Impact of spin-up forcing on vegetation states simulated by a dynamic global vegetation model coupled with a land surface model

2011 ◽  
Vol 28 (4) ◽  
pp. 775-788 ◽  
Author(s):  
Fang Li ◽  
Xiaodong Zeng ◽  
Xiang Song ◽  
Dongxiao Tian ◽  
Pu Shao ◽  
...  
Keyword(s):  
Land Surface ◽  
Land Surface Model ◽  
Surface Model ◽  
Vegetation Model ◽  
Dynamic Global Vegetation Model ◽  
Global Vegetation

scholarly journals The Jena Diversity-Dynamic Global Vegetation Model (JeDi-DGVM): a diverse approach to representing terrestrial biogeography and biogeochemistry based on plant functional trade-offs

2013 ◽  
Vol 10 (6) ◽  
pp. 4137-4177 ◽  
Author(s):  
R. Pavlick ◽  
D. T. Drewry ◽  
K. Bohn ◽  
B. Reu ◽  
A. Kleidon
Keyword(s):  
Functional Diversity ◽  
Land Surface ◽  
Grid Cell ◽  
Surface Fluxes ◽  
Growth Strategies ◽  
Vegetation Model ◽  
Terrestrial Biosphere ◽  
Dynamic Global Vegetation Model ◽  
Trade Offs ◽  
Global Vegetation

Abstract. Terrestrial biosphere models typically abstract the immense diversity of vegetation forms and functioning into a relatively small set of predefined semi-empirical plant functional types (PFTs). There is growing evidence, however, from the field ecology community as well as from modelling studies that current PFT schemes may not adequately represent the observed variations in plant functional traits and their effect on ecosystem functioning. In this paper, we introduce the Jena Diversity-Dynamic Global Vegetation Model (JeDi-DGVM) as a new approach to terrestrial biosphere modelling with a richer representation of functional diversity than traditional modelling approaches based on a small number of fixed PFTs. JeDi-DGVM simulates the performance of a large number of randomly generated plant growth strategies, each defined by a set of 15 trait parameters which characterize various aspects of plant functioning including carbon allocation, ecophysiology and phenology. Each trait parameter is involved in one or more functional trade-offs. These trade-offs ultimately determine whether a strategy is able to survive under the climatic conditions in a given model grid cell and its performance relative to the other strategies. The biogeochemical fluxes and land surface properties of the individual strategies are aggregated to the grid-cell scale using a mass-based weighting scheme. We evaluate the simulated global biogeochemical patterns against a variety of field and satellite-based observations following a protocol established by the Carbon-Land Model Intercomparison Project. The land surface fluxes and vegetation structural properties are reasonably well simulated by JeDi-DGVM, and compare favourably with other state-of-the-art global vegetation models. We also evaluate the simulated patterns of functional diversity and the sensitivity of the JeDi-DGVM modelling approach to the number of sampled strategies. Altogether, the results demonstrate the parsimonious and flexible nature of a functional trade-off approach to global vegetation modelling, i.e. it can provide more types of testable outputs than standard PFT-based approaches and with fewer inputs. The approach implemented here in JeDi-DGVM sets the foundation for future applications that will explore the impacts of explicitly resolving diverse plant communities, allowing for a more flexible temporal and spatial representation of the structure and function of the terrestrial biosphere.

scholarly journals A process-based <i>Sphagnum</i> plant-functional-type model for implementation in the TRIFFID Dynamic Global Vegetation Model

2019 ◽  
Author(s):  
Richard Coppell ◽  
Emanuel Gloor ◽  
Joseph Holden
Keyword(s):  
Water Table ◽  
Primary Productivity ◽  
Photosynthetically Active Radiation ◽  
Land Surface ◽  
Net Primary Productivity ◽  
Type Model ◽  
Surface Model ◽  
Dynamic Global Vegetation Model ◽  
Active Radiation ◽  
Global Vegetation

Abstract. Peatlands are important carbon stores and Sphagnum moss represents a critical peatland genus contributing to carbon exchange and storage. However, gas fluxes in Sphagnum-dominated systems are poorly represented in Dynamic Global Vegetation Models (DGVMs) which simulate, via incorporation of Plant Functional Types (PFTs), biogeochemical and energy fluxes between vegetation, the land surface and the atmosphere. Mechanisms characterised by PFTs within DGVMs include photosynthesis, respiration and competition and, in more recent DGVMs, sub-daily gas-exchange processes regulated by leaf 10 stomata. However, Sphagnum, like all mosses, are non-vascular plants and do not exhibit stomatal regulation. In order to achieve a level of process detail consistent with existing vascular vegetation PFTs within DGVMs, this paper describes a new process-based non-vascular-PFT model that is implemented within the TRIFFID DGVM used by the JULES land surface model. The new PFT model was tested against extant published field and laboratory studies of peat assemblage-net primary productivity, assemblage-gross primary productivity, assemblage respiration, water-table position, incoming 15 photosynthetically active radiation, temperature, and canopy dark respiration. The PFT model’s parameters were roughly tuned and the PFT model easily produced curves of the correct shape for peat assemblage-net primary productivity against water-table position, incoming photosynthetically active radiation and temperature, suggesting that it replicates the internal productivity mechanism of Sphagnum for the first time. Minor modifications should also allow it to be used across a range of other bryophytes enabling this non-vascular PFT model to have enhanced functionality.

scholarly journals Improved simulation of fire–vegetation interactions in the Land surface Processes and eXchanges dynamic global vegetation model (LPX-Mv1)

2014 ◽  
Vol 7 (5) ◽  
pp. 2411-2433 ◽  
Author(s):  
D. I. Kelley ◽  
S. P. Harrison ◽  
I. C. Prentice
Keyword(s):  
Land Surface ◽  
Fire Regimes ◽  
Surface Processes ◽  
Bark Thickness ◽  
Northern Australia ◽  
Decomposition Rates ◽  
Vegetation Model ◽  
Dynamic Global Vegetation Model ◽  
Central Australia ◽  
Global Vegetation

Abstract. The Land surface Processes and eXchanges (LPX) model is a fire-enabled dynamic global vegetation model that performs well globally but has problems representing fire regimes and vegetative mix in savannas. Here we focus on improving the fire module. To improve the representation of ignitions, we introduced a reatment of lightning that allows the fraction of ground strikes to vary spatially and seasonally, realistically partitions strike distribution between wet and dry days, and varies the number of dry days with strikes. Fuel availability and moisture content were improved by implementing decomposition rates specific to individual plant functional types and litter classes, and litter drying rates driven by atmospheric water content. To improve water extraction by grasses, we use realistic plant-specific treatments of deep roots. To improve fire responses, we introduced adaptive bark thickness and post-fire resprouting for tropical and temperate broadleaf trees. All improvements are based on extensive analyses of relevant observational data sets. We test model performance for Australia, first evaluating parameterisations separately and then measuring overall behaviour against standard benchmarks. Changes to the lightning parameterisation produce a more realistic simulation of fires in southeastern and central Australia. Implementation of PFT-specific decomposition rates enhances performance in central Australia. Changes in fuel drying improve fire in northern Australia, while changes in rooting depth produce a more realistic simulation of fuel availability and structure in central and northern Australia. The introduction of adaptive bark thickness and resprouting produces more realistic fire regimes in Australian savannas. We also show that the model simulates biomass recovery rates consistent with observations from several different regions of the world characterised by resprouting vegetation. The new model (LPX-Mv1) produces an improved simulation of observed vegetation composition and mean annual burnt area, by 33 and 18% respectively compared to LPX.

scholarly journals Improved simulation of fire-vegetation interactions in the Land surface Processes and eXchanges dynamic global vegetation model (LPX-Mv1)

2014 ◽  
Vol 7 (1) ◽  
pp. 931-1000 ◽  
Author(s):  
D. I. Kelley ◽  
S. P. Harrison ◽  
I. C. Prentice
Keyword(s):  
Land Surface ◽  
Fire Regimes ◽  
Surface Processes ◽  
Bark Thickness ◽  
Northern Australia ◽  
Decomposition Rates ◽  
Vegetation Model ◽  
Dynamic Global Vegetation Model ◽  
Central Australia ◽  
Global Vegetation

Abstract. The Land surface Processes and eXchanges (LPX) model is a fire-enabled dynamic global vegetation model that performs well globally but has problems representing fire regimes and vegetative mix in savannas. Here we focus on improving the fire module. To improve the representation of ignitions, we introduced a treatment of lightning that allows the fraction of ground strikes to vary spatially and seasonally, realistically partitions strike distribution between wet and dry days, and varies the number of dry-days with strikes. Fuel availability and moisture content were improved by implementing decomposition rates specific to individual plant functional types and litter classes, and litter drying rates driven by atmospheric water content. To improve water extraction by grasses, we use realistic plant-specific treatments of deep roots. To improve fire responses, we introduced adaptive bark thickness and post-fire resprouting for tropical and temperate broadleaf trees. All improvements are based on extensive analyses of relevant observational data sets. We test model performance for Australia, first evaluating parameterisations separately and then measuring overall behaviour against standard benchmarks. Changes to the lightning parameterisation produce a more realistic simulation of fires in southeastern and central Australia. Implementation of PFT-specific decomposition rates enhances performance in central Australia. Changes in fuel drying improve fire in northern Australia, while changes in rooting depth produce a more realistic simulation of fuel availability and structure in central and northern Australia. The introduction of adaptive bark thickness and resprouting produces more realistic fire regimes in savannas, including simulating biomass recovery rates consistent with observations. The new model (LPX-Mv1) improves Australian vegetation composition by 33% and burnt area by 19% compared to LPX.

scholarly journals Accounting for forest age in the tile-based dynamic global vegetation model JSBACH4 (4.20p7; git feature/forests) – a land surface model for the ICON-ESM

2019 ◽  
Author(s):  
Julia E. M. S. Nabel ◽  
Kim Naudts ◽  
Julia Pongratz
Keyword(s):  
Forest Management ◽  
Land Surface ◽  
Gross Primary Production ◽  
Surface Model ◽  
Forest Age ◽  
Age Classes ◽  
Dynamic Global Vegetation Model ◽  
Area Index ◽  
Global Vegetation ◽  
Age Structures

Abstract. Natural and anthropogenic disturbances, in particular forest management, affect forest age-structures all around the globe. Forest age-structures in turn influence biophysical and biogeochemical interactions of the vegetation with the atmosphere. Yet, many dynamic global vegetation models (DGVMs), including those used as land surface models (LSMs) in Earth system models (ESMs), do not account for subgrid forest age structures, despite being used to investigate land-use effects on the global carbon budget or simulating land–atmosphere interactions. In this paper we present a new scheme to introduce forest age-classes in hierarchical tile-based DGVMs combining benefits of recently applied approaches. Our scheme combines a computationally efficient age-dependent simulation of all relevant processes, such as photosynthesis and respiration, without loosing the information about the exact forest age, which is a prerequisite for the implementation of age-based forest management. This combination is achieved by using the hierarchy to track the area fraction for each age on an aggregated plant functional type level, whilst simulating the relevant processes for a set of age-classes. We describe how we implemented this scheme in JSBACH4, the LSM of the ICON-ESM. Subsequently, we compare simulation output against global observation-based products for gross primary production, leaf area index and above-ground biomass to assess the ability of simulations with and without age-classes to reproduce the annual cycle and large-scale spatial patterns of these variables. The comparisons show differences exponentially decreasing with the number of distinguished age-classes and linearly increasing computation costs. The results demonstrate the benefit of the introduction of age-classes, with the optimal number of age-classes being a compromise between computation costs and accuracy.

scholarly journals Accounting for forest age in the tile-based dynamic global vegetation model JSBACH4 (4.20p7; git feature/forests) – a land surface model for the ICON-ESM

2020 ◽  
Vol 13 (1) ◽  
pp. 185-200 ◽  
Author(s):  
Julia E. M. S. Nabel ◽  
Kim Naudts ◽  
Julia Pongratz
Keyword(s):  
Forest Management ◽  
Land Surface ◽  
Surface Model ◽  
Earth System ◽  
Forest Age ◽  
Age Classes ◽  
Dynamic Global Vegetation Model ◽  
Area Index ◽  
Global Vegetation ◽  
Age Structures

Abstract. Natural and anthropogenic disturbances, in particular forest management, affect forest age structures all around the globe. Forest age structures in turn influence key land surface processes, such as photosynthesis and thus the carbon cycle. Yet, many dynamic global vegetation models (DGVMs), including those used as land surface models (LSMs) in Earth system models (ESMs), do not account for subgrid forest age structures, despite being used to investigate land-use effects on the global carbon budget or simulating biogeochemical responses to climate change. In this paper we present a new scheme to introduce forest age classes in hierarchical tile-based DGVMs combining benefits of recently applied approaches the first being a computationally efficient age-dependent simulation of all relevant processes, such as photosynthesis and respiration, using a restricted number of age classes and the second being the tracking of the exact forest age, which is a prerequisite for any implementation of age-based forest management. This combination is achieved by using the tile hierarchy to track the area fraction for each age on an aggregated plant functional type level, whilst simulating the relevant processes for a set of age classes. We describe how we implemented this scheme in JSBACH4, the LSM of the ICOsahedral Non-hydrostatic Earth system model (ICON-ESM). Subsequently, we compare simulation output to global observation-based products for gross primary production, leaf area index, and above-ground biomass to assess the ability of simulations with and without age classes to reproduce the annual cycle and large-scale spatial patterns of these variables. The comparisons show decreasing differences and increasing computation costs with an increasing number of distinguished age classes. The results demonstrate the benefit of the introduction of age classes, with the optimal number of age classes being a compromise between computation costs and error reduction.

scholarly journals Evaluation of global continental hydrology as simulated by the Land-surface Processes and eXchanges Dynamic Global Vegetation Model

2010 ◽  
Vol 7 (4) ◽  
pp. 4219-4251 ◽  
Author(s):  
S. J. Murray ◽  
P. N. Foster ◽  
I. C. Prentice
Keyword(s):  
Land Surface ◽  
Hydrological Cycle ◽  
Fire Regime ◽  
Surface Processes ◽  
Low Flow ◽  
Vegetation Model ◽  
Land Surface Processes ◽  
Dynamic Global Vegetation Model ◽  
Continental Hydrology ◽  
Global Vegetation

Abstract. Global freshwater resources are sensitive to changes in climate, land cover and population density and distribution. The Land-surface Processes and eXchanges Dynamic Global Vegetation Model (LPX-DGVM) is a development of the Lund-Potsdam-Jena model with improved representation of fire-vegetation interactions. It allows simultaneous consideration of the effects of changes in climate, CO2 concentration, natural vegetation and fire regime shifts on the continental hydrological cycle. Here the model is assessed for its ability to simulate large-scale spatial and temporal runoff patterns, in order to test its suitability for modelling future global water resources. Comparisons are made against observations of streamflow and a composite dataset of modelled and observed runoff (1986–1995). The model captures the main features of the geographical distribution of global runoff, but tends to overestimate runoff in much of the Northern Hemisphere (where this can be largely accounted for by freshwater extractions and the unrealistic accumulation of the simulated winter snowpack in permafrost regions) and the southern tropics. Interannual variability is represented reasonably well at the large catchment scale, as are seasonal flow timings and monthly high and low flow events. Further improvements to the simulation of intra-annual runoff might be achieved via the addition of river flow routing. Overestimates of runoff in some basins could likely be corrected by the inclusion of transmission losses and direct-channel evaporation.

scholarly journals Evaluation of global continental hydrology as simulated by the Land-surface Processes and eXchanges Dynamic Global Vegetation Model

2011 ◽  
Vol 15 (1) ◽  
pp. 91-105 ◽  
Author(s):  
S. J. Murray ◽  
P. N. Foster ◽  
I. C. Prentice
Keyword(s):  
Land Surface ◽  
Hydrological Cycle ◽  
Fire Regime ◽  
Surface Processes ◽  
Low Flow ◽  
Vegetation Model ◽  
Land Surface Processes ◽  
Dynamic Global Vegetation Model ◽  
Continental Hydrology ◽  
Global Vegetation

Abstract. Global freshwater resources are sensitive to changes in climate, land cover and population density and distribution. The Land-surface Processes and eXchanges Dynamic Global Vegetation Model is a recent development of the Lund-Potsdam-Jena model with improved representation of fire-vegetation interactions. It allows simultaneous consideration of the effects of changes in climate, CO2 concentration, natural vegetation and fire regime shifts on the continental hydrological cycle. Here the model is assessed for its ability to simulate large-scale spatial and temporal runoff patterns, in order to test its suitability for modelling future global water resources. Comparisons are made against observations of streamflow and a composite dataset of modelled and observed runoff (1986–1995) and are also evaluated against soil moisture data and the Palmer Drought Severity Index. The model captures the main features of the geographical distribution of global runoff, but tends to overestimate runoff in much of the Northern Hemisphere (where this can be somewhat accounted for by freshwater consumption and the unrealistic accumulation of the simulated winter snowpack in permafrost regions) and the southern tropics. Interannual variability is represented reasonably well at the large catchment scale, as are seasonal flow timings and monthly high and low flow events. Further improvements to the simulation of intra-annual runoff might be achieved via the addition of river flow routing. Overestimates of runoff in some basins could likely be corrected by the inclusion of transmission losses and direct-channel evaporation.

Did the rise of highly-transpiring angiosperms influenced Cretaceous climate ? A modelling approach with the IPSL atmosphere-land surface model.

2020 ◽  
Author(s):  
Julia Bres ◽  
Pierre Sepulchre ◽  
Nicolas Vuichard ◽  
Nicolas Viovy
Keyword(s):  
Stomatal Conductance ◽  
Land Surface ◽  
Fossil Record ◽  
Hydrological Cycle ◽  
Land Surface Model ◽  
Plant Evolution ◽  
Surface Model ◽  
Vegetation Model ◽  
Leaf Vein ◽  
Modelling Approach

&lt;p&gt;&lt;span&gt;&lt;span&gt;The Cretaceous angiosperm radiation was a major event for terrestrial plant evolution, and flowering plants represent more than 94 % of present-day plant diversity. The fossil record shows that angiosperm leaf vein densities reached particularly high values (&gt; 12 mm/mm&lt;/span&gt;&lt;/span&gt;&lt;sup&gt;&lt;span&gt;&lt;span&gt;2&lt;/span&gt;&lt;/span&gt;&lt;/sup&gt;&lt;span&gt;&lt;span&gt;)&lt;/span&gt;&lt;/span&gt; &lt;span&gt;&lt;span&gt;between the &lt;/span&gt;&lt;/span&gt;&lt;span&gt;Albian and the Cenomanian (108&amp;#8211;94 Ma) &lt;/span&gt;&lt;span&gt;&lt;span&gt;compared to gymnosperms (~ 2.5 mm/mm&lt;/span&gt;&lt;/span&gt;&lt;sup&gt;&lt;span&gt;&lt;span&gt;2&lt;/span&gt;&lt;/span&gt;&lt;/sup&gt;&lt;span&gt;&lt;span&gt;). Empirical models&lt;/span&gt;&lt;/span&gt; &lt;span&gt;&lt;span&gt;also suggest that stomatal conductance to water vapour increases as a response to higher leaf vein densities. How much do this shift to higher values of stomatal conductance have modified the continental transpiration budget,&lt;/span&gt;&lt;/span&gt; &lt;span&gt;&lt;span&gt;and ultimately global hydrological cycle ? To address this question we used the IPSL coupled atmosphere-vegetation model forced by Cretaceous boundary conditions, and built plant functional types including&lt;/span&gt;&lt;/span&gt; &lt;span&gt;&lt;span&gt;stomatal conductance values consistent with the fossil record. We quantify the transpiration fluxes through different sensitivity experiments and explore the vegetation-atmosphere feedbacks and their impact on the Cretaceous climate.&lt;/span&gt;&lt;/span&gt;&lt;/p&gt;

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