860 kg N ha⁻¹) and liming (in 1958 and 1980, totalling 6000 kg CaCO₃ ha⁻¹) on CH₄ uptake by a boreal forest soil were studied in a stand of Norway spruce. Except for a forested reference plot, the stand was clear-cut in January 1993 and the following year one-half of each clear-cut plot was prepared by mounding. Fluxes of CH₄ were measured with static chambers in the autumn before clear-cutting and during the following four summers. The average CH₄ uptake during 1993–96 in the forested reference plot was 82 μg CH₄ m⁻² h⁻¹(ranging from 10 to 147 units). In the first summer after clear-cutting, the cleared plot showed 42% lower CH₄ uptake rate than the forested reference plot, but thereafter the difference became less pronounced. The short-term decrease in CH₄ consumption after clear-cutting was associated with increases in soil NH₄⁺ and NO₃⁻concentrations. Mounding tended at first to stimulate CH₄ uptake but later to inhibit it. Neither liming nor N-fertilization had significant effects on CH₄ consumption. Our results suggest that over the long term, in N-limited upland boreal forest soils, N addition does not decrease CH₄ uptake by the soil.     

Fluctuations of diptera larvae in soil from a spruce forest in relation to climatic factors

Summary Diptera larvae were extracted by the wash and flotation method according to Healey and Russell-Smith (1970) as modified by Altmüller (1979). The larvae had been kept in alcohol for at least 2 months. After this time their specific gravity changed, and an additional flotation with MgSO₄-water solution of SG = 1.26 g/cm³ was very effective. This new method is described. The working procedure can be reduced to about 50%–70% of the time Altmüller (1979) and Hövemeyer (1984) needed. Many tests have shown that some small sciarid larvae settle out with the needle and humus particles in solution of SG = 1.26 and cannot be found, so that it is necessary to apply a correction factor. Samples taken each August from 1979 to 1984 were extracted and floated off by the methods described. Larvae from seven families of Diptera nematocera and from six families of Diptera brachycera were found. Numbers of sciarid larvae varied between 2500 (1979) and 100/m² (1981), of the cecidomyid larvae between 6700 (1983) and 400/m² (1980) and of the brachyceran larvae between 650 (1979) and 50/m² (1984). The correlation coefficient (= r) of larval population size with temperature and precipitation, respectively, was calculated and hence the coefficient of determination as a percentage (r ² x 100), which represents the proportion of the fluctuations in population size that is accounted for by weather factors. All families were influenced negatively by the temperature and positively by the precipitation in August, i.e., the higher the precipitation and the lower the temperature in August the higher the larval abundance in August. The development of the larvae begins in the previous year, and the influence of monthly climatic factors during the whole period of development was tested. It was shown that: Precipitation is correlated with the abundance of (1) sciarid larvae in June and August of the previous year (positively); (2) brachyceran larvae in June (August) of the previous year and in (February), March, April and August of the same year (positively); and (3) cecidomyid larvae in July of the same year (negatively). Temperature is correlated with the abundance of (1) sciarid larvae in August of the previous year (negatively); (2) brachyceran larvae in August of the previous year (negatively); and (3) cecidomyid larvae in September of the previous year, in January and July of the same year (positively). Monthly data for precipitation and temperature, taken together, showed maximum positive correlations with abundance as follows: (1) for sciarid larvae, with data for August of the previous year; (2) for brachyceran larvae, with data for August of the previous year; (3) for cecidomyid larvae, with data for July of the same year.     

The response of soil microbial biomass and activity of a Norway spruce forest to liming and drought

Long-term effects of liming and short-term effects of an experimentally induced drought on microbial biomass and activity were investigated in samples from the O-layer (Of/Oh) and uppermost mineral soil (0—10 cm) in a spruce forest near Schluchsee (Black Forest, South-West Germany). Seven years after lime application a marked increase of pH values was restricted to the O-layer. The contents of C and N in the O-layer of the limed plot appeared to be lower, whereas in the A-horizon from the limed plot the contents of C and N appeared to be higher than on the control. However, these differences were statistically not significant due to a distinct spatial variability of topsoil conditions. On the limed plots C_mic, N_mic, and P_mic in the O-layer were lower in comparison to the control whereas differences in the A-horizon were negligible. In both sampling depths of the limed plot protease activity was higher while N-mineralization was lower. The other microbial activities studied (basal respiration, catalase activity) followed no consistent pattern after liming. Drought and drought in combination with liming, respectively, had no clear effects on microbial biomass and activity. Only in the A-horizon of the control, there is some evidence for drought stress for microorganisms. The high variability of results from the drought experiment (roof installation) is likely due to the marked spatial variability of top soil properties as well as imperfect and uneven achievement of experimental drought. Nevertheless, our study indicates that long-term effects of liming on microorganisms highly depend on site conditions. Thus, liming operations which currently affect vast areas of forest land should be accompanied by monitoring of soil organisms and their activities to reduce the possibility of a loss in functional diversity of soil organisms.     

Surface area and CEC as related to qualitative and quantitative changes of forest soil organic matter after liming

Water vapor adsorption isotherms were used for estimation of (apparent) surface areas of samples of limed and unlimed plots of an acidic sandy forest soil. Samples were taken at two microrelief (ridge and furrow) positions from five subsequent 10 cm layers. Values of surface area and CEC correlated linearly with organic matter content but only for four bottom layers. Surface areas and CEC values calculated per the unit mass of organic carbon were higher in upper layers than in lower layers for control samples. For limed samples an opposite trend was observed. The estimated average (apparent) charge densities of organic matter showed a better correlation with humic to fulvic acids ratio. Values of surface charge densities for every investigated profile increased with depth and they were lower in limed than in unlimed profiles.     

Patterns of acid deposition to a Danish spruce forest

Bulk precipitation and bulk throughfall was collected during the period September to November 1984 in a Danish spruce forest. Samples were analyzed for all major anions and cations as well as strong and total acidity. The acid load to the forest ecosystem was estimated adding the throughfall fluxes of protons (79 eq ha^?1mo^?1), ammonium (99 eq ha^?1mo^?1) and a calculated estimate oflthe protons buffered by exchange processes in the canopy (75 eq ha^?1 mo^?1). This is still a minimum estimate but it exceeds the proton load determined by pH measurement in bulk throughfall and bulk precipitation by factors 3 and 6, respectively. Throughfall fluxes of all major cations and anions except ammonium decreased with distance from the trunk.     

Chemical deposition to a high elevation red spruce forest

A preliminary analysis of O₃, SO₂, SO _inf4 ^sup2? , and total NO _inf3 ^sup? deposition to the red spruce forest on the summit of Whitetop Mountain, Virginia, illustrates uncertainties in analysis methodologies, establishes the relative importance of three deposition pathways, and suggests areas for further research. Results are presented here for an analysis of the dry, wet (precipitation), and cloud water deposition pathways for the four chemical species during a 26-day period in April and May 1986. Dry and cloud water depositions are estimated using available models along with air and cloud water chemistry measurements made at the summit. For water soluble species, depositions by precipitation and cloud interception are found to be comparable in magnitude, while dry deposition appears to be about an order of magnitude less. High levels of atmospheric O₃ lead to a large estimate of 03 deposition (on a mass flux basis) when compared to the estimated deposition of gaseous SO₂. This is in spite of the fact that computed SO₂ dry deposition velocities exceed those for O₃. Model uncertainties are large for both dry deposition velocity and cloud water flux computations, and some bias in computations probably exists because of the application of the models to a complex terrain situation. Field evaluation of the cloud water deposition model is of greatest priority because of the apparent relative importance of that deposition pathway.     

Leaching of metals from a spruce forest soil as influenced by experimental acidification

Acidified (H₂SO₄+HNO₃, 3:1) throughfall waters (pH 3.16 and 3.40 as volume weighted means or control (untreated throughfall water, pH 3.72) were applied for 3.5 yr by an automatic irrigation device to lysimeters containing podzolized spruce forest soils of 0–5, 0–15 and 0–35 cm soil depth. The total volume of the leachates was measured together with their pH and total content of DOC, Na, K, Ca, Mg, Fe, Mn, Al, Cu, Zn, Cd and Pb and the initial amounts of metals and H in the soil. The main part of H⁺ added with the throughfall waters was retained within the soil. Concentrations and fluxes of Mg, Ca, Mn, Zn and Cd in the soil were significantly increased by addition of acidified throughfall waters; K was less affected. As a consequence of lowered flux of DOC in the A horizon as acid input increased, Fe, Al, Cu, and Pb fluxes also decreased. The mobility of these metals in the A horizon was shown to be regulated mainly by the formation of watersoluble organic compounds rather than directly by pH variations. Compared to the control, the additional annual loss of Mg from the soil profile in the most acid treatment was c. 10% of the currently exchangeable amount.     

Humus macro-morphology and soil microbial community changes along a 130-yr-old Fagus sylvatica chronosequence

We aimed to characterize humus macro-morphology and the associated soil microbial community within the unmodified litter (OL), the fragmented and humified layers (FH) and the organo-mineral (A) layer along a beech (Fagus sylvatica L.) forest chronosequence with four stand age-classes (15-, 65-, 95-, 130-yr-old) in Normandy, France. Humus macro-morphology was described with 36 quantitative and semi-quantitative variables. We measured microbial biomass N (N_mic), microbial N quotient (N_mic-to-N_t), fungal ergosterol, bacterial and fungal DNA using 16S and 18S rDNA real-time qPCR and evaluated the potential metabolic profile of heterotrophic bacteria within each soil layer and stand age-class. The log-transform ergosterol/fungal DNA ratio (EFR index) was used as an indicator related to active fungal biomass and the fungal/bacterial (F/B) ratio was calculated from qPCR results. There was a shift from mull (mainly dysmull) to moder humus forms along the chronosequence. While the N_mic did not change significantly, the N_mic-to-N_t decreased along the chronosequence in the OL layer. Ergosterol content increased in FH and A layers and the F/B ratio increased in the FH layer with increasing beech forest age. The EFR index was significantly higher in the OL and A layers of the oldest stands, whereas the highest EFR index in the FH layer occurred in the 15-yr-old stands. The functional diversity of heterotrophic bacteria was greater within OL and FH layers of 130-yr-old stands, but highest in the A layer of 15-yr-old stands while the Average Well Color Development remained stable for all soil layers. We found significant correlations between macro-morphology and microbial variables, especially between FH-based morphology and fungal biomass. Our main results are that beech forest maturation is accompanied by (1) an increase in fungal biomass in the FH layers and, (2) an increase in heterotrophic bacteria functional diversity in the organic layers. We have identified key macro-morphology variables that are good predictors of the structural and functional profile of the soil microbial community during beech forest development.     

The relationship between the organic matter composition of a forest floor and the structure of a soil arthropod community

The relationship between the amount and conposition of organic matter of a forest floor and the structure of the soil arthropod community was investigated in a temperate mixed forest of beech and pine trees. Seven enivronmental variables, i.e. broad leaves, pine needles, twigs, roots, others, total organic matter (sum of broad leaves, pine needles, twigs and others) and water content, were related to the soil arthropods in the statistical analysis. Pearson correlation was used to analyze the relation between environmental variables and total abundance of Collembola, Oribatida and Mesostigmata. Total abundance of Collembola and Oribatida did not show a clear correlation with total organic matter. Total abundance of Mesostigmata showed the positive correlation with broad leaves or total organic matter. The result in this study might be due to the fact that ‘organic matter’ treated in this study was the material which was left on the 2 mm mesh sieve, and most of small fragmental organic matter in the F or H layer was not included. Canonical correspondence analysis (CCA) was used to relate the variables of the organic matter to the community organizations of Collembola and Oribatida. CCA ordination indicated that the total amount of organic matter was the most important variable for the organization of both communities. These results suggest that the amount and composition of organic matter influenced the community organization of soil arthropods in a mixed forest.     

Response of soil water chemistry and fine-roots to clean rain in a spruce forest ecosystem at Solling,FRG

In the Solling experimental forest in central Germany a ‘clean rain’ roof experiment is conducted in a 60 year old Norway Spruce (Picea abies KARST.) stand. In this experiment with application of artificially prepared pre-industrial throughfall there is now a time series of soil water chemistry data from about 2 yr of pre-experiment and 3.5 yr of manipulation treatment. The response of soil solution chemistry to reduced inputs of N and S was strong and fairly rapid. There is a clear reflection of reduced input in soil solution concentrations, particularly for the N ions. The fine-roots of the Norway spruce trees reacted strongly to these changes in soil water chemistry. Fine-root biomass increased in the clean rain plot by about 40 % compared to pre-experimental conditions. This increase was strongest in the B-horizon, indicating that acid stress has ameliorated in the mineral soil. However, low concentrations of ammonium and nitrate in the root zone may also have contributed to this effect, since more fineroots are needed to maintain the N demand of the trees. No effect was yet found for other variables (photosynthesis, respiration, transpiration). Nutrient cation concentrations in the needles remained on the same low level as in the control groups. However, these aboveground variables may react after some time lag. The results demonstrate that in spruce forests on acid soil atmospheric element input largely controls soil solution chemistry and that air pollution control measures would have a significant effect with respect to ameliorating soil water chemistry, acidity and forest health.     

Soil biota effects on soil structure: Interactions between arbuscular mycorrhizal fungal mycelium and collembola

Soil aggregation is an important ecosystem process mediated by soil organisms. Collembola and arbuscular mycorrhizal (AM) fungi are major soil biota representing different functional groups, and are known as two key promoters of soil aggregation. Although several studies have experimentally demonstrated that AM fungi and, more recently, collembola affect soil structure, there is no study investigating how both soil organisms affect soil aggregation excluding the influence of plant roots, another important driver of soil aggregation. Considering the importance of AM fungi and collembola in terrestrial ecosystems, here we asked if both organisms have any influence on soil aggregation when roots are not present.In order to examine this question we conducted a completely factorial greenhouse study manipulating the presence of both collembola and AM fungi and excluded the roots of Plantago lanceolata using a 38 μm nylon screen compartment. We quantified soil aggregation as water stable soil aggregates in four size classes in the hyphal compartment and monitored a number of other explanatory variables, including AM (and non-AM) fungal soil hyphal length.The soil in the hyphal compartment showed greater soil aggregation with larger mean weight diameter when collembola were present, and a similar result was found in the presence of AM fungi, compared to control treatments. Moreover, combined presence of both AM fungi and collembola resulted in a non-additive increase of soil aggregation.Our study clearly indicated that collembola can enhance soil aggregation, that they can partially complement effects of AM fungi, and that these effects are independent of roots.     

Nitrogen transformations in particle size fractions from a second rotation pine forest soil

Abstract

A second rotation forest sand (Mt Burr sand) was separated by a combination of dry sieving and winnowing into different particle sizes rich in either soil or organic matter. These fractions were analysed for % loss on ignition, % organic carbon, total organic nitrogen and mineral nitrogen. Mineralization of soil organic nitrogen and nitrification of ammonium sulphate added to these fractions were studied. Amongst the heavier fractions obtained by sieving, the <125 μm fraction (the finest) contained the highest concentration of organic and exchangeable nitrogen and was the most active in nitrogen transformations. Amongst the lighter fractions obtained by winnowing, the 125 to 500 μm fraction had the highest organic nitrogen content but mineralization of nitrogen was greatest in the 500 to 2000 μm. Nitrification of native and applied ammonium nitrogen was similar in both the 125 to 500 μm and 500 go 2000 μm organic matter fractions.     

Changes in plant community structure and soil biota along soil nitrate gradients in two deciduous forests

Anthropogenic nitrogen (N) deposition is a serious threat to biodiversity and the functioning of many ecosystems, particularly so in N-limited systems, such as many forests. Here we evaluate the associations between soil nitrate and changes in plant community structure and soil biota along nitrate gradients from croplands into closed forests. Specifically, we studied the composition of the understory plant and earthworm communities as well as soil microbial properties in two deciduous forests (Echinger Lohe (EL) and Wippenhauser Forst (WF)) near Munich, Germany, which directly border on fertilized agricultural fields. Environmental variables, like photosynthetically active radiation, distance to the edge and soil pH were also determined and used as co-variates. In both forests we found a decrease in understory plant coverage with increasing soil nitrate concentrations. Moreover, earthworm biomass increased with soil nitrate concentration, but this increase was more pronounced in EL than in WF. Soil microbial growth after addition of a nitrogen source increased significantly with soil nitrate concentrations in WF, indicating changes in the composition of the soil microbial community, although there was no significant effect in EL. In addition, we found changes in earthworm community composition along the soil nitrate gradient in WF. Taken together, the composition and functioning of forest soil communities and understory plant cover changed significantly along soil nitrate gradients leading away from fertilized agricultural fields. Inconsistent patterns between the two forests however suggest that predicting the consequences of N deposition may be complicated due to context-dependent responses of soil organisms.     

Seasonal changes in multi-scale spatial structure of soil pH and related parameters along a tropical dry evergreen forest slope

Seasonal changes in multi-scale spatial variation in soil chemical properties, which may be controlled simultaneously by biotic and abiotic factors, have not been studied in tropical dry forests. We evaluated the spatial variation of physico-chemical soil properties, plant litter and terrain attributes at multiple scales in a tropical dry evergreen forest using multivariate geostatistics. Soil samples were collected at different depths using nested interval sampling during 1- and 10-m intervals in both the wet and dry seasons. We measured pH, exchangeable cations (Ex-K⁺ and Ex-Ca²⁺), acidity (Ex-H⁺ and Ex-Al³⁺), particle size (clay and sand contents), and forest floor mass (O_i and O_a). Pronounced spatial variation in pH was observed in surface soil (0-5 cm) but not in deeper soil (5-55 cm). Multi-scale spatial structures with short (20 m) and long (86 m) ranges were observed in the auto- and cross-variograms of soil, litter and slope gradient. Pronounced multi-scale structures were observed simultaneously in pH and Ex-Ca²⁺ both in the wet and dry seasons. Only a short-range structure was observed in Ex-K⁺ and O_a, whereas a long-range structure was pronounced in sand contents and slope gradients. Although the variograms had similar shapes between wet and dry seasons for almost all variables, the short-range structure of the cross-variogram between O_a with pH and base cations was more pronouncedly developed in the wet season than in the dry season. Scale-dependent correlation coefficients suggest that a small-scale spatial variation in pH was connected to heterogeneous litter accumulation via base-cation input, whereas long-range spatial variation was simultaneously linked to particle size and slope gradient. This multivariate geostatistical approach applied within a stand detected biotic and abiotic factors controlling spatial variation in soil properties at both short and long distances.     

Response of the soil fungal community to multi-factor environmental changes in a temperate forest

Both environmental and climatic changes are known to influence soil microbial biomes in terrestrial ecosystems. However, there are limited data defining the interactive effects of multi-factor environmental disturbances, including N-deposition, precipitation, and air temperature, on soil fungal communities in temperate forests. A 3-year outdoor pot experiment was conducted to examine the temporal shifts of soil fungal communities in a temperate forest following N-addition, precipitation and air temperature changes. The shifts in the structure and composition of soil fungal communities were characterized by denaturing gradient gel electrophoresis and DNA sequencing. N-addition regimen induced significant alterations in the composition of soil fungal communities, and this effect was different at both higher and lower altitudes. The response of the soil fungal community to N-addition was much stronger in precipitation-reduced soils compared to soils experiencing enhanced precipitation. The combined treatment of N-addition and reduced precipitation caused more pronounced changes in the lower altitude versus those in the higher one. Certain fungal species in the subphylum Pezizomycotina and Saccharomycotina distinctively responded to N fertilization and soil water control at both altitudes. Redundancy discrimination analysis showed that changes in environmental factors and soil physicochemical properties explained 43.7% of the total variability in the soil fungal community at this forest ecosystem. Variations in the soil fungal community were significantly related to the altitude, soil temperature, total soil N content (TN) and pH value (P < 0.05). We present evidence for the interactive effects of N-addition, water manipulation and air temperature to reshape soil fungal communities in the temperate forest. Our data could provide new insights into predicting the response of soil micro-ecosystem to climatic changes.