176
8.3 Mechanisms by Which Aboveground Vegetation
Attributes Influence Belowground Processes
Aboveground community composition and vegetation chemistry are tightly linked
with belowground communities through belowground inputs and subsequent
decomposition and nutrient uptake (Hobbie 1992; Wardle et al. 2004). Plant biomass, structure, and chemical composition are all important drivers of belowground
processes to such an extent that plant traits may be the dominant control on litter
decomposition, outweighing the influence of climate even over large spatial scales
(Cornwell et al. 2008).
8.3.1 Total Aboveground Inputs
Standing aboveground biomass and NPP are among the most important attributes of
vegetation that impact belowground systems (Chapin et al. 2002) and are widely
measured via RS techniques with increasing accuracy (Kokaly et al. 2009; Serbin
et al., this issue). Belowground respiration is tightly linked with aboveground productivity (Högberg et al. 2001), and leaf litter can provide roughly half of organic
inputs into some belowground systems (Coleman and Crossley 1996). The amount
of aboveground biomass can be critical to litter decomposition (Lohbeck et al.
2015) and microbial community function and diversity (Fierer et al. 2009; Cline
et al. 2018), and its influence may surpass the effects of plant quality, as measured
by plant chemistry and functional traits (Lohbeck et al. 2015).
Plant traits related to biomass, such as leaf area index (LAI), are also linked to
belowground processes, with belowground carbon (C) turnover peaking at intermediate LAI levels (Berryman et al. 2016; others). Importantly, LAI can be measured
with RS products over large spatial scales (Serbin et al. 2014; Lausch et al., Chap.
13 this volume, Morsdorf et al. Chap. 4). While there have been few explicit links
of remotely sensed LAI to soil respiration (but see Huang et al. 2015), the conceptual link has been recognized for decades (Landsberg and Waring 1997). Other
remotely sensed variables tightly coupled with biomass, including vegetation cover
(Wang et al. 2019), also predict soil respiration (Fig. 8.4).
The effects of biomass on belowground processes have been recognized by ecologists employing RS to estimate belowground C stocks (e.g., Bellassen et al. 2011).
Across large scales, aboveground biomass is generally correlated with belowground
root biomass (Cairns et al. 1997). While aboveground biomass is commonly measured, the calculation of belowground biomass is less common and is often limited
to estimates of shoot biomass as a simple proportion of aboveground biomass
(Mokany et al. 2006). Nonetheless, the belowground estimates based on aboveground
measurements can be useful for estimating above- and belowground C stores via RS
products over large spatial scales (Saatchi et al. 2011). Allocation of C to belowground systems varies among systems, with annual grassland systems differing
M. Madritch et al.
8.3 Mechanisms by Which Aboveground Vegetation
Attributes Influence Belowground Processes
Aboveground community composition and vegetation chemistry are tightly linked
with belowground communities through belowground inputs and subsequent
decomposition and nutrient uptake (Hobbie 1992; Wardle et al. 2004). Plant biomass, structure, and chemical composition are all important drivers of belowground
processes to such an extent that plant traits may be the dominant control on litter
decomposition, outweighing the influence of climate even over large spatial scales
(Cornwell et al. 2008).
8.3.1 Total Aboveground Inputs
Standing aboveground biomass and NPP are among the most important attributes of
vegetation that impact belowground systems (Chapin et al. 2002) and are widely
measured via RS techniques with increasing accuracy (Kokaly et al. 2009; Serbin
et al., this issue). Belowground respiration is tightly linked with aboveground productivity (Högberg et al. 2001), and leaf litter can provide roughly half of organic
inputs into some belowground systems (Coleman and Crossley 1996). The amount
of aboveground biomass can be critical to litter decomposition (Lohbeck et al.
2015) and microbial community function and diversity (Fierer et al. 2009; Cline
et al. 2018), and its influence may surpass the effects of plant quality, as measured
by plant chemistry and functional traits (Lohbeck et al. 2015).
Plant traits related to biomass, such as leaf area index (LAI), are also linked to
belowground processes, with belowground carbon (C) turnover peaking at intermediate LAI levels (Berryman et al. 2016; others). Importantly, LAI can be measured
with RS products over large spatial scales (Serbin et al. 2014; Lausch et al., Chap.
13 this volume, Morsdorf et al. Chap. 4). While there have been few explicit links
of remotely sensed LAI to soil respiration (but see Huang et al. 2015), the conceptual link has been recognized for decades (Landsberg and Waring 1997). Other
remotely sensed variables tightly coupled with biomass, including vegetation cover
(Wang et al. 2019), also predict soil respiration (Fig. 8.4).
The effects of biomass on belowground processes have been recognized by ecologists employing RS to estimate belowground C stocks (e.g., Bellassen et al. 2011).
Across large scales, aboveground biomass is generally correlated with belowground
root biomass (Cairns et al. 1997). While aboveground biomass is commonly measured, the calculation of belowground biomass is less common and is often limited
to estimates of shoot biomass as a simple proportion of aboveground biomass
(Mokany et al. 2006). Nonetheless, the belowground estimates based on aboveground
measurements can be useful for estimating above- and belowground C stores via RS
products over large spatial scales (Saatchi et al. 2011). Allocation of C to belowground systems varies among systems, with annual grassland systems differing
M. Madritch et al.