Cleary, M. B.

Ewers, B. E.

Kwon, H.

Naithani, K.

Pendall, E.

English

University of Kentucky

University of Kentucky UKnowledge International Grassland Congress Proceedings 21st International Grassland Congress / 8th International Rangeland Congress Resilience of Ecosystem Structure and Function during Succession Following Prescribed Burning in a Shrub‐Steppe Ecosystem in Wyoming, USA E. Pendall University of Wyoming M. B. Cleary University of Wyoming B. E. Ewers University of Wyoming K. Naithani University of Wyoming H. Kwon University of Wyoming Follow this and additional works at: https://uknowledge.uky.edu/igc  Part of the Plant Sciences Commons, and the Soil Science Commons This document is available at https://uknowledge.uky.edu/igc/21/4-1/29 The 21st International Grassland Congress / 8th International Rangeland Congress took place in Hohhot, China from June 29 through July 5, 2008. Proceedings edited by Organizing Committee of 2008 IGC/IRC Conference Published by Guangdong People's Publishing House This Event is brought to you for free and open access by the Plant and Soil Sciences at UKnowledge. It has been accepted for inclusion in International Grassland Congress Proceedings by an authorized administrator of UKnowledge. For more information, please contact UKnowledge@lsv.uky.edu. 　 Multifunctional Grasslands in a Changing World 　 Volume Ⅰ 　 瞯 ]587　 瞯Grasslands/Rangelands Resources and Ecology ——— Indicators for Sustainable Use and Conservation of Grasslands/Rangelands ResourcesResilience of ecosystem structure and function during succession following prescribed burning ina shrub‐steppe ecosystem in Wyoming , USAE . Pendall , M .B . Cleary , B .E . Ewers , K . Naithani , and H . K wonDepartment o f Botany and Program in Ecology , University o f W yoming , L aramie , WY 82071 USA , E‐mail : Pendall＠uwyo .eduKey words : aboveground biomass , roots , soil organic matter , N availability , sagebrush steppeIntroduction Prescribed burning is applied in mountain big sagebrush ( A rtemisia tritentata var . v aseyana) communities acrossthe Intermountain West , USA , to reduce shrub cover , increase herbaceous biomass , and enhance wildlife habitat and rangelandhealth . When properly managed , succession following burning in these upper elevation rangelands follows a predictablepathway . Initially , perennial bunchgrasses ( including Festuca spp . , Stip a spp . and Poa spp .) dominate , and sagebrush coverincreases to pre‐burn levels within about ４０ years as grasses decline ( Ewers and Pendall ２００８ ) . We hypothesized that Navailability would be stimulated following burning , and that aboveground and belowground biomass and soil organic matterstorage would increase as shrub cover increased during succession .　 Figure 1 Soil C pools in top 10‐cm oversuccession . SOM‐C , total ; NHC , non‐hydrolyz able C ; Cs , slow pool C ; Ca , activepool C .Methods We studied the effects of burning on ecosystem structure andfunction at three chronosequence sites in Wyoming , ranging in age from ０ to～ ４０ years since disturbance . We measured vegetation cover and leaf areaindex ( LAI ) , and developed new allometric relationships for estimatingaboveground and coarse root biomass for sagebrush ( Cleary et al . ２００７ ) .Fine root biomass , soil organic matter ( SOM ) and KCl‐extractable NH４ ＋and NO３ － content were also measured at one chronosequence to ２‐m soildepth . SOM was further fractionated into active , slow , and non‐hydrolyzableC ( NHC ) pools using long‐term incubations and ６‐N HCl digestion . Weapplied a vector approach , by repeated sampling of several parameters atmultiple time points , and replicated the chronosequences , to testchronosequence assumptions .Results and discussionWe found that increases in aboveground biomass , coverand LAI were driven by sagebrush establishment and grow th over ４０ years ofsuccession following burning . Aboveground biomass accumulated at a net rateof approximately １５ g C m‐２ y‐１ , to a maximum of about ６００ g C m‐２ . Coarseroot biomass in the top ２５‐cm soil accumulated at approximately ８ g C m‐２ y‐１to a maximum of ３５０ g C m‐２ . Fine root biomass was maintained near steadystate , at approximately ４５０ g C m‐２ , throughout succession , for a totalbiomass C inventory of about １４００ g m‐２ in the climax shrub‐dominatedcommunity . Total SOM in the top １０‐cm depth increased from about ３２００ gm‐２ to ５０００ g m‐２ over ４０ years , with the largest increases observed in theslow and NHC pools ( Figure １) , which have mean residence times of decadesto centuries . The regrow th of aboveground biomass and maintenance ofbelowground biomass and SOM indicate that this ecosystem is resilient to　 Figure 2 A nnually repeated measurements o fsoil N H ＋4 and NO －3 pools during successionin a burn chronosequence .fire .A pulse of available N was observed in the first ３‐４ years after a burn ,mainly in the form of NH ＋４ （Figure ２ ) . This available N was likelyresponsible for vigorous grow th of herbaceous biomass following burning .Repeated measurements confirmed the validity of our chronosequenceapproach . Changes in net N mineralization during succession were notobserved due to high variability .Conclusions Aboveground biomass and C stocks in SOM increased duringsuccession , corresponding to changes in shrub cover , while N availabilitypeaked in the first few years following burning . Maintenance of fine rootbiomass , provided by perennial grasses , appears to be critical to resilience ofecosystem structure and function in sagebrush steppe .ReferencesCleary , M .B . , Pendall , E . , and Ewers , B .E . ( ２００７ ) . Journal o f A ridEnv ironments . DOI :１０ .１０１６ / j .jaridenv .２００７ .０７ .０１３ .Ewers , B .E . , and Pendall , E . (２００８ ) . Plant Ecology １９４ ,６７‐８３ , DOI １０ .１００７ / s１１２５８‐００７‐９２７５‐z .5000 4000 5 3000 0 0 2000 1= (.) o, 1 ODO _ 16 L 14 0 "' Jl.l 12 z 10 r 8 1= 6 ~ 4 0 " z 2 ·o (J) 0 0 10 20 30 40 Growth Stages(Years Since Fire) NH/ I . j . NO, . NH 4+N 0 3 i1 - Total N = 2.98 + 8.57 e-0.63t It T~ , I I .+: ·!· n 1T: • ..0 10 20 30 40 50 Ti me Since Burn (y) 

Resilience of Ecosystem Structure and Function during Succession Following Prescribed Burning in a Shrub‐Steppe Ecosystem in Wyoming, USA

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Resilience of Ecosystem Structure and Function during Succession Following Prescribed Burning in a Shrub‐Steppe Ecosystem in Wyoming, USA

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