Evaluation of a system of wind tunnels for field studies of ammonia loss from grassland through volatilisation

Rates of ammonia (NH₃) loss from a ryegrass sward measured using a system of small wind tunnels were compared with concurrent measurements made using a micrometeorological mass balance method. Measurements were made during two experiments within a circular plot (radius 10m) treated with urea at a rate of 200kgNha^?1. In the first experiment, air speed through the tunnels was adjusted as necessary to maintain a value of approximately 1ms^?1. This value differed on most occasions from the mean ambient wind speed which was measured at a height of 250mm and which ranged from 0.61 to 2.95ms^?1. Rates of loss measured using the wind tunnels differed by a factor of between two and five from those measured using the mass balance method; there was no consistent pattern in the differences between the rates of loss. The total losses of NH₃ measured during 15 days were equivalent to 49.1 and 30.2kg Nha^?1 for the mass balance and wind tunnel methods, respectively. In the second experiment, air speed through the tunnels was adjusted as necessary to maintain a value as close as possible to the mean ambient wind speed measured at a height of 250mm. Rates of NH₃ loss measured using the two methods did not differ significantly; total losses of NH₃ during 17 days were equivalent to 96.9 and 101kg Nha^?1 for the mass balance and wind tunnel methods, respectively. The difference between the findings of the two experiments could be attributed to the direct effect of air speed through the tunnels rather than to differences between ambient temperatures and those inside the tunnels. During and following periods of rain the rates of loss measured using the tunnels were up to six times greater than those observed with the mass balance method. Rates of loss measured by the two methods became similar again when the tunnels were moved following rain. The study demonstrates that enclosures can be designed and operated to provide reliable measurements of the rate of NH₃ loss from grassland. Potential applications of the two methods are discussed.     

Assessing terrestrial wildlife populations in the Toronto and Region Area of Concern

Beneficial use impairments (BUIs) under the Great Lakes Water Quality Agreement identify environmental issues requiring remedial action within the Great Lakes Areas of Concern (AOCs). We conducted this study to support the assessment of the wildlife component of BUI 3: degradation of fish and wildlife populations. We compared bird and amphibian (frogs and toads) data from the Toronto and Region Conservation Authority’s Terrestrial Long-term Monitoring Program in the Toronto and Region AOC to an adjacent, but otherwise similar, reference watershed, Duffins Creek. Twelve of 13 targets were met within the AOC for forest bird, wetland bird, meadow bird and amphibian populations based on averages of mean annual values at sites within the AOC that were within two standard deviations of averages at sites in the Duffins Creek reference watershed between 2008 and 2017. Even though wildlife populations within the AOC were within the normal range of variability expected from a reference watershed, they were often at lower levels than within the Duffins Creek reference watershed. In addition, forest bird and amphibian populations were negatively affected by urbanization within the AOC and meadow bird indices declined. We conclude that while wildlife populations within the AOC currently meet targets for BUI 3, they continue to be negatively impacted by numerous stressors that are primarily related to past and ongoing urbanization. Thus, continued restoration of wildlife habitat and protection of existing habitat within the AOC is highly recommended.     

Phosphorus fractions and adsorption characteristics in grassland soils of varied soil phosphorus status

Characterization of phosphorus (P) in soils is important both agronomically and environmentally, although the outcome may depend on the technique applied. Consequently, we evaluated fractionation and adsorption, individually and jointly, and relevant ancillary soil attributes, to determine the dominant functional characteristics of soil P in 32 fertilized temperate grassland Inceptisols classified by eight soil series, and by two soil-P index and parent material groups. Residual P was low (30.7%) and organic P (Po) prominent, 42.0% vs. 17.5% for equivalent soils in unfertilized natural ecosystems. Labile fractions comprised 6.8% inorganic P (Pi) and 9.1% Po. The proportional increase in high vs. low index soils (Morgan P > 6.0 mg l⁻¹ vs. ≤ 6.0 mg l⁻¹) was higher for Pi, and highest for labile and moderately labile fractions. Only moderately labile Pi and Po differed significantly between soils of limestone and non-limestone origin. Oxalate extractable Fe (Fe_ox) and buffering (EBC) were higher in the latter. The equilibrium P concentration (EPC) was substantially higher in the high index group, and EBC and binding energy (k) substantially lower, with no significant difference in sorption maximum (Pmax). EBC equated with weak to strong buffering in different soil series, and conformed better than k to ancillary attributes. Pmax correlated in order Al_ox > clay > OC > Fe_ox, and more broadly reflected sorption attributes than oxalate-based sorption capacity (PSC). Principal component (PC) analysis showed consistent differentiation of P fractions, mostly labile and moderately labile, in PC 1 vs. adsorption and ancillary attributes in PC 2. However, scatterplots of PC scores showed that adsorption characteristics provided better functional differentiation than P fractions for distinguishing individual soil series, which may have implications in selection and interpretation of extractants not only for environmental but also for agronomic soil-tests.     

草原人居环境保护与发展三元论 ——以新疆伊犁河谷为例

坚守"山水林田湖草是一个生命共同体"的理念,聚焦伊犁河谷草原人居环境背景资源、活动方式、规划建设的三元一体,将草原人居环境作为三元互动、不断成长的生命体,尝试寻找一种构建荒野、乡村、城市共存融合的草原人居环境保护与发展模式。以客观规律为依据,以主观需求为准绳,寻找及保留草原人居环境演化中相对稳定不变的基因,构建草原人居环境CVA三力评价体系,建立草原人居环境发展CVA量化模型,以求指导草原人居环境未来的保护与发展。推行这种模式不仅可为中国西部地区提供生态安全保障,也将使伊犁河谷成为多种人居环境生命共同体的典范。     

基于ENVI-met模拟的不同用地类型居住小区绿地布局对PM2.5的影响

居住区绿地作为城市绿地的主要组成肌理,对改善空气质量起着重要作用。首次将ENVI-met用于居住小区绿地布局与PM2.5的模拟,选取武汉市典型的一类、二类、三类小区,定量分析不同草地、乔木布局对PM2.5的影响。研究表明,集中型的草地布局、四周型的乔木布局能更有效降低小区PM2.5浓度;分散型的草地布局、集中型的乔木布局最不利于消减PM2.5;四周型的乔木布局对阻滞道路上PM2.5的扩散效果最佳。同种绿地布局形式下,二类小区的平均PM2.5浓度最低,三类小区最高,PM2.5空间分布在3类小区中也具有一定的差异。研究揭示了居住小区绿地布局对PM2.5的影响机制,为小区绿地的规划设计实践提供一定参考。     

草原露天矿区草地沙化的遥感分析--以霍林河矿区为例

研究了霍林河矿区1987—2003年的草地沙化情况；探讨了露天煤矿区草地沙化的影响因子；采用线性光谱混合分解模型(LSMM)完成了草地沙化信息的提取，对引发草地沙化的直接破坏信息则采用决策树和BP神经网络相结合的方法进行了提取．结果表明：随着累计原煤产量的增加，草地破坏面积和草地沙化面积在逐年扩大；矿区建设期内草地沙化速率远高于生产期；草地直接破坏面积与草地沙化面积具有明显的正相关关系，故可将草地直接破坏面积作为评价、预测该区煤炭开发对周围草地沙化影响的重要依据．     

Nitrogen losses by denitrification and leaching in grassland

In this study nitrogen losses by denitrification and leaching have been quantified in a natural grassland, comparing the losses produced by a mineral fertilization (calcium ammonium nitrate) and an organic fertilization (cow slurry). It has been stated that in the edafoclimatic conditions of the Basque Country denitrification losses are more important than those produced by leaching, spring and autumn being the seasons with a greater risk of losses. These losses are great and immediately occurring after mineral fertilization and small but distributed along the time when organic fertilization is applied.     

我国草原生产力

分析我国草原植物生产和动物生产,比较国内外草原生产力。结果表明,在过去的30余年中,我国一部分草原产草量下降,局部变化不显著。世界草原对畜产品生产的贡献率为40.08%,中等收入国家为67.35%。全球24.1%的牛肉和31.9%的羊肉来自草原,低收入国家草原载畜量分别高出高收入国家和中等收入国家87.4%和66.4%,畜产品生产分别只有两者的37.3%和71.9%。适宜的放牧利用,可使我国的草原生产能力达到6.35×109畜产品单位(APU);全国草原单纯依靠放牧每年可产肉2.959×106 t,占全国肉类总产量的3.5%,占全国牛羊肉总产量的27.4%。通过草原畜牧业的现代化转型可接近高收入国家水平,增产潜力约为50%~200%。     

海南岛热带草地的数量分类研究

本文用一些数量分类和排序的方法对海南岛鹦歌岭热带草地进行了分类和排序。所用的方法包括两种多元等级聚合分类——最近邻体法(NN)和最远邻体法(FN),极点排序(PO)和主分量分析(PCA)排序,研究结果表明:可以把19个样地分为3大类型、9个群落,其分布格局与坡度、放牧强度和土壤肥力密切相关。所用的4种方法在热带草地的研究中均有一定的适用性。     

A model of nitrogen efficiency in contrasting grass-based dairy systems

Nitrogen (N) efficiency is one of the key drivers of environmentally and economically sustainable agricultural production systems. An N balance model was developed, evaluated, and validated to assess N use efficiency and N surplus and to predict N losses from contrasting grass-based dairy production systems in Ireland. Data from a 5-yr study were used to evaluate and validate the model. Grass-based and high-concentrate production systems combined with 3 divergent strains of Holstein-Friesian (HF) dairy cows—high-production North American (HP), high-durability North American (HD), and New Zealand (NZ)—were evaluated. As concentrate input increased, N surplus per hectare increased and N use efficiency per hectare decreased (23 and 10%, respectively). When the N required to rear replacement animals to maintain the production system was considered, the N surplus of the HP genetic strain was greater (156 kg of N/cow) than that of the HD (140 kg of N/cow) or the NZ (128 kg of N/cow). The model estimated N leaching of 8.1 mg of NO₃-N/L, similar to that measured by others at the same site. The model creates awareness of methods and indicators available to assess the most suitable and environmentally sustainable grass based dairy production systems.