A gradient model of vegetation and climate utilizing NOAA satellite imagery. Phase 1: Texas transect

A climatological model/variable termed the sponge (a measure of moisture availability based on daily temperature maxima and minima, and precipitation) was tested for potential biogeograhic, ecological, and agro-climatological applications. Results, depicted in tabular and graphic form, suggest that, as generalized climatic index, sponge is particularly appropriate for large-area and global vegetation monitoring. The feasibility of utilizing NOAA/AVHRR data for vegetation classification was investigated and a vegetation gradient model that utilizes sponge and AVHRR data was initiated. Along an east-west Texas gradient, vegetation, sponge, and AVHRR pixel data (channels 1 and 2) were obtained for 12 locations. The normalized difference values for the AVHRR data when plotted against vegetation characteristics (biomass, net productivity, leaf area) and sponge values along the Texas gradient suggest that a multivariate gradient model incorporating AVHRR and sponge data may indeed be useful in global vegetation stratification and monitoring

Soil Microbial Networks Shift Across a High-Elevation Successional Gradient.

While it is well established that microbial composition and diversity shift along environmental gradients, how interactions among microbes change is poorly understood. Here, we tested how community structure and species interactions among diverse groups of soil microbes (bacteria, fungi, non-fungal eukaryotes) change across a fundamental ecological gradient, succession. Our study system is a high-elevation alpine ecosystem that exhibits variability in successional stage due to topography and harsh environmental conditions. We used hierarchical Bayesian joint distribution modeling to remove the influence of environmental covariates on species distributions and generated interaction networks using the residual species-to-species variance-covariance matrix. We hypothesized that as ecological succession proceeds, diversity will increase, species composition will change, and soil microbial networks will become more complex. As expected, we found that diversity of most taxonomic groups increased over succession, and species composition changed considerably. Interestingly, and contrary to our hypothesis, interaction networks became less complex over succession (fewer interactions per taxon). Interactions between photosynthetic microbes and any other organism became less frequent over the gradient, whereas interactions between plants or soil microfauna and any other organism were more abundant in late succession. Results demonstrate that patterns in diversity and composition do not necessarily relate to patterns in network complexity and suggest that network analyses provide new insight into the ecology of highly diverse, microscopic communities

Scientific results of the Bryotrop expedition to Zaire and Rwanda : 7., life strategies of epiphytic bryophytes from tropical lowland and montane forests, ericaceous woodlands and the Dendrosenecio subpáramo of the eastern Congo basin and the adjacent mountains (Parc National de Kahuzi-Biega/Zaire, Forêt de Nyungwe/Rwanda)

Life strategies of epiphytic bryophytes are studied along an altitudinal gradient from the eastern Congo basin (tropical lowland zone) to the mountains of the East-African graben (tropical subalpine/alpine Zone; BRYOTROP III-transect). Three strategies, Colonists, Perennial shuttle species and Perennial stayers can be observed, which are further subdivided according to their reproduction tactic (high sexual reproductive effort, high asexual reproductive effort, moderately or low sexual and asexual reproductive effort). Of these, only taxa with a long life span (perennials) are of importance, indicating the unchanging and constant ecological conditions and long-lasting microsites, provided by the epiphytic habitats. The basis for the life strategy pattern analysis along the altitudinal gradient were plant sociological investigations and the determination of the mean percentage cover values for the different life strategy categories. By this, the distribution and occurrence of the different strategies within the communities and the altitudinal zones can be shown

Symmetric competition as a general model for single-species adaptive dynamics

Adaptive dynamics is a widely used framework for modeling long-term evolution of continuous phenotypes. It is based on invasion fitness functions, which determine selection gradients and the canonical equation of adaptive dynamics. Even though the derivation of the adaptive dynamics from a given invasion fitness function is general and model-independent, the derivation of the invasion fitness function itself requires specification of an underlying ecological model. Therefore, evolutionary insights gained from adaptive dynamics models are generally model-dependent. Logistic models for symmetric, frequency-dependent competition are widely used in this context. Such models have the property that the selection gradients derived from them are gradients of scalar functions, which reflects a certain gradient property of the corresponding invasion fitness function. We show that any adaptive dynamics model that is based on an invasion fitness functions with this gradient property can be transformed into a generalized symmetric competition model. This provides a precise delineation of the generality of results derived from competition models. Roughly speaking, to understand the adaptive dynamics of the class of models satisfying a certain gradient condition, one only needs a complete understanding of the adaptive dynamics of symmetric, frequency-dependent competition. We show how this result can be applied to number of basic issues in evolutionary theory.Comment: 26 pages, 1 figur

Benefits of Spatial Regulation in a Multispecies System

Spatial heterogeneity in multispecies systems affects both ecological interactions and the composition of harvest. A bioeconomic model is used to analyze the nonselective harvest of two stocks with generalized ecological interaction and different persistent distributions across two spatial strata. Harvester response to aggregate effort controls is shown to partially dissipate rents relative to the case where the spatial distribution of effort can be specified. Numerical solutions for time paths of spatial (first-best) and aggregate (secondbest) input constraints indicate factors affecting their relative efficiency. In the scenarios studied, benefits of spatial specificity range from 0 to 15% of total net present value (NPV), depending upon the spatial correlation of stocks, their relative growth rates and prices, and the cost gradient across space. The benefits of spatial regulation are also heightened by the presence of ecological interaction, especially predator-prey dynamics.Bycatch, multispecies system, second-best regulation, spatial, Q20, Q22, Q28, Resource /Energy Economics and Policy,

Quinoa crop biodiversity in Chile: an ancient plant cultivated with sustainable agricultural practices and producing grains of outstanding and diverse nutritional values

Quinoa crop (Chenopodium quinoa) has been cultivated since the last seven thousand years in Latin America. However the nutritional and functional properties have been diffused only since the last decade. The exportation market to Northern countries is increasing at levels not seen previously for an organic product. Its ancient cultivation practices were normally sustainable even in Chile. However strong isolation of today' small farmers in Chile has provoked less access to international markets and also great genetic distances among cultivars from the long latitudinal and ecological gradient where this crop is cultivated (4000 m.a.s.l. at 19ºS to coastal areas at sea level between 18ºS to 40ºS). The nutritional diversity along this gradient has not been previously studied. This study focuses on the nutritional properties of five distinctive local land races found along Chile, belonging to different genetic pools, but collected from farmers that have not developed formal crop improvement, with the exemption of a single hybrid variety, also included in this study. Results showed that genetic variability of quinoa ecotypes plus the environmental diversity allow an also great nutritional diversity. Protein content had significant lower levels (12%) for northern ecotypes while higher values (16%) were found among the less known southern seed origins, cultivated by Mapuche people. While other properties like Vitamin B2 showed higher values in northern ecotypes, supporting the idea that genetic richness or diversity of quinoa ecotypes hide an also rich nutritional diversity. All the cultivars are managed under sustainable ecological practices, unique possibility among small-scale farmers. (Résumé d'auteur

Relationship between forest clearing and biophysical factors in tropical environments: Implications for the design of a forest change monitoring approach

The relationship between forest clearing, biophysical factors (e.g, ecological zones, slope gradient, soils), and transportation network in Costa Rica was analyzed. The location of forested areas at four reference datas (1940, 1950, 1961, and 1977) as derived from aerial photography and LANDSAT MSS data was digitilized and entered into a geographically-referenced data base. Ecological zones as protrayed by the Holdridge Life Zone Ecology System, and the location of roads and railways were also digitized from maps of the entire country as input to the data base. Information on slope gradient and soils was digitized from maps of a 21,000 square kilometer area. The total area of forest cleared over four decades are related to biophysical factors was analyzed within the data base and deforestation rates and trends were tabulated. The relatiohship between forest clearing and ecological zone and the influence of topography, sils, and transportation network are presented and discussed