Revegetation Sites Research Articles

Revegetation of serpentine substrates: Response to phosphate application

Revegetation was studied on stockpiled serpentine substrate. The native vegetation surrounding the revegetation site is annual grassland. The seed mixture applied to both subsoil and topsoil plots was largely ineffective for revegetation. No growth occurred in the subsoil plots and most of the growth in the topsoil plots was from indigenous seed. Phosphate application (100 kg P ha−1 as NaH2PO4 · H2O) to the topsoil plots resulted in a significant increase in total above-ground productivity. Annual legumes (mostlyLotus subpinnatus Lag.) and, to a lesser degree,Plantago erecta Morris responded to the added phosphate with an increased above-ground productivity. Other annual forbs and annual grasses showed no significant response. The legumes also increased in abundance. Mycorrhizal root colonization forPlantago was not significantly affected by phosphate application, but was lower in this disturbed serpentine site compared to other undisturbed serpentine annual grassland sites nearby.

Extent of Regeneration of the Microbial Community in Reclaimed Spent Oil Shale Land

AbstractSince the microbial community is an integral component of the soil ecosystem, an understanding of the microbiological parameters of reclaimed spent oil shale land is essential for environmental assessment of the potential for reclamation of such land. It was found that determination of the numbers of microorganisms, bacterial diversity and richness (number of genera), and biogeochemical activity indicated by relative rates of cellulose decomposition, yielded significant information regarding the regenerative potential of the microbial communities sampled from three shale mining areas in Colorado and Wyoming that had undergone varying degrees of weathering, leaching, fertilization, and revegetation. Compared to regional soils used as controls, the spent oil shale soils were characterized by low numbers of microorganisms, depressed values of bacterial diversity and richness, and low rates of cellulose decomposition. However, samples taken from 6‐yr revegetated sites were characterized by the least reduction in microbial numbers, higher indices of diversity and richness, and highest rates of cellulose decomposition, in comparison to intermediate values for the 3‐yr revegetated site, and the most extreme values for the nonrevegetated site. The latter site was characterized by very reduced numbers of bacteria, actinomycetes, and fungi, the lowest indices of richness and diversity indicative of a high level of environmental stress, and no decomposition of cellulose. It may be concluded that oil shale processing had a drastic negative impact on indigenous microbial communities in reclaimed, shale land. However, conditioning by weathering, fertilization, and revegetation does have a partially restorative effect on the microbial community; the degree of restoration progressively increasing with increasing length of time of these environmental conditions.

A comparison of soil and vegetation properties of seeded and naturally revegetated pyritic alpine mine spoil and reference sites

We compared physical and chemical soil properties and vegetation characteristics of seeded revegetated and naturally revegetated mine sites and native undisturbed reference sites on two high-elevation gold and copper mines using samples collected in August 1984. Because nitrogen is often the most limiting nutrient in alpine systems and levels of available nitrogen (NO 3 and NH 4) fluctuate, we measured nitrogen three times during the growing season. Significant differences in physical and chemical soil properties and vegetation characteristics were observed between reference area and seeded and naturally revegetated sites. Revegetated areas had high levels of P, K and Ca, reflecting use of fertilizer and lime in reclamation. However, extractable P was higher on reference than naturally revegetated sites. Limestone outcrops provided a favorable chemical environment for plant colonization of naturally revegetated sites. Larger pools of organic matter and total nitrogen existed on reference sites than on seeded or naturally revegetated sites. Both seeded and naturally revegetated sites exhibited lower overall levels and smaller fluctuations in NH 4 and NO 3 during the growing season than did the reference sites. The seeded revegetated site that had been fertilized the previous year was similar to the reference area in vegetation biomass and cover, while the site that had not been fertilized for 3 years had significantly less biomass and cover.

Acid mine drainage from inactive eastern coal operations

The most widely used technique for abatement of acid drainage from inactive surface mines and refuse disposal areas is revegetation of a soil cover applied to the waste material. Nonetheless, acid production often persists and in some cases, limits establishment of vegetation. This paper reports on several field studies intended to determine the location of pyrite oxidation zones and migration pathways of oxidation products at inactive spoil and refuse sites.Oxygen required for pyrite oxidation is believed to he provided in the gaseous state from the atmosphere. Therefore, the oxygen concentration in unsaturated mine waste should provide an estimate of the weathering tendency in the local environment. We are currently monitoring gas composition in refuse and spoil at six sites. Barren refuse appeared to be oxygenated (>2% 02) in a shallow zone extending less than 1 metre below the surface during most of the year. Preliminary data from coal spoil showed that oxygen can be available throughout the unsaturated thickness, even at a revegetated site. Gas composition varied vertically and laterally at a single site and also appeared to show seasonal dependence.Hydrologic factors are also important in acid production and transport. Discharge monitoring alone does not adequately describe the mass transport of acid products through the spoil. For example, at one reclaimed mine the mean sulfate content in six monitoring wells ranged from 24% to 240% of the mean concentration at the discharge point. Sources of recharge and relative flow rates determine the contribution of a particular zone to overall discharge quality.These basic studies of acid production and transport indicate some shortcomings of standard reclamation practices at certain sites. This information will he used to develop alternative abatement technology designed to mitigate acid production at the source.

Reptile and frog utilisation of rehabilitated bauxite minesites and dieback-affected sites in Western Australia's Jarrah Eucalyptus marginata forest

Alcoa of Australia Limited rehabilitate bauxite mined areas in the southwest of Western Australia. One of the aims of the revegetation programme is to promote the return of fauna species which inhabit areas prior to mining. This paper discusses the extent to which reptile and frog species utilise revegetated bauxite minesites. It was shown that 4–6 year old revegetated sites support similar numbers of reptile species as unmined sites, although densities are comparable to values recorded in poorer quality forest. Species utilisation of revegetated sites depended largely on the particular species microhabitat preferences. Comparison of community composition in various sites demonstrated high degrees of similarity between some rehabilitated sites and high quality forest sites. The effects of jarrah dieback disease on reptile and frog populations was also assessed. From the results, it is possible to assess the likely combined impact of dieback and mining on the longer term conservation of jarrah forest reptile and frog species.

ACID MINE DRAINAGE FROM INACTIVE EASTERN COAL OPERATIONS

The most widely used technique for abatement of acid drainage from inactive surface mines and refuse disposal areas is revegetation of a soil cover applied to the waste material. Nonetheless, acid production often persists and in some cases, limits establishment of vegetation. This paper reports on several field studies intended to determine the location of pyrite oxidation zones and migration pathways of oxidation products at inactive spoil and refuse sites. Oxygen required for pyrite oxidation is believed to he provided in the gaseous state from the atmosphere. Therefore, the oxygen concentration in unsaturated mine waste should provide an estimate of the weathering tendency in the local environment. We are currently monitoring gas composition in refuse and spoil at six sites. Barren refuse appeared to be oxygenated (>2% 02) in a shallow zone extending less than 1 metre below the surface during most of the year. Preliminary data from coal spoil showed that oxygen can be available throughout the unsaturated thickness, even at a revegetated site. Gas composition varied vertically and laterally at a single site and also appeared to show seasonal dependence. Hydrologic factors are also important in acid production and transport. Discharge monitoring alone does not adequately describe the mass transport of acid products through the spoil. For example, at one reclaimed mine the mean sulfate content in six monitoring wells ranged from 24% to 240% of the mean concentration at the discharge point. Sources of recharge and relative flow rates determine the contribution of a particular zone to overall discharge quality. These basic studies of acid production and transport indicate some shortcomings of standard reclamation practices at certain sites. This information will he used to develop alternative abatement technology designed to mitigate acid production at the source.

Density and Production of Seeded Range Grasses in Southeastern Arizona (1970-1982)

Density and Production of Seeded Range Grasses in Southeastern Arizona (1970-1982)