کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
5780781 1635355 2017 14 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Steady as a rock: Biogeomorphic influence of nurse rocks and slope processes on kūpaoa (Dubautia menziesii) shrubs in Haleakalā Crater (Maui, Hawai'i)
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات فرآیندهای سطح زمین
پیش نمایش صفحه اول مقاله
Steady as a rock: Biogeomorphic influence of nurse rocks and slope processes on kūpaoa (Dubautia menziesii) shrubs in Haleakalā Crater (Maui, Hawai'i)
چکیده انگلیسی
This study examines biogeomorphic interactions between nurse rocks, slope processes, and 300 kūpaoa (Dubautia menziesii) shrubs in Haleakalā Crater (Maui, Hawai'i). Research objectives were to: assess the association of kūpaoa with substrates upslope and downslope of plants, and proximity to the closest rock uphill; contrast shrub/substrate relationships with site frequency of sediment types; measure surface soil shear-strength and compressibility on 50 paired locations near boulders; and investigate the aggregation characteristics and spatial patterns of kūpaoa in relation to rock and substrate variation. Data analyzed came from three 100-plant surveys at 3 sites: a plant census at 2720-2975 m altitude, and wandering-quarter transects (WQTs) across two areas (2610-2710 m); ground sediment cover was estimated along four phototransects on these sites. Data for the three 100-plant surveys included substrate type-outcrops, blocks, cobbles, pebbles, exposed soil, organic litter-upslope from each plant, and distance to the largest rock upslope. The two surveys examined along WQTs included substrate type found downslope from kūpaoa, plant height, plant diameters across and along the slope, and distance between successively censused plants. Most plants grew downslope of nurse rocks; > 74% were adjacent to blocks or outcrops, and > 17% near cobbles. Plants showed avoidance for finer substrates; only ~ 5.3% and 2.7% grew on/near bare soils and pebbles, respectively. About 92% of kūpaoa were ≤ 10 cm downslope of rocks; > 89% grew ≤ 2 cm away, and ~ 83% in direct contact with a rock. Some seedlings also grew on pukiawe (Leptecophylla tameiameiae) nurse plants. Several stable rock microsites protected plants from disturbance by slope processes causing debris shift. Site sediments were significantly finer than substrates near plants; shrubs grew preferentially adjacent to boulders > 20 cm wide, which were more common near plants than across sites. Soils downslope of 50 boulders-mean 41.3 cm-showed higher shear strength and compressibility than soils along rock sides. These boulder dams stop descending debris, steadily deflecting them toward rock sides, whereas protected soils downslope of blocks are infrequently disturbed and develop into downslope elongated, clast-free fine-earth flags. Kūpaoa were uniformly dispersed across slopes, showing a single-phase mosaic arrangement, without apparent aggregation. Slopes where kūpaoa grows had a relatively uniform distribution of surface sediments; observed kūpaoa patterns may have resulted from the array of microsites generated by surface rocks and sediments, as shrubs simply responded to such spatial structure.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Geomorphology - Volume 295, 15 October 2017, Pages 631-644
نویسندگان
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