Modeling Slovenian Forests under climate change and future management

Abstract

Forests’ high importance due to the ecosystem services they supply is undisputed. The mitigation of climate change through net uptake of carbon dioxide from the atmosphere (carbon sinks) is one of them and the biodiversity hosted by a forest is an important underpinning of its functioning and may help promote the resilience of forest ecosystem services to future change. Uneven-aged forests generally support high levels of biodiversity, but how can management also fulfill the goal of increased carbon storage? This question was addressed by studying the case of Slovenia, a European country with high coverage of uneven-aged forest.

Using LPJ-GUESS, a dynamic vegetation model, Slovenian forests were modeled under climate change and future forest management for a management period from 2011 to 2100. Three different climate change scenarios were combined with management alternatives in which harvest intervals were altered to differ gap sizes created during harvest while keeping the overall harvest the same. Forest regeneration, net ecosystem production (NEP), plant functional type distribution, several biodiversity indices, and an optimization index that quantified the degree of balance between carbon storage and biodiversity maintenance goals were calculated and analyzed to determine optimal management.

Increasing harvest intervals led to increases in regeneration, NEP, diameter diversity, and beta diversity between forest patches. These positive impacts are were identified as the result of larger gaps during harvest, which allow for better regeneration and recruitment. More severe climate change scenarios increased regeneration, NEP, and most of the biodiversity indices. This is mainly explained by fertilization effects occurring with higher levels of atmospheric CO2, longer vegetation periods, and beneficial conditions for more temperate and even Mediterranean species. The optimization index indicated the optimal management during all climate change scenarios is the longest examine interval (70 years) which corresponds to the creation of larger gap sizes.

The finding that larger gap sizes optimize carbon storage and biodiversity in uneven-aged forests indicates that group selection or shelterwood forestry may be ideal methods to achieve these goals while maintaining a constant harvest. Confirmation through field studies focusing on more aspects of biodiversity and providing a clearer picture of tree species diversity would be necessary to confirm these results. However, forestry biodiversity strategies will always require a diverse set of management strategies and the mitigation of climate change cannot rely on carbon storage in forests alone.

Popular Abstract

Forest management for climate change and biodiversity

Forests fulfill many important functions for humans. Wood is harvested for economic gain, the storage of carbon in biomass and soil mitigates climate change, and high biodiversity ensures that many species are supported, and forests can adapt to change and recover from disturbance. Forest management offers the opportunity of tailored interventions to maintain those functions and services in the face of factors that affect them, such as climate change.

In Slovenia, forest management is multi-faceted. The forests are uneven-aged, i.e. trees within a forest stand are always of different age classes, and close-to-nature forestry is practiced. This means that continuous forest cover is maintained by removing only a few or a group of trees during harvest. The national forest regulations prohibit clear-cutting. This kind of management ensures natural dynamic forest processes and high levels of biodiversity. But is there a way to optimize the forest’s carbon storage as well?

To explore this question, I modelled Slovenian forests under three climate change scenarios of differing severity using LPJ-GUESS, a dynamic vegetation model, incorporating an explicit representation of forest growth, age structure dynamcis and tree species succession. Different harvest strategies were applied that modified harvest intervals while maintaining overall harvest harvest amount constant. The goal was to uncover which harvest interval would benefit biodiversity and carbon storage most, and how different climate change scenarios would impact management outcomes.

Longer harvest intervals, associated with bigger gaps, led to more carbon stored and a bigger diversity in tree diameters as well as higher diversity between forest patches. Bigger gaps increase the regeneration because more light reaches the forest floor. This allows more trees to grow and increases the carbon uptake. Climate change scenarios that are more severe led to higher carbon storage and increased biodiversity for most indicators in the simulations. This is likely because forests’ vegetation periods were extended and because they were fertilized with additional atmospheric CO2 which is associated with several emission scenarios. Higher temperatures in these scenarios also meant that more temperate and Mediterranean species could establish and grow. The optimal management for both biodiversity and carbon storage was determined to be long harvest intervals.

With a global forest carbon management, climate change could be slowed down. Higher levels of biodiversity ensure that forests can adapt to, recover from, or resist future change. My findings suggest that, larger gaps optimize carbon storage and especially structural biodiversity in forests while keeping the overall harvest constant. This suggests that forestry methods such as shelterwood forestry and group selection, which produce bigger gaps, could be useful in uneven-aged forests especially in the face of climate change and when applied on a broad scale. It is, however, still important to reduce emissions and have a diverse set of strategies to manage forest biodiversity. Neither climate change nor biodiversity can solely be controlled through harvest management.

Master’s Degree Project in Conservation Biology
Department of Biology, Lund University

Advisor: Mats Lindeskog
Department of Physical Geography, Lund University

• author: Schild, Laura
• supervisor: Mats Lindeskog
• organization: Degree Projects in Biology
• course: BIOM02 20202
• year: 2021
• type: H2 - Master's Degree (Two Years)
• subject: Biology and Life Sciences
• language: English
• id: 9059648
• date added to LUP: 2021-06-29 10:51:17
• date last changed: 2021-06-29 10:51:17