2012-06-20_PERMIT FILE - C2010089 (62)

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The significantly different production observed among sampling years at both sites demonstrates the complexity of plant - soil - climate relationships. Plants are influenced by climate and soil parameters in addition to competition between plant species. Soils are influenced by plant inputs and establishment as well as climate variables. Changes in soil quality through time contribute to variations plant community production; however, climatic influences on plant establishment may be more important. Soil EC decreased and pH increased between 1979 and 2003 for both the ZSW and SSW (Table 4). Decrease in EC was due to leaching of the soils for close to 30 years as well as high spring precipitation in 2003 compared to 1979. This indicates that changes in soil properties can lead to changes in plant community properties through time. EC and pH both increased with depth in 2003 due to effects of the sodic spoil material at the ZSW and SSW. Table 4. Average soil EC and pH values from all soil depths. * indicates significance at the 0.01 level of probability. "All subsoils" are significantly different from each other at the 0.01 level of probability. 1979 and 2003 EC values are significantly different for subsoil type (A,B,C) and 2003 pH values are significantly different for subsoil type (A,B,C). zsw EC pH mmhos cm'' mmhos cm' 1979 2003 1979 2003 1979 2003 1979 2003 All Subsoils 4.69* 1.85* 7.31* 7.72* 3.02* 1.62* 739* 8.14* Subsoil A 5.94* 3.15* 7.29 7.51* Subsoil B 4.32* 1.63* 7.35 7.94* Subsoil C 3.78* 0.90* 7.29 7.65* 1239 ssw EC pH Production Results for 2003 Production values were significantly lower (F <0.01) in toe slope positions for smooth brome and crested wheatgrass plots with total soil depths ranging from 0 to 40 cm at the ZSW. Highest productivity for 2003 was found on 40 to 120 cm depths. Crested wheatgrass plot production was significantly higher (F <0.01) than production values of other vegetation types for toe and shoulder slope positions. Crested wheatgrass plot production was significantly higher (F <0.05) than production of other vegetative plots for the mid slope position. Production was significantly higher (F <0.01) in the mid slope position for crested wheatgrass and alfalfa plots on the SSW. This is equivalent to 60 to120 cm total soil. No statistical relationship could be determined among vegetation plots because the number of observations (n) was less than 20 at the SSW (Table 5). There was a significant (F <0.01) but weak relationship (R 0.1836) at the ZSW among production and soil properties. Total soil depth had the greatest affect on total production compared to other soil properties. At the SSW, there were weak relationships that were not significant (R 0.2038) among production, total soil depth and soil properties. There has been substantial change after 30 years of development on the wedges. Plant community production is no longer as dependent upon soil depth and soil properties compared to initial establishment. Production ma be more influenced by other soil properties not examined in this study or by precipi ation and temperature.