BackgroundA regional-scale sensitivity study has been carried out to investigate the climatic effects of forest cover change in Europe. Applying REMO (regional climate model of the Max Planck Institute for Meteorology), the projected temperature and precipitation tendencies have been analysed for summer, based on the results of the A2 IPCC-SRES emission scenario simulation. For the end of the 21st century it has been studied, whether the assumed forest cover increase could reduce the effects of the greenhouse gas concentration change.ResultsBased on the simulation results, biogeophysical effects of the hypothetic potential afforestation may lead to cooler and moister conditions during summer in most parts of the temperate zone. The largest relative effects of forest cover increase can be expected in northern Germany, Poland and Ukraine, which is 15–20% of the climate change signal for temperature and more than 50% for precipitation. In northern Germany and France, potential afforestation may enhance the effects of emission change, resulting in more severe heavy precipitation events. The probability of dry days and warm temperature extremes would decrease.ConclusionsLarge contiguous forest blocks can have distinctive biogeophysical effect on the climate on regional and local scale. In certain regions of the temperate zone, climate change signal due to greenhouse gas emission can be reduced by afforestation due to the dominant evaporative cooling effect during summer. Results of this case study with a hypothetical land cover change can contribute to the assessment of the role of forests in adapting to climate change. Thus they can build an important basis of the future forest policy.

Climate change particularly threatens the xeric limits of temperate-continental forests. In Hungary, annual temperatures have increased by 1.2 °C–1.8 °C in the last 30 years and the frequency of extreme droughts has grown. With the aim to gain stand-level prospects of sustainability, we have used local forest site variables to identify and project effects of recent and expected changes of climate. We have used a climatic descriptor (FAI index) to compare trends estimated from forest datasets with climatological projections; this is likely for the first time such a comparison has been made. Four independent approaches confirmed the near-linear decline of growth and vitality with increasing hot droughts in summer, using sessile oak as model species. The correlation between droughts and the expansion of pest and disease damages was also found to be significant. Projections of expected changes of main site factors predict a dramatic rise of future drought frequency and, consequently, a substantial shift of forest climate classes, especially at low elevation. Excess water-dependent lowland forests may lose supply from groundwater, which may change vegetation cover and soil development processes. The overall change of site conditions not only causes economic losses, but also challenges long-term sustainability of forest cover at the xeric limits.

Climatic effects of forest cover change have been investigated for Hungary. For the time period 2071-100 we have analyzed whether the climate change signal for summer precipitation and the probability of droughts can be reduced assuming maximal afforestation for the entire country (forests covering all vegetated areas). The biogeophysical effects of land cover change have been assessed using the results of an A1B IPCC-SRES emission scenario from REMO (regional climate model at the Max Planck Institute for Meteorology, Hamburg). The simulation results indicate that afforestation may reduce the projected climate change through higher evapotranspiration and precipitation as well as lower surface temperature for the entire summer period. The magnitude of the feedback of the forest cover increase on precipitation differs among regions. The strongest effects are visible in the northeastern part of the country. Here, half of the projected precipitation decrease can be relieved and the total number of drought events can be reduced, assuming maximal afforestation. Afforestation brings about the smallest climatic effect in the southwestern region, in the area that shows the strongest climate change. The results can help to identify areas where forest cover increase should most effectively support the alleviation of climate change effects.

No abstract

No abstract

KivonatA fafajmegválasztás és az erdészeti célú döntéstámogatás megalapozásához az éghajlati tendenciák hosszútávú előrevetítése szükséges. Cikkünk célja a fafajok elterjedése, vitalitása, növekedése és szervesanyag-produkciója (növedéke) szempontjából meghatározó hónapok klimatikus viszonyaiban várható változás értékelése. A várható klíma becslése 12 regionális klímaszimuláció eredményeinek együttes elemzésével történt, az IPCC A1B kibocsátási forgatókönyvének feltételezésével. Az erdészeti klímakategóriákat az erdészeti szárazsági mutató (FAI) alapján definiáltuk és határoltuk le. Az aszályos évek gyakoriságát és 30 éves jövőbeli periódusokra becsült változását szintén a FAI segítségével határoztuk meg. A 21. századi klímaelőrebecslések alapján az átlaghőmérséklet emelkedése és a csapadékmennyiség csökkenése az erdészeti szempontból meghatározó időszakok közül a kritikus hónapokban (július-augusztus) a legnagyobb, de jelentős a fő növekedési periódusban (május-augusztus) is. A század közepére előrevetített klimatikus viszonyok mellett az olyan klímaadottságú területek, ahol a természetes előfordulású zárt erdők még eredményesen termeszthetők, nagymértékben csökkenhetnek, a jövedelmező gazdálkodásra kevésbé alkalmas erdőssztyep klímájú területek nagysága pedig jelentősen (a jelenlegi erdőterület több mint egyharmadára) növekedhet. Az eddigi erdőssztyep klímakategória területének fele (az ország területének több mint 10%-a) a mainál még melegebb és szárazabb (sztyep klímájú) lehet. Az átlagos klimatikus viszonyok változásával egyidejűleg az 1981-2010-es periódushoz képest 2021-2050-re az aszályos és a szélsőségesen aszályos évek száma megduplázódhat, mely az érzékeny fafajok mortalitásának kockázatát fokozza. A jövőbeli időszakokra várható klíma alapját képezi a projekt keretében kifejlesztett döntéstámogató rendszernek is, mely egy adott területre meghatározza az erdészeti klímakategóriát és ennek, valamint a többi termőhelyi tényezőnek alapján javasol célállományt.Kulcsszavak: éghajlatváltozás, klímaszcenárió, erdészeti klímakategória, FAI, aszálygyakoriság. CLIMATE PROJECTIONS FOR FORESTRY IN HUNGARY AbstractTree species selection and decision support in forestry require long term climate projections. Our study is focusing on the future temperature and precipitation conditions for the months that are determining and limiting the distribution, vitality, growth and production of forests. For the 21st century, results of 12 regional climate model simulations were analyzed assuming the A1B emission scenario of the lPCC. Forest climate categories as well as the droughts were defined based on the forestry aridity index (FAI). Increase of temperature and decrease of precipitation are expected to be the largest in the critical period (July-August), but they are also significant in the main growing period (May-August). In the Hungarian lowland the drier conditions (Forest steppe climate category) are expected to expand (replacing the former Oak climate category) and cover more than 35% of the total forest area. This wi...

This paper analyses the recent recurring dieback and growth decline of Black pine (P. nigra Arn. var austriaca) in the Keszthely mountains of south-west Hungary, and their relations to water deficits due to droughts. These relations were studied in five stands with low soil water storage capacity for the period 1981-2016. The vitality was assessed using 60 tree-ring samples and changes in remotely sensed vegetation activity indices, i.e., the normalized difference vegetation index (NDVI) and the normalized difference infrared index (NDII). Water deficit was estimated by using meteorological drought indices such the standardized precipitation-evapotranspiration index (SPEI) and the forestry aridity index (FAI), as well as the relative extractable water (REW), calculated by the Brook90 hydrological model. Results revealed a strong dependency of annual tree ring width on the amount of water deficit as measured by all the above estimators, with the highest correlation shown by the summer REW. Droughts also showed a long-term superimposed effect on tree growth. NDII seemed to be more sensitive to drought conditions than NDVI. The robust dependency of tree growth on the summer water availability combined with the projected increasing aridity might lead to decreasing growth of Black pine in Hungary towards the end of the century. We thus argue that the suggestion by several papers that Black pine can be a possible substitute species in the Alpine and Mediterranean region in the future should be revisited.

- A regional-scale case study has been carried out to assess the possible climatic benefits of forest cover increase in Europe. For the end of the 21st century (2071-2090) it has been investigated, whether the projected climate change could be reduced assuming potential afforestation of the continent. The magnitude of the biogeophysical effects of enhanced forest cover on temperature and precipitation means and extremes have been analyzed relative to the magnitude of the climate change signal applying the regional climate model REMO. The simulation results indicate that in the largest part of the temperate zone potential afforestation may reduce the projected climate change through cooler and moister conditions, thus could contribute to the mitigation of the projected climate change for the entire summer period. The largest relative effect of forest cover increase can be expected in northern Germany, Poland and Ukraine. Here, the projected precipitation decrease could be fully compensated, the temperature increase could be relieved by up to 0.5 °C, and the probability of extremely warm and dry days could be reduced. Results can help to identify the areas, where forest cover increase could be the most effective from climatic point of view. Thus they can build an important basis of the future adaptation strategies and forest policy.