Treesearch

Armillaria mexicana and/or A. mellea cause Armillaria root disease that results in mortality of peach (Prunus persica) trees in orchards of the Mexican sub-tropics. Resistance/susceptibility reactions to A. mexicana and A. mellea were evaluated for three Prunus rootstocks under greenhouse and field conditions. For greenhouse tests, independent inoculations of A. mexicana and A. mellea were conducted on 14 trees for each of three rootstocks: P. persica × P. davidiana ‘Nemaguard’, P. persica landrace ‘Criollos of La Goleta’ genotypes, and P. salicina Japanese plum ‘Mondragon’, with four...

Over the last several decades in forest and woodland ecosystems of the southwestern United States, wildfire size and severity have increased, thereby increasing the vulnerability of these systems to type conversions, invasive species, and other disturbances. A combination of land use history and climate change is widely thought to be contributing to the changing fire regimes. We examined climate-fire relationships in forest and woodland ecosystems from 1984 to 2015 in Arizona and New Mexico using 1) an expanded satellite-derived burn severity dataset that incorporates over one million...

Several recent studies have documented how fire severity affects the density and spatial patterns of tree regeneration in western North American ponderosa pine forests. However, less is known about the effects of fire severity on fine-scale tree regeneration niche attributes such as understory plant composition and cover, surface fuel abundance, and soil properties, or how these attributes in turn affect regenerating ponderosa pine growth. Using 1-m2 plots centered on 360 ponderosa pine seedlings that regenerated naturally after the Pumpkin Fire in 2000 in Arizona, we quantified regeneratio...

In 2009, new guidance for wildland fire management in the United States expanded the range of strategic options for managers working to reduce the threat of high-severity wildland fire, improve forest health and respond to a changing climate. Markedly, the new guidance provided greater flexibility to manage wildland fires to meet multiple resource objectives.Weuse Incident Status Summary reports to understand how wildland fire management strategies have differed across the western US in recent years and how management has changed since the 2009 Guidance for Implementation of Federal...

Este experimento, realizado en el Área de Investigación El Verde, en el Bosque Experimental de Luquillo, Puerto Rico; se incluye dentro del proyecto llamado StreamFRE. Este proyecto perteneciente al programa Luquillo-Long Term Ecological Research (LTER) pretende dar respuesta a los cambios en los ecosistemas acuáticos y riparios de bosques tropicales ante el cambio climático, simulando efectos de sequía con experimentos de reducción de flujo en arroyos/quebradas. El estudio de la reducción de flujo será puesto en práctica con la colocación de una presa hidráulica en la quebrada experimental...

Despite the importance of tropical forests to global carbon balance, our understanding of how tropical plant physiology will respond to climate warming is limited. In addition, the contribution of tropical forest understories to global carbon cycling is predicted to increase with rising temperatures, however, in situ warming studies of tropical forest plants to date focus only on upper canopies. We present results of an in situ field-scale +4°C understory infrared warming experiment in Puerto Rico (Tropical Responses to Altered Climate Experiment; TRACE). We investigated gas exchange...

Residential green spaces are increasingly gaining attention for their potential to contribute to ecosystem services of social and ecological value for cities. This research evaluated the potential of residential yards of San Juan, Puerto Rico, to contribute to urban sustainability through the provision of ecosystem services using a social-ecological approach. The study builds upon prior work at this site led by the San Juan Urban Long Term Research Area (ULTRA) Collaborative Network and addressed the following overarching question: Which social-ecological factors could be influencing the...

Aerosols can interact with radiation directly through scattering and absorption and indirectly by serving as cloud condensation nuclei. The uncertainty of how particles and clouds interact with radiation is still high amidst the progress made in recent years, which hinders our current understanding of how these particles affect the Earth’s radiation budget. This works aims to reduce this uncertainty by targeting the two most light-absorbing atmospheric particles, mineral dust and black carbon, and study how they interact with radiation, how they serve as cloud condensation nuclei, assessing...

Freshwater environments are highly dynamics but are subject to natural and anthropogenic influences. Although lotic ecosystems have resilience to deal with natural disturbance, the additional pressure from anthropogenic stresses can often lead to irreversible changes. Particularly, urban activities have resulted in increased anthropogenic discharge into freshwater environments with significant effects on organisms. The main objective of this thesis was to evaluate the toxicity of the freshwater shrimp Xiphocaris elongata to synthetic pyrethroid and organophosphate pesticides. Experiments...

Regardless of how soil is defined, soils are the most diverse of all ecosystems. It is estimated that 25-30% of all species on Earth live in soils for all or part of their lives (Decaëns et al. 2006). A single gram of soil is estimated to contain 1 × 109 microorganisms, roughly the same population size as the number of humans in Africa (Microbiology by Numbers 2011). That same gram of soil likely contains 4000 species. They are only one part of a larger food web, however, that includes roundworms (phylum Nematoda), springtails (order Collembola), and other fauna (Fig. 5.1). The soil fauna...