幼龄桔园套种对土壤流失的影响及其模拟研究

在幼龄桔园套种紫云英 (Ⅰ )、套种 (混播 )黑麦草和紫云英 (Ⅱ )、不套种 (Ⅲ )及套种黑麦草 (Ⅳ ) ,分析和模拟了下垫面性状和降雨与土壤流失量的关系及规律 .套种牧草使土壤流失量大大下降 ,平均侵蚀量仅为自然裸露区的 1 4.7% ;各小区 (折算成hm2 )单位降雨的土壤侵蚀量随降雨过程次序的增加而呈指数规律下降 ,土壤流失量随覆盖度指数而下降 .     

土壤-植物下垫面对微生态环境的影响

综述了土壤植物下垫面对辐射平衡、热量条件、土壤侵蚀、土壤肥力、光能利用率等微生态环境的影响．结果表明,有植被下垫面的反射率、有效辐射、土壤热通量的日变幅和感热通量均小于荒坡裸地;坡地植草和减少翻耕次数有利于水土保持;下垫面栽种牧草可提高土壤肥力和光能利用率．这对合理开发和利用土地资源具有一定的参考价值     

小议“Rubisco酶”

农作物光能利用率低一直是限制作物高产的“瓶颈”。从理论上推算,在无明显逆境的条件下田间光能利用率可以达到5％．但即便是666．7m^2产0．5t的高产田光能利用率也不过1％。因此人们一直试图找出限制光能利用率提高的因素,从而提高农作物产量。终于人们研究发现了光合作用中的一种酶——Ruhisco酶．正是这种酶限制了光能利用率的提高。     

土壤干旱条件下保水剂对多年生黑麦草光合特性的影响

以多年生黑麦草（Lolium perenne Linn．）为研究对象,对土壤干旱条件下（土壤含水量12．6％、10．5％、8．4％和6．3％）使用保水剂后叶片光合特性的动态变化进行了分析。结果显示：随土壤含水量的降低和胁迫时间（12d）的延长,多年生黑麦草叶片的净光合速率（Pn）、气孔导度（Gs）、蒸腾速率（Tr）和光能利用效率（LUE）呈逐渐下降的趋势;随土壤含水量的降低,胞间CO2浓度（Ci）逐渐升高、瞬时水分利用效率（WUE）逐渐降低,但随胁迫时间的延长Ci和WUE则呈现不同的变化趋势;总体上,在土壤含水量不同的条件下及不同的胁迫时间各指标均有显著差异（P〈0．05）。与未添加保水剂的各处理组相比,添加质量分数2％保水剂后多年生黑麦草叶片的Pn、Gs、WUE和LUE值均增大,而Ci和Tr值则降低,差异达显著水平（P〈0．05）。研究结果表明：合理使用保水剂能提高多年生黑麦草叶片的光合能力以及土壤的保水能力,增强多年生黑麦草对干旱环境的适应性。     

土壤—植物下垫面对微生物环境的影响

综述了土壤－植物下垫面对辐射平衡,热量条件,土壤侵蚀,土壤肥力,光能利用率等微生态环境的影响。结果表明,有植被下垫面的反射率,有效辐射,土壤热能量的日变幅和感热通量均小于荒坡裸地,坡地植草和减少翻耕次数有利于水土保持;下垫面栽种牧草可提高土壤肥力和光能利用率,这对合理开发和利用土地资源具有一定的参考价值。     

充分利用光能发展立体种植

由于全球性的人口剧增和资源紧缺，农作物高产问题一直是世界性的重大课题。我国人多地少，资源相对不足的矛盾尤为突出，食物压力甚大，高产要求的迫切性更为强烈。因而，如何提高单位面积耕地上的作物产量日益受到人们的关注。众所周知，农作物高产的核心是提高光能利用率，即“向太阳光要粮”，“收获太阳能”。理论上，作物的光能利用率可达5％～6％，但实际光能利用率远远低于理论潜力值。目前，世界农田平均光能利用率只有0．2％，我国约为0．3％～0．4％。由此可见，提高光能利用率及作物单产水平的潜力也是非常巨大的。作物生长前期…     

农林复合系统中物种间水肥光竞争机理分析与评价

低丘红壤农林复合系统被认为能通过引入树木而利用土壤深层水分及防治水土流失,从而作为亚热带地区应对季节性干旱的有效利用方式。然而,复合也可引起光能、水分和养分的竞争,导致农作物减产。通过作物生长量的测定、利用多年监测的土壤水文数据、15N微区试验及光合有效辐射的测量,综合探讨了南酸枣-花生复合系统引起的物种间水肥光的变化;通过其交互作用形成的协同,竞争关系分析,较为全面地评价了农林复合系统水肥光竞争特征。研究表明：低丘红壤上南酸枣与花生复合,促进了南酸枣生长,却减小了20％～50％的花生产量和生物量。其原因不单是南酸枣遮荫引起复合花生光合有效辐射减弱,还与水、肥竞争有关。复合系统在旱季加大利用50～100cm土层土壤水分,从而缓冲了干旱造成的影响;但南酸枣与花生间作系统也存在着一定的水分竞争。复合使得南酸枣能够利用施于花生区及淋失到60cm深处的养分,提高了养分的利用率;但同时也导致养分的竞争并影响花生的生长。在花生产量、生物量受复合南酸枣竞争影响因子中,以光最大、养分其次、水分最小。农林复合系统水肥光交互作用因其组分类型与时空配置而异,需从生态、经济、社会效益方面对复合模式加以优化。     

种植方式对夏玉米光合生产特征和光温资源利用的影响

为研究套种与直播两种种植方式对夏玉米光合生产特征和光温资源利用的影响,选取郑单958和登海661为研究对象,设置3个播期,密度为67500株.hm-2,以地上干物质积累量和作物生长速率、叶面积指数、穗位叶的单叶光合速率来评价夏玉米的光合生产特征;以Richards模型拟合籽粒灌浆过程;结合气象数据计算夏玉米光能利用率.结果表明:直播处理比套种处理籽粒产量增加1.17%～3.33%(P0.05),但千粒重显著降低;生育期随播期提前而延长;直播条件下叶面积指数和单叶光合速率在灌浆前期显著高于套种,但灌浆后期下降较快;与套种相比,直播开花前和开花后具有较高的干物质积累量和较快的作物生长速率.Richards模型解析表明,直播处理达到最大灌浆速率的时间明显早于套种,起始势较套种高,但灌浆期、活跃灌浆期和灌浆速率最大时的生长量均低于套种;与套种相比,直播处理生育期间总积温和总辐射量分别减少150～350℃.d和200～400MJ.m-2,但籽粒光能利用率较套种提高10.5%～24.7%.因此,直播较套种有优势,在夏玉米大田生产条件下,重视叶片的光合生产特征,延缓叶片衰老,有利于提高夏玉米的光能利用率,进一步挖掘增产潜力.     

幼龄枇杷园套种科杂1号大豆的效应

幼龄枇杷园套种科杂1号,显著提高土壤肥力,土壤速效P由清耕对照的痕迹增至18．27mg/kg;全P和速效K分别增加260．0％和183．6％,有机质、全N、全K和速效N的增幅在40％左右;研究还表明,套种提高了枇杷树树体营养和促进丰产树冠的形成,叶片N、P、K、Ca、Mg含量均比对照区增加9％以上,冠幅和枝梢数分别地加27．3％和57．7％,枝梢抽穗率提高86．8％,同时,套种对改善果实品质也有一定作用。     

蚯蚓-秸秆及其交互作用对黑麦草修复Cu污染土壤的影响

以高沙土为供试土壤,加入Cu^2＋以模拟成：0,100,200,400mg／kgCu^2＋的Cu污染土壤,设置接种蚯蚓（E）、表施秸秆（M）,同时加入蚯蚓和秸秆（ME）及不加蚯蚓和秸秆的对照（CK）4个处理,并种植黑麦草。研究蚯蚓、秸秆相互作用对黑麦草吸收、富集铜的影响。结果表明：加入秸秆显著提高了蚯蚓的生物量,一定程度上缓解了重金属对蚯蚓的毒害,同时蚯蚓显著提高了秸秆的分解率,较无蚯蚓对照提高了58．11％～77．32％。接种蚯蚓（E,ME）还提高了土壤有效态重金属（DTPA-Cu）含量,秸秆处理（M）则降低了土壤有效态重金属含量。研究还发现,E处理促进了黑麦草地上部生长,而M和ME处理均显著提高了黑麦草地下部的生物量。E和ME处理同时提高了植物地上部和地下部的Cu浓度及Cu吸收量,M处理则只对植物的地下部Cu浓度和Cu吸收量有显著促进作用。总体来看,E处理、M处理及ME处理分别使黑麦草地上部Cu富集系数提高了31．22％～121．07％．2．12％～61．28％和25．56％～132．64％。     

林网保护区冬小麦生长过程的数值模拟

给出了一个模拟冬小麦生长过程的产量生态学模式 ,并对黄淮海平原林网保护区冬小麦的生长过程进行了数值模拟 .模型输出变量包括作物的叶面积指数 ,根、茎、叶、籽等地上和地下器官生物量 ,以及与作物生长密切相关的土壤水分变化情况、作物水分利用率、光合 /呼吸效率等生理生态因子 .结果表明 ,由于林网地区小气候条件的改善 ,使得农林复合系统较之单作农田有更强的抗旱能力 ,在干旱的 1 994年 ,林网保护下的农林复合系统生产力较单作农田提高 1 1 .6%左右 .模式输出的小麦地上部分生物量与生长监测资料十分一致     

The Effects of Cropping Systems on Avian Communities in Cacao and Banana Agro‐Forestry Systems of Talamanca,Costa Rica

Multispecies agro‐forestry is generally lauded for providing ecosystem services, especially in tropical environments. Avian communities contribute to services such as biodiversity and pest management. Characterizing and evaluating avian community composition in similar cropping systems will help optimize management for ecosystem services. We examined the relationship between cropping system vegetation and avian communities in four shaded agro‐forestry systems common to the Limón province of Costa Rica: abandoned and managed systems of cacao, cacao with banana, and banana. During two field seasons, we detected 2605 birds from 106 species and identified 2791 trees and shrubs from 62 morphospecies. We compared vegetation and avian species richness across systems with mixed‐effects linear models. Canopy, understory, and groundcover vegetation differed among agro‐forestry systems. More ground‐ and understory‐foraging forest species were detected in agro‐forestry systems lacking banana, whereas richness of agricultural generalist species was highest in systems with banana. Richness of understory‐ and ground‐foraging species correlated with understory tree species richness and leaf litter. Our results indicate that shaded cacao and banana systems can have similar canopy‐foraging species richness that includes both agricultural and woodland generalist species, but that interspersing banana with cacao can adversely influence understory forest bird community composition. Agro‐forests with diverse understory vegetation support more understory‐foraging bird species that have proven valuable in pest management. Abstract in Spanish is available at http://www.blackwell‐synergy.com/loi/btp .     

城市污泥土地利用研究

通过培养试验、盆栽试验和田间试验系统地研究了污泥的组分特征、性质及其农地和城市园林绿化地利用对作物或绿化灌木、土壤肥力及其环境的影响,结果表明,污泥富含有机质和氮磷养分,且养分当季有效性介于化肥农家肥之间。施用污泥将明显提高土壤肥力,表现改善土壤物理性质;增加土壤肥机质和氮磷水平,并增加土壤生物活性,因此施用污泥的处理作物产量较高,并有利于后茬作物的稳健生长。但污泥施用也存在重金属、病原物等污染     

宁夏引黄灌区春小麦的生态条件分析及其改善途径

本文系统分析了影响宁夏引黄灌区春小麦生产的生态条件,从作物品种、黄河肥水、土壤肥力与盐渍化、气候等方面分析了小麦与生态环境的关系,提出小麦与生态环境的平衡失调是限制灌区小麦生产潜力的关键问题,对最隹施用化肥量、合理灌溉定额及改善小麦生态环境、实现高产稳产等进行了探讨。     

Integrated management for sustainable cropping systems: Looking beyond the greenhouse balance at the field scale

Cover crops (CC) promote the accumulation of soil organic carbon (SOC), which provides multiple benefits to agro‐ecosystems. However, additional nitrogen (N) inputs into the soil could offset the CO₂ mitigation potential due to increasing N₂O emissions. Integrated management approaches use organic and synthetic fertilizers to maximize yields while minimizing impacts by crop sequencing adapted to local conditions. The goal of this work was to test whether integrated management, centered on CC adoption, has the potential to maximize SOC stocks without increasing the soil greenhouse gas (GHG) net flux and other agro‐environmental impacts such as nitrate leaching. To this purpose, we ran the DayCent bio‐geochemistry model on 8,554 soil sampling locations across the European Union. We found that soil N₂O emissions could be limited with simple crop sequencing rules, such as switching from leguminous to grass CC when the GHG flux was positive (source). Additional reductions of synthetic fertilizers applications are possible through better accounting for N available in green manures and from mineralization of soil reservoirs while maintaining cash crop yields. Therefore, our results suggest that a CC integrated management approach can maximize the agro‐environmental performance of cropping systems while reducing environmental trade‐offs.     

三峡库区移民安置区生态农业发展模式的研究

就三峡库区农用土地的分布、开发方式、存在问题、生态农业发展模式等方面进行了初步的探讨．在分析三峡库区现已开发的农用土地存在着地力衰退、生产力低、自然灾害频繁及生态环境恶化等问题的基础上,从人与自然相协调的角度,提出了建立农林复合生态系统、木本粮油型、农林牧复合型、农林牧渔复合型的发展模式的思路和建议．     

磷胁迫对不同杉木无性系酸性磷酸酶活性的影响

 缺磷是限制目前农林业产量的一个重要因子,传统的农林业生产主要通过施肥和土壤改良来满足植物对磷的需求,近年来人们开始发掘磷高效利用植物来替代传统方法提高磷的利用效率。杉木(Cunninghamia lanceolata)是我国亚热带地区最重要的造林树种之一,生长快、材质好、产量高,在中国人工林经营中占有重要地位。为揭示磷素胁迫条件下杉木无性系酸性磷酸酶的变化规律和筛选磷高效利用杉木无性系,通过土培试验,设计4种磷素处理水平(正常供磷16 mg•kg－1、轻度磷胁迫8 mg•kg－1、中度磷胁迫4 mg•kg－1、重度磷胁迫0 mg•kg－1),进行磷素胁迫条件下不同杉木无性系酸性磷酸酶(APA)活性的比较研究。结果表明：缺磷条件下1年生杉木叶片和根际的APA活性明显高于正常供磷处理。随缺磷时间的延长、不同杉木无性系酸性磷酸酶的变化规律不同,其中8号、24号、37号无性系叶片和根际的APA活性明显高于正常供磷处理;5号、9号无性系根际APA活性虽然增幅较大,但其叶片酶活性变化较小;3号、23号、34号无性系整体而言对磷胁迫不敏感,缺磷条件不对其叶片APA及根系APA活性造成显著影响。在磷胁迫条件下,杉木无性系可通过叶片及根际酸性磷酸酶活性的增强来适应环境磷缺乏,但不同杉木无性系对磷缺乏的适应性存在明显差异,因此能否将APA活性作为杉木无性系磷效率的评价指标之一仍需作进一步研究。     

Strategies for genetic conservation of trees in the Peruvian Amazon

Forestry practices and high rates of land clearance for agriculture are causing genetic erosion of valuable tree species in the Peruvian Amazon, thereby endangering the economic sustainability of rural communities and limiting Peru's opportunities for the development of new timber and non-timber forest products. The potential utility and limitations of six low-input interventions to help forestall further genetic erosion in the region are discussed, with a focus on local community involvement. Improved agroforestry systems may help reduce deforestation by increasing farm productivity, although methods to increase the currently low adoption rate of these technologies need to be developed. Use of strategic tree domestication techniques can also improve farm productivity and prevent inadvertent genetic drift and inbreeding associated with traditional domestication practices, although to have a major impact, current programs need to be extended across the region. Woodlot forestry could supplant selective extraction of timber and offers an attractive opportunity for poverty alleviation if appropriate credit and land tenure policies can be developed. However, it may also result in increased deforestation if activities on public land cannot be controlled. The implementation of improved seed collection systems and simple seed transfer guidelines would help to reduce the collection of seed of poor quality and low genetic diversity, and avoid maladapted plantings, although such programs are difficult to monitor and seed costs may increase. Strategic identification and design of in situ conservation areas would help to ensure the viability of conserved populations, but requires the forfeiture of significant revenue from timber concessions.     

Effects of land use change and management on the European cropland carbon balance

We model the carbon balance of European croplands between 1901 and 2000 in response to land use and management changes. The process‐based ORCHIDEE‐STICS model is applied here in a spatially explicit framework. We reconstructed land cover changes, together with an idealized history of agro‐technology. These management parameters include the treatment of straw and stubble residues, application of mineral fertilizers, improvement of cultivar species and tillage. The model is integrated for wheat and maize during the period 1901–2000 forced by climate each 1/2‐hour, and by atmospheric CO₂, land cover change and agro‐technology each year. Several tests are performed to identify the most sensitive agro‐technological parameters that control the net biome productivity (NBP) in the 1990s, with NBP equaling for croplands the soil C balance. The current NBP is a small sink of 0.16 t C ha^?1 yr^?1. The value of NBP per unit area reflects past and current management, and to a minor extent the shrinking areas of arable land consecutive to abandonment during the 20th Century. The uncertainty associated with NBP is large, with a 1‐sigma error of 0.18 t C ha^?1 yr^?1 obtained from a qualitative, but comprehensive budget of various error terms. The NBP uncertainty is dominated by unknown historical agro‐technology changes (47%) and model structure (27%), with error in climate forcing playing a minor role. A major improvement to the framework would consist in using a larger number of representative crops. The uncertainty of historical land‐use change derived from three different reconstructions, has a surprisingly small effect on NBP (0.01 t C ha^?1 yr^?1) because cropland area remained stable during the past 20 years in all the tested land use forcing datasets. Regional cross‐validation of modeled NBP against soil C inventory measurements shows that our results are consistent with observations, within the uncertainties of both inventories and model. Our estimation of cropland NBP is however likely to be biased towards a sink, given that inventory data from different regions consistently indicate a small source whereas we model a small sink.     

Response of soil microbial communities to changes in a forest ecosystem brought about by pine wilt disease

Japan has suffered a lot from forestry losses due to pine wilt disease caused by pinewood nematode infestations. Studies were conducted regarding its causative agent and the effects of natural vegetation succession after pine wilt disease, but its effects on microorganisms were not given equal attention. This study determined the effects of pine wilt disease on light conditions, soil microbial biomass, litter decomposition, microbial abundance and the physical and chemical properties of the soil. Results showed that in a forest currently affected by pine wilt disease, there was higher light penetration, greater microbial biomass carbon, and a faster rate of litter decomposition. Microbial abundance was shown to be reduced in pine wilt affected areas. There were close correlations between the biological and physicochemical properties of the soil, but the reason for the decrease in microbial abundance is not yet well understood, and thus requires further study.