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There is a close relationship between agricultural production and environmental meteorological conditions. In the study of the correlation between them, the simulation models are paid more attention to the crop growth. In this paper the development of the studies on the crop growth dynamic simulation model in China is briefly reviewed. The relationships between meteorological conditions and each process of crop growth (such as photosynthesis, respiration, accumulation and distribution of assimilation products and growth of leaf area) are studied and simulated basing on the results from field experiments. Preliminary models for rice, wheat, maize and soybean have been developed, and some investigations about modelling methods, procedures and parameters in simulation models are made. 相似文献
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论中国农业持续发展研究中的若干问题 总被引:11,自引:0,他引:11
“持续农业的研究对象”、“农牧结合问题”、“粮食问题”“农业生产布局”以及“中国农业生产效率”一直是我国学术界与政策决策阶层争论与关注的热点。五大“热点”不仅影响我国农业生产的正确决策,也影响着我国农业研究的方向。作者根据近年研究实践,结合国内外的大量研究成果,从理论与实践2个方面对上述问题进行了实事求是的分析、论述。①“持续农业”是学术术语,并不是农业替代模式,持续农业的研究对象则是促进农业持续发展的技术体系与管理战略,以此促进农业向环境健康与安全的方向发展,并不是“创造”一种新的农业生产模式完全替代常规农业;②我国农牧结合研究依然停留在古时期“种植业提供饲料,畜牧业提供畜粪还田培肥地力”这一传统观念阶段。农牧结合研究应该在我国农、牧生产专业化进一步深化的基础上,从饲料能量蛋白质供给与消费平衡这一深层次上优化和把握农牧结合强度及其协调性,同时要高度重视我国畜牧业生产专业化可能引发的农、牧“分离”及其潜在的环境问题;③有计划地节制食物消费的增长速度、引导膳食结构的转变与合理引导并积极寻找粮食替代资源,是解决我国粮食生产在经济高速增长前提下粮食供需缺口不断扩张的主要途径;④我国种植业生产发展空间格局的重心应摆 相似文献
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1IntroductionThesoutheastareasofShanxiProvincestandinthesoutheastoftheLoesPlateauandhaveavariedtopography.Thesoiloftheseareas... 相似文献
676.
湖南烟区烤烟钾含量与土壤钾素的分布特点之间的关系 总被引:11,自引:0,他引:11
采用野外调查和室内分析相结合的方法,分析了湖南烟区烤烟钾含量与土壤钾含量的分布特点及相互关系,结果表明:湖南烟区土壤全钾质量比偏低,平均为14.92 g·kg-1,有19.90%的土样全钾质量比低于10 g·kg-1;土壤速效钾质量比较低(140.28 mg·kg-1),10.80%土壤样品中速效钾质量比≤80 mg·kg-1,63.04%土壤样品中速效钾质量比在80~160 mg·kg-1之间.不同产地间相比较,全钾质量比由高到低顺序为:凤凰、张家界、龙山、宁乡、常德、怀化、浏阳、永州、桂阳;速效钾质量比的高低顺序与全钾质量比有所不同.湖南烟区烤烟钾质量分数适中,平均为2.28%,不同等级烟叶钾质量分数的变化规律是X2F>C3F>B2F.各等级烟叶的钾质量分数在不同产地间差异均达到0.05显著水平.在对土壤速效钾质量比分组后,烟叶钾质量分数随着土壤速效钾质量比的增加而增加,其中在速效钾质量比较低时,烟叶钾质量分数增加速度较快.在相关分析基础上,建立了土壤养分与烤烟钾质量分数的逐步回归方程,所筛选得到的4个土壤因子(水溶性氯、有机质、交换性钙和速效钾)对烤烟钾质量分数的影响均达到极显著水平. 相似文献
677.
喀斯特地区地表地下的二元储水结构导致地表水渗漏严重,而土被浅薄且分布不连续,土壤蓄水量不足,易导致作物出现缺水。以贵州省为例,基于FAO-56 Penman-Monteith公式和气象资料,估算了贵州省1961~2014年参考作物蒸散量ET_O,在此基础上运用反距离权重插值法对贵州省ET_O进行空间插值,分析了贵州省ET_O的时空变化特征,并用多元回归分析方法探讨了影响贵州省ET_O的主要因素。结果表明:贵州省西部地区的ET_O高于中、东部地区;1年之中ET_O主要集中于夏季和春季,冬季最少;60年代的ET_O高于多年平均值,70年代之后逐渐降低,90年代达到最低值,2000年以来ET_O急剧升高;从年际变化看,贵州省年平均ET_O总体呈波动上升趋势,1961~2002年持续降低,2003年以后显著升高;年际变化中秋季ET_O变化最大,其次为春季、夏季,冬季变化最小;影响贵州省ET_O的主导气象因素是日照时数,两者呈显著的正相关,地理纬度与ET_O存在明显的负相关。贵州省ET_O的时空特征研究及其影响因素分析将为其他喀斯特地区的农业发展和水资源合理配置提供科学依据。 相似文献
678.
Mechanistic understanding of human–wildlife conflict through a novel application of dynamic occupancy models 下载免费PDF全文
Varun R. Goswami Kamal Medhi James D. Nichols Madan K. Oli 《Conservation biology》2015,29(4):1100-1110
Crop and livestock depredation by wildlife is a primary driver of human–wildlife conflict, a problem that threatens the coexistence of people and wildlife globally. Understanding mechanisms that underlie depredation patterns holds the key to mitigating conflicts across time and space. However, most studies do not consider imperfect detection and reporting of conflicts, which may lead to incorrect inference regarding its spatiotemporal drivers. We applied dynamic occupancy models to elephant crop depredation data from India between 2005 and 2011 to estimate crop depredation occurrence and model its underlying dynamics as a function of spatiotemporal covariates while accounting for imperfect detection of conflicts. The probability of detecting conflicts was consistently <1.0 and was negatively influenced by distance to roads and elevation gradient, averaging 0.08–0.56 across primary periods (distinct agricultural seasons within each year). The probability of crop depredation occurrence ranged from 0.29 (SE 0.09) to 0.96 (SE 0.04). The probability that sites raided by elephants in primary period t would not be raided in primary period t + 1 varied with elevation gradient in different seasons and was influenced negatively by mean rainfall and village density and positively by distance to forests. Negative effects of rainfall variation and distance to forests best explained variation in the probability that sites not raided by elephants in primary period t would be raided in primary period t + 1. With our novel application of occupancy models, we teased apart the spatiotemporal drivers of conflicts from factors that influence how they are observed, thereby allowing more reliable inference on mechanisms underlying observed conflict patterns. We found that factors associated with increased crop accessibility and availability (e.g., distance to forests and rainfall patterns) were key drivers of elephant crop depredation dynamics. Such an understanding is essential for rigorous prediction of future conflicts, a critical requirement for effective conflict management in the context of increasing human–wildlife interactions. 相似文献
679.
Cheng''ai Jiang Qitang Wu Shucai Zeng Xian Chen Zebin Wei Xinxian Long 《环境科学学报(英文版)》2013,25(9):1890-1896
Previous soil pot and field experiments demonstrated that co-cropping the hyperaccumulator Sedum alfredii with maize increased Zn phytoextraction by S. alfredii and decreased Zn uptake by maize shoots. This hydroponic experiment was conducted to investigate whether the facilitation of Zn phytoextraction by S. alfredii resulted from improved dissolution in this co-cropping system and its relation to root exudates. S. alfredii and maize were mono-and co-cropped (without a root barrier) in nutrient solution spiked with four Zn compounds, ZnS, ZnO, Zn3(PO4)2 and 5ZnO·2CO3·4H2O (represented as ZnCO3 ) at 1000 mg/L Zn for 15 days without renewal of nutrient solution after pre-culture. The root exudates were collected under incomplete sterilization and analyzed. The results indicated that the difference in Zn salts had a greater influence on the Zn concentration in maize than for S. alfredii, varying from 210-2603 mg/kg for maize shoots and 6445-12476 mg/kg for S. alfredii in the same order: ZnCO3 > ZnO >Zn3(PO4)2 > ZnS. For the four kinds of Zn sources in this experiment, co-cropping with maize did not improve Zn phytoextraction by S. alfredii. In most cases, compared to co-cropped and mono-cropped maize, mono-cropped S. alfredii resulted in the highest Zn2+ concentration in the remaining nutrient solution, and also had a higher total concentration of low molecular weight organic acids (LMWOA) and lower pH of root exudation. Root exudates did partly influence Zn hyperaccumulation in S. alfredii. 相似文献
680.