Rates of decay in wood measured by carbon dioxide production

The applicability of two methods of respirometry to measurement of the carbon dioxide output of naturally decaying branches and wood of standing trees was studied. The Warburg respirometer was judged unsuitable for general use on decaying wood. A conductivity respirometer was found satisfactory. Carbon dioxide production was essentially unaffected by fragmentation suggesting that the measurements obtained are likely to be a valuable indication of decay in the intact tree or branch. The carbon dioxide production of samples was fairly stable when conditions were kept constant but responded promptly to increased or decreased moisture. Wood from branches infested with Polyporus tulipiferae in which moisture was increased from approximately 20%–50% (fresh weight basis) increased its carbon dioxide output over a 4-day period by some seven times. Comparable wood in which the moisture content was reduced from 45 to 20 % showed an almost linear reduction in rate over a similar period to about one-sixth the original rate. Rate of decay in stained and unstained zones of living trees showed no consistent effect of the stain. However, rates of decay in heart-rot of poplar caused by Fomes igniarius were only one-third those reported by Verrall (1937) for decay in culture.     

Testing models of female reproductive migratory behaviour and population structure in the Caribbean hawksbill turtle, Eretmochelys imbricata, with mtDNA sequences

Information on the reproductive behaviour and population structure of female hawksbill turtles, Eretmochelys imbricata , is necessary to define conservation priorities for this highly endangered species. Two hypotheses to explain female nest site choice, natal homing and social facilitation, were tested by analyzing mtDNA control region sequences of 103 individuals from seven nesting colonies in the Caribbean and western Atlantic. Under the social facilitation model, newly mature females follow older females to a nesting location, and subsequently use this site for future nesting. This model generates an expectation that female lineages will be homogenized among regional nesting colonies. Contrary to expectations of the social facilitation model, mtDNA lineages were highly structured among western Atlantic nesting colonies. These analyses identified at least 6 female breeding stocks in the Caribbean and western Atlantic and support a natal homing model for recruitment of breeding females. Reproductive populations are effectively isolated over ecological time scales, and recovery plans for this species should include protection at the level of individual nesting colonies.