Water quality in New Zealand’s planted forests: a review

Abstract

This paper reviewed the key physical, chemical and biological water quality attributes of surface waters in New Zealand's planted forests. The purpose was to: a) assess the changes in water quality throughout the planted forestry cycle from afforestation through to harvesting; b) compare water quality from planted forests with other land uses in New Zealand; and c) identify knowledge gaps and opportunities for future research. Afforestation of pasture land significantly improved a wide range of water quality attributes such as stream temperature, nutrient and sediment concentrations and microbial contamination within 4-6 years of planting. Water quality in mid-rotation to mature forests, a large proportion of the forestry cycle, was highly variable but characterised by cool water temperatures, low concentrations of sediment and nutrients, with aquatic invertebrate communities indicative of high water quality. Impacts of timber harvesting on water quality attributes were greatest when clear-cut harvesting up to the stream edge. Harvest impacts were mediated by the retention of intact riparian buffers and to a lesser extent by retention of moderate quantities of logging slash across small stream channels. Temporal and spatial factors influenced the magnitude of response to harvesting activities and duration of the recovery period. Land-use comparisons generally showed improving water quality from pasture to planted forest to indigenous forest. Continued research to identify management systems that mitigate impacts on water quality, particularly during harvesting, remains a priority. Consistent approaches to water quality monitoring will improve the ability to report on water quality in planted forests. Future water quality research in New Zealand's planted forests needs to encompass emerging contaminants of national and international concern such as pesticides and pharmaceuticals. As New Zealand moves toward increasing productivity from planted forests, use of potential interventions such as intensified herbicide and fertiliser use, will need to be within sustainable freshwater limits. A future challenge is to quantify the economic value of freshwater ecosystems services provided by New Zealand's planted forests. This review showed that with continued prudent stewardship and ongoing improvements in management practices, particularly during harvesting, New Zealand's planted forests can provide a sustainable source of well-maintained and high quality water resources.

Riparian management: A restoration tool for New Zealand streams

“…). This on‐ground work stimulated research around their benefits for stream water quality and ecosystem health in farming and forestry landscapes (see and a recent review of the role of streamside management zones in forestry by Baillie & Neary ). The first riparian guidelines were produced in the early 1990s (Collier et al .…”

Cumulative Effects Analysis of the Water Quality Risk of Herbicides Used for Site Preparation in the Central North Island, New Zealand

“…Exceptions occur on the lower end of the precipitation 2 of 25 range for forests (<1000 mm·year −1 ; [5]). Second, forests generally have lower levels of physical and chemical disturbance depending on global location, climate, management history, etc., so they are able to yield higher quality water than alternative uses such as agricultural or urban catchments [7,8]. The challenge to forest land managers is to conduct management operations while keeping water quality within the acceptable range for current and projected uses [4,9].…”

Ecological Models to Infer the Quantitative Relationship between Land Use and the Aquatic Macroinvertebrate Community

“…The impact that land use poses on surface waters is not limited to river ecosystems [13,14], but also affects ponds [15] and lakes [16,17]. The change in the physico-chemical and hydromorphological characteristics of the impacted river or catchment will consequently affect the richness and abundance of aquatic organisms, such as fish [18,19], macroinvertebrates [20,21], and plants [22,23].…”