Plant Litter Mass Research Articles

Contributions of plant litter to soil microbial activity improvement and soil nutrient enhancement along with herb and shrub colonization expansions in an arid sandy land

Shrubs and herbs are two important types of vegetation that play a pivotal role in combating land desertification in arid sandy land. Yet, the effects of plant litter on sandy soil microbial activities and soil nutrients during the shrub and herb colonization process are still unclear. Here, contributions of plant litter to soil microbial activity improvement and soil nutrient enhancement along herb and shrub colonization expansion interfaces were studied in an arid sandy landscape. Plant litter mass, soil water content, pH, nutrient content, extracellular enzyme activities, and microbial community structure (taxon composition, α-diversity, β-diversity, and co-occurrence pattern) of soils at depths of 0–10 cm were examined relative to the colonization processes of shrubs and herbs (shrub and herb vegetation → sand-shrub and sand-herb interface → a sand dune) in an arid sandy land. We found that the processes of both herb and shrub colonization significantly increased litter cumulative mass at the soil surface to soil depths of 5 cm, and shrub colonization contributed several folds more litter than herb colonization. Plant litter input significantly decreased soil pH, accelerated soil extracellular enzyme activities, increased abundances of some microbial phyla (Actinobacteria, Chloroflexi, Acidobacteria, Gemmatimonadetes, Patescibacteria, Armatimonadetes, Ascomycota, Moritierellomycota, and Chytridiomycota), enhanced both prokaryotic and fungal α-diversities, altered both prokaryotic and fungal communities, and promoted complexity of microbial networks during both herb and shrub colonization. As a result, microorganisms actively participated in litter decomposition and soil nutrient enhancement. Nevertheless, shrub colonization process exhibited greater potential in nutrient input than herb colonization process due to its greater plant litter input, though both colonization played a comparable role in accelerating soil enzyme activity and improving soil microbial community diversity and co-occurrence. Therefore, xeromorphic shrubs are still more important plants than herbs should be used for vegetation construction and ecological restoration in arid sandy land.

Maize/peanut intercropping has greater synergistic effects and home-field advantages than maize/soybean on straw decomposition.

The decomposition of plant litter mass is responsible for substantial carbon fluxes and remains a key process regulating nutrient cycling in natural and managed ecosystems. Litter decomposition has been addressed in agricultural monoculture systems, but not in intercropping systems, which produce species-diverse litter mass mixtures. The aim here is to quantify how straw type, the soil environment and their combined effects may influence straw decomposition in widely practiced maize/legume intercropping systems. Three decomposition experiments were conducted over 341 days within a long-term intercropping field experiment which included two nitrogen (N) addition levels (i.e. no-N and N-addition) and five cropping systems (maize, soybean and peanut monocultures and maize/soybean and maize/peanut intercropping). Experiment I was used to quantify litter quality effects on decomposition; five types of straw (maize, soybean, peanut, maize-soybean and maize-peanut) from two N treatments decomposed in the same maize plot. Experiment II addressed soil environment effects on root decomposition; soybean straw decomposed in different plots (five cropping systems and two N levels). Experiment III addressed 'home' decomposition effects whereby litter mass (straw) was remained to decompose in the plot of origin. The contribution of litter and soil effects to the home-field advantages was compared between experiment III ('home' plot) and I-II ('away' plot). Straw type affected litter mass loss in the same soil environment (experiment I) and the mass loss values of maize, soybean, peanut, maize-soybean, and maize-peanut straw were 59, 77, 87, 76, and 78%, respectively. Straw type also affected decomposition in the 'home' plot environment (experiment III), with mass loss values of maize, soybean, peanut, maize-soybean and maize-peanut straw of 66, 74, 80, 72, and 76%, respectively. Cropping system did not affect the mass loss of soybean straw (experiment II). Nitrogen-addition significantly increased straw mass loss in experiment III. Decomposition of maize-peanut straw mixtures was enhanced more by 'home-field advantage' effects than that of maize-soybean straw mixtures. There was a synergistic mixing effect of maize-peanut and maize-soybean straw mixture decomposition in both 'home' (experiment III) and 'away' plots (experiment I). Maize-peanut showed greater synergistic effects than maize-soybean in straw mixture decomposition in their 'home' plot (experiment III). These findings are discussed in terms of their important implications for the management of species-diverse straw in food-production intercropping systems.

Changes in the nitrogen isotopic composition during the transformation of peat-forming plant litter at dried and post-pyrogenic sites of oligotrophic bogs

The aim of the study. Assessment of changes in the nitrogen isotopic composition (δ15N) during the decomposition of the main peat-forming plants’ litter in peat of oligotrophic bog ecosystems in the southern taiga subzone of West Siberia. Location and time of the study. The studies were carried out in 2019–2021 in two oligotrophic bogs: “Bakcharskoye” (field station “Vasyuganye” (IMCES SB RAS)) and “Iksinskoye”, which are the north-eastern spurs of the Great Vasyugan mire and located in the Bakcharsky district of the Tomsk region, Russia. Methods. The decomposition rate of peat-forming plants’ litter was determined by the method of partially isolated samples, which is widely used to study the transformation of plant material and peat. The nitrogen isotopic composition in the original and decomposed samples of the plant material was determined by isotope ratio mass spectrometry using a DELTA V Advantage mass spectrometer combined with a Flash 2000 elemental analyzer (EA-IRMS). Results. A three-year study of the decomposition of peat-forming plants (Sphagnum fuscum, Chamaedaphne calyculata, Eriophorum vaginatum and a Mixed sample) in four ecosystems (natural - VASnat, drained - VASdry, post-pyrogenic - Iksa1 and Iksa2) showed that melioration and fire influenced the litter decomposition rate, increasing the latter in the drained bog and slowing down Sph. fuscum and Mixed sample decomposition by 1.5–9.0% at the site with pyrogenic effects. During the plant litter transformation carbon and nitrogen were released as 24–62% and 21–46%, respectively. In all studied samples, except for Sph. fuscum, a relationship was revealed between the plant litter mass loss and changes in the nitrogen isotopic composition. Conclusions. The effect of peat fires is manifested by a decrease in the plant residue decomposition rate. The dynamics of changes in the isotopic composition during the transformation of the studied plant residues depended on the plant species, but does not depend on decomposition duration (1, 2, 3 years) and sample location. Key words: transformation of plant residues; nitrogen isotopes; biogeochemical cycle; pyrogenic peatlands; drained peatlands; West Siberia.

Grazing season regulates plant community structure and production by altering plant litter mass in a typical steppe

AbstractAimsGrazing different grasslands with seasonal changes is the tradition in pastoral systems in natural grassland regions worldwide. The effects and mechanisms of different grazing seasons on semi‐arid steppe vegetation are less explored on the Mongolian Plateau. Therefore, we assessed the impact and underlying mechanisms of grazing seasons on grassland community structure and production.LocationXilingol, Inner Mongolia, China.MethodsWe conducted a three‐year experiment to investigate the effects of grazing in four different seasons under the same grazing intensities on plant community structure and production in a typical steppe rangeland. The experiment was a random‐block design, with 20 grassland paddocks of 50 m × 50 m, representing five treatments (i.e., early spring, summer, autumn, mid‐winter, and no grazing), replicated by four blocks. We monitored the changes in soil properties, plant litter mass (i.e., standing dead biomass and dead plant material on the soil surface) and plant species composition and production across grazing treatments.ResultsPlant community height and above‐ground biomass were higher under early spring and winter grazing than autumn and summer grazing and no grazing. This divergence in plant community structure was mainly mediated by the seasonal patterns of plant litter mass across the grazing regimes. A high plant litter mass enhanced soil moisture by accumulating snow in winter and reducing soil evaporation during the growing season, which benefit plant growth. The removal of plant litter before the growing season increased the reception of solar radiation, thus improving soil temperature and plant production. The changes in community microenvironment and selective grazing led to the changes in plant species composition especially under summer and autumn grazing.ConclusionsOur results imply that grazing in winter or in early spring before plants start to turn green is more efficient than the complete animal exclusion for the natural recovery of degraded grassland in Inner Mongolia. It is suitable to incorporate cold‐season grazing in the development of sustainable grassland management systems.

Soil degradation influences soil bacterial and fungal community diversity in overgrazed alpine meadows of the Qinghai-Tibet Plateau

Over half of the alpine meadows in the Qinghai-Tibet Plateau (QTP) are degraded due to human activities. Soil degradation from overgrazing is the most direct cause of grassland degradation. It is thus important to synthesize the effects of multiple soil degradation indicators on the belowground biomass of plants and soil microorganisms in the degraded QTP. We studied the diversities and structures of soil bacterial and fungal communities using soil bacterial 16S rRNA and the fungal ITS gene under four degradation gradients, D1: lightly degraded, D2: moderately degraded, D3: highly degraded, and a non-degraded control site (CK). The bacterial Shannon diversity in D3 was significantly lower than that in D1 (p < 0.001), and the bacterial richness index in D3 was significantly lower than that in D1 (p < 0.001). There was no difference in soil fungal diversity among the different degradation levels; however, soil fungal richness decreased significantly from CK to D3. The phyla Actinobacteria, Acidobacteria and the genus Mortierella were differed significantly under the four degradation gradients. Plant litter mass and root C/N ratio were important factors associated with bacterial and fungal diversity and richness. These results indicated that alpine meadow degradation can lead to variations in both microbial diversity and the potential functioning of micro-organisms in the QTP.

Effects of a glyphosate-based herbicide on soil animal trophic groups and associated ecosystem functioning in a northern agricultural field

Despite an increasing concern of consequences of using vast amounts of glyphosate-based herbicides in agroecosystems, their potential effects on non-target soil organisms and soil functioning are mostly unknown. It has also been argued that fields in northern latitudes should be under special surveillance as the short active period of decomposers may restrict glyphosate degradation. We investigated the effects of a glyphosate-based herbicide, Roundup, on the abundance of enchytraeids and nematodes, both essential groups in decomposer food webs, and plant litter mass loss and soil availability of mineral N in a two-year agricultural field setting in south-west Finland. Our experiment consisted of (1) non-treated weed plots, (2) plots, where weeds were killed by hoeing, and (3) plots treated with both Roundup and hoeing. We found that killing plants by hoeing had drastic effects on soil fauna and functioning, and apparently, distinguishing these effects from direct glyphosate effects is profoundly important when evaluating glyphosate risks in soils. In contrast, the effects of Roundup on soil fauna and functioning were minor and transient and no glyphosate remains were found in the soil at the end of the experiment. These results suggest that side-effects can be minor and glyphosate degradation effective also in soil under northern climatic conditions.

Warming effects on the decomposition of two litter species in model subtropical forests

Warming has the potential to alter plant litter mass loss and nutrient release during decomposition. However, a great deal of uncertainty remains concerning how other factors such as litter species or substrate quality might modify the effects of increased temperature on decomposition. Meanwhile, the temperature sensitivity of plant litter decay in tropical and subtropical forest ecosystems remains poorly resolved. This study was designed to assess the effects of experimental warming on litter decomposition and nutrient release of two contrasting tree species (Schima superba and Machilus breviflora) by translocating model forest ecosystems from the high-elevation sites to the lower-elevation sites in subtropical China. Translocating model mountain evergreen broad-leaved forest (MEBF) to the altitude of 300 m and 30 m increased the average monthly soil temperature at 5 cm depth by 0.88 and 1.84 °C, respectively during the experimental period. Translocating model coniferous and broad-leaved mixed forest (CBMF) to the altitude of 30 m increased the average monthly soil temperature at 5 cm depth by 0.85 °C. We found that experimental warming accelerated litter decomposition in both model forest types, and the promoting efficiency was greater when the temperature increased. The litter with high quality (Schima superba) had stronger response to warming than low quality litter (Machilus breviflora). Warming accelerated Na, K, Mg, P, N and Ca release from Schima superba litter, but only simulated Ca release from Machilus breviflora litter. Overall, litter decomposition was controlled by the order: soil temperature > litter quality > soil moisture > litter incubation forest type under experimental warming in the subtropical China. We conclude that leaf litter decomposition was facilitated by experimental warming in subtropical China. Litter species might modify the effects of increased temperature on litter decomposition; however, forest type has no effect on litter decomposition.

Comparison of plant litter and peat decomposition changes with permafrost thaw in a subarctic peatland

Organic matter decomposition in response to thawing permafrost has critical implications for carbon release. This study examined how thaw induced plant community and environmental changes influenced litter and peat decomposition in a subarctic peatland. We conducted laboratory incubations under current site pre-thaw (dry and large oxic peat layer) and thawed (wet and small oxic peat layer) conditions, and mimiced pond thaw conditions (water saturated and anoxic) at 4 and 22 °C. Carbon dioxide (CO2) and methane (CH4) releases from ground surface plant litter and top 1 m peat samples at permafrost area (Palsa) and wet thawed lawn (WL) were quantified under current site conditions. Dissolved organic carbon (DOC) released from litter was additionally quantified under pond thaw conditions. Plant litter mass significantly increased from Palsa to WL. Under current site conditions, litter in WL had significantly higher CO2 and CH4 production rates than litter in Palsa. Pond thaw conditions changed litter carbon loss partitioning into lower CO2 but higher DOC and CH4 production, and increased total carbon release. Whole peat decomposition was restricted from Palsa to WL with thaw. Estimated growing season gas carbon loss (CO2 and CH4) in WL was greater than that in Palsa due to significantly increased litter carbon loss after thaw. Changes in organic matter decomposition, especially litter decomposition, enlarged carbon losses from this subarctic peatland with permafrost thaw.

Understory plant functional groups and litter species identity are stronger drivers of litter decomposition than warming along a boreal forest post-fire successional gradient

Increasing surface temperatures due to climate change have the potential to alter plant litter mass loss and nutrient release during decomposition. However, a great deal of uncertainty remains concerning how ecosystem functioning may be affected by interactions between warming and other drivers, such as plant functional group composition and environmental context. In this study, we investigated how vascular plant litter decomposition and nutrient release were affected by experimental warming, moss removal and shrub removal along a post-fire boreal forest successional gradient. Our results show that litter decomposition and nutrient loss were primarily driven by understory plant functional group removal. The removal of mosses generally reduced litter mass loss and increased litter phosphorus (P) loss, while shrub removal typically increased litter mass loss and in one litter species reduced immobilization of P. Litter nitrogen (N) loss was unaffected by plant functional group removal. Warming interacted with successional stage and species identity of the litter decomposed, but these effects were uncommon and generally weak. As climate change advances, moss cover is expected to decrease, while shrub cover is expected to increase. Taken together with our results, this suggests that lower moss cover will decrease leaf litter decomposition rates and increase P release from litter, while increasing shrub cover will decrease decomposition rates and may reduce P release from litter. Our results demonstrate that in the short term, the direct effects of warming and successional stage will play a relatively minor role in driving litter decomposition processes in the boreal forest. In the long term, as the climate warms, temperature and its indirect effects via changes in the understory vegetation will play an important role in driving litter decomposition, thereby potentially altering C storage and nutrient cycling.

Grazing intensifies degradation of a Tibetan Plateau alpine meadow through plant-pest interaction.

Understanding the plant–pest interaction under warming with grazing conditions is critical to predict the response of alpine meadow to future climate change. We investigated the effects of experimental warming and grazing on the interaction between plants and the grassland caterpillar Gynaephora menyuanensis in an alpine meadow on the Tibetan Plateau in 2010 and 2011. Our results showed that grazing significantly increased nitrogen concentration in graminoids and sward openness with a lower sward height, sward coverage, and plant litter mass in the community. Grazing significantly increased G. menyuanensis body size and potential fecundity in 2010. The increases in female body size were about twofold greater than in males. In addition, grazing significantly increased G. menyuanensis density and its negative effects on aboveground biomass and graminoid coverage in 2011. We found that G. menyuanensis body size was significantly positively correlated with nitrogen concentration in graminoids but negatively correlated with plant litter mass. Even though warming did not significantly increased G. menyuanensis performance and the negative effects of G. menyuanensis on alpine meadow, the increases in G. menyuanensis growth rate and its negative effect on aboveground biomass under the warming with grazing treatment were significantly higher than those under the no warming with grazing treatment. The positive effects of grazing on G. menyuanensis performance and its damage were exacerbated by the warming treatment. Our results suggest that the fitness of G. menyuanensis would increase under future warming with grazing conditions, thereby posing a greater risk to alpine meadow and livestock production.

Priming in the microbial landscape: periphytic algal stimulation of litter-associated microbial decomposers.

Microbial communities associated with submerged detritus in aquatic ecosystems often comprise a diverse mixture of autotrophic and heterotrophic microbes, including algae, bacteria, protozoa, and fungi. Recent studies have documented increased rates of plant litter mass loss when periphytic algae are present. We conducted laboratory and field experiments to assess potential metabolic interactions between natural autotrophic and heterotrophic microbial communities inhabiting submerged decaying plant litter of Typha angustifolia and Schoenoplectus acutus. In the field, submerged plant litter was either exposed to natural sunlight or placed under experimental canopies that manipulated light availability and growth of periphytic algae. Litter was collected and returned to the laboratory, where algal photosynthesis was manipulated (light/dark incubation), while rates of bacterial and fungal growth and productivity were simultaneously quantified. Bacteria and fungi were rapidly stimulated by exposure to light, thus establishing the potential for algal priming of microbial heterotrophic decay activities. Experimental incubations of decaying litter with 14C- and 13C-bicarbonate established that inorganic C fixed by algal photosynthesis was rapidly transferred to and assimilated by heterotrophic microbial decomposers. Periphytic algal stimulation of microbial heterotrophs, especially fungal decomposers, is an important and largely unrecognized interaction within the detrital microbial landscape, which may transform our current conceptual understanding of microbial secondary production and organic matter decomposition in aquatic ecosystems.

Grazing exclusion affects soil and plant communities, but has no impact on soil carbon storage in an upland grassland

We evaluated the impact of 7 years of grazing exclusion on vegetation and belowground properties related to soil carbon (C) and nitrogen (N) cycling in grazed, upland grassland in northern England. For this, we compared a landscape-level, moorland restoration project (grazing exclusion) with adjacent continuously grazed acidic grasslands to test whether changes in vegetation composition after restoration impacted on soil properties including soil C storage. Grazing exclusion significantly increased the proportion of dwarf-shrubs at the expense of graminoids. Despite high seasonal variability, this change in vegetation was associated with increased plant litter mass, soil moisture content and the ratio of dissolved organic to inorganic N, and reductions in rates of ammonium mineralisation, soil microbial activity, and microbial biomass N. Our observations suggest that grazing-exclusion as a restoration tool for upland habitats results in a slowing down of rates of C and N cycling. However, as yet, this has had no detectable impact on total C and N stocks in surface soil. Whereas increases in soil C and N stocks might be expected in the longer term, our results suggest that a certain level of grazing is compatible with the provision of ecosystem services such as soil C storage under traditional upland farming practices.

The decomposition of Lolium perenne in soils exposed to elevated CO 2: comparisons of mass loss of litter with soil respiration and soil microbial biomass

Two key questions regarding the effects of elevated atmospheric CO 2 on soil microbial biomass are, (a) will future levels of elevated CO 2 affect the amount of microbial biomass in soil? and (b) how will any observed changes impact on C-flux from soils? These questions were addressed by examining soil microbial biomass, and in situ estimations of soil respiration in grassland soils exposed to free air carbon dioxide enrichment (60 Pa). Corresponding measurements of plant litter mass loss were taken using litter bags, ensuring that ambient litter was decomposed in ambient soil, and elevated CO 2 grown litter was decomposed in soils exposed to elevated CO 2. Significantly greater levels of microbial biomass ( p < 0.05, paired t-test) were detected in soils exposed to elevated CO 2 (1174.1 compared to 878.9 μg N g −1 dry soil for ambient CO 2 exposed soils). This corresponded with a significant increase ( p < 0.005, paired t-test) in in situ soil respiration from the elevated CO 2 acclimatised soils (28.7 compared to 20.4 μmol CO 2 m 2 h −1 from soils exposed to ambient CO 2). However, when soil respiration was calculated per unit of microbial biomass, no differences in activity per unit biomass were detected (approx. 0.02 μmol CO 2 m 2 h −1 unit biomass −1), suggesting that increased soil microbial biomass, rather than increased activity was responsible for the observed differences. The mass loss of litter was greater in the elevated CO 2 acclimatised soils ( p < 0.05, ANOVA), even though the initial nutrient ratios of the litter were not significantly different.