Catalogue Search | MBRL
Are you sure you want to remove the book from the shelf?
{{itemTitle}}
85
result(s) for
"Biosphere 2"
Sort by:
Pushing our limits : insights from Biosphere 2
Biospherian Mark Nelson offers insider perspectives on Biosphere 2 and bold insights into today's global ecological challenges--Provided by publisher.
Book
Pushing Our Limits
Pushing Our Limits is a fresh examination of Biosphere 2,
the world's first man-made mini-world, twenty-five years after its
first closure experiment. Author Mark Nelson, one of the eight crew
members locked in the enclosure during the 1991-1993 experiment,
offers a compelling insider's view of the dramatic story behind
Biosphere 2. Biosphere 2 helped change public understanding of what
our global biosphere is and how it provides for our health and
well-being. However, the experiment is often dismissed as a
failure, and news outlets at the time focused on interpersonal
conflicts and unexpected problems that arose. Delving past the
sensationalism, Nelson presents the goals and results of the
experiment, addresses the implications of the project for our
global situation, and discusses how the project's challenges and
successes can change our thinking about Biosphere 1: the Earth.
Pushing Our Limits offers insights from the project that
can help us deal with our global ecological challenges. It also
shows the intense and fulfilling connection the biospherians felt
with their life support system and how this led to their vigilant
attention to its needs. With current concerns of sustainability and
protection of our global biosphere, as well as the challenge of
learning how to support life in space and on Mars, the largest,
longest, and most important experiment in closed ecosystems is more
relevant than ever. The book explores Biosphere 2's lessons for
changing technology to support and not destroy nature and for
reconnecting people to a healthy relationship with nature.
eBook
Hysteresis of soil moisture spatial heterogeneity and the \homogenizing\ effect of vegetation
By partitioning mass and energy fluxes, soil moisture exerts a fundamental control on basin hydrological response. Using the design characteristics of the Biosphere 2 hillslope experiment, this study investigates aspects of soil moisture spatial and temporal variability in a zero‐order catchment of a semiarid climate. The hydrological response of the domain exhibits a particular structure, which depends on whether topography‐induced subsurface stormflow is triggered. The occurrence of the latter is conditioned by topography, soil depth, and pre‐storm spatial distribution of moisture. As a result, a non‐unique behavior of soil moisture spatial heterogeneity emerges, manifested through a hysteretic dependence of variability metrics on mean water content. Further, it is argued that vegetation dynamics impose a “homogenizing” effect on pre‐storm moisture states, decreasing the likelihood that a rainfall event will result in topographic redistribution of soil water. Consequently, post‐rainfall soil moisture dynamics associated with the effect of topography that could lead to the enhancement of spatial heterogeneity are suppressed; a potential “attractor” of catchment states emerges. The study thus proposes several hypotheses that will be testable within the framework of long‐term hillslope experiments.
Journal Article
Soil microbial composition and carbon mineralization are associated with vegetation type and temperature regime in mesocosms of a semiarid ecosystem
ABSTRACT
Transition from historic grasslands to woody plants in semiarid regions has led to questions about impacts on soil functioning, where microorganisms play a primary role. Understanding the relationship between microbes, plant diversity and soil functioning is relevant to assess such impacts. We evaluate the effect that plant type change in semiarid ecosystems has for microbial diversity and composition, and how this is related to carbon mineralization (CMIN) as a proxy for soil functioning. We followed a mesocosm experiment during 2 years within the Biosphere 2 facility in Oracle, AZ, USA. Two temperature regimes were established with two types of plants (grass or mesquite). Soil samples were analyzed for physicochemical and functional parameters, as well as microbial community composition using 16S rRNA amplicon metagenomics (Illumina MiSeq). Our results show the combined role of plant type and temperature regime in CMIN, where CMIN in grass has lower values at elevated temperatures compared with the opposite trend in mesquite. We also found a strong correlation of microbial composition with plant type but not with temperature regime. Overall, we provide evidence of the major effect of plant type in the specific composition of microbial communities as a potential result of the shrub encroachment.
Relative role of plant type and temperature regime in soil microbial community assembly and associated functional dynamics in semiarid ecosystems.
Journal Article
Hillslope-scale experiment demonstrates the role of convergence during two-step saturation
Subsurface flow and storage dynamics at hillslope scale are difficult to ascertain, often in part due to a lack of sufficient high-resolution measurements and an incomplete understanding of boundary conditions, soil properties, and other environmental aspects. A continuous and extreme rainfall experiment on an artificial hillslope at Biosphere 2's Landscape Evolution Observatory (LEO) resulted in saturation excess overland flow and gully erosion in the convergent hillslope area. An array of 496 soil moisture sensors revealed a two-step saturation process. First, the downward movement of the wetting front brought soils to a relatively constant but still unsaturated moisture content. Second, soils were brought to saturated conditions from below in response to rising water tables. Convergent areas responded faster than upslope areas, due to contributions from lateral subsurface flow driven by the topography of the bottom boundary, which is comparable to impermeable bedrock in natural environments. This led to the formation of a groundwater ridge in the convergent area, triggering saturation excess runoff generation. This unique experiment demonstrates, at very high spatial and temporal resolution, the role of convergence on subsurface storage and flow dynamics. The results bring into question the representation of saturation excess overland flow in conceptual rainfall-runoff models and land-surface models, since flow is gravity-driven in many of these models and upper layers cannot become saturated from below. The results also provide a baseline to study the role of the co-evolution of ecological and hydrological processes in determining landscape water dynamics during future experiments in LEO.
Journal Article
Hillslope hydrology under glass: confronting fundamental questions of soil-water-biota co-evolution at Biosphere 2
Recent studies have called for a new unifying hydrological theory at the hillslope and watershed scale, emphasizing the importance of coupled process understanding of the interactions between hydrology, ecology, pedology, geochemistry and geomorphology. The Biosphere 2 Hillslope Experiment is aimed at tackling this challenge and exploring how climate, soil and vegetation interact and drive the evolution of the hydrologic hillslope behavior. A set of three large-scale hillslopes (18 m by 33 m each) will be built in the climate-controlled experimental biome of the Biosphere 2 facility near Tucson, Arizona, USA. By minimizing the initial physical complexity of these hillslopes, the spontaneous formation of flow pathways, soil spatial heterogeneity, surface morphology and vegetation patterns can be observed over time. This paper documents the hydrologic design process for the Biosphere 2 Hillslope Experiment, which was based on design principles agreed upon among the Biosphere 2 science community. Main design principles were that the hillslopes should promote spatiotemporal variability of hydrological states and fluxes, facilitate transient lateral subsurface flow without inducing overland flow and be capable of supporting vegetation. Hydrologic modeling was used to identify a hillslope configuration (geometry, soil texture, soil depth) that meets the design objectives. The recommended design for the hillslopes consists of a zero-order basin shape with a 10 degree overall slope, a uniform soil depth of 1 m and a loamy sand soil texture. The sensitivity of the hydrologic response of this design to different semi-arid climate scenarios was subsequently tested. Our modeling showed that the timing of rainfall in relation to the timing of radiation input controls the spatiotemporal variability of moisture within the hillslope and the generation of lateral subsurface flow. The Biosphere 2 Hillslope Experiment will provide an excellent opportunity to test hypotheses, observe emergent patterns and advance the understanding of interactions.
Journal Article
Land surface modeling inside the Biosphere 2 tropical rain forest biome
Tropical rain forests contribute substantially to regional and global energy, water, and carbon exchanges between the land surface and the atmosphere, and better understanding of the mechanisms of vegetation response to different environmental stresses is needed. The Biosphere 2 facility provides an opportunity to link laboratory‐scale and plot‐scale studies in a controllable environment. We compiled a consistent quality‐controlled time series of climate data from Biosphere 2 and used it to drive the Simple Biosphere model (SiB3) to test how well it represented the behavior of soils and vegetation inside the tropical rain forest biome of Biosphere 2 (B2‐TRF). We found that soil respiration parameterization in SiB3 was not suitable for use in B2‐TRF, so several alternative parameterizations were tested. None gave outstanding results, but a modified version of the parameterization originally proposed for SiB3 gave the best results. With this modification, SiB3 well simulated the observed net ecosystem exchange in B2‐TRF but, significantly, only after additionally modifying parameters describing the thermal tolerance of plants so that photosynthetic capacity was reduced on average but maintained to higher temperatures. This implies either that tropical rain forest species can acclimate to higher temperatures than allowed for by vegetation models or that the plant community assembly in B2‐TRF has shifted to allow continued functioning at higher temperatures, and plants in natural ecosystems could also. In either case, this suggests that the Amazon rain forest may be more resilient to climate change than hitherto thought.
Journal Article
Solid phase evolution in the Biosphere 2 hillslope experiment as predicted by modeling of hydrologic and geochemical fluxes
A reactive transport geochemical modeling study was conducted to help predict the mineral transformations occurring over a ten year time-scale that are expected to impact soil hydraulic properties in the Biosphere 2 (B2) synthetic hillslope experiment. The modeling sought to predict the rate and extent of weathering of a granular basalt (selected for hillslope construction) as a function of climatic drivers, and to assess the feedback effects of such weathering processes on the hydraulic properties of the hillslope. Flow vectors were imported from HYDRUS into a reactive transport code, CrunchFlow2007, which was then used to model mineral weathering coupled to reactive solute transport. Associated particle size evolution was translated into changes in saturated hydraulic conductivity using Rosetta software. We found that flow characteristics, including velocity and saturation, strongly influenced the predicted extent of incongruent mineral weathering and neo-phase precipitation on the hillslope. Results were also highly sensitive to specific surface areas of the soil media, consistent with surface reaction controls on dissolution. Effects of fluid flow on weathering resulted in significant differences in the prediction of soil particle size distributions, which should feedback to alter hillslope hydraulic conductivities.
Journal Article
A physical derivation of nutrient-uptake rates in coral reefs: effects of roughness and waves
Mass-transfer rates between water and benthos are derived based on the dissipation of energy by the benthic communities of coral reefs. Roughness of the benthic communities causes currents and waves to dissipate energy on reef flats at rates which far exceed ocean values of energy dissipation. The derivation here shows that first-order rate constants for nutrient uptake are (1) proportional to energy dissipation to the 0.25 root, (2) proportional to the bottom shear stress to the 0.4 root, and (3) proportional to current speed to the 0.75 root (decreasing to the 0.4 root under extreme wave activity). The shear stress, thus nutrient uptake, is positively correlated to the large-scale roughness, and to excess wave height (above the breaking height) of incoming waves. These causal relationships between nutrient-uptake rates and dissipation of energy support the general observations of reef zonation and reef metabolic rates, and are the paramount reason that coral reefs can maintain high productivity in low-nutrient tropical waters.
Journal Article