Nova Scotia will begin using a new tool aimed at making sure soil in a specific area is healthy enough to support future logging and can rejuvenate the forest once wood is harvested.

The Department of Natural Resources's code of forest practices already calls for harvests and biomass removals to remain below rates that would impact long-term productivity. 

However, a paper published in September in the Open Journal of Forestry points out that much of the existing Nova Scotia soil data and nutrient information on record is no longer accurate.

New soil samples were collected as part of the research, and the paper looks at using a "nutrient budget model" to determine if woodlands can sustain prospective cuts, based on intensity and volume. 

The model considers a variety of factors, most notably soil quality and nutrients such as calcium and nitrogen.

'An exceptionally stressed area'

Researchers looked at 25 plantations around the province and, using the budget model, gauged the nutrient sustainability of those areas based on desired harvest yields. Using several evaluations, between 25 and 50 per cent of projections were not sustainable.

The findings come as no surprise to David Patriquin, a retired biology professor at Dalhousie University. Of greatest note to Patriquin is the finding that some of the lowest calcium levels are in the southwestern part of the province, where large clearcuts could be coming and where soil and rivers continue to struggle from the impacts of acid rain.

"It's an exceptionally stressed area," said Patriquin. "The big issue is that they're inherently poor soils. These are granites and slates and so they essentially have nothing in them. And so they will not support very intensive forestry over many cycles … In my mind there's little question that can only worsen the situation."

Patriquin said the low calcium levels and poor soil, coupled with existing impacts of acidification, makes the region a bad candidate for any clear cutting. He argues selective cutting would allow the forests to remain healthy.

The nutrient bank account

Nova Scotia's soil tends to be acidic at the best of times and has suffered from acid rain. In light of that, the new model helps predict what level of harvesting an area can sustain while still being able to regenerate.

The paper found the level and base saturation of positively charged ions called cations to be much lower in sample areas than what's reported in previous soil surveys.

Cations help neutralize acid and both factors are critical in an area's ability to manage acid inputs and regenerate.

"Think of it as a nutrient bank account," said Paul Arp, a forestry professor at the University of New Brunswick and one of the paper's co-authors. 

The balance of that nutrient bank account is the difference between what's put in and what's taken out, which means nutrients must be replenished to ensure forest health.

The lead author of the paper is Natural Resources scientist Kevin Keys.

Only a suggestion for private land

A spokesman for the department said eight sites slated for harvest in the St. Margarets Bay block were put through the nutrient budget model test following the first release of the paper. All sites passed the test.

Bruce Nunn said in an email the nutrient budget model, along with a new soil sampling program, would be integrated into Crown land management.

But Crown land only accounts for about a third of the province. And while the model will become part of the code of practices for private landowners, there will be no requirement to observe it.