Structural and Functional Diversity of Weed Species in Organic and Conventional Rice Agro-Ecosystems

پژوهشهای زراعی ایران

Article 4, Volume 13, Issue 3 - Serial Number 39, October 2015, Pages 496-512   

Document Type: Research Article

DOI: 10.22067/gsc.v13i3.25978

Authors

S. Y Mousawi Toghani¹; P Rezvani Moghaddam^{* 1}; M Nasiri mahalati¹; M. R Damavandian²

¹Ferdowsi University of Mashhad

²Sari University of Agriculture Science and Natural Resource

Abstract

Introduction
Diversity reflects the complexity of a system and can maintain its sustainability. Higherdiversity, results in higher inherent complexity of agro-ecosystems and strengthen their processes. It is necessary to realize the spatial distribution and temporal properties of the biodiversity components in agro-ecosystems, for the conservation and optimal utilization. Since weeds as a complementary component of agro-ecosystems and are inseparable, so the study of species, their functional and structural diversity of them can play an important role in weed management and balance in ecological systems.
Materials and Methods
This study was performed to determine the effects of different management systems on structural, and functional diversity of paddy weeds in Mazandaran province. Three rice fields, ranged from 0.3 to 0.5 ha, were chosen for each management system. Samples were collected from three fields running under each selected management system (organic and conventional). Data (number of weed species and their density) were randomly gathered from 9 quadrates (1m×1m) per each field in four stages (tillering, stem elongation, grain filling and after harvest). The diversity, evenness, frequency and similarity indices for weeds were determined at genera and species level. Data analysis carried out through T-test and grouping performed via cluster analysis as hierarchy.
Results and Discussion
All monitored weeds can be classified into four plant family including cereals (Poaceae), sedges (Cyperaceae), plantain (Plantaginaceae) and chicory (Asteraceae).Under conventional systems the values of weed diversity indices were higher during tillering and stem elongation compared with organic ones, and were lower during grain filling and after harvest stages. However indices of weed evenness showed contrary tendency. Both Sympson and Shanon-Wiener diversity indices, consist of two clusters in 76% similarity. Evenness indices of Kamargo and Smith-Wilson included two clusters in 83% and 82%, respectively. Range of similarity index was between 1.89% and 83.96%. Weed grouping based on relative frequency during the sampling stages showed two clusters in 78% and four clusters in 85% similarity. Clustering weeds centered on relative frequency during sampling stages, according to the family, showed different results. It might be the reason that the relative abundance of weeds, sedge family (79%) were in two clusters. However, sampling stages grouping based on weed density, induced two clusters in 39% similarity. Both conventional and organic systems, are included 10 species of 8 genera of four families. The 75 percent of families based on the vegetative form were monocots and 25% of them were dicots, so monocots had more diversity. Perhaps the presence of Alismaplantagoin the conventional system could be as a unique species and its absence in the organic system, attributable to duck existence in it. Based on life-cycle, 6 species were annual and 4 were perennial. While, according to the photosynthetic pathway, 50 percent species were C3 and others had C4 pathway. Based on the characteristics of the interference, 4 species were noxious and 6 species were non-noxious. Poaceae were the most diversity of weeds in monocotyledon and C4 pathway (three species). Two species of noxious weeds and herbicide resistant belong to Poaceae too. The Cyperaceae consist of two species from four perennial ones. The weeds of Poaceae and Cyperaceae families include 70% of total weed. Generally, weeds in ecosystems usually change thehabitat conditions or impact on the resources availability for other species.
Conclusions
Due to repeated or severe disturbances, agro-ecosystems are limited to the early stages of succession. Thus, the widespread destruction of agro-ecosystems during consecutive years, by changing the succession, weed population dynamics was affected as well. It should be noted that the differences of weed distribution in the various stages of the sampling in both conventional and organic systems, can be related to dissimilarities in management practices. The presence of various species of grass and sedge family in paddies, could be related to the ecological niche differentiation, because of ecological divergence amongst the different photosynthetic pathways (such as C. rotundus, C4 and C. difformis, C3) or the variance between water requirements (such as Echinochloa crus-galli in wet conditions and flooding and Digittaria spp. in dry conditions). Sound management in these conditions can the switch a threat into an opportunity, so that with regard to interaction among weeds and other communities such as insects, in rice agro-ecosystems, the emerging phenomena at this level would be beneficial. It seems, realizing species, structural and functional diversity of weeds in rice agro-ecosystems, can be result in better management of farm production with the aim of provide ideal use of resources.

Keywords

Clustering; Density; Frequency; Kamargo index; Sympson index

References

1. Adair, R. J., and Groves, R. H. 1998. Impact of environmental weeds on biodiversity: A review and development of a methodology. Biodiversity Group, Environment Australia. 55p.

2. Bhatt, M. D., Tewari, A., and Singh, S. P. 2009. Floristic composition of weeds in paddy fieldsin Mahendranagar, Nepal. Ecological Society (Nepal), 16: 15-19.

3. Caton, B. P. M., Mortimer, J. E., and Johnson, D. E. 2010. A practical field guide to weeds of rice in Asia (Second Edition). Los Banos (Philippines): International Rice Research Institute. 120 pp.

4. Clements, D. R., Weise, S. F., and Swanon, C. J. 1994. Integrated weed management and weed species diversity. Phytoprotection 75 (1).

5. Douglas, A. G. P., Derksen, A., Lafond, A. L., Heather and Clarence, J. S. 1993. Impact of Agronomic practices on weed communities: Tillage Systems. Weed Science (41): 409-417.

6. Elahi, S., Sadrabadi Haghighi, R., and Alimoradi, L. 2010. Evaluation species, structural and functional diversity for weed communities in Pistachio (Pistachia vera L.) orchards in Bardeskan. Journal of Agroecology 2 (4): 574-586. (in Persian with English abstract).

7. Flynn, D. F. B., Prokurat, M. G. T., Nogeire, N., Molinari, B. T., Richers, B. B., Lin, N., Simpson, M., Mayfield, M., and Declerck, F. 2009. Loss of functional diversity under land use intensification across multiple taxa. Ecology Letters 12: 22-33.

8. Jahani Kondori, M., Koocheki, A., Nassiri Mahallati, M., and Rezvani Moqaddam, P. 2012. Evaluation of weed species diversity in wheat fields of the east of Mashhad. Iranian Journal of Field Crop Research 10 (3): 468-475. (in Persian with English abstract).

9. Jastrzebska, M. M.,Wanic, M. K., Kostrzewska, K., and Trederand, N. 2012. An attempt to use functional diversity indices for the assessment of weed communities. Acta Agrobotanica 65 (1): 129-140.

10. Matinzadeh, H., Alimoradi, L., and Bahari Kashani, R. 2011. Evaluation of species, functional and structural weed of apple orchads of Fariman. Quarterly of Weed Ecology 2 (1): 19-31. (in Persian with English abstract).

11. Mohammaddoust, H. R., Baghestani, M. A., and Mikhailovic, A. 2006. The impact of agronomic practices on weed community in winter rye. Pakistan Journal of Weed Sciences Research 12 (4): 281-291.

12. Mohammadi, M., Pirdashti, H., Aghajani Mazandarani, G., and Mousawi Toghani, S. Y. 2012. Assessing of duck efficiency as biological factor affecting on diversity and density of weed in rice-duck mixed culture. Journal of Agroecology 4 (4): 335-346. (in Persian with English abstract).

13. Nassiri Mahallati, M., Koocheki, A., Rezvani Moghaddam, P., and Beheshti, A. 2009. Agroecology (Fourth edit.). Ferdowsi University of Mashhad Publication. (in Persian).

14. Noruzzadeh, S., Rashed Mihasel, M. H., Nassiri Mahallati, M., Koocheki, A., and Abbas poor, M. 2009. Evaluation of species, functional and structural diversity of weeds in wheat fields of Northern, Southern and Razavi Khorasan provinces. Iranian Journal of Field Crop Research 6: 471-485. (in Persian with English Abstract).

15. Organization of Meteorology of Mazandaran province. Available at http://www.mazandaranmet.ir (visited 6 June 2013).

16. Salonen, J., Hyvonen, T., and Jalli, H. 2001. Weed flora in organically grown spring cereals in Finland. Agricultural and Food Science in Finland (10): 231-242.

17. Zand, E., and Baghestani, M. A. 2002. Weed resistance to herbicides. Ferdowsi University of Mashhad Publication. (in Persian).