Empirical estimates to reduce modeling uncertainties of soil organic carbon in permafrost regions: a review of recent progress and remaining challenges oleh U Mishra, J D Jastrow, R Matamala, G Hugelius, C D Koven, J W Harden, C L Ping, G J Michaelson, Z Fan, R M Miller, A D McGuire, C Tarnocai, P Kuhry, W J Riley, K Schaefer, E A G Schuur, M T Jorgenson, L D Hinzman