Effects Of Litter Cover Research Articles

Effects of Pinus tabulaeformis litter cover on the sediment transport capacity of overland flow

Sediment transport capacity (Tc) plays a pivotal role in process-based soil erosion models. Surface cover is an important factor that affects Tc; investigation into the potential effect of litter cover on Tc is limited. The objectives of this study were to quantify the effects of Pinus tabulaeformis litter cover on Tc; to explore various relationships between hydraulic variables, litter cover, and Tc; and to compare the similarities and differences of the effect of litter and stem cover on Tc. Experiments were conducted in a 5×0.38 m flume. The unit flow discharge varied from 1.316 × 10−3 to 3.947 × 10−3 m2 s−1, and the slope gradient varied from 8.8 to 26.8 %. Pine needles of Pinus tabulaeformis were selected to simulate litter cover. Seven levels of litter cover were considered: 0%, 5%, 10 %, 20 %, 30 %, 50 %, and 70 %. The median diameter of the test sediment was 0.35 mm. The results showed that Tc decreased exponentially as litter cover increased. Measured Tc could be predicted adequately (R2 = 0.96) by unit flow discharge, slope gradient and litter cover, or the stream power and litter cover. Flow velocity or unit stream power could predict the Tc equally well (R2 = 0.95) without including the cover term because the effect of litter cover on the Tc manifests itself in the increased resistance and reduced flow velocity. Tc is most sensitive to the slope gradient when the level of cover is low. The effect of litter cover on Tc could be greater than the unit flow discharge and slope gradient in relative terms when the level of cover exceeded 38 % and 81 %, respectively. The effect of stem cover on Tc is greater than that of litter cover, other variables being the same.

The Effects of Litter Cover on the Early Growth of Manchurian Wild Rice (Zizania latifolia)

ABSTRACT The effects of a standing layer of litter on the shoot emergence and subsequent growth of Zizania latifolia were evaluated by removing the litter layer in three plots. Three other plots were kept as controls with litter layer. Shoot emergence and growth parameters were observed for seven months. Light incidence through the litter layer was measured. New shoots emerged about a month earlier in the plots without litter than in the plots with litter layer. The maximum shoot density in the plots where the litter layer was removed was 590 m−2 at the time when average shoot height was 61 cm, whereas the shoot density was 316 m−2 with an average shoot height of 71 cm in the control plots. Maximum shoot density was reached three weeks later in the plots with litter. Although removal of standing litter significantly increased initial shoot density, plant growth was essentially comparable regardless of the presence or absence of accumulated litter.

Seed dormancy, germination, seedling emergence, and survival of some temperate perennial pasture grasses in northern New South Wales

A series of seed and seedling studies was undertaken in northern New South Wales for the temperate perennial grasses phalaris (Phalaris aquatica cv. Sirosa and Australian), tall fescue (Festuca arundinacea cv. Demeter), perennial ryegrass (Lolium perenne cv. Kangaroo Valley), and 2 wallaby grasses (Austrodanthonia bipartita syn. Danthonia linkii cv. Bunderra and A. richardsonii syn. D. richardsonii cv. Taranna). Studies were conducted to determine the level of dormancy in freshly harvested seed and the time required to overcome it, effects of alternating daily temperatures on the germination of non-dormant seed, effect of time-of-sowing on seedling emergence (2 studies) and survival, levels of seed production and soil seedbanks, and the effect of litter cover and soil type on the emergence of Sirosa phalaris seedlings.Grass species, time, and their interaction all had a significant effect (P < 0.05) on both dispersal unit and caryopses germination. One month after harvest, germination of caryopses was lower (P < 0.05, 2 and 1%, respectively) for Taranna and Bunderra than for Sirosa (79.5%). In March 1993, germination of the 2 wallaby grasses was also lower (P < 0.05) than that of Sirosa. Dormancy of freshly harvested seeds of Sirosa was mainly associated with the structures surrounding the caryopses (7.7 v. 79.5% mean germination), but for Taranna and Bunderra it was related to physiological dormancy of the caryopses.Germination levels that were not significantly different to the maximum occurred for temperature ranges of 35/30–15/10�C [Sirosa (commercial)], 35/25–15/10�C (Australian phalaris), and 35/30–15/05�C (Kangaroo Valley ryegrass). In contrast, maximum germination of wallaby grasses only occurred for Taranna in the temperature range 25/20–20/10�C, and for Bunderra at 25/15 and 20/15�C.Seedling emergence in the field was episodic, occurring on only 3 occasions from 1993 to 1996. No seedlings of Sirosa phalaris, Demeter tall fescue, or Kangaroo Valley ryegrass were successfully recruited, but Taranna and Bunderra successfully recruited new plants from natural seedfalls. Whereas seed production of the perennial grasses studied was relatively high (~10 000 seed/m2 in 1992), soil seedbank levels were much lower (generally <1000 seeds/m2). These data were used to indicate the likely successful establishment of sown perennial grasses or by regeneration from natural seedfall.

The effects of small-scale environmental heterogeneity on seed germination in experimental treefall gaps in New Zealand

Seed germination of woody species was studied in treefall gaps in NewZealand to assess how environmental heterogeneity affects regeneration fromseed. Gaps were created in a relictual Pinus radiataplantation destined for restoration to native forest. Seeds of the nativespecies Alectryon excelsus, Macropiperexcelsum, and Fuchsia excorticata, and theinvasive alien species Cytisus scoparius andBerberis darwinii were sown in sites differing inexposure,with and without 3 cm of pine litter. Litter promoted germinationof Alectryon and Macropiper,independent of site. Without litter, percent germination ofMacropiper was negatively correlated with percent open skyoverhead. Germination of Fuchsia was significantly higherin treefall gaps than in the forest understory, with litter having littleeffect. Cytisus germinated most successfully in sitesexposed to direct solar radiation, with or without litter. Percent germinationof Berberis was high in all sites, and was consistentlypromoted by litter. Glasshouse trials for each species showed the same effectsof litter cover as found in the field. These results suggest thatmicroenvironmental heterogeneity can be an important influence on the speciescomposition of regenerating vegetation within and around treefall gaps.

Effect of litter on the incidence of leaf-fungal pathogens and herbivory in seedlings of the tropical tree Nectandra ambigens

Effects of litter cover on insect herbivory, leaf-fungal damage, and seedling performance (survival, growth in height and leaf number), were assessed on established Nectandra ambigens seedlings in three sites of a Mexican tropical rain forest. Naturally occurring seedlings were measured for height, leaf number and standing levels of leaf damage by herbivores and pathogens. Thereafter, seedlings were exposed for 1 y to three litter treatments: (1) litter addition, (2) control and (3) continuous litter removal. There was a significant effect of site on the proportion of surviving seedlings and on the relative growth rates in terms of leaf number. Overall, seedlings with higher initial leaf number showed higher survival and produced more leaves after 12 mo than seedlings with lower initial leaf number. Litter addition resulted in seedlings with lower relative growth rates in height and higher levels of damage by herbivores and pathogens. On average, leaf area damaged by pathogens was < 6% and herbivory was < 27%. Seedlings with higher levels of herbivory showed higher levels of pathogen attack. Herbivory and pathogen attack had no effect on seedling performance. This study reveals the importance of litter-cover on the interactions between seedlings, herbivores and pathogens, as well as on the performance of tropical seedlings.

Effect of litter cover on the process of water movement in the vicinity of ground surface : An consideration using the lysimeter

Effect of litter cover on the process of water movement in the vicinity of ground surface : An consideration using the lysimeter

Effects of litter from a tropical rainforest on tree seed germination and establishment under controlled conditions.

The effects of litter cover on the germination of seeds of three tropical rainforest, pioneer tree species (Cecropia obtusifolia, Heliocarpus appendiculatus and Piper auritum) was investigated. Germination of seeds of all tree species was partially or totally inhibited when the seeds were covered with litter, whereas uncovered seeds or seeds covered with paper instead of litter germinated. Seed size was directly correlated with the capacity of the germinated seeds to emerge through the litter. In soil experiments in the greenhouse, seedling emergence from the soil was inhibited by the presence of litter on the soil surface.