Treesearch

Ecological resilience is essential for maintaining ecosystem services in an era of rapid global change, but successful attempts to operationalize it for managing ecosystems at risk have been limited. Clear formulation and application of ecological resilience concepts can guide ecosystem management so that it enhances the capacity of ecosystems to resist and recover from disturbances and provides adaptive space for periods of ecological reorganization. As originally defined, ecological resilience measures the amount of perturbation required to change an ecosystem from one set of processes...

Past research on plant-soil feedbacks (PSF), largely undertaken in highly controlled greenhouse conditions, has established that plant species differentially alter abiotic and biotic soil conditions that in turn affect growth of other conspecific and heterospecific individuals in that soil. Yet, whether feedbacks under controlled greenhouse conditions reflect feedbacks in natural environments where plants are exposed to a range of abiotic and biotic pressures is still unresolved. To address how environmental context affects PSF, we conducted a meta-analysis of previously published studies...

We developed a technique for reconstructing annual gravel yields and generated a 55‐year record of gravel transport for the North Fork catchment of the Caspar Creek Experimental Watersheds in Northern California. The technique relies on field data collection including annual surveys of weir pond volumes and suspended sediment measurements, as well as an accounting for settling of suspended sediment and organic matter in the pond. We compared these annual yields to gravel yields predicted by the Wilcock two‐fraction bed load transport model, which we calibrated from measured values at...

To evaluate the reliability of lumber structures, good models for the strength and stiffness distributions of visual and machine stress–rated (MSR) grades of lumber are necessary. Verrill and coworkers established theoretically and empirically that the strength properties of visual and MSR grades of lumber are not distributed as 2-parameter Weibulls. Instead, strength properties of grades of lumber must have “pseudo-truncated” distributions. To properly implement the pseudo-truncation theory (to correctly estimate the MOR and MOE distributions of graded subpopulations), one must know the...

Pyrolysis and combustion of a solid fuel representing a vertically oriented leaf of manzanita (Arctostaphylos glandulosa) were computationally investigated. Various fuel moisture content (FMC) values corresponding to four manzanita leaf treatments studied experimentally by others, were considered. The fuel was exposed to an upward stream of hot gases in a computational configuration resembling the experimental setup where leaves were burned. Time evolution of the normalized mass of the leaves was used to validate the simulations against the experimental data. Examining the time history of...

The fungal pathogen Pyricularia grisea has been studied to evaluate its production of phytotoxins for the biocontrol of the buffelgrass (Cenchrus ciliaris L.) weed. A first investigation allowed to isolate several new and known phytotoxic metabolites. However, the further investigation on the organic extract obtained from the fungus liquid culture showed the presence of other metabolites possibly contributing to its phytotoxicity. Thus, four known metabolites were isolated and identified by spectroscopic (nuclear magnetic resonance [NMR] and high-resolution electrospray ionization mass...

Conflicting priorities for livestock grazing management in the context of rare plant conservation are common worldwide, especially in semiarid and arid ecosystems, where open-range livestock grazing is a primary land use. Detailed information on the interaction between livestock impacts and rare plant demography would facilitate improved management, yet this information is most often not available. In this study we examined the direct impacts of cattle trampling on dormant season survival of Astragalus holmgreniorum (Fabaceae), a globally endangered perennial spring ephemeral of the...

This article details techno-economic analyses for producing alternative jet fuel (AJF) at a greenfield integrated biorefinery (IBR) using softwood forest residues. The scenarios and their corresponding economic outcomes differ based on the co-product selections. The selected technology to produce AJF uses a mild bisulfite pretreatment process to prepare the feedstock for enzymatic hydrolysis and fermentation to isobutanol, which is then upgraded to hydrocarbon ‘drop-in’ fuels using an alcohol-to-jet process. The hydrocarbons are a combination of jet fuel and aviation gasoline (AvGas). The...

The above-ground performance of decking treated with two alternative copper-based preservative formulations is being evaluated at a test site near Madison, Wisconsin, USA. Southern pine sapwood lumber specimens (38 mm by 140 mm by 910 mm) were pressure treated with 0,93 %, 1,40 % or 2,34 % (oxide basis) actives concentrations of a boron-copper formulation (BC) composed of 7,2 % copper hydroxide and 92,8 % sodium tetraborate decahydrate. Similar specimens were pressure-treated with 0,66 % or 1,32 % actives concentrations of a copper-zinc formulation (CZDP) composed of 18 % copper (CuO...