Plant Litter Production Research Articles

Dynamics of leaf litter accumulation and its effects on riparian vegetation: A review

The total production of plant litter and the proportion of leaf litter are higher in riparian corridors than in upland ecosystems throughout the world. Periodical water-level fluctuation is believed to be the major cause of these differences. During flood periods, much plant litter is redistributed locally and between regions, following erosion, transport, and deposition of litter. The importance of litter redistribution varies with factors such as flood regime, topography, and vegetation. Litter from the riparian corridor is usually a major constituent of the litter transported by the river. The decomposition of litter is faster in riparian corridors than in upland systems due to a higher rate of leaching and a higher decomposer activity. Relative warmth and soil fertility may also enhance litter decomposition in riparian corridors. In general, accumulated litter affects plants physically by burying them, chemically by adding nutrients and phytotoxins, and biologically by adding diaspores. The physical impact of a certain amount of litter may be weaker in riparian corridors than in uplands because the rapid decomposition reduces the time that litter is present. In other words, higher amounts of litter are needed to affect riparian vegetation than are needed to affect other types of vegetation. The nutrient content of riverborne litter is reduced by leaching, but dissolved nutrients from litter might still reach the riparian vegetation, e.g., by adsorbing to inorganic particles. Phytotoxins are probably unimportant in riparian systems. The input to the riparian corridor of plant diaspores, borne by litter packs in the river, may be large. Indirect biological effects of litter, including its diaspores, are the attracting of animals and microbes that may influence the plant community, and the creation of bare soil for plant colonization.

The Occurrence and Consequences of Grasshopper Herbivory in an Alpine Grassland, Swiss Central Alps

Biomass removal by grasshoppers was determined nondestructively in two alpine grassland communities in the Central Alps at 2470 m a.s.l. During the 1993 growth period, grasshoppers removed between 19 and 30% of the aboveground phanerogam biomass. Herbivory impact was therefore found to be higher in alpine environments than that given in published estimates of low elevation grasslands. Data on biomass as well as carbon and nitrogen contents of herbage, grasshoppers, and feces were used to model the effects of herbivory on the Carex curvula community. Thirty-six percent of the removed biomass was actually ingested by the grasshoppers of which merely 3% was invested in body tissues. Since herbivores did not emigrate from the site and predation was negligible, nitrogen consumed by grasshoppers remained in communities, while appreciable amounts of carbon were respired. Herbivory tends to accelerate nutrient turnover via concentration of nitrogen in rapidly decomposable body tissues and feces, as well as the production of green plant litter originating from dropped plant material.

Soil Microbial Communities Beneath Populus Grandidentata Grown Under Elevated Atmospheric CO2

In most terrestrial ecosystems, the amount of substrate entering the soil from plant litter production is only sufficient to meet the maintenance requirements of soil microorganisms, allowing for no net annual growth. However, the rising atmospheric CO2 concentration has the potential to alter such a balance by increasing plant litter production, and hence the amount of substrate available for heterotrophic metabolism in soil. In a recent experiment, we observed that greater belowground plant litter production at elevated atmospheric CO2 significantly increased the biomass of soil microorganisms in both rhizosphere and non‐rhizosphere soil. Because soil microorganisms differ in their ability to convert substrate into biomass, we hypothesized that greater plant litter production at elevated CO2 should shift community composition as fungal populations increase in response to greater substrate availability. We used a molecular technique, phospholipid fatty acid (PLFA) analysis, to gain insight into the composition of soil microbial communities beneath Populus grandidentata growing at ambient and twice‐ambient atmospheric CO2. PLFAs extracted from rhizosphere and non‐rhizosphere soil were derivatized and identified using gas chromatography and mass spectrometry. After one growing season the proportions of bacterial, actinomycetal, and fungal PLFAs were not significantly influenced by elevated atmospheric CO2 in either rhizosphere or non‐rhizosphere soil. However, clear differences were present between microbial communities in rhizosphere and non‐rhizosphere soil. Although enhanced belowground plant litter production under elevated atmospheric CO2 increased the biomass of soil microorganisms, we have no evidence to suggest that such an increase occurred through a shift in community composition, at least in the short term.

World Patterns and Amounts of Terrestrial Plant Litter Production

Leaf and total plant litter amounts worldwide are estimated by climatic curve-fits and mapped by computer using a world climatic data base. Computer planimetry of the maps produced estimates of yearly terrestrial leaf litter (35.1 x 10 to the power of 9t) and total litter production (54.8 x 10 to the power of 9t). This is about 1.3% and 2.0% respectively, of the estimated world totals of detrital soil organic matter. (Refs. 20).

Degradation of mangrove leaf litter by the tropical sesarmid crab Chiromanthes onychophorum

In high-diversity tropical mangrove swamps, the relationship between the breakdown to detritus of mangrove plant litter and secondary production of associated estuaries is little understood. This study examined one step in this relationship, the breakdown of mangrove leaf litter to detrital-sized particles by the sesarmid crab Chiromanthes onychophorum, locally very abundant in mangrove swamps of peninsular Malaysia. Contents of the proventriculus (stomach) and of the posterior hindgut, including rectum, were analyzed and particle sizes were measured. Gut contents consisted of more than 95% by volume of mangrove leaf fragments. Particles in the hindgut were of smaller mean size than those in the proventriculus. It is concluded that C. onychophorum consumes fallen leaves or their fragments, incompletely digests them, and returns them to the environment as fecal matter in a more finely-divided state than when they were ingested. C. onychophorum may therefore be a significant agent of mangrove leaf degradation to detrital-sized particles in swamp areas where it is abundant.

Soil Erosion in Relation to Properties of Eastern and Western Washington Forest Soils

AbstractSoil was sampled under Douglas‐fir stands (Pseudotsuga meanziesii) located on similar parent materials in eastern and western Washington. Simulated rainfall applied to soil blocks showed real differences in erodibility of east‐ and west‐side soils. All soil properties tested, except texture, differed significantly between the two locations.Over 70% of the variation in soil erodibility was accounted for by a multiple regression equation using erodibility as the dependent variable and loss on ignition, permanent wilting percent, and percent silt as independent variables. Differences in soil properties were attributed to influences of climate on production of plant litter and ensuing decomposition and incorporation of litter in soil by organisms.