EKOSISTEM SAWAH

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Rice production systems are ephemeral habitats in which rice is sowed and
harvested over a period of 3 to 4 months. Many of the important rice pests are
monophagous and r-strategists or opportunistic species and under normal
circumstances cause little yield loss on rice farms with adequate biodiversity and
ecosystem services. However, when r species, such as planthoppers, invade rice
fields that are vulnerable with low biodiversity and ecosystem services, they tend to
increase exponentially into outbreak proportions and destroy crops. In mainland
China every year, planthoppers destroy at least a million hectares of rice (Cheng
2009) and, in years like 2005, when summer temperatures were elevated, 7.5
million hectares were destroyed.
In Hainan Island, about 30,000 hectares are affected annually by
planthoppers, but records of losses are not available. In the 1960s and 70s, when
rice sufficiency was the primary national objective, policies and farmers adopted
high pesticide routines. Today, such practices are still rampant in China and on
Hainan Island as well. Research at IRRI and by Chinese scientists at Zhejiang
University has now shown that routine insecticide sprays have very little economic
gains but huge negative impacts on arthropod biodiversity, the food chain, and
ecosystem services, which bring about planthopper outbreaks and rapid
development of insecticide resistance. The important functions of biodiversity and
ecosystem services had not been recognized or researched or taught in universities
and had certainly not been factored into agricultural policies. It has been shown that
when insecticide load is reduced arthropod biodiversity and ecosystem services can
be restored (Heong et al. 2007).
Lahan sawah = Wetlands
Atmospheric methane (CH4) is an important greenhouse gas. On a scale of
100 years, it is approximately 20 times more effective than carbon dioxide (CO2). The
total annual CH4 emission both from natural and anthropogenic terrestrial sources
to the atmosphere is about 580 Tg (CH4) yr -1 . The contribution of natural and manmade
wetlands (e.g. rice paddy) to this global total varies between 20 and 40%.
Thereby, natural wetlands are the major non-anthropogenic source of methane at
present and rice agriculture accounts for some 17% of the anthropogenic CH4
emissions. This is because of the prevailing anaerobic conditions in these
ecosystems, their high organic matter contents and their global distribution.
Northern wetlands (>30° N) for example constitute about 60% of the global wetland
area and emit a quarter to a third of the total CH4 originating from wet soils.
In our research we focus on the understanding and quantification of key-processes
involved in the formation, consumption and transport of methane in wetlands. This
is crucial for reliable estimations on the impact of wetlands on the earth climate
system
Current and recently completed projects:
1. In-situ quantification of soil microbial processes controlling methane
emissions from rice paddy soils
2. Methane production and consumption in polygonal tundra
environments of the Lena Delta, Siberia
3. Methane turnover and fluxes in alpine wetlands.