Carbon Depletion by Plowing and its Restoration by No‐Till Cropping Systems in Oxisols of Subtropical and Tropical Agro‐Ecoregions in Brazil

The continuous use of plowing for grain production has been the principal cause of soil degradation. This project was formulated on the hypothesis that the intensification of cropping systems by increasing biomass‐C input and its biodiversity under no‐till (NT) drives soil restoration of degraded agro‐ecosystem. The present study conducted at subtropical [Ponta Grossa (PG) site] and tropical regions [Lucas do Rio Verde, MT (LRV) site] in Brazil aimed to (i) assess the impact of the continuous plow‐based conventional tillage (CT) on soil organic carbon (SOC) stock vis‐à‐vis native vegetation (NV) as baseline; (ii) compare SOC balance among CT, NT cropping systems, and NV; and (iii) evaluate the redistribution of SOC stock in soil profile in relation to soil resilience. The continuous CT decreased the SOC stock by 0·58 and 0·67 Mg C ha⁻¹ y⁻¹ in the 0‐ to 20‐cm depth at the PG and LRV sites, respectively, and the rate of SOC sequestration was 0·59 for the PG site and ranged from 0·48 to 1·30 Mg C ha⁻¹ y⁻¹ for the LRV site. The fraction of C input by crop residues converted into SOC stock was ~14·2% at the PG site and ~20·5% at the LRV site. The SOC resilience index ranged from 0·29 to 0·79, and it increased with the increase in the C input among the NT systems and the SOC sequestration rates at the LRV site. These data support the hypothesis that NT cropping systems with high C input have a large potential to reverse the process of soil degradation and SOC decline. Copyright © 2013 John Wiley & Sons, Ltd.     

Changes in Physical Properties of Soils with Land Use Time in the Brazilian Savanna Environment

Soils from central Brazil have been intensively used over the last decades because of the rapid conversion of savannas ( Cerrado ) into corn/soybean fields. The objective of this work is to study modifications in the physical properties of soils in the Rio Verde watershed, as a function of the land use time for agriculture, determined from classification of Landsat satellite images between 1980 and 2010. Soil samples were collected at surface (0–20 cm) and subsurface (20–40 cm) horizons for the different classes of land use time (<10, 10–20, 20–30, and >30 years). The following physical properties were measured: bulk density (BD), air permeability (K_a), penetration resistance (PR), microporosity (MI), macroporosity (MA), and total porosity (TP). Results showed a strong expansion with time of agriculture that occupied 35·3% (1980), 37·4% (1990), 51·3% (2000), and 60·9% (2010) of the watershed area. When properties were compared with those from the reference areas (preserved soils under native vegetation), significant differences were observed for all the physical attributes of soils for a land use time higher than 20 years. Overall, BD and PR increased with land use time, and the opposite was verified for K_a, MA, and TP. Some physical properties presented values (e.g., 1·54 g cm⁻³ for BD and 0.06 cm³ cm⁻³ for MA) close to the critical ones reported to affect crop development, but they were not still impacting on local soybean yield. Copyright © 2013 John Wiley & Sons, Ltd.     

Impact of Land Use and Land Cover Changes on Organic Carbon Stocks in Mediterranean Soils (1956–2007)

During the last few decades, land use changes have largely affected the global warming process through emissions of CO₂. However, C sequestration in terrestrial ecosystems could contribute to the decrease of atmospheric CO₂ rates. Although Mediterranean areas show a high potential for C sequestration, only a few studies have been carried out in these systems. In this study, we propose a methodology to assess the impact of land use and land cover change dynamics on soil organic C stocks at different depths. Soil C sequestration rates are provided for different land cover changes and soil types in Andalusia (southern Spain). Our research is based on the analysis of detailed soil databases containing data from 1357 soil profiles, the Soil Map of Andalusia and the Land Use and Land Cover Map of Andalusia. Land use and land cover changes between 1956 and 2007 implied soil organic C losses in all soil groups, resulting in a total loss of 16·8 Tg (approximately 0·33 Tg y⁻¹). Afforestation increased soil organic C mostly in the topsoil, and forest contributed to sequestration of 8·62 Mg ha⁻¹ of soil organic C (25·4 per cent). Deforestation processes implied important C losses, particularly in Cambisols, Luvisols and Vertisols. The information generated in this study will be a useful basis for designing management strategies for stabilizing the increasing atmospheric CO₂ concentrations by preservation of C stocks and C sequestration. Copyright © 2012 John Wiley & Sons, Ltd.     

呼伦贝尔地区不同土地利用下土壤蒸发野外试验研究

土壤蒸发是水文过程的关键环节之一,控制着水分由土壤环境向大气环境的扩散。通过在呼伦贝尔地区典型草地与林地设置相同口径不同深度微型蒸发仪(Micro-Lysimeter,简称ML)的对比,寻求适合林地草地使用的微型蒸发仪,并研究不同土地利用方式对土壤蒸发的影响,探讨环境因素对土壤蒸发结果的影响。结果表明:土壤蒸发量随ML长度的增加先增大后减小,相同直径长度不同ML的蒸发量在0.05水平下显著相关,测定林地的蒸发量小于草地蒸发量,不封底ML所测定结果比封底ML大,其结果更接近真实情况,测量呼伦贝尔地区土壤蒸发时,亦采用15cm的不封底ML,结果较好。     

Habitat use and home range of black-backed jackals (Canis mesomelas) on farmlands in the Midlands of KwaZulu-Natal,South Africa

Black-backed jackals (Canis mesomelas) are an abundant mesopredator on farmlands (croplands and rangelands) across South Africa. Given their adaptability in a changing anthropogenic landscape, knowledge of spatial movements can provide important ecological information on the species. We captured, collared and monitored five black-backed jackals in the Midlands of KwaZulu-Natal to determine their home range and habitat use in farmlands. The 95% fixed kernel (95% FK) home range sizes were large, showing a marked seasonal variation in movement. One adult male dispersed 150?km over two seasons (winter and spring) and thereafter settled into a home range that it maintained. Transient home ranges of males and juveniles were larger than resident home ranges. The mean resident home ranges (95% FK) across seasons for adult males, adult female and juvenile males were 11.4 ± 4.3 km², 5.6 ± 0.36?km² and 2.15 ± 0.45?km², respectively. The mean transient home ranges (95% FK) of all the seasons for adult and juvenile males were 1 181.93 ± 575.81 km² and 104.27 ± 35.64?km², respectively. Adult jackal preferred croplands in spring, summer and autumn but avoided croplands in winter. Variable habitat use and large home ranges in our study confirmed the species’ ability to adapt to agricultural areas.     

江苏省高品质棉生产经营现状与发展对策

江苏省是全国产棉大省,在全国占有重要地位.近年来,江苏高品质棉有了很大发展,但也面临一些问题,如品种单一,缺乏有效的产销衔接等.本文提出了江苏高品质棉优势区域发展战略措施.     

A dynamic, optimal disease control model for foot-and-mouth disease: I. Model description

A dynamic optimization model was developed and used to evaluate alternative foot-and-mouth disease (FMD) control strategies. The model chose daily control strategies of depopulation and vaccination that minimized total regional cost for the entire epidemic duration, given disease dynamics and resource constraints. The disease dynamics and the impacts of control strategies on these dynamics were characterized in a set of difference equations; effects of movement restrictions on the disease dynamics were also considered. The model was applied to a three-county region in the Central Valley of California; the epidemic relationships were parameterized and validated using the information obtained from an FMD simulation model developed for the same region. The optimization model enables more efficient searches for desirable control strategies by considering all strategies simultaneously, providing the simulation model with optimization results to direct it in generating detailed predictions of potential FMD outbreaks.     

北方农牧交错带土地利用结构的线性规划——以定西县为例

探讨了用线性规划方法优化土地利用结构,并以北方农牧交错带定西县土地利用结构的经济效益作为目标函数,以人口和自然条件作为约束条件,进行优化分析,规划结果为定西县土地利用结构由2005年的农、林、草面积比例54:10:36调整为30:13:57.     

农牧交错带灌溉和旱作模式下马铃薯耗水差异

为揭示北方农牧交错带地区马铃薯“水改旱”种植对其产量和水分利用的影响,选取中国北方农牧交错带地区27个站点,基于站点的气象数据、土壤数据和管理数据驱动充分验证的APSIM-Potato模型,模拟分析农牧交错带地区灌溉和雨养马铃薯的耗水差异。结果表明：北方农牧交错带地区马铃薯种植连续灌溉10、20 a和30 a的产量分别为15 900～35 600、16 400～34 800 kg·hm^-2和16 600～34 800 kg·hm^-2,改为旱作后对应的产量分别为12 800～30 600、13 900～29 100 kg·hm^-2和12 700～25 500 kg·hm^-2;灌溉马铃薯产量均表现为西部较高,旱作马铃薯产量则为东部较高。连续灌溉10、20 a和30 a的播前1 m土层土壤含水量分别为163～388、161～394 mm和154～398 mm,改为旱作后分别下降31.8%、35.3%和36.9%。连续灌溉10、20 a和30 a后的地下水消耗量分别为5 360～21 330、8 910～4...     

氮肥配施生物炭和脲酶抑制剂对夏玉米-冬小麦产量及氮素利用的影响

于2019—2021年采用再裂区设计,设置氮肥、生物炭和脲酶抑制剂3个因素,主处理设5个氮水平：0、75、150、225 kg·hm^-2和300 kg·hm^-2,副处理设2个生物炭水平：0 t·hm^-2和7.5 t·hm^-2,副副处理设2个脲酶抑制剂水平：0%和2%,共20个处理,研究氮肥配施生物炭和脲酶抑制剂对夏玉米-冬小麦轮作体系作物产量和氮肥吸收利用的影响。结果表明,施用生物炭显著提高夏玉米和冬小麦产量、植株氮素吸收量、氮肥表观利用率、氮素收获指数以及夏玉米地上部生物量,较不施生物炭处理分别增加4.4%和2.9%、2.3%和3.0%、25.8%和13.5%、4.9%和6.1%、4.5%;氮肥单独配施生物炭可显著提高夏玉米和冬小麦产量、植株氮素吸收量和氮肥表观利用率,且氮肥和生物炭具有显著的交互效应。施用脲酶抑制剂显著增加夏玉米植株氮素吸收量和氮肥表观利用率,较不施脲酶抑制剂处理分别提高1.5%和3.0%;氮肥单独配施脲酶抑制剂可提高夏玉米植株氮素吸收量和氮肥表观利用率,但氮肥与脲酶抑制剂无显著...