Functional Traits Influencing Plant Species Distribution in the Himalayas

Saptaparna Dasgupta, Bennett University

The functional traits of a plant are responsible for the determination of the performance of the plant. It depends in terms of shape and distribution along the environmental gradient. Global warming affects the distribution range of the species and directs it towards the poles. As climate warming has become a major concern and is increasing at a steady rate, it is termed ‘elevation-dependent warming’. Thus, apprehension of the mechanism that influences plant species’ distribution is crucial for future planning activities. 

A recent study published in the Journal of Ecology aimed to analyze the traits that affect the distribution of the plant species along the Himalayan altitudes in Nepal

Fundamental axis of evolutionary specialization

An analysis by (Díaz et al., 2004) revealed the concept of the fundamental axis of evolutionary specialization throughout the ecosystem. It was also disclosed that at one extremity of the axis, the plant species are characterized by small, thick, and resilient leaves. And on the other extremity, the plant species were characterized by larger, thinner, and delicate leaves. Therefore, the thick and resilient characteristics are termed conservative strategies, and the delicate and soft characteristics are termed as acquisitive strategies. Further, the variation traits in the plant species were also studied, important for the growth, survival, and reproduction of plant species worldwide. 

Acquisitive and conservative strategy

At lower altitudes, the environmental conditions are favorable and hence support the plant growth and survival. These plants possess taller stems and thinner leaves, conductive stems, higher leaf nutrient capacity, etc., and are characteristics of acquisitive strategy. On the contrary, the plants growing at higher altitudes possess shorter stems, smaller and thicker leaves, etc., and are characteristics of conservative strategy. 

The study

The samples were collected from the higher altitudes along the slopes of the Southern Himalayas in central Nepal. 31 common and abundant plant species were selected based on the altitudinal gradient. The sampling design was done to get the assurance that the traits were completely expressed. The traits important for resource acquisition and conservation were measured following the standard protocols. The traits were measured on the basis of whole-tree traits, branch traits, and leaf traits. 

Data obtained based on the plant strategy was evaluated using parametric analysis and later by preliminary analysis. The plant species were then evaluated based on their position along the elevational extent followed by the selection of the desired traits.

Results

The results were analyzed on the basis of the variations amongst the traits in different species. Based on the clusters of correlated traits, trait covariations influencing the plant strategies were analyzed (in Table 1).  The analyzed clusters were also visualized in the CatPCA; the first CatPCA axis reveals that 28% of the traits were associated with vertical expansion and metabolic efficiency. The second CatPCA axis reveals trait variations associated with physical defense and differences between the conifer and broadleaf tree species. A bivariate correlation analysis was used to evaluate the traits and strategies of the plant, related to the elevation. 

Table 1. Analysis of the identified five trait clusters associated with different functionality. 

Observations from the study

• Across the elevational gradient in the Himalayas, plant species with several traits were observed. Himalayan tree species are found to exhibit a broad variety of strategies, ranging from conservative to acquisitive. 
• Two orthogonal strategy axes were found, amongst which, the first axis was tightly linked to elevation. On the other hand, the second axis was associated with physical defense and the difference between the conifer and broadleaf tree species. 

The uncoupling of both the strategies of the two axes could be the phylogenetic split of conifers and Rhododendrons as a result. 

• Harsh environmental conditions are selected for species having conservative strategies and hence, rather than individual traits, the combination of traits has been found to be better sustained. 
• It was also found that a high-elevation species has trait characteristics that promote safety against extreme environmental circumstances and resource conservation.

Also read: RCoNet: Diagnosing COVID-19 using chest X-rays

REFERENCE

1. Maharjan, S. K., Sterck, F. J., Dhakal, B. P., Makri, M., & Poorter, L. (n.d.). Functional traits shape tree species distribution in the Himalayas. Journal of Ecology, n/a(n/a). https://doi.org/10.1111/1365-2745.13759

Proper APA: Maharjan, S. K., Sterck, F. J., Dhakal, B. P., Makri, M., & Poorter, L. (2021). Functional traits shape tree species distribution in the Himalayas. Journal of Ecology, 1365-2745.13759. https://doi.org/10.1111/1365-2745.13759

2. Díaz, S., Hodgson, J. G., Thompson, K., Cabido, M., Cornelissen, J. H. C., Jalili, A., Montserrat-Martí, G., Grime, J. P., Zarrinkamar, F., Asri, Y., Band, S. R., Basconcelo, S., Castro-Díez, P., Funes, G., Hamzehee, B., Khoshnevi, M., Pérez-Harguindeguy, N., Pérez-Rontomé, M. C., Shirvany, A., … Zak, M. R. (2004). The plant traits that drive ecosystems: Evidence from three continents. Journal of Vegetation Science, 15(3), 295. https://doi.org/10.1658/1100-9233(2004)015[0295:TPTTDE]2.0.CO;2

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