Natural regeneration of Norway spruce on spoil banks is more effective than technical recultivation methods

This conclusion comes from a recent study conducted by scientists from Charles University, the Forestry and Game Management Research Institute (VÚLHM), and the Biological Centre of the Academy of Sciences of the Czech Republic, which was published in the journal Ecological Engineering.

The research compared the growth of fourteen-year-old Norway spruce that had naturally regenerated in the undergrowth of pioneer trees on successional (naturally developing) areas with that of those planted on technically recultivated sites in the Sokolov basin.

Photo 1: This image compares the growth of a 14-year-old Norway spruce that was planted directly into tailings as part of a traditional recultivation effort (A). The spruce is growing in an area that lacks significant soil horizon development (B). In contrast, there is an adjacent area that has undergone spontaneous succession for 40 years after the tailings were filled (C). In this area, Norway spruce naturally regenerates in the undergrowth of pioneer tree species such as linden, poplar, aspen, and birch, demonstrating greater growth. This enhanced growth is attributed to the positive impact of the pioneer trees on soil properties, particularly pH levels. The soil here is more optimal due to a higher accumulation of organic matter, which naturally acidifies the soil. A more suitable pH level likely improves nutrient availability and fosters the development of ectomycorrhizal fungi. Authors: Doubravka Šimáňová, Olga Vindušková.

Main Results

• Norway spruce individuals growing in naturally developing stands were significantly taller, contained more chlorophyll and phosphorus in their needles, and had a higher proportion of mycorrhizal root tips.
• The soil in successional areas had a lower pH but a higher ergosterol content, along with stronger mycorrhizal colonisation of the roots. These factors together create more favourable conditions for the growth of Norway spruce.
• Although the density of young Norway spruce individuals in the successional areas was significantly lower than in the recultivated (reclaimed) areas (approximately 700 vs. 11,600 trees per hectare), the individual trees in the successional areas thrived more effectively.

Photo: Norway spruce thrives in the cover of various pioneer tree species, author Jan Řezáč

Relevance for practice

The study indicates that traditional technical methods of recultivation (reclamation)—such as levelling the terrain and planting numerous seedlings—may result in less favourable conditions than allowing natural succession to occur. Natural development, combined with the presence of pioneer tree species, fosters an environment conducive to the growth of desirable climax commercial tree species like Norway spruce. While these species can naturally regenerate in such areas, their growth could be further enhanced by underplanting with appropriate target tree species.

“Our results indicate that allowing space for pioneer trees and leveraging their beneficial effects can make forest restoration on dumps more cost-effective, efficient, and ecologically sustainable. For instance, soil restoration utilising pioneer stands could be complemented with underplanting of target climax tree species and other cultivation interventions“, says Dr Olga Vindušková from Charles University, the lead author of the study.

Photo: A little spruce tree growing in the inhospitable environment with a birch, author Jan Řezáč

This research was funded by the Technology Agency of the Czech Republic through the SIGMA program (project no. TQ03000234), which focuses on the reclamation potential of pioneer tree species in restoring calamity clearings and degraded habitats (projekt č. TQ03000234 Meliorační potenciál pionýrských druhů dřevin při obnově kalamitních holin a degradovaných stanovišť).

The paper „Natural regeneration of Norway spruce under pioneer trees outperforms conventional reclamation on post-mining sites“ can be downloaded here.

Authors: Olga Vindušková, Doubravka Šimáňová, Erika Reitschmiedová (Univerzita Karlova v Praze); Jakub Černý (Výzkumný ústav lesního hospodářství a myslivosti, v. v. i.); Jan Frouz (Biologické centrum AV ČR, Univerzita Karlova)

Prepared according to the original: Jakub Černý, VÚLHM, v. v. i., e-mail: cerny@vulhmop.cz