Soil erosion alters soil chemical properties and limits grassland plant establishment on an oceanic island even after goat eradication

Abstract

Soil erosion after vegetation degradation induced by disturbance by feral goats, an invasive mammal, can lead to loss or accumulation of soil at a local scale and can alter soil chemical properties. This alteration of soil properties can in turn affect the establishment of plant species. We evaluated relationships among the extent of soil erosion, soil chemical properties, and the distribution of plant species in grassland ecosystems after goat eradication on Nakodo-jima Island in the northwestern Pacific. In 105 1 × 1-m quadrats, changes were measured in the position of topsoil over 2 years. Surface soils were sampled for analysis of chemical properties, and plant species in the quadrat were recorded. Changes in the position of topsoil were related to the area of bare ground. Soil loss occurred at sites where areas of bare ground were extremely large. Significantly higher values of soil exchange acidity and smaller amounts of available phosphorus, total carbon, and total nitrogen were detected in soils at sites with large soil losses. Most of the 11 dominant plant species were absent from sites with large losses of soil. The presence of eight species was significantly negatively related to soil exchange acidity, and three species were significantly positively related to available phosphorus. Our results indicated that exposure of subsoils at the soil surface after vegetation degradation can increase soil loss, which can alter soil chemical properties, and this alteration can continue to limit the establishment of plant species, even long after goat eradication.

Historic deforestation and non‐native plant invasions determine vegetation trajectories across an oceanic archipelago

“…In the Mukojima island group, characterized by a small resident population, reforestation endeavors were not substantial, as with the results of Ono and Okutomi (1985) and Shimizu (1993) 5). On Nakoudojima, 5 km southeast of Mukojima and where eradication of feral goats also took place in the late 1990s, the recovery of native species has been observed , although the invasion of Leucaena leucocephala (Osawa et al, 2016) and disruption of vegetation recovery because of soil erosion has also been noted in some areas (Hata et al, 2019). Although species thought to be extinct or previously undiscovered may survive in remote or inaccessible areas of the islands where they were protected from goat grazing and trampling, and theoretically could spread again with goat eradication (Garcillán et al, 2008), our results…”

Do Invasive Mammal Eradications from Islands Support Climate Change Adaptation and Mitigation?

“…Following the removal of rabbits, low rainfall appeared to be the primary factor inhibiting native plant regeneration and, although significant increases in plant species richness occurred, it was largely driven by introduced plant species better adapted to warmer, drier climates [117,147]. Following a successful eradication, the legacy effects of invasive species may hamper the ability of ecosystems to naturally recover at the pace needed to become resilient to climate change [150]. Thus, subsequent management (e.g., reforestation, erosion control, restoring seabird populations) is an important restoration component following successful eradication [134,151,152].…”

Predicting ecosystem changes by a new model of ecosystem evolution

“…In short, the determining factor as to whether forests were restored was not the difference in the characteristics of arboreous plant species but low underground nutrient content and low numbers of animal and plant species. Earlier studies suggested that one cause of delayed restoration of forests was oligotrophic soil 19 , 20 , 22 , 39 . This was also true in the model.…”

“…Forests were restored within 10,000 time-steps only 14 times. For Nakoudojima Island, the fact that its forests have not been restored more than 20 years after the eradication of goats is considered problematic 20 – 22 ; however, this may be unavoidable at this point.…”