Experimental evidence for sustained carbon sequestration in fire-managed, peat moorlands.

Peat moorlands are important habitats in the boreal region, where they store approximately 30% of the global soil carbon (C). Prescribed burning on peat is a very contentious management strategy, widely linked with loss of carbon. Here, we quantify the effects of prescribed burning for lightly managed boreal moorlands and show that the impacts on peat and C accumulation rates are not as bad as is widely thought. We used stratigraphical techniques within a unique replicated ecological experiment with known burn frequencies to quantify peat and C accumulation rates (0, 1, 3 and 6 managed burns since around 1923). Accumulation rates were typical of moorlands elsewhere, and were reduced significantly only in the 6-burn treatment. However, impacts intensified gradually with burn frequency; each additional burn reduced the accumulation rates by 4.9 g m−2 yr−1 (peat) and 1.9 g C cm−2 yr−1, but did not prevent accumulation. Species diversity and the abundance of peat-forming species also increased with burn frequency. Our data challenge widely held perceptions that a move to 0 burning is essential for peat growth, and show that appropriate prescribed burning can both mitigate wildfire risk in a warmer world and produce relatively fast peat growth and sustained C sequestration

Gedrag van gewasbeschermingsmiddelen in substraatteelten na toepassing via het druppelsysteem. : Interpretatie van het 2014 pilot-experiment

The Greenhouse Emission Model has recently been adopted as a model package for assessing emissions to and concentrations in groundwater and surface water after use of plant protection products in greenhouse crops. Stakeholders advised that the model be tested against experimental data. In October 2014, facilities of WUR Plant Research were used to perform a pilot experiment in which cucumber plants on stone wool substrate were treated with three plant protection products, using a drip irrigation method. Concentrations of the active substances were measured in both the water flowing to and draining from the substrate. GEM was tailored to the experimental conditions and used to predict concentrations in parts of the experimental system. Measured and simulated concentrations of imidacloprid and fluopyram were comparable from approximately 36 hours after the start of the experiment onwards. Prior to this, concentrations in the inflowing water were underestimated and concentrations in the drain water were overestimated, probably because of incomplete mixing. For dimethomorph, agreement between the measured and calculated concentrations was reached after approximately 80 hours. This more lengthy period may be due to exceeding the solubility of the substance, causing precipitation or settling on the tube walls, and redissolving later on; the model does not account for these processes. Degradation of all three substances was found to be negligible over the duration of the experiment. Plant uptake was the major dissipation process. Experimental results show that uptake of substances was lower than uptake of water, thereby supporting the transpiration stream concentration approach proposed by Briggs et al. (1982); this approach is often applied however experimental evidence is scarce. Transpiration stream concentration factors far below one were found to fit experimental results best.Door het gebruik van gewasbeschermingsmiddelen in kassen kunnen restanten van deze middelen in het nabijgelegen oppervlaktewater terechtkomen en het waterleven aantasten. Bij de toelatingsbeoordeling worden de effecten op het waterleven geëvalueerd met het zogeheten Greenhouse Emission Model (GEM). Dit model is door het RIVM ontwikkeld in samenwerking met Wageningen Environmental Research en Wageningen Plant Research. Het RIVM heeft het model getoetst in een 'semi-praktijkexperiment' met drie stoffen. Hieruit blijkt dat het vertrouwen waarmee dit model de concentraties in het teeltsysteem kan voorspellen, aanzienlijk is vergroot. Om te kunnen berekenen in welke mate de stoffen in oppervlaktewater terechtkomen als water wordt geloosd, is het van belang om de concentraties in het teeltsysteem goed te kunnen voorspellen. In het experiment zijn de gewasbeschermingsmiddelen met het gietwater aan een komkommergewas op substraat toegediend. Vervolgens zijn zes dagen lang de concentraties in het gietwater en het drainwater gemeten. Dit is voldoende lang om belangrijke processen in het teeltsysteem, het hergebruik van water en de opname van stoffen door planten, te onderzoeken. Van twee stoffen blijken de berekende concentraties in het water dat uit het teeltsysteem stroomt vanaf ongeveer 36 uur na aanvang van het experiment in de buurt van gemeten concentraties te liggen. Bij de derde stof was dit na ongeveer 80 uur het geval. De belangrijkste reden waardoor de stoffen uit het water verdwenen was dat ze door de planten worden opgenomen; afbraak speelde in dit experiment geen rol van betekenis.Ministerie van I&M ; Ministerie van E