# Effects of Grazer Exclusion on Carbon Cycling in Created Freshwater Wetlands
## 3 Results
### Vegetation  
A total of 12 species were found in experimental plots, with distinct differences in composition and abundance across seasons and treatments (Figure 2). Aboveground biomass showed a predictable seasonal pattern, with biomass increasing from spring into summer and peaking in mid to late summer (Table 1, Figure 2). Aboveground biomass in 2017, which was unusually hot and dry, was lower across seasons and treatments than in 2018. The exclosure treatment resulted in a significant reduction in aboveground biomass in both 2017 and 2018, and in 2018 there was a significant interaction between treatment and month, with the effect of grazer exclusion on aboveground biomass increasing from spring into summer (Table 1). During the height of the growing season (July), aboveground biomass was 3-fold (2017) and 2-fold (2018) higher in caged plots than uncaged plots. In the 2017, both grazer treatment and season were highly significant (\(p\) < 0.0001), with no interaction. However, in 2018, there was a significant interaction between season and treatment (\(p\) = 0.003), with the difference between caged and uncaged treatments increasing over the course of the growing season. Similar seasonal and treatment patterns were seen for plant cover (Supplemental Information, Figure S3, Table S2). The species selected for biomass assessment in both years comprised greater than 90% of the overall cover. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Variable** & **Date** & \multicolumn{3}{c}{**Treatment**} & \multicolumn{3}{c}{**Dt x Tr**} \\ \hline  & F & \(p\) & F & \(p\) & F & \(p\) \\ \hline Aboveground biomass 2017 & F\({}_{2,87}\) = 20.5 & \(p\) **\textless{} 0.0001** & F\({}_{1,87}\) = 17.0 & \(p\) **\textless{} 0.0001** & F\({}_{2,87}\) = 2.6 & \(p\) = 0.08 \\ Aboveground biomass 2018 & F\({}_{3,117}\) = 34.2 & \(p\) **\textless{} 0.0001** & F\({}_{1,117}\) = 35.7 & \(p\) **\textless{} 0.0001** & F\({}_{2,117}\) = 4.9 & \(p\) **\textless{} 0.003** \\ \hline GPP 2017 & F\({}_{1,25}\) = 23.2 & \(p\) **\textless{} 0.0001** & F\({}_{1,25}\) = 11.6 & \(p\) **\textless{} 0.002** & F\({}_{1,25}\) = 6.5 & \(p\) **\textless{} 0.02** \\ GPP 2018 & F\({}_{1,26}\) = 7.7 & \(p\) **\textless{} 0.01** & F\({}_{1,26}\) = 4.0 & \(p\) = 0.06 & F\({}_{1,26}\) = 3.9 & \(p\) = 0.06 \\ \hline ER 2017 & F\({}_{1,27}\) = 7.7 & \(p\) **\textless{} 0.01** & F\({}_{1,27}\) = 6.4 & \(p\) **\textless{} 0.02** & F\({}_{1,27}\) = 0.01 & \(p\) = 0.9 \\ ER 2018 & F\({}_{1,26}\) = 0.003 & \(p\) = 0.95 & F\({}_{1,26}\) = 5.1 & \(p\) **\textless{} 0.03** & F\({}_{1,26}\) = 3.1 & \(p\) = 0.09 \\ \hline NEE 2017 & F\({}_{1,26}\) = 17.4 & \(p\) **\textless{} 0.0003** & F\({}_{1,26}\) = 7.5 & \(p\) **\textless{} 0.01** & F\({}_{1,26}\) = 7.5 & \(p\) **\textless{} 0.01** \\ NEE 2018 & F\({}_{1,27}\) = 10.4 & \(p\) **\textless{} 0.003** & F\({}_{1,27}\) = 2.7 & \(p\) = 0.1 & F\({}_{1,27}\) = 3.6 & \(p\) = 0.07 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Results of analysis of variance examining the effect of date (May, June, July, August or summer, fall) and grazing treatment (caged, uncaged) on aboveground biomass, gross primary productivity (GPP), ecosystem respiration (ER) and net ecosystem exchange (NEE) measured in 2017 and 2018. Significant \(p\)-values are bolded. The species composition of aboveground biomass shifted seasonally and between treatments (Figure 2). _S. Latifolia_ had the highest biomass across years and seasons, with the exception of spring 2018 when _Leersia oryzae, T. Latifolia, Alisma plantago-aquatica_ were present but overall biomass was low. _S. Latifolia_ was particularly dominant in uncaged plots during the peak of the growing season, contributing >90% of the aboveground biomass in uncaged plots in 2017 and 75-85% of the biomass in uncaged plots in 2018. In 2018, _N. odorata_ was also prominent in uncaged plots, contributing 11% of the peak growing season biomass, while being almost entirely absent from caged plots across both years.