EFFECTS OF POST-FIRE SOIL HYDROPHOBICITY ON INORGANIC SOIL NITROGEN AND SULFUR CYCLING

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1 EFFECTS OF POST-FIRE SOIL HYDROPHOBICITY ON INORGANIC SOIL NITROGEN AND SULFUR CYCLING Kitlynn J. Fernelius, Mtthew D. Mdsen, Kerri A. Russell*, Bruce A. Roundy, nd Bryn G. Hopkins Brighm Young University; * = presenting uthor ABSTRACT Fire plys n importnt role in mny ntive ecosystems, nd its suppression hs incresed woody encrochment cross the gloe. Restoring ntive herceous communities following fire in encroched systems is often chllenging. Post-fire soil hydrophoicity is one fctor tht my further limit site restortion y limiting soil moisture, which my in turn ffect soil nutrient dynmics. We conducted field study in urned pinion-juniper woodlnd to understnd the effects of postfire soil hydrophoicity on soil moisture nd soil nutrients. Plots centered on Juniperus osteosperm or Pinus monophyll trees were either left untreted or treted with surfctnt to meliorte soil hydrophoicity, nd then left re or seeded with Pseudoroegneri spict. Mesurements were tken two yers fter fire in My, y which time the surfctnt tretment hd 124.4% higher soil wter content thn the repellent control. This effect ws function of thick, hydrophoic lyer in the control s compred to hydrophilic soil conditions when treted with surfctnt fter the fire. Soil nutrient levels were 45.5%, 37.8%, nd 52.3% lower in the surfctnt tretment compred to the repellent control for sulfte, nitrte, nd mmonium respectively. The development of restortion tools nd prctices to mnge these effects of soil hydrophoicity my help reduce invsive species nd fcilitte the estlishment of desired ntive herceous communities. INTRODUCTION Fernelius (2013) reviewed how ltered fire regimes cn hve devstting effects on ntive ecosystems. Anthropomorphic fire suppression hs incresed woody encrochment worldwide over the pst century. When fires occur in these encroched systems, they often ecome more severe. This incresed severity cn cuse further ecosystem degrdtion y decresing microil communities, nd incresing soil erosion nd weed invsion. While fire cn destilize woody encroched systems, it lso gives ntive grss systems n opportunity to reestlish. Post-fire soil hydrophoicity is one fctor tht my limit site restortion y ltering soil-wter interctions. Soil hydrophoicity is soil condition cused y hydrophoic orgnic compounds inding to soil prticles, which delys wter infiltrtion longer thn 5 seconds. Soil hydrophoicity decreses wter infiltrtion nd percoltion, which consequently increses surfce runoff fter fire. Such incresed runoff my decrese surfce moisture levels s wter moves grvimetriclly towrd more hydrophilic soils. Post-fire soil hydrophoicity, y decresing soil moisture, my lter soil nutrient dynmics. Following fire, urned woody mound fertile islnds contin high soil nitrogen (N) levels reltive to the surrounding interspce (Vitousek nd Mtson 1985; Kloptek 1987; Hird et l. 2001). Although the cretion of sulfur (S) islnds of fertility my not occur (Cross nd Western Nutrient Mngement Conference Vol.11. Reno, NV. Pge 129

2 Schlesinger 1999), inorgnic S levels do increse following fire (Vlmis nd Gowns 1961). While studies hve shown soil hydrophoicity to increse erosion nd therefore nutrient loss nd redistriution (Rvi et l. 2009), soil hydrophoicity my ctully increse nutrient retention within the hydrophoic zone. Low moisture conditions limit wter-dependent N nd S cycling processes, such s immoiliztion nd leching (Bhrdwj nd Novák 1978; Eriksen et l. 1998; Ketterings et l. 2003; Austin et l. 2004). By inhiiting wter infiltrtion (nd soil wetting), hydrophoicity my therefore prolong nutrient retention within woody islnds of fertility. The ojective of this study ws to identify the effects of post-fire soil hydrophoicity on soil nutrient cycling. MATERIALS AND METHODS Reserch ws conducted on the Ry My Fire ner Reno, Nevd. This pinion-juniper woodlnds fire occurred during August From the time the fire finished urning in August 2011 to the end of the August 2012 smpling, the site received 73.1mm of precipittion. From the August 2012 smpling to the August 2013 smpling, the site received 126.6mm of precipittion. Averge precipittion is mm The experiment ws instlled s rndomized complete lock design with seven locks confined to two-cre re of the fire. Ech lock contined four mture trees (i.e. tree ge greter thn 50 yers) of either Pinus monophyll (Torr. & Frém.) singlelef piñon or Juniperus osteosperm (Torr. Little) Uth juniper. Ech tree sucnopy comprised one 1.5 m rdius plot. Tretments were ssigned in fctoril comintion to trees within ech lock nd included (1) control (wter) or surfctnt tretment (to meliorte soil hydrophoicity) nd (2) unseeded (re) or seeded with Pseudoroegneri spict (lueunch whetgrss). Ech tree rndomly received one of these four tretments. In order to meliorte soil hydrophoicity, the nonionic surfctnt ACA2045 (Aqutrols, New Jersey, USA) ws pplied to surfctnt plots. A concentrtion of 1.47 (v/v) surfctnt ctive ingredient ws identified nd selected s the lowest ctive ingredient concentrtion needed to penetrte the hydrophoic lyer in under 5 s using the WDPT test. The volume of pplied surfctnt ws enough to sturte the sh nd hydrophoic lyers, which ws determined to e L per plot. Following surfctnt ppliction, n dditionl 19.0 L of wter ws pplied to ech plot to wsh the surfctnt from the surfce nd prevent potentil toxicity issues for the seeds. The remining non-surfctnt tretment plots were treted with n equl volume of wter. Following surfctnt nd wter ppliction, plots were seeded with P. spict t 25 kg h -1 PLS nd were rked to ury the seed just elow the soil surfce. Plots were smpled two yers lter in the spring (My). Response vriles chosen to ssess tretment effects included in-situ mesurement of hydrophoic lyer thickness. Soil smples were collected for 2-4 cm elow the ottom of the sh lyer. These smples were trnsported ck to the l to ssess ex-situ ctul hydrophoicity severity, grvimetric soil wter content (ir-dried for 72 h), nd soil nitrte-n, mmonium-n, nd sulfte-s. Actul soil hydrophoicity severity ws ssessed using the WDPT test. Under this test, soils were considered hydrophoic if infiltrtion ws delyed longer thn 5 s. The test ws performed using five 95 µl wter droplets per smple. Nitrte nd mmonium were extrcted from soils using 2 M KCl solution nd nlyzed using LACHAT Flow Injection Autonlyzer (LACHAT 1994). Sulfte ws extrcted from soils using monoclcium phosphte solution (Fox et l. 1964) nd were nlyzed using inductively coupled plsm spectroscopy (Iris Intrepid II XSP, ICP-OES, Thermo Electron Corportion, Wlthm, MA, USA). Western Nutrient Mngement Conference Vol.11. Reno, NV. Pge 130

3 Dt were nlyzed using SAS softwre version 9.3 (SAS Institute Inc. Cry, NC). Mixed model nlysis ws used to nlyze grvimetric soil wter content, soil sulfte, soil nitrte, soil mmonium, nd hydrophoicity severity nd thickness. Block ws considered rndom while soil tretment nd seed tretment were considered fixed fctors. To ccount for zero vlues, constnt (1) ws dded to the mesured vlues, nd ll dt were log-trnsformed efore nlysis. Men vlues were seprted using the Tukey-Krmer honestly significnt difference multiple-comprison method. Differences were considered significnt when P < RESULTS Hydrophoicity severity ws influenced y soil tretment nd not y seed tretment or their interction (Tle 1). Averge severity levels for the surfctnt tretment were elow 5 s, qulifying the surfctnt-treted soils s hydrophilic nd the controls (wter pplied without ddition of surfctnt) remined hydrophoic (Fig. 1). The thickness of the hydrophoic lter ws influenced y soil tretment, ut not y seed tretment or their interction (Tle 1). However, seed tretment ws nerly significnt (P = ). Hydrophoic control soils nd surfctnt-treted soils were sttisticlly different (Fig. 1). Appliction of surfctnt thus decresed soil hydrophoicity severity nd thickness, while the wter-treted plots remined severely hydrophoic. Soil wter content levels were influenced y soil tretment nd lyer, ut not y seed tretment or their interctions (Tle 1). Differences were significnt, with 124.4% greter levels in the surfctnt tretment (Fig. 1c). The 2-4cm lyer exists within the hydrophoic lyer. Anlysis showed inorgnic N to not e influenced y species (nitrte P = ; mmonium P = ). For this study, ll soil nutrients were therefore comined y species tretment. Soil sulfte smples were comined y species tretment prior to sulfte nlysis. Soil sulfte, nitrte, nd mmonium were influenced y soil tretment (Tle 2). Soil nutrient levels were 45.5%, 37.8%, nd 52.3% lower in the surfctnt tretment compred to the repellent control for sulfte, nitrte, nd mmonium respectively (Fig. 2). DISCUSSION We significntly reduced soil hydrophoicity levels in the surfctnt-treted plots. A previous study, which used the sme surfctnt chemicl nd grss species s this study, indicted tht the surfctnt hs neither negtive nor eneficil effects on seedling germintion nd estlishment, fter controlling for meliortion effects (Fernelius 2013). Our soil moisture results showed tht meliorted post-fire soil hydrophoicity with surfctnt to increse soil moisture in the repellent zone. This is consistent with previous reserch, which hs lso shown meliorting soil hydrophoicity to incresed soil moisture (Osorn et l. 1967; Krmmes nd Osorn 1969; DeBno nd Conrd 1974; Mdsen et l. 2012). Although less reserch hs een performed on the effect of fire on S thn on N, oth re similr in their cycling processes (Deno 1991), so some level of similrity in response ws expected. Fire increses soil inorgnic levels for oth of these nutrients directly fter fire (Vlmis nd Gowns 1961). Generlly these heightened levels re short lived (Wn et l., 2001; Certini 2005), ut our reserch suggests tht hydrophoic soils my retin elevted levels longer thn hydrophilic soils for ll three mesured nutrients. Differences in nutrient levels etween hydrophoic nd hydrophilic soils were likely driven y differences in microil nd plnt immoiliztion, which in turn were driven y differences in soil wter content etween the two soil tretments. Becuse S is primrily cycled through microe-influenced processes (Eriksen et Western Nutrient Mngement Conference Vol.11. Reno, NV. Pge 131

4 l. 1998), decresing microil ctivity likely lso decreses S cycling processes such s minerliztion, immoiliztion, oxidtion, nd reduction. Likewise, N cycling is lso hevily medited y microil ctivity through processes such s minerliztion, immoiliztion, nitrifiction, nd denitrifiction (Ketterings et l. 2003). One consequence of these ltered nutrient dynmics my e n increse in weed invsion following hydrophoicity dissiption. While these dt do not investigte the effects of elevted nutrient levels in hydrophoic soils on weed invsion, incresed weed invsion following fire hs een well documented (Dukes nd Mooney 1999; Ott et l. 2001; Esque et l. 2010) nd is generlly ttriuted to the increse in unused resources found fter fire (Dvis et l. 2000; Lowe et l. 2003). Following the dissiption of the hydrophoic lyer severl yers fter fire, high nutrient levels my ecome ville to nutrient-exploiting invsives (Huenneke et l. 1990; Burke nd Grime 1996), fcilitting their estlishment. CONCLUSIONS This study identifies soil hydrophoicity s one fctor tht my limit ntive plnt reestlishment fter fire in woody encroched systems through its influences on soil moisture nd soil nutrient cycling. As humns continue to suppress nturl fire regimes nd s woody plnts continue to encroch, it will e importnt to understnd the mechnisms controlling ntive plnt reestlishment fter fire in order to fcilitte the development of restortion tools nd mngement prctices. REFERENCES Austin AT, Yhdjin L, Strk JM, Belnp J, Porporto A, Norton U, Rvett DA, Scheffer SM Wter pulses nd iogeochemicl cycles in rid nd semirid ecosystems. Oecologi 141: Bhrdwj K, Novák B Effect of moisture level on nitrogen immoiliztion s ffected y whet strw decomposition in soil. Zentrlltt Für Bkteriologie 133: Burke MJW, Grime JP An experimentl study of plnt community invsiility. Ecology 77: Certini G Effects of fire on properties of forest soils: review. Oecologi 143: Cross AF, Schlesinger WH Plnt regultion of soil nutrient distriution in the northern Chihuhun Desert. Plnt Ecology 145: Dvis MA, Grime JP, Thompson K Fluctuting resources in plnt communities: generl theory of invsiility. Journl of Ecology 88: DeBno LF The effect of fire on soil properties. In Proceedings mngement nd productivity of western-montne. Forest Soils, DeBno LF, Conrd CE Effect of wetting gent nd nitrogen fertilizer on estlishment of ryegrss nd mustrd on urned wtershed. Journl of Rnge Mngement 27: Dukes JS, Mooney HA Does glol chnge increse the success of iologicl invders? Trends in Ecology & Evolution 14: Eriksen J, Murphy MD, Schnug E The soil sulphur cycle. Sulphur in Agroecosystems. Springer Netherlnds Esque TC, Kye JP, Eckert SE, DeFlco LA, Trcy CR Short-term soil inorgnic N pulse fter experimentl fire lters invsive nd ntive nnul plnt production in Mojve Desert shrulnd. Oecologi 164: Western Nutrient Mngement Conference Vol.11. Reno, NV. Pge 132

5 Fernelius K Post-fire Interctions etween Soil Wter Repellency, Islnds of Fertility, nd Bromus tectorum Invsiility. Mster s Thesis. Brighm Young University, Provo. Fox RL, Olson RA, nd Rhodes HF Evluting the sulfur sttus of soils y plnts nd soil tests. Soil Sci. Soc. Am. Proc. 28: Hird KA, Archer S, Schimel DS, Vlentine DW Biogeochemicl chnges ccompnying woody plnt encrochment in sutropicl svnn. Ecology 82: Huenneke LF, Hmurg SP, Koide R, Mooney HA, Vitousek PM Effects of soil resources on plnt invsion nd community structure in Clifornin serpentine grsslnd. Ecology 71: Ketterings QM, Klusner SD, Czymmek KJ Nitrogen guidelines for field crops in New York. Kloptek JM Nitrogen minerliztion nd nitrifiction in minerl soils of pinyon-juniper ecosystems. Soil Science Society of Americ Journl 51: Krmmes J, Osorn J Wter-repellent soils nd wetting gents s fctors influencing erosion. In Proceedings of symposium on wter repellent soils. DeBno LF, Letey J (eds). University of Cliforni Riverside, Cliforni; LACHAT QuickChem method B. LACHAT Instrument, Milwukee, WI. Lowe PN, Luenroth WK, Burke IC Effects of nitrogen vilility on competition etween Bromus tectorum nd Boutelou grcilis. Plnt Ecology 167: Mdsen MD, Petersen S, Fernelius KJ, Roundy B, Tylor AG, Hopkins B Influence of soil wter repellency on seedling emergence nd plnt survivl in urned semi-rid woodlnd. Arid Lnd Resource nd Mngement 26: Osorn J, Letey J, DeBno F, Terry E Seed germintion nd estlishment s ffected y non-wettle soils nd wetting gents. Ecology 48: Ott JE, McArthur ED, Snderson SC Plnt community dynmics of urned nd unurned sgerush nd pinyon-juniper vegettion in West-Centrl Uth. In Shrulnd Ecosystem Genetics nd Biodiversity, McArthur ED, Firnks DJ (eds). USDA Forest Service Proceedings RMRS-P-21, Rocky Mountin Reserch Sttion: Fort Collins, Colordo; Rvi S, D Odorico P, Wng L, White CS, Okin GS, Mcko SA, Collins SL Post-fire resource redistriution in desert grsslnds: possile negtive feedck on lnd degrdtion. Ecosystems 12: Vitousek PM, Mtson PA Disturnce, nitrogen vilility, nd nitrogen losses in n intensively mnged lololly pine plnttion. Ecology 66: Vlmis J, Gowns KD Avilility of nitrogen, phosphorus, nd sulfur fter rush urning. Journl of Rnge Mngement 14: Wn S, Hui D, Luo Y Fire effects on nitrogen pools nd dynmics in terrestril ecosystems: met-nlysis. Ecologicl Applictions 11: Western Nutrient Mngement Conference Vol.11. Reno, NV. Pge 133

6 Tle 1. Results of mixed ANOVA models for soil hydrophoicity severity nd thickness, nd grvimetric soil wter content y soil tretment, seed tretment, nd their interction. Severity Thickness Wter content F P F P F P Soil tretment <0.0001* Seed tretment Soil Seed * Significnt fctors (P < 0.05) re highlighted in old ) Severity (s) ) Wter (Ctrl) Surfctnt Soil tretment c) Soil wter content (g/g) Wter (Ctrl) Surfctnt Soil tretment Thickness (cm) Wter (Ctrl) Soil tretment Surfctnt Figure 1. () Soil hydrophoicity severity, () hydrophoicity thickness nd (c) grvimetric soil wter content for oth soil tretments (surfctnt nd wter) in My of the second yer fter fire. Vlues re mens, with unique letters indicting significnt differences etween soil tretments (P < 0.05). Western Nutrient Mngement Conference Vol.11. Reno, NV. Pge 134

7 Concentrtion (ppm) Wter (Ctrl) Surfctnt 0 Sulfte Nitrte Ammonium Soil nutrient Figure 2. Soil nitrte nd soil sulfte levels for oth soil tretments (surfctnt nd wter) mesured in My of the second yer fter fire. Soils were smpled 2-4 cm from the ottom of the sh lyer. Vlues re mens, with unique letters indicting significnt differences etween soil tretments within ech nutrient (P < 0.05). Western Nutrient Mngement Conference Vol.11. Reno, NV. Pge 135

8 PROCEEDINGS OF THE WESTERN NUTRIENT MANAGEMENT CONFERENCE Volume 11 MARCH 5-6, 2015 RENO, NEVADA Executive Committee Glen Mooso, Simplot, Chirmn Jon Dvenport, Wshington Stte University, Vice Chirmn Jim Wlworth, University of Arizon, Secretry Progrm Chir Dvid Trklson USDA - ARS 3793 N 3600 E Kimerly, ID (208) Dvid.trklson@rs.usd.gov Coordintor Phyllis Ptes Interntionl Plnt Nutrition Institute 2301 Reserch Prk Wy, Suite 126 Brookings, SD (605) pptes@ipni.net