Browsing by Author "Davis, Kimberley T."

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Pinus contorta Alters Microenvironmental Conditions and Reduces Plant Diversity in Patagonian Ecosystems
(MDPI AG, 2023-02) García, Rafael A.; Fuentes-Lillo, Eduardo; Cavieres, Lohengrin; Cóbar-Carranza, Ana J.; Davis, Kimberley T.; Naour, Matías; Núñez, Martín A.; Maxwell, Bruce D.; Lembrechts, Jonas J.; Pauchard, Aníbal
Pinus contorta is considered one of the most invasive tree species worldwide, generating significant impacts on biodiversity and ecosystems. In several Patagonian ecosystems in southern Chile, it has escaped from plantations established mainly in the 1970s, and is now invading both forests and treeless environments. In this study, we evaluated the impact of the invasion of P. contorta on microenvironmental conditions in Araucaria araucana forest and Patagonian steppe ecosystems, and assessed how these changes related to the richness and abundance of native and non-native plant species. In each ecosystem, 24 plots of 100 m2 were established along a gradient of P. contorta biomass, where 18 environmental variables and the composition of native and non-native vegetation were measured at a local scale. Our results indicated that increased pine biomass was associated with differences in microclimatic conditions (soil and air temperature, photosynthetically active radiation (PAR), and soil moisture) and soil properties (potassium, nitrate, pH, and litter accumulation). These changes were ecosystem dependent, however, as well as associated with the level of invasion. Finally, the reduction in the richness and abundance of native plants was associated with the changes in soil properties (accumulation of leaf litter, pH, and organic matter) as well as in the microclimate (minimum air temperature, PAR) generated by the invasion of P. contorta. Overall, our results confirm that the invasion of P. contorta impacts microenvironmental conditions (i.e., canopy cover, litter accumulation, minimum air temperature, and maximum soil temperature) and reduces native plant diversity. For future restoration plans, more emphasis should be given to how environmental changes can influence the recovery of invaded ecosystems even after the removal of the living pine biomass (i.e., legacy of the invasion).
Simulation model suggests that fire promotes lodgepole pine (Pinus contorta) invasion in Patagonia
(2019-07) Davis, Kimberley T.; Maxwell, Bruce D.; Caplat, Paul; Pauchard, Anibal; Nunez, Martin A.
To best understand plant invasions and predict unexpected outcomes it is necessary to integrate information on disturbance, the local environment, and demography. Disturbance by fire has been shown to promote invasions worldwide, but precise interactions between fire, native and invading species remain unclear. Indeed, trade-offs exist between fire-induced mortality of seed sources and increased establishment, driving invasion outcomes. A positive feedback between lodgepole pine (Pinus contorta) invasions and fire has been identified but only above a certain pine density. Above this threshold, fire resulted in increased pine dominance at the plot level, however below this threshold establishment rates did not change. We used a spatially explicit invasion simulation model modified to include fire to explore the implications of these complex interactions between pine invasions and fire. We asked if fire promoted P. contorta invasion across a Patagonian steppe site and if this depended on the age of the invasion when it burned. Our simulations indicated that, although fire was not necessary to initiate invasion, fire in communities where pine invasions were at least 10 years old resulted in increased spatial extent and maximum invasion density compared to unburned simulations. Fire through younger invasions did not alter the progression of the invasion compared to unburned simulations. Pine invasions should be managed before they reach an advanced stage where positive feedbacks between fire and pine invasion could lead to dramatic increases in invasion rate.