Rainfall interception represents the amount of water trapped in natural cover that is not drained directly to the ground. Intercepted rainfall may evaporate after a rain event, making it one of the main drivers of water balance and hydrologic regionalization. This process can be affected by factors such as climate, altitude, vegetation type, and topography. Here is a simple method of calculating rainfall interception in temperate forests using in Santa Maria Yavesia, Oaxaca, and Mexico as an illustrative study area. We used two rain gauges to measure net precipitation (Np) under the canopy at each study site and one gauge outside the canopy to obtain gross precipitation (Gp). Throughfall (Th) was indirectly measured using hemispherical photographs. Rainfall interception was obtained through a combination Th and Gp and Np. The mean rainfall interception was 50.6% in the Abies forests, 23%–40% in the coniferous‐mixed forests, and 27.4% in the broad‐leaved forests. We classified rainfall events by intensity to determine the effect of canopy structure and precipitation and found that 75% of the events were weak events, 24% were moderate events, and 1% were strong events. In addition, we found that rainfall interception was lower when the intensity of precipitation was higher. Our method can be replicated in different ecosystems worldwide as a tool for assessing the influence of rainfall interception in terms of ecological services. 相似文献
Objective: The objective of this article is to provide empirical evidence for safe speed limits that will meet the objectives of the Safe System by examining the relationship between speed limit and injury severity for different crash types, using police-reported crash data.
Method: Police-reported crashes from 2 Australian jurisdictions were used to calculate a fatal crash rate by speed limit and crash type. Example safe speed limits were defined using threshold risk levels.
Results: A positive exponential relationship between speed limit and fatality rate was found. For an example fatality rate threshold of 1 in 100 crashes it was found that safe speed limits are 40 km/h for pedestrian crashes; 50 km/h for head-on crashes; 60 km/h for hit fixed object crashes; 80 km/h for right angle, right turn, and left road/rollover crashes; and 110 km/h or more for rear-end crashes.
Conclusions: The positive exponential relationship between speed limit and fatal crash rate is consistent with prior research into speed and crash risk. The results indicate that speed zones of 100 km/h or more only meet the objectives of the Safe System, with regard to fatal crashes, where all crash types except rear-end crashes are exceedingly rare, such as on a high standard restricted access highway with a safe roadside design. 相似文献
A standardized method of moss exposition for assessing variations in nitrogen deposition was tested in the western part of
Germany. Six pleurocarpous moss species were transplanted to two sites differing in their deposition rates but being comparable
as to their climatic conditions. The mosses were exposed in standardized containers over a period of 12 months; the focus
of interest was the effect of N deposition on nitrogen content and on 15N natural abundance (δ15N-values). Within the first nine months only trends could be observed. However, after one year all species tested showed significantly
higher N concentrations at the highly polluted site. Besides, more negative δ15N-values possibly reflecting the higher ammonium input were detected at this site. Surprisingly, most of the plants though
being kept in plastic containers without a favourable substratum did not show any conspicuous deficiency symptoms. The potential
advantages of a standardized moss exposition for N monitoring purposes are discussed. It is concluded that the method presented
here can yield significant results in particular if the number of testing sites is increased. 相似文献