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The accumulation, decomposition and ecological effect of above-ground litter in terrestrial ecosystem
Abstract
Understanding of the accumulation and decomposition processes of above-ground litter is of importance for us to study its ecological function and service in terrestrial ecosystems. The current paper first reviews the accumulation and decomposition processes of above-ground litter in terrestrial ecosystem and factors that affect these two ecological processes, then summarizes the ecological effects of above-ground litter in terrestrial ecosystem as a result of its accumulation and decomposition. Finally, under the view of global climate change, based on previous research progress, we review the perspectives of research on above-ground litter in terrestrial ecosystem. On the temporal scale, the accumulation of above-ground litter commonly follows the plant life cycle, and it is also regulated by environment factors, such as climatic conditions, soil temperature and moisture. On the large spatial scale, the accumulation of above-ground litter is primarily controlled by hydrothermal factors, resulting in the change in vegetation type, which show a decreased trend with the elevated latitude. However, on the local scale, apart from the constraints of hydrothermal factors, the accumulation of above-ground litter are also impacted by community structure, soil conditions, activities of herbivores, which shows more variability. Human disturbance is also an important factor that induces change of terrestrial vegetation cover and litter accumulation, and in many cases the changes are even irreversible. The decomposition processes of above-ground litter in terrestrial ecosystem include leaching, photo-degradation, soil animal and microbial decomposition. These decomposition processes occur simultaneously and interactively. Although still it is not well known now, distinguishing these decomposition process and fate of decomposition products with them are of importance for understanding the nutrient recycle in terrestrial ecosystem. Litter decomposition firstly is determined by its type, chemical composition, species diversity, but also affected by decomposer community and abiotic environment factors. Among these factors, the relationships between decomposition and litter chemical traits, species diversity and soil nutrient status are the key focus of this study. Through its accumulation and decomposition, above-ground litter has significant effects on terrestrial ecosystem physically, chemically and biologically. Currently, there are ample studies on the physical and chemical properties of above-ground litters, but there are very few studies on the biological property of above-ground litter, especially for the effects above-ground litters on vegetation that are still controversial as they are limited by complicated factors, including litter quantity, environment condition, the traits from impacted plants, even some unknown factors by now. Global climate change may change the accumulation and decomposition of above-ground litter and their ecological effects on the distribution, growth and traits of terrestrial plants in terrestrial ecosystem, through changes of climate and soil conditions. Under the global climate change, it is necessary to study the litter production and trait change on the spatial scales, expound the compartment model of litter decomposition on the temporal and spatial scales, deeply analyze the relationships between above-ground litter traits and decomposition, and further reveal the ecological effects of above-ground litter when relative limited factors are integrated into analysis, understand and predict the impact of above-ground litter on terrestrial ecosystem function and service under the scenario of the future environment change.
... Geographical location and climate influence not only moisture and temperature but also soil biochemical properties and litter quality (Li et al. 2014). Consequently, the limiting factors of litter decomposition and their effects (which depend greatly on the unique soil biochemical properties in a given region, especially the nutrient contents and decomposers characteristics) are altered along with the site of the research area. ...
... litters for the poor nutrient availability of these two litters (Gartner and Cardon 2004;Hattenschwiler et al. 2005). In addition, the decomposition of litter from coniferous species could lead to a decrease of soil pH (Li et al. 2014), which is an adverse condition for the decomposers. However, even if these two litter species have similar litter qualities, their influence on nutrient release were very different, which may be caused by different N/P ratios and lead to different limitations of N or P in mixed decomposition (Gusewell and Gessner 2009). ...
The productivity of Robinia pseudoacacia (R.p.) pure forest usually declines at the late growth stage, and reforming it into mixed forests could be a promising way to resolve this problem. When choosing a suitable tree species that can be mixed with R.p., the interspecific relationship is an important issue. Therefore, we gathered the autumn litter fall from R.p. and 10 other species from the Loess Plateau of China were mixed in dual species litterbags (R.p. + each other species) and buried them in soil for a 345 days lab decay incubation. We measured the litter mass loss and nutrient contents to determine whether the nutrient release was affected by mixed species litter decomposition. The impacts of mixed litter decomposition on macro-elements release were more obvious than on micro-elements. The litters with similar substrate quality might show variable impacts on nutrients release in mixed decomposition. The C loss and release of nutrient was improved by descending order when R.p. litter was mixed with Hippophae rhamnoides, Ulmus pumila, Populus simonii, Larix principis-rupprechtii and Quercus liaotungensis (Q.l.). But, except for Q.l., only the other species were recommended as suitable mix-plants for R.p. since promoting a high turnover of the nutrient in the litter compartment and a rapid availability for tree. © 2015 Northeast Forestry University and Springer-Verlag Berlin Heidelberg
... Within the same plantation, however, a decrease in BD was observed following the close-to-nature transformation. This decrease can be attributed to the formation of coarse woody debris and litter after girdling, which creates an environment that supports soil microorganisms [47]. Although photosynthetic products and water are no longer transported to the roots due to girdling, leading to the death and contraction of many fibrous roots, this results in reduced root fixation to the soil, which indirectly reduces BD [48]. ...
Girdling is a crucial technique for promoting the close-to-nature transformation of plantation forests in Hainan Tropical Rainforest National Park (HNNP). It has shown effectiveness in aspects such as community structure and biodiversity restoration. However, its impacts on ecological functions like eco-hydrology still require further in-depth investigation. This study analyzes the impact of girdling on the eco-hydrological indices of three plantations—Acacia mangium, Pinus caribaea, and Cunninghamia lanceolata—through field investigations and laboratory tests. The data was evaluated using a game theory combination weighting-cloud model. The results show that the eco-hydrological indicators of leaf litter in A. mangium increased by 5.77% while those of P. caribaea and C. lanceolata decreased by 11.86% and 5.29%, respectively. Soil bulk density decreased slightly across all plantations while total porosity increased, with A. mangium showing the highest increase of 20.31%. Organic carbon content increased by 76.81% in A. mangium and 7.24% in C. lanceolata, whereas it decreased in P. caribaea. Saturated hydraulic conductivity increased by 33.32% in P. caribaea and 20.91% in A. mangium but decreased in C. lanceolata. Based on the cloud model, the eco-hydrological function of A. mangium improved from ‘medium’ to ‘good’, while that of P. caribaea and C. lanceolata declined towards the ‘poor’ level. In summary, during the process of close-to-nature transformation of tropical rainforests, girdling is an effective method to enhance the ecohydrological functions of broadleaf planted forests. However, for coniferous species, the ecohydrological functions of the planted forests weaken in the short term following the transformation.
... The surface litter layer is the thickest in the over-mature forest, and the carbon content is the lowest. This may be because the trees in the over-mature forest grow slowly, and the accumulation rate of fallen leaves and branches is greater than the decomposition rate (Li et al., 2014). In general, the increase of forest age had a significant effect on the biomass and carbon content of shrubs and herbs, while the change of surface litter was more affected by the decomposition process. ...
Larix gmelinii is an important ecological construction tree species in northern China, and its carbon storage and distribution characteristics are of great significance for evaluating the carbon balance and climate effect of forest ecosystems. However, at present, there is a lack of systematic research on the carbon storage of L. gmelinii forests and its change with forest age. In this paper, the biomass and carbon density of L. gmelinii forests at different ages and the distribution of carbon storage in vegetation and soil were analyzed by means of sample plot investigation and model simulation in the northern forest area of Daxing’anling, Inner Mongolia. The influence of forest age on the carbon storage and carbon pool distribution characteristics of L. gmelinii forests and the mechanism of influencing factors were also discussed. Results show that: (1) As forest age increased, the total amount of carbon pools initially increased and then decreased, and the distribution structure of carbon pools showed a trend of transferring from soil to trees. The proportion of soil carbon pools gradually decreased (72.72–51.87%), while the proportion of tree carbon pools gradually increased (23.98–39.33%). The proportion of shrub and grass carbon pools was also relatively stable (0.51–0.53%). (2) Soil carbon pool was affected by the input and output of soil organic matter, soil depth, soil carbon content, and soil bulk density, shrub–grass carbon pool was affected by undergrowth light conditions and soil moisture, litter carbon pool was affected by litter input and output, and the carbon pool of trees was affected by the growth rate and carbon balance of trees. This study provides scientific basis and management suggestions for the carbon storage capacity of L. gmelinii forests and the mitigation of climate change.
... Our results are consistent with the study by Zhao et al. [33] on the litter stocks of native forest litter in the Maolan Karst. The decomposition of the surface litter layer mainly includes water leaching, photodegradation, natural fragmentation, soil animal feeding, and microbial decomposition [34]. The frequent precipitation and strong leaching in the study area led to the rapid loss and degradation of carbohydrates and water-soluble substances in the litter of the un-decomposed layer [35], while cellulose, lignin, and other substances are difficult to decompose, and accumulate in the semi-decomposed and decomposed layers, resulting in a decrease in the decomposition rate of litter, so that litter can accumulate [36]. ...
To reveal the changes on the stock of the litter layer and its nutrient storage capacity during Moso bamboo expansion in subtropical coniferous and broad-leaved forests, permanent plots were set up in the transitional zone in Wuxie National Park, Zhuji, Zhejiang, China. The plots contained conifer and broad-leaved forests (CFs), transition forests (TFs), and Moso bamboo forests (MFs), which represented three stages of the expansion of Moso bamboo to the surrounding forests. Litter samples were collected and analyzed by un-decomposed, semi-decomposed, and decomposed layers. The stock of the litter layer, the content and storage of the main nutrient elements, and their release rate were measured. It was revealed that the stock of the litter layer and each decomposition layer decreased as the bamboo expands. However, the litter decomposition rate exhibited a positive correlation with the expansion of Moso bamboo, which might be due to the change in the physical properties of the litter. Meanwhile, there were no significant differences in the un-decomposed and semi-decomposed layers of the litter contents of C, N, and P between the three forests, but the contents of C, N, and P in the decomposed layer gradually decreased with the expansion of Moso bamboo. There were no remarkable differences in the N content, C/N, C/P, and lignin/N values of the un-decomposed layer of the three forests, indicating that the litter quality was not the principal reason affecting the decomposition rate. The total nutrient storage in the litter layer decreased significantly with the bamboo expansion, and the release rate of nutrient elements increased, which was adverse to the accumulation and storage of the nutrients. The material cycle of the original forest ecosystem is likely to deteriorate gradually with the bamboo expansion.
... Warming [14,15], affects soil organic carbon through its effect on plant growth, which alters the number of plant residues returned to the soil, the pace of organic carbon decomposition, and the amount of organic carbon released from the soil [16]. Many studies have shown that climate change can affect litter decomposition [17,18], the amount of organic carbon released from litter [19,20], and the carbon cycle of entire ecosystems [21][22][23]. Litter has a major effect on the organic carbon in soil [24,25], but few studies have examined the carbon dynamics of mixed coniferous forests in seasonal freeze-thaw areas. ...
We investigated the residual rate and mass loss rate of litter, as well as the carbon release dynamics of litter and soil across seasons, to better understand the effects of seasonal fluctuations on carbon dynamics in mixed coniferous forests. The study was carried out in natural mixed coniferous forests in the Xiaoxinganling region of Heilongjiang Province, China, and the number of temperature cycles in the unfrozen season, freeze–thaw season, frozen season, and thaw season was controlled. The goal of the study was to examine how the carbon release dynamics of litter and soil respond to the freeze–thaw process and whether there are differences in carbon release dynamics under different seasons. Repeated-measures analysis of variance was used to analyze the residual mass rate and mass loss rate of litter, litter organic carbon and soil organic carbon during the unfrozen season, freeze-thaw season, frozen season, and thaw season. Litter decomposition was highest in the unfrozen season (15.9%~20.3%), and litter and soil carbon were sequestered throughout this process. Temperature swings above and below 0°C during the freeze–thaw season cause the litter to physically fragment and hasten its decomposition. Decomposition of litter was still feasible during the frozen season, and it was at its lowest during the thaw season (7.2%~7.8%), when its organic carbon was transported to the soil. Carbon migrates from undecomposed litter to semi-decomposed litter and then to soil. The carbon in the environment is fixed in the litter (11.3%~18.2%) and soil (34.4%~36.7%) in the unfrozen season, the carbon-fixing ability of the undecomposed litter in the freeze-thaw season is better, and the carbon in the semi-decomposed litter is mostly transferred to the soil; the carbon-fixing ability of the litter in the frozen season is worse (-3.9%~ -4.3%), and the organic carbon in the litter is gradually transferred to the soil. The carbon-fixing ability of the undecomposed litter in the thaw season is stronger, and the organic carbon in the semi-decomposed litter is mostly transferred to the soil. Both litter and soil can store carbon; however, from the unfrozen season until the thaw season, carbon is transported from undecomposed litter to semi-decomposed litter and to the soil over time.
... Soil properties such as surface litter, temperature, moisture, and nutrients influence soil microbial biomass carbon (Li et al. 2014). The accumulation of litter on the soil surface regulates soil temperature and moisture, thus affecting the living environment of soil microorganisms and determining their number and activity. ...
Effects of litter return of Leymus chinensis grassland on soil microbial biomass carbon of the Songnen sandy land were investigated. Characteristics of soil microbial biomass carbon (SMBC) from subhumid area of L. chinensis grassland ecosystem at different content of litter returns (0, 200 and 400 g/m2) and soil depths (0-10, 10-20, 20-30 and 30-40 cm) were evaluated. Results showed that the content of SMBC increased with the increase in litter return at the same soil depth. The content was highest (426.17 mg/kg) at 400 g/m2 litter return, which was 1.61 and 1.50 times higher than at 0 and 200 g/m2, respectively at the depth of 0-10 cm, and decreased sharply at 10-40 cm. These results showed that increasing the amount of litter return and suitable management measures can effectively enhance the carbon content of soil microbial biomass and improve soil microbial activity and fertility to ensure the balance of grassland ecosystem. Bangladesh J. Bot. 51(4): 907-912, 2022 (December) Special
... The return of straw to the field increased the contents of nitrogen, phosphorus, potassium and other elements in the soil 19 , providing nutrients for microbes and soil fauna. In addition, straw return can further improve the soil water content, reduce the soil bulk density, increase soil permeability, and provide a variety of habitats 46 . In summary, straw return provided a beneficial environment for the survival of soil fauna. ...
Soil fauna play a crucial role in sustaining agro-ecosystem functions. Crop straw is recommended for application to agricultural fields to improve soil quality. However, the effects of crop straw combined with different synthetic fertilizers on the soil faunal community remain unclear, and knowledge regarding purple soil is limited. Using the conserved cytochrome c oxidase I (COI) gene as markers, we examined the responses of the soil faunal community to different fertilization in upland purple soil of southwestern China. The accuracy of the morphological and molecular methods in characterizing soil nematodes was compared. Our results showed that different fertilization treatments significantly changed the soil faunal community structure (Adonis test, R² = 0.43, P = 0.011). Sixteen biomarkers were identified according to LEfSe (linear discriminant analysis effect size). The diversity and species number of soil fauna were closely related to soil organic matter (SOM) and total phosphorus (TP) (P < 0.05). This study indicates that crop straw return can improve the soil fertility and diversity of soil fauna in purple soil. Additionally, the morphological approach and molecular method based on the COI gene can be considered as complementary approaches in characterizing soil nematode community.
... The return of straw to the eld increased the contents of nitrogen, phosphorus, potassium and other elements in the soil 17 , providing nutrients for microbes and soil fauna. In addition, straw return can further improve the soil water content, reduce the soil bulk density, increase soil permeability, and provide a variety of habitats 41 . In summary, straw return may provide a bene cial environment for the survival of soil fauna. ...
Soil fauna play a key role in the soil food web and is an important index to evaluate the soil environment and ecosystem. Crop straw residue is recommended for application to agricultural fields to improve soil quality. However, the effects of continuous straw return on the soil faunal community remain unclear, and knowledge regarding purple soil is limited. Using the conserved cytochrome oxidase I (COI) gene fragment of eukaryotic cells as a molecular marker, we examined the responses of the soil faunal community to eighteen-year continuous straw return in upland purple soil of southwestern China, i.e., RSDN (crop residues plus synthetic nitrogen), RSDNP (crop residues returned with nitrogen and phosphorus) and RSDNPK (crop residues returned with nitrogen, phosphorus and potassium), and treatments without straw, i.e., N (synthetic N fertilizer) and NPK (synthetic fertilizer: nitrogen, phosphorus and potassium). Soil nematodes were also examined using traditional morphological methods, and the accuracy of the morphological and molecular methods in characterizing soil nematodes was compared. Our results showed that different fertilization treatments significantly changed the soil faunal community structure (Adonis test, R2 = 0.43, p = 0.011). According to LEfSe (linear discriminant analysis effect size), Lymnaeidae, Tetragnathidae, and Pyramidulidae et al. were associated with straw return, and Coryne, Corynidae, and Anthoathecata et al. were associated with phosphate addition. Diplopoda was associated with both straw and phosphate amendments. Straw return significantly increased the Margalef richness index (D) and species number (S), which were closely related to soil organic matter (SOM) and total phosphorus (TP) (p < 0.05). Structural equation model (SEM) analysis revealed that straw and phosphorus addition promoted the diversity and species number of soil fauna by changing soil SOM and AP (available phosphorus), respectively. These results highlighted that SOM and P were important factors that changed the soil faunal community and promoted diversity. Additionally, we found that both the traditional morphological approach and molecular method based on the COI gene had biases in characterizing the soil nematode community.
... Vegetation coverage is a key bridge linking surface and underground ecological processes. It is also an intuitive reflection of global climate and hydrological changes, which play a key role in regional climate regulation, water conservation, and the global carbon cycle (Li et al. 2014). Vegetation growth is closely related to changes in regional water resources and is also an intuitive reflection of regional water resource vulnerability. ...
Water resource vulnerability in ecologically vulnerable karst areas is a key issue for regional sustainable development and the sustainable use of water resources. In this study, geographical information system (GIS) and remote sensing (RS) technology were employed to explore the vulnerability characteristics and spatial distribution of water resources in Guiyang City. The water resource vulnerability indicator in Guiyang ranged from 0.10 to 0.59, with an average value of 0.26. Yanglongsi Town, in Xifeng County, in the northern and main central urban area exhibited the highest water resource vulnerability, whereas Huaxi District in the south, and regions around Hongfeng Lake and Baihua Lake, in Qingzhen City, exhibited the lowest water resource vulnerability. Water resource vulnerability was predominantly mild, accounting for 35.85% of the total land area, followed by moderate (28.99%), with some non-vulnerable areas (13.60%) and very few extremely vulnerable areas (3.20%). Compared with traditional methods, the proposed index selection and assessment methods, based on GIS/RS, are both scientific and intuitive. In addition, the results are presented in detail, accurately reflecting the actual situation of water resource system vulnerability. HIGHLIGHTS
GIS spatial analysis technology was better in identifying the characteristics and spatial differences in water resource vulnerability than traditional assessment methods.;
The spatial distribution of water resources and water resource vulnerability in Guiyang is highly uneven.;
The water resource vulnerability index of Guiyang ranged from 0.10 to 0.59, and predominantly belonged to the mildly vulnerable category.;
... Additionally, the decomposition rate of plant litter varies among different species, partly affecting the rate of their phytolith dissolution (Li et al. 2014b). For example, herbaceous litter generally has a higher decomposition rate than litter from woody plants (Li et al. 2014a), and the phytoliths of grasses decompose more easily than those of trees (Albert et al. 2000). Sariyildiz et al. (2005) also reported that the decomposition Content courtesy of Springer Nature, terms of use apply. ...
PurposeThe karst region in southwestern China is undergoing soil erosion and rocky desertification. The different silicon (Si) fractions along the hillslopes in this mountainous region could benefit plant growth and alleviate the ecological deterioration. However, extensive distribution of carbonate rocks may lead to limited plant available Si. The mountainous terrain in karst region also leads to more Si output, which seriously affects the biogeochemical cycle of Si in this area. Yet, the soil Si fractions in the karst region have not been fully evaluated.Methods
Soil profiles and their corresponding plants were sampled from two typical karst mountains in Guizhou, China. The different fractions of non-crystalline Si in soil, accounting for the most important pool for Si availability to plants, were analyzed by the improved sequential chemical extraction and Si concentrations in plants grown in this region were also measured.ResultsThe concentration and storage of non-crystalline Si were higher at lower slopes (storage was 2.44, 2.73, and 3.25 kg·m−2 for upper, middle, and lower slopes, respectively) than other slope positions. Grasses dominated at lower slopes and contained significantly higher Si (mean ± SD: 14.42 ± 6.63 mg·g−1) than trees and shrubs (1.94 ± 1.78 and 1.29 ± 1.00 mg·g−1, respectively), which were primarily distributed on upper slopes. However, Si concentrations of the same plant species in different slope positions had no significant correlation with soil acid Na acetate–Si, the Si regarded as directly available for plants.Conclusions
This study suggests that plant species and soil properties have a significant impact on the soil Si distribution of hillslopes in karst region. Soil erosion may decrease non-crystalline Si concentrations in soils and impair Si uptake in grasses, which need to be considered in ecosystem management in this region.
... Second, E. maideni and D. viscosa are angiosperms, while P. massoniana is a gymnosperm. Litter from gymnosperms contain high contents of lignin, cellulose and secondary metabolites, leading to the slower decomposition rate of litter from gymnosperms than that from angiosperms [36], which accounted for the lower soil nutrients concentration in PDP compared to the other two plantations. Moreover, the productivity of DM was significantly lower than that of PDP and EDP, resulting in the lower consumption of soil nutrients in DM. ...
Biomass and carbon (C) distribution are suggested as strategies of plant responses to resource stress. Understanding the distribution patterns of biomass and C is the key to vegetation restoration in fragile ecosystems, however, there is limited understanding of the intraspecific biomass and C distributions of shrubs resulting from plant interactions in karst areas. In this study, three vegetation restoration types, a Dodonaea viscosa monoculture (DM), a Eucalyptus maideni and D. viscosa mixed-species plantation (EDP) and a Pinus massoniana and D. viscosa mixed-species plantation (PDP), were selected to determine the effects of plant interactions on the variations in the C distributions of D. viscosa among the three vegetation restoration types following 7 years of restoration. The results showed that: (1) plant interactions decreased the leaf biomass fraction. The interaction of P. massoniana and D. viscosa decreased the branch biomass fraction and increased the stem and root biomass fraction, but not the interaction of E. maideni and D. viscosa. Plant interactions changed the C concentrations of stems and roots rather than those of leaves and branches. (2) Plant interactions affected the soil nutrients and forest characteristics significantly. Meanwhile, the biomass distribution was affected by soil total nitrogen, clumping index and gap fraction; the C concentrations were influenced by the leaf area index and soil total phosphorus. (3) The C storage proportions of all the components correlated significantly with the proportion of biomass. Our results suggested that both the biomass distribution and C concentration of D. viscosa were affected by plant interactions, however, the biomass fraction not the C concentration determines the C storage fraction characteristics for D. viscosa.
... During the process of plant growth, the elements contained in litter will be returned to the soil after decomposition and release, where they are available for plant absorption and utilization. The quality and quantity of litter are closely related to soil fertility and are key characteristics of forest ecological system services [2][3][4][5]. Moreover, as the basic carrier of matter and energy flow, forest litter affects the capacity of carbon sink storage [6,7]. ...
Forest litter is the main contributor to soil fertility and the main carrier of circulating material and energy in forest ecosystems. Abies faxoniana (Minjiang fir) is one of the dominant species in alpine forest ecosystems. Its litter input plays important roles in soil organic matter formation and biogeochemical cycles in these ecosystems, but the annual litterfall pattern and its components remain largely unknown. To determine the litter input and nutrient return of A. faxoniana, we measured the litterfall and element (carbon (C), nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), sodium (Na), magnesium (Mg), aluminium (Al), iron (Fe), and manganese (Mn)) contents of different litter components (branches, leaves and epiphytes) from 2016 to 2020. The results showed that the annual litterfall in the A. faxoniana forest ranged from 2055.96 to 5384.15 kg·ha⁻¹·a⁻¹, and the average mass proportions of branches, leaves and epiphytes were 30.12%, 62.18% and 7.7%, respectively. The litterfall yield varied significantly with time and component; not only was the yield of litter in the nongrowing season higher than that in the growing season, but it also exhibited dramatic interannual variations. We also found that time had significant effects on the contents of all elements except for Ca in the litter. The return and input amounts of each element followed the same dynamics, which closely resembled a bimodal pattern. Moreover, there was significant interannual variability in the returned amounts of each element. The ranges of annual returns of C, N and P were 744.80~2275.12, 19.80~59.00 and 1.03~2.81 kg·ha⁻¹·a⁻¹, respectively. The ranges of annual returns of K, Ca, Na, Mg, Al, Fe and Mn were 0.91~2.00, 7.04~18.88, 0.13~0.58, 0.33~1.20, 0.55~2.29, 0.41~1.37 and 0.16~0.48 kg·ha⁻¹·a⁻¹, respectively, reflecting a seasonal double-peak pattern. These results have important implications for understanding the biogeochemical cycles and material migration processes in alpine forest ecosystems.
... However, genetic variation has an accumulating process. When accumulation reaches a certain level, the variation may affect the genetic structure, population differentiation and even species evolution of the species (Hopper and Gioia 2004;Qiang et al. 2014). Besides, founder effect, bottleneck, population subdivision and inbreeding may contribute to the observed low genetic diversity (Parisod et al. 2005), and the events require a long time of accumulate to achieve. ...
In this study, we first evaluated the genetic effects of the stock enhancement program of silver carp (Hypophthalmichthys molitrix) on wild populations in the middle Yangtze River using the sequences of the mitochondrial Cytochrome b gene and control region (D-loop). 129 cytb individuals and 135 D-loop individuals were sequenced successfully, and the results obtained by two markers were similar. T test results showed that there was no significant difference in haplotype diversity (Hd) values and nucleotide diversity (Pi) values before and after release. The exact test result of population differentiation based on haplotype frequencies was consistent with no significant change in haplotype frequency after release. Pairwise genetic differentiation index (FST) and gene flow (Nm) revealed no genetic differentiation among four populations. Results of the Bayesian clustering analysis performed with STRUCTURE and analysis of molecular variance (AMOVA) confirmed that the genetic component did not change after release. In summary, there was no significant genetic effect of broodstock enhancement of silver carp on wild populations in the middle Yangtze River.
... Bacteria can survive in the gaps which produced by fungi activities. Macromolecules organic matters translate into small molecules for crops under the common action of fungi and bacteria [21] . If oxygen is lacked in the soil, the quantity and activity of soil microorganism will decline as well as organic matters decomposition. ...
Air is squeezed out of the soil in the process of traditional irrigation. Hypoxia stress of the root zone is harmful to the yield and quality of crops. It was found that the improvement of the soil oxygen condition can increase the crop yield and quality in the root zone. In recent years, a number of studies showed that hypoxia stress has bad influence on root zone, and the ventilation technologies have some positive effects on crop yield and quality. This paper introduces and analyzes the mechanism of hypoxia stress in root zone, and provides an overview about characteristics and application on airjection irrigation. Simultaneously, the advantages and disadvantages of different airjection irrigation technologies were investigated, the achievements that have been made in this filed were summarized, and some existed problems were discussed. Based on the previous studies, the research trends of the airjection irrigation technology were proposed, which can provide a reference for the further research in the research field.
Addition of organic wastes such as animal manures and straw is a feasible practice to alleviate soil degradation, and the mitigation is closely related to the activities of soil-dwelling fauna. In this study, the community structure of soil fauna were compared under four treatment regimes: straw only, and straw combined with the use of chicken manure, ox manure and pig manure. A total of 12459 soil fauna were captured, belonging to 23 groups. Treatments animal manure combined with straw led to increased the number of soil fauna groups and individuals, diversity index, richness index and dominance index, while reduced the evenness index of soil fauna. Compared to the other treatments, maize straw plus chicken manure and maize straw plus pig manure treatments had the largest number of soil fauna groups. Among all the treatments, Oribatida, Astigmata, Desoria and Folsomia were the dominant species, accounting for 69.94 % of the total number of individuals. Maize straw plus pig manure treatment had the largest diversity index soil fauna community. The richness index of soil fauna community in maize straw plus chicken manure and maize straw plus pig manure treatments were higher compared to other treatments. The highest dominance index of soil fauna was recorded in maize straw plus ox manure treatment. In conclusion, our findings suggested that animal manure combined with straw, especially the application of maize straw plus pig manure was the most effective treatment for enhancing soil fauna community.
Aims: Litter is an important component of terrestrial ecosystems, which plays significant roles in carbon and nutrient cycles. Quantifying regional-scale pattern of litter standing crop would improve our understanding in the mechanism of the terrestrial ecosystem carbon cycle, also with help in predicting the responses of carbon cycle of terrestrial ecosystems to future climate change. Our objective was to examine variation in litter standing crop of shrublands along the environmental gradients in southern China. Methods: During 2011-2014, we investigated the litter standing crop at 453 shrublands sites by the stratified random sampling, reflecting climatic and soil attributes across southern China. Important findings: We found that the mean value of litter standing crop in these shrubland ecosystems across southern China was 0.32 kg·m⁻². It was 68% of forest litter standing crop (0.47 kg·m⁻²) and was five times higher than that in grasslands (0.06 kg·m⁻²) in China. Litter standing crop increased with latitude. Our results showed that litter standing crop was negatively correlated with mean annual temperature, soil total P and soil pH, but not significantly correlated with other environmental variables, including mean annual precipitation, soil carbon, nitrogen and soil organic matter. The conversion coefficient of carbon in litter standing crop was 0.41, which is significantly lower than that of vegetation in shrublands (0.50), resulting in an overestimate in carbon storage of litter standing crop in shrubland up to 22% by applying wrong conversion coefficient. We concluded that litter standing crop of shrublands is an important component in terrestrial ecosystems. Mean annual temperature was the most important environmental variable, accounting for the variation in litter standing crop of shrublands in southern China. To our best of knowledge, this is the first study to quantify variation in litter standing crop of shrublands at the regional scale. Therefore, our study will have important implications for assessing the carbon budget of terrestrial ecosystems in China.
Abstract
Aims Litter is an important component of terrestrial ecosystems, which plays significant roles in carbon and nutrient cycles. Quantifying regional-scale pattern of litter standing crop would improve our understanding in the mechanism of the terrestrial ecosystem carbon cycle, also with help in predicting the responses of carbon cycle of terrestrial ecosystems to future climate change. Our objective was to examine variation in litter standing crop of shrublands along the environmental gradients in southern China.
Methods During 2011-2014, we investigated the litter standing crop at 453 shrublands sites by the stratified random sampling, reflecting climatic and soil attributes across southern China.
Important findings We found that the mean value of litter standing crop in these shrubland ecosystems across southern China was 0.32 kg•m-2. It was 68% of forest litter standing crop (0.47 kg•m-2) and was five times higher than that in grasslands (0.06 kg•m-2) in China. Litter standing crop increased with latitude. Our results showed that litter standing crop was negatively correlated with mean annual temperature, soil total P and soil pH, but not significantly correlated with other environmental variables, including mean annual precipitation, soil carbon, nitrogen and soil organic matter. The conversion coefficient of carbon in litter standing crop was 0.41, which is significantly lower than that of vegetation in shrublands (0.50), resulting in an overestimate in carbon storage of litter standing crop in shrubland up to 22% by applying wrong conversion coefficient. We concluded that litter standing crop of shrublands is an important component in terrestrial ecosystems. Mean annual temperature was the most important environmental variable, accounting for the variation in litter standing crop of shrublands in southern China. To our best of knowledge, this is the first study to quantify variation in litter standing crop of shrublands at the regional scale. Therefore, our study will have important implications for assessing the carbon budget of terrestrial ecosystems in China.
Concentrations of nitrogen, phosphorus, and acid insoluble substances were followed in decomposing forest foliage litters in some different forest biomes and in a laboratory study. In all cases, the concentration of these substances increased linearly with litter mass loss. In contrast, absolute amounts of these materials in the litter began decreasing at some point during decay, usually following a period of absolute increase (i.e., immobilization of nutrients or humification for acid insoluble substances). The point during decomposition at which a net release (net disappearance) of a substance began (point for maximum amount), was estimated using the linear relations between concentrations of the substance and accumulated litter mass loss. In addition, the concentrations of acid insoluble substances at maximum absolute amounts of nitrogen and phosphorus were estimated. The results indicate that the points in decay at which a net release of nitrogen and phosphorus began were linearly related to one another and to the onset of acid insoluble substance disappearance. In all litters studied, net release of nitrogen and phosphorus began after a net release of the recalcitrant acid insoluble substance fraction had begun. The relationship between the onset of acid insoluble substance loss and nitrogen and phosphorus release differed between deciduous and coniferous foliage litters. Key words: decomposition, litter, nitrogen, phosphorus, lignin, nitrogen release, phosphorus release.
1. Plant litter is a key component in terrestrial ecosystems. It plays a major role in nutrient cycles and community organization. Land use and climate change may change the accumulation of litter in herbaceous ecosystems and affect plant community dynamics. Additionally, the transfer of seeds containing plant material (i.e. litter) is a widespread technique in grassland restoration.
2. Ecosystem responses to litter represent the outcome of interactions, whose sign and strength will depend on many variables (e.g. litter amount, seed size). A previous meta-analysis (from 1999) reported that litter had an overall negative effect on seed germination and seedling establishment in different ecosystems. However, recent studies indicated that this might not be the case in grassland ecosystems.
3. We used 914 data from 46 independent studies to analyse the effects of litter on seedling (i) emergence, (ii) survival and (iii) biomass, employing meta-analytical techniques. Each data set was stratified according to methodology, grassland type, irrigation conditions, litter amount and seed size.
4. We found an overall neutral effect of litter presence on seedling emergence and survival and a positive effect on seedling biomass. However, whereas for field experiments the response remained neutral, it was positive for common garden studies. In glasshouse experiments, litter effects were negative for emergence and positive for biomass.
5. Litter may have a positive effect on seedling recruitment in dry grasslands or under water-limited conditions, or in the presence of low to medium litter amounts (< 500 g m�2). However, high litter amounts (> 500 g m�2) will inhibit seedling recruitment. Large seeds showed a more positive response to litter presence with respect to seedling emergence and survival, but not concerning biomass.
6. Synthesis. Under dry conditions (e.g. dry grasslands or dry periods) or with low to medium litter amounts, litter presence has a positive effect on seedling establishment. However, climate and land use change may promote litter accumulation and reduce seedling establishment, affecting grasslands composition and ecosystem functions.
We investigated variation in carbon stock in soils and detritus (forest floor and woody debris) in chronosequences that represent the range of forest types in the US Pacific Northwest. Stands range in age from <13 to >600 years. Soil carbon, to a depth of 100 cm, was highest in coastal Sitka spruce/western hemlock forests (36±10 kg C m−2) and lowest in semiarid ponderosa pine forests (7±10 kg C m−2). Forests distributed across the Cascade Mountains had intermediate values between 10 and 25 kg C m−2. Soil carbon stocks were best described as a linear function of net primary productivity (r2=0.52), annual precipitation (r2=0.51), and a power function of forest floor mean residence time (r2=0.67). The highest rates of soil and detritus carbon turnover were recorded on mesic sites of Douglas-fir/western hemlock forests in the Cascade Mountains with lower rates in wetter and drier habitats, similar to the pattern of site productivity. The relative contribution of soil and detritus carbon to total ecosystem carbon decreased as a negative exponential function of stand age to a value of ∼35% between 150 and 200 years across the forest types. These age-dependent trends in the portioning of carbon between biomass and necromass were not different among forest types. Model estimates of soil carbon storage based on decomposition of legacy carbon and carbon accumulation following stand-replacing disturbance showed that soil carbon storage reached an asymptote between 150 and 200 years, which has significant implications to modeling carbon dynamics of the temperate coniferous forests following a stand-replacing disturbance.
a b s t r a c t It was hypothesized that litter with higher N concentration would decompose faster than that with lower N concentration and that increased soil nutrient availability would stimulate litter decomposition. To examine the interspecific differences in decomposition rate of leaf litter in relation with differences in litter chemistry and soil nutrient availability, senescent leaves of four species Pennisetum flaccidum, Artemisia scoparia, Chenopodium acuminatum and Cannabis sativa, and soil samples with different fertilization treatments (no fertilization, N, P, and N þ P fertilizations, respectively) were collected from a sandy grassland in Northeast China and incubated under laboratory conditions. The decomposition rate of leaf litter was determined by measuring the CO 2 emission during decomposition of litter. We found remarkable interspecific differences in leaf decomposition rates. Moreover, rates of litter decomposition at different incubation stages were correlated with different litter quality indices. The rate of litter decomposition was positively correlated with initial litter N concentration in the initial stage of the incubation, whereas it was negatively correlated with litter N and P concentrations in the late stage. Responses of litter decomposition to soil nutrient availability differed among species. Our results suggest that both indirect changes in litter quality through shifts of species composition/dominance and direct changes in soil nutrient availability under nutrient addition conditions could affect litter decomposition and consequently C and nutrient cycling of grassland ecosystems.
Summary • We studied seedling emergence in four familial pairs of floodplain herbs in response to the experimental manipulation of soil moisture and litter cover to analyse (i) whether the effect of litter changes from negative under humid to positive under dry conditions, and (ii) whether the response to changing water and light conditions with increasing litter cover varies among species and plant families. • We carried out a controlled pot experiment using four levels of litter cover (0 g, 2 g, 4 g and 8 g litter per pot, corresponding to 0 kg m−2, 0.2 kg m−2, 0.4 kg m−2 and 0.8 kg m−2) and two levels of water-addition, leading to constantly humid substrate or intermittently dry topsoil. • Across water-additions, percentage emergence reached a peak at low levels of litter cover (0.2 kg m−2 and 0.4 kg m−2). There was a significant litter × water-addition interaction in six species, with positive effects of litter under intermittently dry conditions and negative or neutral effects under constantly humid conditions. Litter lowered maximum temperature as well as amplitude, and alleviated soil humidity under low water supply, while imposing increasingly shaded conditions. Analysis of species- and family-specific responses suggested that germination under a litter cover of 0.8 kg m−2 was significantly reduced in smaller-seeded species (i.e. those that tend to have higher light demands for germination). • Our results suggest that transfer of seed-containing plant litter can aid restoration projects if applied at 0.2–0.4 kg m−2. Below these levels, establishment of most species may be inhibited by drought, while higher amounts will increasingly suppress seedling emergence, especially of small-seeded species. • In addition to facilitation effects observed between living plants, dead plant remains may also exert positive effects on establishment. The sign of the litter effect on seedling emergence depends on soil humidity, with negative effects seen above a threshold amount, which is species- and family-specific and is closely related to seed size. Whether positive litter effects in grasslands are a consequence of coevolution remains to be examined. Journal of Ecology (2005) doi: 10.1111/j.1365-2745.2005.01015.x
The effect of litter quality and climate on the rate of decomposition of plant tissues was examined by the measurement of mass remaining after 3 years’ exposure of 11 litter types placed at 18 forest sites across Canada. Amongst sites, mass remaining was strongly related to mean annual temperature and precipitation and amongst litter types the ratio of Klason lignin to nitrogen in the initial tissue was the most important litter quality variable. When combined into a multiple regression, mean annual temperature, mean annual precipitation and Klason lignin:nitrogen ratio explained 73% of the variance in mass remaining for all sites and tissues. Using three doubled CO2 GCM climate change scenarios for four Canadian regions, these relationships were used to predict increases in decomposition rate of 4–7% of contemporary rates (based on mass remaining after 3 years), because of increased temperature and precipitation. This increase may be partially offset by evidence that plants growing under elevated atmospheric CO2 concentrations produce litter with high lignin:nitrogen ratios which slows the rate of decomposition, but this change will be small compared to the increased rate of decomposition derived from climatic changes.
We studied the occurrence of nonadditive effects of litter mixtures on the decomposition (the deviation of decomposition rate of litter mixtures from the expected values based on the arithmetic means of individual litter types) of litters from three plant species (i.e., Stipa krylovii Roshev., Artemisia frigida Willd., and Allium bidentatum Fisch. ex Prokh. & Ikonn.-Gal.) endemic to the grassland ecosystems of Inner Mongolia, northern China and the possible role of initial litter N and P on such effects. We mixed litters of the same plant species that differed in N and P concentrations (four gradients for each species) in litterbags and measured mass losses of these paired mixtures after 30 and 80days under field conditions. We found the occurrence of positive, nonadditive effects of litter mixtures and showed that the magnitude of the nonadditive effects were related to the relative difference in the initial litter N and P concentrations of the paired litters.
The present article centres on the contribution of soil animals to organic. matter decomposition and nitrogen mineralization
in natural and agro-ecosystems. Criteria are presented for the categorisation of the soil fauna in functional groups in order
to be able to quantify the contribution of the soil fauna. Three types of classifications: size, habitat and food, are discussed.
For various natural ecosystems, such as prairies and forests, and for agro-ecosystems a rather similar outcome of the faunal
contribution to nitrogen mobilization of approximately 30% appears to exist. This value is dependent on various types of interactions
among functional groups, changes in population density of microorganisms and soil fauna, seasonally changing abiotic factors
and management, such as fertilization, harvesting and addition of harvest residues to the soil. Finally, to improve management
of ecosystems as related to soil faunal activity in decomposition, lines are set out for further research such as the development
of dynamic models, studies concerning the effects of perturbation in relation to microbial dominance and the integration of
the study of below-ground food webs with ecological theories.
In order to analyze the extent to which allelopathic action of Cistus ladanifer may influence the successional progression towards Mediterranean sub-climacic shrublands and the geographical distribution
of other species, the inhibitory effect of Cistus ladanifer extracts on the germination of 20 Mediterranean species was analyzed. Five of the species tested were characteristic of maquis
sub-climacic shrublands: Arbutus unedo, Adenocarpus argyrophyllus, Phillyrea angustifolia, Phillyrea latifolia, and Rhamnus alaternus. Tests were also carried out on 6 Cistaceae species in order to evaluate the auto-toxicity rate of allelopathic extracts:
Halimium umbellatum subsp. viscosum, Halimium ocymoides, Cistus ladanifer, Cistus salvifolius, Cistus monspeliensis, and Cistus populifolius. Nine herbaceous species sharing the natural habitat with C. ladanifer were also examined. Results confirmed a clear inhibitory and delaying effect of aqueous C. ladanifer-leaf extracts on the germination of P. angustifolia, P. latifolia, R. alaternus, H. ocymoides, C. populifolius, Erysimum lagascae, Brassica barrelieri, Silene tridentata, and Moricandia moricandioides. Assays with soil collected below the canopy of the C. ladanifer community showed more pronounced inhibitory effect on sub-climacic shrub species than the aqueous extracts. In contrast,
the opposite pattern was detected when analyzing the allelopathic effect of natural soil on Cistaceae and herbaceous species.
Allelopathic compounds produced by C. ladanifer showed little auto-toxicity. The inhibitory effect of phytotoxic compounds accumulated in the jaral soil upon germination of A. unedo, B.␣barrelieri, and M. moricandioides was eliminated by heating soil at 150°C for 10min. Phenolic compounds (i.e. ferulic, p-hydroxybenzoic, vanillic, p-coumaric,
and caffeic acids) and terpenes (i.e. α and β-pinene) with allelopathic documented effect were detected in the aqueous extracts
and soil samples used in the analyses. We suggest that the allelopathic effect of C. ladanifer may influence the composition and structure of Mediterranean communities where the species is present, since it hinders the
establishment of some sub-climacic species and may reduce the area occupied by numerous herbaceous species.
Aim
This study was aimed to assess the role that leaf litter play in nutrient cycling, nutrient soil availability and ecosystem processes in an oligotrophic tropical savanna.
Methods
A four year experiment was performed in a Neotropical savanna from the Brazilian plateau (cerrado), in which litter levels were modified, and the resulting changes in biophysical and chemical soil properties were studied. Changes in organic matter decomposition, soil respiration and stem growth of the six most common tree species were also monitored.
Results
Compared to litter removal plots, double litter plots had lower maximum soil temperature and higher soil water content, and litter decomposition rates in one of three species studied, consistent with higher soil respiration rates observed in this treatment. With the exception of Ca, there were no significant differences in nutrients between the removal, natural and double litter plots, even though most nutrients tended to increase in the double litter plots by the end of the experimental period, while in the control plots nutrient levels remained relatively constant. Of the six tree species used for growth analysis, only one, Sclerolobium paniculatum, a fast growing species with shallow roots, had a significant increase in stem growth due to litter addition.
Conclusion
Preliminary results over four years indicate that litter removal and addition resulted in some significant changes and tendencies that indicate that litter is effectively altering ecosystem processes. The information obtained also suggest that nutrient cycling in plots with natural litter levels (control plots) was in a closed loop; most nutrients released by litter decomposition and mineralization were absorbed and reutilized immediately by the plants, thus minimizing nutrient leakage outside the system.
A statistically significant linear relationship was found between annual mass loss of foliar litter in the late stages of
decomposition and Mn concentration in the litter. We used existing decomposition data on needle and leaf decomposition of
Scots pine (Pinus sylvestris L.), lodgepole pine (Pinus contorta var. contorta), Norway spruce (Picea abies (L.) Karst.), silver birch (Betula pendula L.), and grey alder (Alnus incana L.) from Sweden and Aleppo pine (Pinus halepensis Mill.) from Libya, to represent boreal, temperate, and Mediterranean climates. The later the decomposition stage as indicated
by higher sulfuric-acid lignin concentrations, the better were the linear relationships between litter mass loss and Mn concentrations.
We conclude that Mn concentrations in litter have an influence on litter mass-loss rates in very late decomposition stages
(up to 5years), provided that the litter has high enough Mn concentration. The relationship may be dependent on species as
the relationship is stronger with species that take up high enough amounts of Mn.
Knowledge of how ecosystem carbon (C) processes respond to variations in precipitation is crucial for assessing impacts of
climate change on terrestrial ecosystems. In this study, we examined variations of shoot and root biomass, standing and surface
litter, soil respiration, and soil C content along a natural precipitation gradient from 430 to 1200mm in the southern Great
Plains, USA. Our results show that shoot biomass and soil respiration increased linearly with mean annual precipitation (MAP),
whereas root biomass and soil C content remained relatively constant along the precipitation gradient. Consequently, the root/shoot
ratio linearly decreased with MAP. However, patterns of standing, surface, and total litter mass followed quadratic relationships
with MAP along the gradient, likely resulting from counterbalance between litter production and decomposition. Those linear/quadratic
equations describing variations of ecosystem C processes with precipitation could be useful for model development, parameterization,
and validation at landscape and regional scales to improve predictions of C dynamics in grasslands in response to climate
change. Our results indicated that precipitation is an important driver in shaping ecosystem functioning as reflected in vegetation
production, litter mass, and soil respiration in grassland ecosystems.
Differences in litter decomposition patterns among mesic, semiarid, and arid grassland ecosystems cannot be accurately explained
by variation in temperature, moisture, and litter chemistry alone. We hypothesized that ultraviolet (UV) radiation enhances
decomposition in grassland ecosystems via photodegradation, more so in arid compared to mesic ecosystems, and in litter that
is more recalcitrant to microbial decomposition (with high compared to low lignin concentrations). In a 2-year field study,
we manipulated the amount of UV radiation reaching the litter layer at three grassland sites in Minnesota, Colorado, and New
Mexico, USA, that represented mesic, semiarid, and arid grassland ecosystems, respectively. Two common grass leaf litter types
of contrasting lignin:N were placed at each site under screens that either passed all solar radiation wavelengths or passed
all but UV wavelengths. Decomposition was generally faster when litter was exposed to UV radiation across all three sites.
In contrast to our hypothesis, the contribution of photodegradation in the decomposition process was not consistently greater
at the more arid sites or for litter with higher lignin content. Additionally, at the most arid site, exposure to UV radiation
could not explain decomposition rates that were faster than expected given climate constraints or lack of N immobilization
by decomposing litter. Although photodegradation plays an important role in the decomposition process in a wider range of
grassland sites than previously documented, it does not fully explain the differences in decomposition rates among grassland
ecosystems of contrasting aridity.
Keywordsphotodegradation-litter decomposition-ultraviolet (UV) radiation-tallgrass prairie-shortgrass steppe-desert grassland-lignin-extracellular enzymes-nitrogen immobilization-precipitation gradient
Plant species effects on soil nutrient availability are relatively well documented, but the effects of species differences
in litter chemistry on soil carbon cycling are less well understood, especially in the species-rich tropics. In many wet tropical
forest ecosystems, leaching of dissolved organic matter (DOM) from the litter layer accounts for a significant proportion
of litter mass loss during decomposition. Here we investigated how tree species differences in soluble dissolved organic C
(DOC) and nutrients affected soil CO2 fluxes in laboratory incubations. We leached DOM from freshly fallen litter of six canopy tree species collected from a tropical
rain forest in Costa Rica and measured C-mineralization. We found significant differences in litter solubility and nutrient
availability. Following DOM additions to soil, rates of heterotrophic respiration varied by as much as an order of magnitude
between species, and overall differences in total soil CO2 efflux varied by more than four-fold. Variation in the carbon: phosphorus ratio accounted for 51% of the variation in total
CO2 flux between species. These results suggest that tropical tree species composition may influence soil C storage and mineralization
via inter-specific variation in plant litter chemistry.
The total production of plant litter and the proportion of leaf litter are higher in riparian corridors than in upland ecosystems throughout the world. Periodical water-level fluctuation is believed to be the major cause of these differences. During flood periods, much plant litter is redistributed locally and between regions, following erosion, transport, and deposition of litter. The importance of litter redistribution varies with factors such as flood regime, topography, and vegetation. Litter from the riparian corridor is usually a major constituent of the litter transported by the river. The decomposition of litter is faster in riparian corridors than in upland systems due to a higher rate of leaching and a higher decomposer activity. Relative warmth and soil fertility may also enhance litter decomposition in riparian corridors. In general, accumulated litter affects plants physically by burying them, chemically by adding nutrients and phytotoxins, and biologically by adding diaspores. The physical impact of a certain amount of litter may be weaker in riparian corridors than in uplands because the rapid decomposition reduces the time that litter is present. In other words, higher amounts of litter are needed to affect riparian vegetation than are needed to affect other types of vegetation. The nutrient content of riverborne litter is reduced by leaching, but dissolved nutrients from litter might still reach the riparian vegetation, e.g., by adsorbing to inorganic particles. Phytotoxins are probably unimportant in riparian systems. The input to the riparian corridor of plant diaspores, borne by litter packs in the river, may be large. Indirect biological effects of litter, including its diaspores, are the attracting of animals and microbes that may influence the plant community, and the creation of bare soil for plant colonization.
A field experiment was conducted in a semi-natural grassland to study the interspecific variation in the effect of litter
on seedling emergence and establishment and separate physical from chemical effects. Seeds of seven forb species were sown
in plots subjected to either litter amendment (0, 400 or 900gm−2) or water extracts of litter (corresponding to 400 and 900glitterm−2). In addition, an extract was treated with activated carbon to estimate the possible effects of secondary chemical compounds.
The response to plant litter differed amongst species: negative, neutral and positive responses were observed. Anthriscus sylvestris was the only species with a strong positive response to litter. We found no consistent relation between seed size and response
to plant litter. Physical effects of litter were generally stronger than chemical effects. However, water extract of litter
inhibited emergence in three species. Activated carbon removed the negative effect of the litter extract, which suggests that
the effect was caused by an inhibitory chemical compound rather than by increased competition in response to nutrients added
via the extract. The balance between facilitative and inhibitory effects of litter depended on species identity and litter
quantity. Facilitative effects dominated at low and intermediate quantities of litter, and inhibitory effects at high litter
quantities. One species, Campanula rotundifolia, showed a switch from positive to negative responses with increasing quantities of litter. However, we found no general threshold
for litter quantity valid across species.
Weight loss and nutrient dynamics of Quercus mongolica leaf litter during decomposition were investigated from December 2005 through August 2008 in Mt. Worak National Park as a part of National Long-Term Ecological Research Program in Korea. The decay constant (k) of Q. mongolica litter was 0.26. After 33 months decomposition, remaining weight of Q. mongolica litter was 49.3 ± 4.4%. Initial C/N and C/P ratios of Q. mongolica litter were 43.3 and 2,032, respectively. C/N ratio in decomposing litter decreased rapidly from the beginning to nine months decomposition, and then showed more or less constant. C/P ratio increased to 2,407 after three months decomposition, and then decreased steadily thereafter. N and P concentration increased significantly during decomposition. N immobilization occurred from the beginning through 18 months decomposition, and mineralization occurred afterwards in decomposing litter. P immobilized significantly from fifteen months during decomposition. K concentration decreased rapidly from the beginning to six months decomposition. However it showed an increasing pattern during later stage of decomposition. Remaining K decreased rapidly during early stage of decomposition. There was no net K immobilization. Ca concentration increased from the beginning to twelve months decomposition, and then decreased rapidly till twenty one months elapsed. However, it increased again thereafter. Ca mineralization occurred from fifteen months. Mg concentration increased during decomposition. There was no Mg immobilization during litter decomposition. After 33 months decomposition, remaining N, P, K, Ca and Mg in Q. mongolica litter were 79.2, 110.9, 36.2, 52.7 and 74.4%, respectively.
According to the rate of living theory of aging, the longevity of living organisms should be negatively correlated with body metabolic rate. For the organisms having the same body size, the metabolic rate is usually greater in favorable habitats than in poor-quality sites, as demonstrated in many previous studies. Therefore, it is expected that organisms would live longer in environments with low-resource availability than in their counterparts. Specifically, we hypothesize that plant branches or twigs would live shorter in sun-lit microhabitats than in shaded or partial-shaded ones. This hypothesis is consistent with the recently established leaf and wood economic spectrums, in which leaf longevity is positively associated with leaf mass per area but negatively with leaf nitrogen content and photosynthetic capacity that often characterize favorable sites. A similar hypothesis has also been interspecifically tested to be true at whole-individual level of tree species, where long-lived species are often associated with low respiration rates. In order to test the above hypothesis, we in this study examined the effects of light level on branch longevity and on the relationship between crown shape and the longevity for an evergreen species (Osmanthus fragrans) and a deciduous species (Metasequoia glyptostroboides) in Nanjing, southeast China. We measured plant size (height and diameter at breast height), crown depth (i. e. vertical crown length) that was obtained by plant height minus under branch height, crown profile that was calculated as the ratio of crown depth to crown width, and relative crown width that was defined as the ratio of crown width to plant height; we also determined the longevity of shed branches by bud scales for plants (with similar size) grown in different light conditions (under full sun light/unshaded, partial shaded, fully shaded). In both species, branch longevity was found to be significantly greater for plants living in the fully-shaded environments than for those grown in open sites; the longevity increased with increasing shading level, consistent with the theoretical prediction. Crown depth and crown profile increased, but relative crown width decreased with increasing shading level in both species, i. e. shading tended to result in narrow and deep plant crowns. In addition, branch longevity was positively correlated with crown depth and crown profile but negatively with relative crown width in both species, and branch longevity was positively related to relative crown depth in O. fragrans, not in M. glyptostroboides. The possible underlying mechanism is that shading might have increased the level of apical dominance but decreased the self-shading level of crown interior (as reflected by increased crown profile and decreased crown width), which potentially led to low metabolic rates. These results collectively suggest that the morphological responses of plant crowns to light may largely account for the variation in branch longevity under different shading levels. However, the current study did not address the importance of life form to plant metabolic rates and organism longevity despite two different species being investigated. Future studies need to examine branch biomass allocation, leaf photosynthetic capacity and respiration rates to fully understand the relationship between branch longevity and habitat quality for species differing in life forms.
The effects of subzero temperatures on soil are varied, influencing a wide range of physical, biological, and chemical processes. Since the formation of ice in soil requires an understanding of thermal gradients and water movement, the major thrust of recent work has been from a physically based approach. The visible effects of freezing and thawing, such as changes in soil structure and damage to building and road foundations, have also received considerable attention. There is far less information available concerning possible effects on chemical and biological soil reactions. Our aim, therefore, is to present an overview of the freeze/thaw cycle, placing particular emphasis on factors relating to the less well-documented and understood influences on nutrient availability.
In forested karst ecosystems , the effects of litter on soil properties are not fully understood. We conducted a study in 60 years old mature forest( Si) , 20 years old earlier arbor forest( S2) and 10 years old shrub ( S3) in the Nongla karst ecosystem of Guangxi , China. Physical and chemical properties of Litter and soil ware examined to understand the effects of litter on soil properties. Our data showed that the reserves of litters in Si, S2 and S3 were 18. 4 · 16. 9 · 1. 9 t/hm2, respectively. The total nanual nmounts of nutrient elements ( (N, P, K, Ca-, Mg. Si, Al, Fe, Zn, Cu, Na and Mn) returning to soil from the litters at Si , S2 and S3 were 4. 657, 4.068 t/hm2 and 0. 193 t/hm2, respectively. The reserves of litters at Si were ten times greater than that at S3. The effective water holding depth of litter layer at Si were 11 times greater than that of S3, enhancing the eco-hydrological function of forest soil. Properties of deeper soils are less influenced by litter than shallower ones. Properties of deeper soils are more influenced by the rock, while the upper soils are more influenced by plants and litter. Nutrient behavior in the upper soil , including contents of organic matter, available N/P/K , were controlled by the reserves, content and decomposition of litters. Litter can speed up the formation of limestone soil in karst area. Litter can improve water storage in the epikarst dynamic system. At the same time, it can imputs more orgemic matter and COj to the karst ecosystem, accelerating its evolution.
This chapter discusses the sources of emergent plant organic matter reaching the fresh water and the impact of various agents of decomposition on it. The distinctive environmental features of emergent macrophyte swamp are also discussed. Detritus, the resource of decomposition, can originate from any nonpredatory loss of organic matter from any trophic level. The primary resources are those that are derived directly from the plant. They include litter and the soluble matter, which may be lost from plants while they are alive. The secondary resources are provided indirectly, for example, by the defecation or death of animals feeding on the litter. Weight loss from the litter exhibits a high initial rate, which subsequently declines. Although it is difficult experimentally to separate the two processes, the initial rapid decomposition is a case of leaching, the abiotic loss of soluble components. The later phase depends predominantly on the activities of decomposer organisms and is generally assessed as a breakdown rate, the speed at which weight is lost from contained or tethered litter.
A system of dimension analysis of woody plants, applied to stand data for the Brookhaven forest, Long Island, permits its characterization. The forest is a woodland of small oaks and pine with an open canopy, of 88% tree coverage and a leaf area ratio of 3.4, admitting sufficient light (13% of incident sunlight) to support a well-developed stratum of low, vacciniaceous shrubs (78% coverage). Net annual production of the community is 856 g/m2 above ground, about 1195 g/m2 above and below ground, hence in the range of other small tree forests of moderately limiting environments; biomass is low, being 6560 g/m2 above ground and 10190 g/m2 above and below ground. Efficiency of net production (relative to incident sunlight energy in the visible spectrum) is 0.91; efficiency of gross production is about 2.22%. The forest is distinctive in its low biomass accumulation ratio (7.7) and massive oak roots, older than the shoots they now bear. Both characteristics are aspects of fire adaptation: the dominant oaks resprout from root systems that survive fires, and the low biomass accumulation ratio reflects the youth (about 45 years) of the present community in the cycle of fire and regrowth.
We investigated the mechanism by which grass litter (dead Poa pratensis L. shoots) suppressed the emergence of seedlings of four old-field forbs (Centaurea nigra L., Dipsacus sylvestris Huds., Hypericum perforatum L., Verbascum thapsus L.) by determining the effect of litter on their seed germination and shoot extension. 2. When seeds were placed beneath litter (715 gm-2) that had been collected from an old-field, the germination of all species except Verbascum was reduced significantly by 26% to 41% compared to a no-litter control. 3. When seeds were placed in plastic dishes containing a leachate solution made from litter (7 g dish-1), the germination of two species (i.e. Centaurea and Dipsacus) was reduced significantly by 10% to 34% compared to the distilled water control. 4. When germinated seeds were placed beneath litter, the emergence of seedlings of all species was reduced significantly by 95% to 100% compared to a no-litter control. 5. These results indicate that grass litter may suppress forb seedling emergence by reducing seed germination and (or) by preventing shoot extension and that these effects are species dependent.
We conducted studies of mass losses from surface and buried litter bags in four North American hot desert areas to test the following hypotheses: (1) leaf litter disappearance in hot deserts is independent of actual evapotranspiration, (2) buried litter disappearance is a function of actual evapotransporation, (3) the pattern of microarthropod colonization of buried leaf litter is a function of the stage of decomposition, and (4) elimination of microarthropods results in reduced rates of decomposition and increased numbers of free-living nematodes. Mass losses from surface Larrea tridentata leaf litter bags ranked highest to lowest: Chihuahuan desert, Sonoran desert, Mojave desert, Coloradan desert. Mass losses from buried litter bags were essentially equal. @?40%, in each of the deserts for bags buried from March to October. There was low correlation between rainfall and mass loss of buried litter and surface litter in the North American hot deserts. Mass losses from insecticide-treated buried bags were lower than from untreated bags. There was a greater abundance of nematodes in insecticide-treated bags than in untreated bags. Tarsonemid mites were found only in litter bags from the Chihuahuan desert. The most abundant microarthropods in buried leaf litter in the other deserts were predatory raphignathids, tydeids, and arctacarids. Decomposition (litter disappearance) in North American hot deserts was highly correlated with long-term rainfall patterns, which we hypothesize have served as the selective agents for the soil biota active in the decomposition process. Thus litter disappearance does not respond to annual fluctuations in rainfall amounts.
Although most plant products eventually enter the below-ground subsystem as plant litter, relatively little is known about the effects of plant litter diversity or composition on ecosystem processes and no study has considered the responses of plant growth to these factors. We conducted an experiment in which humus substrate was collected from three field sites in the boreal forest of northern Sweden. Litter was then placed on the humus surface, and the litter used consisted of monocultures of Empetrum hermaphroditum (dwarf shrub), Betula pendula (tree), and Pleurozium schreberi (feather moss), as well as mixtures containing all the possible (two-way and three-way) combinations of these species; the experiment was maintained in out-door conditions. Although decomposition rates of this surface-placed litter differed between species few effects of litter mixing on litter mass loss were apparent. Added litter of Pinus sylvestris litter broke down most slowly when placed in E. hermaphroditum litter but sometimes showed elevated decomposition rates when placed in some of the multiple species litter mixes. Soil microbial biomass and activity was lowest when plant litter was absent, but as long as plant litter was present on the humus surface the species composition and diversity of the litter was irrelevant. There were few effects of litter treatments on growth of seedlings of either B. pendula or P. sylvestris planted into the humus. However, for one site there were significant effects of mixing litter of P. schreberi and E. hermaphroditum in reducing growth of both seedling species. Litter treatments generally did not alter the competitive balance between B. pendula and P. sylvestris seedlings when grown together but for all sites litter treatments had significant effects on the overall intensity of competition, and mixing of litter of B. pendula and P. schreberi had significant non-additive effects on competition intensity for two of the three sites. The abundance of mycorrhizae on seedlings was only weakly related to litter treatment but there were some positive effects of litter mixing on one of the most abundant mycorrhizal morphotypes on both species of seedlings for one of the sites. Our results suggest that litter presence was important in influencing a range of above ground and below ground properties and processes. In some instances individual species effects and litter mixing effects were also important but few general patterns emerged, and the nature of significant effects tended to be idiosyncratic. Ultimately our results show that plant litter has important "afterlife effects" which need to be considered in order to develop a more complete understanding of how biodiversity affects ecosystems.
The normal course of succession was a decrease in density and biomass of annuals, while the density and biomass of perennials doubled. Species more characteristic of early old-field successional stages were more apt to be inhibited by treatment than species characteristic of later successional stages. Shade reduced biomass and density, except in Cynodon. Litter alone produced a major decrease in the number of individuals and in biomass; perennial grasses were affected the least and some (Andropogon, Aristida, Leptoloma) showed a major increase over controls. Shade + litter drastically reduced (60-70%) density and biomass (stems and leaves) of annuals and increased the density of perennials, especially Cynodon with shade and pine litter and Andropogon on shade and hardwood litter. Annuals showed no real response in trenched, litter-intact quadrats, while perennials increased fourfold in density. Annuals had higher densities (100% increase) in response to trenched + litter removal treatment; perennials showed no enhancement of density with the trenched, litter-removal treatment. The largest number of species invaded trenched, litter-removal quadrats. Plants on unshaded quadrats produced more root biomass than on shaded quadrats. More root biomass was produced on hardwood litter plots than under pine litter. Less root biomass was produced on shaded or unshaded + litter plots after 2 yr. Annuals were inhibited by dense shade, root competition and litter. Root competition and shade were more important in suppressing perennials that was litter. -from Authors
Standing crop values of mowed plots were 67-70% lower than controls, but they produced significantly larger amounts of both biomass and total N. Maximum season-long production values in the mowed plots were 43% above controls, with major differences developing as a result of fertilization. Fertilized plots produced 67% more foliage than unfertilized plots. Over-compensatory growth occurred as a result of simulated grazing treatments. Normalized difference vegetation index and greenness, derived from the reflectance data, were poorly correlated with biomass. The correlation of NDVI with N content of the canopy foliage was stronger. -from Authors
1. A field experiment was conducted to test whether control of seedling emergence by ground cover and seed predation depended on seed size. Sown seeds of 12 old-field species with seed masses ranging from 0.06 to 12.2 mg were used for the test. Species response to experimental removal of ground cover and (or) to the addition of a cage to reduce seed predation was recorded. Results were used to determine the relationship between seed mass and effects of ground cover and (or) seed predation on seedling emergence. 2. Adding a cage to reduce seed predation did not increase seedling emergence significantly for each of the four species with the smallest seeds (<0.14 mg). In contrast, seedling emergence increased significantly for each of the eight species with larger seeds. 3. Experimental removal of ground cover increased seedling emergence significantly for the four species with the smallest seeds. Seedling emergence also increased significantly for two species with larger seeds and hard seed coats. The remaining six species only responded to removal of ground cover when seed predators were present. 4. Experimental results indicate that control of seedling emergence by seed predation is directly related to seed size while control by ground cover is inversely related to seed size. Under natural conditions, the combined effect of ground cover and seed predation may reduce seedling emergence equally for species with small seeds and with large seeds.
Among organic components, lignin is the primary controlling factor of decomposition rates of surface litter during the later phase of decomposition in most habitats and during the initial phase in warm, moist habitats (those with a high actual evapotranspiration, AET). In habitats with moderate AETs, the decreased control by lignin over annual decomposition rates of surface litter is due in part to a significant periodic or seasonal influence of other carbon-based plant secondary metabolites over rates in the initial phase of decomposition. The influence of other secondary metabolites over decomposition rates should be a function of other correlates of AET: phytochemical composition of the community and persistence of various secondary metabolites in litter. As AET decreases from the highest extreme, one expects more, but perhaps short-term seasonal, influence of monomeric phenolics and tannins. In warm, dry environments with still-lower AETs, one expects some control by terpenes. On an annual basis, the relative influence of components other than lignin should therefore increase with decreasing AET, and the influence of lignin content alone on decomposition rates of surface litter should be reduced proportionately. Effects of these various classes of compounds should exhibit different temporal patterns in litter and soil. Complexity is added to this model by the multifarious effects of stress on the production of specific secondary metabolites, changes that occur in secondary-metabolite composition during senescence of tissues, and differential effects of specific secondary metabolites on decomposition. -from Authors
An experiment was designed to test the importance of the potential interaction (inhibition or enhancement) between slow and fast decaying leaf species on processing rates in a stream and its floodplain. The decomposition of water oak (Quercus nigra) and sweetgum (Liquidambar styraciflua) in single-species packs was compared with water oak plus sweetgum in mixed-species packs within three habitats (stream snags, floodplain pools, and elevated floodplain surfaces) at three sites in coastal plain streams. Fast-decaying sweetgum leaves did not enhance the rate of oak decomposition. Sweetgum leaves in mixed packs decomposed more slowly than single species packs in seven out of nine comparisons. Increases in bacterial density on leaves were depressed in mixed-species packs relative to single-species sweetgum packs. Fungal hyphae could not be observed in mixed or single-species packs. The effect of oak leaves on sweetgum leaves was affected by frequency and period of inundation. Macroinvertebrate shredders were rare or absent from most leaf packs collected from stream snags and floodplain pools. Over 40% of leaf packs placed in the stream contained no shredders, while another 28% contained <0.001 g shredders/g leaf dry weight. Therefore, shredders were to rare to influence overall leaf processing rates. These studies suggest that microbial processing accounts for most leaf decomposition and oak leaf leachate is shown to be inhibitory to microbial processing of sweetgum leaves.
hardwood site (BLH) and 500 g dry wt/m2 for a baldcypress-water tupelo site (CT). Litter-fall was 574 g dry wt/m2/yr for BLH and 620 g dry wt/m2/yr for CT. Harvest samples within the two plots yielded 200 g dry wt/m2 and 20 g dry wt/m2 for BLH and CT, respectively. Minimum net primary production was calculated as the sum of the three: 1574 g dry wt/m2/ yr for BLH and 1140 g dry wt/m2/yr for CT. Maximum estimates of herbaceous production and insect consumption were made by using values from the literature. Estimated total net primary productivity was 1733 g dry wt/m2/yr for BLH and 1516 g dry wt/m2/yr for CT. Tree composition was determined by the point-centered quarter method. Relative frequency, relative density, absolute density, relative dominance, and importance value (IV) were calculated for the tree species along each transect. In the bottomland hardwood area many woody species exist with Acer rubrum var. drummondii (IV = 23.9) and Nyssa aquatica (IV = 18.4) the most dominant. In the baldcypress-water tupelo area, fewer woody species exist and Taxodium distichum (IV - 39.2) and N. aquatica (IV = 37.6) dominated. Comparison of productivity data from several southeastern swamps indicate that flowing water regimes tend to result in the highest swamp forest productivity.
Systematic and compatible databases to quantify composition, distribution, and turnover times of carbon in global litter were developed and evaluated. The study employs an integrated approach, estimating related litter pools and fluxes using a variety of data-based and model-based techniques. The analysis includes direct estimates and indirect, or proxy, estimates of litter production and pools; steady-state turnover times are estimated from the two. Proxies for litter production include net primary productivity and root respiration-soil respiration relationships. In addition to implementing a suite of regression models, >1100 published measurements of litter components, along with site characteristics, were integrated into a baseline data set and used to estimate litter production and pools. Historically, global estimates of litter production have ranged from 75 to 135 Pg dm/yr; several estimates from this study suggest values in the middle of this range, from 90 to 100 Pg dm/yr. The estimate of aboveground litter production from the compiled measurements, 39 Pg dm/yr, includes mainly forest, woodland, and wooded grassland; other grassland, shrubland, and xeromorphic communities that occupy ~25% of the ice-free land surface are unrepresented in the present compilation. Aboveground litter production may be 5-10 Pg dm/yr higher with the inclusion of these ecosystems, and the total, including belowground production, may approach 90-110 Pg dm/year. Two novel production estimates derived from soil- and root-respiration relationships are 93 Pg and 100 Pg dm/yr. These estimates have the major advantage of accounting for both aboveground and belowground litter; the latter is rarely included and can account for a substantial fraction of total production. Production of coarse woody detritus may add ~12Pgdm/yr to the fine litter total. The global litter pool has previously been estimated at ~100 to 400 Pg dm. The fine litter pool estimated here from the measurement compilation is 136 Pg dm. Although this partial estimate includes ecosystems covering just under half the ice-free land surface, it encompasses forests and woodlands which have the largest pools. Inclusion of the remaining ecosystems may add ~25Pg, raising the total to ~160Pgdm. An additional ~150Pgdm is estimated for the coarse woody detrital pool. Global mean steady state turnover times of litter estimated from the pool and production data range from 1.4 to 3.4 years; mean turnover time from the partial forest/woodland measurement compilation is ~5years, and turnover time for coarse woody detritus is ~13years. By encompassing spatial distribution, composition, and magnitude, along with numerous field measurements, this integrated approach has begun to yield compositional and ecosystem constraints on modeled global and regional litter fields and NPP allocation schemes in ecosystem models.
Livestock grazing is recognized as one of the main causes of vegetation and soil degradation and desertification in arid and semiarid northern China. In this paper, soil properties and plant characteristics in a typical degraded area in desert steppe of Alxa were studied. The study focused on the effects of grazing on soil properties and vegetation changes under three management regimes: continuous year-long livestock grazing (FG), grazing excluded for 2 years (2EX) and grazing excluded for 6 years (6EX). Results showed that exclosure enhanced soil organic carbon (SOC) and total N accumulation, and decreased pH and bulk density. Soil organic carbon and total N in the 0–20cm soil increased significantly with exclosure period, with 22% higher SOC, and 14% higher N in 6EX as compared with FG. Data indicated a considerable difference in soil particle size distribution between the exclosure and grazed area, and soil coarse sand fraction (>0.25mm) in the grazed area was 16–26% higher than that in the exclosure. Plant cover was ranked according to 6EX>2EX>FG, with a high of 46% (6EX) to a low of 31% (FG). Plant biomass was similarly ranked and vegetation diversity increased with increasing exclosure period. The results suggested that while continuous overgrazing in the erosion-prone desert steppe was detrimental to soil and vegetation, this can be reversed and significant increases in soil fertility, vegetation diversity, cover and biomass can be achieved with the implementation of protecting practices.
Patterns of litterfall and decomposition in adjacent floodplain and upland forest communities were investigated at Robert Allerton Park in central Illinois. Floodplain and upland litterfall were similar in terms of dry weight and most nutrients, and were higher than litterfall for other similar forest communities. Leaf litter decomposed rapidly at the floodplain site, and substantial amounts of nutrients were transferred to the mineral soil prior to flooding. This may have been advantageous to individuals of the forest community because the mineral soil nutrient pool was enriched prior to removal of forest floor litter by spring floods. Dry weight loss from leaf litter in the upland forest was much slower than for floodplain litter. Retention of N during leaf litter decomposition was high, indicating a probable demand for this element by heterotrophic decomposer organisms. Assimilation of N from external sources suggests that leaf litter may act as a temporary sink for N. Calcium was moderately retained, P was lost at the same rate as dry weight, and K, Mg, and Na were rapidly leached. This study shows that differences in species characteristics and variability of the physical environment in floodplain and upland forests produce contrasting patterns of nutrient transfer. Forest Sci. 28:667-681.
We studied the effects of litter of the annual grass Setaria faberii, the perennial herb Solidago spp. (mostly S. canadensis), and leaves of the hardwood tree Quercus alba on a successional plant community. We also assessed light interception by these litter types in the laboratory. Light extinction followed the Beer-Lambert exponential law. Solidago litter had the highest transmittance constant and Quercus litter the lowest. The three types of litter produced different light mosaics at the microsite (0.8 cm diameter) scale. In the field, all three litter types affected community structure, but the effect of Quercus was the strongest. Litter reduced the density of the two dominant grasses, Setaria faberii and Panicum dichotomiflorum. Quercus and Setaria litter resulted in biomass compensation (i.e., fewer but larger individuals) by S. faberii but not by P. dichotomiflorum, which probably was always outcompeted by S. faberii. Solanum carolinense, the main dicot in the community, was unaffected by litter addition. Setaria and Solidago litter enhanced the establishment of Erigeron annuus, but Quercus litter reduced it. Litter reduced the number of flowering individuals of S. faberii and the number of seeds per plot; Quercus litter increased the production of seeds per individual. We conclude that species-dependent effects of litter on plant populations may significantly alter interspecific interactions and change plant community structure through direct and indirect effects.
Water repellency is influenced by soil management and biological process. We carried out a 60-day laboratory incubation experiment to evaluate the effects of straw amendment, together with the intensity and frequency of wetting and drying (W/D), on microbial processes and water repellency. One W/D cycle consisted of 1.5-day wetting at −0.03 kPa from the soil core bottom and different drying lengths in a temperature-controlled laboratory, resulting in different drying intensities. At a regular interval, soil respiration rate (SRR) on drying and wetting, soil microbial biomass C and N (SMB-C and N), and soil water repellency (SWR) after the wetting were measured simultaneously. Rice straw amendment had a greater effect on SRR, but smaller influences on SMB and SMB-C : N than W/D frequency and drying intensity. The first W/D caused the largest decrease in soil respiration and the soil respiration recovered partly in the subsequent W/D cycles. The increase in SMB and SMB-C : N as well as metabolic quotient with W/D frequency and intensity suggested a shift of microbial community from bacterial dominance to fungal dominance. SWR was significantly related to SMB-C (R2= 0.689, P < 0.001). However, this study was limited to these indirect measurements. Direct measurements of fungal biomass and microbial community are needed in the future. The results suggest that rice straw amendment in dry season may increase C sequestration due to reduced decomposition and stabilize soil structure due to the enhancement of microbial induced water repellency.
20 plant species (10 monocots and 10 dicots) grown in Kerqin sandy grassland were incubated under indoor conditions to monitor the amount and rate of CO2 release from the leaf litter. 11 traits of mature fresh leaves including caloric value, contents of Mg, P, N, K, C, C/N, N/P, specific leaf area, dry matter content and leaf surface area were measured to determine the relationship between CO2 release and leaf characteristics. All those traits have great variation among the 20 species with over 3 fold differences between the maximum and minimum values, and a few traits such as leaf Mg content reached as high as 9 folds. After 28 d's incubation, the average CO2 release amount from all the species was (4121 ± 1713) μg kg−1 dry soil. The highest level from Chenopodium acuminatum was (8767 ± 177) μg kg−1 dry soil, which was 5 folds higher than the lowest level ((1669 ± 47)μg kg−1 dry soil) from Digitaria sanguinalis. However, CO2 release rate showed the same trend in all the 20 species, i.e., the leaf litter decomposed faster initially (0–4 d), and gradually slowed down during extended cultural periods. Comparison between monocots and dicots showed that these two taxonomic groups had significant differences in terms of the amount and rate of CO2 released from leaf litter, and N and C contents, leaf C/N, and dry matter content of mature leaves. Contents of N, C and dry matter, and C/N of mature leaves are significantly correlated with CO2 release from leaf litter decomposition, which has been revealed by the Pearson correlation test. It can be concluded that these three traits of mature leaves can be used indirectly to predict decomposition rate of the leaf litter.
Litter layers have a negative effect on seedling recruitment in many ecosystems. Successional fen grasslands are characterized by the built-up of litter layers which might be a key-factor influencing species composition and diversity during succession. Seed size is thought to be an important feature for the regeneration niche of species. Large seed size has been shown to be of advantage for germination and establishment under shaded conditions and beneath litter layers and thus for late-successional species.We investigated the effects of litter (control, litter layer of 3 cm and 8 cm) on seedling recruitment in 35 grassland species varying in seed size and successional status and on the abiotic conditions temperature, light quantity and light quality. Furthermore, we analyzed the species' light requirement for germination and its relation to seed size, successional status and establishment beneath litter.Light quantity was significantly lower beneath litter (reduction of 78% and 91% beneath 3 cm and 8 cm litter, respectively). The R/FR-ratio decreased from 1.2 without litter to 0.8 and 0.6 in presence of 3 cm and 8 cm litter. Seedling recruitment of 33 species was hampered by a litter layer. Establishment in presence of litter was positively related to seed size (r = 0.62, p < 0.001 and r = 0.46, p < 0.01 for 3 cm and 8 cm litter, respectively). In addition, establishment of early-successional species was hampered by litter to a significantly greater extent than recruitment of late-successional species independent of seed mass (ANCOVA: F = 7.6, p < 0.01). We found a positive relation between seed mass and the proportion of germination in darkness (r = 0.57, p < 0.001) indicating that small-seeded species had a higher light requirement for germination. We also found positive relationships between the proportion of germination in darkness and establishment in the 3 cm and the 8 cm litter treatment (r = 0.4, p < 0.05 and r = 0.3, p < 0.05 for 3 cm and 8 cm litter, respectively).We conclude that species-specific effects on seedling establishment are mainly due to differences in seed mass, successional status, and light requirement for germination and that these factors thus influence species composition and diversity during abandoned fen grassland succession.Nach der Nutzungsaufgabe ist die Sukzession auf Feuchtgrünland-Brachen durch die Bildung mächtiger Streuauflagen gekennzeichnet. Durch Effekte auf Keimung und Etablierung beeinflusst die Streuauflage die Artenzusammensetzung und -vielfalt und wird deshalb als ein Schlüsselfaktor für die Vegetationsentwicklung angesehen.In einem Gewächshaus-Experiment wurde der Einfluss unterschiedlicher Streumächtigkeiten (Kontrolle, 3 cm und 8 cm) auf die abiotischen Faktoren Temperatur, Lichtintensität und Lichtqualität sowie auf die Keimlingsetablierung von 35 Grünlandarten untersucht. Die ausgewählten Arten unterscheiden sich hinsichtlich ihres Samengewichts (von 0,1 bis 4,8 mg) sowie ihres Verhaltens im Sukzessionsverlauf (Arten früher sowie später Sukzessionstadien). Weiterhin wurden die Zusammenhänge zwischen der Lichtbedürftigkeit der Keimung und dem Samengewicht, dem Verhalten im Sukzessionsverlauf und der Keimlingsetablierung unter Streuauflagen analysiert.Unter den Streuvarianten war die Lichtintensität signifikant niedriger als in der Kontrolle (Reduktion um 78% und 91% unter 3 und 8 cm Streuauflage). Das Hellrot/Dunkelrot-Verhältnis sank von 1,2 ohne Streuauflage auf 0,8 und 0,6 unter 3 bzw. 8 cm Streumächtigkeit. Die Keimlingsetablierung von 33 Arten wurde durch die Streu signifikant verringert. Die Etablierung von Arten mit einem hohen Samengewicht wurde weniger durch die Streuauflagen beeinflusst als diejenige kleinsamiger Arten (r = 0,62, p < 0,001 und r = 0,46, p < 0,01 für 3 cm und 8 cm Streumächtigkeit). Zusätzlich wurde (auch bei Berücksichtigung des Samengewichts als Kovariable) die Keimlingsetablierung von Arten früher Sukzessionsstadien stärker verringert als die von Arten später Sukzessionsstadien (ANCOVA: F = 7,6, p < 0,01). Weiterhin wurde ein positiver Zusammenhang zwischen dem Samengewicht und dem Keimungsprozentsatz im Dunkeln gefunden (r = 0,57, p < 0,001), was zeigt, dass kleinsamige Arten eine höhere Lichtbedürftigkeit für die Keimung aufweisen. Auch zwischen dem Anteil der Keimung im Dunkeln sowie der Keimlingsetablierung unter Streuauflagen wurden positive Zusammenhänge nachgewiesen (r = 0,4, p < 0,05 und r = 0,3, p < 0,05 für 3 cm bzw. 8 cm Streumächtigkeit).Die Ergebnisse zeigen, dass die artenspezifischen Unterschiede hinsichtlich der Keimlingsetablierung unter Streuauflagen im Wesentlichen durch die Faktoren Samengewicht, Lichtbedürftigkeit für die Keimung sowie das Sukzessionsverhalten erklärt werden können und dass diese Eigenschaften somit die Artenzusammensetzung und -vielfalt während der Sukzession auf Feuchtgrünland-Brachen beeinflussen.
Using the litter bag technique, the decomposition rates and their influencing factors were studied by investigating three wetland macrophytes, Calamagrostics angustifolia, Carex meyeriana and Carex lasiocapa, in Sanjiang Plain, Northeast China. It was revealed that C. lasiocapa lost 28.91% of its weight, C. angustifolia lost 31.98% and C. meyeriana lost 32.99% after 164 days. Another finding was that the amount of organic carbon in the litter of C. angustifolia and C. lasiocapa fluctuated, but continuously decreased in that of C. meyeriana. However, all the three types of litter released organic carbon. Nitrogen was released substantially from the litter of both C. angustifolia and C. meyeriana, but accumulated in the litter of C. lasiocapa. Phosphorus concentrations in all the three types of litter apparently decreased first and then slightly increased. Overall, P release was observed in all the three types of litter. The C/N and C/P ratios varied significantly in the decomposition process. The decomposition rates and nutrient content variations were simultaneously influenced by the quality of the litter as well as the environmental factors in the Sanjian Plain, but they were more strongly affected by the quality of the litter.
We report data on leaf litter production and decomposition from a manipulative biodiversity experiment with trees in tropical Panama, which has been designed to explore the relationship between tree diversity and ecosystem functioning. A total of 24 plots (2025 m ² ) were established in 2001 using six native tree species, with 1‐, 3‐, and 6‐species mixtures. We estimated litter production during the dry season 2005 with litter traps; decomposition was assessed with a litter bag approach during the following wet season.
Litter production during the course of the dry season was highly variable among the tree species. Tree diversity significantly affected litter production, and the majority of the intermediate diverse mixtures had higher litter yields than expected based on yields in monoculture. In contrast, high diverse mixtures did not show such overyielding in litter production. Litter decomposition rates were also highly species‐specific, and were related to various measures of litter quality (C/N, lignin/N, fibre content). We found no overall effect of litter diversity if the entire litter mixtures were analyzed, i.e. mixing species resulted in pure additive effects and observed decomposition rates were not different from expected rates. However, the individual species changed their decomposition pattern depending on the diversity of the litter mixture, i.e. there were species‐specific responses to mixing litter. The analysis of temporal C and N dynamics within litter mixtures gave only limited evidence for nutrient transfer among litters of different quality.
At this early stage of our tree diversity experiment, there are no coherent and general effects of tree species richness on both litter production and decomposition. Within the scope of the biodiversity‐ecosystem functioning relationship, our results therefore highlight the process‐specific effects diversity may have. Additionally, species‐specific effects on ecosystem processes and their temporal dynamics are important, but such effects may change along the gradient of tree diversity.
Changes in the carbon, hydrogen, nitrogen and polyphenol content of chestnut and beech leaves were measured during the first year after fall. Chestnut leaves had an initial carbon, hydrogen and nitrogen content (by weight) of 48.71%, 5.56% and 0.77% respectively; beech had a similar carbon and hydrogen content (47.77% and 5.36%) but less nitrogen (0.56%). Both leaf litter types showed percentage increases in nitrogen content during the study period but only the beech showed absolute increases in nitrogen content of up to 66.7% of the initial weight present in the leaves. The percentage increases in the nitrogen content of chestnut litter were largely attributable to more rapid losses of non-nitrogenous leaf constituents while the weight of nitrogen present in the leaves remained relatively constant. The percentage carbon and hydrogen contents of the chestnut and beech litter showed changes of less than 1% throughout the year, indicating that carbohydrate losses were directly proportional to weight losses. Soil animals fed on chestnut leaves to a far greater extent than beech leaves; this difference did not appear to be directly attributable to differences between the nitrogen contents or C/N ratios of the two leaf litter species. The gross polyphenol contents of chestnut and beech litter showed an intraspecific inverse correlation with the feeding activities of soil animals on the leaves, but did not account for interspecific differences in leaf palatability since chestnut leaves were eaten when they contained higher polyphenol concentrations than beech leaves. However, there was an interspecific negative correlation between palatability and the presence of protocatechuic and gallic acids.
We assessed whether exposure to solar ultraviolet-B radiation (UV-B) affects the mass loss of Larrea tridentata (creosotebush) litter in the Sonoran Desert of central Arizona. We placed three types of litter (leaves, twigs, or a natural
mixture of leaves, twigs, and seeds) in bags constructed of UV-B-transmitting or UV-B-absorbing filter material that allowed
either 85% (near-ambient UV-B treatment) or 15% (reduced UV-B treatment) of the biologically effective solar UV-B to reach
litter inside the bags. Bags were placed outdoors for 4–5months during the winter at two sites: a balcony or on the soil
surface of the desert. Mass loss of leaf litter was greater under near-ambient UV-B than reduced UV-B at both sites: 21 (near-ambient)
vs. 18% (reduced) on the balcony, and 18 vs. 14% at the desert site. Mass loss of twig litter was also greater under near-ambient
UV-B at the desert site. Mass loss of the natural mixture of litter was also greater when exposed to near-ambient UV-B on
the balcony, and tended to be greater at the desert site. We estimate that about 14–22% of the total mass loss of leaf litter
during our 4–5 month experiments was attributable to solar UV-B exposure. Leaf litter exposed to near-ambient UV-B had lower
concentrations of lignin, and fats and lipids, and slightly higher concentrations of holocellulose. The greater mass loss
of litter under near-ambient UV-B appeared mainly attributable to loss of lignin, although losses of fats and lipids were
also appreciable. A primary reason for greater mass loss of litter under solar UV-B appeared to be photodegradation, particularly
of lignin.
Question
What are the physical and chemical effects of plant litter on annual grassland community composition, above‐ground net primary production (ANPP), and density?
Location
California annual grassland.
Methods
We manipulated litter and light levels independently and in concert. Litter removal and litter addition treatments tested both the physical and chemical impacts of litter's presence. We additionally simulated the effect of litter physical shading by using shade cloth, and added powdered litter to test for the chemical impacts of decomposing litter.
Results
Increased whole litter and shading decreased grass germination and establishment, but not that of forbs or legumes. Species shifts occurred within all groups across treatments, including a transition from small‐seeded to large‐seeded grass and legume species with increased shading. ANPP was highest in control plots (473 ± 59 g/m ² ), and species richness was highest in litter removal plots. While the physical effects of litter via shading were significant, the chemical effects of adding powdered litter were negligible.
Conclusions
This work suggests that over one growing season, the physical impacts of litter are more important than chemical impacts in shaping community structure and ANPP in annual grasslands. Changes in light availability with altered litter inputs drive shifts in species and functional group composition. Litter feedbacks to ANPP and species composition of local patches may help maintain diversity and stabilize ANPP in this grassland.
Controls of temperature and moisture on root decomposition have not been well studied despite their direct relevance to climate change impacts on root carbon flux. The main objective of this laboratory study was to examine the respiration response of Sitka spruce, Douglas-fir, western hemlock, ponderosa pine, and lodgepole pine decomposing roots (1–3 cm in diameter) to temperature and moisture change. Roots of Sitka spruce, Douglas-fir and western hemlock, and ponderosa pine and lodgepole pine were collected from Cascade Head, H.J. Andrews, and Pringle Falls site, respectively. Dead root respiration increased with temperature and reached the maximum at 30–40°C, and then decreased. Analysis of covariance indicated that the Q10 of root decomposition rate was influenced significantly (p<0.01) by incubation temperature range 5–40°C, but not by species, decay class or the direction of temperature change. At 5–10°C, Q10 averaged 3.99 and then decreased to 1.37 at 30–40°C. Over a range of 5–60°C, Q10 could be predicted by a single-exponential model using temperature as the independent variable. Analysis of variance showed that the respiration rate of dead roots was significantly (p<0.01) influenced by root moisture, species, and decay class as well as temperature. Dead root respiration increased with root moisture, reached the optimum range when moisture was between 100 and 275% and then decreased. Moreover, there were apparent interactions of root moisture and temperature on root respiration. Our study showed the direction of temperature and moisture change did not significantly influence root respiration, indicating that hysteresis may not occur for the temperature and moisture ranges examined. To better model global climate warming effects on root carbon flux, we suggest a temperature dependent Q10 function should be incorporated into current root dynamics models. The short-term laboratory incubation approach provided a good way to examine temperature and moisture controls on root decomposition, although we are cautious about long-term mass-loss extrapolations based on these short-term results.