Alzérreca, H.

Kreuzer, Michael

Marquardt, Svenja

Mayer, Andrea C.

Miranda, M.

English

University of Kentucky

University of Kentucky UKnowledge International Grassland Congress Proceedings XXI International Grassland Congress / VIII International Rangeland Congress Effect of Cattle Grazing on Native Forage Biomass Yield in Extensive Grazing Systems of Southern Bolivia H. Alzérreca Herbario Nacional de Bolivia, Bolivia M. Miranda Herbario Nacional de Bolivia, Bolivia Svenja Marquardt ETH Zurich, Switzerland Michael Kreuzer ETH Zurich, Switzerland Andrea C. Mayer ETH Zurich, Switzerland 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/21/10-1/28 The XXI International Grassland Congress / VIII 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. 瞯 ]218　 瞯 　 Multifunctional Grasslands in a Changing World 　 Volume Ⅱ 　Grasslands/Rangelands Production Systems——— Integration of Crops , Forage and Forest SystemsEffect of cattle grazing on native forage biomass yield in extensive grazing systems of southernBoliviaH . Alzérreca 1 , M . M iranda1 , S . Marquardt2 , M . K reuzer2 and A .C . Mayer 21 Herbario Nacional de Boliv ia , L a Paz , Boliv ia ,2 ET H Zurich , Institute o f A nimal Science , Zurich , Sw itz erland .E‐mail : alzerrec＠ iname .comKey words : animal nutrition , defoliation , grazing intensity , silvopastoral system , Criollo cattleIntroduction Boliviano‐Tucumano mountain forests in Southern Bolivia are used for grazing Criollo cattle . Great parts of thesegrazing areas are located in the nature reserve Parque Natural de Fauna y Flora Tariquí a . Near the villages , grazing pressurecan be high , especially during the rainy season , whereas remote forests are only utilized for grazing in the dry and pre‐humidseason . Grazing and browsing might affect biomass production of specific plant species in the Boliviano‐Tucumano forest ,however , this has not been investigated . The objective of this study was to determine the effect of different grazing intensitiesof Criollo cattle on forage biomass production during the grazing period and in the subsequent year , and the contribution ofdifferent vegetation types to the overall forage supply .Materials and methods The experimental site�El Meson" ( S２１° ４５′ ０６″ , W６４°１２′ １６″) is located at an altitude of １２８０ masl nearthe village of Salinas in the Department of Tarija , Bolivia , and belongs to the Boliviano‐Tucumano formation ( Navarro andMaldonado , ２００４ ) . The annual precipitation is １ .３３４ mm ( need to check this value ) . Three intensities of grazing wererandomly assigned to three plots ,３ ha each . T reatments were : low ( L ) , medium (M ) and high ( H) grazing intensity , with ０ .８ , １ .３ and ２ .２ animal units / ha , respectively ( au ＝ ３００ kg live weight mature criollo cow ) . The grazing period in ２００６ and ２００７was from March to June . Yield was measured before ( PRE) and after the grazing experiments ( POS ) in both years . Foragewas harvested utilizing different techniques according to the vegetation types ; in grasslands , all forage plants present in ３０randomly distributed quadrants (０ .５ m２ ) were harvested ; in forested areas , the herbaceous plants were harvested in １８ (５ × ５m２ ) quadrants . In shrubs , the reference unit technique was used ( Bonham １９８９ ) . Data were analyzed utilizing the Mixedmodel ( LS Means) and results were reported in kg of dry matter per ha .Results Principal forage species were ; Paspalum notatum , Panicum laxum and A xonopus comp ressus in grasslands ;Pseudechinolaena polystachya , Pteris def lexa and Panicum sp . in forest ; and within the woody plants Barnadesia odorata ,Ocotea cf . puberula and A llophy lus edulis . Herbaceous species contributed most to the total available forage . POS showssignificantly ( P ＜ ０ .０５ ) less defoliation effects for the low grazing intensity plot in both years . The only pre‐grazing meansignificantly lower than the POS was in the high grazing intensity plot in the second year of the experiment , suggesting a heavygrazing accumulated effect from the previous year . PRE and POS differed significantly , except for the low grazing intensitytreatment in the first year of the experiment . On the low grazing intensity plot , the effects of defoliation on biomass productionwere not severe . In general , on the high grazing intensity plot , herbaceous plants had a significantly lower yield than undermedium and low grazing intensity . However , higher yields in these treatments in the second year of the experiment suggest aremarkable re‐grow th capacity of these plant species . Overall , woody plants contributed less to the forage yield than theherbaceous plant species . Interestingly , there were no significant differences among the plots grazed with different intensities( POS treatments) .Conclusions Grazing intensities higher than applied here could reduce biomass production in subsequent years . However , theherbaceous plant species showed a remarkable resilience capacity when moderate grazing intensities are applied . The result maycontribute to decisions regarding the sustainable management of the nature reserve by adapting grazing intensities to the specificconditions of a grazing site , in order to ensure both ecological and economic sustainability .ReferencesBonham , C . D . (１９８９) . Measurements for terrestrial vegetation . John Wiley & Sons . New York , US . ３３８ p .Navarro , G . and Maldonado , M . ( ２００４ ) . Geografía Ecológica de Bolivia :Vegetación y Ambientes Acuáticos . ２nd edition .Editorial :Centro de Ecología Simón I . Pati鼻o‐Departamento de Difusión . Talleres de Industrias Graficas SIRENA . SantaCruz de la Sierra , Boliv ia . ７１９ p .

Effect of Cattle Grazing on Native Forage Biomass Yield in Extensive Grazing Systems of Southern Bolivia

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Effect of Cattle Grazing on Native Forage Biomass Yield in Extensive Grazing Systems of Southern Bolivia

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