Baseline Results

Study of Fire Effect in Soil Conditions

Physical and Chemical Analysis

Study design

Comparing soil conditions in burnt and unburnt Pine forest plots.

Test plots

NCBurnt forest(Negative Control)
ISBurnt forest(Intervention site)
PCUnburnt forest(Positive Control)

Timeline

Summer 2025Wildfire
March 2026Soil Sampling
Ash2Soil Intervention Site
February 2027Assessment of intervention effect

Location

Ourondo, Covilhã, Portugal

NDVI scale*

Dead plantStressed plantModerately stressed plantHealthy plant

*Normalized Difference Vegetation Index: measure the health, density, and amount of living vegetation using satellite imagery or remote sensing

Results

Texture

Feel Method

Relatively coarse
Rapid infiltration and drainage
Lower water- and nutrient-holding capacity
Prone to erosion

Fine-textured
High water- and nutrient-holding capacity
Slow drainage
Prone to compaction when wet

Intermediate-to-fine texture
Relatively high water and nutrient retention
Moderate-to-slow drainage
Vulnerable to compaction when wet

pH VALUE

All plots are acidic.

PCISNC

AcidicNeutralAlkaline

Cation exchange capacity and base saturation

	CEC (cmol⁺/kg)	BS (%)
NC	2.93 cmol⁺/kg	76.7%	High
IS	2.89 cmol⁺/kg	53.7%	Medium
PC	2.98 cmol⁺/kg	32.2%	Low

All plots have very low CEC.Medium = 10-20 cmol⁺/kg | Very High > 40 cmol⁺/kg

Base saturation should always be read alongside CEC:P0 has high base saturation, but its very low CEC still limits the absolute reserve of Ca, Mg, and K.

Organic matter & macronutrients

NC*Very high C:N (17.3)

Organic Matter: High
Nitrogen*: High
Phosphorus: Very low
Potassium: Excess
Calcium: Low
Magnesium: Excess

IS*Very high C:N (17.5)

Organic Matter: High
Nitrogen*: Medium
Phosphorus: Very low
Potassium: High
Calcium: Very low
Magnesium: High

PC*High C:N (14.6)

Organic Matter: High
Nitrogen*: Excess
Phosphorus: Very low
Potassium: High
Calcium: Very low
Magnesium: Low

Key findings & conclusions

All three plots are acidic and weakly buffered. With low pH and CEC values, nutrient availability and root conditions are constrained. The soils also have limited capacity to retain added nutrients.
Phosphorus and Calcium are critically low in all plots.
NC has the highest calcium and manganese reserves, but remains nutrient-limited.
IS is the most vulnerable plot for organic-matter and nitrogen restoration. It has the lowest organic matter (4.8%) and total nitrogen (0.16%), as well as the lowest P and Ca. Its C:N ratio of 17.5 also suggests that nitrogen will be released slowly from organic matter.
PC has the largest organic and nitrogen reserve, but is not a fertile benchmark. With 12.6% organic matter, 0.50% total N and a lower C:N ratio of 14.6, P3 has the greatest potential for gradual nitrogen mineralisation. However, it also has the lowest base saturation, no detectable extractable P, low Mg and extremely low Mn, so its high organic matter does not compensate for its severe chemical limitations.
Management should prioritise erosion control, conservative acidity correction, targeted phosphorus supply, and protection or restoration of organic cover.