Integrated Biosphere Simulator

Last updated April 09, 2019

IBIS-2 is the version 2 of the land-surface model Integrated Biosphere Simulator (IBIS), which includes several major improvements and additions to the prototype model developed by Foley et al. [1996]. IBIS was designed to explicitly link land surface and hydrological processes, terrestrial biogeochemical cycles, and vegetation dynamics within a single physically consistent framework ^[1]

Vegetation is an assemblage of plant species and the ground cover they provide. It is a general term, without specific reference to particular taxa, life forms, structure, spatial extent, or any other specific botanical or geographic characteristics. It is broader than the term flora which refers to species composition. Perhaps the closest synonym is plant community, but vegetation can, and often does, refer to a wider range of spatial scales than that term does, including scales as large as the global. Primeval redwood forests, coastal mangrove stands, sphagnum bogs, desert soil crusts, roadside weed patches, wheat fields, cultivated gardens and lawns; all are encompassed by the term vegetation.

IBIS Functionality

The model considers transient changes in vegetation composition and structure in response to environmental change and is, therefore, classified as a Dynamic Global Vegetation Model (DGVM) ^[2] This new version of IBIS has improved representations of land surface physics, plant physiology, canopy phenology, plant functional type (PFT) differences, and carbon allocation. Furthermore, IBIS-2 includes a new belowground biogeochemistry submodel, which is coupled to detritus production (litterfall and fine root turnover). All process are organized in a hierarchical framework and operate at different time steps, ranging from 60 min to 1 year. Such an approach allows for explicit coupling among ecological, biophysical, and physiological processes occurring on different timescales.

Physiology is the scientific study of the functions and mechanisms which work within a living system.

Phenology is the study of periodic plant and animal life cycle events and how these are influenced by seasonal and interannual variations in climate, as well as habitat factors. The word, coined by the Belgian botanist Charles Morren around 1849, is derived from the Greek φαίνω (phainō), "to show, to bring to light, make to appear" + λόγος (logos), amongst others "study, discourse, reasoning" and indicates that phenology has been principally concerned with the dates of first occurrence of biological events in their annual cycle. Examples include the date of emergence of leaves and flowers, the first flight of butterflies and the first appearance of migratory birds, the date of leaf colouring and fall in deciduous trees, the dates of egg-laying of birds and amphibia, or the timing of the developmental cycles of temperate-zone honey bee colonies. In the scientific literature on ecology, the term is used more generally to indicate the time frame for any seasonal biological phenomena, including the dates of last appearance.

Plant functional types (PFTs) is a system used by climatologists to classify plants according to their physical, phylogenetic and phenological characteristics as part of an overall effort to develop a vegetation model for use in land use studies and climate models. PFTs provide a finer level of modeling than biomes, which represent gross areas such as desert, savannah, deciduous forest. In creating a PFT model, areas as small as 1 km² are modeled by defining the predominant plant type for that area, interpreted from satellite data or other means. For each plant functional type, a number of key parameters are defined, such as fecundity, competitiveness, resorption, etc.; the value of each parameter is determined or inferred from observable characteristics such as plant height, leaf area, etc.

IBIS Structure

The land surface module is based on the land surface transfer model (LSX) package of Thompson and Pollard,^[3] and simulates the energy, water, carbon, and momentum balance of the soil-vegetation-atmosphere system. The model represents two vegetation canopies (e.g., trees versus shrubs and grasses), eight soil layers, and three layers of snow (when required). The solar radiative transfer scheme of IBIS-2 has been simplified in comparison with LSX and IBIS-1; sunlit and shaded fractions of the canopies are no longer treated separately. The model now follows the approach of Sellers et al. [1986] and Bonan [1995]. Infrared radiation is simulated as if each vegetation layer is a semitransparent plane; canopy emissivity depends on foliage density. Another difference between IBIS-2 and IBIS-1 and LSX, is that IBIS-2 uses an empirical linear function of wind speed to estimate turbulent transfer between the soil surface and the lower vegetation canopy, and IBIS-1 and LSX use a logarithmic wind profile. The total evapotranspiration from the land surface is treated as the sum of three water vapor fluxes: evaporation from the soil surface, evaporation of water intercepted by vegetation canopies, and canopy transpiration.

Evapotranspiration (ET) is the sum of evaporation and plant transpiration from the Earth's land and ocean surface to the atmosphere. Evaporation accounts for the movement of water to the air from sources such as the soil, canopy interception, and waterbodies. Transpiration accounts for the movement of water within a plant and the subsequent loss of water as vapor through stomata in its leaves. Evapotranspiration is an important part of the water cycle. An element that contributes to evapotranspiration can be called an evapotranspirator.

IBIS simulates the variations of heat and moisture in the soil. The eight layers are described in terms of soil temperature, volumetric water content and ice content.^[4] All the process occurring in the soil are influenced by the soil texture and amount of organic matter within the soil. One difference from the physiological processes in previous version of the model is that IBIS-1 calculates the maximum Rubisco carboxylation capacity (Vm) by optimizing the net assimilation of carbon by the leaf.^[5] IBIS-2 prescribes constant values of Vm for the plant functional typed (PFT). To scale photosynthesis and transpiration from the leaf level to canopy level, IBIS-2 assumes that the net photosynthesis within the canopy is proportional to the APAR within it.

Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organisms' activities. This chemical energy is stored in carbohydrate molecules, such as sugars, which are synthesized from carbon dioxide and water – hence the name photosynthesis, from the Greek φῶς, phōs, "light", and σύνθεσις, synthesis, "putting together". In most cases, oxygen is also released as a waste product. Most plants, most algae, and cyanobacteria perform photosynthesis; such organisms are called photoautotrophs. Photosynthesis is largely responsible for producing and maintaining the oxygen content of the Earth's atmosphere, and supplies all of the organic compounds and most of the energy necessary for life on Earth.

Soil Biogeochemistry

In the original version of IBIS ^[6] there was no explicit below ground biogeochemistry model to complete flow of carbon between the vegetation, detritus, and soil organic matter pools. IBIS-2 includes a new soil biogeochemistry module.^[7]

Soil organic matter (SOM) is the organic matter component of soil, consisting of plant and animal residues at various stages of decomposition, cells and tissues of soil organisms, and substances synthesized by soil organisms. SOM exerts numerous positive effects on soil physical and chemical properties, as well as the soil’s capacity to provide regulatory ecosystem services. Particularly, the presence of SOM is regarded as being critical for soil functions and soil quality.

Related Research Articles

The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth. Carbon is the main component of biological compounds as well as a major component of many minerals such as limestone. Along with the nitrogen cycle and the water cycle, the carbon cycle comprises a sequence of events that are key to make Earth capable of sustaining life. It describes the movement of carbon as it is recycled and reused throughout the biosphere, as well as long-term processes of carbon sequestration to and release from carbon sinks.

Rainforests are forests characterized by high rainfall, with annual rainfall in the case of tropical rainforests between 250 and 450 centimetres, and definitions varying by region for temperate rainforests. The monsoon trough, alternatively known as the intertropical convergence zone, plays a significant role in creating the climatic conditions necessary for the Earth's tropical rainforests.

Soil science is the study of soil as a natural resource on the surface of the Earth including soil formation, classification and mapping; physical, chemical, biological, and fertility properties of soils; and these properties in relation to the use and management of soils.

Soil erosion is the displacement of the upper layer of soil, one form of soil degradation. This natural process is caused by the dynamic activity of erosive agents, that is, water, ice (glaciers), snow, air (wind), plants, animals, and humans. In accordance with these agents, erosion is sometimes divided into water erosion, glacial erosion, snow erosion, wind (aeolean) erosion, zoogenic erosion, and anthropogenic erosion. Soil erosion may be a slow process that continues relatively unnoticed, or it may occur at an alarming rate causing a serious loss of topsoil. The loss of soil from farmland may be reflected in reduced crop production potential, lower surface water quality and damaged drainage networks.

In ecology, primary production is the synthesis of organic compounds from atmospheric or aqueous carbon dioxide. It principally occurs through the process of photosynthesis, which uses light as its source of energy, but it also occurs through chemosynthesis, which uses the oxidation or reduction of inorganic chemical compounds as its source of energy. Almost all life on Earth relies directly or indirectly on primary production. The organisms responsible for primary production are known as primary producers or autotrophs, and form the base of the food chain. In terrestrial ecoregions, these are mainly plants, while in aquatic ecoregions algae predominate in this role. Ecologists distinguish primary production as either net or gross, the former accounting for losses to processes such as cellular respiration, the latter not.

Biogeochemistry is the scientific discipline that involves the study of the chemical, physical, geological, and biological processes and reactions that govern the composition of the natural environment. In particular, biogeochemistry is the study of the cycles of chemical elements, such as carbon and nitrogen, and their interactions with and incorporation into living things transported through earth scale biological systems in space through time. The field focuses on chemical cycles which are either driven by or influence biological activity. Particular emphasis is placed on the study of carbon, nitrogen, sulfur, and phosphorus cycles. Biogeochemistry is a systems science closely related to systems ecology.

The pedosphere is the outermost layer of the Earth that is composed of soil and subject to soil formation processes. It exists at the interface of the lithosphere, atmosphere, hydrosphere and biosphere. The pedosphere is the skin of the Earth and only develops when there is a dynamic interaction between the atmosphere, biosphere, lithosphere and the hydrosphere. The pedosphere is the foundation of terrestrial life on Earth.

Ecosystem ecology The study of living and non-living components of ecosystems and their interactions

Ecosystem ecology is the integrated study of living (biotic) and non-living (abiotic) components of ecosystems and their interactions within an ecosystem framework. This science examines how ecosystems work and relates this to their components such as chemicals, bedrock, soil, plants, and animals.

Ecohydrology is an interdisciplinary scientific field studying the interactions between water and ecological systems. It is considered a sub discipline of hydrology, with an ecological focus. These interactions may take place within water bodies, such as rivers and lakes, or on land, in forests, deserts, and other terrestrial ecosystems. Areas of research in ecohydrology include transpiration and plant water use, adaption of organisms to their water environment, influence of vegetation and benthic plants on stream flow and function, and feedbacks between ecological processes and the hydrological cycle.

The International Geosphere-Biosphere Programme (IGBP) was a research programme that studies the phenomenon of global change that ran from 1987 to 2015.

The Global Environmental Multiscale Model (GEM), often known as the CMC model in North America, is an integrated forecasting and data assimilation system developed in the Recherche en Prévision Numérique (RPN), Meteorological Research Branch (MRB), and the Canadian Meteorological Centre (CMC). Along with the NWS's global forecast system (GFS), which runs out to 16 days, the ECMWF's Integrated Forecast System (IFS), which runs out 10 days, the Naval Research Laboratory Navy Global Environmental Model (NAVGEM), which runs out eight days, and the UK Met Office's Unified Model, which runs out to six days, it is one of the five predominant synoptic scale medium-range models in general use.

In climate science, a biosphere model, is used to model the biosphere of Earth, and can be coupled with atmospheric general circulation models (GCMs) for modelling the entire climate system.

A Dynamic Global Vegetation Model (DGVM) is a computer program that simulates shifts in potential vegetation and its associated biogeochemical and hydrological cycles as a response to shifts in climate. DGVMs use time series of climate data and, given constraints of latitude, topography, and soil characteristics, simulate monthly or daily dynamics of ecosystem processes. DGVMs are used most often to simulate the effects of future climate change on natural vegetation and its carbon and water cycles.

Climate change feedback is important in the understanding of global warming because feedback processes may amplify or diminish the effect of each climate forcing, and so play an important part in determining the climate sensitivity and future climate state. Feedback in general is the process in which changing one quantity changes a second quantity, and the change in the second quantity in turn changes the first. Positive feedback amplifies the change in the first quantity while negative feedback reduces it.

The permafrost carbon cycle is a sub-cycle of the larger global carbon cycle. Permafrost is defined as subsurface material that remains below 0^o C for at least two consecutive years. Because permafrost soils remain frozen for long periods of time, they store large amounts of carbon and other nutrients within their frozen framework during that time. Permafrost represents a large carbon reservoir that is seldom considered when determining global terrestrial carbon reservoirs. Recent and ongoing scientific research however, is changing this view.

DPHM-RS is a semi-distributed hydrologic model developed at University of Alberta, Canada.

The atmosphere is one of the Earth's major carbon reservoirs and an important component of the global carbon cycle, holding approximately 720 gigatons of carbon. Atmospheric carbon plays an important role in the greenhouse effect. The most important carbon compound in this respect is the gas carbon dioxide. Although it is a small percentage of the atmosphere, it plays a vital role in retaining heat in the atmosphere and thus in the greenhouse effect. Other gases with effects on the climate containing carbon in the atmosphere are methane and chlorofluorocarbons. Emissions by humans in the past 200 years have almost doubled the amount carbon dioxide in the atmosphere.

The Amazon Tall Tower Observatory or ATTO is a scientific research facility in the Amazon rainforest of Brazil. Infrastructure includes a 325 metres (1,066 ft) tall tower that extends far above the forest canopy and two smaller towers that allow researchers to collect samples from the soil surface to above the forest canopy. Additionally, there are container-labs, a base camp and nearby sites for studying vegetation and soil processes. The tall research tower is as high as the Eiffel Tower and is the tallest research tower in South America. The two further towers are 80 metres (260 ft) in height. All towers are equipped with a broad range of instruments to measure chemical and physical properties of the atmosphere, such as greenhouse gas concentrations, aerosols and meteorological data.

Ecosystem Functional Type (EFT) (Fig.1) is a new ecological concept to characterize ecosystem functioning. Ecosystem Functional Types are defined as groups of ecosystems or patches of the land surface that share similar dynamics of matter and energy exchanges between the biota and the physical environment. The EFT concept is analogous to the Plant Functional Types (PFTs) concept, but defined at a higher level of the biological organization. As plant species can be grouped according to common functional characteristics, ecosystems can be grouped according to their common functional behavior.

(Iain) Colin Prentice holds the AXA Chair in Biosphere and Climate Impacts at Imperial College London and an Honorary Chair in Ecology and Evolution at Macquarie University in Australia.

References

↑ [Kucharik et al. 2000].
↑ [Steffeen et al. 1992; Walker, 1994; W. Cramer et al., Dynamic responses of global terrestrial vegetation changes in CO2 and climate, submitted to Global Change Biology, 1999].
↑ [1995a,b]
↑ [Pollard and Thompson, 1995; Foley et al. 1996]
↑ [Haxeltine and Prentice, 1996]
↑ [Foley et al. 1996]
↑ [Kucharik et al., submitted manuscript, 1999]

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[1] [Kucharik et al. 2000].

[2] [Steffeen et al. 1992; Walker, 1994; W. Cramer et al., Dynamic responses of global terrestrial vegetation changes in CO2 and climate, submitted to Global Change Biology, 1999].

[3] [1995a,b]

[4] [Pollard and Thompson, 1995; Foley et al. 1996]

[5] [Haxeltine and Prentice, 1996]

[6] [Foley et al. 1996]

[7] [Kucharik et al., submitted manuscript, 1999]