Abstract
BackgroundStemflow is an essential hydrologic process shaping the soil of forests by providing a concentrated input of rainwater and solutions. However, the transport of metazoans by stemflow has yet to be investigated. This 8-week study documented the organisms (< 2 mm) present in the stemflow of different tree species. Because the texture of the tree bark is a crucial determination of stemflow, trees with smooth bark (Carpinus betulus and Fagus sylvatica) and rough bark (Quercus robur) were examined.ResultsUp to 1170 individuals per liter of stemflow were collected. For rotifers and nematodes, a highly positive correlation between abundance and stemflow yield was determined. Both taxa were predominant (rotifers: up to 70%, nematodes: up to 13.5%) in the stemflow of smooth-barked trees whereas in that of the oak trees collembolans were the most abundant organisms (77.3%). The mean number of organisms collected per liter of stemflow from the two species of smooth-barked trees was very similar. A higher number of nematode species was found in the stemflow of these trees than in the stemflow of rough-barked oak and all were typical colonizers of soil- and bark-associated habitats.ConclusionThis pilot study showed for the first time that stemflow is a transport vector for numerous small metazoans. By connecting tree habitats (e.g., bark, moss, lichens or water-filled tree holes) with soil, stemflow may influence the composition of soil fauna by mediating intensive organismal dispersal.
Highlights
Stemflow is an essential hydrologic process shaping the soil of forests by providing a concentrated input of rainwater and solutions
Stemflow was collected in 85.7% of the samplings from the stems of F. sylvatica and 73.9% and 45.8% of the stems of C. betulus and Q. robur (Fig. 1C–E)
The maximal stemflow volume collected over the 8-week period from a single Q. robur tree was 1 L, and from single trees of C. betulus and F. sylvatica up to 31.5 and 49.9 L
Summary
Stemflow is an essential hydrologic process shaping the soil of forests by providing a concentrated input of rainwater and solutions. Because the texture of the tree bark is a crucial determination of stemflow, trees with smooth bark (Carpinus betulus and Fagus sylvatica) and rough bark (Quercus robur) were examined. The stemflow yield increases with increasing precipitation during intensive rain events it decreases because water reaches the ground as throughfall [1]. Rough bark has a higher water storage capacity than smooth bark such that a larger amount of precipitation is necessary before the bark is saturated and stemflow is generated [5]. In one study, stemflow along the trunk of rough-barked Quercus robur (rough bark) was generated following 5.4 mm of precipitation whereas in smooth-barked Fagus sylvatica only 2.8 mm was required [6]. Additional factors influencing the stemflow yield are wind, snowfall, and the morphometry of the tree (e.g., stem diameter and number of branches) [2]
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