ISSN:1061-2971    

DOI:10.1111/j.1526-100X.1995.tb00090.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe unique marine ecosystems of coral reefs express varying levels of degradation as a result of increasing anthropogenic pressures. This is the main reason why more than 200 coral reef localities were proclaimed as natural reserves or marine parks under varying legislation, rules, and monitoring and management programs. Ironically, the conventional management plans increased accessibility to many reef localities and enhanced dramatically the impact of tourism on reef habitats. Recreational activities including SCUBA and skin diving, fishing, human trampling, sediment re‐suspension, and other damage caused by “innocent” visitors are causing a rapid deterioration of many reefs. Their destruction requires years and decades for full recovery. I propose to rehabilitate such damaged habitats by the alternate strategy of “gardening coral reefs” with asexual and sexual recruits. Coral branches, colony fragments, and whole small colonies (asexual recruits) and laboratory or in situ settled planula‐larvae (sexual recruits) are designed to be transplanted into denuded reefs for restoration. This approach is further improved when the sexual and asexual recruits are maricultured in situ within special protected areas, before being transplanted. The use of sexual recruits ensures an increase in genetic diversity. I discuss several methodologies and results already accumulated showing the applicability of this gardening strategy for rehabilitation of denuded coral reefs. This restoration strategy should be integrated with proper management similar to that of already established reforestation in terrestrial habitats. The best candidates for employing this strategy are the fast‐growing coral species, usually branching forms and species that brood their pl

ISSN:1061-2971    

DOI:10.1111/j.1526-100X.1995.tb00091.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

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

ISSN:1061-2971    

DOI:10.1111/j.1526-100X.1995.tb00092.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThroughout tropical moist climates,Dicranopteris linearisfernlands can develop as a result of rain forest clearance followed by frequent burning. In Sri Lanka,D. linearisfern‐lands are capable of suppressing the regeneration of rain forest. Field experiments were conducted at Sinharaja Man and Biosphere Reserve, a rain forest where fernlands occupy substantial areas of the reserve boundary. The experiment's objective was to identify methods for initiating forest regeneration in fernlands dominated byD. linearisThree disturbance treatments were used to initiate seedling regeneration: clean weed, root removal, and till. We hypothesized that increasing the severity of the soil disturbance would establish vegetation with higher species richness and diversity, greater above‐ground dry biomass, and higher percentage cover and seedling density. Results indicate only partial support for this hypothesis. Dry biomass was greatest in till treatments, the most severe soil disturbance. By comparison, species richness and diversity, seedling density, and percentage cover were greatest in root‐removal treatments, though in many instances the differences were not significant. The study clearly demonstrated that any kind of soil disturbance can facilitate the establishment of herbs, shrubs, and trees in a fernland dominated byD. linearis.Results showed that herbs, sedges, grasses, and pioneer shrubs represented greater proportions of seedling recruits than did pioneer trees. Seedlings of primary‐forest tree species were nearly nonexistent. In general, results showed that soil disturbance can play an important role in site preparation for the purpose of initiating non‐fern vegetation in fernlands dominated byD.

ISSN:1061-2971    

DOI:10.1111/j.1526-100X.1995.tb00093.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractPrescribed burns are increasingly being used in ecological restoration and vegetation management. Despite the accumulation of scientific information on fire behavior and fire effects, however, in many cases fires are prescribed without consideration of such information and often simply because of evidence of past fires. Rather than basing fire management plans on ideas of the historical “natural” occurrence of fire, we present the case for fire management being based on the fire effects desired. Effective fire management and development of proper fire prescriptions require an understanding of fire processes and heat transfer that explain fire behavior characteristics, as well as an understanding of how fire behavior is coupled to specific fire effects. We provide a basic introduction to these concepts and processes, which will help in understanding the importance of having a more technical understanding of fire. The discussion includes the processes of heat transfer and the relative role of various fuel variables in these processes, as well as the concepts of fire intensity, rate of spread, fuel consumption, duff consumption, fire frequency, and the ecological effects associated with variation in these characteristics of fire behav

ISSN:1061-2971    

DOI:10.1111/j.1526-100X.1995.tb00094.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

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 do

ISSN:1061-2971    

DOI:10.1111/j.1526-100X.1995.tb00095.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

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 grassesAgropyron cristatum(crested wheat grass) and Bromusinermis(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 restorat

ISSN:1061-2971    

DOI:10.1111/j.1526-100X.1995.tb00096.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractAt least 43 agriculture fields were built in south Louisiana wetlands between 1900 and 1920 using pumps and levees. All but one project is now abandoned as a result of soil subsidence, financial difficulties, or multiple levee failures. Some are now in flood‐protected urban zones, and the remainder are mostly open water. The total area of abandoned agricultural fields in 1990 is large (>80,000 ha), and their levees continue to deteriorate naturally. Ten failed or abandoned coastal agricultural impoundments (22,680 ha) were examined to determine recent wetland restoration or regression rates from 1978 to 1988. Wetland area and levee length were determined from aerial photography for 1978,1983,1985, and 1988. Average wetland change rates for all areas ranged from −4.28 to +2.54% per year from 1978 to 1988. One site gained wetland area between 1978 and 1988 (77 ha/yr), and four sites gained wetland area between 1985 and 1988 (range 14–439 ha/yr). Wetland area in the other sites either remained stable or declined during the study period. The results from a multiple regression model indicate that restoration is inversely related to impoundment size and directly related to levee reduction. Results from a multiple regression model indicate that active levee removal will probably enhance wetland restoration rates at a very favorable cost (<$1/ha) and will be sustainable with little additional manag

ISSN:1061-2971    

DOI:10.1111/j.1526-100X.1995.tb00097.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

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 rese

ISSN:1061-2971    

DOI:10.1111/j.1526-100X.1995.tb00098.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractSeed 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 C4annuals such asEchinochloa crusgalliand 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

ISSN:1061-2971    

DOI:10.1111/j.1526-100X.1995.tb00099.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY