Afforested Soils Research Articles

Organic matter properties in soils afforested with Pinus radiata

Afforestation causes important alterations in SOM content and composition that affect the soil functions and C balance. The aim of this study was to identify the mechanisms that determine the changes in SOM composition following afforestation of grasslands. The study included 4 chronosequences and 5 paired plots comprising pastures and land afforested with Pinus radiata. The SOM was characterized by 13C CP-MAS NMR spectroscopy and differential scanning calorimetry. During the first 10–20 year after afforestation, the changes in SOM content varied from slight gains to large losses (>40 %). The analyses revealed that even SOM compounds considered resistant to decomposition were degraded during this time. The SOM gains, observed 20 year after stand establishment, were favoured by the higher recalcitrance of pine litter and possibly by soil acidification. The concentrations of most SOM compounds, particularly the stable compounds, were higher at the end of the rotation. The low degree of protection, along with the favourable climatic conditions, may also explain the rapid decomposition of SOM, including resistant compounds, in these soils. DSC analysis complemented the information about SOM composition provided by other techniques. The accumulation of stable SOM compounds at the end of the rotation suggests a longer soil C turnover in these afforested soils, which may alleviate the gradual loss of SOC in intensively managed forest soils.

A synthesis of change in deep soil organic carbon stores with afforestation of agricultural soils

Afforestation is known as an available mitigation activity to climate change because it causes sequestration of CO2 from the atmosphere and stores it as the living biomass and the dead organic matter. However, the response of soil organic carbon (SOC) to afforestation in deep soil layers is still poorly understood. We surveyed previously published literature for changes in deep SOC (defined as at least 10cm deeper than the 0–10cm layer) after afforestation of croplands and grasslands (total 63 sites from 56 literature), in order to examine changes in deep SOC and quantify the relationship between SOC change rates in topsoil and subsoil. The results of the meta analysis indicated that the responses of SOC to afforestation were opposite for cropland than grassland. The SOC in soil depth layers of 0–10, 10–20, 20–40, 40–60 and 60–80cm were reduced with afforestation of grassland but not significantly (p>0.05), while conversion of cropland to forests (trees or shrubs) increased SOC significantly for each soil depth layer up to 60cm depth (p<0.05). Significant relationships of SOC change rate were found between topsoil (0–20cm) and deeper soil layers (20–40 and 40–60cm). The linear regression showed that SOC change rate in 0–40cm, 0–60cm, and 0–100cm soil profiles was 1.33, 1.49, and 1.55 times greater, respectively than the change rates in the corresponding 0–20cm depth profile. Partial correlation analysis revealed that stand age and initial SOC content were determinants of deep soil SOC change after afforestation of agricultural soils. This study also showed that the O horizon can play an important role in carbon sequestration after afforestation of agricultural sites. We concluded that subsoil carbon must be taken into account when evaluating of SOC change with afforestation and, therefore, recommended that the soil sampling depth for afforested soils be set to at least 60cm in mineral soils and include the O horizon. However, due to poor study designs and lack of standardized sampling protocols in the literature, these results were high in uncertainty.

Accumulation of soil organic carbon in aggregates after afforestation on abandoned farmland

To understand how organic C (OC) accumulates in afforested soils and to quantify the contribution of aggregate-associated OC to OC accumulation, we investigated the changes in soil structure, total soil OC, and aggregate-associated OC from 0- to 10- and 10- to 20-cm depths in afforested forests and adjacent farmlands of northwestern China. We assessed the contribution of macroaggregate-associated OC increase to total soil OC accumulation. Afforestation increased macroaggregate amount, mean weight diameter, and mean geometric diameter but decreased the amount of microaggregate and silt + clay-sized fractions. The improvement of soil structure was greater in surface than subsurface soils and was greater in soils afforested with white birch than in soils afforested with other tree species. Fifty years after afforestation, total soil OC concentrations and stocks and aggregate-associated OC concentrations increased depending on soil depth and tree species. Afforestation increased macroaggregate-associated OC stocks but decreased microaggregate- and silt + clay-associated OC stocks. Soil OC stocks and changes in OC stocks after afforestation mainly depended on macroaggregate-associated OC stocks and their changes. The results from this study suggest that OC accumulation in afforested soils is due to the accumulation of OC in macroaggregates and the redistribution of OC from fine particles to coarser fractions.

Spatial variability and temporal changes in the heavy metal content of soils with a deep furrow-and-ridge microrelief formed by an afforestation plowing

An appropriate sampling method that provides for the representation of the collected material and the reliability of results plays a crucial role in environmental monitoring. This is especially important in soil quality investigations on sites with a differentiated surface microrelief, as in the case of afforested post-arable soils that have a specific, deep furrow-and-ridge microrelief. The present research was carried out on three sites afforested with pine (4-, 8-, and 15-year-old stands) located near a large tailings pond collecting the wastes from copper ore enrichment. Soils were sampled at depths of 0–10 and 0–30 cm, separately in the furrows and ridges. The “wide-furrow plow” contributed to the spatial variation in soil properties, including higher pH, organic carbon, and Cu content in soils of the ridges. The difference in Cu content in the ridges and furrows initially reached 300 %, and decreased with the decline of the furrow-and-ridge microrelief to 60 % at 15 years after the plowing. Observed rate of the furrow shallowing allows for an estimation of the time necessary for the complete disappearance of the furrow-and-ridge microrelief and associated variability in soil properties to at least 30–40 years after the plowing. Afforestation plowing had little impact on the Zn variability which was not influenced by the emissions from the tailings pond. Soil sampling in contaminated sites with furrow-and-ridge microrelief must collect equal quantities of soil samples from both furrows and ridges to allow a reliable estimation of the mean trace elements’ concentration.

The impact of agricultural land use changes on soil organic carbon dynamics in the Danjiangkou Reservoir area of China

Over recent decades, a large uncultivated area has been converted to woodland and shrubland plantations to protect and restore riparian ecosystems in the Danjiangkou Reservoir area, a water source area of China’s Middle Route of the South-to-North Water Transfer Project. Besides water quality, afforestation may alter soil organic carbon (SOC) dynamics and stock in terrestrial ecosystems, but its effects remain poorly quantified and understood. We investigated soil organic C and nitrogen (N) content, and δ 13C and δ 15N values of organic soil in plant root-spheres and open areas in an afforested, shrubland and adjacent cropped soil. Soil C and N recalcitrance indexes (RIC and RIN) were calculated as the ratio of unhydrolyzable C and N to total C and N. Afforestation significantly increased SOC levels in plant root-spheres with the largest accumulation of C in the afforested soil. Afforestation also increased belowground biomass. The C:N ratios in organic soil changed from low to high in the order the cropped, the shrubland and the afforested soil. The RIC in the afforested and shrubland were higher than that in cropped soil, but the RIN increased from the afforested to shrubland to cropped soil. The δ15N values of the organic soil was enriched from the afforested to shrubland to cropped soil, indicating an increased N loss from the cropped soil compared to afforested or shrubland soil. Changes in the δ13C ratio further revealed that the decay rate of C in the three land use types was the highest in the cropped soil. Afforestation increased the SOC stocks resulted from a combination of large C input from belowground and low C losses because of decreasing soil C decomposition. Shifts in vegetation due to land use change could alter both the quantity and quality of the soil C and thus, have potential effects on ecosystem function and recovery.

Dominant trees affect microbial community composition and activity in post-mining afforested soils

The aim of this work was to quantify the effects of vegetation on the activity of extracellular enzymes in the litter and soil. To achieve this, we investigated a set of post-mining sites in a brown-coal mine deposit area near Sokolov, Czech Republic. The sites were 22–33 years old and had been established on the same initial substrate by planting with six tree genera or leaving for spontaneous revegetation, with four replicate sites per vegetation type. The activity of extracellular hydrolytic and oxidative enzymes and the microbial community composition of the litter and topsoil were compared in the spring, summer and autumn using the dominant tree, pH, soil nutrient content and soil moisture as the explanatory variables. Sites under individual trees exhibited significant differences in the chemical properties of both the litter and soil, and the tree effect was identified as the most important factor affecting the activity of extracellular enzymes either directly or in the interaction with seasonal effects, although not all pairs of tree species were significantly different from each other. Seasonal effects on enzyme activity were only important in the litter. The effects of dominant trees and of seasons contributed equally to the variation in the microbial community composition at individual sites. Only a minor part of the tree effect could be explained by differences in the litter or soil chemistry. Among the chemical variables, the N content most affected the microbial biomass content, increasing fungal (but not bacterial) biomass in the litter and bacterial (but not fungal) biomass in the soil. The results indicate that other factors, such as nutrient quality or the specific association of microorganisms with rhizospheres of different trees or the understory, are likely important mediators of the vegetation effects. When comparing the revegetated sites with sites under spontaneous succession, the enzyme activities and microbial biomass were similar except for the sites revegetated with Alnus which may indicate similar rates of soil development at revegetated and succession sites. Spontaneous succession in temperate Europe may thus be a suitable option for land restoration.

Effects of afforestation with four unmixed plant species on the soil–water interactions in a semiarid Mediterranean region (Sicily, Italy)

Purpose An assessment of the effect of plant cover on the properties of four afforested soils in central Sicily was performed with the aim of discriminating among them after 60 years of afforestation.

The Accumulation of Organic Carbon in Mineral Soils by Afforestation of Abandoned Farmland

The afforestation of abandoned farmland significantly influences soil organic carbon (OC). However, the dynamics between OC inputs after afforestation and the original OC are not well understood. To learn more about soil OC dynamics after afforestation of farmland, we measured the soil OC content in paired forest and farmland plots in Shaanxi Province, China. The forest plots had been established on farmland 18, 24, 48, 100, and 200 yr previously. The natural 13C abundance of soil organic matter was also analyzed to distinguish between crop- and forest-derived C in the afforested soils. We observed a nonlinear accumulation of total OC in the 0–80 cm depth of the mineral soil across time. Total soil OC accumulated more rapidly under forest stands aged 18 to 48 yr than under forest stands aged 100 or 200 yrs. The rate of OC accumulation was also greater in the 0–10 cm depth than in the 10–80 cm depth. Forest-derived OC in afforested soils also accumulated nonlinearly across time, with the greatest increase in the 0–20 cm depth. Forest-derived OC in afforest soils accounted for 52–86% of the total OC in the 0–10 cm depth, 36–61% of the total OC in the 10–20 cm depth, and 11–50% of the total OC in the 20–80 cm depth. Crop-derived OC concentrations in the 0–20 cm depth decreased slightly after afforestation, but there was no change in crop-derived OC concentrations in the 20–80 cm depth. The results of our study support the claim that afforestation of farmland can sequester atmospheric CO2 by increasing soil OC stocks. Changes in the OC stocks of mineral soils after afforestation appear to be influenced mainly by the input of forest-derived C rather than by the loss of original OC.

Corrigendum to &amp;quot;Stand age and tree species affect N&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O and CH&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt; exchange from afforested soils&amp;quot; published in Biogeosciences, 8, 2535–2546, 2011

Corrigendum to &amp;quot;Stand age and tree species affect N&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O and CH&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt; exchange from afforested soils&amp;quot; published in Biogeosciences, 8, 2535–2546, 2011

SOIL ORGANIC MATTER IN AFFORESTED POST-AGRICULTURAL SOILS

The studies were carried out in central Poland. Total organic carbon (Corg), total nitrogen (Nt) and C of humus fractions in uppermost soil horizons were analyzed in afforested meadow soils in first and fifth year of afforestation (2 profiles) and compared to about 70-year-old continuous forest soils. Soil was collected from 0-5, 5-10, 10-15 and 15-20 cm layers depth. The results showed that the soil Corganic (Corg) and Ntotal (Nt) decreased with depth in both studied periods. The Corg amounts were higher in the second period (5 years after afforestation) in almost every layer of the humus horizons in comparison to the first year of afforestation. The Nt content rather decreased in particular layers during five years, but mean values of 0-20 cm depth were lower or higher in dependence on soil type. The content of both elements in the studied layers was lower in the 5-year afforested soils than in the continuous forest soils. The results indicated changes in organic matter properties too, but the distribution of the different soil organic matter fractions in humus layers in time was dependent on soil properties. Soil plays a significant role in carbon sequestration. A few comparative studies of organic matter in forest, grassland, arable, former grassland and post arable soils do not supply an unequivocal answer on the influence of afforestation on the organic carbon and organic matter content in soils. Most research is focused on soil quality after land use change from arable to forest. This is because this land management conversion is most common. Studies conducted by the team of Szujecki (23) indicate that C org content in the sub-surface soil horizons of younger forest stands is higher in post-arable soils than in forest soils. In turn, in deeper horizons an opposite trend is observed and the forest soils are characterized by a higher content of C org and Nt in comparison to post-arable soils. Other studies evidence an increasing C org content subsequently

Effects of afforestation with Eucalyptus grandis on soil physicochemical and microbiological properties

It is generally believed that plantations of Eucalyptus bring about a decrease in soil fertility. Soil physicochemical and microbiological properties were measured across a range of E. grandis plantation ages (1–10 years) in south-western China to determine whether and how eucalypt afforestation of agricultural land affected the soil fertility. The results indicate that afforestation with E. grandis caused changes in soil properties with soil depth, and the changes were dependent on the stand age. Soil bulk density decreased significantly, but water-holding capacity increased significantly with time. Soil organic matter content, C : N ratio, and soil microbial biomass C and N concentrations showed an initial phase of decline and then increased significantly over time in the upper soil layers of E. grandis plantations aged from 1 to 4 or 5 years. Soil pH in E. grandis plantations did not change significantly with stand age or soil layer. Cation exchange capacity in the upper soil layer of E. grandis plantations increased significantly over time. Total exchangeable bases and base saturation in the soil decreased significantly with depth and with increasing plantation age. Furthermore, E. grandis afforestation of arable soils had no significant effects on total N, total P, and available P contents. The requirements of the trees, understory microenvironmental conditions, and allelopathic effects might play important roles in the dynamic changes of soil physicochemical and microbiological properties. The results demonstrate the progressive development of processes that lead to the restoration of soil fertility following E. grandis afforestation of arable soils. However, most of the properties measured for the afforested soils resembled the properties of arable soils and did not resemble those of the soil of control forests. Thus, reversion of soil properties in the study plantations is likely to require a considerable period of time. Long-term research is needed to understand changes in the soil properties resulting from afforestation with Eucalyptus and to predict future trends.

Former agriculture impacts on properties of Norway spruce forest

Forest floor is considered a major feature distinguishing forest from agricultural soils. Forest floor develops as forest stands grow and is composed of more or less altered plant-tissue biomass accumulated on the soil surface. Our study’s aim was to find whether properties of both the organic layers and mineral soil differ according to the land-use history of the sites compared. Each site included an afforested area of immature 50-year-old spruce forest (AFF) on formerly agricultural land plus an adjacent area of old-growth 100-year-old spruce stand (FOR). The localities are situated at altitudes ranging between 600 and 850 metres above sea level. From the results of our study it can be concluded that both forest floor and mineral soil had higher pH and Ca concentration at formerly agricultural sites. C/N ratio is significantly lower in afforested soil. First-generation humus was significantly higher in phosphorus.

Carbon Sources and Dynamics in Afforested and Cultivated Corn Belt Soils

Afforestation of degraded cropland can sequester atmospheric C; however, source partitioning and turnover of soil organic C (SOC) in such ecosystems are not well documented. This study assessed SOC dynamics in two 35‐yr‐old, coniferous afforestation sites (i.e., a forest plantation situated in northwestern Iowa on a silty clay loam soil and a shelterbelt situated in eastern Nebraska on a silt loam soil) and the adjacent agricultural fields. Soil samples were collected at both sites to determine SOC and total N concentrations and stable C isotope ratios (δ13C, natural abundance) in both whole soil and the fine particulate organic matter (POM) fraction (53–500 μm size). In these fine‐textured soils, afforestation of cropland performed through either shelterbelt or forest plantation caused substantial increases in surface SOC storage compared with conventionally tilled cropping systems (≥57%; P &lt; 0.05); this confirms the direct benefits of tree planting on SOC sequestration. Relative to cropped soils, afforested soils exhibited a more depleted δ13C signature (−17 vs. −22‰), indicating a shift in C sources. Source‐partitioning assessment revealed that tree‐derived C contributed roughly half of the SOC found directly beneath the trees. The C‐enriched afforested surface soils exhibited SOC turnover rates of 0.018 to 0.022 yr−1 and mean residence times of 55 to 45 yr. Fine POM in afforested surface soils accounted for a large proportion (21%) of the existing SOC, 79% being derived from tree inputs. This supports the role of POM as a significant sink for recently sequestered SOC in these ecosystems.

Influence of leaf litter types on microbial functions and nutrient status of soil: Ecological suitability of forest trees for afforestation in tropical laterite wastelands

The impact of forest tree leaf litters on microbial activity and nutrient status of red laterite soil was tested for the ecological suitability of Cassia siamea, Shorea robusta, Acacia auriculiformes and Dalbergia sissoo, which are typically used for afforestation of wastelands in eastern India. The objectives were to compare seasonal variation in soil enzyme activity in 30-years old afforested sites, and to study nutrient status and microbial biomass and function during short-term in-situ incubation of litter in decomposition pits. In afforested soils, enzyme activities significantly varied between litters and seasons. All enzyme activity except invertase dominated in the soils containing Dalbergia and Cassia litters compared to the others. The seasonal effect was enzyme-dependent, with amylase and cellulase reaching peaks during the rainy season but invertase activity showed a reverse trend with lowest values in rainy season, except in Acacia soil, and protease activity was lowest in the soil containing Cassia and Dalbergia during the rainy season. Dehydrogenase activity was negligible in the soils containing Shorea and Acacia, but remained high with respect to Dalbergia and Cassia during all seasons. The decomposition pit study showed significant increase of soil nutrients with respect to litter types and intervals, except with respect to electrical conductivity. Cassia and Dalbergia litters enabled notable increase of soil nutrients than Shorea and Acacia. The soil enzyme activity, in general, increased with duration of litter decay, but microbial biomass C (MBC) decreased over time except in Shorea. Therefore, the enzyme rates normalized to the MBC indicated inverse relations for all enzymes, except in the soil containing Shorea. A positive relationship existed between MBC and soil respiration in Cassia, Acacia and Dalbergia. Analysis of variance revealed main effects of litter types for increasing protease, MBC and CO2 output, and a main effect of intervals for enhancing enzymes other than cellulase. Rates of soil respiration were greater in soils contain Cassia and Dalbergia, and showed significant differences between litters and between intervals. All enzymes were significantly correlated with electrical conductivity, organic carbon and available phosphorus contents, and all enzymes except invertase were correlated with nitrate concentrations. The acidic soil pH did not affect enzyme activities, and soil nutrients exerted only weak effect on MBC and respiration. Our study showed that leaf litters of Cassia and Dalbergia trees improved the nutrient status and microbial activity in soil more so than Shorea and Acacia litters, and therefore, afforestation using Cassia and Dalbergia trees may be particularly suitable for soil restoration in tropical laterite wastelands.

How does legacy of agriculture play role in formation of afforested soil properties?

Soil properties of forest ecosystems depend on synergy of both parent material and organisms living in the soil, i.e. tree species communities including related plant and animal species. However these soils were not left intact being converted into agricultural land; addition of both nutrients and organic matter and cultivation using tillage led to increased fertility of topsoil. Even long-term afforested soils show differences which are considered as legacy of past agriculture. The change remains detectable for decades; though the altered properties are obvious especially couple of years after planting (approximately 10 years). We found increased concentrations of nutrients (P, K, Ca, and Mg) and subsequent increased base saturation (V %) in former tilled soil only. Moreover, there were no differences between topsoil and subsoil properties (69% and 72%, respectively). In addition to significantly lower saturation (both 0–10 cm and 11–30 cm layers) detected in the long-term-forest and 50-year-afforested (both covered with Norway spruce stands) soils in comparison with adjacent 10-year-old afforestations, there was found significantly lower base saturation in topsoil horizons compared to underlying ones.

Stream acidification and base cation losses with grassland afforestation

Afforestation of natural grasslands with fast‐growing pine and eucalyptus species is increasing globally, but little is known about its effect on ecosystems and watersheds and, ultimately, the quality of water resources. To investigate the biogeochemical and hydrological consequences of this land use change, we sampled stream water in paired watersheds in Uruguay and Argentina. In watersheds planted with pine, we found no change in stream pH following afforestation, while in watersheds planted with eucalyptus, pH was 0.7 units lower on average than in streams draining grasslands. To further investigate the mechanism behind the decrease in pH, we sampled soils and streams of eucalypt catchments in Uruguay and analyzed exchangeable base cation concentrations, alkalinity, and dissolved inorganic carbon (DIC). At these sites, Ca, Mg, and Na concentrations were &gt;30% lower in afforested soils than in grassland soils, and pH was significantly lower below 10 cm depth. Stream measurements taken over three years illustrate that these soil changes were also manifested in stream water chemistry. In the eucalypt watersheds, base cation concentrations were &gt;40% lower, and alkalinity and DIC were halved in stream water. A test with data from additional sites where both pines and eucalypts were planted nearby showed that eucalyptus has a stronger acidifying effect than pine. Overall, our data suggest that repeated harvesting cycles at some locations could negatively impact the soil store of base cations and reduce downstream water quality. Our results can be used to help minimize negative impacts of this land use and to inform policy in this and other regions targeted for plantation forestry.

The effect of afforestation with Scots pine (Pinus silvestris L.) of sandy post-arable soils on their selected properties. II. Reaction, carbon, nitrogen and phosphorus

Despite the extensive literature on the effect on soil properties of afforestation of former arable land, we still lack full understanding of whether the changes proceed in the same direction and at the same rate, and of how long is required to achieve a state of soil equilibrium typical of a natural forest ecosystem. Therefore, as part of a study comparing post-arable sandy soils (Dystric Arenosols) afforested with Scots pine (Pinus silvestris L.) with arable soils and soils of continuous coniferous forests, the range and direction of changes in pH, organic carbon (Corg), total nitrogen (Ntot), ammonium (N-NH4) and nitrates (N-NO3) in soil solution, total (Ptot) and available (Pav) phosphorus were determined. The studies were carried out in south-east Poland (51°30′-51°37′N, 22°20′-22°35′E). Ten paired sites of afforested soils (five with 14- to 17-year-old stands and five with 32- to 36-year-old stands) with adjacent cultivated fields, and five sites of continuous forest with present stands of ca. 130–150 years old were selected. Soil samples were taken from the whole thickness of master horizons and, in the case of the A horizon of the afforested soils, from three layers: 0–5 (A0–5), 5–10 (A5–10) and 10–20 cm (A10–20). The cultivated soils in the Ap horizon showed higher pH (by ca. 1.0 unit), lower Corg and C:N, similar Ntot, lower N-NH4, higher N-NO3, higher Ptot and Pav contents compared with the Ah horizon of continuous forest soils. The results indicated decreased soil pH in the former plough layer of the afforested soils, with the greatest decrease observed in the 0–5 cm layer. In these soils, the Corg content was considerably higher in the A0–5 layer, but lower in the two deeper layers and in the whole A horizon (0–20 cm) compared with the Ap horizon of the arable soils. The results indicate that the Corg content, after an initial phase of decline, again achieved a level characteristic of arable soils. The Ntot content in all layers of the A horizon of the afforested soils was lower than in the Ap horizon of the arable soils, and showed a reduction with stand age, especially in deeper layers. The C:N ratios in the mineral topsoil increased with stand age. N-NH4 content increased and N-NO3 decreased after afforestation. The Ptot and Pav contents in all layers and in the whole A horizon of the afforested soils, on stands of both ages, was lower than in the Ap of the cultivated soils. From the results, it could be concluded that, after more than 30 years of tree growth, the soils of the A horizon were still more similar to arable than to continuous forest soils with respect to Corg, Ptot and Pav. With respect to pH, N-NH4 and N-NO3, especially in the 0–5 cm layer, they were more similar to continuous forest soils than to cultivated soils, but with respect to Ntot and C:N ratio they were somewhere in between.

The effect of afforestation with Scots pine (Pinus silvestris L.) of sandy post-arable soils on their selected properties. I. Physical and sorptive properties

Despite the extensive literature on the effect of afforestation of former arable land on soil properties, we still do not fully understand whether the changes proceed in the same direction and at the same rate or how long it takes to achieve a state of soil equilibrium typical of a natural forest ecosystem. Therefore, as part of a comparative study of post-arable sandy soils (Distric Arenosols) afforested with Scots pine (Pinus silvestris L.) with respect to arable soils and soils of continuous coniferous forests, a range and direction of the changes in some of their physical and sorptive properties were determined. The studies were carried out in SE Poland, 51°30′–51°37′N, 22°20′–22°35′E. Ten paired sites of the afforested soils (five with 14- to 17-year-old stands and five with 32- to 36-year-old stands) with adjacent cultivated fields and five sites of continuous forests with present stands of ca. 150 years were selected. For the physical properties, undisturbed soil cores were sampled from the upper part of each horizon while in the case of A horizon of the afforested soils, from two layers: 0–5 cm and 10–15 cm. For the remaining analyses, soil was taken from the whole thickness of the master horizons and in the case of A horizon of the afforested soils, from three layers: 0–5, 5–10 and 10–20 cm. The following properties were analysed: texture, bulk density (BD), total porosity (TP), water content at potential of −0.098, −9.81 and −49.03 kPa, hydrolytic acidity (Ha), base exchangeable cations: Ca2+, Mg2+, K+, Na+, total exchangeable bases (TEB), cation exchange capacity (CEC) and base saturation (BS). Afforestation caused a decrease in BD, an increase in TP and had no affect on water properties when compared with the cultivated soils. The changes referred to the A horizon, particularly to its 0–5 cm layer, and were related to the stand age. The CEC gradually rose in the former plough layer, beginning from the uppermost part, but during the first two decades its increase in the 0–5 cm layer was offset by a decline in the deeper layers. No substantial increase in CEC, in the whole A horizon, was recorded until three to four decades of afforestation. Afforestation also invoked an increase in Ha, a drop in TEB, particularly Ca2+, Mg2+ and K+, and reduction in BS. No differences between soils for all the studied properties for B and C horizons were observed. It was noted that more than 30 years after afforestation, the TEB and BS as well as Ca2+, Mg2+ and K+ content differed substantially, but in most cases not significantly, from their values in the cultivated soils and reached a level more similar to the soils of continuous coniferous forests. With respect to the water properties, Ha and CEC of the afforested soils still resembled arable soils, whereas regarding the TP and BD, they were somewhere in the middle. This implies that to understand changes in the soil properties resulting from afforestation and to predict future trends, long-term research is needed.

Tardigrade species composition in young soils and some aspects on life history of Macrobiotus richtersi J. Murray, 1911

Summary In an afforested coal-mining site at Berzdorf, Germany, the soil tardigrade community was investigated. Tardigrade densities ranged from 300 to 33,600 individuals m −2 . Tardigrade distribution was very aggregated with standard deviations of up to 220% of mean densities. Fourteen species belonging to five eutardigrade genera were identified. Soils were dominated by the carnivorous tardigrade Macrobiotus richtersi that contributed 60% of overall densities. A comparison between nine soils of different forest ages (4–46 years) and tree species (poplar, alder, pine, mixed deciduous and mixed coniferous) showed no relationship of tardigrade species distribution and abundance to tree species, thickness of organic or litter layer, humus form, pH or soil moisture. Further, no correlation between nematode biomass and Macrobiotus richtersi abundances were detected. The age of afforested soils, however, affected tardigrade densities: younger soils (7–17 years) yielded higher tardigrade numbers compared to 46-year-old sites. Life history investigations on a strain of parthenogenetic Macrobiotus richtersi demonstrated a significant influence of temperature on egg development, survival rate, body growth and generation time. Hatching, first to fourth molts and maturing, on the other hand, were dependent upon body size alone. The simple, new culture method for carnivorous tardigrades described has successfully been utilized for parthenogenetic Macrobiotus richtersi for 6 years.

Changes in soil N status and N supply rates in agricultural land afforested with eucalypts in south-western Australia

In south-western Australia, plantations of Eucalyptus globulus are being established on land that has previously been used for conventional agriculture. Sustaining the productivity of these tree plantations in second and subsequent rotations will depend partly on maintenance of soil fertility, especially soil nitrogen (N) supply rates. We compared soil N status and supply rates between adjacent pasture and 6–11 year old first-rotation eucalypt plantations at 31 paired sites in south-western Australia. Total soil N varied widely among sites (0.07–0.68% in the fraction <2 mm of the 0–10 cm soil layer), but concentrations averaged over all sites did not differ between land-use types. However, measurements of the indices of mineralization (mineral N produced during incubation of intact cores), potentially available N (from short-term anaerobic incubation) and model-predicted mineralization rates during 28-day aerobic incubations were generally lower in afforested soils than in pasture soils. This finding was supported by in situ field estimates of N mineralization over a full year at two contrasting paired pasture-plantation sites. At each site there was a marked reduction (2–3-fold) in net annual mineral N flux rates in soils under eucalypt plantations. Reduced N mineralization associated with tree plantations was due to both changes in soil organic matter quality and the generally lower soil moisture content under trees in comparison with pasture. These results suggest that N supply rates of pasture soils are likely to decline when the land is planted to successive crops of eucalypts. Eucalypt plantation managers will need to take account of this and implement management strategies to maintain adequate N nutrition to sustain tree growth in future rotations.