## 3 Results
### Timber Harvest Impact  
When viewing the monthly means of calculated _GPP_ before the harvest, there was little apparent separation between N1 and N2 (Figure 6). There appears to be a greater separation, with higher monthly averages of GPP more often occurring at N1 than at N2, during the post-harvest. Mean monthly rates of _CR_ also seemed to be quite similar during the pre-harvest, with the same apparent downstream decrease observed during the post-harvest (Figure 7). Although there were apparent decreases at N2 relative to N1 in both _GPP_ and _CR_, we did not find these to be significant harvest-induced changes; nor were there significant harvest-caused changes in _NEP_ or _GPP_/CR (Table 1). A direct comparison of the pre- to post-harvest relationships between upstream and downstream monthly averages of _GPP_ also resulted in a finding of no significant difference between the two time periods (Figure 8; ANCOVA; slope \(\rho=0.798\), y-intercept \(\rho=0.165\)). Relative differences between _GPP_, _CR_, _NEP_, and _GPP_/_CR_ from both N1 and N2 can be compared pre- and post-harvest (Figure 9). Figure 5: Diel trends of dissolved oxygen concentration (mg L\({}^{-1}\)) at (N1) and (N2) over two-day periods in the spring, summer, fall, and winter of 2007. Figure 6: Time series of monthly averaged gross primary productivity (_GPP_; g O\({}_{2}\) m\({}^{-2}\) day\({}^{-1}\)) at N1 and N2 over the study period. Harvest is indicated by the vertical, dashed line. Figure 7: Time series of monthly averaged community respiration (_CR_; g O\({}_{2}\) m\({}^{-2}\) day\({}^{-1}\)) at N1 and N2 over the study period. Harvest is indicated by the vertical, dashed line. As was the case with metabolic rates, monthly turbidity measurements in Turkey Creek were not significantly altered by the timber harvest (pre-harvest means: 23.57 \(\pm\) 21.8 NTU at N1 and 24.51 \(\pm\) 15.3 NTU at N2; post-harvest means: 20.58 \(\pm\) 14.0 NTU at N1 and 23.43 \(\pm\) 15.0 NTU at N2) (two-way ANOVA with interaction; \(p=0.772\)). Likewise, monthly total suspended solids measurements were not significantly changed by the timber harvest (pre-harvest means: 36.62 mg L\({}^{-1}\)\(\pm\) 40.6 mg L\({}^{-1}\) at N1 and 38.24 mg L\({}^{-1}\)\(\pm\) 54.2 mg L\({}^{-1}\) at N2; post-harvest means: 18.33 mg L\({}^{-1}\)\(\pm\) 18.8 mg L\({}^{-1}\) at N1 and 27.52 mg L\({}^{-1}\)\(\pm\) 43.1 mg L\({}^{-1}\) at N2) (two-way ANOVA with interaction; \(p=0.632\)). \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \multirow{2}{*}{**Metabolic**} & \multicolumn{4}{c}{**Pre-Harvest**} & \multicolumn{4}{c}{**Post-Harvest**} \\ \cline{2-10}  & \multicolumn{2}{c}{**N1**} & \multicolumn{2}{c}{**N2**} & \multicolumn{2}{c}{**N1**} & \multicolumn{2}{c}{**N2**} & \multicolumn{2}{c}{**_p_**} \\ \cline{2-10}  & **Mean** & **Std** & **Mean** & **Std** & **Mean** & **Std** & **Mean** & **Std** & \\ \hline _GPP_ & 0.99 & 1.99 & 1.03 & 1.71 & 1.34 & 2.61 & 0.88 & 2.07 & 0.352 \\ _CR_ & 1.41 & 3.38 & 1.35 & 2.65 & 2.30 & 4.48 & 1.55 & 3.60 & 0.451 \\ _NEP_ & 0.26 & 0.69 & 0.33 & 0.64 & 0.25 & 0.87 & 0.12 & 0.50 & 0.242 \\ _GPP/CR_ & 0.98 & 1.23 & 1.02 & 1.13 & 0.74 & 1.19 & 1.02 & 2.45 & 0.548 \\ \hline \end{tabular}
\end{table} 
Table 1: Means and standard deviations of gross primary productivity (_GPP_, g O\({}_{2}\) m\({}^{-2}\) day\({}^{-1}\)), community respiration (_CR_, g O\({}_{2}\) m\({}^{-2}\) day\({}^{-1}\)), net ecosystem productivity (_NEP_, g O\({}_{2}\) m\({}^{-2}\) day\({}^{-1}\)), and the productivity/respiration ratio (_GPP_/_CR_) during both the pre- and post-harvest at N1 and N2 (pre-harvest \(n\) = 56 for all variables, post-harvest \(n\) = 80 for all variables). Listed _p_-values taken from the interaction between site (N1 compared with N2) and harvest (pre- compared to post-) (Two-way ANOVA with interaction; \(\alpha=0.05\)).