The strategies of Norway spruce [Picea abies (L.) Karst.] to increasing atmospheric CO2 concentration (C a) are not entirely clear. Here, we reconstructed centennial trajectories of leaf internal CO2 concentration (C i) and intrinsic water-use efficiency (WUEi) from the amount of 13C in tree-ring cellulose. We collected 57 cores across elevations, soil, and atmospheric conditions in central Europe. Generally, WUEi and C i increased over the last 100 years and the C i/C a ratio remained almost constant. However, two groups were distinguished. The first group showed a quasi-linear response to C a and the sensitivity of C i to C a (s = dC i/dC a) ranged from 0 to 1. Trees in the second group showed nonmonotonic responses with extremes during the peak of industrial air pollution in the 1980s and s increase from -1 to +1.6. Our study shows a marked attenuation of the rise in WUEi during the 20th century leading to invariant WUEi in recent decades.

• Keywords
• Picea abies, carbon dioxide enrichment, photosynthesis, stable carbon isotopes, tree rings, water-use efficiency,
• MeSH
• Photosynthesis MeSH
• Plant Leaves * metabolism   physiology   MeSH
• Carbon Dioxide * metabolism   MeSH
• Picea * metabolism   physiology   MeSH
• Water * metabolism   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Carbon Dioxide * MeSH
• Water * MeSH

BACKGROUND: We analyze the forest carbon stock development following the recent historically unprecedented dieback of coniferous stands in the Czech Republic. The drought-induced bark-beetle infestation resulted in record-high sanitary logging and total harvest more than doubled from the previous period. It turned Czech forestry from a long-term carbon sink offsetting about 6% of the country's greenhouse gas emissions since 1990 to a significant source of CO2 emissions in recent years (2018-2021). In 2020, the forestry sector contributed nearly 10% to the country's overall GHG emissions. Using the nationally calibrated Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3) at a regional (NUTS3) spatial resolution, we analyzed four scenarios of forest carbon stock development until 2070. Two critical points arise: the short-term prognosis for reducing current emissions from forestry and the implementation of adaptive forest management focused on tree species change and sustained carbon accumulation. RESULTS: This study used four different spruce forest dieback scenarios to assess the impact of adaptive forest management on the forest carbon stock change and CO2 emissions, tree species composition, harvest possibilities, and forest structure in response to the recent unprecedented calamitous dieback in the Czech Republic. The model analysis indicates that Czech forestry may stabilize by 2025 Subsequently, it may become a sustained sink of about 3 Mt CO2 eq./year (excluding the contribution of harvested wood products), while enhancing forest resilience by the gradual implementation of adaptation measures. The speed of adaptation is linked to harvest intensity and severity of the current calamity. Under the pessimistic Black scenario, the proportion of spruce stands declines from the current 43-20% by 2070, in favor of more suited tree species such as fir and broadleaves. These species would also constitute over 50% of the harvest potential, increasingly contributing to harvest levels like those generated by Czech forestry prior to the current calamity. The standing stock would only be recovered in 50 years under the optimistic Green scenario. CONCLUSION: The results show progress of adaptive management by implementing tree species change and quantify the expected harvest and mitigation potential in Czech forestry until 2070.

• Keywords
• Adaptation, Bark-beetle, Carbon stock change, Ecology, Forest management, Forestry, LULUCF, Mitigation, Model scenarios,
• Publication type
• Journal Article MeSH

The forests of central Europe have undergone remarkable transitions in the past 40 years as air quality has improved dramatically. Retrospective analysis of Norway spruce (Picea abies) tree rings in the Czech Republic shows that air pollution (e.g. SO2 concentrations, high acidic deposition to the forest canopy) plays a dominant role in driving forest health. Extensive soil acidification occurred in the highly polluted "Black Triangle" in Central Europe, and upper mineral soils are still acidified. In contrast, acidic atmospheric deposition declined by 80% and atmospheric SO2 concentration by 90% between the late 1980s and 2010s. In this study we oserved that annual tree ring width (TRW) declined in the 1970s and subsequently recovered in the 1990s, tracking SO2 concentrations closely. Furthermore, recovery of TRW was similar in unlimed and limed stands. Despite large increases in soil base saturation, as well as soil pH, as a result of repeated liming starting in 1981, TRW growth was similar in limed and unlimed plots. TRW recovery was interrupted in 1996 when highly acidic rime (originating from more pronounced decline of alkaline dust than SO2 from local power plants) injured the spruce canopy, but recovered soon to the pre-episode growth. Across the long-term site history, changes in soil chemistry (pH, base saturation, Bc/Al soil solution ratio) cannot explain observed changes in TRW at the two study sites where we tracked soil chemistry. Instead, statistically significant recovery in TRW is linked to the trajectory of annual SO2 concentrations or sulfur deposition at all three stands.

• MeSH
• Hydrogen-Ion Concentration MeSH
• Forests MeSH
• Soil MeSH
• Retrospective Studies MeSH
• Picea * MeSH
• Air Pollution * MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Soil MeSH