10/11/20101What is the future of Amazon fsts d lit h ?forests under climate change?-Increase in temperatures of ~3C-20% reduction in precipitation over 21st-20% reduction in precipitation over 21cent.Two kinds of philosophy in predicting Amazon futureClimate Model coupled with Vegetation DynamicsSimilar scenarios in history used to predict futureNowPast (~21,000 years BP) Future (2100)Savana grasslands/dry forestsRainforest Savana grassland/dry forest?10/11/20102What are the dis/advantages of two methods?What is the future of Amazon, savana or dry forest?What is the key to predict Amazon future?Climate Model coupled with Vegetation DynamicsSimilar scenarios in history used to predict futureNowPast (~21,000 years BP) Future (2100)Savana grasslands/dry forestsRainforest Savana grassland/dry forest?Outline1. Some terminologies reviewg2. What is Pollen Analysis?3. What kind of information can we get from pollen analysis?4. What kind of question can we ask?5Further inference & discussion5.Further inference & discussion10/11/20103TerminologyReviewHolocene: a geological epoch which began approximately 12,000 years ago (10 000 14C years ago)Pleistocene:the epoch from Pleistocene:the epoch from 1.8 million to 12,000 years BP covering the world's recent period of repeated glaciations10/11/20104Pollen Analysis•The study of assemblages of dispersed palynomorphs such as those isolated from samples of peat (Von Post 1916) of peat (Von Post, 1916). • A technique for reconstructing former vegetationby means of pollen grains it produced (Faegri and Iverson, 1989)• Pollen analytical data obtained from lake and bog sedimentsprovide direct information relevant to sedimentsprovide direct information relevant to the reconstruction of the past flora and vegetationof the area under study (Birks and Birks 2005).Assumption of Pollen Analysis• The basic assumption of the technique is that the number of pollen grains deposited per unit i i i i di l ld h time, at a given point, is directly related to the abundance of the associated species in the surrounding vegetation (Davis 1963).10/11/2010510/11/20106Sample: every two ti t sLake Sediment & Pollen AnalysisChronology: Accelerator Mass Spectrometry (AMS)14C datesPalynology: vegetation typecentimeters& abundance Pollen Analysis & Paleoclimate•As both modern floras and modern vegetation are related in a broad way to modern climate, pollen analysis can provide indirect information relevant to the reconstruction of past climates over particular time spans (102-105years) with a sample resolution of 10-1000years.10/11/20107Pollen Analysis & Paleoclimate• John Imbrie and Nilva Kipp (1971) “transfer function”where Ym is modern pollen data, Xm is modern climate data• Then apply the inverse of f to fossil pollen data Yf t if t lim tXfto infer past climateXfStep 1: Get lake sedimentStep 2: Sample and identificationStep 3: Paleo-VegetationReconstructionStep 4: Paleo-ClimateReconstruction10/11/20108Disadvantages of Pollen Analysis• Poor Representatives– pollen data are presented as proportions of a total pollen sum, rather than as discrete numbers(Davis pm,m(1963)– Therefore, difficulties with the representativity both between and within species are experienced, as some taxa produce far greater quantities of pollen, which are more widely dispersed than others (Birks and Birks 2005). – Data representativity will be biased due to the differences in pollen productivity, dispersal and ff p p y, ppreservation (Faegri and Iverson 1989).• Circular Reasoning– Paleo-Vegetation & Paleo-Climate are reconstructed by same data setWhat kind of questions can we ask?1. What is the vegetation dynamics from past to now?past to now?2. How did vegetation respond to past climate change?3. What is the inference of the past to future (prediction)?4Can this data set resolve the debate on 4.Can this data set resolve the debate on the origin of Amaznonian biodiversity?10/11/20109Bush et al. 2004•Location:–Lower montane cloud Lower montane cloud forests of Peru–Lago Consuelo– Elevation = 1360m•Proxy– Sediment cores• Chronology based on 10 AMS 14C dates• Pollen analysesBush et al. 2004• Pollen Diagram– Different Pleistocene and Holocene forest ftypes– Gradual transition– Composition similarity analysis based on DCA analysis (Detrended Correspondence Analysis)10/11/201010Bush et al. 2004Bush et al. 2004From Titicaca pollen site, we can get:Bush et al. 2004•Purpose-designed transfer functions–Way to infer past Way to infer past temperature from pollen–2 periods of relatively stable temperatures–No substantial deviationfrom surrounding Pleistocene conditions– Late Pleistocene at least 5 C colder than today1000 m of elevation increase=6 C of temperature decrease10/11/201011Bush et al. 2004•Nearly constant sedimentation rate, absence of abrupt changes in sedimentL C l did t–Lago Consuelo never dried out– No major drought episodes• Wet Andean cloud forest continuous • Rate of change in forest composition indistinguishable from stochastic changes f t bl i dof stable periodsBush et al. 2004• Detrended Correspondence Analysis (DCA)T tbl id–Two stable periods– Directional change rather than random drift10/11/201012Bush et al. 2004•Key Points– Cloud forest existed at or close to Lago Consuelo elevation for the past 48,000 yearsTemp change from Pleistocene to Holocene began –Temp change from Pleistocene to Holocene began ~19 ka– “rates of forest community change during the most substantial climate change of the past were no greater than during the relative stability of the pre-Industrial Holocene”Bush et al. 2004• Implications for future climate change–Climate changesin these systems gradual• 5-9 C/10000yearsNo precipitation information?•No precipitation information?– Projected climate change in next 100 years fundamentally different from any in the last 50ky• 3 C increase by 2100• 20% decrease in precipitation – Andean plants with broad elevational distributionsshould survive climate changes•Plants can safely shift under such a rapid rate of Plants can safely shift under such a rapid rate of temperature increase?• What is the threshold value of climate variability for plants to survive?–Plants with narrow ranges may be moved outside of their niche10/11/201013Mayle et al. 2004•Aim:– Determine responses of Amazonian ecosystems to changes in T, P, and atmospheric CO2since LGM (21 k