How environmental stressors affect reproductive potential in a saltmarsh plant species Plantago maritima

Abstract

We examined whether the presence or absence of different environmental stressors influenced the reproductive potential of a saltmarsh species-Plantago maritima. We focused on total seed output, seed quality, and biomass of progeny. So far, there are no studies trying to answer the question of how different saltmarsh management affects the quality of seed in saltmarsh species. For the purposes of the study, plots subjected to light mowing, light or heavy grazing, trampling, or rooting were designated in three nature reserves in Poland. On each plot, the abundance of infructescences per sq. meter was calculated. Mature infructescences were collected, and their length and number of fruit capsules were measured. The seeds obtained from fruit capsules were weighted and sown in controlled conditions. The germination rate and the final germination percentage were calculated. A representative number of sprouts were grown. After a period of 2 months, the individuals of P. maritima were harvested and their total dry mass was measured. It was found that heavy grazing had the greatest effect on all of the studied characteristics. The presence of this factor resulted in shorter infructescences with a smaller number of fruit capsules. However, this phenomenon was compensated by the higher abundance of infructescences per sq. meter. At the same time, seeds produced by grazed individuals were significantly lighter. Interestingly, intensive trampling by people affected P. maritima individuals in a similar way to heavy grazing, while mowing and rooting had less impact on the considered characteristics. Although a positive correlation between seed mass and germination success was found, the altogether lower seed mass had a negligible effect on germination parameters. Also, the differences in seed parameters did not affect dry mass of obtained progeny grown in laboratory conditions. Synthesis and applications: Different environmental stressors, such as grazing and mowing, have an effect on reproductive potential of a saltmarsh species P. maritima. In the case of habitats created anthropogenically, such as brackish saltmarshes, the role of management is crucial for their conservation. Therefore, searching for the best active protection methods is important. In light of the results obtained, extensive or rotational grazing appears to be the best form of saltmarsh management.

Keywords: active protection; brackish saltmarshes; germination; grazing; mowing; phenotypic plasticity; rooting; seed mass; trampling.

FIGURE 1

Study site location. (a) “Słone Łąki” nature reserve, (b) “Beka” nature reserve, (c) “Mechelińskie Łąki” nature reserve

FIGURE 2

Density plots of eight tested response variables, which were influenced by six management types (gray curve) in comparisons with no treatment (black curve). GrazH, heavy grazing; GrazL, light grazing; MowL, light mowing; RootNew, fresh marks of rooting; RootOld, old marks of rooting; TramH, heavy trampling

FIGURE 3

Scatter plots with two‐dimensional density functions presenting the relationship between selected response variables, with fitted linear regressions. The gray circles represent selected management types (1), while the empty ones represent no treatment (0). GrazH, heavy grazing; GrazL, light grazing; r, Pearson's correlation coefficient; TramH, heavy trampling. The gray area along regression lines describes confidence intervals