Leaf transport and retention in a high gradient stream

Abstract

To a large extent, the invertebrate fauna in wooded streams rely upon detritus inputs from the surrounding vegetation as their main food source. Conifer plantations may alter the timing and nutritional quality of leaf inputs into streams, but detritus retention may also be reduced. While it has often been assumed that conifer needles are retained less than broadleaved species, this has never been tested experimentally. This study describes the results of a leaf release experiment carried out in a small headwater stream, comparing the retention of pine needles and oak leaves (wet and dry) over a range of discharges. In addition, retention was compared before and after placing logs in the stream to examine the effect of woody debris on retention efficiency. Retention efficiency was significantly different among the three leaf types tested with wet oak leaves being most retentive, followed by dry oak leaves with dry pine needles being least retentive. Retention efficiency declined significantly with increasing discharge for all three leaf types. The addition of logs increased the retention of dry oak leaves and pine needles, but not wet oak leaves. The predominant features (stones, logs, eddies and bankside vegetation) that accounted for retention varied with discharge and the leaf type used. The results indicate that while conifer needles may be inherently less retentive than broadleaves, the presence of woody debris within the stream channel increases their retention. However, this small-scale study would need to be expanded to investigate the retention dynamics of conifer needles in plantation streams. Nevertheless, management strategies that allow the formation of woody debris accumulations in plantation streams could be valuable in enhancing detritus retention and consequently could benefit invertebrate communities.

Storage and export of organic matter in a headwater stream: responses to long‐term detrital manipulations

“…In Virginia, a five-fold increase in the number of debris dams in a lowgradient headwater stream resulted in 6-113 increases in organic matter storage (Smock et al 1989). Other studies have demonstrated that small wood alone can be important for the retention of leaves in headwater streams (Trotter 1990, Pretty andDobson 2004). Results from the exclusion/removal phase of our study demonstrated that leaves and small wood are both extremely important in retention (Fig.…”

Input of litter in deforested and forested areas of a tropical headstream

“…Other authors (Canhoto and Graça, 1998;Afonso and Henry, 2002;Pretty and Dobson, 2004) also found that during rainfall events, leaf retention also decreases greatly. In the same way, when retention structures are submerged or carried downstream, it will result in greater loss of sediments (Díez et al, 2000;Afonso and Henry, 2002).…”

Input, retention, and invertebrate colonization of allochthonous litter in streams bordered by deciduous broadleaved forest, a conifer plantation, and a clear-cut site in southwestern Japan

“…Sampling was not conducted in the clear-cut site in summer because litter patches were scarce Limnology (2012) 13:207-219 215 similar species was found in Washington, USA (Bilby and Bisson 1992). For retentiveness, although studies comparing conifer needles and broadleaves are limited, conifer needles are generally believed to be less retentive due to their size and shape (e.g., Riipinen et al 2010); Pretty and Dobson (2004) actually demonstrated that conifer needles [Scots pine (Pinus sylvestris)] were less retentive than broadleaves, unlike in our case. The absence of strong seasonality in litterfall and the high retentiveness in our conifer plantation stream can be attributed to species-specific properties of Japanese cedar.…”

“…In northern Europe, the effects of conifer plantations have been examined from several aspects, such as litter abundance (Murphy and Giller 2000a, b), retention (Pretty and Dobson 2004) and breakdown (Murphy and Giller 2001;Collen et al 2004;Riipinen et al 2010), and invertebrate communities (Ormerod et al 1993;Friberg 1997;Clenaghan et al 1998;Murphy and Giller 2000a;Riipinen et al 2010). Although knowledge of the ecological effects of conifer plantations has been gained from these studies, the effects of plantations on stream ecosystems can vary regionally, depending on the region-specific environmental conditions (e.g., climate, geology).…”