Research Article |
Corresponding author: Quadri A. Anibaba ( qanibaba@man.poznan.pl ) Academic editor: Moritz von der Lippe
© 2023 Quadri A. Anibaba, Marcin K. Dyderski, Gabriela Woźniak, Andrzej M. Jagodziński.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Anibaba QA, Dyderski MK, Woźniak G, Jagodziński AM (2023) Native plant community characteristics explain alien species success in post-industrial vegetation. NeoBiota 85: 1-22. https://doi.org/10.3897/neobiota.85.97269
|
Biological invasions are one of the major challenges to the restoration of post-mining sites. Most post-mining sites are under technical reclamation with only a few left to spontaneous vegetation processes. Therefore, we know little about alien plant species on spontaneously-vegetated post-coal mine heaps and how native community characteristics predict their establishment. To fill the knowledge gap, we aimed to determine the drivers of alien species colonisation on post-coal mine heaps. Specifically, we asked: (i) Which alien species are the most successful on post-coal mine heaps and why? (ii) What are the drivers of alien species richness and cover, and how are they affected by the native community? (iii) What does it mean for predicting threats from alien species and management? We recorded vascular plant species and their abundance across 400 plots on post-coal mine heaps in Upper Silesia, Poland. We calculated plant community taxonomic and functional characteristics and, using mixed-effects models, we estimated predictors of alien species richness and cover. We found 65 alien species on post-coal mine heaps, comprising 20.4% of all recorded species, including 36 neophytes and 29 archaeophytes. Amongst them – Erigeron canadensis, Solidago gigantea, Solidago canadensis, Erigeron annuus and Impatiens parviflora – were the most frequent on the studied heaps. We showed that native functional richness significantly predicts alien species richness and cover. Similarly, native community-weighted mean (CWM) seed mass and plant height predict alien species cover. However, CWM of specific leaf area for native species marginally predicts alien species richness. We showed that alien species cover decreases with native species cover. Our findings revealed the ecological significance of niche-filling and the biotic acceptance hypotheses on post-coal mine heaps. We demonstrated how exploring native community characteristics can help in understanding the invasibility and management of post-industrial vegetation.
Biological invasions, coal mines, community-weighted means, functional diversity, native species, oligotrophic mineral material, post-coal mine heaps
Invasion by alien species severely threatens the biodiversity and function of transformed ecosystems and may interfere with ecosystem restoration and establishment efforts after disturbance, for example, due to high competitiveness. In natural and semi-natural ecosystems invaded by alien plants, several attempts have been made to explain the relationships between the alien species richness and cover and the increase in native species functional richness. The niche-filling hypothesis states that niches are available for alien species in a community of functionally-rich native species. In contrast, in a functionally-poor community, the niches are fewer and already occupied by native species (
Alien species invasion represents one of the major challenges in restoration ecology (
In habitats that have been established due to human activity, such as post-excavation mineral sites, the relationship between alien species occurrence and native plant community functional richness is unknown. Understanding the relationship between the alien and native species and communities has become increasingly important as ecosystems transformed by mining occupy approximately 1% of the global land area (
Possible mechanisms for alien species establishment in man-made habitats have been proposed by
Most post-industrial sites are under active technical reclamation with only a few left to spontaneous vegetation processes (
The study was conducted in Upper Silesia – the region has a long tradition of coal mining (since the 18th century). The long-lasting black coal mining activities have resulted in large areas of post-coal mine sites, occupying > 2000 ha (
From the list of 112 post-mining sites with available information about age, size, vegetation and reclamation method (
These traits include a broad category of plant life history, leaf morphology and reproductive characteristics (Table
Functional traits and life history characteristics of plant species recorded within the study plots.
Plant traits | Code | Data type | Unit | Value (Min., Max.) | Missing data (%) |
---|---|---|---|---|---|
Leaf dry matter content | LDMC | Numeric | mg g-1 | 0.3, 509.5 | 18.9 |
Seed mass | SM | Numeric | mg g-1 | 0.001, 13737.6 | 5.5 |
Specific leaf area | SLA | Numeric | mm2 mg-1 | 51.8, 899.1 | 12.1 |
Plant height | PH | Numeric | m | 0.033, 60.0 | 1.1 |
Light EIV | EIV-L | Ordinal | Ordinal | 1, 9 | 1.9 |
Moisture EIV | EIV-M | Ordinal | Ordinal | 2, 11 | 13.2 |
Temperature EIV | EIV-T | Ordinal | Ordinal | 2, 8 | 27.1 |
Nitrogen EIV | EIV-N | Ordinal | Ordinal | 1, 9 | 12.3 |
Soil reaction EIV | EIV-SR | Ordinal | Ordinal | 1, 9 | 30.9 |
Start of flowering | Flow_start | Ordinal | Month | 1, 9 | 1.1 |
Duration of flowering | Flow_dur | Ordinal | Month | 1, 12 | 1.1 |
Insect pollinated | Poll-ins | Binary | 4.1 | ||
Wind pollinated | Poll-wind | Binary | 4.1 | ||
Self-pollinated | Poll-self | Binary | 4.1 | ||
Alien status | Alien_stat | Categorical | 2 categories | 0.0 | |
Life form | Life_form | Categorical | 8 categories | 0.0 |
The functional approach was based on a set of traits known to have significant ecological implications for plant species competitive ability, dispersal, establishment and stress tolerance on post-coal mine heaps. Specific leaf area (SLA) and leaf dry-matter content (LDMC) serve as proxies of species status on the leaf economic spectrum (
We used a random forest algorithm in combination with phylogenetic trait imputation to fill gaps in the trait data and not omit missing data (
To understand important aspects of the functional community structure, we combined plant trait data with species cover to calculate the community-weighted means (CWMs) and the functional diversity indices. We calculated the CWMs of seed mass, plant height and specific leaf area using the FD::FunctComp() function (
All analyses were performed in R software (version 4.2.1) (
To assess the drivers of alien species richness and cover in post-coal mine heaps, we built a generalised linear mixed effect model (GLMM) and linear mixed effect model (LMM), assuming a Poisson distribution with a log linking function and Gaussian distribution, respectively. In these models, heap age and native community characteristics (i.e. native species richness, native species cover, native CWM SLA, native CWM SM, native CWM PH, native FDis and native FRich) were predictors. In our models, blocks of plots nested within the heap are random variables to account for the spatial dependence of the study design. We used the ‘lme4’ package (
Prior to model development, we assessed correlations between variables using variance inflation factors (VIF). Hypothesised predictors with high collinearity (VIF > 5) were not included in the global model. The final model for alien species richness and abundance on post-coal mine heaps was: glmer(formula = alien.rich ~ native.rich + native.FRich + native.CWM.SLA + (1 |heap/block)); lmer(formula = alien.abundance ~ native.abundance + native.FRich + native.CWM.H + native.CWM.SM + (1|heap/block)), where alien.rich = alien species richness, native.rich = native species richness, alien.abundance = alien species cover, native.abundance = native species cover, native.FRich = Functional richness of native species, native.CWM.SLA = native community-weighted means of specific leaf area, native.CWM.H = native community-weighted means of plant height, native.CWM.SM = native community-weighted means of seed mass.
To identify models with variables that best predict alien species richness and cover on post-coal mine heaps, we used a model selection in the MuMIn::dredge() function (
Amongst the 318 plant species recorded in our dataset, we found 253 (79.6%) native species, 36 (11.3%) neophytes (four casual, 15 naturalised and 17 invasive) and 29 (9.1%) archaeophytes (two casual, 24 naturalised and three invasive). Amongst the 65 recorded alien species, 15 occurred in more than 11 plots and 17 had a percentage mean > 9.0% (Table
Frequency and cover of the 15 most common alien species occurring on post-coal mine heaps. Status and historical-ecological group – Neo (Neophyte), Ar (Archaeophytes) source:
Species | Native region | Life form | Status | Frequency (number of plots) | Mean cover (%) | Pollination agent | Dispersal agent |
---|---|---|---|---|---|---|---|
Erigeron canadensis | N America | Therophyte | Invasive (Neo) | 108 | 2.5 | Self | Anemochory & Autochory |
Solidago gigantea | N America | Hemicryptophyte | Invasive (Neo) | 87 | 14.25 | Insect | Anemochory & Autochory |
Solidago canadensis | N America | Hemicryptophyte | Invasive (Neo) | 77 | 7.29 | Insect | Anemochory & Autochory |
Erigeron annuus | N America | Therophyte | Invasive (Neo) | 67 | 5.24 | Insect | Anemochory & Autochory |
Impatiens parviflora | Asia | Therophyte | Invasive (Neo) | 40 | 14.7 | Insect, Self | Autochory |
Tripleurospermum inodorum | Anecophytes | Therophyte | Naturalized (Ar) | 38 | 2.21 | Insect | Autochory |
Echinochloa crus-galli | Anecophytes | Therophyte | Invasive (Ar) | 30 | 1.97 | Wind, Self | Autochory |
Silene latifolia | S Europe, Mediterranean, Asia | Hemicryptophyte | Naturalized (Ar) | 27 | 1.74 | Insect | Autochory |
Hordeum jubatum | N America | Hemicryptophyte | Naturalized (Neo) | 18 | 3.06 | Self | Autochory |
Kali turgidum | Europe, Mediterranean | Therophyte | Casual (Neo) | 16 | 1.75 | Wind, Insect, Self | Autochory |
Lepidium ruderale | Mediterranean | Therophyte | Naturalized (Ar) | 15 | 1.53 | Self | Autochory |
Pastinaca sativa | Mediterranean | Hemicryptophyte | Naturalized (Ar) | 14 | 2.29 | Insect | Autochory |
Setaria viridis | Mediterranean | Therophyte | Invasive (Ar) | 13 | 9.62 | Wind | Autochory & Epizoochory |
Diplotaxis muralis | Mediterranean | Therophyte | Invasive (Neo) | 12 | 2.33 | Insect, Self | Autochory |
Prunus serotina | N America | Phanerophyte | Invasive (Neo) | 12 | 16.33 | Wind, Insect | Autochory & Endozoochory |
Amongst all tested predictors for alien species richness in post-coal mine heaps, the best-fit model was explained by the native functional richness and SLA CWM (AICc global model = 618.08; AICc null model = 663.40; AICc best model = 599.66). Predicted alien species richness increased by 0.47 per unit change in native functional richness (P < 0.001) (Table
Estimates of the most parsimonious GLMM and LMM predicting native cover, native richness, functional richness, community-weighted means (CWMs) of specific leaf area (SLA), plant height and seed mass on the alien richness and cover, respectively.
Predictor | Estimate | SE | Z/t value* | P |
---|---|---|---|---|
Alien species richness | ||||
Intercept | 0.57 | 0.08 | 6.74 | <0.001 |
Native species richness | -0.08 | 0.08 | -1.12 | 0.26 |
Native functional richness | 0.51 | 0.07 | 7.79 | <0.001 |
Native CWM of SLA | 0.15 | 0.08 | 1.94 | 0.052 |
Alien species cover | ||||
Intercept | 9.71 | 4.44 | 2.19 | 0.083 |
Native functional richness | 4.54 | 1.44 | 3.15 | <0.01 |
Native species cover | -7.02 | 1.72 | -4.07 | <0.001 |
Native CWM of plant height | 2.94 | 1.37 | 2.15 | 0.033 |
Native CWM of seed mass | 3.49 | 1.53 | 2.28 | 0.023 |
Alien species richness, estimated using GLMM, assuming the Poisson distribution of the dependent variable (Table
For alien species cover, the most parsimonious model contained native species cover, functional richness, CWM plant height and CWM seed mass as predictors (AICc global model = 1641.71; AICc null model = 1660.71; AICc best model = 1641.18). Predicted alien species cover decreased by 7.01 with native cover (LMM, χ2 = 16.56, P < 0.001) (Table
Alien species cover, estimated using LMM assuming a Gaussian distribution of the response variable (Table
We found that alien plant species accounted for 20.4% of all recorded vascular plants (65 out of 318 taxa) on heaps, with 55% of those being neophytes and the rest being archaeophytes. A higher proportion of native species is well-known from other post-industrial sites (e.g. old Solvay process heaps (
Erigeron canadensis, Solidago gigantea, Solidago canadensis, Erigeron annuus and Impatiens parviflora were the most frequent alien plant species in the studied plots on heap sites. Most important were S. gigantea and I. parviflora which had a high mean percentage cover. Solidago gigantea was found mainly in open habitats characterised by high light intensity and heap sites with early-successional communities. The species germinates by seed and rhizomes (
We found Impatiens parviflora in forest habitats within gaps in the herbaceous layer and heap sites at the late-successional stage. I. parviflora colonises sites with high native species richness (
Prunus serotina was relatively less frequent on heap sites; however, in plots where it occurred, it had a high cover, thus, giving the species a high mean percent cover. Prunus serotina is a woody plant that encroaches on intermediate stages of succession due to its persistence in the shade and quick growth after disturbance (
The most frequent alien species in the studied spoil heaps were mainly herbaceous plants, self or insect-pollinated and self or wind-and-self dispersed. These are traits associated with the invasiveness of alien plants (
We found that alien species richness and cover increased with native functional richness in the studied heap sites. Our finding is consistent with the niche-filling hypothesis (
Our findings revealed that alien species cover decreased with native species cover on heap sites. Early native colonisers may control the establishment of later-arriving species by occupying niches and ensuring their persistence by creating abundant shade (
Our results showed that native CWM seed mass and plant height significantly predict alien species cover. Studies on the relationship between vegetation cover and the participation of species with different seed masses have shown that low cover (i.e. more open habitats) favoured the occurrence of species with small seed masses, while species with heavy seeds are successful in shaded habitats (
Plant height is an important ecological parameter in spontaneously-vegetated heap sites (
Our findings showed that alien species establishment was prominent in the early stage of post-coal mine vegetation development, but not on newly-formed heaps. Heap sites at the early developmental stage were characterised by alien species showing ruderal features that benefit from disturbance, for example, Solidago gigantea, Solidago canadensis, Erigeron canadensis and Erigeron annuus. These species reached a high level of ecological success. Therefore, to reduce invasibility, we recommend that the management objectives should be directed to the early stage of spontaneous vegetation formation on heap sites. Similarly, reduced ecological disturbance should be encouraged on heap sites to prevent ruderal colonising species and promote competitive native species.
Monitoring alien species invasion level and establishment on heaps and the surrounding landscape has high importance. Recent findings have shown that landscapes surrounding roads, railways and arable land harbour neophytes (
To prevent secondary invasion – an increase in the colonisation of non-target alien species after the removal of targeted invasive plants (
Our study identified successful alien species and developed models on how native community characteristics explain alien species invasion level (alien richness) and ecological success (alien cover) on spontaneously-vegetated post-coal mine heaps. Amongst studied plant communities, those at the early stage of spontaneous vegetation development are the most threatened by alien species, thus requiring active management and conservation. Erigeron canadensis, Solidago gigantea, Solidago canadensis, Erigeron annuus and Impatiens parviflora should be designated as priority aliens for management action on post-industrial vegetation. Introducing native species at early stages of vegetation development can decrease the level of threat from invasive species.
The study was supported by the National Science Centre Poland, Grant Number: OPUS 2019/35/B/ST10/04141 and the Institute of Dendrology, Polish Academy of Sciences, Kórnik. MKD acknowledges support from the Foundation for Polish Science (FNP) from the START scholarship. We thank the two anonymous Reviewers for their helpful comments and suggestions on the earlier draft of the manuscript.
Frequency and cover of alien species occurring on post-coal mine spoil heaps
Data type: table (word document)