No description available.

No description available.

An exploratory investigation of tree growth and climate relationships in Abies religiosa from Michoacan, Mexico, produced the first crossdated and standardized tree-ring chronology from the North American tropics. Pearson correlation coefficients and principal components response function analysis were employed. Results indicate that ring-width series from this species have moderately high signal-to-noise ratio (S/N = 13.42). A substantial percentage of the ring-width signal can be explained by instrumented monthly climate data, particularly spring precipitation and winter temperature. Although correlation between climate data and the tree-ring measurements indicate that growth of Abies religiosa is highly influenced by year-to-year climate variation, longer climate records and tree-ring chronologies are needed from this tropical region to improve understanding of climate -tree growth relationships, and for dendroclimatic reconstruction.

I propose an approach to provide 95% confidence intervals for a chronology of low-frequency tree-ring variation so that a level of significance or importance for trends can be inferred. The approach also visually reveals the portions of a chronology in which sample depth is so poor that low-frequency variation is not robustly estimated. A key characteristic of the approach is that it is essentially a reordering of the individual steps commonly used in constructing standard tree-ring chronologies; consequently, it is computationally simple for researchers who already routinely construct standard tree-ring chronologies. The most important ramification of the approach is that each year of the chronology has a distribution of smoothed index values with which to estimate confidence intervals around the chronology of low-frequency variation. It can be argued that the approach constitutes multiple significance testing of means, which causes the α level for the confidence interval to be unknown. Nonetheless, the approach is still useful in that it provides a way to evaluate the probable importance of low-frequency trends expressed in tree-ring chronologies.

No description available.

No description available.

This paper describes an interactive computer program which simulates daily cell growth and differentiation in a single radial file of tree cells. The growth processes are controlled by 22 model parameters, half of which are constants, the remainder time-dependent. The program user specifies the constants and the form of the time variations desired. The program computes daily values for the time-dependent parameters, and applies these values to the calculation of cell diameters, cell division, cell wall thickness, and ring width for each day of the growing season. Output is in tabular and graphical form. The tabular listing consists of the cell diameter at each position in the radial file, and for the xylem it also prints cell wall thickness and a relative density for each cell. The graphical output plots cell diameter, wall thickness, and relative density vs. file position. The program was designed primarily as an instructional tool and has been used for this purpose with good results. Because of its flexibility it has potential for research, and some possibilities for such use are discussed.

The basis for the selection of trees to be used in the production of dendrochronologies has long been an issue (Douglass 1946; Fritts 1976). In humid regions the common practice has been to use trees that appear to be in good health. As a part of a larger study involving the impact of ice storms on tree-ring increments (Travis 1989), we show that trees stressed as a result of ice damage produced a stronger climatic signal than nondamaged trees.

The "many fragments curse," a special case of the segment length curse, occurs in den- drochronology when time series are broken into fragments, either because of missing part of a sample (e.g., a rot pocket) or when a section of ring growth cannot be crossdated (e.g., a section with extremely suppressed growth and/or many rings absent). We exorcise this curse by inserting values to connect fragments of measurements. This technique permits fitting a single detrending curve to the connected series and thus preserves the low-frequency variance contained in the entire series. Inserted values are discarded after detrending and do not otherwise affect calculations of final corn- posite chronologies. As an example from junipers sampled at a site in Qinghai Province, China, 66 of 117 increment cores have nondatable sections of wood and one core has a gap of rotten wood between dated fragments. After connecting fragments by inserting values and then detrending, the chronology constructed from connected fragments has stronger century to multicentury scale variation than the chronology constructed from separate fragments. This approach is adapted to the library of computer programs developed for dendrochronological research under the auspices of the International Tree-Ring Data Bank.

Diss. (sammanfattning). Umeå : Sveriges lantbruksuniv. / Härtill 5 uppsatser.