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Accueil du site → Doctorat → États-Unis → 2013 → Resource partitioning in invasive annuals, native shrubs and native grasses in California : An investigation of soil respiration, Nitrogen partitioning and allocation to reproduction

SAN DIEGO STATE UNIVERSITY (2013)

Resource partitioning in invasive annuals, native shrubs and native grasses in California : An investigation of soil respiration, Nitrogen partitioning and allocation to reproduction

Maurtiz, Marguerite

Titre  : Resource partitioning in invasive annuals, native shrubs and native grasses in California : An investigation of soil respiration, Nitrogen partitioning and allocation to reproduction

Auteur : Maurtiz, Marguerite

Université de soutenance : SAN DIEGO STATE UNIVERSITY

Grade : Doctor of Philosophy (PhD) 2013

Résumé
The spread of invasive species into natural, native habitats threatens the species diversity and function of many ecosystems globally, and locally. In California the past and future expansion of invasive annual plants is linked to human disturbance and climate change. The invasive annuals differ from native plants in growth form and phenology. Understanding how these differences impact resource dynamics in invaded ecosystems is important for predicting the response of these ecosystems to future climate change. In this dissertation I focused on three aspects of resource dynamics. The carbon (C) cycle and how soil respiration differs between invasive annuals and native coastal sage scrub species ; the nitrogen (N) cycle and how altered rainfall patterns mediate N availability and partitioning between invasive annuals, native shrubs and microbes ; seed production of two native grasses and how competition from invasive annuals affects their contribution to a future seed bank. In chapter 1, I evaluated how soil respiration (Rs), a critical component of ecosystem carbon (C) storage, differs between native shrubs and inter-shrub patches dominated by invasive annuals. Rs can be partitioned into a root associated, autotrophic component (Ra) and a microbial, heterotrophic component (Rh). Discriminating between Ra and Rh provides insight into the underlying mechanisms which determine seasonal patterns in Rs. I found that phenology played an important role in the difference between invaded and shrub areas. Rs was 40% higher in invaded areas, primarily due to higher Ra early in the season. Overall the shrubs had a shorter respiration season due to more constrained phenology and contributed less C loss to the atmosphere. In invaded areas higher respiration rates were in part due to higher temperature tolerance of Ra and Rh. This suggests that water is more limiting than temperature in invaded areas. If, as expected, rainfall patterns shift in the future then C losses may be even higher from invaded areas.

Mots clés : Ecology, Soil respiration, Invasive annuals, Biological sciences, Native shrubs, Native grasses Nitrogen partitioning

Présentation (Gradworks)

Page publiée le 11 mars 2015, mise à jour le 8 octobre 2017