Oecologia (2011) 165:1095–1107 Characteristic Leaf N Chemistry P K Ca Mg Na Biomass Herbaceous above ground Utilization Herbaceous off-take Herbaceous plants Table 2 A comparison between control and kraal sites in terms of the leaf chemistry of Urochloa mosambicensis leaves sampled in control and kraal sites, the herbaceous above ground biomass (dry mass), herbaceous biomass (dry mass) off take by large herbivores and the percentage of herbaceous plants grazed n 17 17 17 17 17 17 18 16 18 Unit % % % % % % kg DM ha-1 kg DM ha-1 day-1 % Mean (95% CL) Control 1.6 (0.8–2.6) 0.13 (0.06–0.23) 2.15 (1.1–3.6) 0.57 (0.28–0.95) 0.26 (0.13–0.44) 0.24 (0.11–0.42) 6 (0–5) 12 (6–21) 928 (562–1,532) 781 (494–1,233) Kraal 2.8 (2.2–3.3) 0.46 (0.33–0.61) 3.58 (2.96–4.27) 0.73 (0.67–0.79) 0.39 (0.29–0.49) 0.20 (0.12–0.31) 9 (5–13) 45 (29–62) The sampling and measurements were done in February 2007. Back transformed means, 95% conﬁdence limits and the signiﬁcance level of group differences are given Signiﬁcance levels *** P \ 0.001, ** P \ 0.01, * P \ 0.05, ns P C 0.05 higher than the 621 kg DM ha-1 measured outside cages at kraal sites (t7 = 4.31, P \ 0.01). At control sites, the dif- ference between the herbaceous biomass inside and outside of exclosures was not signiﬁcant (P [ 0.05), indicating that grazers signiﬁcantly reduced swards at kraal sites but not at control sites. In agreement, the frequency of herbaceous plant utilization was more than threefold higher on kraal sites than on control sites (Table 2). Dung accumulation and herbivore species composition The density of all large herbivore dung piles combined was higher in kraal sites than control sites (Wald Chi- square = 22.9, P \ 0.001). Individual species with sig- niﬁcantly higher average dung accumulation rates on kraal sites were impala, duiker, waterbuck and steenbok. The densities of buffalo, elephant, giraffe and warthog were not higher on kraals compared to controls (Table 3). No dung of kudu or wildebeest were found in control transects (Table 3). Using mean dung pile dry mass and the mean fecal N and P content values, the N inputs by individual species were calculated (Table 3). The N deposition rate through large herbivore dung at kraal sites was calculated as 1.2 g N m2 year-1, compared to only 0.1 g N m2 year-1 for control sites. At kraal sites, impala deposited the most N (on average 40% of total), followed by elephant (31%) and giraffe (8%). Conversely, at control sites, elephants deposited the most N (on average 53% of total), followed by giraffe (18% of total) and impala (16% of total; Table 3). In the experiment where vegetation structure was altered, open areas themselves attracted more herbivores such as impala. Shortly after clearing, four times more (Chi-square = 4.2, df = 1, P \ 0.05) impala dung piles were recorded in bush-cleared sites compared to control sites covering the same surface area (564 vs. 138 dung piles). Soil nutrients, herbivore use and tree recruitment For the ﬁeld fertilization and exclosure experiment, trans- planted C. mopane survival after 4 months in the ﬁeld was signiﬁcantly related to fertilizer treatments (Wald Chi- square = 13.981, df = 3, P \ 0.01; Fig. 1), but was neither related to herbivore exclusion (Wald Chi-square = 0.448, df = 1, P [ 0.05) or the fertilizer 9 exclosure interaction (Wald Chi-square = 5.104, df = 3, P [ 0.05). For the fertilizer treatments, the establishment success was signiﬁ- cantly lower in the 6 and 30 g N m-2 treatments compared to controls, but not for the 1.2 g N m-2 treatment (Fig. 1). The pot experiment data suggest that herbaceous competition intensiﬁed with increasing soil N and P availability. The relative competition index, RCI, for leaf number per tree seedling was positively correlated with inorganic soil N and P concentration, indicating that seedlings grew less under fertile conditions when 123 1101 P ** ** ** ns ns ns ns ns **