TY  - JOUR
A1  - Bae, Soyeon
A1  - Müller, Jörg
A1  - Förster, Bernhard
A1  - Hilmers, Torben
A1  - Hochrein, Sophia
A1  - Jacobs, Martin
A1  - Leroy, Benjamin M. L.
A1  - Pretzsch, Hans
A1  - Weisser, Wolfgang W.
A1  - Mitesser, Oliver
T1  - Tracking the temporal dynamics of insect defoliation by high‐resolution radar satellite data
JF  - Methods in Ecology and Evolution
N2  - Quantifying tree defoliation by insects over large areas is a major challenge in forest management, but it is essential in ecosystem assessments of disturbance and resistance against herbivory. However, the trajectory from leaf-flush to insect defoliation to refoliation in broadleaf trees is highly variable. Its tracking requires high temporal- and spatial-resolution data, particularly in fragmented forests.
In a unique replicated field experiment manipulating gypsy moth Lymantria dispar densities in mixed-oak forests, we examined the utility of publicly accessible satellite-borne radar (Sentinel-1) to track the fine-scale temporal trajectory of defoliation. The ratio of backscatter intensity between two polarizations from radar data of the growing season constituted a canopy development index (CDI) and a normalized CDI (NCDI), which were validated by optical (Sentinel-2) and terrestrial laser scanning (TLS) data as well by intensive caterpillar sampling from canopy fogging.
The CDI and NCDI strongly correlated with optical and TLS data (Spearman's ρ = 0.79 and 0.84, respectively). The ΔNCDII\(_{Defoliation(A−C)}\) significantly explained caterpillar abundance (R\(^{2}\) = 0.52). The NCDI at critical timesteps and ΔNCDI related to defoliation and refoliation well discriminated between heavily and lightly defoliated forests.
We demonstrate that the high spatial and temporal resolution and the cloud independence of Sentinel-1 radar potentially enable spatially unrestricted measurements of the highly dynamic canopy herbivory. This can help monitor insect pests, improve the prediction of outbreaks and facilitate the monitoring of forest disturbance, one of the high priority Essential Biodiversity Variables, in the near future.
KW  - Sentinel-1
KW  - canopy herbivory
KW  - defoliation severity
KW  - gypsy moth
KW  - insect disturbance
KW  - intra-annual time-series
KW  - Lymantria dispar
KW  - remote sensing
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-258222
VL  - 13
IS  - 1
ER  - 
TY  - JOUR
A1  - Latifi, Hooman
A1  - Holzwarth, Stefanie
A1  - Skidmore, Andrew
A1  - Brůna, Josef
A1  - Červenka, Jaroslav
A1  - Darvishzadeh, Roshanak
A1  - Hais, Martin
A1  - Heiden, Uta
A1  - Homolová, Lucie
A1  - Krzystek, Peter
A1  - Schneider, Thomas
A1  - Starý, Martin
A1  - Wang, Tiejun
A1  - Müller, Jörg
A1  - Heurich, Marco
T1  - A laboratory for conceiving Essential Biodiversity Variables (EBVs)—The ‘Data pool initiative for the Bohemian Forest Ecosystem’
JF  - Methods in Ecology and Evolution
N2  - Effects of climate change‐induced events on forest ecosystem dynamics of composition, function and structure call for increased long‐term, interdisciplinary and integrated research on biodiversity indicators, in particular within strictly protected areas with extensive non‐intervention zones. The long‐established concept of forest supersites generally relies on long‐term funds from national agencies and goes beyond the logistic and financial capabilities of state‐ or region‐wide protected area administrations, universities and research institutes.
We introduce the concept of data pools as a smaller‐scale, user‐driven and reasonable alternative to co‐develop remote sensing and forest ecosystem science to validated products, biodiversity indicators and management plans. We demonstrate this concept with the Bohemian Forest Ecosystem Data Pool, which has been established as an interdisciplinary, international data pool within the strictly protected Bavarian Forest and Šumava National Parks and currently comprises 10 active partners. We demonstrate how the structure and impact of the data pool differs from comparable cases.
We assessed the international influence and visibility of the data pool with the help of a systematic literature search and a brief analysis of the results. Results primarily suggest an increase in the impact and visibility of published material during the life span of the data pool, with highest visibilities achieved by research conducted on leaf traits, vegetation phenology and 3D‐based forest inventory.
We conclude that the data pool results in an efficient contribution to the concept of global biodiversity observatory by evolving towards a training platform, functioning as a pool of data and algorithms, directly communicating with management for implementation and providing test fields for feasibility studies on earth observation missions.
KW  - bohemian forest ecosystem
KW  - data pool
KW  - forest ecosystem science
KW  - remote sensing
KW  - remote sensing‐enabled essential biodiversity variables
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-262743
VL  - 12
IS  - 11
ER  -