Reassessment of cyperaceous weed biodiversity at Bangladesh Agricultural University campus

ARTICLE INFO A floristic survey has been carried out from January 2015 to January 2016 to investigate the species diversity of Cyperaceous weeds present at Bangladesh Agricultural University campus. A total of 48 species belonging to 11 genera has been collected and identified. Among these, the prominent genus was Fimbristylis (13 species) followed by Cyperus (12 species) and three genera viz. Actinoscirpus, Bolboshoenus and Fuirena were represented by single species. Result of the present study revealed that some of these species are major and common obnoxious weeds in different crop fields. A good number of these species have great medicinal uses, fodder, raw materials for small industries and other economic values. The detailed taxonomic studies of these weeds will be helpful for the management practices of Cyperaceous weeds at this campus as well as in the whole country. It might be concluded that development of improved cultivation procedures will be helpful for getting high economic benefits from Cyperaceous weeds without affecting our crop yield and agro-ecosystem. There is no direct evidence of climate change threatening or eliminating Cyperaceae taxa from this locality. Article history: Received: 31 May 2018 Accepted: 09 August 2018


Introduction
Cyperaceae, commonly known as sedges, is one of the largest monocotyledonous families with 5,500 known species described in about 90 genera (Christenhusz and Byng, 2016).Many species of sedges have evolved as weeds (Bryson and Carter, 2008).Weeds of the cyperaceae family are widely distributed in tropical Asia and South America with various harmful, taxonomic, ethno-botanical and horticultural importance.These weeds can grow in diverse environments and compete with crop plants for space, food, water, light environment, etc. Weeds generally have no positive economic importance in agriculture/production system, though in some cases weeds also have some beneficial uses -forage, soil binder, medicinal, raw materials for small industries, etc.
The Bangladesh Agricultural University (BAU) campus is positioned under the Agro-Ecological zone 9 i.e., Old Brahmaputra Floodplain; roughly the whole area can be divided into three main topographic types -basinshaped low lying area, slightly undulated area and plain area.The campus exhibit diverse habitats, such as marshy land, wetland, crop fields, fallow lands, etc. which support abundance growth of sedges in this campus (Sarwar and Prodhan, 2011).Agricultural productivity, human health and livestock are adversely affected by weedy sedges due to competition for natural resources with crops; allergens & anti-nutrition compounds for human and livestock.
Weeds cost billions of dollars in agriculture, forestry, and urban areas and threaten diversity in natural communities worldwide.Of an estimated 8,000 species of weeds worldwide, only about 200 species cause 95% of the problems in production of food, feed, fibre, and livestock (Bryson and Carter, 2008).About 25% of the world's weeds are monocots (Bryson and Carter, 2008).In Bangladesh, the increase of population growth and the low yields of crops are the main reasons for severe food deficits every year.Through proper weed management practices, the production of food grains can be increased (Karim, 1998).An up to date knowledge on different weed species of Bangladesh is essential to manage them below threshold level for sustainable crop production and/or to use them for our economic benefit especially the sedges as their control is very difficult.The taxonomic study of this family is still unattended in the "Flora of Bangladesh".Some information is available as a part of other Agronomic or Horticultural research (Huda et al., 2017 and older references therein).Two significant research works were carried out on the sedges of BAU campus, one in early seventies (Anwer, 1971) and the other is originally a relatively older work (during 2000-2002) published recently (Sarwar and Prodhan, 2011).The objective of this present study to update our knowledge on biodiversity of sedges at the Bangladesh Agricultural University campus including their habitat, flowering times, and other uses; which may be helpful for the green management practices and for getting higher economic benefits from Cyperaceous weeds without affecting our crop yield and agro-ecosystem.The other objective is to use Cyperaceae as a model family (Simpson et al., 2011) for climate change work on biodiversity and conservation of this campus.

Materials and Methods
An intensive field survey of Cyperaceous weeds growing throughout the BAU campus was carried out during January 2015 to January 2016.Frequent visits were made to assess the flowering time of these species.The fresh plant samples/specimens were collected at the flowering stage and other relevant information e.g., location, date, habitat, crop/plant association, etc. were recorded.Plant samples were properly dried for making voucher specimens.The fresh and/or dried specimens were identified in the field or by matching with herbarium specimens and/or published literature or consulting with experienced taxonomist at the Bangladesh National Herbarium, Dhaka.All the specimens are preserved in Prof. Dr. Arshad Ali Herbarium at the Botanical Garden, Department of Crop Botany, Bangladesh Agricultural University.The major literature consulted was "Encyclopedia of Flora and Fauna of Bangladesh (Siddiqui et al., 2007) and other taxonomy related books (Sarwar and Prodhan, 2011 for details).

Results and Discussion
The species collected and identified are presented in Table 1 with their botanical names, common & English name, habitat, flowering time and other uses.A total of 48 species belong to 11 genera were identified.Among them, the prominent genus was Fimbristylis (13 species) followed by Cyperus (12 species), Pycreus (6), Eleocharis (5) and Kyllinga (3); three genera viz.Actinoscirpus, Bolboshoenus and Fuirena were represented by single species (Fig. 1).Species reported in this paper occupy diverse habitat such as various crop fields, wetlands, open grasslands, waysides, marshy places, riverbank and the bank of other water reservoirs, etc.Most of them are very common in rice fields, especially the species of the genus Fimbristylis, Pycreus, Cyperus, Eleocharis, etc. (Table 1).
The control methods used for weedy sedges are much diversified such as cultural methods, mechanical tillage, chemical treatments, shading with cover crops or black plastic, etc. (Bryson and Carter, 2008).The knowledge of flowering period may play a very important role for the controlling of weedy sedges.For example, flowering period of collected species showed a wide range of variation like Rabi season, Kharif season or all the year around (Table 1).If we uproot sedges before attaining the flowering stage, their propagation and spreading will be reduced.Moreover, we can easily take the appropriate methods for controlling the weeds according to their habitat.
Comparing with the previous study of Sarwar and Prodhan (2011), the presence of seven species viz.Eleocharis retroflexa, Fimbristylis falcata, Kyllinga brevifolia, K. cylindrica, Pycreus polystachyos, P. sanguinolentus and Scirpus triqueter var.segregatus, has newly been identified (with * in Table 1, Fig. 2).The number of genera represented by single species decreased from five to three (Anwer, 1971) which might be due to the identification of new species for any of these genera, as the numbers of species have been increased.These may support Simpson et al. (2011) who concluded that some species of Cyperaceae appear to be vulnerable, although, as yet, there is no direct evidence of climate change threatening or eliminating taxa.The occurrence of new species may be for various reasons; first of all, it may exist in this locality but somehow unidentified/missed during the previous studies.Secondly, anthropogenic activities may act as a vector to introduce these species from other location with various crop seeds.Among these, Kyllinga brevifolia, Scirpus triqueter are edible and used as fodder, so they may be dispersed here through grazing animals.Cyperaceae are especially important forage genetic resources in cold, damp sites, Carex and Cyperus are locally common and Kobresia covers large areas of the closely grazed mountain meadow in Himalaya and China (Ruijun, 2003).Moreover, they may be introduced here due to winds, flying animals (birds), water currents, changing cropping pattern, etc.
Most of the studied species are major and common weeds of various crop fields e.g., rice, jute, wheat, etc. and some of them act as obnoxious weeds.Some species have various medicinal values e.g., Cyperus rotundus, used in leprosy, thirst, fever, blood diseases, biliousness, dysentery, pruritus, pain, vomiting, urinary concertinas, stomach disorder and irritation of the bowels etc.Moreover, Cyperus laxus, Scirpus articulatus and some other species have also some important medicinal values.Some species are used as fodders in different countries such as Cyperus difformis, Fimbristylis milliaceae, Kyllinga brevifolia, K. monocephala, etc.Some species of the genus Pycreus, Cyperus flavidus, etc. act as a soil binder.Fimbristylis schoenoides and some other species are used to make green manures.Some species have various ethno-botanical importances such as Actinoscirpus grossus, Cyperus iria, C. babakan, etc.These are used to make the mat, bags, various handicrafts, etc. (Table 1).Water treatments using Cyperaceae have demonstrated up to 92% removal of total nitrogen (Tanner, 1996) and significant sequestration of metals such as copper (Murray-Gulde et al., 2005).

Conclusion
Results of the present study revealed that weeds of the family Cyperaceae are widely distributed in Bangladesh Agricultural University campus.Some species are major and common obnoxious weeds for rice and other crop fields.A good number of these species have various medicinal and other values.It may be concluded that knowledge generated from the present research would be helpful for the management practices of weed sedges as well as for getting benefits from other uses of different species.The micro-site (BAU campus) climate change has little or no effect on Cyperaceous weed biodiversity of this campus.

Table 1 . Cyperaceous weeds in the Bangladesh Agricultural University campus
Fimbristylis aestivalis (Retz.)Vahl _ Summer Fimbry Rice fields, Open wet places.September-February A weed of rice fields.
*indicates newly identified species