1

9/3/2010

Tropical ecosystem & soil development (presentation)
        We will examine the ecosystem/ soil development paradigm in two contexts: (1) long-term evolution from rock- to atmospheric-derived nutrients (Chadwick et al. 1999) and (2) rapid secondary forest recovery after agricultural use (Davidson et al. 2007). 
        Key related questions:  Do soil nutrients structure plant community composition? (John et al., 2007), How do forests respond to fertilization?, Do different plant species access nitrogen in different forms? (Houlton et al. 2007), and, What determines the global distribution of N-fixation?  (Davidson, 2008).

Joost van Haren

(Questions & bibliography)

* Chadwick et al. (1999) (tropical ecosystem development paradigm)
* Davidson et al. (2007) (does deforestation recovery follow the paradigm?)
* John et al. (2007) (soil nutrients influence spatial variability 
of plant species)

ADDITIONAL/BACKGROUND READINGS
 Davidson (2008) (perspective on determinants of N-fixing plants)
 Houlton et al. (2007) (changing N-uptake form across plant types)
Lodge et al. (1994) (nutrient temporal variability)
Vitousek & Sanford (1986) (classical work in tropical nutrient dynamics,
an excellent background)

2

9/10/2010

What is the fate of the Amazon under climate change?  (presentation)
      We will look at predictions of increased drought under climate change and consequent widescale forest dieback (Malhi et al 2009 provides model background, McDowell on plant mortality), and contemporary observations (Saleska et al. 2007; Phillips et al., 2009) & experiments (Markewitz et al., 2010). Consider the question: are the observations in these 3 readings consistent or contradictory?
     Additional background readings cover some details of the water cycle (in the classic reference, Salati & Vose, 1984), details of one model's prediction of Amazon dieback (Betts et al., 200), and the big 2005 Amazon drought (Marengo et al., 2008).

3

9/17/2010

Plasticity of plant ecophysiological responses to stress/resource variation (presentation)      Phenotypic plasticity is a key mechanism by which organisms deal with environmental variability and change, yet it is poorly represented in most vegetation models used to predict global change consequences, and is little-studied in the tropics. We will discuss one study addressing plasticity in the context of a classical problem in tropical succession: gap dynamics and light limitation (Valladares et al., 2000), and also two broader reviews: a Tansley review on the ecological limits to plasticity (Valladares et al, 2007), and a TREE review on the distinction between changes due to development (ontogeny) and those due to plasticity (Coleman et al., 1994)

BACKGROUND
Sultan (2007) (TREE review of Ecological Development:
integrating plastic vs fixed ("canalized") phenotypic expression)
Reddy et al. (2010) (photosynthetic acclimation to elevated CO2)

4

9/24/2010

Bush and Oliviera (2006). Rise and Fall of the Refugial 
     Hypothesis of Amazonian speciation, Biota Neotropica v6 (n1)
Mayle et al. (2004). Responses of Amazonian ecosystems to 
   climatic and CO2 changes since the last glacial maximum 
Bush et al. (2004) 48,000 years of Climate and Forest change
   in a biodiversity hot spot. Science. 303: 827.

NOTE: added after class:
Solomon et al (2008): Comparative molecular phylogeography of leaf
cutter ants provide new insight into the origins of Amazonian diversity

5

10/1/2010

Community level selection of plant functional traits and implications for ecosystem change (presentation)
     A 'trait' is a property of organisms, measured at the individual level and compared across species.  A 'functional trait' influences organismal performance (McGill et al 2006). We will discuss a 'response- effect framework' (Suding et al., 2008) for assessing functional trait selection following environmental change and its effects on ecosystem function. This context will structure a discussion of particular functional traits that might be important in a changing climate. Finally, we'll talk about the implications of the process of trait selection (as seen in these particular cases) for informing global change models.

KEY READING
Suding et al (2008) (laying out a trait-based 'response and effect'
framework. For discussion, know the difference between a
response trait and an effect trait)

ALSO READ ONE (about a particular trait) OF:
Penuelas et al (2005) (isoprene emissions and plant
     thermotolerance)
Weng & Lai (2005) (heat tolerance and chlorophyll fluorescence)
Markewitz et al (2010) (posted in week 2, above)
BACKGROUND
McGill et al. (2006) (Rebuilding community ecology from functional traits)

6

10/8/2010

What controls the phenology of tropical ecosystems? (presentation)
     Seasonal patterns of productivity in the Amazon influence climate and carbon cycles globally, but our understanding of them remains poor, as biophysical models have predicted seasality of fluxes opposite to that observed (Baker et al., 2008). We will examine a classic evolutionary/optimality model of the phenology of leaves, a driver of seasonal flux patterns (Kikuzawa 1995), and also observed seasonal patterns in non-structural carbohydrate (a reservoir for the production of new leaves or for buffering against drought) which may also importanty influence phenology (Newell et al., 2002). Background readings give an overview of observed relationships between irradiance (sunlight) and leaf and flower production in tropical forests worldwide, from ground studies (Wright & van Schaik), from remote sensing (Huete et al., 2006), and in the context of experimental drought (Brando et al 2006).

Kikuzawa (1995) Leaf phenology as an optimal strategy for
    carbon gain in plants. Can. J. Forestry
Baker et al. (2008) Seasonal drought stress in the Amazon:
    reconciling models and observations, JGR-Biogeosci.
Newell et al (2002). Seasonal patterns of carbohydrate storage
    in four tropical tree species
BACKGROUND
Wright & van Schaik (1994). Light and the phenology of tropical
   trees, Am. Nat.
Huete et al (2006) Amazon rainforests green-up with sunlight in 
   the dry season, GRL
Brando et al (2006) Effects of partial throughfall exclusion on
   the phenology of Coussarea racemosa (Rubiaceae) in an
   east-central Amazon rainforest

NOTE: additions after class:
- Kikuzawa, 1991. the full-blown Kikuzawa phenology model
(which gets the biomodal evergreen v. lattitude distribution)
- Wurth et al. 1995. the follow-on to Newell with the full seasonal
NSC budget at Panama's Parque Natural

7

10/15/2010

Deforestation in the Amazon: impacts, monitoring and regulation
      We will discuss the positive feedbacks among drought, forest fire and economic activities that ensue from deforestation, and could lead to a near-term Amazon forest dieback (Nepstad et al 2008). We will then look at REDD, as a policy which aims to Reduce Emissions from Deforestation and Degradation (Stickler et al). Finally, we will examine an innovative technique to map tropical carbon stocks and land-use change emissions - by combining satellite data, airborne LiDAR and field plots (Asner et el 2010).

8

10/22/2010

Precipitation recycling and hydrometeorology of the Amazon (presentation)

I will start with the Van der Ent et al, discussing the general role land-atmosphere interactions play in recycling water for precipitation.  I will then move to the classic Salati & Vose study, and get into a basic understanding of how precipitation recycling works and how deforestation is believed to affect it. Finally, we will look at Eltahir and Bras and show the dynamic based processes of how recycling works.    

Van det Ent et al (2010) Origin and fate of atmospheric moisture
over continents (gives appearance of mathematically density in parts,
but it actually straightforward conceptually the ideas are clear and
the results very interesting).
Salati & Vose (1984) Amazon Basin: a system in equilibrium
(a classic reference; read all except for the longish middle section
on soil nutrients); 
Eltahir & Bras (1994) Precipitation recycling in the Amazon basin

9

10/29/2010

Niche conservatism and phylogeographic structure in tropical forests (presentation)

Our discussion this week will focus on the imprint of phylogenetic history at local to regional scales in tropical forests. Donoghue (2008) provides a general argument for the importance of a phylogenetic perspective for understanding major patterns of plant distribution and diversity. A pioneering study by Cam Webb (Webb 2000) provided some of the first quantitative evidence of local scale phylogenetic structuring in tropical rain forests. Two studies by Toby Pennington and colleagues (Pennington 2009, Simon 2009) document contrasting patterns of niche evolution and phylogeographic structure in two major but under-studied tropical vegetation types: seasonally dry tropical forests and the cerrado savannahs of Brazil.

Donoghue M. 2008. A phylogenetic perspective on the distribution
of plant diversity

Pennington RT, Lavin M, Oliveira-Filho A. 2009. Woody plant diversity,
evolution, and ecology in the tropics: perspectives from
seasonally dry tropical forests.

Simon MF, Grether R, de Queiroz LP, et al. 2009. Recent assembly of the
Cerrado, a neotropical plant diversity hotspot, by in situ evolution
of adaptations to fire.

Webb CO. 2000. Exploring the phylogenetic structure of ecological
communities: an example for rain forest trees.

10

11/5/2010

Muller-Landau, et al. (2006a) Comparing tropical forest tree-size 
   distributions with the predictions of metabolic ecology 
Enquist, West, Brown (2009) Metabolic scaling of forest 
   structure and dynamics: Theoretical extensions and empirical 
   evaluations
Kerkoff and Enquist (2007) The Implications of Scaling Approaches
   for Understanding Resilience and Reorganization in Ecosystems

BACKGROUND:
West, Brown, Enquist (2009) Metabolic scaling of forest 
   structure and dynamics: a general theory
Enquist & Niklas (2001) Invariant Scaling relations across tree-
   dominated communities, Nature

11

11/12/2010

Kohyama (2006) The effect of patch demography on the
     community structure of forest trees
Kellner & Asner (2009) Pervasive canopy dynamics produce
     short-term stability in a tropical rain forest landscape

12

11/19/2010

13

12/3/2010

How should tropical forests respond to temperature increases? Scaling from leaf physiology to ecosystem ecology.

Guest discussion leader Travis Huxman will build on these (non-tropical) papers to develop a simple conceptual model for what we might expect in the tropics. We will start with the regulation of photosynthesis by soluable carbohydrates at the leaf scale (Turnbull et al. 2002), and then extend this to the canopy scale (Griffen et al, 2002) (both of these based on work in Biosphere 2 IFB cottonwood poplar trees), and then, to the ecosystem scale (Wan et al., 2009).

Turnbull et al. (2002) The relative impacts of daytime and night-
     time warming on photosynthetic capacity in Populus deltoides

Griffin et al., (2002) Leaf respiration is differentially affected by leaf
     vs. stand-level nighttime warming.

Wan et al. (2009) Photosynthetic overcompensation under nocturnal warming
     enhances grassland carbon sequestration