Biomorphological traits and leaf dry matter content are important to plant persistence in a highly unstable volcanic ground

Abstract

The colonisation of newly formed territories by plants during primary succession is a crucial stage in the formation of ecosystems. Adaptations of species to withstand harsh environment allow them to survive and form pioneer communities. We analysed ten categorical and quantitative plant traits to examine their role in plant resistance to substrate instability in primary volcanic habitats. The research questions were: 1) which plant traits enable plants to persist under the most unstable ground conditions?; 2) what are the ecological strategies of species that grow under the condition of stress, such as low mineral nutrition, coupled with intense disturbance, such as unstable ground? The research was conducted on the Tolbachinsky Dol plateau in Kamchatka, Russia, on loose volcanic sediments of the 1975 eruption. At altitudes ranging from 700 m a.s.l. to 1000 m a.s.l., 40 sample plots were established along the gradients of altitude and degrees of ground instability. The species composition of vascular plants and the percentage cover of species, as well as other habitat characteristics, were assessed. Linear models were used to investigate the relationship between traits and ground instability. The principal component analysis was used to identify groups of characteristic traits. Leaf dry matter content (LDMC) had the largest explained variance. The LDMC community weighted means decreased with increasing disturbance (ground instability). A whole set of categorical traits, i.e. plant functional types, characterised the adaptation of plants to unstable ground. These characteristics include life-form (according to Serebryakov classification), density of shoots arrangement, morphology of underground organs, and, to a lesser extent, dispersal mode. The study analysed 45 species, and it was found that only four of them were adapted to perform under conditions of high substrate instability. The study showed that the mutual interaction of a suite of biomorphological traits and leaf density characteristics formed a syndrome of pioneer species adapted to unstable ground. The ecological strategies of the majority of species in the studied communities were characterised by the predominance of the stress-tolerant strategy, explained by the extremely poor mineral nutrition in the primary habitats. Under conditions of both low nutrient availability and high disturbance intensity, species with a mixed stress-tolerant-ruderal strategy are favoured. In the gradient of increasing disturbance, the role of the ruderal axis increased while stress tolerance decreased. However, the role of ecological strategy may be weakened by the presence of other important adaptive traits.