| Description |
Red Butte Garden is located on the University of Utah campus in Salt Lake City, UT. It is a nonprofit arboretum and botanical garden. Red Butte Creek runs through the Garden as it transitions from a mainly undeveloped to an urbanized watershed. This study investigates some of the environmental benefits and impacts of the Garden on Red Butte Creek. In late August 2013, riparian Box elder (Acer negundo) foliage samples were collected upstream, downstream, and within the Garden. The natural abundance of total leaf nitrogen isotope ratio was determined to assess nitrogen (N) sources and extent of fertilizer influence downstream. Red Butte Creek water was sampled biweekly from September through December 2013 (total of 7 sampling events) upstream, downstream, and within the Garden. Water samples were analyzed for ammonium, nitrate, chloride, orthophosphate, and dissolved oxygen (DO) concentrations as well as temperature and pH. Total suspended solids (TSS) was measured in Red Butte Creek upstream, downstream, and within the Garden at two flow rates, 0.8 and 1.1 cfs. The mean total leaf nitrogen 𝛿15N downstream (1.4 ‰) of the Garden is significantly (p=0.03) higher than the upstream mean (-0.1 ‰). Leaf 𝛿15N in the Garden ranged from -0.2 to 6.7 ‰ (μ=2.7 ‰) and is significantly higher than upstream (p=0.02). The mean C:N ratio of leaves upstream, downstream, and within the Garden is 28.8, 20.0, and 20.7, respectively. Both the Garden and downstream leaves are significantly higher than upstream (p≤0.05). There was no statistical difference between mean upstream and downstream ammonium (p=0.95) and nitrate (p=0.32) concentrations. Orthophosphate was below the laboratory reporting limit (0.5 mg/l) for every sample. Average chloride concentrations were slightly higher downstream (14.43 mg/l upstream and 14.62 mg/l downstream) though not significantly (p=0.59). TSS concentrations in Red Butte Creek upstream, downstream, and within the Garden were measured three times throughout this experiment. The average TSS concentration upstream, downstream, and within the Garden is 4.33, 17.47, and 13.35 mg/l, respectively.The results indicate 15N enrichment in Garden and downstream leaves which is likely caused by the use of organic fertilizer, fish activity, or net N losses. The leaf C:N is higher within the Garden and downstream than upstream, but the source of this increased N cannot be directly associated with Garden activity because of the multiple nonpoint contributors (e.g., urbanization). Ammonium and nitrate concentrations up- and downstream show no change in stream water quality. Overall, the Garden has little impact to Red Butte Creek and is an example of sustainable landscape management. |
