TY - JOUR A1 - Bose, Arun K. A1 - Scherrer, Daniel A1 - Camarero, j. Julio A1 - Ziche, Daniel A1 - Babst, Flurin A1 - Bigler, Christof A1 - Bolte, Andreas A1 - Dorado-Liñán, Isabel A1 - Etzold, Sophia A1 - Fonti, Patrick A1 - Forrester, David I. A1 - Gavinet, Jordane A1 - Gazol, Antonio A1 - González de Andrés, Ester A1 - Karger, Dirk Nikolaus A1 - Lebourgeois, Francois A1 - Lévesque, Mathieu A1 - Martínez-Sancho, Elisabet A1 - Menzel, Annette A1 - Neuwirth, Burkhard A1 - Nicolas, Manuel A1 - Sanders, Tanja G. M. A1 - Scharnweber, Tobias A1 - Schröder, Jens A1 - Zweifel, Roman A1 - Gessler, Arthur A1 - Rigling, Andreas T1 - Climate sensitivity and drought seasonality determine post-drought growth recovery of Quercus petraea and Quercus robur in Europe JF - Science of The Total Environment N2 - Recent studies have identified strong relationships between delayed recovery of tree growth after drought and tree mortality caused by subsequent droughts. These observations raise concerns about forest ecosystem services and post-drought growth recovery given the projected increase in drought frequency and extremes. For quantifying the impact of extreme droughts on tree radial growth, we used a network of tree-ring width data of 1689 trees from 100 sites representing most of the distribution of two drought tolerant, deciduous oak species (Quercus petraea and Quercus robur). We first examined which climatic factors and seasons control growth of the two species and if there is any latitudinal, longitudinal or elevational trend. We then quantified the relative departure from pre-drought growth during droughts, and how fast trees were able to recover the pre-drought growth level. Our results showed that growth was more related to precipitation and climatic water balance (precipitation minus potential evapotranspiration) than to temperature. However, we did not detect any clear latitudinal, longitudinal or elevational trends except a decreasing influence of summer water balance on growth of Q. petraea with latitude. Neither species was able to maintain the pre-drought growth level during droughts. However, both species showed rapid recovery or even growth compensation after summer droughts but displayed slow recovery in response to spring droughts where none of the two species was able to fully recover the pre-drought growth-level over the three post-drought years. Collectively, our results indicate that oaks which are considered resilient to extreme droughts have also shown vulnerability when droughts occurred in spring especially at sites where long-term growth is not significantly correlated with climatic factors. This improved understanding of the role of drought seasonality and climate sensitivity of sites is key to better predict trajectories of post-drought growth recovery in response to the drier climate projected for Europe. KW - Climate change KW - Warming KW - Drought KW - Legacy effects KW - Acclimation KW - Tree rings Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:eb1-opus-2609 SN - 1879-1026 VL - 784 PB - Elsevier ER - TY - JOUR A1 - Krause, Stuart A1 - Sanders, Tanja G. M. A1 - Mund, Jan-Peter A1 - Greve, Klaus T1 - UAV-Based Photogrammetric Tree Height Measurement for Intensive Forest Monitoring JF - Remote Sensing N2 - The measurement of tree height has long been an important tree attribute for the purpose of calculating tree growth, volume, and biomass, which in turn deliver important ecological and economical information to decision makers. Tree height has traditionally been measured by indirect field-based techniques, however these methods are rarely contested. With recent advances in Unmanned Aerial Vehicle (UAV) remote sensing technologies, the possibility to acquire accurate tree heights semi-automatically has become a reality. In this study, photogrammetric and field-based tree height measurements of a Scots Pine stand were validated using destructive methods. The intensive forest monitoring site implemented for the study was configured with permanent ground control points (GCPs) measured with a Total Station (TS). Field-based tree height measurements resulted in a similar level of error to that of the photogrammetric measurements, with root mean square error (RMSE) values of 0.304 m (1.82%) and 0.34 m (2.07%), respectively (n = 34). A conflicting bias was, however, discovered where field measurements tended to overestimate tree heights and photogrammetric measurements were underestimated. The photogrammetric tree height measurements of all trees (n = 285) were validated against the field-based measurements and resulted in a RMSE of 0.479 m (2.78%). Additionally, two separate photogrammetric tree height datasets were compared (n = 251), and a very low amount of error was observed with a RMSE of 0.138 m (0.79%), suggesting a high potential for repeatability. This study shows that UAV photogrammetric tree height measurements are a viable option for intensive forest monitoring plots and that the possibility to acquire within-season tree growth measurements merits further study. Additionally, it was shown that negative and positive biases evident in field-based and UAV-based photogrammetric tree height measurements could potentially lead to misinterpretation of results when field-based measurements are used as validation. KW - tree height KW - UAV KW - intensive forest monitoring KW - photogrammety KW - precision forestry Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:eb1-opus-3240 SN - 2072-4292 IS - 11(7) PB - MDPI ER -