Stephen H. Pearce

Assessing drivers of plantation forest productivity on eroded and non-eroded soils in hilly land, eastern North Island, New Zealand

BackgroundThe effect of soil erosion on New Zealand production forestry is not well known and there has been no research prior to our study into the relationship between soil nutrient status and planted forests growing in eroded soils in steeplands.MethodsThe impact of soil erosion by mass movement on forest productivity was investigated in a paired plot trial in a planted forest in a mainly hilly to steepland catchment (Pakuratahi) near Napier, eastern North Island, New Zealand. Tree growth and form were measured and soil properties analysed to compare productivity and productivity drivers in adjacent non-eroded and eroded plots.ResultsRegression analysis showed that the decreased soil total nitrogen, total carbon, total phosphorus, and soil organic matter content in eroded plots had a negative impact on tree volume, resulting in a 10% decrease in measured tree volume. Based on an assessment of log quality, trees in the eroded plots were forecast to produce 16% less volume from high-quality pruned logs (with associated reduction in revenue of around

Chemical properties of two soils irrigated with thermo-mechanical pulp mill effluent

4000 per hectare), than trees in non-eroded plots. The total recoverable volume (TRV), estimated (for a 25-year rotation) from the measured Pinus radiata D. Don trees growing on the eroded sites, was valued at

Decomposition of Pinus radiata coarse woody debris in New Zealand

68,500, about 9% less than the estimated TRV from trees measured on non-eroded plots (

Allometric Equations for Estimating Carbon Stocks in Natural Forest in New Zealand

76,000). Tree form and mean tree height in eroded and non-eroded plots were not significantly different.ConclusionsSoil erosion impacts production in planted forests. Afforestation of erodible land provides a valuable ecosystem service through land and soil stabilisation but this service is currently not reflected in the market prices for timber in New Zealand. Maintaining the productive capacity of erodible soils through practices such as fertilisation or continuous-cover forestry can add further costs to production forestry. To ensure that sustainable forest practices are carried out to protect the productivity of soils, financial incentives may be justified.

Leaf Area Index, Biomass Carbon and Growth Rate of Radiata Pine Genetic Types and Relationships with LiDAR

The effect of land application of thermo-mechanical pulp (TMP) mill effluent on soil chemical properties was examined using barrel lysimeters. Twelve lysimeters, 500 mm in diameter and 800 mm high, containing either a volcanic soil (Udivitrand) or a pallic soil (Haplustalfs), were collected from 2 plantation forest sites. A TMP mill effluent containing high concentrations of total organic C (1136 mg/L) was irrigated at 30 mm/week over a period of 16 months. Soil sample analysis indicated that build up of soil organic C was negligible despite large additions of organic C (equivalent to 19 t/ha) through irrigation with TMP mill effluent. Mass balance calculation implied that microbial degradation or mineralisation of the organic compounds might be the main mechanism involved in the high renovation rates. Irrigation with TMP mill effluent significantly increased soil pH, concentrations of soil total S, available P, and exchangeable K and Na, but it had no significant effect on concentrations of soil total N, and exchangeable Ca and Mg. The results from this study indicate that TMP mill effluent irrigated at a loading rate not greater than 30 mm/week would cause little detrimental effect on the quality of soils at these 2 plantation forest sites.