. 2006. Influence of coarse wood and fine litter on forest organic matter composition. Can. J. Soil Sci. 86: [35][36][37][38][39][40][41][42][43][44][45][46]. Forest soil organic matter (SOM) is affected by inputs from coarse wood (CW) and fine litter (FL, e.g., leaves, twigs, cones, and needles). The influence of these materials on forest SOM was studied in a lodgepole pine (Pinus contorta) forest in southeastern Wyoming. Organic materials in CW sites were significantly (P < 0.05) more acidic, but contained half the total N of FL sites. Forest floor materials and SOM C contents were significantly greater in CW samples. Lignin decomposition products (CuO analysis) accumulated primarily in organic horizons of both sites, with significantly higher (60-70%) contents in CW materials. Vanillyl compounds were the primary lignin products from both sites, with cinnamyl compounds also important in SOM from FL sites. Vanillic acid to vanillin ratios were significantly higher in mineral soils under CW. 13 C-NMR spectra indicated CW materials were enriched in lignin, and that humic acids from both site types were very similar and unusually high in alkyl C. Fulvic acids were also high in O-alkyl and carboxyl C, particularly in the CW sites. Results suggest there are differences in forest C constituents and that removal of CW could possibly alter forest soil dynamics that would impact forest productivity and biodiversity. Les auteurs ont étudié l'incidence de ces matériaux sur la MOF d'une forêt de pins tordus (Pinus contorta) dans le sud-est du Wyoming. La matière organique des sites DG était significativement (P < 0,05) plus acide, mais renfermait la moitié du N total des sites DF. Les échan-tillons DG contenaient significativement plus de matériaux forestiers et de C de la MOF. Aux deux types d'endroits, les produits de la décomposition de la lignine (analyse au CuO) s'accumulent principalement dans les horizons organiques, mais les concentrations sont significativement plus élevées (60 à 70 %) dans les DG. Les composés vanillyle sont les principaux dérivés de la lignine dans les deux cas, les composés cinnamyle ayant toutefois leur importance dans la MOF des sites DF. Le rapport entre l'acide vanillique et la vanilline est significativement plus élevé dans les sols minéraux enrichis de DG. Le spectre obtenu au RMN-13 C révèle que les DG sont riches en lignine et que les acides humiques se ressemblent beaucoup dans les deux cas. Ils sont aussi inhabituellement riches en alcoyle-C. Les acides fulviques renferment beaucoup d'alcoyle-O et de carboxyle-C, surtout aux sites DG. Ces résultats laissent croire que la composition du C forestier varie et que la récupération des DG pourrait altérer la dynamique des sols forestiers, donc nuire à la productivité et à la biodiversité des forêts.

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1999) A field lysimeter study to evaluate herbicide transport in a wyoming irrigated pastureABSTRACT A field study was conducted to assess the fate and mobility of two commonly used herbicides, dicamba (3,6-dichloro-2-methoxybenzoic acid), and picloram (4-amino-3,5,6, trichloro-2 pyridinecarboxylic acid), in an irrigated pasture. The herbicides were applied at two application rates to four plots (two replicates) that contained soil-water collectors. Herbicide concentrations as a function of depth and application rate were evaluated statistically to determine if replicate data could be combined. Results indicated dicamba concentration variations were low, suggesting the mean value of the replicate plots could be compared; however, picloram concentration variations were high, and the replicate plot data could not be combined. Half-time values for herbicide disappearance (time required for herbicide concentration to diminish from its maximum to half maximum levels), calculated from the arithmetic mean of the logistic equations, were found to be useful in describing herbicide transport. Half-time values were dependent upon application rate, collector 245 Downloaded by [McMaster University] at 03:34 17 June 2016 246 KRZYSZOWSKA-WAITKUS ET AL.depth, pesticide type, and plot location. Dicamba applied at the low application rate was detected at 15 and 30 cm depths only, and was not detected throughout the entire study period (467 days) at deeper depths. Significant differences occurred between plots receiving the high dicamba application rate, which was attributed to permeability differences that affected herbicide migration in the soil profile. Picloram half-time values were also affected by soil organic carbon, which increased picloram adsorption. In general, differences in herbicide concentrations were observed within plots receiving the high picloram application rates, which was primarily attributed to spatial differences in hydraulic conductivity. Herbicide disappearance was most rapid at the shallow depth (e.g., 15 cm) within plots receiving lower herbicide application rates.