Stability Recovery in London Plane Trees Eight Years After Primary Anchorage Failure

Abstract

As the intensity and frequency of strong storms increase, the potential for damage to urban trees also increases. So far, the risk of ultimate failure for partially uprooted trees and how they may recover their stability is not well understood. This study sets out to explore if and to what extent trees can regain anchoring strength after their root systems have been overloaded. In 2010, ten London Plane (Platanus × acerifolia) trees were subjected to destructive winching tests. Two trees were pulled to the ground while eight were loaded until primary anchorage failure occurred and were left standing with inclined stems. In 2013, two trees had failed and six were re-tested nondestructively. By 2018, another tree had failed, and we tested the remaining five again. Rotational stiffness was derived for all trials and served as a nondestructive proxy for anchoring strength (R² = 0.91). After eight years, one tree had regained its original strength, while four had reached between 71 and 82% of their initial rotational stiffness. However, three trees failed during the observation period. The results indicate that partially uprooted trees may re-establish stability over time, but some will not and may fail. In our small data set, it was not possible to identify visual criteria that could provide a reliable indication of tree stability recovery, but our data support the assumption that nondestructive pulling tests can be successfully employed to determine good vigorous candidates for retention after partial uprooting.

Unveiling Falling Urban Trees before and during Typhoon Higos (2020): Empirical Case Study of Potential Structural Failure Using Tilt Sensor

“…For each individual tree, the presence of internal and external defects, the elastic modulus of soil and trunk, trunk and crown geometry, and root architecture all affect the response of load-deflection of tree trunk and root anchorage [11]. Researchers have routinely simulated trees and their failures to understand the response of particular species, including under storm events [12]. Sometimes, these controlled trials are also modeled using wind simulation post-rainstorm to demonstrate the correlation between trees and high wind or strong wind gusts [13,14].…”

“…According to field observation, root anchorage was partly loosened, and the lateral roots were tightly adhered at the leeward side and detached from the ground at the windward side, with severe cavity decay on the inner trunk flare. To further investigate the extent of the current phenomenon, T a was identified for "close monitoring" to keep track of its tilt variation to see if the tree could regain its anchoring strength and stabilize itself in the following years, as suggested by Detter et al [12]. Yet, this situation remained unchanged for a month before Typhoon Higos (2020) approached.…”

Silver Birch (Betula pendula Roth.) on Dry Mineral Rather than on Deep Peat Soils Is More Dependent on Frozen Conditions in Terms of Wind Damage in the Eastern Baltic Region

“…The sufficient soil-root anchorage predetermines tree mechanical stability to be dependent on stem strength [13], which is also reported to increase under the frozen conditions [8,15]. However, tree failure occurs in two stages [16,17]. Prior to the fatal (secondary) failure at the maximum loading (SF), internal primary wood failure (PF), which is not apparent during the stem bending, occurs [16,17].…”

“…However, tree failure occurs in two stages [16,17]. Prior to the fatal (secondary) failure at the maximum loading (SF), internal primary wood failure (PF), which is not apparent during the stem bending, occurs [16,17]. This PF alters tree hydraulics, which can cause physiological drought stress [16,17], subjecting the storm-surviving trees to legacy effects [18,19].…”

“…Prior to the fatal (secondary) failure at the maximum loading (SF), internal primary wood failure (PF), which is not apparent during the stem bending, occurs [16,17]. This PF alters tree hydraulics, which can cause physiological drought stress [16,17], subjecting the storm-surviving trees to legacy effects [18,19]. Therefore, the shortening of the soil freezing period might also contribute to increasing the frequency of synergic legacy effects of wind events [20,21], including on wind-tolerant species [22].…”