20 g / m 2 或 32 g / m 2 时生物量最高。 2) 土壤全量养分和速效养分在施肥量为 20 g / m 2 或 32 g / m 2 时较高,施肥量增加 到 40 g / m 2 时土壤资源逐渐降低。 3) 不同施肥梯度矮嵩草草甸土壤有机碳和微生物生物量碳在 0-10 cm 土层明显较高,且随 着施肥量的增加,分布在 0-40 cm 土层的土壤有机碳含量呈单峰曲线变化。 施肥 20 g / m 2 或 32 g / m 2 时土壤有机碳和微生物 量碳含量最高。 4) 30 g / m 2 施肥量可作为高寒草甸最佳施氮水平。 施肥梯度下土壤有机碳和微生物量碳含量可作为衡量土壤 肥力和土壤质量变化的重要指标。 高施肥量(逸40 g / m 2

Grassland is an important and terrestrial ecosystem and one of the most widely distributed ecosystems in the world. In the context of climate change, grassland has a significant impact on global carbon source / sink dynamics and carbon cycling. The focus of the present study was the grassland vegetation of the Loess Plateau. We analyzed the effects of natural and degraded grassland grazing pre鄄 and post鄄prohibition to combine the policy of returning farmland to forest or grassland and grazing prohibition. Using multi鄄point transect surveys and long鄄term fixed monitoring sites, plant distribution, leaf litter, and distribution and zonation of below ground carbon density of different types of grassland in the Loess Plateau were recorded. The temporal鄄spatial variability of biomass and carbon density with respect to the altitudinal

No abstract

收稿日期：２０１５• ０９• １７； 网络出版日期：２０１６• ０６• １４ * 通讯作者 Ｃｏｒｒｅｓｐｏｎｄｉｎｇ ａｕｔｈｏｒ．Ｅ•ｍａｉｌ： ｒｊｈｏｎｇ•０１＠ １６３．ｃｏｍ ＤＯＩ： １０．５８４６ ／ ｓｔｘｂ２０１５０９１７１９１３ 蒋政权，李凤山，冉江洪，刘伟，赵晨皓，张波，李华．若尔盖湿地保护区黑颈鹤巢期及影响因子．生态学报，２０１７，３７(３) ：１０２７• １０３４． Ｊｉａｎｇ Ｚ Ｑ， Ｌｉ Ｆ Ｓ， Ｒａｎ Ｊ Ｈ， Ｌｉｕ Ｗ， Ｚｈａｏ Ｃ Ｈ， Ｚｈａｎｇ Ｂ， Ｌｉ Ｈ． Ｎｅｓｔ ｂｕｉｌｄｉｎｇ ｄｕｒａｔｉｏｎ ａｎｄ ｉｔｓ ｃｏｎｔｒｉｂｕｔｉｎｇ ｆａｃｔｏｒｓ ｆｏｒ ｂｌａｃｋ•ｎｅｃｋｅｄ ｃｒａｎｅｓ (Ｇｒｕｓ ｎｉｇｒｉｃｏｌｌｉｓ) ａｔ Ｒｕｏｅｒｇａｉ， Ｓｉｃｈｕａｎ， Ｃｈｉｎａ．Ａｃｔａ Ｅｃｏｌｏｇｉｃａ Ｓｉｎｉｃａ，２０１７，３７(３) ：１０２７• １０３４．

The concept of an eco鄄city is the ultimate trend for future cities. Supported by the principles of ecology and sustainable development theory, an eco鄄city is a sustainable urban area developed and designed to create a regional natural city environment. An eco鄄city is an artificial ecosystem featuring a clean and desirable environment compatible with continuous economic improvement. An eco鄄city is beneficial to human health, prosperity, social harmony and progress, and it allows for expanding opportunities and is full of complexity. Urbanization continues to increase along with the development of human society, civilization and the economy. Prosperity also brings ecological and environmental problems to cities, such as climate change, pollution, energy shortages, ecological damage and the disruption and destruction of local communities, all of which seriously threaten the health of urban ecosystems. In general, people have started to look at cities from the perspective of maintaining a balance between ecological integrity and sustainable development. The construction of eco鄄cities has gradually become a global focus point. Urban ecological systems are complex with natural, economic and social subsystems. The primary functions of urban ecosystems are to provide the human residents with satisfactory and productive lives, and with entertainment and local transportation. The characteristics of urban ecosystems are: (1) they are mainly artificial man鄄made ecosystems, (2) they are incomplete ecosystems, and (3) there is an obvious flow of human harnessed energy in urban ecosystems. The structure and characteristics of urban ecosystems determine their basic function. Because urban ecosystems are similar to natural ecosystems, urban ecosystems have the functions of production, energy flow,