Phytoindication Is a Useful Tool for Assessing the Response of Plant Communities to Environmental Factors

Phytoindication represents a long-established ecological approach; however, its conceptual basis remains contested, particularly concerning whether it is merely a surrogate for measuring environmental factors or a distinct method for assessing biotic system responses. In this study, we analysed vegetation communities of the sandy terrace in the Dnipro-Oril Nature Reserve (Ukraine) using ecological indicator values, naturalness, and hemeroby indices. The Dnipro-Oril Nature Reserve provides an ideal setting for this study, as it integrates strong natural gradients of soil moisture, nutrient availability, and topography with pronounced anthropogenic influences from the surrounding industrial landscape. This allows the assessment of both natural and human-driven components of ecological variability within a single system. A dataset of 1079 relevés was collected and classified into 24 associations. Multivariate analyses were applied to reveal different aspects of vegetation–environment relationships: MANOVA was used to assess whether plant associations differed significantly in their ecological indicator profiles, CCA to identify the main gradients of species composition constrained by environmental factors, and partial CCA to isolate the specific patterns of vegetation response attributable to individual predictors while controlling for covariates. We found that the indicator values were not independent but strongly intercorrelated, reflecting integrated biotic responses rather than methodological artefacts. This was confirmed by consistent ecological interpretation of the principal component structure and the concordance between ordination patterns and vegetation classification results. Two primary gradients were identified: a natural gradient, which combines soil moisture and nutrient availability with decreasing light, temperature, continentality, and soil pH; and an anthropogenic gradient, represented by the hemeroby–naturalness axis. The interplay of these gradients offers a comprehensive explanation for vegetation structure across various spatial scales, with natural factors shaping community types and anthropogenic influences exerting broader, less specific effects due to their diffuse impact across multiple plant associations. Our findings reveal a novel conceptual perspective, supporting the view that phytoindication is a unique ecological tool for assessing the integrated response of plant communities to environmental drivers, including both natural and anthropogenic gradients, rather than a simplified or less precise substitute for instrumental measurements. Nevertheless, the use of phytoindication does not eliminate the need for instrumental measurements in situations requiring precise quantification of specific physical or chemical environmental parameters. The correlated structure of indicator values revealed in this study demonstrates that phytoindication patterns are specific to each landscape. Therefore, comparative assessments across regions or time periods should be based on the correlation patterns of indicator values rather than their absolute scores.