Unlimed Plots Research Articles

Forest growth responds more to air pollution than soil acidification.

The forests of central Europe have undergone remarkable transitions in the past 40 years as air quality has improved dramatically. Retrospective analysis of Norway spruce (Picea abies) tree rings in the Czech Republic shows that air pollution (e.g. SO2 concentrations, high acidic deposition to the forest canopy) plays a dominant role in driving forest health. Extensive soil acidification occurred in the highly polluted "Black Triangle" in Central Europe, and upper mineral soils are still acidified. In contrast, acidic atmospheric deposition declined by 80% and atmospheric SO2 concentration by 90% between the late 1980s and 2010s. In this study we oserved that annual tree ring width (TRW) declined in the 1970s and subsequently recovered in the 1990s, tracking SO2 concentrations closely. Furthermore, recovery of TRW was similar in unlimed and limed stands. Despite large increases in soil base saturation, as well as soil pH, as a result of repeated liming starting in 1981, TRW growth was similar in limed and unlimed plots. TRW recovery was interrupted in 1996 when highly acidic rime (originating from more pronounced decline of alkaline dust than SO2 from local power plants) injured the spruce canopy, but recovered soon to the pre-episode growth. Across the long-term site history, changes in soil chemistry (pH, base saturation, Bc/Al soil solution ratio) cannot explain observed changes in TRW at the two study sites where we tracked soil chemistry. Instead, statistically significant recovery in TRW is linked to the trajectory of annual SO2 concentrations or sulfur deposition at all three stands.

Thirty-year effects of liming on soil and foliage chemistry and growth of northern hardwoods in Pennsylvania, USA

The longevity of a single 22.4 Mg·ha−1 application of dolomitic limestone at four northern hardwood stands was evaluated over 30 years (1986–2016) to determine whether changes in soils, foliage, and tree growth were sustained on the unglaciated Allegheny Plateau in northern Pennsylvania, USA. In limed plots, soils, sampled to 45–55 cm depth, and sugar maple (Acer saccharum Marsh.) and black cherry (Prunus serotina Ehrh.) foliage had significantly (P ≤ 0.05) greater concentrations of calcium (Ca) and magnesium (Mg) through 2016 compared with samples from unlimed plots. Ca and Mg capitals (g·m−2) in the Oi through A horizons combined were greater on limed plots than unlimed plots, largely due to increases in the thickness and nutrient concentration in the A horizon. Over 30 years, sugar maple basal area increment (cm2·year−1 BAINC) was greater in limed plots (30.6 cm2·year−1 vs unlimed 13.3), American beech (Fagus grandifolia Ehrh.) BAINC was unaffected by lime application, and black cherry BAINC was reduced in limed plots compared with unlimed plots. The sustained effect of this one-time lime treatment shows the strong role of efficient nutrient cycling in forests and suggests that the benefits over a substantial portion of a stand rotation may increase the feasibility of operational liming.

The effects of lime on pasture composition and production in western Waikato hill country

A 4-year lime rate trial was established on a hill country sheep and cattle property near Te Akau to determine lime effects on pasture utilisation. Four rates of lime were applied (1.25 t/ha, 2.5 t/ha, 5 t/ha and 10 t/ha) to 2 m × 2 m plots, from which soil Al, Ca and pH, pasture grazing heights, dry matter production, pasture species composition, feed quality and brix levels were measured. Lime application reduced soil Al (14.6 to 1.1 mg/kg), and increased Ca and pH (5.0 to 6.2) over time in the highest application rate. Dry matter production responded to all rates of lime in each year, and by the fourth year it was 27% greater (1.25 t/ha treatment), 35% greater (2.5 t/ha treatment), 69% greater (5 t/ha treatment), and 97% greater (10 t/ha treatment) than in the un-limed plots. Ryegrass and subterranean clover content increased with lime rate, whereas chewings fescue and dicot weed content declined. There were no sustained differences in pasture grazing heights, feed quality or brix levels between the control and rates of lime. On this site, all rates of lime were economic to apply by truck or plane when the benefits were spread over 4 years, with the greatest cost-benefit from thelower rates of lime.

Temporal changes in the ground vegetation in spruce forests in the Erzgebirge (Ore Mountains) — bryophytes are better indicators of the impact of liming and of sulphur and nitrogen deposition than the herb layer

AbstractQuestionsHow have species composition and diversity in the herb and bryophyte layer of spruce forest communities developed on unlimed plots and on plots with varying liming intensity under the conditions of decreasing sulphur (S) deposition and unabated high nitrogen (N) deposition?LocationSpruce stands in the Erzgebirge, East Germany.MethodsWe repeated herb and bryophyte layer surveys on 36 quasi‐permanent plots after approx. 23 years (1989/1991 vs 2012/2014). Over this period, the study area experienced a sharp decline in S deposition and repeated liming of the spruce stands. Our plots represent a gradient of liming from zero to four applications. We analyse the change in species composition and species diversity depending on the liming intensity using Ellenberg indicator values (EIV), correspondence analysis, indicator species analysis and diversity parameters (alpha diversity, Lennon similarity).ResultsOn the unlimed plots, the species composition of the herb layer remained unchanged over the study period, despite the decrease in the coverage of Calamagrostis villosa and Deschampsia flexuosa and in the total coverage of the herb layer. In contrast, the bryophyte layer showed a significant increase in coverage and species richness with the decrease in S deposition. Liming led to a sharp increase in species richness in the herb layer, due to the appearance of disturbance indicators. The mean EIVs for acidity and nitrogen (EIV‐R and EIV‐N) also increased significantly. All observed effects increased with increasing liming intensity. We also noticed an increase in species richness over time in the bryophyte layer on the limed plots. However, this was less pronounced than on the unlimed plots, and decreased with increasing liming intensity. This was because the appearance of disturbance indicators or of typical species for the Calamagrostio villosae‐Piceetum was partially compensated for by the disappearance of acid indicators as a result of liming. The species turnover was thus much higher in the bryophyte layer than in the herb layer.ConclusionsIn contrast to the herb layer, the bryophyte layer proves to be a sensitive indicator of changes in air pollution. The effects of greatly reduced S deposition on the bryophyte layer outweigh those of continuous N deposition in the study area. Liming acts as a disturbance in both the herb layer and the bryophyte layer. This influence increases with increasing liming intensity. Our results do not support a general application of liming in large, contiguous forest areas. Rather, this measure should be applied in a differentiated manner.

The distribution of soil nitrifiers and efficacy of 3,4-dimethylpyrazole phosphate changes with soil depth and calcium carbonate application

The nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) is used to limit nitrogen (N) losses incurred following nitrification of applied N fertilisers. Inhibitor efficacy changes with soil conditions including pH and organic matter (OM) content, both of which can be stratified down the soil profile. An incubation study was conducted using acidic soil that exhibited pH stratification. Soil samples were collected from the field in 2 cm depth increments to a depth of 10 cm. Two liming treatments were applied to each depth where the pHCa was raised above 6 or left in its initial acidic state. Nitrogen treatments (urea ammonium nitrate (UAN) with and without DMPP) were applied to each liming treatment per depth and incubated for four weeks. Destructive sampling for mineral N, DMPP concentration and pH occurred every week. The abundance of nitrifiers was determined using semi-quantitative real-time polymerise chain reaction (PCR) targeting the amoA gene at weeks 0, 1 and 4. Liming significantly increased nitrification rates and bacterial amoA gene abundance. Results showed the top 0–2 cm recorded the largest population of bacterial nitrifiers. Changes in pH influenced the composition of nitrifiers present in the soil. Bacterial nitrifiers were absent from the 8–10 cm soil layer in unlimed soils (pHCa 4.25) but liming caused an increase in gene abundance. Archaeal amoA gene abundance was highest in unlimed plots at 4–8 cm depth although populations decreased over the incubation period and also with lime application. DMPP effectively inhibited nitrification in limed plots, however no significant difference existed between UAN and DMPP treatments for unlimed treatments. DMPP successfully decreased bacterial amoA gene abundance in all depths that were limed but not in unlimed soils. Decreases in inhibitor concentrations occurred within one week in the 0–2 cm layer possibly due to bacterial decomposition associated with greater OM concentration at the soil surface. This study highlighted that DMPP use is more effective in relatively neutral soils and liming will change the abundance and distribution of nitrifiers within the top 10 cm of soil.

Historical trends in iodine and selenium in soil and herbage at the Park Grass Experiment, Rothamsted Research, UK

AbstractLong‐term trends in iodine and selenium retention in soil, and uptake by herbage, were investigated in archived samples from the Park Grass Experiment, initiated in 1856 at Rothamsted, UK. Soil (0–23 cm) and herbage samples from plots receiving various mineral fertilizers and organic manures, with and without lime, were analysed for selenium (Se) and iodine (I) to assess the effect of soil amendments, annual rainfall, crop yield and changes in soil chemistry from 1876 to 2008. Comparing soil from limed and unlimed control (unfertilized) plots, TMAH‐extractable Se and I concentrations both diverged, with time, with greater retention in unlimed plots; differences in concentration amounted to 92 and 1660 μg/kg for Se and I, respectively, after 105 yr. These differences were broadly consistent with estimated additions from rainfall and dry deposition. Offtake of both elements in herbage was negligible compared to soil concentrations and annual inputs (<0.003% of total soil I and <0.006% of total soil Se). A positive correlation was observed between I and Se concentrations in herbage, suggesting some common factors controlling bioavailability. A growth‐dilution effect for I and Se was suggested by the positive correlation between growing season rainfall (GSR) and herbage yield together with soil‐to‐plant transfer factors decreasing with yield. Phosphate and sulphate fertilizers reduced I and Se herbage concentrations, both through ion competition and increased herbage yield. Results suggest that in intensive agriculture with soil pH control, the I requirement of grazing animals is not likely to be met by herbage alone.

Long-term effect of lime application on the chemical composition of soil organic carbon in acid soils varying in texture and liming history

There is ample evidence to suggest that liming can regulate soil organic carbon (SOC) pools either directly through influencing the solubility of SOC or indirectly by altering total organic C input as crop residue and SOC loss via change in microbial activity. The aim of this study was to determine the long-term impact of lime application on the quantity and quality of SOC in acid soils. Soils were collected at depths of 0–10, 10–20, 20–30, 30–40, and 40–50 cm from four long-term lime trials with various lime rates (0–25 t ha−1), lime histories (5–35 years), and soil textures (clay content 5–36 %). Surface application of lime was effective in ameliorating both topsoil and subsoil acidities at sites with low clay content. Liming decreased dissolved organic C (DOC) at 0–30 cm but increased its aromaticity. Total SOC at 0–10 cm decreased or remained unchanged following long-term liming, depending on the rates of lime application and crop management. Changes in the contents of particulate organic C (POC) and humic organic C (HOC) predicted by mid-infrared spectroscopy (MIR) and partial least squares regression (PLSR) showed a similar trend to total SOC at all sites. Lime application had no significant effect on SOC below 10-cm layers and on the MIR-predicted resistant organic C (ROC) fraction. Solid-state 13C nuclear magnetic resonance (NMR) spectra indicated that the alkyl C content and alkyl/O-alkyl C ratio were lower in the limed than unlimed plots. Liming possibly had a marked effect on regulating the decomposition and preservation of certain C compounds. The apparent accumulation of alkyl C in the unlimed soil could indicate the potential ability of acid soils to store SOC.

Long-term Effects of Canopy Opening and Liming on Soil Nutrient Dynamics in a European Beech (Fagus sylvatica L.) Forest

Forest management has a considerable influence on the soil nutrient dynamics of forest ecosystems. This study was designed to examine the long-term effects of lime application and canopy removal on soil nutrient budgets in a mature European beech (Fagus sylvatica L.) forest. In 1989, trees were felled to create four 30-m wide circular gaps in this beech forest, and two of these gaps and the surrounding area were limed with 3 t ha−1 of fine dolomite, whereas the remaining two gaps and most parts of the stand were not limed. Main nutrient concentrations in the forest floor and in the mineral soil were determined in 1989, 1997, and 2011. In addition, we examined the influence of liming and gaps on the forest floor organic matter. The significant effects of liming and gap creation on the forest floor dry mass in 1997 were no longer obvious in 2011, unlike their influence on the C and N pools, which was still significant in 2011. In the long-term, the forest floor C and N pools increased less in the limed and opened plots compared with the untreated stand, and the N pool only decreased in the mineral soil of the limed gaps. Soil acidity was reduced significantly 8 years after liming at any depth in the limed plots (limed stand, limed gaps) and in the deeper layers (5–40 cm) of the unlimed plots, indicating a general soil recovery from acid depositions in earlier decades. After 22 years, the pH values were still higher at 5 to 10 cm mineral soil depth in the limed plots, which partly reflected the higher base saturation in the mineral soil of the limed gaps. However, the pH values were surprisingly dropping from 1997 to 2011 in the upper soil layers of all plots. Overall, some effects of canopy opening and liming on soil nutrients lasted for more than two decades in this European beech forest.

Rate of litter decay and litter macroinvertebrates in limed and unlimed forests of the Adirondack Mountains, USA

Acid deposition can reduce the rate of litter decay in forests by changing environmental and substrate quality for macroinvertebrates and microbes. Terrestrial application of lime can ameliorate many of the negative effects of acid deposition, but the effects of liming on forest litter decay and fauna are poorly understood. We used reciprocal transplants of litter bags to better understand the effects of substrate calcium content and incubation context (limed plots versus unlimed plots) on rate of litter decay and abundance of litter-dwelling macroinvertebrates. Our study took place in the Adirondack Mountains (Adirondacks) of New York State, USA, a region affected by chronic acid deposition. Lime was added to randomly-selected plots at a rate of 10Mgha−1; control plots were not limed. Leaves for high-calcium litter bags were collected under trees grown in limed plots, and leaves for low-calcium litter bags were collected in unlimed plots. High-calcium and low-calcium leaves differed in %Ca but not in %N or C:N at the beginning of our study. Leaf litter decay was faster for bags containing high-calcium leaves than for those litter bags containing low-calcium leaves, and decay was slower in limed than unlimed plots. Assemblages of litter-dwelling macroinvertebrates were markedly different between litter bags collected from limed and those collected from unlimed plots. Snails increased in abundance; whereas, millipedes and spiders decreased in abundance at limed plots following liming. Millipedes likely were important litter-eating macroinvertebrates at these sites, and the decline in millipedes may have contributed to the reduction in rate of litter decay. The liming of areas negatively affected by acid deposition may decrease rate of litter decay immediately following lime application. This was a short-term study. Understanding the long-term, as well as immediate, effects of liming is necessary to determine the advisability of lime application in regions affected by acid deposition.

Effects of liming on survival and reproduction of two potentially invasive earthworm species in a northern forest Podzol

During the last several decades, colonization of soil by exotic earthworms and their effects on soil properties and biodiversity have been reported in forests of North America. In some northern hardwood stands, acid soils or harsh climate may have prevented earthworm colonization. However, climatic change and the increasing use of liming to restore the vigor of declining sugar maple (Acer saccharum Marsh.) stands, situated on base-poor soils in USA and Canada, could make many of these sites more suitable for earthworm colonization. We tested survival and reproduction of two exotic earthworm species (Lumbricus terrestris and Amynthas hawayanus) in unlimed and limed soils at the northern limit of the northern hardwood forest distribution in Canada. Improving soil parameters of base-poor, acidic soils by liming positively influenced activity, survivability and reproductive output of L. terrestris in this northern hardwood forest. In contrast, the high mortality and low vigor of L. terrestris observed in the unlimed plots show that soils in this area with a pH of 4.3 are not favorable to this species. Our results suggest that A. hawayanus was very active prior to winter at both soil pHs, but was not able to complete its life cycle during one year at this latitude. Both earthworm species significantly reduced organic C and total N, and increased the C/N ratio of the forest floor. Given that forest liming activities are increasing in proximity to human activities, there is high probability that some earthworm species, such as L. terrestris, will invade limed northern hardwood forests in the next decades, with possible consequences for soil organic matter turnover, nutrient cycling and forest biodiversity and dynamics.

Calcium Induces Long-Term Legacy Effects in a Subalpine Ecosystem

Human activities have transformed a significant proportion of the world’s land surface, with profound effects on ecosystem processes. Soil applications of macronutrients such as nitrate, phosphorus, potassium or calcium are routinely used in the management of croplands, grasslands and forests to improve plant health or increase productivity. However, while the effects of continuous fertilization and liming on terrestrial ecosystems are well documented, remarkably little is known about the legacy effect of historical fertilization and liming events in terrestrial ecosystems and of the mechanisms involved. Here, we show that more than 70 years after the last application of lime on a subalpine grassland, all major soil and plant calcium pools were still significantly larger in limed than in unlimed plots, and that the resulting shift in the soil calcium/aluminium ratio continues to affect ecosystem services such as primary production. The difference in the calcium content of the vegetation and the topmost 10 cm of the soil in limed vs. unlimed plots amounts to approximately 19.5 g m−2, equivalent to 16.3% of the amount that was added to the plots some 70 years ago. In contrast, plots that were treated with nitrogen-phosphorus-potassium fertilizer in the 1930s did not differ from unfertilized plots in any of the soil and vegetation characteristics measured. Our findings suggest that the long-term legacy effect of historical liming is due to long-term storage of added calcium in stable soil pools, rather than a general increase in nutrient availability. Our results demonstrate that single applications of calcium in its carbonated form can profoundly and persistently alter ecosystem processes and services in mountain ecosystems.

Effect of Lime, Inorganic, and Organic Sources on Soil Fertility, Yield, Quality, and Nutrient Uptake of Sweet Potato in Alfisols

Field experiments were conducted in Alfisols to study the effect of integrated use of lime, inorganic, and organic manures on soil health and sweet potato performance. Integrated use of nitrogen, phosphorus, and potassium and farmyard manure recorded a significantly higher tuber yield (18.7 Mg ha−1) followed by lime + farmyard manure + neem cake + green manure (17.7 Mg ha−1). Incorporation of organics and 100% nitrogen, phosphorus, and potassium showed a yield response of 23%, 2%, and 10% in respect of farmyard manure, neem cake, and green manure over nitrogen, phosphorus, and potassium. A yield response of 12%, 10%, and 13% was observed due to incorporation of lime along with ½ nitrogen, phosphorus, and potassium and organics (farmyard manure, neem cake, and green manure) over that of unlimed plots. Conjunctive use of organic manures along with balanced fertilizers and lime not only produces higher crop yields but also enhanced the efficiency of added nutrients and sustains the soil fertility.

INFLUENCE OF TWENTY-THREE ANNUAL APPLICATIONS OF NITROGEN AND SULFUR FERTILIZERS, AND ONE-TIME LIMING ON DRY MATTER YIELD OF GRASS AND SOME SOIL PROPERTIES ON A DARK GRAY CHERNOZEM SOIL

Most soils in the Prairie Provinces of Canada are deficient in plant-available nitrogen (N), and many soils in the Parkland region also contain insufficient amounts of plant-available sulfur (S) for high crop production. A field experiment with perennial grass stand was conducted to determine the effects of long-term annual N (112 kg N ha−1), S (11 kg S ha−1) and potassium (K) (40 kg K ha−1) fertilization, and one-time lime application on forage dry matter yield (DMY) and soil properties [pH, total organic carbon (TOC) and N (TON), and light fraction organic C (LFOC) and N (LFON)] on a Dark Gray Chernozem (Boralfic Boroll) loam at Canwood in north-central Saskatchewan, Canada. The experiment had surface-broadcast annual treatments of no fertilizer (Nil), N, S, NS, and NSK fertilizers from 1980 to 2002, and one-time lime application in 1992 to bring soil pH to about 7. Application of N or S alone had only a little effect on DMY compared to unfertilized Nil treatment, while application of both NS together substantially increased DMY, and forage yield was further increased when K was also applied (NSK). The DMY following one-time liming was greater in limed plots than in unlimed plots for at least 10 years. Decline of soil pH by fertilization mainly happened in the 0–10 cm depth with N only, and in the 0–5 cm layer with NS treatment, whereas these treatments tended to increase soil pH in layers below 10 cm. One-time surface application of granular lime increased soil pH, mainly in the 0–5 cm layer, and the effect was maintained for at least 9 years. Mass of TOC, TON, LFOC, and LFON in different soil layers increased with combined applications of N and S fertilizers (NS), but the effect was much more pronounced in the 0–7.5 cm soil layer, and also varied with organic fraction. Light organic fractions were more responsive to applied NS than total organic fractions. The findings suggest that application of N and S together was effective in sustaining high forage yield and increasing C and N sequestration in a soil deficient in both N and S.

Long-term impact of liming on growth and vigor of northern hardwoods

Sugar maple (Acer saccharum Marsh.) is a keystone species in the northern hardwood forest, and decline episodes have negatively affected the growth and health of sugar maple in portions of its range over the past 50+ years. Crown health, growth, survival, and flower and seed production of sugar maple were negatively affected by a widespread decline event in the mid-1980s on the unglaciated Allegheny Plateau in northern Pennsylvania. A long-term liming study was initiated in 1985 to evaluate responses to a one-time application of 22.4 Mg·ha–1 of dolomitic limestone in four northern hardwood stands. Over the 23-year period ending in 2008, sugar maple basal area increment (BAINC) increased significantly (P ≤ 0.05) in limed plots from 1995 through 2008, whereas American beech (Fagus grandifolia Ehrh.) BAINC was unaffected. For black cherry (Prunus serotina Ehrh.), the third principal overstory species, BAINC and survival were reduced in limed plots compared with unlimed plots. Foliar Ca and Mg remained significantly higher in sugar maple foliage sampled 21 years after lime application, showing persistence of the lime effect. These results show long-term species-specific responses to lime application.

Effects of liming on chemical properties of soil, needle nutrients and growth of Scots pine transplants

The effects of limestone (2.0 and 4.0 Mg ha −1) on chemical properties of soil, nutrient concentrations of needles and growth of Scots pine ( Pinus sylvestris L.) transplants were investigated on three reforestation areas on infertile acidic sites in southern Finland. The limestone was applied either on the soil surface (unploughed plots) or was mixed into the topsoil (ploughed plots). All the treatments were replicated four times. Surface broadcast of lime elevated the pH in the organic layer and in the 0–10 cm layer of mineral soil. The increase in the pH of the organic layer after 21 years was, on average, 0.7 and 1.1 pH units, with a dose of lime 2 and 4 Mg ha −1, respectively. On the ploughed plots, the pH in the uppermost 0–10 cm soil layer was 0.4–0.5 units higher than on the corresponding unlimed plots. Both doses of lime significantly increased the amount of exchangeable Ca and the base saturation (BS) in the topsoil on the ploughed plots, and the amount of exchangeable Ca and Mg, as well as the base saturation (BS) in the organic layer + the 0–10 cm layer of mineral soil on the unploughed plots. Regardless of the techniques used for application of lime, after 21 growing seasons the Ca and Mg concentrations in needles were significantly higher on the limed plots than on the controls. In needles, the Ca/Mn ratio was the best indicator for measuring the response to liming. Only on the unploughed plots did liming increase stand volume and dominant diameter of pines. Intensive disc ploughing produced significantly more stems and increased both stand volume and the dominant height of pines compared to unploughed plots.

Effect of understory vegetation management through liming and sewage sludge fertilisation on soil fertility and Pinus radiata D. Don growth after reforestation

Tree–understory competition is one of the most important aspects that control tree growth after reforestation. The relationship between trees and the understory can be modified by improving acidic soils with lime and by fertilisation. This experiment aims to evaluate the effect of soil improvements on the pasture–tree relationship by liming and fertilisation on different dates in a Pinus radiata-reforested area. Both lime and sewage sludge improved soil fertility by increasing Ca and reducing Al in the soil. Initially, tree development was reduced by lime, which improved the establishment of competitive grasses. Tree growth in limed treatments did not initially respond to sludge inputs, likely because both tree and grass roots shared the same soil depth layer. Three years after establishment, the use of high doses of sewage sludge in limed plots caused a growth rate similar to the best treatments of unlimed plots, which grew with a poorly sown grass establishment. After 2 years of the experiment, the presence of Erica woody shrub diminished tree development. High doses of sewage sludge with lime, as well as high doses of sewage sludge without lime, applied in April and low doses of sewage sludge without lime added in early February improved tree growth. From a practical point of view, lime and sewage sludge dose close to 100 kg total N ha−1 should be recommended if a silvopastoral system is established, as it enhances pasture production and tree growth.

Resilience of acid subalpine grassland to short-term liming and fertilisation

A fertilisation experiment was started in the French Alps on an acid grassland at 2000 m in 1989 where lime as calcium carbonate (“liming”) and Thomas Slag enriched by potassium chloride (“fertilisation”) were added in a random block design until 1992. Since then, no further amendments were applied. Fifteen years after the last application, we revisited the experiment and observed that soil pH was still significantly higher on limed plots, while nitrogen (N) concentrations were lower. On fertilised plots, soil carbon (C) and N concentrations were lower compared to unfertilised plots. However, litter quality (C and N concentrations, near infrared spectroscopy [NIRS] data) was similar for both treatments. Vegetation composition, but not species richness, nor Shannon–Wiener or evenness differed between limed and unlimed plots, and fertilised and unfertilised plots. Liming explained about 18% and fertilisation about 6% of the variability of the vegetation composition. These changes in the vegetation composition are probably due to lower abundances of former dominant grass species and to an increase in generalist grasses. However, these changes did not influence the total above-ground productivity, which was similar for all treatments. Tissue N and C concentrations and NIRS data indicated a changed chemical composition of the biomass which persisted during time. We conclude that the 3 years of fertilisation and liming did substantially influence the vegetation composition at our site and lead to an increase in the agricultural value of the grassland. These changes are long-lasting as they changed key features of the functioning in the soil of grasslands ecosystems. From an ecological point of view, specialised vegetation was replaced by generalist species leading to a trivialisation of the vegetation.

Soil acidity and aluminium toxicity as affected by surface liming and cover oat residues under a no‐till system

AbstractA 3‐year field trial examined in a long‐term no‐till system the effects of surface‐applied lime and cover black oat (Avena strigosa Schreb) residues on soil chemical attributes, root growth and grain yield of corn (Zea mays L.) and soybean (Glycine max L. Merrill) on a loamy, kaolinitic, thermic Typic Hapludox in Paraná State, Brazil. The treatments consisted of dolomitic lime broadcast on the soil surface at 0 or 12 t/ha, with and without cover of black oat residues. Corn and soybeans were grown without rainfall limitation. Applying lime on the surface improved soil acidity and decreased aluminium (Al) toxicity to a 10‐cm depth 1 year after application. Surface liming increased pH and the content of exchangeable Ca2+ to a 20‐cm depth, and decreased Al toxicity to a 40‐ to 60‐cm depth, 3 years after application, indicating that the surface‐applied lime moved deeper. Cover black oat residues did not favour the mobility of surface‐applied lime to alleviate subsoil acidity and an increase in the Al3+ saturation level at the soil surface was found in unlimed plots with black oat residues. Root growth and grain yields of corn and soybean were not influenced by surface liming with or without cover black oat residue. Despite the soil acidity level, root length of corn and soybean ranged from 55 to 60% at 0‐ to 10‐cm depth. The results suggest that Al toxicity is low in no‐till systems during cropping seasons with adequate and well‐distributed rainfall, but this effect is not related to the presence of cover oat residues.

Recent Mechanical Cultivation of Lawns Enhances Lime Application Efficacy

While the relationship between soil acidity and thatch accumulation in maintained lawns has been reported, interacting effects of cultivation and surface lime applications on soil acidity have not. The experimental objective was to determine how antecedent mechanical cultivation of mature turfgrasses interacts with surface application of liming agents to neutralize soil acidity within the upper and lower depth segments of a hectare furrow slice (2.24 × 106 kg soil). Various liming agents were applied to three lawn systems, each afflicted with soil acidity and thatch accumulations, at rates from 0 to 200% of soil test lime recommendations (LR). In Experiment 1, resulting active acidity (pHw) was measured in the 0 to 5 (thatch excluded) and 5 to 10 cm soil depths over 23 mo. In Experiments 2 and 3, described lime applications followed mechanical cultivation treatments; core aeration, vertical mowing, or none. Resulting pHw and exchangeable acidity (pHKCl) were measured in 0 to 6 (thatch excluded) and 6 to 12 cm soil depths after 1 or 2 yr. Application of the prescribed LR (100%) to uncultivated surfaces did not increase 5 to 10 or 6 to 12 cm pHw levels above unlimed plot levels. One or 2 yr following either lime application rate, statistically higher pHKCl values corresponded to either cultivation treatment in the 6 to 12 cm soil depth. Mechanical cultivation, conducted before surface application of the LR, accelerated the rate of acid neutralization throughout the 0 to 12 cm soil depths of mature lawn systems.

Health condition of spruce stands in the Orlické hory Mts. in relation to climatic, anthropogenic and stand factors

In stands with the majority of spruce and aged over 70 years, 35 sample plots were laid out (in total 700 trees) in the vicinity of Anenský vrch Hill at altitudes over 800 m above sea level. In the course of the growing season 2005, the following parameters were determined: total defoliation, defoliation of the primary structure, percentage of secondary shoots, presence and extent of yellowing and browning. In 10 selected trees, branches were taken from crowns for morphological analyses and annual length increments of branches and numbers of secondary shoots in the particular years were determined. Total defoliation and the occurrence of yellowing were related to slope orientation and position of the plot towards the ridge. The number of shoots produced in the given year correlated with the level of annual NO<sub>3</sub> deposition. The determined difference in the occurrence of yellowing between limed and unlimed plots cannot be interpreted unambiguously because limed and unlimed plots differ in exposure at the same time. The determined importance of slope orientation for the health condition of a stand shows that under the simultaneous air pollution load climatic factors are a factor deciding on the resulting effect of the synergetic action of stressors on forest stands.