This blog post is provided by Shuang Xing and tells the #StoryBehindthePaper for the paper “Ecological patterns and processes in the vertical dimension of terrestrial ecosystems”, which was recently published in Journal of Animal Ecology. In their paper they explore how forests show ecological patterns from forest floor to canopy.
The vertical structures of terrestrial vegetation provide important habitats for diverse forms of life to occur, disperse and reproduce. From the ground to the forest top, the changes in resources, microclimate, and habitat structure create a complex combination of environmental gradients within a short spatial distance. In this review, we explore the ecological evidence that the vertical gradient is an influential engine driving the ecology and evolution of forest species, shaping larger biogeographic patterns in space and time.
Ecological patterns in the vertical dimension
Evidence from different taxa and ecosystems shows that the forest ecosystem is a three-dimensional realm, allowing species to move, adjust and select their favourite microhabitat horizontally and vertically. The architecture of the tree crown and the profile of foliage, together with the tree’s height, provide a high heterogeneity of vertical environment for arboreal biota (Fig. 1). The forest layers and vertical distance generate a climatic gradient from the ground to the canopy. In general, the canopy microclimate is drier, warmer, and more variable than the understory. As such, the arboreal distribution of species can be uneven, resulting in vertical stratification patterns observed from different groups of animals. The interplay between variances in microclimate, resources and vegetation structure along the vertical gradient can affect the vertical distribution of species, and may further shape the distribution of species at larger spatial scale. Accordingly, the vertical distribution of species can change at different time scales from daily to annually, depending on the changing rate of critical environmental factors and the life history of the organisms involved. In addition, the vertical niche of a species can be further refined by species interactions, spanning within trophic levels such as competition, and across trophic levels including parasitism, predation, herbivory, pollination, and frugivory.
Ecological mechanisms in the vertical dimension
Species have developed multiple mechanisms to adapt to living conditions at certain vertical strata. We grouped them into three main categories: climatic adaptation, dispersal capacity, and specialised life history (Fig. 2). With changes in microclimate from the ground to the canopy, the physiology, morphology, and behaviour of organisms can also vary to adapt to those changes. For instance, canopy species tend to have a broader physiological tolerance for living with highly variable environmental conditions than ground-dwelling species. Vertical differences in climatic-related morphological traits such as body size and body colour have also been observed in animals such as frogs and ants. To overcome the challenges of moving vertically, the movement of many arboreal animals involves aerial behaviours such as flying, parachuting, and gliding. For instance, some mammals and reptiles such as Belomys pearsonii Gray (see Fig. 3 below) and Chrysopelea ornate (see Fig. 4 below) move across tree crowns by gliding. For tree frogs like Rhacophorus dennysi (see Fig. 5 below), the adhesive toe pads can help them to grip and attach on the smooth surface of leaves and branches. Some species “migrate” from the ground to the canopy within their life cycle and make full use of different microhabitats and microclimatic conditions provided by vertical tree structures.
Future directions
We encourage ecologists to acknowledge and embrace the multidimensionality of ecosystems and test ecological theories within and beyond the vertical dimension. We suggest that only by including the patterns, processes, and mechanisms in the vertical dimension in addition to those in the horizontal dimension, can we have a complete understanding of the mechanisms underlying current biodiversity distribution, and how these may respond to global changes.
About the author
I am Shuang Xing, an assistant professor at the Sun Yat-sen University. I study how species and ecological networks respond to environmental changes. I aim to understand the vulnerability of species and ecosystems to multiple threats, including climate change, deforestation, and wildlife trade.
Twitter account: @ShannonXing
Read the paper
Read the full paper here: Xing, S., Leahy, L., Ashton, L. A., Kitching, R. L., Bonebrake, T. C., & Scheffers, B. R. (2023). Ecological patterns and processes in the vertical dimension of terrestrial ecosystems. Journal of Animal Ecology, 00, 1– 14. https://doi.org/10.1111/1365-2656.13881
Animal Ecology in Focus 