Hydrogeomorphic Assessment of Beanblossom Bottoms Nature Preserve Sycamore Land Trust Thuy Thi Hong An SPEA E 440 – Wetlands Fall 2011 Introduction Methods 2.1 Site description 2.2 HGM assessment Results and discussion Conclusion Literature cited Figures and Tables Thuy Thi Hong An HGM Assessment Introduction We were asked by the Sycamore Land Trust, a local conservation organization, to evaluate the wetland ecological functions of the Beanblossom Bottoms Nature Preserve This wetland had been converted from an agriculture site to gain wetland mitigation credits The Sycamore Land Trust is interested in selling these mitigation credits to INDOT to compensate for the loss of wetlands caused by the construction of I – 69 Hydrogeomorphic (HGM) approach was applied to calculate the mitigation ratio by evaluating wetland functions of the mitigation site compared to the reference site Methods 2.1 Site description The Beanblossom Bottoms Nature Preserve is a high quality hardwood wetland owned by the Sycamore Land Trust The latitude and longitude of this site are North 39 16.612 and West 86 34.713 respectively (Cyberindiana 2011) The Beanblossom Bottoms Nature Preserve used to be a farm land According to the Soil survey of Monroe County, Indiana (1981), the soils in the reference site are Zipp silty clay loam and Bonnie silt loam while the soil in the restored site is Stendal silt loam (Figure 1) The mitigation site is marked by a star in Figure The reference site is the nearby forested wetland which has minimum disturbance 2.2 HGM approach The HGM classification system is based on three main criteria including landscape position, water source, and hydrodynamics (Craft 2011) This approach was applied to evaluate the functional indices of the mitigation wetland in comparing with the reference wetland of the same type Wetlands deliver a wide range of functions associated with four general categories: Thuy Thi Hong An HGM Assessment Hydrology, biogeochemistry, plant habitat, and animal habitat (Hauer 1998) Therefore, it is impossible to assess all functions In this project, we evaluated only one function for each category as following Table 1: Ecological functions evaluated in HGM method No Category Evaluated function Hydrology Long-term surface water storage Biogeochemistry Nutrient cycling Plant habitat Maintain characteristic plant communities Animal habitat Maintain spatial structure of habitat Due to time limitation, only one sampling plot was established at the mitigation site and a similar sampling plot was established at the reference site Direct measurements were done on-site while indirect measurements were estimated off-site The detail information and results are summarized in Table The reference site was given a score of one for each index of variable The scores assigned for variables of the mitigation site were based on their likeness to the reference site The total function index was the average scores of the four functional categories The ratio of total function index of the reference site to the mitigation site is called the HGM mitigation ratio Because forested wetlands have a failure rate of 71%, an adjusted HGM mitigation ratio is necessary (Robb 2002) The below equation is used to calculate the adjusted HGM mitigation ratio Adjusted HGM mitigation ratio = HGM mitigation ratio Success rate In the case of forested wetlands, the success rate is 29% or 0.29 (Robb 2002) Thuy Thi Hong An HGM Assessment Results and discussion The overall results are shown in Table Comparing to the reference standard, the mitigation site had the long-term surface water storage score of 0.75 Therefore, it can provide about 75% of ecological functions related to long-term surface water storage delivered by the reference site This result is logical since the mitigation site is adjacent to the reference site accounting for their similar macrotopography The nutrient cycling score of the restored site was only 0.1 proving that the restored site was not good at providing biogeochemical functions The scores for maintaining characteristic plant community and spatial structure of habitat were 0.51 and 0.52 respectively In other words, the mitigation wetland can deliver a half level of functions as plant and animal habitats compared to those provided by the reference wetland Table 2: Index of variables for reference site and mitigation site at Beanblossom Bottoms Nature Preserve Wetland functions Index of variable Reference site Mitigation site Long-term surface water storage 0.75 Nutrient cycling 0.1 Maintain characteristic plant communities 0.51 Maintain spatial structure of habitat 0.52 0.47 Total function index Mitigation ratio Failure adjusted mitigation ratio : 0.47 = 2.13 : (2.13/0.29) : = 7.34 : The total function index based on the above four wetland ecological functions was 0.47 It means that the mitigation site can perform about 47% of ecological functions provided by the reference site The mitigation ratio was 2.13 indicating that we need 2.13 hectares of mitigation Thuy Thi Hong An HGM Assessment wetlands to deliver the same level of functions provided by hectare of reference wetlands Due to a failure rate of 71% for forested wetlands, 7.34 hectares of constructed forest wetland was recommended to compensate for the loss of hectare of natural forested wetland Conclusion Sycamore Land Trust should proceed with creating the mitigation bank to sell mitigation credits for INDOT The recommended scale is 2.13 : which means that 2.13 hectares of the mitigation wetland is needed to replace hectare of the natural wetland destroyed However, a mitigation ratio of 7.34 : could be applied to ensure higher successful mitigation Thuy Thi Hong An HGM Assessment Literature cited Craft, Christopher B (2011) Wetlands: Biology and Regulation Classpak Publishing Indiana University Hauer, F R and R D Smith (1998) "The hydrogeomorphic approach to functional assessment of riparian wetlands: evaluating impacts and mitigation on river floodplains in the U.S.A." Freshwater Biology 40(3): 517-530 Robb, J T (2002) "Assessing wetland compensatory mitigation sites to aid in establishing mitigation ratios." Wetlands 22(2): 435-440 Soil survey of Monroe County, Indiana 1981 Soil Conservation Service, U S Department of Agriculture U.S Department of Agriculture Natural Resources Conservation Service http://websoilsurvey.nrcs.usda.gov/app/HomePage.htm Last accessed December 6th, 2011 Syscamore Land Trust http://sycamorelandtrust.org Last accessed December 6th, 2011 Cyberindiana http://cyberindiana.com/outdoors/beanblossom_bottoms_nature_preserve.shtml Last accessed December 6th, 2011 Thuy Thi Hong An HGM Assessment Figures and Tables Figure 1: Soil surveys at Beanblossom Bottoms Nature Preserve Data from US Department of Agriculture Natural Resources Conservation Service November, 2011 Thuy Thi Hong An HGM Assessment Figure 2: Sycamore Land Trust property boundaries for the Beanblossom Bottoms Nature Preserve, Monroe County, IN (After Sycamore Land Trust Website, accessed on December 5th, 2011) Thuy Thi Hong An HGM Assessment Table 3: Summary of values and calculation for wetland functions using hydrogeomorphic index at Beanblossom Bottoms Nature Preserve, Sycomore Land Trust (Data collected on December 2nd, 2011) Model Measure VSURWAT VMACRO Indicators of surface water present Macrotopographic relief VPROD Aerial net primary productivity VTURNOV Annual turnover of detritus VCOMP Species composition for tree (T), sapling (SAP), shrub (S), and ground cover (GC) strata VREGEN Seedlings/saplings and/or clonal shoots Measure Reference Wetland LONG-TERM SURFACE WATER STORAGE ~30.5 cm flooding observed from Visual observation of water watermarks, buttressing and moss on mark, buttress, moss trees Estimated by viewing aerial Uniformly flat photograph (Google earth) Minor elevation changes (dead trees) NUTRIENT CYCLING Index of Variable Restored Wetland Index of Variable 1.0 ~ 15.25 cm flooding observed from watermarks on trees 0.5 1.0 Uniformly flat 1.0 Index of Function = (VSurfacewater + VMacro)/2 0.75 cm cm Determined by measuring 1.0 cm = 7.8 cm average = 6.0 cm average thickness of leaf litter layer 10 cm (130% calculated) cm No observable organic A Determined by measuring Very thin organic layer if present horizon the thickness of A < 1.0 cm of darker organic matter at 1.0 Larger chunks of organic horizontal layer the top of the soil sample matter (leaf litter) than reference site Index of Function If VAerial NPP > VTurnover then index is VTurnover otherwise use V Aerial NPP MAINTAIN CHARACTERISTIC PLANT COMMUNITY T: Fraxinus pennsylvanica, Platanus occidentalis, Acer Determined dominant T: Fraxinus pennsylvanica, Quercus rubrum [1] species for each strata bicolor, Quercus palustris SAP: Acer rubrum, Platanus Plot size: occidentalis, Quercus alba Trees >5cm DBH in 10 m SAP: Acer rubrum, Fraxinus [1] 1.0 radius pennsylvannica S: None Saplings/shrubs in m S: None GC: Boehmeria cylindrical, radius GC: Boehmeria cylindrical, Misc Misc Sedge, Misc Poacea Herbaceous in m radius Sedge, Misc Poacea spp spp., Lysimachia nummularia [3] cm cm cm cm cm Estimated ratio of seedlings to saplings (DBH5 cm DBH) in 10 m radius HGM Assessment T: 90% 1.0 T: 80% 60 1.0 180 0.1 Acer rubrum- 16 22 20 18 14 16 18 30 16 20 Fraxinus pennsylvanica- 20 13 10 15 15 20 10 10 18 Measured DBH in a 10 m Platanus occidentalis- 28 13 radius plot for all tree 28 18 27 25 28 32 47 40 34 1.0 species > cm DBH using a 20 35 32 15 20 22 20 20 21 standard DBH tape 29 Populus deltoides- 99 Quercus palustris- 35 32 30 15 Total = 3295 Total = 1086 (33%) Index of Function = [(VComposition + VRegeneration + VCanopry Cover) + (VTree Density + VBasal Area)/2] /4 MAINTAIN SPATIAL STRUCTURE OF HABITAT Acer rubrum- 28 33 15 13 19 25 27 28 30 31 30 16 24 Fraxinus pennsylvanica- 83 74 117 90 80 100 25 75 116 84 42 27 80 65 85 59 16 75 69 70 83 84 75 65 Quercus spp- 134 96 78 80 90 65 79 82 77 68 83 Ulmus Americana- 29 30 35 42 40 30 27 39 33 0.5 0.51 Counted standing dead trees in 10 m radius plot 10 1.0 0 Counted very mature trees as far as able to view 24 1.0 0.1 Estimated number of strata and their percent coverage Trees: 90% Saplings: 80% Shrubs: 10% Ground cover: 30% 1.0 80% 0% 0% 100% 0.5 Appeared uniform 1.0 Appeared uniform Appeared uniform 1.0 Appeared uniform Viewed aerial photograph using Google Earth Viewed aerial photograph using Google Earth Index of Function = (VSnags + VMature Trees + VStrata + VPatch + VGaps) /5 Total function index Mitigation ratio Failure adjusted mitigation ratio 0.52 0.47 2.13 : 7.34 :