Drained peat soils are a significant source of greenhouse gas (GHG) emissions to the atmosphere. ... more Drained peat soils are a significant source of greenhouse gas (GHG) emissions to the atmosphere. Rewetting these soils is considered an important climate change mitigation tool to reduce emissions and create suitable conditions for carbon sequestration. Long term monitoring is essential to capture inter-annual variations in GHG emissions and associated environmental variables and to reduce the uncertainty linked with GHG emission factor calculations. In this study, we present GHG balances; carbon dioxide (CO2 ), methane (CH4 ) and nitrous oxide (N2 O) calculated for a 5-year period at a rewetted industrial cutaway peatland in Ireland (rewetted 7 years prior to start of the study), and compare the results with an adjacent drained area (2-year dataset), and with ten long-term datasets from intact (i.e. undrained) peatlands in temperate and boreal regions. In the rewetted site, CO2 exchange (or net ecosystem exchange (NEE)) was strongly influenced by ecosystem respiration (Reco ) rathe...
Biochar and hydrochar application to soil holds promise for climate change mitigation. This study... more Biochar and hydrochar application to soil holds promise for climate change mitigation. This study provides first insights into the nutrient concentration and removal of grassland vegetation after addition of various carbon compounds together with pig slurry. Four treatments: control (no carbon application), feedstock, hydrochar and biochar from Miscanthus x giganteus were applied at a permanent grassland site near Giessen, Germany. Changes in plant functional groups, biomass production and nutrition status were monitored over 2 years. Total biomass production was not affected by the carbon amendments. However, biochar favoured growth of forbs over grasses, while legume growth was increased by all carbon amendments. The initial nutrient concentrations of the carbon compounds were enriched according to their degree of carbonization, potentially providing nutrients to plants. The plant biomass from hydro- and biochar amended plots, added up over 2 years, exhibited higher potassium conc...
A B S T R A C T Nutrient-poor organic soils under maritime grassland are often located in remote ... more A B S T R A C T Nutrient-poor organic soils under maritime grassland are often located in remote wet locations in the landscape. Leaving these soils without drainage maintenance often raise the water table but continuous management (grazing) means they could remain a source of carbon dioxide (CO 2) while also turning into a small source of methane (CH 4). Due to geographical and socioeconomic reasons, removing these sites from agricultural production may be an option to mitigate greenhouse gas (GHG) emissions. To test this hypothesis we measured GHG fluxes over a four year period, at a drained and a rewetted organic soil under grassland, which were both grazed for the first two years and not grazed for the following two years. Statistical response functions estimated for gross primary production (GPP) and ecosystem respiration (R eco) were used to reconstruct annual CO 2 –C balances using site-specific models driven by soil temperature, solar radiation, soil water table (WT) and leaf area index (LAI). Annually, soil CO 2 emissions were comparable when grazed, although the rewetted site had a lower net ecosystem carbon balance (NECB) despite displaying higher CH 4 emissions. Both sites have lower CO 2 emissions than typical drained organic soils due to management practices: extensive grazing, no fertilisation and mean annual water tables above À25 cm. When grazing stopped, GPP and R eco increased dramatically driven by vigorous growth of vegetation at both sites. The shallow drained site remained a source of CO 2 and small source of CH 4 while the rewetted site became either neutral or a small sink of CO 2 with decreased CH 4 emissions compared to the grazing period. Nitrous oxide (N 2 O) emissions were negligible at either site. Removing grazing significantly reduced the NECB at both sites but in terms of global warming potential (GWP), the greatest GHG mitigation was in the rewetted site which exerted a cooling effect in the second year after the management shift.
The rising concentration of carbon dioxide in the atmosphere ([CO2]) has a direct effect on terre... more The rising concentration of carbon dioxide in the atmosphere ([CO2]) has a direct effect on terrestrial vegetation through shifts in the rates of photosynthetic carbon uptake and transpirational water-loss. Free Air CO2 Enrichment (FACE) experiments aim to predict the likely responses of plants to increased [CO2] under normal climatic conditions. The Giessen FACE system operates a lower [CO2] enrichment regime (480 mmol mol–1) than standard FACE (550–600 mmol mol–1), permitting the analysis of a mixed species temperate meadow under a [CO2] level equivalent to that predicted in 25–30 years. We analysed the physiological and morphological responses of six species to investigate the effect of moderate [CO2] on spring biomass production. Carbon dioxide enrichment stimulated leaf photosynthetic rates and supressed respiration, contributing to enhanced net assimilation and a 23% increase in biomass. The capacity for photosynthetic assimilation was unaffected by [CO2] enrichment, with no downregulation of rates of carboxylation of Rubisco or regeneration of ribulose- 1,5-bisphosphate. Foliar N content was also not influenced by increased [CO2]. Enhanced [CO2] reduced stomatal size, but stomatal density and leaf area index remained constant, suggesting that the effect on gas exchange was minimal.
A high number of bacterial species is inhabiting the aboveground part (phyllosphere) of plants. G... more A high number of bacterial species is inhabiting the aboveground part (phyllosphere) of plants. Global climate changes lead to an increasing atmospheric CO 2 concentration which can directly or indirectly (by increasing plant growth) affect the abundance and community structures of the phyllosphere-inhabiting bacteria and in consequence influence plant-microbe-interactions. The aim of this study was to gain a first insight into the effects of elevated atmospheric CO 2 (eCO 2) on the composition and diversity of phyllosphere inhabiting bacteria. Two different plant species, Arrhenatherum elatius and Galium mollugo, were investigated at two time points (spring/summer 2014). Samples were collected at the permanent grassland of the Giessen Free Air Carbon Dioxide Enrichment (GiFACE) system, which is continuously exposed to eCO 2 since more than 15 years. Phyllosphere bacteria collected from plants of control FACE-rings (ambient CO 2 , aCO 2) were compared to those of FACE rings exposed ...
The increase of greenhouse gases (GHG) in the atmosphere is of concern due to its effect on globa... more The increase of greenhouse gases (GHG) in the atmosphere is of concern due to its effect on global temperatures. Nitrous oxide (N 2 O) with a Global Warming Potential of 298 over a 100 year period is of particular concern because strong feedback effects of elevated atmospheric CO 2 on N 2 O emissions have been observed. However, so far the changes in processes which are responsible for such a feedback effect are only poorly understood. Our study was carried out in situ in a long-term Free Air Carbon dioxide Enrichment (FACE) study on permanent grassland at atmospheric CO 2 concentrations 20% above ambient which expected at the middle of this century. We performed an in situ 15 N tracing with differentially labelled NH 4 NO 3 to trace the main N 2 O emission pathways. Over a period of more than one year we monitored at least weakly the N 2 O emissions with the closed chamber technique and analyzed the 15 N signature of the N 2 O. The observed gaseous emissions under ambient and eleva...
Managing ecosystems for carbon storage may also benefit biodiversity conservation, but such a pot... more Managing ecosystems for carbon storage may also benefit biodiversity conservation, but such a potential ‘win-win’ scenario
has not yet been assessed for tropical agroforestry landscapes. We measured above- and below-ground carbon stocks as
well as the species richness of four groups of plants and eight of animals on 14 representative plots in Sulawesi, Indonesia,
ranging from natural rainforest to cacao agroforests that have replaced former natural forest. The conversion of natural
forests with carbon stocks of 227–362 Mg C ha21 to agroforests with 82–211 Mg C ha21 showed no relationships to overall
biodiversity but led to a significant loss of forest-related species richness. We conclude that the conservation of the forestrelated
biodiversity, and to a lesser degree of carbon stocks, mainly depends on the preservation of natural forest habitats.
In the three most carbon-rich agroforestry systems, carbon stocks were about 60% of those of natural forest, suggesting
that 1.6 ha of optimally managed agroforest can contribute to the conservation of carbon stocks as much as 1 ha of natural
forest. However, agroforestry systems had comparatively low biodiversity, and we found no evidence for a tight link
between carbon storage and biodiversity. Yet, potential win-win agroforestry management solutions include combining
high shade-tree quality which favours biodiversity with cacao-yield adapted shade levels
Biochar and hydrochar application to soil holds promise for climate change mitigation. This study... more Biochar and hydrochar application to soil holds promise for climate change mitigation. This study provides first insights into the nutrient concentration and removal of grassland vegetation after addition of various carbon compounds together with pig slurry. Four treatments: control (no carbon application), feedstock, hydrochar and biochar from Miscanthus x giganteus were applied at a permanent grassland site near Giessen, Germany. Changes in plant functional groups, biomass production and nutrition status were monitored over 2 years. Total biomass production was not affected by the carbon amendments. However, biochar favoured growth of forbs over grasses, while legume growth was increased by all carbon amendments. The initial nutrient concentrations of the carbon compounds were enriched according to their degree of carbonization, potentially providing nutrients to plants. The plant biomass from hydro- and biochar amended plots, added up over 2 years, exhibited higher potassium conc...
Climate change scenarios predict increases in the frequency and duration of ENSO-related droughts... more Climate change scenarios predict increases in the frequency and duration of ENSO-related droughts for parts of South-East Asia until the end of this century exposing the remaining rainforests to increasing drought risk. A pan-tropical review of recorded drought-related tree mortalities in more than 100 monitoring plots before, during and after drought events suggested a higher drought-vulnerability of trees in South-East Asian than in Amazonian forests. Here, we present the results of a replicated (n = 3 plots) throughfall exclusion experiment in a perhumid tropical rainforest in Sulawesi, Indonesia. In this first large-scale roof experiment outside semihumid eastern Amazonia, 60% of the throughfall was displaced during the first 8 months and 80% during the subsequent 17 months, exposing the forest to severe soil desiccation for about 17 months. In the experiment's second year, wood production decreased on average by 40% with largely different responses of the tree families (ranging from −100 to +100% change). Most sensitive were trees with high radial growth rates under moist conditions. In contrast, tree height was only a secondary factor and wood specific gravity had no influence on growth sensitivity. Fine root biomass was reduced by 35% after 25 months of soil desiccation while fine root necromass increased by 250% indicating elevated fine root mortality. Cumulative aboveground litter production was not significantly reduced in this period. The trees from this Indonesian perhumid rainforest revealed similar responses of wood and litter production and root dynamics as those in two semihumid Amazonian forests subjected to experimental drought. We conclude that trees from paleo- or neotropical forests growing in semihumid or perhumid climates may not differ systematically in their growth sensitivity and vitality under sublethal drought stress. Drought vulnerability may depend more on stem cambial activity in moist periods than on tree height or wood specific gravity.
Background and aims
Within the last decades, considerable knowledge has been gained on the impa... more Background and aims
Within the last decades, considerable knowledge has been gained on the impacts of carbonaceous soil additives such as hydrochar (or HTC) and biochar (or pyrochar) on plant growth and various soil properties. However, still little is known about the effects of hydrochar and biochar on soil microorganisms, especially from field studies. Microorganisms are closely linked to nutrient dynamics in soil and therefore are tightly linked to soil fertility. As a consequence, possible changes in the microbial community structure due to HTC/biochar soil application may lead to considerable changes in soil nutrient dynamics. Methods
To gain insights into HTC/biochar associated long-term effects on microorganisms, soil samples were taken from a grassland field study 2.6 years (31 months) after its initiation (April 2011), where Miscanthus × giganteus feedstock, HTC and biochar, each mixed with pig slurry had been applied as top-dressing in a randomized block design, next to a slurry-only control (n = 4, 16 plots). The samples were analyzed for microbial activity and biomass by substrate induced respiration (SIR). Bacterial and fungal fractions in soil microbial biomass (SMB) were determined using the inhibitors streptomycin and cycloheximide respectively. Results
Total SMB in biochar-amended soils was significantly higher compared to all other treatments; fungal biomass was significantly higher compared to feedstock and control treatments. The percentage of bacterial biomass was higher in the feedstock and HTC amended soil, as compared to the control. Additionally, HTC exhibited a significantly higher percentage of fungal biomass compared to the feedstock treatment, indicating a microbial community shift. Conclusion
While the uncarbonized feedstock material depleted both total SMB and especially fungi, HTC and biochar did not trigger any adverse long-term effects on SMB. Rather, the observed biochar-induced stimulation of SMB may improve soil aggregation and increase the soil organic carbon content in the long term.
Drained peat soils are a significant source of greenhouse gas (GHG) emissions to the atmosphere. ... more Drained peat soils are a significant source of greenhouse gas (GHG) emissions to the atmosphere. Rewetting these soils is considered an important climate change mitigation tool to reduce emissions and create suitable conditions for carbon sequestration. Long term monitoring is essential to capture inter-annual variations in GHG emissions and associated environmental variables and to reduce the uncertainty linked with GHG emission factor calculations. In this study, we present GHG balances; carbon dioxide (CO2 ), methane (CH4 ) and nitrous oxide (N2 O) calculated for a 5-year period at a rewetted industrial cutaway peatland in Ireland (rewetted 7 years prior to start of the study), and compare the results with an adjacent drained area (2-year dataset), and with ten long-term datasets from intact (i.e. undrained) peatlands in temperate and boreal regions. In the rewetted site, CO2 exchange (or net ecosystem exchange (NEE)) was strongly influenced by ecosystem respiration (Reco ) rathe...
Biochar and hydrochar application to soil holds promise for climate change mitigation. This study... more Biochar and hydrochar application to soil holds promise for climate change mitigation. This study provides first insights into the nutrient concentration and removal of grassland vegetation after addition of various carbon compounds together with pig slurry. Four treatments: control (no carbon application), feedstock, hydrochar and biochar from Miscanthus x giganteus were applied at a permanent grassland site near Giessen, Germany. Changes in plant functional groups, biomass production and nutrition status were monitored over 2 years. Total biomass production was not affected by the carbon amendments. However, biochar favoured growth of forbs over grasses, while legume growth was increased by all carbon amendments. The initial nutrient concentrations of the carbon compounds were enriched according to their degree of carbonization, potentially providing nutrients to plants. The plant biomass from hydro- and biochar amended plots, added up over 2 years, exhibited higher potassium conc...
A B S T R A C T Nutrient-poor organic soils under maritime grassland are often located in remote ... more A B S T R A C T Nutrient-poor organic soils under maritime grassland are often located in remote wet locations in the landscape. Leaving these soils without drainage maintenance often raise the water table but continuous management (grazing) means they could remain a source of carbon dioxide (CO 2) while also turning into a small source of methane (CH 4). Due to geographical and socioeconomic reasons, removing these sites from agricultural production may be an option to mitigate greenhouse gas (GHG) emissions. To test this hypothesis we measured GHG fluxes over a four year period, at a drained and a rewetted organic soil under grassland, which were both grazed for the first two years and not grazed for the following two years. Statistical response functions estimated for gross primary production (GPP) and ecosystem respiration (R eco) were used to reconstruct annual CO 2 –C balances using site-specific models driven by soil temperature, solar radiation, soil water table (WT) and leaf area index (LAI). Annually, soil CO 2 emissions were comparable when grazed, although the rewetted site had a lower net ecosystem carbon balance (NECB) despite displaying higher CH 4 emissions. Both sites have lower CO 2 emissions than typical drained organic soils due to management practices: extensive grazing, no fertilisation and mean annual water tables above À25 cm. When grazing stopped, GPP and R eco increased dramatically driven by vigorous growth of vegetation at both sites. The shallow drained site remained a source of CO 2 and small source of CH 4 while the rewetted site became either neutral or a small sink of CO 2 with decreased CH 4 emissions compared to the grazing period. Nitrous oxide (N 2 O) emissions were negligible at either site. Removing grazing significantly reduced the NECB at both sites but in terms of global warming potential (GWP), the greatest GHG mitigation was in the rewetted site which exerted a cooling effect in the second year after the management shift.
The rising concentration of carbon dioxide in the atmosphere ([CO2]) has a direct effect on terre... more The rising concentration of carbon dioxide in the atmosphere ([CO2]) has a direct effect on terrestrial vegetation through shifts in the rates of photosynthetic carbon uptake and transpirational water-loss. Free Air CO2 Enrichment (FACE) experiments aim to predict the likely responses of plants to increased [CO2] under normal climatic conditions. The Giessen FACE system operates a lower [CO2] enrichment regime (480 mmol mol–1) than standard FACE (550–600 mmol mol–1), permitting the analysis of a mixed species temperate meadow under a [CO2] level equivalent to that predicted in 25–30 years. We analysed the physiological and morphological responses of six species to investigate the effect of moderate [CO2] on spring biomass production. Carbon dioxide enrichment stimulated leaf photosynthetic rates and supressed respiration, contributing to enhanced net assimilation and a 23% increase in biomass. The capacity for photosynthetic assimilation was unaffected by [CO2] enrichment, with no downregulation of rates of carboxylation of Rubisco or regeneration of ribulose- 1,5-bisphosphate. Foliar N content was also not influenced by increased [CO2]. Enhanced [CO2] reduced stomatal size, but stomatal density and leaf area index remained constant, suggesting that the effect on gas exchange was minimal.
A high number of bacterial species is inhabiting the aboveground part (phyllosphere) of plants. G... more A high number of bacterial species is inhabiting the aboveground part (phyllosphere) of plants. Global climate changes lead to an increasing atmospheric CO 2 concentration which can directly or indirectly (by increasing plant growth) affect the abundance and community structures of the phyllosphere-inhabiting bacteria and in consequence influence plant-microbe-interactions. The aim of this study was to gain a first insight into the effects of elevated atmospheric CO 2 (eCO 2) on the composition and diversity of phyllosphere inhabiting bacteria. Two different plant species, Arrhenatherum elatius and Galium mollugo, were investigated at two time points (spring/summer 2014). Samples were collected at the permanent grassland of the Giessen Free Air Carbon Dioxide Enrichment (GiFACE) system, which is continuously exposed to eCO 2 since more than 15 years. Phyllosphere bacteria collected from plants of control FACE-rings (ambient CO 2 , aCO 2) were compared to those of FACE rings exposed ...
The increase of greenhouse gases (GHG) in the atmosphere is of concern due to its effect on globa... more The increase of greenhouse gases (GHG) in the atmosphere is of concern due to its effect on global temperatures. Nitrous oxide (N 2 O) with a Global Warming Potential of 298 over a 100 year period is of particular concern because strong feedback effects of elevated atmospheric CO 2 on N 2 O emissions have been observed. However, so far the changes in processes which are responsible for such a feedback effect are only poorly understood. Our study was carried out in situ in a long-term Free Air Carbon dioxide Enrichment (FACE) study on permanent grassland at atmospheric CO 2 concentrations 20% above ambient which expected at the middle of this century. We performed an in situ 15 N tracing with differentially labelled NH 4 NO 3 to trace the main N 2 O emission pathways. Over a period of more than one year we monitored at least weakly the N 2 O emissions with the closed chamber technique and analyzed the 15 N signature of the N 2 O. The observed gaseous emissions under ambient and eleva...
Managing ecosystems for carbon storage may also benefit biodiversity conservation, but such a pot... more Managing ecosystems for carbon storage may also benefit biodiversity conservation, but such a potential ‘win-win’ scenario
has not yet been assessed for tropical agroforestry landscapes. We measured above- and below-ground carbon stocks as
well as the species richness of four groups of plants and eight of animals on 14 representative plots in Sulawesi, Indonesia,
ranging from natural rainforest to cacao agroforests that have replaced former natural forest. The conversion of natural
forests with carbon stocks of 227–362 Mg C ha21 to agroforests with 82–211 Mg C ha21 showed no relationships to overall
biodiversity but led to a significant loss of forest-related species richness. We conclude that the conservation of the forestrelated
biodiversity, and to a lesser degree of carbon stocks, mainly depends on the preservation of natural forest habitats.
In the three most carbon-rich agroforestry systems, carbon stocks were about 60% of those of natural forest, suggesting
that 1.6 ha of optimally managed agroforest can contribute to the conservation of carbon stocks as much as 1 ha of natural
forest. However, agroforestry systems had comparatively low biodiversity, and we found no evidence for a tight link
between carbon storage and biodiversity. Yet, potential win-win agroforestry management solutions include combining
high shade-tree quality which favours biodiversity with cacao-yield adapted shade levels
Biochar and hydrochar application to soil holds promise for climate change mitigation. This study... more Biochar and hydrochar application to soil holds promise for climate change mitigation. This study provides first insights into the nutrient concentration and removal of grassland vegetation after addition of various carbon compounds together with pig slurry. Four treatments: control (no carbon application), feedstock, hydrochar and biochar from Miscanthus x giganteus were applied at a permanent grassland site near Giessen, Germany. Changes in plant functional groups, biomass production and nutrition status were monitored over 2 years. Total biomass production was not affected by the carbon amendments. However, biochar favoured growth of forbs over grasses, while legume growth was increased by all carbon amendments. The initial nutrient concentrations of the carbon compounds were enriched according to their degree of carbonization, potentially providing nutrients to plants. The plant biomass from hydro- and biochar amended plots, added up over 2 years, exhibited higher potassium conc...
Climate change scenarios predict increases in the frequency and duration of ENSO-related droughts... more Climate change scenarios predict increases in the frequency and duration of ENSO-related droughts for parts of South-East Asia until the end of this century exposing the remaining rainforests to increasing drought risk. A pan-tropical review of recorded drought-related tree mortalities in more than 100 monitoring plots before, during and after drought events suggested a higher drought-vulnerability of trees in South-East Asian than in Amazonian forests. Here, we present the results of a replicated (n = 3 plots) throughfall exclusion experiment in a perhumid tropical rainforest in Sulawesi, Indonesia. In this first large-scale roof experiment outside semihumid eastern Amazonia, 60% of the throughfall was displaced during the first 8 months and 80% during the subsequent 17 months, exposing the forest to severe soil desiccation for about 17 months. In the experiment's second year, wood production decreased on average by 40% with largely different responses of the tree families (ranging from −100 to +100% change). Most sensitive were trees with high radial growth rates under moist conditions. In contrast, tree height was only a secondary factor and wood specific gravity had no influence on growth sensitivity. Fine root biomass was reduced by 35% after 25 months of soil desiccation while fine root necromass increased by 250% indicating elevated fine root mortality. Cumulative aboveground litter production was not significantly reduced in this period. The trees from this Indonesian perhumid rainforest revealed similar responses of wood and litter production and root dynamics as those in two semihumid Amazonian forests subjected to experimental drought. We conclude that trees from paleo- or neotropical forests growing in semihumid or perhumid climates may not differ systematically in their growth sensitivity and vitality under sublethal drought stress. Drought vulnerability may depend more on stem cambial activity in moist periods than on tree height or wood specific gravity.
Background and aims
Within the last decades, considerable knowledge has been gained on the impa... more Background and aims
Within the last decades, considerable knowledge has been gained on the impacts of carbonaceous soil additives such as hydrochar (or HTC) and biochar (or pyrochar) on plant growth and various soil properties. However, still little is known about the effects of hydrochar and biochar on soil microorganisms, especially from field studies. Microorganisms are closely linked to nutrient dynamics in soil and therefore are tightly linked to soil fertility. As a consequence, possible changes in the microbial community structure due to HTC/biochar soil application may lead to considerable changes in soil nutrient dynamics. Methods
To gain insights into HTC/biochar associated long-term effects on microorganisms, soil samples were taken from a grassland field study 2.6 years (31 months) after its initiation (April 2011), where Miscanthus × giganteus feedstock, HTC and biochar, each mixed with pig slurry had been applied as top-dressing in a randomized block design, next to a slurry-only control (n = 4, 16 plots). The samples were analyzed for microbial activity and biomass by substrate induced respiration (SIR). Bacterial and fungal fractions in soil microbial biomass (SMB) were determined using the inhibitors streptomycin and cycloheximide respectively. Results
Total SMB in biochar-amended soils was significantly higher compared to all other treatments; fungal biomass was significantly higher compared to feedstock and control treatments. The percentage of bacterial biomass was higher in the feedstock and HTC amended soil, as compared to the control. Additionally, HTC exhibited a significantly higher percentage of fungal biomass compared to the feedstock treatment, indicating a microbial community shift. Conclusion
While the uncarbonized feedstock material depleted both total SMB and especially fungi, HTC and biochar did not trigger any adverse long-term effects on SMB. Rather, the observed biochar-induced stimulation of SMB may improve soil aggregation and increase the soil organic carbon content in the long term.
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Papers by Gerald Moser
through shifts in the rates of photosynthetic carbon uptake and transpirational water-loss. Free Air CO2 Enrichment (FACE)
experiments aim to predict the likely responses of plants to increased [CO2] under normal climatic conditions. The Giessen
FACE system operates a lower [CO2] enrichment regime (480 mmol mol–1) than standard FACE (550–600 mmol mol–1),
permitting the analysis of a mixed species temperate meadow under a [CO2] level equivalent to that predicted in 25–30 years.
We analysed the physiological and morphological responses of six species to investigate the effect of moderate [CO2] on
spring biomass production. Carbon dioxide enrichment stimulated leaf photosynthetic rates and supressed respiration,
contributing to enhanced net assimilation and a 23% increase in biomass. The capacity for photosynthetic assimilation was
unaffected by [CO2] enrichment, with no downregulation of rates of carboxylation of Rubisco or regeneration of ribulose-
1,5-bisphosphate. Foliar N content was also not influenced by increased [CO2]. Enhanced [CO2] reduced stomatal size, but
stomatal density and leaf area index remained constant, suggesting that the effect on gas exchange was minimal.
has not yet been assessed for tropical agroforestry landscapes. We measured above- and below-ground carbon stocks as
well as the species richness of four groups of plants and eight of animals on 14 representative plots in Sulawesi, Indonesia,
ranging from natural rainforest to cacao agroforests that have replaced former natural forest. The conversion of natural
forests with carbon stocks of 227–362 Mg C ha21 to agroforests with 82–211 Mg C ha21 showed no relationships to overall
biodiversity but led to a significant loss of forest-related species richness. We conclude that the conservation of the forestrelated
biodiversity, and to a lesser degree of carbon stocks, mainly depends on the preservation of natural forest habitats.
In the three most carbon-rich agroforestry systems, carbon stocks were about 60% of those of natural forest, suggesting
that 1.6 ha of optimally managed agroforest can contribute to the conservation of carbon stocks as much as 1 ha of natural
forest. However, agroforestry systems had comparatively low biodiversity, and we found no evidence for a tight link
between carbon storage and biodiversity. Yet, potential win-win agroforestry management solutions include combining
high shade-tree quality which favours biodiversity with cacao-yield adapted shade levels
Within the last decades, considerable knowledge has been gained on the impacts of carbonaceous soil additives such as hydrochar (or HTC) and biochar (or pyrochar) on plant growth and various soil properties. However, still little is known about the effects of hydrochar and biochar on soil microorganisms, especially from field studies. Microorganisms are closely linked to nutrient dynamics in soil and therefore are tightly linked to soil fertility. As a consequence, possible changes in the microbial community structure due to HTC/biochar soil application may lead to considerable changes in soil nutrient dynamics.
Methods
To gain insights into HTC/biochar associated long-term effects on microorganisms, soil samples were taken from a grassland field study 2.6 years (31 months) after its initiation (April 2011), where Miscanthus × giganteus feedstock, HTC and biochar, each mixed with pig slurry had been applied as top-dressing in a randomized block design, next to a slurry-only control (n = 4, 16 plots). The samples were analyzed for microbial activity and biomass by substrate induced respiration (SIR). Bacterial and fungal fractions in soil microbial biomass (SMB) were determined using the inhibitors streptomycin and cycloheximide respectively.
Results
Total SMB in biochar-amended soils was significantly higher compared to all other treatments; fungal biomass was significantly higher compared to feedstock and control treatments. The percentage of bacterial biomass was higher in the feedstock and HTC amended soil, as compared to the control. Additionally, HTC exhibited a significantly higher percentage of fungal biomass compared to the feedstock treatment, indicating a microbial community shift.
Conclusion
While the uncarbonized feedstock material depleted both total SMB and especially fungi, HTC and biochar did not trigger any adverse long-term effects on SMB. Rather, the observed biochar-induced stimulation of SMB may improve soil aggregation and increase the soil organic carbon content in the long term.
through shifts in the rates of photosynthetic carbon uptake and transpirational water-loss. Free Air CO2 Enrichment (FACE)
experiments aim to predict the likely responses of plants to increased [CO2] under normal climatic conditions. The Giessen
FACE system operates a lower [CO2] enrichment regime (480 mmol mol–1) than standard FACE (550–600 mmol mol–1),
permitting the analysis of a mixed species temperate meadow under a [CO2] level equivalent to that predicted in 25–30 years.
We analysed the physiological and morphological responses of six species to investigate the effect of moderate [CO2] on
spring biomass production. Carbon dioxide enrichment stimulated leaf photosynthetic rates and supressed respiration,
contributing to enhanced net assimilation and a 23% increase in biomass. The capacity for photosynthetic assimilation was
unaffected by [CO2] enrichment, with no downregulation of rates of carboxylation of Rubisco or regeneration of ribulose-
1,5-bisphosphate. Foliar N content was also not influenced by increased [CO2]. Enhanced [CO2] reduced stomatal size, but
stomatal density and leaf area index remained constant, suggesting that the effect on gas exchange was minimal.
has not yet been assessed for tropical agroforestry landscapes. We measured above- and below-ground carbon stocks as
well as the species richness of four groups of plants and eight of animals on 14 representative plots in Sulawesi, Indonesia,
ranging from natural rainforest to cacao agroforests that have replaced former natural forest. The conversion of natural
forests with carbon stocks of 227–362 Mg C ha21 to agroforests with 82–211 Mg C ha21 showed no relationships to overall
biodiversity but led to a significant loss of forest-related species richness. We conclude that the conservation of the forestrelated
biodiversity, and to a lesser degree of carbon stocks, mainly depends on the preservation of natural forest habitats.
In the three most carbon-rich agroforestry systems, carbon stocks were about 60% of those of natural forest, suggesting
that 1.6 ha of optimally managed agroforest can contribute to the conservation of carbon stocks as much as 1 ha of natural
forest. However, agroforestry systems had comparatively low biodiversity, and we found no evidence for a tight link
between carbon storage and biodiversity. Yet, potential win-win agroforestry management solutions include combining
high shade-tree quality which favours biodiversity with cacao-yield adapted shade levels
Within the last decades, considerable knowledge has been gained on the impacts of carbonaceous soil additives such as hydrochar (or HTC) and biochar (or pyrochar) on plant growth and various soil properties. However, still little is known about the effects of hydrochar and biochar on soil microorganisms, especially from field studies. Microorganisms are closely linked to nutrient dynamics in soil and therefore are tightly linked to soil fertility. As a consequence, possible changes in the microbial community structure due to HTC/biochar soil application may lead to considerable changes in soil nutrient dynamics.
Methods
To gain insights into HTC/biochar associated long-term effects on microorganisms, soil samples were taken from a grassland field study 2.6 years (31 months) after its initiation (April 2011), where Miscanthus × giganteus feedstock, HTC and biochar, each mixed with pig slurry had been applied as top-dressing in a randomized block design, next to a slurry-only control (n = 4, 16 plots). The samples were analyzed for microbial activity and biomass by substrate induced respiration (SIR). Bacterial and fungal fractions in soil microbial biomass (SMB) were determined using the inhibitors streptomycin and cycloheximide respectively.
Results
Total SMB in biochar-amended soils was significantly higher compared to all other treatments; fungal biomass was significantly higher compared to feedstock and control treatments. The percentage of bacterial biomass was higher in the feedstock and HTC amended soil, as compared to the control. Additionally, HTC exhibited a significantly higher percentage of fungal biomass compared to the feedstock treatment, indicating a microbial community shift.
Conclusion
While the uncarbonized feedstock material depleted both total SMB and especially fungi, HTC and biochar did not trigger any adverse long-term effects on SMB. Rather, the observed biochar-induced stimulation of SMB may improve soil aggregation and increase the soil organic carbon content in the long term.