Acknowledgments University of Toledo, Maumee Valley Audubon Society, Daryl Moorhead, Tom Weicht, Alison Spongberg, Li Fafeng, Brian Marlow, Jayne Belnap. MICROBIOTIC CRUST COMMUNITIES: NITROGEN FIXATION AND LEACHING WITHIN A MESIC TEMPERATE OAK SAVANNA Cladina cristatella Tuck. by Roberta Veluci & Deborah A. Neher

ABSTRACT Microbiotic crust is a biological soil crust composed of lichens, cyanobacteria, green algae, mosses, and fungi. Although crusts are a dominant source of nitrogen in arid ecosystems, this study is the first to examine their contribution to nitrogen (N) availability in xeric temperate habitats in Northwest Ohio. N fixation occurs in these crusts covering sandy, low N soil. Moss-crust surfaces are covered with cyanobacteria responsible for N fixation and cyanobacterial abundance was independent from days since last rainfall. Moreover, increases in temperature correspond with amount of N fixed. N leaching from the crust layer was quantified using ion exchange resin bags inserted at 2.5-cm depth from surface of intact cores. Leaching of NO 3 - and NH 4 + were reduced in forest edge relative to shrub or grass vegetations, and did not vary significantly among months. Leaching of NO 3 - is retarded with temperature rise and, thus, a function of temperature. Conversely, precipitation increased N leaching, and is expected to maximize during rain fall events. Furthermore, environmental parameters such as moisture and temperature fluctuations in soil are moderated under crust compared to bare soil without crust. We conclude that biological crusts in northwestern Ohio enhance N fixation, moderate soil microclimate and, impact N leaching.

STUDY SITE Oak Openings Metropark 4.0 to 5.4 pH 91-94% sand Low N soil

A) Well established crust, B) Intermediate crust and C) Bare Soil. A C B Moss Lichen Bare Algae Video Imaging Analysis: estimate crust type and extent NITROGEN FIXATION Acetylene Reduction Assay: confirmed N fixation in 50% of samples.

Moss cover and lichen explained more N fixation than did cyanobacteria or bare soil

Result: Abundance of cyanobacteria decreased with crust depth Method: Fluorescent microscopy to quantify cyanobacterial populations 369 Crust depth (mm) Cyanobacteria (10 5 cells/g of dry soil) b a ab Contrasting letters (p = ) Fig. 8

Moss surfaces are covered with cyanobacteria and its abundance was independent from days since last rainfall 0714 Days since rainfall Cyanobacteria (10 6, total cells/g of dry soil) p = 0.70 Fig. 7

Fig. 2 Recovery efficiency of resin bags Volume (ml) Recovery efficiency of NO 3 - and NH 4 + from resins were 33 and 70%, respectively. NO 3 - = 1N KHSO 4 - NH 4 + = 0.5 N K 2 SO 4 + NH 4 + = 1N K 2 SO 4 NITROGEN LEACHING 1)Method Development

Fig. 3 Relatively flow of N to resin bags flush with bottom of core inside corearound corebelow core Nitrogen source Mean recovery (µg/g) NH NO 3 - % Total Recovery 2) Method Development Ion exchange resin bags placed flush with the bottom surface of an intact core collected most NO 3 - or NH 4 + from outside the core than from directly above or underneath the resin bag inside the core (p < ). Therefore, resin bags were inserted at 2.5- cm depth from surface of intact cores in field experiments. NITROGEN LEACHING

Time (weeks) Fig. 4 Dynamic equilibrium of N on resins and in soil  = resins O = soil Resin and soil nitrogen (µg/g) NO 3 - NH 4 + 2) Field Measurements Concentrations of NO 3 - (r 2 = 0.33) and NH 4 + (r 2 = 0.21) on resins were associated linearly with soil concentrations. Concentrations of N on resins were typically greater than in soil (p = ), although they were in equilibrium through time (p = 0.18).

▲ = FOREST ■ = SHRUB ● = GRASS Fig. 5 N leaching among vegetation types Concentration of NO 3 - (A, p = ) and NH 4 + (B, p = ) leaching were less at forest edge than shrub or grass, and did not vary significantly among months. A B

Fig 1. Soil A) water potential & B) temperature for bare ( ) or crust soils ( ) through time. Soil crusts moderate soil climate Time since deployment (weeks) Moisture (MPa) Temperature (°C) A B MAYSEPT

CONCLUSIONS This is the first study to: Confirm N fixation of microbiotic crusts in mesic temperate biome Employ IRN-77/78 resins in sandy soil, low in both N & organic matter