Here we present a new terrestrial biosphere model (the Integrated Biosphere Simulator ‐ IBIS) which demonstrates how land surface biophysics, terrestrial carbon fluxes, and global vegetation dynamics can be represented in a single, physically consistent modeling framework. In order to integrate a wide range of biophysical, physiological, and ecological processes, the model is designed around a hierarchical, modular structure and uses a common state description throughout. First, a coupled simulation of the surface water, energy, and carbon fluxes is performed on hourly timesteps and is integrated over the year to estimate the annual water and carbon balance. Next, the annual carbon balance is used to predict changes in the leaf area index and biomass for each of nine plant functional types, which compete for light and water using different ecological strategies. The resulting patterns of annual evapotranspiration, runoff, and net primary productivity are in good agreement with observations. In addition, the model simulates patterns of vegetation dynamics that qualitatively agree with features of the natural process of secondary succession. Comparison of the model's inferred near‐equilibrium vegetation categories with a potential natural vegetation map shows a fair degree of agreement. This integrated modeling framework provides a means of simulating both rapid biophysical processes and long‐term ecosystem dynamics that can be directly incorporated within atmospheric models.
The equilibrium terrestrial biosphere model BIOME3 simulates vegetation distribution and biogeochemistry, and couples vegetation distribution directly to biogeochemistry. Model inputs consist of latitude, soil texture class, and monthly climate (temperature, precipitation, and sunshine) data on a 0.5° grid. Ecophysiological constraints determine which plant functional types (PFTs) may potentially occur. A coupled carbon and water flux model is then used to calculate, for each PFT, the leaf area index (LAI) that maximizes net primary production (NPP), subject to the constraint that NPP must be sufficient to maintain this LAI. Competition between PFTs is simulated by using the optimal NPP of each PFT as an index of competitiveness, with additional rules to approximate the dynamic equilibrium between natural disturbance and succession driven by light competition. Model output consists of a quantitative vegetation state description in terms of the dominant PFT, secondary PFTs present, and the total LAI and NPP for the ecosystem. Canopy conductance is treated as a function of the calculated optimal photosynthetic rate and water stress. Regional evapotranspiration is calculated as a function of canopy conductance, equilibrium evapotranspiration rate, and soil moisture using a simple planetary boundary layer parameterization. This scheme results in a two‐way coupling of the carbon and water fluxes through canopy conductance, allowing simulation of the response of photosynthesis, stomatal conductance, and leaf area to environmental factors including atmospheric CO2. Comparison with the mapped distribution of global vegetation shows that the model successfully reproduces the broad‐scale patterns in potential natural vegetation distribution. Comparison with NPP measurements, and with an FPAR (fractional absorbed photosynthetically active radiation) climatology based on remotely sensed greenness measurements, provides further checks on the model's internal logic. The model is envisaged as a tool for integrated analysis of the impacts of changes in climate and CO2 on ecosystem structure and function.
The challenges of sustainable development (and climate change and peak oil, in particular) demand system-wide transformations in sociotechnical systems of provision. An academic literature around coevolutionary innovation for sustainability has recently emerged as an attempt to understand the dynamics and directions of such sociotechnical transformations, which are termed 'sustainability transitions'. This literature has previously focused on market-based technological innovations. Here we apply it to a new context of civil-society-based social innovation and examine the role of community-based initiatives in a transition to a low-carbon sustainable economy in the UK. We present new empirical research from a study of the UK's Transition Towns movement (a 'grassroots innovation') and assess its attempts to grow and infl uence wider societal sociotechnical systems. By applying strategic niche management theory to this civil society context, we deliver theoretically informed practical recommendations for this movement to diff use beyond its niche: to foster deeper engagement with resourceful regime actors; to manage expectations more realistically by delivering tangible opportunities for action and participation; and to embrace a community-based, action-oriented model of social change (in preference to a cognitive theory of behaviour change). Furthermore, our study indicates areas where theory can be refi ned to better explain the growth and broader impacts of grassroots innovations-namely, through a fuller appreciation of the importance of internal niche processes, by understanding the important role of identity and group formation, and by resolving how social practices change in grassroots innovations.
This article responds to increasing public and academic discourses on social innovation, which often rest on the assumption that social innovation can drive societal change and empower actors to deal with societal challenges and a retreating welfare state. In order to scrutinise this assumption, this article proposes a set of concepts to study the dynamics of transformative social innovation and underlying processes of multi-actor (dis)empowerment. First, the concept of transformative social innovation is unpacked by proposing four foundational concepts to help distinguish between different pertinent ‘shades’ of change and innovation: 1) social innovation, (2) system innovation, (3) game-changers, and (4) narratives of change. These concepts, invoking insights from transitions studies and social innovations literature, are used to construct a conceptual account of how transformative social innovation emerges as a co-evolutionary interaction between diverse shades of change and innovation. Second, the paper critically discusses the dialectic nature of multi-actor (dis)empowerment that underlies such processes of change and innovation. The paper then demonstrates how the conceptualisations are applied to three empirical case-studies of transformative social innovation: Impact Hub, Time Banks and Credit Unions. In the conclusion we synthesise how the concepts and the empirical examples help to understand contemporary shifts in societal power relations and the changing role of the welfare state
Estimates of glacial-interglacial climate change in tropical Africa have varied widely. Results from a process-based vegetation model show how montane vegetation in East Africa shifts with changes in both carbon dioxide concentration and climate. For the last glacial maximum, the change in atmospheric carbon dioxide concentration alone could explain the observed replacement of tropical montane forest by a scrub biome. This result implies that estimates of the last glacial maximum tropical cooling based on tree- line shifts must be revised.
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