Approximation approach to the SRM based on root decomposition in the simulation of spatially varying ground motions

The spectral representation method （SRM） is widely used to simulate spatially varying ground motions. This study focuses on the approximation approach to the SRM based on root decomposition, which can improve the efficiency of the simulation. The accuracy of the approximation approach may be affected by three factors： matrix for decomposition, distribution of frequency interpolation nodes and elements for interpolation. The influence of these factors on the accuracy of this approach is examined and the following conclusions are drawn. The SRM based on the root decomposition of the lagged coherency matrix exhibits greater accuracy than the SRM based on the root decomposition of the cross spectral matrix. The equal energy distribution of frequency interpolation nodes proposed in this study is more effective than the counter pith with an equal spacing. Elements for interpolation do not have much of an effect on the accuracy, so interpolation of the elements of the decomposed matrix is recommended because it is less complicated from a computational efficiency perspective.

Simulation of in situ Root Decomposition of Two Barley Cultivars

Root C and root-released C are closely related to soil organic matter content and mechanistic simulation modeling has proven to be useful for studying root and soil organic C dynamics in plant-soil ecosystems. A computer model was designed in this study to simulate the dynamics of root C and root released C decomposition in situ and the dynamics of different forms of C in soil under two barley cultivars （Abee and Samson）. The results showed that on the 15th day, about 48% of the total 14C fixed in roots was respired for Abee and 42% for Samson. This indicated that the turnover rate of root ^14C of Abee was higher than that of Samson. The percentage of water-soluble organic ^14C, active microbial ^14C and stable ^14C over the total fixed ^14C were not different between two barley cultivars. From the analysis of the model for two barley cultivars, the total ~4C transformed into different soil pools （excluding CO：-C and root C pools） for the two barley cultivars was similar （26% for Abee and 25% for Samson）, but the difference of ^14C remaining in soil between the two barley cultivars was mainly because of the difference of ^14C remaining in roots which have not been yet decomposed. Some of the information which could not be measured in the laboratory conditions was obtained in this studv.

Additive effects of warming and grazing on fine-root decomposition and loss of nutrients in an alpine meadow

Fine-root decomposition is a critical process regulating ecosystem carbon cycles and affecting nutrient cycling and soil fertility.However,whether interaction between warming and grazing affects fine-root decomposition is still under-researched in natural grasslands.A two-factorial experiment with asymmetric warming(i.e.daytime vs.nighttime and growing season vs.nongrowing season)and moderate grazing(i.e.about average 50%forage utilization rate)was conducted to explore whether warming and grazing affect fine-root decomposition and loss of nutrients during a 2-year decomposition period in an alpine meadow on the Tibetan Plateau.Both warming and grazing facilitated carbon cycling through increase in fine-root decomposition,and influenced element cycling which varies among elements.The effects of warming and grazing on fine-root decomposition and loss of nutrients were additive.Both warming and grazing significantly increased cumulative percentage mass loss and total organic carbon loss of fine roots during the 2-year experiment.Only warming with grazing treatment reduced percentage nitrogen loss,whereas warming,regardless of grazing,decreased percentage phosphorus loss.Warming and grazing alone increased percentage loss of potassium,sodium,calcium and magnesium compared with control.There were no interactions between warming and grazing on fine-root decomposition and loss of nutrients.There was greater temperature sensitivity of decreased phosphorus loss than that of decreased nitrogen loss.Different temperature sensitivities of percentage loss of nutrients from fine-root decomposition would alter ratios of the available nutrients in soils,and may further affect ecosystem structure and functions in future warming.

Do root modules still exist after they die?

Background:The terminal branch orders of plant root systems are increasingly known as an ephemeral module.This concept is crucial to recognize belowground processes.However,it is unknown if root modules still exist after they die?Methods:The decomposition patterns of the first five root orders were observed for 3 years using a branch-order classification,a litter-bag method and sequential sampling in a common subalpine tree species(Picea asperata)of southwestern China.Results:Two root modules were observed during the 3-year incubation.Among the first five branch orders,the first three order roots exhibited temporal patterns of mass loss,nutrients and stoichiometry distinct from their woody mother roots throughout the experimental period.This study,for the first time,reported the decomposition pattern of each individual root order and found a similar decomposition dynamic among ephemeral root branches in a forest tree species.Conclusions:Results from this study suggest that root modules may also exist after death,while more data are needed for confirmation.The findings may further advance our understanding of architecture-associated functional heterogeneity in the fine-root system and also improve our ability to predict belowground processes.

Age-related changes in root dynamics of a novel perennial grain crop

Background:Standing root biomass stocks are larger in the perennial grain intermediate wheatgrass(IWG;Thinopyrum intermedium[Host]Barkworth and Dewey)than annual spring wheat(Triticum aestivum L.).However,previous studies have not separated root growth from root decomposition,which presents a significant gap in our understanding of how roots can contribute to soil organic carbon(C)accrual or other soil properties through time.Methods:We used paired sequential coring and root ingrowth cores to measure standing root stock,new root production,root decomposition,and decomposed root C and N from 0 to 15 cm soil depth of 1-year-old IWG(IWG-1),2-year-old IWG(IWG-2),and annual spring wheat.Results:Standing root stock was 3.2–6.5 and 6.3–9.9 times higher in IWG-1 and IWG-2 than wheat.Total root production was 1.7 times greater in IWG-1 than IWG-2.Conversely,root decomposition almost doubled from 1.39 to 2.43 kg m-3 between IWG-1 and IWG-2.Conclusions:In IWG,decreased root production and increased root decomposi-tion with stand age suggest a change in growth strategy that could reduce the contribution of root-derived C to stabilized soil C pools as IWG stands age.

Fine root litter quality regulates soil carbon storage efficiency in subtropical forest soils

●High-quality and low-quality root litter had contrasting patterns of mass loss.●Greater litter-derived C was incorporated into soils under high-quality root litter.●Root litter decay rate or litter-derived C were related to soil microbial diversity.●Root litter quality had little effect on soil physicochemical properties.●High root litter quality was the main driver of enhanced soil C storage efficiency.Decomposing root litter is a major contributor to soil carbon(C)storage in forest soils.During decomposition,the quality of root litter could play a critical role in soil C storage.However,it is unclear whether root litter quality influences soil C storage efficiency.We conducted a two-year greenhouse decomposition experiment using 13C-labeled fine root litter of two tree species to investigate how root litter quality,represented by C to nitrogen(C/N)ratios,regulates decomposition and C storage efficiency in subtropical forest soils in China.‘High-quality’root litter(C/N ratio=26)decayed faster during the first year(0−410 days),whereas‘low-quality’root litter(C/N ratio=46)decomposed faster toward the end of the two-year period(598−767 days).However,over the two years of the study,mass loss from high-quality root litter(29.14±1.42%)was lower than‘low-quality’root litter(33.01±0.54%).Nonetheless,root litter C storage efficiency(i.e.,the ratio of new root litter-derived soil C to total mineralized root litter C)was significantly greater for high-quality root litter,with twice as much litter-derived C stored in soils compared to low-quality root litter at the end of the experiment.Root litter quality likely influenced soil C storage via changes in microbial diversity,as the decomposition of high-quality litter declined with increasing bacterial diversity,whereas the amount of litter-derived soil C from low-quality litter increased with fungal diversity.Our results thus reveal that root litter quality mediates decomposition and C storage in subtropical forest soils in China and future work should consider the links between root litter quality and soil microbial diversity.

ON SOLVABLE COMPLETE LIE SUPERALGEBRAS

The authors discuss the properties of solvable complete Lie superalgebra, proving that solvable Lie superalgebras of maximal rank are complete.