bluuebunny/crossref_metadata_2025_split huggingface dataset:
Seed Ecology of Woody Species in a Caribbean Dry Forest
Authors: Ray Gary J. , Brown Becky J. 
Published: April 2006

AbstractPeak 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

AbstractThe 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

AbstractThe 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

AbstractDieout 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

AbstractOur 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

AbstractSurvival 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

AbstractThe 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

AbstractNative 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

AbstractWe 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

AbstractThe 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

AbstractRestoration 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

AbstractLarge 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

AbstractThe 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.