Aboveground Fresh Weight Research Articles

A retrospective early test of <i>Pinus sylvestris</i> seedlings grown at wide and dense spacing

Stored seeds from 30 open-pollinated families that had been field tested for 28 years provided a retrospective opportunity to assess the efficiency of early testing in Scots pine (Pinus sylvestris L.). Seedlings height at the end of first (HGP1), second (HGP2) and third growth period (HGP3), and in the third growth period, leader length (LEADER3), basal stem diameter (DIA3), number of stem units (NSU3), mean stem unit length (MSUL3), aboveground fresh weight (AGFWT3), stem dry weight (STDWT3), and shoot and needle dry weight (SHNDWT3) were studied under wide and dense spacing. Families differed at the 1 or 0.1% level of probability. Differences between spacing were significant at the 0.01% level of probability for all traits measured in the third growth period. Families interacted significantly with spacing for HGP2, HGP3, LEADER3, AGFWT3, SHNDWT3 and MSUL3. Interactions were due to rank changes and the interaction component of variance varied from 26 to 96% of the family variance. Estimates of hi2 over wide and dense spacing ranged between 0.23 ± 0.11 (HGP2) and 0.51 ± 0.14 (NSU3). Spacing did not alter the variance structure, hi2 for each trait under wide or dense spacing were similar. However, spacing affected the phytotron-field genetic correlations. The average of 80 genetic correlation estimates was 0.52 under wide spacing and 0.29 under dense spacing. Averaged over eight field traits, the efficiency of indirect juvenile selection for the field traits indirect-direct selection percentage ranged from -15% for NSU3 under dense spacing to 99% for HGP3 under wide spacing.

Comparison of formulae for biomass content determination in a tropical rain forest site in the state of Pará, Brazil

The aboveground biomass content of a region can be estimated by either direct or indirect methods. The direct method corresponds to sampling the biomass content by weighing and extrapolating results to larger areas. It is a destructive and very laborious procedure. The indirect method utilizes formulas whose predictor parameters are obtained from forest inventories. Forest inventories are conducted with the purpose of planning exploitation and land use, and the data derived from inventory are frequently not suitable for biomass estimation. Problems with both these methods increase in the Amazon region, where little information is available on forest biomass. The objective of this paper is to compare a number of biomass equations taken from previous studies and establish an appropriate mathematical formula to estimate the vegetation weight of a particular region in the Amazon forest. A 0.2 ha area of `terra firme' forest was chosen for the comparison. This effort was part of a major forest clearing experiment conducted in Tomé Açu, a town located 250 km south of Belém, the capital of the Brazilian state of Pará. The entire biomass in the 0.2 ha area was weighed. A detailed inventory was carried out in the area prior to the cut and then the biomass was estimated with the inventory data inserted in the selected equations. Fourteen different biomass equations taken from previous studies were used. A comparison of the data of real mass and the mass obtained through the application of the fourteen formulas indicated that the two formulas more suitable for the region are given by (a) FW= αD β H γ, where FW is total fresh weight (kg), D the diameter at breast height (cm), H the total height of the tree (m) and α, β, and γ the regression coefficients, equal to 0.026, 1.529, and 1.747, respectively, and (b) FW= αD β/(1− M), where α and β are 0.465 and 2.202, respectively, and M the moisture content, defined in terms of mass of moisture per unit mass of fresh biomass. The aboveground fresh biomass weight predicted by the above equations were within ±0.6% of the weight determined in the field.

Reproductive Development in Evergreen vs. Deciduous Blueberry Production System

Two cultivars of southern highbush blueberry (Vaccinium corymbosum interspecific hybrid) were grown in containers under the traditional deciduous production system, or the dormancy-avoiding evergreen production system. In the dormancy-avoiding system, plants are maintained evergreen and do not enter dormancy in the winter. This alleviates the chilling requirement, thus extending the potential growing area of blueberries into subtropical regions. Plants in the evergreen production system were maintained in active growth through weekly or biweekly N fertilization (≈21–23 g N/ plant per year). Keeping foliage through the year lengthens the duration of the photosynthetic season of the plant and is hypothesized to improve the carbohydrate (CHO) status of the evergreen plants. This, in turn, may decrease source limitations to reproductive development and potentially increase fruit number and/or size. In both cultivars, the evergreen production system advanced the time of anthesis by 3 to 4 weeks compared to the deciduous production system. Plants in the evergreen system initiated 10% to 25% more flower buds than plants in the deciduous system, depending on cultivar. Average leaf area, leaf fresh weight, total above-ground fresh weight, bud density, and cane length were greater in the evergreen plants than deciduous. The evergreen production system increased plant fresh weight and flower bud number compared to the deciduous system, and may ultimately increase yield.

Biomass and litter dynamics in a Melaleuca forest on a seasonally inundated floodplain in tropical, northern Australia

Litterfall from a Melaleuca forest was investigated as part of chemical cycling studies on the Magela Creek floodplain in tropical, northern Australia. The forest contained two species of tree, Melaleuca cajaputi and Melaleuca viridiflora, with a combined average density of 294 trees ha−1. The M. viridiflora trees had diameter breast height measurements ranging from 11.8 to 62.0 cm, median class 25.1–30.0cm and a mean value of 29.2±1.0 cm, compared to 13.0 to 66.3 cm, 30.1−35.0cm and 33.5±1.0cm for M. cajaputi trees. A regression model between tree height, diameter breast height and fresh weight was determined and used to calculate average tree weights of 775±1.6kg for M. viridiflora and 1009±1.6kg for M. cajaputi, and a total above-ground fresh weight of 263±0.3t ha−1. The weight of litter recorded each month on the ground beneath the tree canopy ranged from 582±103 to 2176±376 g m−2 with a monthly mean value of 1105±51 g m−2. The coefficient of variation of 52% on this mean indicates the large spatial and temporal variability in litter distribution over the study site. This variability was greatly affected by the pattern of water flow and litter transport during the Wet season. Litterfall from the trees was evaluated using two techniques - nets and trays. The results from these techniques were not significantly different with annual litterfall collected in the nets being 705 ± 25 g m−2 and in the trays 716±49 g m−2. The maximum monthly amount of litterfall, 108 ±55g m−2, occurred during the Dry season months of June–July. Leaf material comprised 70% of the total annual weight of litter, 480±29 g m−2 in the nets and 495 ± 21 g m−2 in the trays. The tree density and weight of litter suggest that the Melaleuca forests are highly productive and contribute a large amount of material to the detrital/debris turnover cycle on the floodplain.

Evaluation of Preemergent Herbicide Phytotoxicity to Tissue, Culture-propagated `Heritage' Red Raspberry

Five greenhouse and two Geld experiments were conducted to evaluate tissue culture-propagated (TC) raspberry (Rubus idaeus cv. Heritage) sensitivity to preemergent herbicides. Plant performance was measured by plant vigor, above-ground fresh weight, root development, and primocane number. Simazine and oryzalin caused significant injury to newly planted TC raspberry plants in greenhouse and field experiments. The severity of injury was generally linear with respect to herbicide rate, but no appreciable differences in injury were observed between the granular and spray applications. Napropamide wettable powder caused some foliar injury, but plants recovered within one growing season and growth was equal or superior to the hand-weeded controls. The granular formulation of napropamide produced similar results, but did not cause the initial foliar burn. Pre-plant dipping of roots into a slurry of activated carbon did not prevent simazine or oryzalin injury, but injury was reduced when herbicide applications were delayed. Simazine applied 4 weeks after planting was not Injurious, and oqzalin applied 2 or 4 weeks after planting caused some foliar injury, hut no reduction in plant fresh weight. Delayed treatments of napropamide increased foliar injury. Herbicide tolerance of tissue-cultured plantlets appeared to be less than that of conventionally propagated plants. Chemical names used: N,N-diethyl-2-(1-napthalenyloxy)propanamide (napropamide), 4-(dipropylamino)-3,5-dinitrobenzenesulfonamide (oryzalin), 6-chloro-N,N'diethyl-1,3,5-triazine-2,4-diamine (simazine).

Cut‐Off, Break‐Over, and Defoliation Effects on a Determinate Soybean Cultivar1

AbstractExtensive research has been conducted on the response of indeterminate soybeans [Glycine max(L.) Merr.] to different types of plant damage, but information on the effect on determinate growth types is limited. This research compared the responses of a determinate soybean cultivar to different intensities of cut‐off, break‐over, and defoliation at five stages of plant growth. The experiments were conducted on a Captina silt loam (fine silty, mixed, Typic Fragiudnlt) during 1981 and 1982 at Fayetteville, AR. Plants were cut off at the point that removed half fresh weight and defoliated below the cut, broken over at the point that divided the aboveground fresh weight in half and defoliated below the break, or completely defoliated. Treatments were applied to 33,66, or 100% of the plants at growth stages V10, R2, R3, R4, and R5. Yields generally were not reduced when 33% of the plants were treated. The cut‐off treatments generally caused greater yield reduction than break‐over or defoliation; defoliation generally caused a greater yield reduction than breakover when 66 or 100% of the plants were damaged. Yield reductions were greater when treatments were imposed at progressively later growth stages. Cut‐off and defoliation influenced seed weight and date of maturity more than break‐over, especially when all plants were treated. Seed weight was reduced when yield reductions were severe, but the loss in seed weight did not account for all the yield loss. Maturity was delayed up to 2 weeks by treatments at R2, R3, and R4, and hastened by treatments at R5.

DIFFERENTIAL GROWTH AND COMPETITIVE ABILITY OF Amaranthus retroflexus, A. powellii AND A. hybridus

The frequency of occurrence of Amaranthus powellii and A. hybridus relative to that of A. retroflexus in agricultural fields in southwestern Ontario is increasing. Rates of germination and growth and development of the three species were compared at 28/22 °C and 22/14 °C in the growth chamber. Amaranthus powellii exhibited a faster rate of germination and greater early growth with respect to height and leaf number than either of the other species under both temperature regimes. Amaranthus hybridus had a greater root dry weight, took 3 wk longer to reach maturity and produced more seeds than either of the other species. In the field, when sown in pure stands and mixtures at constant density but varying proportions, A. powellii showed a greater competitive ability than A. retroflexus or A. hybridus with respect to number of plants, aboveground fresh weight, and number of seeds produced per square metre.Key words: Pigweed, germination, seed production, competition