111
half of the known tropical forest canopy species worldwide with measured foliar
traits (Table 5.1). From investigations of these data and the fundamental patterns
they uncover, Spectranomics has evolved into a new pathway to biological and ecological discovery, as well as a new tool for conservation-relevant mapping, particularly in high-diversity tropical forests.
5.3 Lessons Learned from Spectranomics
As the Spectranomics database has grown through the years, new relationships
among plant phylogeny, canopy chemical traits, and spectral properties have
emerged that reveal patterns at nested biogeographic scales. The extent of sampling
across continents, along regional environmental gradients, and within local tree
communities, coupled with consistent methods and analysis, has provided for quantitative testing of these relationships at multiple scales such that they can now be
used to forecast the functional traits and biodiversity components that can be
remotely mapped and monitored with spectral RS instrumentation.
5.3.1 Nested Geography of Canopy Chemical Traits in Humid
Tropical Forest
Humid tropical forests cover over 20 million km of land area, span an enormous
range of environmental conditions from hot lowland forests to cool montane rainforests along equatorial tree line at almost 3500 m on a variety of geological substrates, and support thousands of tree species. The high degree of complexity of this
region provided an ideal setting to develop and use Spectranomics to test how environment and phylogeny interact to sort the spectral-chemical diversity of forest
canopies. Based on results from multiple field studies throughout this region (Martin
et al. 2007; Asner and Martin 2011; Asner et al. 2014b; McManus Chauvin et al.
2018) as well as their collective analysis (Asner and Martin 2016), we discovered
that canopy chemical trait diversity of humid tropical forests occurs in a nested pattern driven by long-term adjustment of tree communities to large-scale environmental factors, particularly geologic substrate and climate. More specifically, geographic
variation at the soil order level, expressing broad changes in fertility, underpins
major shifts in foliar phosphorus (P) and calcium (Ca) (Fig. 5.2). Additionally,
elevation- dependent shifts in average community leaf dry mass per area (LMA),
chlorophyll, and carbon allocation (including nonstructural carbohydrates) are most
strongly correlated with changes in foliar Ca. We also found that chemical diversity
within communities is driven by differences between species rather than by plasticity within species. Finally, elevation- and soil-dependent changes in nitrogen (N),
LMA, and leaf carbon allocation are mediated by canopy compositional turnover,
5 Lessons Learned from Spectranomics: Wet Tropical Forests
half of the known tropical forest canopy species worldwide with measured foliar
traits (Table 5.1). From investigations of these data and the fundamental patterns
they uncover, Spectranomics has evolved into a new pathway to biological and ecological discovery, as well as a new tool for conservation-relevant mapping, particularly in high-diversity tropical forests.
5.3 Lessons Learned from Spectranomics
As the Spectranomics database has grown through the years, new relationships
among plant phylogeny, canopy chemical traits, and spectral properties have
emerged that reveal patterns at nested biogeographic scales. The extent of sampling
across continents, along regional environmental gradients, and within local tree
communities, coupled with consistent methods and analysis, has provided for quantitative testing of these relationships at multiple scales such that they can now be
used to forecast the functional traits and biodiversity components that can be
remotely mapped and monitored with spectral RS instrumentation.
5.3.1 Nested Geography of Canopy Chemical Traits in Humid
Tropical Forest
Humid tropical forests cover over 20 million km of land area, span an enormous
range of environmental conditions from hot lowland forests to cool montane rainforests along equatorial tree line at almost 3500 m on a variety of geological substrates, and support thousands of tree species. The high degree of complexity of this
region provided an ideal setting to develop and use Spectranomics to test how environment and phylogeny interact to sort the spectral-chemical diversity of forest
canopies. Based on results from multiple field studies throughout this region (Martin
et al. 2007; Asner and Martin 2011; Asner et al. 2014b; McManus Chauvin et al.
2018) as well as their collective analysis (Asner and Martin 2016), we discovered
that canopy chemical trait diversity of humid tropical forests occurs in a nested pattern driven by long-term adjustment of tree communities to large-scale environmental factors, particularly geologic substrate and climate. More specifically, geographic
variation at the soil order level, expressing broad changes in fertility, underpins
major shifts in foliar phosphorus (P) and calcium (Ca) (Fig. 5.2). Additionally,
elevation- dependent shifts in average community leaf dry mass per area (LMA),
chlorophyll, and carbon allocation (including nonstructural carbohydrates) are most
strongly correlated with changes in foliar Ca. We also found that chemical diversity
within communities is driven by differences between species rather than by plasticity within species. Finally, elevation- and soil-dependent changes in nitrogen (N),
LMA, and leaf carbon allocation are mediated by canopy compositional turnover,
5 Lessons Learned from Spectranomics: Wet Tropical Forests