Changing forest area and forest productivity - climatic and human causes, effects, monitoring options, and climate mitigation potential

Informations

Funding country

Norway

Acronym

-

URL

-

Start date

1/1/2018

End date

12/31/2022

Budget

1,225,203 EUR

Fundings

Abstract

Global climate predictions show a trend of faster forest growth and advancing forests into the boreal-alpine ecotone. To maintain biodiversity and fulfill international obligations to reduce GHG emissions, it is important to understand how changes in the boreal-alpine ecotone will influence vegetation and carbon sequestration potentials. Summer farming and herbivory have historically been important factors influencing the boreal-alpine ecotone. One of the main tasks in FORESTPOTENTIAL is to assess how forest area may change near alpine regions. To enable such analyses, field data of the establishment, growth and mortality of pioneer trees in the tree line on 36 sites along a 1 100-km latitude gradient were collected during 2018. At the same time, we collected vegetation data. Furthermore, in 2020 and 2021 we have collected soil samples to enable analyses of the relationship between tree properties and soil carbon. This dataset will be an important asset in analyses of the effect of tree migration on carbon storage in soils. The same sites have been measured before (2008 and 2012), within a project financed under the NORKLIMA program. On the earlier measurement occasions, data from airborne laser scanners were also collected as an transect from the southernmost to the northernmost site. This data set gives a unique opportunity to follow the tree line dynamics over time. For each site, we also have data describing herbivory pressure climate. Based on this data, we are able to do analyses that distinguish between climatic and anthropogenic impacts on the tree line dynamics. To enable analyses of the effect of the different drivers on the expansion of trees into the current alpine zone, measurements of tree growth were performed in an area used for sheep grazing in 2019. The same area was previously used in controlled experiments where the vegetation was exposed to different grazing intensities by means of enclosures. The different grazing intensities were 0, 25, and 80 sheep per square km. In 2016, after the experiment had been going on for 15 years, the fences were removed, and from that time the entire area was exposed to an identical grazing pressure. The analyzes show that sheep herbivory affect the establishment of birch trees. On those areas within the experimental site where sheep where excluded during the experimental period, the recruitment of birch were significantly reduced when the sheep where re-introduced. Within the same areas, the prevalence of the larger trees were higher compared to the prevalence on those areas where herbivory had been going on the whole time for the duration of the experiment. This indicates, not only that herbivory can change the tree line dynamic and the distribution of trees in different life stages, but also that the current size distribution of trees at the time when herbivory is introduced, decides the effect of the herbivory. Climate change affects also the productivity of existing forests. For Norway a positive growth trend has been anticipated in recent years. Monitoring of future changes in productivity is essential because the forest resources are of great importance to private sector activity and the nation?s economy, and climate mitigation potential. Current methods to determine productivity are based on the average productivity over a tree's lifetime. In times with rapidly changing climate, productivity determined according to conventional methods may not reflect current and future productivity. Instant productivity may be determined by use of modern remote sensing techniques such airborne laser scanning, and we have already carried out a study that that analyses the possibility of using bitemporal laser scanner data to determine productivity. The method is based on observing height growth over a known period. The results show that the method is accurate, and that it most likely will replace the current methods. We have carried out an operational, large scale test, where the effectiveness of our new method was compared to the effectiveness of the current methods. The results showed that the new methods were more economically effective than the other methods in the comparison. Furthermore, the research activities related to productivity are continued in the Centre for research-based innovation, SMARTFOREST. FORESTPOTENTIAL will study how changes in forest area and forest productivity influence economic opportunities in the sector. Scenario analyses with bio-economic and global economic equilibrium modeling tools accommodating carbon sequestration to consistently address economic management opportunities and climate mitigation will be performed to jointly address effects of climate change on nature and society. We are close to finishing the construction of a new forest simulator which will be a main tool in these analyses. The simulator will provide scenarios of the potential development of Norwegian forests under different framework conditions.