Allometric models for estimating aboveground biomass in tree sprouts of three dendroenergetic crops

Recurrent problems have been observed for biomass measurement in tree sprouts, mainly dueto differences in patterns of biomass distribution and the bias generated by using models for mature trees.The objective of this research was to evaluate models to estimate aboveground biomass in sprouts from two-year-old stumps of Short Rotation Woody Crops (SRWC) used for energetic purposes. The study was conducted in Central Chile (Bío-Bío region) under a complete block design and four replications.Three plant species were included: Eucalyptus globulus, E. denticulata, and Acacia dealbata, established in three population densities (5,000, 10,000 and 15,000 trees per ha). Two groups of nonlinear models wereused on three independent variables: root collar diameter (squared mean of two dominant stems), height (mean of two dominant stems) and number of epicormic stems. In the allometric model, the total aboveground biomass and the aboveground biomass by component were explained as the product of the mean square of the root collar diameter, mean height of the two dominant new sprouts and total number of epicormic sprouts as the predictive variable. Values of coefficient of determination (R2) ranged from 0.78 to 0.95 and RMSE ranged from 168 to 913 g. The species of E. globulus showed higher RMSE for biomass estimation in the all components except the branch component. The inclusion of dummy variables to identify the differences in each parameter of the models explained the seasonalityof the biomass accumulation in tree sprouts at 10, 21, and 31 months of age, improving the model goodness of fit RMSE by 27%. Accurate prediction of sprouts aboveground biomass was obtained by the models only evaluating the two dominant epicormic sprouts in the stump, avoiding the need of individual sprouts evaluation or using destructive methods for biomass measurement.

Vegetative rescue of Cedrela fissilis Vell. by the rooting of cuttings from epicormic and canopy sprouts

ABSTRACT: Cedrela fissilis is a species of great genetic diversity, with low population density and seminal propagation, which causes difficulties in the vegetative propagation process. This research evaluated the vegetative rescue and propagation of stem cutting rooting originated from epicormic and canopy sprouts of C. fissilis. For this, the induction of epicormic sprouts was evaluated 52 days after the complete girdling and semi-girdling 20 and 40 cm from the ground, and no girdling treatment, during spring (2018), summer (2018) and autumn (2019). The variables evaluated were, survival (%), sprouting (%), number, length (cm) and diameter (mm) of sprouts. The cuttings were made from spring epicormic sprouts, divided in two categories: 10 cm cuttings placed vertically in pits and 5 cm cuttings placed horizontally in furrows. The canopy sprouts were collected in the summer, then cut in apical and intermediate cuttings (15 cm). After 60 days, the cuttings were evaluated in survival (%), rooting (%), callus (%), average number and length of roots (cm). Results showed that only the complete girdling produced sprouts (average >67%) with no difference between 20 and 40 cm heights, with a greater number of sprouts during spring. The cuttings from epicormic sprouts, planted vertically in pits presented higher percentage of rooting (44%) than cuttings planted horizontally in furrows (17%). Cuttings from the canopy had inconsiderable rooting (apical - 2%; intermediate - 0%). The girdling periods influences the number of epicormic sprouts and its use for cutting was more efficient in rooting.

Vegetative rescue of Camu-Camu from epicormic sprouts of detached branches

The cloning of camu-camu by cuttings has shown distinct and sometimes controversial results. The use of juvenile materials has been indicated for difficult rooting species. Thus, this work aimed to evaluate the emission of epicormic sprouts in mega-cuttings and cuttings of detached branches, as well as the cloning of camu-camu from these sprouts. The research was developed by conducting four experiments, the first two being related to the emission of epicormic sprouts, while the others referred to the cloning of camu-camu from these sprouts. In experiments evaluating sprout emission, the following factors were studied: mother plant x branch position; mother plant x substrate. In the other tests, using standard cuttings with two pairs of leaves made from epicormic sprouts, the following factors were evaluated: mother plant x cutting type x indolbutyric acid concentration (IBA); mother plant x hydroretentive polymer x environment. The number and speed of sprouts vary depending on the mother plant. IBA has negative influence on cutting and cuttings from the lower portion of sprouts have greater rooting potential than those from the upper portion. Environment with intermittent mist irrigation is more suitable for the propagation of camu-camu by cuttings. Vegetative rescue by means of epicormic sprouts in mega-cuttings and cuttings of detached branches presents potential application for the clonal propagation of camu-camu, requiring improvement in order to increase efficiency.

Methods of combating Acer negundo L. in specially protected natural areas

The possibility of using chemical and mechanical methods to control the undesirable growth of the invasive species Acer negundo L. at the expositions of the Main Botanical Garden of the Russian Academy of Sciences, which has the status of a specially protected natural area, was studied. It was found that treatment of freshly cut stumps of A. negundo with glyphosphate in concentration of 7.2 g/l causes death of 65% of plants. In the rest of the specimens of A. negundo from this option the amount of growing epicormic sprouts decreased by 5.2 times in comparison with the usual cutting (control).

Callery pear (Pyrus calleryana) Response to Fire in a Managed Prairie Ecosystem

Callery pear (Pyrus calleryana Decne.) was introduced to North America as an ornamental tree in the early 1900s. Due to widespread planting, P. calleryana has become common throughout the eastern United States and has invaded natural areas, especially disturbed areas. Prescribed fire is a common management technique in prairie ecosystems to mimic natural disturbances. We tested the effectiveness of prescribed fire as a control technique for P. calleryana in a managed prairie system. Fire top-killed all established P. calleryana individuals. However, these individuals responded to fire with 3 to 4 epicormic sprouts each. Similar sprouting behavior occurred in 2-yr-old seedlings. Exposed seeds, fruits, and 1-yr-old seedlings were killed by fire. Established P. calleryana were single-stemmed individuals before exposure to fire. After the prescribed fire, they all were multistemmed, which increased the potential flower-bearing stems within the prairie. We conclude that fire alone is not a suitable technique for managing P. calleryana invasion. Cut and herbicide application methods are labor-intensive. However, combining cut and spray methods with prescribed fire may be effective. Fire removes standing grass and forb biomass, leaving exposed P. calleryana stems, which would make locating individuals and directly applying herbicides easier.

Epicormic sprouting of pruned western larch

Western larch (Larix occidentalis Nutt.) trees in western Montana, U.S.A., were monitored for 6 years following pruning to assess incidence of epicormic sprouting. Trees were pruned to either 2.4 or 5.5 m. Epicormic sprouts were more prevalent in smaller diameter trees and in trees pruned to shorter live crown lengths than larger or longer crowned trees. Number of sprouts declined since pruning, but over 30% of trees still had epicormic sprouts 6 years after pruning. Sprouts that did not extend from the bole were prone to becoming dormant or dying over time. Extended sprouts were more persistent and will probably form wood-quality defects that remain outside the defect core. Pruning of western larch may still be successful for enhancing clearwood production if trees are pruned to retain at least a 50% live crown ratio and if pruning is delayed until trees reach about 16 cm diameter at breast height for a short pruning lift (2.4 m) or 22 cm for a higher pruning lift (5.5 m).

Epicormic Sprouts from Branch Segments of Mature Juglans nigra L. as an Explant Source for in Vitro Culture

At monthly intervals for 1 year, one branch was removed from the lower crown of three 30-year-old trees of black walnut (Juglans nigra L.). The basal 1.3 m of each branch was cut into four 32-cm-long segments that were placed horizontally in shallow plastic trays filled with perlite and watered daily with tap water. Branch segments cut early in the dormant season (29 Sept., 31 Oct., or 1 Dec.) or shortly after flushing (6 June) produced few, if any, epicormic sprouts. Approximately half the branch segments cut on 3 Jan. or 3 Feb. produced one sprout that elongated slowly. Most branch segments cut in the late dormant season (2 Mar., 30 Mar., 3 May) or growing season (5 July, 4 Aug., 6 Sept.) produced one or two sprouts >20 mm long. To prepare explants for in vitro culture, the terminal 2.5 cm was harvested when sprouts exceeded 3.0 cm, trimmed of all leaves, and disinfested. Explants were placed vertically in liquid Long & Preece (LP) medium supplemented with 3% sucrose, 0.3 μM TDZ, 0.05 μM IBA, and 1 μM BA. When shoots began to elongate (4 to 6 weeks), they were then placed horizontally on agar-solidified LP medium with liquid LP overlays to induce axillary shoot proliferation. Advantages of forcing epicormic sprouts on large branch segments are: 1) they can be a source of in vitro explant material for 6 to 7 months a year, 2) aseptic cultures can be easily obtained, 3) shoots from the base of branches may show more juvenility than shoots forced from branch tips, 4) softwood shoot wilting is not a problem as with forcing shoots from branch tips, 5) the procedure does not require preparing and changing forcing solutions, and 6) branch segments should have more stored food than dormant branch tips for forcing softwood growth.