Fast grassland recovery from viable propagules after reintroducing traditional mowing management on a steep slope

Abstract

Semi-natural grasslands on steep slopes often show high plant species diversity. These grasslands were traditionally maintained through mowing and/or grazing. The traditional management practices help to maintain species diversity, whereas land abandonment reduces diversity by increasing competition from dominant species and reducing seedling recruitment. The reintroduction of management can reverse species diversity declines, but suitable grassland restoration programs are scarce in Japan. To study the effect of short-term abandonment on seedling ecology, we monitored the vegetation of a Susogari grassland that had been abandoned for 3 years; the grassland occupies a steep slope (ca. 50°) on a hillside above paddy fields, and was traditionally mown. We monitored the vegetation before abandonment, in the 3rd year of abandonment, and in the 1st and 2nd years after restoration of mowing management. Emergence and survival of seedlings was monitored for 18 months after reintroduction of management. We monitored 1,183 seedlings of grassland species and non-target annuals in ten 1-m² plots. After mowing was reintroduced, most grassland species reappeared or increased in the first and second years. Few seedlings of perennial plants and no seedlings of annuals flowered. An exotic species, Solidago altissima, had a lower survival rate (10%) than grassland species (>30%), and all but two grassland species survived over the 18-month period. Although vegetation composition was not fully recovered, our findings suggest that a steep slope acts as a strong filter that inhibits the establishment of non-target species while enhancing persistence of target grassland species.

Keywords: Seedling emergence; Seedling establishment; Semi-natural grassland; Survival rate; Susogari grassland.

Figure 1. Description of the study area.

(A) Location of the study site; (B) land use map of the study area; (C) photo taken before the clear-cut of the upslope woodland (October 2017); (D) photo taken after the clear-cut of the upslope woodland and before the reintroduction of mowing (May 2018); (E) photo taken after the reintroduction of mowing (October 2018) and layout of □ survey plots; (F) layout of □ the 10 plots and × soil sampling points (added to the photo taken in May 2018). Maps in (A) and (B) were published in Yamada, Kitagawa & Okubo (2013).

Figure 2. (A–H) Changes in species richness at a sampling scale of 1 m² according to functional groups.

Figure 3. Annual changes in average frequency of major species according to functional groups.

Individual species and detailed description for the criteria of major species are shown in Table S2.

Figure 4. Scatterplots of the first two NMDS axes in each survey period.

• = 2008; $○$ = 2018; × = 2019; △, 2020. “P01–10” = quadrat numbers.

Figure 5. (A) Emergence and (B) mortality of annuals and perennials in each period.