Expertise
Good conditions for spring budburst
Tanja Sanders, Marco Natkhin | 04.03.2024
There has not been this much rain in winter since the series of measurements began in 1993: between November 2023 and February 2024, 311 millimetres of precipitation fell at the Thünen research station in Britz. This means that the plant world has the best conditions for spring - at least on the permeable sandy soils of Brandenburg.
In recent months, it has not only felt like it has rained a lot - this winter has set a new record: For 30 years, precipitation and seepage have been measured alongside other parameters at the forest hydrology test site in Britz near Eberswalde. With 311 millimetres (mm) of rain and snow measured, there was more water than ever before since the time series began. The amount of precipitation is good news for the upcoming vegetation period. Winter precipitation is important to refill the soil and creating good conditions for the plants to develop in spring.
By way of comparison, the record for drought in winter was set in 1996 with only 105 mm during the same period, closely followed by 2003 with only 108 mm. The long-term average annual precipitation (1993-2022) is 619 mm; this means that half of the average annual precipitation fell last winter.
Monthly precipitation amounts in mm for the years 2023-2024 and long-term average
| Jan | Feb | Mrz | Apr | Mai | Jun | Jul | Aug | Sep | Okt | Nov | Dez | Jahr | |
| Average 1993–2022 | 53 | 41 | 42 | 31 | 57 | 68 | 76 | 59 | 52 | 45 | 45 | 51 | 619 |
| Year 2023 | 81 | 50 | 100 | 49 | 12 | 53 | 42 | 58 | 12 | 82 | 54 | 103 | 696 |
| Year 2024 | 64 | 90 | 154 |
It general the most rain falls between May and August but most of this evaporates again from the crowns. The months from November to February are therefore important for groundwater recharge. After the end of the growing season, this precipitation ensures that the soil is rehydrated to a depth below the rooting zone. Depending on the amount of precipitation and soil moisture, the saturation is already below the rooting zone from November and then seeps further towards the groundwater-bearing layers until March with the start of the vegetation period.
In general, we see the most groundwater recharge under beech. With nine percent of precipitation in deep percolation, beech trees are the waterworks of the forest. In contrast, deep seepage only occurs under pine trees in very wet years. This is especially a problem in pine-covered Brandenburg. However, this rainy winter has even seen the first deep seepage under the pine trees.
However, the situation under pine is changing due to climate change: now extreme precipitation in summer leads to deep seepage, which contributes to groundwater recharge. Up to 71 percent of the deep seepage under pine trees comes from this extreme precipitation. For beech it amounts to only 15 percent. However, with an average of 53 mm per year, many times more precipitation seeps under a beech tree than under a pine tree of the same age. And this again is due to winter precipitation.
