Implications of Uncertainty in a Pre-treatment Dataset when Estimating Treatment Effects in Paired Catchment Studies: Phosphorus Loads from Forest Clear-cuts

Abstract

Estimates of increased nutrient export caused by forest clear-cuttings are mostly based on long-term paired catchment studies, where the treatment effect is calculated using pre-treatment dataset regression and post-treatment records of nutrient loads. In these studies uncertainty in the regression between the pre-treatment loads from the control and from the treatment catchments is typically neglected, even though it affects determination of the magnitude and duration of the treatment effect. This uncertainty is described in terms of variance in regression coefficients and residuals. The aim was to study how uncertainty in a pre-treatment dataset is propagated to estimates of the treatment effects using two sets of paired catchment data in eastern Finland, where the total phosphorus loads following forest clear-cutting and site preparation were investigated. The results showed that neglecting the uncertainty in the pre-treatment data did not change the conclusions when the treatment effect was strong enough. However, when the treatment effect was small, neglecting the uncertainty in the pre-treatment dataset easily leads to over-interpretation of the results. The uncertainty in a pre-treatment dataset should be taken into account in the paired catchment studies in order to avoid bias in the estimation of management effects on the loads.

A method to estimate the impact of clear-cutting on nutrient concentrations in boreal headwater streams

“…There is also uncertainty in the relationship between the treatment and control catchments during the pre-treatment period. Unlike many other studies, we took into account the uncertainty in the regression between the pre-treatment concentrations from the control and the treatment catchments and avoided the overinterpretation of the results (Laurén et al 2009). The number of existing studies is small considering large site-specific variation in responses to clear-cutting but produced specific concentration values cannot be improved without new data.…”

“…The concentrations for the treatment catchments as if they had not been treated are calculated as f j (a j C ij f j -1 ). This approach is based on the work by Laurén et al (2009) and Nieminen et al (2010) and further information can be found therein. The advantage of this approach, as compared to more conventional methods is that the random variability between treatment and control catchments during the calibration period and the proportional size of the treated area can be taken into account in the interpretation of the treatment effects.…”

Environmental Services Provided from Riparian Forests in the Nordic Countries

“…Some P reaches the stream, especially outside the growing season when the biological activity is low (Väänänen et al 2006). An uncut forested buffer between the clear cut area and the receiving surface water is found to be effective in mitigating P leaching from clear cuts (Niemelä 2001;Laurén et al 2009) (Box 1; Fig. 2).…”

“…During the first 3 years after cutting, the increase without buffer was 1.4 kg ha -1 year -1 of catchment area. Background leaching was 0.1-0.2 kg ha -1 year -1 (modified from Laurén et al 2009) Box 1 An intact RF buffer zone reduced suspended solids and nutrient export to water bodies after forest clear cutting in Finland…”

“…In the Murtopuro catchment suspended solids, N and P leaching increased due to the treatment. However, in the Kivipuro catchment with the RF buffer zone, none of the factors increased (Ahtiainen and Huttunen 1999;Laurén et al 2009). The measured effect on P is illustrated in Fig.…”