Plant Functional Traits in Tropical Dry Forests: A Review

Introduction

Plants influence ecosystem functioning and processes across local to global scales and are one of the primary organisms that perform photosynthesis via solar radiation. They also play a substantial role in nutrient cycling and contribute to provisioning, regulatory, cultural, and supporting services (Grime 1998; Naeem et al. 2012). Plants have certain characteristics that allow them to respond to various environmental conditions like changes in climate, water loss in the soil, and lack of minerals, among others. In some of these traits, plant responses to climatic phenomena, such as drought, can be evidenced through morphological adaptations (e.g. regulation of water potential at the cellular level, concentration of nutrients, etc.). Plants also contribute to a more biodiverse ecosystem, which comprises three main components that complement ecosystem functioning and services: (i) taxonomic diversity that accounts for species composition and abundance; (ii) phylogenetic diversity that accounts for the evolutionary history of species, and (iii) functional diversity that accounts for the ecological traits of species. In a forest, taxonomic diversity, functional diversity and phylogenetic diversity support ecosystem functions (e.g., primary productivity, litter decomposition, nutrient cycling, etc.) and promote a wide range of ecosystem services (e.g., food production, carbon sequestration, climate regulation, etc.); (Mori et al. 2017). At the community level, functional properties are being extensively used to quantify ecosystem functions and services (Kuster et al. 2010).

The study of these functional properties that drive forest structure and dynamics is a major challenge in tropical ecosystems. Difficulties are primarily due to higher species richness, smaller populations, inadequate infrastructure, and fewer researchers conducting studies compared to the temperate zone. Tropical forests are also highly threatened by human activities, such as logging and conversion to agricultural lands (Stibig et al. 2014; Both et al. 2019). In Southeast Asian forests, a few species are extensively used for their commercial value, resulting in higher rates of degradation of these species. These extensively exhausted forests reflect slow vegetation recovery due to complex interactions among species, propagules and climatic conditions (Khurana and Singh 2001). The composition and successional traits of these forests (i.e. pioneer and non-pioneer) along with species’ nitrogen fixing ability, tree size, habitat preferences, etc. may respond differently to the gradient of disturbance (e.g., logging, herbivory, grass competition) and available resources (e.g. light, water and nutrients) (Chapin et al. 2000; Tilman 1987) due to nutrient poor soils (Singh et al. 1989; Bhadouria et al. 2017). Water availability (Hulshof et al. 2013) and soil fertility (Buzzard et al. 2016) are two major features of tropical dry forests that can influence the functional composition of woody plant communities (Sfair et al. 2018). In the last decade, use of advanced techniques in spatial distribution of plant species to understand the functional properties as well as community dynamics, contributed immensely in the field of plant functional ecology (Getzin et al. 2006).

Tropical Dry Forests are considered to be the most exploited forests in the world due to increased anthropogenic pressure and also increased temperature leading to drought and stressful environment. This chapter as a whole, will add information regarding roles played by different traits and their effect, as well as how they are being affected by other factors in Tropical dry forest environment. The chapter will be helpful to readers in providing a comprehensive understanding of role of plant functional traits in Tropical Dry forest ecosystems. This chapter focuses on the traits that are commonly measured in tropical dry forests (i.e., leaf traits, stem traits, and regenerative traits). Topics that will be covered in this chapter are: