Pteridophyte flora of Udawattakele forest the past, present and future

Abstract

Pteridophytes represent an important group in the plant kingdom. Approximately 11,300 Pteridophytespecies have been described worldwide, ofwhich about 360 species have been recorded in Sri Lanka.Most of Sri Lankan Pteridophyte species is concentrated in the understory of the rainforests ofCentral Highlands. Udawattakele forest with 132 ha was one of such highlands (510 m above sealevel) which received special attention by European Pteridologists, even during the colonial era. It hasbeen reported that 13 species are already extinct from Sri Lanka mainly because of various threatsfaced by Pteridophytes. Thus, the objective of this study was to compare the diversity of Pteridophyteflora at present with the previous records and identify possible conservation issues.

Species diversity of Pteridophytes at Udawattakele forest in the past was obtained from reviewing ofliterature (Karunarathne, 1986; Sledge, 1950-1981) and observations of preserved specimens at theNational Herbarium. Two line transects (10m x 4000 m) on both side of Lady Horton's Walk wereassessed to identify the present level of Pteridophyte diversity. Almost all Pteridophyte species wereidentified at species level through morphological observations and subsequently with the help of keys.The Lady Horton's Walk was selected for the study, because the majority of Pteridophytes atUdawattakele was concentrated in this area and previous assessments of Pteridophytic diversityhave been conducted in the area. At the selected locations species were counted to identify dominantspecies.

According to literature, 25 Ptridophytic species and 4 hybrids (29 taxa) have been collected fromLady Horton '5 Walk in Udawattakele forest. Chronologically 7, 17,2 and 3 taxa have been recordedfrom 1888-1900, 1950-1954, 1973 and 1993, respectively. Out of 29 taxa collected by foreignPteridologists, only preserved specimens of27 taxa have been deposited in the British Museum andthe Kew Herbarium. Karunarathne (1986) recorded 23 Pteridophyte species from the forest. Thepresent study was able to identify 36 Pteridophyte species belong to 9 families and 20 genera from theforest, of which 29 species are common and usually grow on harsh environment in the disturbed areasand roadside banks. Seven species occur in relatively high moist and shaded areas of the forest. Thepresent study was able to record 13 additional species compared to Karaunarathne (1986). However,out of 29 taxa recorded in the literature, 9 species were recorded during the present study. Further, 7species iArthropteris palisotti, Christella hispidula x C. parasitica, Diplazium sylvasticum,Microlepia speluncae, Pronephrium articulatum, Teetaria subtriphylla and T trimenii) had notbeen recorded even in the other parts ofthe country during the last 50 years. The present study wasalso unable to record such species from Udawattakele forest. Out of the above 7 species, two rarespecies namely, Pronephrium artieulatum and Christella hispidula x C. parasitiea had beenrecorded only once over the last century. Such records were also found from Lady Horton's Walk inUdawattakele forest before 50 years.

However, at present the Lady Horton's walk has severely been invaded by Myroxylon balsamumsuppressing its native biodiversity. Further, roadside banks of the Lady Horton's walk have very dryconditions. Few wet and shaded areas are also invaded by a naturalized fern species such as Adiantumpulverulent um and it has become dominant species in the area. Such causes may have contributedfor loss of some Pteridophyts species from Udawattakele forest. It is well known that Pteridophytesare very sensitive to changes of environmental conditions and human activities. This raises the issueof necessity of continuous monitoring ofPteridophytic biodiversity for their conservation even withintheir natural habitats.