Raisa Mäkipää Natural Resources Institute Finland Forest ecology and carbon: tree species competition and allometry of trees Raisa Mäkipää Natural Resources Institute Finland

Current target - sustainable forest management Multiple targets of the forest management include timber production, recreation values, maintenance of biodiversity and mitigation of climate change by forest carbon sinks. Even-aged management of monocultures, which has been prevailing silvicultural system, may not be the economically most profitable system (Pukkala et al., 2013; Rämö and Tahvonen, 2014, 2015; Tahvonen et al., 2010). Even-aged monocultures are suggested to be vulnerable to disturbances and the consequences of climate change (O’Hara et al., 2007; Seidl et al., 2011). The low structural diversity of the tree stand is not optimal for biodiversity, ecosystem productivity and forest carbon sequestration. NEED to develop tools that facilitate analysis of the various strand stuctures and multiple targets of forest management. Teppo Tutkija 19.9.2018

This is art – cannot be measured by conventional methods, which accounts height, canopy height and diameter (at height of 1.3 m) Source Kalela 1945 drawing by Miettinen & Liuksiala Raisa Mäkipää 19.9.2018

70 years later – we can model forest carbon dynamics, but direct measurements of whole tree volume haven’t been possible before TLS Teppo Tutkija 19.9.2018

This is art and more. Exact information on tree dimensions, incl This is art and more! Exact information on tree dimensions, incl .whole tree volume estimate that can be used in forest C models Source: Data processing Raumonen, data from Luke/Mäkipää, scanned by NGC Teppo Tutkija 19.9.2018

Estimation of the C flux from trees to forest soil – current approach Biomass estimation, models based on sample branches,etc Litefall esitimated, based on estimated canopy biomass and changes in the height of the living canopy Terrestrial laser scanning provide data on whole tree volume and biomass -> possible to use stand lspecific estimates and not only gereralized biomass and litter models. Teppo Tutkija 19.9.2018

Teppo Tutkija 19.9.2018

Flowchart of EFIMOD we used the ecosystem model EFIMOD (Komarov et al., 2003). It is built on population ecology and matter-balance principles, and it can capture the important ecological processes in a forest stand: soil decomposition processes, growth processes and light and root competition that enables us to simulate ecosystem response to fast and severe environmental changes. The model is individual-tree based and utilizes the exact spatial location of each tree. This feature allows us to simulate cuttings (harvesting) of any strength, with the ability of ‘fine-tuning’ a treatment such as individual tree selection. Another important feature is that EFIMOD accounts for below-ground competition between tree individuals with a submodule that describes growth and competition of roots.

The simulated scenarios of stand development - from even-aged management to uneven-aged stand structure and management. Simulation starts with two precommercial thinnings. After reaching the certain values of stand basal area (denoted here as ‘trigger point’) a series of selection cuttings are simulated. The period between two consecutive selection cuttings is defined by the harvesting interval. The intensity of selection cutting was defined by the limiting value of stand basal area (‘cutting limit’) which should be reached after removal of the part of trees.

Simulated selection cutting scenarios contained variations of both harvest interval (10–30 years) and postharvest stand density (basal area 8–16 m2 ha-1). ‘R’ denotes the harvesting interval, years, and ‘T’ denotes threshold value of stand basal area, [m2 ha–1], to be reached after harvesting

Simulations showed that net ecosystem production (NEP) increased from 0.25 to 0.5 kg m-2 a-1 of carbon with longer harvest intervals and higher postharvest density, and was generally lower less than that at undisturbed developments. BA 8 10 12 14 16 Interval 10 yr Interval 15 yr Interval 20 yr Interval 30 yr Net ecosystem production NEP calculated as the difference between net primary production and carbon emission due to respiration of soil biota. The solid horizontal line on upper pane is the median line for NEP at undisturbed development; dashed horizontal lines denote 1st and 3rd quantiles, respectively.

TSL facilitate testing of the hypothesis that are based on simulated stand development Teppo Tutkija 19.9.2018

Once again we can draw and model stand structures like this Source Kalela 1945 drawing by Miettinen & Liuksiala Raisa Mäkipää 19.9.2018

Teppo Tutkija 19.9.2018

Teppo Tutkija 19.9.2018

Climate change and plasticity of trees Scots pine in Finland has high plasticity for changing climate. In favorable climatic conditions in southern Finland, trees have stronger apical dominance and they allocate to the height growth more than in the northern Finland. The shoot/branch-ratio applies independently from the origin of the trees, showing high plasticity. Teppo Tutkija 19.9.2018

Objective The objective of the study was to assess the influence of harvest intensity in selection cuttings on net ecosystem production, nitrogen use efficiency, carbon sequestration, and timber production by means of simulation modelling. The model was calibrated and validated against experimental data from 20 permanent forest plots where stand responses to uneven-aged management had been monitored for 20 years. Teppo Tutkija 19.9.2018

Process-based ecosystem model (Komarov et al 2003) Model is built on population ecology and matter-balance principles, and it can capture the important ecological processes in a forest stand: soil decomposition processes, growth processes and light and root competition that enables us to simulate ecosystem response to fast and severe environmental changes. The model is individual-tree based and utilizes the exact spatial location of each tree. This feature allows us to simulate cuttings (harvesting) of any strength, with the ability of ‘fine-tuning’ a treatment such as individual tree selection. The model accounts for below-ground competition between tree individuals with a submodule that describes growth and competition of roots.

Model performance Development of stand basal area. A set of runs were performed with varying initial stand density (30% variation in terms of basal area) and initial soil conditions (30% variation in terms of values of SOM pools). Black dots denote data measured on ‘ERIKA’ plots, solid line denotes predicted dynamics, dashed lines are envelopes for maximum and minimum values among the whole set of simulations. ‘pr’ – measurements made before selection cuttings in 1996 and 2011; ‘po’ – measurements made after selection cutting in 1996.

Simulations Teppo Tutkija 19.9.2018

Nitrogen use efficiency (NUE) varied between from 100 kg NPP per kg consumed N for heavy cuttings to 300 kg NPP per kg consumed N for light removal of trees. Mean values and variations are shown. The solid horizontal line on upper pane is the median line for the relative uptake at undisturbed development; dashed horizontal lines denote 1st and 3rd quantiles, respectively. Nitrogen use efficiency (kg NPP per kg consumed N – lower panel) for different scenarios of management.

Changes in soil carbon stocks were negative for most scenarios (5–20% decline in terms of total soil C), and the decline was most pronounced with lowest postharvest density and short harvest intervals. Changes in soil carbon stocks (% of initial values) during second half of simulation period (a series of selection cuttings). ‘Whiskers’ denote standard error.

The volume of harvested timber was between 320 and 400 m3 ha-1 for the a 60-year period. The cumulative volume of deadwood of 80–120 m3 ha-1 was substantially higher with the longest harvest interval (30 years) than with the shorter alternatives where it comprised 40–60 m3 ha-1. Ttotal amount of harvested wood at different scenarios. Different colours indicate the volumes obtained at different selection cuttings; blank blocks with black boundary represent the standing volume at the end of simulation period, blank blocks with grey boundary are cumulative volume of dead wood.

Longer harvest intervals resulted in increased timber production Longer harvest intervals resulted in increased timber production. Stem volume growth (5–7 m3 ha-1 a-1) was affected by both harvesting interval and intensity. Mean annual volume growth during the period of selection cuttings at different scenarios. The dashed horizontal line denotes the mean annual volume growth during the period before selection cuttings.

Summary Lower harvest intensity (longer interval and greater postharvest stand density) affected the net primary production, mean annual volume growth and indicators of sustainable management (such as carbon sequestration and nutrient use efficiency) positively. Low postharvest stand density resulted in somewhat lower volume production than higher densities.

Teppo Tutkija 19.9.2018