Introduction
Grasslands cover 30 to 40% of the Earth’s land surface (Blair et al.,
2014) and are responsible for up to a third of net primary productivity
on land (Vitousek, 2015), providing many important ecosystem services,
from water flow regulation and purification to erosion control and
pollination (Bengtsson et al., 2019: Peciña et al., 2019). Grasslands
also contribute significantly to livestock farming through grazing and
fodder production (Erb et al., 2016).
Natural and semi-natural grasslands are often characterised by high
community complexity (Wilson et al., 2012), making them important
sources of, and contributors to, plant biodiversity (referred to as just
“biodiversity” hereafter) (Russo et al., 2022). Surveys carried out on
experimental plots have shown that increased grassland biodiversity can
contribute to greater yields, improved yield stability and increased
carbon sequestration (Craven et al., 2018; Finn et al., 2013; Haughey et
al., 2018; Isbell et al., 2015; Lange et al., 2015,). However, through
land-use change, abandonment, urbanisation and intensive agriculture,
natural and semi-natural grasslands have become endangered ecosystems
(Johansen, Henriksen and Wehn, 2022; Pärtel et al., 2005) with decreases
in their area and reductions in their biodiversity in recent decades
(Henle et al., 2008; O’Mara, 2012; Newbold et al., 2016).
In addition to the diversity of plant species, plant functional traits
(biochemical, physical and morphological properties that affect fitness
in response to the environment) and trait diversity are key features of
(semi-)natural grasslands. For example, traits such as high leaf dry
matter (LDM) content, low specific leaf area (SLA) and low leaf nitrogen
content indicate stress tolerance strategies of grass species and
adaptation to low temperature and low precipitation (Wingler and Sandel,
2023). The relationship between such plant functional traits and their
role in ecosystem functioning and ecosystem services (e.g., water
regulation, carbon storage, stress tolerance) are well-established
(Kattge et al., 2011; Tilman et al., 1997).
Remote sensing offers the ability to monitor biodiversity and functional
traits across a range of scales, from centimetres to kilometres, in a
consistent and repeatable manner. The physical and chemical properties
of plants influence how sunlight interacts with them. By examining the
absorption and reflection of light across different parts of the
electromagnetic spectrum, information about the species diversity
(Figure 1) (Wang and Gamon, 2019), functional traits (Homolová et al.,
2013) and thus α-diversity (diversity at a local scale) and β-diversity
(ratio between regional and local diversity) can be extracted.