Abstract
Proper estimation of the herb layer annual net primary production (ANPP) can help to appreciate the role of this layer in carbon assimilation and nutrient cycling. Simple methods of ANPP estimation often understate its value. More accurate methods take into account biomass increments of individual species but are more laborious. We conducted our study in an oak-hornbeam forest (site area 12 ha) dominated by beech in NW Poland during two growing seasons (2010 and 2011). We collected herb layer biomass from 7 to 10 square frames (0.6 × 0.6 m). We collected plant biomass every week in April and May and every two weeks for the rest of the growing season. We compared six methods of calculating ANPP. The highest current-year standing biomass (1st method of ANPP calculation) was obtained on May 15, 2010—37.8 g m−2 and May 7, 2011—41.0 g m−2. The highest values of ANPP were obtained by the 6th method based on the sum of the highest products of shoot biomass and density for individual species: 74.3 g m−2 year−1 in 2010 and 94.0 g m−2 year−1 in 2011. The spring ephemeral Anemone nemorosa had the highest share of ANPP with 50% of the total ANPP. Two summer-greens, Galeobdolon luteum and Galium odoratum, each had a ca. 10% share of ANPP. The best results of ANPP calculation resulted from laborious tracking of dynamics of biomass and density of individual shoots.
Highlights
Herbaceous vegetation plays an underestimated role in forest ecosystems
The dominant share in biomass peaks were spring ephemerals. In both years they were responsible for over 30 g m-2 year-1, while at the same time summer-greens amounted to 5.6 g m-2 year-1 in 2010 and 8.8 g m-2 year-1 in 2011 (Figure 1)
The seasonal herb layer biomass dynamic shows a twopeak shape; a bigger peak occurred in spring and was composed of spring ephemerals and a lesser peak occurred in late summer or early autumn and was composed of summer-greens
Summary
Herbaceous vegetation plays an underestimated role in forest ecosystems. From the viewpoint of total forest ecosystem biomass, the herb layer comprises only 1%, and about 4% of net primary production (Muller 2014). The herbaceous layer enhances leaf mass production by overstory trees (Elliott and others 2015). Forest herbaceous species are often strictly connected with forests and do not occur elsewhere (Hermy and others 1999). Some forest herb species suffer from silvicultural systems applied on the landscape, for example forest tree stand rotations of less than 100 years, clearcuttings, and site preparation (Halpern and Spies 1995). Herbaceous species are endangered in fragmented and transformed temperate forests in highly populated regions (Landuyt and others 2019). The role of the herb layer is unappreciated in many ways, so one point of its significance is proper estimation of its contribution to biomass production, which allows us to properly define the herb layer role in carbon assimilation and nutrient cycling
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