bluuebunny/crossref_metadata_2025 huggingface dataset:
Social policy in rich and poor countries
Authors: Schmidt Manfred G. , KEMAN HANS
Published: April 2006

Abstract To what extent can the dramatic differences in social policy efforts in rich and poor countries be accounted for by genuinely political explanations? The hypothesis that is advanced in this article rests upon the combination of two schools of thought in comparative social policy analysis: socioeconomic models which focus attention on levels of economic wealth, need and demand for social security, and models of a comparative‐historiographic and political‐institutionalist nature. Empirical applications of socio‐economic models with lagged dependent variables reveal the existence of two deviant families of nations: overspenders in social policy (such as overspenders of social‐democratic complexion and of Christian‐democratic composition) and underspenders (such as superpowers in East and West as well as Japan and East Germany). The residuals mat can be derived from these models are amenable to an explanation which resides in comparative‐historiographic political analysis of social policy.
Dimensions of democracies
Authors: Lijphart Arend , SCHMIDT MANFRED G.
Published: April 2006

Abstract The conventional wisdom concerning the choice between majoritarian electoral systems and proportional representation (PR) ‐ and, more broadly, between majoritarian and consensus forms of democracy ‐ is that there is a trade‐off: PR and consensus democracy provide more accurate representation and better minority representation, but majoritarianism provides more effective government. A comparative analysis of 18 older and well‐established democracies, most of which are European democracies, shows that PR and consensus democracy indeed give superior political representation, but that majoritarian systems do not perform better in maintaining public order and managing the economy, and hence that the over‐all performance of consensus democracy is superior. This conclusion should also be tested among the growing number of slightly newer non‐European democracies, which are already old enough to have proved their viability and can be studied over an extended period of time. If its validity is confirmed ‐ and the evidence so far is very promising ‐it can have great practical significance for the future of democracy in the world.
Who's the chef? Economic voting under a dual executive
Authors: LEWIS‐BECK MICHAEL S.
Published: April 2006

Abstract. Standard economic voting models assume a dominant locus of policy responsibility, a single chief executive whose powers are fixed by certain inviolate institutional rules. The president‐centred US system serves as the paradigm here. However, economic voting may occur under a dual executive, whose powers change in response to the institutional rules themselves. France represents this second scenario. There are two executives, the President and the Prime Minister. Under conditions of cohabitation, with a partisan division of the power between the two offices, economic voting becomes more sophisticated. According to data from the 1993–1995 cohabitation, voters perceived that the Prime Minister, not the President, was responsible for the economy. Therefore, in the 1995 presidential contest, they directed their economic evaluations at the Gaullist party of the Prime Minister, not the Socialist party of the President.
Voting strength in the European Parliament: The influence of national and of partisan actors
Authors: HOSLI MADELEINE O.
Published: April 2006

Abstract. Most decisions by the European Parliament are taken by an absolute majority of its members. Some decisions however – such as the approval of the budget of the European Union – require a two‐thirds majority. The paper analyzes the a priori voting strength of the member states when their representatives vote coherently. It is shown that the increase in votes for Germany in the 1994 reallocation enhanced its position. A less favourable effect, however, can be seen for the other large members (France, Italy, the United Kingdom, and Spain). However, since votes in the EP tend to be cast according to partisan rather than national affiliation, the relative voting power of the political groups with respect to the two quotas is also analyzed. The tool to measure this is the (normalized) Banzhaf power index, partially extended to account for connected coalitions. The paper demonstrates that the distribution of votes between the present EU member states as allocated in proportion to their population size indeed roughly corresponds to their a priori voting power. However, the relative influence of the largest political groups, the European Socialists and the European People's Party, tends to be overestimated by their share of seats in the framework of the simple majority rule, but it is considerable if the quota is two‐thirds. Finally, under the two‐thirds majority rule, the European Liberal, Democratic and Reformist Party as well as the small groups appear to be almost powerless. The more the EP gains political leverage – a further increase in its institutional powers is to be expected in the framework of the ongoing Intergovernmental Conference – the more the distribution of voting power between the member states and between the political groups will be a crucial factor in the shaping of EU policies.
Is Restoration Ecology Practical?
Authors: Cairns John
Published: April 2006

We now recognize that humans have the power to alter the planet irreversibly, on a global scale. Humans must be concerned with the condition of the planet that is passed to future generations.2
Alkalinity Tolerance of Woody Species Used in Bauxite Waste Rehabilitation, Western Australia
Authors: Bell David T. , Wilkins Carol F. , van der Moezel Paul G. , Ward Samuel C.
Published: April 2006

Glasshouse trials, using trickle irrigation and increasing levels of NaOH‐induced alkalinity, identified species that could be expected to tolerate the high‐pH conditions of bauxite processing waste residue sites. Of 29 taxa tested, the most tolerant were Casuarina obesa, Melaleuca lanceolata, M. armillaris, M. nesophila, Eucalyptus loxophleba, E. halophila, E. platypus, Tamarix aphylla, and a particular clone of E. camaldulensis; E. spathulata, E. tetragona, E. preissiana, E. gomphocephala, E. diptera, and E. occidentalis proved to be relatively sensitive to severe alkaline conditions. Tolerance appeared to relate to an ability to maintain root membrane function, nutrient uptake balance, and ultimately root tissue structure while under increasing levels of alkalinity stress. Species normally inhabiting alkaline soils tended to have increased growth rates in nutrient irrigation conditions between pH 8 and 10 compared with control plants irrigated with nutrient solutions of pH values near 7.4. However, once the irrigation solutions reached pH 12 and the buffering capacity of the soil appeared to be exceeded, the condition of susceptible plants rapidly declined and death followed. Sensitive plants initially showed symptoms related to nutrient deficiency, followed by wilting and death as the root systems failed. Field trial conditions in the bauxite residue impoundments at Kwinana, Western Australia, include soils with pH values as high as 11.00. In general, the relative survival and growth of seedlings after eight months were predicted by the response under glasshouse trial conditions. Appropriately designed stress trials can be important ecological techniques in choosing species most capable of surviving difficult environmental conditions in the rehabilitation of damaged landscapes.
Ecological Restoration and NonIndigenous Plant Species: A Review
Authors: Berger John J.
Published: April 2006

In ecological restoration, nonindigenous species can pose a major problem because they are often aggressive and can overwhelm native species, thus altering ecosystem structure. This article identifies the circumstances in which prospects for use of restoration technology in controlling invaders are favorable or unfavorable, the factors that make certain species good colonizers, and the characteristics that make ecosystems susceptible to invasion. It discusses prospects for using restoration technology in controlling nonindigenous species by influencing hydroperiod, photo‐period, thermoperiod, edaphic conditions, and availability of biological control agents so as to produce ecological conditions that are inhospitable to invaders. The limitations of restoration are discussed, as well as specific ecological situations in which it is likely to be the method of choice for control of nonindigenous species. Use of fire, flooding, manual removal, shading, substrate removal, and herbicide application as control techniques in conjunction with restoration efforts are considered. Specific examples, including the techniques employed, indicate the potential for controlling nonindigenous species in the process of ecosystem restoration.
Propagation of Rare Plants from Historic Seed Collections: Implications for Species Restoration and Herbarium Management
Authors: Bowles Marlin L. , Betz Robert F. , DeMauro Marcella M.
Published: April 2006

Herbaria are potentially important repositories of living seeds that could be useful for recovery of rare plant species. To examine this capacity, we tested seed germination of rare milkweed (Asclepias) and milkvetch (Astragalus) species representing different collection dates and different herbaria. These groups have contrasting seed characteristics, with greater potential for longevity in the nonpermeable hard‐coated milkvetch seeds. Twelve‐year‐oldAsclepias lanuginosaseeds failed to germinate. However, we achieved 45% germination from three‐year‐oldAsclepias meadiiseeds, but germination dropped to 0% after ages of four to five years.Astragalus neglectusseeds germinated from 97‐, 48‐, and 28‐year‐old herbarium specimens, andAstragalus tennesseensisseeds germinated from a four‐year‐old collection. Seedlings produced from these experiments were incorporated intoex situgarden populations for recovery or restoration of rare species populations. Different herbarium pest control techniques may have significant bearing on the viability of seeds stored on herbarium specimens. Microwaving can cause precipitous loss of seed viability, while deep‐freezing appears to allow some seeds to remain viable. Potentially live seeds of rare species should be stored under conditions that enhance their long‐term viability.
The Flora and Invertebrate Fauna of a Relocated Grassland at Thrislington Plantation, County Durham, England
Authors: Cullen W. Rod , Wheater C. Philip
Published: April 2006

In order to extend quarrying near Thrislington Plantation, County Durham, England, 8.5 ha of magnesian limestone grassland was relocated over a period of eight years from October 1982. The effects of this on the flora and invertebrate fauna were examined within the Festuca‐Helianthemum community at five plots relocated at different times. Plants were sampled with a point‐quadrat, and invertebrates by pitfall trapping. Comparisons were made between age of the relocation, numbers of species and individuals, and diversity of flora and invertebrates. The plots were examined using the percentage similarity measure. The plots showed an initial change in some aspects of community structure for flora and invertebrate fauna, followed by a “recovery” period. This was particularly evident in the numbers of species and species diversity of plants and in the numbers of individuals and species diversity of invertebrates. Bare ground, left by the relocation process, was still evident between relocated turfs in the early plots, but it was successfully colonized by resident species in later plots. These results have implications for the future management of this and similar sites, particularly with respect to the emphasis placed on subsequent monitoring and the need to consider invertebrate faunas when implementing management strategies.
Senescent Reservoirs and Ecological Restoration: An Overdue Reality Check
Authors: Cairns John , Palmer Sarah E.
Published: April 2006

The recent publication of Restoration of Aquatic Ecosystems: Science, Technology, and Public Policy has generated much scientific, public, and political discussion. Although the book emphasizes the restoration of entire aquatic ecosystems, discussion of senescent dams and human‐made reservoirs is absent. The important societal and ecological roles of reservoirs warrant a closer examination of the potential ecological restoration of aging reservoirs. Problems with long‐term reservoir management include lack of long‐term management strategies, sedimentation, hazardous waste accumulation, impacts of recreational use, and the creation of new aquatic and riparian habitats. Policy conflicts may arise when habitats created in the reservoir are destroyed to restore the downstream habitats or when created habitats upstream undergo successional changes that impact the commercial or recreational value of the reservoir. Rare or endangered species may also create similar conflicts. The establishment of an ecological restoration bonding program that includes environmental education and conservation prior to new dam construction may aid in resolving potential conflicts in the future.
An Evaluation of Reclamation Success on Idaho's Phosphate Mines
Authors: Chambers Jeanne C. , Brown Ray W. , Williams Bryan D.
Published: April 2006

To evaluate reclamation success on the Wooley Valley phosphate mine in southeastern Idaho, we compared vegetation structure and soil physical, chemical, and elemental properties of several different reclamation treatments with those of a nearby reference area (a nativeArtemisia tridentata vaseyana/Festuca idahoensisassociation) after 14 years. Vegetation data had been collected four years after reclamation, and we were able to compare differences in biomass and species composition between dates on the reclaimed area. Four years after reclamation there were no differences in total biomass between topsoil or spoil or between seed only, seed + mulch, or control treatments on the different soil types. Most treatments were dominated by seeded perennial grasses. Fourteen years after reclamation there were no differences in biomass or cover between spoil and topsoil plots, but on spoil plots the seeded and mulched treatment had higher total biomass and vegetation cover than on control or seed‐only treatments. The seeded perennial legumeMedicago sativawas codominant with the seeded forage grasses on all of the treatments. High initial fertilization rates probably facilitated the early establishment and dominance of the forage grasses; once nutrient levels, especially nitrogen, began to decline, the legume increased in abundance. Similarity between the reclaimed area and the reference or native area was low. Reclaimed treatments had higher biomass but lower species richness. The topsoil and spoil plots had similar soil texture, bulk density, pH, cation exchange capacity, electrical conductivity, and phosphorus. Differences in organic carbon, total nitrogen, carbon: nitrogen ratios, and available moisture were related more to treatments than to soil type. High biomass and, thus, litter input on the seed + mulch treatment on spoil plots resulted in both higher OC and TN than any on other soil/treatment combination. The reclaimed area had lower OC, TN, and available moisture than did the reference area on all but seed + mulch spoil plots. Bulk density was higher on reclaimed plots. The long‐term differences observed between the reclaimed and reference areas parallel those obtained for other western reclamation sites. Although successional trajectories depend on the attribute measured, similarity to native reference areas depends on the initial reclamation methods. We discuss reclamation methods that would increase the structural and functional similarity of reclaimed and reference areas on the Wooley Valley phosphate mine.
Wetland Restoration at a Former Nike Missile Base in the Great Lakes Basin
Authors: Mitsch William. , van der Valk Arnold , Jaworski Eugene
Published: April 2006

Restoration of an abandoned 16‐ha Nike missile base site located on a former wetland in the lower Detroit River (Michigan, U.S.A.) was investigated with an emphasis on wetland restoration. The site included a 2.7‐ha abandoned missile base, a 1.3‐ha lake, 10.4 ha of emergent and submersed wetlands, and 1.8 ha of uplands. Aquatic beds in the shallow bay connected to the river supported floating leaved and submersed aquatics including Nymphaea tiiberosa, Vallisneria antericana, Elodea canadensis, and Heteranthera dubia, with mats of green, filamentous algae. A 10‐ha diked wetland adjacent to the site was dominated by Typha spp., Salix spp., Nymphaea tuberosa, Myriophyllum spicatum, Elodea canadensis, Chara sp., and Juncus effusus. Restoration objectives included a nature preserve, an outdoor recreation area, an experimental wetland complex, and an environmental education center. Ten alternative designs were suggested, including four with wetlands open to the bay, three with diked wetlands, and the rest involving island construction, a reconstructed upland site, or a wetland research facility. Alternatives were evaluated for their contribution to local ecology, research, education and wildlife, ease of maintenance, and probability of success. Construction of a wetland resembling conditions before construction of the base was recommended for its low maintenance and opportunity for research on non diked wetland design and construction in protected bays in the Laurentian Great Lakes. Recreational and educational opportunities were also recommended as part of the site restoration.
Effect of a Zooplankton Community on Seston Elimination in a Restored Pond in Japan
Authors: Urabe Jotaro
Published: April 2006

The rates of seston elimination by zooplankton and primary production were measured in Funada‐ike Pond, typical of human‐made impoundments in Japan, from April to September in order to evaluate various treatments of the pond aimed at improving water quality by reducing seston abundance. The treatments included draining the pond water, dredging the bottom mud, eliminating the wastewater inflow, and biomanipulation through removal of all fish. After the treatment, seston abundance was reduced from more than 10 to 0.4–2.5 mg C/liter, and large daphnid species, Daphnia similis and D. magna, occurred and predominated in the zooplankton community. Seston abundance remained at a relatively low level from June to August but increased markedly in late August, while the biomass of zooplankton became high from June to mid‐August and then decreased. A decrease in seston abundance was found when the elimination rate exceeded the primary production rate. The results indicate that the development of daphnid populations was effective in keeping seston abundance at a low level. The relationship between the rate of primary production and the zoo‐plankton biomass required to offset this rate, however, suggests that biomanipulation aimed at increasing zooplankton biomass alone is less effective in a pond with a high primary production. The success in improving water quality in this pond seems to depend not only on the increase in biomass of large daphnid species that resulted mainly from the removal of fish, but also on the decrease in nutrient load that was realized by the other treatments.
Assessing Restoration Perspectives of Disturbed Brook Valleys: The Gorecht Area, The Netherlands
Authors: van Diggelen Rudy , Grootjans Ab , Burkunk Rob
Published: April 2006

Several landscape restoration alternatives were evaluated in the Gorecht area, a cultivated river plain in the northern part of the Netherlands. A landscape analysis was performed to investigate the hydrological functioning of this area. Groundwater composition in the area was assessed by using distribution patterns of indicative plant species. Results proved to be consistent with an interpolation of actual data of the groundwater composition. Groundwater flow was simulated with hydrological models to explain the observed patterns in water chemistry. It appeared that upwelling Ca‐rich groundwater is now absent in the area, contrary to the past situation. Because a constant supply of Ca‐rich water is an essential condition for mesotraphent fen vegetation, we concluded that under the present conditions the regeneration prospects for these vegetation types are poor. We suggest that the plan to regenerate groundwater‐fed fens be abandoned for a plan to create surface‐water‐fed marshes.
Barriers to Lowland Tropical Forest Restoration in the Sierra Nevada de Santa Marta, Colombia
Authors: Aide T. Mitchell , Cavelier Jaime
Published: April 2006

Extensive areas of the tropics have been converted into pasture for cattle ranching. Frequently, abandoned pasture does not revert to forest. The goal of this project was to identify barriers to lowland moist forest regeneration in highly degraded grasslands in the Sierra Nevada de Santa Marta, Colombia. The barriers we considered were seed source, seed predation, competition with grasses, microclimate and soil limitations on plant growth, and fire. Seed dispersal into the grasslands is limited to within 10 meters of forest fragments, but this barrier can be overcome by sowing seeds and planting seedlings and by establishing perches to attract dispersers. In these degraded grasslands, seed predation was lower than in the adjacent forest patches, and there was no evidence that grasses inhibited the establishment of woody species. The most important barrier was the severe degradation of the soils. In much of the area, the A and B horizons have been eroded away, leaving saprolite at the soil surface. Seedlings of two fast‐growing pioneer species, Ochroma pyramidale and Cochlospermum vitifolium, grew to a maximum height of only 2.5 and 12 cm, respectively, during the first eight months. The slow plant growth in the degraded grassland soils compared to forest soils was associated with lower levels of cation‐exchange capacity, calcium, magnesium, and potassium. Even if these barriers could be overcome, the frequent and extensive use of fire in the region must be controlled to avoid killing established woody plants.
Seed Ecology of Woody Species in a Caribbean Dry Forest
Authors: Ray Gary J. , Brown Becky J.
Published: April 2006

Peak flowering activity among woody species in the tropical dry forests of St. John, U.S. Virgin Islands, coincided with the brief spring rainy season but continued at moderate levels for six months, abating with the autumn rains. Fruit maturation showed a major peak in the long winter dry season and a minor crest during the summer dry season. Seeds of wind‐dispersed species disseminated mainly during the winter dry season, while animal dispersal of seeds (74% of all woody species) followed the bimodal pattern (for wet and dry seasons) described for the community as a whole. Under shadehouse conditions, most dry forest tree species germinated well (> 80%) and emerged promptly (within four weeks of planting) and synchronously (90% emergence within a four‐week interval). Nine of 29 species tested in the shadehouse manifested dormancy of at least six weeks. Seed germinability varied among tree species, and the viability of most species began to decline following six months of dry storage. Few species retained high germinability after nine months of dry storage. The species composition of soil seed banks did not correspond closely with above‐ground communities on three forested sites of varying stand age. In the youngest stand (35 years old), dominated by the weedy, arborescent legume Leucaena leucocephala, the soil seed bank was also dominated by this species, but no seeds of any other tree species were found in the soil samples. Seeds of native trees were scarcely encountered (only one indigenous species) in soil seed bank samples of three forest sites. Local seed rain from less disturbed forest may not be sufficient for prompt recovery of the dry forest community on degraded sites.
Spontaneous Establishment of Woody Plants in Central European Derelict Sites and their Potential for Reclamation
Authors: Prach Karel , Pyšek Petr
Published: April 2006

The performance of woody plants was analyzed in 15 successional seres starting at bare ground in central European manmade habitats. The total cover of woody species after 10 years of succession was significantly related neither to initial soil moisture nor to nitrogen (expressed using Ellenberg indicator values). But the comparison of seres indicates that establishment of woody plants was easier under moderate environmental conditions and retarded in extreme habitats (dry, nutrient‐poor, or acid). The arrival of the first woody plants was delayed in dry sites. No significant differences were found between primary and secondary seres, either with respect to the total cover of woody plants reached after 10 years of succession or considering the time of their arrival. In total, 24 woody species (10 shrubs and 14 trees) appeared in the series investigated. Their successional performance (in terms of the number of seres in which the species occurred and maximum cover reached in any sere) was not related to species traits (life strategy, type of mycorrhizae, mode of dispersal, diaspore weight), except for the regeneration strategy, species with seasonal regeneration by seeds were capable of creating higher cover. Betula pendula (European birch) was the most successful species in spontaneous succession, especially on moist sites. Practical suggestions for the management of particular habitats (sites disturbed by mining, sites reclaimed after acid rain deforestation, urban sites, abandoned fields) are provided regarding the establishment of woody plants.
Effect of Exclosure and Topography on Rehabilitation of Overgrazed Shrub‐Steppe in the Loess Plateau of Northwest China
Authors: Hongo Akio , Matsumoto Satoshi , Takahashi Hidenori , Zou Houyan , Cheng Jimin , Jia Hengyi , Zhao Zhiyi
Published: April 2006

The purpose of this study was to clarify the effect of grazing exclosures on the recovery and rehabilitation of overgrazed steppe vegetation on varying slope aspects in the Loess Plateau of northwest China. The annual precipitation in the area studied was 400–480 mm. Soil samples were taken on nine slopes in the five‐year exclosure and on five slopes outside the exclosure after a vegetation survey; they were then analyzed chemically. Mean number of species recorded per 0.25 m2 was lower on the south‐facing slope than all other slopes. The reverse trend was observed for aerial biomass. Species diversity estimated by information content was higher in the grazing zone than in a 3200‐ha protected zone within an exclosure. From species ordination by principal component analysis, species with lower coverage in the grazing zone were Poa sphondylodes, Roegneria purpurascens, Hierochloe odorata, and Potentilla bifurca, which are all recognized as indicator species for rehabilitation efforts. In the soil surface layer, calcium contents were low, and the total contents of carbon and nitrogen were high on the north‐facing slope in the exclosure. The protection by exclosure of overgrazed steppe was seen to be effective because the accumulation of soil organic matter increased and water balance improved.
Coastal Dune Restoration: A Strategy for Alleviating Dieout of Ammophila breviligulata
Authors: Seliskar Denise M.
Published: April 2006

Dieout of Ammophila breviligulata— death of the major dune‐stabilizing plants — has been observed along the north and mid‐Atlantic coast of the United States for the past decade and a half. Pathogenic nematodes have been identified as the probable causal agents; they can bring about a complete dieout of sand dune vegetation, with Ammophila breviligulata being the first species to die. Typically, such an area would remain barren for up to five years before plants could be successfully introduced. Applications of fertilizer and dolomitic limestone were tested in the field as a possible management strategy to alleviate the vulnerability of a denuded dune to erosion by making it possible to plant such a site earlier than usual. These applications were also tested in an area of weakened and dying plants to determine if the vegetation could be saved before complete dieout occurred. By creating soil conditions conducive to vigorous plant growth, it was hypothesized that the plants could better withstand the stress of nematode attack. The addition of N‐P‐K macronutrient fertilizer resulted in increased growth and spread of plants introduced into a site where the grass had been dead for only one to two years. Results indicate that application of fertilizer would be necessary only every other year at most. Micronutrient application, at the concentration used in this study, had little or a somewhat detrimental effect. The addition of dolomitic limestone increased the survival of newly introduced plants. It was also found that the application of macronutrients to a site of moribund vegetation could not only rescue the plants in that site, but could also increase their growth, vigor, and spread, thereby preventing further loss of plant cover essential to dune stabilization.
Initiating Autogenic Restoration on Shallow Semiarid Sites
Authors: Whisenant Steven G. , Thurow Thomas L. , Maranz Steven J.
Published: April 2006

Our objectives were to evaluate the use of microcatchments in the establishment of Leucaena retusa (little‐leaf leadtree) and Atriplex canescens (four‐wing saltbush) and their role in the initiation of autogenic landscape restoration processes on a shallow semiarid site. Three six‐month‐old seedlings of either Leucaena retusa or Atriplex canescens were planted in 1.5‐m2 microcatchments. An equal number of seedlings was planted in control plots (unmodified soil surface). The water collection effects on shrub survival, standing biomass, and the natural immigration of herbaceous vegetation were determined over 42 months. Planting in microcatchment basins doubled Leucaena seedling survival and resulted in a five‐fold increase in standing biomass, compared to the control, during the first growing season. There was a significant increase in soil organic matter in the microcatchment basins within 32 months. At the same time, microcatchments planted with Atriplex canescens seedlings had a ten‐fold increase in seedling standing biomass compared to the control. Forty‐two months after transplanting, the herbaceous standing crop was significantly greater near Atriplex canescens or in microcatchment basins than in plots with unmodified surface soil. Basins containing Atriplex produced significantly more herbaceous vegetation than basins containing Leucaena, and empty basins produced the least herbaceous vegetation of three basin treatments. These data suggest that landscape‐scale procedures that concentrate scarce resources (water, organic matter, nutrients, and propagules), establish keystone species, and ameliorate microenvironmental conditions can initiate autogenic restoration of degraded semiarid ecosystems.
Restoring Caribbean Dry Forests: Evaluation of Tree Propagation Techniques
Authors: Ray Gary J. , Brown Becky J.
Published: April 2006

Survival and height growth of tree seedlings and rooted cuttings introduced into artificially shaded and unshaded plots in a degraded dry forest were measured at intervals for nine months. Ten tree species were selected to represent a range of ecological characteristics of the dry–forest plant community on St. John, U.S. Virgin Islands. Of three propagule types – seeds, seedlings, and rooted cuttings – introduced to field plots, seedlings survived best (52%) over the initial nine‐month period. Cuttings of six species rooted successfully in a shadehouse, but only two of these species survived the nine–month field experiment. Seed germination was low, under 11% for eight of ten species tested, and four species did not germinate. Subsequent mortality of seedling recruits was moderately high. Plumeria alba was the only species for which seedling height growth was not significantly greater than cutting height growth. Shading treatment (25% of full sun) significantly increased seedling survivorship (p= 0.03) but suppressed growth slightly for some species. Shading enhanced survival of seedlings produced from broadcast seeds, but not seed germination. Mortality occurred during dry periods, apparently from drought stress. Results suggest (1) that seedling introductions are the preferred propagule type (over seeding or rooted cuttings) for ecological restoration of degraded tropical dry forests, and (2) that some level of shading is required to increase the survivorship of many dry‐forest species or to avert complete mortality of some species. This study suggests that early secondary dry forest may be best restored by underplanting within the existing vegetation. Sufficient shading suitable for growth of native dry‐forest trees may be attained using a nurse crop of fast‐growing leguminous trees.
Jarrah Forest Restoration in Western Australia: Canopy and Topographic Effects
Authors: McChesney Catherine J. , Koch John M. , Bell David T.
Published: April 2006

The restoration of the northern jarrah (Eucalyptus marginata) forest after bauxite mining is a major objective of Alcoa of Australia Limited. The typically variable and sometimes low emergence of broadcast seed of jarrah‐forest plant species may relate to microclimatic changes associated with mining disturbance. This study examined the effect of the presence and absence of a canopy and topographic position in the post‐mining landscape on the emergence of four canopy species (E. marginata, E. calophylla, E. patens, and E. diversicolor) and related these patterns to detailed measures of surface soil temperature and moisture. The absence of a canopy in the restoration appeared to result in adverse microclimatic conditions for the successful early establishment of E. marginata and E. calophylla from seed, particularly in the low topographic regions of the restoration. Emergence beneath a canopy compared to that in the open was 17% and 6%, respectively, for E. marginata and 23% and 2%, respectively, for E. calophylla. For both species, emergence was also greater at upland than at lowland open restoration sites (9% and 3%, respectively, for E. marginata; 4% and 0.3%, respectively, for E. calophylla). In contrast, canopy removal and position on the topographic landscape did not reduce the early establishment success of E. patens and E. diversicolor. Field measurements revealed that soils were drier and that diurnal temperature fluctuations were wider in the open restoration sites than beneath a canopy. Furthermore, cold conditions were more frequent at lowland than at upland restoration sites, suggesting the occurrence of cold‐air drainage to Jew‐lying areas. It is therefore possible that the field emergence patterns reflected the lower tolerance of E. marginata and E. calophylla than both E. diversicolor and E. patens to cold and dry surface‐soil conditions. The ecological significance and practical implications of the results are discussed.
Native Grass Cultivars for Multiple Revegetation Goals on a Proposed Mine Site in Southcentral Alaska
Authors: Helm D. J.
Published: April 2006

Native grasses may be used for multiple, sometimes conflicting, goals in revegetation projects. Woody plants are frequently desired for moose browse and timber in Alaska, but naturally occurring Calamagrostis canadensis (bluejoint reedgrass) hinders the establishment of these desired species. Seven grass cultivars of Alaskan origin were evaluated for their ability (1) to stabilize the soil, (2) to reduce regeneration of C. canadensis, (3) to allow openings for natural colonization, and (4) to permit establishment of desirable rooted cuttings. Cultivars tested are “Arctared” Festuca rubra (red fescue), “Alyeska”Arctagrostis latifolia (polar‐grass), “Nugget”Poa pratensis (bluegrass) “Norcoast”Deschampsia beringensis (Bering hairgrass), “Nortran”Deschampsia caespitosa (tufted hairgrass), “Gruening” Poa alpina (alpine bluegrass), and “Sourdough” Calamagrostis canadensis. These were tested as single species and in multi‐species mixtures, with two seeding rates of the multi‐species mixture (0.5, 0.25 seeds/cm2). Experimental plots included unfertilized, unfertilized with rooted Salicaceae cuttings, and fertilized (350 kg/ha 20:20:10). A control plot was not seeded. After three growing seasons, Nortran D. caespitosa and Arctared F. rubra were the most successful cultivars. They provided 87% to 98% of the seeded‐species cover for soil stabilization and suppressed C. canadensis on the fertilized subplots without reducing species diversity. Gruening Poa alpina was less than 3 cm tall, and it helped stabilize the site without interfering with woody plant establishment. Although cuttings were shorter under some seed treatments compared to the nonseeded control, heights of cuttings were not related to cover of seeded cultivars (r = 0.09, p > 0.55) but were positively correlated with total vascular plant cover (r= 0.61, p < 0.001).
The Role of Panicum virgatum (Switch Grass) in the Revegetation of Iron‐Mine Tailings in Northern New York
Authors: Choi Young D. , Wali Mohan K.
Published: April 2006

We investigated the role of artificially introduced Panicum virgatum (switch grass) on the sequential natural revegetation of 15‐ and 35‐year‐old tailings in the Adirondack region of northern New York. Switch grass covered approximately 48% of the 15‐year‐old Chaumont Tailings. Establishment of switch‐grass stands improved the fertility of the site by adding organic matter, raising pH, and elevating cation exchange capacity and concentrations of major nutrients (N, P, and K). Switch‐grass stands also aided the initial recruitment of such pioneer species as Populus spp. (aspens), Salix spp. (willows), and Betula spp. (birches). This facilitation of recruitment of woody species is explained as follows: (1) robust switch‐grass stands physically captured the wind‐disseminated seeds of these species; (2) switch grass acted as a “nurse crop” for these species, thus these species were able to increase their density vigorously through root or stem sprouting; (3) a combination of both. Switch grass decreased its cover (14%), however, as observed in the 35‐year‐old South Tailings. As switch grass declined, such vigorous “root‐suckering” species as aspens increased in dominance, followed by the invasion of Prunus pensylvanica (pin cherry).
Early Woody Invasion Under Tree Plantations in Costa Rica: Implications for Forest Restoration
Authors: Guariguata Manuel R. , Rheingans Richard , Montagnini Florencia
Published: April 2006

The role of tree plantations as facilitators of tropical forest restoration in degraded lands has been explored recently, but there are few data on the effect of different tree species on invasion of the plant understory. We evaluated early patterns of understory composition in three‐year‐old native tree plantations in lowland Costa Rica using two pure‐species treatment (Jacaranda copaia and Vochysia guatemalensis) and one mixed‐species treatment (J. copaia, V. guatemalensis, Stryphnodendron microstachyum, and Calophyllum brasiliense). We also monitored woody invasion in unplanted control areas dominated by grasses. The understory of the different plantation treatments differed in light environment, woody‐plant growth and recruitment, and quantity and quality of woody regeneration. Forest tree invasion appeared to be enhanced under Vochysia, while shrubs were more abundant under the Jacaranda and mixed‐species treatments. Woody plant growth, herbaceous cover, and understory light availability were highest under Jacaranda, intermediate under mixed species, and lowest under Vochysia. Soil‐stored seeds seemed an important source for woody plant recruitment in Jacaranda and mixed species and of minimal importance under Vochysia, probably due to light suppression. It appears that competition from grasses is a major factor influencing early woody invasion in our study area. We found no woody recruitment after one year in the unplanted controls. We suggest that to promote the use of plantations as tools of forest restoration, there is a need to gather basic ecological information on how different tree species may influence patterns of plant understory colonization.
Re‐creating Semi‐natural Communities: Effect of Sowing Rate on Establishment of Calcareous Grassland
Authors: Stevenson Mark J. , Bullock James M. , Ward Lena K.
Published: April 2006

Restoration ecologists are increasingly aware of the potential to re‐create chalk grassland on abandoned farmland. Success is often hampered by lack of desirable species in the seed bank and by poor dispersal from nearby sites. In certain schemes, the input of seed may be essential. Locally collected seed is desirable but availability is limited. We examined whether lower sowing rates than currently recommended may be successfully utilized, facilitating more‐efficient use of available seed. Experimental plots on former agricultural land were sown at different rates in a randomized complete block, and the vegetation was surveyed for two years. We compared species richness and cover for chalk grassland plants and weeds ‐ species not associated with chalk grassland communities. Values for cover and abundance were matched with data for communities of the British National Vegetation Classification (NVC). Species richness for chalk grassland plants increased with sowing rate and with time, although after two years there was no significant difference between the treatments sown at 0.4, 1.0, and 4.0 grams of seed per square meter. Weed species decreased with increasing rate and time. After two seasons, the vegetation on all treatment plots was similar to that of recognized NVC chalk grassland communities, while the controls were dominated by weeds and showed signs of developing into species‐poor grassland. Higher rates rapidly eliminated weeds, but even a small inoculum of seed seemed to significantly enhance establishment of desirable plants and to reduce weed cover. We conclude that lower sowing rates would enable the desired vegetation to become established successfully, under appropriate conditions and management regimes. Lower rates allow for the re‐creation of sizable areas using local seed, and they minimize damage to donor sites.
Strategies for Mixed‐Grass Prairie Restoration: Herbicide, Tilling, and Nitrogen Manipulation
Authors: Wilson Scott D. , Gerry Ann K.
Published: April 2006

Large areas of North American prairie have been planted with grasses introduced from Eurasia. We examined three strategies (herbicide, tilling, and nitrogen manipulation) for enhancing the establishment of seedlings of native species and suppressing the introduced grasses Agropyron cristatum (crested wheat grass) and Bromus inermis (smooth brome). Plots (5 × 15 m) were subjected to one of three levels of tilling (none, intermediate, complete) and four levels of nitrogen (none, intermediate, high, and sawdust added to immobilize nitrogen). Treatments were applied in a factorial design with twelve treatments and ten replicates. Seeds of 41 native species were drilled into the plots in May 1992. Following the failure of seeds to establish in 1992, a subplot (5 × 13 m) within each main plot was sprayed with the herbicide glyphosate in April 1993. The nitrogen treatments were repeated in Spring 1993. In August 1993, the density of native seedlings in sprayed subplots was 20 times that in unsprayed subplots. Within sprayed subplots, native seedling density and the cover of bare ground decreased significantly with increasing nitrogen availability. Plots receiving sawdust had significantly higher mean cover of bare ground and significantly lower concentrations of soil available nitrogen. Native seedling density was significantly higher in plots receiving the highest intensity of tilling. The responses of native seedlings to all these factors point to the importance of neighbor‐free establishment sites as a prerequisite for prairie restoration.
The Effect of a Disturbance Corridor on an Ecological Reserve
Authors: Zink Thomas A. , Allen Michael F. , Heindl‐Tenhunen Bärbel , Allen Edith B.
Published: April 2006

The effect of a pipeline corridor constructed through an ecological reserve in Southern California was investigated by assessing plant species composition and soil chemistry. A homogeneous plant community comprised primarily of exotic annuals was found along the entire length of the corridor. This community has low similarity to the adjacent native plant communities. Soil organic matter was significantly less on the disturbed corridor than in contiguous undisturbed areas. Both available nitrogen and extractable phosphorus values were greater in the disturbed corridor. By contrast, total nitrogen was significantly higher outside the pipeline. The more labile litter of the exotic annuals allows increased mineralization along the corridor than does the more recalcitrant litter of the native perennial shrubs in the undisturbed areas. Once established, the weedy exotic annual litter may completely turn over organic matter and nitrogen, favoring the persistence of the weedy annuals. These exotic annuals appear to be moving into three of the native communities ‐ grassland, coastal sage, and oak woodland ‐ that have less organic matter and a more open plant canopy. Poor restoration efforts can lead to the establishment of such exotics, subsequent invasion into the surrounding undisturbed habitat, and degradation of the reserve.
Seed Banks and Species Richness Potential of Coal Slurry Ponds Reclaimed as Wetlands
Authors: Middleton Beth A.
Published: April 2006

Seed bank experiments are described to assess the species richness potential of coal slurry ponds reclaimed as wetlands (ranging from 6 to more than 40 years old). Experimental treatments test the drawdown and flooded conditions characteristic of the vegetation dynamics of emergent wetlands in the Upper Mississippi Valley. More seedlings, primarily annuals, emerged from exposed wet sediments (freely drained) than under continuous flooded sediments in cold ponds (339 versus 136 seedlings m−2, respectively) and in natural ponds (163 versus 47, respectively). More seeds were produced by plants established in freely drained conditions than under flooded conditions from sediments in the coal ponds (26546 versus 1842 seeds m−2, respectively) and the natural ponds (28430 versus 4526, respectively). Similarly, more biomass was also produced by these plants in freely drained than under flooded conditions in coal ponds (118 versus 47 g m−2, respectively) and natural ponds (118 versus 52, respectively). Fertilization (NPK) did not affect germination for the most part, but it did affect seed set and biomass production, especially for C4 annuals such as Echinochloa crusgalli and Panicum dichotomiflorum. I propose that lime (calcium carbonate) and fertilizer be applied during the first few scheduled drawdowns for these coal slurry ponds reclaimed as wetlands to increase the number of species and to allow their more rapid development as self‐sustaining systems.