A Comparison of Temporal Patterns in Trace Metal Concentration in Tree Rings of Four Common European Tree Species Adjacent to a Cu-Cd Refinery

Metal processing at a Cu-Cd refinery at Prescot in N.W. England has led to severe contamination of the surrounding soils and vegetation, although Cu and Cd in bulk deposition declined dramatically between 1975 and 1990. Despite high spatial and temporal variability in metal deposition, mean Cd concentrations in annual tree rings of sycamore (Acer pseudoplatanus L.), lime (Tilia europaea L.) and beech (Fagus sylvatica L.) at Prescot were correlated with annual bulk Cd deposition. In contrast, mean Cd concentrations in ash (Fraxinus excelsior L.) were unrelated to Cd deposition and there was no significant relationship between mean Cu concentrations in tree rings and Cu deposition in any species. Mean Pb concentrations in sycamore, lime and beech at Prescot and the reference site also decreased over time. At Prescot however, Cd concentrations in tree rings formed in the mid 1990s were up to 10-fold higher than the reference site despite Cd deposition values during this period that were typical of levels expected for urban areas in the UK. The high Cd concentrations in wood during this period indicate that the majority of Cd in tree rings at Prescot is derived from soil, limiting the usefulness of dendrochemistry for monitoring temporal changes in metal deposition. It appears that trees are not simply passive recorders of metal deposition and other possibilities, in addition to decreasing atmospheric deposition, may explain the patterns of Cd and Pb found in sycamore, lime and beech. More research on the physiology of metal cycling in trees is required before dendrochemical techniques can be applied with confidence in environmental monitoring programs.     

Improving soil organic carbon pools through inclusion of summer mungbean in cereal-cereal cropping systems in Indo-Gangetic plain

Long-term effect of mungbean inclusion in lowland rice-wheat and upland maize-wheat systems on soil carbon (C) pools, particulate organic C (POC), and C-stabilization was envisaged in organic, inorganic and without nutrient management practices. In both lowland and upland systems, mungbean inclusion increased very-labile C (Cfrac₁) and labile C (Cfrac₂) in surface soil (0–0.2 m). Mungbean inclusion in cereal-cereal cropping systems improved POC, being higher in lowland (107.4%). Lowland rice-based system had higher passive C-pool (11.1 Mg C ha^?1) over upland maize-based system (6.6 Mg C ha^?1) indicating that rice ecology facilitates the stabilization of passive C-pool, which has longer persistence in soil. Organic nutrient management (farmyard manure + full crop residue + biofertilizers) increased Cfrac₁ and carbon management index (CMI) over inorganic treatment. In surface soil, higher CMI values were evident in mungbean included cropping systems in both lowland and upland conditions. Mungbean inclusion increased grain yield of cereal crops, and yield improvement followed the order of maize (23.7–31.3%) > rice (16.9–27.0%) > wheat (lowland 7.0–10.7%; upland 5.4–16.6%). Thus, the inclusion of summer mungbean in cereal-cereal cropping systems could be a long-term strategy to enrich soil organic C and to ensure sustainability of cereal-cereal cropping systems.     

Foliar Accumulation of Zinc in Tree Species Grown in Hardwood Bark Media Amended with Crumb Rubber

Abstract

Artificial nursery medium sources of uniformity and quality are becoming more difficult to locate. Alternative components such as recycled crumb rubber (CR) may have potential to be incorporated into bark or other growing media. Recycled CR is a waste product from automobile tires. Mixtures of CR and hardwood bark were evaluated in production of container‐grown trees. Leaf tissue analysis revealed that linear or nonlinear increases in zinc (Zn) levels exceeded normal levels. Stem caliper, height, and quality of river birch (Betula nigra L.), pecan [Carya illinoinensis (Wangenh.) C. Koch], and lacebark elm (Ulmus parvifolia Jacq.) decreased with increasing percentages of CR.     

Arbuscular Mycorrhizal Association in Plants Growing on Metal-Contaminated and Noncontaminated Soils Adjoining Kanpur Tanneries, Uttar Pradesh, India

A pot experiment was conducted to study the effect of 7 intercrops on Cd uptake by maize. The intercrops included cowpea (V. unguiculata (L.) Walp.), purple haricot (L. purpureus (L.) Sweet.), chickpea (C. arietinum L.), alfalfa (M. sativa L.), teosinte (E. mexicana Schrad.), amaranth (A. paniculatus L.) and rape (B. napus L.). The results showed that most legumes substantially increased Cd uptake by maize during vegetative growth. Leaf tissue of maize grown with legumes averaged 5.05 mg kg^?1 higher Cd than that grown with nonlegumes, or 2.42 mg kg^?1 higher than the control. However, the effect of intercrops on Cd uptake by maize became small during reproductive growth. Since chickpea resulted in a relatively large maize bioconcentration factor of 2.0 and large transfer factor of 0.55, it is regarded as the most valuable intercrop for enhancing Cd extraction from soil by maize. The results suggest that intercropping might be a feasible practice in facilitating phytoremediation.     

Gingers of Manipur: diversity and potentials as bioresources

The gingers are well-known for their medicinal and economic significance and occur chiefly in the tropical regions of the world mainly in the Indo-Malaysian area of Asia. From Manipur in northeast India, 33 species under 9 genera have been collected from different parts of the State. Collected specimens were planted in the Experimental Field of the Department of Life Sciences, Manipur University. The morphological details of the various species were worked out. The characteristic features of the specimen, their traditional uses, anti-oxidant compounds present and biological activities are described. The identified genera are Alpinia (3 spp.), Amomum (5 spp.), Boesenbergia (1 sp.), Curcuma (10 spp.), Elettaria (1 sp.), Hedychium (7 spp. and 1 variety), Kaempferia (2 spp.), Roscoea (1 sp.) and Zingiber (3 spp.). Of these, 26 species have been used variously as food (15), traditional medicine (21) and ornamental plants (9) by the ethnic people in their culture. Ten species have been identified to possess various bioactive molecules.     

Mountain oases in northern Oman: An environment for evolution and<Emphasis Type="Italic"> in situ</Emphasis> conservation of plant genetic resources

Several botanical studies have been conducted in different parts of Oman, but knowledge about agro-biodiversity in the rapidly decaying ancient mountain oases of this country remains scarce. To fill this gap we assessed the genetic resources of three mountain oases in the al-Hajar range using a GIS-based field survey and farmer interviews. While arid conditions prevail throughout the mountain range, the different elevations of Balad Seet (950–1020 m a.s.l.), Maqta (930–1180 m a.s.l.) and Al Jabal al Akhdar (1750–1930 m a.s.l.) provide markedly differing agro-climatic conditions. Overall, 107 different crop species were identified belonging to 39 families. Species number was highest among fruits (33 spp.), followed by vegetables (24 spp.). Intensive irrigation allows cultivation of a broad range of species at all oases. However, the number of species varied significantly between sites. Fruit species diversity and homogeneity of distribution of individual fruit species was highest at Balad Seet and lowest at Maqta as indicated by respective Shannon indices of 1.00 and 0.39 and evenness values of 32% and 16%. Century plant (Agave americana L.), faba bean (Vicia faba L. var. minor Peterm. em. Harz) and lentil (Lens culinaris Medik.) were identified as relict crops, supporting oral reports of past cultivation and providing evidence of genetic erosion. Some species, such as the temperate fruits of Al Jabal al Akhdar, were exclusively found at the coolest site, while others only occurred at the hotter locations. Overall greatest species similarity was found between Balad Seet and Al Jabal al Akhdar as indicated by a Sørensen coefficient of similarity of 67%. At all oases a multilayered vegetation structure dominated with a canopy, an understory and a ground layer. Greatest species richness was recorded in the lowest stratum. Overall the study shows a location-specific but surprisingly diverse mosaic of crops in Omani mountain oases which merits further studies and conservation efforts.     

Residual nitrogen effects on wheat following legumes in the southern plains

Increasing nitrogen (N) fertilizer prices give rise to the question of N benefits from legumes in cropping systems in the Southern Great Plains. This study quantified wheat (Triticum aestivium L.) hay production and N uptake over seven years following six years of alfalfa (Medicago sativa L.), cicer milkvetch (Astragalus cicer L.), or grass (Old World bluestem, Bothriochloa ischaemum L.) production in western Oklahoma. Precipitation over the seven years averaged 550 mm·yr^‐1. The major residual N effects were measured within the first five years. On a fine sandy loam soil, wheat hay yields averaged 3,070 kg·ha^‐1·yr^‐1 over five years following alfalfa, 2,580 kg·ha^‐1·yr^‐1 following milkvetch, and 950 kg·ha^‐1·yr^‐1 following grass with N uptake attributed to the residual effect from legumes (calculated by the difference method) averaged 34 kg N ha^‐1·yr^‐1 from alfalfa and 25 kg·ha^‐1·yr^‐1 from milkvetch. On a deep loamy sand soil, wheat hay yields averaged 1,290 kg·ha^‐1·yr^‐1 over five years following alfalfa and 710 kg·ha^‐1·yr^‐1 following grass with N uptake attributed to the residual effect from alfalfa averaged 8 kg N ha^‐1·yr^‐1. Thus, the residual N effect attributed to legumes was substantial on the fine sandy loam soil and relatively small on the deep loamy sand soil.     

冬季覆盖作物对南方稻田水稻生理生化及生长特性的影响

2004～2009年以冬闲-双季稻为对照,对黑麦草-双季稻、紫云英-双季稻、油菜-双季稻和马铃薯-双季稻4种不同冬季覆盖作物稻田水稻植株的生理生化和生长特性进行了研究。结果表明:4种稻田冬季覆盖作物处理均能提高双季稻植株叶片的叶绿素含量和超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性,而丙二醛(MDA)含量除早稻的苗期和分蘖期外,其他生育时期均低于对照;各处理早稻有效穗分别比对照增加18.08万穗·hm-2、21.25万穗·hm-2、12.75万穗·hm-2和17.26万穗·hm-2,结实率分别增加4.98%、8.50%、13.62%和6.99%,千粒重分别增加0.24g、0.10g、0.14g和0.43g,产量分别增加324.44kg·hm-2、381.17kg·hm-2、91.04kg·hm-2和303.46kg·hm-2;各处理晚稻有效穗分别比对照增加9.81万穗·hm-2、11.48万穗·hm-2、5.06万穗·hm-2和14.91万穗·hm-2,结实率分别增加6.29%、8.81%、15.11%和8.50%,千粒重分别增加0.93g、0.88g、0.10g和0.90g,产量分别增加302.28kg·hm-2、316.03kg·hm-2、110.13kg·hm-2和468.17kg·hm-2。该研究显示,在南方双季稻田种植冬季覆盖作物可增强水稻叶片的抗氧化酶活性,促进其生长发育,从而改善水稻的产量及其构成因素,有利于水稻产量的增加。     

Effects of Nitrogen Fertilization on Upland Rice based on Pot Experiments

Abstract

Limited information is available regarding the utilization and loss of fertilizer nitrogen (N) applied to intensively managed upland rice. Effects of N fertilization on upland rice were conducted as N0 (no N applied), N225 (225 kg N · ha^?1), N300 (300 kg N · ha^?1), and N375 (375 kg N · ha^?1) in pot experiments. ¹⁵N‐labeled techniques were used in basal and topdressing N fertilizations. Results showed with the increase of N quantity applied, tiller, panicle numbers per pot, and spikelet number per panicle increased significantly (P<0.05). Chlorophyll b content of N225 and N300 were significantly higher than N0 (P<0.05), and net photosynthetic rate (Pn) of N300 increased significantly compared with N0 and N225. Under basal fertilization, N use efficiency (NUE) of root, stem, leaf, and grain in N300 was the highest. The NUE and loss rate ranged from 23.3% to 30.3% and 62.4% to 73.8%, respectively, under basal fertilization. They varied from 16.5% to 27.5% and 70.7% to 80.4%, respectively, under topdressing fertilization. The highest NUE was observed in N300 under basal fertilization. As increased quantities of N were applied, Pn and biological characteristics improved, thus crop yield of upland rice increased. Grain yield of N300 and N375 were significantly higher than that of N0 and N225 (P<0.01); however, there was no significant difference between them. Therefore, N fertilization with medium applied quantity under basal fertilization will facilitate growing, photosynthesis, and grain yield increase of upland rice.     

Multiple cropping in rainfed upland entisol under different soil management conditions in the sub-humid tropics

Field experiments were conducted for 2 years on a well drained upland sandy loam soil under rainfed conditions to study the effects of previous summer season crops of jute (Corchorus olitorius L.) and direct seeded rice (Oryza sativa L.) in unpuddled and unbunded soil followed by a short duration legume crop (rice bean (Vigna umbellata (Thunb.) Ohwi and Ohashi) for forage or greengram (Vigna radiata (L.) Wilczek) for grains) and fallow on the (i) productivity winter crops of barley (Hordeum vulgare L.), lentil (Lens esculenta Moench), field peas (Pisum sativum L.), linseed (Linum usitatissimum L.), mustard (Brassica juncea (L.) Czern & Coss) and sunflower (Helianthus annuus L.), (ii) soil profile moisture storage and (iii) its utilization. The winter crops were established with minimum (making sowing slots of 5 cm depth with a hand-drawn seed drill and without maintenance of mulch over surface) and conventional (four ploughings up to 15 cm depth with bullock drawn plough) methods of land preparation. The results revealed that compared to jute/fallow and jute/legume sequences, rice/fallow and rice/legume sequences resulted in higher soil moisture storage and, hence, a greater degree of seedling emergence per unit area, higher root weight and water use, and consequent higher grain yields and water use efficiency (WUE) of the subsequent winter crops. Winter crops yielded 17% more following direct seeded rice than after jute. Growing of short duration legume (rice bean or greengram) after jute or rice depleted stored moisture but increased yield and WUE of all winter crops.Grain yields of winter crops were 19% higher in tilled than in untilled soils. Under conventional tillage the soil moisture was slightly reduced at the time of sowing of winter crops but it resulted in increments in root weight, water use, grain yields and WUE of winter crops. WUE of barley was highest followed by field peas, which utilized more of soil moisture conserved at lower soil depths than other crops. Mustard gave the highest return (Rs.4663) followed by field peas (Rs.4603).     

Analysis of the biodiversity of hawthorn (<Emphasis Type="Italic">Crataegus</Emphasis> spp.) from the morphological,molecular, and ethnobotanical approaches,and implications for genetic resource conservation in scenery of increasing cultivation: the case of Mexico

One hundred and forty Mexican hawthorn (Crataegus spp.) accessions from six regions are preserved at the BGT-UACH germplasm bank (Mexico), comprising the most comprehensive living collection of Mexican hawthorns with different degrees of human management. The objective of this study was to assess the biodiversity of this valuable collection from morphological, molecular (microsatellite), and ethnobotanical viewpoints in order to delineate the most adequate strategy for the conservation of the native hawthorn germplasm in the present scenario of incipient establishment of commercial hawthorn plantations, which is likely to increase. Molecular characterisation revealed that the biodiversity was chiefly (90%) placed within the regions. Morphological characterisation indicated that the group from Chiapas was the most different germplasm pool compared with the other five. This was confirmed by molecular analysis, because in spite of the lack of a phylogeographical pattern, two germplasm pools were detected: one composed mainly by accessions from Chiapas and the other mainly by accessions from the other regions. The only clear differences among the regions in the ethnobotanical study were those derived from putting hawthorns into commercial cultivation, which occurred in just one region in the centre of the country (Mexico–Puebla–Tlaxcala). As a consequence, an ex situ conservation programme is necessary for those regions shifting patterns of cultivation from traditional to commercial, regardless of whether other on-farm programmes are also implemented. The germplasm collections within each region must be exhaustive due to their high genetic diversity.     

Nutritional Status of Mediterranean Trees Growing in a Contaminated and Remediated Area

Soil contamination may contribute to forest decline, by altering nutrient cycling and acquisition by plants. This may hamper the establishment of a woody plant cover in contaminated areas, thus limiting the success of a restoration program. We studied the nutritional status of planted saplings of Holm oak (Quercus ilex subsp. ballota (Desf.) Samp.), white poplar (Populus alba L.), and wild olive tree (Olea europaea var. sylvestris Brot.) in the Guadiamar Green Corridor (SW Spain) and compared it with established adult trees. Soils in this area were affected by a mine-spill in 1998 and a subsequent restoration program. The spill resulted in soil acidification, due to pyrite oxidation, and deposited high concentrations of some trace elements. In some sites, we detected a phosphorus deficiency in the leaves of Q. ilex and O. europaea saplings, as indicated by a high N:P ratio (>16). For O. europaea, soil contamination explained 40% of the variability in leaf P and was negatively related to chlorophyll content. Soil pH was a significant factor predicting the variability of several nutrients, including Mg, P, and S. The uptake of Mg and S by P. alba was greater in acidic soils. The monitoring of soil pH is recommended since long-term effects of soil acidification may negatively affect the nutritional status of the trees.     

二甲基二硫熏蒸对保护地连作土壤微生物群落的影响

随着保护地高附加值经济作物的连年栽培, 土传病害问题愈发突出, 熏蒸剂也因此得以更广泛的应用。但鉴于熏蒸剂的广谱性, 在杀死有害生物的同时, 不可避免地对非靶标生物产生一定的影响。为明确溴甲烷替代药剂二甲基二硫(dimethyl disulfide, 简称DMDS)熏蒸对土壤微生物群落的影响, 本研究在室内条件下采用BIOLOG 方法, 测定不同浓度DMDS 熏蒸对保护地连作土壤微生物群落的影响。研究结果表明: 不同浓度DMDS(170.00 mg·kg^-1、85.20 mg·kg^-1、42.50 mg·kg^-1、21.30 mg·kg^-1 和10.62 mg·kg^-1)熏蒸处理对镰孢菌属(Fusarium spp.)和疫霉菌属(Phytophthora spp.)的LC₅₀(抑制中浓度)分别为42.08 mg·kg^-1 和115.15 mg·kg^-1。DMDS 熏蒸后恢复培养0 d 取样, 温育120 h 时, 170.00 mg·kg^-1、42.50 mg·kg^-1 和10.62 mg·kg^-1 的DMDS 处理土壤的AWCD 值(平均每孔颜色变化率, average well-color development, AWCD)分别比空白对照升高8.46%、6.02%、19.31%, 表明DMDS 促进了土壤微生物的生长。恢复培养14 d 后, 各处理土壤微生物的AWCD 值恢复至对照水平。多样性指数分析显示, DMDS 熏蒸后恢复培养0 d 时, 土壤微生物群落的Shannon 指数、Simpson指数均高于空白对照, McIntosh 指数与对照无显著性差异; 恢复培养7 d 后, Shannon 指数与Simpson 指数恢复至对照水平。主成分分析结果显示, DMDS 熏蒸后恢复培养0 d 时, 各处理间微生物对碳源的利用方式差异显著, 恢复培养14 d 后, DMDS 对微生物碳源利用方式的影响逐渐减弱, 恢复至对照水平。结果表明, DMDS 熏蒸处理对土壤微生物的生长具有促进作用, 影响了微生物对碳源的利用方式, 但在恢复培养14 d 后, 被干扰的土壤微生物逐渐恢复至对照水平。DMDS 熏蒸处理在有效防控土传病原真菌的同时, 不会对土壤微生物群落产生明显的扰动影响, 对环境较安全。     

沙棘林退化对土壤性质及水土流失的影响

辽宁省建平县有亚洲最大的人工沙棘(Hippophae rhamnoides Linn.)林,对防治当地水土流失具有重要的作用。然而由于多种原因,该区沙棘林呈现大面积死亡的现象。通过样地调查沙棘林的死亡程度,并进行土壤理化性质和水土流失的测定,研究了沙棘林退化对土壤性状和水土流失量的影响。结果表明,随着沙棘活立木数量的减少,土壤容重增加1.40%~7.31%,有机碳含量和全氮含量分别降低7.81%~21.89%和9.33%~27.65%,说明沙棘林退化对土壤结构和养分产生显著的破坏作用。人工模拟降雨试验表明,纯沙棘林地的水土流失较轻,侵蚀模数为539t/(a·km2)。随着沙棘死亡率的提高,水土流失逐步加剧,入侵树种榆树纯林(Vlmus pumila)地达到1 526t/(a·km2)。土壤性质的恶化和水土流失的加剧,会对土壤有机质和土壤结构进一步破坏,使沙棘死亡速度加快,从而形成恶性循环。     

Effects of tree identity dominate over tree diversity on the soil microbial community structure

This study investigated the possible effects of tree species diversity and identity on the soil microbial community in a species-rich temperate broad-leaved forest. For the first time, we separated the effects of tree identity and tree species diversity on the link between above and belowground communities in a near-natural forest. We established 100 tree clusters consisting of each three tree individuals represented by beech (Fagus sylvatica L.), ash (Fraxinus excelsior L.), hornbeam (Carpinus betulus L.), maple (Acer pseudoplatanus L.), or lime (Tilia spec.) at two different sites in the Hainich National Park (Thuringia, Germany). The tree clusters included one, two or three species forming a diversity gradient. We investigated the microbial community structure, using phospholipid fatty acid (PLFA) profiles, in mineral soil samples (0–10 cm) collected in the centre of each cluster.The lowest total PLFA amounts were found in the pure beech clusters (79.0 ± 23.5 nmol g⁻¹ soil dw), the highest PLFA amounts existed in the pure ash clusters (287.3 ± 211.3 nmol g⁻¹ soil dw). Using principle components analyses (PCA) and redundancy analyses (RDA), we found only for the variables ‘relative proportion of beech trees’ and ‘living lime fine root tips associated with ectomycorrhiza’ a significant effect on the PLFA composition. The microbial community structure was mainly determined by abiotic environmental parameters such as soil pH or clay content. The different species richness levels in the clusters did not significantly differ in their total PLFA amounts and their PLFA composition. We observed a tendency that the PLFA profiles of the microbial communities in more tree species-rich clusters were less influenced by individual PLFAs (more homogenous) than those from species-poor clusters.We concluded that tree species identity and site conditions were more important factors determining the soil microbial community structure than tree species diversity per se.     

Soil organic carbon stock for reclaimed minesoils in northeastern Ohio

Reclamation of disturbed soils is done with the primary objective of restoring the land for agronomic or forestry land use. Reclamation followed by sustainable management can restore the depleted soil organic carbon (SOC) stock over time. This study was designed to assess SOC stocks of reclaimed and undisturbed minesoils under different cropping systems in Dover Township, Tuscarawas County, Ohio (40°32·33′ N and 81°33·86′ W). Prior to reclamation, the soil was classified as Bethesda Soil Series (loamy‐skeletal, mixed, acid, mesic Typic Udorthent). The reclaimed and unmined sites were located side by side and were under forage (fescue—Festuca arundinacea Schreb. and alfa grass—Stipa tenacissima L.), and corn (Zea mays L.)—soybean (Glycine max (L.) Merr.) rotation. All fields were chisel plowed annually except unmined forage, and fertilized only when planted to corn. The manure was mostly applied on unmined fields planted to corn, and reclaimed fields planted to forage and corn. The variability in soil properties (i.e., soil bulk density, pH and soil organic carbon stock) ranged from moderate to low across all land uses in both reclaimed and unmined fields for 0–10 and 10–20 cm depths. The soil nitrogen stock ranged from low to moderate for unmined fields and moderate to high in some reclaimed fields. Soil pH was always less than 6·7 in both reclaimed and unmined fields. The mean soil bulk density was consistently lower in unmined (1·27 mg m⁻³ and 1·22 mg m⁻³) than reclaimed fields (1·39 mg m⁻³ and 1·34 mg m⁻³) planted to forage and corn, respectively. The SOC and total nitrogen (TN) concentrations were higher for reclaimed forage (33·30 g kg⁻¹; 3·23 g kg⁻¹) and cornfields (21·22 g kg⁻¹; 3·66 g kg⁻¹) than unmined forage (17·47 g kg⁻¹; 1·98 g kg⁻¹) and cornfield (17·70 g kg⁻¹; 2·76 g kg⁻¹). The SOC stocks in unmined soils did not differ among forage, corn or soybean fields but did so in reclaimed soils for 0–10 cm depth. The SOC stock for reclaimed forage (39·6 mg ha⁻¹ for 0–10 cm and 28·6 mg ha⁻¹ for 10–20 cm depths) and cornfields (28·3 mg ha⁻¹; 32·2 mg ha⁻¹) were higher than that for the unmined forage (22·7 mg ha⁻¹; 17·6 mg ha⁻¹) and corn (21·5 mg ha⁻¹; 26·8 mg ha⁻¹) fields for both depths. These results showed that the manure application increased SOC stocks in soil. Overall this study showed that if the reclamation is done properly, there is a large potential for SOC sequestration in reclaimed soils. Copyright © 2005 John Wiley & Sons, Ltd.     

Production,oxidation, emission and consumption of methane by soils: A review

Methane emission by soils results from antagonistic but correlated microbial activities. Methane is produced in the anaerobic zones of submerged soils by methanogens and is oxidised into CO₂ by methanotrophs in the aerobic zones of wetland soils and in upland soils. Methanogens and methanotrophs are ubiquitous in soils where they remain viable under unfavourable conditions. Methane transfer from the soil to the atmosphere occurs mostly through the aerenchyma of aquatic plants, but also by diffusion and as bubbles escaping from wetland soils. Methane sources are mainly wetlands. However 60 to more than 90 % of CH₄ produced in the anaerobic zones of wetlands is reoxidised in their aerobic zones (rhizosphere and oxidised soil-water interface). Methane consumption occurs in most soils and exhibits a broad range of values. Highest consumption rates or potentials are observed in soils where methanogenesis is or has been effective and where CH₄ concentration is or has been much higher than in the atmosphere (ricefields, swamps, landfills, etc.). Aerobic soils consume atmospheric CH₄ but their activities are very low and the micro-organisms involved are largely unknown. Methane emissions by cultivated or natural wetlands are expressed in mg CH₄·m^–2·h^–1 with a median lower than 10 mg CH₄·m^–2·h^–1. Methanotrophy in wetlands is most often expressed with the same unit. Methane oxidation by aerobic upland soils is rarely higher than 0.1 mg CH₄·m^–2·h^–1. Forest soils are the most active, followed by grasslands and cultivated soils. Factors that favour CH₄ emission from cultivated wetlands are mostly submersion and organic matter addition. Intermittent drainage and utilisation of the sulphate forms of N-fertilisers reduce CH₄ emission. Methane oxidation potential of upland soils is reduced by cultivation, especially by ammonium N-fertiliser application.     

Differences in soil organic carbon stocks and fraction distributions between rice paddies and upland cropping systems in China

Purpose

A large body of research suggests that rice (Oryza sativa L.) cropping facilitates soil organic carbon (SOC) storage, while the stability of the sequestered carbon is still not well understood. The objective of this study was to determine the differences in SOC stocks and fraction distributions between rice paddies and upland cropping fields and their variation in different rice cropping areas.

Materials and methods

Data from the national soil survey were analyzed to assess the differences in SOC contents between paddy and upland cropping fields at the regional scale. In addition, three pairs of rice and upland cropping systems were selected in Heilongjiang [single rice vs. single corn (Zea mays L.) cropping], Jiangsu [rice-wheat (Triticum aestivum L.) vs. corn-wheat cropping], and Jiangxi (double rice vs. double corn cropping) provinces, representing the major cropping patterns in China. Physical fractionation techniques were used to investigate the differences in SOC stocks and distribution among different pools between rice-based cropping systems and non-rice cropping systems in China.

Results and discussion

SOC concentrations were, on average, 74.9% higher at the regional scale and 56.8% higher at the field scale in paddy than in upland cropping fields. Carbon proportion of particulate organic matter within microaggregates increased from 14.4% in upland cropping soils to 25.3% in paddy soils at the Heilongjiang site and from 12.4 to 25.5% at the Jiangxi site. Meanwhile, the free silt and clay-associated carbon was significantly greater in paddy than in upland cropping soils at the both sites. Nevertheless, SOC distribution did not markedly differ between paddy and upland cropping fields at the Jiangsu site where rice was rotated with winter wheat annually.

Conclusions

As compared to upland cropping or rice-upland crop rotation, continuous rice cropping, such as single and double rice cropping, could favor SOC stabilization by occlusion within microaggregates and adsorption to the silt and clay outside microaggregates, which may promote the long-term storage of SOC in paddies.     

The Dynamics of Macroinvertebrate Assemblages in Response to Environmental Change in Four Basins of the Etueffont Landfill Leachate (Belfort, France)

We investigated the relationships between the composition and structure of macroinvertebrate communities and some environmental variables over a year in four basins of the Etueffont landfill leachate (Belfort, France) using co-inertia analysis. Culicidae larvae were the dominant macroinvertebrate group in the studied basins, contributing to 87% of the total zoobenthos density, followed by Corixidae (8.8%), Chironomids (2.5%) and other larvae (each <1%). The lowest density of chironomid larvae was recorded in the first basin which is used as a discharge system for the leachate produced by the landfill. In basin 4, however, the Baetidae, Orthocladiinae (Orthocladius spp., Chaetocladius spp. and Isocladius spp.) and Tanypodinae (Psectrotanypus spp.) developed favoured by low levels in ammonia, COD, BOD, EC, metals and high oxygen concentrations. The co-inertia analysis illustrated both temporal and spatial variabilities in the basins and revealed a strong relationship between environmental conditions and benthic macroinvertebrates assemblages. This ordination technique showed that the chironomid community structure might be used successfully to differentiate between sites with different levels and types of pollution.     

Distribution and stand characteristics of relict populations of Mexican beech (Fagus grandifolia var. mexicana)

Fagus grandifolia var. mexicana (Mexican beech) is limited to about 10 populations (2-35 ha) in the Sierra Madre Oriental, Mexico. The objectives were to assess the current status and distribution of beech by surveying five sites. Species richness varied between three to 27 tree species in the canopy, and from nine to 29 species in the understorey. Basal area of trees?5 cm dbh varied between 27.87 and 70.98 m² ha⁻¹, and density from 370 to 1290 individual ha⁻¹. Beech represented 22-99.6% of total basal area, and 6.8-83.3% of total density. Beech dominance varied from monodominant to codominance with Carpinus caroliniana, Quercus spp., Liquidambar styraciflua, Magnolia schiedeana, and Podocarpus spp. Beech total population size ranged from 180 to 6300 trees with a total of less than 1300 individuals in four sites. Anthropogenic disturbance remains a major threat to these forests. It is uncertain whether Mexican beech will be able to survive without conservation efforts.