公刘故里农耕文明溯源及其农业生态适应性变迁

大约距今4000年前,周部族首领公刘带领族人移居至戎狄(今甘肃庆阳),开垦荒地,豢养家畜,繁衍生息。我国农耕文化在此衍发孕育。经过数千年的积淀,延续至今形成了长期稳定的“耕—牛”模式,成为全中国的农耕滥觞。然而近些年来,由于特定的资源禀赋和社会经济因素,曾经以粮食生产为主的农业生产模式使当地生态环境更加脆弱,无法应对迅速发展的人口经济压力。“耕—牛”农业难以为继,周祖的农耕文化根基发生悄然动摇,耕地农业正在一步步向现代草地农业过渡。庆阳农业生产结构的调整不仅是周祖时期农业文化的历史回归,更是农业生态适应性变迁的必然结果,是农业现代化的必然趋势。

草业生产的环境影响评价教学实验设计

草业生产过程会造成显著的资源消耗与负面环境影响,量化评价草畜产品在生产过程中的环境影响情况,是进行农业环境改良与绿色消费引导的重要基础。教学中采用生命周期评价方法,通过目标与范围定义、建模、清单分析、结果解释与应用4个步骤,设计了1 kg紫花苜蓿鲜草生产的环境影响评价模拟教学实验。该实验可以培养草学专业学生进行草畜产品清洁生产设计与绿色等级认证的技能,同时实验方法也对其他类型农产品生产的环境影响评价适用。

三江源地区可持续发展的生态足迹

三江源的生态问题对全国生态和经济具有十分重要的影响,研究其环境与社会经济发展的可持续性具有重要意义。本研究利用生态足迹模型对三江源2000–2012年的生态足迹、生态承载力和生态盈余进行计算分析。结果表明,2000–2012年三江源人均生态足迹呈上升趋势,各土地利用类型分配不均,其中耕地供给率最大,其后依次为林地、水域、草地、化石燃料用地和建筑用地。人均生态承载力呈下降趋势,按降幅由多到少依次为建筑用地40%、草地29.95%、耕地20%、林地14.81%、水域2%。另外,草地对生态承载力的贡献最大,年均贡献率达41%,其次为林地,为38%。三江源整体呈生态盈余,但盈余有下降趋势,且不同土地类型生态盈亏也存在差异,其中草地和林地为生态盈余,耕地和化石燃料用地为生态赤字,水域和建筑用地开始由生态盈余转为生态赤字。

基于经济和生态视角的民勤县种植结构效益对比分析

农业种植结构调整是干旱地区在生态重建时期的重要手段之一。选择水资源短缺的甘肃省民勤县,对不同种植结构效益进行对比分析,对于我国干旱地区农业种植结构调整具有启示意义。本研究基于对民勤县3个样本乡镇的实地调研及对应的农田土壤采样,通过建立C-D函数模型和计算相关生态指标,从经济和生态视角探索,传统粮食种植结构、粮经二元种植结构和"粮改饲"种植结构的综合效益。结果表明:在上述三种种植结构中,"粮改饲"种植结构的总投入最少,收益率最高;现阶段苜蓿、小麦、玉米和葵花均处于规模报酬递增阶段,但相比较,苜蓿各要素的弹性系数之和更高。增加种子、肥料和机械费用投入可实现苜蓿增产;种植饲草作物较种植粮食作物和经济作物土壤有机碳的平均含量更高,绿期更长,水经济效益也更高。

Changes in global potential vegetation distributions from 1911 to 2000 as simulated by the Comprehensive Sequential Classification System approach

Vegetation classification models play an important role in studying the response of the terrestrial ecosystem to global climate change. In this paper, we study changes in global Potential Natural Vegetation (PNV) distributions using the Comprehensive Sequential Classification System (CSCS) approach, a technique that combines geographic information systems. Results indicate that on a global scale there are good agreements among maps produced by the CSCS method and the globally well-accepted Holdridge Life Zone (HLZ) and BIOME4 PNV models. The potential vegetation simulated by the CSCS approach has 6 major latitudinal zones in the northern hemisphere and 2 in the southern hemisphere. In mountainous areas it has obvious altitudinal distribution characteristics due to topographic effects. The distribution extent for different PNV classes at various periods has different characteristics. It had a decreasing trend for the tundra and alpine steppe, desert, sub-tropical forest and tropical forest categories, and an increasing trend for the temperate forest and grassland vegetation categories. The simulation of global CSCS-based PNV classes helps to understand climate-vegetation relationships and reveals the dynamics of potential vegetation distributions induced by global changes. Compared with existing statistical and equilibrium models, the CSCS approach provides similar mapping results for global PNV and has the advantage of improved simulation of grassland classes.