Jökull - 01.12.2007, Side 46

McPeek et al.
ÁGRIP
Myndun jarðvegs vegna veðrunar bergs stjórnast af
berggerð, veðurfari, líffræðilegum ferlum og tíma.
Líf- og jarðefnafræðilegar mælingar eru notaðar til
að ákvarða samspils lífveruvirkni og jarðvegsmynd-
unar úr basaltlögum mynduðum á sögulegum tíma.
Jarðvegssýni voru tekin ofan af Eldgjárhrauninu frá
934, Hekluhraunumfrá 1300 og 1554, og Skaftárelda-
hrauni (1783). Kolefnis- (C) og fosfórmagn (P) var
ákvarðað í jarðveginum. Lífrænt efni mældist á bilinu
3, 30, 1,01, 0,80 og 0,21 kg m!2. Lífrænt efni í eld-
fjallajarðvegi (Andisol) er í lægri kantinummiðað við
kolefnismagn (0,1–14,9 kg m!2) í öðrum fjalllendis-
og norðlægum vistkerfum. Meðalkolefnisbinding í
jarðveginum var 1–3 g m!2ár!1 samanborið við 0,8–
11,7 g m!2ár!1 í norðlægum vistkerfum. Lífrænn
P jókst með tíma og mældist 13,7, 8,6, 6,5 og 4,5
mg cm!2 í jarðvegi á hraununum frá 934, 1300, 1554
og 1783 en magn ásogaðs P 44,5, 9,4, 7,7 og 2,7
mg cm!2. Aukið C og P magn í eldri jarðvegi eins og
mældist í þessari rannsókn sýnir að líffræðileg virkni
og heildarveðrun hrauna á Suðurlandi vex með tíma.
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