Distribution and survival of overwintering adults of the Dutch elm disease vector, Hylurgopinus rufipes (Coleoptera: Scolytidae), in American elm trees in Manitoba

Abstract 1 The native elm bark beetle, Hylurgopinus rufipes, is the principal vector of Dutch elm disease in Manitoba, Saskatchewan and North Dakota, and disease management measures include applying residual insecticides to the lower part of elm tree trunks where the adult beetles overwinter. 2 In American elm trees in southern Manitoba, we counted entrance holes produced by beetles then felled and dissected trees to determine numbers of tunnels and numbers and survival of overwintering beetles. 3 Densities of entrance holes, tunnels and beetles followed a logistic relationship with tree trunk diameter; densities were near zero at diameters < 10 cm and reached a site‐specific asymptote at diameters > 20 cm. 4 Asymptotic densities of holes, tunnels and beetles in samples from 55 to 190 cm above the ground were, respectively, 22%, 22% and 0.7% of those within 25 cm of the ground. 5 Within the height range 0–190 cm, the proportion of living beetles declined steeply with increasing height. 6 Average density of holes at height 0–25 cm estimated from a sample of several trees of diameter ≥15 cm could be used to predict the asymptotic maximum density of overwintering beetles in the site; predictions of beetle densities for individual trees were not reliable.     

Estimation of stem and tree level biomass models for Prosopis juliflora/pallida applicable to multi-stemmed tree species

The aim of this paper is to develop biomass models for commonly multi-stemmed Prosopis juliflora/pallida trees. The data were collected on three of the Cape Verde islands (Maio, Santiago and Santo Antao). The dataset covers 240 trees containing 1,882 stems with stem diameter at breast height over 2 cm; of that 255 individual tree stems were sampled destructively. These calibration data were used to construct stem and tree-level models for estimation of total aboveground biomass and its fine and course fractions with diameter threshold of 5 cm. A set of parameterized biomass models for multi-stemmed Prosopis spp. trees suited for biomass estimation at tree and stem levels using appropriate set of independent variables, commonly available in forest inventory programs, was created. The effect of site (island) on tree allometry was not detected. The two-phase construction of tree biomass models based on destructive sampling limited to individual stems combined with a routine field measurement of entire multi-stemmed tree specimen represents a practicable approach leading to biomass and carbon assessment that may be generally suited for tree species with complex multi-stemmed growth form similar to that of Prosopis spp.     

Establishment of woody species across 26 years of revegetation on a Queensland coal mine

The establishment success of woody plant species at 56 revegetation sites, four to 26 years old, across the Meandu open‐cut coal mine in south‐east Queensland was assessed. The revegetation process involved returning stockpiled topsoil, deep ripping and mechanical sowing of a mix of native seeds. Blakes Wattle (Acacia blakei) and less often Black Wattle (A. leiocalyx), both primarily derived from respread topsoil seed, dominate the vegetation canopy at 59% and 20% of revegetation sites, respectively. The additional sowing of seeds of many tree and shrub species within the sites has had limited success with most failing to persist or grow well. Revegetation management, for example selective thinning of acacias (Acacia spp.) saplings within the first 5 years is recommended to release the competition pressure on the poorly performing tree species. This will also allow opportunities for other less well represented shrub and herb species to persist. This study has shown that a range of tree and shrub species, including Eucalyptus spp., are performing poorly under the current revegetation regime, suggesting adjustments to revegetation species selection and/or methodologies are needed. The natural colonization of woody native species within the sites from nearby remnant vegetation is shown to be limited to only four species, and therefore is unlikely to significantly supplement the species diversity of the revegetation.     

Environmental Manipulation to Avoid a Unique Predator: Drinking Hole Excavation in the Agile Wallaby, Macropus agilis

The simplest way of avoiding an ambush predator is to entirely avoid the habitat in which it hunts. However, this strategy requires that the prey species find alternative, risk‐free sources of essential resources. Herein we describe a novel strategy used by agile wallabies (Macropus agilis) to avoid saltwater crocodile (Crocodylus porosus) predation: the creation of risk‐free sites to obtain water. We studied the anti‐predator behaviour of agile wallabies for 3 yr during the dry season along the Daly River, Northern Territory, Australia. Wallabies excavated holes in the sand 0.5–18.0 m from the water's edge, and preferred to drink from these holes over drinking from the river. We determined a hierarchy of preferred drinking‐site options for the wallabies: non‐river sites: springs, puddles, excavated holes; and river sites: sites with cover, shallow water sites and deep water sites. Drinking holes were twice as far from the water's edge in a river stretch with high crocodile density (2/km) than those in a stretch with low crocodile density (0.08/km). However, site differences could also be explained by river bank morphology. Collectively, our findings indicate that agile wallabies excavate drinking holes to avoid crocodile predation. We contend that this behaviour represents environmental manipulation specifically to alter the risk associated with obtaining a key resource.     

Vegetable Exudates as Food for Callithrix spp. (Callitrichidae): Exploratory Patterns

Marmosets of the genus Callithrix are specialized in the consumption of tree exudates to obtain essential nutritional resource by boring holes into bark with teeth. However, marmoset preferences for particular tree species, location, type, and other suitable factors that aid in exudate acquisition need further research. In the current study, the intensity of exudate use from Anadenanthera peregrina var. peregrina trees by hybrid marmosets Callithrix spp. groups was studied in five forest fragments in Viçosa, in the state of Minas, Brazil. Thirty-nine A. peregrina var. peregrina trees were examined and 8,765 active and non-active holes were analyzed. The trunk of A. peregrina var. peregrina had a lower number of holes than the canopy: 11% were found on the trunk and 89% were found on the canopy. The upper canopy was the preferred area by Callithrix spp. for obtaining exudates. The intensity of tree exploitation by marmosets showed a moderate-to-weak correlation with diameter at breast height (DBH) and total tree height. The overall results indicate that Anadenanthera peregrina var. peregrina provides food resources for hybrid marmosets (Callithrix spp.) and these animals prefer to explore this resource on the apical parts of the plant, where the thickness, location, and age of the branches are the main features involved in the acquisition of exudates.     

Persistence of seed bank under thick volcanic deposits twenty years after eruptions of Mount Usu, Hokkaido Island, Japan

The topsoil that contained the seed bank became buried under thick tephra after the eruptions of Mount Usu during 1977 and 1978. To determine the seed bank potential of the topsoil 20 yr after the eruptions, i.e., in 1998, 408 100-cm(3) samples were excavated under 115-185 cm of volcanic deposits. The topsoil was collected at 10-cm intervals along the horizontal scale and was divided into a 0-5 cm deep upper layer and a 5-10 cm deep lower layer. The seed bank was estimated by both the germination (GM) and flotation (FM) methods. In total, 23 species with an average seed density of 1317 seeds/m(2) were identified by GM, and 30 species with a density of 2986 seeds/m(2) were extracted by FM. The dominant species was Rumex obtusifolius, and perennial herbs, such as Carex oxyandra, Viola grypoceras, and Poa pratensis, were common. For nine species this study provided the first records for field seed longevity >20 yr. The seed density in the upper layer was double that in the lower layer, and the horizontal distribution was heterogeneous even at 10-cm intervals. We concluded that the seed bank has retained the original structure of the seed bank under the tephra and will persist longer with soil water content between 20 and 40%, no light, and low temperature fluctuations (±0.17°C of standard deviation in a day).     

Changes in forest structure, species diversity and spatial pattern following hurricane disturbance in a Piedmont North Carolina forest, USA

Aims: Large hurricanes have profound impacts on temperate forests,but owing to their infrequent nature these effects have rarelybeen examined in detail. In 1996, Hurricane Fran significantlydamaged many long-term tree census plots in the Duke Foreston the North Carolina Piedmont, thereby providing an exceptionalopportunity to examine pre- and post-hurricane forest compositionaltrajectories. Our goal was to examine immediate, short-term(0–4 years) and longer term (5 year) hurricane-inducedstructural, spatial and compositional changes in the tree population(stem d.b.h > 1 cm) in the context of our detailed, long-termknowledge of the dynamics of these forests. Methods: We surveyed stem damage and tree mortality in 34 long-term permanentplots (ca. 70-year record; 404–1 012 m²) and 7 large mappedtree stands (ca. 20-year record; 5 250–65 000 m²) representingboth transition-phase, even-aged pine stands and uneven-agedupland hardwood forests. We employed three types of damage measuresto quantify stand-level damage severity: percentage of stemsdamaged, percentage of basal area lost and a ‘stand-leveldamage index’. Second-order spatial analysis (Ripley'sK-function) was used to investigate patterns in tree mortality. Important findings: Our study found hurricane effects on the structural attributesof Piedmont forests to be variable and patchy. Changes in treespecies composition, however, were modest. Uprooting was themajor damage type for the overstory trees [diameter at breastheight (d.b.h.) >10 cm] apparently due to the exposure ofthe crowns to high wind combined with heavy rainfall prior toand during the storm. Saplings, juvenile trees and small trees(1–10 cm d.b.h.) of the understory and midstory were mainlydamaged by being pinned or bent by their damaged large neighbors.Hurricane-induced tree mortality varied weakly among species,was positively correlated with pre-hurricane tree size and remainedup to 2-fold higher than pre-hurricane background mortality5 years after the hurricane. Spatial point pattern analysisrevealed a patchy distribution of tree mortality during thehurricane sampling interval. Hurricane Fran resulted in a dramaticincrease in average gap size from ca. 400 m² pre-hurricane toca 1100 m² after the hurricane, whereas maximum gap sizes reached18–34 times larger than the pre-hurricane levels.     

Influence of cultivation method on root grafting in Norway spruce (Picea abies (L.) Karst.)

Root grafting is the process by which a functional union of two or more roots subsequent to their formation is formed. The above- and below-ground parts of three Norway spruce stands (natural stand, Umbric Luvisol; row-culture and group-culture, Planosol; stand ages 40, 43 and 43, respectively) of high site quality (I) were investigated. Stand densities were 1550, 1783 and 1722 stems ha^-1, respectively. In all investigated stands, root grafting was most sensitive to tree spacing. Grafts were observed in case the distance between the trees was 0.7–1.2 m. Grafts occurred always in areas of higher rooting density, in a row of the row-culture and within a tree group in the group-culture. Root grafting was enhanced in case of a narrower humus horizon in the group culture compared with the row-culture, 16.5 and 30 cm, respectively; the humus horizon contained 99% and 95% of conducting roots with d ≥ 5 mm, respectively. Root graftings occurred in 75% of excavated trees in the group-culture, in 37.5% of excavated trees in the row-culture and in 33.3% of excavated trees in the natural stand. Stand age was 24 years in the row-culture and 22 years in the group-culture at the beginning of root grafting. No grafts occurred between two suppressed trees, whereas in 86–100% of all cases, at least one tree was dominant or codominant. In row- and group-cultivated Norway spruce stands, the initial minimum diameter of the grafted root without bark was from 1 to 3 cm in 63% of cases. Grafting of roots with d < 1 cm or d > 10 cm was rare or absent. Root grafting had usually begun at the root age of 10–20 years (46% of cases). This revised version was published online in June 2006 with corrections to the Cover Date.     

Implications of Seedling Emergence to Site Restoration following Bauxite Mining in Western Australia

Seedling emergence of 12 selected northern jarrah (Eucalyptus marginata Donn ex Smith) forest species were investigated to assist Alcoa of Australia Ltd. in maximizing the establishment of topsoil species in rehabilitated bauxite mining sites. The species, which encompassed a range of seed weights (0.024 mg to 87 mg), plant families, seed-storage types, life forms, and germination requirements, were placed on the soil surface and at depths of 1, 2, 5, 10, and 15 cm under controlled conditions in a glasshouse. Ability to emerge from deep burial was found to depend on seed size for species that annually release their seed to the topsoil but not for species that store their seed on the plant. All selected species were capable of emerging from 2 cm depth of burial, but eight of the 12 species were either unable to emerge from 5 cm or showed a significant reduction in emergence from 5 cm depth of burial compared to optimally buried seed. This group included two small-seeded species, Stylidium calcaratum and Chamaescilla corymbosa; the major forest dominant, Eucalyptus marginata; the serotinous canopy-borne seed of Hakea amplexicaulis; and the wind-dispersed seed of Xanthorrhoea gracilis. A few seeds of the legume species Kennedia coccinea, Acacia pulchella, and Bossiaea aquifolium established seedlings from depths of 15 cm. Currently, Alcoa removes the upper 15 cm of topsoil separately from the underlying soil prior to the commencement of mining. This topsoil is respread at a similar depth following mining as part of the rehabilitation procedure. It is recommended that Alcoa continue to strip topsoil to a depth of 15 cm but investigate the option of re-spreading topsoil onto rehabilitated pits at a shallower depth to maximize establishment via the soil seed bank.     

Internal structure and contents of three badger (Meles meles) setts

Three badger ( Meles meles L.) setts in the south of England, which formed a single sett complex belonging to one social group of badgers, were excavated prior to being destroyed by construction of a new road. Setts 1 and 2, classified as annexes, were excavated completely; sett 3, classified as a main sett, was only excavated partially, but its total size was estimated from the excavated portion. The setts consisted of tunnels totalling 16 m, 140 m and 879 m, respectively; contained one, nine and 50 chambers; and had five, 42 and 178 entrances. The total volume of the three setts was about 45 m³, and their construction was estimated to have required the removal of about 70 tonnes of soil. In the two smaller setts tunnels ran on a single level with an average depth of 99 cm; in the larger sett they ran on two levels with modal depths of 50 cm and 110–120 cm, respectively. All three setts contained bedding material (dry grass and plastic bags) but only the main sett contained latrines. None of the setts contained badger bones and the interiors of all three setts were remarkably clean and orderly. We discuss hypotheses as to why badgers sometimes continue to extend even large well-established setts but conclude that the survival value of very large setts remains problematical.     

棉花根系生长和空间分布特征

结合田间根钻取样和图像扫描分析方法, 研究了不同棉花品种根系的长度、直径和表面积动态及 0~ 10 0cm深和 0~ 4 0cm宽土壤范围内的空间分布特征。该方法与常规直尺测量结果相比相关系数R2 达到 0.899 (n =1318), 显示了较好的可靠性。研究结果表明, 棉花平均根长密度 (RLD) 在花铃期为 1.2 1~ 1.2 7mm·cm-3, 吐絮后降至 1.0 4~ 1.12mm·cm-3, 收花时为 0.76mm·cm-3 。棉花根平均直径在不同基因型间存在显著差异, 抗虫杂交棉的根直径最粗, 平均为 0.5 2mm ;早熟类型品种根直径较细, 平均为 0.36mm。在土壤深度上根直径的差异不显著, 但距棉行距离越远, 根的平均直径越小。在明确根系长度和直径动态规律的基础上, 提出了根表面积指数 (RAI) 的概念, 与地上部叶面积指数具有相似的含义和生物学意义, 且呈较好的指数相关关系 (R2 =0.779) 。RAI在生理发育时间 (PDT) 小于等于 4 0前, 其增长动态符合LOGISTIC生长规律 (R2 =0.84 9), 在PDT大于 4 0后, 呈线性递减趋势 (R2 =0.5 70~ 0.895 ), 且杂交抗虫棉的RAI在全生育期内均明显高于其它类型品种, 而早熟类型品种相对略低。RAI空间分布特征表现为, 开花前在浅根层内 (0~ 30cm) 分布最多, 花铃期以中层根系 (40~ 6 0cm) 为主, 吐絮后主要以深层 (70~ 10 0cm) 和距棉行较远的行间较多。研究结果为制定合理的施肥、灌溉措施提供了理论依据, 并量化了棉花根系的时空变化, 为进一步提高生长发育模拟模型的精度奠定了基础。     

Germination and emergence of annual species and burial depth: Implications for restoration ecology

Due to the high content of viable seeds, topsoil is usually spread on ground left bare during railway and motorway construction to facilitate the regeneration of vegetation cover. However, during handling of the topsoil, seeds are often buried deeply and they cannot germinate or the seedlings cannot emerge from depth. This study experimentally explores the predictive value of seed mass for seed germination, mortality and seedling emergence at different burial depths for 13 common annual species in semiarid Mediterranean environments. We separate the effect of burial depth on germination and emergence by means of two experiments. In the germination experiment, five replicates of 20 seeds for each species were buried at depths ranging from 0 to 4 cm under greenhouse conditions. Germinated and empty or rotten seeds were counted after 8 weeks. In the emergence experiment, five replicates of four newly-germinated seeds per species were buried at the same depths under controlled conditions and emergence was recorded after 3 weeks. The effect of burial depth on percentage of germination and seedling emergence was dependent on seed size. Although all species showed a decrease in germination with burial depth, this decrease was greater for small-than large-seeded species. Percentage of emergence was positively related to seed mass but negatively related to burial depth. Seed mortality was higher for small-than large-seeded species, but there was no general effect of burial depth on this variable. Thus, the current practice of spreading 30 cm deep layers of topsoil in post-construction restoration projects is unadvisable. In this restoration scenario, thinner layers of topsoil should be used to achieve the maximum potential of the topsoil for germination and seedling establishment.     

Improving integrated management of weed control by determination of weed seed bank in sandy and clay soil

Knowledge of soil weed seed bank is important for population dynamics studied, establishment of appropriate weed management programs, a little effort in understanding weed seed bank can give valuable information about what weeds to expect in growing season, weed density, and when most weed germination will take place. In this study, a two - year''s, two sites were carried out with the aim of assessing weed seed bank status of the soil throughout 2018 and 2019. A site was worked out in Sakha Agriculture Research farm act as a clay soil, Kafr El-Sheikh Governorate, Agriculture Research Center (ARC). Another site was worked out in El-Ismailia Agr; Res; farm act as sandy soil, El-Ismailia Governorate, ARC. At each site, soil samples were selected from nine different places as like three Zigzag shapes divided into three, six and nine sites, “W” to act the whole soil area (30 faddan in Sakha farm, and 15 faddan in El-Ismailia farm). The soil samples were taken from topsoil 0–10 cm depth with an auger (core) 10 cm diameter the soils without tillage and before sowing the summer crop. The result of present the study in two different stations and soils, revealed that the number of soil samples to estimate weed seed banks should be either six or nine sites; each sample weighted 0.50 Kg soil with zigzag shape act a direct seed extraction technique to able recognize the abundance of weed species into the soil and their seed density. The aim is to improve integrated weed control.     

Patterns in the within-tree distribution of the emerald ash borer Agrilus planipennis (Fairmaire) in young, green-ash plantations of south-western Ontario, Canada

1 The emerald ash borer Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) is a serious exotic pest of ash trees (Fraxinus spp.) in North America, and is responsible for the deaths of millions of trees in Ontario and Michigan. One of the greatest challenges facing the successful management of the pest is the ability to accurately detect its presence in a tree. 2 Observations were made on A. planipennis larval feeding galleries found within 65 young, green‐ash trees cut from plantations in Essex County, Ontario, Canada. The within‐tree distributions of feeding galleries were described in relation to height‐above‐ground, stem diameter, bark thickness and stem aspect. 3 Galleries were not distributed randomly or evenly; minimum boundaries of stem diameter and bark thickness and a maximum boundary of height‐above‐ground were detected. Indications of maximum boundaries for stem diameter and bark thickness were also observed. Galleries were found most often on the south‐west side of the tree. 4 Using the technique of upper boundary regression, we were able to identify significant quadratic relationships between A. planipennis gallery density and stem diameter and bark thickness, as well as a significant negative linear relationship between gallery density and height‐above‐ground. 5 Agrilus planipennis gallery density in newly‐infested trees was lower than in previously‐infested trees, and was observed to peak at smaller stem diameters and bark thicknesses than in previously‐infested trees. 6 Survey teams would increase their probability of detecting new A. planipennis infestations by initiating searches for exit holes and feeding galleries in trunk sections and branches of approximately 7 cm in diameter.     

Restoration of a Cirsio-Molinietum Fen Meadow on an Agriculturally Improved Pasture

The objective of this study was to identify soil nutrient availability conditions that would allow the establishment of key species of the Molinia caerulea‐Cirsium dissectum fen meadow. The restoration site was a species‐poor agriculturally improved pasture that had received no inorganic fertilizer for greater than 13 years. Treatments designed to reduce site fertility included: cutting and removal of herbage, cultivation, fallowing and topsoil removal. Straw and/or lignitic‐clay were incorporated as soil amendment treatments. Cirsio‐Molinietum species were either sown or planted as seedlings on treated plots. Neither soil nitrogen nor potassium availability, per se, appeared to limit the establishment of Cirsio‐Molinietum species, whereas enhanced phosphorus availability did. Removal of the top 15–20 cm of soil reduced the total soil phosphorus amount by about 85 percent and depleted plant P availability. Nutrient‐poor and relatively calcium‐enriched soil exposed by topsoil removal allowed the development of a community with affinities to the Cirsio‐Molinietum typical fen meadow. Redundancy analysis indicated the existence of marked vegetational gradients within the topsoil removal treatments that were influenced by the straw and the lignitic‐clay amendments. The way in which these two amendments influenced edaphic conditions were unclear. Where the topsoil was not removed the vegetation became dominated by a few competitive species and although many of the planted Cirsio‐Molinietum species were still present after four years, they were found only in trace amounts. Removal of most of the soil organic matter was a practical success in that it created suitable edaphic conditions for all the planted Cirsio‐Molinietum species to remain well established.     

Aerobic Heterotrophic Bacterial and Fungal Communities in the Topsoil of Omo Biosphere Reserve in Southwestern Nigeria1

As a part of the surveillance effort to monitor the ecological status of Omo Biosphere Reserve in the southwestern region of Nigeria, the aerobic heterotrophic bacterial and fungal communities of the topsoil were investigated in March 1995 and April 1996, before the onset of the rainy season. Four distinct wood‐tree plantations, a core strict nature reserve (SNR) area, and a buffer zone were sampled. The topsoil samples (7.5 cm depth), including the litter, were taken with an auger (8 cm diameter) and transported to the laboratory in polyethylene bags. One‐gram dry weight equivalent of sample was suspended in 10 ml sterile water, and serial dilutions from it were used for the estimation of bacterial and fungal densities. The bacterial and fungal densities ranged in the order of 106 and 103 cfu/g, respectively. Out of the 18 bacterial and 16 fungal species that were obtained, 13 and 12, respectively, were isolated from the core SNR. About 46 to 69 percent of the bacteria and 50 to 83 percent of the fungi species found in the SNR were absent in different combinations in the plantations and the buffer zone; these variations were significant among the sites monitored. The bacterial and fungal species compositions were significantly different between the SNR and each of the other sites. Proportional distributions within the sites were significant only for the bacterial communities. It would appear that plantation and human activities have caused significant changes in the distribution and species richness of the heterotrophic bacterial and fungal communities relative to the undisturbed SNR area of the Omo Biosphere Reserve.     

Growth development of a balsam fir (Abies balsamea (L.) Mill.) originating from layering

After a disturbance, balsam fir stands (Abies balsamea (L.) Mill.) regenerate primarily by seedlings, but layering is also known to occur and to contribute to the subsequent population base. We examined in detail the lower part of one balsam fir stem, stump and roots in order to: reconstruct the establishment of one mature balsam fir with evidence of layer-origin. The life history of this tree was then reconstructed by measuring tree-ring widths, dating all the sections, and by identifying the presence or absence of pith to differentiate between stem and root structures. We located a pith structure in this tree 51 cm below ground level. This lowest section with pith was characterized by a diameter of only 3 mm and contained 40 concentric tree-rings, suggesting that it originated from a branch. Radial and height growth measured were small until the beginning of 1930s. This period was abruptly followed by an increase in growth in both height and diameter as well as a massive production of adventitious roots, probably produced by partial harvesting of the parent tree/stand.     

塔里木河下游胡杨空心特征

本文选取塔里木河下游阿拉干断面胡杨林长期监测样地,分析胡杨林空心率、树洞特征及其在不同胸径和树高组间的分布特点。结果表明: 研究区胡杨种群具有较高的空心现象,空心胡杨占调查胡杨总数量的56%,约159株·hm^-2;胡杨空心率在不同胸径和树高组间呈显著差异,其与胸径呈显著正相关,与树高呈显著负相关。该监测样地胡杨树洞密度约560个·hm^-2,平均每株2个;所调查的胡杨树洞大部分出现在树干上(57.1%),均以树干中部洞口为主(31.3%);直径为5~15 cm的树洞(38.2%)所占比例最大。总树洞数量、单株树洞数量、树洞直径等特征与胸径呈显著正相关,与树高呈显著负相关,而各树洞类型在不同胸径和树高组间的分布不同,变化趋势不一致。胡杨树洞在各方位上的分布差异显著,树洞集中分布在正西方向上。胡杨荒漠河岸林的空心发生率较为严重,且胸径越大其空穴化程度越明显。加强保育幼龄胡杨和修复退化荒漠河岸林具有重要意义。     

Effects of Bauxite Mine Restoration Operations on Topsoil Seed Reserves in the Jarrah Forest of Western Australia

We studied the effects of soil handling operations during bauxite mining and restoration on the numbers and depth distribution of seed stored in the surface soil of the jarrah forest. Germinable seed stores were determined in four sites of undisturbed forest, these same sites after clearing and burning of forest residues, in the soil immediately following the construction of topsoil stockpiles, in the respread topsoil and then after deep ripping of the respread topsoil. Average density of germinable seed at four sites prior to disturbance was 352 m^?2. After clearing and burning, the seed store had decreased to a mean 74% of the original forest soil seed store density. When the top-soil was stockpiled prior to respreading, the seed content was further reduced to 31% in freshly constructed stockpiles and had declined to 13% after 10 months in the stockpiles. After ripping of the respread topsoil the seed content was 16% of the original forest seed store density. In one site where the topsoil was directly stripped and respread with no period of stockpiling but with a period of fallow, the seed store was 32% after respreading and then increased to 53% of the original forest store after ripping. This increase may have been caused by an underestimate of the reserves due to insufficient heating of the samples to break dormancy in fire-requiring species. In the forest topsoils seed was concentrated in the upper few centimeters of the soil profile, whereas after the mining and restoration operations seed was evenly distributed throughout the returned soil profile to a depth of 20 cm. Small-seeded annual species, which were common in the forest seed store, were more sensitive to the soil handing operations and declined to very low numbers, whereas hard-seeded plant species such as Acacia spp. were less affected by the soil handling operations. Implications for bauxite mine revegetation operations include the recommendation that direct return of topsoil should be carried out wherever possible with a minimum delay between clearing, stripping, respreading, and ripping.     

Efficacy of organic wastes amendment on the establishment and biomass yield of grass species on a degraded Alfisol

Abstract

Deficiencies of organic matter and essential nutrients are important features of derelict/degraded lands; these characteristics have profound effects on the establishment of functional soil-plant systems on such lands. This work reports on the impact of organic wastes amendments on the establishment, growth and biomass yield of grass mixtures grown on a degraded soil. The experimental site was a heavily compacted and eroded land due to excavation (scrapping) of topsoil layer for urban construction activities. Zero, 10 and 20cm layers each of substrates collected from an old (abandoned) municipal refuse and from site affected by long-term surface disposal of livestock litter and topsoil collected under fallow vegetation were applied on soil surface, before the establishment of a mixture of grass species. Substrates collected from old municipal refuse contained high amount of essential nutrients and metals and, on application, produced upward shift in soil pH and electrical conductivity. Nevertheless, these properties neither significantly retarded plant growth nor impaired biomass yield. Plant establishment and biomass yield were comparable under topsoil application and organic waste amended soil and produced significantly higher biomass yield when spread at 20cm layers were made of them. This experimental group also produced superior biomass yield over the unamended control. The agronomic benefits of organic waste incorporation stemmed from improved soil properties in surface horizon and contents of essential nutrients supportive of the establishment and development of plant cover. Nutrient supply is related to soil organic matter status, organic wastes are therefore important to the reconstruction of effective nutrient cycling and the eventual functional soil-plant system on this degraded ecosystem. The goal of these revegetation efforts is to improve soil and plant productivity, plant diversity, conservation of native grasslands and aesthetic.