Modeling the effect of initial planting density on within tree variation of stiffness in loblolly pine

Context

Modulus of elasticity (MOE) is an important mechanical property determining the end-use and value of loblolly pine (Pinus taeda L.) lumber.

Aim

In this study, a model was developed to predict the within tree variation of MOE, from pith-to-bark and stump-to-tip, using data collected from a 21-year-old unthinned stand where trees were planted under seven initial stand density levels (746?C2,243 trees/hectare).

Methods

The study was laid out in a randomized complete block design, with seven levels of initial planting density, replicated three times. Seven trees were destructively sampled from each plot, and bolts were cut from each tree at heights of 2.4, 7.3, and 12.2?m. Static bending samples (of dimension 2.5?×?2.5?×?40.6?cm) representing pith-to-bark variation were cut from each bolt and MOE measured. A three-parameter logistic function was used to model the pith-to-bark variation in stiffness with distance from pith as an explanatory variable.

Results

Based on the final fitted model, it was found that the asymptotic parameter (maximum outerwood MOE?=?13.48?GPa) was not influenced by sampling height, initial planting density, and stem slenderness. However, the inflection and scale parameters were significantly influenced by these variables.

Conclusions

In summary, we found that initial planting density had a significant influence on the amount of corewood produced with higher initial planting densities producing a lower proportion of corewood as indicated by a linear decrease in inflection point with an increase in planting density.     

Floristic regeneration in five types of teak plantations in Thailand

Teak is the most important timber species in northern Thailand, and as such, large areas of teak forest have been disturbed or become highly degraded. Teak plantations have been established on this highly degraded land, where the rate of natural recovery is relatively slow. At the study site, five mixed or pure teak plantation types have been established to ameliorate limiting soil properties in order that long-term productivity is maintained. Observations within these plantations in northern Thailand have suggested that native species become established naturally under the shade of a “nurse” plantation, one that shades out early successional species. The objective of this study was to investigate the influence of the number of species in nurse plantations on the diversity and number of seedlings representative of mature native forests that become established within the plantations. Five types of plantations were investigated: (1) Tectona grandis L.f. (T); (2) T.grandis and Tamarindus indica L. (TT); (3) T.grandis and Gmelina arborea Roxb. (TG); (4) T.grandis, T. indica and G. arborea (TTG); (5) T.grandis, T.indica and Anacardium occidentale L. (TTA). These plantations were established primarily for the production of T.grandis (teak), with the other species introduced as economic trees. The plantations were surrounded by native stands of species representative of late successional and mature teak forests. In each of the plantations studies measurements were made on species density, species diversity, and evenness of plants regenerating in the understorey. Results showed that plantations consisting of several species in the overstorey had a higher diversity of native forest species in the understorey than the single-species plantation. Mixed plantation types were also found to reduce the density of the grass Imperata cylindrica (L.) P. Beauv. Consideration of the establishment of woody species found that TG and TTA had high densities of trees and shrubs. This suggested that if the goal of management was to regenerate forest with a high diversity of tree species similar to that found in native mature forests, multiple-species plantations, especially TG and TTA, would be more effective nurse communities than the single-species plantation in providing an environment into which seeds of native species could disperse and germinate. In addition, several climax species, such as Xylia xylocarpa (Roxb.) Taub. var. kerrii (Craib & Hutch) I.C. Nielsen, Pterocarpus macrocarpus Kurz, Largerstroemia sp., Afzelia xylocarpa (Kurz) Craib, Lannea coromandelica (Houtt) Merr., Spondias pinnata (L.f.) Kurz, Garuya pinnata Roxb., Terminalia mucronata Craib & Hutchison, Diospyoros mollis Griff., Irvingia malayana Oliv. ex Benn., Milletia leucantha Kurz, Dalbergia oliviri Gamble ex Prain, Chukrasia tabularis A. Juss and Schleichera oleosa (Lour.) Oken, were found in the early stages of succession, thus indicating that some may be suitable for planting in future restoration processes in order to accelerate natural succession and provide economic returns to managers.     

Proteomic analysis of membrane preparations from developing Pinus radiata compression wood

For coniferous gymnosperms, few data exist as to the contribution of the membrane-associated proteome to cell wall and wood formation. In this study, we begin to address this knowledge deficiency by examining the proteomic profile of Golgi-enriched membrane preparations derived from developing Pinus radiata compression wood. These membrane preparations were generated by a combination of discontinuous sucrose gradient centrifugation and Triton X-114-based phase separation. Fractionation by phase separation removed contaminating proteins associated with the cytoskeleton and enabled the discrimination between soluble and membrane-bound/integral proteins. The proteomic analysis of the resulting aqueous and detergent phases using high-performance liquid chromatography-tandem mass spectrometry resulted in the identification of 175 proteins. The majority of the identified proteins were membrane bound/integral and originated from cellular components such as the nucleus, plastids, endoplasmic reticulum, plasma membrane and Golgi vesicles. On the basis of bioinformatic analysis, many of the identified proteins were predicted to be involved either in the regulation of wood formation or in cell wall biosynthesis, which indicated that the proteomic analysis of non-cytosolic proteins in developing xylem is a useful strategy to investigate the molecular aspects of wood formation in pine.     

A periodically active pulsar giving insight into magnetospheric physics

PSR B1931+24 (J1933+2421) behaves as an ordinary isolated radio pulsar during active phases that are 5 to 10 days long. However, when the radio emission ceases, it switches off in less than 10 seconds and remains undetectable for the next 25 to 35 days, then switches on again. This pattern repeats quasi-periodically. The origin of this behavior is unclear. Even more remarkably, the pulsar rotation slows down 50% faster when it is on than when it is off. This indicates a massive increase in magnetospheric currents when the pulsar switches on, proving that pulsar wind plays a substantial role in pulsar spin-down. This allows us, for the first time, to estimate the magnetospheric currents in a pulsar magnetosphere during the occurrence of radio emission.     

Benchmark study on glyphosate-resistant crop systems in the United States. Part 2: Perspectives

A six-state, 5 year field project was initiated in 2006 to study weed management methods that foster the sustainability of genetically engineered (GE) glyphosate-resistant (GR) crop systems. The benchmark study field-scale experiments were initiated following a survey, conducted in the winter of 2005-2006, of farmer opinions on weed management practices and their views on GR weeds and management tactics. The main survey findings supported the premise that growers were generally less aware of the significance of evolved herbicide resistance and did not have a high recognition of the strong selection pressure from herbicides on the evolution of herbicide-resistant (HR) weeds. The results of the benchmark study survey indicated that there are educational challenges to implement sustainable GR-based crop systems and helped guide the development of the field-scale benchmark study. Paramount is the need to develop consistent and clearly articulated science-based management recommendations that enable farmers to reduce the potential for HR weeds. This paper provides background perspectives about the use of GR crops, the impact of these crops and an overview of different opinions about the use of GR crops on agriculture and society, as well as defining how the benchmark study will address these issues.     

Effect of solid residues from the cellulose industry on plant growth

An alternative use of solid organic and inorganic residues as fertilizers from a Kraft pulp industry was studied. Residues of inorganic nature, such as ashes, fly‐ashes, dregs, grits, as well those rich in organic matter, primary sludge and brown stock rejects, were examined for plant growth enhancement. These residues, all alkaline in nature, used in different concentrations together with soil, bark, organic soil or mixed with a nutrient solution, were tested on the growth of Monterey pine (Pinus radiata), Eucalyptus globulus, rice (Oryza sativa. cv. ‘Diamante’), and duckweed (Lemna minor) under greenhouse and in‐vitro conditions, respectively. Responses varied according to plant species, type, and waste content in combination with substrate. For Monterey pine, substrates including ash, fly‐ash, and dregs promoted growth; in Eucalyptus seedlings dregs and fly‐ash were also beneficial. Primary sludge and ash were favorable for rice growth. Duckweed increased frond number and plant biomass when grown in water containing fly‐ash and primary sludge extracts, combined with nutrient salts.     

Characterisation of agricultural drainage ditch sediments along the phosphorus transfer continuum in two contrasting headwater catchments

Purpose

This study investigated the phosphorus (P) source, mobilisation and transport potential of ditch bed sediments as well as surrounding field and bank soils in two agricultural headwater catchments with contrasting soil drainage capacities. This information is important for discerning the potential for ditches to attenuate or augment transfers of P from upstream sources and thus for developing appropriate management strategies for these features.

Materials and methods

Phosphorus sources were characterised using the Mehlich3-P, water-soluble P and total P tests. Phosphorus mobilisation potential was characterised using the Mehlich3-AL/P, Mehlich3-Ca/P and DESPRAL P tests. Phosphorus transport potential was characterised using data collected on the presence/absence of surface water in ditches during field surveys and downstream turbidity data.

Results and discussion

Ditch sediments had similar P source contents (Mehlich3-P, water-soluble P and total P) to the surrounding field soils and higher P contents than bank soils. However, calcium contents of sediments in the poorly drained catchment reflected the deep sub-soils rather than the surrounding field and bank soils. Mehlich3-Al/P and Mehlich3-Ca/P contents of ditch sediments in the well (non-calcareous) and poorly (calcareous) drained catchments respectively indicated potential for P retention (above thresholds of 11.7 and 74, respectively). However, sediments were less aggregated than field soils and may mobilise more particulate P (PP) during rain events. Nevertheless, the majority of surveyed ditches dried out from March to September 2011; thus, their potential to mobilise PP may be less important than their capacity to attenuate soluble and PP during this time.

Conclusions

In these and similar catchments, soluble P attenuation and particulate P mobilisation should be maximised and minimised, respectively, for example, by cleaning out the sediments before they become saturated with P and encouraging vegetation growth on ditch beds. This study also highlighted the influence of deep sub-soils on soluble P retention in ditches and thus the utility of characterising soils below depths normally included in soil classifications.