@article {2707,
	title = {A long-term decrease in the persistence of soil carbon caused by ancient Maya land use},
	journal = {Nature Geoscience},
	volume = {11},
	year = {2018},
	month = {Jan-09-2018},
	pages = {645 - 649},
	abstract = {The long-term effects of deforestation on tropical forest soil carbon reservoirs are important for estimating the consequences of land use on the global carbon cycle, but are poorly understood. The Maya Lowlands of Mexico and Guatemala provide a unique opportunity to assess this question, given the widespread deforestation by the ancient Maya that began ~4,000 years ago. Here, we compare radiocarbon ages of plant waxes and macrofossils in sediment cores from three lakes in the Maya Lowlands to record past changes in the mean soil transit time of plant waxes (MTTwax). MTTwax indicates the average age of plant waxes that are transported from soils to lake sediments, and comparison of radiocarbon data from soils and lake sediments within the same catchment indicates that MTTwax reflects the age of carbon in deep soils. All three sediment cores showed a decrease in MTTwax, ranging from 2,300 to 800 years, over the past 3,500 years. This decrease in MTTwax, indicating shorter storage times for carbon in lake catchment soils, is associated with evidence for ancient Maya deforestation. MTTwax never recovered to pre-deforestation values, despite subsequent reforestation, implying that current tropical deforestation will have long-lasting effects on soil carbon sinks.},
	issn = {1752-0894},
	doi = {10.1038/s41561-018-0192-7},
	url = {https://www.researchgate.net/publication/327119047_A_long-term_decrease_in_the_persistence_of_soil_carbon_caused_by_ancient_Maya_land_use},
	author = {Douglas, Peter M. J. and Pagani, Mark and Eglinton, Timothy I. and Brenner, Mark and Curtis, Jason H. and Breckenridge, Andy and Johnston, Kevin}
}
@article {66,
	title = {Pre-aged plant waxes in tropical lake sediments and their influence on the chronology of molecular paleoclimate proxy records},
	journal = {Geochimica et Cosmochimica Acta},
	volume = {141},
	year = {2014},
	pages = {346-364},
	abstract = {Sedimentary records of plant-wax hydrogen (δDwax) and carbon (δ13Cwax) stable isotopes are increasingly applied to infer past climate change. Compound-specific radiocarbon analyses, however, indicate that long time lags can occur between the synthesis of plant waxes and their subsequent deposition in marginal marine sediments. The influence of these time lags on interpretations of plant-wax stable isotope records is presently unconstrained, and it is unclear whether such time lags also affect lacustrine sediments. We present compound-specific radiocarbon (14Cwax) data for n-alkanoic acid plant waxes (n-C26 to n-C30) from: 1) a sediment core from Lake Chichancanab, Yucatan Peninsula, Mexico, 2) soils in the Lake Chichancanab catchment, and 3) surface sediments from three other lakes in southeastern Mexico and northern Guatemala. 14Cwax ages in the surface sediments are consistently older than modern, and may be negatively correlated with mean annual precipitation and positively correlated with lake catchment area. 14Cwax ages in soils surrounding Lake Chichancanab increase with soil depth, consistent with deep, subsoil horizons being the primary source of lacustrine aged plant waxes, which are likely delivered to lake sediments through subsurface transport. Plant waxes in the Lake Chichancanab core are 350 to 1200 years older than corresponding ages of bulk sediment deposition, determined by 14C dates on terrestrial plant macrofossils in the core. A δDwax time series is in closer agreement with other regional proxy hydroclimate records when a plant-wax 14C age model is applied, as opposed to the macrofossil-based core chronology. Inverse modeling of plant-wax age distribution parameters suggests that plant waxes in the Lake Chichancanab sediment core derive predominantly from millennial-age soil carbon pools that exhibit relatively little age variance (< 200 years). Our findings demonstrate that high-temporal-resolution climate records inferred from stable isotope measures on plant waxes in lacustrine sediments may suffer from possible chronologic distortions as a consequence of long residence times of plant waxes in soils. They also underscore the importance of direct radiocarbon dating of these organic molecules.},
	issn = {0016-7037},
	doi = {10.1016/j.gca.2014.06.030},
	url = {http://www.sciencedirect.com/science/article/pii/S0016703714004451},
	author = {Douglas, Peter M. J. and Pagani, Mark and Eglinton, Tim E. and Brenner, Mark and Hodell, David A. and Curtis, Jason H. and Ma, Keith and Breckenridge, Andy}
}
@article {532,
	title = {A 4000-Year Lacustrine Record of Environmental Change in the Southern Maya Lowlands, Pet{\'e}n, Guatemala},
	journal = {Quaternary Research},
	volume = {57},
	year = {2002},
	note = {id: 2106},
	pages = {183-190},
	abstract = {A 4000-yr sediment core record from Lake Salpet{\'e}n, Guatemala, provides evidence for Maya-induced forest clearance and consequent soil erosion between \~{}1700 cal yr B.C. and 850 cal yr A.D. Radiocarbon ages of wood, seeds, and charcoal support an age-depth model with average errors of {\textpm}110 cal yr. Relatively low carbonate δ18O values between 1300 and 400 cal yr B.C. coincide with pollen evidence for forest loss, consistent with increased surface and groundwater flow to the lake. Minimum δ18O values between 400 cal yr B.C. and 150 cal yr A.D. suggest a high lake level, as do 14C-dated aquatic gastropods as much as 7.5 m above the present lake stage. High lake levels resulted from reduced evaporation-to-precipitation ratios, increased hydrologic input caused by anthropogenic deforestation, or both. The Preclassic abandonment (150 A.D.) and Early Classic/Late Classic boundary (550 A.D.) are marked by relatively high δ18O values indicating reduced lake levels. Oxygen isotope composition increased further coincident with the Terminal Classic Maya demographic decline between 800 and 900 A.D. This period of high δ18O may have been caused by the greater aridity that has been documented in northern Yucat{\'a}n lakes or by decreased hydrologic input to the lake as a consequence of forest recovery. Reduced soil erosion after 850 cal yr A.D. coincided with the Terminal Classic Maya demographic decline and permitted forest recovery and resumption of organic sedimentation.},
	issn = {0033-5894},
	doi = {10.1006/qres.2001.2305},
	author = {Rosenmeier, Michael F. and Hodell, David A. and Brenner, Mark and Curtis, Jason H. and Guilderson, Thomas P.}
}
