优化施肥对设施蔬菜地土壤线虫群落的影响

高强度利用下设施蔬菜地的施肥过量问题导致了土壤质量的严重退化,合理施肥是维持蔬菜地生产力和可持续发展的重要措施.本研究比较了常规施肥和优化施肥两种施肥方式下连续种植番茄和辣椒后土壤理化性质、线虫群落及蔬菜产量的差异.结果表明: 优化施肥处理土壤pH显著高于常规施肥处理,且番茄和辣椒产量分别提高了9.0%和6.9%.与常规施肥相比,优化施肥提高了土壤线虫数量和食细菌线虫的相对多度,但降低了食真菌线虫和植食性线虫的相对多度.两季蔬菜种植过程中,不同施肥处理土壤寄生线虫成熟指数、多样性指数和丰富度指数无显著差异.优化施肥土壤线虫通路比值(0.67～0.84)显著高于常规施肥(0.39～0.64),前者土壤食物网的分解途径以细菌为主,而后者则为真菌控制.综合土壤理化性质、线虫数量和群落及蔬菜产量指标,优化施肥措施能够在促进蔬菜生长的同时,显著改善土壤生态环境.     

森林经营与管理下的温室气体排放、碳泄漏和净固碳量研究进展

森林在减缓全球气候变化和大气CO₂浓度升高上具有重要作用.森林经营与管理下的新造林和森林保护具有显著的固碳功能,其中,新造林和森林保护的固碳速率分别为0.04～7.52、0.33～5.20 t C·hm^-2·a^-1.同时,营造林过程中物资的生产和运输导致边界内产生温室气体排放;营造林导致的活动转移、市场效应和生态环境变化导致边界外产生碳泄漏.本文综述了国内外森林经营与管理活动边界内温室气体排放源的界定、计量方法、温室气体排放量与排放速率;边界外碳泄漏的类型、计量方法与碳泄漏量;净固碳量以及温室气体排放和碳泄漏对固碳的抵消强度.边界内温室气体排放对固碳的抵消强度为0.01%～19.3%,进一步考虑碳泄漏时可增至95%.若仅考虑森林经营与管理在边界内直接产生的温室气体排放与可测量的活动转移碳泄漏,森林经营与管理具有较好的净固碳效益,且相比于农田固碳措施在温室气体净减排方面具有更好的应用前景.随着我国各项重大生态工程新一期的开展和对工程固碳效益的关注,为增加重大生态工程对温室气体的净减排量,有必要在工程开展前进行合理规划、在工程开展过程中加强控制和监测以减少工程实施导致的边界内温室气体排放和边界外碳泄漏.     

黄瓜连作土壤酚酸类物质积累对土壤微生物和酶活性的影响

伴随连作年限的增加,日光温室黄瓜连作土壤中酚酸类物质(对羟基苯甲酸、阿魏酸、苯甲酸)明显积累,连作5～9年的土壤酚酸类物质含量显著高于连作1～3年的土壤.伴随外源酚酸类物质处理浓度的增加,黄瓜根区土壤中细菌、放线菌和微生物总量以及N生理群均呈先升后降趋势,在80 μg·g^-1处理浓度下细菌、放线菌数量最多,处理浓度在120μg·g^-1以下土壤真菌数量(包括尖孢镰刀菌、疫霉)急剧增长;多酚氧化酶、过氧化氢酶、蔗糖酶、脲酶和蛋白酶活性也同样呈先升后降趋势,但其峰值对应的浓度不同.     

尿素和包膜尿素对大棚内有害气体浓度变化的影响

通过室内模拟和塑料大棚试验,研究了普通尿素和矿物改性包膜尿素对土壤pH值及大棚内有害气体浓度变化的影响.结果表明,在室内模拟试验条件下,两种氮肥施用初期均导致土壤pH值上升,并于1周后达到最大值,上升幅度超过50％,随后开始下降,至第5周回到初始水平.大棚内施用两种氮肥均使棚内NH₃、NO₂和O₃浓度增加,其中施用普通尿素处理的NH₃、NO₂日均挥发量均大于矿物改性包膜尿素;施用普通尿素处理使大棚内土壤的NH₃、棚内NO₂和O₃的最高浓度达到42.36、41.95和86.00 μg·m^-3·d^-1,3种气体浓度均达到了有害气体伤害植物的临界阈值;NH₃、NO₂挥发强度受棚温和光照强度的影响,O₃浓度随光照强度变化而改变.     

Effect of shading and high temperature amplitude in greenhouse on growth,photosynthesis, yield and phenolic contents of tomato (Lycopersicum esculentum Mill.)

Low temperature is the major environmental factor that limits the optimal field production of tomato in the high altitude mountain regions. Studies were conducted to determine the feasibility of growing tomato, a temperature sensitive crop, in a naturally ventilated passive solar greenhouse with high temperature amplitude (24.7 ± 3.0 °C). The study also aimed to determine the application of shade net combined with low-cost greenhouse technology. Despite the temperature fluctuation from 6.6 ± 2.1 °C at night to 39.1 ± 4.7 °C day temperature, flowering and fruiting were observed under the greenhouse conditions. The marketable yield inside the greenhouse was 1.8-times higher compared to open-field. Shading significantly affected the photosynthesis and results in increased sub-stomatal CO₂ concentration. Shading resulted in delayed flowering and 48% reduction in marketable yield. Total phenolic contents (TPC) of tomato grown under open-field and greenhouse conditions were similar. However, greenhouse conditions resulted in a 35% decrease in total flavonoid contents (TFC) of tomato fruit. Shading reduced the TPC and TFC by 29 and 16%, respectively under greenhouse conditions.Supplementary InformationThe online version contains supplementary material available at 10.1007/s12298-021-01032-z.     

Biogenic vs. geologic carbon emissions and forest biomass energy production

In the current debate over the CO₂ emissions implications of switching from fossil fuel energy sources to include a substantial amount of woody biomass energy, many scientists and policy makers hold the view that emissions from the two sources should not be equated. Their rationale is that the combustion or decay of woody biomass is simply part of the global cycle of biogenic carbon and does not increase the amount of carbon in circulation. This view is frequently presented as justification to implement policies that encourage the substitution of fossil fuel energy sources with biomass. We present the opinion that this is an inappropriate conceptual basis to assess the atmospheric greenhouse gas (GHG) accounting of woody biomass energy generation. While there are many other environmental, social, and economic reasons to move to woody biomass energy, we argue that the inferred benefits of biogenic emissions over fossil fuel emissions should be reconsidered.     

A geography‐based critique of new US biofuels regulations

The new renewable fuels standard (RFS 2) aims to distinguish corn‐ethanol that achieves a 20% reduction in greenhouse gas (GHG) emissions compared with gasoline. Field data from Kim et al. (2009) and from our own study suggest that geographic variability in the GHG emissions arising from corn production casts considerable doubt on the approach used in the RFS 2 to measure compliance with the 20% target. If regulators wish to require compliance of fuels with specific GHG emission reduction thresholds, then data from growing biomass should be disaggregated to a level that captures the level of variability in grain corn production and the application of life cycle assessment to biofuels should be modified to capture this variability.     

Energy balances and greenhouse gas emissions of palm oil biodiesel in Indonesia

This study presents a cradle‐to‐gate assessment of the energy balances and greenhouse gas (GHG) emissions of Indonesian palm oil biodiesel production, including the stages of land‐use change (LUC), agricultural phase, transportation, milling, biodiesel processing, and comparing the results from different farming systems, including company plantations and smallholder plantations (either out growers or independent growers) in different locations in Kalimantan and Sumatra of Indonesia. The findings demonstrate that there are considerable differences between the farming systems and the locations in net energy yields (43.6–49.2 GJ t^?1 biodiesel yr^?1) as well as GHG emissions (1969.6–5626.4 kg CO_2eq t^?1 biodiesel yr^?1). The output to input ratios are positive in all cases. The largest GHG emissions result from LUC effects, followed by the transesterification, fertilizer production, agricultural production processes, milling, and transportation. Ecosystem carbon payback times range from 11 to 42 years.