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Slash Management in New Zealand

Tigercat Product Support Representative, Warren Nolan reports on the Tigercat 4161-15 mulching head, deployed to New Zealand’s North Island to mitigate the potential impact of slash and erosion on steep and sensitive terrain. 

— Warren Nolan, Tigercat Product Support Representative

Blake Speirs (left) along with machine operator Cory Malcolm.
Blake Speirs (left) along with machine operator Cory Malcolm.
Blake and Caree Speirs are the owners of Speirs Logging Ltd., based in Gisborne, New Zealand. Blake’s father, Murray Speirs founded the company in Waitārere Beach, on the lower North Island of New Zealand, around 1998. The business began as a small family operation focused on harvesting and processing trees from the family farm. In its early years, Speirs Logging Ltd. worked primarily on woodlots, servicing various sites across the lower North Island. 

As demand grew, the company expanded its operations to include two hauler crews and one ground-based crew, servicing the Wellington and Wairarapa regions. In 2010, a significant transition occurred when one crew was relocated to Gisborne. At that point, Blake and his wife Caree, took ownership of the company, marking the beginning of a new chapter for Speirs Logging. 

For the first five years in Gisborne, the company operated as a swing yarder crew before shifting to a road line configuration to better meet the needs of its clients and the terrain. Today, Speirs Logging operates as a road line clear-fell operation, utilizing a combination of yarding and ground-based equipment. Speirs Logging also holds the road building contract for its operations, which is currently managed by an external subcontractor.

The company processes approximately 170 000 tonnes of wood annually and employs a dedicated team of twelve. The Tigercat fleet is comprised of two Tigercat LS855 series shovel loggers, two Tigercat 635 series skidders and a new Tigercat L870D track carrier fitted with a 4161-15 mulching head.

Operations

Operating in the Gisborne region presents a unique set of challenges due to steep terrain, poor soil conditions and consistently high rainfall over the past few years. These factors demand robust, reliable equipment capable of performing in this environment. Around 90% of the company’s operations require winch assisting, particularly in high-risk areas where the terrain is more unstable or challenging. “Our harvesting operation includes both cable extraction and steep-slope ground-based logging, with the support of winch assist technology to enhance safety and productivity on challenging terrain,” says Blake. “This approach enables us to maintain consistent output while prioritizing environmental care and crew wellbeing.”

The Speirs Logging team works a structured ten-hour day, typically achieving 85-90% machine availability after factoring in maintenance time and operator breaks. The crew runs a well-coordinated system, falling and extracting a 500-metre (1 640 ft) section of the road line, then relocating the crew and equipment to allow the road building subcontractor to come in. Minimal downtime helps to ease and simplify scheduling between the harvesting and road building crews.
The L870D/4161-15 package mulching in New Zealand
The L870D/4161-15 package is a forward-thinking solution to managing harvesting residue, allowing efficient and precise mulching in challenging environments. 

Impact of Cyclone Gabrielle 

Back in 2023, the destructive Cyclone Gabrielle devastated parts of the North Island of New Zealand. Thousands were displaced and a national state of emergency was invoked. The cyclone had a significant impact on the region, leading to increased scrutiny and tighter compliance regulations across the forestry industry. Leftover harvesting residue suddenly became a matter of utmost urgency and significance. The event highlighted the need for higher standards in slash management and erosion control, pushing everyone in the sector to raise their game. 

There is now a stronger collective focus on proactive risk management and environmental responsibility. The steep terrain mulching system is one of the ways Tigercat is responding — offering a practical, forward-thinking solution that helps reduce slash-related risks and supports more sustainable forestry practices in the wake of extreme weather events.

A portion of the Radiata pine plantations in Gisborne, Hawke’s Bay and Wairarapa, is managed by Forest Enterprises. The forest management and investment services company was founded in 1972 and currently has over 20 000 hectares (49 400 acres) valued at NZ$400 million under management on the North Island. The company offers investors ownership in both the land and timber holdings.

Blake explains that Speirs Logging has been contracted to Forest Enterprises with a specific focus on reducing risk in potentially hazardous cutblocks. “Our primary objective is to mitigate the potential impact of slash and erosion on steep or sensitive terrain. Using drone technology, we conduct aerial surveys of cutover sites [harvested compartments] to identify areas where slash volumes are particularly high. From there, we strategically deploy the Tigercat L870D equipped with the 4161-15 mulching head to reduce that material, aiming to minimize the volume left on the hill, especially in locations prone to landslips.”

This combination of power, flow capacity, and slope stability made this mulcher package the ideal choice for our needs.


— Blake Speirs, Speirs Logging Ltd.

This proactive approach helps prevent debris movement during heavy rain events and improves site stability. Additionally, the mulched material supports better conditions for second-rotation growth and delivers environmental benefits such as reduced runoff and improved ground cover. “By laying down mulch mats over gullies and exposed soils, we help to minimize erosion and retain moisture. When it rains, the mulch absorbs the water, preventing it from washing away the soil and promoting better land stability,” explains Blake.

Speirs Logging is currently supporting this risk reduction strategy across five separate logging operations, helping Forest Enterprises manage its forest assets with a strong focus on environmental responsibility and long-term sustainability. 

Historically, the responsibility for slash management has fallen to either the forest owners or the contractors themselves. In many cases, this meant absorbing the cost through reduced productivity, where machinery and crews would need to divert time and resources to manually move slash to safer areas. 

With the introduction of this dedicated mulching operation, Speirs Logging aims to significantly reduce both the operational burden and the associated risks. By proactively targeting high-risk zones, the goal is to provide a more efficient, cost-effective solution that not only improves safety but also supports positive environmental outcomes across the forest estate. 

Machine productivity can vary depending on the terrain and conditions, but overall, Speirs Logging is achieving the results it budgeted for. “We find that wood in the 20-30 cm (8-12 in) diameter range is the most productive for our operations. Larger diameter wood takes longer to process, although we can still handle stumps effectively with the mulching teeth. Our focus isn’t to mulch everything. Rather, we’re targeting high-risk areas where the land is more likely to shift,” explains Blake.

While the creation of windrows increases costs due to the additional work involved in forming them, it has led to an overall increase in production. By setting up windrows, the mulcher carrier can process more volume with fewer movements, allowing the operator to focus more on masticating with far less machine travel. However, it’s crucial to get the direction of the windrows right. Properly positioned windrows help to avoid mulched material accumulation in sensitive areas such as waterways and roads, ensuring that the company maintains environmental compliance and prevents potential damage to the surrounding landscape. 
mulching treatment before and after
Before and after. A treated area shows a remarkable difference.

Steep slope mulching system

Blake chose the Tigercat L870D equipped with the 4161-15 mulching head primarily because it offered the highest hydraulic flow of any comparable machine on the market, an essential feature for efficient and effective mulching performance. “Having operated various Tigercat machines over the years, we’ve consistently experienced strong reliability and performance, particularly in challenging conditions,” says Blake. “Tigercat machines are exceptionally well-suited to steep terrain, offering excellent stability on the hill — something that’s critical for our operations in the Gisborne region. This combination of power, flow capacity, and slope stability made this mulcher package the ideal choice for our needs.”

When mulching material that is spread over a cutblock, medium-grade, impact-resistant tools are used on the mulching head. This setup allows the head to work through variable terrain, including areas with hard soil, without experiencing excessive wear or damage to the tooling. When the machine transitions to processing large slash piles, the tooling is switched to sharper, knife-style tools. These are better suited for high-volume mulching where there's less risk of hitting dirt or rocks, ensuring cleaner cuts and greater efficiency in breaking down the material. This dual-tool approach gives Speirs Logging the flexibility to adapt to different conditions and slash types while maximizing performance and longevity. 

Blake has seen a significant increase in productivity since the Feed Control Rotor system (FCR) was added. The FCR system utilizes a drum with rakers installed that effectively limit the engagement of the tools, reducing the potential for stalling out the drum, while making the operator’s job easier.
Historical group photo
Speirs Logging Ltd. founder, Murray Speirs, had a long-term association with Tigercat. Photo taken in September 2007 at a Speirs Logging operation near Foxton, New Zealand. (L-R) Ken MacDonald (President, Tigercat Industries), Gary Olsen (Vice President Sales – Southern Hemisphere and Central America), Murray Speirs (former owner and founder of Speirs Logging Ltd.), Glen Marley (Tigercat District Manager, Australia and New Zealand).
“Since adding the rakers and adjusting to the right set of teeth, we’ve noticed a substantial improvement, especially in handling larger material. I estimate that the rakers have boosted productivity by about 30%,” says Blake. “The key benefit is that the rakers allow the machine to take smaller bites and prevent it from stalling out. For our operations, the rakers have proven to be the right solution.”

In Blake’s view, the Tigercat L870D simply isn't comparable to a standard excavator fitted with a mulching head. The key differences include the leveling system and the 370 hp (276 kW) engine output, which gives the Tigercat a significant advantage, especially on steep and uneven terrain. The added power, stability and control not only improve operator safety but also allow for more efficient and precise mulching in challenging environments. 

The Speirs Logging operators are very positive about the Tigercat machines. One of the standout features for them is the high level of comfort in the cab, which makes a big difference over long shifts. “When you're working in demanding conditions for extended periods, operator comfort isn’t just a bonus, it’s essential. Tigercat delivers on that, contributing to both productivity and overall job satisfaction,” adds Blake. “Tigercat machines are purpose-built for the demanding work we do. They stand out for their excellent fuel efficiency, robust construction, and superior stability, especially on steep terrain where leveling is essential. In our experience, Tigercat equipment handles tough conditions better than many other brands, and that performance translates directly into safer, more productive operation.”

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