Thus it is unlikely that a lack of motivation could be a sufficient explanation for all, as Bickerton puts it, “relatively large-brained species” (Bickerton, 2003, p. 83). On the more technical side, Nowak et al. have some other possible explanations (Nowak & Komarova, 2001). Certain conditions have to be met before natural selection can see the advantages of compounding: 1. The total number of relevant messages has to exceed a critical value, 2. The compound signals must be able to encode the relevant messages in such a way that individual components occur in many different messages. Plausibly, these conditions Protease Inhibitor Library cost are not met by non-humans. But why? We hypothesize that the degree of differentiation

of conceptual structure in non-humans is insufficient to support these conditions. Specifically, there seems to be something unique about the human capacity for hierarchical conceptualization (but it is difficult to tell what exactly – see Chomsky, 2010, Dessalles, 2008, Fauconnier and Turner, 2008, Hauser et al., 2002, Luuk and Luuk, 2008, Penn and Povinelli, 2007, Penn et al., 2008, Premack and Woodruff, 1978, Suddendorf and Corballis, 2007, Tomasello et al., 2003 and Tulving, 2005, for different hypotheses, some of which appear to be already falsified – Correia et al., 2007 and Osvath, 2009). Curiously, only one possible example of a semantically compositional syntax, the extremely limited communication

system of honeybees,7 is found in non-humans in the wild, and no clear example of semantically compositional communication has been found in non-human ABT 263 vertebrates (Hurford, 2004, Michelsen, 1999 and von Frisch and Lindauer, 1996). There are bird songs, cetacean songs, and primate ‘long calls’ built up out of smaller units, but the units are not meaningful on their own, and/or different combinations are not distinctively meaningful (Jackendoff, 1999 and Ujhelyi, 1998). This argument applies also to the Molecular motor special case of putty-nose

monkeys (Arnold & Zuberbuhler, 2006). These monkeys produce two calls, ‘pyows’ and ‘hacks’ in response to, mainly, leopards and eagles, respectively. The researches found that the monkeys also produce a third call, ‘pyow–hack’ (P–H), and observed that P–H triggers group movement. In addition, although the putty-nosed monkeys sometimes move through the canopy to escape from an approaching leopard, this strategy is avoided when threatened by large raptors, as it would increase the risk of attack. Leopard growls were played back to 17 different monkey groups. In nine groups, the male produced call series containing at least one P–H. The researchers found that, 20 min later, the groups whose males had produced P–H had traveled significantly farther than other groups. It is important to note that P–H is not a semantic combination, and complies with P and H due to loud call repertoire constraints only (Arnold, p.c.).

The years post-fire corresponded with different calendar years

depending on when different find more sites were burned, complicating relating vegetation dynamics with weather patterns. Other long-term studies gathered post-treatment measurements in years of below average (Huisinga et al., 2005) or near average precipitation (Thill et al., 1983). Numerous factors could relate to why most short-term (<4 years) studies found declines in understory plant abundance after treatments. In the two shortest-term studies of 0.5 years, for example, cutting or prescribed fire was implemented in fall and the post-treatment measurement occurred the following spring or early summer, so warm-season plants in particular may not have had opportunity to initiate growth (Bêche et al., 2005 and Cram et al., 2007). It should be noted, however, that primary goals of these studies were to evaluate short-term treatment effects on stream chemistry (Bêche et al., 2005) or soil erosion (Cram et al., 2007), not on understory vegetation. Moreover, temporal photos in follow-up by Cram et al. (2007) suggested increasing amounts of understory cover (Appendix B1). Treatments that do not appreciably reduce overstory tree canopy cover may not substantially change the understory. The four fire and fire surrogate studies – all of which

reported short-term declines in understory abundance – buy CP-673451 noted that reductions in overstory cover were often relatively subtle, post-treatment overstory cover was likely greater than in historical forests, and acetylcholine relatively dense post-treatment overstories may have limited understory growth (e.g., Metlen et al., 2004 and Dodson et al., 2008). Prescriptions were not tailored specifically to promote understories, as the primary objective of these studies was to modify fuel conditions such that 80% of dominant or co-dominant trees in the post-treatment forest would survive wildfire modeled under 80th percentile weather conditions (McIver et al., 2013). Some authors of other studies,

such as Mason et al. (2009), also suspected that minimal treatment effects on the overstory tempered understory response within one or more of their treatment units. Relationships depicted in regression equations between overstory tree abundance and understory measures in untreated mixed conifer forests may provide a framework for estimating overstory reductions needed to stimulate understory vegetation (Larson and Wolters, 1983 and Page et al., 2005). For example, in Rocky Mountain mixed conifer forests of Colorado, Mitchell and Bartling (1991) reported that understory biomass averaged 535 g m−2 when tree canopy cover was 11–40%, but when tree cover exceeded 60%, understory biomass was reduced by 84% to only 86 g m−2. In Idaho Abies grandis (grand fir)–P. menziesii forest, understory biomass exceeded 1000 kg ha−1 only up to 40% tree canopy cover ( Pyke and Zamora, 1982). Similarly, Hedrick et al.