Objective indicators of pasture degradation from spectral mixture analysis of Landsat imagery

Author Posting. © American Geophysical Union, 2008. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 113 (2008): G00B03, doi:10.1029/2007JG000622.Degradation of cattle pastures is a management concern that influences future land use in Amazonia. However, “degradation” is poorly defined and has different meanings for ranchers, ecologists, and policy makers. Here we analyze pasture degradation using objective scalars of photosynthetic vegetation (PV), nonphotosynthetic vegetation (NPV), and exposed soil (S) derived from Landsat imagery. A general, probabilistic spectral mixture model decomposed satellite spectral reflectance measurements into subpixel estimates of PV, NPV, and S covers at ranches in western and eastern Amazonia. Most pasture management units at all ranches fell along a single line of decreasing PV with increasing NPV and S, which could be considered a degradation continuum. The ranch with the highest stocking densities and most intensive management had greater NPV and S than a less intensively managed ranch. The number of liming, herbiciding, and disking treatments applied to each pasture management unit was positively correlated with NPV and negatively correlated with PV. Although these objective scalars revealed signs of degradation, intensive management kept exposed soil to <40% cover and maintained economically viable cattle production over several decades. In ranches with few management inputs, the high PV cover in young pastures declined with increasing pasture age, while NPV and S increased, even where grazing intensity was low. Both highly productive pastures and vigorous regrowth of native vegetation cause high PV values. Analysis of spectral properties holds promise for identifying areas where grazing intensity has exceeded management inputs, thus increasing coverage of senescent foliage and exposed soil.This research was supported by grant NNG06GE88A of NASA’s Terrestrial Ecology Program as part of the Large-scale Biosphere-Atmosphere Experiment in Amazonia (LBA) project

Evaluation of two short-term stress interventions in the context of mobility

Objectives: In our lives we experience different types of stress that emanate from a variety of situations. This stress can potentially spill over into unrelated situations, including the operation of a vehicle in a safe manner. It is not well known which types of countermeasures can actually mitigate such stress during driving. For this purpose, one needs valid stress intervention methods for the different types of stress that commonly occur during driving. In this study, it was therefore evaluated whether or not two stress interventions were effective in reducing stress. These two stress interventions were Positive Psychology–i.e., being an activity to reflect about thankful moments–and Biofeedback–i.e., being an activity aimed at continued relaxation based on the display of the participants own stress level. Methods: A study with 41 (n =21 male) participants was conducted in a stationary vehicle to evaluate the effectiveness of Positive Psychology and Biofeedback on stress reduction. Stress was induced using the Stroop Task. During a Stroop Task high stress is caused by naming color words displayed in another, incongruent color. In the Baseline Condition, participants looked at neutral images, which were expected to have no effect on stress levels. These conditions were then compared. Findings: The results revealed that participant stress levels were significantly higher during each stress induction period in comparison to each stress intervention period. This indicated that a reduction of stress is possible by administering stress interventions in a stationary setting. Yet, there was no difference between Positive Psychology, Biofeedback, and the Baseline Condition, supposedly due to the short administration, stress-reducing attributes of the Baseline Condition itself, or regression to the mean effects. Novelty: The overall goal of this research is the development of stress interventions to target different types of stress that can occur in the context of mobility, an application context not yet investigated. These interventions are expected to improve well-being and safety inside the vehicle by improving concentration, attention, and psychomotor control, which can be reduced by high stress. The study took a first step to achieve this goal by developing and evaluating Positive Psychology and Biofeedback as stress intervention activities to mitigate stress in a stationary vehicle–a situation comparable to automated driving. The developed interventions showed stress- reducing effects in the stationary setting whereas looking at neutral pictures–although serving as the baseline–was similarly stress-reducing. This enables the next step–adding the task of manual driving to the interventions to look into both the effectiveness of the interventions during manual driving and driving safety at the same time

The role of deep roots in the hydrological and carbon cycles of amazonian forests and pastures

DEFORESTATIONS and logging transform more forest in eastern and southern Amazonia than in any other region of the world(1-3). This forest alteration affects regional hydrology(4-11) and the global carbon cycle(12-14), but current analyses of these effects neglect an important deep-soil link between the water and carbon cycles. Using rainfall data, satellite imagery and field studies, we estimate here that half of the closed forests of Brazilian Amazonia depend on deep root systems to maintain green canopies during the dry season. Evergreen forests in northeastern Para state maintain evapotranspiration during five-month dry periods by absorbing water from the soil to depths of more than 8 m. In contrast, although the degraded pastures of this region also contain deep-rooted woody plants, most pasture plants substantially reduce their leaf canopy in response to seasonal drought, thus reducing dry-season evapotranspiration and increasing potential subsurface runoff relative to the forests they replace. Deep roots that extract water also provide carbon to the soil. The forest soil below Im depth contains more carbon than does above-ground biomass, and as much as 15% of this deep-soil carbon turns over on annual or decadal timescales. Thus, forest alteration that affects depth distributions of carbon inputs from roots mag also affect net carbon storage in the soil