Halina M. Zaleski

Germination after simulated rat damage in seeds of two endemic Hawaiian palm species

Seed predation by native and alien rodents can limit plant recruitment and ultimately affect forest dynamics and composition (Campbell & Atkinson 2002, Cote et al . 2003, Hulme 1998, Sanchez-Cordero & Martinez-Gallardo 1998). Even partial consumption of seeds by predators may affect plant community structure, though its importance is poorly understood (Steele et al . 1993, Vallejo-Marin et al . 2006). Despite consumption of relatively large portions of seeds by herbivores, seeds can retain their ability to germinate if the embryo remains intact (Dalling & Harms 1999, Janzen 1972, Mack 1998). Germination of damaged seeds may be accelerated or prolonged (Karban & Lowenberg 1992, Koptur 1998, Vallejo-Marin et al . 2006). Damage by seed pests also facilitates ageing stress; which manifests as decreased seedling vigour, decreased seed viability, lower germination percentages and slower germination rates (Priestley 1986).

High yielding tropical energy crops for bioenergy production: Effects of plant components, harvest years and locations on biomass composition

The composition of lignocellulosic feedstock, which depends on crop type, crop management, locations and plant parts, significantly affects the conversion efficiency of biomass into biofuels and biobased products. Thus, this study examined the composition of different parts of two high yielding tropical energy crops, Energycane and Napier grass, collected across three locations and years. Significantly higher fiber content was found in the leaves of Energycane than stems, while fiber content was significantly higher in the stems than the leaves of Napier grass. Similarly, fiber content was higher in Napier grass than Energycane. Due to significant differences in biomass composition between the plant parts within a crop type, neither biological conversion, including anaerobic digestion, nor thermochemical pretreatment alone is likely to efficiently convert biomass components into biofuels and biobased products. However, combination of anaerobic digestion with thermochemical conversion technologies could efficiently utilize biomass components in generating biofuels and biobased products.

Anaerobic digestion of high-yielding tropical energy crops for biomethane production: Effects of crop types, locations and plant parts

This study examined the composition and anaerobic digestibility of the different plant parts of two high-yielding tropical energy crops, Energycane and Napier grass, collected across three locations and two seasons. Both biomass composition and biomethane yields varied significantly with crop types, plant parts and harvest seasons. In Energycane, specific methane yield (SMY) (Nm3 (kg VSadded)-1) was higher from stems (0.232 ± 0.003) than leaves (0.224 ± 0.003), while in Napier grass, SMY was higher from leaves (0.243 ± 0.002) than stems (0.168 ± 0.002). Energycane had higher specific and total (Nm3 ha-1 year-1) methane yields (0.230 ± 0.002 and 8749 ± 494, respectively) than Napier grass (0.192 ± 0.002 and 5575 ± 494, respectively). The SMYs from biomass correlated negatively with acid detergent fiber, cellulose and lignin content in the biomass. Energycane and Napier grass had lower specific but comparable total methane yields (TMYs) with maize. The ecological, economic and environmental merits associated with perennial crops suggest they could outperform maize as a substrate for bioenergy production.