中国西北干旱区的地下水资源及其特征

分析了中国西北干旱区自然地理环境、水资源形成和分布及其利用状况,重点讨论了该区地下水资源分布的地区差异与赋存特征。该区平原地下水资源是山区水资源(包括降水和雪冰融水)在平原区内的转化;山区水资源是内陆河流和平原地下水的惟一补给来源;盆地平原地下水和地表水构成一个统一的水资源系统、独立的水文单元和完整的水生态体系。充分了解干旱区降水-地表水-地下水资源链的特征,正确认识干旱区“三水”转化自然规律,合理利用“三水”,对该区域社会经济持续发展具有重要意义。     

稻田冬闲期CO2气体排放的观测研究

亚热带红壤稻作区是华中地区的主要生态系统类型,在生态、经济以及社会效益方面都起着非常重要的作用。为了解这一生态区域的碳循环过程的因素和机理,同时为进一步解释农田碳循环过程对温室气体CO2的影响提供科学依据,采用静态箱式法对亚热带红壤性稻田长达约5个月的冬季休闲期(2005年11月—2006年4月)CO2气体排放通量进行了田间原位观测,并结合同步气象资料进行了分析。结果表明:亚热带红壤性稻田冬闲期CO2通量与近地面CO2体积分数的季节变化基本同步,与地面稻田生态系统的CO2通量对大气CO2体积分数的影响60%;CO2通量日变化规律基本为昼吸夜排:白天表现为田间杂草光合作用的结果,受光合有效辐射的影响,CO2通量与光合有效辐射的关系符合对数曲线,相关性达到显著水平;夜晚则以呼吸过程为主,主要受温度的影响,CO2通量与温度呈线性关系,其中气温和5cm地温最适宜用作于描述夜间CO2通量对温度变化的响应的指标。亚热带红壤性稻田生态系统在149d的休闲期内从大气中累积吸碳量(以CO2计)约4.03t·hm-2,表现为大气的碳汇。     

Using spatially explicit,time-dependent analysis to understand how social factors influence conservation outcomes

Conservation across human-dominated landscapes requires an understanding of the social and ecological factors driving outcomes. Studies that link conservation outcomes to social and ecological factors have examined temporally static patterns. However, there may be different social and ecological processes driving increases and decreases in conservation outcomes that can only be revealed through temporal analyses. Through a case study of the invasion of Falcataria moluccana in Hawaii, we examined the association of social factors with increases and decreases in invader distributions over time and space. Over 7 years, rates of invader decrease varied substantially (66–100%) relative to social factors, such as building value, whether land was privately or publically owned, and primary residence by a homeowner, whereas rates of increase varied only slightly (<0.1–3.6%) relative to such factors. These findings suggest that links between social factors and invasion in the study system may be driven more by landowners controlling existing invasive species, rather than by landowners preventing the spread of invasive species. We suggest that spatially explicit, time-dependent analyses provide a more nuanced understanding of the way social factors influence conservation outcomes. Such an understanding can help managers develop outreach programs and policies targeted at different types of landowners in human-dominated landscapes.     

轮作休耕对劳动力转移的影响——以河北、甘肃、云南三省为例

近年来,中国耕地的不合理利用引发了一系列严重的问题,为此国家提出“探索实行耕地轮作休耕制度试点”这一重要举措。劳动力是农业的主要生产要素,归纳总结农户休耕和劳动力转移的情况,准确掌握休耕面积对劳动力转移产生的影响,对进一步推动国家轮作休耕政策、现代化发展和城镇化具有重要的战略意义。基于此,利用河北、甘肃、云南三省六县1542户农户家庭的相关调研数据,对农户休耕、劳动力转移等情况进行了分析,并运用Tobit回归模型定量分析农户休耕面积对劳动力转移数量的影响。研究结果表明：（1）研究区内农户休耕比例与户均休耕面积存在差异,且休耕比例与户均休耕面积大小均为甘肃省>云南省>河北省。（2）研究区内有62.97%的家庭存在劳动力转移现象,且休耕农户劳动力转移数量远超未休耕农户。（3）核心变量休耕面积对劳动力转移存在显著的正向影响;控制变量中,农户家庭总人口、户主性别、劳动力受教育水平、医疗支出、住宅距公路距离和劳均工资对劳动力转移存在显著的正向影响,而家庭抚养比则对劳动力转移存在显著的负向影响。     

Exploiting pattern and sustainable development of marginal lands in the Three Gorge Reservoir Areas

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Impact of land clearing methods and cropping systems on labile soil C and N pools in the humid zone Forest of Nigeria

Labile soil C and N play vital roles in soil–plant nutrient dynamics, especially in the low input cropping system and are vulnerable to perturbation. Surface (0–0.15 m) soils from three land clearing methods (slash and burn, bulldozed non-windrowed and bulldozed windrowed) and each with two cropping systems (5-and 4-year cropping/2-year cassava fallow) were collected in the humid forest ecosystem of Nigeria.The soils were analysed for total C and N, microbial biomass C and N (SMB C and N), particulate organic matter C and N (POM C and N), water-soluble C, potentially mineralizable N (PMN) and mineral N. The size of the labile C and N and their relative contributions to the organic C and total N differed significantly among land clearing methods, irrespective of the cropping system. Soils under slash and burn had a significantly (p > 0.05) higher particulate organic matter C, N (10.80 and 0.16 g kg⁻¹, respectively) and microbial biomass C and N (1.07 and 0.12 g kg⁻¹) compared to the bulldozed windrow, regardless of the cropping system. Four years cropping/2-year cassava fallow resulted in a significant higher labile C and N, relative to 5-year cropped plots across the land clearing methods. Effect of the treatments on the concentration of PMN and mineral N mirrored the SMB N and POM N. However, the quantity of most of the labile C and N pool and crop yield obtained from the slash and burn and bulldozed non-windrowed treatment did not differ significantly. Hence, bulldozed non-windrowed clearing could be a viable alternative to slash and burn in the case of large-scale farming in ensuring reduced losses of soil organic matter and nutrient during land clearing in the humid tropics.     

耕地资源等值模型的建立及应用

以耕地基本产出模型为基础，结合我国农业生产中存在隐性失业等情况，提出了符合我国国情的耕地产出模型，并在建模过程中剔除了科技进步因素对产量的影响。从效用原理出发，以一定投入水平和自然条件下的拟合耕地复合产量作为衡量耕地资源质量的标准，从理论上建立了一套完整的评价方法和体系。在此基础上，以江苏省20世纪90年代耕地投入和产出数据为依据，建立了各市的耕地产出模型，并以1999年江苏省平均投入水平为标准，计算了经耕地资源等值化后的人均耕地资源拥有状况。研究结果表明，在耕地资源等值化前后，人均耕地资源拥有水平 出现了不同程度的变化，这种变化的原因在于耕地等值模型不仅考虑了耕地资源的数量，还考虑了耕地的质量，而耕地质量的高低取决人于耕地本身的基础地力和对投入的反馈能力。     

Bioretention Design for Xeric Climates Based on Ecological Principles1

Abstract: Bioretention as sustainable urban stormwater management has gathered much recent attention, and implementation is expanding in mesic locations that receive more than 1,000 mm of annual precipitation. The arid southwestern United States is the fastest growing and most urbanized region in the country. Consequently, there is a need to establish design recommendations for bioretention to control stormwater from expanding urban development in this ecologically sensitive region. Therefore, we review the ecological limits and opportunities for designing bioretention in arid and semiarid regions. We incorporated USEPA Stormwater Management Model (SWMM) simulations to synthesize ecologically based design recommendations for bioretention in arid climates. From our review, an ideal bioretention garden area should be 6 to 8% of the contributing impervious drainage area (depending on region) with two layers of media, a 0.5‐m low‐nutrient topsoil layer above a 0.6‐m porous media layer that acts as temporary storage during a storm event. When planted with the suggested vegetation, this design maximizes stormwater treatment by promoting ecological treatment in the topsoil while promoting infiltration and evapotranspiration of stormwater by deep‐rooted shrubs that require no irrigation after establishment. This synthesis improves water resources management in arid and semiarid regions by introducing a sustainable bioretention design that protects local surface waters while reducing regional water demands for irrigation.     

Assessing intervention effectiveness at promoting voluntary conservation practice adoption in agrienvironments

Although implementing conservation practices on private farms and forests can produce substantial environmental benefits, these practices are not being adopted widely enough to result in measurable improvements at regional scales. Researchers have investigated the production and program factors influencing producer choices to voluntarily adopt these practices. However, the findings of reviews are inconsistent, raising questions about review methods, including the omission of relevant variables. Further, applying lessons from past work to promote adoption is difficult because many reviews investigated dispositional or demographic variables that practitioners and policy makers cannot directly observe or influence. We conducted a new review of 146 empirical studies that tested the effects of different interventions (e.g., financial incentives, outreach events, and nudges) on increasing the likelihood of producers adopting conservation practices. We conducted a metaregression of quantitative studies from diverse disciplines that filtered studies by quality (i.e., use of randomization and clear analysis reporting). We synthesized these results with a thematic analysis of qualitative studies on producer perspectives about conservation practices. Financial incentives had the strongest evidence of increasing producers’ likelihood of adopting conservation practices (odds ratio 1.86, p < 0.05). However, this effect was only apparent after filtering by study quality, which also improved model fit and identified significant regional differences (odds ratio –1.69, p < 0.01). The thematic review of qualitative studies revealed that peer groups may be successful in reinforcing adoption behaviors due to homophily effects and that financial incentives not only offset implementation costs but also mitigated perceived risks of adoption. Given the problems we encountered in testing hypotheses about the magnitude of variability explained by intervention types and practice characteristics, we recommend additional experimental and longitudinal work that accounts for financial incentives and pairs qualitative and quantitative data to clarify relationships between program design and practice adoption rates.     

Creating and sustaining community capacity for ecosystem-based management: Is local government the key?

Recently, collaborative approaches to natural resource management have been widely promoted as ways to broaden participation and community involvement in furthering the goals of ecosystem management. The language of collaboration has even been incorporated into controversial legislation, such as the US Healthy Forests Restoration Act of 2003. This research examines collaboration and sharing management responsibility for federal public land with local communities through a case study of the Ashland Municipal Watershed in southern Oregon. A policy sciences approach is used to analyze community participation and institutional relationships between the US Department of Agriculture, Forest Service, and local city government in the planning processes of five land management actions occurring over a 7-year period. The knowledge gained from examining differing approaches to planning and decision making in the Ashland watershed is used to suggest future planning processes to develop and sustain the community capacity necessary to support implementation of community-based ecosystem management.