Uncertainty in the Extrapolation from Individual Effects to Impacts upon Landscapes

Uncertainty is inherent in extrapolating from effects upon the individual to alterations in ecological structure or function. Subtle differences in individuals within a population can give rise to significant evolutionary events. Populations are part of ecological structures, systems that are clearly complex, requiring an understanding of the interacting components, stochastic inputs and spatial scales. A series of patch-dynamic models is used to illustrate the importance of spatial arrangement and initial population size in predicting effects at a landscape level. The importance of understanding the spatial structure of a population in uncertainty reduction is addressed.     

Carbon emission and sequestration by agricultural land use: a model study for Europe

A model was developed to calculate carbon fluxes from agricultural soils. The model includes the effects of crop (species, yield and rotation), climate (temperature, rainfall and evapotranspiration) and soil (carbon content and water retention capacity) on the carbon budget of agricultural land. The changes in quality of crop residues and organic material as a result of changes in CO₂ concentration and changed management were not considered in this model. The model was parameterized for several arable crops and grassland. Data from agricultural, meteorological, soil, and land use databases were input to the model, and the model was used to evaluate the effects of different carbon dioxide mitigation measures on soil organic carbon in agricultural areas in Europe. Average carbon fluxes under the business as usual scenario in the 2008–2012 commitment period were estimated at 0.52 tC ha^?1 y^?1 in grassland and ?0.84 tC ha^?1 y^?1 in arable land. Conversion of arable land to grassland yielded a flux of 1.44 tC ha^?1 y^?1. Farm management related activities aiming at carbon sequestration ranged from 0.15 tC ha^?1 y^?1 for the incorporating of straw to 1.50 tC ha^?1 y^?1 for the application of farmyard manure. Reduced tillage yields a positive flux of 0.25 tC ha^?1 y^?1. The indirect effect associated with climate was an order of magnitude lower. A temperature rise of 1 °C resulted in a ?0.05 tC ha^?1 y^?1 change whereas the rising CO₂ concentrations gave a 0.01 tC ha^?1 y^?1 change. Estimates are rendered on a 0.5 × 0.5° grid for the commitment period 2008–2012. The study reveals considerable regional differences in the effectiveness of carbon dioxide abatement measures, resulting from the interaction between crop, soil and climate. Besides, there are substantial differences between the spatial patterns of carbon fluxes that result from different measures.     

Growth responses of littoral mayflies to the phosphorus content of their food

We examined how mayfly growth rates and body stoichiometry respond to changing phosphorus (P) content in food. In two experiments, mayfly nymphs were given high or low quantities of food at different carbon:phosphorus (C:P) ratios and their growth was measured. Low food quantity resulted in negative growth rates in both experiments, regardless of food P content. However, under high food availability, mayfly growth was affected by the type of food eaten, with low C:P ratio food producing more rapid growth. In addition, mayfly growth increased somewhat when P-poor food was artificially enriched with inorganic P although this effect was not statistically significant. Mayfly body P content was inversely related to body size but increased in animals fed artificially P-enriched food. A model was constructed to simulate mass balance constraints on mayfly growth imposed by the relative supply of two elements (C and P) in food. The model shows that mayfly growth should be limited by food P content at moderately low C:P ratios ( c . 120, by mass). Given high C:P ratios (mean c.  270, by mass) in periphyton from oligotrophic boreal lakes, our experimental and theoretical results indicate that stoichiometric constraints are important factors affecting benthic food webs in lakes from the Canadian Shield and perhaps in other systems with similarly high C:P ratios in periphyton.     

Stoichiometry of nutrient recycling by vertebrates in a tropical stream: linking species identity and ecosystem processes

Ecological stoichiometry offers a framework for predicting how animal species vary in recycling nutrients, thus providing a mechanism for how animal species identity mediates ecosystem processes. Here we show that variation in the rates and ratios at which 28 vertebrate species (fish, amphibians) recycled nitrogen (N) and phosphorus (P) in a tropical stream supports stoichiometry theory. Mass-specific P excretion rate varied 10-fold among taxa and was negatively related to animal body P content. In addition, the N : P ratio excreted was negatively related to body N : P. Body mass (negatively related to excretion rates) explained additional variance in these excretion parameters. Body P content and P excretion varied much more among taxonomic families than among species within families, suggesting that familial composition may strongly influence ecosystem-wide nutrient cycling. Interspecific variation in nutrient recycling, mediated by phylogenetic constraints on stoichiometry and allometry, illustrates a strong linkage between species identity and ecosystem function.     

Breeding Perennial Grain Crops

Referee: Ms. Peggy Wagoner, Rodale Institute, 611 Siegfriedale Road, Kutztown, PA 19530-9749 One-third of the planet's arable land has been lost to soil erosion in recent decades, and the pace of this degradation will increase as the limits of our food production capacity are stretched. The persistent problem of worldwide soil erosion has rekindled interest in perennial grain crops. All of our current grain crops are annuals; therefore, developing an array of new perennial grains - grasses, legumes, and others – will require a long-term commitment. Fortunately, many perennial species can be hybridized with related annual crops, allowing us to incorporate genes of domestication much more quickly than did our ancestors who first selected the genes. Some grain crops — including rye, rice, and sorghum — can be hybridized with close perennial relatives to establish new gene pools. Others, such as wheat, oat, maize, soybean, and sunflower, must be hybridized with more distantly related perennial species and genera. Finally, some perennial species with relatively high grain yields — intermediate wheatgrass, wildrye, lymegrass, eastern gamagrass, Indian ricegrass, Illinois bundleflower, Maximilian sunflower, and probably others — are candidates for direct domestication without interspecific hybridization. To ensure diversity in the field and foster further genetic improvement, breeders will need to develop deep gene pools for each crop. Discussions of breeding strategies for perennial grains have concentrated on allocation of photosyn-thetic resources between seeds and vegetative structures. However, perennials will likely be grown in more diverse agro-ecosystems and require arrays of traits very different from those usually addressed by breeders of annuals. The only way to address concerns about the feasibility of perennial grains is to carry out breeding programs with adequate resources on a sufficient time scale. A massive program for breeding perennial grains could be funded by diversion of a relatively small fraction of the world's agricultural research budget.     

Synoptic assessment of wetland function: a planning tool for protection of wetland species biodiversity

We present a synoptic assessment intended to maximize the benefits to wetland species biodiversity gained through Clean Water Act regulatory efforts within 225 sub-basins in Missouri, Iowa, Nebraska and Kansas (US Environmental Protection Agency, Region 7), USA. Our assessment provides a method for prioritizing sub-basins potentially critical for supporting wetland species biodiversity and may assist environmental managers and conservationists constrained by limited resources. We prioritize sub-basins based on the projected increase in the risk of wetland species extirpation across Region 7 that would be avoided by applying a unit of regulatory protection effort within a sub-basin. Because the projected increase in risk avoided per unit effort has not been directly measured, we represent this quantity with an index of indicators drawn from readily available data. A conceptual model incorporating landscape and anthropogenic factors guides index development via a series of simple benefit-cost equations. We rank and map the final index scores to show the relative priority among sub-basins for protection effort. High priority sub-basins appear to be concentrated along the major river systems within the region, where sensitive wetland species and intensive agriculture tend to coincide. Protection of wetland species biodiversity is an important, but not exclusive, attribute around which priorities should be set. Nevertheless, incorporation of our results into management strategies should allow managers to cast their local decisions in the context of regional scale maintenance of wetland species biodiversity, increasing ecological benefits for a given protection effort.     

Ecological perspectives for the restoration of plant communities in European temperate forests

Simultaneously with increasing afforestation efforts in western Europe, among conservationists the consciousness is growing that protecting areas to conserve biodiversity will not be sufficient in the long term, and that also the ecological restoration of more or less severely altered areas will be necessary. The probability that recently established forest stands develop towards their ecological reference (i.e. ancient forest) depends largely on the possibility of the target species to colonize them. We focused on the colonization ability of forest plant species and particularly on so-called ancient forest plant species. Major constraints for ecological forest restoration are the spatial characteristics of the target site (isolation, shape and area), imposing dispersal limitations, and in the duration and intensity of the historical land use, leading to changes in habitat characteristics influencing recruitment probability. We reviewed the ecological literature with respect to these constraints and conclude that it takes at least a century to restore the understorey layer of recent forests, even when the target stand is adjacent to a well-developed ancient forest. Both recruitment and dispersal limitation of the target species are responsible for this. Newly established forests should therefore be situated at a minimal distance of the ancient forest source. In other cases, forest plant species will not be able to colonize the newly established forest on a measurable time scale and artificial introduction of forest plant species can be taken into consideration. The negative effects of habitat characteristics, and mainly high soil nutrient values in the recent forest stand can be mitigated by soil nutrient lowering measures. Disturbances in the recent forest should be minimized to maintain a high canopy closure level, preventing light demanding, high competitive species from establishing a stable population. An additional negative consequence of soil disturbances is that it stimulates germination of species from the soil seed bank, which is mainly composed of highly competitive or ruderal species.     

Establishment of Transplants on Machine-Graded Ski Runs Above Timberline in the Swiss Alps

The suitability of 24 native species for restoration above the timberline in Switzerland was assessed with demographic monitoring of their populations after transplanting. The plots were laid out in 1985–1986 and 1995–1996 on machine‐graded ski runs using a total of 8,603 transplants of native grasses, legumes and forbs. Establishment conditions were improved with biodegradable wood‐fiber mats and a small addition of garden soil. Transplant survival rates were generally good after 12 years. The regeneration of mixed stands was clearly recognizable because some transplants successfully reproduced by seed, and colonizers immigrated from the adjacent natural vegetation and neighboring restoration plots. Comparative studies of reproductive parameters in transplants and their donor population revealed that differences in seed production may become nonsignificant within a short time span. These fitness features have important diagnostic value for assessing restoration success and provide information on the performance of the same or closely related genotypes in their natural populations and in the restoration site. The plants studied showed species‐specific traits in establishment after transplanting. Most species can be recommended for restoration in the alpine vegetation belt. The risk of restoration failure can be considerably reduced by using species with different life‐history characteristics. From an ecological point of view, this method is a valid alternative to commercial revegetation using seed mixtures of non‐native species and large amounts of fertilizers.     

Spatial and Temporal Considerations in Restoring Habitat for Wildlife

An accumulated body of theory and empirical evidence suggests that habitat selection by animals is a scale‐dependent, hierarchical process. Hierarchy theory predicts that habitat suitability is influenced by the interaction of factors at multiple spatial scales from the microsite to the landscape and that higher‐order factors impose constraints at lower levels. For instance, large‐scale factors such as landscape context may make a site unsuitable for a species even if the vegetation structure and composition are appropriate. In addition, the spatial arrangement of habitat elements at all scales must be considered when planning restoration efforts. For example, the presence of snags does not ensure that the site will be suitable for snag‐dependent species. The size, age, and spacing of snags and their juxtaposition to other habitat elements must also be considered. Finally, all habitats are dynamic, and therefore the ecological processes that contribute to those dynamics must be maintained or suitable substitutes included in the recovery plan. When considering restoring habitat for wildlife, we recommend that managers: (1) identify the wildlife species they want to target for restoration efforts, (2) consider the size and landscape context of the restoration site and whether it is appropriate for the target species, (3) identify the habitat elements that are necessary for the target species, (4) develop a strategy for restoring those elements and the ecological processes that maintain them, and (5) implement a long‐term monitoring program to gauge the success of the restoration efforts.     

Historical Ecology, Responses to Current Ecological Changes and Conservation of Australian Spiders

In response to geohistorical events from the Mesozoic through the Tertiary with contraction of mesic forest to southwestern and eastern montane and coastal regions, and expansion of woodlands and xeric shrublands, nobreak Australian spiders today comprise relict families and genera (confined to Gondwanan habitats and refuges) along with later evolved representatives which have adapted to changing environments. Tropical relicts also persist in refugia in the arid interior while some spiders (both mygalomorphs and araneomorphs) have adapted to arid conditions, mainly through specialized behaviours. Although fire has become increasingly a phenomenon of the Australian environment it is doubtful whether any spiders are adapted to fire per se. European settlement has impacted differentially on relictual and later evolved representatives; a few species, including the funnelweb (Atrax robustus) and redback spider (Latrodectus hasselti) have benefited through enhanced habitat opportunities and some species of Badumna and other genera have become synanthropic. It is suggested that conservation strategies need to consider the ecoevolutionary history of particular spiders and their natural vulnerability or resilience to environmental factors.