RESUMEN
Increasing nitrogen depositions adversely affect European landscapes, including habitats within the Natura2000 network. Critical loads for nitrogen deposition have been established to quantify the loss of habitat quality. When the nitrogen deposition rises above a habitat-specific critical load, the quality of the focal habitat is expected to be negatively influenced. Here, we investigate how the quality of habitat types is affected beyond the critical load. We calculated response curves for 60 terrestrial habitat types in the Netherlands to the estimated nitrogen deposition (EMEP-data). The curves for habitat types are based on the occurrence of their characteristic plant species in North-Western Europe (plot data from the European Vegetation Archive). The estimated response curves were corrected for soil type, mean annual temperature and annual precipitation. Evaluation was carried out by expert judgement, and by comparison with gradient deposition field studies. For 39 habitats the response to nitrogen deposition was judged to be reliable by five experts, while out of the 41 habitat types for which field studies were available, 25 showed a good agreement. Some of the curves showed a steep decline in quality and some a more gradual decline with increasing nitrogen deposition. We compared the response curves with both the empirical and modelled critical loads. For 41 curves, we found a decline already starting below the critical load.
Asunto(s)
Ecosistema , Monitoreo del Ambiente , Nitrógeno , Nitrógeno/análisis , Monitoreo del Ambiente/métodos , Países Bajos , Suelo/química , Plantas/metabolismoRESUMEN
OBJECTIVE: To evaluate the feasibility and results of prosthetic venous replacement, as inferior vena cava (IVC) and iliofemoral vein resection and replacement are sometimes necessary when they are extensively involved by a large and fixed tumour thrombus from renal cell carcinoma (RCC) or other urological malignancies. PATIENTS AND METHODS: Five men and two women (age range 41-75 years) were treated over a 10-year period (1991-2001) by aggressive venous surgery to achieve complete tumour resection, with prosthetic graft replacement to re-establish venous flow. The tumours included RCC of the right kidney (two), retroperitoneal liposarcoma (two), bladder cancer (one), retroperitoneal fibrosarcoma (one) and inguino-pelvic lymphoma (one). Two patients had a vena caval replacement, of whom one had a circular reinforced PTFE and one a Dacron silver graft; five patients had either an iliofemoral or an ilio-iliac circular reinforced PTFE graft. The prosthetic diameter was 18-20 mm for the IVC grafts and 8-10 mm for the iliac grafts. In all the patients, graft patency was evaluated during the follow-up by colour flow duplex imaging, and in one it was determined by angio-computed tomography scan and venography. RESULTS: One patient died 30 days after surgery; of the remaining six patients one had no evidence of regional recurrence or metastatic disease at 12 months, and five died from recurrent tumour 8-30 months after surgery. The mean time to death was 23 months. At 3 months all six prosthesis were patent; at 6 months four were patent and at 12 months three of five prostheses were patent. CONCLUSION: Resecting and replacing the IVC allows complete tumour resection and avoids renal failure, providing durable relief from the symptoms of venous obstruction. Iliofemoral prosthetic reconstruction for urological-related malignancies represents a viable option to avoid venous engorgement and lower extremity swelling, at least in the early postoperative period. The mean time to death for the present patients must be considered the limit for these aggressive operations.