Does afforestation of pastures with pine trees reduce net emissionsofmmethane in New ethane Zzeeaaland?Land?

摘要

New Zealand’s methane (CH4) inventory is dominated by emissions from grazing ruminants (enteric fermentation),currently estimated to be 1123 Gg y-1.By contrast,a recentassessment of the potential of New Zealand soils to oxidise CH4 suggests total sink strength is about 147 Gg CH4 y-1 or 11% of New Zealand’s total CH 4 CH4 emissions.An indigenous beech forest had the highest average oxidation rate (10.5 kg CHCH4 ha-1 y-1),exotic pine forest intermediate rates (4.2–14 kgCH4 CH4 ha-1 y-1),and pasture and cropped soils the lowest oxidation rates (<1 kg CH4 ha-1 y-1).Our recent estimates suggest the New Zealand soil CH4-sink capacity could have increased by about 7 Gg CH4 since 1990,mainly because of afforestation of pastures; this appears to result in enhanced sink capacityover a decade or so.If confirmed,this increase in soil CH4 oxidation could offset about one fourth ofemissions from manure management.We here report further on changes in rates of CH4 oxidation withafforestation of grazed pastures based on two paired-site comparisons of pasture and Pinus radiata.