Environmental sciences

In situ 13 C pulse labelling was used to measure the temporal and spatial carbon¯ow through an upland grassland. The label was delivered as 13 C-CO 2 to vegetation in three replicate plots in each of two treatments: control and lime addition. Harvests occurred over a two month period and samples were taken along transects away from the label delivery area. The 13 C concentration of shoot, root, bulk soil, and soil-respired CO 2 was measured. There was no difference in the biomass and 13 C concentration of shoot and root material for the control and lime treatments meaning that the amount of 13 C-CO 2 assimilated by the vegetation and translocated below ground was the same in both treatments. The 13 C concentration of the bulk soil was lower in the lime treatment than in the control and, conversely, the 13 C concentration of the soil-respired CO 2 was higher in the lime. Unlike the difference in bulk soil 13 C concentration between treatments, the difference in the 13 C concentration of the soil-respired CO 2 was obvious only at the delivery site and primarily within 1 d after labelling. An observed increase in the abundance of mycorrhizal fungi in the lime treatment was a possible cause for this faster carbon throughput. The potential key role of mycorrhizas in the soil carbon cycle is discussed. The importance of a better understanding of soil processes, especially biological ones, in relation to the global carbon cycle and environmental change is highlighted.

At an upland field site in Scotland on an established Festuca-Agrostis pasture, the effects of soil amendment on root dynamics, using nitrogen and lime and the regular application of insecticide, were studied over a period of 1 year. The most common insect root herbivore at the site was Tipula paludosa, and the application of insecticide (chlorpyrifos) reduced numbers of all insect larvae of all species. Root biomass, root appearance, root disappearance and root density were all reduced by insecticide. This reduced rooting could reflect reduced root replacement, due to the reduction in root herbivory in insecticide-treated plots or could be a direct affect of insecticide application on the roots. Root appearance, root disappearance and C and N input to the soil were increased by treatment with nitrogen and lime, while root survival time was reduced. The nitrogen and lime treatment also increased bacterial numbers in the soil and enhanced their potential C utilization. An altered rooting density and longevity was brought about by the two soil treatments, which could have both direct and indirect effects on the soil biota.

Understanding of plant interactions is greatly limited by our ability to identify and quantify roots belonging to different species. We proposed and compared two methods for estimating the root biomass proportion of each species in artificial mixtures: near-infrared reflectance spectroscopy (NIRS) and plant wax markers.

This study examined how root growth and morphology were affected by variation in soil moisture at four Amazon rainforest sites with contrasting vegetation and soil types. Mean annual site root mass, length and surface area growth ranged between 3-7 t ha −1 , 2-4 km m −2 and 8-12 m 2 m −2 respectively. Mean site specific root length and surface area varied between 8-10 km kg −1 and 24-34 m 2 kg −1 . Growth of root mass, length and surface area was lower when soil water was depleted (P< 0.001) while specific root length and surface area showed the opposite pattern (P<0.001). These results indicate that changes in root length and surface area per unit mass, and pulses in root growth to exploit transient periods of high soil water availability may be important means for trees in this ecosystem to increase nutrient and water uptake under seasonal and longer-term drought conditions.

Bentgrass (Agrostis capillaris) and clover (Trifolium repens) were grown as pure swards and mixtures in pots containing soil from the NERC Soil Biodiversity field site located in Scotland. Six weeks after plant establishment leatherjacket larvae (Tipula paludosa) were added at field density to half the pots and the impacts of their feeding on plant shoot and root biomass and soil microbial communities was determined after 10 days. Plate counts and community level physiological profiles (CLPP) were used to characterise the microbial communities. Larval herbivory had a significant negative effect on shoot growth of both grass and clover and root biomass of grass. In mixed swards, larvae preferentially fed on clover. Soil microbial community structure was altered in the presence of larvae with populations of pseudomonads being significantly increased. These community differences may be attributed to increased quantity and qualitative changes in carbon flux to the soil as a result of root herbivory, as indicated by differences in the CLPPs of microbial communities in the presence and absence of larvae. This was mainly due to increased utilisation of some sugars, carboxylic and amino acids in the presence of larvae.

The linkages between plants and soil biota are both important and complex, involving both positive and negative feedbacks between soil organisms and their physical environment. An experiment was established in an upland grassland system to investigate the impact of addition of nitrogen and lime (NL) fertiliser on plant communities and the soil biota. The NL treatment increased above ground plant biomass and accelerated root returns to the soil, providing increased plant-derived energy for the soil food web. No changes were seen in fungal biomass, as indicated by PLFA, but bacterial biomass was reduced. However, the numbers of bacterial feeding and predatory nematodes increased in the NL treatment and may be masking the effects at the lower trophic levels, indicating top-down control mechanisms. Although the NL treatment changed nematode community structure, there was an overall depression in the abundance of nematodes. This decrease was likely to be related to soil moisture content, which was reduced significantly in the NL treatment by increased evapotranspiration due to the larger above ground biomass production. This study highlights the strong bottom-up control over the soil dwelling nematodes both in terms of driving changes in diversity and in modifying the soil physical environment. #

We investigated the impacts of root feeding, cranefly (Tipula paludosa) larvae on rhizosphere chemistry and soil microbial communities. Microcosms were constructed that allowed for the collection of rhizosphere solutions (containing rhizodeposits and soluble larval wastes) for chemical characterization. Solutions were collected from the rhizospheres of three grassland plants (Agrostis capillaris, Lolium perenne, and Trifolium repens) in microcosms with and without cranefly larvae. The activity of larvae resulted in significantly reduced plant biomass and enhanced organic carbon (C) input into rhizosphere solutions collected from L. perenne and T. repens. For A. capillaris, plant biomass and rhizosphere solution organic C were not affected significantly by larvae, but this may have been a consequence of a lower larval biomass in this experiment. Solutions collected from all three plants contained more ammonium (NH 4 + ) when larvae were present, likely due to the deamination of larval wastes. The presence of larvae also increased the amount of carbohydrates in solutions from A. capillaris and L. perenne, but carbohydrates decreased in solutions from T. repens. Rhizosphere solutions were applied to soil and changes in microbial communities were assessed. Bacterial and fungal biomass increased in soils receiving solutions from L. perenne with larvae, as indicated by the quantity of microbial phospholipid fatty acid (PLFA) biomarker lipids extracted. Fungal biomass was also higher in soils receiving solutions from larvae-treated A. capillaris. Fungal biomass decreased and some Gram-positive biomarker PLFAs were reduced in soils receiving rhizosphere solutions from larvae-treated T. repens. Analysis of community-level physiological profiles showed significantly lower sugar use for soils receiving solutions from T. repens with larvae, which correlates with the measured reduction in carbohydrate content. Our results suggest that the activity of these root feeding larvae leads to shifts in soil microbial communities that are linked to changes in rhizosphere chemistry. In grasslands, root herbivory may exert considerable control over the structure of soil microbial communities. #

We investigated the effect of competition from grass roots (as controlled by herbicide application) on the depth distribution of white roots in cherry trees, grown with varying rates and frequency of application of N in an agroforestry system. Statistical summaries of distribution, namely mean and skewness, produced a concise and interpretable analysis of the data.

This paper describes research on the relationships between grassland management practices and the diversity of biological communities in soil. Observations are being made in field trials with applications of nitrogen and lime and of insecticide to an original diverse sward and to a single species grass re-seed. The treatments are designed to produce different degrees of diversity in communities of soil animals and microbes. Assessments are being made over three years of the effects on the populations, activity and diversity of root-feeding animals, arbuscular mycorrhizal fungi, soil bacteria, fungi and micro fauna, including nonplant feeding nematodes. Associated laboratory experiments assess the effects of root herbivores with different feeding sites and mechanisms on the quality and quantity of rhizosphere deposition and it relationship to microbial communities. In this way, we shall develop an understanding of the relationships between root-herbivory and soil biodiversity and between of biodiversity and soil energy and nutrient transformations.

Urea-N in sheep urine returned to soil is an important component in the N-cycle of extensively managed grassland soils but relatively little is known of its effects on P and C cycling. Previous studies using sward boxes sown with Agrostis capillaris and soil mixed from the Ah and AB horizon of a brown ranker showed that the application of synthetic sheep urine (SSU) increased soil pH and the soil solution concentration of dissolved organic C (DOC) and organic and inorganic forms of N and P. To extend information to the ®eld, we compared the effects of SSU addition to soil in sward boxes with that in the ®eld using an application rate corresponding to the upper value of the range found in urine patches (500 kg urea-N ha 21 ). For 50-mm deep soil cores taken at intervals up to 56 d after treatment, the magnitude of the change in soil pH and the soil solution concentrations of the dissolved nutrients were less in the ®eld and lagged behind in time compared with the sward boxes. The difference was attributed to the larger mass of roots, the existence of a discrete Ah horizon and the greater moisture content of the soil in the ®eld that were able to buffer effects. Synthetic sheep urine, prepared according to published formulae, may provide a greater concentration of urea-N than found in natural sheep urine (NSU) from hill sheep and, additionally, does not contain minor components such as hippuric acid that in¯uences nitri®cation and pH changes associated with the presence of NH 3 /NH 1 4 . To compare effects of SSU and NSU we used sward boxes and applied equal volumes of SSU (9.97 g l 21 of urea-N) or NSU (4.04 g l 21 of urea-N) from ewes fed on grass. Natural sheep urine increased the concentration of dissolved nutrients in soil solution but the increases were disproportionately less than for SSU. Synthetic sheep urine was toxic to roots in sward boxes and in the ®eld, increasing the proportion of roots that were dead or decomposing, especially in the sward boxes. The study highlights differences in soil solution chemistry and root dynamics between sward box and ®eld soils and between SSU and NSU, demonstrating a need for caution in extrapolating results from sward boxes to the ®eld. q

We studied the effects of the root endoparasitic nematode Heterodera trifolii on rhizodeposition and the root architecture of white clover (Trifolium repens). Rhizosphere solutions were collected from the root systems of plants growing with and without H. trifolii (200 juveniles per inoculated plant) in sand-based microlysimeters. The organic carbon (C) content of these solutions was analyzed, and they were applied to plantfree soils to investigate microbial responses. Although plant biomass was unaffected by nematodes, the architecture of the root systems was significantly altered, with a decrease in overall root length and an increase in the density of lateral branches from the primary root. The presence of nematodes reduced the concentration of organic compounds in the rhizosphere solutions but only on the final sampling date (75 days). Analysis of microbial signature phospholipid fatty acids revealed no change in the structure of the microbial communities in soils to which rhizosphere solutions were applied. However, these microorganisms did respond with changes in substrate utilization patterns (community-level physiological profiles). Microbes in soils that received rhizosphere solutions from the nematode-infected clover showed lower utilization of most substrates but higher utilization of oligosugars. These responses appear to be related to changes in roots and rhizodeposition associated with nematode infection of clover roots. The results of this study suggest that root herbivory can negatively impact carbon-limited soil microbial communities via changes in root architecture that moderate rhizodeposition.

Using middle cerebral artery occlusion (MCAO) and in vivo microdialysis, we have evaluated the changes in extracellular concentrations of the excitatory amino acids (EAA) glutamate and aspartate during varying periods of MCAO (0, 30, 60 min) in the striatum of spontaneously hypertensive rats (SHR). A positive correlation between occlusion time-dependent elevations in EAAs and the resulting ischemic injury was observed. This is the first demonstration of the temporal profile of EAA efflux during transient focal ischemia in SHRs. Possible sources and mechanisms of ischemia-induced EAA efflux were examined during 60 min of MCAO. Removal of Ca 2؉ from the microdialysis infusion media significantly attenuated ischemiainduced increases in both glutamate (from ischemic peak of 4892 ؎ 1298 to 1144 ؎ 666% of preischemic values) and aspartate (from 2703 ؎ 682 to 2090 ؎ 599% of preischemic values).

Although the 5-HT 6 receptor subtype was identi®ed some 5 years ago, very little is known about its function within the brain. Here we demonstrate, for the ®rst time, the neurochemical eects of a selective 5-HT 6 receptor ligand. Using in vivo microdialysis in the freely moving rat, we evaluated the eects of the selective 5-HT 6 receptor antagonist SB-271046 by simultaneous measurement of 5hydroxytryptamine (5-HT), dopamine (DA), noradrenaline (NA), glutamate and aspartate from the striatum and frontal cortex. SB-271046 did not alter basal levels of 5-HT, DA and NA in either brain region. Similarly, there was no change basal levels of either of the excitatory amino acids within the striatum. In contrast, administration of SB-271046 (10 mg kg 71 s.c.) produced a signi®cant (P50.05), tetrodotoxin-dependent, increase in extracellular levels of both glutamate and aspartate within the frontal cortex, reaching maximum values of 375.4+82.3 and 215.3+62.1% of preinjection values, respectively.

1 Using in vivo microdialysis in the frontal cortex of the freely moving rat we evaluated the eects of chronic treatment with the serotonin speci®c reuptake inhibitor (SSRI)¯uoxetine in the presence and absence of the 5-HT 1A /b-adrenergic antagonist (+)pindolol. 2 Chronic vehicle treated animals produced no signi®cant response to a challenge with¯uoxetine (10 mg kg 71 ) on day 8 and 15. Alternatively, a signi®cant (P50.05) decrease in extracellular 5-HT was observed in control animals upon challenge with the 5-HT 1A agonist 8-hydroxy-2-(di-npropylamino)tetralin (8-OH-DPAT; 0.03 and 0.1 mg kg 71 ). 3 Conversely, animals treated with¯uoxetine (10 mg kg 71 o.d.) for 7 and 14 days produced a signi®cant (P50.05) 2 fold increase in extracellular 5-HT when challenged with¯uoxetine (10 mg kg 71 ) on day 8 and 15. Moreover, no signi®cant decrease in extracellular 5-HT was observed upon challenge with either dose of 8-OH-DPAT. 4 Animals chronically treated with (+)pindolol (10 or 20 mg kg 71 b.i.d.) produced a signi®cant dose-related increase in extracellular 5-HT upon challenge with¯uoxetine on day 15 only. Furthermore, both doses produced a signi®cantly blunted response to the low dose challenge of 8-OH-DPAT (0.03 mg kg 71 ). In addition, 20 mg kg 71 (+)pindolol treated animals also had no response to the higher 0.1 mg kg 71 dose of 8-OH-DPAT. 5 Animals treated for 14 days with a combination of (+)pindolol (10 or 20 mg kg 71 ) and uoxetine were not signi®cantly dierent from vehicle treated animals when challenged with uoxetine or 8-OH-DPAT. 6 Taken together it would therefore appear that although (+)pindolol alone has sucient intrinsic activity to produce a desensitization of the 5-HT 1A receptor, when given in combination with uoxetine it is able to prevent the desensitization induced by not only¯uoxetine but also itself. This may suggest that the clinical augmentation of antidepressant action by pindolol, when coadministered with a SSRI, is via antagonism of the 5-HT 1A receptor.

BACKGROUND: This study was undertaken to determine outcomes of stereotactic body radiotherapy for colorectal liver metastases in a pooled patient cohort. METHODS: Patients with colorectal liver metastases from 3 institutions were included if they had 1 to 4 lesions, received 1 to 6 fractions of stereotactic body radiotherapy, and had radiologic imaging 3 months post-treatment. Sixty-five patients with 102 lesions treated from August 2003 to May 2009 were retrospectively analyzed. A tumor control probability (TCP) model was used to estimate the 3-fraction dose required for >90% local control after converting the schedule into biologically equivalent dose (BED), single-fraction equivalent dose, or linear quadratic model-based single-fraction dose. RESULTS: Forty-seven (72%) patients had 1 chemotherapy regimen before stereotactic body radiotherapy, and 27 (42%) patients had 2 regimens. The median followup was 1.2 years (range, 0.3-5.2 years). The median dose was 42 gray (Gy; range, 22-60 Gy). When evaluated separately by multivariate analysis, total dose (P ¼ .0015), dose/fraction (P ¼ .003), and BED (P ¼ .004) all correlated with local control by lesion. On multivariate analysis, nonactive extrahepatic disease was associated with overall survival (OS; P ¼ .046), and sustained local control was closely correlated (P ¼ .06). By using single-fraction equivalent dose, BED, or linear quadratic model-based single-fraction dose in the TCP model, the estimated dose range needed for 1-year local control >90% is 46 to 52 Gy in 3 fractions. CONCLUSIONS: Liver stereotactic body radiotherapy is well tolerated and effective for colorectal liver metastases. The strong correlation between local control and OS supports controlling hepatic disease even for heavily pretreated patients. For a 3-fraction regimen of stereotactic body radiotherapy, a prescription dose of 48 Gy should be considered, if normal tissue constraints allow. Cancer 2011;117:4060-9

Soil, streamwater and climatic variables were measured hourly over several month periods in two situations in North-East (NE) Scotland, using data loggers and other measuring instruments. One of the locations was on agricultural land near Inverness while the other was at an acidic peat moorland site in the River Dee catchment. The data sets were used to train neural networks using three different methods, including a novel, biologically plausible system. Temporal pattern recognition capabilities using each method were investigated. The novel method proved equally capable in predicting future variable values using large data sets as the other two methods. An argument is made for this method, termed the 'Local Interaction' method, providing valid competition to other neural network and statistical methods in the detection of patterns and prediction of events in complex biological systems.