Nature’s hierarchical materials

48 pags., 25 figs. Available online 21 December 2013. The definitive version is available at: http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1097-0088

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Standardized precipitation evapotranspiration index (SPEI) revisited: parameter fitting, evapotranspiration models, tools, datasets and drought monitoring

Wood Formation in Trees

Several simplified design procedures for solar energy systems require monthly average meteorological data. Monthly average daily totals of the solar radiation incident on a horizontal surface are available. However, radiation data on tilted surfaces, required by the design procedures, are generally not available. A simple method of estimating the average daily radiation for each calendar month on surfaces facing directly towards the equator has been presented by Liu and Jordan [1]. This method is verified with experimental measurements and extended to allow calculation of monthly average radiation on surfaces of a wide range of orientations.

Calculation of monthly average insolation on tilted surfaces

This review of late-Holocene palaeoclimatology represents the results from a PAGES/CLIVAR Intersection Panel meeting that took place in June 2006. The review is in three parts: the principal high-resolution proxy disciplines (trees, corals, ice cores and documentary evidence), emphasizing current issues in their use for climate reconstruction; the various approaches that have been adopted to combine multiple climate proxy records to provide estimates of past annual-to-decadal timescale Northern Hemisphere surface temperatures and other climate variables, such as large-scale circulation indices; and the forcing histories used in climate model simulations of the past millennium. We discuss the need to develop a framework through which current and new approaches to interpreting these proxy data may be rigorously assessed using pseudo-proxies derived from climate model runs, where the `answer' is known. The article concludes with a list of recommendations. First, more raw proxy data are required from the diverse disciplines and from more locations, as well as replication, for all proxy sources, of the basic raw measurements to improve absolute dating, and to better distinguish the proxy climate signal from noise. Second, more effort is required to improve the understanding of what individual proxies respond to, supported by more site measurements and process studies. These activities should also be mindful of the correlation structure of instrumental data, indicating which adjacent proxy records ought to be in agreement and which not. Third, large-scale climate reconstructions should be attempted using a wide variety of techniques, emphasizing those for which quantified errors can be estimated at specified timescales. Fourth, a greater use of climate model simulations is needed to guide the choice of reconstruction techniques (the pseudo-proxy concept) and possibly help determine where, given limited resources, future sampling should be concentrated.

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High-resolution palaeoclimatology of the last millennium: a review of current status and future prospects:

Daily increments in stem radius were determined from hourly dendrometer measurements in each of three irrigated Eucalyptus nitens and E. globulus trees. Multiple regressions determined from daily weather variables accounted for 40–50% of the variance in increment. The use of weather variables lagged by 1–2 days increased the variance explained. The diurnal variation in stem radius was resolved into three mathematically defined phases: shrinkage, recovery and increment. The positive daily net increment in stem radius, by definition, occurred in the increment phase. Average weather conditions during this phase (predominantly night-time) did not explain any more variance in increment than the average daily conditions, determined over a 24 h period. Daily increment was resolved into a rate of stem radius increase during the increment phase and the duration (hours) of that phase. Significant species by month interactions were evident with growth in summer characterised by faster rates of stem expansion over shorter time periods within each diurnal cycle. E. nitens tended to have longer increment phases in spring and autumn, and faster phase rates in autumn than E. globulus. Interactions between weather variables and cambial growth were complicated and varied over the year. The correlation between temperature and stem growth varied from positive in spring to zero or negative during summer. The data indicate a need to understand weather-by- climate interactions at the level of whole tree physiology in order to fully understand the effect of weather on cambial activity and therefore stem increment and wood properties.

Daily stem growth patterns in irrigated Eucalyptus globulus and E. nitens in relation to climate.

The use of precision dendrometers in research on daily stem size and wood property variation: A review

Variation in tracheid cross-section dimensions has been mapped in a 19 year old radiata pine tree. An instrument recently developed for the rapid estimation of transverse tracheid dimensions was used for the analysis. Sixty radii (four directions at each of fifteen heights) were processed. Variation was mapped for properties important to the pulp and paper industry: wood density, tracheid perimeter, coarseness and wall thickness. In this tree, coarseness, wall thickness and density trends were approximately linear from pith to bark, and the rate of rise was similar at all sampling heights. As a result, variation of these properties in the three was approximately cylincrically symmetric. Average coarseness, density and wall thickness fell by 25% from the 0.8 metre level to the 20 metre level in the tree. Average tracheid perimeter was almost independent of sampling height. At breast height, coarseness rose by 86% from pith to bark (350 to 650 μg m -1 ), density rose by 45% (380 to 550 kg m -3 ) and wall thickness by 57% (2.1 to 3.3 μm). Unweighted breast height core properties for this tree were similar to volume-weighted whole tree properties above breast height. Correlations between properties such as coarseness and wall thickness were strong when ring averages or trends were considered, but poor within individual tree rings. Understanding of the mechanisms of short term regulation of tracheid properties should allow increased selectivity in the silvicultural and genetic control of individual properties

Rapid measurement of variation in tracheid transverse dimensions in a radiata pine tree

Summary Eucalyptus globulus Clones Path analysis Wood quality Wood density Fibre length Microfibril angle Handsheet Tensile index Tear index Paper strength Pulp yield Fibre length, microfibril angle and wood density were measured in eight-year-old Eucalyptus globulus clones planted on three different sites. Samples were chipped and pulped, and the pulps beaten prior to preparation of 60g/m 2 handsheets. Eleven physical handsheet properties, together with pulp freeness, were measured using standard methods. Direct relationships between wood properties and pulp/paper properties were studied using path analysis. Fibre length had a strong, direct effect on tear index, bending stiffness, freeness, pulp yield and active alkali consumption. Wood density was a strong predictor of most handsheet properties: high density woods produced bulkier, more porous sheets with higher bending stiffness, while lower density woods produced smoother, denser sheets with higher tensile strength. The effect of microfibril angle was small and more evident in handsheets made from beaten pulp.

Direct Effects of Wood Characteristics on Pulp and Handsheet Properties of Eucalyptus globulus

The relationships between wood anatomy in standing trees and the strength of boards were examined in Pinus radiata D. Don (thinned vs thinned and fertilized) at 2 contrasting sites. Fertilizer treatments were applied after mid-rotation thinning. Logs were taper sawn and boards, near the pre-treatment / post-treatment boundary, subjected to acoustic and strength assessment. Average wood property data from a 12-mm increment core obtained prior to harvest, was extracted from the relevant portion of the radius.In general, fertilizer resulted in lower density, higher microfibril angle (MFA) and slightly lower stiffness. However, stiffness was still relatively high as the affected wood was from the more mature portion of the radius. SilviScan density and MFA data were good predictors of stiffness. Acoustic measurements on boards were strongly correlated with board stiffness. Path analyses explained up to 45% of the variance in stiffness, as a function of estimated MOE and log sweep.

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Geoffrey M. Downes

Papers

Daily stem growth patterns in irrigated Eucalyptus globulus and E. nitens in relation to climate.

The use of precision dendrometers in research on daily stem size and wood property variation: A review

Rapid measurement of variation in tracheid transverse dimensions in a radiata pine tree

Direct Effects of Wood Characteristics on Pulp and Handsheet Properties of Eucalyptus globulus

Relationship between wood density, microfibril angle and stiffness in thinned and fertilized pinus radiata