Chris L. Beadle

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

Abstract 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.

Effects of green pruning on growth and stem shape of Eucalyptus nitens (Deane and Maiden) Maiden

An experiment was established in two high quality Eucalyptus nitens Deane and Maiden (Maiden) plantations in Tasmania. At the start of the experiment the trees were three years old and the plantations were on the point of canopy closure. Selected trees were pruned to remove 0, 50% or 70% of the lower green crown length, and each was surrounded by eight unpruned trees. The 50% treatment had no impact on height or diameter increment in the two years following treatment, but removal of 70% of the lower crown length resulted in significant decreases in both height and diameter increment. There were no changes in the height of 50%-pruned trees relative to the height of surrounding unpruned trees (relative height), and it was concluded that dominance would not be affected by this treatment. The relative height of 70%-pruned trees was less at one site, and this treatment may result in loss of dominance. Stem taper was generally unaffected by either pruning treatment. Changes in stem form were restricted to trees in the 70% pruning treatment and were only transient. It was concluded that removal of 50% of the lower green crown length is an appropriate level of pruning for the species provided that growth rates are rapid and pruning is timed to coincide with canopy closure. Since dominance was unaffected by this level of pruning, thinning at the time of pruning is unnecessary. It may be possible to minimise the impact on growth of higher levels of pruning by thinning at the time of pruning.

Temporal variation of tannins (galloylglucoses), flavonols and anthocyanins in leaves of Eucalyptus nitens seedlings: implications for light attenuation and antioxidant activities

Leaves of Eucalyptus nitens (Deane & Maiden) Maidenwere sampled during establishment of seedlings that were deprived of nutrientsor fertilised at planting. Extracts were analysed for polyphenolic compoundsusing high pressure liquid chromatography (HPLC) in conjunction with UV diodearray and electrospray ionisation mass spectrometry (ESI-MS) with negative iondetection as well as direct MS injection. The presence of quercetin, rutin,sideroxylonal A and B andpenta-galloylglucose were confirmed by comparison with standards. Othergalloylglucoses were identified by first principles. Galloylglucoses comprisedabout 75% of polyphenolics. Quercetin and various quercetin glycosidescomprised ca 85% of flavonols. The anthocyanins,cyanidin-3-glycoside and cyanidin-3,5-diglycoside were identified from directinjection MS data. HPLC–ESI-MS was found to be a superior analyticaltechnique compared to conventional HPLC–UV diode array detection due toco-elution of peaks under UV. Temporal variation of anthocyanins may berelated to the severity of cold-induced photoinhibition. Changes ingalloylglucoses and flavonols were similar with time and related to levels offoliar nitrogen. The suitability of HPLC–ESI-MS for the study of foliarpolyphenolics, the phenolic constitution of E. nitensfoliage, and temporal variation of the phenolic constituents during a seedlingestablishment period of 29 weeks are demonstrated.

Photosynthetic responses of Eucalyptus nitens (Deane and Maiden) Maiden to green pruning

Abstract Three-year-old Eucalyptus nitens (Deane and Maiden) Maiden trees and 1-year-old ramets of a single clone of E. nitens were pruned to remove 0, 50% or 70% of the green crown length. This was equivalent to removal of 0, 55% or 88% of foliage area of trees, and 0, 77% or 94% of foliage area of ramets. CO2 assimilation (A) and stomatal conductance (gs) were measured at constant illumination in five height zones and three foliage-age classes of trees over a 16-month period following pruning. Foliar nitrogen (N) and phosphorus (P) concentrations were determined for each measurement time during the first 12 months of the experiment. In ramets A and gs were measured in four height zones and two foliage-age classes over a six-week period, and N and P concentrations were measured only once, at the end of the experiment. Rates of A increased by up to 175% following pruning. This response occurred throughout the canopy irrespective of position in the crown or foliage age. The magnitude of the response was generally greater in ramets than in trees, and increased with increasing severity of pruning. The initiation of the response was later, and the duration of the response was longer, in trees than ramets. In the lower crown of trees there was evidence of delayed senescence following pruning. Photosynthetic enhancement was not related to changes in foliar N concentrations. The ratio of A/N increased in many zones following pruning, especially after more severe defoliation. There was no evidence that changes in P concentrations were responsible for the result. The increases in A may have been related to changes in gs, as maximum values of gs were greater, and the ratio of A/gs was generally lower, in pruned than unpruned plants.

The impact of timing and duration of grass control on growth of a young Eucalyptus globulus Labill. plantation

Interference by an introduced grass, Holcus lanatus L. (Yorkshire fog grass) in a young E. globulus (Tasmanian blue gum) plantation was investigated. The objectives were to determine (1) the ‘critical period’ of competition, and (2) how the timing and duration of competition was related to the interaction between tree growth and resource availability. This was investigated during the first two years of establishment. Weed interference was severe with height and diameter growth of weedy trees being 52% and 40% of weed-free trees, respectively, at age two years. Most growth losses occurred during the first year. The critical period of weed interference was from planting to age 18 m and effective weed control was required for this period to maximise tree growth potential. The application of nitrogen to weedy trees promoted a significant growth response suggesting that competition for nitrogen was occurring. There was no significant response to level of irrigation. The use of critical period analysis is discussed.

Allometric relationships for Eucalyptus nitens (Deane and Maiden) Maiden plantations

Abstract Allometric relationships between stem, leaf area and crown dimensions were determined for Eucalyptus nitens (Deane and Maiden) Maiden using 81 trees sampled from 13 post-canopy closure sites and 34 trees sampled from 6 pre-canopy closure sites. These sites differed in site quality, stand age, fertiliser treatment, stand density and levels of weed infestation. Overall, tree age ranged from 2 to 13 years, tree height from 1.4 to 26.1 m and diameter at breast height from 0.6 to 38.7 cm. Pre-canopy closure trees exhibited site-specific relationships which were to some extent confounded with tree age. However, post-canopy closure trees had relationships which were independent of site, age and silvicultural treatments. Strong relationships between structural components were found for both stem and crown. Stem diameter at breast height was non-linearly related to tree height and crown length. Stem sapwood area (breast height or crown base) could be predicted from stem cross-sectional area. For post-canopy closure trees, a functional relationship between sapwood area (breast height and crown base) and leaf area was site-independent. The lack of specificity in terms of both site and management techniques enables these relationships to be applied generally to E. nitens plantations in Tasmania.

Evaporatranspiration and growth of two contrasting species of eucalypts under non-limiting and limiting water availability

Abstract Changes in root zone water storage between 0 and 1 m depth were monitored at 14-day intervals under contrasting canopies of Eucalyptus nitens (a gum) and Eucalyptus delegatensis (an ash) during their fourth and fifth years of growth and periods of non-limiting and limiting water availability, respectively. The leaf area index of the gum remained approximately double that of the ash throughout this time. Stem volume growth differed by factors of 1.8 and 2.0 between E. nitens and E. delegatensis while total water use differed by factors of 1.1 and 0.9 in two periods, respectively. A cumulative plot of volume growth as a function of total evapotranspiration suggested that stem volume growth of E. nitens was less sensitive to severe water stress than that of E. delegatensis .

Cold-induced photoinhibition and foliar pigment dynamics of Eucalyptus nitens seedlings during establishment

The effects of cold-induced photoinhibition on chlorophyll and carotenoid dynamics and xanthophyll cycling in Eucalyptus nitens (Deane and Maiden) Maiden were assessed between planting and 32 weeks after planting. The seedlings were fertilised or nutrient-deprived (non-fertilised) before planting and shaded or not shaded after planting. The experimental site was 700 m a.s.l., which is considered marginal for establishment of E. nitens plantations in Tasmania due to low mean annual minimum temperatures. Low temperature–high light conditions caused a reduction in variable to maximal chlorophyll fluorescence ratio (F v /F m ), which was more pronounced in non-fertilised than in fertilised seedlings. Shadecloth shelters alleviated this depression. Except in shaded fertilised seedlings, F v /F m did not recover to the level before planting until after 20 weeks. Total chlorophyll content was initially reduced in shaded treatments but subsequently increased with increasing temperatures and F v /F m. Total xanthophyll content and xanthophylls per unit chlorophyll remained relatively constant in fertilised seedlings but decreased in non-fertilised seedlings within 2 weeks after planting. Total xanthophyll and xanthophylls per unit chlorophyll subsequently recovered in non-shaded, non-fertilised seedlings with increasing temperatures and F v /F m. Diurnal [yield and non-photochemical quenching (NPQ) and seasonal (F v /F m) variation in chlorophyll fluorescence parameters were not reflected in xanthophyll cycling during the period of most severe photoinhibition. This result may indicate that chlorophyll–xanthophylls protein complexes form in winter-acclimated E. nitens foliage as have been demonstrated to occur in Eucalyptus pauciflora Sieb. ex Spreng. (Gilmore and Ball 2000, Proceedings of the National Academy of Sciences USA 97, 11098–11101).

Growth and stem form responses of plantation-grown Acacia melanoxylon (R. Br.) to form pruning and nurse-crop thinning

Abstract This study investigated the feasibility of silvicultural intervention in Acacia melanoxylon (R. Br.) plantations grown with Pinus radiata (D. Don) nurse crops, to improve stem form and growth rate. The objective of the study was to evaluate silvicultural options for managing a nurse-crop to avoid suppression but improve stem form of A. melanoxylon . Using a 5-year-old A. melanoxylon – P. radiata plantation, various levels of form pruning of the A. melanoxylon were tested by removing prescribed proportions of leaf area from treatment trees. In addition, a range of thinning treatments was imposed on the nurse-crop. The effects of these treatments on A. melanoxylon growth rate, stem form, rate of crown development, and canopy light environment were assessed. Altering the canopy structure of the plantations by thinning the P. radiata nurse-crop had a positive effect on A. melanoxylon diameter growth. However, less desirable changes were also evident following thinning of the P. radiata , such as reduced height increment, loss of dominance and a greater incidence of large branches in A. melanoxylon trees. Appreciable changes in the light environment of the A. melanoxylon crowns occurred only after more than 50% of P. radiata trees were removed. Crowns of A. melanoxylon trees pruned of 50% of their foliage area took 12 months to recover to pre-pruning foliage area levels. Form pruning A. melanoxylon significantly reduced growth when 50% of foliage area was removed. Improvements in form by pruning were transient in nature, highlighting the need for on-going, low-intensity form pruning treatment to establish good stem form. The rapid deterioration in form after heavy thinning of the nurse-crop indicated the need to establish form before reducing nurse-crop competition.

Growth and water use of Eucalyptus globulus and E. nitens in irrigated and rainfed plantations

Summary Early patterns of growth and water use of Eucalyptus globulus subsp globulus Labili, and Eucalyptus nitens (Deane and Maiden) Maiden were measured for the first four years in a plantation established on a low rainfall site in south-east Tasmania. Half the plantation was irrigated to maintain soil water deficits at levels where available water did not limit growth: the other half was subjected to a series of water stress cycles which were interrupted by rainfall or terminated by supplementary irrigation to end severe drought stress. Height of E. globulus was greater than that of E. nitens irrespective of water status. For both height and diameter, differences due to levels of available water remained insignificant until the third year of growth. Increments in volume were significantly higher in E. globulus than E. nitens in the third and fourth year of growth and these differences were more apparent in the rainfed than the irrigated treatment. However there were no differences in water use between ...