A comparison of the effects of cypermethrin, parathion-methyl and DDT on cereal aphids, predatory beetles, earthworms and litter decomposition in spring wheat

Extracellular enzyme activity and stoichiometry: The effect of soil microbial element limitation during leaf litter decomposition

PDF HTML阅读 XML下载 导出引用 引用提醒 三峡库区森林凋落叶化学计量学性状变化及与分解速率的关系 DOI: 10.5846/stxb201304090653 作者: 作者单位: 中国林业科学研究院亚热带林业研究所,中国林业科学研究院森林生态环境与保护研究所,中国林业科学研究院森林生态环境与保护研究所,中国林业科学研究院森林生态环境与保护研究所,中国林业科学研究院亚热带林业研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 林业公益性行业科研专项(201104008); 长江三峡库区(秭归)森林生态定位站资助 Dynamic of leaf litter stoichiometric traits dynamic and its relations with decomposition rates under three forest types in Three Gorges Reservoir Area Author: Affiliation: Research Institute of Subtropical Forestry, Chinese Academy of Forestry,Research Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry,Research Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry,Research Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:凋落物分解是森林生态系统生物元素循环和能量流动的重要环节,其过程是植物与土壤获得养分的主要途径。为了量化凋落叶化学计量学性状变化过程对分解的影响及对凋落物-土壤生物化学连续体的深层理解,用凋落物分解袋法研究了不同林型各自凋落叶化学计量学性状变化及与分解速率关系,结果表明:林下各自凋落叶分解速率是马尾松林 <栓皮栎林 <马尾松-栓皮栎混交林,马尾松林、栓皮栎林、马尾松-栓皮栎混交林凋落叶分解50%和95%的时间分别是2.11 a和9.15 a,1.93 a和8.45 a,1.76 a和7.77 a;凋落叶分解过程中,化学计量学性状变化明显,分解450 d后马尾松-栓皮栎混交林碳释放最快,栓皮栎林最慢;3种凋落叶起始N含量是栓皮栎林最高,马尾松林最低,分解450 d后马尾松林、栓皮栎林和马尾松-栓皮栎混交林N含量分别增加了66.67%、44.91%和44.52%,而P含量分别释放了30.80%、38.89%和42.29%。凋落物不同化学计量学性状与分解速率关系不同,3种林型凋落叶分解速率均与N含量呈正相关 (P<0.01),与C含量 (P<0.01)、C/N比 (P<0.01)呈负相关,与N/P比呈负二次函数关系 (P<0.01),而P含量与3种林型关系不同,与栓皮栎林 (P<0.01)和马尾松林(P < 0.05)呈负线性关系,与马尾松-栓皮栎混交林呈负二次函数关系 (P < 0.05)。研究表明,不同林型凋落叶分解中的养分动态趋向利于分解变化,N、P养分动态是生态系统碳平衡和凋落物分解速率的主要因素,混交林中混合凋落物的养分迁移是分解相对较快的原因。 Abstract:Litter decomposition is an important link between bioelement cycles and energy flow in the forest ecosystems, and the main source of nutrients for plants and soil. The relationships were studied between leaf litter stoichiometric traits dynamic and decomposition rate under different forest types using litter bag method in this paper to quantify the effects of stoichiometric traits dynamic on leaf litter decomposition and to get a better understanding to the biochemistry of litter-soil continuum. The results were showed as follows: the sequence of litter decomposition rate for the three forest types was Pinus massoniana stand (PM)< Quercus variabilis stand (QV)< P. massoniana-Q.variabilis mixed stand (PQ) and the litter decomposition rate was more and more significant with time. The remaining dry mass of litter in PM, QV and PQ were 67.59%, 64.75% and 62.13%, respectively after 450 d decomposition. The predicated period of litter decomposition 50% and 95% for PM, QV and PQ was 2.11 a and 9.15 a, 1.93 a and 8.45 a, as well as 1.76 a and 7.77 a, respectively. In these forest types, the concentration of C and P in decomposing litter decreased while N concentration increased with not significant. Leaf litter element dynamic was significantly different. The sequence of the initial C concentration was PQ< QV P<0.01), negatively with C concentration (P<0.01), C/N ratio (P<0.01), and negative quadratic function with N/P ratio (P<0.01). P concentration was different in three stands, and negatively linearly related to the decomposition rate for QV (P<0.01) and PM (P < 0.05), and negative quadratic related for PQ (P < 0.05). The decomposition rate and leaf litter stoichiometry was different among the three stands. The dynamic of C, C/N ratio and N/P ratio in the three stands were similar showing a significant positive correlation with N concentration. The possible reason for this may be that the plants in high latitudes are more susceptible to N restrictions, while those in low latitudes are more susceptible to P restrictions. Whether the plant is limited by N or P, the stoichiometry for different plants is influenced by different environmental factors. This study indicated that the nutrient dynamic during the decomposition of litter leaf under different forest types tend to help itself decompose. The concentration dynamic for N and P was the major factors in regulating carbon balance of ecosystem and litter decomposition, nutrient transfer in mixed litter is the reason for decomposition acceleration. 参考文献 相似文献 引证文献

Litter decomposition plays a pivotal role in carbon (C) and nutrient cycling in terrestrial ecosystems. However, little is known about the litter decomposition processes and nutrient dynamics in urban green space. In this study, the decomposition and nutrient dynamics of leaf litter and fine roots from Cinnamomum officinarum Nee ex Wall. and Elaeocarpus decipiens Hemsl. were studied in an urban forest in subtropical China. The results showed that the leaf litter mass loss, and nitrogen (N) and phosphorus (P) mineralization of E. decipiens were faster than that of C. officinarum in the first 180 days, but in the whole decomposition period, the leaf litter decomposition constant of C. officinarum was higher than that of E. decipiens. There was no difference in fine root decomposition constant and P mineralization, although the fine root N immobilization was higher relative to C. officinarum during the 90th to 270th days. Additionally, both the leaf litter mass loss, decomposition rate, and nutrient mineralization were faster than fine roots for these two tree species. The soil microbial biomass showed positive effects on leaf litter decomposition and negative effects on fine root decomposition. The correlation analysis indicated that initial litter quality, soil physicochemical properties, and microbial activity mainly affected early-stage litter decomposition and nutrient mineralization. Also, the leaf litter production and N and P storages of E. decipiens were higher than that of C. officinarum, suggesting faster decomposition rate and nutrient return for E. decipiens leaf litter. Consequently, we propose that tree species with fast nutrient return, such as E. decipiens, could be introduced to urban green space with pervious surfaces in respect of the nutrient balance. This work improves the understanding of litter decomposition and nutrient cycling and promotes the management for urban green space.

Elucidating the processes of leaf litter and fine root decomposition has been a major research focus, while how the correlation between leaf litter and fine root decomposition is unclear. We studied the in situ decomposition and N dynamics of leaf litter and fine root of four subtropical tree species (Pinus massoniana, Castanopsis hystrix, Michelia macclurei and Mytilaria laosensis) to determine whether leaf litter and fine root decomposition is correlated across species as well as which factors influence decomposition above versus below ground. Decomposition rate of leaf litter was related to that of fine root across species. The strong correlation between leaf litter and fine root decomposition rates arose largely for several reasons. First, soil moisture had the similar influences on both leaf litter and fine root decomposition rates. Second, traits (i.e., initial Ca concentration) important to both leaf litter and fine root decomposition rates showed significant similarity among species. Third, initial P, N and aromatic C concentrations, and C/N ratio were uniquely important for fine root decomposition rate, while no unique traits for leaf litter decomposition rate. This also could account for the strong correlation between leaf litter and fine root decomposition rates. Our study suggests that among these subtropical trees, species effects on in situ decomposition rates of leaf litter and fine root are very similar. Thus, species differences in decomposition rates may be as large as they would be if faster decomposition of leaf litter was correlated with faster decomposition of fine root. N immobilization rate of leaf litter was unrelated to that of fine root across species. Our results help explain some important mechanisms by which tree species influence litter in situ decomposition.

Defoliation and neighbouring legume plants accelerate leaf and root litter decomposition of Leymus chinensis dominating grasslands

Investigations to determine the optimum timing and placement of a supplementary food spray, Envirofeast® on the abundance of predatory insects on cotton was conducted in irrigated commercial cotton fields at Yarral near Narrabri, New South Wales, Australia, in 1998 v - v 99. Plots treated with the supplementary food product at the four-true leaf stage recorded a significantly higher number of predatory beetles, bugs and lacewings per metre compared with plots treated at two, six and eight-true leaf stages and unsprayed (control) plots. The cumulative total number of predatory beetles, bugs and lacewings recorded throughout the season in both treated and control plots was 23.81 per m. Of this total, plots treated at four true leaf stage recorded the highest (7.15 per v m) (i.e 30.03%), followed by two true leaf (5.81 per m) (24.41%), six true-leaf (4.31 per v m (18.12%), eight true-leaf stage (4.63 per v m) (i.e. 19.44%) and the unsprayed (control) plot recorded the lowest (1.91 per m (8.03%). The number of spiders per metre were not significantly different ( p v > v 0.05) among treatments and the control plots. The number of predators recorded in cotton crops treated with the supplementary food product as a band spray (33 v - v 50% band) or skip row spray (i.e. to every second row) was not significantly different ( p v > v 0.05) from plots where the product was applied as a solid spray to the entire crop (no skip row and/or no banding). Thus, tailoring Envirofeast® treatment in this way will ultimately reduce the quantity of product used, the cost of the product and allow cotton growers to adopt a multiple-use pattern for the product to support integrated pest management programmes in cotton.

To determine the importance of beetle predators on the natural control of cabbage root fly, experiments were carried out in 1958 and 1959 using various types of barriers to obtain different levels of beetle populations on cauliflower plots. A barrier of DDT‐treated straw, placed in the soil around some plots, decreased the numbers of beetles within them and allowed a greater number of eggs and larvae of cabbage root fly to survive than on the untreated plots, resulting in a greater crop damage. Another type of barrier allowed the beetles to enter plots but made it difficult for them to leave. On these, fewer cabbage root‐fly eggs and larvae survived and the crop damage was much less than on the plots surrounded by straw barriers. Where plants were treated with insecticide the root‐fly population was reduced to a minimum and crop yields were considerably increased. The insecticide, however, caused a reduction in the numbers of predatory beetles.

Chemistry and decomposition of leaf litter are integral to the carbon cycle in forest ecosystems. As leaves detach from trees, they accumulate on the forest floor, forming organic matter that serves as a source of energy and nutrients for soil microorganisms. Leaf litter decomposition releases carbon dioxide into the atmosphere and returns nutrients to the soil, which plants absorb. Climate change is expected to affect leaf litter chemistry and decomposition in forests significantly. Elevated temperatures may accelerate leaf litter decomposition, increasing carbon dioxide emissions. However, higher temperatures could worsen soil water stress, reducing water availability for plant growth and potentially slowing decomposition. Changes in precipitation patterns, such as increased drought frequency, can influence leaf litter chemistry and decomposition. Drought conditions may reduce soil moisture, slow decomposition and alter nutrient balance within leaf litter. Increased rainfall can enhance decomposition by providing moisture to support decomposer organisms. The chemical composition of leaf litter influences its decomposition rate. Leaves from different tree species contain varying levels of nitrogen, phosphorus, and other nutrients, affecting decomposition patterns. The chemistry and decomposition of leaf litter are key components of the carbon cycle within forest ecosystems, influenced by environmental and biotic factors. As climate change advances, these processes will be affected in complex ways, highlighting the importance of understanding their mechanisms. This understanding is essential for sustainable forest management in a changing world.

Microbes play an important role in decomposition of macrophytes in shallow lakes, and the process can be greatly affected by bacteria-fungi interactions in response to material composition and environmental conditions. In this study, microbes involved in the decomposition of leaf litter from three macrophyte species, Zizania latifolia, Hydrilla verticillata and Nymphoides peltata, were analysed at temperatures of 5, 15 and 25 °C. Results indicate that the decomposition rate was affected by temperature. Bacterial alpha diversity increased significantly along the time, while both temperature and plant species had a significant impact on the bacterial community, and plant type was shown to be the most important driving factor for the fungal community. The cosmopolitan bacterial taxa affiliated with Gammaproteobacteria, Bacteroidetes, Deltaproteobacteria, Firmicutes and Spirochaetes were key species in the investigated ecological networks, demonstrating significant co-occurrence or co-exclusion relationships with Basidiomycota and Ascomycota, according to different macrophyte species. This study indicates that bacteria involved in the decomposition of macrophyte leaf litter are more sensitive to temperature variance, and that fungi have a higher specificity to the composition of plant materials. The nutrient content of Hydrilla verticillata promoted a positive bacteria-fungi interaction, thereby accelerating the decomposition and re-circulation of leaf litter.

We examined the effects of elevated CO2 and O3 and their interaction on leaf litter chemistry and decomposition in pure stands of aspen (Populus tremuloides) and mixed stands of birch (Betula papyrifera) and aspen at the Aspen Free Air CO2 Enrichment (FACE) experiment. A 935-day in situ incubation study was performed using litterbags filled with naturally senesced leaf litter. We found that elevated CO2 had no overall effects on litter decomposition rates, whereas elevated O3 reduced litter mass loss (−13%) in the first year. The effect of O3 on mass loss disappeared in the second year. For aspen litter but not mixed birch-aspen litter, decomposition rates were negatively correlated with initial concentrations of condensed tannins and phenolics. Most soluble components (94% of soluble sugars, 99% of condensed tannins, and 91% of soluble phenolics) and any treatment effects on their initial concentrations disappeared rapidly. However, the mean residence time (MRT) of birch-aspen litter (3.1 years) was significantly lower than that of aspen litter (4.8 years). Further, because of variation in total litterfall, total litter mass, C, lignin and N remaining in the ecosystem was highest under elevated CO2 and lowest under elevated O3 during the incubation period. Our results indicate that elevated CO2 and O3 can alter short-term litter decomposition dynamics, but longer-term effects will depend more on indirect effects mediated through changes in forest community composition. Treatment effects on soluble components are likely to influence cyclical microbial processes and carbon pulses in the ecosystem only when coupled with increased (CO2) or decreased (O3) litter inputs.

Antagonistic effect of nitrogen additions and warming on litter decomposition in the coastal wetland of the Yellow River Delta, China

A new transgenic cotton producing the Vegetative Insecticidal Protein (Vip) is being developed to control Lepidopteran pests, especially Helicoverpa larvae. Before its introduction its efficacy against Helicoverpa larvae under field conditions needs to be confirmed, and any non-target effects it may have on the arthropod community need to be identified. We conducted field trials to compare the arthropod community in unsprayed conventional (Sicala 40) and Vip (Coker 312 Vip3A, event 102) cotton using visual searches, beatsheets, and suction samplers at 2 sites in Australia. At both sites, Vip controlled Helicoverpa larvae leading to much higher boll counts. There were no major differences in either species richness or diversity of the beneficial and non-target communities between Vip and conventional cotton, although cotton cultivar accounted for 2.7% of the variance in arthropod communities. There was no detrimental effect of Vip cotton on egg parasitoids. The number of predatory beetles and the pest mirid Creotiades dilutus (Stål) was higher in the Vip, although the increase in mirids was probably the result of more food (bolls) in the Vip crop. In a small plot experiment, we found higher numbers of whitefly in Vip, but this may be driven by differences in leaf hair between the cotton cultivars. Vip cotton appeared to have little effect on the arthropod community other than on Helicoverpa . As such it has the potential to be a useful tool in the management of Helicoverpa and may relieve resistance pressure on existing Bt cultivars (transgenic cotton containing genes for insecticidal Cry proteins), thereby increasing the durability of both technologies.

A new transgenic cotton producing the Vegetative Insecticidal Protein (Vip) is being developed to control Lepidopteran pests, especially Helicoverpa larvae. Before its introduction its efficacy against Helicoverpa larvae under field conditions needs to be confirmed, and any non-target effects it may have on the arthropod community need to be identified. We conducted field trials to compare the arthropod community in unsprayed conventional (Sicala 40) and Vip (Coker 312 Vip3A, event 102) cotton using visual searches, beatsheets, and suction samplers at 2 sites in Australia. At both sites, Vip controlled Helicoverpa larvae leading to much higher boll counts. There were no major differences in either species richness or diversity of the beneficial and non-target communities between Vip and conventional cotton, although cotton cultivar accounted for 2–7% of the variance in arthropod communities. There was no detrimental effect of Vip cotton on egg parasitoids. The number of predatory beetles and the pest mirid Creotiades dilutus (Stål) was higher in the Vip, although the increase in mirids was probably the result of more food (bolls) in the Vip crop. In a small plot experiment, we found higher numbers of whitefly in Vip, but this may be driven by differences in leaf hair between the cotton cultivars. Vip cotton appeared to have little effect on the arthropod community other than on Helicoverpa. As such it has the potential to be a useful tool in the management of Helicoverpa and may relieve resistance pressure on existing Bt cultivars (transgenic cotton containing genes for insecticidal Cry proteins), thereby increasing the durability of both technologies.

Farming practices for managing Inopus rubriceps (Macquart) (Diptera: Stratiomyidae) in sugarcane in Australia

SUMMARYThe effects of predation by carabid and staphylinid beetles and birds (blue‐ and great‐tits) on mature larvae of the codling moth Cydia pomonella were investigated in a field experiment. The number of predatory beetles on the ground beneath eight of 16 apple trees was reduced by an insecticide spray, and tits were excluded from the trunks and lower branches of eight trees by means of Terylene netting. Beetles had no significant effect on survival of larvae on trees, but only 8% of larvae survived to adulthood on trees exposed to blue‐ and great‐tits, whereas on trees protected from them 48% survived. Larvae were taken rapidly by the tits from the time larvae first built cocoons in summer and, by the time the majority of larvae had emerged from apples in late summer or autumn, tits had removed most from cocoons beneath flakes of bark glued to trees. Thus tits fed on larvae mainly in summer and autumn. On trees protected from tits, 8% of mature larvae were killed by fungi, of which Verticillium lecanii was most important. It was calculated that, of the larvae maturing in apples, 44% failed to build cocoons on the trees, 47% were taken by tits, then 1% were killed by fungi. Larvae failing to build cocoons on trees may build them on the ground. Of larvae in cocoons planted on or in the ground in 1975, only one (0.3%) persisted through the winter; 98.6% disappeared, and 1.1% were found dead, covered by fungi; in 1976, all larvae disappeared by December. Larvae disappeared even in the absence of predators, and are thought to have moved in response to damp ground conditions.