Effects of herbicide treatment on the structure and functioning of agro-ecosystems II. Structural changes in the plant community after the application of herbicides over several years

Abstract

The paper reports the effects of the continued application of herbicides over 5 years on the structure of the plant community in a selected agro-ecosystem with cereals within the crop rotation. The application of herbicides led to quantitative changes in the structure of the weed population, both in the numbers of individuals and the development of biomass. In contrast, the number of species involved remained almost constant. The biomass and the grain yield of the crops on the treated areas did not exceed that on the controls until towards the end of the experiment. In contrast to the majority of relatively rapidly decomposing herbicides (phenoxy-acetic acid derivatives) which remained effective only in the year of application, the application of a persistent herbicide (simazine) produced more enduring effects on several omponents of the ecosystem. These effects were still evident during the following year and reduced the yield of the crop. The multivariate statistical tests used to interpret the primary data proved suitable for obtaining quantitative measures of change in the structure of the plant community and other parameters characterizing the ecosystem, even at an early stage. The use of these methods in investigations at ecosystem level (e.g., in questions relating to bioindicators) are promising.