Nutrient Budgeting for AP068499 Beals Meadow

I have asked some questions of personnel at Nova Scotia Natural Resources & Renewables (NSNRR) about the application of  the forest Nutrient Budget Model for Nova Scotia (NBM-NS)  to Crown land block  AP068499 Beals Meadow  which lies an area of highly nutrient-stressed, “depleted” soils. The questions and replies are given below, after a section ‘About the Model’.   There is a  Comments & Conclusions section at the end. The story  involves some fairly complex chemistry; I do what I can to simplify it, but the reader might want to jump to  the Comments & Conclusion  for the meat of the matter.

An Overview of the “Depleted Soil” Issue as it relates to the forests (left) & aquatic systems (centre);   and ways it is being addressed (right).  Click on image for larger version. Graphic from a  presentation to the 2022 Nature NS Celebration of Nature.

View graphic at right, and this NSFN post for some background to this topic:

On logging of Nova Scotia Crown land parcel AP068499 Beals Meadow : 3. The Depleted Soils 19Jun2022

Generally on this page  I have not specifically referenced scientific literature; see items under Scientific Literature in the menu below for the literature I have reviewed. 

Stand-level concerns
Watershed-level concerns
Prescience of the protests
at AP068499 Beals Meadow

A final comment/reflection on NBM-NS

Scientific Literature

Diagram illustrates the major inputs (green arrows) and  outputs (red arrows)  of “base cations” ( calcium, magnesium and potassium) to and from  forest soils that are quantified in the  Nutrient Budget Model. The yellow arrows represent enhanced outputs from the soil caused  by acid rain. NBM-NS is a “mass balance” or  “black box” model (see figure above). It looks simply at the major inputs of nutrients to forest soils and the major outputs, not at the processes the go on in-between such as formation of humus and storage of nutrients in humus, or effects of nutrient fluxes on soil acidity and mobile aluminum levels.


In principle, use of the NBM-NS ( Nutrient Budget Model for Nova Scotia), to calculate “nutrient-sustainable” harvest levels for our forests should allow harvests to occur without reducing site productivity due to net loss of nutrients,  and allow some increase in nutrient  levels on more deficient sites.  At least that is the purpose of the model  as I understand it.

Given information on the location and composition of a forest stand  being considered for harvest,  the  model uses various databases to estimate quantities of nutrients going into the forest stand via weathering of rock and deposition from the atmosphere over the course of a rotation,  and quantities of nutrients going out via leaching over the course of a rotation; the difference is used is to calculate “SusMAI”,  the amount of product in a particular tree species or mix of tree species that could be harvested without causing the nutrient level in the soil to decline; units for “SusMAI” are m3.ha-1.yr-1 (cubic meters per hectare per year)

This SusMAI value is compared with the proposed harvest level, the HarvMAI, which is generally estimated initially as the “merchantable mean annual increment” (MMAI) – basically how much wood was produced on the site over the last rotation (or equivalent of a rotation).

If the SusMAI is equal to or greater than than the HarvMAI, the proposed harvest is considered to be ‘nutrient sustainable’. If SusMAI is very much lower than HarvMAI, it would likely be recommended that there be no harvest at all.

If SusMAI is only a little less or perhaps moderately less than the initially proposed HarvMAI,  then the model can be used to consider  “adjustments to accommodate predictable nutrient deficits”. Keys et al., 2016 cite these examples of adjustments:

For example, species selection, percent removals, and rotation lengths can all be adjusted to varying degrees to reduce the amount and timing of nutrient outputs and related shortfalls. In some cases, as in intensive plantation management, soil amendments could also be applied to offset nutrient losses from harvesting and continued soil leaching.

There is an additional consideration for sites that have been heavily impacted by acid rain (and possibly also by past harvests), and the %BS (percent Base Saturation) has dropped below 15-20%. Then a ‘depletion factor’ (as I call it) is introduced to allow some increase in soil nutrient levels over time, and the SusMAI is reduced accordingly.


For the record, the questions and answers are shown below with some minor editing; there was no editing of the text of actual questions and answers as presented below, only some of the irrelevant or less relevant portions are excluded. I have bolded some of the text in black for questions I asked, in brown for responses.


QUESTION 1 (posed to NSNRR Feb 2, 2020)
Subject: Beals Meadow question

...You were cited in a CBC article saying that the pending cut adheres to the Lahey report recommendations, a position later re-iterated by Minister Rushton.

I am wondering if any nutrient budgeting was conducted as part of that assessment, as that is a component of the SGEM (2021).
Any comment appreciated. I may cite it on NS Forest Notes

RESPONSE  TO QUESTION 1 (from NSNRR Feb 2, 2020)


..Yes, the Nutrient Budget Model (NBM) was considered during the review process by our regional forester for this proposed harvest area.</strong

The sustainable mean annual increment (SusMAI) for this site, as determined by the NBM and based on it’s location within Ecodsitrct 720, is 0.7m3/ha/yr.

The harvest mean annual increment (HarvMAI) is also estimated to be 0.7m3/ha/yr. When applying the NBM, the SusMAI must be greater than or equal to the HarvMAI otherwise the harvest is deemed to be un-sustainable from a soil nutrient point of view.

In this case, the HarvMAI is equal to the SusMAI therefore the soils are deemed to be able to sustain this type of prescription, which is a Uniform Shelterwood.

I would also add that as part of our conditions of approval, we instruct the licensee to avoid all un-mapped inclusions of both shallow and organic soils due to their high sensitivity to operational impacts.

QUESTION 2 (posed to NSNRR Feb 2, 2022)

Am I correct in concluding that if the %BS is low (<15%) in those soils, and I assume it is, than if the harvest mean annual increment (HarvMAI) = sustainable mean annual increment (SusMAI), there will be no improvement in the soil base % BS?

RESPONSES (from NSNRR Feb 3, 2022)

[Our Soil Scientist] would be the best resource on that level of detail.

As it turned out, I had sent a set of questions to the NSNRR Soil Scientist Kevin Keys on Jan 31, 2022 and he responded shortly after the reply I received above. In the response, he cited the questions I had posed on Jan 31, 2022.:

My Question/Comment: “The revised SGEM includes a procedure for assessing sustainability of nutrient supply as a factor in harvest planning. However the guide is vague in regard to what happens when the calculations show that a proposed harvest is not compatible with maintaining nutrient supply: “If HarMAI is greater than SusMAI for a given vegetation type (VT) and soil type (ST) combination, then harvest plan adjustments will be made.” What are the adjustments? These must be specified.

Response: By adjustments must be made, it means that the harvest volume must be reduced so that HarMAI is not greater than SusMAI. This is stated at the end of page 18 in the guide. In other words, no plan should be submitted where retention levels do not also meet SusMAI criteria. This will also be checked as part of the review process.

My Question/Comment: “But more serious in my view is that the objective, as I understand it, is to maintain the current nutrient status. There is no provision to allow the nutrient status to improve on soils which are severely calcium depleted because of acid rain combined with the inherently poor soils that dominate on much of our landscape; previous harvesting has also contributed.”

Response: The objective is not just to maintain current nutrient status, but to also allow for gradual recovery of base cation stores. A reference to this is made on page 18 of the guide where it states: estimated SusMAI values consider historic and ongoing acid rain impacts on base cation nutrient (calcium, magnesium, potassium) contents.

I can appreciate that this detail is easily missed when reading the guide, and that there is no supporting information provided to back this up.

I am working on a progress report that discusses the NBM-NS model and the soil sampling program that supports its use. The plan is to publish this later this spring…In this …report … NBM-NS has been used to generate SusMAI values that incorporate acid rain impacts, and [you can see ] how important and necessary our soil and tissue sampling program has been in allowing the model to generate representative and meaningful output.

I hope that this gives you the information you are looking for. Let me know if you have any questions, or would like to have clarification on any of the topics discussed

QUESTION 3 (posed to NSNRR Feb 21, 2022)

…I do have a follow-up, technical question. You said thatThe sustainable mean annual increment (SusMAI) for this site, as determined by the NBM and based on it’s location within Ecodsitrct 720, is 0.7m3/ha/yr. The harvest mean annual increment (HarvMAI) is also estimated to be 0.7m3/ha/yr.”
*From Keys et al., 2016: One run assumed 80-year-old red spruce (Picea rubens ) with qdbh of 20 cm and 60% stocking with an average merchantable volume of 247 m3/ha (Figure 4). The resulting estimates for sustainable mean annual increment (SusMAI) values ranged from less than 3.0 to more than 8.0 m3?ha?1?yr?1 (Figure 4).

These values seem exceptionally low*

The info given in the PTA is pretty minimal (compared to 2 years ago or so) & I cant make the kinds of calculations I would need to do to figure out whether these numbers are based on a partial (rather than complete) harvest. Also I am wondering what assumption is made about the length of the next rotation.

RESPONSE  (from NSNRR Feb 22, 2022)

… I had to go to the source on this question after reviewing the PTA data associated with this harvest area, here was [our Soil Scientist’s] response:

In this case the SusMAI is low because of the generally higher percent concentration of nutrients in hardwood versus softwood bark and wood, the low clay content and slow weathering of granite tills found in ecodistrict 720, and the requirement to account for acid rain impacts (i.e., use of a 30% base saturation criterion in the model runs).

FYI, we are updating the western region SusMAI tables as we continue to integrate new data from our sampling program.
The updated IH2/ST2-G has SusMAI = 0.8. The updated SP9/ST2-G has SusMAI = 1.4.

So the SusMAI listed above relate to the site conditions at Beals Meadow which is calculated using an 80 year age, and estimates 0.7m3/ha/yr HarvMAI based on the harvest prescription of a Uniform Shelterwood, therefore it is a sustainable treatment from a nutrient point of view, since the HarvMAI is equal to or lower than the SusMAI.

QUESTION 4 (posed to NRR Mar 13, 2022) & RESPONSES
On March 13, 2022, I asked some questions about the assignment of soil type for the Beal’s meadow PTA. View  questions and reply  (given under Current Issues/APO..Beals Meadow/Soil Type). Included in the reply was this statement from the NSNRR Soil Scientist:

The NBM does not take into account the current balance in a nutrient “bank account”, only the estimated inputs and outputs in relation to the soil type and vegetation type combination at a given site. We know base cation nutrient levels are lower than desired, which is why we build in a recovery factor in the NBM runs. If we did not do this, calculated SusMAI values would be higher.

QUESTION 5 (posed to NRR Soil Scientist on Mar 15, 2022) & RESPONSES

Hopefully this will be the last questions for a while anyway. I am trying to get a clear understanding of what the FNBM accomplishes, specifically for the AP068499 Beals Meadow harvest.
#1. As I understand it, a significant portion the NS landscape remains “in exceedance”, although levels of acidifying components in rain are falling. Is this correct?

RESPONSE (from NRR Soil Scientist, Mar 19, 2022)
to # 1: Based on the last critical loads assessment I’m aware of using 2002-2003 data, there were still calculated exceedances over about 60% of forest area in NS (NEG-ECP, 2007). I believe you know the report I’m referring to. Since that time (almost 20 years now) acid deposition rates have continued to decline as noted, so this percentage is likely lower, but I don’t think a new assessment using the same methodology has been conducted, so I don’t know what the comparative picture is now. If you are aware of more recent work, please let me know. What other recent studies have shown, however, is that “recovery” of acidified forest soils across the northeastern region has been slower than expected or hoped, and that is the case here as well.

#2. With the NBM, SustainMAI etc., re: AP068499 Beals Meadow, with the 30% factor, actual BS% will increase but it is not actually predicted or expected to reach ‘acceptable’ /desired levels (15-20% BS) after 80 years – or is it?
Or is that dependent on further reductions in acid rain?
‘Grateful for your patience.
Pls sign me up for a webinar on the topic!

RESPONSE (from NRR Soil Scientist, Mar 19, 2022)
SusMAI output from the model builds in a “recovery” factor to make harvest levels compatible with maintenance of a 30% BS level. This theoretically will allow %BS levels to build back up over time, but we don’t know what the new relative steady-state value will end up being for any given site, and we are not predicting what that value will be or how long it will take (there are lots of factors at play here as you can appreciate, including what the current %BS is at a given site). All we are doing with the nutrient budget model is making sure nutrient removals by harvesting is compatible with maintenance of a 30% BS based on our knowledge of soil and vegetation types, and our estimates of primary nutrient inputs and outputs associated with these units within a given ecodistrict.


I appreciate the assistance NSNRR personnel in helping me to understand some of the ins and outs of NSNBM.

Stand-level concerns

However,  I am left still having to question whether it is appropriate to conclude that the approved-but-not-yet-conducted harvest  at AP068499 Beals Meadow would indeed be  “sustainable treatment from a nutrient point of view” (Re: REPLY  from NSNRR Feb 22, 2022).

The key word is “theoretically” in the final response cited above: “SusMAI output from the model builds in a “recovery” factor to make harvest levels compatible with maintenance of a 30% BS level. This theoretically will allow %BS levels to build back up over time, but we don’t know what the new relative steady-state value will end up being for any given site, and we are not predicting what that value will be or how long it will take.” 

The uncertainty expressed in the ‘but” part relates, I assume,  to the high aluminum, high acidity, low calcium, overall low %BS (percent Base Saturation) state of these soils  that causes them not to respond  or to respond only very weakly to  a net excess of (release of base nutrients via weathering) over (leaching + tree uptake of base nutrients). From the Update on Salmon & Soils:

For NS forest soils, BS% values vary between 5 and 35% (Fig 3 in Keys et al. 2016). Studies in the US cited by Keys et al. indicate that historical pre-acid rain values were above 20%, thus  BS20% is regarded as a threshold for recovery from acid rain.

Other studies suggest 15% BS as a threshold below which “aluminum stress” occurs in forest soils. At these low BS& values,  aluminum becomes mobilized and thereby potentially toxic,  and it also displaces base cations causing more of them to be flushed out of the soil. Acid rain, combined with inherently “poorly buffered soils” that cover more than 60% of NS,  is the major cause of forest soil BS% values falling below 15-20% in NS – the nitric and sulphuric acids cause aluminum to be mobilized, and the mobilized aluminum (Ali) in turn displaces the base cations. The condition is exacerbated by clearcutting.

AP068499 Beals Meadow is situated within the area of base depleted, highly acidic, high aluminum “chronically depleted” soils..   Sketch after Fig 3. in Keys et al., 2016. *Calcium, potassium, magnesium

This issue was widespread over northeastern North America and northern Europe when it was first recognized; regional and international agreements were introduced to reduce acid rain in the 1980s and 1990s and in turn the extent and intensity acid rain-affected soils and watersheds declined. However not in Nova Scotia and not in some other areas with extremely poorly buffered soils.   Nova Scotia  remains the area in eastern North America most severely affected by acid rain, with soils over more than 60% of the landscape exhibiting chronically low calcium/high aluminum/high acidity,  or “chronic depletion” for short.

Why that is so has puzzled the aquatic scientists who have been most involved in studying the issue because of the effects on aquatic life, particularly salmon. Recently Shannon Sterling at Dalhousie University & colleagues have identified some new mechanisms involved (see Fig 3 in Sterling et al. 2020). It is these type of mechanisms  that are not taken into account in the NBM-NS and are the reason (or at least amongst the reasons) for  the uncertainty expressed in the ‘But” part of the statement by the NRR soil scientist.

To state that the AP068499Beals Meadow Harvest   is “is a sustainable treatment from a nutrient point of view” is misleading because it implies that the model fully predicts that these harvests are “sustainable treatment from a nutrient point of view”. One simply cannot say that because it does not take into account the now chronic nutrient-depleted, high aluminum state of these soils.

Likewise, I find that some of the statements in the paper by Keys et al, 2016 convey a sense that the model is highly predictive, that treatments can be adjusted to make harvests sustainable etc, e.g. the following:

Although not perfect, models like NBM-NS (combined with necessary GIS data) al- low forest managers to better evaluate planned management regimes with respect to re- gional and local nutrient inputs, and to make adjustments to accommodate predictable nutrient deficits. For example, species selection, percent removals, and rotation lengths can all be adjusted to varying degrees to reduce the amount and timing of nutrient outputs and related shortfalls. In some cases, as in intensive plantation management, soil amendments could also be applied to offset nutrient losses from harvesting and continued soil leaching.

In fact from what we know, it seems quite likely that future growth of  forests  on these sites will be reduced in comparison to the past because of nutrient limitations. There is already anecdotal evidence of poor recovery of some recently clearcut forest stands in the area of AP068499Beals Meadow.

So I have to  conclude that at the stand level,  use of NBM-NS to reduce  harvest levels will  do very little to actually ameliorate/mitigate the highly depleted state of the soils.  It could be expected to  reduce somewhat the negative effects of harvesting that otherwise add to the ongoing negative effects of acid rain on chronically depleted  soils and waters*;  at best,  it might speed recovery by a few years or more over the period of perhaps several  decades it will take for full recovery in comparison to the time it would take if  a higher level of harvesting occurred –  but that will be slower than the recovery if the stand is not harvested at all.
* Noseworthy (2011) estimated that stem only-clearcuts increase Base Cation Depletion over the background acid rain effect averaged for all of Nova Scotia by 52%. Keys et al., 2016 do not provide a figure, but comment that “Nutrient assessments are even more important in areas that have been impacted by long-term acid deposition since harvest removals can exacerbate declines in base cation levels (especially Ca) in affected soils.”

Watershed level concerns
I have an additional concern at  the watershed level  about application of NBM-NS to estimate nutrient sustainable harvests:

If, in an acid stressed watershed, harvests are focussed on the higher volume stands on above average fertility soils, e.g., on a drumlin, those harvests will lower reserves of key sources of calcium in the watershed as a whole, i.e. the harvest may be “sustainable” at the stand level, but the fact remains that reserves of calcium are being reduced in  an already calcium stressed watershed.

This has big implications for aquatic life. Thus I have suggested that decisions about harvesting should be made at the watershed level and harvesting be avoided or greatly reduced in highly acid-stressed watersheds.*
*I have discussed this suggestion directly with DNR/L&F and aquatic scientists, put it in submissions etc.; See On Salmon and Soils, An Update/Concerns Remain; Acid Rain + Clearcuts = permanent loss (an op-ed in 2016); A critical issue: nutrient depletion in soils of Nova Scotia’s forests (Comments and diagram prepared for meetings with MLAs, re: clearcutting for biomass electricity).   A slightly modified form of the suggestion made its way into the Addendum of the Independent Review (p.30) but went no further.

It’s quite likely that clearcutting in NS has exacerbated water quality issues for salmonids, and possibly even humans (via high aluminum levels) – view literature cited  Rotteveel & Sterling 2021*;  in their  research, they observed  that “Forest cover has moderate negative correlations with base cation concentrations…; This may be due to several factors: regional bedrock composition, selection of the most productive (that is, base cation rich) lands for agriculture, and base cation rich depletion due to past and unknown current harvesting.” The impact of current harvesting specifically (versus the broader category of forest cover) was unknown, apparently because the NS Government does not make the data publicly available; under Future Research they comment “To advance our understanding of the effects of forest harvesting on water chemistry, the Nova Scotian government could make forest harvest publicly available.”
*The full paper has restricted access online , the related   Dalhousie University thesis by Lobke  Rotteveel (2020) contains the same literature reviews.

Did a clearcut cause the crash of the brook trout population at Beals Meadow?

Headwaters of Beals Brook, photo by Daniel Baker.

AP068499 Beals Meadow is a possible case in point where clearcutting has tipped an already stressed aquatic system over the edge. Said Daniel Baker about the fishing:

“My dad, myself, my son camped out in tents at the duck pond to the left of that picture they clear-cut a huge chunk of the forest and it ruined the fishing up there. Before they cut it, my father and I could stand in one spot and catch 10 trout as fast as we could bait our hooks after they cut it not a bite for over 10 years.”

Clearcuts on such depleted landscapes can be expected to be a shock event to the aquatic systems chemically and physically; the latter  is well understood:

Silt clogs spawning beds in stream channels, causing fish eggs to suffocate and die. After heavy rains repeatedly rip their way downstream, stream channels are left wide and shallow. Summer water levels become very low. Increased amounts of sunlight overheat the water, increasing evaporation and causing cold water species like salmon and trout to suffocate for lack of oxygen in the water. – Bob Bancroft in Clearcutting & wildlife don’t mix – Saltscapes Magazine

It seems likely there is a chemical shock as well. Initially, after a clearcut there would be a flush of nutrients into the aquatic systems, followed by the normal drip-drip-drip, but at a lower level than before the clearcuts;   in an already stressed system, that could be sufficient, especially in combination with the physical disruptions,  to exceed critical thresholds for the trout. Climatic warming may accentuate  the chemical effect, as described by Sterling et al. 2020.


In practice, the only treatment that has proved effective in relieving chronically acid-stressed forest soil is the addition of  neutralizing amendments, principally lime, which is calcium rich so it acts to both reduce acidity and add calcium.  Experiments on the use of lime to mitigate effects of acid rain were initiated by aquatic scientists and managers in late 1970s and 1980s in efforts to improve water quality, for salmon fry in particular. Later-on, catchment liming – the addition of lime to the usually forested watershed of salmon populations – has been tested and proved effective in both raising the aquatic pH and in some cases ameliorating calcium deficiencies and related stresses of the forest soils. Based on information gained from successful trials in NS, the Hydrology Research group at Dalhousie University produced a comprehensive Terrestrial Liming Guidebook for South Western Nova Scotia in 2018.

Adding lime to forest soils to address local deficiencies has been limited largely to to sugar maple stands where it  has proven effective in reducing “sugar maple decline”.

Fertilizing forest soils is not a step to be taken quickly because there are potentially serious adverse effects, especially with more complex fertilizers such as processed sewage products  studied by NSNRR Soil Scientist Kevin keys for possible use in HPF sites (view related research by Keys).

By and large the use of lime has proved relatively innocuous with the exception that it may make the soils more conducive to invasion by earthworms.

So the question has to be asked, why hasn’t DNR/L&F/NRR been more actively considering and even promoting routine liming of forest soils in areas of chronically depleted soils? This option has been mentioned in the various  documents produced by NRR related to Ecological Forestry  only in relation to High Production Forestry.  From the 2016 paper by Keys et al on the  NBM-NS:

3.4. Management Implications

Although differences in site quality and species suitability are well understood by forest managers, it is often assumed that increased yields predicted through intensive man- agement are sustainable on any given site. This perception is likely due to (i) the long time frames associated with forest management, including plantation management, (ii) the relatively short history of intensive forest management in Canada, (iii) gradual rather than abrupt changes in growth-limiting factors, and (iv) the lack of effective tools to evaluate forest nutrient sustainability.

Although not perfect, models like NBM-NS (combined with necessary GIS data) allow forest managers to better evaluate planned management regimes with respect to regional and local nutrient inputs, and to make adjustments to accommodate predictable nutrient deficits. For example, species selection, percent removals, and rotation lengths can all be adjusted to varying degrees to reduce the amount and timing of nutrient outputs and related shortfalls. In some cases, as in intensive plantation management, soil amendments could also be applied to offset nutrient losses from harvesting and continued soil leaching.

In that paper  ‘amendments’ are cited as relevant only for High Production Forestry.

Likewise, in the HPF Phase 1 Final Report (2021), there is a fairly lengthy section on Soil Amendments (p9), including liming. In the SGEM (Nova Scotia Silvicultural Guide for the Ecological Matrix, “Integrating soil nutrient sustainability into harvest prescriptions” is considered necessary for “stand-level management, maintenance of soil health and related biodiversity” (p17), but the only mechanism advised for for addressing it is  use of NBM-NS “to ensure nutrient sustainability.’ (p18);  as discussed above, for currently  chronically depleted soils that seems to mean, ongoing chronically depleted soils – and ongoing harvesting, even if somewhat reduced, when in most cases, no harvesting is likely more approbate from a sustainabilty perspective..

Surely  a coordinated approach between NS Natural Resources and Renewables, NS Fisheries & Aquaculture, and other aquatic and forest researchers and managers in NS to identify and treat watersheds where forest liming is appropriate is called for and would  benefit for both aquatic systems and forests.

In fact, while not mentioned anywhere on the NRR website, NRR Soil Scientist Kevin Keys has recently collaborated with aquatic scientists at Dal and the Atlantic Salmon Federation in a project on helicopter liming, with very promising results for the forests:

Helicopter Liming to Help Restore Acidified Forest Soil Productivity
vEGU21, the 23rd EGU General Assembly, held online 19-30 April, 2021, id.EGU21-13660
Caitlin McCavour  and   Shannon Sterling (Dalhousie University, Earth and Environmental Science, Canada);
Kevin Keys (Nova Scotia Department of Lands and Forestry);
Edmund Halfyard (Nova Scotia Salmon Association)SUMMARY (bolding inserted)
Decades of acid deposition across northeastern North America has caused excess leaching of soil base cations (Ca2+, Mg2+, K+) and increases in bioavailable aluminum (Al3+) that, in combination, have resulted in widespread decreases in potential forest productivity. Despite major reductions in SO2 and NOx emissions since the 1990s, forest soils across the region have shown few signs of recovery from acid deposition impacts and it could take decades or centuries for natural recovery to occur. As a result, affected forests are stressed, less productive, and more prone to climate change-induced damage. Helicopter liming of upland forests may be an effective way to jump-start the soil recovery process. Here we report on early results (one-year) from a helicopter liming trial in Nova Scotia, Canada where 10 tonnes/ha of dolomitic limestone was applied to approximately 8 ha of mature red spruce (Picea rubens) and mature tolerant hardwood (Acer spp. and Betula spp.) forest. Data are presented on (i) the effectiveness of helicopter liming in forests; (ii) the initial chemical response of forest floor organic and mineral soil horizons; and (iii) the initial chemical response of red spruce foliage, maple foliage, and ground vegetation. Preliminary results showed that despite non-uniform lime distribution, there were significant increases (P < 0.05) in Ca2+, Mg2+, pH, and base saturation (BS), and significant decreases in total acidity in forest floor organic horizons in both the mature red spruce and tolerant hardwood stands; however, there were no significant changes in Al3+. The initial chemical response in sugar maple and red spruce foliage showed significant increases in the Ca/Al molar ratio . The initial response in ground vegetation (Schreber”s moss; Pleurozium schreberi and wood fern; Dryopteris intermedia) showed significant increases in Ca2+ and decreases in K+ for both species; however, Schreber”s moss also showed significant increases in Mg2+ and Al3+ while wood fern did not. These early chemical results are promising and further support the use of helicopter liming as an effective tool to combat lingering effects from acid deposition in acidified forests.

Of particular note is the statement that “Helicopter liming of upland forests may be an effective way to jump-start the soil recovery process.”  I was pleased to see it, as it is at least an implicit acknowledgment that application of NBM-NS without amendments is not going to be  effective, that indeed, we need liming  to “jump- start” the soil recovery process.

Are there potential downsides? Yes. $, and perhaps it would facilitate earthworm invasions so some precautions would be appropriate; there could some other subtle effects on biodiversity.

Are there downsides to doing nothing? Very definitely. We are going to lose aquatic and terrestrial biodiversity,  we are going to lose forest productivity and potential carbon capture; and if we keep logging – even partial logging on these already extensively clearcut landscapes,  we could end up with barrens.

So liming of chronically depleted forest soils in NS – even if they are not being harvested –  is a strategy for mitigating effects of acid rain and past clearcutting that should be actively considered and broadly discussed, with   forestry and aquatic folks, managers and scientists, foresters and fishers,  politicians and every day folks.

Without a meaningful strategy for addressing the chronic depletion issue, it’s very hard from a climate-biodiversity perspective and even ‘future forestry perspective,  to justify anything more than very conservative logging on these lands, and  that should be reserved for local use, not operations on the scale of WestFor.

By the same logic, one could argue that very  limited High Production Forestry with use of amendments as currently envisaged could  be justified – but not if it involves harvesting the last remaining older stands on already heavily clearcut landscapes, as in the area of AP068499 Beals Meadow.

Prescience of the protests at  AP068499 Beals Meadow

The protests and concerns  about harvesting at AP068499 Beals Meadow have proven to be  highly prescient , and not by accident. They were initiated because of landscape level concerns about a proposed harvest, concerns that were intuitively obvious to people who knew the area well.

As laid out in this Series of Posts on Logging  in the vicinity of AP068499 Beals Meadow:
1. On the extent of clearcutting  23Jan2022
2. On Highgrading at the Landscape Level 27Jan2022
3. On the depleted soils

those concerns are well backed up.

The government/NRR response, contending that the harvests as announced  comply with  Lahey Recommendations  simply shows their limited grasp of those recommendations or more concerning, a deliberate attempt to ignore the parts they don’t like.   

We have to do better, at beginning with AP068499 Beals Meadow

Some final comments/reflection on NBM-NS

I have been critical of some of the statements by Keys or Keys & Co. related to use of NBM-NS. I am doing so from the perspective of an academic and scientist  (retired but hopefully not yet mentally moribund).

While I think some of the statements by Key’s & Co are misleading,  I don’t think at all that they were written to be deliberately misleading.  Keys has very high scientific standards, and his regular publishing in peer reviewed scientific journals really sets him apart from criticisms I have had about some of the other scientific research conducted by DNR/L&F/NRR.* He has been completely open to discussing NBM-NS with me.
*Notably in  relation to  Natural Disturbance Regimes (see NSDNR’s nature-based forestry; XXX 

From my perspective, what’s lacking in the paper by Keys et al., 2016 and in the brief  mention of the use of NBM-NS in the SGEM  is an explicit description of the limitations of the NBM-NS as a predictive tool for predicting the future nutrient supply for forests stands on  highly depleted soils, e.g., as he acknowledge in the Q&A’s above: What other recent studies have shown, however, is that “recovery” of acidified forest soils across the northeastern region has been slower than expected or hoped, and that is the case here as well.” 

The language around use of the model  implies – at least to me and probably many others –  some confidence that its application will result in  harvests being sustainable “nutrient-wise”, not ‘theoretically sustainable’ as Keys explained separately.  Given  the uncertainties of the model and that this is apparently a trial of an approach not application of a proven approach, one would expect  that  followup observations to evaluate its effectiveness and allow some “adaptive management” would be part and parcel of the use of model, but none are mentioned.  Even if site-specific soil sampling is not required to run the model, surely it’s appropriate as  baseline info. to assess the model’s effectiveness.

There is a more detailed description of how NBM-NS will be applied in the HPF Phase 1 Final Report  than there is in the SGEM. I  am not very concerned about application of NBM-NS in HPF as it explicitly involves using amendments, which as stated in the ‘Helicopter Liming paper’ – but not in the HPF document – seems to “jump start” a more normal nutrient regime on highly depleted soils.

One might say that I have ‘mis-understood the science’. There is some truth to that; I certainly mis-understood earlier on what NBM-NS can do and what it can’t. In particular, I assumed that there was a soil compartment in the model with the actual levels of soil nutrients, that the current levels are specified, and that the model would predict how that level changes with time.* I read a lot of literature in an effort to better understand the model, the context etc, stated my understanding and how I got there and asked Keys & Co, for comment to which they responded, and that led to my  conclusions above including  my realization that the model doesn’t predict actual level of soils nutrients. Over the last several years, I have  also had discussions with two aquatic scientists about the broader topic (soil and aquatic acidification),  and with one other co-author of the Keys et al paper.  So that’s how I arrived at my ‘final’ set of conclusions, now publicly shared.
*That was a bias that probably came from my own use, eons ago, of a similar but simpler model to predict levels of soil organic-N and cereal yields in an organic farming system.

Those of course may also ‘call for a response’, and if so, I hope Keys & Co, will respond. A major reason I make this all public is because  there is a dearth of information on the  DNR/L&F/NRR website or discussion otherwise  about  the depleted forest soils in Nova Scotia and their relation to aquatic acidification issues. It’s a critical issue for biodiversity, for future wood production  and carbon capture by our forests and for inland fisheries and aquatic life broadly in Nova Scotia.  Yet the topic  is not  mentioned  in the last State of the Forest Report (2016), the Field Guide to Forest Biodiversity Stewardship (2019),  the Ecological Land Classification (2017), or in the Woodlot Management Home Study Series. Nor is the  topic is not mentioned in the two recent  scientific papers on Natural Disturbance Regimes in which multiple factors affecting nutrient supply and forest composition are discussed. No wonder we are not talking about it.

Aquatic scientists have been raising the alarm bells clearly and comprehensively, including a call for more open access to forestry data  so they can more precisely assess the impacts of forestry practices on water quality in NS (Rottevel and Sterling 2020).

“This Guidebook was developed to inform future mitigation and recovery strategies for Atlantic salmon and support effective terrestrial liming in SWNS.”

Surely  a coordinated approach between NS Natural Resources and Renewables, NS Fisheries & Aquaculture, and other aquatic and forest researchers and managers in NS to identify and treat watersheds where forest liming is appropriate is called for and would  benefit  both aquatic systems and forests both harvested and not harvested the areas of depleted depleted soils.

It’s not cheap,  and perhaps that is the reason DNR/L&F/NRR has not been  discussing liming in relation to management of Ecological Matrix (in contrast to the HPF sites); the return is simply too low. I suggest if that is the case,  those are situations  in which no harvesting at all should occur.

AP068499 Beals Meadow is  likely case in point. At the very least, soil samples should be taken to assess the current state of the soils – are they still in the range 5-15% Base Saturation; are there signs of some recovery? OR have they fall even further (to less than 5-15% Base Saturation)?

If there are no signs of recovery from the depleted state of the soils in the area of AP068499 Beals Meadow, that in combination with  extensive clearcutting in the past  followed by “high grading at the landscape level” would call  for a complete stop on harvesting of Old Forest AND  beginning some catchment liming.