Species resilience on spatial floating mat

Background/Question/Methods

Different plant species adapted to floating mats are beneficial in different ways; Lygodium microphyllum and Stenochlaena palustris are known for pharmaceutical benefits. The presence of these two species on floating mats raises the question of whether their resilience to frequent human exploitation depends on area size (limited growth area by other species) or seasonal fluctuations (limited growth by wet-dry conditions). The objectives are to investigate the presence of L. microphyllum and S. palustris on floating mats of different size at different time in a year. Bung Khong Long Lake was selected as a case study because it is normally exploited by local residents, and the land use pattern across the lake has rarely changed over time. The field investigation was carried out in October 2010, January 2011, and April 2011, representing wet, medium, and dry seasons. Size classes of floating mats were divided into three stands (small: covers less than 100 m²; medium: covers between 100 and 1,000 m²; large: covers more than 1,000 m²). The field data obtained was compared with Udomsri et al. (2004).

Results/Conclusions

L. microphyllum was found only at the medium size stands in October (wet condition) whereas S. palustris was found on every size stands. S. palustris was found on small size stands in October and April; on medium size stands in every period; on large size stands in only in October and January. In all, 20 species were found for all size classes. Interestingly, in stands where both species were observed, Chromolaena odorata was absent. In addition, L. microphyllum was found only at the lake but not on the mats in 2001 whereas S. palustris was observed at the lake as well as on the mats in 2001. On the other hand, C. odorata was not found both at the lake and on mats in 2001. This suggests that even though L. microphyllum and S. palustris have been exploited since 2001, L. microphyllum seems likely to be less resilience compared to S. palustris since it takes time to grow on the mat (found in 2010). Thus the comparatively better resilience of these two species in relation to C. odorata could be attributed to difference in life form; L. microphyllum and S. palustris (fern) whereas C. odorata is a chamaephyte plant that requires more light and space. Further study is suggested to quantitatively measure the resilience of L. microphyllum and S. palustris to intensive exploitation.