Short-rotation Poplar Plantations Research Articles

Logging residue chipping options for short rotation poplar plantations

Short rotation poplar plantations grow on flat and even terrain, and the interrow spacing is wide enough for easy machine access. If the terrain is firm enough, one may consider moving the classic roadside chipping operation directly into the field (i.e., terrain chipping), thus saving on wood extraction cost. This study compared the efficiency and cost of roadside and terrain chipping conducted with exactly the same equipment, to assess the benefits offered by the versatile deployment of a standard chipping operation, whereby the operation can be moved inside the stand whenever terrain conditions are suitable. The study was conducted at 12 sample plots, containing about one truck load of chips each (i.e., approximately 11 bone-dry tons or BDT). Plots were arranged as alternate windrows on a 8.5 ha field. Data was collected for the whole supply chain, from field to factory. The factory was located 14 km from the field. Delivered cost was 53 € BDT-1 and 70 € BDT-1 for roadside and terrain chipping, respectively, i.e., terrain chipping was 1/3 more expensive than roadside chipping, even if the latter included the additional cost of forwarding the residues to the roadside. The chipper-truck used for the test could not cope with small scattered residue piles (32 BDT ha-1), and the cumbersome reposition maneuver became the main hurdle to efficient operation. Further improvements might be achieved by pre-bunching the residues, introducing a dedicated terrain chipper or bundling the residues and taking the bundles to the factory for centralized chipping.

Produkcija biomase klonova evroameričke topole (Populus x euramericana (Dode) Guinier) u zasadima kratke ophodnje sa različitim razmacima sadnje

Biomass from short rotation poplar plantations presents a good alternative as a material for energy production, either as a substitute or as an addition to fossil fuels. This research presents the investigation of the potential of the Serbian forestry's most commonly used clones (a) Populus × euramericana cl. I-214 and (b) Populus × euramericana cl. "Pannonia" for the production of biomass for energy in different plant density plantations (2500, 3333, 5000 and 10000 plants ha-1) on the marginal soil for the poplar production. Measured parameters included (a) diameter at breast height, (b); tree height, (c) wood biomass per unit of the area, (d) potentially produced energy per unit of the area, (e) individual tree volume and (f) wood volume per unit of the area. Obtained results indicated significant influence of the plant density on the investigated parameters, while there was no effect of the selected clone or clone x plant density interactio. Such results can be explained by the site conditions and production cycle duration.

First trial of a prototype chainflail delimber for the European short rotation poplar plantations

Small tree size represents a main challenge for single-tree handling techniques and caps harvesting productivity in short rotation poplar (SRP) plantations. That challenge is best met by a shift towards mass-handling. Chainflail delimbing is one of the best solutions for multi-tree processing, but commercially available equipment is often too heavy and expensive for European operations. Therefore, an Italian company developed a compact chainflail delimber-debarker (CFDD) specifically designed for small-scale SRP. The machine was tested in Western Slovakia in early March 2022. The test included a five-days endurance trial and a controlled experiment on 16 carefully measured wood piles representing “strong” and “weak” trees, i.e. trees with a mean diameter at breast height (DBH) of 12 and 10 cm, respectively. The endurance trial was quite successful since no mechanical problems were recorded during the five-days period. Delimbing and crosscutting quality were as good as those obtained with a standard processor head, while log yield was generally better, averaging 42% and 68% for the “weak” and the “strong” trees, respectively. Productivity was on a par with the alternative cut-to-length technology options and can be significantly increased once the prototype will be further developed. In general, the new compact CFDD may become the best option for handling the small trees offered by underdeveloped SRP plantations, which cannot be efficiently harvested with the cut-to-length system.

First trial of a prototype chainfail delimber for the European short rotation poplar plantations

First trial of a prototype chainfail delimber for the European short rotation poplar plantations

A cost-benefit analysis of pre-sorting using a feller-buncher in underdeveloped short rotation poplar plantations

ABSTRACT Underdeveloped tree crops (⩽ 30 bone-dry tons ha−1) offer a main harvest of biomass-trees, which lack the size and the form for producing a log. However, about 1/3 of the available stems may yield at least one log, which could significantly increase the overall value of the harvest. Under those circumstances, it may make sense to sort log-trees from biomass-trees at an early stage, rather than having a harvester or a processor go through all of the treesonly to toss almost 70 out of 100 trees into the biomass pile. The Authors set up a controlled experiment to quantify the eventual benefit obtained by early pre-sorting, performed by the feller-buncher. Pre-sorting resulted in a 15% productivity loss for the feller-buncher, which was repaid by a 100% productivity increase for the processor. Considering the different hourly cost of the two machines, three Euros were saved for each additional Euro invested in pre-sorting. Pre-sorting made whole-tree harvesting (WTH) a significantly cheaper option than cut-to-length (CTL) , whereas the two systems would be almost equally expensive when no pre-sorting was applied. Pre-sorting would also facilitate multiple-tree delimbing, implemented through the introduction of a chainflail; that is likely to further reduce harvesting cost, returning financial viability to the harvesting of underdeveloped plantations.

Is it necessary to apply chemical weed control in short-rotation poplar plantations on deep soil sites?

Chemical weed control has been widely applied in plantation forests around the world. However, understanding the long-term influence of weed control on stand growth and its underlying mechanisms is still limited. We conducted a six-year (2016–2021; an entire rotation) weed control study in Chinese white poplar (Populus tomentosa Carr.) plantations established using tall planting stock on a deep soil site, which is a typical afforestation mode for poplars in north China. Three treatments of chemical weed control degree were implemented: no weeding (W0), removing weeds within 50 cm distance from the tree row (W50) and removing all weeds on the ground (W150). Different tree growth indicators, soil water content (θ), tree root distribution, and soil physical properties were measured. There was no weed control degree effect on θ in 2017 (P = 0.4408) but significant θ difference (P = 0.0140) among treatments existed in 0–30 cm soil in 2021. Different degrees of weed control did not change soil physical properties (P > 0.05) after the long-term application of chemical weeding. There were no differences (P > 0.05) in all growth indicators. But the cumulative increments of tree diameter, height, stand volume index, and biomass at the end of the rotation in W150 were numerically 2–27% lower than W0 and 11–26% lower than W50. The total fine roots biomass increased with decreasing weed control degree, although the difference was non-significant (P > 0.05). The fine root distribution pattern indicated that there might be many fine roots below 200 cm depth. The tree growth response to weed control may be attributed to tall planting stock that avoids light competition from weeds and deep soil resource exploration by tree roots that alleviate competition by shallow weed roots. Consequently, it may be unnecessary to apply chemical weed control in poplar plantations established using tall planting stock on deep soil sites. Our findings provide guidance for the sustainable management of industrial plantation forests.

The Effect of Target Log Length on Log Recovery and Harvesting Cost: The Example of Short-Rotation Poplar Plantations

Log production is the main target of new short-rotation poplar plantations, and their profitability depends on maximizing log yield. The authors set up a controlled experiment to determine the log yield increase obtained by shortening log length specification from 4 to 2 m, and to quantify the additional cost incurred by this change. The experiment indicated that reducing log length specifications allows a significant increase (+40%) in log yield in low-yielding (<25 BDT ha−1) plantations, only. Such increase is matched by a parallel increase in harvesting cost (+33%) that must be balanced against the recovered additional value. Measures are suggested to mitigate the harvesting cost increment, such as: dual log length specifications, modifications of the forwarder load bay and changing from cut-to-length to whole-tree harvesting.

Organic carbon, total nitrogen and macronutrients in soil under short-rotation willow and poplar plantations

Organic carbon, total nitrogen and macronutrients in soil under short-rotation willow and poplar plantations

Manipulating grading strategy for the efficient harvesting of industrial poplar plantations

ABSTRACT New short rotation poplar plantations yield a mix of biomass and logs, whereby the latter are used for board production and represent the most valuable component. Therefore, there is an interest in maximizing log yield, which must be balanced against the incremental time consumption incurred for manufacturing any additional logs. This study explored the optimization potential of manipulating log specifications and grading instructions in order to decrease time consumption or increase log yield. A controlled experiment was set up to determine the merits of 1) renouncing the manufacturing of a second small log to expedite processing or 2) decreasing small end diameter to increase the proportion of viable logs in any given stem. The experiment indicated that strategy one did not pay, since the productivity increase was minimal and non-significant, while the log yield losses were meaningful and significant. In contrast, strategy two was efficient in increasing log yield, without any negative effects on harvesting productivity.

Multi-tree cut-to-length harvesting of short-rotation poplar plantations

Small tree size represents the main challenge when designing a cost-effective harvesting system for European short-rotation plantations. This challenge is further complicated by the need to obtain 4-m logs for high-end products, which rules out the possibility of deploying whole-tree chipping. Both challenges can be met through mass or multi-tree handling (MTH), which must begin at the time of felling and continue uninterrupted along the whole supply chain. The objective was to: (1) gauge the productivity and the cost of CTL harvesting applied to these plantations; (2) assess log yield and capacity to match dimensional specifications; (3) determine if MTH applied to CTL technology offers a real benefit compared with conventional single-tree handling. The authors conducted a time study using a block design with a two-machine cut-to-length harvesting system (i.e. harvester and forwarder) in single- and multi-tree handling operations on the clear cutting of a hybrid poplar plantation in Poland, as well as we manually measured the produced volumes of the study. Higher productivity (+ 8%) was achieved under the multi-stem handling mode. The MTH system proved capable of containing harvesting costs below € 15 per green ton, while fulfilling set timber quality requirements in terms of value recovery and log quality specifications. A new, software-based, MTH system is recommended to be used in short-rotation poplar plantation for logs and biomass harvesting. When the coppicing season is over, the system can be deployed for the conventional thinning operations.

Multi-tree cut-to-length harvesting of short-rotation poplar plantations

Multi-tree cut-to-length harvesting of short-rotation poplar plantations

The effect of cutting technique on the mortality and resprouting vigor of poplar stumps in short-rotation plantations

Mechanical felling is the most cost-effective solution for harvesting short-rotation poplar plantations, but the damage inflicted by conventional shear-cutting devices on tree stumps has raised concerns about stump mortality and resprouting vigor, both of which are crucial to coppice regeneration. To determine whether such concerns are justified, this experiment monitored the survival and resprouting vigor of 11 sample blocks composed of two 10-stump row segments that were cut according to one of two methods: (1) a chainsaw or (2) an excavator-mounted shear. The sample blocks were located within the same plantation, established 7 years earlier with hybrid poplars (Populus nigra × Populus deltoides) belonging to the AF8 clone. One year after cutting, no differences were found between treatments in terms of stump mortality, number of shoots per stump, shoot diameter at 30 cm from the insertion, or shoot height. These results support the use of mechanical shears to fell short-rotation poplar coppice. However, further studies should be conducted on multiple fields and clones in order to safely generalize these preliminary findings.

A Low-Investment Option for the Integrated Semi-mechanized Harvesting of Small-Scale, Short-Rotation Poplar Plantations

In recent years, industrial roundwood production has enjoyed a steady success due to the development of a new bioeconomy and the rapid structural changes of the wood market. A very promising new solution for industrial fiber crops is the integrated production of logs and biomass in short rotation poplar plantations. In Europe, the expansion of these crops is concentrated in the Eastern regions, where contractors face strict limitations in their capital availability: hence the interest in developing semi-mechanized, low-investment harvesting systems based on general-purpose equipment that may serve as a stop-gap solution to assist the transition to fully mechanized systems. This study focused on designing and testing such a system, based on two low-cost machines (an excavator with a grapple saw and a second-hand forwarder) and requiring a minimum workforce (two operators only). The system was tested for productivity, cost and work quality, under two variants: production of 2 or 4 m logs. This system can produce approximately 3 loads (90 t) per day, at a cost between 14.5 and 16 € t−1, from stump to roadside landing, ready for loading and transportation. The 4 m log variant was more efficient, resulting in a 10% cost reduction around 1.5 € t−1. However, log yield was relatively low: between 1/3 and 1/4 of the total harvest, the balance consisting of lower-value biomass. The 2 m log treatment offered a higher log yield. The introduction of simple technology may allow increasing log yield and should be the subject of future research.

A Low-Investment Option for the Integrated Semi-mechanized Harvesting of Small-Scale, Short-Rotation Poplar Plantations

A Low-Investment Option for the Integrated Semi-mechanized Harvesting of Small-Scale, Short-Rotation Poplar Plantations

Cost-effective Integrated Harvesting of Short-Rotation Poplar Plantations

Small tree size represents the main challenge when designing a cost-effective harvesting system for European short-rotation plantations. This challenge is further complicated by the need to obtain 4-m logs for high-end products, which rules out the possibility to deploy whole-tree chipping. Both challenges can be met through mass handling, which must begin at the time of felling and continue uninterrupted along the whole supply chain. The authors designed and tested a simple system based on an excavator-based feller buncher, two farm tractors converted into grapple skidders and an excavator-based grapple saw adapted to operate as an impromptu slasher. This system proved capable of containing harvesting cost below 17 € per green ton, while matching the necessary work quality requirements, in terms of value recovery and log quality specifications. Furthermore, the whole system can be acquired with a limited capital investment, estimated at ca. 400,000 €. Being based on general purpose equipment, the system is also versatile enough for deployment in a number of alternative jobs, when the coppicing season is over.

Biomass and Volume Modeling along with Carbon Concentration Variations of Short-Rotation Poplar Plantations

Short-rotation forestry is of interest to provide biomass for bioenergy and act as a carbon sink to mitigate global warming. The Poplar tree (Populus × xiaohei) is a fast-growing and high-yielding tree species in Northeast China. In this study, a total of 128 Populus × xiaohei trees from the Songnen Plain, Heilongjiang Province, Northeastern China, were harvested. Several available independent variables, such as tree diameter at breast height (D), tree’s total height (H), crown width (CW), and crown length (CL), were differently combined to develop three additive biomass model systems and eight stem volume models for Populus × xiaohei tree. Variance explained within the three additive biomass model systems ranged from 83% to 98%, which was lowest for the foliage models, and highest for the stem biomass models. Similar findings were found in the stem volume models, in which the models explained more than 94% of the variance. The additional predictors, such as H, CL, or CW, evidently enhanced the model fitting and performance for the total and components biomass along with the stem volume models. Furthermore, the biomass conversion and expansion factors (BCEFs) of the root (118.2 kg/m3), stem (380.2 kg/m3), branch (90.7 kg/m3), and foliage (31.2 kg/m3) were also calculated. The carbon concentrations of Populus × xiaohei in root, stem, branch, and foliage components were 45.98%, 47.74%, 48.32%, and 48.46%, respectively. Overall, the newly established models in this study provided complete and comprehensive tools for quantifying the biomass and stem volume of Populus × xiaohei, which might be essential to be specifically utilized in the Chinese National Forest Inventory.

Cost-effective Integrated Harvesting of Short-Rotation Poplar Plantations.

Cost-effective Integrated Harvesting of Short-Rotation Poplar Plantations.

Low-Investment Fully Mechanized Harvesting of Short-Rotation Poplar (populus spp.) Plantations

European short-rotation poplar plantations are harvested at 5–8 year rotations and produce relatively small stems (0.05–0.10 m3), which represent a major challenge when designing a cost-effective harvesting chain. Until now, the challenge has been met through whole-tree chipping, which allows mass-handling all through the harvesting chain. However, the production of higher value logs for the panel industry requires devising different solutions. This study presents a fully mechanized low-investment system using an excavator-based feller-buncher shear, a grapple skidder obtained from the conversion of a common farm tractor and an excavator-mounted grapple saw adapted to work as a makeshift slasher. The system was tested in Northwestern Italy, achieving high productivity (between 14 and 20 t fresh weight per scheduled machine hour) and low harvesting cost (between 9 and 14 € t−1 fresh weight). However, crosscutting quality needs further improvement, because almost 50% of the logs did not meet factory specifications. Solutions to solve this issue are proposed. The tested system is suitable for local small-scale operators because it can be acquired with a reasonable capital investment (400,000 €) and it is versatile enough for use in a number of alternative jobs, when the coppice harvesting season is over.

Low-Investment Fully Mechanized Harvesting of Short-Rotation Poplar (populus spp.) Plantations

Low-Investment Fully Mechanized Harvesting of Short-Rotation Poplar (populus spp.) Plantations

Habitat structure influences the spider fauna of short-rotation poplar plantations more than forest age

Plantation forests comprise an important part of the forested areas in European countries. Intensive forestry management and short-rotation cycles of plantation forests reduce habitat diversity and change the composition of invertebrate assemblages, mainly by reducing the number of habitat specialist species. Here, we analysed the effect of vegetation structure, amount of dead organic matter (DOM) and plantation age on spider functional diversity and assemblage structure in short-rotation plantations of native silver poplar in Hungary. Three stages, representing young plantations, 6- to 10-year-old stands (five stands), middle-aged plantations, aged between 23 and 26 years (five stands) and mature, 35- to 37-year-old forests at commercial maturity (five stands) were sampled. Each sample consisted of the data of ten pitfall traps. Traps were installed 5 m from each other in a 2 × 5 grid. Functional diversity was positively related to vegetation structure. High functional diversity indicates a higher number of available niches and potential resources. The abundance of moist habitat species and forest specialist species was positively correlated with DOM. Furthermore, moist habitat species were also related to vegetation structure. The most important environmental parameters affecting spiders were factors attributed to trees (litter and DOM), understory vegetation structure and, to a lesser extent, forest age. Different-aged stands may be similar in terms of species composition of their spider fauna if they comprise the same habitat structural patterns. Our study emphasises that the simple habitat structure of plantation forests has a negative effect on spider communities.