Scholarly article on topic 'Soil CO2 Respiration Along Annual Crops or Land-cover Type Gradients on West Kalimantan Degraded Peatland Forest'

Soil CO2 Respiration Along Annual Crops or Land-cover Type Gradients on West Kalimantan Degraded Peatland Forest Academic research paper on "Earth and related environmental sciences"

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Abstract of research paper on Earth and related environmental sciences, author of scientific article — Dwi Astiani, Mujiman, Muhammad Hatta, Hanisah, Firda Fifian

Abstract Kalimantan peatland spans ∼5.9million ha (∼11% of Kalimantan's total terrestrial land area) as a part ofIndonesian peatlands, covers∼21 million ha, contains∼57.8 Gtof terrestrial carbon. Land cover change of peatland forest results in significant sources CO2 emissions. Thus, we identified to estimate carbon emissions generated by crop land and ex burnt activities in Kalimantan's peatlands degraded forest.Soil CO2 respiration was measured under four of the most prominent land cover and annual agricultural crops on 4-5 year post fire (fern, corn, pineapple) and newly burnt areas in West Kalimantan peatlands. Measurements were obtained from Licor 8100 and gatheredby monthly assessments. Among the land cover types showed different meanmonthly CO2 fluxes.Soil CO2 respiration on newly burnt peatland, pineapple plantation and fern covered showed the highest and not significantly different among them. Cornsmall-scale plantation soil respired the lowest and significantly different from the other three land covers. Dry vs. rainy month comparisons show huge different (>50%) monthly CO2 fluxes rate. Each land cover type has distinctive peat environmental factors that significantly affect CO2 respiration. Theresult indicates that each crop/cover types generate different level site factors, which affect different level of peat CO2 rates. The regression models of site factors measured for each specific land cover can be applied to obtain better estimate CO2 respiration rates of degraded peatland and agricultural crop cover types. Moreover, it is able to be applied as a baseline for degraded peatland management and CO2 emission mitigation.

Academic research paper on topic "Soil CO2 Respiration Along Annual Crops or Land-cover Type Gradients on West Kalimantan Degraded Peatland Forest"

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Procedia Environmental Sciences 28 (2015) 132 - 141

The 5th Sustainable Future for Human Security (SustaiN 2014)

Soil CO2 respiration along annual crops or land-cover type gradients on West Kalimantan degraded peatland forest

Dwi Astiania*, Mujimanb, Muhammad Hattab, Hanisaha, Firda Fifiana

a Forestry, Tanjungpura University, Jl. Imam Bonjol Pontianak, 78124, Indonesia, Landscape Livelihood Indonesia (LLI) Institute,Jl. Parit H Husin 2 Gg. Wisata 1 No. 11B, Pontianak, 78121, Indonesia

Abstract

Kalimantan peatland spans ~5.9million ha (~11% of Kalimantan's total terrestrial land area) as a part of Indonesian peatlands, covers~21 million ha, contains~57.8 Gtof terrestrial carbon. Land cover change of peatland forest results in significant sources CO2 emissions. Thus, we identified to estimate carbon emissions generated by crop land and ex burnt activities in Kalimantan's peatlands degraded forest.Soil CO2 respiration was measured under four of the most prominent land cover and annual agricultural crops on 4-5 year post fire (fern, corn, pineapple) and newly burnt areas in West Kalimantan peatlands. Measurements were obtained from Licor 8100 and gatheredby monthly assessments. Among the land cover types showed different meanmonthly CO2 fluxes.Soil CO2 respiration on newly burnt peatland, pineapple plantation and fern covered showed the highest and not significantly different among them. Cornsmall-scale plantation soil respired the lowest and significantly different from the other three land covers. Dry vs. rainy month comparisons show huge different (>50%) monthly CO2 fluxes rate. Each land cover type has distinctive peat environmental factors that significantly affect CO2 respiration. The result indicates that each crop/cover types generate different level site factors, which affect different level of peat CO2 rates. The regression models of site factors measured for each specific land cover can be applied to obtain better estimate CO2 respiration rates of degraded peatland and agricultural crop cover types. Moreover, it is able to be applied as a baseline for degraded peatland management and CO2 emission mitigation.

© 2015 Published by Elsevier B.V This is an open access article under the CC BY-NC-ND license

(http://creativecommons.Org/licenses/by-nc-nd/4.0/).

Peer-reviewunderresponsibilityofSustainSociety

Keywords:CO2fluxes; land cover change; site factors;degraded peatland;dry and rainy months

*Corresponding author.

Email address: astiani.dwi@gmail.com

1878-0296 © 2015 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license

(http://creativecommons.org/licenses/by-nc-nd/4.0/).

Peer-review under responsibility of Sustain Society

doi:10.1016/j.proenv.2015.07.019

1. Introduction

Since the 1980s, tropical peatland forests have experienced considerable anthropogenic change1, 2. Tropical forests are under a lot of pressure, resulting increased deforestation and degradation of intact forests. The deforestation rates of intact forest in Southeast Asian tropical peatlands- concentrated in Sumatra and Kalimantan, Indonesia - has been reported as 2.2% y-1 from 2002-20053.These deforestation rates exceed those reported for Central America and the Caribbean (1.2% y-1 ) and South America (0.5% y-1) 4,5 Currently, only ~ 41% to 44% of the original peatland forests of Southeast Asia remain5.Tropical peatland accounts for 25% of current deforestation from 2000 to 2005 in Southeast Asia6.

Large areas of tropical peatland have been logged for wood products to supply regional and global demand7 and developed for either small-scale farming (e.g., sago, corn, pineapple, and vegetables) or large-scale agricultural plantations (e.g., oil palm) involving extensive peatland drainage in Indonesia8,9,10.These peatlands have also incurred synergistic exposure to drought and wildfires3, 11, 12.As a result of both natural and anthropogenic changes, deforested and drained tropical peatlands have become potentially a globally significant, yet largely unquantified, source of CO2 emissions.

Increased forest degradation, and forest land conversion to agricultural lands or urban areas accelerates this release of organic carbon to the atmosphere13, 14. However, among carbon components, emissions from land-use and land-cover change are perhaps one of the most uncertain components of the global carbon cycle, with enormous implications for estimating the current carbon budget and for modeling scenarios of climate change over the next 10-50 years15. Therefore, there is a recognized need to reduce uncertainity in carbon emission estimates (i.e., CO2 respiration) over different land cover types, with studies that seek to improve CO2 emission estimates and degraded peatland management.

Moreover, land cover changes from forested land are complex processes with some degree of ecological recovery and a strong interaction with climatic fluctuations16, 17.Anthropogenic biomass burning facilitates conversion and degradation of forests and emits high amounts of carbon into the atmosphere and the fire occurrence nearly tripled from a wet La Niña year (2008) to a drier 2009 El Niño year18. Therefore, large uncertainties in land-based carbon emissions (i.e., CO2 respiration) exist and, in particular, from degraded peatland across different agricultural crops/land cover types. Moreover, the interactive effects of site factors, climate, land-use/land cover changes and CO2 emissions are poorly understood.

Here, we estimate soil carbon respiration across annual crops/agricultural land covers within coastal peatlands with nearby recently burned peatlands. Then we examine several factors or combination of factors that may affect carbon respiration rates (e.g., land cover at relatively similar range of peat depth, and several site conditions such peat temperature, bulk density, relative humidity, water vapor, pH, water content and water table). Then we assess the relative strength of these edaphic and biophysical relationships on rates of soil carbon respiration across sites.

This study aims to estimate peat CO2 emission from agricultural peatland. We address three major questions. First, within the agricultural crops or land cover types with an average 4 - 5.5 m peat depth, how does tropical peatland respiration differ by land cover-newly burnt, 4-5 years ex burnt covered by fern, 3-4 year ex burnt planted with small-scale pineapple and corn plantation? Second, how do dry and rainy months affect peat CO2 respiration across the land covers? Third, how do the microsite conditions correspond with peat CO2 respiration among the newly burnt peatland, 4-5 year ex burnt covered with fern, small-scale pineapple and corn plantation?

2. Materials and Methods

2.1. Study Sites

This study was conducted in a coastal peatland in Kubu Raya district, West Kalimantan, Indonesia (0013' S and109026' E, ca~ 4 m a.s.l., ~3km from northern perimeter of Kuala Dua peatlands; Figure 1.

Fig 1. Study site; a) Pineapple, b) Corn, c Newly burnt, and d) Fern area on Kuala Dua peatland West Kalimantan

From the Supadio Airport weather station in Pontianak (~8 km from study), daily rainfall and temperature measurements were also compiled for regional climatic records in 2011. Mean annual rainfall is 3171 mm ± 300mm. In a 'typical' non ENSO year, all months received >100 mm in rainfall during this study.Both relatively dry months (July-Aug) and rainy months (Nov-Dec) displayed distinctive levels of precipitation (dry vs rainy mean were 165 mm vs463 mm/month; Pontianak Supadio Airport Weather Station2011). Mean monthly ambient temperature is 26.5 ± 0.6oC with minimum and maximum temperature ranging 22.8oC to 32.2oC.

Soil respiration was measured in: 1) 4-5 years ex burnt covered by fern, 2) 4-5 year ex burnt planted with pineapple, 3) 4-5 years ex burnt covered by corn small-scale plantation and 4) newly burnt peatland on Sept-Nov 2010. All measured sites were ~ 4 - 5.5 m in peat depth. The peatland area was opened forested land, intentionally burned for agricultural activities. Plots in the 4-5 years post burn (August 2007-2008) and recently burned areas (July 2010) are peatlands cleared of their forest cover, burned and drained for 6-12 months before planting with corn, cassava, pineapple or left and then invaded by fern and Imperata grasslands. The recently burned parcel was added after wildfires in December 2010. These burned sites are adjacent to crops measurement area and also affected by canal enlargement.

Two drainage canals, located parallel to the plot running North West and South East, 2 m deep 3 m wide and the distances ± 300 - 1000 mfrom plots, are maintained and enlarged by the local government in Aug-Sept 2009. The peat canals are typical in tropical peatland areas, built by local government to drain peat area in order to be cultivated by local communities. The ditch development caused the site to be drier and more degraded than before canal 'improvement'.

2.2. Peat CO2Respiration Measurements

Soil respiration was measured with Li-Cor 8100 Automated soil CO2 flux system using 20 cm diameter fixed site PVC soil collars (IRGA, Li-Cor 8100, Li-Cor Inc., Lincoln, Nebraska 68504, USA). The PVC soil collar was inserted 10 cm beneath soil surface and 2 cm above soil surface and then connected to a Li-Cor 8100-102 soil flux Survey Chamber. Soil CO2 respiration was assessed for 2 consecutive days from January through December2011. Based on our pre-measurements, mean diurnal peat CO2 respiration in these peatlands on the equator can be represented effectively by measuring the minimum (6:00-8:00) and maximum (12:00-14:00) daily respiration and then averaging values to represent diurnal soil CO2 emissions. Simultaneously with these assessments, several site conditions were also recorded.

To investigate the El-Nino or precipitation effects of this ombrogenous peatland on each annual crop/land cover, mean monthly measurement on each site, we compared dry and rainy months (July-Aug vs Nov-Dec) among four sites. The measurements were obtained across all sites simultaneously. The total number of sample collars varied

across sites. In the newly burnt site, nine collars were applied. At 4-5 years ex burnt fern, corn and pineapple sites, five collars were established, thus 24 collars were simultaneously measured at relatively similar schedule/time.

2.3. Soil Properties and Microclimate Measurements

The Li-Cor 8100 contains an Infrared Gas Analyzer to measure site conditions such as soil surface relative humadity, CO2 consentration, water vapor, and soil temperature and water content at 0-20cm peat depth, exactly at the CO2 respiration measurement. Soil water tables were monitored by water level logger (Solinst Level Logger Gold, Forestry Suppliers) near collar sites weekly and averaged for mean monthly values.

Soil bulk density and carbon content at degraded peatland area were measured in August 2011. Using Standard Russian Peat Borer (Aquatic Research Instrument), four undisturbed soil core samples at site were obtained to determine soil bulk density. Soil samples were drained for 24 hours at ambient temperature, weighed for water holding capacity measurement, oven dried at 700C for 2-3 days and then weighed. Soil bulk density was calculated as oven dried mass per volume sample reported in g cm-1.

Soil C was then determined using Spectrophotometer method19. Carbon determination used 0.5 g soil/peat sample, sieved with 0.5 mm, and placed into 100 ml Erlenmeyer tube. Then 5 ml K2Cr2O7 1N and 7.5ml H2SO4 were added to wet destruct the soil and aquadest added to reach 100 ml. The clear solution was then placed into spectrophotometer in 561nm wavelength. The standard 0 and 250 ppm C were used as comparison. Percentage C content equals to ppm curve x ml extract 1000 ml-1x 100mg soil sample-1x cf, where cf is correction factor of water content (100/(100-%water content).

Soil pH was quantified by taking 10 g soil with aquadest until 50 ml (for pH H2O) and 50 ml KCl 1 M (for pH KCl), stirred 30 minutes then measured with calibrated pH meter (pH/DO2/ Conductivity Meter Sension 156, -2 to 19,9 pH ± 0,002 Model 54650-15 HACH Company).

2.4. Data Analysis

Throughout the estimation of soil CO2 respiration, data are presented as mean and standard error (SE) in selected intervals unless otherwise noted. Repeated Measures analysis of variance ANOVA was used and then Pairwise comparisons (Tukey Procedures) were tested among land cover types (newly ex-burnt, ex-burnt sites covered by fern, corn plantation and pineapple plantation) areas and to compare soil CO2 respiration between the rainy and dry month measurements means across the year. Pearson Product Moment Correlation was applied to test several microsite factors (e.g., peat water content, peat water vapor fluxes, peat relative humidity, peat temperature, peat CO2 concentration, peat bulk density and pH) and relationships among them. Multiple Linear Regression analyses were used to measure potential effects of these independent microsite variables on soil CO2 respiration. If two or more of those site factors were covariates, site factor with the larger correlation with peat CO2 respiration was added to the Multiple Linear Regression analysis.

3. Results

3.1. Peat CO2Respiration Among Agricultural Plant Soils

Peat CO2 respiration results indicate that monthly soil respiration rates fluctuated considerably from 2.4 to 15.1 umol CO2 m-2s-1 or ~ 33.3 to 209.5 Mg ha-1 y-1. Comparation among land covers demonstrated that peatland soil mean monthly respirations and monthly distribution were significantly different among others (Fig. 2a & 2b). Newly burnt peatland, pineapple and fern land covers respired the highest and not significantly different among them, while corn cover on peatland showed the lowest CO2 respiration rate. The mean CO2 respiration on newly burnt, fern, pineapple and corn cover were 10.1, 8.9, 9.5, and 6.0 umol CO2 m-2s-1 or ~139.9, 123.2, 132.6, and 83.8 Mg CO2 ha-1 y-1 consecutively. As a comparation or baseline from our previous study, the least disturbed (no drainage) logged-forested peatland emitted ~41.6 ton ha-1 y-1in dry season, while in rainy season, this level declined to 27.0 ton ha-1 y-1. Higher degraded forest (with drainage present at nearby) mean respiration is 75.6 ton ha-1 y-1(Astiani et al. 2015, in process to be published).

Fig 2 (a) Mean soil CO2 respiration rate among crops/land covers within agricultural peatland; (b) Mean monthly peatland soil CO2 respiration distribution among four crops/land covers in 2011.

3.2. Dry vs Rainy Months of Peat CO2 Respiration

Significant seasonal differences were detected when the dry vs. rainy months are compared (dry: 11.0±1.5 vs. wet: 6.6±0.9 umol CO2 m"2s_1). Thus, droughts or drier periods appeared to increase CO2 respiration by ~ 67% in these agriculture peatlands. However, among four agricultural plants covers, soil CO2 respiration responded differently. The fluxes gaps were wider on soil with pineapple cover and bare newly burnt peatlands (Fig 2c).

i Rainy

Newly Burnt Fern Pineapple Corn

Fig 3. Peat CO2 respiration on rainy and dry months among crops/land covers.

3.2. Site Factors among Crops/Land Covers and Peat CO2 Respiration

Pearson Correlation test among some environment factors assessed at four crops/land covers (e.g., peat H2O (mmol/mol), peat CO2 concentration (ppm), peat temperature (0C), peat relative humidity (%), peat water content (vol/vol), peat bulk density (g/cm3), pH and soil carbon content indicated that some of these factors are moderately to strongly correlated (30-70% and >70%)such as peat relative humidity vs temperature (R= -0.55- -0.94), peat CO2 concentration vs peat relative humidity(R=-0.31- -0.89); peat CO2 concentration vs peat temperature (R=-0.38- -0.87) whilst other site factors indicated that they are weakly positive or negatively correlated or appeared to be independent factors. However, each crop/land cover site factors responded differently to peat CO2 respiration rates. Site factors which were significantly different among crops/land covers and their statistical comparation of each site

factor measured at the assessment period are illustrated in Fig. 4(a) through 4(e). The interaction among site factors on each land covers could cause significant difference on peat CO2 respiration rates (Fig. 5)

150,8 -

S0,6 -

£0,4 -

0,2 -0,0-

C orn Pineapple

120 -r

NeWy burnt Fern Corn Pineapple (e)

Fern Corn Pineapple

E 50 H o

^ 40 H

Fern Corn Pineapple

Newly burnt Fern Pi >le Corn

Fig 4. Several site factors (a) Peat water content; (b) peat temperature; (c) CO2 concentration at soil surface; (d) peat relative humidity; and (e) Water Table levels; and their statistical comparison using ANOVA (p= <0.001) and All Pairwise Multiple Comparison Procedures (Tukey Test, p<0.05), among four crops/land cover types on peatland.

At newly burnt site, Multivariate Regression analysis showed that peat water content was asite factor that can linearly predict peat CO2 respiration rates (Fig. 5a); other site factors were not found to strongly influence the fluxes. Similar to newly burnt site, at fern cover site, peat CO2 respiration was regulated significantly by peat water content. The results indicated that increasing water content from peat will decrease peat CO2 respiration at newly post-burned and fern cover sites. At corn small-scale plantation the fluxes were influenced by soil surface CO2 concentration, while at pineapple site, the peat CO2 respiration regulated significantly by soil water vapor, soil relative humidity and soil water contents. These multiple regression analyses indicated that peat CO2 respiration at each crop/cover type of each site can be predicted from a linear combination of these site factors. The scatter plots showing the trend of each variable are presented in Figure 5.

Peat water level seems to have relation with CO2 fluxes. Monthly mean data analysis between CO2 flux and peat water levels shows that three sites water levels (i.e., newly burnt, fern and pineapple sites) significantly determine peat CO2 respiration. The regression model is CO2 Fluxes = 4,485 + (0,108 * Water Level), N = 48, R = 0,475, R2 = 0,226, AdjR2 = 0,209, SE of Estimate = 2,46 (Fig 5e). However, unfortunately we did not have adequate data to simultaneously compare and statistically analyse the data with other site conditions/factors.

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Fig 5. (a) Site factor water content was significantly regulating peat CO2 respiration on newly burnt sites (CO2 Flux = 9.728 - (4.450 * Water Content), N = 58; R = 0.316; R2 = 0.1996; AdjR2 = 0.1835; SE of Estimate = 2.774; and (b) Fern cover sites (CO2 Flux = 20.652 - (10.854 * Water Content) N = 80, R= 0.428, R2= 0.183, AdjR2 = 0.173; SE of Estimate = 4.327); (c) Soil surface CO2 concentration was the only site factor influencing soil CO2 respiration at corn cover peatland; (d) Site factors water vapor, soil relative humidity and water content were dictating peat CO2 respiration at pineapple cover sites (CO2 Flux = 34.314 - (0.513 * H2O) - (0.0768 * RH) - (5.344 * Water Content) N = 143; R = 0.472; R2= 0.223; AdjR2 = 0.206; SE of Estimate = 3.785); (e) Linear regression of water table levels and overall peat CO2 respiration.

4. Discussion

4.1. Crops/Land Cover Types Response to Peat Soil CO2 fluxes

The result indicates that agricultural crops/land covers respond differently on emitting CO2 to the atmosphere. Moreover, it shows that each crop formulates different site factors which confoundly affected soil CO2 fluxes. Based on our previous assessment on forester peatland (Astiani et al., unpublished yet), it is proven that forest cover change on peatland into crop land causes the increase of soil CO2 emission on peatland to 3-4 folds from least disturbed and to 2 folds from drained-logged peatland forests.

Further, the result shows thatagricultural small scale crop plantation on this tropical peatland forest at Kubu Raya, West Kalimantan emitts119.9 Mg CO2 ha-1 y-1CO2in averaged as peat soil respiration. This rate is also much higher than reported values from other relatively intact forests as well as secondary peatlands studies. Our previous study on degraded peatland planted with oilpalm respires 86.5 Mg ha-1 yr-1 20. Other study examinessecondary peatlands in Central Kalimantan and reports soil respiration rates at ~21.8 Mg ha-1 yr-1 21, only 18% of respiration rates reported here. Moreover, this West Kalimantan's crop land CO2 respiration rates are 240% greater than peat CO2 respiration recorded in Central Kalimantan (~35 Mg ha-1 yr-1)22.

Under peatland agricultural crops/land covers, there is no suitable proxy for peatland degradation levels can be expressed, yet the site factors resultant from crops/land covers can determine their environmental condition. Our

study shows that peat soil CO2 respiration differs significantly among the crop species/land covers.

Drainage canals are established surround this degraded peatland area (± 300 - 1000 m) appeared to play an important role in altering peatland CO2 respiration. Increasing the distance of water table from peat surface will add CO2 fluxes from peat. Lowering the water table can expose new peat layers and thus affect CO2 respiration rates, 22, 23, 24, 25, 26. Our result estimates that, with assumption of all other site factors remain constant, lowering 10 cm of water table will increase ~15 Mg CO2 ha-1 y-1 (R2= 0.21).

These significant changes in carbon fluxes will play an increasingly important role by disrupting carbon balance in these peatlands and will elevate when degraded peatland are drained and burned and/or transformed especially into open area or covered with crops. It is implied that planting annual crops or leaving it open as ex burnt peatland on degraded peatland, will escalate the soil CO2 fluxes from peatland.

4.2. How Will More Frequently Future Dry Month Influence Soil Co2 Respiration?

Peat CO2 respiration increases considerably during the dry months when compared with the rainy months. Year 2011 was not considered to be ENSO year. However, CO2 respiration on the four crop land/cover types differed by dry vs. rainy season. Since precipitation is merely source of water and nutrient input in this ombrotrophic peatland, rainfall distribution and quantity are important in influencing hydrological characteristics in this ecosystem, particularly the peat water table and water content. Thus, precipitation becomes critical for predicting the effects of land use change on peatland CO2 fluxes.

ENSO events could increase the CO2 fluxes by extended droughts associated with these events. Reducing rainfall will lower the water table and change peatland hydrological characteristics. As the peat soil layers dry out, more below ground CO2 previously sequestered is then released into the atmosphere27. Newly burnt peatlands and pineapple crop sites will emit the highest CO2 respiration during the driest months. Our result demonstrates that areas newly burnt site has>50% greater CO2 respiration in drier months than in rainy month, other crop land/cover type shows lower/narrower distance between the two seasons. The increase of precipitation during the rainy months can decrease these changes in relative fluxes as our result indicates that those land cover types do not differ in CO2 respiration rates in wet months except for corn field.

4.3. Environment Factors Affecting Peat Respiration

Site factors are controlling CO2 respiration rate on each cropland/land cover types.Peat water content, peat water level, peat surface CO2 and peat water vapor are among the site factors affecting CO2 fluxes. However, each crop site shows different and distinctive peat site factors that significantly affect CO2 respiration. The regression models of site factors measure for each specific land cover can be applied to obtain better estimate CO2 respiration rates of these degraded peatlands. At newly burnt peatland and pineapple site, the increased of soil water content, will decrease the CO2 flux. At 4-5 years post-burn cover with fern peatland, increasing CO2 concentration will elevate the respiration rate, while in corn site, the CO2 flux rate is influenced by soil water content, peat water vapor and peat CO2 relative humidity. The result implies that each land cover types generate different level of site factors, which affect different level of peat CO2 rates.

Degraded peatland with variety of crop/land cover types will have significant spatial and temporal effects on peat CO2 respiration. All sites with typical cropland conditionhaving total open canopy tend to decrease peat water content, increase water vapor and will also increase the fluxes. This finding indicates that water exchanges from peat layers to soil surface also contribute to peat CO2 respiration. Deforestation, fire and small-scale crop plantation on peatland forest caused canopy openings. They do not only disturb or change site factors in peatland forest ecosystem, but also increase soil carbon emissions.

These results highlight critical importance of protecting forested peatlands from land cover changes, fires and draining the water table. The conversion of peatland forest cover into annual, small-scale crop plantations and previously burned yet relatively abandoned fern/grasslands results in almost complete loss of canopy cover. By 2010, Kalimantan peatlands experienced ~50% loss of forest cover18. Over 65% of this deforested area was converted into oil palm plantations with an additional 24% of the area transformed into open previously burned

/agriculture lands. These 2.3 M ha of converted peatland areas are now major sources of CO2 emissions. Regardless of the carbon input into these peatlands, estimated CO2 respired from peatland soil in Kalimantan are 0.09 - 0.21Gt y-1 from perennial crops (i.e., oil palm) area20, and 0.03 - 0.10Gt y-1 from these open burned peatland. Mitigation of these huge carbon emissions from Kalimantan peatland is urgently needed.

5. Conclusions

• Agricultural crops/land covers respond differently on emitting CO2 to the atmosphere. Mean CO2 respiration among newly burnt, fern, pineapple are not significantly different (~139.9, 123.2, 132.6Mg CO2 ha-1 y-1 consecutively), however corn cover isa lot lesser than the former three land covers (~83.8 Mg CO2 ha-1 y-1).

• CO2 respiration on the four crop land/cover types differed by dry vs. wet season. Drought or drier periods can increase CO2 respiration by ~ 67% than rainy one in these agriculture peatlands. However, among the four agricultural plants coversthere are different responses on soil CO2 respirationconcerning dry vs rainy periods.

• Our assessment of environment factors simultaneously on the CO2 respiration indicates several site factors significantly influencing the fluxes. Each land cover type has distinctive peat environmental/site factors that significantly affect CO2 respiration. Across the four crops/land cover types, these site factors are explained as synchronous impacts of soil and ambient microclimatic conditions, that are influenced by above ground vegetation and soil water 14,28, 29, 3°The models of site factors measures for each specific land cover can be applied to obtain better estimation CO2 respiration rates of four crops and or land cover types.

Acknowledgements

We would like to thank to people of Kampung Bakti Suci, Kampung Parit H Ali and Kampung Jawa Kubu Raya, West Kalimantan, Indonesia for their open hearts and supports on our works in 2° 11. Moreover, thankful to Indonesian Institute of Science (LIPI) Jakarta, Agency for the Assessment and Application of Technology Bogor, Tanjungpura University, Agency for Industrial Assessment-Ministry Of Trade of Pontianak for laboratory facilities and works. Our incredible appreciation to members of LLI (D. Ratnasari, N. Lisnawati, W. I. Suci, A. Rochman, D. Firnata, Y. Purwanto, Hartono, Murti Anom, T. Mardiantoro, E. Supardi and Umar) who always relentlessly support our works in many incredible ways and endless help. Our great appreciation goes to Tanjungpura University (UNTAN) Pontianak for enormous supports and acquiescence for having 4th year students to share short term field experiences with us. Great thanks to other parties who cannot be mentioned personally for giving us their hands to accomplish this works.

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