海拔和植被对三峡库区梨香溪消落带土壤酶活性的影响

消落带土壤生态环境对水库水质及坡岸稳定性具有较大影响，土壤酶活性具有驱动土壤物质循环进而影响生态系统的功能。本文以三峡库区梨香溪消落带土壤为研究对象，研究了四个海拔梯度和五种植被样地的土壤蔗糖转化酶、脲酶、碱性磷酸酶和蛋白酶的活性及相关环境因子。结果表明，在不同海拔样地中，表层土壤的有机质、总氮、总磷和有效磷的含量均高于土壤下层，并且有效磷和总磷含量随海拔高度的增加而增大。四种土壤酶活性随高程的增加均总体呈现出增大的趋势。除脲酶外，167~180 m样地的下层土壤的土壤酶活性均高于165 m样地。在不同植被样地中，苔藓结皮样地的表层土壤中，蔗糖转化酶、碱性磷酸酶和蛋白酶的活性均为最大。有植被覆盖的样地土壤酶活性和土壤有机质、总氮、总磷和有效磷含量均高于裸地，其中虎杖和藻结皮植被对土壤的养分和土壤酶活性影响作用高于狗压根和苔藓结皮。四种土壤酶的酶活性与土壤总氮、总磷、有效磷和有机质含量大体都呈现正相关关系。以上结果表明，消落带土壤酶活性和土壤肥力供给能力受水淹影响，藻类结皮和苔藓结皮对消落带土壤肥力具有促进作用。     

Effects of human land-use on the global carbon cycle during the last 6,000 years

Humanity has become a major player within the Earth system, particularly by transforming large parts of the land surface and by altering the gaseous composition of the atmosphere. Deforestation for agricultural purposes started thousands of years ago and might have resulted in a detectable human influence on climate much earlier than the industrial revolution. This study presents a first attempt to estimate the impact of human land-use on the global carbon cycle over the last 6,000 years. A global gridded data set for the spread of permanent and non-permanent agriculture over this time period was developed and integrated within the Lund-Potsdam-Jena Dynamic Global Vegetation Model (LPJ-DGVM). The model was run with and without human land-use, and the difference in terrestrial carbon storage was calculated as an estimate of anthropogenic carbon release to the atmosphere. The modelled total carbon release during the industrial period (a.d. 1850–1990) was 148 gigatons of carbon (GtC), of which 33 GtC originated from non-permanent agriculture. For pre-industrial times (4000 b.c.–a.d. 1850), the net carbon release was 79 GtC from permanent agriculture with an additional 35 GtC from non-permanent agriculture. The modelled pre-industrial carbon release was considerably lower than would be required for a substantial influence on the climate system.     

Gradient in seaweed vegetation patterns along the North Icelandic coast,related to hydrographic conditions

The benthic algal vegetation of the North Icelandic coast exhibits particular features, different from those found in southern and western Iceland on the one hand and in eastern Iceland on the other. It is characterised by low-eulittoral belts of Devaleraea ramentacea, Petalonia species and Chordaria flagelliformis as well as by meadows of diverse Acrosiphonia species. In the tide pools Atlantic and typical North Icelandic associations occur side by side. This area thus represents an intermediate region between Atlantic and subarctic growth conditions. A certain gradient in the west-east direction was observed within the North Icelandic vegetation type and is possibly related to the gradual cooling and dilution of the water masses which pass the North Icelandic shelf. The hydrographic discontinuity in the extreme NW creates a sharp floristic and vegetational boundary for benthic algae, whereas in the NE a gradual transition towards the subarctic East Icelandic vegetation was observed. The Atlantic character of the vegetation was more pronounced in the western than in the eastern part of the north coast. An enclave of warm water vegetation was interposed along the western banks of the Tjörnes peninsula.This paper is based on a presentation at the XIII^th International Seaweed Symposium in Vancouver, Canada.     

Classification and mapping of the ecoregions of Italy

Ecological regions or ecoregions derive from ecological classification of land and represent broad and discrete ecologically homogeneous areas within which natural communities and species interact with the physical elements of the environment. The aim of this paper is to define the ecoregions of Italy, southern Europe, based on a robust methodological process for classification and mapping. The ecoregions of Italy comprise 2 Divisions, 7 Provinces, 11 Sections and 33 Subsections and constitute the first comprehensive ecological classification of the country that integrates accurate and updated cartographies and knowledges on climate, vegetation, land units and biogeography. This classification has the strength to be adopted as a proper framework for ecological modelling, biodiversity conservation policies and sustainable territorial planning at the national and subnational level.