www.futureforest.eu Good Practice Guide

Adapting forestmanagement toincreased droughtrisk in Europe

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Catalonia and Brandenburg Natural Risks

Understanding drought-related impactWater-stressed forests are likely to spread according tomost climate change forecasts. Even under scenariosshowing a slight reduction or a constant averageannual rainfall, physiological drought is expected toincrease due to:• Higher evaporative demand by a warmeratmosphere

• Changes in rainfall regimes in relation to growingperiods

• Lower soil water content: increased runoff (stormfrequency and severity)

• Longer vegetative periods

The measures proposed here to address theconsequences of climate change are feasible if theforeseen increase in temperature is +2ºC (X. Castro,Barcelona September 2009). With a higher impact -+6ºC - the possibility of success is reduced, as forestplasticity is limited (Brandenburg).

Specific problems Deterioration of woodland health leading to individualtrees becoming stressed and death occurs either fromdirect consequences of drought or pests attackingweaker trees.

Ultimately this can lead to a loss of woodlandbiodiversity and changes to ecosystems.

To address these problems silviculture must use:• Fast intervention, do not postpone decisions.• Drought resistant genetic stock to replace speciesat the limit of their site suitability.

• More intensive management, bringing in tomanagement under exploited forest.

• Extended - or reduced – crop rotation periods.• Prioritised silviculture inputs to protect valuablebiodiversity stands.

• Be adaptive in use of silviculture systems.

Adapting forestmanagement toincreaseddrought risk inEurope

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Pinus pinaster dieback in les Gavarres (Catalonia)

Soil water content in European forest soils simulatedwith the forest growth process based model Gotilwa+.Simulations use a pixel of 10’x10’ combined with climatepredictions of HadCM3 model under a socioeconomic scenarioA2. Source: Gracia et al 2002

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Adaptive management actions

Changes of species /genetic management /selection of certain traits/provenances.A number of foreign species could be listed in eachregion which would provide a good alternative in casenatural evolution of the present species is too slow inrelation to the adoption of these new species. Another alternative for adaptation to the newconditions is the adoption of nursery techniques toobtain a hardening in the plant characteristics -irrigation regime, root development, inoculation bymichorrhyzae.Knowledge of the traits of the different provenances isa demand needs to be improved.

Promotion of mixed stands / uneven-aged stands/ forest conversion.Mixed stands are expected to be more resilient.Composed of species with different rotation periodsthey offer advantages as they allows greater diversityof structure, valuable especially when there isexcessive competition for water. They also reactdifferently to rain interception and soil quality. The most important advantage forests gain with amixed structure is the wider range of natural risks theycan successfully adapt to.On the other hand mixed stands need highermanagement intensity and therefore probably moreinvestment is needed. Specialised silviculturalprotocols can help. Using alternative species can achieve in advance thechanges that natural evolution would produce.

Re-evaluated silvicultural techniques:• reafforestation techniques • management models • thinning regimes• management of understory

Reafforestation techniques, plantation design, electionof stand structure and silvicultural treatments shouldalso be adapted to the expected new droughtconditions, applying experiences from semi arid lands.Traditional forest management models usually designoptimal stand densities to maximise timberproduction. Thinning regimes will have to be re-evaluated from a water-saving point of view. Thereforeintegrating eco-physiological knowledge into forestmodelling is required.Forest management operations should avoid soilerosion and compaction to preserve water storageproperties.Silvicultural treatments will be directed to obtainshorter trunks but with a bigger diameter, delayingpruning and shortening the rotations. These practiceswill cause changes in the root system, avoiding decayof species facing a drought episode.The understory composition and its coverage play animportant role in the amount of water available for treeseedlings and reduce drying of the soil. Selection,thinning and treatment of the understory should takeinto account dominant winds and horizontalprecipitation to ahcieve the most appropriatemicroclimates. Some appropriate techniques wouldinclude burning, grazing, mechanical treatments,mulching.

Brandenburg private state where the mixed stand has been established

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Other measuresTo promote agro-forestry systems or multifunctionalforest combining wood and secondary forest products.To apply one made to order silviculture focussed in thespecifics goals.

Increase of monitoring in forest health.An increase of monitoring is needed in this field todetermine the pest and pathogen damage thresholdsfor the water stressed stands. National and regional inventories must include thoseaspects.It’s also important to increase the research andimprove the training of the technical staff in this fieldand about internal physiology mechanism too.

Management planning documentsThe adoption of these silvicultural measures adaptedto drought, including a vulnerability assessment in theplanning documents will be essential at national andregional level and these management instrumentsestablish compulsory guidelines which should beincluded in the planning documents of the estates.

Examples of good practice:

CataloniaWhen forest owners produce their forest managementplans forestry advisors suggest the promotion ofmixed and uneven-aged stands, planning intensivethinning to reduce density and favour vitality of theremaining trees.Also forests owners are advised to choose carefullyspecies for new plantations that will be harvesting 60to 100 years later.The forest management plan must best options for thefuture incorporating the available knowledge at thetime the plan is produced.

BrandenburgWithin the fenced regeneration area, a single-tree togroup-mixture of planted oaks, pine, birch, and aspenregeneration has established itself, creating optimalconditions for a new, stable, and climate-adaptedforest generation.

This new mixed stand can withstand a wider range ofnatural risks because different species have differentresponses to drought periods.

Further reading:

• Legay, M., Ginisty, C., Bréda, N. 2006. Que peut faire legestionnaire forestier face au risque de sécheresse?.ONF. Rendez-vous techniques, 11: 35-40

• Vanclay, J. K. 2009. Managing water use from forestplantations. Forest Ecology and Management, 257:385-389

• McDowell, N. Pockman, W.T.; Allen, C. D. Breshears,D.D. Cobb, N. Kolb, T. Plaut, J. Sperry, J. West, A.Williams, D.G. Yepez, E.A. 2008 . Mechanisms of plantsurvival and mortality during drought: why do someplants survive while others succumb to drought?.

• Gracia C, Sabaté S, Martínez JM, Albeza E (1999)Functional responses to thinning. In Rodà F, Retana J,Gracia C, Bellot J (eds) Ecology of Mediterraneanevergreen oak forests. Springer, Berlin, pp. 329-338.

• Jump A, Peñuelas J (2005) Running to stand still:adaptation and the response of plants to rapid climatechange. Ecology Letters 8: 1010–1020.

• www.creaf.uab.cat• www.efimed.efi.int

Pinus pinea cones production in Aleppo Pine (grafting)