Optimizing grain yields reduces CH4 emissions from rice paddy fields.

Microbial production in anoxic wetland rice soils is a major source of atmospheric CH4 the most important non-CO2 greenhouse gas. Much higher CH4 emissions from well managed irrigated rice fields in the wet than in the dry season could not be explained by seasonal differences in temperature. We hypothesized that high CH4 emissions in the wet season are caused by low grain to biomass ratios. In a screenhouse experiment, removing spikelets to reduce the plants' capacity to store photosynthetically fixed C in grains increased CH4 emissions, presumably via extra C inputs to the soil. Unfavorable conditions for spikelet formation in the wet season may similarly explain high methane emissions. The observed relationship between reduced grain filling and CH4 emission provides opportunities to mitigate CH4 emissions by optimizing rice productivity.

Linking plants to rocks: ectomycorrhizal fungi mobilize nutrients from minerals.

Plant nutrients, with the exception of nitrogen, are ultimately derived from weathering of primary minerals. Traditional theories about the role of ectomycorrhizal fungi in plant nutrition have emphasized quantitative effects on uptake and transport of dissolved nutrients. Qualitative effects of the symbiosis on the ability of plants to access organic nitrogen and phosphorus sources have also become increasingly apparent. Recent research suggests that ectomycorrhizal fungi mobilize other essential plant nutrients directly from minerals through excretion of organic acids. This enables ectomycorrhizal plants to utilize essential nutrients from insoluble mineral sources and affects nutrient cycling in forest systems.

Spatial and temporal performance of the miniface (free air CO2 enrichment) system on Bog Ecosystems in northern and Central Europe.

The Bog Ecosystem Research Initiative (BERI) project was initiated to investigate, at five climatically different sites across Europe, the effects of elevated CO2 and N deposition on the net exchange of CO2 and CH4 between bogs and the atmosphere, and to study the effects of elevated CO2 and N deposition on the plant biodiversity of bog communities. A major challenge to investigate the effects of elevated CO2 on vegetation and ecosystems is to apply elevated CO2 concentrations to growing vegetation without changing the physical conditions like climate and radiation. Most available CO2 enrichment methods disturb the natural conditions to some degree, for instance closed chambers or open top chambers. Free Air CO2 Enrichment (FACE) systems have proven to be suitable to expose plants to elevated CO2 concentrations with minimal disturbance of their natural environment. The size and spatial scale of the vegetation studied within the BERI project allowed the use of a modified version of a small FACE system called MiniFACE. This paper describes the BERI MiniFACE design as well as its temporal and spatial performance at the five BERI field locations. The temporal performance of the MiniFACE system largely met the quality criteria defined by the FACE Protocol. One minute average CO2 concentrations measured at the centre of the ring stayed within 20% of the pre-set target for more than 95% of the time. Increased wind speeds were found to improve the MiniFACE system's temporal performance. Spatial analyses showed no apparent CO2 gradients across a ring during a 4 day period and the mean differences between each sampling point and the centre of the ring did not exceed 10%. Observations made during a windy day, causing a CO2 concentration gradient, and observations made during a calm day indicated that short term gradients tend to average out over longer periods of time. On a day with unidirectional strong winds, CO2 concentrations at the upwind side of the ring centre were higher than those made at the centre and at the downwind side of the ring centre, but the bell-shaped distribution was found basically the same for the centre and the four surrounding measurement points, implying that the short term (1 sec) variability of CO2 concentrations across the MiniFACE ring is almost the same at any point in the ring. Based on gas dispersion simulations and measured CO2 concentration profiles, the possible interference between CO2-enriched and control rings was found to be negligible beyond a centre-to-centre ring distance of 6 m.

How Sphagnum bogs down other plants.

Recent research on the organo-chemical composition of Sphagnum and on the fate of its litter has further clarified how this plant builds acidic, nutrient-poor, cold and anoxic peat bogs. The bog environment helps Sphagnum to outcompete other plants for light. Its morphology, anatomy, physiology and composition make it an effective ecosystem engineer and at the same time benefit the plant in the short term. This may have facilitated the evolution of the genus.

Ecosystem effects of atmospheric deposition of nitrogen in The Netherlands.

Atmospheric deposition of inorganic N, mainly ammonium volatilized from manure produced in intensive stockbreeding, on sensitive terrestrial and aquatic ecosystems in The Netherlands is in the order of 40 to 80 kg ha(-1) year(-1). Proven effects of this deposition are (i) eutrophication with N, leading to floristic changes (ii) acidification of base-poor sandy soils and of moorland pools, leading to higher concentrations of dissolved, potentially toxic metals such as Al3+, and (iii) increased levels of nitrate in groundwater below woodlands. In acid forest soils, but not in soils under heathland, nitrification and leaching of nitrate is common. However, in very poor sandy forest soils and at very high ammonium inputs, nitrification may be too slow to prevent the development of high concentrations of ammonium. Both excessive acidification and excessive levels of ammonium probably play an important role in the general forest decline, which is most severe in the southern and central parts of the country, where ammonium inputs are highest.