Linking the Spectra of Decomposing Litter to Ecosystem Processes: Tandem Close-Range Hyperspectral Imagery and Decomposition Metrics

Efforts to monitor terrestrial decomposition dynamics at broad spatial scales are hampered by the lack of a cost-effective and scalable means to track the decomposition process. Recent advances in remote sensing have enabled the simulation of litter spectra throughout decomposition for grasses in general, yet unique decomposition pathways are hypothesized to create subtly different litter spectral signatures with unique ecosystem functional significance. The objectives of this study were to improve spectra–decomposition linkages and thereby enable the more comprehensive monitoring of ecosystem processes such as nutrient and carbon cycles. Using close-range hyperspectral imaging, litter spectra and multiple decomposition metrics were concurrently monitored in four classes of naturally decayed litter under four decomposition treatments. The first principal component accounted for approximately 94% of spectral variation in the close-range imagery and was attributed to the progression of decomposition. Decomposition-induced spectral changes were moderately correlated with the leaf carbon to nitrogen ratio (R2 = 0.52) and sodium hydroxide extractables (R2 = 0.45) but had no correlation with carbon dioxide flux. Temperature and humidity strongly influenced the decomposition process but did not influence spectral variability or the patterns of surface decomposition. The outcome of the study is that litter spectra are linked to important metrics of decomposition and thus remote sensing could be utilized to assess decomposition dynamics and the implications for nutrient recycling at broad spatial scales. A secondary study outcome is the need to resolve methodological challenges related to inducing unique decomposition pathways in a lab environment. Improving decomposition treatments that mimic real-world conditions of temperature, humidity, insolation, and the decomposer community will enable an improved understanding of the impacts of climatic change, which are expected to strongly affect microbially mediated decomposition.

Preliminary Study on Water Bodies’ Effects on the Decomposition Rate of Goldenrod Litter

Leaf-litter input constitutes a major load in natural waters; therefore, to achieve and maintain high water quality, it is important to thoroughly examine and understand the litter decomposition process. The widespread Solidago canadensis exerts a negative effect on the composition of the ecosystem, causes extinction of species, and modifies the function of the system. In Hungary, goldenrod constantly spreads to newer areas, which can also be observed around Lake Balaton and at the bank of the Hévíz canal. In our investigation, we examined the decomposition rate of the leaves and stems of the goldenrod with the commonly applied method of leaf litter bags. As water temperature, ranging from 24.0 °C to 13.7 °C, decreases in Hévíz canal away from Lake Hévíz (−0.32 °C/100 m), we chose three different sampling sites with different water temperatures along the canal to determine how water temperature influences the rate of decomposition. For both leaves and stems, the fastest decomposition rate was observed at the first site, closest to the lake. At further sites with lower water temperatures, leaf litter decomposition rates decreased. Results observed through Hévíz canal demonstrated that higher water temperature accelerated the goldenrod decomposition dynamics, while the drift also impacted its efficiency.

Pairing litter decomposition with microbial community structures using the Tea Bag Index (TBI)

Including information about soil microbial communities into global decomposition models is critical for predicting and understanding how ecosystem functions may shift in response to global change. Here we combined a standardised litter bag method for estimating decomposition rates, Tea Bag Index (TBI), with high-throughput sequencing of the microbial communities colonising the plant litter in the bags. Together with students of the Federal College for Viticulture and Fruit Growing, Klosterneuburg, Austria, acting as citizen scientists, we used this approach to investigate the diversity of prokaryotes and fungi colonising recalcitrant (rooibos) and labile (green tea) plant litter buried in three different soil types and during four seasons with the aim of (i) comparing litter decomposition [decomposition rates (k) and stabilisation factors (S)] between soil types and seasons, (ii) comparing the microbial communities colonising labile and recalcitrant plant litter between soil types and seasons (iii) correlating microbial diversity and taxa relative abundance patterns of colonisers with litter decomposition rates (k)and stabilisation factors (S). Stabilisation factor (S), but not decomposition rate (k), correlated with the season and was significantly lower in the summer. This finding highlights the necessity to include colder seasons in the efforts of determining decomposition dynamics in order to quantify nutrient cycling in soils accurately. With our approach, we further showed selective colonisation of plant litter by fungal and prokaryotic taxa sourced from the soil. The community structures of these microbial colonisers differed most profoundly between summer and winter, and rooibos litter was generally a stronger selector than green tea litter. Moreover, this study indicates an equal, if not higher, importance of fungal versus prokaryotic degraders for recalcitrant and labile plant litter decomposition. Our results collectively demonstrate the importance of analysing decomposition dynamics over multiple seasons and isolating the effect of the active component of the microbial community.

Decomposition Dynamics of Cooking-oil-soaked Paper in Media With a Low Inorganic Nitrogen Content

Many paper-related products are in daily use all over the world. Although paper is one of the most recycled materials in the European Union, no end-of-waste criteria have been defined. Typical paper and cardboard should be recycled, but paper materials with impurities, such as water, cooking oil, sand, or plastic, are much more problematic. In particular, paper polluted with cooking oil or butter (e.g., pizza boxes) is difficult waste. Composting could be a solution, but in many municipal solid waste collection systems, this waste type is collected with the mixed waste stream. Paper and cardboard contain potentially much CH4 and, in landfills, are a source of CO2 and CH4. Incineration of these materials also causes CO2 emission. The aim of this study was to investigate the degradation of cooking-oil-polluted paper in media with a low inorganic nitrogen content. Office paper usually used for printouts was used as pre-test material. Two types of paper usually used in the kitchen were used: pizza box cardboard and parchment paper highly polluted with cooking oil. Two types of low inorganic nitrogen media were tested: mature municipal waste compost (MSWC) and leaf mold. The decrease in mass of both paper sample types was correlated with process time. All tested samples—raw cellulose materials and paper with cooking oil added—were partly or completely decomposed after 6 weeks of bioprocessing without an additional dose of inorganic nitrogen.

Fauna epiedáfica associada a fragmentos florestais de Araucaria angustifolia em diferentes condições edafoclimáticas no estado do Paraná

A fauna edáfica desempenha funções ecológicas fundamentais na interface solo-serapilheira, sendo dependente das condições ambientais que está inserida. Neste sentido, este estudo objetivou avaliar a diversidade de organismos epiedáficos em fragmentos florestais de Araucaria angustifolia na região Sudoeste do Paraná sob diferentes condições edafoclimáticas. A amostragem da fauna foi realizada em três áreas com diferentes condições edafoclimáticas, em função da variação da altitude, nos municípios de Dois Vizinhos, Pato Branco e Mangueirinha, Sudoeste do PR. Instalou-se oito armadilhas de queda em cada fragmento que permaneceram a campo por um período de sete dias. Os organismos amostrados foram identificados com auxílio de lupa binocular e chaves dicotômicas de classificação. Em cada ponto de coleta também amostrou-se o solo na camada de 0-10 cm para avaliação dos atributos químicos do solo. As diferentes condições edafoclimáticas na região Sudoeste do Paraná não afetam significativamente a abundância, riqueza e a diversidade de organismos epiedáficos associados a fragmentos florestais de Araucaria angustifolia. Porém, a temperatura interferiu na dinâmica de decomposição da matéria orgânica do solo. Epiedaphic fauna associated with Araucaria angustifolia forest fragments in different edaphoclimatic conditions in the state of Paraná A B S T R A C TThe edaphic fauna plays fundamental ecological functions in the soil-litter interface, being dependent on the environmental conditions that are inserted. In this sense, this study aimed to evaluate the diversity of epiedaphic organisms in forest fragments of Araucaria angustifolia in the Southwest region of Paraná under different edaphoclimatic conditions. The fauna sampling was carried out in three areas with different edaphoclimatic conditions, depending on the altitude variation, in the municipalities of Dois Vizinhos, Pato Branco and Mangueirinha, Southwest of PR. Eight drop traps were installed in each fragment that remained in the field for a period of seven days. The sampled organisms were identified with the aid of a binocular loupe and dichotomous classification keys. At each collection point, the soil was also sampled in the 0-10 cm layer to assess the chemical attributes of the soil. The different edaphoclimatic conditions in the Southwest region of Paraná do not significantly affect the abundance, richness and diversity of epiedaphic organisms associated with forest fragments of Araucaria angustifolia. However, the temperature interfered in the decomposition dynamics of the soil organic matter.Keywords: soil biota, Atlantic Forest, invertebrates, bioindicators