水氮互作对不同小麦品种生理参数及产量形成的影响

为明确河北山前平原区合理的小麦水氮互作方式,以济麦22（JM-22）和藁优2018（GY-2018）为材料,设置高氮/高水（GD/GS）、中氮/高水（ZD/GS）、低氮/高水（DD/GS）、高氮/中水（GD/ZS）、中氮/中水（ZD/ZS）、低氮/中水（DD/ZS）、高氮/低水（GD/DS）、中氮/低水（ZD/DS）和低氮/低水（DD/DS）9个处理,研究水氮互作对不同小麦品种生理参数和产量形成的影响。结果表明,随着水氮量的增加,株高、旗叶面积和地上部干重增加,旗叶面积成熟期在ZD处理下最大,且GS>ZS>DS,GY-2018的植株生长和干物质积累量高于JM-22。此外,水氮越多,2个品种的叶绿素相对含量（SPAD）越大,各处理均表现出GD>ZD>DD的变化趋势,而GS、ZS和DS在3个时期无明显变化规律,2个品种相比较,JM-22的SPAD值较大,可溶性蛋白和可溶性糖含量均表现为GD>ZD>DD,而后期ZD处理最高,且GS>ZS>DS,GY-2018较JM-22更有利于碳水化合物的积累,丙二醛和活性氧含量随着施氮量的增加而降低,而超氧化物歧化酶和过氧化物酶活性却升高,但不同灌水量使酶活性在不同时期的变化不同,GY-2018的酶活性更高,有利于延缓后期叶片衰老。产量及其构成因素均表现为ZD处理下最高,且GS>ZS>DS,JM-22在ZD/GS处理下的氮肥生产效率和水分利用效率最高,产量也最高,为9927.78kg/hm²,较GY-2018提高10.07%。综上,ZD/GS（210kg/hm²,1200m³/hm²）是最理想的水氮互作方式。     

Similar spaces,different usage : A comparative study on how residents in the capitals of Finland and Denmark use cemeteries as recreational landscapes

Several studies from the Nordic countries show that cemeteries not only fulfil an important societal function as places for the disposal of bodily remains; they are also recreational landscapes that people visit to reflect, experience nature or perhaps go for a walk with the dog. In this comparative study, based on PPGIS data collected between 2018 and 2020 from residents in Copenhagen (Denmark) and Helsinki (Finland), we explored the extent to which residents use urban cemeteries as everyday recreational landscapes. We also assessed users’ characteristics and the values they attached to the cemeteries. The results show that several of Copenhagen’s cemeteries were actively used for recreation, while those in Helsinki were used much less frequently for this purpose. Of the total 7276 mapped visiting points in Copenhagen, 16.5% were located within cemeteries, compared with 1.9% of the 4298 mapped visiting points in Helsinki, hence conclusions from Helsinki should be drawn with caution. Physical activity and experiencing nature were the most common values attached to cemeteries in Copenhagen, whereas social interaction, spirituality and tranquillity were most common for Helsinki cemeteries. The results also revealed that younger Danes were particularly inclined to use cemeteries for social interactions, physical activity and spirituality and tranquillity. In the discussion, we elaborate on spatial differences between the cases, such as the availability of other green spaces, the size of cemeteries or people living in proximity to a cemetery, as well as on differences in policies and practices, including how Copenhagen stands out in actively promoting municipal cemeteries as recreational landscapes.     

Analysing resilience in dryland agro‐ecosystems: a case study of the Makanya catchment in Tanzania over the past 50 years

Dryland agro‐ecosystems in sub‐Saharan Africa provide the resource base for some of the fasted growing populations today. However, rainfall variability and poor soils make these systems inherently vulnerable, and land degradation reduces their capacity to cope with disturbances. In this paper we propose a theoretical framework for interpreting dynamics and resilience in such systems, where two aggregate variables, the agricultural soil water index and the ecosystem insurance capacity, are particularly important. We apply the framework to the case of the Makanya catchment in Tanzania and conclude that the studied area has moved towards an increasingly degraded state, where ecosystem services other than food have been lost, over the past 50 years. Three main drivers behind this are identified; a) institutional changes affecting strategies for natural resource management, b) increased dry‐spell frequency, and c) high population growth. We suggest that the reason for the dramatic effects is that these changes occurred simultaneously, reducing the adaptive capacity of the local population. However, several trends in the area today indicate that there is a window of opportunity for positive change. Copyright © 2007 John Wiley & Sons, Ltd.