Habitat management and patterns of predation of Northern Lapwings on wet grasslands: The influence of linear habitat structures at different spatial scales

In managed landscapes, habitat structure is frequently manipulated through the creation of features such as tracks, hedges, and waterways. If predator and prey activity are concentrated around these features, levels of predation may be elevated in these landscapes. This issue is of particular importance when habitat structures are used to attract species of conservation concern. For example, the installation of linear waterways in wet grasslands is a common form of habitat management to benefit breeding waders and wader nests and foraging chicks tend to be aggregated around wet features. If predator activity is also focused around these features, and if their linearity increases the probability of prey being located, then the conservation benefits of this management technique may be eliminated. We explore predator movement in relation to the structure and complexity of linear wet features within a lowland wet grassland landscape. We examine patterns of nest and chick predation in lapwing (Vanellus vanellus) at the whole-site, between-field and within-field scales. Mammalian predators were responsible for the majority of nest predation. However, we found no evidence that mammalian predators used linear wet features disproportionately within the landscape, or that wet feature distribution influenced the probability of nest or chick predation. At the whole-site scale, nest predation rates were significantly higher in areas with greater predator presence and lowest where the number of breeding neighbours was high. Thus, predation levels were influenced by large-scale patterns of predator presence and lapwing density but not by the use of linear wet features as a habitat management tool. Managing predator impacts is therefore likely to require empirical assessments of local predator distribution and abundance in order to target measures effectively.     

Invasive and native plant responses to shrubland fuel reduction: comparing prescribed fire, mastication, and treatment season

Fuel reduction in the wildland-urban interface is a widely used international strategy for assisting human communities regarding wildfire threats, but very little research has examined whether certain fuel reduction methods and their seasonal timing promote nonnative invasion. To address this issue, we evaluated nonnative and native plant response to five of the most commonly-practiced shrubland fuel reduction methods in Mediterranean climates, including (a) fall prescribed fire, (b) winter prescribed fire, (c) spring prescribed fire, (d) fall mastication (slashing) and (e) spring mastication. Treatments were replicated four times in mature northern California chaparral and surveyed for three years after treatment; treatment type was randomly assigned. We found that the effects of treatment type (fire/mastication) were more apparent than the effects of treatment season (fall/winter/spring), but there were some differences among seasons of prescribed fire. Mastication treatments had the highest number of nonnative invasive species. Mastication treatments also had 34% higher nonnative annual grass abundance than the fire treatments. Winter and spring prescribed fire treatments were most resistant to nonnative invasion since these areas had the fewest nonnative species, lowest nonnative species abundances, and highest relative proportions of native plants. In shrublands where controlling nonnative annual grass is an important objective, managers should consider cool season prescribed fire as a viable fuel reduction treatment. In cases where prescribed fire is not feasible, mastication provides an alternative that can exacerbate nonnative grass production in the short term but may maintain native plant seedbanks over the long term if the site remains undisturbed for several decades. Results from this study could be applicable to other areas of Mediterranean shrublands.     

Molecular species of acylglycerols incorporating radiolabeled fatty acids from castor (Ricinus communis L.) microsomal incubations

Sixty-one molecular species of triacylglycerols (TAG) and diacylglycerols produced from castor microsomal incubations incorporating six different (14)C-labeled fatty acids have been identified and quantified. The preference for incorporation into TAG was in the order ricinoleate > oleate > linoleate > linolenate > stearate > palmitate. Ricinoleate was the major fatty acid incorporated, whereas stearate, linolenate, and palmitate were incorporated at low levels. Twenty-one molecular species of acylglycerols (HPLC peaks) in castor oil have also been assigned. The levels of TAG in castor oil are RRR (triricinolein) > RR-TAG > R-TAG > no R-TAG. The levels of the molecular species within the groups of RR-TAG, RL-TAG, and LL-TAG individually are ricinoleate > linoleate > oleate > linolenate, stearate, and palmitate. The results of the labeled fatty acid incorporation are consistent with ricinoleate being preferentially driven into TAG and oleate being converted to ricinoleate in castor oil biosynthesis.     

Organic amendments to enhance herbicide biodegradation in contaminated soils

Pesticide contamination of soil and groundwater at agricultural chemical distribution sites is a widespread problem in the USA. Alternatives to land-farming or solid waste disposal include biostimulation and phytoremediation. This research investigated the ability of compost, corn stalks, corn fermentation byproduct, peat, manure, and sawdust at rates of 0.5% and 5% (w/w) to stimulate biodegradation of atrazine [6-chloro-N-ethyl-N'-(1-methyethyl)-1,3,5-triazine-2,4-diamine], metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide], and trifluralin [2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine] added as a mixture to soil. Initial concentrations were 175ᆾ mg atrazine kg^-1 soil, 182ᆭ mg metolachlor kg^-1 soil, and 165ᆫ mg trifluralin kg^-1 soil. After amendment addition, 30% of the atrazine, 33% of the metolachlor, and 44% of the trifluralin was degraded over 245 days, which included 63 days' aging prior to amendment additions. Atrazine degradation was enhanced by 0.5% manure, 5% peat, and 5% cornstalk amendments compared to nonamended soils. Metolachlor degradation was enhanced by all amendments at the 5% level, except for compost and peat. Amendments had no effect on trifluralin degradation. The 5% addition of compost, manure, and cornstalks resulted in significant increases in bacterial populations and dehydrogenase activity. A second experiment compared the persistence of atrazine, metolachlor, and trifluralin applied in a mixture to their persistence in soil individually. A combined average of 123 mg atrazine kg^-1 remained in soil treated with the three-herbicide mixture compared to 31 mg atrazine kg^-1 remaining in soil treated with atrazine only. Atrazine mineralization and atrazine-degrading microorganisms were suppressed by high concentrations of metolachlor, but not by trifluralin.     

Population isolation exacerbates conservation genetic concerns in the endangered Amargosa vole, Microtus californicus scirpensis

The ability of a taxon to maintain adaptive flexibility in a stochastic environment is a function of the genetic diversity within the population. In small, fragmented populations, genetic variation can become depleted more quickly than in larger, more contiguous populations. Characterizing the patterns of genetic variation and differentiation associated with these processes is an important step in establishing conservation priorities. The Amargosa vole, Microtus californicus scirpensis, is an endangered rodent persisting in the small, fragmented marsh complex surrounding the Amargosa River near Death Valley, California. This naturally patchy system has existed since the end of the Pleistocene (approximately 10,000 y.b.p.), however, fragmentation has been exacerbated by recent anthropogenic changes. For this study, I used five nuclear microsatellite loci and the cytochrome-b region of the mitochondrial genome to quantify levels of genetic variation, population substructure, and patterns of gene flow in M.c. scirpensis. These data were compared to a broadly distributed subspecies, Microtus californicus sanctidiegi. Overall levels of nuclear genetic variation were significantly lower in M.c. scirpensis, whether measured in terms of diversity or heterozygosity, compared to more broadly distributed conspecifics. Moreover, only two haplotypes were recovered from the mitochondrial data with over 90% of the observed haplotypes being identical. Despite low genetic diversity, significant genetic subdivision among M.c. scirpensis populations was detected using both pairwise F_ST and Bayesian clustering methods. Furthermore, isolation by distance analyses reveal that an important landscape feature, ephemeral tributaries, is critical for dispersal among population clusters. Recommendations for conservation management are presented.     

Antioxidant activity of coffee model systems

Coffee model systems prepared from combinations of chlorogenic acid (CGA), N(alpha)-acetyl-1-arginine (A), sucrose (S), and cellulose (C) were roasted at 240 degrees C for 4 min prior to analysis by UV-visible spectrophotometry, capillary zone electrophoresis (CZE), and the ABTS radical cation decolorization assay. The A/CGA/S/C and A/S/C systems were also fractionated by gel filtration chromatography. Antioxidant activity of the systems showed a positive, nonlinear relationship with the amount of CGA remaining after roasting. Sucrose degradation was a major source of color in the heated systems. There was no relationship between antioxidant activity and color generation.