Pakuratahi and Tamingimingi experimental basin
Past, Present and Future
To view this interactive story map online, please go to: https://arcg.is/1iPuvq0
The Pakuratahi land use study was a 12 year paired catchment study with the purpose of comparing the effects of pastoral farming and production forestry on erosion and stream environments.
This is an overview of the catchment study's past, present and future
Location and land use history
Location
Pakuratahi and Tamingimingi experimental catchments are two adjacent catchments located in the coastal hill country of Hawke’s Bay, north of Napier.
Tamingimingi
Tamingimingi catchment (795ha) is an extensively grazed pasture catchment.
Pakuratahi
Pakuratahi catchment (345 ha) was planted in Radiata Pine in the early 1970s .
Timeline
Early 1900's
Tamingimingi catchment was (and still is) a grazed pasture catchment . Prior to land conversion, Pakuratahi catchment was predominantly native scrub.
1970
In 1970, the first rotation of Pinus Radiata was planted at the Pakuratahi catchment.
1988
Tropical Cyclone Bola hit New Zealand. Over 753 mm of rain over a four day period. Widespread landslides and sediment deposition from flood waters across New Zealand.
1998
Pakuratahi's first rotation harvested between 1998 and 1999. In January 1998, logging operations began where roads were constructed.
1999
Harvesting operations completed using clear felling.
2000
Second rotation planting of Pinus Radiata at Pakuratahi Catchment completed.
Paired catchment study
1993 - 2005
As part of a collaborative venture between the Hawke’s Bay Regional Council and the local forest industry, a paired catchment study was established. Research partners included:
(the former)
Purpose of study
To compare the effects of pastoral farming and production forestry on erosion and stream environments.
Research
Over the 12 year study period, a range of research was conducted including:
• Water quantity • Water quality • Soil erosion • Sediment yield • Stream morphology • Aquatic biota • Effects of forestry operations
Data
Data sources include but were not limited to: • Rain gauges • Flow gauging stations • LiDAR • Stream physio-chemical properties • Macro Invertebrate surveys • Soil profile descriptions • Soil physical and chemical analysis
Outputs
Both during the study period and after the study period, at least:
11 technical Reports
10 scientific papers
1 masters study
3 summary reports and review documents
1265 citations
Summary of Research Findings
Water yield
Annual water yields from the mature forest were 6% less than pasture. The progressive removal of the forest canopy (harvesting) caused annual water yield to exceed those from the pasture by an average of 22%.
Sediment yield and Forestry operations
Sediment yield from pasture was 4 times higher than mature forests
During harvest, there was a 6 fold increase in sediment yield to levels 2.5 times the pasture catchment.
This returned to mature forest levels within 2 - 3 year
Forestry operations
The main sources of sediment associated with forestry operations: • Road cut bank • Sidecast failure • Shallow landslides • Stream bank erosion The main sources of sediment in the pastoral catchment: • Shallow landslides • Stream bank erosion Forestry operations in the coastal hill country of Hawke’s Bay are unlikely to cause any substantial and long-term changes in water quality.
Aquatic Biota
During harvest, native fish and macroinvertebrate communities declined to levels similar to those observed in pasture, but recovered within 3-5 years.
Stream Morphology
Measurement Stations
Mature pine forests were more effective at moderating storm impacts on stream channels than pasture.
Soil erosion
Between 1 and 3km 2 of land in Pakuratahi would be at high risk of erosion following an 80-year and a 100-year extreme rainfall event. This equates to soil losses of 2630 and 7890 tons.
Soil quality
Soil erosion impacts soil physical and chemical properties by between 3 and 52 %.
For all slips mapped across Pakuratahi, soil and nutrient loss equates to:
• 2385 tons of soil • 271 tons of carbon • 20 tons of nitrogen • 3 tons of phosphorus
Wood quality
Tree volume was significantly correlated with reduced amounts of total N, C, and P and soil organic matter in eroded soils.
High quality pruned logs for a 25 year rotation were valued at 9% less in eroded plots for total recoverable volume, with a reduction in total recoverable revenue at $7,500 per hectare.
What next for Pakuratahi and Tamingimingi?
Connect, Collect, Collate, Collaborate, Create
• Connect with people involved in previous research
• Create a resource library of existing resources, data and contacts
• Collate a list of knowledge gaps discussed in reports and papers. Can these now be filled? Do we need more information?
• Collect a list of existing instrumentation. Can it be resurrected?
• Collaborate with previous and new stakeholders to reflect on and discuss past, present and future research ideas
Future research - New Technology
• Is the existing dataset enough for future research?
• If not, what additional or new data needs to be collected?
• Do we use measurement protocols used previously or create a new set of measurement protocols?
• New technology allows higher spatio-temporal measurements and greater data storage capacity.
• What spatio-temporal scale is required?
• What new technology can be adopted?
Impact of plantation and harvesting on soil (hydrological) functioning
• Timber harvests may lead to negative ecological impacts to soil environment, thus reducing both soil and forest long-term productivity.
Extreme Weather Events
• Extreme weather events are becoming more common with our changing climate. How can we:
• Use new and existing data to model the effects of extreme weather events in pasture and forest environments
• How resilient is Radiata Pine to extreme weather events, particularly on erosion prone land. How does this compare to pasture and other plant species?
• Are planted forests an important source of water during the summer, particularly during summer drought?
Trees, water use, and forest water yield
• Increasing concern with water availability & quality
• Increasing concern with water availability & quality•Concern about impact of large-scale forest plantings
• Increasing questions on how much water radiata pine and other species use and downstream impacts on water supply
• Little research in forest hydrology over the last 40 years Concern about impact of large-scale forest plantings
