TeaTime4Schools: Using Data Mining Techniques to Model Litter Decomposition in Austrian Urban School Soils

Aims Grazing intensity and grazing exclusion affect ecosystem carbon cycling by changing the plant community and soil micro-environment in grassland ecosystems. The aims of this study were: 1) to determine the effects of grazing intensity and grazing exclusion on litter decomposition in the temperate grasslands of Nei Mongol; 2) to compare the difference between above-ground and below-ground litter decomposition; 3) to identify the effects of precipitation on litter production and decomposition. Methods We measured litter production, quality, decomposition rates and soil nutrient contents during the growing season in 2011 and 2012 in four plots, i.e. light grazing, heavy grazing, light grazing exclusion and heavy grazing exclusion. Quadrate surveys and litter bags were used to measure litter production and decomposition rates. All data were analyzed with ANOVA and Pearson’s correlation procedures in SPSS. Important findings Litter production and decomposition rates differed greatly among four plots. During the two years of our study, above-ground litter production and decomposition in heavy-grazing plots were faster than those in light-grazing plots. In the dry year, below-ground litter production and decomposition in light-grazing plots were faster than those in heavy-grazing plots, which is opposite to the findings in the wet year. Short-term grazing exclusion could promote litter production, and the exclusion of light-grazing could increase litter decomposition and nutrient cycling. In contrast, heavy-grazing exclusion decreased litter decomposition. Thus, grazing exclusion is beneficial to the restoration of the light-grazing grasslands, and more human management measures 杨丽丽等: 内蒙古温带草原不同放牧强度和围栏封育对凋落物分解的影响 749 doi: 10.17521/cjpe.2016.0051 are needed during the restoration of heavy-grazing grasslands. Precipitation increased litter production and decomposition, and below-ground litter was more vulnerable to the inter-annual change of precipitation than above-ground litter. Compared to the light-grazing grasslands, heavy-grazing grasslands had higher sensitivity to precipitation. The above-ground litter decomposition was strongly positively correlated with the litter N content (R = 0.489, p < 0.01) and strongly negatively correlated with the soil total N content (R = 0.450, p < 0.01), but it was not significantly correlated with C:N and lignin:N. Below-ground litter decomposition was negatively correlated with the litter C (R = 0.263, p < 0.01), C:N (R = 0.349, p < 0.01) and cellulose content (R = 0.460, p < 0.01). Our results will provide a theoretical basis for ecosystem restoration and the research of carbon cycling.

Mountainous areas exhibit highly variable decomposition rates as a result of strong local differences in climate and vegetation type. This paper describes the effect of these factors on two major determinants of the local carbon cycle: litter decomposition and carbon stabilization. In order to adequately reflect local heterogeneity, we have sampled 12 typical plant communities of the Russian Caucasus. In order to minimize confounding effects and encourage comparative studies, we have adapted the widely used tea bag index (TBI) that is typically used in areas with low decomposition. By incubating standardized tea litter for a year, we investigated whether (1) initial litter decomposition rate (k) is negatively correlated with litter stabilization (S) and (2) whether k or S exhibit correlations with altitude and other environmental conditions. Our results show that S and k are not correlated. Altitude, pH, and water content significantly influenced the stabilization factor S, while soil-freezing had no influence. In contrast, none of these factors predicted the decomposition rate k. Based on our data, we argue that collection of decomposition rates alone, as is now common practice, is not sufficient to understand carbon input to soils and can potentially lead to misleading results. Our data on community-specific decomposition and stabilization rates further constrain estimates of litter accumulation in subalpine communities and the potential effects of climate change.

Long-term impact of an extreme wildfire and salvage logging legacies on ecosystem services provision: Decomposition and nutrient cycling in fire-prone Mediterranean pine forests

The decomposition of the litter changes its indicators under the influence of climatic changes. Taking into account the impact of this process on the global carbon cycle, the decomposition process is a feedback affecting future climate change. The special role of the litter decomposition process in the overall carbon cycle on a regional and global scale determines the importance of studying the regularity of the influence of climatic parameters on the rate of decomposition of forest litter. Known approaches to solving this problem are based on a probabilistic analysis of the relationship between climatic factors. It is indicated that the task of determining the relationship between temperature and soil moisture when assessing their joint impact on the decomposition rate of forest litter can be formulated in a slightly different way. From the point of view of the ecology of the forest ecosystem, the following statement of the problem is no less interesting: under what relationship of these factors can the decomposition rate reach extreme values? The author proposes a representation of the problem being solved in the form of an extreme problem, taking into account some restrictive conditions imposed on the desired function of the relationship between temperature and soil moisture. The proposed new approach to solving the problem of the influence of climatic factors such as soil temperature and humidity, which consists of calculating the conditions leading to an extremum of the decomposition rate of forest litter, allows us to determine the function of the relationship between these factors and the point at which the decomposition rate reaches a peak. The solution to the problem allowed us to calculate the optimal type of the studied relationship, at which the rate of decomposition of the forest litter reaches an extreme. The results of the study can be used in modeling the processes of the influence of climatic factors on the overall carbon cycle of the forest ecosystem

&amp;lt;p&amp;gt;With the Tea Bag Index (TBI) App, we aim to foster awareness of the importance of soils and their ecosystem services to students above the age of 10. The TBI app consists of three categories of hands-on activities: Basic soil attributes, Soil observations, and Tea Bag Index. Basic soil attributes include land use, soil colour and soil life, whereas soil observations go further to Texture by Feel, Spade Test and observation of soil pollution. The Tea Bag Index (Keuskamp et al., 2013) provides an easy and scientifically recognized way to measure decomposition rates and stabilisation of organic matter in soils. The method consists of burying tea bags and measuring the degradation of organic material after three months&amp;amp;#8217; time. Each of the methods includes clear instructions and extra information in the app. Data gathered are interactively shown on a map in the App as well as online. Hence, students are encouraged to gain hands-on science experience and to witness how science connects across regions, countries and cultures. By using playful tools such as rewards, badges and a point system, we attract and maintain the interest of students. Social media channels are used to exchange and share their results as well as to reach teachers and citizen scientists in order to inspire them to use the educational App.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Having this awareness on soil and its functions, citizen scientists can make valuable contributions to the sustainable use of soils. They also have the opportunity to participate in a global scientific initiative, acquire skills in conducting a scientific experiment and gain knowledge on soil functions. The science community, on the other hand, increases its understanding of factors influencing decomposition (and associated soil functions) at different times and in different places globally.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Moreover, the TBI App can be used for &amp;amp;#8222;Content Language Integrated Lessons&amp;amp;#8220; (CLIL), which is the use of a foreign language for the integrative teaching of content and language competence outside of language teaching in agricultural schools in Austria. Individual learning outcomes (ILOs) of an agricultural school class testing the TBI App were evaluated in an online questionnaire. Results showed high appreciation of activities offered by the TBI App and high motivation of students to contribute to science.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;&amp;amp;#160;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;&amp;amp;#160;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Keuskamp, J.A., Dingemans, B.J.J., Lehtinen, T., Sarneel, J.M. and Hefting, M.M. (2013), Tea Bag Index: a novel approach to collect uniform decomposition data across ecosystems. Methods Ecol Evol, 4: 1070-1075. doi:10.1111/2041-210X.12097&amp;lt;/p&amp;gt;

Direct and indirect pathways of land management effects on wetland plant litter decomposition

PurposeThe standardized ‘Tea Bag Index’ enables comparisons of litter decomposition rates, a key component of carbon cycling, across ecosystems. However, tea ‘litter’ may leach more than other plant litter, skewing comparisons of decomposition rates between sites with differing moisture conditions. Therefore, some researchers leach tea bags before field incubation. This decreases comparability between studies, and it is unclear if this modification is necessary.MethodsWe submerged green and rooibos tea bags in water, and measured their leaching losses over time (2 min – 72 h). We also compared leaching of tea to leaf and root litter from other plant species, and finally, compared mass loss of pre-leached and standard tea bags in a fully factorial incubation experiment differing in soil moisture (wet and dry) and soil types (sand and peat).ResultsBoth green and rooibos tea leached strongly, levelling-off at about 40% and 20% mass loss, respectively. Mass loss from leaching was highest in green tea followed by leaves of other plants, then rooibos tea, and finally roots of other plants. When incubated for 4 weeks, both teas showed lower mass loss when they had been pre-leached compared to standard tea bags. However, these differences between standard and pre-leached tea bags were similar in moist vs. dry soils, both in peat and in sand.ConclusionsThus, despite large leaching losses, we conclude that leaching tea bags before field or lab incubation is not necessary to compare decomposition rates between systems, ranging from as much as 5% to 25% soil moisture.

Soil microbial-derived litter decomposition represents an important step in the global carbon and nutrient cycling and, at the local level, is primarily driven by litter chemistry. Here, we assessed how mixed-species plantations with Eucalyptus urograndis and Acacia mangium could be a key to enhancing litter production, decomposition, and soil microbial activity. The relationships between litter decomposition and litter quality and quantity were compared among 6-year-old monocultures of E. urograndis and A. mangium (E100+N and A100, respectively) and a mixed plantation of both species (E50A50). Additionally, we evaluated soil microbial biomass carbon (MBC) and nitrogen (MBN), soil basal respiration (SBR), soil enzymes and the N mineralization potential. The return to soil of N via litterfall in E50A50 was greater than E100+N, while the return of P in E100+N and E50A50 were higher than A100. The decomposition rate in A100 was slower than in the E50A50 and E100+N. The microbial activity, represented by soil enzyme activities (proteases and N-acetyl-β-glucosaminidases), was consistently higher in E50A50 than in A100. The E50A50 presented a more balanced supply of N and P associated to a better structural quality of the litter for microbial metabolism, with synergic reflections on decomposition rates and release of nitrogen.

Interactive effects of land-use intensity, grazing and fire on decomposition of subtropical seasonal wetlands

Litter decomposition is a key driver of ecosystem processes and carbon cycling. Decomposition rate is influenced by numerous factors, such as temperature, humidity, litter properties, soil properties, and properties of soil fauna/microbial communities. The aim of this review was to summarize current knowledge on litter decomposition above the treeline in alpine regions worldwide and identify: I) factors that have been studied in great detail, II) factors that have been less intensively investigated, III) geographical regions that have been less well studied, and IV) factors with consistent or inconsistent effects on decomposition. The review showed inconsistent results for all factors covered by two or more studies regarding their effect on decomposition rate (positive, negative, no effect), usually a result of interactions between factors. Studies examining one or several factors in the physical environment (i.e., altitude, experimental warming, microclimate, snow cover and soil moisture) were most common, while studies on different aspects of resource quality were the second most common. The impacts of trophic interactions on soil microbes and fauna were less frequently studied. Europe and Asia were the best-represented regions, in terms of number of studies and geographical distribution, while there were no studies from Africa and very few from South America and Australia. North American studies were all from Colorado, and those from Asia were all from China. In order to obtain better global representation, there is a need for studies in Africa, South America, and Australia. There is also a need for more studies to explain the large variation in responses of litter decomposition rates to different influencing factors in alpine environments. Future research should focus on interactions between different factors and on experiments testing specific relationships, such as the potential interaction between temperature and soil moisture and its effect on litter decomposition above the treeline in alpine regions.

ABSTRACTLitter decomposition is a crucial biogeochemical process for C and nutrient cycling in nutrient-constrained environments, but the controlling factors on litter decomposition in an extremely arid desert region such as the Taklimakan Desert are relatively unknown. To evaluate the litter decomposition and nutrient dynamic characteristics, five primary litter types of three woody halophytes (Haloxylon ammodendron, Calligonum arborescens, and Tamarix ramosissima) along the Taklimakan Desert Highway Shelterbelt were monitored in litterbags during 420 days, when placed on the soil surface and buried by sand, respectively. The results indicated that the decomposition rate decreased in the order of assimilative branches of H. ammodendron (HA, 0.94), branches of T. ramosissima (TB, 0.55), assimilative branches of C. arborescens (CA, 0.53), seeds of C. arborescens (CS, 0.41), and old branches of H. ammodendron (HB, 0.21) in the surface placement. In contrast, the litters buried by sand displayed a significantly accelerated decomposition rate (F = 12.28, P < 0.01), which were 1.3, 1.8, 1.3, 2.3, and 2.8 times of that at surface placement for HA, TB, CA, CS, and HB, respectively. Decomposition of the litters was primarily affected by initial content of C and K, lignin and cellulose in both placements, and varied among decomposition stages and conditions. The old branches of H. ammodendron and branches of T. ramosissima presented P accumulation in both placements, whereas nutrients (N, P, K) and C showed a release pattern during the litter decomposition process, which was influenced by initial litter contents and decomposition rate.

Soils of the high mountain areas are very diverse by their organic matter content (SOM), by the factors underlying such diversity are still not fully known. In 16 subalpine, alpine and subnival plant communities of the Teberda national park (the north-western Caucasus) we studied physico-chemical and microbiological soil properties, and estimated parameters of standard material decomposition based on the Tea bag index (TBI): stabilization factor (STBI) and decomposition constant (kTBI). We tested the following hypitheses: (1) the SOM is one of predictors of STBI and kTBI in high mountain zone along with other physico-chemical soil properties; (2) the most of SOM content belongs to high STBI and low kTBI values; (3) the SOM content correlates with below-ground plant productivity. The main gradients of the studied soils are water content (automorphic vs. hydromorphic soils) and the concurrent SOM accumulation, as well as the altitudinal gradient with the decrease of soil basal respiration with elevation. The extent of nitrogen enrichment (e.g. SOM quality) of the labile fraction was the best predictor of the decomposition constant. STBI decreased with the increase of total carbon content and the losses on ignition, while the positive link between kTBI and SOM was observed only in automorphic soils. Thus, the soils rich in organic matter typically have low stabilization factor and relatively high decomposition constant. In the plant communities with herbaceous dominants, the SOM content was positively correlated with fine root production, this stresses the important role of productivity in the accumulation of organic matter.

AimsRoots contribute greatly to carbon cycling in agriculture. Measuring aboveground litter decomposition could approximate belowground turn-over if drivers of decomposition, f.e. litter traits and plant presence, influence shoot and root decomposition in a comparable manner. We tested coordination of above- and belowground litter traits and decomposition rates for six pairs of crops and closely related wild plants and studied the influence of plant presence on decomposition.MethodsAbove- and belowground traits were measured, compared and related to decomposition rates. Shoot and root litters were incubated in presence of the same plant species as the litter species (own) or in presence of two other plant species (a grass or forb).ResultsShoots decomposed 1.43–1.98 times faster than (resp.) wild plant and crop roots. Decomposition correlated negatively with litter carbon and lignin concentrations, except crop root decomposition which correlated negatively with nitrogen concentration. Unexpectedly, plant presence reduced litter decomposition, with strongest effects for root litters in presence of forbs.ConclusionsCarbon cycling might be slower than predicted solely based on shoots decomposition rates, especially in presence of growing plants. While root decomposition of wild plants can be approximated by shoot decomposition, crop shoots are a poor proxy for crop root decomposition.

Grassy ecosystems cover ~40% of the global land surface and are an integral component of the global carbon (C) cycle. Grass litter decomposes via a combination of photodegradation (which returns C to the atmosphere rapidly) and biological decomposition (a slower C pathway). As such, decomposition and C storage in grasslands may vary with climate and exposure to solar radiation. We investigated rates of grass litter decomposition in Australian temperate grasslands along a climate gradient to uncouple the relative importance of photodegradation and climate on decomposition. Litterbags containing leaf litter from two common native grass species (Poa labillardierei, Themeda triandra) were deployed at six grassland sites across a precipitation gradient (380-890 mm) in south-eastern Australia. Bags were retrieved over 39 weeks to measure mass loss from decomposition. We used shade treatments on the litter of one species (T. triandra) to partition photodegradation from biological decomposition. The shade treatment reduced the rate of decomposition of T. triandra relative to the full-sun treatment at all sites, by an average of 38% at 39 weeks; the effect size of the shade treatment was not correlated with site productivity. The rate of decomposition in both species was positively correlated with rainfall midway through the experiment, but there were no significant differences in total decomposition among sites after 39 weeks. By week 39, total decomposition of T. triandra was significantly greater than for P. labillardierei. In general, we observed relatively linear decomposition rather than the strong negative exponential decay observed in many global litter decomposition studies. Synthesis: We found that solar radiation exposure was a strong contributor to litter decomposition in temperate Australian grasslands across a broad climate gradient, which may be related to a period of photopriming prior to further biotic decomposition. This study highlights the importance of litter composition and solar radiation exposure in our understanding of how decomposition patterns contribute to global C cycling.

Grazing mediates soil microbial activity and litter decomposition in salt marshes