Similarity between the soil seed bank and the standing vegetation in the Strandveld Succulent Karoo,South Africa

The similarity in species composition and abundance between the soil seed bank and its associated vegetation was studied in six vegetation units of the Strandveld Succulent Karoo, South Africa. A total of 103 taxa were recorded in the vegetation, of which 34 taxa were also present in the seed bank. Five taxa were unique to the soil seed bank. In general, the taxa most abundant in the vegetation were also recorded in the seed bank and vice versa. Mean seed bank density varied between different plant types. Perennial taxa were most abundant in the vegetation, while annual taxa were most abundant in the seed bank. Annual taxa (excluding grasses) yielded the highest similarity between vegetation and seed bank (67ċ9 per cent), while that of perennial (excluding grasses) and grass taxa were 34ċ2 per cent and 40ċ0 per cent respectively. An overall similarity of 47ċ0 per cent between the seed bank and its associated vegetation was obtained for this part of the Strandveld Succulent Karoo. The seed bank of the study site will be a good source of future annual vegetation, but not of perennial vegetation. Topsoil replacement, sowing and transplanting of selected species will be essential for the success of post‐mining revegetation efforts following complete destruction of the existing vegetation. Annual species may be recruited from the soil stored seed bank, while many perennial species will have to be reintroduced by means of sowing and/or transplanting. Copyright © 2003 John Wiley & Sons, Ltd.     

Three hydro‐seeding revegetation techniques for soil erosion control on anthropic steep slopes

Erosion control at low–medium radioactive waste disposal sites is an important concern. A study was carried out in El Cabril (Córdoba, Spain) on two 40 per cent anthropic steep slopes in order to test the effectiveness of hydro‐seeding techniques for controlling soil erosion. Two groups of 10 m × 3 m plots were established. The treatments tested were: hydro‐seeding with the application of vegetal mulch (VM); hydro‐seeding with added humic acids (HA); hydro‐seeding with vegetal mulch and humic acids added (VM + HA); and a control without hydro‐seeding or soil amendment (C). Fifteen run‐off producing rainfall events were recorded during the study period, with intensities ranging between 2 mm h⁻¹ and 33·6 mm h⁻¹. All treatments significantly reduced runoff and soil loss (p < 0·05). The VM+HA treatment was the most effective, reducing 98·5 per cent of total soil loss. The HA treatment (97·1 per cent reduction) was also more effective than the VM treatment (94·8 per cent reduction). A great reduction in runoff and sediment yield was observed in the treated plots during the first stages after hydro‐seeding. This result may be attributed to the combined effect of: (a) the protection against raindrop impact due to the application of straw and mulch to the soil surface, and (b) a general improvement in the soil's structure brought by the organic amendments. Seven months after hydro‐seeding, an increase in the density of the plant cover could be added to the beneficial effects mentioned above. Copyright © 2000 John Wiley & Sons, Ltd.     

Metal contamination from open-cast copper and sulphur mining in southeast Ireland

The metal content was determined in soil and vegetation around the eastern zone of the disused sulphur and copper mines at Avoca (southeast Ireland). A 250 m × 250 m grid survey was conducted covering a total area of 4 km². The mining belt was in the centre of the investigated site and was sampled separately. Iron, Zn, Cu and Cd concentrations in soil and plant material were determined, in addition to soil organic matter content and soil pH. Soil samples taken from the spoil showed elevated Cu and Cd concentrations, and low soil pH and organic matter content. At least 50 per cent of the agricultural sites examined around the East Avoca Mine showed elevated soil Cu and Cd concentrations, whereas Zn and Fe soil concentrations were within the range for unpolluted soils. None of the vegetation analysed had elevated Zn, Cd, Fe or Cu concentrations. Overall there was no indication of serious metal contamination in either soils or vegetation surrounding the mine in spite of extensive dust deposition during open-pit mining activity 15–30 years ago. However, a plume of elevated Cu in the soil was identified, which originated from a large spoil heap and had been spread for some 2·0 km by the prevailing wind.     

Phytosociology of Sinharaja—A contribution to rain forest conservation in Sri Lanka

The structure and floristic composition of the vegetation over 30 cm girth at breast height (gbh) in five relatively undisturbed forest sites, each 5 ha in extent, in the Sinharaja International Man and Biosphere rain forest reserve investigated reveal a similarity in their (a) mean density of individuals (594–769) per ha, (b) basal area (36·0–41·6 m²) per ha and vertical distribution of individuals. The 17 427 individuals enumerated were identified into 211 species, 119 genera and 43 families. Contribution of endemic species to density, basal area and floristic richness in terms of total species complement ranged between 75–93%, 87–93% and 64–75% respectively.Clusiaceae [Improtance Value Index (IVI) = 27·3–78·1] and Dipterocarpaceae (IVI = 39·9–50·3) were the two most dominant families in this forest. Based on height attained by mature individuals of a species, 59 canopy, 49 subcanopy and 103 understorey tree species were discerned. In all except sample site 2, Garcinia hermonii (Clusiaceae) followed by Xylopia championii (Annonaceae) dominated the understorey tree stratum, but in the subcanopy and canopy the dominants were more diverse.Of the 211 species recorded, 40% had population densities of 10 individuals or less per 25 ha and 43% were restricted either to one or two sites sampled. These species, particularly the endemics among them, may be considered vulnerable species and further encroachments into the reserve will jeopardise their survival. Even for those endemics once widespread in the lowland wet zone of the island, Sinharaja has now become the last refugium as most of their habitats have been modified, leaving a mere 9% of the wet zone land area under natural forest cover. This too, is fragmented and inadequately protected. Conserving Sinharaja in its entirety is therefore all the more important and is highlighted in this phytosociological survey.     

Vegetation diversity of the Brand-se-Baai coastal dune area,west coast,South Africa: a pre-mining benchmark survey for rehabilitation

Prior to the mining of heavy minerals, the vegetation diversity of the Brand-se-Baai coastal area was investigated to serve as a benchmark for the future rehabilitation of the area. The vegetation was surveyed using the Braun–Blanquet procedure to classify the different plant communities. Six plant communities, some of which include several variants, were identified, described and mapped. A revegetation goal of 30 per cent, rather than 60 per cent, of the number of plant species present prior to mining are recommended. Copyright © 1999 John Wiley & Sons, Ltd.     

Secondary succession and resource use in tropical fallows: A case study from the Coromandel Coast of South India

Agricultural fallows, village commons and degraded forests, serve as important common community property resources throughout India, but due to their degraded status they are considered as ‘wastelands’, having little economic value and poor biodiversity. A study on secondary succession was conducted in agricultural fallows around Puducherry, India to review the negative image of ‘wastelands’. Chronosequences of four sites aged 2, 4, 10 and 50 years were used to investigate change in species composition and abundance, convergence with a nearby forest and to examine their economic use. A comparison of life‐forms, species richness and diversity indices showed that herbaceous species dominated up to 10th year sere, from which point in succession, woody species became more common. It was in the 50th year sere that shrubs and secondary tree species occurring in nucleated clumps became dominant. A cluster analysis based on Bray–Curtis similarity index shows a sequential development of vegetation through time, though 50th year plots showed no convergence with the Tropical dry evergreen forest (TDEF), but the principal component analysis demonstrates a change in community structure from grasslands to shrub and secondary tree species' dominance. Presence of adults of five primary forest species found in the clumps indicates a fast rate of secondary succession, considering that grazing and resource removal occurred in the sites. The potential value of the ‘wastelands’ is evident from the fact that 64 per cent of recorded species have economic use, which underlines the need for their sustainable utilization for better management of bioresources rather than converting them into monocultures. Copyright © 2008 John Wiley & Sons, Ltd.     

Land degradation factors in arid irrigated areas: the case of Wafra in Kuwait

A large area in Wafra, south of Kuwait, was developed for crop production both in open fields and agriculture units. For more than a decade, farmers had been using groundwater and desalinated water for irrigating crops under both conditions. The study area occupied about 125 000 ha lying within the northwestern sandbelt. Land-use pattern, soil characteristics and vegetation attributes were studied to assess the extent of land degradation in the area. Land-use classes in the developed area showed a total area of about 9371 ha. About 35 per cent of this area was uncultivated due to sand encroachment and soil salinity build-up problems. Soil chemical and physical properties were described and determined at various depths in representative profiles. The soil belonged to the three categories: Typic Torripsamments, Typic Haplocalcids and Typic Aquisalids. The total vegetative cover was poor, covering about 18 per cent of the marginal areas and about 33 per cent of arable lands. Plant community type was altered from Rhanterium epapposum to Cyperus conglomeratus and Stipagrostis plumosa. Annual forbs dominated species composition. Results of the study indicated that land degradation occurred both in marginal and arable areas. To expand in the Wafra agricultural area and to increase productivity potential of the existing farms, implementation of irrigation and drainage systems as well as projects to combat sand encroachment are recommended. © 1998 John Wiley & Sons, Ltd.     

The effect of land management on carbon and nitrogen status in plants and soils of alpine meadows on the Tibetan plateau

Large‐scale grassland rehabilitation has been carried out on the severely degraded lands of the Tibetan plateau. The grasslands created provide a useful model for evaluating the recovery of ecosystem properties. The purposes of this research were: (1) to examine the relative influence of various rehabilitation practices on carbon and nitrogen in plants and soils in early secondary succession; and (2) to evaluate the degree to which severely degraded grassland altered plant and soil properties relative to the non‐disturbed native community. The results showed: (1) The aboveground tissue C and N content in the control were 105·97 g m⁻² and 3·356 g m⁻², respectively. The aboveground tissue C content in the mixed seed treatment, the single seed treatment, the natural recovery treatment and the severely degraded treatment was 137 per cent, 98 per cent, 49 per cent and 38 per cent, respectively, of that in the control. The corresponding aboveground tissue N content was 109 per cent, 84 per cent, 60 per cent and 47 per cent, respectively, of that in the control. (2) Root C and N content in 0–20 cm depths of the control had an average 1606 g m⁻² and 30·36 g m⁻², respectively. Root C and N content in the rehabilitation treatments were in the range of 26–36 per cent and 35–53 per cent, while those in the severely degraded treatment were only 17 per cent and 26 per cent of that in the control. (3) In the control the average soil C and N content at 0–20 cm was 11 307 g m⁻² and 846 g m⁻², respectively. Soil C content in the uppermost 20 cm in the seeded treatments, the natural recovery treatment and the severely degraded treatment was 67 per cent, 73 per cent and 57 per cent, respectively, while soil N content in the uppermost 20 cm was 72 per cent, 82 per cent and 79 per cent, respectively, of that in the control. The severely degraded land was a major C source. Restoring the severely degraded lands to perennial vegetation was an alternative approach to sequestering C in former degraded systems. N was a limiting factor in seeding grassland. It is necessary for sustainable utilization of seeding grassland to supply extra N fertilizer to the soil or to add legume species into the seed mix. Copyright © 2005 John Wiley & Sons, Ltd.     

Development options of natural habitats in a post‐mining landscape

Rehabilitation of the post‐mining landscape of Lower Lusatia (Brandenburg, Germany) represents a complex problem: 85 per cent of this area is currently being recultivated for forests or agriculture and 15 per cent is reserved for nature development. After mining, soil conditions are dry, acidic and nutrient poor. The ‘LENAB’ project aimed at conservation strategies and management options for natural habitats. Two competing basic motives of nature conservation on a small or medium scale were defined: (1) close‐to‐naturalness (allowing natural dynamics to take place without human interference) and (2) biodiversity (selective species and habitat protection). An overall strategy for sustainability of a cultural landscape can only be applied to the entire post‐mining landscape. The application of the two basic motives leads to different management options; this is illustrated by two important vegetation types. Copyright © 2000 John Wiley & Sons, Ltd.     

LAND USE CHANGES EFFECT ON FLORISTIC COMPOSITION,DIVERSITY AND SURFACE OCCUPIED BY ERICA CILIARIS AND ERICA TETRALIX HEATHLANDS OF NW SPAIN

The extent of heathland decline is well documented in countries of the north and west of Europe, not so in southern European countries. In this paper, temporal changes produced in wet heathlands of Erica ciliaris and Erica tetralix in the last 26 years in NW Spain were analysed. Thirteen wet heathlands that had been studied in 1980 were again sampled in 2006. Plant species composition, cover, diversity, surface area occupied and soil pH were analysed in each sampling site. The results obtained showed changes in the management of almost all the sampling sites and in their surrounding area, with an increase in non‐traditional practices (afforestation, repeated burning) with respect to 1980, resulting in a general decrease in the surface area occupied by these communities. A decrease of the woody cover and, as a result, an increase in the herbaceous cover was observed. Species richness did not show significant changes, but the identity of the species changed, with 73·9 per cent of the exclusive species of these communities declining or disappearing in favour of non‐exclusive species. The pH values remained within the normal ranges for these communities, although a slight decrease was recorded. It was concluded that traditional management (cutting, grazing, sporadic burning) favoured the conservation of these ecosystems, with non‐severe effects on the vegetation, and this should be noted by conservation planners. Management of the surrounding area should also be controlled to enhance preservation of these landscapes. Copyright © 2012 John Wiley & Sons, Ltd.     

Soil quality indices for evaluation of long‐term land use and soil management practices in semi‐arid sub‐tropical India

Land use changes and soil management can potentially alter soil quality. A study was conducted to assess the long‐term (>20 years) effects of perennial trees (PT), vegetable crops (VC), rice–wheat (RW) system, sewage‐irrigated fields (SF), maize–wheat (MW) system and uncultivated soils (US) on soil quality. Soil physical quality parameters were significantly affected only in the SF system when compared with the US soil, particularly for bulk density (BD 1·51 Mg m⁻³ in SF vs. 1·34 in US). Among chemical parameters, electrical conductivity was high in SF, and soil nutrients (N, P, K, S, Zn, Fe, Cu and Mn) were well above the critical limits of deficiency in all the systems. Soil parameters were integrated into soil quality indices (SQIs) by unscreened transformation and principal component analysis (PCA). SQI observed under each system were compared with the US to assess the degree of degradation. Mean SQI differences showed that PT (+16·02 per cent), VC (+4·80 per cent), RW (+10·04 per cent), and MW (+11·30 per cent) are aggrading, whereas SF (−2·06 per cent) is degrading with respect to the reference soil (US). Adoption of MW system proved to be better than traditional RW; and in general agricultural crops have a significant advantage than VC, in terms of maintaining soil quality. Sewage irrigation is not a sustainable practice and long‐term use may degrade the soil. Among the SQIs, PCA with nonlinear scoring function (NLSF) based SQI was effective in judging land degradation due to soil quality changes as affected by long‐term land use and soil management practices. Copyright © 2008 John Wiley & Sons, Ltd.     

Deforestation effects on soil degradation and rehabilitation in western Nigeria. IV. Hydrology and water quality

Hydrological and water-quality measurements were made on a 44·3 ha watershed under forest cover and following deforestation and conversion to an agricultural land-use. Under secondary tropical rainforest, water yield ranged from 2·2 per cent to 3·1 per cent of annual rainfall. Deforestation of 7 per cent of the watershed area increased water yield to 7·0 per cent of annual rainfall. Baseflow increased with deforestation, and increased progressively with time after deforestation. It was 5·1 per cent of annual rainfall in 1979, 15·1 per cent in 1980, 16·4 per cent in 1981 and 17·9 per cent in 1982. In comparison, surface flow was 4·5 per cent in 1979 and 6·2 per cent in 1980, but decreased to 2·3 per cent in 1981 and 2·4 per cent in 1982. Total water yield following deforestation and conversion to agricultural land-use ranged from 9·6 per cent to 21·3 per cent of the annual rainfall received. The dry season flow decreased with time as the dry season progressed, but increased over the years following deforestation. Surface runoff during the rainy season depended on ground cover and soil quality. The extent and severity of soil degradation affected the dynamics of surface flow. Because of actively growing crops, plant nutrient concentrations in surface runoff were low. Forested lysimeters had higher seepage losses than cropped lysimeters, and the water-use efficiency was 1·9–3·6 kg ha⁻¹ mm⁻¹ for cowpeas compared with 6·1–11·0 kg ha⁻¹ mm⁻¹ for maize. The delivery ratio was high immediately after deforestation and decreased to a steady value of about 3·2 per cent within 7 years. The data show five distinct phases of soil degradation in relation to generation of surface runoff. © 1997 John Wiley & Sons, Ltd.     

The relative efficiency of four representative cropland conversions in reducing water erosion: evidence from long‐term plots in the Loess hilly area,China

Large areas of traditional slope cropland were recently converted to other land‐use types in the semiarid Loess Plateau of China. In this study, we selected four representative conversion options of slope croplands, i.e., pastureland rotated with cropland (cultivated with Medicago sativa L. and rotated with Triticum aestivum L.), shrubland and woodland (afforested with Hippophae rhamnoides L. and Pinus tabulaeformis), and grassland (native herbage Stipa breviflora) to study the effect of land‐use conversion by comparing with traditional cropland. Compared with slope cropland, the relative effects of different conversion options on surface runoff and soil erosion were assessed over a 14‐year measurement period. Observations showed that distinct features and consequences of vegetation succession were found among the conversion options. Plots of shrubland had the highest vegetation coverage with dense undergrowth; natural herbaceous and subshrub species gradually spread into plots of grassland resulting in higher vegetation cover. Neither bushes nor herbs colonized the plots of Pinus tabulaeformis, which resulted in a higher percentage of bare soil. Significant differences in runoff generation, sediment yield and conservation efficiencies among the selected conversion options were detected through an analyses of variance (ANOVA). Compared with cropland, total runoff and sediment decreased by 65 per cent and 95 per cent in shrubland, 41 per cent and 92·5 per cent in grassland, 18 per cent and 77 per cent in woodland, and 12 per cent and 58 per cent in pastureland, respectively. The ranking of soil and water conservation efficiencies was shrubland > grassland > woodland > pastureland > cropland. Based on the effectiveness of soil and water conservation, shrubland and grassland are highly recommended as promising options for cropland conversion projects. However, pastureland and woodland are not suggested as potential options for slope‐cropland conversion because of low soil and water conservation in the long term. Copyright © 2006 John Wiley & Sons, Ltd.     

Subsurface drainage for reversing degradation of waterlogged saline lands

In irrigated agriculture of arid and semiarid regions waterlogging coupled with salinity is a serious problem. Experimental evidence at several locations has led to the realization that subsurface drainage is an essential intervention to reverse the processes of land degradation responsible for the formation of waterlogged saline lands. This paper presents the results of a study conducted from 1995 to 2000 to evaluate the impacts of subsurface drainage on soil properties, groundwater‐table behaviour and crop productivity in a waterlogged saline area of 2200 ha. A subsurface drainage system was installed at 1·6 m depth with 60 m drain spacing covering an area of 1200 ha (23 blocks) during 1997–99 and compared with an undrained block of 1000 ha. Subsurface drainage facilitated the reclamation of waterlogged saline lands and a decrease in the soil salinity (EC_e, dS m⁻¹) that ranged from 16·0 to 66·3 per cent in different blocks. On average, 35·7 per cent decrease in salt content was observed when compared with the initial value. Provision of subsurface drainage controlled the water‐table below the root zone during the monsoon season and helped in bringing the soil to optimum moisture content for the sowing of winter crops. In the drained area, the increase in yields of different crops ranged from 18·8 to 27·6 per cent. However, in the undrained area the yield of different crops decreased due to the increased waterlogging and soil salinity problems. Overall the results indicated that investment in subsurface drainage is a viable option for reversing the land degradation of waterlogged saline lands in a monsoon climate. Copyright © 2006 John Wiley & Sons, Ltd.     

黄土丘陵沟壑区红砂灌丛土壤种子库及其自然更新潜力评估

[目的]对黄土丘陵沟壑区红砂灌丛植被土壤种子库的特征及红砂灌丛植被自然更新潜力进行分析和评估,以说明红砂灌丛土壤种子库在植被恢复与重建中的重要作用。[方法]采用土壤种子库"萌发法"(每个地段10个2m×2m样方内分表土层0—2cm和2—5cm土层采集土样)及野外植被调查方法,对黄土丘陵沟壑不同坡位红砂灌丛土壤种子库进行研究。[结果]黄土丘陵沟壑区红砂灌丛植被土壤种子库发芽试验共观察到的4 251株幼苗,分属于9个物种。土壤种子库密度在100~1 000粒/m2,物种数在0.8~1.2种/0.01m2,下坡段的土壤种子库平均种子密度和平均物种数均比上坡段高。3个坡段的2个层次的平均种子密度和平均物种数均随土层加深而减小。3个坡段土壤种子库和地上植被的组成物种多为草本植物和红砂灌丛,地上植被与其土壤种子库的密度及物种数均呈不显著相关;物种组成的Sorensen相似性指数较高,均达到0.60以上,且土壤种子库比地上植被具有更高的物种丰富度。[结论]黄土丘陵沟壑区红砂灌丛具有依靠土壤种子库实现自然更新的潜力,但由于物种组成种类较少,现存灌丛植被一旦遭到破坏,仅靠土壤种子库恢复现存植被是困难的,需要在对自然恢复潜力评估的基础上,积极采取人工保护促进自然恢复的策略。     

Improved fallow with pigeon pea for soil fertility improvement and to increase maize production in a smallholder crop–livestock farming system in the subhumid zone of Ghana

Pigeon pea is cultivated by most smallholder crop–livestock farmers mainly as a border crop. It is quite often sparsely intercropped in cereal‐based cropping systems in the subhumid zone of Ghana. Management of pigeon pea and its biomass is a promising means of improving many abandoned arable fields but has not been consciously undertaken. The objective of this trial was to explore the use of pigeon pea and the management of its pruned biomass as part of an improved fallow for crop–livestock farming. Three pigeon‐pea management options and a natural fallow (two‐year fallow period) were compared in terms of maize grain yield and changes in soil organic carbon, total nitrogen and cation exchange capacity. Pigeon pea grain yield ranged between 615 and 678 kg ha⁻¹ and 527 and 573 kg ha⁻¹ in the first and second year of fallow, respectively. In the first year after fallow, maize grain yield ranged between 0·43 and 2·39 t ha⁻¹ and was significantly influenced by the fallow system. There was a marked decrease in maize grain on the pigeon pea fallow plots in the second year, ranging between 50 and 38·6 per cent in Kumayili and between 42·6 and 17·6 per cent in Tingoli. After the two‐year fallow period, increase of soil organic carbon on the pigeon pea fallow plot compared with the natural fallow plot was 30·5 per cent, and there was an improvement of total nitrogen (48·5 per cent) and CEC (17·8 per cent). Copyright © 2005 John Wiley & Sons, Ltd.     

Accumulation and composition of total organic carbon in reclaimed coal mine lands

Reclaimed coal mine lands have the potential to sequester atmospheric carbon (C); however, limited information exists for the western USA coalfields. This study was carried out on two chronosequences (BA‐C₃ grasses and DJ‐shrubs) of reclaimed sites at two surface coal mines to determine the effects of vegetation, soil texture, and lignin content on soil total organic carbon (TOC) accumulations. In the BA chronosequence, TOC increased over 26 years at an average rate of 0·52 Mg C ha⁻¹ yr⁻¹ in the 0–30 cm depth and was significantly correlated with clay content. Comparison between < 1 and 16‐year‐old stockpile soils indicated TOC content did not differ significantly. In the DJ chronosequence, TOC content in the 0–30 cm depth declined from 31·3 Mg ha⁻¹ in 5‐year‐old soils to 23·4 Mg ha⁻¹ in 16‐year‐old soils. The C:N ratios suggested that some (up to 2·0 per cent) of the TOC was potentially derived from coal particles in these reclaimed soils. Soil total N (TN) contents followed a similar trend as TOC with TOC and TN concentrations strongly correlated. Lignin contents in TOC of all reclaimed soils and topsoil stockpiles (TSs) were higher than that of nearby undisturbed soils, indicating the recalcitrant nature of TOC in reclaimed soils and/or possibly the slow recovery of lignin degrading organism. Results indicated that TOC accumulations in DJ were largely controlled by its composition, particular lignin content. In BA sites TOC accumulation was strongly influenced by both clay and lignin contents. Copyright © 2008 John Wiley & Sons, Ltd.     

Comparison of soil microfungi in 40-year-old stands of pure alder,pure conifer,and alder-conifer mixtures

The species composition of soil microfungal populations in adjacent stands of red alder Alnus rubra, conifers Pseudotsuga menziesii, Tsuga heterophylla, and Picea sitchensis, and mixed alder conifer correlated strongly with the dominant vascular vegetation. A total of 92 species were isolated: 55 from the alder stand; 45 from the conifers; and 46 from the mixed alder-conifer, with few species (16.7, and 5 in the three plots, respectively) reaching average frequencies of 50 per cent or higher. Penicillium nigricans, Aureobasidiiim pullulans, Cephalosporium curtipes, and Cladosporium herbarium were present with high frequency at all sites. Penicillium daleae, which occurred with a frequency of 83 per cent in alder soil, appears to be a rare fungus elsewhere. There was little difference in species composition among soil horizons within a stand.     

Costing yield loss from acidity,sodicity and dryland salinity to Australian agriculture

Salinity, sodicity and acidity are three major soil constraints that limit crop and pasture yields in Australia. In this paper estimates are made of the potential benefits arising from their treatment by measuring and mapping their impact on agricultural profit. This is achieved by estimating the increase in profit for Australia's main commodities that would occur if the three soil constraints were costlessly ameliorated. These estimates reveal the upper achievable limit on investment returns. They are also indicative of each soil constraint's economic significance to Australian agriculture. It was found that costless removal of salinity would increase annual profits by A$187 million, sodicity by A$1034·6 million and acidity by A$1584·5 million. This equates to 2·9 per cent, 15·8 per cent and 24·2 per cent of total net economic return. It was also found that worsening salinity extent and severity over 2000–2020 has a present value of A$496–A$712 million. Although soil salinity is currently the focus of much public attention, this analysis suggests that from a production viewpoint the correction of sodic and acidic soils may create greater private economic benefit. Opportunities vary considerably among industries. In particular, there is considerable opportunity for the horticultural and viticultural sector to address acidity issues. Whether gross benefits translate into net benefits is a complex question requiring access to context and location‐specific information. Copyright © 2005 John Wiley & Sons, Ltd.     

SOIL SEED BANK CHARACTERISTICS BENEATH AN AGE SEQUENCE OF CARAGANA MICROPHYLLA SHRUBS IN THE HORQIN SANDY LAND REGION OF NORTHEASTERN CHINA

To understand how shrub cover affects the spatiotemporal patterns of the soil seed bank and to assess the role of vegetation in the restoration of desertified land in a semi‐arid region of China, we investigated the species composition and seed density of the soil seed bank under and outside the canopies over two seasons for an age sequence of Caragana microphylla shrubs in the Horqin Sandy Land region, Inner Mongolia. The results showed that a total of 24 plant species seeds were present in the soil seed bank, of which 20 were annuals or biennials. The seed densities in the soil seed bank were in the range of 830 – 13882·5 seeds m⁻² at 10 cm depth. Species richness in the soil seed bank did not increase as the shrubs aged, whereas the seed densities increased significantly. Five annual species: Setaria viridis, Eragrostis pilosa, Chenopodium acuminatum, Chenopodium glaucum and Corispermum acuminatum, contributed above 90 per cent of the seeds to the soil seed bank. On the basis of seed characteristics and seed reduction amount during the growing season, we concluded that it represents a mixture of persistent and transient seeds in different proportions. More seeds accumulated under the canopies than outside the mature shrub cover, but no significant difference was found the younger cover. These results suggest that shrub size and age had an important role in augmenting seed abundance of the soil seed bank but not the species richness. We confirmed the important effects of shrub cover on seed accumulation and vegetation recovery, especially the value of more mature age vegetation for countering land degradation. Copyright © 2012 John Wiley & Sons, Ltd.