Rain chemistry and volume data from Climoor fieldsite in Clocaenog Forest

Rainfall is also measured at the site using a ground level storage rain gauge (funnel diameter 12.7 cm). Rain collected in the gauge accumulated over a period of two weeks. Exception to this occurred over holiday periods, particularly Christmas, when samples accumulated over 3 or 4 weeks, as oppose to 2 - however the quantity of rainfall accumulated never exceeded the storage capacity of the gauge. Samples of rainfall intended for chemical analysis were collected using warren spring rainfall collectors emptied on a bi-weekly basis. Samples were transported in the bottle they were collected into from the field back to the lab, and were filtered through a 45 micrometre cellulose nitrate filter, and stored in the dark at 4 degrees C before analysis. pH was measured on a Metrohm 888 Titrando fitted with a 20ml burette and 815 Robotic USB Sample Processor XL (Metrohm, Switzerland). Nitrate (NO3), chloride (Cl), sulphate (SO4) was determined using Dionex DX100 chemically suppressed ion chromatograph using carbonate eluant and AS4a columns (Dionex Corporation, Sunnyvale California 94088-3603 USA). Sub-samples were acidified with 2M HCl and sparged with oxygen to remove any inorganic carbon in the sample before analysis. The remaining non-purgeable organic carbon (assumed to be DOC) was determined with a Shimadzu TOC-V CPH (Shimadzu Corporation, Kyoto, 604-8511, Japan). Ammonium was analysed colormetrically using a SEAL AQ2 discrete analyser. Bi-weekly measurements of rain volume (measured by the storage rain gauge) were pooled to give monthly totals for rainfall. Throughfall data is collected bi-weekly at the same time as the storage rain gauge data (above). A funnel (diameter 16.8 cm) and bottle (3000 ml capacity) captures the rainfall for each experimental plot and the volume of this is noted. A degree of calculation is needed with this data to make it comparable with other annual data from the site, such as annual rainfall. This is because samples can over-flow in these samplers during periods of high rainfall, sometimes freeze, bottles get blown over, funnels fall off or get cracked, etc. The throughfall data is used to calculate a % change figure for each treatment, and this % difference is applied to the ground level rain gauge data (site level rainfall) to give the number for rainfall in each treatment. Within the calculation of % difference in throughfall, when data is lost or the measurement is compromised (for example, the funnel falls off the bottle at some point in the week), then this plot is excluded from the treatment mean. This does mean that on occasion, the treatment mean is calculated with less than the full 3 replicates. Also occasionally data has been infilled using an average reduction over all years. In the dataset provided, there is the (unadjusted) monthly plot level throughfall data, along with the estimated rainfall mean for each treatment (which has undergone infilling - data is flagged where this has occurred).