Disturbed Forest Soils Research Articles

Mobility of Pb, Zn, Cu and As in disturbed forest soils affected by acid rain

Early efforts at remediation of contaminated soils involve overturn or removal of the uppermost soil horizons. We find that such disruption is counterproductive, as it actually increases the mobility of the heavy metals involved. In our study, we sought to replicate in a controlled manner this commonly used remediation strategy and measure Pb, Zn, Cu and As concentrations in all soil horizons-both prior to and 1year after disruption by trenching. BCR analyses (sequential leaching) indicate that Pb is affected to the greatest degree and is most highly mobile; however, Zn and As remain insoluble, thus partially ameliorating the detrimental effect. Differences in vegetation cover (i.e. spruce vs. beech forest) have little influence on overall element mobility patterns. The Krušné hory (Ore Mts., Czech Republic) study area is one of the more heavily contaminated areas in Central Europe, and thus the results reported here are applicable to areas affected by brown-coal-burning power plants.

Recent spruce decline with biotic pathogen infestation as a result of interacting climate, deposition and soil variables

Decline or health deterioration of Norway spruce (Picea abies (L.) Karst.) dominated forest stands has recently been observed mainly in sub-mountainous parts of Central Europe. Forest inventory of 208 randomly distributed circular plots including field observations of spruce tree health and rot symptoms by honey fungus (Armillaria ostoyae) was used for assessing intensity of spruce forest health decline in a managed forest area of 12.7 th. ha located in Beskids Mts., NE Czech Republic. First, principal component analysis was used to separate inventory variables related to environmental stress (reduced apical increment, dry tree top and stem resin exudation due to A. ostoyae infestation) into PC1, and health deterioration symptoms associated with mechanical damage (peeling, crown breaks) into PC2. The first two principal components explained 59% of the total variability in health decline symptoms. Spatial variability of both principal components was explained using spatial lag regression model identified from a set of environmental variables including sulfur and nitrogen deposition, elevation, solar radiation, age of the forest stands and geological properties (geochemical reactivity index). Environmental stress (PC1) was associated with low elevations (sub-optimal for spruce), high level of nitrogen and sulfur deposition (their interaction), low geochemical reactivity and also stand age. On the other hand, mechanical damage (PC2) significantly increased with elevation and stand age. As the forest decline in Beskids Mts. is related to A. ostoyae spreading from local infestation hot spots, both principal components had a significant spatial autocorrelation, partly distorting the signal of environmental conditions. The results indicate that the disturbed forest soils by long-term acid deposition and subsequent nutrient degradation and more pronounced drought stress at low elevations are the most important drivers of the recent spruce health decline in Beskids Mts.

Windstorm disturbance effects on mountain stream ecosystems and the Plecoptera assemblages

Abstract Within the investigated river basins the deforestation ranged from 0-45.5%, dependent on the amount of windstorm damage. Our water temperature readings revealed that the canopy elimination above the streams in the areas damaged by the windstorm caused increase in daily and annual water temperature and also wider daily water temperature range, than those in the undisturbed reference stream, which caused the decline of cold stenotherm species abundance. The stream basins deforestation was collinear with FPOM and UFPOM concentrations, water temperature gradient and nitrate concentrations. Statistical analysis showed that size of stream, conductivity, catchment area and discharge were negatively correlated with the stonefly mesotherm ratio and nitrate contents. Higher average concentrations of nutrients (like NO−3) in samples from some streams are a consequence of their mobilization from disturbed forest soils due to the windstorm. Most streams located in the deforested area were found by us in a higher trophic status, especially due the particulate organic matter (POM) content and biofilms amount, what caused increase in some functional feeding groups occurrence (collectorgatherers, scrapers and mainly predators). Stream degradation positively correlated with the percentage of deforested area, ratio of eurytherm taxa, transported organic matter, dissolved organic matter, and biofilms occurrence. The conductivity values measured in water samples were collinear with alkalinity and pH values and increased with watersheds areal extent. We established environmental variables influenced by the windstorm event along the catchment degradation gradient using measurable characteristics of stonefly assemblages and metrics. The proportion of the Leuctridae family and the Nemoura genus expressed as the LN index (1) shows a negative correlation with part undisturbed forested areas and channel stability, and positive correlation with stream erosion (expressed as the TAM quantity) in river basins. Proportion of shredders among the investigated streams was significantly higher in deforested streams, and shows lower stability of stonefly community in these habitats, where significantly fluctuate channel stability, water temperature and discharge of these streams.

Association of soil organic carbon with physically separated soil fractions in different land uses of Costa Rica

Studies on soil organic carbon (SOC) storage and stability require the separate assessment of soil fractions in relation to protection against loss. This on-farm study assessed the role of primary (sand, silt, and clay) and secondary (micro- and macroaggregates) particle size fractions on the physical protection of SOC to 30-cm depth of nine agricultural and three forest land uses within three contrasting ecoregions of Costa Rica (i.e., Isthmian-Atlantic moist, Pacific dry, and Montane forest). Specific objectives were to: (1) determine the effect of land use in each ecoregion on particulate organic matter carbon (POM-C), silt plus clay-associated carbon (S+C-C), and micro- and macroaggregate associated water-stable aggregate carbon (WSA-C), and (2) establish the relationships among aggregate properties and SOC concentration. Aggregate stability was characterized by studying the WSA, mean weight diameter (MWD), and tensile strength (TS). Soils under coffee (Coffea arabica), oil palm (Elaeis guineensis), and pineapple (Ananas comosus) plantations had high clay contents to 30-cm depth (ranging between 42.9 and 60.7%), which indicated a high potential for SOC storage. In comparison to less disturbed forest soils, micro- and macroaggregation was not strongly affected by agricultural land use. At coffee and pasture land uses, POM-C concentration was significantly lower (ranging between 0.4 and 2.0 g C kg−1). Between 58 and 98% of SOC was associated with S+C fractions indicating the importance of these particle size fractions to SOC storage. The S+C-C and micro- and macroaggregate-C concentrations differed mainly among pineapple, mango (Mangifera indica), pasture, and other land uses within ecoregions. Further, there was no general tendency of higher C concentrations in the macro- vs. the microaggregate fractions in contrast to the aggregate hierarchy theory. The MWD was affected by land use only for pineapple and organic farming, and it decreased for mango and coffee with increase in soil depth. Correlations among SOC, texture, and TS were site-specific. Silt content was more important than the other particle size fractions in explaining SOC contents. In summary, the amount of physically separated soil fractions and their C storage and stability to 30-cm depth differed mainly among pineapple, mango, pasture, and coffee in specific ecoregions. Well-designed long-term field experiments in Costa Rica are needed to develop management practices for enhancing SOC storage and stabilization in physically separated soil fractions.

Soil properties discriminating Araucaria forests with different disturbance levels.

Soil biological, chemical, and physical properties can be important for monitoring soil quality under one of the most spectacular vegetation formation on Atlantic Forest Biome, the Araucaria Forest. Our aim was to identify a set of soil variables capable of discriminating between disturbed, reforested, and native Araucaria forest soils such that these variables could be used to monitor forest recovery and maintenance. Soil samples were collected at dry and rainy season under the three forest types in two state parks at São Paulo State, Brazil. Soil biological, chemical, and physical properties were evaluated to verify their potential to differentiate the forest types, and discriminant analysis was performed to identify the variables that most contribute to the differentiation. Most of physical and chemical variables were sensitive to forest disturbance level, but few biological variables were significantly different when comparing native, reforested, and disturbed forests. Despite more than 20 years following reforestation, the reforested soils were chemically and biologically distinct from native and disturbed forest soils, mainly because of the greater acidity and Al3+ content of reforested soil. Disturbed soils, in contrast, were coarser in texture and contained greater concentrations of extractable P. Although biological properties are generally highly sensitive to disturbance and amelioration efforts, the most important soil variables to discriminate forest types in both seasons included Al3+, Mg2+, P, and sand, and only one microbial attribute: the NO2- oxidizers. Therefore, these five variables were the best candidates, of the variables we employed, for monitoring Araucaria forest disturbance and recovery.

The influence of environmental variables on larval growth of stoneflies (Plecoptera) in natural and deforested streams

A total 14 streams located in the Tatra Mts (Slovakia) were investigated. The studied river basins have different deforestation range (0–45.5%) influenced by windstorm. Daily and annual water temperature suggested that in streams overflowing through the area deforested by windstorm the temperature was higher than in selected non-disturbed streams. Higher average nutrient concentrations in samples from these streams are connected with nutrient mobilization from disturbed forest soils after the windstorm. Most of the damaged streams have higher trophic status, including POM and biofilms. The growth of the most abundant larvae increases with deforestation. Growth of species Leuctra rauscheri, Protonemura Montana, and Perlodes intricatus correlates with the sum of daily temperatures over a given time interval. Growth of species Brachyptera seticornis, Leuctra autumnalis and Isoperla sudetica are affected by stream trophy.

Molecular Characterization of Soil Bacterial Community in a Perhumid, Low Mountain Forest

Forest disturbance often results in changes in soil properties and microbial communities. In the present study, we characterized a soil bacterial community subjected to disturbance using 16S rRNA gene clone libraries. The community was from a disturbed broad-leaved, low mountain forest ecosystem at Huoshaoliao (HSL) located in northern Taiwan. This locality receives more than 4,000 mm annual precipitation, one of the highest precipitations in Taiwan. Based on the Shannon diversity index, Chao1 estimator, richness and rarefaction curve analysis, the bacterial community in HSL forest soils was more diverse than those previously investigated in natural and disturbed forest soils with colder or less humid weather conditions. Analysis of molecular variance also revealed that the bacterial community in disturbed soils significantly differed from natural forest soils. Most of the abundant operational taxonomic units (OTUs) in the disturbed soil community at HSL were less abundant or absent in other soils. The disturbances influenced the composition of bacterial communities in natural and disturbed forests and increased the diversity of the disturbed forest soil community. Furthermore, the warmer and humid weather conditions could also increase community diversity in HSL soils.

Soil bacterial communities in native and regenerated perhumid montane forests

Forest management often results in changes in soil properties and microbial communities. In the present study, we characterized differences in soil bacterial communities caused by forest management practices using 16S ribosomal RNA (rRNA) gene clone libraries. The communities were from a disturbed Chamaecyparis (DCP) forest subjected to harvesting of snags and downed logs, a secondary Chamaecyparis (SCP) plantation subjected to harvesting of old-growth trees, and a secondary cedar plantation (SCD). These forests were compared to a nearby native Chamaecyparis (NCP) forest in a perhumid montane ecosystem. At this locality, the elevation is from 1500 to 2100 m a.s.l., the mean annual precipitation >4000 mm, the mean annual temperature about 12 °C, and the soil pH <4. The phyla Acidobacteria and Proteobacteria predominated among the three disturbed forest soil communities. Several diversity indices and rarefaction curves revealed that the diversity of the SCD community was higher than that of the DCP soils. The diversity of the SCP community was intermediate. The bacterial diversity of the NCP community was lower than communities in the three disturbed forest soils. Analysis of molecular variance revealed that the bacterial community in SCD soils significantly differed from those in the three Chamaecyparis forest soils. Some of the abundant operational taxonomic units (OTUs) significantly differed among the four forest soils. Compared to the three disturbed forest soil communities, the NCP community was dominated by Proteobacteria, which accounted for more than half of the community. These results suggest that the disturbance of forest harvesting and tree species conversion influence the composition of bacterial communities in natural and disturbed forests and increase the diversity of the disturbed forest soil community.

Enzyme Activities in Undisturbed and Disturbed Forest Soils Under Oak (Quercus brantii var. persica) as Affected by Soil Depth and Seasonal Variation

Enzyme Activities in Undisturbed and Disturbed Forest Soils Under Oak (Quercus brantii var. persica) as Affected by Soil Depth and Seasonal Variation

Soils apart from equilibrium – consequences for soil carbon balance modelling

Abstract. Many projections of the soil carbon sink or source are based on kinetically defined carbon pool models. Para\\-meters of these models are often determined in a way that the steady state of the model matches observed carbon stocks. The underlying simplifying assumption is that observed carbon stocks are near equilibrium. This assumption is challenged by observations of very old soils that do still accumulate carbon. In this modelling study we explored the consequences of the case where soils are apart from equilibrium. Calculation of equilibrium states of soils that are currently accumulating small amounts of carbon were performed using the Yasso model. It was found that already very small current accumulation rates cause big changes in theoretical equilibrium stocks, which can virtually approach infinity. We conclude that soils that have been disturbed several centuries ago are not in equilibrium but in a transient state because of the slowly ongoing accumulation of the slowest pool. A first consequence is that model calibrations to current carbon stocks that assume equilibrium state, overestimate the decay rate of the slowest pool. A second consequence is that spin-up runs (simulations until equilibrium) overestimate stocks of recently disturbed sites. In order to account for these consequences, we propose a transient correction. This correction prescribes a lower decay rate of the slowest pool and accounts for disturbances in the past by decreasing the spin-up-run predicted stocks to match an independent estimate of current soil carbon stocks. Application of this transient correction at a Central European beech forest site with a typical disturbance history resulted in an additional carbon fixation of 5.7±1.5 tC/ha within 100 years. Carbon storage capacity of disturbed forest soils is potentially much higher than currently assumed. Simulations that do not adequately account for the transient state of soil carbon stocks neglect a considerable amount of current carbon accumulation.

Reduction of Natural Ferric Iron Chelators in Disturbed Forest Soils

AbstractHydroxymate siderophores (HS) are high affinity FE3+ chelators which are produced and secreted into the soil by various soil microflora, including mycorrhizal fungi. HS are important in the iron nutrition of both the microorganisms which produce them and higher plants, and they may also protect higher plants from soil‐borne pathogens. We used a standard bioassay technique to compare HS concentrations in soils from 10 pairs of logged and adjacent unlogged sites in various areas of Oregon. In 8 of the 10 sites HS concentrations were significantly lower in soils from logged areas than in those from adjacent undisturbed forests. HS reductions were greater where slash was burned than where it was unburned or windrowed. Pot tests of soils from one site indicated that Douglas‐fir seedlings (Pseudotsuga menziesii [Mirb.] Franco) were iron limited in logged and burned but not in undisturbed forest soils. Soil pasteurization induced iron limitation in undisturbed soils, which suggests that iron limitation in soils from the logged and burned area may have been due to reduction of HS‐producing organisms.