Juha Heikkinen | Natural Resources Institute Finland (original) (raw)

Papers by Juha Heikkinen

Forest Ecology and Management, 2014

ABSTRACT To understand the global carbon cycle and the impact of human activity on climate, it is... more ABSTRACT To understand the global carbon cycle and the impact of human activity on climate, it is necessary to quantify the net CO2 exchange of ecosystems in different land uses on a large scale. Methods to estimate soil net CO2 exchange (NECO2soil) for drained peatland forests have been largely based on chamber measurements and statistical models. The uncertainty in these methods has not been assessed. Yet, disturbed organic soils are a globally important, potential CO2 source due to their vast carbon storage and its sensitivity to changes in soil moisture. In this study, we estimated the countrywide NECO2soil for the 4.76 million ha of forestry-drained peat soils in Finland. We gathered available litter production and CO2 efflux data and constructed models to be used for the upscaling of NECO2soil from forest inventory data. The contribution of each model and the inventory sampling to the precision of the countrywide estimate was calculated. Also, the sensitivity to possible bias in selected model components was estimated. Compared to the estimated mean NECO2soil, ranging from a source of +20 g m−2 year−1 of C to a sink of −40 g m−2 year−1 of C, the uncertainty was high. The precision of the estimate (±1 standard deviation) was ±20 g m−2 year−1 of C. Due to possible bias in the estimated belowground litter input, the overall uncertainty was much higher, around ±60 g m−2 year−1 of C. The main reason for the high relative uncertainty was NECO2soil being on average close to zero in these boreal forestry-drained peatlands. Forest inventory sample size was large enough and the data for the models were mainly sufficient. To reduce the uncertainty, better understanding of belowground carbon fluxes in order to accurately determine the C input to soil, is crucial.

Managing Forest Ecosystems, 2011

The estimation of area in NFI is based on the official land area of Finland as presented in Sect.... more The estimation of area in NFI is based on the official land area of Finland as presented in Sect. 3.1. The official land area estimates from January 1st in the year succeeding the inventory of each region was used in the calculations of the NFI9 results. Finland’s total land area used in the NFI9 calculations was 30.447 million ha, of

Managing Forest Ecosystems, 2011

International Journal of Wildland Fire

Abstract. To study the poorly known fire history of Larix-dominated forest in central Siberia, we... more Abstract. To study the poorly known fire history of Larix-dominated forest in central Siberia, we collected samples from 200 trees in 46 systematically located study plots. Our study area stretches ,90 km from north to south along the River Nizhnyaya Tunguska in northern Irkustk district. Cross-dated tree-ring chronology for all samples combined extended from the year 1360 AD to the present and included 76 fire years and 88 separate fire events. Average fire cycle gradually lengthened from 52 years in the 18th century to 164 years in the 20th century. During the same time, the number of recorded fires decreased even more steeply, i.e. by more than 85%. Fires were more numerous but smaller in the past. Contrary to expectations, climate change in the 20th century has not resulted in increased forest fires in this region. Fire suppression may have contributed to the scarcity of fires since the 1950s. However, a significant decline in fires was evident earlier; therefore an additional e...

Scandinavian Journal of Statistics, 1998

Journal of Environmental Management, 2015

... 81 Anssi Pekkarinen and Sakari Tuominen: Allocation of field sample by means of aerial photog... more ... 81 Anssi Pekkarinen and Sakari Tuominen: Allocation of field sample by means of aerial photographs and image segmentation ..... ... 163 Annika Kangas and Jyrki Kangas: MCDS methods in strategic forest management – alternatives for the AHP ...

Working Papers of the Finnish Forest Research Institute 74 http://www. metla. fi/julkaisut/workin... more Working Papers of the Finnish Forest Research Institute 74 http://www. metla. fi/julkaisut/workingpapers/200x/mwp074. htm 43 Monitoring changes in the carbon stocks of forest soils Raisa Mäkipää 1), Mikko Peltoniemi 1), Margareeta Häkkinen 1), Juha ...

Page 1. 17 E. Tomppo et al., Designing and Conducting a Forest Inventory - case: 9th National For... more Page 1. 17 E. Tomppo et al., Designing and Conducting a Forest Inventory - case: 9th National Forest Inventory of Finland, Managing Forest Ecosystems 21, DOI 10.1007/978-94-007-1652-0_2, © Springer Science+Business Media BV 2011 ...

ABSTRACT Hakkinen, M., Heikkinen, J. and Makipaa, R. 2010. Tree influence on carbon stock and C:N... more ABSTRACT Hakkinen, M., Heikkinen, J. and Makipaa, R. 2010. Tree influence on carbon stock and C:N ratio of the soil organic layer in boreal Scots pine forests. Can. J. Soil Sci. 90: 559-566. Observed small-scale spatial variation of forest soil is suggested to be produced by tree influence. We examined spatial variation of the tree influences by modelling tree influence potential that accounts for location and size of trees. Thereafter, we tested significance of the correlations between the tree influence potential and soil properties (carbon stock and C:N ratio of the organic layer) with Monte Carlo permutation tests. The methods were applied to five Scots pine stands located in the boreal vegetation zone in Finland. We found, statistically significant tree influence on soil C:N ratio in all studied stands, but the tree influence on soil carbon stock was significant only in three of five stands. This indicates that location of trees has a relatively steady and remarkable influence on spatial variation of a soil parameter that reflects soil fertility and nutrient balance, but variation of soil carbon stock is not that clearly affected by current tree stand. The correlations between C:N ratios and tree influences were positive in four of the five stands, indicating that soil was less fertile near the trees. The methods described here produce statistically reliable information pertaining to the influence of trees on soil properties.

Forest Ecology and Management, 2014

ABSTRACT To understand the global carbon cycle and the impact of human activity on climate, it is... more ABSTRACT To understand the global carbon cycle and the impact of human activity on climate, it is necessary to quantify the net CO2 exchange of ecosystems in different land uses on a large scale. Methods to estimate soil net CO2 exchange (NECO2soil) for drained peatland forests have been largely based on chamber measurements and statistical models. The uncertainty in these methods has not been assessed. Yet, disturbed organic soils are a globally important, potential CO2 source due to their vast carbon storage and its sensitivity to changes in soil moisture. In this study, we estimated the countrywide NECO2soil for the 4.76 million ha of forestry-drained peat soils in Finland. We gathered available litter production and CO2 efflux data and constructed models to be used for the upscaling of NECO2soil from forest inventory data. The contribution of each model and the inventory sampling to the precision of the countrywide estimate was calculated. Also, the sensitivity to possible bias in selected model components was estimated. Compared to the estimated mean NECO2soil, ranging from a source of +20 g m−2 year−1 of C to a sink of −40 g m−2 year−1 of C, the uncertainty was high. The precision of the estimate (±1 standard deviation) was ±20 g m−2 year−1 of C. Due to possible bias in the estimated belowground litter input, the overall uncertainty was much higher, around ±60 g m−2 year−1 of C. The main reason for the high relative uncertainty was NECO2soil being on average close to zero in these boreal forestry-drained peatlands. Forest inventory sample size was large enough and the data for the models were mainly sufficient. To reduce the uncertainty, better understanding of belowground carbon fluxes in order to accurately determine the C input to soil, is crucial.

Managing Forest Ecosystems, 2011

The estimation of area in NFI is based on the official land area of Finland as presented in Sect.... more The estimation of area in NFI is based on the official land area of Finland as presented in Sect. 3.1. The official land area estimates from January 1st in the year succeeding the inventory of each region was used in the calculations of the NFI9 results. Finland’s total land area used in the NFI9 calculations was 30.447 million ha, of

Managing Forest Ecosystems, 2011

International Journal of Wildland Fire

Abstract. To study the poorly known fire history of Larix-dominated forest in central Siberia, we... more Abstract. To study the poorly known fire history of Larix-dominated forest in central Siberia, we collected samples from 200 trees in 46 systematically located study plots. Our study area stretches ,90 km from north to south along the River Nizhnyaya Tunguska in northern Irkustk district. Cross-dated tree-ring chronology for all samples combined extended from the year 1360 AD to the present and included 76 fire years and 88 separate fire events. Average fire cycle gradually lengthened from 52 years in the 18th century to 164 years in the 20th century. During the same time, the number of recorded fires decreased even more steeply, i.e. by more than 85%. Fires were more numerous but smaller in the past. Contrary to expectations, climate change in the 20th century has not resulted in increased forest fires in this region. Fire suppression may have contributed to the scarcity of fires since the 1950s. However, a significant decline in fires was evident earlier; therefore an additional e...

Scandinavian Journal of Statistics, 1998

Journal of Environmental Management, 2015

... 81 Anssi Pekkarinen and Sakari Tuominen: Allocation of field sample by means of aerial photog... more ... 81 Anssi Pekkarinen and Sakari Tuominen: Allocation of field sample by means of aerial photographs and image segmentation ..... ... 163 Annika Kangas and Jyrki Kangas: MCDS methods in strategic forest management – alternatives for the AHP ...

Working Papers of the Finnish Forest Research Institute 74 http://www. metla. fi/julkaisut/workin... more Working Papers of the Finnish Forest Research Institute 74 http://www. metla. fi/julkaisut/workingpapers/200x/mwp074. htm 43 Monitoring changes in the carbon stocks of forest soils Raisa Mäkipää 1), Mikko Peltoniemi 1), Margareeta Häkkinen 1), Juha ...

Page 1. 17 E. Tomppo et al., Designing and Conducting a Forest Inventory - case: 9th National For... more Page 1. 17 E. Tomppo et al., Designing and Conducting a Forest Inventory - case: 9th National Forest Inventory of Finland, Managing Forest Ecosystems 21, DOI 10.1007/978-94-007-1652-0_2, © Springer Science+Business Media BV 2011 ...

ABSTRACT Hakkinen, M., Heikkinen, J. and Makipaa, R. 2010. Tree influence on carbon stock and C:N... more ABSTRACT Hakkinen, M., Heikkinen, J. and Makipaa, R. 2010. Tree influence on carbon stock and C:N ratio of the soil organic layer in boreal Scots pine forests. Can. J. Soil Sci. 90: 559-566. Observed small-scale spatial variation of forest soil is suggested to be produced by tree influence. We examined spatial variation of the tree influences by modelling tree influence potential that accounts for location and size of trees. Thereafter, we tested significance of the correlations between the tree influence potential and soil properties (carbon stock and C:N ratio of the organic layer) with Monte Carlo permutation tests. The methods were applied to five Scots pine stands located in the boreal vegetation zone in Finland. We found, statistically significant tree influence on soil C:N ratio in all studied stands, but the tree influence on soil carbon stock was significant only in three of five stands. This indicates that location of trees has a relatively steady and remarkable influence on spatial variation of a soil parameter that reflects soil fertility and nutrient balance, but variation of soil carbon stock is not that clearly affected by current tree stand. The correlations between C:N ratios and tree influences were positive in four of the five stands, indicating that soil was less fertile near the trees. The methods described here produce statistically reliable information pertaining to the influence of trees on soil properties.