Soil degradation and soil surface process intensities on abandoned fields in Mediterranean mountain environments

The Pyrenean and Pre‐Pyrenean mountain areas have been intensively used at least since roman times, but nowadays depopulation has lead to widespread land abandonment without a steering land‐management. Vegetation recovery is weak in most abandoned fields. Soil formation and characteristics are conditioned by this fact, and for this, soils show past degradation processes and are mostly predominant factors for continuing land degradation or restoration. Three study areas were set up along a climatic gradient with increasing summer water deficit in the sub‐humid zone between the Central Pyrenees and Pre‐Pyrenees. Soil survey combined with experiments for the determination of infiltration, runoff and erosion were applied for understanding the degradation history and the future development of the soils. All areas are dominated by Entisols, but also Inceptisols and Alfisols are found, and even soils with hydromorphic features. The soils show signs of heavy erosion. The parental material determines the nutrient supply and the general chemical properties. All sites show a weak water storing capacity, as a result of the removal of fine material by erosion and due to the depletion of soil organic matter. In addition, infiltration capacity and runoff generation are high within the studied areas, averaging between 27 and 37 per cent. The driest area studied shows an ongoing trend to degradation, with high erosion rates combined with a high degradations status of the soil. The other areas are characterised by a patchy pattern of soil degradation and regradation processes. Copyright © 2008 John Wiley & Sons, Ltd.     

Validating the effectiveness and sensitivity of two soil quality indices based on natural forest soils under Mediterranean conditions

Soils from natural ecosystems have specific physical, chemical and biochemical properties determined by the conditions in which these soils have developed. These soils that develop without external disturbance reach a balance amongst their properties. Thus, the creation of a model that represents the established balance of different soil properties from stable ecosystems can be used as a soil quality index, thus any perturbation must lead to modifications in this natural balance. Two regression models with soils from undisturbed forest regions in eastern Spain were previously developed, representing the balance between organic carbon and some physical, chemical and biochemical properties. For undisturbed forest soils, the prediction of soil organic carbon (SOCc) with the calibrated models should be similar to the actual value of this variable (SOCa) (SOCc ≈ SOCa). Consequently, the residuals (SOCc − SOCa) should be around 0. On the contrary, disturbance practices cause a disruption in the balance defined between the different properties and SOC. As a consequence, residuals must be < or >0. Furthermore, the more the degree of degradation increases, the more the values of SOCc must differ from the values of SOCa. According to this, two soil quality indices (SQI) were defined, one for each model, by the calculation of the model residuals (SQI = SOCc − SOCa). The SQIs have been applied to different undisturbed forest soils to evaluate their validity. In addition, they have also been applied to severely altered soils, like agricultural soils, and abandoned agricultural fields, to assess the sensibility of this index to perturbations. After applying the soil quality indices to eleven undisturbed forest soils, it has been verified that a balance exists between organic matter content and different physical, chemical and biochemical properties in forest soils from SE Spain, and the proposed calibrated models are capable of reflecting that balance (SQI ≈ 0). Our results confirm that our models are sensitive to soil perturbation, because agricultural and abandoned agricultural soils have shown an imbalance between organic carbon content and the physical, chemical and biochemical properties (SQI > 0). Moreover, soils from abandoned fields showed lower deviation in the natural equilibrium, indicating a recovery of soil quality.     

Assessment of arbuscular mycorrhizal fungal propagules and colonization from abandoned agricultural fields and semi-arid grasslands in riparian floodplains

Prior to the onset of extensive grazing and clearing for agriculture, riparian floodplains of southeastern Arizona, USA, historically supported large grassland communities dominated by Sporobolus wrightii Munro ex Scribn., big sacaton grass. Large-scale abandonment of agricultural operations has occurred in this region in the past 50 years, but natural re-establishment of big sacaton into abandoned fields has typically been slow. This study assesses whether arbuscular mycorrhizal fungi (AMF) may be one factor in recovery rates of abandoned fields within three riparian areas in southeastern Arizona (San Pedro river, the Babocomari river and Cienega creek). In each riparian area, soil samples were collected along paired 100 m transects, one in an extant grassland and one in a neighboring abandoned agricultural field. At one site (San Pedro), a third transect was established in a second adjoining abandoned agricultural field to enable comparisons between fields showing differing rates of recovery at a single site. Roots were assessed for mycorrhizal colonization using the modified intercept method and the modified mean infection percentage (MIP) method was used to determine inoculum potential of each soil sample. No significant differences were found between the levels of mycorrhizal colonization in roots collected from the grassland and those collected from the abandoned field for any of the sample sites. Levels of colonization did differ among the three sample sites, with higher levels seen at the San Pedro site than at the Babocomari and Cienega sites. With one exception, MIPs were greater in the soil from the abandoned agricultural field than in the soil from the nearby grassland. In the exception, no difference was detected in inoculum potentials at the San Pedro site between the paired grassland and the abandoned field that had the lower level of sacaton recovery. MIPs were also greater in the soil from the abandoned agricultural field at Babocomari, where Salsola tragus L. growth for cattle feed was promoted by discing every 3–4 years. These results indicate that higher inoculum potentials in abandoned fields were not always linked to the high levels of recovery of native vegetation.     

Hydrolytic enzyme activities in agricultural and forest soils. Some implications for their use as indicators of soil quality

Although a great deal of information exists about the effect of land use on soil enzyme activities, much of this is contradictory and brings into question the suitability of soil enzyme activities as indicators of how land use affects soil quality. The purpose of this study was to investigate the effect of land use on different soil biochemical properties, especially hydrolytic enzyme activities, with the aim of providing knowledge about the problems related to the use of enzymes as indicators of soil quality. The data presented derive from various studies in which a large number of soils under different types of forest or agricultural management were analysed by the same methods. All of the soil samples were characterized in terms of their main physical and chemical properties, the activity of several hydrolases, microbial biomass C and soil basal respiration. The results indicate that soil use causes a large reduction in organic matter content and that the effect on enzyme activity varies depending on the type of land use or management and the type of enzyme. Furthermore, the enzyme activities per carbon unit (specific activities) in soils affected by land use are almost always higher than in maximum quality soils (climax soils under oak vegetation or oak soils), and land use also generates greater increases in the specific activity as the C content decreases. The mechanism responsible for these increases probably involves loss of the most labile organic matter. Enzyme enrichment is not always produced to the same degree, as it varies as a function of the enzyme and the type of land use under consideration. It is concluded that the complexity of the behaviour of the soil enzymes raises doubts about the use of enzyme activities as indicators of soil degradation brought about by land use.     

Soil erosion and hydrological response to land abandonment in a central inland area of Portugal

This paper analyses the effects of land abandonment on runoff and sediment yield in a central inland area of Portugal. Rainfall simulation experiments were performed in areas of traditional land use (land cultivated with cereals) with various types of soil plant cover associated with the period of abandonment (4–5 years, 15–20 years and 30–40 years) in two different seasons, namely under very dry conditions and after a long wet period. Statistical analysis showed a notable difference between the cultivated soils and those abandoned for a long period of time, which included appreciable vegetation recovery, higher organic matter content and negligible overland flow and soil loss. Cereal cultivation, in particular ploughing, is a very negative land management practice, due to the high runoff and soil loss. Within 4–5 years a crust develops over abandoned soils with sparse herbaceous plant cover, particularly after a dry season, which enhances runoff and sediment yield. In scrubland and oak plots, although marked water repellency was registered at the end of a dry, warm season, its influence seems to be irrelevant in terms of overland flow and erosion yield. The major factor in controlling overland flow and reducing soil erosion rates appears to be the role played by vegetation in protecting the soil surface and supplying organic carbon to the top layer. Copyright © 2010 John Wiley & Sons, Ltd.     

Effect of vegetation manipulation of abandoned arable land on soil microbial properties

 The effect of vegetation composition on various soil microbial properties in abandoned arable land was investigated 2 years after agricultural practice had terminated. Microbial numbers and processes were determined in five replicate plots of each of the following treatments: continued agricultural practice (monoculture of buckwheat in 1997), natural colonization by the pioneer community (arable weeds), and manipulated colonization from low (four species, three functional groups: grasses, forbs and legumes) or high diversity (15 species, three functional groups) seed mixtures from plant species that are characteristic of abandoned fields in later successional stages. The results indicated that differences in above-ground plant biomass, plant species composition and plant species diversity had no significant effect on soil microbial processes (net N mineralization, short-term nitrification, respiration and Arg ammonification), microbial biomass C and N (fumigation-incubation) or colony-forming units of the major microbial groups. Hence, there were no indications that soil microbial processes responded differently within 2 years of colonization of abandoned arable land by later successional plants as compared to that by plants from the natural pioneer weed community. Therefore, it seems that during the first few years after arable field abandonment, plants are more dependent on the prevailing soil microbiological conditions than vice versa. Received: 8 April 1999     

不同恢复方式下盐渍化弃耕地土壤生物学活性的变化

以干旱区新疆玛纳斯河流域冲积扇缘定点定位试验地为研究对象, 研究灌溉处理、人工草地处理和补植处理对盐渍化弃耕地土壤微生物量、酶活性及土壤呼吸速率的影响。结果表明, 不同恢复方式均明显增加了土壤微生物数量和土壤微生物量碳、氮及土壤酶活性。不同处理土壤微生物量碳、氮分别比原始弃耕地高17.80%、26.38%、5.33%和7.89%、12.75%、21.93%; 不同处理土壤微生物数量分别是原始弃耕地的4.72倍、6.04倍和4.56倍; 不同处理土壤蔗糖酶活性分别比原始弃耕地高3.4倍、3.2倍和7.7倍, 多酚氧化酶活性比原始弃耕地高1.7倍、1.2倍和1.5倍, 脲酶活性比原始弃耕地高11.1%、52.3%和37.1%; 灌溉处理土壤过氧化氢酶活性最高, 是原始弃耕地的1.53倍, 土壤呼吸速率变化表现为人工草地处理>灌溉处理>补植处理>原始弃耕地, 其中, 人工草地处理土壤呼吸速率比弃耕地高52.25%。相关分析表明, 微生物量碳与微生物C/N和微生物数量之间均呈显著正相关关系(P<0.05); 土壤呼吸速率与土壤脲酶、微生物数量和微生物量碳的相关性达到显著水平(P<0.05), 与土壤微生物量氮呈负相关关系, 但相关性不显著; 土壤蔗糖酶与其他3种酶以及微生物量氮呈显著正相关关系, 土壤脲酶与微生物数量呈显著正相关关系, 多酚氧化酶与过氧化氢酶相关性达到显著水平(P<0.05)。本研究表明干旱区盐渍化弃耕地采用灌溉与人工草地处理有利于土壤养分积累, 可在一定程度上改善土壤质量。     

广东丘陵红壤土壤水分性能特征比较研究

对不同植被、不同利用方式下广东丘陵红壤水分性能进行了比较研究.结果表明,与自然地带性植被下的赤红壤比较,次生植被、人工植被下红壤类土壤导水性、持水能力和供水能力一般均较低.在同样的吸力下,次生植被、人工植被下红壤类土壤持水量较少,在同样吸力段.土壤释放的水量较少.玄武岩砖红壤持水量较大,但土壤水分有效性低.研究表明.广东丘陵旱地土壤局部干旱的发生,与其本身的土壤水分性能有密切关系,改良土壤水分性状,是调控广东丘陵旱地土壤水分的重要环节.     

Rainfall/runoff/erosion relationships and soil properties survey in abandoned shallow soils of NE Spain

Purpose

Shallow soils previously cultivated under terraced systems may change their properties after agricultural release and spontaneous plant colonization. Investigations were conducted in terraced fields (NE Spain) to prove that vegetation installed after the abandonment may generally improve soil properties by the formation of stable organic horizons. However, restriction in plant species along the natural vegetation succession and intensification of erosion processes may occur after abandonment depending on fire frequency and soil use history.

Materials and methods

Ten environments with different plant covers under a Lithic Xerorthent were selected and erosion plots (Gerlach type) installed providing their best adaptability at the terrace scale. Selected soil environments represented the sequence of abandonment: from current poorly cultivated soils, soils under pasture, soils under shrubs, and soils under stands of pine and cork trees. Relevant rainfall events producing runoff and erosion were recorded from November 2011 to May 2012. Erosion rates and erosion components were analysed in sediments and water in order to monitor carbon, nitrogen and other nutrient removal by overland flow. Similarly, the physical and chemical properties of the soil environments under study were determined at the same time interval of runoff erosion.

Results and discussion

Soils under pasture, vines and recently burnt pine forest produced the highest runoff followed by soils under shrubs and forest. However, eroded soil yields and nutrient removal were much higher in cultivated soils and soils in recently burnt sites, which had shown poorer soil properties with respect to soils abandoned for longer and preserved by fire. Fire-affected soil environments also showed a thinner organic horizon and reduced water retention. Although erosion rates and nutrient depletion were low in all environments with respect to other areas of Spain, higher splash than water erosion was an early warning indicator of the high susceptibility to degradation of these shallow soils.

Conclusions

Results outlined that the renaturalization dynamics after agricultural abandonment are complex biophysical processes involving the parent material, depth to bedrock and other soil properties as well as the succession of vegetative cover and plant associations responsible for building a new soil mantle contrasting with erosion processes. Planning for management of land abandonment is strongly recommended.

     

ADAPTING TO CLIMATE CHANGE BY IMPROVING WATER PRODUCTIVITY OF SOILS IN DRY AREAS

Considering extreme events of climate change and declining availability of appropriate quality water and/or highly productive soil resources for agriculture in dryland regions, the need to produce more food, forage and fibre will necessitate the effective utilization of marginal‐quality water and soil resources. Recent research and practices have demonstrated that effective utilization of these natural resources in dry areas can improve agricultural productivity per unit area and per unit water applied. This paper focuses on the following three case studies as examples: (1) low productivity soils affected by high levels of magnesium in soil solution and on the cation exchange complex; (2) degraded sandy soils under rainfed conditions characterized by low water‐holding capacity, organic matter and clay content and (3) abandoned irrigated soils with elevated levels of salts inhibiting growth of income generating crops. The results of these studies demonstrate that application of calcium‐supplying phosphogypsum to high‐magnesium soils, addition of clays to light textured degraded soils and phytoremediation of abandoned salt‐affected soils significantly improved productivity of these soils. Furthermore, under most circumstances, these interventions were economically viable, revealing that the efficient use of marginal‐quality water and soil resources has the potential to improve livelihoods amid growing populations in dry areas while reversing the natural resource degradation trend. However, considerably more investment and policy‐level interventions are needed to tackle soil degradation/remediation issues across both irrigated and dryland agricultural environments if the major challenge of producing enough food, forage and fibre is to be met. Copyright © 2011 John Wiley & Sons, Ltd.     

黄土高原典型植被群落对土壤表面电化学性质的

为探究黄土高原不同区域典型植被生长对土壤表面电化学性质的影响,以黄土高原自南向北的3个典型区域(永寿墚、坊塌、六道沟)及2种典型乡土草本植物(铁杆蒿(Artemisia gmelinii Web.)、长芒草(Stipa bungeanaTrin.))为研究对象,以退耕1年的撂荒地作为对照,通过土壤样品采集和土壤表面电化学性质的测定,研究典型植被群落对土壤表面电化学性质的影响及其空间差异。结果表明:(1)在黄土高原地区,相较于撂荒地,典型植被群落生长使土壤黏粒、粉粒、有机质含量增加,土壤pH、容重、砂粒含量减少;(2)同一区域内,相较于撂荒地,植被恢复促进了土壤阳离子交换量、比表面积的增加,减少了表面电荷密度和表面电场强度,其变化范围分别为6.69~24.34 cmol/kg,[JP]7.29~182.29 m²/g,0.08~2.04 C/m²,1.23~28.46 10⁸ V/m;不同区域间,同一植被群落下永寿墚土壤阳离子交换量、比表面积的增量最高,而六道沟土壤表面电化学性质的变化率最高,说明典型植被群落对土壤表面电化学性质的影响具有空间差异性;(3)典型植物群落下土壤粉粒含量和有机质含量与土壤表面电化学性质具有显著的相关性,其变化是影响黄土高原地区土壤电化学性质变化的主要原因,解释率分别为61.0%,11.1%。研究结果为认识黄土高原地区植被恢复及其调控作用提供参考。     

Changes in copper content and distribution in young,old and abandoned vineyard acid soils due to land use changes

We studied total Cu content and its distribution in 33 surface soil samples cultivated with vines for variable lengths of time in the Monterrei designation of origin (DO), located in Galicia (NW Spain). The study was focused on the influence of land use changes on soil degradation by effect of Cu accumulation and availability. Total copper concentration in soils ranged from 25 to 272 mg kg⁻¹. The time during which each soil was cultivated with vines was found to affect both the total concentration of copper and its distribution. The average concentration of copper in young vineyards was 64 mg kg⁻¹, whereas those in old and abandoned vineyards were 100 and 132 mg kg⁻¹, respectively. Copper bound to organic matter and to amorphous inorganic colloids were greater in old and abandoned vineyards, where they accounted for 51 and 52 per cent, respectively, of total copper, than in young vineyards (39 per cent). Copper bound to crystalline Al and Fe colloids accounted for 21, 22 and 12 per cent of total Cu in old, abandoned and young vineyards respectively. The prevalence of Cu bound to the organic fraction reduces the adverse environmental effects of this metal on soil organisms and plants. However, some management practices such as organic matter addition or liming should be implemented in order to delay or avoid soil degradation in young vineyards. For abandoned vineyards, the influence of new land uses on potential Cu mobilisation necessitates careful examination. Copyright © 2007 John Wiley & Sons, Ltd.     

水蚀风蚀交错带植被恢复对土壤有机质和氮素的影响

以陕西省神木县六道沟小流域为研究区域,探讨了植被恢复对土壤有机质(SOM)和氮古量的影响.结果表明,研究区不同植被恢复模式表层(0-20 cm)SOM和全氮(TN)的变化顺序为:天然草地灌丛人工草地弃耕地农田,但是相互间统计差异不显著(p0.05).意味着不同模式对促进土壤质量恢复均有一定的作用,但效果并不明显,因此考虑到研究区水分的限制性,建议植被恢复模式以草地为主,植被恢复阶段对SOM和TN的影响表现为前期(<14 a)降低而后期稳定增加的趋势.但对矿质氮(N_(min))则无显著影响.坡向比较结果表明,南坡(背风坡)SOM,TN以及矿质氮均显著高于北坡(迎风坡).这与其它地区的研究结果恰恰相反,这一特征意味着土壤沙化导致土壤肥力退化的机理可能在于土壤沙化因增强SOM的矿化消耗而降低了土壤养分的累积.     

Bodenkundlicher Vergleich von Kultur- und Brachland im Schweizer Jura

Comparison of soil properties in agricultural and abandoned fields in Swiss Jura Changes of physico-chemical soil properties occurring after abandonment of agricultural fields were investigated at 14 north exposed locations situated between elevations 500 and 900 m in the Jura mountains of Switzerland. These old fields were compared with adjacent fertilized and non-fertilized meadows. All investigated soils were silty clay loams of the type slightly acid brown earth. In old fields the real density remained unchanged but the bulk density decreased significantly to a depth of 20 cm and with it, the soil water content increased. The pH fell from about 6 to 5 probably due to increased leaching, large production of plant litter and different decomposition of soil organic matter. The increase of C/N-ratio in abandoned fields from 10 to 15 further contributes to the deterioration of the site. The absence of fertilization and important N-fixing plants may be the major reasons why soils in old fields are poorer in nitrogen. In spite of the fact, that the entire primary production is left on the field, the organic carbon content mostly decreased upon abandonment of the meadows.     

黄河三角洲滨海滩涂不同微地形改造的盐地碱蓬恢复效应评价

为提高植被覆盖率,探索适宜的植被恢复模式,以光滩裸地为对照,在黄河三角洲滨海滩涂地势平坦地段设置S形、条带形、品字形和月牙形4种微地形改造模式,测定分析其工程量、地表粗糙度、植被生长及改良土壤效应指标,并采用主成分及模糊数学隶属函数法分析评价其植被恢复效应。结果表明:微地形显著影响土壤理化性质与植被生长状况(P0.05),与裸地相比显著降低了土壤容重、含盐量、pH值等,增加了土壤养分,孔隙度,持水量等。4种微地形改造模式中月牙形模式与光滩裸地相比显著降低了44.19%的土壤盐分,并且月牙形改造模式最利于促进植被恢复效果;条带形模式可显著增加土壤养分,其坑底土壤有机质含量为裸地的2.87倍;品字形模式可显著提高土壤孔隙度,显著降低了15.24%的土壤容重;S形模式在植被恢复及土壤改良效应上表现较差。不同微地形改造模式对植物生长和改良土壤效应综合评价结果从大到小依次为:月牙形、条带形、品字形、S形、裸地,建议在黄河三角洲滨海滩涂进行微地形改造时,首先考虑月牙形,其次是条带性、品字形,S形可不采用。研究结果可为黄河三角洲滨海滩涂植被恢复与生态修复提供理论依据与技术支持。     

Critical limits of the degree of compactness and soil penetration resistance for the soybean crop in N Brazil

In agricultural fields soil compaction is a major cause of physical degradation. Degree of compactness (DC) is a useful parameter for characterizing compaction and the response of crops for different soils. The objectives of this study were: (1) to identify the critical DC and PR values for soybean [Glycine max (L.) Merrill] using plant growth variables and (2) to verify the relationship between DC and PR, and assess which parameter is recommended for the evaluation of soil compaction. The study was conducted in a greenhouse in a completely randomized factorial design of 4 textures × 5 compaction levels for sandy loam and sandy clay loam soils, and 3 compaction levels for the clayey and very clayey soils. Soil samples were collected from the surface of a Xantic Kandiudox from the NE region of the State of Pará, Brazil. The DC was calculated from the maximum bulk density obtained by the Proctor test, and the PR curve was determined in undisturbed samples equilibrated in different matric potentials. The growth and development of the soybean was favored in the DC range of 80 to 85%, regardless of soil texture. The critical degree of compactness for the growth of soybean was around 98% regardless of soil texture, while the critical values for penetration resistance at field capacity varied according to soil texture and bulk density and were 28.2, 5.6, 3.5, and 5.2 MPa for the sandy loam, sand clay loam, clayey and very clayey soils, respectively. The root length was the plant growth variable most susceptible to soil compaction. Change in soil penetration resistance was poorly related with change in degree of compactness showing that one parameter cannot be replaced by the other. Because PR is quickly determined in field and have a direct relationship with plant growth, for the soils evaluated in this study we recommend the use of soil PR to assess the state of soil compaction.     

The effects of soil moisture variability on the vegetation pattern in Mediterranean abandoned fields (Southern Spain)

The demographic pressure decrease in Southern Spanish Mediterranean mountainous areas in the mid twentieth century led to the abandonment of agriculture and rupture in the geo-ecosystem balance which had existed until then. Since then, different phases of recovery have been put into action to return the landscape to its earlier natural condition according to climate and soil degradation state after the abandon. In Mediterranean climatic conditions (between subhumid and semi-arid regimes), degraded soil recovery has followed different tendencies rendering the landscape in heterogenic and complex one. This heterogeneity has manifested in the vegetation pattern of abandoned fields. In this paper, we analyze the state of three abandoned fields situated under different Mediterranean climatic conditions from the recovery point of view by means of monitoring the effects of spatial and temporal variability of soil moisture in the vegetation pattern over a period of two years sampling (Nov. 2002–Nov. 2004). The results showed that: i) more annual rainfall volume did not guarantee success in the biological recovery of the system due to the influence of other factors such as the degradation state of the soil post-abandonment or the steep slope gradient; ii) soil moisture variability tended to play a more important role in affecting vegetal cover in semi-arid conditions; and iii) in dry climatic conditions the system demonstrated greater signs of recovery (greater biodiversity).     

尾矿池里添加大理石废料和有机物五年后植被覆盖和土壤生化特性研究

Tailing ponds pose environmental hazards,such as toxic metals which can contaminate the surroundings through wind and water erosions and leaching.Various chemical and biochemical properties,together with extractable and soluble metals were measured five years after reclamation of a polluted soil affected by former mining activities.This abandoned mine site contains large amounts of Fe-oxyhydroxides,sulphates,and heavy metals.As a consequence,soils remain bare and the soil organic matter content is low(< 3 g kg 1).Marble waste,pig manure and sewage sludge were applied in 2004.Plant cover and richness,and soil chemical,biochemical and biological parameters were analysed five years later.Results showed that all soil biochemical properties as well as vegetation cover and richness were higher in treated soils than in the untreated contaminated plots(control),although organic matter,pH values and extractable metals concentrations were similar among treatments.Soluble cadmium and zinc were lower in the amended plots than in control.As a general pattern,soil amended with pig manure showed higher values of most biochemical properties compared to sewage sludge application,while the doses did not have a great effect,being only significant for β-glucosidase,phosphodiesterase and arylsulfatase.Significant correlations were found between vegetation cover,richness and soil biochemical properties,suggesting a high interdependence between plant colonization and reactivation of biogeochemical cycles during five years.This study confirms the high effectiveness of an initial application of the amendments tested to initialize the recovery of ecosystems in bare mine soils under Mediterranean semiarid conditions.This research also shows the high sensitivity of certain biochemical properties in order to evaluate soil quality and reactivation of nutrients cycles in reclaimed mine soils.     

巢湖低丘山区典型植被群落与土壤环境因子特征研究

本文系统调查了巢湖低丘山区5种典型植被类型,即弃耕地、灌木林、人工马尾松林、草地以及次生马尾松林植被群落学特征、土壤养分状况,并分析了巢湖低丘山区典型植被群落与土壤环境因子的关系.研究结果表明:弃耕地显示了最高的植物物种数,其次为人工马尾松林和灌木林,草地物种数最低,平均仅为4种.总盖度以草地最高,达到95％,其次为次生马尾松林和灌木林,人工马尾松林总盖度最低.此外,弃耕地显示了最高的生物多样性与均匀度指数,其次为灌木林,而草地多样性指数和均匀度指数均最低.弃耕地土壤养分含量最高:次生马尾松林表层土壤有机碳、总氮、总磷与有效氮高于灌木林与草地,显示了较明显的土壤养分随植被演替过程的积累效应.相关分析表明生物多样性指数和均匀度指数与土壤养分状况呈良好的正相关关系,表明这一地区植被恢复处于演替发展阶段.     

Changes in soil microbial community structure following the abandonment of agricultural terraces in mountainous areas of Eastern Spain

In Eastern Spain, almond trees have been cultivated in terraced orchards for centuries, forming an integral part of the Mediterranean forest scene. In the last decades, orchards have been abandoned due to changes in society. This study investigates effects of changes in land use from forest to agricultural land and the posterior land abandonment on soil microbial community, and the influence of soil physico-chemical properties on the microbial community composition (assessed as abundances of phospholipids fatty acids, PLFA). For this purpose, three land uses (forest, agricultural and abandoned agricultural) at four locations in SE Spain were selected. Multivariate analysis showed a substantial level of differentiation in microbial community structure according to land use. The microbial communities of forest soils were highly associated with soil organic matter content. However, we have not found any physical or chemical soil property capable of explaining the differences between agricultural and abandoned agricultural soils. Thus, it was suggested that the cessation of the perturbation caused by agriculture and shifts in vegetation may have led to changes in the microbial community structure. PLFAs indicative of fungi and ratio of fungal to bacterial PLFAs were higher in abandoned agricultural soils, whereas the relative abundance of bacteria was higher in agricultural soils. Actinomycetes were generally lower in abandoned agricultural soils, while the proportions of vesicular–arbuscular mycorrhyzal fungi were, as a general trend, higher in agricultural and abandoned agricultural soils than in forests. Total microbial biomass and richness increased as agricultural < abandoned agricultural < forest soils.