Supplementary material to "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"

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.

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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

Geoscientific Model Development ◽

10.5194/gmd-13-185-2020 ◽

2020 ◽

Vol 13 (1) ◽

pp. 185-200 ◽

Cited By ~ 1

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.

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

Biogeosciences ◽

10.5194/bg-10-4137-2013 ◽

2013 ◽

Vol 10 (6) ◽

pp. 4137-4177 ◽

Cited By ~ 121

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.

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Supplementary material to "Modelling sun-induced fluorescence and photosynthesis with a land surface model at local and regional scales in northern Europe"

10.5194/bg-2016-514-supplement ◽

2016 ◽

Author(s):

Tea Thum ◽

Sönke Zaehle ◽

Philipp Köhler ◽

Tuula Aalto ◽

Mika Aurela ◽

...

Keyword(s):

Land Surface ◽

Land Surface Model ◽

Northern Europe ◽

Surface Model ◽

Supplementary Material

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

10.5194/gmd-2019-51 ◽

2019 ◽

Cited By ~ 1

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.

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