RETROGRESS

Trees Trigger Trouble – Landsliding by Biomass Surcharge and Wind Disturbance in Patagonian Rainforests (RETROGRESS) (DFG-funded 11/2021)

Coastal temperate rainforests are key components of the global carbon cycle (Keith et al., 2009), yet they are frequently disturbed by volcanic eruptions, rainfall, and windstorms. Such disturbances can trigger shallow landslides that release large carbon pulses from biomass and soils. Whether these forests act as carbon sinks or sources depends on the balance between disturbance intensity, recurrence, and ecosystem recovery. Areas with very high or very low disturbance frequencies tend to store less carbon, while moderately disturbed zones may maximize carbon storage in biomass and soils — the central hypothesis of RETROGRESS.

RETROGRESS investigates the steep, glacially sculpted hillslopes of Douglas Tompkins Pumalín NP (Northern Patagonia), which host dense evergreen broadleaf forests under a cool, wet Pacific climate. Dominant species include Nothofagus nitida, Podocarpus nubigenus, Drimys winterii, Amomyrtus meli, Luma apiculata, and the long-lived Fitzroya cupressoides (Lara et al., 1993). These forests store at least 370 tC/ha in biomass and up to twice that in soil organic carbon (Mohr et al., 2017). Disturbances are largely topography-driven, as shown by landslides linked to volcanic and wind events (Sommerfeld et al., 2018, Korup et al., 2019, Parra et al., 2021).

Biota strongly mediate hillslope processes: forest biomass loading can promote slope failure, while regrowth after landslides enhances root cohesion and wind exposure (Mohr et al., 2022). RETROGRESS tests this biomass–wind–landsliding–carbon nexus using process-based models (Landlab) incorporating time-varying biomass, root cohesion, and wind forcing. Models are informed by LiDAR, field surveys, hydroclimatic monitoring, and environmental seismology to capture tree–soil energy transfer.

As climate and disturbance regimes shift globally, insights from Patagonian rainforests can inform comparative studies in the Pacific Northwest and New Zealand through collaboration with the Coastal Rainforest Margins Research Network.

Trees Talking Wind?

Have you ever wondered what a tree swaying in the wind sounds like? (Micha Dietze)

Volcán Chaiten 360°Volcán Chaiten 360°

Caleta Gonzalo - Región de Los Lagos, Chile.Caleta Gonzalo - Región de Los Lagos, Chile.

The 2023 RETROGRESS field trip successfully done

Wow! What a blast!

The 2023 field campaign of the RETROGRESS has been successfully accomplished. Thanks to all the committed crew members Niels Hovius, Gerd Helle, Torsten Queisser, Violeta Tolorza, Benja Sotomayor, Sten Gilfert, Frieder Tautz and me) we are several steps closer to deciphering how carbon cycling, surface processes, and their interplay may (or may not?) function. Please find some (commented) appetizers on the left and some short videos below. Did you ever thought of a decoupled carbon cycle in mountains without erosion? Or Zombie trees bypassing the terrestrial carbon cycle? Stay tuned for exciting results from the Patagonian woods.

ANID Kick-off 2023

Suicidal Forests? Disturbances? Landslides? Thank you ANID and UACh for hosting me during this interesting kick-off meeting on Natural Hazards in the Southern Chilean Andes. Looking forward to hosting you Galo and Andres this October in Potsdam.

Gerd's tree coring skills

Gerd Helle coring here Coihue (Nothofagus dombeyi) trees within our Caleta and Michinmahuida catchments. Besides coihue, canelo was also neither safe from Gerd. See also exciting MSc projects on the dendroecology of the Patagonian rainforests.

Hasta la proxima, Pumalindo

Flying out of Pumalin NP after some intense, inspiring and concept-challenging three weeks with an incredible team and an unparalleled team spirit.

First RETROGRESS field trip successfully accomplished

Thanks to the exceptional teamwork, we achieved much more than we initially aimed on. Thank you Violeta, Micha, Benja, Erwin and the entire CONAF crew @Amarillo who literally opened all doors for us. It was a great experience again! On the left you can see some impressions from the field.

Pumalin Critical Zone Observatory launched

Between 03/2022 and 04/2022 we (Violeta Tolorza, Micha Dietze, Benjamon Sotomayor and myself) successfully deployed the first instruments and scientific stations in the Caleta Gonzalo catchment within the boundaries of Pumalin National Park. This network will form a crucial part of the future Pumalin Critical Zone Observatory. This observatory will be the first of its kind along the Chilean Coast of Patagonia (see picture on the left) and provide the scientific community with unparalleled insights into one of Earth's biomass-richest forest biomes.

As of 05/2022, our setup comprises a total of 8 seismic stations of which two were directly attached to tree trunks. Aside from these two seismic stations, we deployed 6 into the shallow subsurface. Out of these 6, we installed two of them in close vicinity to the monitored trunks while the other 4 are installed to develop a suitable array geometry - including a transect between Caleta Gonzalo and Amarillo CONAF station. We are confident that the seismic array now delivers unprecedented data of the energy transfer from the atmosphere into the soil via tree sway. The array may as well as allow us to monitor both landsliding location, timing and magnitude, bedload sediment transport rates and even streamflow discharge and potentially rainfall events.

The meteorological station is running! We may now also compare the seismically estimated hydroclimatic quantities with our newly setup Vaisala meteorological station that monitors temperature, air humidity, rainfall and, maybe most importantly, wind speed and direction (see below). We added Campbell soil moisture sensors to the Vaisala setup to estimate infiltration.

We lastly complemented the monitoring network with 4 wild cams that survey streams (water stage) and hillslopes (landsliding) on a 15 to 30 minute resolution. These image data allows us to independently test our seismic data.

With the upcoming field campaigned scheduled for November 2022, the RETROGRESS team will hopefully set up a comparable network of instruments and stations into the second core area: The Rio Michinmahuida catchment.

Left: Overview of Pumalin NP and the sites selected for the instruments and stations. For the two catchments Caleta Gonzalo (north) and Rio Michinmahuida (south) a recently acquired airborne LiDAR survey provides canopy height models and DEMs at very high resolution. Upper left: Close-range of Caleta Gonzalo airfield with meteorological station (lower right), seismometer and wild cam. Small inset on the left shows potentially Chile's tallest tree (drone footage by Benjamin Sotomayor).

Post-eruptive landslididing along the Yelcho River Valley (picture taken by Benjamin Sotomayor)