2005—2019年洞庭湖平原耕地面源污染迁移轨迹及空间格局

洞庭湖平原因不合理的农业生产活动导致严重的耕地面源污染问题,揭示洞庭湖平原近10余年耕地面源污染迁移轨迹及空间格局,可为洞庭湖平原下一步科学防治耕地面源污染提供参考。该研究以洞庭湖平原湖南省部分的21个区（县、市）为实例,利用清单分析法构建农田化肥、人畜排泄物和农田固废3类污染单元,测算化学需氧量（Chemical Oxygen Demand,COD）、总氮（Total Nitrogen,TN）和总磷（Total Phosphorus,TP）3类污染物排放情况,并运用空间分析、重心模型和冷热点分析研究2005－2019年洞庭湖平原耕地面源污染轨迹迁移变化及空间格局。结果表明：1）从时序上看,2005－2019年间3类污染物排放总量和排放强度总体上均呈现下降趋势;从空间分布上看,COD排放强度等级分布更为集中,洞庭湖平原耕地面源污染程度呈现出"东部>西部>中部"的空间格局;2）从重心模型分析来看,3类污染物排放强度重心在东西方向上的移动更显著,并且重心移动速度呈现阶段变化;3）从冷热点分析来看,3类污染物空间分布格局差异性显著,COD最为明显,TP次之,TN最小,热点区域大多分布于洞庭湖平原东部,冷点区域大多分布于洞庭湖平原中部。研究说明了在生态文明建设过程中,洞庭湖平原耕地面源污染情况有所好转,并且各地区耕地面源污染程度和治理都具有差异性,为今后因地制宜治理耕地面源污染提供理论依据和思路。     

灌溉方式对西辽河平原玉米产量和水氮利用效率的影响

为科学选择适于西辽河平原春玉米生产的灌溉方式,于2018—2020年在通辽市、赤峰市、兴安盟,采用3种灌溉方式——浅埋滴灌、膜下滴灌和传统畦灌开展试验,探究其对春玉米产量和水、氮利用效率的影响。结果表明,在玉米吐丝后,通辽市和赤峰市浅埋滴灌的干物质积累量显著(P<0.05)高于传统畦灌。浅埋滴灌下,玉米茎鞘干物质转运率和转运贡献率较膜下滴灌、传统畦灌分别高9.31%、15.25%和13.45%、29.07%,叶片干物质转运率和转运贡献率分别提高15.17%、32.38%和6.93%、47.82%。在3种灌溉方式下,春玉米吐丝前、吐丝后的干物质积累量均与产量呈显著(P<0.05)正相关。总的来看,浅埋滴灌下春玉米的产量较膜下滴灌和传统畦灌平均增产3.43%和7.43%,膜下滴灌较传统畦灌平均增产3.87%。在灌溉水利用效率上,浅埋滴灌和膜下滴灌均显著(P<0.05)高于传统畦灌;在氮肥偏生产力上,除2018年兴安盟试验点外,浅埋滴灌均显著(P<0.05)高于传统畦灌。综合产量、水氮高效利用等因素,浅埋滴灌的灌溉方式为西辽河平原和拟生态区适宜的灌溉方式。     

坚持“八个围绕”完善生态屏障——亳州市全力推进千万亩森林增长工程建设

本文围绕落实省委、省政府重大决策，立足平原特点和生态强市建设，坚持“八个围绕”，努力拓展造林空间，建立和完善平原农业生态屏障，奋力推进千万亩森林增长工程建设。     

江汉平原棉花—小麦种植制氮磷肥料的合理分配研究

采用定位试验连续3年研究了江汉平原棉花—小麦种植制氮、磷肥料的合理分配,结果表明,在周年氮、磷肥料施用总量不变的条件下(N 375 kg/hm2和P2O5150 kg/hm2),棉花—小麦种植制氮、磷肥料最佳分配方式为棉花季N 270 kg/hm2、P2O575 kg/hm2,N小麦季105 kg/hm2、P2O575 kg/hm2。根据市场上棉花和小麦的销售价格,仅从增产增收的角度,在棉花预期产量为中、高水平的情况下,可以酌情将小麦季的部分氮肥(50%)前移到棉花季,适当增加棉花季的产量和收入,从而增加两季作物的总收入;但从环境保护的角度出发,氮、磷肥料的分配方式仍以推荐施肥更好,这样可以提高整个种植周期氮、磷肥料的累计利用率,减少土壤剖面硝态氮素积累,降低氮、磷损失风险。在本研究条件下,施肥的经济效益和环境效应难以完全协调统一。     

Low yield gap of winter wheat in the North China Plain

The yield gap (YG) between the potential yields (Yp) and the average on-farm yields (Ya) is an indicator of the potential improvement for crop production. Understanding how large the current gap is and how this gap has changed over the past few decades is essential for increasing wheat production to meet increased food demand in China. This paper describes a study conducted using an APSIM-Wheat model and farm-level crop yield to analyze the spatio-temporal distribution of the yield gap of winter wheat from 1981 to 2010 in the North China Plain. Nine varieties were calibrated and evaluated based on the data from 16 agro-meteorological experimental sites and then potential yields were estimated considering cultivar replacement. In addition, a trend pattern analysis of on-farm yields for the period 1981–2010 was conducted. Results revealed an estimated yield gap across the entire North China Plain region of 1140–6810 kg ha⁻¹, with a weight average of 3630 kg ha⁻¹ in 1981–2010. Expressed as a relative yield (yield gap % of potential yields), the range was 15–80%, and the weight average was 45%. Despite the negative effects of increasing temperature and decreasing radiation, the potential yields significantly increased by 45 kg ha⁻¹ per year due to cultivar improvement. On-farm yields increased even more notably because of new cultivar selection, increased fertilizer application and other management improvements, but were stagnating in 32.3% of wheat areas, located mainly in Hebei province, Shandong province, Beijing and Tianjin. The improvement of on-farm yields have substantially contributed to yield gap spatio-temporal variation. As a result, the yield gap decreased from 4200 kg ha⁻¹ (56%) in 1981–1990 to 3000 kg ha⁻¹ (35%) in 2001–2010 at a rate of −69 kg ha⁻¹ per year. However, yields stagnation will expand to the northern Henan province without cultivar potential productivity improving, where yield gap was close to or less than 20% of the potential yields and proved difficult to reduce. To further improve the total production of winter wheat in the coming decades, efforts should be paid to break the potential ceiling and reduce the yield gap by breeding higher yield variety and introduction of new agricultural technology.     

探讨江西平原地区商品林政策研究设计

通过分析我国木材供给的现状和平原商品林业建设存在的问题，从而探索出江西平原商品林的政策设计。     

Revisiting the relationship between common weather variables and loblolly–shortleaf pine seed crops in natural stands

Seed production was monitored during24 years using seed-collection traps inloblolly–shortleaf pine (Pinus taeda L.–P.echinata Mill.) stands located in southeast Arkansas,north-central Louisiana, and southwest Mississippi onthe southeastern Coastal Plain, USA. Sound seedproduction was correlated with mean monthlyprecipitation and temperature from National Oceanicand Atmospheric Administration weather stationslocated near the seed-collection areas to determinethe potential of weather factors in forecasting pineseed crops. Correlations were restricted to threecritical periods in the pine reproductive cycle –strobili primordia differentiation, pollination, andfertilization. The most important (P 0.05)variables correlated with pine seed production for combined locations were cumulative precipitation (r = +0.60) during July, August, and September at 27 to 25 months before seed dispersal and mean temperature (r = –0.45) in August at 26 months before seed dispersal. Because multiple environmental factors can negatively impact pine seed development during the two yearsfollowing strobili primordia differentiation,seed-production forecasts based on weather variablesshould be verified by on-site cone counts during thesummer preceding autumn seed dispersal.     

玉米叶片气孔特征及气体交换过程对气候变暖的响应

气孔是植物叶片表面控制大气与植物间气体交换的孔状结构,对于生态系统碳、水循环过程的调节起着非常重要的作用。本文利用典型农田生态系统实验增温平台,研究了未来气候变暖对玉米叶片的气孔特征(包括气孔频度、气孔开口大小和形状以及气孔分布格局)和气体交换过程的影响。结果表明:(1)尽管增温并没有改变气孔密度(P0.05),但却由于表皮细胞数目的减少导致气孔指数显著增加12%(P0.05);(2)增温使气孔开口的长度显著减小18%(P0.01),宽度增加26%(P0.01),面积和周长分别增加31%(P0.01)和13%(P0.05);(3)实验增温还使单个气孔之间最近邻域的平均距离显著增加,表明气孔在玉米叶片上的分布变得更加均匀;(4)增温导致玉米叶片的净光合反应速率(Pn)、气孔导度(Gs)和蒸腾速率(Tr)分别增加52%(P0.05)、163%(P0.001)和81%(P0.05);与此相反,玉米叶片的暗呼吸速率(Rd)却显著降低24%(P0.01)。增温没有对细胞间CO2浓度(Ci)和水分利用效率(WUE)产生显著的影响(P0.05)。本研究结果表明,未来全球气候变暖可能通过改变玉米叶片的气孔频度、气孔开口大小和形状及其在叶片上的空间分布格局来改变其气体交换过程。     

基于SEBAL模型与MODIS产品的松嫩平原蒸散量研究

利用MODIS的地表温度/比辐射率、植被指数、地表反照率3种产品,结合气象站点的观测资料,通过基于地表能量平衡方程的SEBAL模型估算了松嫩平原2008年5月16日、6月16日、7月13日、8月15日、9月13日不同下垫面的地表蒸散量,并采用涡动相关数据对模型估算结果进行验证,发现估算值与实测值的变化趋势大体一致,平均误差在20%以内,基本上可以满足区域蒸散研究的精度要求。此外,还通过GIS空间分析方法探讨了松嫩平原2008年生长季内不同时相蒸散量的时空分布特征,并分析了蒸散量土地利用类型的关系,结果表明松嫩平原蒸散量的空间分布在很大程度上受气候特征、土壤供水条件及土地利用类型的影响,各时相的蒸散量大致表现为从西南部向东北部逐渐增加的变化趋势,水体、林地、沼泽湿地具有较高的蒸散量,耕地、居工地次之,草地的蒸散量最低。     

三江平原水稻田耕层土壤铁随开垦年限的动态变化

以三江平原不同开垦年限水稻田为研究对象,分析了水稻田耕层土壤铁随开垦年限的动态变化情况。结果表明,随开垦年限增加,水稻田耕层土壤全铁呈指数形式递增;游离态铁以波动形式增加,3和11a时为波谷,5和14 a时为波峰;络合态铁开垦前期逐年增加,8 a后增加到1 562.41 mg/kg,随后逐渐减少;无定形态铁呈指数递减趋势。氧化铁的游离度先升高后降低,开垦8 a时达到最高值0.46;络合度在开垦前8 a逐年上升,5～8 a增速降低,8 a时达到最高值0.18,之后逐年下降;活化度则呈指数形式下降。土壤淹水状况和耕作管理方式的不同造成水稻田和大豆田氧化铁游离度、络合度和活化度随开垦年限变化趋势的差异。水田开发使湿地表土游离态铁、络合态铁和无定形态铁含量增加,氧化铁游离度升高,水稻田耕层土壤氧化铁络合度和活化度低于天然湿地,高于大豆田。