-1 Foliar and shoot allometry of pollarded black locust, Robinia pseudoacacia L. D.M. Burner 1, *, D.H. Pote 1 and A. Ares 2 1 United States Department of Agriculture, Agricultural Research Service, Dale Bumpers Small Farms Research Center, 6883 South State Highway 23, Booneville, AR 72927, USA; 2 Weyerhaeuser Company, 505 N. Pearl Street, Centralia, WA 98531, USA; *Author for correspondence (e-mail: dburner@spa.ars.usda.gov; phone: +1-479-675-3834; fax: +1-479-675-2940) Received 22 June 2004; accepted in revised form 17 January 2006 Key words: Allometric relationship, Foliar mass, Nonlinear analysis, Shoot diameter, Shoot mass Abstract Browse of multipurpose tree species such as black locust could be used to broaden grazing options, but the temporal distribution of foliage has not been adequately studied. Our objective was to determine effects of harvest date, P fertilization (0 and 600 kg ha À1 yr À1 ), and pollard height (shoots clipped at 5-, 50-, and 100- cm above ground) on foliar and shoot allometry of black locust. The experiment was conducted on a naturally regenerated 2-yr-old black locust stand (15,000 trees ha À1 ). Basal shoot diameter and foliar mass were measured monthly in June to October 2002 and 2003. Foliar and shoot dry mass (Y) was estimated from basal shoot diameter (D) by the function Y = aD b , with regression explaining ‡95% of variance. Allometry of foliar mass was affected by harvest date, increasing at a greater rate with D in September than in June or July, but not by P fertilization or pollard height. Foliar mass was predicted best by month- specific equations for the June to October growth interval. Allometry of shoot dry mass was unaffected by harvest date, P fertilization, or pollard height. These equations could be used as a first approximation of foliar and shoot mass for pollarded black locust. Introduction Variations in summer rainfall (Hu 2002) can cause localized water deficits that constrain yields of C 3 and C 4 herbaceous forages, and require supple- mental hay feeding to sustain livestock. Producers could substantially increase profit margins by developing forage systems that extend the grazing season, thus decreasing or eliminating the high costs of harvesting and feeding hay during these dry periods. Multipurpose trees could have a particular niche for rotational livestock browse when drought limits forage options and live- stock productivity, as has been demonstrated for temperate (Oppong et al. 2002) and sub-Mediterranean regions (Papanastasis et al. 1998). However, the browse potential of multi- purpose tree species and the temporal distribution of foliar biomass need further study. Black locust is a rapid-growing, N 2 -fixing, multipurpose species native to the USA (Bongarten et al. 1992) that could be integrated with herbaceous species for livestock production. Depending on row configuration, black locust yielded 900–5000 kg dry matter ha À1 yr À1 of pruning (foliage plus shoot) biomass in Oregon, USA (Seiter et al. 1999). In west-central Arkansas, USA, black locust yielded as much as 5300 kg dry matter ha À1 when harvested in August (Burner et al. 2005), while the Agroforestry Systems (2006) 68:37–42 Ó Springer 2006 DOI 10.1007/s10457-006-0001-y