Unearthing the hidden world of roots: Root biomass and architecture differ among species within the same guild

Abstract

The potential benefits of planting trees have generated significant interest with respect to sequestering carbon and restoring other forest based ecosystem services. Reliable estimates of carbon stocks are pivotal for understanding the global carbon balance and for promoting initiatives to mitigate CO2 emissions through forest management. There are numerous studies employing allometric regression models that convert inventory into aboveground biomass (AGB) and carbon (C). Yet the majority of allometric regression models do not consider the root system nor do these equations provide detail on the architecture and shape of different species. The root system is a vital piece toward understanding the hidden form and function roots play in carbon accumulation, nutrient and plant water uptake, and groundwater infiltration. Work that estimates C in forests as well as models that are used to better understand the hydrologic function of trees need better characterization of tree roots. We harvested 40 trees of six different species, including their roots down to 2 mm in diameter and created species-specific and multi-species models to calculate aboveground (AGB), coarse root belowground biomass (BGB), and total biomass (TB). We also explore the relationship between crown structure and root structure. We found that BGB contributes ~27.6% of a tree’s TB, lateral roots extend over 1.25 times the distance of crown extent, root allocation patterns varied among species, and that AGB is a strong predictor of TB. These findings highlight the potential importance of including the root system in C estimates and lend important insights into the function roots play in water cycling.

Drought Differentially Affects Growth, Transpiration, and Water Use Efficiency of Mixed and Monospecific Planted Forests

“…We scaled sapwood area growth to stand growth for all treatment plots. Individual tree aboveground biomass (AGB, kg) was estimated using species-specific allometric equations based on excavation data from a nearby site ( [43]; also see [44]) for the entire plantation (including sap flow trees). We estimated AGB for D. retusa using the equation:…”

Phosphatase activity and nitrogen fixation reflect species differences, not nutrient trading or nutrient balance, across tropical rainforest trees

“…We measured the aboveground nutrient demand from aboveground biomass growth and tissue nutrient content. Leaf and wood growth rates were determined from basal diameter measurements in 2009 and 2011 using locally derived allometric equations (Sinacore et al 2017), and the tissue-specific nitrogen and phosphorus demand was determined by multiplying growth rates by species-specific nutrient contents from the literature (Supporting Information).…”

Nitrogen fixer abundance has no effect on biomass recovery during tropical secondary forest succession

“…The biomass of trees comprises the majority of biomass in tropical forests and trees (Saatchia et al, 2011), but nevertheless the role of below-ground biomass pools and interactions require further examination as resource competition is a net measure of above-and below-ground plant-plant interactions. Roots account for a substantial proportion of tree biomass (almost 30 percent of the total biomass of young trees in a nearby plantation; Sinacore et al, 2017) and root:shoot ratios and root architecture are likely to shift along successional and other environmental gradients (Jaramillo, Ahedo-Hernández, & Kauffman, 2003;Rasmann, Bauerle, Poveda, & Vannette, 2011;van Noordwijk, Cadisch, & Ong, 2004;Zangaro, Alves, Lescano, Ansanelo, & Nogueira, 2012) and to differ across tree species and functional groups (Becker & Castillo, 1990;Markesteijn & Poorter, 2009;Shukla & Ramakrishnan, 1984;Sinacore et al, 2017). Including roots in future studies is a major challenge but will refine our ability to understand the role of N 2 fixer species in secondary forest succession.…”