Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2025 Jan 20;15(1):e70837.
doi: 10.1002/ece3.70837. eCollection 2025 Jan.

Deer Browsing Increases Stem Slenderness and Crown Irregularity and Modifies the Effects of Light Gradients on Architecture of Forest Tree Saplings

Affiliations

Deer Browsing Increases Stem Slenderness and Crown Irregularity and Modifies the Effects of Light Gradients on Architecture of Forest Tree Saplings

Cecilia Cacciatori et al. Ecol Evol. .

Abstract

Browsing by ungulates is commonly assumed to target the upper parts of sapling crowns, leading to reduced vertical growth or even growth cessation. However, the extent to which browsing induces shifts in resource allocation toward lateral growth remains unclear. This study explores the impact of browsing intensity (BI) and light availability on the architectural traits of six temperate tree species, focusing on height-diameter ratio (H/D), crown slenderness (CL/CW), and crown irregularity (CI) across sapling height classes. Browsing pressure and architectural responses varied across height groups, reflecting diverse adaptive strategies. BI was weakly but negatively correlated with sapling height, indicating that even tall saplings (> 2 m) experience browsing, particularly in the lower crown. H/D consistently increased with BI across all height classes, with stronger effects in medium and tall saplings. Light influenced H/D differently between browsed and unbrowsed saplings: unbrowsed saplings showed reduced H/D only under high light conditions, while browsed saplings exhibited consistent reductions regardless of light levels. CL/CW was negatively but insignificantly affected by BI. Light increased CL/CW in unbrowsed saplings across all height classes but decreased it in browsed short and medium saplings, suggesting a 'pruning' effect of browsing that altered competition dynamics. Species-specific analysis of Fagus sylvatica revealed an increase in CL/CW with BI, reflecting unique adaptive responses. CI increased significantly with BI across all height classes, with the strongest effects in medium and tall saplings. Light reduced CI in browsed short saplings but had inconsistent effects on unbrowsed individuals. Variation partitioning showed that light explained most variation in H/D and CL/CW for shorter saplings, while BI predominantly influenced CI in taller ones. By integrating the effects of browsing and light, this study provides insights into juvenile tree adaptations and resilience under ecological stressors, advancing our understanding of tree growth strategies in challenging environments.

Keywords: browsing pressure; crown irregularity; crown slenderness; light gradient; sapling slenderness.

PubMed Disclaimer

Conflict of interest statement

The authors declare no conflicts of interest.

Figures

FIGURE 1
FIGURE 1
GAMLSS showing linear regression of BI on sapling height. Confidence intervals are shown in grey.
FIGURE 2
FIGURE 2
GAMLSS showing regression of H/D on: (a) BI; (b) light intensity for unbrowsed saplings; and (c) light intensity for browsed saplings. Confidence intervals are shown as coloured bands.
FIGURE 3
FIGURE 3
Variation partitioning for H/D explained by BI and light for: (a) short saplings; (b) intermediately tall saplings; (c) tall saplings.
FIGURE 4
FIGURE 4
GAMLSS regression of CL/CW on: (a) BI; (b) light intensity for unbrowsed saplings; and (c) light intensity for browsed saplings.
FIGURE 5
FIGURE 5
Robust regression of CL/CW on BI for browsed saplings of Fagus sylvatica .
FIGURE 6
FIGURE 6
Variation partitioning for CL/CW explained by BI and light for: (a) short saplings; (b) medium saplings; (c) tall saplings.
FIGURE 7
FIGURE 7
GAMLSS regression of crown irregularity (CI) on: (a) BI; (b) light intensity for unbrowsed saplings; and (c) light intensity for browsed saplings.
FIGURE 8
FIGURE 8
Variation partitioning for crown Irregularity Index explained by BI and light for: (a) short; (b) medium; (c) tall saplings.

References

    1. Ametzegui, A. , and Coll L.. 2011. “Tree Dynamics and Coexistence in the Montane‐Subalpine Ecotone the Role of Different Light‐Induced Strategies.” Journal of Vegetation Science 22: 1049–1061.
    1. Ammer, C. 1996. “Impact of Ungulates on Structure and Dynamics of Natural Regeneration of Mixed Mountain Forests in the Bavarian Alps.” Forest Ecology and Management 88: 43–53.
    1. Bebre, I. , Annighöfer P., Ammer C., and Seidel D.. 2020. “Growth, Morphology, and Biomass Allocation of Recently Planted Seedlings of Seven European Tree Species Along a Light Gradient.” iForest 13: 261–269. 10.3832/ifor3370-013. - DOI
    1. Borcard, D. , Legendre P., and Drapeau P.. 1992. “Partialling Out the Spatial Component of Ecological Variation.” Ecology 73: 1045–1055.
    1. Brisson, J. 2001. “Neighbourhood Competition and Crown Irregularity in Acer Saccharum.” Canadian Journal of Forest Research 31: 2151–2159. 10.1139/x01-161. - DOI

LinkOut - more resources