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- The stoichiometry of resources is increasingly acknowledged as a major control of consumer activity and abundance. Chemical properties of litter, the main source of food for decomposers, are likely to be important drivers of decomposer activity.
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- Theory predicts a high control of resource stoichiometry on the abundance of consumer organisms that maintain strict homeostasis, due to costs associated with the regulation of nutrient balance in their body tissue. Decomposer efforts in nutrient acquisition should be related to imbalances in resource stoichiometry.
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- A 21 year old experimental plantation of monospecific plots of trees with leaves of contrasting chemistry was used to test four hypotheses: (i) soil and litter nutrient stoichiometry (C, N, P) are linked; (ii); soil enzyme activity ratios and stoichiometry are linked; (iii) earthworms’ tissue stoichiometry does not depend on soil and litter stoichiometry (homeostasis); (iv) earthworm density is dependent upon phosphorus availability, the most limiting nutrient in soils at this site, and, to a lesser extent, to nitrogen availability.
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- We found (i) no relationship between litter and soil stoichiometry, (ii) microbial activity was linked to soil stoichiometry, (iii) earthworms showed strict homeostasis in their tissue and (iv) earthworm abundance increased with P availability.
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- We discuss the mechanisms that might lead to these patterns.
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Synthesis: Thresholds in conservation and management 总被引：3，自引：0，他引：3
This paper is a brief overview of some of the key issues which have emerged from the preceding set of papers on ecological thresholds. These include:
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- Whether threshold relationships are common and widespread.
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- The potential for large variations in the use and application of the threshold concept to lead to adverse conservation outcomes, particularly when overly simplistic levels of vegetation cover are specified by policy makers and land managers.
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- The inherent multi-variate nature of landscape processes and responses of individual species and assemblages that creates variability in datasets. This may lead to a limited ability to make accurate predictions from threshold relationships, even when those relationships are highly statistically significant.
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- Primary production on semiarid floodplains supports a diverse local and regional fauna. Reduced flooding from water resource development (WRD) may affect floodplain production by decreasing water and nutrient supply. 相似文献
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Bin Zhang Ben W. Thomas Ryan Beck Walter D. Willms Mengli Zhao Xiying Hao 《Journal of Soils and Sediments》2018,18(11):3228-3234
Purpose
Grasslands play a crucial role in offsetting greenhouse gas emissions and mitigating climate change. A moderate change in grassland carbon (C) and nitrogen (N) stocks may substantially alter the global C and N cycle and thereby influence climate. But how grassland C and N stocks respond to grazing and slope position remains uncertain. This research investigates how C and N stocks respond to cattle grazing along a landscape slope.Materials and methods
We studied a grassland that has been grazed by cattle at four cattle stocking rates (0, 1.2, 2.4, and 4.8 animal unit months (AUM) ha?1) since 1949, representing control (CK), light (L), heavy (H), and very heavy (VH) grazing intensities, respectively. Samples were taken from the top and bottom slope positions within each paddock (only the top position in CK); C and N stocks in soil, roots, litter, and standing crop were estimated. Soil C and N stocks were estimated based on equivalent mass (1500 Mg ha?1). Root C and N stocks were estimated to the depth of 15 cm.Results and discussion
All parameters, except for litter N stock and standing crop C stock, significantly responded to the interaction of grazing intensity and slope position. In the bottom position, soil and standing crop C and N stocks as well as litter C stock were higher with the L treatment than with VH, while no significant differences were found among the three grazed treatments for root C and litter N stocks. In the top position, soil and root C and N stocks were higher with the VH treatment than with L, whereas litter C and N stocks and standing crop C stock were lower with VH than with L.Conclusions
Our results provide evidence that slope position plays an important role in regulating the response of C and N stocks to grazing and may need to be considered when developing optimal grazing management strategies.14.
Stephen Harris 《Biological conservation》1984,28(4):349-375
Few towns and cities in Britain were found to contain badgers, and in most the numbers of setts were low. Urban areas most likely to contain badgers were those in which badgers were common in the surrounding rural areas; most urban badger populations were thought to be relicts that had survived urban encroachment. In a detailed survey of Bristol, 346 setts were located in an area of 129·4 km2. These setts were confined mainly to three areas; their past history, present distribution, habitat selection and levels of disturbance are discussed. The damage caused by badgers in north-west Bristol to garden crops and other aspects of their nuisance value are documented. The food of badgers in the same area of Bristol is also described; unlike rural badgers they took a diversity of food types, but specialized in feeding on fruit in the autumn. 相似文献
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The hydrolase activity was studied using the fluorescein diacetate (FDA) hydrolysis assay in order to assess the microbial activity in composts and vermicomposts obtained with participation of Eisenia fetida andrei, Aporrectodea caliginosa, and A. rosea earthworms from cattle manure, leaves, and peat. The hydrolase activity (the Michaelis—Menten constant, K m ) was found to be lower in the vermicomposts than in the composts and correlated with a corresponding decrease in the length of fungal hyphae. The determination of the hydrolase activity according to the reaction of FDA hydrolysis may be recommended to control the process of vermicomposting and the quality of vermicomposts. Thus, the process of vermicomposting may be characterized with the use of the functional (hydrolase activity) and structural (microbial biomass, length of fungal hyphae) approaches. 相似文献
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Xavier Domingo-Roura Josep Marmi Aïnhoa Ferrando Francesc López-Giráldez Hugh A.H. Jansman 《Biological conservation》2006,128(3):425-430
The Eurasian badger (Meles meles) is included in Appendix III of the Bern Convention and protected by national laws in many European countries. Badger hair is used to manufacture luxury shaving brushes, although it is frequently argued that the hog badger (Arctonyx collaris), which in Europe is an introduced and unprotected species, is the origin of the hair used. We applied an extraction protocol to recover DNA from the unrooted hair of shaving brushes obtained from commercial companies in The Netherlands and Spain. The tested brushes originated from The Netherlands, Spain, France, Italy and the United Kingdom where the Eurasian badger is a protected species. We sequenced 191 bp of the mitochondrial DNA control region and 170 bp of the cytochrome b gene and compared the sequences obtained with Eurasian badger and hog badger reference sequences of the same mitochondrial DNA regions obtained in our laboratory and from GenBank. Sequences obtained from four shaving brushes were clearly hog badger sequences, whereas four sequences clustered with Eurasian badger sequences of both European and Asian origins. One of the shaving brushes made of Eurasian badger was produced in France, where it is legal to capture or trade the species under certain conditions. The remaining three brushes originated from The Netherlands, where it is illegal to possess, sell, transport or use for commercial purposes dead Eurasian badgers or products derived from them. 相似文献
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Qing Teng Xue-Feng Hu Chang Cheng Zhiqing Luo Fan Luo Yong Xue Yijun Jiang Zhen Mu Liming Liu Minyong Yang 《Journal of Soils and Sediments》2016,16(10):2395-2407
Purpose
This paper aims to study the ecological effects of rice-duck integrated farming on soil fertility and weed and pest control.Materials and methods
A field experiment was carried out in the suburb of Shanghai in 2014, which included a rice-duck integrated treatment and non-duck treatment (CK) under organic management. Each treatment was in triplicate, and the experiment included six plots in total, with each plot 667 m2 in area.Results and discussion
(1) The number of weeds in the plots with the duck treatment was significantly lower than that with CK (p?<?0.01). (2) The incidence of stem borers (Chilo suppressalis) with the duck treatment was significantly lower than that with CK (p?<?0.05). The incidences of rice leaf rollers (Cnaphalocrocis medinalis), rice sheath blight (Rhizoctonia solani), and planthoppers with the duck treatment were extremely significantly lower than those with CK (p?<?0.01). (3) The contents of NH4 +-N, alkali-hydrolyzable N, available P, and available K in the soils with the duck treatment were higher than those with CK, and the activities of urease, phosphatase, sucrase, and catalase in the soils with the duck treatment were also much higher than those with CK. The grain yield with the duck treatment was 1.9 times that with CK. (4) The number of soil nematodes with the duck treatment was significantly higher than that with CK in the late rice growing stage (p?<?0.01).Conclusions
Raising ducks in the paddy fields not only showed a potential of controlling weed hazards and reducing rice pests and diseases but also raised soil fertility, improved soil biodiversity, and increased grain yield effectively. Implementing the rice-duck integrated farming could highly reduce the amount of pesticides and herbicides and was beneficial to develop the organic rice farming in the suburbs of Shanghai, Southeast China.19.
Sarah F.L. Lynch Lesley C. Batty Patrick Byrne 《Journal of Soils and Sediments》2017,17(11):2691-2707
Purpose
Diffuse pollution emanating from metal mining-impacted sediment could serve as a barrier to achieving European Union Water Framework Directive and US Clean Water Act requirements. UK climate projections (UKCP09) predict increases in rainfall and aridity that will influence river stage alternately exposing and submersing contaminated riverbank sediment. Research focuses on the environmental contaminant dissolved Zn and investigates patterns of release, key geochemical mechanisms controlling Zn mobilisation and the environmental risk of sediment subjected to these perturbations.Materials and methods
Using two laboratory mesocosm experiments, metal mining-contaminated sediment was subjected to alternate wet and dry sequences of different duration and frequency. The first experiment was run to determine the influence of submersion and exposure of contaminated sediment on releases of Zn and to establish environmental risk. The second experiment utilised diffusional equilibration in thin film (DET) to observe the patterns of Zn release, with depth, in the sediment. Pore water chemical analysis at the sediment-water interface enabled elucidation of key geochemical mechanisms of control of Zn mobilisation.Results and discussion
Patterns of Zn release were found to be different, depending on the length of wet and dry period. High concentrations of dissolved Zn were released at the start of a flood for runs with longer dry periods. A buildup of soluble Zn sulphate minerals over long dry periods followed by dissolution on first flood wetting was a key geochemical mechanism controlling Zn release. For longer wet runs, increases in dissolved Mn and Zn were observed over the flood period. Key geochemical mechanisms controlling Zn mobilisation for these runs were: (i) reductive dissolution of Mn (hydr)oxides and release of partitioned Zn over prolonged flood periods followed by (ii) oxidation and precipitation of Mn (hydr)oxides and sorption of Zn on exposure to atmospheric conditions.Conclusions
Mesocosm experiments were a first step in understanding the effects of UK climate projections on the riverbank environment. Contaminated sediment was found to pose a significant environmental risk in response to hydrological perturbations. The ‘transient’ nature of dissolved Zn release could make identifying the exact sources of pollution a challenge; therefore, further field studies are advised to monitor contaminant releases under a range of hydrological conditions and account for complex hydrology at mining sites.20.
Alessandro Florio Anita Maienza Maria Teresa Dell’Abate Silvia Rita Stazi Anna Benedetti 《Journal of Soils and Sediments》2016,16(12):2687-2697