Vertical root distribution and biomass allocation along proglacial chronosequences in Central Switzerland

Abstract

Investigating changes in belowground functional plant traits is an important step toward a better understanding of vegetation dynamics during primary succession. However, in alpine glacier forelands, we still lack an accurate assessment of plant rooting patterns. In this study, we established two proglacial chronosequences with contrasting bedrocks to investigate changes in rooting patterns and biomass allocation with terrain age. We extracted soil cores up to 1 m depth and measured root traits every 10 cm of each drilled core. Furthermore, we sampled aboveground biomass determining the contributions of functional groups to total aboveground biomass. We found that root traits associated with the root economics spectrum varied significantly along the chronosequences. Vertical root distribution coefficients revealed that early successional communities had more evenly distributed root systems compared to late successional communities. Biomass allocation showed diverging patterns. We found evidence for both the isometric allocation and optimal partitioning hypotheses. In addition, we observed a significant correlation between rooting parameters and plant community composition, suggesting that the dominance of distinct plant functional groups was one important factor explaining the observed rooting patterns. Our results shed light on the often neglected belowground compartments during plant succession and contribute to a better understanding of hillslope functioning.

The impact of soil development, rainfall intensity and vegetation complexity on subsurface flow paths along a glacial chronosequence of 10 millennia

“…Three plots (1.0 x 1.5 m) were selected on each moraine for the brilliant blue tracer experiments. At each plot the structural vegetation complexity measure (Greinwald et al, 2021a) was estimated. This measure was developed in the larger context of the interdisciplinary chronosequence study (e.g.…”

“…Additionally, root length density (RLD), root density (RD), and specific root length (SRL) of the fine roots (diameter < 1 mm), as well as above ground biomass (BM) were measured as described in Greinwald et al (2021a) at each experiment plot.…”

“…The pore space of coarse-textured, unsorted, sandy soil is mainly made out of large pores, which provides only a low water retention capacity and leads mostly to a fast downward transport of water (Hartmann et al, 2020b). The root system has a low density (Table 1, Greinwald et al (2021a)) at the early stages of vegetation succession and does not impact the water transport. The low vegetation cover also does not inhibit infiltration and the water can infiltrate deep into the soil.…”

“…We assume that a strong link between vegetation, soil properties, and subsurface flow paths exists. Vegetation complexity combines both, surface characteristics (vegetation coverage) and functional aspects of the vegetation (Greinwald et al, 2021a) in one measure. Hydrologists often link indicators such as vegetation coverage and land use to hydrological functioning as they are likely to affect water infiltration patterns and soil water transport (Bachmair et al, 2009).…”

“…Our research, which focuses on the evolution of hydrological flow paths across a chronosequence in the Swiss Alps, is part of a larger interdiscplinary chronosequence study covering aspects of geomorphology (Musso et al (2019), Musso et al (2020)), geobotany (Greinwald et al (2021a), Greinwald et al (2021b)), and surface (Maier et al, 2020) and subsurface hydrology (Hartmann et al (2020a), Hartmann et al (2020b). This interdisciplinary study opens up a broader view of the various processes either driving the feedback loop of landscape evolution or affected by it.…”