Association of brook trout and Oncorhynchus spp. with large wood jams in a Lake Superior tributary in a northern old‐growth watershed

Wood in streams functions as fish habitat, but relationships between fish abundance (or size) and large wood in streams are not consistent. One possible reason for variable relationships between fish and wood in streams is that the association of fish with wood habitat may depend on ecological context such as large‐scale geomorphology. We studied the relationship between salmonid assemblages and large wood jams (LWJ) in four settings that differed geomorphically at the scale of the stream corridor along a tributary to Lake Superior in old‐growth conifer–hardwood forest in northern Michigan. The focal fish species of this study were brook trout (Salvelinus fontinalis), which were wild in the stream. Relocation efforts for coaster brook trout (an adfluvial life history variant of brook trout) were ongoing in the study stream. We measured fish abundance and length in pairs of pools of similar size and substrate, but varying in the presence of LWJ; this allowed us to evaluate associations of fish simply with the presence of LWJ rather than with other channel or flow‐shaping functions of LWJ. The length of Oncorhynchus spp. and young introduced brook trout was not strongly correlated with LWJ presence; however, the presence of LWJ in pools was positively correlated with larger wild brook trout. We also found that the correspondence of LWJ with the abundance of salmonids appears to be moderated by the presence of alternative habitat in this relatively natural, old‐growth forest stream.     

Intra-varietal variation. In lolium perenne

The intra-varietal variation of plants of Irish and S. 23 perennial ryegrass (Lolium perenne) growing in nutrient solution was studied in separate experiments.The variation in shoot growth was due to differences in both the rate of production and size of the tillers, while in root growth it was related to the size of individual roots. Root relative to shoot growth was also related to the size of the individual roots.In both varieties the frequency-distribution of size of individual roots and rate of root growth compared with shoot growth was positively skew. Root characters were more variable than shoot characters. The results are discussed in relation to possible selection pressures and morphology.     

Dynamics of natural infection by Toxoplasma gondii in goat herds in the semiarid region of northeastern Brazil: transitional antibody observation

Veterinary Research Communications - This study aimed to describe the transmission of T. gondii in naturally infected goats in the semiarid region of northeastern Brazil, through evaluating the...     

Mineral nutrition and adventitious rooting in microcuttings of Eucalyptus globulus

We characterized the adventitious rooting response of Eucalyptus globulus Labill. to various concentrations of calcium, nitrogen, phosphorus, iron, manganese, zinc, boron and copper. The parameters analyzed were percent rooting, root number, root length and mean rooting time. Root number and root length were significantly affected by mineral nutrition, whereas mean rooting time and rooting percentage seemed to be closely related to auxin availability. Root number was affected by calcium, nitrogen source and zinc, whereas root length was influenced by concentrations of phosphorus, iron and manganese, and by nitrogen source. Based on these results, we evaluated various combinations of several concentrations of these minerals in each rooting phase. Cuttings that were rooted in an optimized mineral nutrient medium and acclimatized to ex-vitro conditions for two months showed significantly higher survival after transplanting and drought stress than cuttings rooted in basal medium and treated in the same way.     

Regeneration of Psychotria umbellata and production of the analgesic indole alkaloid umbellatine

Psychotria umbellata Vell. (Rubiaceae), a Brazilian coastal woody species, produces umbellatine (also known as psychollatine), an analgesic indole alkaloid. An in vitro embryogenic regeneration protocol capable of yielding alkaloid-accumulating plants was developed. Rhizogenic calli, which were obtained from stem segments derived from rooted apical cuttings, were cultured on Murashige and Skoog's (MS) medium containing either 1 mg l(-1) NAA (naphthalene acetic acid) and no kinetin, or 5 mg l(-1) NAA + 1 mg l(-1) kinetin. Calli did not accumulate umbellatine. Segments of rhizogenic callus were cultured on complete MS medium with various concentrations of kinetin and sucrose. Plant regeneration was best in the light with 0.25 mg l(-1) of kinetin and 1.5% sucrose. After 3 months of acclimatization in soil mixture, plant survival was 81%. Leaves of 10-month-old regenerated plants yielded umbellatine concentrations equivalent to those of adult forest-grown plants.     

Effects of prescribed fire on canopy foliar chemistry and suitability for an insect herbivore

We assessed the effects of a prescribed fire on the phytochemical characteristics and vigor of overstory chestnut oak, scarlet oak, and red maple, and measured the impact of potential changes on herbivore fitness. We compared foliar carbohydrates, tannins, nutrients, and fiber concentrations in foliage from burned and non-burned forest canopies. There were significant differences in most foliar characteristics between tree species. Total non-structural carbohydrate concentrations in scarlet oak and red maple foliage, and calcium levels in red maple foliage, were significantly lower in burned plots, but other phytochemical characteristics were largely unaffected by burning. Tree growth also varied with species. Burning increased chestnut oak relative growth, decreased scarlet oak growth, and had no affect on red maple growth. Scarlet oak and red maple foliage from burned and non-burned forest canopies were assayed for gypsy moth performance. Caterpillars fed foliage from scarlet oak, the preferred host, grew larger and developed more rapidly than did those fed red maple foliage. There were no significant burn treatment differences in caterpillar development within either tree species, suggesting that managers using prescribed fire to promote oak regeneration need not worry about enhancing forest stand susceptibility to gypsy moth. However, the fire in this study was of low to moderate intensity; more intense fires may alter foliar palatability.