Quantification of the effects of management factors on maize (Zea mays L.) and cotton(Gossypium hirsutum L.) residues decomposition rate

Efforts to quantify management effects on decomposition rate of added substrates to the soil is important especially where such information is to be used for prediction in mathematical or simulation models. Using data from a short term (60 days) greenhouse simulation study, a procedure for quantifying effects of management on SOM and substrate decomposition is presented. Using microbial growth rate u (q), microbial efficiency in substrate utilization e (q), specific decomposition rates for added plant residues to two contrasting soils, red earth (Ferrasol) and black earth (Acrisol) were estimated. The treatments included straw addition + buried, (T1); straw addition + mineral N (T2); and straw addition + tillage, (T3). Sampling was done every 15 days. Straw decomposition rate was affected by external mineral N sources (Urea 46% N). Addition of an external N source significantly increased decomposition rates. The study could not, however, fully account for the effect of tillage on residues because of the limited effect of the tillage method due to the artificial barrier to mechanical interference supplied by the mesh bags. It is concluded that using few decomposer parameters, decomposition rates and consequently SOM trends in a soil system can be monitored and quantification of the influence of perturbations on decomposition rate of added substrates possible.

Grass Litter Decomposition Rate and Water-Holding Capacity in Dry-Hot Valley of Jinshajiang River

The decomposition rate and the water-holding capacity of 6 kinds of grass litters were studied in the Jinshajiang river dry-hot valley. The results showed that the dry weight remains reduced with time but did not have a direct correlation with time. The decomposition litters were affected by climate, character of litter, animalcule and soil animal. The climate factors of temperature and humidity were important especially. The water-holding capacity was in the sequence ofN. wightii （336%）, P. notatum Flugge （248%）, H. contortus （L.） Beauv （209%）, B. pertusa （L.） A. Camus（206%）, L endecaphylla Jacq （174%）, D. annulatum （Forsk.） Stapf （168%）. After 24 months decomposition the remaining dry weight of the litter was in the sequence as follows： 15.12% for N. wightii, 26.38% for I. endecaphylla Jacq, 27.23% for B. pertusa （L.） A. Camus, 30.78% for P. notatum Flugge, 39.72% for H. contortus （L.） Beauv and 39.76% for D. annulatum （Forsk.） Stapf. The decomposition rate and water-holding capacity ofN. wightii are at the highest level. It is important for the development, improvement and conservation of the grassland soil.

A growth kinetics model of rate decomposition for Si_(1-x)Ge_x alloy based on dimer theory

According to the dimer theory on semiconductor surface and chemical vapor deposition（CVD） growth characteristics of Sil_xGex, two mechanisms of rate decomposition and discrete flow density are proposed. Based on these two mech- anisms, the Grove theory and Fick＇s first law, a CVD growth kinetics model of Sil-xGex alloy is established. In order to make the model more accurate, two growth control mechanisms of vapor transport and surface reaction are taken into account. The paper also considers the influence of the dimer structure on the growth rate. The results show that the model calcuated valne is consistent with the experimental vahles at different ternnerntllres.

Contrasting effects of nitrogen addition on litter decomposition in forests and grasslands in China

Nitrogen(N)addition has profound impacts on litter-mediated nutrient cycling.Numerous studies have reported different effects of N addition on litter decomposition,exhibiting positive,negative,or neutral effects.Previous meta-analysis of litter decomposition under N addition was mainly based on a small number of samples to allow comparisons among ecosystem types.This study presents the results of a meta-analysis incorporating data from 53 published studies(including 617 observations)across forests,grasslands,wetlands,and croplands in China,to investigate how environmental and experimental factors impact the effects of N addition on litter decomposition.Averaged across all of the studies,N addition significantly slows litter decomposition by 7.02%.Considering ecosystem types,N addition significantly accelerates litter decomposition by 3.70%and 11.22%in grasslands and wetlands,respectively,clearly inhibits litter decomposition by 14.53%in forests,and has no significant effects on litter decomposition in croplands.Regarding the accelerated litter decomposition rate in grasslands due to N addition,litter decomposition rate increases slightly with increasing rates of N addition.However,N addition slows litter decomposition in forests,but litter decomposition is at a significantly increasing rate with increasing amounts of N addition.The responses of litter decomposition to N addition are also influenced by the forms of N addition,experiential duration of N addition,humidity index,litter quality,and soil pH.In summary,N addition alters litter decomposition rate,but the direction and magnitude of the response are affected by the forms of N addition,the rate of N addition,ambient N deposition,experimental duration,and climate factors.Our study highlights the contrasting effects of N addition on litter decomposition in forests and grasslands.This finding could be used in biogeochemical models to better evaluate ecosystem carbon cycling under increasing N deposition due to the differential responses of litter decomposition to N addition rates and ecosystem types.

Catalytic decomposition and mass transfer of aqueous ozone promoted by Fe-Mn-Cu/γ-Al2O_(3) in a rotating packed bed

This study investigated catalytic decomposition and mass transfer of aqueous ozone promoted by Fe-MnCu/γ-Al_(2)O_(3)(Cat)in a rotating packed bed(RPB)for the first time.The results showed that the value of the overall decomposition rate constant of ozone(K_(c))and overall volumetric mass transfer coefficient(K_(L)a)are 4.28×10^(-3) s^(-1) and 11.60×10^(-3) s^(-1) respectively at an initial pH of 6,βof 40,Co3(g)of 60 mg·L^(-1)and Q_(L) of 85 L·h^(-1) in deionized water,respectively.Meanwhile,the K_(c) and K_(L)a values of Fenhe water are0.88×10^(-3) s^(-1) and 2.51×10^(-3) s^(-1) lower than deionized water,respectively.In addition,the K_(c) and K_(L)a values in deionized water for the Cat/O_(3)-RPB system are 44.86%and 47.41%higher than that for the Cat/O_(3)-BR(bubbling reactor)system,respectively,indicating that the high gravity technology can facilitate the decomposition and mass transfer of ozone in heterogeneous catalytic ozonation and provide some insights into the industrial wastewater.

Litter production, decomposition and nutrient mineralization dynamics of Ochlandra setigera: A rare bamboo species of Nilgiri Biosphere Reserve, India

Litter production, decomposition and nutrient release dynam-ics of Ochlandra setigera, a rare endemic bamboo species of Nilgiri biosphere were studied during 2011-2012 using the standard litter bag technique. Annual litter production was 1.981 t？ha-1 and was continuous throughout the year with monthly variations. Litterfall followed a tri-phasic pattern with two major peaks in November, 2011 and January, 2012 and a minor peak in July, 2011. The rate of decomposition in O. setigera was a good fit to the exponential decay model of Olson （1963）. Litter quality and climatic conditions of the study site （maximum tem-perature, monthly rainfall and relative humidity） influenced the rate of decomposition. Nutrient release from the decomposing litter mass was in rank order N=Mg＆gt;K=Ca＆gt;P. Nutrient release from litter was con-tinuous and it was in synchrony with growth of new culms. Study of litter dynamics is needed before introduction of a bamboo species into degraded or marginal lands or Agroforestry systems.

Dependency of litter decomposition on litter quality,climate change,and grassland type in the alpine grassland of Tianshan Mountains,Northwest China

Litter decomposition is an important component of the nutrient recycling process and is highly sensitive to climate change.However,the impacts of warming and increased precipitation on litter decomposition have not been well studied,especially in the alpine grassland of Tianshan Mountains.We conducted a manipulative warming and increased precipitation experiment combined with different grassland types to examine the impact of litter quality and climate change on the litter decomposition rate based on three dominant species(Astragalus mongholicus,Potentilla anserina,and Festuca ovina)in Tianshan Mountains from 2019 to 2021.The results of this study indicated there were significant differences in litter quality,specific leaf area,and leaf dry matter content.In addition,litter quality exerted significant effects on litter decomposition,and the litter decomposition rate varied in different grassland types.Increased precipitation significantly accelerated the litter decomposition of P.anserina;however,it had no significant effect on the litter decomposition of A.mongholicus and F.ovina.However,warming consistently decreased the litter decomposition rate,with the strongest impact on the litter decomposition of F.ovina.There was a significant interaction between increased precipitation and litter type,but there was no significant interaction between warming and litter type.These results indicated that warming and increased precipitation significantly influenced litter decomposition;however,the strength was dependent on litter quality.In addition,soil water content played a crucial role in regulating litter decomposition in different grassland types.Moreover,we found that the litter decomposition rate exhibited a hump-shaped or linear response to the increase of soil water content.Our study emphasizes that ongoing climate change significantly altered litter decomposition in the alpine grassland,which is of great significance for understanding the nutrient supply and turnover of litter.

Medium and Long Term Decomposition Process of Litter in Abies Fabri Forest

Litter is an important part of forest ecosystem and its decomposition process is the key link of nutrient cycling in forest ecosystem.Accurate determination of litter decomposition dynamics is very important to study the pattern and process of forest ecosystem.This paper selected The Gongga Mountain Alpine Ecosystem Observation and Experiment Station at an altitude of 3000 m to observe and determine litter decomposition process of the Abies fabri forest over a long period of time.The results showed that:①The decomposition rate of litter was broadleaf>needles>dead branches,and the time required to decompose half of broadleaf,needles and dead branches was 6.8 years,10.5 years and 14.5 years respectively;the time of decompose 95%of them was 29.3 years,45.6 years and 63.1 years,respectively;②Regardless of broadleaf,needles or dead branches,the organic carbon content of them decreased with time,while the decomposition rate of organic carbon increased with time;By using the exponential decay model the decomposition coefficient of litter organic carbon calculated was broadleaf>needle>dead branches;③The organic carbon released by the annual decomposition of broadleaf,needles and dead branches in Abies fabri forest was 52.18,4.32 and 0.67 kg/hm^2,respectively.The total amount of organic carbon released by various litter was 61.13 kg/hm^2 per year,accounting for 6.58%of the total organic carbon of litter.

Rates of litter decomposition in terrestrial ecosystems:global patterns and controlling factors

Aims We aim to construct a comprehensive global database of litter decomposition rate(k value)estimated by surface floor litterbags,and investigate the direct and indirect effects of impact factors such as geographic factors(latitude and altitude),climatic factors(mean annual tempePlrature,MAT;mean annual precipitation,MAP)and litter quality factors(the contents of N,P,K,Ca,Mg and C:N ratio,lignin:N ratio)on litter decomposition.Methods We compiled a large data set of litter decomposition rates(k values)from 110 research sites and conducted simple,multiple regression and path analyses to explore the relationship between the k values and impact factors at the global scale.Important findings The k values tended to decrease with latitude(LAT)and lignin content(LIGN)of litter but increased with temperature,precipitation and nutrient concentrations at the large spatial scale.Single factor such as climate,litter quality and geographic variable could not explain litter decomposition rates well.However,the combination of total nutrient(TN)elements and C:N accounted for 70.2%of the variation in the litter decomposition rates.The combination of LAT,MAT,C:N and TN accounted for 87.54%of the variation in the litter decomposition rates.These results indicate that litter quality is the most important direct regulator of litter decomposition at the global scale.This data synthesis revealed significant relationships between litter decomposition rates and the combination of climatic factor(MAT)and litter quality(C:N,TN).The global-scale empirical relationships developed here are useful for a better understanding and modeling of the effects of litter quality and climatic factors on litter decomposition rates.

Soil carbon budget in different-aged Chinese fir plantations in south China

Understanding the age effect on soil carbon balance in forest ecosystems is important for other material cycles and forest man-agement. In this research we investigated soil organic carbon density, litter production, litter decomposition rate, soil respiration, and soil mi-crobial properties in a chronosequence of four Chinese fir plantations of 7, 16, 23 and 29 years at Dagangshan mountain range, Jiangxi Province, south China. There was a significant increasing trend in litter production with increasing plantation age. Litter decomposition rate and soil respira-tion, however, declined from the 7-year to the 16-year plantation, and then increased after 16 years. This was largely dependent on soil micro-organisms. Soil carbon output was higher than carbon input before 16 years, and total soil carbon stock declined from 35.98 t＆#183;ha-1 in the 7-year plantation to 30.12 t＆#183;ha-1 in the 16-year plantation. Greater litter produc-tion could not explain the greater soil carbon stock, suggesting that forest growth impacted this microbial process that controlled rates of soil car-bon balance together with litter and soil respiration. The results highlight＆amp;nbsp;the importance of the development stage in assessing soil carbon budget and its significance to future management of Chinese fir plantations.

Litterfall dynamics and soil carbon and nitrogen stocks in the Brazilian palm swamp ecosystems

Background: This study aimed to determine the litterfall production, accumulation, decomposition rate and nutrient stocks, and to estimate the soil carbon(C) and nitrogen(N) stocks in three palm swamp ecosystems with different land use intensities in the Southeast of Brazil.Methods: Three palm swamp ecosystems with different land use intensities were evaluated: Agua Doce(AD),conserved area;Capivara(CV), area with small agricultural practices;and Buriti Grosso(BG), area with an intensive land use. Produced and accumulated litterfall from the Cerrado areas surrounding the palm swamps were collected from October 2014 to September 2015, and the Ca, Mg, K, and P concentrations were determined in the dry and rainy seasons. Soil samples were collected in the surrounding Cerrado and within the palm swamps until 100 cm soil depth to determine bulk density and soil C and N contents and stocks.Results: Annual litterfall production in the Cerrado surrounding palm swamps was similar in AD(3.58 Mg·ha^-1·year^-1) and CV(3.79 Mg·ha^-1·year^-1), and was lower in BG(2.84 Mg·ha^-1·year^-1), and was more intense during the dry season. Furthermore, litterfall accumulation was higher in CV(7.12 Mg·ha^-1·year^-1) and BG(6.75 Mg·ha^-1·year^-1), culminating in lower decomposition rates. AD showed the highest decomposition rate(0.60) due to its vegetation structure and conservation. The macronutrient contents from the production and accumulated litterfall had a low influence of the land use, decreasing in the following order: Ca > K > Mg > P. Soils in CV and BG palm swamp areas showed higher values of C and N contents, due to the use of land for agricultural crops and cattle raising in an extensive(rangeland) system. The BG palm swamp, showed the highest C(124.03 Mg·ha^-1) and N(10.54 Mg·ha^-1) stocks due to the land use history with different agricultural practices over time.Conclusions: The litterfall dynamics in the Cerrado surrounding palm swamps was more affected by climatic variables than the intensity of land use, but the litter decomposition was more accelerated in the conserved area.Anthropic interventions with soil organic matter(SOM) inputs contributed to an increase in soil C and N stocks in the palm swamp ecosystems.

Decomposition of Phragmites australis rhizomes in artificial land-water transitional zones （ALWTZs） and management implications

Rhizomes are essential organs for growth and expansion of Phragmites australis. They function as an important source of organic matter and as a nutrient source, especially in the artificial land-water transitional zones （ALWTZs） of shallow lakes. In this study, decomposition experiments on 1- to 6-year-old R australis rhizomes were conducted in the ALWTZ of Lake Baiyangdian to evaluate the contribution of the rhizomes to organic matter accumulation and nutrient release. Mass loss and changes in nutrient content were measured after 3, 7, 15, 30, 60, 90, 120, and 180 days. The decomposition process was modeled with a composite exponential model. The Pearson correlation analysis was used to analyze the relationships between mass loss and litter quality factors. A multiple stepwise regression model was utilized to determine the dominant factors that affect mass loss. Results showed that the decomposition rates in water were significantly higher than those in soil for 1- to 6-year-old rhizomes. However, the sequence of decomposition rates was identical in both water and soil. Significant relationships between mass loss and litter quality factors were observed at a later stage, and P-related factors proved to have a more significant impact than N-related factors on mass loss. According to multiple stepwise models, the C/P ratio was found to be the dominant factor affecting the mass loss in water, and the C/N and C/P ratios were the main factors affecting the mass loss in soil. The combined effects of harvesting, ditch broadening, and control of water depth should be considered for lake administrators.

Larger floods reduce soil CO_(2)efflux during the post-flooding phase in seasonally flooded forests of Western Amazonia

Seasonally flooded várzea forests of Western Amazonia are one of the most productive and biodiverse wetland forests in the world.However,data on their soil CO_(2)emissions,soil organic matter decomposition rates,and soil C stocks are scarce.This is a concern because hydrological changes are predicted to lead to increases in the height,extent,and duration of seasonal floods,which are likely to have a significant effect on soil C stocks and fluxes.However,with no empirical data,the impact of altered flood regimes on várzea soil C cycles remains uncertain.This study quantified the effects of maximum annual flood height and soil moisture on soil CO_(2)efflux rate(R_(s))and soil organic matter decomposition rate(k)in the várzea forests of Pacaya Samiria National Reserve,Peru.The study was conducted between May and August 2017.The results showed that R_(s)(10.6–182.7 mg C m^(-2)h^(-1))and k(0.016–0.078)varied between and within sites,and were considerably lower than the values reported for other tropical forests.In addition,R_(s)was negatively affected by flood height(P<0.01)and soil moisture(P<0.001),and it decreased with decreasing river levels post flooding(P<0.001).In contrast,k was not affected by any of the above-mentioned factors.Soil moisture was the dominant factor influencing R_(s),and it was significantly affected by maximum flood height,even after the floods had subsided(P<0.001).Consequently,we concluded that larger floods will likely lead to reduced R_(s),whilst k could remain unchanged but with decomposition processes becoming more anaerobic.

The Impacts of the Growth of the Three Industries and Industrial Price Structural Changes on China’s Economic Growth between 1952 and 2019

This paper focuses on the impacts and effects of China’s growth of the three industries and price structural change on the real GDP growth rate.First of all,it presents a new accounting method for decomposing growth rates on the basis of existing accounting method for decomposing growth rates.By using this method,we can identify the impacts and effects of structural changes on the growth rate.The paper uses a new decomposition method to recalculate China’s industry-based real GDP growth rates between 1952 and 2019,focuses on the driving effect of growth of the three industries on the real GDP growth,and the impacts of price structural change on GDP growth rate and the contributin of the growth of the three industries on GDP growth rate.By analysis,this paper shows that between 1952 and 2019 China’s economic growth was mainly driven by the secondary industry,which had contributed to the economic growth by over 50%,the role of the tertiary industry in driving economic growth rose,but that of the secondary industry declined over the time;in the short run,the overall effect of the price structural changes of the three industries has a little impact on the economic growth,but the price change of each industry has strong effects,and the price structural change has signifi cantly changed the effect of the growth of the three industries on the real economic growth;in the long term,the price structural change plays a relatively big hindering effect on economic growth due to the Baumol’s cost disease.