The coarse‐root system of mature Populus tremuloides in declining stands in Alberta,Canada

Abstract. The coarse‐root dynamics of ramets of Populus tremuloides (aspen) were investigated with respect to persistence of the original root connections (roots of parent trees from which the ramets originated), the time of establishment of new roots at the base of the stem and the fate of the communal root system after death of individual trees. Parts of the root systems of three declining stands of aspen ramets were hydraulically excavated. From each stand, sections of all structural roots were collected at the base of live and dead trees and were analysed using dendrochronology techniques. Parent roots were identified in the root system of every tree. The trees initiated new structural roots shortly after suckering. Live roots were often connected to the stump of dead and decayed trees. Grafting was common, especially at or near the stumps. Death of trees along the parent roots over time did not seem to favour the entry of significant decay, nor promote breakage of the original root connections. Instead of becoming independent of the parent root system the ramets incorporated the parent roots into their own root systems, remaining interconnected.     

基因组水平的基因挖掘与功能分析方法的探讨

为了实现基因组中特定基因功能的注释,研究者提出一种新的思路,即利用对目的基因启动子上游的顺式元件的功能的分析,进一步来推断目的基因的功能。在此主要对基因组水平的基因挖掘与功能分析方法及其研究进展进行了探讨。     

Simple rules based on pile slope are used in the self organization of sand pile formation by <Emphasis Type="Italic">Pheidole oxyops</Emphasis> ants

We tested the hypothesis that slope influences where worker ants deposit excavated soil on piles near the nest entrance. We predicted that ants will deposit their load near the top of a pile where the slope changes from upward to downward, to prevent material rolling back towards the entrance. We tested this hypothesis by studying five natural colonies of Pheidole oxyops ants at a field site at S?o Sim?o, Brazil. At this site, each colony was dumping sandy soil excavated from its underground nest in a crescent-shaped pile c. 13 cm from and perpendicular to the nest entrance. Each nest was given an experimental sand pile of symmetrical curved cross section on a plywood platform that could be tilted 15 degrees up or down. From videos, the locations where individual ants dumped their soil loads were measured in relation to the inner (position = 0) and outer (position = 1) edges of the pile. When the platform was tilted down the ants deposited their loads significantly closer to the inner edge (0.458 ± 0.007) than when not tilted (0.530 ± 0.006). When the platform was tilted up the ants deposited their loads significantly further from the inner edge (0.626 ± 0.006) than when not tilted (0.522 ± 0.006). These results support the hypothesis that ants use pile slope in deciding where to dump their load. A similar rule is probably used in other ant species that place excavated soil in steep piles near the nest entrance. Received 5 February 2007; revised 10 June 2007; accepted 9 October 2007.     

An improved method for estimating original mineral contents in excavated bone using sulfur

Trace element analysis in excavated bones is complicated by the lack of a reliable index for estimating the original amount of bone material. In this study, we subjected modern human bones to alkali treatment to simulate aging. Alkali treatment of vertebrae with attached muscle did not affect sulfur (S) content; it increased the magnesium (Mg), phosphorus (P), and zinc (Zn) contents, and tended to decrease iron (Fe) content of the bones. When vertebrae cleaned of muscle were used, alkali treatment did not affect S and Fe contents but increased Mg, P, Ca, and Zn contents Ca and S contents were higher in excavated bones (200–1300 yr old) than in their surrounding soils. In contrast, S, Mg, and Ca contents per dry weight did not differ between the excavated bones and the alkali-treated modern bones. These results indicate that S can provide a more accurate index of excavated bones than the often-used Ca content or dry wt measures, especially for bones excavated from calcium-rich soils.     

Artificial nest site preferences of Black-capped Chickadees

ABSTRACT.   To facilitate study of the breeding biology of parids, Grubb and Bronson (1995; Condor 97: 1067–1070) designed artificial "snags" made from polyvinyl chloride (PVC) tubes. Because the cost of artificial snags is greater than that of traditional wooden boxes, we examined alternatives to PVC snags for attracting chickadees to artificial nesting sites. From 2005 to 2007, we compared the use of PVC snags and wooden nest boxes by Black-capped Chickadees ( Poecile atricapillus ) in Sapsucker Woods Sanctuary in Ithaca, New York. We also quantified the use of cavities with and without wood shavings. The probability of chickadee excavation was greater (60–70% per yr) in filled snags (with wood shavings) than in filled boxes (40–50%; logistic mixed model, P = 0.01), and chickadees initiated more nests in filled snags (25–30%) than filled boxes (15%; P = 0.03). Chickadees also initiated significantly more nests ( P = 0.03) in filled than unfilled boxes. Although wooden boxes filled with wood shavings were used more often by Black-capped Chickadees than unfilled wooden boxes, artificial snags filled with wood shavings were used most, were no more likely than boxes to be usurped by House Wrens ( Troglodytes aedon ), and were less likely than boxes to be occupied by mice. Thus, artificial snags may be the better option for investigators studying the breeding biology of chickadees.