Aims: The partitioning of the total soil CO sub(2) efflux into its two main components: respiration from roots (and root-associated organisms) and microbial respiration (by means of soil organic ...matter (SOM) and litter decomposition), is a major need in soil carbon dynamics studies in order to understand if a soil is a net sink or source of carbon. Methods: The heterotrophic component of the CO sub(2) efflux was estimated for 11 forest sites as the ratio between the carbon stocks of different SOM pools and previously published ( Delta super(14)C derived) turnover times. The autotrophic component, including root and root-associated respiration, was calculated by subtracting the heterotrophic component from total soil chamber measured CO sub(2) efflux. Results: Results suggested that, on average, 50.4 % of total soil CO sub(2) efflux was derived from the respiration of the living roots, 42.4 % from decomposition of the litter layers and less than 10 % from decomposition of belowground SOM. Conclusions: The Delta super(14)C method proved to be an efficient tool by which to partition soil CO sub(2) efflux and quantify the contribution of the different components of soil respiration. However the average calculated heterotrophic respiration was statistically lower compared with two previous studies dealing with soil CO sub(2) efflux partitioning (one performed in the same study area; the other a meta-analysis of soil respiration partitioning). These differences were probably due to the heterogeneity of the SOM fraction and to a sub-optimal choice of the litter sampling period.
Aims The partitioning of the total soil CO.sub.2 efflux into its two main components: respiration from roots (and root-associated organisms) and microbial respiration (by means of soil organic matter ...(SOM) and litter decomposition), is a major need in soil carbon dynamics studies in order to understand if a soil is a net sink or source of carbon. Methods The heterotrophic component of the CO.sub.2 efflux was estimated for 11 forest sites as the ratio between the carbon stocks of different SOM pools and previously published (Δ sup.14C derived) turnover times. The autotrophic component, including root and root-associated respiration, was calculated by subtracting the heterotrophic component from total soil chamber measured CO.sub.2 efflux. Results Results suggested that, on average, 50.4% of total soil CO.sub.2 efflux was derived from the respiration of the living roots, 42.4% from decomposition of the litter layers and less than 10% from decomposition of belowground SOM. Conclusions The Δ sup.14C method proved to be an efficient tool by which to partition soil CO.sub.2 efflux and quantify the contribution of the different components of soil respiration. However the average calculated heterotrophic respiration was statistically lower compared with two previous studies dealing with soil CO.sub.2 efflux partitioning (one performed in the same study area; the other a meta-analysis of soil respiration partitioning). These differences were probably due to the heterogeneity of the SOM fraction and to a suboptimal choice of the litter sampling period. Keywords Soil respiration partitioning * Carbon-14 isotope * Soil organic matter fractions * Forest ecosystems
The partitioning of the total soil CO2 efflux into its two main components: respiration from roots (and root-associated organisms) and microbial respiration (by means of soil organic matter (SOM) and ...litter decomposition), is a major need in soil carbon dynamics studies in order to understand if a soil is a net sink or source of carbon. The heterotrophic component of the CO2 efflux was estimated for 11 forest sites as the ratio between the carbon stocks of different SOM pools and previously published (Delta^sup 14^C derived) turnover times. The autotrophic component, including root and root-associated respiration, was calculated by subtracting the heterotrophic component from total soil chamber measured CO2 efflux. Results suggested that, on average, 50.4 % of total soil CO2 efflux was derived from the respiration of the living roots, 42.4 % from decomposition of the litter layers and less than 10 % from decomposition of belowground SOM. The Delta^sup 14^C method proved to be an efficient tool by which to partition soil CO2 efflux and quantify the contribution of the different components of soil respiration. However the average calculated heterotrophic respiration was statistically lower compared with two previous studies dealing with soil CO2 efflux partitioning (one performed in the same study area; the other a meta-analysis of soil respiration partitioning). These differences were probably due to the heterogeneity of the SOM fraction and to a sub-optimal choice of the litter sampling period.PUBLICATION ABSTRACT
Aims
The partitioning of the total soil CO
2
efflux into its two main components: respiration from roots (and root-associated organisms) and microbial respiration (by means of soil organic matter ...(SOM) and litter decomposition), is a major need in soil carbon dynamics studies in order to understand if a soil is a net sink or source of carbon.
Methods
The heterotrophic component of the CO
2
efflux was estimated for 11 forest sites as the ratio between the carbon stocks of different SOM pools and previously published (Δ
14
C derived) turnover times. The autotrophic component, including root and root-associated respiration, was calculated by subtracting the heterotrophic component from total soil chamber measured CO
2
efflux.
Results
Results suggested that, on average, 50.4 % of total soil CO
2
efflux was derived from the respiration of the living roots, 42.4 % from decomposition of the litter layers and less than 10 % from decomposition of belowground SOM.
Conclusions
The Δ
14
C method proved to be an efficient tool by which to partition soil CO
2
efflux and quantify the contribution of the different components of soil respiration. However the average calculated heterotrophic respiration was statistically lower compared with two previous studies dealing with soil CO
2
efflux partitioning (one performed in the same study area; the other a meta-analysis of soil respiration partitioning). These differences were probably due to the heterogeneity of the SOM fraction and to a sub-optimal choice of the litter sampling period.
In dieser Arbeit wird die Entwicklung eines Gebäudeenergiemodells (BEM) und eines Schemas für die mittlere Strahlungstemperatur ($T_mrt$) vorgestellt, das in das Doppel-Canyon basierte städtische ...Bestandsschichtsschema (DCEP) integriert ist. Das erweiterte DCEP-BEM Modell zielt darauf ab, eine Verbindung zwischen anthropogener Wärme und dem Stadtklima herzustellen, indem Gebäude in Straßenschluchten einbezogen werden, um die Energieflüsse auf städtischen Oberflächen, die Auswirkungen der anthropogenen Wärme auf die Atmosphäre, die Innenraumlufttemperatur und die Abwärme von Klimaanlagen zu untersuchen. Das DCEP-BEM wird mit dem mesoskaligen Klimamodell COSMO-CLM (COnsortium for Small-scale MOdelling in CLimate Mode, im Folgenden CCLM) gekoppelt und zur Simulation des Winters und Sommers 2018 in Berlin.;
;
Die Auswertung der Wintersimulationen zeigt, dass CCLM/DCEP-BEM den mittleren Tagesverlauf der gemessenen turbulenten Wärmeströme gut reproduziert und die simulierte 2-m-Lufttemperatur und den städtischen Wärmeinseleffekt (UHI) verbessert. Im Sommer bildet das CCLM/DCEP-BEM die Innenraumlufttemperatur richtig ab und verbessert die Ergebnisse für die 2-m-Lufttemperatur und die UHI leicht. Außerdem wird das CCLM/DCEP-BEM angewendet, um die Abwärmeemissionen von Klimaanlagen im Sommer zu untersuchen. Die Abwärmeemissionen der Klimaanlagen erhöhen die Lufttemperatur in Oberflächennähe erheblich. Der Anstieg ist in der Nacht und in hochurbanisierten Gebieten stärker ausgeprägt. Es werden zwei Standorte für die AC-Außengeräte betrachtet: entweder an der Wand eines Gebäudes (VerAC) oder auf dem Dach eines Gebäudes (HorAC). Die Auswirkung von HorAC ist im Vergleich zu VerAC insgesamt geringer, was darauf hindeutet, dass HorAC einen kleineren Einfluss auf die oberflächennahe Lufttemperatur und den UHI hat. Ein Schema für $T_mrt$ wird für das CCLM/DCEP-BEM entwickelt und umfassend validiert. Es wird gezeigt, dass dieses Schema eine zuverlässige Darstellung von $T_mrt$ bietet.
This work presents the development of a building energy model (BEM) and a mean radiant temperature ($T_mrt$) scheme integrated in the urban canopy scheme Double Canyon Effect Parametrization (DCEP). The extended DCEP-BEM model aims to establish a link between anthropogenic heat emissions and urban climate by including the interior of buildings in urban street canyons to investigate the energy fluxes on urban surfaces, the effects of anthropogenic heat on the atmosphere, the evolution of indoor air temperature, and waste heat from air conditioning (AC) systems. DCEP-BEM is coupled with the mesoscale climate model COSMO-CLM (COnsortium for Small-scale MOdelling in CLimate Mode, hereafter CCLM) and applied to simulate the winter and summer 2018 of Berlin.;
;
The evaluation for winter simulations indicates that CCLM/DCEP-BEM reproduces well the average diurnal characteristics of the measured turbulent heat fluxes and considerably improves the simulated 2-m air temperature and urban heat island (UHI). In summer, CCLM/DCEP-BEM accurately reproduces the indoor air temperature, and slightly improves the performance of the 2-m air temperature and the UHI effect. Furthermore, CCLM/DCEP-BEM is applied to explore the waste heat emissions from AC systems in summer. AC waste heat emissions considerably increase the near-surface sensible heat flux and air temperature. The increase is more pronounced during the night and in highly urbanised areas. Two locations for the AC outdoor units are considered: either on the wall of a building (VerAC) or on the rooftop of a building (HorAC). The effect of HorAC is overall smaller compared to VerAC, indicating that HorAC has a smaller impact on the near-surface air temperature and the UHI effect. A $T_mrt$ scheme is developed for CCLM/DCEP-BEM and extensively evaluated. It is shown that this scheme provides a reliable representation of $T_mrt$.
Temperate forest ecosystems have recently been identified as an important net sink in the global carbon budget. The factors responsible for the strength of the sinks and their permanence, however, ...are less evident. In this paper, we quantify the present carbon sequestration in Thuringian managed coniferous forests. We quantify the effects of indirect human‐induced environmental changes (increasing temperature, increasing atmospheric CO2 concentration and nitrogen fertilization), during the last century using BIOME‐BGC, as well as the legacy effect of the current age‐class distribution (forest inventories and BIOME‐BGC). We focused on coniferous forests because these forests represent a large area of central European forests and detailed forest inventories were available.
The model indicates that environmental changes induced an increase in biomass C accumulation for all age classes during the last 20 years (1982–2001). Young and old stands had the highest changes in the biomass C accumulation during this period. During the last century mature stands (older than 80 years) turned from being almost carbon neutral to carbon sinks. In high elevations nitrogen deposition explained most of the increase of net ecosystem production (NEP) of forests. CO2 fertilization was the main factor increasing NEP of forests in the middle and low elevations.
According to the model, at present, total biomass C accumulation in coniferous forests of Thuringia was estimated at 1.51 t C ha−1 yr−1 with an averaged annual NEP of 1.42 t C ha−1 yr−1 and total net biome production of 1.03 t C ha−1 yr−1 (accounting for harvest). The annual averaged biomass carbon balance (BCB: biomass accumulation rate‐harvest) was 1.12 t C ha−1 yr−1 (not including soil respiration), and was close to BCB from forest inventories (1.15 t C ha−1 yr−1). Indirect human impact resulted in 33% increase in modeled biomass carbon accumulation in coniferous forests in Thuringia during the last century. From the forest inventory data we estimated the legacy effect of the age‐class distribution to account for 17% of the inventory‐based sink. Isolating the environmental change effects showed that these effects can be large in a long‐term, managed conifer forest.
Increased carbon uptake of land in response to elevated atmospheric CO sub(2) concentration and nitrogen deposition could slow down the rate of CO sub(2) increase and facilitate climate change ...mitigation. Using a coupled model of climate, ocean, and land biogeochemistry, we show that atmospheric nitrogen deposition and atmospheric CO sub(2) have a strong synergistic effect on the carbon uptake of land. Our best estimate of the global land carbon uptake in the 1990s is 1.34 PgC/yr. The synergistic effect could explain 47% of this carbon uptake, which is higher than either the effect of increasing nitrogen deposition (29%) or CO sub(2) fertilization (24%). By 2030, rising carbon uptake on land has a potential to reduce atmospheric CO sub(2) concentration by about 41 ppm out of which 16 ppm reduction would come from the synergetic response of land to the CO sub(2) and nitrogen fertilization effects. The strength of the synergy depends largely on the cooccurrence of high nitrogen deposition regions with nonagricultural ecosystems. Our study suggests that reforestation and sensible ecosystem management in industrialized regions may have larger potential for climate change mitigation than anticipated.
Increased carbon uptake of land in response to elevated atmospheric CO
2
concentration and nitrogen deposition could slow down the rate of CO
2
increase and facilitate climate change mitigation. ...Using a coupled model of climate, ocean, and land biogeochemistry, we show that atmospheric nitrogen deposition and atmospheric CO
2
have a strong synergistic effect on the carbon uptake of land. Our best estimate of the global land carbon uptake in the 1990s is 1.34 PgC/yr. The synergistic effect could explain 47% of this carbon uptake, which is higher than either the effect of increasing nitrogen deposition (29%) or CO
2
fertilization (24%). By 2030, rising carbon uptake on land has a potential to reduce atmospheric CO
2
concentration by about 41 ppm out of which 16 ppm reduction would come from the synergetic response of land to the CO
2
and nitrogen fertilization effects. The strength of the synergy depends largely on the cooccurrence of high nitrogen deposition regions with nonagricultural ecosystems. Our study suggests that reforestation and sensible ecosystem management in industrialized regions may have larger potential for climate change mitigation than anticipated.
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