Photodegradation and Its Effect on Plant Litter Decomposition in Terrestrial Ecosystems: A Systematic Review

Photodegradation is an important mechanism that affects carbon and nutrient cycling; a significant amount of data has been reported previously. The present review includes the effect of a wider spectrum of solar radiation (sun light, UV, and visible light) on plant litter decay in terrestrial ecosystems. Although the positive effect of photodegradation on decomposition is most common, a substantial number of studies reports contrasting results. Litter from 148 plant species, from 41 families, have been used in photodegradation studies, representing functional groups of trees (33%), graminoids (30%), shrubs (23%), forbs (11%), and peat (1%). Although the majority of studies focused on mass loss, a growing number focuses on nutrient release. Positive effects on mass loss are most common across different climate regions and laboratory studies, whereas “positive” influence and “no effect” on nitrogen and lignin release are equally common in temperate and sub-tropical environments. This may potentially be due to other decomposition processes which increase in relevance with increasing moisture and can facilitate microbial activity, leaching, and fractioning by soil fauna. In addition to climate region, initial litter quality influences photodegradation. Field-based and laboratory experiments frequently obtain contrasting results, suggesting that the mechanisms controlling the responses are unclear and might be dependent on several interactions, and/or the differences in experimental approaches (such as UV filters), or coverage by particles. Future research should focus on interactions between different factors, and on conducting experiments that test specific relationships such as the potential interaction between photodegradation, soil moisture, microbial communities, soil fauna, and their effects on litter decomposition (both mass loss and nutrient release). Furthermore, the topic would benefit from international studies applying the same experimental approach, as has successfully been conducted in other fields.This research was funded by [Qatar Petroleum] grant number [QUEX-CAS-QP-RD-18/19]

Reading tea leaves worldwide: Decoupled drivers of initial litter decomposition mass‐loss rate and stabilization

The breakdown of plant material fuels soil functioning and biodiversity. Currently, process understanding of global decomposition patterns and the drivers of such patterns are hampered by the lack of coherent large-scale datasets. We buried 36,000 individual litterbags (tea bags) worldwide and found an overall negative correlation between initial mass-loss rates and stabilization factors of plant-derived carbon, using the Tea Bag Index (TBI). The stabilization factor quantifies the degree to which easy-to-degrade components accumulate during early-stage decomposition (e.g. by environmental limitations). However, agriculture and an interaction between moisture and temperature led to a decoupling between initial mass-loss rates and stabilization, notably in colder locations. Using TBI improved mass-loss estimates of natural litter compared to models that ignored stabilization. Ignoring the transformation of dead plant material to more recalcitrant substances during early-stage decomposition, and the environmental control of this transformation, could overestimate carbon losses during early decomposition in carbon cycle models

Reading tea leaves worldwide: decoupled drivers of initial litter decomposition mass-loss rate and stabilisation

The breakdown of plant material fuels soil functioning and biodiversity. Currently, process understanding of global decomposition patterns and the drivers of such patterns are hampered by the lack of coherent large-scale datasets. We buried 36,000 individual litterbags (tea bags) worldwide and found an overall negative correlation between initial mass-loss rates and stabilization factors of plant-derived carbon, using the Tea Bag Index (TBI). The stabilization factor quantifies the degree to which easy-to-degrade components accumulate during early-stage decomposition (e.g. by environmental limitations). However, agriculture and an interaction between moisture and temperature led to a decoupling between initial mass-loss rates and stabilization, notably in colder locations. Using TBI improved mass-loss estimates of natural litter compared to models that ignored stabilization. Ignoring the transformation of dead plant material to more recalcitrant substances during early-stage decomposition, and the environmental control of this transformation, could overestimate carbon losses during early decomposition in carbon cycle models

Reading tea leaves worldwide: decoupled drivers of initial litter decomposition mass‐loss rate and stabilization

The breakdown of plant material fuels soil functioning and biodiversity. Currently, process understanding of global decomposition patterns and the drivers of such patterns are hampered by the lack of coherent large‐scale datasets. We buried 36,000 individual litterbags (tea bags) worldwide and found an overall negative correlation between initial mass‐loss rates and stabilization factors of plant‐derived carbon, using the Tea Bag Index (TBI). The stabilization factor quantifies the degree to which easy‐to‐degrade components accumulate during early‐stage decomposition (e.g. by environmental limitations). However, agriculture and an interaction between moisture and temperature led to a decoupling between initial mass‐loss rates and stabilization, notably in colder locations. Using TBI improved mass‐loss estimates of natural litter compared to models that ignored stabilization. Ignoring the transformation of dead plant material to more recalcitrant substances during early‐stage decomposition, and the environmental control of this transformation, could overestimate carbon losses during early decomposition in carbon cycle models

Variation in plant litter decomposition rates across extreme dry environments in Qatar

Decomposition of plant litter is a key process for transfer of carbon and nutrients in ecosystems. Carbon contained in decaying biomass is released to the atmosphere as respired CO2, a greenhouse gas that contributes to global warming. To our knowledge, there have been no studies on litter decomposition in terrestrial ecosystems in the Arabian peninsula. Here we used commercial teabags (green tea, rooibos tea) as standard substrates to study decomposition rates across contrasting ecosystems in Qatar. Teabags were buried under and beside Acacia tortilis trees, in depressions with abundant grass vegetation, in saltmarsh without and with vegetation, under Zygophyllum qatarense in drylands, in natural mangrove and in planted mangrove. There were significant site effects across ecosystems on decomposition rate (k), litter stabilisation factor (S), final weight of green tea and final weight of rooibos tea. Mangrove and depressions with grassland had the smallest amounts of remaining green and rooibos tea after the incubation period (69-82 days), while teabags buried under A. tortilis and in saltmarsh without vegetation had the largest amounts. Thus decomposition rates differ among ecosystems in the desert environment. Further multi-year and site studies are needed to identify factors that influence decomposition rates across sites in extreme environments.The authors wish to thank Marafi Abdelhameed Dafaalla and Mariana Tavelin-Sj�berg for their assistance during laboratory work. The study was partly funded by a grant from Qatar University to JMA (grant QUUG-CAS-DBES-15/16-5). JS conducted her work within the strategic theme Sustainability, sub-theme Water, Climate, and Ecosystems, at Utrecht University and was funded by the Swedish Research Council, Vetenskapsr�det.Scopu

Diversity of arbuscular mycorrhizal fungi and its chemical drivers across dryland habitats

Qatar is largely characterized by a hyper-arid climate and low soil fertility which create a stressful soil environment for arbuscular mycorrhizal (AM) fungi. In a study of AM fungal communities and their relationship with soil chemical characteristics, we used a high-throughput sequencing technique to explore AM fungal diversity and community composition in different habitats across Qatar. We identified a total of 79 AM fungal taxa, over 77% of which were species from the Glomeraceae family. The lowest AM fungal diversity was observed in saltmarsh and in one rawdha site, while the highest richness, effective number of species, and diversity were observed in rawdha and sabkha communities. NMDS and multiple regression analyses showed that AM fungi were negatively correlated with soil pH and TC, but positively correlated with K and NO3−. AM fungi also were positively correlated with Cd, with the latter suggesting that very low levels of heavy metals may not always be harmful to AM fungi. These findings provide baseline information on AM fungal assemblages and the chemical drivers of diversity across communities in Qatar. This work partly compensates for the current lack of broad-scale studies in the Arabian Peninsula by providing understanding of overall patterns of AM fungi and their drivers in the region.- NMDS - This work was supported by a grant from Qatar Petroleum to JMA (QUEX-CAS-QP-RD-18/19)

Use of mobile learning module improves skills in chest tube insertion

Just-In-Time Learning is a concept increasingly applied to medical education, and its efficacy must be evaluated. A 3-minute video on chest tube insertion was produced. Consenting participants were assigned to either the video group, which viewed the video on an Apple® iPod Touch immediately before chest tube insertion, or the control group, which received no instruction. Every participant filled out a questionnaire regarding prior chest tube experience. A trained clinician observed participants insert a chest tube on the TraumaMan® task simulator, and assessed performance using a 14-item skills checklist. Overall, 128 healthcare trainees participated, with 50% in the video group. Participants included residents (34.4%, n = 44), medical students (32.8%, n = 42), and U.S. Army Forward Surgical Team members (32.8%, n = 42). Sixty-nine percent of all participants responded that they had never placed a chest tube, but 7% had placed more than 20. Only 25% of the participants had previously used TraumaMan®. Subjects who viewed the video scored better on the skills checklist than the control group (11.09 ± 3.09 versus 7.17 ± 3.56, P < 0.001, Cohen's D = 1.16). Medical students (9.33 ± 2.65 versus 4.52 ± 3.64, P < 0.001), Forward Surgical Team members (10.07 ± 2.52 versus 8.57 ± 3.22, P < 0.001), anesthesia residents (8.25 ± 2.56 versus 5.9 ± 2.23, P = 0.017), and subjects who had placed fewer than 10 chest tubes (9.7 ± 3 versus 6.6 ± 3.9, P < 0.001) performed significantly better with the video. The procedural animation video is an effective medium for teaching procedural skills. Embedding the video on a mobile device, and allowing trainees to access it immediately before chest tube insertion, may enhance and standardize surgical education for civilians and military personnel

Identifying Pitfalls in Chest Tube Insertion: Improving Teaching and Performance

Chest tube thoracostomies are common surgical procedures, but little is known about how practitioners learn the skill. This study evaluates the frequency with which correctly performed tasks are executed by subjects during chest tube thoracostomies. In this prospective study, we developed a mobile-learning module, containing stepwise multimedia guidance on chest tube insertion. Next, we developed and tested a 14-item checklist, modeled after key skills in the module. Participants, defined as “novice” (fewer than 10 chest tubes placed) or “expert” (10 or more placed), were assigned to either the video or control group. A trained clinician used the checklist to rate participants while they inserted a chest tube on a TraumaMan simulator. University of Miami, Miller School of Medicine, a tertiary care academic institution. Current medical students, residents, and the United States Army Forward Surgical Team members rotating through the institution. One hundred twenty-eight subjects entered and finished the study. One hundred twenty-eight subjects enrolled in the study; 86 (67%) were residents or US Army Forward Surgical Team members, 66 (77%) were novices, and 20 (23%) were experts. Novices most frequently connected the tube to suction (91%), adequately dissected the soft tissue (82%), and scrubbed or anesthetized appropriately (80%). They least frequently completed full finger sweeps (33%), avoided the neurovascular bundle (35%), and performed a controlled pleural puncture (39%). Comparing the novice video group with the novice control group, the video group was more likely to correctly perform a finger sweep (42%, p<0.001) and clamp the distal end of the chest tube (42%, p<0.001). Of all the steps, experts least frequently completed full finger sweeps (70%) and avoided the neurovascular bundle (75%). Comparing the expert video group with the expert control group, the video group was more likely to correctly perform finger sweeps, the incision, and clamping the distal chest tube (20%, p = not significant). Avoiding the neurovascular bundle, controlled pleural entry, and finger sweeps are most often performed incorrectly among novices. This information can help instructors to emphasize key didactic steps, possibly easing trainees' learning curve