Carbon sequestration and reclamation of severely degraded soils in Iceland

H÷fundur┌tgefandi┌tgßfußr┌tgßfusta­ur
Ëlafur Arnalds, GrÚtar Gu­bergsson, Jˇn Gu­mundssonRALA , B═, BŠndaskˇlinn ß Hvanneyri, Rannsˇknast÷­ SkˇgrŠktar rÝkisins, Tilraunast÷­ hßskˇlans Ý meinafrŠ­i og Vei­imßlastofnun 2000ReykjavÝk
Rit┴rgangurT÷lubla­Bls.
B˙vÝsindi1387-97

bu13-oa.pdf

Frß vefstjˇra: Greinina Ý heild sinni er a­ finna Ý pdf-skjalinu hÚr a­ ofan

SUMMARY

Iceland has extensive deserts and barren patches in spite of it’s humid environment. The soils of the deserts are sandy Andisols, with limited sources of macronutrients and low water holding capacity. Andisols have a general tendency to immobilize carbon, and undisturbed, fully vegetated Andisols in Iceland often contain >40 kg C m–2, often to more than 1.5 m depth. The difference between soils of barren areas, with <1 kg C m–2 and undisturbed Andisols indicates that reclamation of degraded sites may have high potential for carbon sequestration.

The objective of this research was to develop methods to determine carbon sequestration rates in soils in relation to reclamation of degraded land in Iceland and to verify sequestration rates for reclamation activities. Carbon was determined in soils of 33 reclamation areas of different age throughout Iceland. At many sites, adjacent non-reclaimed areas were also sampled for comparison.

The results show that reclamation of Icelandic deserts results in an average sequestration rate in soils of 0.6 t C ha–1 yr–1, which is maintained >50 yrs. This number does not include sequestration in above-ground or belowground biomass, (0.01–0.5 t ha–1 yr–1), which is reported in a concurrent paper (Aradˇttir et al., 2000).

Soil carbon sequestration rates were highly variable. In some areas, sequestration rates slowed when plant succession was restrained ecological thresholds. It is important to determine these thresholds and find economic means to overcome them to promote carbon sequestration over longer periods. Results suggest that sequestration of carbon to mitigate greenhouse gas emissions can be monitored and verified in Iceland.

Key words: Andisols, carbon sequestration, climate change, deserts, reclamation, restoration.

YFIRLIT

Binding kolefnis Ý jar­vegi ß uppgrŠ­slusvŠ­um ß ═slandi

═ greininni er fjalla­ um ni­urst÷­ur rannsˇkna ß bindingu kolefnis ß uppgrŠ­slusvŠ­um. Verkefni­ er unni­ Ý tengslum vi­ sÚrstakt ßtak rÝkistjˇrnarinnar til a­ auka bindingu kolefnis me­ skˇgrŠkt og landgrŠ­slu til a­ vega ß mˇti losun grˇ­urh˙salofttegunda. Ger­ hefur veri­ grein fyrir fyrstu ni­urst÷­um rannsˇkna ß bindingu me­ skˇgrŠkt ß ÷­rum vettvangi (Arnˇr Snorrason o.fl., 2000), en auk ■ess er ger­ grein fyrir bindingu kolefnis Ý grˇ­ri ß landgrŠ­slusvŠ­um Ý ■essu sama hefti B˙vÝsinda (┴sa L. Aradˇttir o.fl., 2000).

Mun meira er bundi­ af kolefni Ý jar­vegi (>1500–2300 Gt C) en ÷­rum hlutum lÝfkerfisins a­ heimsh÷funum undanskildum. Um 750 Gt C eru Ý andr˙msloftinu, en 500–560 Gt C Ý grˇ­ri, ■ar af um 360 Gt C Ý skˇgi (sjß IPCC, 2000). ŮvÝ er n˙ bŠ­i liti­ til jar­vegs og grˇ­urs sem hugsanlegra valkosta til a­ binda kolefni ˙r andr˙msloftinu. Binding Ý jar­vegi er ekki sÝst gˇ­ur kostur ■ar sem um lei­ er aukin framlei­ni og virkni vistkerfa ■ar sem vistkerfi eru endurheimt ß au­num og hnignu­um svŠ­um.

═slenskur jar­vegur telst til svonefndrar eldfjallajar­ar (Andosol e­a Andisol), en slÝkur jar­vegur hefur tilhneigingu til a­ binda kolefni Ý jar­vegi umfram annan jar­veg ■urrlendis (sjß t.d. Wada, 1985; Shoji o.fl., 1993). Miki­ af kolefni er bundi­ Ý Ýslenskum jar­vegi, oft >40 kg/m2 Ý ■urrlendisjar­vegi, en >90 kg/m2 Ý jar­vegi votlendis. Jar­vegur au­nanna telst einnig til ■essarar jar­vegsger­ar, en ■ar er lÝti­ af kolefni. Ůegar grˇ­ur festir rŠtur Ý au­nunum taka lÝfrŠn efni a­ safnast fyrir Ý jar­veginum, jafnframt ■vÝ sem hann ver­ur smßm saman frjˇsamari. ŮvÝ er hugsanlegt a­ binda umtalsvert kolefni Ý jar­vegi vi­ landgrŠ­slu ß ═slandi. Ůa­ er mj÷g mikilsvert a­ komast a­ ■vÝ hve hra­fara ■essi binding er, ef h˙n ß a­ ver­a vi­urkennd mˇtvŠgislei­ vegna losunar grˇ­urh˙salofttegunda.

Markmi­ rannsˇknanna var a­ ■rˇa a­fer­ir til kanna bindingu kolefnis Ý jar­vegi vi­ landgrŠ­slu og ßkvar­a hve mikil binding hefur or­i­ vi­ hi­ sÚrstaka ßtak rÝkisstjˇrnarinnar til a­ binda kolefni me­ landgrŠ­slu og skˇgrŠkt.

Kolefni var kanna­ Ý jar­vegi ß 62 st÷­um ß 33 landgrŠ­slusvŠ­um ß landinu (1. mynd, 2. tafla). Jar­vegssřnum var yfirleitt safna­ me­ jar­vegsbor (2 og 5 cm Ý ■vermßl) og ■au voru tekin ˙r ßkve­num dřptarbilum ß hverjum sta­: 0–10, 10–20 og 20–30 cm. Hvert sřni var samsett ˙r fimm kj÷rnum, og ■rj˙ slÝk sřni voru tekin ß hverjum sta­. Ůar sem miki­ grjˇt kom Ý veg fyrir notkun jar­vegsbors voru sřni tekin ˙r jar­vegssni­um. Sřnin voru tekin ˙r jar­vegi ß misg÷mlum landgrŠ­slusvŠ­um, en einnig voru sřni tekin til samanbur­ar Ý ja­ri svŠ­anna ■ar sem engin landgrŠ­sla haf­i ßtt sÚr sta­. Grjˇt (>2 mm) var ßkvar­a­ Ý hverju sřni sem og r˙m■yngd og kolefni fÝnefna (<2 mm). Allar dřptir voru lag­ar saman og ■essar stŠr­ir eru sÝ­an nota­ar til a­ ßkvar­a kolefnismagn jar­vegsins Ý kg C/m2.

Bindihra­i var bŠ­i kanna­ur me­ a­hvarfsj÷fnum (3. mynd) og me­ ■vÝ a­ bera saman landgrŠ­slusvŠ­i og svŠ­i ■ar sem engin landgrŠ­sla hefur ßtt sÚr sta­. Binding ■ar sem sß­ er Ý sendnar au­nir er a­ me­altali um 0,6 t C/ha ß ßri. Ůessi binding er sambŠrileg e­a meiri en binding sem ver­ur vi­ a­ breyta rŠktarlandi Ý graslendi vÝ­a annars sta­ar (sjß Sampson og Scholes, 2000; IPCC, 2000), en er bŠ­i ÷rari og varir Ý lengri tÝma en vÝ­a annars sta­ar vi­ ß landgrŠ­slu ß r÷sku­um svŠ­um (IPCC, 2000).

Rannsˇknirnar sřna ljˇslega a­ ß sumum svŠ­um hŠgir mj÷g ß bindingunni ■egar nßtt˙ruleg grˇ­urframvinda er hŠg e­a st÷­vast. ŮvÝ er mikilvŠgt a­ finna hagkvŠmar lei­ir til ■ess a­ yfirvinna ■r÷skulda sem st÷­va framvindu vistkerfanna ■ar sem ■a­ gerist.

Me­ ■vÝ a­ nota me­albindihra­a og t÷lulegar upplřsingar frß hverju svŠ­i fyrir sig mß fß gl÷gga mynd af bindingu ß landgrŠ­slusvŠ­um ß ═slandi, en slÝkra upplřsinga er krafist Ý tengslum vi­ loftslagssamning Sameinu­u ■jˇ­anna (FCCC).

INTRODUCTION

Efforts to sequester carbon by restoring severely degraded lands are among major actions taken by the Icelandic government in relation to the implementation of the Framework Convention for Climate Change (FCCC). Efforts are made to sequester carbon both in soils and aboveground biomass. This program is termed the “Carbon Sequestration by Reclamation Program” (CSR-Program).

An important part of the CSR-Program is to verify the carbon sequestration accompanying ecosystem restoration activities. A special project was established at the initial stages of the CSR-Program to develop methods for measuring sequestration. This project contained four components: sequestration in trees and by forestation, sequestration in biomass other than trees, sequestration in soils, and measurements of carbon fluxes. Here we report carbon sequestration in soils undergoing revegetation/restoration efforts in Icelandic deserts. Aradˇttir et al. (2000) reported results for sequestration by rangeland vegetation. Sequestration by reforestation was discussed by Snorrason et al. (2000).

The terms “revegetation” and “reclamation” will be used interchangeably to refer to treatments aimed at restoring ecological processes on degraded lands.