Simulating the dynamics of linear forests in Great Plains agroecosystems under changing climates

Most forest growth models are not suitable for the highly fragmented, linear (or linearly shaped) forests in the Great Plains agroecosJrstems (e.g., windbreaks, riparian forest buffers), where such forests are a minor but ecologically important component of the land mosaics. This study used SEEI)SCAPE, a recently modified gap model designed for cultivated land mosaics in the Creat Plains, to simulate the effects of climate change on the dynamics of such linear forests. We simulated the dynamics of windbreaks with different initial planting species richness and widths flight changes as the selected resulting factor) using cuirent climate data and nested regional circulation models (RegCMs). Results indicated that ( i ) it took 70-80 simuhtion years for the linear forests to reach a steady state under both normal (present-day) and warming climates; (ii) warming climates would reduce total aboveground tree biomass and the spatial variation in biomass, but increase dominance in the linear forests, especially in the upland forests; (iii) linear forests with higher planting species richness and smaller width produced higher aboveground tree biomass per unit area; and (iv) the same species performed very differently with different climate scenarios, initial planting diversity, and forest widths. Although the model still needs further improvements ('e.g., the effects of understory species should be includedj, the model can serve as a useful tool in modeling the succession of linear forests in human-dominated land mosaics under changing climates and may also have significant practical implications in other systems. RGsurn6 : La plupart des modbles de cmissance ne sont pas adapt& aux for& fortement EragmenttSes et linCaires (ou de fonne linezire) dans les ago-6cosyst5mes des Crandes Plaines @. ex., les coupe-vents ou les bandes riveraines) 03 de telles forgts representent une composante mineure mais non moins ~cologiquement importante de la mosaique du paysage. Dans cette etude, les auteurs ont utilist? SEEDSCAPE, un modble de trouCe recement modifit? et conp pour la mosdque du paysage agricole, pour sirnuler les effets des changements climatiques sur la dynamique de telles fort% linCaires. 11s ont simult? la dynamique des coupe-vents de diffcrentes largeurs (la lumibre change en consequence) et diversigs spdcifiques au moment de la planmtion initiale, l'aide de donndes climatiques actuelles et de modbles hiCrarchisks de circulation regionale (MCReg). Les resultats ont montrC (i) que 1'6tat d'equilibre a 6tC atteint dans les foets linkaims ap&s 70-80 ans de simulation, tant sous le climat normal (actuel) que sous un climat plus chaud; (ii) qu'un climat plus chaud rkduirait la biomasse abiienne des arbres et sa variabilite spatide mais augmenterait la dominance dans les for& lineaires, plus spgcifiquement dans les for& des hautes terres; (iiQ que les for& IinCaires plus ktmites avec une plus grande iichesse sp&citique au moment de la plantation produiraient plus de biomasse ligneuse atfrienne par unit6 de surface; et iiv) que les m&mes e@ces se comportent de fa~on trbs diffbrente selon le s&nario climatique. la diversite au moment de la plantation et la largeur de la forbt. Mgme si le modble requiert certaines ambliorations (p. ex., I'effet des esphces du sous-bois devrait &tre inclus), ce dernier peut &re utilistl pour modkliser la succession forestibre des fohts linetiires dans des mosaiques du paysage domine par l'homme sous des conditions climatiques changeantes et peut cjgalement avoir d'autres implications pratiques importantes dans d'autres syst&mf:s. [Traduit pas la RtMaction] introduction of the a,oricultural land mosaics, yet provide m y vital services. These woody areas enhance crop protection and Human-dominated in the Great are 'peproduction through their sheltering effects, provide habitats culated to be especially sensitive to climate changes because and eavel conidors for plmcs and wildlife, and water of their highly fragmented nature. In the Great Plains, woody quality sort 1988; Guertin et al. 997; Rosenberg et al. areas* predominantly agroforesm planting$ (such 1997; Guo 2WO; Easterling et &. 2001). However, the sueforest buffers and windbreaks, but also natural woody draws cession and functions of ~ e s e G~~~~ plains forests under and fences and field borders) make up only a srnall portion varying climates have been largely overlooked and little inReceived 25 March 2004. Accepted 30 July 2004. Pubfished on the NRC Research Press Web site at http://cjfr.nrc.ca on 12 January 2005. Q. GUU?~ J. Brandle, anit D. Buettner. School of Natural Resources, University of Nebraska, Lincoln, NE 68583-081 4. USA. M. Schoeneberger. USDA National Agroforestry Center, Rocky Mountain Research Station, East Campus, University of Nebraska, Lincoln, NE 68583-0822, USA. Corresponding author (e-mail: qguo@ usgs.gov). "resent address: US Geological Survey, 8711 37th Street SE, Jamestown. ND 58401, USA. Can. J. For. Res. 34: 2564-2572 (2004) doi: 10.1139K04-138 Q 2004 NRC Canada