The potential for soil carbon sequestration in three tropical dryland farming systems of Africa and Latin America: A modelling approach

Historically, agriculturally induced CO₂ release from soils has contributed to rising levels in the atmosphere. However, by using appropriate management, soils can be turned into carbon sinks. Many of the dryland regions of the world are characterised by degraded soils, a high incidence of poverty and a low capacity to invest in agriculture. Two well-proven soil organic matter models (CENTURY 4.0 and RothC-26 3) were used two explore the effects of modifying agricultural practices to increase soil carbon stocks. The changes to land management were chosen to avoid any significant increase in energy input whilst using technologies that would be available without radically altering the current agricultural methodology. Case studies were selected from dryland farming systems in Nigeria, Sudan and Argentina. Modelling showed that it would be possible to make alterations within the structure of the current farming systems to convert these soils from carbon sources to net sinks. Annual rates of carbon sequestration in the range 0.08–0.17 Mg ha⁻¹ year⁻¹ averaged over the next 50 years could be obtained. The most effective practices were those that maximised the input of organic matter, particularly farmyard manure (up to 0.09 Mg ha⁻¹ year⁻¹), maintaining trees (up to 0.15 Mg ha⁻¹ year⁻¹) and adopting zero tillage (up to 0.04 Mg ha⁻¹ year⁻¹). Verification of these predictions will require experimental data collected from field studies.     

Structural characteristics of a low Arctic tundra ecosystem and the retreat of the Arctic fox

We conducted a large-scale, campaign-based survey in Finnmark, northern Norway to evaluate the proposition that declining Arctic fox populations at the southern margin of the Arctic tundra biome result from fundamental changes in the state of the ecosystem due to climatic warming. We utilized the fact that the decline of the Arctic fox in Finnmark has been spatially heterogeneous by contrasting ecosystem state variables between regions and landscape areas (within regions) with and without recent Arctic fox breeding.Within the region of Varanger peninsula, which has the highest number of recorded dens and the most recent breeding records of Arctic fox, we found patterns largely consistent with a previously proposed climate-induced, bottom-up trophic cascade that may exclude the Arctic fox from tundra. Landscape areas surrounding dens without recent Arctic breeding were here more productive than areas with recent breeding in terms of biomass of palatable and climate sensitive plants, the number of insectivorous passerines and predatory skuas. Even the frequency of unspecified fox scats was the highest in landscape areas where arctic fox breeding has ceased, consistent with an invasion of the competitively dominant red fox. The comparisons made at the regional level were not consistent with the results within the Varanger region, possibly due to different causal factors or to deficiencies in Arctic fox monitoring at a large spatial scale. Thus long-term studies and adequate monitoring schemes with a large-scale design needs to be initiated to better elucidate the link between climate, food web dynamics and their relations to Arctic and red foxes.     

Temporal Changes in the State of a Pine Stand in a Bog Affected by Air Pollution in Northeast Estonia

We used the needle trace method to investigate changes in the state of a Scots pine (Pinus sylvestris L.) stand in a bog (Voorepera) in the north-eastern part of Estonia, the most polluted area of the country. Additionally, we chose six sampling sites in other parts of Northeast Estonia (polluted area) and eight sites in southern Estonia (unpolluted area) to compare the state of pine stands in different bogs. During the period of 1964–1997, the radial growth had increased from 0.27 to 2.16 mm yr^–1 and the annual shoot length from 0.10 to 0.28 m in Voorepera. Mean values of the period (1.13 mm yr^–1 and 0.26 m, respectively) were two and four times higher in Voorepera than the average of the other bogs (0.5 mm yr^–1 and 0.06 m, respectively). Maximum needle age fluctuated between three and five growing seasons in Voorepera, the mean (four growing seasons) was similar to that of other bogs (four growing seasons). Except radial growth, which was 0.6 mm yr^–1 in the polluted area and 0.4 mm yr^–1 in the unpolluted area, other indices of trees' health (shoot growth, needle age, nitrogen concentration in needles) and substrate conditions (water pH and N concentration) did not show clear differences between polluted and unpolluted areas. We conclude that air pollution from oil shale industry (thermal power plant and chemical factories) enhances the growth of pines in bogs, which can induce drastic changes in these ecosystems. However, the effect is currently obvious only in the vicinity of pollution sources.     

Nitrous oxide emissions from fertilised grassland: A 2-year study of the effects of N fertiliser form and environmental conditions

The aim was to investigate the effects of different N fertilisers on nitrous oxide (N₂O) flux from agricultural grassland, with a view to suggesting fertiliser practices least likely to cause substantial N₂O emissions, and to assess the influence of soil and environmental factors on the emissions. Replicate plots on a clay loam grassland were fertilised with ammonium sulphate (AS), urea (U), calcium nitrate (CN), ammonium nitrate (AN), or cattle slurry supplemented with AN on three occasions in each of 2 years. Frequent measurements were made of N₂O flux and soil and environmental variables. The loss of N₂O-N as a percentage of N fertiliser applied was highest from the supplemented slurry (SS) treatment and U, and lowest from AS. The temporal pattern of losses was different for the different fertilisers and between years. Losses from U were lower than those from AN and CN in the spring, but higher in the summer. The high summer fluxes were associated with high water-filled pore space (WFPS) values. Fluxes also rose steeply with temperature where WFPS or mineral N values were not limiting. Total annual loss was higher in the 2nd year, probably because of the rainfall pattern: the percentage losses were 2.2, 1.4, 1.2, 1.1 and 0.4 from SS, U, AN, CN and AS, respectively. Application of U in the spring and AN twice in the summer in the 2nd year gave an average emission factor of 0.8% – lower than from application of either individual fertiliser. We suggest that similar varied fertilisation practices, modified according to soil and crop type and climatic conditions, might be employed to minimise N₂O emissions from agricultural land. Received: 30 August 1996     

陶瓷管负压控温栽培系统在番茄日光温室冬季生产中的应用效果

设施蔬菜冬季生产中，土壤温度低是蔬菜生长的一个限制因子。该文在番茄冬季生产中应用微多孔陶瓷管负压加温栽培系统，试验表明通过循环温水利用同一根陶瓷管边灌水边加温是完全可行的；加温处理白天、夜间平均温度分别比不加温处理的高出2.7℃，1.2℃。加温处理的植株长势、果实中可溶性糖、滴定酸度的含量和糖酸比、产量、特别是前期产量显著高于不加温处理。在温室冬季生产中仅仅对土壤进行加温就可显著促进植株生长，提高果实的产量和品质。     

不同时期施用生物炭对稻田N_2O和CH_4排放的影响

通过分别在水稻季(R)和小麦季(W)设置对照(RB0-N0、WB0-N0)、单施氮肥(RB0-N1、WB0-N1)、20 t hm-2生物炭与氮配施(RB1-N1、WB1-N1)、40 t hm-2生物炭与氮配施(RB2-N1、WB2-N1)等8个处理,研究稻麦轮作周年系统N2O和CH4排放规律及其引起的综合温室效应(Global warming potential,GWP)和温室气体强度(Greenhouse gas intensity,GHGI)特征。结果表明:稻季配施20 t hm-2生物炭对N2O和CH4的排放、作物产量及GWP和GHGI均都无明显影响;稻季配施40 t hm-2生物炭能显著降低8.6%的CH4的排放和9.3%的GWP,显著增加作物产量17.2%。麦季配施20 t hm-2生物炭虽然对温室气体及GWP影响不明显,但显著增加21.6%的作物产量,从而显著降低21.7%的GHGI;麦季配施40 t hm-2生物炭能显著降低20.9%和11.3%的N2O和CH4排放,显著降低15.7%和23.5%的GWP和GHGI。因此麦季配施生物炭对减少N2O和CH4的排放、增加稻麦轮作产量及降低GWP和GHGI的效果较稻季配施生物炭效果更好。     

冻融交替对土壤CO2及N2O释放效应的研究进展

在秋冬交替和冬春交替时期高纬度地区和高海拔生态系统表层土壤常有冻融交替频繁发生。由于冻融交替作用通过改变土壤水热性质而对土壤物理、化学、生物学特性产生效应。冻结通常导致土壤团聚体破裂、微生物细胞及细根死亡,释放出活性较高的有机物,增强随后融解的土壤的反硝化和呼吸活性,从而影响土壤生物、生物化学过程以及生物地化循环。已有对苔原、泰加林等北极和亚北极生态系统的研究表明,土壤冻融交替次数、冻融极端温度、土壤水分、土壤团聚体结构变化等对CO2和N2O的释放通量影响较为显著,一般在冻融的最初几个循环温室气体排放会增加,随后会降至一个较为稳定的水平。目前,冻融循环变化背景下的温室气体排放研究主要是针对北方高纬度地区,而且对冻融交替影响土壤温室气体排放的机理研究也不够。我国面积广大的青藏高原高海拔地带在全球增温背景下,轻微增温会导致季节性冻土表层冻融交替次数增加,甚至冻土季节消失,加强全球增温背景下我国高山亚高山季节性冻土生态系统效应和过程研究,特别是土壤暖化导致的温室气体排放变化通量和变化机理的研究,对揭示全球变化的区域效应以及高海拔生态系统的管理都具有重要作用。     

Predicting the severity of Dothistroma on Pinus radiata under current climate in New Zealand

Despite being a damaging foliar disease of Pinus species little research has characterised spatial variation in disease severity of Dothistroma needle blight at a macroscale. Using an extensive dataset describing Dothistroma needle blight severity (S_sev) on plantation grown Pinus radiata stands distributed widely across New Zealand the objectives of this research were to (i) develop a regression model describing S_sev, (ii) use this model to identify key drivers of S_sev, their functional form and relative importance, and (iii) develop spatial predictions of S_sev for New Zealand P. radiata under current climate. Using an independent validation dataset, the final model accounted for 72% of the variance in S_sev using four significant (P < 0.001) explanatory variables and an isotrophic exponential model to account for the spatial covariance in the data. S_sev was most sensitive to mean air temperature from November to April (T_Nov-Apr), followed by mean relative humidity from October to April (RH_Oct-Apr), mean total November rainfall (P_Nov), and then stand age (A). There was a quadratic correlation between A and S_sev with S_sev increasing to a maxima at 12 years before declining. S_sev exponentially increased to a threshold with increases in both P_Nov and RH_Oct-Apr. The relationship between S_sev and T_Nov-Apr was quadratic with S_sev increasing to a maximum at T_Nov-Apr of 15.5 °C before declining at higher values of T_Nov-Apr. Spatial predictions of S_sev varied widely throughout New Zealand. Values of S_sev were highest in moderately warm wet environments in the North Island, and on the west coast of the South Island. In contrast, relatively low values of S_sev were predicted in drier eastern and southern regions of New Zealand.     

Climate change and nature conservation in Central European forests: A review of consequences, concepts and challenges

With a predicted rise in average global surface temperature at an unprecedented rate, as well as changes in precipitation and disturbance regimes, climate change will bring forth new challenges for nature conservation in forest ecosystems. Species and habitats to be protected will be affected as well as related concepts and area specific objectives. Climate change impacts are likely to be aggravated by other anthropogenic stresses such as fragmentation, deposition or habitat destruction. To be reliable and effective, current objectives and guidelines of forest conservation need to be reassessed and improved. Our study analyses possible impacts of climate change on forests and identifies key future challenges for nature conservation in forests and ecosystem research. We reviewed 130 papers on climate change impacts on forest ecosystems and species published between 1995 and 2010. The geographical focus of the study is Central Europe. Papers were analysed accounting for direct and indirect impacts of gradual changes as well as stochastic disturbance events in forest ecosystems and their possible consequences for nature conservation.Even though broader aspects of nature conservation (protected areas, biodiversity) are frequently mentioned, little attention is given to forest-specific nature conservation. Particular aspects are insufficiently represented, such as the influence of climate change on different forest succession stages, the development of dead wood volume and quality, responses of secondary broadleaved species, azonal or extrazonal forests as well as ancient woodlands or remnants of historical silvicultural systems. Challenges arise in the context of great uncertainties about future developments. Nature conservation concepts and objectives in forests need to be adapted either within a permanent evaluation process or through the inclusion of further changes a priori, even if they are to some extent unpredictable. In some cases adaptation measures within nature conservation (e.g. adjusting protected areas) may conflict with interests of other stakeholders. Further research, particularly on interrelations between different impacts and the adaptive capacity of current forest ecosystems, associated species and existing genotypes is urgently needed. The scale and complexity of the task at hand calls for the establishment and further strengthening of international research networks.     

Needle Collection Time for Nutrient Evaluation in Christmas Tree Production

Christmas tree needle sampling to evaluate nutrient need is an established practice. Data to support the recommended fall sampling time in Oregon and Washington were not found. In addition, the recommendation for needle sampling of Fraser fir in North Carolina was made without data from winter months. The goal for this article is to affirm or modify recommended needle sampling time. Needles of Douglas fir, Turkish fir, Nordmann fir, Noble fir, Grand fir, and Fraser fir Christmas trees were collected monthly for a year, dried, and analyzed for nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and boron (B). No single period was found for any species when needle nutrient concentration was stable for all elements determined. Needle collection time was chosen by integrating cultural practices, likelihood of nutrient deficiency, and needle nutrient concentration changes for species grown in an area. Needle collection is recommended during February in western Oregon and Washington. The current sampling time, fall, is logical for Fraser fir Christmas tree production in North Carolina.