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首页> 外文期刊>Catena: An Interdisciplinary Journal of Soil Science Hydrology-Geomorphology Focusing on Geoecology and Landscape Evolution >The role of tephra covers on soil moisture conservation at Haleakala's crater (Maui, Hawai'i)
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The role of tephra covers on soil moisture conservation at Haleakala's crater (Maui, Hawai'i)

机译：蒂法拉覆盖物在哈雷阿卡拉火山口（夏威夷毛伊岛）对土壤水分保持的作用

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The influence of tephra covers on soil water was studied in Haleakala (Maui, Hawai'i) during two summers; eight sites with tephra layers and silverswords (Argyroxiphium sandwicense DC.) were sampled at 2415-2755 m. At each site, eight paired-sample sets were obtained in bare soils and under adjacent tephra, at three depths. Tephra were sharply separated from underlying soils and showed prominent vertical stratification. Tephra clast size-distribution was assessed by photosieving and on interstitial-gravel samples; stones included 45.6% cobbles, 29.4% pebbles, and 25% blocks.Moisture content increased with depth in both positions, but soils below tephra had more water at all depths than exposed areas. Surface soils beneath tephra contained 83% more water than bare ground. Soils at 5-10 cm had similar to 106% greater moisture under rocks, but only similar to 70% at 10-15 cm. Differences between plots were statistically significant (similar to p < 0.001) for surface soils, but less pronounced for subsoils. Soils above 2650 m had greater water content than at lower elevations, and moisture disparity between sample pairs increased with altitude.All soils were coarse, with similar to 20% gravel and similar to 94% sand; most fine material (<= 0.063 mm) was silt, as clay content was negligible. Organic-matter percentage was low (1.65%). Bulk density and porosity were associated with moisture variation both in tephra-insulated and bare soils; 80% of field moisture was statistically (p < 0.001) accounted for by pore space. Air and soil temperatures were recorded at three sites during similar to one-week periods prior to moisture sampling. Tephra substantially decreased soil maxima and daily thermal amplitude in underlying soils, but did not noticeably affect nightly minima. Thin (5-6 cm) tephra layers were nearly as effective as thicker (9-15 cm) deposits in depressing soil maxima. Possible water-conservation mechanisms under tephra include: decreased evaporation due to ground shielding and lower maxima; reduced capillary flow; greater infiltration depth: nocturnal dew condensation: and fog interception by blocks. (c) 2008 Elsevier B.V. All rights reserved.
机译：在两个夏天的哈雷阿卡拉（毛伊岛，夏威夷）研究了天麻覆盖物对土壤水的影响。在2415-2755 m采样了8个带提弗拉层和银剑的站点（Argyroxiphium sandwicense DC。）。在每个地点，在三个深度的裸露土壤和邻近的提夫拉下方获得了八对配对样本。特非拉与下层土壤急剧分离，并表现出明显的垂直分层。通过光筛和间质砾石样品评估了Tephra碎屑的大小分布。石头包括45.6％的鹅卵石，29.4％的鹅卵石和25％的块石。两个位置的含水量均随深度的增加而增加，但是在提夫拉下方的土壤在所有深度的含水量都比裸露的区域多。特非拉下方的表层土壤比裸露的土地多含水83％。 5-10厘米处的土壤在岩石下的水分含量高出约106％，而10-15厘米处的土壤水分仅约70％。对于表层土壤，地块之间的差异具有统计学意义（类似于p <0.001），但对于下层土壤则不那么明显。 2650 m以上的土壤比低海拔的土壤含水量更高，并且样品对之间的水分差异随着海拔的升高而增加。所有土壤都是粗糙的，砾石接近20％，沙子接近94％。大多数细料（<= 0.063毫米）是淤泥，因为粘土含量可忽略不计。有机物百分比低（1.65％）。在特法拉绝缘的土壤和裸露的土壤中，容重和孔隙率都与水分变化有关。统计上80％的田间水分是由孔隙空间造成的（p <0.001）。在湿度采样之前的大约一周期间，在三个地点记录了空气和土壤温度。 Tephra显着降低了下层土壤的土壤最大值和每日热量振幅，但并未显着影响夜间的最小值。在压低土壤最大值时，薄的（5-6厘米）的特非拉层几乎与较厚的（9-15厘米）的沉积层一样有效。特非拉膜下可能的节水机理包括：由于地面屏蔽而导致的蒸发减少和最大值降低;以及减少毛细管流量;更大的渗透深度：夜间结露：雾气被块体拦截。 （c）2008 Elsevier B.V.保留所有权利。

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