No abstract

Acid deposition has been identified as one of several possible factors contributing to the decline of some waterfowl populations in North America. In an effort to examine the effects of acidification on black duck (Anas rubripes) recruitment, growth and physiological condition were monitored in ducklings foraging for a 10–day trial (days 10–20 of life) on acidified (pH 5.0) and circumneutral (pH 6.8) fish-free emergent wetlands. Acidification of these wetlands suppressed phytoplankton and algal growth, and reduced invertebrate biomass. Ducklings maintained on acidified wetlands grew poorly compared with ducklings reared on circumneutral wetlands, as evidenced by lower final body weight and culmen and tarsus length. Plasma growth hormone concentration was elevated and triiodothyronine levels were lower in stunted ducklings, in part substantiating impairment of growth-regulating processes. Ducklings exhibiting poor growth tended to have lower hematocrit, lower plasma protein, glucose, and cholesterol concentrations, and higher uric acid levels, presumably reflecting alterations in metabolism and development due to inanition. These findings suggest that acid deposition may lower food production in wetlands and ultimately impair duckling growth, condition, and survival.

Two groups of filial generations derived from two different Pinus massoniana complete-diallel crosses were analyzed. Results show that the general combining ability (GCA), specific combining ability (SCA) and reciprocal effects were significant for some growth traits, including height, DBH and volume index. The heredity of these growth traits was controlled by additive and nonadditive genes, of which the additive genes played a dominant role. The epistatic effect was greater for group I (cross in 1992) than group II (cross in 1993). The SCA of P. massoniana growth traits was significantly greater than GCA, which may be related to different geographical provenance for parents and the indirect selection by GCA. Inbreeding depression was commonly observed for P. massoniana growth traits. The extent of inbreeding depression was K17.8% -K18.4%, K23.3% -K27.7% and K44.3%-K50.6% for height, DBH and volume index, respectively. It was observed that parents with small GCA values exhibited a greater extent of inbreeding depression. Large differences in hybrid vigor of different crosses were observed and the difference between original cross and reciprocal cross was not significant. Based on the volume index, 10 fine crosses were selected for two groups respectively, and the average increment of volume index was 59.41% and 41.76%, respectively, in comparison with the average of the testing groups, and was 100.58% and 74.61% in comparison with the local commercial variety.