Seed germination of coastal monsoon vine forest species in the Northern Territory, Australia, and contrasts with evergreen rainforest

Abstract

Seed germination traits of seasonal rainforest species differ from permanently moist evergreen rainforest species due to the prolonged seasonal drought. We investigated whether seed germination traits used to categorise evergreen rainforest species into pioneer and climax guilds were applicable to seasonal rainforest species. Seed dormancy, light requirements for germination and seed storage types of five climax and thirteen pioneer species of a coastal vine thicket were studied. Results were compared with published studies of evergreen rainforest species. Evergreen rainforest pioneer species are typically dormant, require light to germinate and tolerate desiccation, whereas climax species are typically non-dormant, tolerate shade during germination and are sensitive to desiccation. In seasonal rainforest we found that a high proportion of pioneer species had seeds that were non-dormant (62%), and a high proportion of pioneer species germinated equally well in light and dark conditions. In seasonal rainforest, we found that the majority of climax species had desiccation tolerant seeds, whereas in evergreen rainforest the proportion of climax species producing desiccation sensitive seeds is equal to or greater than the proportion of species with desiccation tolerant seeds. In seasonal rainforest species physical, physiological and epicotyl dormancy types were found. Generally, for seasonal rainforest species, the prevalent form of dormancy in pioneer species was physical dormancy whereas physiological dormancy was most common in evergreen rainforest pioneer species with dormancy. Our results suggest that the contrasting seed biology traits that typically apply to pioneer and climax species of evergreen rainforest species don’t typically apply to seasonal rainforest species.

Seeds of the threatened dry rainforest tree Cadellia pentastylis (Surianaceae) are non-dormant

“…Many other rainforest species are reported to produce non-dormant seeds that readily germinate under suitable environmental conditions. Non-dormant seeds occur for approximately 41 and 49% of pioneer evergreen rainforest trees and non-pioneer rainforest trees, respectively, while seeds from 62% of pioneer species in seasonal rainforest in Northern Territory, Australia, were also non-dormant (Baskin and Baskin, 2014; Thusithana et al, 2018).…”

Dormancy in seeds of brazilian cerrado and dense Ombrophilous forest

“…This restriction is believed to be caused mainly by dormancy in their seeds, which are small, though numerous and allows the formation of a persistent soil seed bank, where it requires light to germinate and tolerate desiccation (Peres et al, 2009). According to Bonner (1990) and Thusithana et al (2018), climax species tolerate shade during germination and tend to be more sensitive to desiccation, not having long-term viability in the soil seed banks; thus, the dormancy does not seem to be advantageous. Moreover, they present seasonal behavior in seed production.…”

Investigating the Relationship between Fire Severity and Post-Fire Vegetation Regeneration and Subsequent Fire Vulnerability

“…Cury et al [89] proposed that rainforest seedlings might not resprout under open canopies; due to the seed source being killed, or the foliage loss of rainforest canopies destroy the soil stored seed bank by drying the surface. A study by Thusithana et al [90] found that seed germination of evergreen rainforest species varied after prolonged seasonal drought. The desiccation-sensitive seeds had low oil content and high seed moisture (low flammability), where the desiccation-tolerant had high oil content and low seed moisture (high flammability) [90].…”

“…A study by Thusithana et al [90] found that seed germination of evergreen rainforest species varied after prolonged seasonal drought. The desiccation-sensitive seeds had low oil content and high seed moisture (low flammability), where the desiccation-tolerant had high oil content and low seed moisture (high flammability) [90]. Hill and Reed [91], found rainforest species were regenerating to their naturally occurring vegetation structure, post low-severity fires.…”