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Hydrological effects of forest conversion of pure pine stands in broadleaf forests and mixed pine-broadleaf forests
Project
Project code: TI-WO-08-PID1352
Contract period: 01.01.2001
- 31.12.2020
Purpose of research: Inventory & Assessment
The present pattern of forests in Germany is dominated by spacious spruce stands in the south and large-scale Scots pine forests in the north. These stands are endangered by calamities. The future distribution of forests should be formed by multifariously structured mixed stands as possible. This intention is pursued by the forest conversion of the federal state Brandenburg as well. The programme of forest conversion needs scientific attendance and foundation.
Along with the question for the contribution of mixed forests to landscape water budget, investigations of water consumption and growth of forests form a substantial research focus. These research fields have to consider increasing water shortage within the vegetation period. Against the background of climate change this question gains in importance.
Underplanting of pure Scots pine stands with beeches and oaks is partly restricted by the hydro-ecological conditions of the local region. It has to be scrutinised how these conditions are modified by silviculture and how they can be influenced by changes of stand structure.
Focal point of research are changes of water budget in up-growing mixed stand of pine, beech and oak in comparison with pure Scots pine stands and resultant relevant consequences.
In the foreground there are the following questions:
- How are the water fluxes modified by the upgrowing understorey of beeches and oaks and how change the particular components of evaporation by the structural conversion from pure pine stands toward mixed stands?
- How does the modified water flux influence the amount of seepage water and thereby the gains of water management?
In order to investigate the hydrological conditions of just established mixed stands, existing pure Scots pine stands at large lysimeters of the research station Britz were underplanted with beech and oak in the year 2000. Besides the investigations concerning the water budget of younger mixed stands, cause-and-effect-relationships between drought and tree growth are researched. The great advantage of large lysimeters consists in the opportunity of balancing of energy and water fluxes with high temporal resolution under exactly differentiating conditions. This trait of lysimeters enables the research under miscellaneous questions. By use of dendrometers, for instance, climate-growth relationships can be analysed. Lysimeters serve as an important tool to parameterise process models for energy and water fluxes if innovative measuring techniques are used (weighing cells for determination of moisture changes and seepage fluxes, soil moisture sensors and tensiometers to observe seepage water movement).
Besides of large lysimeters for the determination of evapotranspiration of beeches and oaks in the understorey, special, weighable lysimeters were developed and mounted into mixed stands of pine, beech and oak.
The evapotranspiration of beeches and oaks, grown at undisturbed soil monoliths, can be determined with an accuracy of 0,1 mm. Another field of application of weighable lysimeters consists in the investigation of effects of watershortage on growth and water budget of young beeches and oaks exposed to different degrees of withering.
Section overview
Subjects
- Silviculture
- Agricultural hydrology
- Agroecology
