Ecological optima and tolerances of Thelypteris limbosperma,Athyrium distentifolium,and Matteuccia struthiopteris along environmental gradients in Western Norway

The distribution and abundance of Thelypteris limbosperma, Athyrium distentifolium, and Matteuccia struthiopteris are modelled statistically in relation to 14 environmental variables along the major climatic, topographic, and edaphic gradients in western Norway. The data are from 624 stands from which measurements or estimates of mean January and mean July temperatures, humidity, altitude, aspect, and slope are available. From 182 of these stands eight soil variables have also been measured. The species responses are quantified by two numerical methods: Gaussian logit regression and weighted averaging (WA) regression. The estimated WA optima suggest that A. distentifolium has an ecological preference for low July and January temperatures, high altitudes, and soils of low-medium pH and base content. The species shows statistically significant Gaussian responses with summer temperature, humidity (= Martonnes humidity index), altitude, slope, aspect, pH, cation exchange capacity, and base saturation with optima of 8.7 °C, 188.9, 1220 m, 28°, 29°, 4.8, 13.77 mEq 100 g dry soil^-1, and 13.4%, respectively. These suggest that the occurrence and relative abundance of A. distentifolium are well predicted by summer temperature, topography, and soil pH and base status. T. limbosperma has WA optima that suggest that it favours moderately high winter and summer temperatures, high humidity, medium altitude, and soils of low pH and base content. It has significant Gaussian responses to summer temperature (optimum =12.6 °C), winter temperature (-1.8 °C), humidity (179.2), altitude (459.5 m), slope (22.5°), and Na (0.7 mg 100 g dry soil^-1). These suggest that climatic factors, altitude, and slope are significant predictors for its occurrence and abundance. M. struthiopteris has high WA optima for summer temperature, pH, Ca, Mg, K, Na, cation exchange capacity (CEC), and base saturation, and a low optima for humidity and winter temperature. Of these, summer temperature (16.0 °C), Ca (63.1 mg 100 g dry soil^-1), Mg (41.0 mg 100 g dry soil^-1), K (23.6 mg 100 g dry soil^-1), Na (5.0 mg 100 g dry soil^-1), CEC (60.7 mEq 100 g dry soil^-1), and base saturation (56.3%) have significant Gaussian logit responses, as do aspect (150.2°) and loss-on-ignition (9.4%). These results suggest that the occurrence and relative abundance of M. struthiopteris are well predicted by high soil base cations, a generally southern aspect, low organic content in the soil, and high July temperatures.     

Litter fall and nutrient dynamics in a Nigerian rain forest seven years after a ground fire

Abstract. Seasonal litter fall and mineral element content (N, P, Ca, Mg, K) of regrowth forest communities at the base and on the slope of an inselberg in Ile-Ife, Nigeria, were studied 7 yr after a ground fire ravaged the forest. Litter fall (tha^?1 yr^?1) was 4.6 (total), 4.2 (leaf), 0.3 (small wood < 2.5 cm diameter) and 0.1 (reproductive parts: fruits and flowers) in the base community and 6.4 (total), 5.4 (leaf), 0.9 (small wood) and 0.1 (reproductive parts) in the slope community. There was significant monthly variation in litter fall in the two communities with lowest amount of litter recorded during the wettest months of the year (May - August) and the highest amount during the dry season. Significant monthly variation (P<0.05) in Ca, Mg and K concentration in leaf litter and for Mg (P < 0.01) in fruit litter occurred, with the lowest concentration recorded during the wettest months (May-August). In leaf and wood litter the order of mineral element concentration was Ca>N>K> Mg > P while in fruit litter it was N > K > Ca > Mg > P. Quantities of mineral element (kg ha^-1 yr¹) returned to the soil via litterfall were N: 66; P: 4; Ca: 97; Mg: 15; K: 45 in base forest, and N: 112; P: 5; Ca: 142; Mg: 20; K: 66 in slope forest. Through leaf litter >88.5% of these elements was returned into the two communities, through wood > 4.0% and through reproductive organs > 0.3%. The order of quantities of these elements returned in leaf and wood litter was Ca > N > K > Mg > P, in fruit litter N ～ K > Ca > Mg > P. Significant monthly variation in the amounts of the various elements returned were recorded in leaf litter, but not in wood and fruit litter. The lowest amount of various elements was returned during the wettest months (May-August) which coincided with the period of the lowest element concentration and litter fall.     

Importance of soil calcium for composition of understory vegetation in boreal forests of Finnish Lapland

To focus conservation efforts into forest areas with high biodiversity, more information is needed about soil-vegetation dependencies in Finnish Lapland. We studied understory vegetation and soil variables along a transect across a felsic?Cmafic lithological sequence in central Finnish Lapland. At 119 northern boreal forest sites, coverages of understory vegetation, several mineral soil chemical elements, soil electrical conductivity, pH, and dielectric permittivity, as a measure of soil volumetric water content, were measured. We found that soil Ca concentration and Ca:Al ratio were the main variables determining vegetation composition and diversity. Ca-rich soils were characterised by high electrical conductivity, pH, and Mg concentration, and by low concentration of Al, S, Zn, and low C:N ratio. Soil Ca concentration is a diagnostic measure of plant diversity as concentration higher than 100 mg kg^?1 resulted in a considerable increase in plant diversity. Sites with Ca concentration this high were rare, and probably important in maintaining high biodiversity. The median soil Ca:Al ratio was only 0.02, suggesting, according to general theory, a considerable risk for aluminium stress. We found Geranium sylvaticum and Rubus saxatilis to be good indicators for Ca-rich regimes and high plant diversity.     

Is the Ca:Al ratio superior to pH,Ca or Al concentrations of soils in accounting for the distribution of plants in deciduous forest?

The distributions of vascular plants in south Swedish deciduous forests were related to exchangeable (exc) and soil solution concentrations of H⁺ (pH), Ca, Al and the Ca:Al ratios within these fractions. Topsoils (0–5 cm) of 172 sites with a pH_KCl of 3.2–3.9 (corresponding to 3.7–4.4 in soil solution) were used. In the soil solution both total Al_t and quickly reacting Al_r were determined. Exchangeable concentrations were generally well related to plant distributions, the highest correlation coefficients usually being given by pH_KCl>Ca_exc>Al_exc.>(Ca:Al)_exc. The (Ca:Al)_exc ratio was clearly inferior. Out of the soil solution variables studied, Ca concentration, followed by pH, was best correlated with plant distributions, Al_t, Al_r, and the Ca:Al ratios having similar and lower coefficients. It is concluded that the use of Ca:Al ratios as a general measure of Al toxicity in controlling plant distributions is rather problematic. It seems difficult to apply evidence for Ca-Al interactions from solution culture experiments to field conditions when measured as exchangeable or soil solution concentrations of the soil.     

The effects of acid deposition on the biogeochemical cycles of major nutrients in miniature red spruce ecosystems

As part of an experimental study of air pollution effects on tree growth and health, we combined process studies with an ecosystem approach to evaluate the effects of acidic deposition on soil acidification, nutrient cycling and proton fluxes in miniature red spruce ecosystems. Ninety red spruce saplings were transplanted into 1-m diameter pots containing reconstructed soil profiles and exposed to simulated acid rain treatments of pH 3.1, 4.1 and 5.1 for four consecutive growing seasons. All the principal fluxes of the major elements were measured. During the first year of treatments, the disturbance associated with the transplanting of the experimental trees masked any treatment effects by stimulating N mineralization rates and consequent high N0₃ ⁻ cation, and H⁺ flux through the soil profile. In subsequent years, leaching of base cations and labile Al was accelerated in the most intensive acid treatment and corresponding declines in soil pH and exchangeable pools of Ca and Mg and increases in exchangeable Al concentrations were observed in the organic horizon. Leaching of Ca²⁺ and Mg²⁺ also was significantly higher in the pH 4.1 than in the pH 5.1 treatment. Flux of Ca from foliage and soil was increased in response to strong acid loading and root uptake increased to compensate for foliar Ca losses. In contrast, K cycling was dominated by root uptake and internal cycling and was relatively insensitive to strong acid inputs. Cation leaching induced by acidic deposition was responsible for the majority of H⁺ flux in the pH 3.1 treatment in the organic soil horizon whereas root uptake accounted for most of the H⁺ flux in the pH 4.1 and 5.1 treatments. Although no measurable effects on tree nutrition or health were observed, base cation leaching was significantly accelerated by acidic deposition, even at levels below that observed in the eastern U.S., warranting continued concern about acid deposition effects on the soil base status of forested ecosystems.     

Effects of litter incorporation and nitrogen fertilization on the contents of extractable aluminium in the rhizosphere soil of tea plant (Camallia sinensis (L.) O. Kuntze)

The effects of litter incorporation and nitrogen application on the properties of rhizosphere and bulk soils of tea plants (Camellia sinensis (L.) O. Kuntze) were examined in a pot experiment. Total of 8 treatments included four levels of tea litter additions at 0, 4.9, 9.8, and 24.5 g kg^–1 in combination with two N levels (154.6 mg kg^–1 and without). After 18 months of growth the rhizosphere soil was collected by removing the soil adhering to plant roots and other soil was referred to as bulk soil. The dry matter productions of tea plants were significantly increased by N fertilization and litter incorporation. The effect of litter was time-depending and significantly decreased the content of exchangeable Al (Al_ex, by 1 mol L^–1 KCl) and Al saturation at 9 months after litter incorporation whereas soil pH was not affected, although the litter contained high Al content. After 18 months, the contents of extractable Al by dilute CaCl₂, CuCl₂ + KCl, NH₄OAC, ammonium oxalate and sodium citrate (Al_CaCl2, Al_Cu/KCl, Al_NH4OAC, Al_Oxal, and Al_Cit respectively) and Al_ex, were not affected by litter application, except that of Al_CaCl2 in the rhizosphere soil which was decreased following litter additions. Nitrogen fertilization with NH₄ ⁺ (urea and (NH₄)₂SO₄) significantly reduced soil pH, the contents of exchangeable Ca, K, Mg and base saturation while raised extractable Al levels (Al_CaCl2, Al_Cu/KCl, Al_NH4OAC, and Al_ex). In the rhizosphere soils exchangeable K accumulated in all treatments while exchangeable Ca and Mg depleted in treatments without litter application. The depletions of Ca and Mg were no longer observed following litter incorporation. This change of distribution gradients in rhizosphere was possibly due to the increase of nutrient supplies from litter decomposition and/or preferable root growth in soil microsites rich in organic matter. Lower pH and higher extractable Al (Al_CaCl2, Al_ex, and Al_NH4OAC) in the rhizosphere soils, regardless of N and litter treatments, were distinct and consistent in all treatments. Such enrichments of extractable Al in the rhizosphere soil might be of importance for tea plants capable of taking up large amounts of Al.     

Inexpensive biological tests for soil calcium deficiency and aluminum toxicity

Two relatively simple procedures based on 4-day seedling growth were developed for identifying soil calcium (Ca) deficiency and/or aluminum (Al) toxicity. Test A uses any large-seeded cultivar that a farmer might consider planting and reveals whether the cultivar will suffer from Ca deficiency by comparing root growth in untreated soil to that in soil receiving a minimal Ca addition (0.1 meq.100mL⁻¹ soil), sufficient to eliminate possible deficiency. Al toxicity is detected by comparing root growth in a sample receiving the minimal Ca treatment with growth in the soil treated with enough lime to neutralize exchangeable Al. In test B, potential Al toxicity problems are detected for any widely-grown standard crop by comparing its growth with that of a different, Al-tolerant variety on soil samples receiving 0.1 meq.100mL⁻¹ Ca. With this test Ca deficiency in the untreated sample is detected by an increase in root growth of the Al-tolerant variety resulting from a small addition of Ca. The tests agreed with diagnoses made by standard chemical methods in about 84% of the cases examined. The proposed tests can be carried out using simple, easily-available materials without the necessity of sending soils to an analytical laboratory.     

Interactions between aluminium,phosphorus and pH in the response of barley to soil acidity

Summary Two acid soils showing different Al solubility as a function of pH were limed to a range of pH values (in 10^–2 M CaCl₂) between 4.1 and 5.6. The apparent critical pH for the growth of barley in pots was 0.25 lower in the soil showing lower Al solubility. The addition of phosphate reduced exchangeable and soluble Al in the soils, and lowered the apparent critical pH by 0.35 while maintaining the difference between the soils. The Al concentration at the critical pH, measured after cropping to take account of the treatment effects on soil Al, also varied with soil and with phosphate addition. These apparent critical values of both pH and soluble Al varied linearly with available phosphate, over the range 18 to 73 mg P/kg soil, as follows: pH from 4.9 to 4.3; soluble Al, from 0.010 mM to 0.056 mM; and the soluble Ca/Al mole ratio, from 1270 to 214.     

Biomass, morphology and nutrient contents of fine roots in four Norway spruce stands

Fine root systems may respond to soil chemical conditions, but contrasting results have been obtained from field studies in non-manipulated forests with distinct soil chemical properties. We investigated biomass, necromass, live/dead ratios, morphology and nutrient concentrations of fine roots (<2 mm) in four mature Norway spruce (Picea abies [L.] Karst.) stands of south-east Germany, encompassing variations in soil chemical properties and climate. All stands were established on acidic soils (pH (CaCl₂) range 2.8–3.8 in the humus layer), two of the four stands had molar ratios in soil solution below 1 and one of the four stands had received a liming treatment 22 years before the study. Soil cores down to 40 cm mineral soil depth were taken in autumn and separated into four fractions: humus layer, 0–10 cm, 10–20 cm and 20–40 cm. We found no indications of negative effects of N availability on fine root properties despite large variations in inorganic N seepage fluxes (4–34 kg N ha⁻¹ yr⁻¹), suggesting that the variation in N deposition between 17 and 26 kg N ha⁻¹ yr⁻¹ does not affect the fine root system of Norway spruce. Fine root biomass was largest in the humus layer and increased with the amount of organic matter stored in the humus layer, indicating that the vertical pattern of fine roots is largely affected by the thickness of this horizon. Only two stands showed significant differences in fine root biomass of the mineral soil which can be explained by differences in soil chemical conditions. The stand with the lowest total biomass had the lowest Ca/Al ratio of 0.1 in seepage, however, Al, Ca, Mg and K concentrations of fine roots were not different among the stands. The Ca/Al ratio in seepage might be a less reliable stress parameter because another stand also had Ca/Al ratios in seepage far below the critical value of 1.0 without any signs of fine root damages. Large differences in the live/dead ratio were positively correlated with the Mn concentration of live fine roots from the mineral soil. This relationship was attributed to faster decay of dead fine roots because Mn is known as an essential element of lignin degrading enzymes. It is questionable if the live/dead ratio can be used as a vitality parameter of fine roots since both longevity of fine roots and decay of root litter may affect this parameter. Morphological properties were different in the humus layer of one stand that was limed in 1983, indicating that a single lime dose of 3–4 Mg ha⁻¹ has a long-lasting effect on fine root architecture of Norway spruce. Almost no differences were found in morphological properties in the mineral soil among the stands, but vertical patterns were apparently different. Two stands with high base saturation in the subsoil showed a vertical decrease in specific root length and specific root tip density whereas the other two stands showed an opposite pattern or no effect. Our results suggest that proliferation of fine roots increased with decreasing base saturation in the subsoil of Norway spruce stands.     

Effects of soil acidification and subsequent leaching on levels of extractable nutrients in a soil

Summary The effects of soil acidification (pH values from 6.5 to 3.8), and subsequent leaching, on levels of extractable nutrients in a soil were studied in a laboratory experiment. Below pH 5.5, acidification resulted in large increases in the amounts of exchangeable Al in the soil. Simultaneously, exchangeable cations were displayed from exchange sites and Ca, Mg, K and Na in soil solution increased markedly. With increasing soil acidification, increasing amounts of cations were leached; the magnitude of leaching loss was in the same order as the cations were present in the soil: Ca²⁺>Mg²⁺>K⁺>Na⁺. Soil acidification appeared to inhibit nitrification since in the unleached soils, levels of NO ₃ ⁻ clearly declined below pH 5.5 and at the same time levels of NH ₄ ⁺ increased greatly. Significant amounts of NH ₄ ⁺ and larger amounts of NO ₃ ⁻ , were removed from the soil during leaching. Concentrations of NaHCO₃-extractable phosphate remained unchanged between pH 4.3 and 6.0 but were raised at higher and lower pH values. No leaching losses of phosphate were detected. For the unleached soils, levels of EDTA-extractable Mn and Zn increased as the soil was acidified whilst levels of extractable Fe were first decreased and then increased greatly and those for Cu were decreased slightly between pH 6.5 and 6.0 and then unaffected by further acidification. Significant leaching losses of Mn and Zn were observed at pH values below 5.5 but losses of Fe were very small and those of Cu were not detectable.     

Adaptation of Denitrifying Populations to Low Soil pH

Natural denitrification rates and activities of denitrifying enzymes were measured in an agricultural soil which had a 20-year past history of low pH (pH ca. 4) due to fertilization with acid-generating ammonium salts. The soil adjacent to this site had been limed and had a pH of ca. 6.0. Natural denitrification rates of these areas were of similar magnitude: 158 ng of N g⁻¹ of soil day⁻¹ for the acid soil and 390 ng of N g⁻¹ of soil day⁻¹ at the neutral site. Estimates of in situ denitrifying enzyme activity were higher in the neutral soil, but substantial enzyme activity was also detected in the acid soil. Rates of nitrous oxide reduction were very low, even when NO₃⁻ and NO₂⁻ were undetectable, and were ca. 400 times lower than the rates of N₂O production from NO₃⁻. Denitrification rates measured in slurries of the acid and neutral soil showed distinctly different pH optima (pH 3.9 and pH 6.3) which were near the pH values of the two soils. This suggests that an acid-tolerant denitrifying population had been selected during the 20-year period of low pH.     

Variation in leaf area index and stand leaf mass of European beech across gradients of soil acidity and precipitation

Leaf area index (LAI, the one-sided foliage area per unit ground surface area) is a key determinant of plant productivity which has a large influence on water and energy exchange between vegetation and the atmosphere. The variation in forest LAI across landscapes and environmental gradients and its causes are not sufficiently understood. We measured the LAI of European beech (Fagus sylvatica) by litter trapping in 23 closed, mature stands across gradients of rainfall and soil acidity or fertility. With a mean LAI of 7.4 m² m⁻² (minimum: 5.6, maximum: 9.5 m² m⁻²), beech stands maintained a comparably high leaf area index with relatively small variation along steep environmental gradients. Contrary to expectation, decreasing water availability (rainfall gradient from 1030 to 520 mm yr⁻¹) or increasing soil acidity (pH 3–7) had no significant effect on LAI. Stand leaf mass (M _l) increased slightly with soil fertility (C/N ratio, base saturation). We regressed parameters of site water availability (rainfall), soil fertility or acidity (pH, base saturation, C/N ratio, exchangeable Mg and Al content), and stand structure (stand age and stem density) against LAI and M _l in order to detect environmental controls of stand leaf area. Stand age was the most influential factor for both LAI and M _l (negative relationship). Stem density and the base saturation of the soil affected M _l significantly, but had a weak influence on LAI. We conclude that the leaf area index of beech is mainly under control of age-related physiological factors, whereas the influence of soil chemistry and rainfall is comparably low.     

Estimating the organic carbon stabilisation capacity and saturation deficit of soils: a New Zealand case study

The capacity of a soil to sequester organic carbon can, in theory, be estimated as the difference between the existing soil organic C (SOC) concentration and the SOC saturation value. The C saturation concept assumes that each soil has a maximum SOC storage capacity, which is primarily determined by the characteristics of the fine mineral fraction (i.e. <20 µm clay + fine silt fraction). Previous studies have focussed on the mass of fine fractions as a predictor of soil C stabilisation capacity. Our objective was to compare single- and multi-variable statistical approaches for estimating the upper limit of C stabilisation based on measureable properties of the fine mineral fraction [e.g. fine fraction mass and surface area (SA), aluminium (Al), iron (Fe), pH] using data from New Zealand’s National Soils Database. Total SOC ranged from 0.65 to 138 mg C g^?1, median values being 44.4 mg C g^?1 at 0–15 cm depth and 20.5 mg C g^?1 at 15–30 cm depth. Results showed that SA of mineral particles was more closely correlated with the SOC content of the fine fraction than was the mass proportion of the fine fraction, indicating that it provided a much better basis for estimating SOC stabilisation capacity. The maximum C loading rate (mg C m^?2) for both Allophanic and non-Allophanic soils was best described by a log/log relationship between specific SA and the SOC content of the fine fraction. A multi-variate regression that included extractable Al and soil pH along with SA provided the “best fit” model for predicting SOC stabilisation. The potential to store additional SOC (i.e. saturation deficit) was estimated from this multivariate equation as the difference between the median and 90th percentile SOC content of each soil. There was strong evidence from the predicted saturation deficit values and their associated 95 % confidence limits that nearly all soils had a saturation deficit >0. The median saturation deficit for both Allophanic and non-Allophanic soils was 12 mg C g^?1 at 0–15 cm depth and 15 mg C g^?1 at 15–30 cm depths. Improving predictions of the saturation deficit of soils may be important to developing and deploying effective SOC sequestration strategies.     

Nitrogen deposition contributes to soil acidification in tropical ecosystems

Elevated anthropogenic nitrogen (N) deposition has greatly altered terrestrial ecosystem functioning, threatening ecosystem health via acidification and eutrophication in temperate and boreal forests across the northern hemisphere. However, response of forest soil acidification to N deposition has been less studied in humid tropics compared to other forest types. This study was designed to explore impacts of long‐term N deposition on soil acidification processes in tropical forests. We have established a long‐term N‐deposition experiment in an N‐rich lowland tropical forest of Southern China since 2002 with N addition as NH₄NO₃ of 0, 50, 100 and 150 kg N ha^?1 yr^?1. We measured soil acidification status and element leaching in soil drainage solution after 6‐year N addition. Results showed that our study site has been experiencing serious soil acidification and was quite acid‐sensitive showing high acidification (pH_(H2O)<4.0), negative water‐extracted acid neutralizing capacity (ANC) and low base saturation (BS,< 8%) throughout soil profiles. Long‐term N addition significantly accelerated soil acidification, leading to depleted base cations and decreased BS, and further lowered ANC. However, N addition did not alter exchangeable Al³⁺, but increased cation exchange capacity (CEC). Nitrogen addition‐induced increase in SOC is suggested to contribute to both higher CEC and lower pH. We further found that increased N addition greatly decreased soil solution pH at 20 cm depth, but not at 40 cm. Furthermore, there was no evidence that Al³⁺ was leaching out from the deeper soils. These unique responses in tropical climate likely resulted from: exchangeable H⁺ dominating changes of soil cation pool, an exhausted base cation pool, N‐addition stimulating SOC production, and N saturation. Our results suggest that long‐term N addition can contribute measurably to soil acidification, and that shortage of Ca and Mg should receive more attention than soil exchangeable Al in tropical forests with elevated N deposition in the future.     

Interacting effects of wildfire severity and liming on nutrient cycling in a southern Appalachian wilderness area

Aims

Wilderness and other natural areas are threatened by large-scale disturbances (e.g., wildfire), air pollution, climate change, exotic diseases or pests, and a combination of these stress factors (i.e., stress complexes). Linville Gorge Wilderness (LGW) is one example of a high elevation wilderness in the southern Appalachian region that has been subject to stress complexes including chronic acidic deposition and several wildfires, varying in intensity and extent. Soils in LGW are inherently acidic with low base cation concentrations and decades of acidic deposition have contributed to low pH, based saturation, and Ca:Al ratio. We hypothesized that wildfires that occurred in LGW followed by liming burned areas would accelerate the restoration of acidic, nutrient depleted soils. Because soils at LGW had extremely low concentrations of exchangeable Ca²⁺ and Mg²⁺ dolomitic lime was applied to further boost these cations. We evaluated the effectiveness of dolomitic lime application in restoring exchangeable Ca²⁺ and Mg²⁺ and subsequently increasing pH and Ca:Al ratio of soils and making Ca and Mg available to recovering vegetation.

Methods

Five treatment areas were established: severely burned twice (2000 & 2007) with dolomitic lime application (2xSBL); moderately burned twice with lime application (2xMBL); severely burned twice, unlimed (2xSB); moderately burned once (2000), unlimed (1xMB); and a reference area (REF; unburned, unlimed). In 2008 and 2009, we measured overstory, understory, and ground-layer vegetation; forest floor mass and nutrients; and soil and soil solution chemistry within each treatment area.

Results

All wildfire burned sites experienced substantial overstory mortality. However, understory biomass doubled between sample years on the most recently burned sites due to the rapid regrowth of ericaceous shrubs and prolific sprouting of deciduous trees. Burning followed by lime application (2xSBL and 2xMBL) significantly increased shallow soil solution NO₃-N, but we found no soil solution NO₃-N response to burning alone (2xSB and 1xMB). Surface soil base saturation and exchangeable Ca²⁺ were significantly affected by liming; Ca²⁺ concentrations were greater on 2xMBL and 2xSBL than 2xSB, 1xMB and REF. There was a smaller difference due to moderate burning along with greater soil Ca²⁺ on 1xMB compared to REF, but no difference between 2xSB and REF. Surface and subsurface soil exchangeable Al³⁺ were lower on 2xSBL than 2xSB, 2xMBL, 1xMB, and REF. Liming decreased soil acidity somewhat as surface soil pH was higher on the two burned sites with lime (pH?=?3.8) compared to 2xSB without lime (pH?=?3.6).

Conclusions

Liming resulted in decreased soil Al³⁺ on 2xSBL coupled with increased soil Ca²⁺ on both 2xSBL and 2xMBL, which improved soil Ca/Al ratios. However, the soil Ca/Al ratio response was transitory, as exchangeable Al³⁺ increased and Ca/Al ratio decreased over time. Higher lime application rates may be necessary to obtain a substantial and longer-term improvement of cation-depleted soils at LGW.     

Optimizing the bioindication of forest soil acidity,nitrogen and mineral nutrition using plant species

Soil moisture and nutritional characteristics are frequently assessed using plant species and community bioindication, e.g., the Ellenberg system of species indicator values. This method, based on complete inventories of plant species present in plots, is time-consuming, which could prevent its general use for forest or other natural land management. Our aim was to determine the impact of a reduction in the time spent to carry out a floristic inventory on the quality of soil characteristic assessment using plant bioindication. We compared the measurements of soil pH-H₂O (pH), organic carbon to total nitrogen ratio (C:N) and base saturation (BS) in the 0–5 cm soil layer of 470 plots with the same variables estimated from floristic inventories of increasing duration, using plant indicator values (IV) from the EcoPlant database. The performance of predictions was evaluated by the square of the linear correlation coefficient between measured and predicted values (R²) and the root mean square error (RMSE) of predictions.The number rather than the percentage of total plot species used for the estimations was determinant for the prediction of soil pH quality. Performance of bioindication of pH, BS and C:N reached the maximum R² using the first 20–25 species recorded per plot, corresponding to a 14-min-long floristic inventory in comparison to a mean of 28 min spent to carry out a complete floristic inventory. A precision of prediction of 80% of the maximal precision was obtained after 4–5 min (6–12 inventoried species) for the three studied variables. These results are independent of the nutritional capability of the soils and were similar at the national and local scales. In order to estimate soil nutritional resources by plant bioindication, it is feasible to significantly reduce the time spent on floristic inventories and, thus, their cost. This is especially useful when the goal is to map the soil quality for decision-making in forest management.     

Long-term changes of ecosystem services at Solling,Germany: Recovery from acidification,but increasing nitrogen saturation?

Time series of values of ingenious parameters indicating ecosystem services from European beech and Norway spruce ecosystems at Solling, Germany, were evaluated with respect to resilient or adaptive behaviour. Studied indicators comprise the use of monitoring data with up to more than 40 years of observation on deposition of potential acidity, sulphate (SO₄²⁻) budgets, exchangeable base cation pools, Bc/Al ratio in soil solution, nitrogen (N) budgets, foliar nutrition as indicated by the foliar Bc/N ratio, and defoliation. Deposition of potential acidity decreased considerably at both ecosystems. SO₄²⁻ budgets reveal retention of sulphur in the soils affecting acid/base budgets. Exchangeable base cation pools decreased at both ecosystems by about 60%. Bc/Al ratio in soil solution in the mineral soil was mostly below critical limits indicating potential toxic stress to tree roots. N retention in the soils decreased from about 40 kg ha⁻¹ yr⁻¹ in the 1970s to currently very low rates of 0–20 kg ha⁻¹ yr⁻¹ indicating increasing N saturation. Foliar Bc/N ratio decreased at the spruce ecosystem indicating possible nutrient imbalances. Defoliation at both Solling ecosystems is on a high level compared to other forests in Germany, but reveals no distinct relation to soil acidification or N saturation. From the selected indicators, SO₄²⁻ and N budgets reveal resilient behaviour, whereas indicators related to the acid/base status tend to adaptive behaviour.     

Embryonic and larval development of brown trout, Salmo trutta L.: exposure to aluminium, copper, lead or zinc in soft, acid water

Freshly fertilized ova, eyed ova and yolk-sac fry of brown trout, Salmo trutta L., were exposed to each of four trace metals (aluminium: 6000 nmol l^?1; copper: 80 nmol l^?1; lead: 50 nmol l^?1; zinc: 300 nmol l^?1) while held in flowing artificial soft-water media maintained at pH 4.5 or 5.6 and [Ca] 20 or 200 μmol l^?1. In continuous exposure from fertilization, survival of ova was severely affected at pH 4.5 and [Ca] 20 μmol l^?1, regardless of the presence of Cu, Pb or Zn; Al reduced embryonic mortality and improved hatching success. High ambient [Ca] at pH 4.5 increased egg survival. At ‘swim-up’, surviving fry exposed to Al or Pb had lower whole body Ca, Na and K content, irrespective of pH or ambient [Ca]. Cu reduced whole body Ca and K content at pH 5.6 and [Ca] 200 μmol^?1, and whole body Ca, Na and K content in the other media. Zn reduced whole body mineral content at pH 5.6 and [Ca] 20 μmol l^?1. Whole body Mg content was reduced by all trace metals at pH 5.6 and [Ca] 20 μmol l^?1, and by Cu at pH 5.6 and [Ca] 200 μmol l^?1. Al and Cu impaired skeletal calcification at pH 5.6 at both ambient [Ca]; Pb only at [Ca] 20 μmol I^?1. Zn enhanced calcification at pH 4.5 and [Ca] 200 μmol l^?1. In the absence of trace metals, low pH reduced body Ca, Na, K content and skeletal calcification at [Ca] 200 μmol l^?1. The uptake of Ca, Na and K, measured at regular intervals from hatching was impaired to the same extent by all treatments at pH 4.5, irrespective of ambient [Ca] or trace metal presence. At pH 5.6, irrespective of ambient [Ca], Al, Cu and Pb impaired Ca and K uptake. The rate of Na uptake was reduced by Al and Cu. Al-treated yolk-sac fry, exposed to low ambient [Ca] from 200–300° days post-hatch, suffered high mortalities regardless of pH. Ca, Na and K uptake was impaired by all treatments at pH 4.5, and by Al and Cu at pH 5.6 in a similar exposure period. The development of the early stages of brown trout in the presence of trace metals is discussed in relation to recruitment failure in areas of soft, acid water.     

NUTRIENT REQUIREMENTS OF THE DINOFLAGELLATE PERIDINIUM GATUNENSE1

Optimum nutrient conditions for growth and photosynthesis of Peridinium gatunense (Nygaard) (Peridinium cinctum fa. westii) were investigated using axenic clones in batch cultures. Selenium (Se) had previously been found to be an indispensable growth factor for P. gatunense. Optimal, suboptimal, and supraoptimal concentrations of HCO₃^?, N, Ca, Cl, Mg, P, K, S, Si, EDTA-Na, Fe, Mo, Zn, Mn, Co, Se, B, Br, I, and various trace element mixtures were determined by measuring biomass development, growth rates, ¹⁴C uptake, and/or oxygen production at various concentration gradients of these elements. The general characteristics of the best formulation, medium-L 16, relative to other media, are its high content of NaHCO₃ (1 meq · L^?1) and Mo (0.2 μM) but low concentrations of NO_3-N (150 μM), PO_4-P (10 μM), and Fe (0.4 μM), in addition to its content of Se. The total content of trace metals, except for Se, may be reduced to one-fourth of that in medium-L 16 without altering the major growth-promoting properties of the medium. Medium-L 16 deviated considerably from Lake Kinneret (Israel) water, being much lower in macroelements except for N and P. The pH (8.1–8.4) was in the same range, but the values of conductivity (140 μS · cm^?1), alkalinity (1 meq · L^?1) and NaCl (200 μM) were > 8, 2, and 30 times higher, respectively, in the lake water. Selenium deficiency may limit the growth of P. gatunense in this lake.     

Adsorption Mechanism of Cr(VI) onto Coir Pith

Reductive adsorption of Cr(VI) on coir pith (hereafter CP) was examined as a function of pH, ionic strength, and temperature. The CP contains 1.33 meq g^{? 1} phenolic, 0.43 meq g^{? 1} of lactonic, and 0.35 meq g^{? 1} carboxylic sites. Thus the CP surface is enriched with electron-donating oxygen functionalities. As evidenced by infrared (IR) spectroscopy, the Cr(VI) → Cr(III) conversion is facilitated by CP sites that are enriched with O─ O functional groups. The adsorption of reduced Cr(VI) was found to occur via C─ O─ functional groups first forming innersphere complexes with the CP surface, yielding keto (> C═ O) groups on the CP surface. The reductive adsorption of Cr(VI) was almost completed within 3 to 4 h, and it was dependent on pH and background ionic strength, yielding the highest monolayer coverage (9.56E-7 mol m^{? 2}) at pH 3.7 in 0.1 M NaNO₃. The Γ_Cr(III) followed the order with respect to the ionic strength: Γ_{0.1 M} > Γ_{0.01 M} > Γ_{0.001 M}. The initial rate constant, k _i , increased with temperature as k _i ^{313 K} > k _i ^{303 K} > k _i ^{293 K} > k _i ^{283 K}.