Scots pine and Douglas-fir did not grow because of drought 2018: Bas Lerink at NOS News about the impact

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Scots pine and Douglas-fir did not grow because of drought 2018: Bas Lerink at NOS News about the impact

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13 augustus 2019

Because of the drought in 2018, growth of Scots pine and Douglas-fir nearly halted in the Netherlands. Researcher Bas reveals in the news on Dutch National TV, the impact drought has on these tree species and which pilot projects Wageningen University & Research is executing in search of ways to make forests more resilient in a changing climate.

No CO2- uptake

Trees have to grow in order to stay alive. They grow by making new vessels in the wood to transport nutrients and water. When the growth comes to a standstill, the tree cannot absorb CO2 anymore and, with a continuing and lengthy drought, would die. Growth can be measured by means of a sophisticated dendrometer: a sensor, tied with a string around the tree, that measures the circumference of the trunk. Every hour the sensor will store a reading with an accuracy of just below one micrometer.

Dendrometer
Dendrometer

Dendrometer research

Wageningen Environmental Research installed 100 of these dendrometers on trees all over the Netherlands in 2008. Selected species are Scots pine, beech, common oak and Douglas-fir. Data from last year showed that the Scots pine and Douglas-fir had hardly been growing during 2018 (figure 1). That year's total growth turned out to be significantly below that of the three preceding years. “One year of drought should not be of too much consequence to these trees,” researcher Bas Lerink explains to the NOS News. “The trees could come in real trouble after two or three consecutive dry years.”

Figure 1: The circumference growth of the Douglas-fir in forest reserve "t Leest". The blue line indicates the average circumference growth in the period 2015-2017, the orange line shows this growth during 2018. The total growth in 2018 is significantly lower than in the three preceding years.
Figure 1: The circumference growth of the Douglas-fir in forest reserve "t Leest". The blue line indicates the average circumference growth in the period 2015-2017, the orange line shows this growth during 2018. The total growth in 2018 is significantly lower than in the three preceding years.

Forest of the future

The Netherlands has around 112,000 hectares of Scots pine, that have on average an age of 75 years. WUR is implementing pilots at this moment, to vitalise these forests. Tree species are being planted that are better adapted to a changing climate. Aim of the revitalisation is to make the forest more resilient and to go forward from a low- to a high-productive forest. Experiments are being carried out to test different tree species and ways of management.