Rocks create nitrogen hotspots and N:P heterogeneity by funnelling rain

We postulated that soil nutrient heterogeneity arises not only through physical and biological processes in the soil, but also through emergent rocks diverting precipitation containing nutrients to the surrounding soil. To test this idea—which we call the ‘funnelling effect' of such rocks—we placed ion-exchange resin in small boxes beside rocks and in open soil on a pristine glacial forefield site in Switzerland, and measured the amounts of NH4 +, NO3 −, NO2 − and PO4 3− that were adsorbed. We also placed resin bags beneath PVC funnels of different sizes so that we could calibrate the natural funnelling effect of rocks. We obtained strong linear relationships between nitrogen (N) adsorbed and rain-collecting area of both rocks and funnels. Although the mean rain-collecting area of rocks was only 0.02m2, mean N adsorption was around 10 times higher within 1cm of rocks than further away. In contrast, phosphorus (P) was not concentrated beside rocks, so that N:P stoichiometry varied spatially. Rumex scutatus and Agrostis gigantea plants that rooted beside rocks had significantly higher foliar N concentrations than those growing further away, in line with the resin data. However, the two species showed differing responses in foliar P and N:P. We propose that R. scutatus benefits from the increased N supply by increasing its uptake of soil P, while A. gigantea is unable to do so. This study clearly demonstrates that aboveground rain-funnelling structures can produce spatial heterogeneity in N supply, thereby creating a diversity of nutritional niches for plants

Patient outcome after surgical management of the spinal accessory nerve injury: A long-term follow-up study

OBJECTIVES: A lesion in the spinal accessory nerve is typically iatrogenic: related to lymph node biopsy or excision. This injury may cause paralysis of the trapezius muscle and thus result in a characteristic group of symptoms and signs, including depression and winging of the scapula, drooped shoulder, reduced shoulder abduction, and pain. The elements evaluated in this long-term follow-up study include range of shoulder motion, pain, patients' satisfaction, delay of surgery, surgical procedure, occupational status, functional outcome, and other clinical findings. METHODS: We reviewed the medical records of a consecutive 37 patients (11 men and 26 women) having surgery to correct spinal accessory nerve injury. Neurolysis was the procedure in 24 cases, direct nerve repair for 9 patients, and nerve grafting for 4. Time elapsed between the injury and the surgical operation ranged from 2 to 120 months. The patients were interviewed and clinically examined after an average of 10.2 years postoperatively. RESULTS: The mean active range of movement of the shoulder improved at abduction 44° (43%) in neurolysis, 59° (71%) in direct nerve repair, and 30° (22%) in nerve-grafting patients. No or only slight atrophy of the trapezius muscle was observable in 75%, 44%, and 50%, and no or controllable pain was observable in 63%, 56%, and 50%. Restriction of shoulder abduction preceded deterioration of shoulder flexion. Patients' overall dissatisfaction with the state of their upper extremity was associated with pain, lower strength in shoulder movements, and occupational problems

Soil bacterial growth and nutrient limitation along a chronosequence from a glacier forefield

Resource availability and limiting factors for bacterial growth during early stages of soil development (8-138 years) were studied along a chronosequence from the glacial forefield of the Damma glacier in the Swiss Alps. We determined bacterial growth (leucine incorporation) and we investigated which resource (C, N or P) limited bacterial growth in soils formed by the retreating glacier. The latter was determined by adding labile sources of C (glucose), N and P to soil samples and then measuring the bacterial growth response after a 40 h incubation period. Bacterial growth increased with increasing soil age in parallel with the build up of organic matter. However, lower bacterial growth, when standardized to the amount of organic C, was found with time since the glacier retreat, indicating decreasing availability of soil organic matter with soil age. Bacterial growth in older soils was limited by the lack of C. The bacteria were never found to be limited by only N, only P. or N + P. In the youngest soils, however, neither the addition of C, N nor P singly increased bacterial growth, while a combination of C and N did. Bacterial growth was relatively more limited by lack of N than P when the C limitation was alleviated, suggesting that N was the secondary limiting resource. The availability of N for bacterial growth increased with time, as seen by an increased bacterial growth response after adding only C in older soils. This study demonstrated that bacterial growth measurements can be used not only to indicate direct growth effects, but also as a rapid method to indicate changes in bacterial availability of nutrients during soil development. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved

Nitrogen and phosphorus availability at early stages of soil development in the Damma glacier forefield, Switzerland; implications for establishment of N2-fixing plants

Background and aims: Di-nitrogen (N2)-fixing plants are absent in the pioneer stages of glacial forefields in the European Alps despite low amounts of nitrogen (N) in the soil. We aimed to evaluate whether symbiotic N2-fixation is needed to meet the N demand of plants during the early stages of soil formation, and how phosphorus (P) availability affects plant establishment. Methods: We measured total and available N and P in soil and N and P in the vegetation along the 137 year chronosequence in front of the Damma glacier (Switzerland). Results: Available N as determined by in situ resin N decreased from the pioneer stage (<16 years since deglaciation) to the intermediate (57–80 years), likely resulting from increased plant N uptake and reduced funnelling of N by rocks. N concentrations in the vegetation were positively correlated to in situ resin N, and the N:P-ratio of the vegetation was negatively correlated with P concentrations in the vegetation. Conclusions: The N requirement of plants in the pioneer stage of soil development in the forefield is fulfilled by atmospheric N deposition being funnelled between rocks. N2-fixation is not needed as the vegetation is often limited by P, or co-limited by N and P.ISSN:0032-079XISSN:1573-503

Chemical and Biological Gradients along the Damma Glacier Soil Chronosequence, Switzerland

Soils are the product of a complex suite of chemical, biological, and physical processes. In spite of the importance of soils for society and for sustaining life on earth, our knowledge of soil formation rates and of the influence of biological activity on mineral weathering and geochemical cycles is still limited. In this paper we provide a description of the Damma Glacier Critical Zone Observatory and present a first synthesis of our multi disciplinary studies of the 150-yr soil chronosequence. The aim of our research was to improve our understanding of ecosystem development on a barren substrate and the early evolution of soils and to evaluate the influence of biological activity on weathering rates. Soil pH, cation exchange capacity, biomass, bacterial and fungal populations, and soil organic matt er show clear gradients related to soil age, in spite of the extreme heterogeneity of the ecosystem. The bulk mineralogy and inorganic geochemistry of the soils, in contrast, are independent of soil age and only in older soils (>100 yr) is incipient weathering observed, mainly as a decreasing content in albite and biotite by coincidental formation of secondary chlorites in the clay fraction. Further, we document the rapid evolution of microbial and plant communities along the chronosequence