Interactions between litter and water availability affect seedling emergence in four familial pairs of floodplain species

Abstract

Summary 1We studied seedling emergence in four familial pairs of floodplain herbs in response to the experimental manipulation of soil moisture and litter cover to analyse (i) whether the effect of litter changes from negative under humid to positive under dry conditions, and (ii) whether the response to changing water and light conditions with increasing litter cover varies among species and plant families. 2 We carried out a controlled pot experiment using four levels of litter cover (0 g, 2 g, 4 g and 8 g litter per pot, corresponding to 0 kg m ) and two levels of water-addition, leading to constantly humid substrate or intermittently dry topsoil. 3 Across water-additions, percentage emergence reached a peak at low levels of litter cover (0.2 kg m − 2 and 0.4 kg m − 2 ). There was a significant litter × water-addition interaction in six species, with positive effects of litter under intermittently dry conditions and negative or neutral effects under constantly humid conditions. Litter lowered maximum temperature as well as amplitude, and alleviated soil humidity under low water supply, while imposing increasingly shaded conditions. Analysis of species-and family-specific responses suggested that germination under a litter cover of 0.8 kg m − 2 was significantly reduced in smaller-seeded species (i.e. those that tend to have higher light demands for germination). . Below these levels, establishment of most species may be inhibited by drought, while higher amounts will increasingly suppress seedling emergence, especially of small-seeded species. 5 In addition to facilitation effects observed between living plants, dead plant remains may also exert positive effects on establishment. The sign of the litter effect on seedling emergence depends on soil humidity, with negative effects seen above a threshold amount, which is species-and family-specific and is closely related to seed size. Whether positive litter effects in grasslands are a consequence of coevolution remains to be examined.

Variation in life-cycle between three rare and endangered floodplain violets in two regions: implications for population viability and conservation

“…Though germination of V. elatior and V. pumila increased with increasing litter cover especially under dry conditions (Eckstein & Donath 2005; no data for V. stagnina), the release of seeds onto a dense carpet of litter, which impedes seed-soil contact, generally has negative effects on seed survival and germination (Facelli & Pickett 1991 and references therein). The above aspects of habitat quality are not exclusive but may act in concert to reduce net reproductive rate of the Dyje populations, leading to a regressive population stage structure and increased extinction risk in the long run (Oostermeijer et al 1994).…”

Excessive Accumulation of Chinese Fir Litter Inhibits Its Own Seedling Emergence and Early Growth—A Greenhouse Perspective

“…Leaves were rinsed with distilled water to remove dust particles, air-dried at ambient temperature, and stored in paper bags until needed. We did not use oven-drying because the process could induce chemical changes in the litter [26,33].…”

“…Seeds were considered to have emerged once their shoots penetrated through the litter surface and were exposed to light [26]. The seedling emergence rate was calculated for each pot as the number of seedlings that penetrated the litter surface divided by the total number of seeds planted in each pot (i.e., 50).…”

“…Coniferous forests have low litter decomposition rates that make them prone to developing a thick needle layer below the canopy [22,23]. Thus, litter effects are especially important for seedling emergence and growth [14,[24][25][26], given their ability to modify light, moisture, and microhabitat conditions (e.g., nutrient content, competition from established vegetation) [3,[27][28][29][30]. Although litter can have both positive and negative effects on seedling emergence and growth [26,28,[30][31][32], the extent highly depends on litter amount.…”

“…Although litter can have both positive and negative effects on seedling emergence and growth [26,28,[30][31][32], the extent highly depends on litter amount. Moderate litter cover may facilitate seedling emergence and early growth by attenuating extremes in moisture and temperature [26,33]. However, thick litter layers may inhibit seedlings emergence and growth through the reduction of light quantity and quality, leading to deep shade or total darkness [28,31].…”