Fire and the Miocene expansion of C4 grasslands

Ecology Letters - Tập 8 Số 7 - Trang 683-690 - 2005
Jon E. Keeley1,2, Philip W. Rundel3,1
1Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA 90095-1606, USA
2US Geological Survey, Western Ecological Research Center, Sequoia-Kings Canyon Field Station, Three Rivers, CA 93271, USA
3Center for Embedded Networked Sensing, University of California, Los Angeles, CA 90095-1606, USA

Tóm tắt

Abstract

C4 photosynthesis had a mid‐Tertiary origin that was tied to declining atmospheric CO2, but C4‐dominated grasslands did not appear until late Tertiary. According to the ‘CO2‐threshold’ model, these C4 grasslands owe their origin to a further late Miocene decline in CO2 that gave C4 grasses a photosynthetic advantage. This model is most appropriate for explaining replacement of C3 grasslands by C4 grasslands, however, fossil evidence shows C4 grasslands replaced woodlands. An additional weakness in the threshold model is that recent estimates do not support a late Miocene drop in pCO2. We hypothesize that late Miocene climate changes created a fire climate capable of replacing woodlands with C4 grasslands. Critical elements were seasonality that sustained high biomass production part of year, followed by a dry season that greatly reduced fuel moisture, coupled with a monsoon climate that generated abundant lightning‐igniting fires. As woodlands became more open from burning, the high light conditions favoured C4 grasses over C3 grasses, and in a feedback process, the elevated productivity of C4 grasses increased highly combustible fuel loads that further increased fire activity. This hypothesis is supported by paleosol data that indicate the late Miocene expansion of C4 grasslands was the result of grassland expansion into more mesic environments and by charcoal sediment profiles that parallel the late Miocene expansion of C4 grasslands. Many contemporary C4 grasslands are fire dependent and are invaded by woodlands upon cessation of burning. Thus, we maintain that the factors driving the late Miocene expansion of C4 were the same as those responsible for maintenance of C4 grasslands today.

Từ khóa


Tài liệu tham khảo

10.1666/0094-8373(2002)28[1:FAECIT]2.0.CO;2

10.2307/2403708

10.2475/ajs.301.2.182

10.1046/j.1365-2486.2000.00365.x

10.1016/S0254-6299(15)30362-8

10.1046/j.1365-2486.2003.00577.x

10.1111/j.1469-8137.2004.01252.x

10.1023/A:1005383020063

10.1071/BT9920089

10.1111/j.1442-9993.1991.tb01486.x

10.2307/2402965

10.1046/j.1365-2699.1998.00222.x

Cerling T.E., 1999, C4Plant Biology, 445

10.1038/361344a0

10.1038/371112a0

10.1038/38229

Cerling T.E., 1998, Phil. Trans. R. Soc. Lond. Ser. B, 159

10.1007/978-3-642-75395-4_6

10.1146/annurev.es.23.110192.000431

10.1126/science.197.4298.53

10.1130/G19727.1

10.1017/S0022336000021223

10.1146/annurev.es.24.110193.002211

10.1007/s004420050311

10.1046/j.1365-2699.2003.00934.x

10.1146/annurev.es.23.110192.001221

10.1130/G19580.1

10.1016/S0031-0182(04)00045-8

10.1016/0016-7037(94)90210-0

10.1016/S0016-7037(00)00573-1

Furley P.A., 1992, Nature and Dynamics of Forest‐Savanna Boundaries

Gillon D., 1983, Tropical Savannas, 617

10.1016/0031-0182(94)00115-O

10.1007/978-3-642-79354-7_25

10.1029/GM032p0419

10.1890/0012-9658(1999)080[1354:FAPDOW]2.0.CO;2

10.1111/j.1365-2435.2003.00796.x

10.2307/2666186

10.1073/pnas.97.14.7899

10.1016/j.palaeo.2003.09.032

10.1023/A:1026590806682

10.1046/j.1365-2699.2002.00676.x

10.1086/323594

10.1086/374192

Kellogg E.A., 1999, C4Plant Biology, 411

10.1890/0012-9658(2003)084[0337:EOFAHO]2.0.CO;2

10.1016/S0012-821X(96)00231-2

10.1046/j.1365-2699.2000.00422.x

10.1038/367162a0

10.1111/j.1469-8137.1987.tb04688.x

10.1029/1999PA900006

10.1126/science.285.5429.876

10.1038/35021000

10.1016/S0031-0182(03)00232-3

10.1038/342163a0

10.1130/0016-7606(1995)107<1381:LMECIN>2.3.CO;2

Retallack G.J., 1991, Miocene Paleosols and Ape Habitats of Pakistan and Kenya

10.1086/320791

Ripley E.A., 1988, Biol. Soc. Venezuela Cienc. Natur., 33

10.1046/j.1472-4642.2003.00020.x

10.1126/science.292.5525.2310

10.1007/BF00540205

Sage R.F., 1999, C4Plant Biology, 3

10.1055/s-2001-15206

10.1111/j.1469-8137.2004.00974.x

San José J.J., 1991, Changes in tree density and species composition in a protected Trachypogon savanna protected for 25 years, Acta Oecol., 12, 237

10.1111/j.1461-0248.2004.00596.x

10.4159/harvard.9780674418554

10.1007/978-3-642-75395-4_5

10.1130/0091-7613(1994)022<0419:CISOEC>2.3.CO;2

10.1007/BF00347910

10.1669/0883-1351(2000)015<0430:TCEING>2.0.CO;2

10.1126/science.1059412

Thông tin
Thông tin xuất bản

Ecology Letters

Tập 8 Số 7

683-690

Thông tin tác giả