Effects of surrounding crop and semi-natural vegetation on the plant diversity of paddy fields

Abstract

Background: The ecosystems around, and plant composition in, paddy fields in Java are varied, owing to differences in climate, altitude, and traditional farming practice. This study examines the effects of different types of surrounding land use and vegetation on the plant diversity in paddy fields. Methods: We studied three upland (400-850 m asl) and three lowland areas (10-50 m asl) in the island of Java, Indonesia. Samples of vegetation were taken in fields and bunds (partition between paddy field plots) in two rice cultivation seasons from October 2011 through to June 2012, including the peak of rice cultivation in Java between October and February. We used Analysis of Variance Matrix Unbalanced to analyze the effects of area, complexity, location, and season on plant composition. Tukey's Honestly Significant Difference (HSD) test was performed to determine significant differences between groups in the sample. Results: We recorded 14 crop species and 221 non-cultivated plant species, of which 171 species occurred in paddy fields and 190 on bunds. Species numbers in upland areas were higher than in lowland areas. In fallows, twice as many species as in cultivated rice fields were found. The presence of semi-natural vegetation within short distance had no significant effect on plant species numbers in paddy fields. Multiple cropping and intercropping around paddy fields and on bunds had a marked effect on plant diversity. Conclusions: Differences in plant species numbers and composition between lowland and upland areas are more pronounced than the effects of local environmental complexity. To enhance high and varied plant diversity on the field and landscape scale, traditional multiple and intercropping systems should be supported.