Assessment of the erosion control function of forest ecosystems based on GIS: a case study in Zhangjiajie National Forest Park,China

Erosion control is one of the most important functions of forest ecosystems, and its accurate assessment is useful to illuminate the importance of forest ecosystem services for humans so as to rationally conserve forest resources. This paper examines Zhangjiajie National Forest Park, the first national forest park in China, to seek practical methods for assessment of the forest erosion control function using a geographical information system (GIS). The results show that the potential and actual amounts of soil erosion are 2.92 million ton and 0.14 million ton per year, respectively, in Zhangjiajie National Forest Park. The total reduction in soil loss reaches 2.77 million ton per year with the existence of a forest ecosystem. The erosion control function of near mature, mature and over mature broadleaf forest is excellent, and natural forest conservation and natural restoration of the degraded forest ecosystem can provide the largest benefits in soil erosion control. Nearly all the near mature, mature and over-mature forest in the park is at the top and in steep mountain areas, and could be rationally cut and utilized by local communities, but extensive timber felling should be strictly prohibited.     

Past desertification processes of Minqin Oasis in arid China

Irrigated farming has affected most natural oases in western China since the Han Dynasty employed advanced agricultural techniques in dryland areas. To date, little is documented about the process through which these oases were modified by human systems. In this study, a multi-disciplinary approach incorporating analysis of historical documents, archaeological field surveys, satellite imagery, and GIS data was used to understand desertification processes in the Minqin Basin in Gansu Province, China, over the historical period. Results suggest that initial reclamation efforts around the Minqin Oasis were launched in the Han Dynasty (220–121 BC) and culminated in the Wei and Jin Dynasty (220–420). During the following 800 years from the Southern and Northern Dynasties (420–581) to the Yuan Dynasty (1271–1368), farmland disappeared and became desert when the region was taken over by nomadic people. The second period of intense development occurred in the Ming Dynasty (1368–1644) and was followed by another more aggressive development in the Qing Dynasty (1644–1911), which resulted in the largest reclaimed area in history. Oases were constantly reclaimed and subsequently abandoned and desertified over the whole historical period. The causes were complex, but the major cause was related to dynastic transition that often resulted in changes in national policies.     

海州湾生态系统健康诊断

根据开敞海湾浅海生态系统特征,构建了包含环境现状、环境风险、环境背景、系统结构功能和系统稳定性5类诊断指标以及24个诊断因子的浅海生态系统健康诊断指标体系,并采用层次分析法对海州湾浅海生态系统2009年12月和2010年11月的健康状况进行诊断.结果表明,2009年12月和2010年11月海州湾浅海生态系统的综合健康指数值分别为0.500～0.689和0.553～0.750,浅海生态系统处于亚健康～较健康状态,近岸海域基本处于亚健康状态,离岸海域基本处于较健康状态,近岸海域生态系统健康水平低于离岸海域,这与近岸海域开发活动干扰多以及环境压力大有关.     

湿地挺水植物凋落物立枯分解研究进展

在许多湿地生态系统中,挺水植物立枯常组成凋落物总量的主要部分,其分解过程研究对于正确评价湿地生态系统的碳收支状况具有重要意义。对立枯分解过程与传统研究中凋落物分解过程的差异,分解过程中的 CO2排放,立枯分解的研究方法,以及分解过程的影响因素进行了综述。一般认为,湿地挺水植物立枯与传统研究中凋落物所处环境的差异造成了分解过程的差异,其分解过程中产生 CO2是湿地温室气体排放的重要途径;凋落袋和红外气体分析仪是湿地挺水植物立枯分解研究的主要方法;真菌组成了立枯体上微生物的大部分,对于立枯分解具有重要作用;环境因子（温度、水分等）和“基质质量”是影响挺水植物立枯分解过程的重要因素。在全球变化背景下,气候变化因子会直接或间接影响凋落物立枯分解过程,引起对气候变化的反馈,因此,在全球范围内开展气候变化对于湿地生态系统挺水植物立枯分解影响的研究具有重要的意义,必将成为凋落物研究的一个重要方向。     

Feedbacks between conservation and social-ecological systems

Robust ways to meet objectives of environmental conservation and social and economic development remain elusive. This struggle may in part be related to insufficient understanding of the feedbacks between conservation initiatives and social-ecological systems, specifically, the ways in which conservation initiatives result in social changes that have secondary effects on the environments targeted by conservation. To explore this idea, we sampled peer-reviewed articles addressing the social and environmental dimensions of conservation and coded each paper according to its research focus and characterization of these feedbacks. The majority of articles in our sample focused either on the effect of conservation initiatives on people (e.g., relocation, employment) or the effect of people on the environment (e.g., fragmentation, conservation efficacy of traditional management systems). Few studies in our sample empirically addressed both the social dynamics resulting from conservation initiatives and subsequent environmental effects. In many cases, one was measured and the other was discussed anecdotally. Among the studies that describe feedbacks between social and environmental variables, there was more evidence of positive (amplifying) feedbacks between social and environmental outcomes (i.e., undesirable social outcomes yielded undesirable environmental effects and desirable social outcomes yielded desirable environmental effects). The major themes within the sampled literature include conflict between humans and wild animals, social movements, adaptive comanagement, loss of traditional management systems, traditional ecological knowledge, human displacement and risks to livelihoods, and conservation and development. The narratives associated with each theme can serve as hypotheses for facilitating further discussion about conservation issues and for catalyzing future studies of the feedbacks between conservation and social-ecological systems.     

森林土壤氧化（吸收）甲烷研究进展

甲烷是一种重要的温室气体,对全球气候变暖的贡献仅次于CO2,约为25%。大气甲烷可以被土壤中甲烷氧化细菌在有氧条件下吸收利用,陆地生态系统森林土壤氧化吸收甲烷的研究已有大量报道。甲烷氧化菌是以甲烷作为唯一的碳源和能源的一类细菌的总称。但森林土壤在全球甲烷核算中具有一定的不确定性,取决于产甲烷菌和甲烷氧化菌的相对活性。甲烷氧化菌的研究集中在环境对氧化能力的影响和自身氧化能力上。大气甲烷氧化过程为高氧化能力低亲力氧化,受到一些因子,如土壤温度、土壤通气状况、pH、氮肥等的影响,具体机理的研究还有待进一步深入。土壤通气状况受土壤质地与土壤水分影响,土地利用类型可能改变土壤容重、土壤结构和土壤水分,进而影响土壤甲烷氧化。植物可以通过自身对生境的作用或化感作用影响土壤甲烷氧化。土壤动物的研究则相对较少,目前排放清单中仅有白蚁是全球甲烷核算所包括的。从甲烷氧化菌的分类出发,对甲烷氧化菌氧化甲烷的机理、菌的生态分布及甲烷氧化的影响因素、时空异质性、观测方法等作出了综述,为正确认识和准确预测森林土壤在一定气候和土地利用类型条件下的甲烷氧化强度提供理论依据。     

流域河口湿地生态健康与湿地发育关系研究

河口湿地作为一个独立的＂活体＂,有着其自身的地理发育、成熟和衰老的生长过程。以大洋河河口湿地为例,运用面积积分曲线和分维度指数计算大洋河流域发育阶段及河口湿地生长过程,得出如下结论,（1）在河流流域地貌发育早期,河流底蚀、侧蚀、溯源侵蚀强烈,河流含沙量高,泥沙在河口地区沉降而易形成河口湿地;随着流域地貌发育到壮年期,河流泥沙含量输出稳定,河口湿地面积继续扩张;到流域地貌发育晚期,侵蚀减弱,河流含沙量减少,河口湿地缺乏稳定的泥沙供应,在河湾水动力作用下逐渐萎缩、直至消亡。（2）人类活动直接影响河口湿地环境的物理、化学和生物组份,改变了河口泥沙的输入量及沉积环境,人类活动实际上是直接或间接地缩短了河口湿地的发育时间,加速了其发育进程。（3）针对不同发育阶段的河流,在制定河口湿地保护政策和修复措施时,必须充分考虑其地质历史发育特征,政策的制定要符合其生长规律。     

江西省农业可持续发展的生态安全评价

基于农业可持续发展状况建立江西省农业生态安全评价指标体系,采用聚类分析法将江西省农业生态安全度划分为不安全、较不安全、较安全和安全4个等级。从地域分异特征来看,环鄱区域生态系统遭受一定程度的破坏;赣南区域农业生态问题突出,农业生态安全性较差;赣中区域农业生态系统结构基本完整,农业生态安全状况较好。在11个地级市中吉安等6个地级市处于较安全等级,鹰潭等5个地级市处于较不安全等级。针对江西省农业可持续发展状况,探讨了农业生态安全体系建设问题。     

上海城市生态系统健康评价

从城市生态系统健康的内涵出发,采用压力、状态、响应机制构建出城市生态系统健康指标体系框架;运用主成分分析确定出主要指标及权重;并针对目前此类研究中指标评价标准的不确定性问题,建立模糊优选评价模型,从时间纵向上判断城市生态系统的走势;利用所建立的评价方法,以上海城市生态系统为例,最终筛选出3大类25项敏感性评价指标体系进行评价。评价结果表明：从1996-2002年间,上海城市的生态系统健康指标由0.37缓慢上升至0.46,表明上海城市自然生态环境与社会、经济发展的协调性在逐渐加强,但健康改善的程度并不显著,部分指标有所恶化,与2005年城市规划目标值0.72相比,系统现阶段离社会期望值还有很大的差距。本研究为上海城市进一步的生态规划提供可靠的背景状况和研究依据。     

四川省森林生态系统对野生珍稀濒危动物的保护价值计量研究

论文以异地保护成本替代法计算森林生态系统对濒危野生动物的保护价值。栖息于四川省森林生境的濒危野生动物需要生存下去所必需的食物、水、居住环境等一切生存条件完全由人为提供、人为创造和维持的成本就是四川省森林生态系统保护这些野生动物的价值。论文以动物园饲养动物的基本成本作为濒危野生动物异地保护的核算依据,得到四川省森林生态系统对野生珍稀濒危动物的保护价值为15.45×10⁸元/a。