Comparison of greenhouse gas fluxes from tropical forests and oil palm plantations on mineral soil

Abstract. In Southeast Asia, oil palm (OP) plantations have largely replaced tropical forests. The impact of this shift in land use on greenhouse gas (GHG) fluxes remains highly uncertain, mainly due to a relatively small pool of available data. The aim of this study is to quantify differences of nitrous oxide (N2O) and methane (CH4) fluxes as well as soil carbon dioxide (CO2) respiration rates from logged forests, oil palm plantations of different ages, and an adjacent small riparian area. Nitrous oxide fluxes are the focus of this study, as these emissions are expected to increase significantly due to the nitrogen (N) fertilizer application in the plantations. This study was conducted in the SAFE (Stability of Altered Forest Ecosystems) landscape in Malaysian Borneo (Sabah) with measurements every 2 months over a 2-year period. GHG fluxes were measured by static chambers together with key soil physicochemical parameters and microbial biodiversity. At all sites, N2O fluxes were spatially and temporally highly variable. On average the largest fluxes (incl. 95 % CI) were measured from OP plantations (45.1 (24.0–78.5) µg m−2 h−1 N2O-N), slightly smaller fluxes from the riparian area (29.4 (2.8–84.7) µg m−2 h−1 N2O-N), and the smallest fluxes from logged forests (16.0 (4.0–36.3) µg m−2 h−1 N2O-N). Methane fluxes were generally small (mean ± SD): −2.6 ± 17.2 µg CH4-C m−2 h−1 for OP and 1.3 ± 12.6 µg CH4-C m−2 h−1 for riparian, with the range of measured CH4 fluxes being largest in logged forests (2.2 ± 48.3 µg CH4-C m−2 h−1). Soil respiration rates were larger from riparian areas (157.7 ± 106 mg m−2 h−1 CO2-C) and logged forests (137.4 ± 95 mg m−2 h−1 CO2-C) than OP plantations (93.3 ± 70 mg m−2 h−1 CO2-C) as a result of larger amounts of decomposing leaf litter. Microbial communities were distinctly different between the different land-use types and sites. Bacterial communities were linked to soil pH, and fungal and eukaryotic communities were linked to land use. Despite measuring a large number of environmental parameters, mixed models could only explain up to 17 % of the variance of measured fluxes for N2O, 3 % of CH4, and 25 % of soil respiration. Scaling up measured N2O fluxes to Sabah using land areas for forest and OP resulted in emissions increasing from 7.6 Mt (95 % confidence interval, −3.0–22.3 Mt) yr−1 in 1973 to 11.4 Mt (0.2–28.6 Mt) yr−1 in 2015 due to the increasing area of forest converted to OP plantations over the last ∼ 40 years.

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Comparison of greenhouse gas fluxes and microbial communities from tropical forest and adjacent oil palm plantations on mineral soil

10.5194/bg-2020-297 ◽

2020 ◽

Author(s):

Julia Drewer ◽

Melissa M. Leduning ◽

Robert I. Griffiths ◽

Tim Goodall ◽

Peter E. Levy ◽

...

Keyword(s):

Land Use ◽

Soil Respiration ◽

Microbial Communities ◽

Greenhouse Gas ◽

Oil Palm ◽

Soil Microbial Communities ◽

Respiration Rates ◽

N2o Fluxes ◽

The Impact ◽

Ghg Fluxes

Abstract. In Southeast Asia, oil palm plantations have largely replaced tropical forests. The impact of this shift in land-use on greenhouse gas (GHG) fluxes and soil microbial communities remains highly uncertain, mainly due to a relatively small pool of available data. The aim of this study is to quantify differences of nitrous oxide (N2O) and methane (CH4) fluxes as well as soil carbon dioxide (CO2) respiration rates from logged forests, oil palm plantations of different ages and an adjacent small riparian area. The focus of this study is on N2O fluxes, as these emissions are expected to increase significantly due to the introduction of nitrogen (N) fertiliser application. This study was conducted in the SAFE (Stability of Altered Forest Ecosystems) landscape in Malaysian Borneo (Sabah) with measurements every two months over a two-year period. GHG fluxes were measured by static chambers; at the same time soil samples were collected for analysis of the key soil physicochemical parameters and for analysis of microbial biodiversity using next generation sequencing in dry and wet season. N2O fluxes were highly variable across the different sites, with the highest mean flux from OP (46.2 ± 166 µg m−2 h−1 N2O-N) and riparian (31.8 ± 220 µg m−2 h−1 N2O-N) sites, compared to lower fluxes from logged forest (13.9 ± 171 µg m−2 h−1 N2O-N). Methane fluxes were generally small; −2.6 ± 17.2 µg CH4-C m−2 h−1 for OP and 1.3 ± 12.6 µg CH4-C m−2 h−1 for riparian with the range of measured CH4 fluxes largest in logged forests (2.2 ± 48.3 µg CH4- m−2 h−1). Soil respiration rates were larger from riparian areas (157.7 ± 106 mg m−2 h−1 CO2-C) and logged forests (137.4 ± 95 mg m−2 h−1 CO2-C) than OP plantations (93.3 ± 70 mg m−2 h−1 CO2-C) due to larger amounts of decomposing leaf litter. Microbial communities were distinctly different between the different land-use types and sites, bacterial communities linked to soil pH and fungal and eukaryotic communities to land-use. Despite measuring a number of environmental parameters, mixed models could only explain up to 17 % of the variance of measured fluxes for N2O, 3 % of CH4 and 25 % of soil respiration. Scaling up measured N2O fluxes to Sabah using land areas for forest and OP resulted in emissions increasing from 7.6 Mt (95 % confidence interval, −3.0–22.3 Mt) per year in 1973 to 11.4 Mt (0.2–28.6 Mt) per year in 2015 due to the increasing area of forest converted to OP plantations over the last ~40 years.

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Impacts of Low Disturbance Liquid Dairy Manure Incorporation on Alfalfa Yield and Fluxes of Ammonia, Nitrous Oxide, and Methane

Agriculture ◽

10.3390/agriculture11080750 ◽

2021 ◽

Vol 11 (8) ◽

pp. 750

Author(s):

Jessica Sherman ◽

Eric Young ◽

William Jokela ◽

Jason Cavadini

Keyword(s):

Nitrous Oxide ◽

Greenhouse Gas ◽

N Uptake ◽

Dairy Manure ◽

Nutrient Losses ◽

Manure Application ◽

Medicago Sativa L ◽

N2o Fluxes ◽

Ghg Fluxes ◽

Precipitation Events

Surface applied liquid dairy manure application (i.e., broadcasting) after alfalfa (Medicago sativa L.) harvest is a common practice. Low disturbance manure incorporation (LDMI) may offer multiple benefits including lower ammonia (NH3), greenhouse gas (GHG) and hydrologic nutrient losses compared to broadcast. However, few studies have simultaneously quantified LDMI impacts on alfalfa yield, NH3 and greenhouse gas (GHG) fluxes. We measured NH3, nitrous oxide (N2O), and methane (CH4) fluxes for liquid dairy manure treatments applied to alfalfa plots for broadcast and LDMI over three seasons (2014 to 2016) in central Wisconsin, USA. There were minor differences in alfalfa yield and nitrogen (N) uptake across treatments and years. Shallow disk injection and aerator/band reduced NH3 loss by 95 and 52% of broadcast, respectively, however both substantially increased N2O fluxes (6 and 4.5 kg ha−1 year−1 versus 3.6 kg ha−1 year−1 for broadcast, respectively). The magnitude and timing of N2O fluxes were related to manure application and precipitation events. Average CH4 fluxes were similar among methods and increased with soil moisture after manure application. Results highlight the importance of quantitatively evaluating agri-environmental tradeoffs of LDMI versus broadcast manure application for dairy farms.

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Nitrous oxide emission budgets and land-use-driven hotspots for organic soils in Europe

Biogeosciences ◽

10.5194/bg-11-6595-2014 ◽

2014 ◽

Vol 11 (23) ◽

pp. 6595-6612 ◽

Cited By ~ 40

Author(s):

T. Leppelt ◽

R. Dechow ◽

S. Gebbert ◽

A. Freibauer ◽

A. Lohila ◽

...

Keyword(s):

Land Use ◽

Nitrous Oxide ◽

Greenhouse Gas ◽

Ph Value ◽

Emission Factors ◽

Organic Soils ◽

N2o Emissions ◽

The European Union ◽

Study Results ◽

N2o Fluxes

Abstract. Organic soils are a main source of direct emissions of nitrous oxide (N2O), an important greenhouse gas (GHG). Observed N2O emissions from organic soils are highly variable in space and time, which causes high uncertainties in national emission inventories. Those uncertainties could be reduced when relating the upscaling process to a priori-identified key drivers by using available N2O observations from plot scale in empirical approaches. We used the empirical fuzzy modelling approach MODE to identify main drivers for N2O and utilize them to predict the spatial emission pattern of European organic soils. We conducted a meta-study with a total amount of 659 annual N2O measurements, which was used to derive separate models for different land use types. We applied our models to available, spatially explicit input driver maps to upscale N2O emissions at European level and compared the inventory with recently published IPCC emission factors. The final statistical models explained up to 60% of the N2O variance. Our study results showed that cropland and grasslands emitted the highest N2O fluxes 0.98 ± 1.08 and 0.58 ± 1.03 g N2O-N m−2 a−1, respectively. High fluxes from cropland sites were mainly controlled by low soil pH value and deep-drained groundwater tables. Grassland hotspot emissions were strongly related to high amount of N-fertilizer inputs and warmer winter temperatures. In contrast, N2O fluxes from natural peatlands were predominantly low (0.07 ± 0.27 g N2O-N m−2 a−1) and we found no relationship with the tested drivers. The total inventory for direct N2O emissions from organic soils in Europe amount up to 149.5 Gg N2O-N a−1, which also included fluxes from forest and peat extraction sites and exceeds the inventory calculated by IPCC emission factors of 87.4 Gg N2O-N a−1. N2O emissions from organic soils represent up to 13% of total European N2O emissions reported in the European Union (EU) greenhouse gas inventory of 2011 from only 7% of the EU area. Thereby the model demonstrated that the major part (85%) of the inventory is induced by anthropogenic management, which shows the significant reduction potential by rewetting and extensification of agriculturally used peat soils.

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Greenhouse gas emissions from the water–air interface of a grassland river: a case study of the Xilin River

Scientific Reports ◽

10.1038/s41598-021-81658-x ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Xue Hao ◽

Yu Ruihong ◽

Zhang Zhuangzhuang ◽

Qi Zhen ◽

Lu Xixi ◽

...

Keyword(s):

Carbon Dioxide ◽

Land Use ◽

Nitrous Oxide ◽

Greenhouse Gas Emissions ◽

Greenhouse Gas ◽

Ghg Emissions ◽

Nitrous Oxide Emissions ◽

Gas Emissions ◽

Sand Land ◽

Very High

AbstractGreenhouse gas (GHG) emissions from rivers and lakes have been shown to significantly contribute to global carbon and nitrogen cycling. In spatiotemporal-variable and human-impacted rivers in the grassland region, simultaneous carbon dioxide, methane and nitrous oxide emissions and their relationships under the different land use types are poorly documented. This research estimated greenhouse gas (CO2, CH4, N2O) emissions in the Xilin River of Inner Mongolia of China using direct measurements from 18 field campaigns under seven land use type (such as swamp, sand land, grassland, pond, reservoir, lake, waste water) conducted in 2018. The results showed that CO2 emissions were higher in June and August, mainly affected by pH and DO. Emissions of CH4 and N2O were higher in October, which were influenced by TN and TP. According to global warming potential, CO2 emissions accounted for 63.35% of the three GHG emissions, and CH4 and N2O emissions accounted for 35.98% and 0.66% in the Xilin river, respectively. Under the influence of different degrees of human-impact, the amount of CO2 emissions in the sand land type was very high, however, CH4 emissions and N2O emissions were very high in the artificial pond and the wastewater, respectively. For natural river, the greenhouse gas emissions from the reservoir and sand land were both low. The Xilin river was observed to be a source of carbon dioxide and methane, and the lake was a sink for nitrous oxide.

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Greenhouse gas fluxes from an oil palm plantation on mineral soil in Indonesia undergoing riparian restoration

10.5194/egusphere-egu21-7704 ◽

2021 ◽

Author(s):

Stella White ◽

Ribka Sionita Tarigan ◽

Anak Agung Ketut Aryawan ◽

Edgar Turner ◽

Sarah Luke ◽

...

Keyword(s):

Environmental Impact ◽

Greenhouse Gas ◽

Oil Palm ◽

Forest Tree ◽

Native Forest ◽

Forest Trees ◽

Riparian Restoration ◽

Enrichment Planting ◽

Mineral Soils ◽

Ghg Fluxes

Oil palm (OP) growers are under pressure to reduce their environmental impact. Ecosystem function and biodiversity are at the forefront of the issue, but what effect do changes in management practices have on greenhouse gas (GHG) fluxes from plantations?&#160;The Riparian Ecosystem Restoration in Tropical Agriculture (RERTA) Project is a collaboration between the University of Cambridge and the SMART Research Institute in Riau, Indonesia. This project explores the ecological changes resulting from the restoration of riparian margins between plantations and watercourses. Four management strategies were applied on both sides of a river to create 50m riparian buffers, 400m in length: (1) A control treatment of no restoration, the removal of mature OP and replanting of young OP to the river margin; (2) Little to no agricultural management of mature OP; (3) Clearance of mature OP and enrichment planting with native forest trees; (4) Little or no agricultural management of mature OP and enrichment planting with native forest trees. Here we present a specific objective to investigate the effect of riparian restoration &#8211; and related changes in soil characteristics, structure and vegetation cover &#8211; on fluxes of N2O, CH4 and CO2 from mineral soils.The experimental site began as a mature OP plantation, with monthly background measurements taken between January and April 2019. Palms were felled in April 2019 and monthly sampling was resumed when replanting and restoration began, in October 2019. We measured GHGs using static chambers; 6 in each riparian treatment and 16 in the actual OP plantation, 40 chambers in total. Samples were analysed using GC-FID/&#181;ECD.Background measurements before felling showed high variability, but indicated no difference between the four experimental plots and the rest of the plantation. Fluxes measured following replanting were also highly variable, with no significant differences observed between treatments. N2O fluxes were relatively low before felling as the mature palms were no longer fertilised. Higher emissions were seen in the disturbed immature OP and forest tree treatments following replanting. Though the sites appeared to recover quickly and emission fluxes decreased after a few months, presumably as the soil settled and new vegetation began to grow. CH4 uptake was seen in the immature OP treatment immediately after replanting. In subsequent months no clear trends of CH4 uptake or emission were observed, with the greatest variability generally seen in the forest tree treatment. CH4 emissions increased in October 2020 with the beginning of the rainy season, most notably in mature OP and mature OP with forest tree treatments. Following restoration CO2 emissions were higher in treatments with established plant communities &#8211; mature OP and mature OP with forest trees.These results suggest that riparian restoration had no significant effect on GHG fluxes from mineral soils, and would not alter the overall GHG budget of a plantation. If there is no additional GHG burden and riparian restoration results in enhancing biodiversity and ecosystem services as well as improving water quality, it will be a viable management option to improve the environmental impact of an OP plantation.

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Spatial and temporal variability of nitrous oxide emissions in a mixed farming landscape of Denmark

Biogeosciences ◽

10.5194/bg-9-2989-2012 ◽

2012 ◽

Vol 9 (8) ◽

pp. 2989-3002 ◽

Cited By ~ 18

Author(s):

K. Schelde ◽

P. Cellier ◽

T. Bertolini ◽

T. Dalgaard ◽

T. Weidinger ◽

...

Keyword(s):

Land Use ◽

Nitrous Oxide ◽

Agricultural Land ◽

Nitrous Oxide Emissions ◽

Soil Conditions ◽

Spatial And Temporal Variability ◽

N2o Emissions ◽

N2o Production ◽

Mixed Farming ◽

N2o Fluxes

Abstract. Nitrous oxide (N2O) emissions from agricultural land are variable at the landscape scale due to variability in land use, management, soil type, and topography. A field experiment was carried out in a typical mixed farming landscape in Denmark, to investigate the main drivers of variations in N2O emissions, measured using static chambers. Measurements were made over a period of 20 months, and sampling was intensified during two weeks in spring 2009 when chambers were installed at ten locations or fields to cover different crops and topography and slurry was applied to three of the fields. N2O emissions during spring 2009 were relatively low, with maximum values below 20 ng N m−2 s−1. This applied to all land use types including winter grain crops, grasslands, meadows, and wetlands. Slurry application to wheat fields resulted in short-lived two-fold increases in emissions. The moderate N2O fluxes and their moderate response to slurry application were attributed to dry soil conditions due to the absence of rain during the four previous weeks. Cumulative annual emissions from two arable fields that were both fertilized with mineral fertilizer and manure were large (17 kg N2O-N ha−1 yr−1 and 5.5 kg N2O-N ha−1 yr−1) during the previous year when soil water conditions were favourable for N2O production during the first month following fertilizer application. Our findings confirm the importance of weather conditions as well as nitrogen management on N2O fluxes.

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Edaphic and environmental controls of soil respiration and related soil processes under two contrasting manuka and kanuka shrubland stands in North Island, New Zealand

Soil Research ◽

10.1071/sr12248 ◽

2013 ◽

Vol 51 (5) ◽

pp. 390 ◽

Cited By ~ 4

Author(s):

C. B. Hedley ◽

S. M. Lambie ◽

J. L. Dando

Keyword(s):

Nitrous Oxide ◽

New Zealand ◽

Soil Respiration ◽

Respiration Rate ◽

Nitrous Oxide Emissions ◽

Volcanic Soil ◽

Mineral N ◽

Organic C ◽

Respiration Rates ◽

Environmental Controls

The conversion of marginal pastoral land in New Zealand to higher biomass shrubland consisting of manuka (Leptospermum scoparium) and kanuka (Kunzea ericoides var. ericoides) offers opportunity for carbon (C) sequestration, with potential co-benefits of soil erosion control. We therefore selected two areas with different soils in different climatic regions to investigate and compare soil respiration rates, methane and nitrous oxide emission profiles, and key carbon exchange processes controlling carbon sequestration. In addition, two shrubland stands of different ages were selected in each area, providing four sites in total. Regular (almost monthly) soil respiration measurements were made over a 2-year period, with less frequent methane and nitrous oxide flux measurements, and soil sampling once at the end of the study. The cooler, wetter volcanic soils had higher total organic C (6.39 ± 0.12% v. 5.51 ± 0.17%), soil C : nitrogen (N) ratios (20.55 ± 0.20 v. 18.45 ± 0.23), and slightly lower mineral N (3.30 ± 0.74 v. 4.89 ± 0.57 mg/kg) and microbial biomass C (1131 ± 108 v. 1502 ± 37 mg/kg) than the more drought-prone, stony, sedimentary soils. Mineral-N contents at all sites indicated N-limited ecosystems for allocation of below- and above-ground C. The estimated mean annual cumulative respiration rate recorded in the volcanic soil was 10.26 ± 7.45 t CO2-C/ha.year compared with 9.85 ± 8.63 t CO2-C/ha.year in the stony sedimentary soil for the 2 years of our study. Older shrubland stands had higher respiration rates than younger stands in both study areas. Methane oxidation was estimated to be higher in the volcanic soil (4.10 ± 2.13 kg CH4-C/ha.year) than the sedimentary soil sites (2.51 ± 2.48 kg CH4-C/ha.year). The measured natural background levels of nitrous oxide emissions from these shrubland soils ranged between negligible and 0.30 ± 0.20 kg N2O-N/ha.year. A strong climatic control (temperature and moisture) on gas fluxes was observed at all sites. Our sampling strategy at each of the four sites was to estimate the mean soil respiration rates (n = 25) from an 8 by 8 m sampling grid positioned into a representative location. Soil respiration rates were also measured (by additional, less frequent sampling) in two adjacent grids (1-m offset and 100-m distant grid) to test the validity of these representative mean values. The 1-m offset grid (n = 25) provided a statistically different soil respiration rate from the main grid (n = 25) in 25% of the 12 sampling events. The 100-m grid (n = 25) provided a statistically different respiration rate to the main grid in 38% of the 26 sampling events. These differences are attributed to the spatially variable and sporadic nature of gaseous emissions from soils. The grid analysis tested the prediction uncertainty and it provides evidence for strong spatial and temporal control by edaphic processes in micro-sites. A partial least-squares regression model was used to relate the 2009 annual cumulative soil respiration to site-specific edaphic characteristics, i.e. biomass, nutrient availability, porosity and bulk density, measured at the end of that year. The model explained ≥80% of the variance at three of the four sites.

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Required sample size for estimating soil respiration rates in large areas of two tropical forests and of two types of plantation in Malaysia

Forest Ecology and Management ◽

10.1016/j.foreco.2005.02.011 ◽

2005 ◽

Vol 210 (1-3) ◽

pp. 455-459 ◽

Cited By ~ 58

Author(s):

Minako Adachi ◽

Yukiko Sakata Bekku ◽

Akihiro Konuma ◽

Wan Rasidah Kadir ◽

Toshinori Okuda ◽

...

Keyword(s):

Soil Respiration ◽

Sample Size ◽

Tropical Forests ◽

Respiration Rates

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Nitrous oxide emissions at the landscape scale: spatial and temporal variability

Biogeosciences Discussions ◽

10.5194/bgd-8-11941-2011 ◽

2011 ◽

Vol 8 (6) ◽

pp. 11941-11978 ◽

Cited By ~ 4

Author(s):

K. Schelde ◽

P. Cellier ◽

T. Bertolini ◽

T. Dalgaard ◽

T. Weidinger ◽

...

Keyword(s):

Land Use ◽

Nitrous Oxide ◽

Agricultural Land ◽

Mineral Fertilizer ◽

Landscape Scale ◽

Nitrous Oxide Emissions ◽

Spatial And Temporal Variability ◽

N2o Emissions ◽

N2o Production ◽

N2o Fluxes

Abstract. Nitrous oxide (N2O) emissions from agricultural land are variable at the landscape scale due to variability in land use, management, soil type, and topography. A field experiment was carried out in a typical mixed farming landscape in Denmark, to investigate the main drivers of variations in N2O emissions, measured using static chambers. Measurements were done over a period of 20 months, and sampling was intensified during two weeks in spring 2009 when chambers were installed at ten locations or fields to cover different crops and topography and slurry was applied to three of the fields. N2O emissions during the spring 2009 period were relatively low, with maximum values below 20 ng N m−2 s−1. This applied to all land use types including winter grain crops, grassland, meadow, and wetland. Slurry application to wheat fields resulted in short-lived two-fold increases in emissions. The moderate N2O fluxes and their moderate response to slurry application were attributed to dry soil moisture conditions due to the absence of rain during the four previous weeks. Measured cumulated annual emissions from two arable fields that were both fertilized with mineral fertilizer and manure were large (17 kg N2O-N ha−1 yr−1 and 5.5 kg N2O-N ha−1 yr−1, respectively) during the previous year when soil water conditions were favourable for N2O production during the first month following fertilizer application, confirming the importance of the climatic regime on N2O fluxes.

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Land use change and the impact on greenhouse gas exchange in north Australian savanna soils

Biogeosciences Discussions ◽

10.5194/bgd-8-9087-2011 ◽

2011 ◽

Vol 8 (5) ◽

pp. 9087-9123 ◽

Cited By ~ 1

Author(s):

S. P. P. Grover ◽

S. J. Livesley ◽

L. B. Hutley ◽

H. Jamali ◽

B. Fest ◽

...

Keyword(s):

Land Use ◽

Nitrous Oxide ◽

Land Use Change ◽

Greenhouse Gas ◽

Water Content ◽

Soil Water Content ◽

Co2 Fluxes ◽

Soil Co2 ◽

Gas Fluxes ◽

Greenhouse Gas Fluxes

Abstract. Savanna ecosystems are subject to accelerating land use change as human demand for food and forest products increases. Land use change has been shown to both increase and decrease greenhouse gas fluxes from savannas and considerable uncertainty exists about the non-CO2 fluxes from the soil. We measured methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2) over a complete wet-dry seasonal cycle at three replicated sites of each of three land uses: savanna, young pasture and old pasture (converted from savanna 5–7 and 25–30 yr ago, respectively) in the Douglas Daly region of northern Australia. The effect of break of season rains at the end of the dry season was investigated with two irrigation experiments. Land use change from savanna to pasture increased net greenhouse gas fluxes from the soil. Pasture sites were a weaker sink for CH4 than savanna sites and, under wet conditions, old pastures turned from being sinks to a significant source of CH4. Nitrous oxide emissions were generally very low, in the range of 0 to 5 μg N2O-N m−2 h−1, and under dry conditions soil uptake of N2O was apparent. Break of season rains produced a small, short lived pulse of N2O up to 20 μg N2O-N m−2 h−1, most evident in pasture soil. Annual cumulative soil CO2 fluxes increased after clearing, with savanna (14.6 t CO2-C ha−1 yr−1) having the lowest fluxes compared to old pasture (18.5 t CO2-C ha−1 yr−1) and young pasture (20.0 t CO2-C ha−1 yr−1). Clearing savanna increased soil-based greenhouse gas emissions from 53 to ~70 t CO2-equivalents, a 30% increase dominated by an increase in soil CO2 emissions and shift from soil CH4 sink to source. Seasonal variation was clearly driven by soil water content, supporting the emerging view that soil water content is a more important driver of soil gas fluxes than soil temperature in tropical ecosystems where temperature varies little among seasons.

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