Small-scale variation of vegetation in a mixed forest understorey is partly controlled by the effect of overstory composition on litter accumulation

We investigated how richness and composition of vascular plant species in the understory of a mixed hardwood forest stand varied with respect to the abundance and composition of the overstory. The stand is in central Spain and represents the southernmost range of distribution of several tree and herbaceous species in Europe. Understory species were identified in 46 quadrats (0.25 m2) where variables litter depth and light availability were measured. In addition, we estimated tree density, basal area, and percent basal area by tree species within 6-m-radius areas around each plot. Species richness and composition were studied using path analysis and scale-dependent geostatistical methods, respectively. We found that the relative abundance of certain trees species in the overstory was more important than total overstory abundance in explaining understory species richness. Richness decreased as soil litter depth increased, and soil litter increased as the relative proportion of Fagus sylvatica in the overstory increased, which accounted for a negative, indirect effect of Fagus sylvatica on richness. Regarding understory species composition, we found that some species distributed preferentially below certain tree species. For example, Melica uniflora was most frequent below Fagus sylvatica and Quercus petraea while the increasing proportion of Q. pyrenaica in the overstory favored the presence of Cruciata glabra, Arenaria montana, Prunus avium, Conopodium bourgaei, Holcus mollis, Stellaria media and Galium aparine in the understory. Overall, these results emphasize the importance of individual tree species in controlling the assemblage and richness of understory species in mixed stands. We conclude that soil litter accumulation is one way through which overstory composition shapes the understory community.

The estrogen receptor locus is associated with a major gene influencing litter size in pigs.

Identification of individual major genes affecting quantitative traits in livestock species has been limited to date. By using a candidate gene approach and a divergent breed cross involving the Chinese Meishan pig, we have shown that a specific allele of the estrogen receptor (ER) locus is associated with increased litter size. Female pigs from synthetic lines with a 50% Meishan background that were homozygous for this beneficial allele produced 2.3 more pigs in first parities and 1.5 more pigs averaged over all parities than females from the same synthetic lines and homozygous for the undesirable allele. This beneficial ER allele was also found in pigs with Large White breed ancestory. Analysis of females with Large White breed background showed an advantage for females homozygous for the beneficial allele as compared to females homozygous for the other allele of more than 1 total pig born. Analyses of growth performance test records detected no significant unfavorable associations of the beneficial allele with growth and developmental traits. Mapping of the ER gene demonstrated that the closest known genes or markers were 3 centimorgans from ER. To our knowledge, one of these, superoxide dismutase gene (SOD2), was mapped for the first time in the pig. Analysis of ER and these linked markers indicated that ER is the best predictor of litter size differences. Introgression of the beneficial allele into commercial pig breeding lines, in which the allele was not present, and marker-assisted selection for the beneficial allele in lines with Meishan and Large White background have begun.

Effects of sulfuric acid rain on two model hardwood forests : throughfall, litter leachate, and soil solution /

"January 1980."

Technical manual, unit maintenance : truck, utility, cargo/troop carrier, 1-1/4 ton, 4x4, M998 (2320-01-107-7155) ... truck, ambulance, 2-litter, soft top, 4x4, M1035 (2310-01-146-7194).

Includes index.

Hand receipt covering contents of components of end item (COEI), basic issue items (BII), and additional authorization list (AAL) for truck, utility, cargo/troop carrier, 1-1/4 ton, 4x4, M998 (2320-01-107-7155) ... truck, ambulance, 2-litter, soft top, 4x4, M1035 (2310-01-146-7194).

"May 1988."

Direct support and general support maintenance repair parts and special tools list for truck, utility, cargo/troop carrier, 1-1/4 ton, 4x4, M998 (2320-01-107-7155) ... truck, ambulance, 2-litter, soft top, 4x4, M1035 (2310-01-146-7194).

"August 1991."

Unit maintenance repair parts and special tools list for truck, utility, cargo/troop carrier, 1-1/4 ton, 4x4, M998 (2320-01-107-7155) ... truck, ambulance, 2-litter, soft top, 4x4, M1035 (2310-01-146-7194).

"August 1991."