Rolon A S, Godoy R S, Maltchik L
Biological Sciences Institute, Universidade Federal do Rio Grande, São Lourenço do Sul, RS, Brazil.
Ecology and Conservation of Aquatic Ecosystems, Universidade do Vale do Rio dos Sinos, São Leopoldo, RS, Brazil.
Braz J Biol. 2018 May;78(2):224-232. doi: 10.1590/1519-6984.04216. Epub 2017 Sep 28.
Recent studies indicate that rice fields contribute to the conservation of aquatic plants, however, repeated cultivation can reduce the species diversity harbored by rice fields. Repeated tillage, agrochemical application and environmental homogeneity can reduce plant diversity and select for species more tolerant to disturbance. Our hypotheses were: 1) macrophyte richness and biomass decrease with increased rice crop age; and 2) macrophyte species of rice fields are a subsample of natural wetlands and species loss will increase with crop age. We investigated three rice fields of each different ages (old, intermediate and new ones) and three natural intermittent wetlands for this study. Each area was sampled four times throughout the rice cultivation cycle (off-season, initial growth, final growth and post-harvest). Our results showed that the mean macrophyte richness and biomass were similar between rice fields of different ages and lower than that of natural wetlands. Although species composition in the different-aged rice fields was not markedly different, there was nestedness in the rice fields as age increased. In this study, we verified that macrophyte richness and biomass in rice fields was lower than natural wetlands and the species composition was different among wetland types (rice fields and natural wetlands), however our hypothesis that species richness and biomass will decrease with crop age was not confirmed. All rice crops had similar macrophyte assemblage structure (richness, biomass and species composition). However, the another hypothesis tested was confirmed, macrophyte assemblage of rice fields is a subset of natural wetlands and as, the age of a rice field increases, the species that occur in older rice field are subsets of species that occur in younger ones.
最近的研究表明，稻田有助于水生植物的保护，然而，反复种植会降低稻田所蕴含的物种多样性。反复耕作、施用农药和环境同质化会减少植物多样性，并选择出更耐干扰的物种。我们的假设是：1）大型植物的丰富度和生物量会随着水稻种植年限的增加而减少；2）稻田中的大型植物物种是天然湿地物种的一个子集，且物种损失会随着种植年限的增加而增加。为了本研究，我们调查了三个不同种植年限（老稻田、中年稻田和新稻田）的稻田以及三个天然间歇性湿地。在整个水稻种植周期（淡季、初始生长、最终生长和收获后）对每个区域进行了四次采样。我们的结果表明，不同种植年限稻田中的大型植物平均丰富度和生物量相似，且低于天然湿地。虽然不同种植年限稻田中的物种组成没有明显差异，但随着种植年限增加，稻田存在嵌套现象。在本研究中，我们证实了稻田中大型植物的丰富度和生物量低于天然湿地，且湿地类型（稻田和天然湿地）之间的物种组成不同，然而我们关于物种丰富度和生物量会随着种植年限增加而减少的假设未得到证实。所有水稻作物的大型植物组合结构（丰富度、生物量和物种组成）相似。然而，所检验的另一个假设得到了证实，稻田中的大型植物组合是天然湿地的一个子集，并且随着稻田种植年限的增加，老稻田中出现的物种是年轻稻田中出现物种的子集。
