Disturbance (geology)

About: Disturbance (geology) is a research topic. Over the lifetime, 11368 publications have been published within this topic receiving 175735 citations.

Disturbance and site characteristics relate to cheatgrass (Bromus tectorum) abundance on ranches in Montana foothills ecosystems

Abstract: Cheatgrass (Bromus tectorum L.), also known as downy brome, is an invasive, exotic annual grass found throughout North America. Cheatgrass has been extensively studied in the Great Basin region of North America, where the majority of precipitation comes in winter and early spring, and the vegetation consists primarily of cool-season species. However, little research has been done in northern foothills grasslands in and near Montana, where most precipitation comes in spring and summer, supporting a mixture of cooland warm-season plant species. Climate and vegetation differ between the northern foothills grasslands and the Great Basin, so the ecological impacts of cheatgrass in the northern foothills grasslands are unknown. In order to better understand cheatgrass ecology in this region, we assessed cheatgrass abundance in foothills ecosystems in Montana. Fifteen study plots were established at each of two ranches in Montana, both of which are owned and operated by the Montana Agricultural Experiment Station: Thackeray Ranch, southeast of Havre, Montana, and Red Bluff Ranch, east of Norris, Montana. At these plots we examined relationships among cheatgrass abundance, biotic and abiotic site characteristics (e.g. species diversity, soil depth), and disturbance indicators (e.g. livestock fecal counts) in 2014 and 2015. Large generalized linear mixedeffects regression models for each ranch were reduced to simpler models by comparing the Aikake's Information Criterion (AIC) for each fitted model, and selecting for lower AIC to best describe cheatgrass abundance. Multimodel inference based on the best models for each ranch identified important variables to predict cheatgrass abundance. Disturbance and site characteristics such as aspect and soil texture are important predictors that land managers in the northern foothills grasslands could monitor to estimate the risk of cheatgrass invasion or dominance on the landscapes they manage.

Identification of Flows by the Local Disturbance Method

Abstract: A new method of identification of flows is described. The method is based on fixing the wake formed behind a small disturbance on the surface being destroyed in the flow. The method is first of all applied to high-temperature, dense, and aggressive media.

Method and apparatus for compensating disturbance and disk drive and storage media applying the same

Abstract: PURPOSE: A method for compensating disturbance, and an apparatus thereof, a disk drive thereof, and a storage device thereof are provided to estimate disturbance periodically generated due to external shock in advance, thereby compensating the disturbance in a feedforward system. CONSTITUTION: When a disk drive satisfies a disturbance detection mode performing condition, a controller calculates an estimated disturbance value of the next cycle by correlation coefficient COR(x,y) of adjacent cycles of a servo output signal and a servo output signal of the previous cycle(S1301,S1302). The correlation coefficient COR(x,y) is greater than a threshold value M, the controller forwards a calculated estimated disturbance value to a servo control system(S1303,S1304). The controller calculates a servo performance evaluation factor before and after the disturbance compensation(S1305).

Macromoth community structure along a 95‐year post‐harvest chronosequence in managed forests of northwest Washington State ( U.S.A. ), with comparison to old growth forest communities

Abstract: The effects of timber harvest in the moist coniferous forests of western North America are not well documented for ecologically important arthropods such as moths. We assessed the response of macromoth community structure (abundance, sample size‐corrected estimates of species richness and diversity, and overall community composition) to time since deforestation at 20 previously logged sites (1–95 years post‐harvest), and compared the macromoth communities at these stands to four old growth stands. As stand age increased following timber harvest, the number of macromoths captured in ultraviolet light traps increased and the relative abundance of dietary generalists declined, but sample size‐corrected estimates of species richness and diversity did not vary. Macromoth community composition of the youngest stands (<10 years post‐harvest) differed markedly from each other but converged soon thereafter. Macromoth communities at old growth sites featured higher capture rates, lower dominance by dietary generalists, and higher sample size‐corrected estimates of species richness and diversity than at previously logged sites. Community composition profiles for old growth sites differed from all previously logged sites, but the differences were subtle except in comparison to the youngest logged sites. None of the 188 species we sampled were old growth specialists. Our results reveal dramatic initial impacts of deforestation on macromoth communities in moist coniferous forests of western North America. Such effects are largely reversed within two decades post‐harvest but some effects persist for at least 95‐years following logging.