Quantity Of Litter Inputs Research Articles

Factors controlling soil organic carbon stability along a temperate forest altitudinal gradient.

Changes in soil organic carbon (SOC) stability may alter carbon release from the soil and, consequently, atmospheric CO2 concentration. The mean annual temperature (MAT) can change the soil physico-chemical characteristics and alter the quality and quantity of litter input into the soil that regulate SOC stability. However, the relationship between climate and SOC stability remains unclear. A 500-day incubation experiment was carried out on soils from an 11 °C-gradient mountainous system on Changbai Mountain in northeast China. Soil respiration during the incubation fitted well to a three-pool (labile, intermediate and stable) SOC decomposition model. A correlation analysis revealed that the MAT only influenced the labile carbon pool size and not the SOC stability. The intermediate carbon pool contributed dominantly to cumulative carbon release. The size of the intermediate pool was strongly related to the percentage of sand particle. The decomposition rate of the intermediate pool was negatively related to soil nitrogen availability. Because both soil texture and nitrogen availability are temperature independent, the stability of SOC was not associated with the MAT, but was heavily influenced by the intrinsic processes of SOC formation and the nutrient status.

Trends in plant and soil microbial diversity associated with Mediterranean extensive cereal–fallow rotation agro-ecosystems

This study examines plant and soil microbial diversity in a cereal–fallow rotation scheme in the cereal steppes of Castro Verde, Southern Portugal, which have an important conservation value as they provide habitat for many steppic birds with unfavorable conservation status. For that we monitored plant and soil microbial diversity during 4 years including all stages of the rotation cycle.The structure and composition of plant and soil communities during wheat crop were different from those found in the fallow years, although the effect of wheat crop on soil bacteria was still noticeable in the 1st year of fallow. The main changes in the structure of microbial communities happened between the first and second year of fallow, probably due to changes in the quality and quantity of litter inputs. As expected, we observed an overall decrease in plant diversity in the wheat stage. Fallows had a positive effect on plant species diversity by allowing the maintenance of a seed bank and controlling the simplification of weed communities. However, the impact of fallow on microbial communities is more complex: bacterial diversity was higher during the wheat stage while fungal diversity was either higher or unchanged.These results suggest that the rotation stage is the main driver of the diversity and composition of soil microbial communities, probably through changes in the plant community that deserve further examination. Inter-annual fluctuations in rainfall had a stronger impact on plant communities than on microbial communities indicating that the later are likely adapted to the characteristic fluctuation of annual rainfall in areas under Mediterranean climate.

Impacts of invasive riparian knotweed on litter decomposition, aquatic fungi, and macroinvertebrates

Bohemian knotweed (Polygonum × bohemicum), the hybrid between Japanese and giant knotweed, is the most common invasive knotweed species in western North America and the most difficult to control. Invasive knotweed congeners spread aggressively along streams and establish dense monotypic stands, reducing riparian plant species diversity. Allochthonous organic matter inputs from riparian plants are an important source of energy and nutrients for organisms in small streams. However, little information exists concerning the influence of knotweed on stream processes. This study examines the quality of Bohemian knotweed leaves compared to native red alder and black cottonwood leaves, along with leaf-associated fungal biomass accumulation, macroinvertebrate communities, and decay rates from three forested streams in western Washington State. Senesced knotweed leaves were lower in nitrogen and phosphorus, and higher in cellulose, fiber, and lignin content than alder leaves, but were more similar to cottonwood leaves. Fungal biomass differed among species and changed over time. Macroinvertebrate shredders collected from leaf packs after 31 days were proportionately more abundant on alder leaves than knotweed and cottonwood. Decay rates were not significantly different among leaf species, but during the first 31 days alder broke down faster than knotweed. After 56 days, all of the leaf packs were mostly decomposed. Overall, these findings do not show major discrepancies between leaf species except those related to initial litter structural and chemical quality. However, changes in the timing and quantity of litter inputs are also important factors to be considered in understanding the impact of invasive knotweed on stream ecosystem processes.

Effect of litter substrate quality and soil nutrients on forest litter decomposition: A review

Forest litter plays an important role in determining nutrient cycling, balance and maintaining ecosystem function of forest ecosystems. Studies have shown that litter substrate quality is one of the most important factors affecting litter decomposition in a given area. It is, hence, important to understand the factors controlling litter decomposition in the late decomposition stage and determining organic matter changes over the duration of litter decomposition. Decomposition rate of mixed litter may differ with that of a single specie litter. Supply of soil nutrients is an important factor controlling litter decomposition rate, because the essential nutrients in soil or litter material influence community and activity of decomposers (soil organisms). There were clear relationships among soil nutrient, litter substrate quality, and decomposition. Soil nutrient contents were positively correlated with litter substrate quality, showing that higher contents of soil nutrient were accompanied with good quality of litter substrate, and lower soil nutrients with poor litter quality. The effects of soil fertility on litter decomposition rate varied with environmental conditions. It was reported that litter quality regulates the early stage of carbon decomposition and its accumulation in soil, however, it could not predict the long-term dynamics of soil organic carbon. Hence, the formation and stabilization of soil organic carbon are controlled by the quantity of litter input and its interaction with the soil circumstances rather than by the litter quality. The present paper reviewed the research findings about litter decomposition related to litter substrate quality and soil nutrients, including short-term and long-term litter decomposition, decomposition of single-species vs. mixed-litter decomposition and litter nutrients release. The present paper aimed to clarify the relationship between soil nutrients and litter decomposition, which will help to understand forest succession, forest water conservation and soil re-production capacity.

Litter quality impacts short- but not long-term soil carbon dynamics in soil aggregate fractions

Complex molecules are presumed to be preferentially stabilized as soil organic carbon (SOC) based on the generally accepted concept that the chemical composition of litter is a major factor in its rate of decomposition. Hence, a direct link between litter quality and SOC quantity has been assumed, accepted, and ultimately incorporated in SOC models. Here, however, we present data from an incubation and field experiment that refutes the influence of litter quality on the quantity of stabilized SOC. Three different qualities of litter (Tithonia diversifolia, Calliandra calothyrsus, and Zea mays stover; 4 Mg C x ha(-1) yr(-1)) with and without the addition of mineral N fertilizer (0 or 120 kg N x ha(-1)season(-1) were added to a red clay Humic Nitisol in a 3-yr field trial and a 1.5-yr incubation experiment. The litters differed in their concentrations of N, lignin, and polyphenols with the ratio of (lignin + polyphenols): N ranging from 3.5 to 9.8 for the field trial and from 2.3 to 4.0 for the incubation experiment in the order of T. diversifolia < C. calothyrsus < or = Z. mays. Litter quality did not affect the amount of SOC stabilized after three annual additions in the field trial. Even within the most sensitive soil aggregate fractions, SOC contents and C:N ratios did not differ with litter quality, indicating that litter quality did not influence the mechanisms by which SOC was stabilized. While increasing litter quality displayed faster decomposition and incorporation of C into soil aggregates after 0.25 yr in the incubation study, all litters resulted in equivalent amounts of C stabilized in the soil after 1.5 yr, further corroborating the results of the field trial. The addition of N fertilizer did not affect SOC stabilization in either the field or the incubation trial. Thus, we conclude that, while litter quality controls shorter-term dynamics of C decomposition and accumulation in the soil, longer-term SOC patterns cannot be predicted based on initial litter quality effects. Hence, the formation and stabilization of SOC is more controlled by the quantity of litter input and its interaction with the soil matrix than by litter quality.

Lantana invasion alters soil nitrogen pools and processes in the tropical dry deciduous forest of India

Invasive species can alter the soil nutrient pools and processes in ecosystems that they invade by altering the quality and quantity of litter inputs. Studies have shown the impact of vegetative understory invasions on soil nitrogen (N) availability in forest ecosystems. In the dry deciduous Vindhyan forest of India we studied the effect of one of the world's most noxious weeds, lantana ( Lantana camara L.) on soil N availability and N-mineralization beneath the forest canopy and lantana canopy. We observed that the lantana litter inputs increase with increasing lantana cover and the chemical composition of lantana litter was also very much different from the native forest species litter. High N, low lignin content of the lantana litter and favorable microclimate beneath lantana canopy favored faster decomposition and release of N. This alteration in litter inputs and chemistry beneath the lantana canopy positively and significantly altered soil N availability, N-mineralization, and total soil N. The results imply that a positive feed back nutrient cycle might exist beneath the lantana canopy which may favor its growth (cover) by increasing the nutrients beneath its canopy.

Galling by Rhopalomyia solidaginis alters Solidago altissima architecture and litter nutrient dynamics in an old-field ecosystem

Plant–insect interactions can alter ecosystem processes, especially if the insects modify plant architecture, quality, or the quantity of leaf litter inputs. In this study, we investigated the interactions between the rosette gall midge Rhopalomyia solidaginis and tall goldenrod, Solidago altissima, to quantify the degree to which the midge alters plant architecture and how the galls affect rates of litter decomposition and nutrient release in an old-field ecosystem. R. solidaginis commonly leads to the formation of a distinct apical rosette gall on S. altissima and approximately 15% of the ramets in a S. altissima patch were galled (range: 3–34%). Aboveground biomass of galled ramets was 60% higher and the leaf area density was four times greater on galled leaf tissue relative to the portions of the plant that were not affected by the gall. Overall decomposition rate constants did not differ between galled and ungalled leaf litter. However, leaf-litter mass loss was lower in galled litter relative to ungalled litter, which was likely driven by modest differences in initial litter chemistry; this effect diminished after 12 weeks of decomposition in the field. The proportion of N remaining was always higher in galled litter than in ungalled litter at each collection date indicating differential release of nitrogen in galled leaf litter. Several studies have shown that plant–insect interactions on woody species can alter ecosystem processes by affecting the quality or quantity of litter inputs. Our results illustrate how plant–insect interactions in an herbaceous species can affect ecosystem processes by altering the quality and quantity of litter inputs. Given that S. altissima dominates fields and that R. solidaginis galls are highly abundant throughout eastern North America, these interactions are likely to be important for both the structure and function of old-field ecosystems.

Quantity of Standing Litter: A Driving Factor of Root Dynamics

Current understanding of carbon cycling in terrestrial ecosystem views “quantity” of litter input as a parameter determining the size of soil C pools and soil respired CO2: quantity of litter input is not considered a driving factor affecting the patterns of terrestrial ecosystem processes. Emma J. Sayer and collaborators demonstrated that this may not be the case! With a neat and elegant, for its simplicity, manipulation experiment, Sayer et al. (this issue) showed how increasing input of leaf litter affects the patterns of root distribution along the soil profile, in a relatively nutrient rich tropical soil. In their study, roots responded rapidly to changes in fresh leaf litter input and appeared to closely follow the patterns of litter decomposition. Until this study, root exploitation of standing litter was seen solely as an adaptation to nutrient shortage in the mineral soil. Feedback processes between leaf litterfall, decomposition and root dynamics are envisaged. With global climate change likely to alter plant productivity and litterfall, similar feedbacks, if confirmed, will need to be included in terrestrial ecosystem C modelling.