Effect of pruning material compost on the nitrogen dynamic,soil microbial biomass,and plant biomass in different soil types

Landscape and Ecological Engineering - Compost prepared using pruning material (PM) contains a higher amount of mineralizable carbon (C) than conventional compost, readily causing nitrogen (N)...     

Effects of recycled bentonite addition on soil properties, plant growth and nutrient uptake in a tropical sandy soil

The only way to increase the low CEC of sandy tropical soils over the long term is to apply high CEC materials such as 2:1 clay minerals. Acid activated bentonite is used in Thailand in the vegetable oil industry during the clarification process. The waste bentonite is discarded afterwards. The aim of the study was to compare the effects of the addition of these oil bentonites (OB) with the addition of cation beneficiated bentonite (BB) on soil properties and plant growth. Palm, rice and soybean OB, and bentonite beneficiated with calcium, magnesium, and potassium were applied at rates between 5 and 40 t ha⁻¹ to an Arenic Acrisol. Three consecutive crops of sorghum were grown in pots. Biomass and plant nutrient content were determined at each growth phase, and selective soil properties were measured at the start and the end of the study. Beneficiated bentonite was not water repellent, but the addition of OB resulted in soil water repellency. The application of bentonite at the rate of 40 t ha⁻¹ increased the cation exchange capacity (CEC) from 0.6 cmolc kg-1 in the control to 1.9 and 0.7 cmol_c kg⁻¹ in the BB and OB, respectiveley. The lower value of the CEC for OB compared to BB was probably due to the activation process and oil coating. OB applications at rates higher than 20 t ha⁻¹ did not increase biomass, and biomass decreased with increasing water repellency. The other treatments produced a higher biomass than the control. However biomass was below potential because of widespread nitrogen deficiency. Exchangeable K was exhausted in two crops, whatever the initial level, stressing the issue of K management in this soil type. Soybean OB is a promising material for soil chemical properties and biomass production, probably because of its low oil content.     

Short-term soil inorganic N pulse after experimental fire alters invasive and native annual plant production in a Mojave Desert shrubland

Post-fire changes in desert vegetation patterns are known, but the mechanisms are poorly understood. Theory suggests that pulse dynamics of resource availability confer advantages to invasive annual species, and that pulse timing can influence survival and competition among species. Precipitation patterns in the American Southwest are predicted to shift toward a drier climate, potentially altering post-fire resource availability and consequent vegetation dynamics. We quantified post-fire inorganic N dynamics and determined how annual plants respond to soil inorganic nitrogen variability following experimental fires in a Mojave Desert shrub community. Soil inorganic N, soil net N mineralization, and production of annual plants were measured beneath shrubs and in interspaces during 6 months following fire. Soil inorganic N pools in burned plots were up to 1 g m⁻² greater than unburned plots for several weeks and increased under shrubs (0.5–1.0 g m⁻²) more than interspaces (0.1–0.2 g m⁻²). Soil NO₃ ⁻−N (nitrate−N) increased more and persisted longer than soil NH₄ ⁺−N (ammonium−N). Laboratory incubations simulating low soil moisture conditions, and consistent with field moisture during the study, suggest that soil net ammonification and net nitrification were low and mostly unaffected by shrub canopy or burning. After late season rains, and where soil inorganic N pools were elevated after fire, productivity of the predominant invasive Schismus spp. increased and native annuals declined. Results suggest that increased N availability following wildfire can favor invasive annuals over natives. Whether the short-term success of invasive species following fire will direct long-term species composition changes remains to be seen, yet predicted changes in precipitation variability will likely interact with N cycling to affect invasive annual plant dominance following wildfire.     

氯嘧磺隆与尿素对土壤微生物生物量碳、氮及无机氮的影响

通过室内培养试验,研究了不同浓度氯嘧磺隆(20、200、2000 μg·kg-1土)单一施用及与尿素(120 mg· kg-1土)配合施用情况下,土壤微生物生物量碳、氮和土壤铵态氮、硝态氮随时间的动态变化规律.结果表明:各浓度氯嘧磺隆单独处理在整个培养期(60 d)中对微生物生物量碳、氮均有抑制作用,且浓度越高,后期抑制作用越强;各浓度氯嘧磺隆处理在培养前期对硝态氮、铵态氮没有明显影响,中期(15 d)能显著提高土壤中铵态氮的含量,后期(30 d后)显著提高了土壤中硝态氮的含量.尿素单独施用及与氯嘧磺隆配施均能在短时间内增加微生物生物量碳、氮,但随后配施处理的促进作用减弱;尿素单独和配施均能持久增加土壤中铵态氮、硝态氮含量.     

Root, mycorrhiza and earthworm interactions: their effects on soil structuring processes, plant and soil nutrient concentration and plant biomass

Earthworms, arbuscular mycorrhiza fungi (AMF) and roots are important components of the belowground part of terrestrial ecosystem. However, their interacting effects on soil properties and plant growth are still poorly understood. A compartmental experimental design was used in a climate chamber in order to investigate, without phosphorus (P) addition, the single and combined effects of earthworms (Allolobophora chlorotica), AMF (Glomus intraradices) and roots (Allium porrum) on soil structure, nutrient concentration and plant growth. In our experimental conditions, plant roots improved soil structure stability (at the level of macroaggregates) whereas earthworms decreased it. AMF had no effect on soil structure stability but increased P transfer from the soil to the plant and significantly increased plant biomass. Earthworms had no direct influence on P uptake or plant biomass, and the N/P ratio measured in the shoots indicated that P was limiting. Interactions between AMF and earthworms were also observed on total C and N content in the soil and on total root biomass. Their effects varied temporally and between the different soil compartments (bulk soil, rhizosphere and drilosphere). After comparison with other similar studies, we suggest that effects of earthworms and AMF on plant production may depend on the limiting factors in the soil, mainly N or P. Our experiment highlights the importance of measuring physical and chemical soil parameters when studying soil organism interactions and their influence on plant performance.     

Root biomass distribution and soil properties of an open woodland on a duplex soil

Data on the distribution of root biomass are critical to understanding the ecophysiology of vegetation communities. This is particularly true when models are applied to describe ecohydrology and vegetation function. However, there is a paucity of such information across continental Australia. We quantified vertical and horizontal root biomass distribution in a woodland dominated by Angophora bakeri and Eucalyptus sclerophylla on the Cumberland Plains near Richmond, New South Wales. The site was characterised by a duplex (texture contrast) soil with the A horizon (to 70 cm) consisting of loamy sand and the B horizon (to > 10 m) consisting of sandy clay. The topsoil had a smaller bulk density, a smaller water holding capacity but a larger organic component and a larger hydraulic conductivity in comparison to the subsoil. Root biomass was sampled to 1.5 m depth and declined through the soil profile. Whilst total biomass in the B horizon was relatively small, its contribution to the function of the trees was highly significant. Coarse roots accounted for approximately 82% of the root mass recovered. Lateral distribution of fine roots was generally even but coarse roots were more likely to occur closer to tree stems. Variation in tree diameter explained 75% of the variation in total below-ground biomass. The trench method suggested the belowground biomass was 6.03?±?1.21 kg m^?2 but this method created bias towards sampling close to tree stems. We found that approximately 68% of root material was within a 2 m radius of tree stems and this made up 54% of the total number of samples but in reality, only approximately 5 to 10% of the site is within a 2 m radius of tree stems. Based on these proportions, our recalculated belowground biomass was 2.93?±?0.59 kg m^?2. These measurements provide valuable data for modeling of ecosystem water use and productivity.     

Effects of nutrient additions on plant biomass and diversity of the herbaceous-subshrub layer of a Brazilian savanna (Cerrado)

The Brazilian Cerrado is a diversity hotspot due to its high level of endemism and rapid loss of habitats. It is estimated that the number of herbaceous species is four times higher than that of woody species. Increasing levels of nitrogen additions to natural ecosystems have been indicated as a determinant of biodiversity loss. We investigated the effects of nutrient additions on the productivity (aboveground and belowground) and on diversity of the herbaceous-subshrub layer of a Brazilian savanna (cerrado stricto sensu). The experiment was carried out in the IBGE Ecological Reserve, near Brasília, Brazil. Between 1998 and 2006, N, P, N plus P, or Ca were applied to sixteen 225 m² plots, arranged in a completely randomized design. Aboveground biomass was compared 1 year after the first fertilization and 10 years later. Floristic diversity was significantly different (P < 0.01) between the treatments. The highest and lowest species richness were presented in control and NP, respectively. The addition of P alone or in combination with N induced invasion by Melinis minutiflora (exotic C₄ grass). The aboveground biomass of this species was higher in NP and P plots. In the N treatment, Echinolaena inflexa (native C₃ grass) presented elevated cover and biomass but M. minutiflora was absent. The invasion by alien species resulted in negative impacts on native grass species. Besides changes in aboveground biomass, addition of N and P also led, although to a lesser extent, to changes in the root morphology and biomass, but these responses were modulated by seasonal variation in soil moisture. The results suggest that environmental changes in nutrient availability can lead to important consequences for diversity and functioning of this savanna where the numerous rare species have more chance to persist under dystrophic conditions as some species that tend to be dominant would be less competitive.     

Development of ground vegetation biomass and nutrient pools in a clear-cut disc-plowed boreal forest

Nutrient leaching from forest substrate after clear-cutting and subsequent soil preparation is strongly influenced by the capacity of ground vegetation to sequester the released nutrients. We studied the rates and patterns of biomass and nutrient accumulation in ground vegetation growing on ridges, in furrows and on undisturbed surfaces for 2–5 years after disc-plowing in eastern Finland. The biomass of mosses on ridges remained significantly lower than that in furrows and on undisturbed surfaces. Field layer biomass on ridges and in furrows was significantly lower than on undisturbed surfaces throughout the study period. Field layer biomass increased more on ridges than in furrows. Root biomass on ridges and undisturbed surfaces was considerably higher than in furrows. Five years after disc-plowing, total biomass and nutrient pools for ridges (biomass 4,975 kg ha⁻¹, N 40 kg ha⁻¹, P 5 kg ha⁻¹, K 20 kg ha⁻¹ and Ca 18 kg ha⁻¹) and undisturbed surfaces (biomass 5,613 kg ha⁻¹, N 43 kg ha⁻¹, P 5 kg ha⁻¹, K 22 kg ha⁻¹ and Ca 18 kg ha⁻¹) were similar, but considerably lower for furrows (biomass 1,807 kg ha⁻¹, N 16 kg ha⁻¹, P 2 kg ha⁻¹, K 10 kg ha⁻¹ and Ca 6 kg ha⁻¹). Ridges covered 25% of the area, furrows 30 and 45% was undisturbed surfaces. Taking into account the proportion of each type of surface, values for the whole prepared clear-cut area were 4,312, 34, 4, 18 and 14 kg ha⁻¹ for biomass, N, P, K and Ca, respectively. Biomass and nutrient pools had not returned to uncut forest levels at the end of the 5-year study period. The results indicate that mosses and field layer vegetation respond differently to soil preparation, that the development of biomass on ridges, in furrows and on undisturbed surfaces proceeds at different rates, and that the biomass and nutrient uptake of ground vegetation remains below pre-site preparation levels for several years. However, ridges, which are known to be the most susceptible to leaching, revegetate rapidly. Responsible Editor: Tibor Kalapos.     

Responses of a carnivorous plant to prey and inorganic nutrients in a Mediterranean environment

We have analysed the effect of prey and fertilization by inorganic nutrients on the survival, growth, reproduction (sexual and vegetative) and mucilage secretion of Pinguicula vallisneriifolia (Lentibulariaceae), a carnivorous plant inhabiting rocky substrates of southern Spain. We tested the hypothesis that carnivorous plants are more prey dependent when root access to nutrients is strongly limited by (1) analysing the importance of the carnivorous habit to the fitness of P. vallisneriifolia in its natural rocky habitat, and (2) determining whether the effect of trapped prey varies with soil nutrient levels. Our 2-year experimental results indicated prey to be limiting to P. vallisneriifolia growth on its natural rocky substrate. Animal food supply substantially increased the chance of survival, growth, vegetative propagation, sexual reproductive success and mucilage secretion. The differences between prey levels were more evident at the end of the experiment when all the surviving Prey-exclusion plants had lost weight, and the probability of sexual reproduction and of vegetative propagation by axillary buds had accordingly diminished. Furthermore, there were clear benefits from carnivory at the population level, since both the expected individual life span and the lifetime vegetative and sexual output correlated positively with the quantity of prey trapped. Application of insects to non-fertilized plants stimulated growth, but similar application to fertilized plants grown on a complete nutrient solution failed to enhance growth. There was no obvious benefit from the provision of a balanced mineral nutrient solution (alone or with prey). The greatest absolute growth and sexual and vegetative output resulted from providing a surplus of insects to plants on their natural rocky substrate. The strong dependence of P. vallisneriifolia on prey can therefore be considered a useful preadaptation enabling colonization of rocky substrates. Received: 11 November 1996 / Accepted: 31 March 1997     

Impact of soil leachate on microbial biomass and diversity affected by plant diversity

Plant and Soil - High plant diversity is usually linked with high soil microbial diversity, which is hypothesized to be attributed to a high diversity of components in the soil leachate, but...     

Diversity effects under different nutrient addition and cutting frequency environments in experimental plant communities

The effects of biodiversity on productivity have been well studied in the past decades. However, the responses of these biodiversity effects to modern grassland managements have not been explicitly tested. By establishing a five years diversity-manipulated experiment with different cutting frequency and nutrient addition levels, we explored the changes of biodiversity effects and the underlying mechanisms under these managements. Our results showed that community biomass increased with species richness. The correlations were observed under all management regimes, but their strengths varied with management intensity. The net biodiversity effects (NE) increased with nutrient supply, but reduced with frequent cutting. These two factors also interactively influenced NE. Importantly, their influences could last 5 years or longer. The NE changes mainly resulted from the variations of complementarity effects (CE), i.e., the aboveground space partitioning of our species. However, the selection effects (SE) were minimally influenced by nutrient addition and cutting frequency, indicating that under these conditions our species had comparably competitive strength. Especially, CE increased over time in highly cutting subplots, suggesting that this relationship was condition–dependent. We conclude that biodiversity is vitally important for ecosystem functioning even when the ecosystems are disturbed by human activities, and is most effective in enhancing biomass productivity under nutrient supply and low cutting frequency conditions. Field studies with species that come from other functional groups are needed to draw a more general conclusion.     

Soil microbial properties and plant growth responses to carbon and water addition in a temperate steppe: the importance of nutrient availability

Background

Global climatic change is generally expected to stimulate net primary production, and consequently increase soil carbon (C) input. The enhanced C input together with potentially increased precipitation may affect soil microbial processes and plant growth.

Methodology/Principal Findings

To examine the effects of C and water additions on soil microbial properties and plant growth, we conducted an experiment lasting two years in a temperate steppe of northeastern China. We found that soil C and water additions significantly affected microbial properties and stimulated plant growth. Carbon addition significantly increased soil microbial biomass and activity but had a limited effect on microbial community structure. Water addition significantly increased soil microbial activity in the first year but the response to water decreased in the second year. The water-induced changes of microbial activity could be ascribed to decreased soil nitrogen (N) availability and to the shift in soil microbial community structure. However, no water effect on soil microbial activity was visible under C addition during the two years, likely because C addition alleviated nutrient limitation of soil microbes. In addition, C and water additions interacted to affect plant functional group composition. Water addition significantly increased the ratio of grass to forb biomass in C addition plots but showed only minor effects under ambient C levels. Our results suggest that soil microbial activity and plant growth are limited by nutrient (C and N) and water availability, and highlight the importance of nutrient availability in modulating the responses of soil microbes and plants to potentially increased precipitation in the temperate steppe.

Conclusions/Significance

Increased soil C input and precipitation would show significant effects on soil microbial properties and plant growth in the temperate steppe. These findings will improve our understanding of the responses of soil microbes and plants to the indirect and direct climate change effects.     

Effects of Zn and P addition on the microbial biomass in a Zn deficient calcareous soil amended with glucose

A 35-day laboratory incubation experiment at 25°C was carried out to investigate the effects of Zn and P addition on microbial biomass C, N, and P in a Zn deficient calcareous soil, sampled at 15–40 cm depth in Central Anatolia, Turkey, amended with glucose. The underlying hypothesis was that P, but also Zn addition leads to a decrease in the microbial biomass C/N ratio. In the glucose-amended soil, the microbial biomass C/N ratio was not affected by the addition of P at day 5. At day 35 in this treatment, the significant P addition × day interaction revealed a significant decrease in the microbial biomass C/N ratio from 11.3 to 8.9. In the glucose-amended soil, Zn addition also had generally significant negative effects on microbial biomass C in comparison with the pure glucose treatment. A similar tendency was observed for microbial biomass N and consequently the microbial biomass C/N ratio remained unaffected. No evidence was found in the present incubation experiment that the microbial community suffered from Zn deficiency.     

Effects of nitrogen addition on litter decomposition, soil microbial biomass, and enzyme activities between leguminous and non-leguminous forests

Anthropogenic nitrogen (N) deposition is an expanding problem that affects the functioning and composition of forest ecosystems, particularly the decomposition of forest litters. Legumes play an important role in the nitrogen cycle of forest ecosystems. Two litter types were chosen from Zijin Mountain in China: Robinia pseudoacacia leaves from a leguminous forest (LF) and Liquidambar formosana leaves from a non-leguminous forest (NF). The litter samples were mixed into original forest soils and incubated in microcosms. Then, they were treated by five forms of N addition: NH₄ ⁺, NO₃ ^?, urea, glycine, and a mixture of all four. During a 6-month incubation period, litter mass losses, soil microbial biomass, soil pH, and enzyme activities were investigated. Results showed that mixed N and NO₃ ^?-N addition significantly accelerated the litter decomposition rates of LF leaves, while mixed N, glycine-N, and urea-N addition significantly accelerated the litter decomposition rates of NF leaves. Litter decomposition rates and soil enzyme activities under mixed N addition were higher than those under single form of N additions in the two forest types. Nitrogen addition had no significant effects on soil pH and soil microbial biomass. The results indicate that nitrogen addition may alter microbial allocation to extracellular enzyme production without affecting soil microbial biomass, and then affected litter decomposition process. The results further reveal that mixed N is a more important factor in controlling litter decomposition process than single form of N, and may seriously affect soil N cycle and the release of carbon stored belowground.