Altitude and temperature dependence of change in the spring vegetation green-up date from 1982 to 2006 in the Qinghai-Xizang Plateau

Research in phenology change has been one heated topic of current ecological and climate change study. In this study, we use satellite derived NDVI (Normalized Difference Vegetation Index) data to explore the spatio-temporal changes in the timing of spring vegetation green-up in the Qinghai-Xizang (Tibetan) Plateau from 1982 to 2006 and to characterize their relationship with elevation and temperature using concurrent satellite and climate data sets. At the regional scale, no statistically significant trend of the vegetation green-up date is observed during the whole study period (R² = 0.00, P = 0.95). Two distinct periods of green-up changes are identified. From 1982 to 1999, the vegetation green-up significantly advanced by 0.88 days year⁻¹ (R² = 0.56, P < 0.001). In contrast, from 1999 to 2006, a marginal delaying trend is evidenced (R² = 0.44, P = 0.07), suggesting that the persistent trend towards earlier vegetation green-up in spring between 1980s and 1990s was stalled during the first decade of this century. This shift in the tendency of the vegetation green-up seems to be related to differing temperature trends between these two periods. Statistical analysis shows that the average onset of vegetation green-up over the Qinghai-Xizang Plateau would advance by about 4.1 days in response to 1 °C increase of spring temperature. In addition, results from our analysis indicate that the spatial patterns of the vegetation green-up date and its change since 1982 are altitude dependent. The magnitude of the vegetation green-up advancement during 1982-1999, and of its postponement from 1999 to 2006 significantly increases along an increasing elevation gradient.     

Advance of apple and pear tree full bloom dates in response to climate change in the southwestern Cape, South Africa: 1973-2009

Studies from throughout the world have demonstrated that tree phenophases are becoming earlier in spring and are closely associated with rising temperatures. Despite many such studies from the Northern Hemisphere, similar comparative work has not been forthcoming from the Southern Hemisphere or from Africa. In addition, few studies have demonstrated the possible role of changes in precipitation and associated soil moisture to driving fruit tree phenophases. Here we provide changes of mean full bloom dates for three apple Malus domestica (Golden Delicious, Sayaka, Granny Smith) and one pear Pyrus communis (Bon Chrétien) cultivars in the southwestern Cape of South Africa. These phenological changes are correlated with temperature and precipitation changes in the same region between 1973 and 2009. Significant early spring (August/September) temperature increases of +0.45 °C/decade are associated with a mean full bloom advance of 1.6 d/decade over the last 37 years. Golden Delicious apple trees have the strongest sensitivity (+4.2 d/°C) to climate change in the region, whilst Granny Smith apple trees have the lowest (+2.4 d/°C). Although winter and early spring rainfall has also decreased over this time, such decreases are not significant. However, significant correlations are found for both temperature and rainfall when comparing with the mean full bloom dates, and it is proposed that both variables operate synergistically to influence mean full bloom dates in the southwestern Cape.     

基于遥感的黄土高原植被物候监测及其对气候变化的响应

为了分析黄土高原地区植被物候特征,该文基于AVHRR传感器获取的陆地长期数据记录(land long term data record,LTDR)V4 NDVI数据,对黄土高原1982-2011年间植被物候的时空变化进行分析,并借助偏相关分析方法对物候与气温和降雨的关系进行量化分析。结果表明:黄土高原近30 a间春季物候提前显著(0.54 d/a,P0.001),主要集中在北部草地和灌木植被;秋季物候推迟显著(0.74 d/a,P0.001),主要分布在甘肃、陕北、内蒙古和山西北部等地。不同植被的春秋物候稍有差异,稀疏灌木林春季物候提前趋势最多(1.31 d/a),常绿针叶林最小(0.19 d/a);秋季物候推迟最多的为乔木园地(1.18 d/a),最少的是水田(0.17 d/a)。黄土高原植被物候主要受气温影响,降雨的变化也会对物候产生一定影响。冬季和前年秋季气温上升是春季物候提前的主要驱动因子;夏季和秋季降雨则对秋季物候休眠期延迟起着重要作用。该研究可为黄土高原生态环境评价及气候变化预测模型提供一定依据。     

Spatial variability in large-scale and regional atmospheric drivers of Pinus halepensis growth in eastern Spain

In this study we analyzed the influence of general atmospheric circulation patterns and the frequency of weather types on the spatio-temporal variability of tree-ring growth in Pinus halepensis forests in eastern Spain. Three atmospheric circulation patterns affecting the western Mediterranean region were included in the study: the North Atlantic Oscillation (NAO), the Western Mediterranean Oscillation (WeMO) and the Mediterranean Oscillation (MO). In addition, the particular circulation pattern affecting eastern Spain was quantified using the frequency of weather types. The variability of radial growth (width) of earlywood and latewood in P. halepensis was quantified at 19 sites using dendrochronological methods. Two distinct patterns, reflecting growth variability in the northern and southern areas involved in the study, were identified for both earlywood and latewood tree-ring series. The influence of atmospheric circulation modes on tree growth resembled the spatial patterns identified, as earlywood and latewood formation in northern sites was determined by the NAO variability, whereas the WeMO dominated growth at the southern sites. Winter, summer and autumn weather types also exerted a control over tree radial growth. We conclude that both atmospheric circulation indices and weather types exert significant control on the formation of earlywood and latewood, because of their influence on precipitation patterns. The findings also suggest that wet and mild conditions during winter and the following autumn enhance P. halepensis earlywood and latewood formation, respectively. Thus, winter atmospheric patterns may indirectly influence latewood growth through direct effects on previous earlywood development driven by precipitation variability.     

Impacts of grazing on montane heath vegetation in Wales and implications for the restoration of montane areas

The impact of long-term heavy grazing pressure on montane vegetation and soils was investigated on the Carneddau plateau in North Wales. At this site, historical information suggests that formerly extensive Racomitrium- and Vaccinium-dominated heaths have become degraded and reduced in extent over the last 40-50 years. This coincides with a period when both sheep numbers and atmospheric deposition of nitrogen have greatly increased. Vegetation composition, plant tissue chemistry, soil chemistry and sheep presence were compared between areas of ‘good’ condition Racomitrium and Vaccinium heath and degraded areas. Comparison of species composition data with sheep presence and environmental data showed no significant link between current grazing distribution and species composition in the areas investigated, with all habitats having sheep presence above the recommended maximum for this habitat. Soil chemistry showed several differences between degraded and ‘good’ condition habitats, suggesting that degraded areas had experienced loss of soil organic matter and upper organic horizons. Comparison of soil and vegetation nitrogen content with data from other UK sites suggests a build up of nitrogen has occurred in Carneddau vegetation and soils, possibly related to high levels of nitrogen deposition. It is concluded that restoration of severely degraded areas of montane vegetation may be retarded by deleterious changes in soil properties which could slow recolonisation by montane species. Reductions in stocking density aiming to restore montane communities might have more immediate impact on less degraded areas.     

典型喀斯特聚集区不同地貌类型干旱时空特征

为探究西南典型喀斯特聚集区不同地貌类型干旱时空特征,研究选取贵州省作为研究区,基于贵州19个气象站点1951—2020年的气象数据,利用SPI指数、M-K突变检验等方法研究贵州近70 a降水与气温在不同时间尺度变化规律,探讨不同地貌分区干旱的年、季时空尺度耦合特征。结果表明：(1)贵州近70 a的年均降水量整体呈缓慢下降趋势、气温呈现上升的趋势。(2)不同地貌分区干旱情况差异较显著,其中非喀斯特和峰丛洼地地貌背景下干旱呈现微弱上升趋势,其他分区干旱均呈下降趋势。(3)各分区在夏、秋季干旱指数均呈减少态势,冬季干旱指数呈增加态势。除岩溶高原和岩溶断陷盆地外,春季其他地貌分区旱情均呈加剧趋势。旱情加剧程度最大出现在岩溶槽谷春秋季和岩溶断陷盆地夏冬季,旱情加剧程度最小出现在非喀斯特地区的夏秋季和岩溶高原地区冬春季。(4)岩溶槽谷和非喀斯特的SPI12均值无明显突变点,岩溶峡谷的SPI12值在1987发生突变,岩溶高原和峰丛洼地分别在2002年和2019年前后发生显著性跳跃,岩溶断陷盆地在置信范围内发生三次突变。综上,研究结果可以为同类型干旱防灾减灾提供一定的参考依据。     

Comparative water snake ecology: conservation of mobile animals that use temporally dynamic resources

Obtaining information on movement and spatial patterns of animals and understanding the factors that shape their movements about the landscape are critical steps in designing conservation strategies. We conducted a comparative radiotelemetry study of two snake species, the northern water snake, Nerodia sipedon sipedon, and the imperiled copperbelly water snake, Nerodia erythrogaster neglecta, in northwest Ohio and southern Michigan to assess differences in movement patterns, spatial ecology, and resource use. N. e. neglecta moved distances (53.3 ± 7.1 m/day and 4809 ± 603 m/year) over twice as far as N. s. sipedon (25.6 ± 2.7 m/day and 2244 ± 228 m/year), and used areas nearly four times larger (15.8 ± 2.7 ha) than N. s. sipedon (4.0 ± 0.9 ha). When wetlands were widely dispersed in the landscape, N. e. neglecta moved longer distances and used larger areas, whereas spatial and movement patterns in N. s. sipedon were unaffected by wetland spatial distribution. N. e. neglecta’s long movements and large area use are likely related to its use of variable resources such as ephemeral wetlands and anuran prey. N. s. sipedon used more permanent wetlands and preyed more generally on fish and anurans. Habitat alterations that change the spatial distribution of wetlands in the landscape, such as the loss of small isolated wetlands, have likely increased energetic costs and mortality rates for N. e. neglecta. Conservation strategies for vagile wetland animals that use spatially and temporally variable resources over broad spatial scales should focus on protecting and restoring large areas with numerous, heterogeneous wetlands.     

2001-2013年宝鸡地区植被NDVI对气温和降水量的季节响应特征

[目的]研究2001-2013年陕西省宝鸡地区植被变化与气温和降水量的时空变化特征及其相关性,为区域农业发展和区域生态文明建设提供有力支撑.[方法]基于2001-2013年宝鸡地区气温和降水量数据,利用MODIS NDVI数据和11个气象站点实测数据,结合实际调查,采用一元线性回归、标准化处理、相关分析等方法,基于季尺度、参照年尺度分析宝鸡地区植被覆盖季节时空变化及其与气温和降水量的相关性.[结果]夏季植被NDVI增加趋势最为明显,其次为秋季,冬季植被覆盖最差;宝鸡地区四季标准化值NDVI与气温、降水量的变化趋势相接近,其最大值点的出现时间与气温和降水量基本对应.同一季节NDVI与气温的相关系数均高于NDVI与相应季节降水量的相关系数(除夏季);春季NDVI与冬季气温(-0.592)、夏季NDVI与春季降水量(0.640)之间显著相关,表明近13 a来春季植被覆盖变化与冬季气温、夏季植被覆盖与春季降水量的变化较为一致,NDVI与降水之间的滞后关系为0～3个月.[结论]2001-2013年宝鸡地区年均、季NDVI整体均呈增加趋势,8月植被覆盖变化与降水量的变化较为一致,降水量较气温对8月植被生长影响强烈.     

Empirical Orthogonal Function analysis of the palmer drought indices

The aim of the paper is to employ Empirical Orthogonal Function (EOF) analysis to drought indices including Palmer Drought Severity Index (PDSI), Palmer Hydrological Drought Index (PHDI), Palmer Moisture Anomaly (Z) Index (Z-Index), Weighted Palmer Drought Severity Index (WPDSI), and Water Deficit (P-PET) Index and to compare their resultant spatial patterns across Turkey. In this respect, the PDSI, PHDI, Z, WPDSI, Aridity Index (AI) and P-PET Index values are calculated based on observed monthly temperature and precipitation values of the 96 Turkish meteorological stations for the 1929-2009 period, and gridded available water holding capacities (AWHC) in 1-m soil depth are extracted from the soil data sets of the Oak Ridge National Laboratory Distributed Active Archive Centre (ORNL DAAC). By considering the strong match among the PDSI, PHDI, and WPDSI based on the results of the patterns of the first EOFs (EOF1) with the highest eigenvalue, we suggest that using and applying one of these drought indices could be adequate for a drought analysis in Turkey. On the other hand, it is evident that the significant results from the EOF2, EOF3 and EOF4 loadings of the PHDI and WPDSI indices have a similar pattern across Turkey. Therefore, with respect to the geographical autocorrelation and magnitudes of the loading values, it is explained that the PDSI and WPDSI in particular could have originated from the same physical process, and one may have a preference for the effective usage of a combination of PDSI, PHDI and Z-Index. Consequently, in a multi-purpose medium- and long-term drought management plan for Turkey or in any country having similar climatic and physical geographical conditions, using one of the three drought indices along with the Z-Index could be acceptable for successful applications.     

Habitat suitability, threats and conservation of isolated populations of the smooth snake (Coronella austriaca) in the southern Iberian Peninsula

During the Pleistocene, climatic fluctuations due to glacial and interglacial periods greatly modified the distribution of boreal organisms. One direct effect of these distribution shifts is that, along the southern edge of the range of some boreal species, populations persist only in isolated patches of suitable habitats, surrounded by less suitable areas. Isolated populations in marginal habitat are vulnerable to several threats, including climate change, anthropogenic threats, and stochastic events. We developed habitat-suitability models using Ecological Niche Factor Analysis for populations of the smooth snake, Coronella austriaca, at the southernmost limit of the species range. These models were based on historical and current records of occurrence, coupled with remote sensing data including elevation, slope, and climatic variables. Our results indicated that C. austriaca in the Iberian Peninsula occurred in areas associated with high slope and precipitation, low temperatures, and low variation in seasonal temperature and precipitation compared to areas of non-occurrence. At a broad scale, the areas classified as highly suitable for the species in the southern Iberian Peninsula were small and fragmented. At a local scale, extensive field work demonstrated that C. austriaca occurs in low densities in these areas. In addition, we detected several human-induced threats like habitat loss, favoured by temperature increase and rainfall reduction. Several life-history traits, such as dietary specialization and low frequency reproduction, also may contribute to the vulnerability of these populations to local extinctions. Although the most suitable southernmost areas are included in protected reserves, specific guidelines for management are needed to assess conservation needs.     

Temperature sensitivity of soil respiration in different ecosystems in China

Understanding the sensitivity of soil respiration to temperature change and its impacting factors is an important base for accurately evaluating the response of terrestrial carbon balance to future climatic change, and thus has received much recent attention. In this study, we synthesized 161 field measurement data from 52 published papers to quantify temperature sensitivity of soil respiration in different Chinese ecosystems and its relationship with climate factors, such as temperature and precipitation. The results show that the observed Q₁₀ value (the factor by which respiration rates increase for a 10 °C increase in temperature) is strongly dependent on the soil temperature measurement depth. Generally, Q₁₀ significantly increased with the depth (0 cm, 5 cm, and 10 cm) of soil temperature measuring point. Different ecosystem types also exhibit different Q₁₀ values. In response to soil temperature at the depth of 5 cm, alpine meadow and tundra has the largest Q₁₀ value with magnitude of 3.05 ± 1.06, while the Q₁₀ value of evergreen broadleaf forests is approximately half that amount (Q₁₀ = 1.81 ± 0.43). Spatial correlation analysis also shows that the Q₁₀ value of forest ecosystems is significantly and negatively correlated with mean annual temperature (R = −0.51, P < 0.001) and mean annual precipitation (R = −0.5, P < 0.001). This result not only implies that the temperature sensitivity of soil respiration will decline under continued global warming, but also suggests that such acclimation of soil respiration to warming should be taken into account in forecasting future terrestrial carbon cycle and its feedback to climate system.     

The use of camera traps for estimating tiger and leopard populations in the high altitude mountains of Bhutan

We used camera traps in combination with capture-recapture data analysis to provide the first reliable density estimates for tigers and leopards from the high altitude and rugged terrain in Bhutan’s Jigme Singye Wangchuck National Park. Fifty days of camera trapping in each of five study zones collapsed into two trapping blocks, resulted in a sampling effort of 4050 trap days. Camera trapping yielded 17 tiger photos (14 left flanked and 3 right flanked) and 48 leopard photos (25 left flanked and 23 right flanked). Using photos of these left flank, the closed heterogeneous Jackknife Model M_h was the best fit for the capture history data. A capture probability () of 0.04 was obtained for both tigers and leopards, thus generating population size (N) of 8 tigers (SE = 2.12) and 16 leopards (SE = 2.91) with densities of 0.52 tiger 100 km⁻² and 1.04 leopard 100 km⁻². Photographic evidence indicated that tigers and leopards did not overlap in their spatial use of space. Tigers preferred less disturbed areas located further away from settlements, while leopards appeared to be more resilient to disturbances in so far as they were found nearer to human settlements. Camera trapping using a capture-recapture framework was an effective tool for assessing population sizes for tiger and leopard in low density areas such as Bhutan.     

Biotic effects of climate change in urban environments: The case of the grey-headed flying-fox (Pteropus poliocephalus) in Melbourne, Australia

Urban climates are known to differ from those of the surrounding rural areas, as human activities in cities lead to changes in temperature, humidity and wind regimes. These changes can in turn affect the geographic distribution of species, the behaviour of animals and the phenology of plants. The grey-headed flying-fox (Pteropus poliocephalus) is a large, nomadic bat from eastern Australia that roosts in large colonies known as camps. Historically a warm temperate to tropical species, P. poliocephalus recently established a year-round camp in the Royal Botanic Gardens Melbourne. Using a bioclimatic analysis, we demonstrated that on the basis of long-term data, Melbourne does not fall within the climatic range of other P. poliocephalus camp sites in Australia. Melbourne is drier than other summer camps, and cooler and drier than other winter camps. The city also receives less radiation, in winter and annually, than the other summer and winter camps of P. poliocephalus. However, we found that temperatures in central Melbourne have been increasing since the 1950s, leading to warmer conditions and a reduction in the number of frosts. In addition, artificial watering of parks and gardens in the city may contribute the equivalent of 590 mm (95% CI: 450-720 mm) of extra rainfall per year. It appears that human activities have increased temperatures and effective precipitation in central Melbourne, creating a more suitable climate for camps of the grey-headed flying-fox. As demonstrated by this example, anthropogenic climate change is likely to complicate further the task of conserving biological diversity in urban environments.     

3 种挺水植物吸收水体NH4+、NO3-、H2PO4- 的动力学特征比较

本文用动力学试验研究了具有景观价值的3 种挺水植物—— 水生美人蕉(Canna generalis)、细叶莎草(Cyperus papyrus)、紫芋(Colocasia tonoimo)对H₂PO₄^-、NH₄⁺、NO₃^- 的吸收特征及差异。试验结果表明: 3 种挺水植物吸收H₂PO₄^- 时, 美人蕉的吸收速率最快, 且在较低离子浓度条件下也可以吸收该离子, 说明其具有嗜磷特性, 能够适应广范围浓度H₂PO₄^- 环境; 吸收NO₃^- 时, 细叶莎草的速率最快, 但对低浓度NO₃^- 环境的适应能力较差, 美人蕉吸收NO₃^- 的特性与细叶莎草刚好相反; 吸收NH₄⁺ 时, 细叶莎草的吸收速率最快, 且在低浓度NH₄⁺ 环境下仍能吸收该离子, 而美人蕉的吸收速率最慢, 但能在低浓度NH₄⁺ 环境下吸收该离子。说明不同植物对养分的吸收特性存在较大差异, 各自的污染水体修复适用范围也不同。美人蕉可用于各种浓度H₂PO₄^- 污染的水体修复; 而NO₃^- 污染严重的水体最适宜用细叶莎草作先锋植物, 修复到一定程度后再种植美人蕉来维持水质; 细叶莎草在各种浓度NH₄⁺ 污染的水体中均适用, NH₄⁺ 污染较轻的水体也可用美人蕉修复。     

The effects of cattle grazing on tall-herb fen vegetation and molluscs

The effects of light year-round cattle grazing on tall-herb fen vegetation and wetland molluscs were compared to the effects of non-intervention over a period of four years using grazing exclosures. The distribution of cattle within the area of fen was investigated by plotting the position of the herd at 3-4 day intervals throughout the year. Cattle distributed themselves randomly throughout the fen in spring, autumn and winter, but showed a more aggregated distribution in summer. Grazing reduced the biomass of Phragmites australis and increased stem densities of Glyceria maxima, resulting in a shift of dominance from Phragmites to Glyceria. Plant species-richness was also significantly higher in areas open to grazing.Grazing decreased total densities of molluscs and substantially reduced densities of the rare snail Vertigo moulinsiana. V. moulinsiana was particularly associated with areas of fen that had a high water table and high biomass of ungrazed Carex riparia. However, because of the patchy nature of the grazing, V. moulinsiana survived at reasonably high densities in patches of ungrazed vegetation within the grazing unit.     

干季贵州省东西部区域干湿状况差异分析

利用贵州85个气象观测站1960年10月-2010年3月逐日平均气温、降水量、小型蒸发量等资料,选用线性趋势、M-K突变、Morlet小波、积温干燥度指数以及气候干湿指数等方法,对贵州干季（10月-翌年3月）气象干旱进行分析。结果表明：（1）1960-2010年贵州东西部区域干季降水量均无显著线性变化趋势,但有一定的阶段性变化特点;西部区域2002年之后降水量呈极显著减少趋势,其线性变化率为-59.5mm·10a^-1（P<0.01）,东部区域2005年之后降水量呈极显著减少趋势,其线性变化率为-97.7mm·10a^-1（P<0.01）。21世纪前10a贵州东西部区域气象干旱均呈加重趋势。两区域降水量的突变时段和周期性特征均存在显著性差异（P<0.05）,西部区域1979年发生由多到少的突变,存在5～7a的周期振荡,东部区域1995年发生由多到少的突变,存在2～3a的周期振荡。（2）近50a西部区域的积温干燥度、气候干湿指数的变化比东部区域明显偏大、偏低,西部区域的气象干旱比东部区域偏重。（3）贵州东西部区域的积温干燥度、气候干湿指数与降水距平百分率线性拟合率均较高,R²均在0.8以上,但西部区域更高,积温干燥度和气候干湿指数均能真实体现贵州东西部区域干季气象干旱程度。     

东北地区玉米春季渍害指标构建及时空分布特征

为厘清东北地区玉米春季渍害的评价指标及变化特征，该研究利用东北地区164个气象站点1981-2020年逐日气象资料和历史灾情资料，采用相关分析和逐步回归方法，分析玉米春季播种-出苗期降水和温度对渍害等级的影响效应，建立当量降水量和当量温度，在此基础上构建渍害等级指标，探讨东北地区玉米春季渍害的时空分布特征。结果表明：1）玉米春季渍害指标验证基本一致率达82%，能较好地反映东北地区玉米播种-出苗期渍害的实际受灾情况。2）1981-2020年东北地区玉米播种-出苗期渍害的发生存在明显空间差异，高发区集中在辽宁省东部、吉林省东南部以及黑龙江省三江平原地区，渍害频率最高可达45%，轻度渍害发生范围明显扩大；玉米不同程度渍害发生频率存在差异，表现为轻度>中度>重度。3）玉米渍害发生频率总体呈上升趋势，但上升趋势不显著，其中2001年、2002年、2004年为显著突变年。研究结果能够为揭示气候变化背景下东北地区玉米春季渍害灾变机制和时空演变规律提供理论依据。     

Effects of seasonal and diurnal temperature fluctuations on population dynamics of two epigeic earthworm species in forest soil

Temperature fluctuations are a fundamental entity of the soil environment in the temperate zone and show fast (diurnal) and slow (seasonal) dynamics. However, responses of soil ecosystem engineers, such as earthworms, to annual temperature dynamics are virtually unknown. We studied growth, mortality and cocoon production of epigeic earthworm species (Lumbricus rubellus and Dendrobaena octaedra) exposed to temperature fluctuations in root-free soil of a mid-European beech-oak forest. Both earthworm species (3 + 3 individuals of each species) were kept in microcosms containing soil stratified into L, F + H and A_h horizons. In the field, earthworm responses to smoothing of diurnal temperature fluctuations were studied, simulating possible global change. In the laboratory, earthworm responses to seasonal (±5 °C of the annual mean) and diurnal temperature fluctuations (±5 °C of the seasonal levels) were analyzed in a two-factorial design. Both experiments lasted 12 months to differentiate between seasonal and diurnal responses. In the third experiment overwintering success of both earthworm species was investigated by comparing effects of constant temperature regime (+2 °C), and daily or weekly temperature fluctuations (2 °C ± 5 °C).Temperature regime strongly affected population performance of the earthworms studied. In the field, smoothed temperature fluctuations beneficially affected population development of both earthworm species (higher biomass, faster maturity and reproduction, lower mortality). Consequently, density of both species increased faster at smoothed than at ambient temperature conditions. In the laboratory, responses of L. rubellus and D. octaedra to temperature treatments differed; however, in general, earthworms benefited from the absence of diurnal fluctuations. Total earthworm numbers were at a maximum at constant temperature and lowest in the treatment with both diurnal and seasonal temperature fluctuations. However, after one year L. rubellus tended to dominate irrespective of the temperature regime. In the overwintering experiment L. rubellus sensitively responded to even short-term winter frost and went extinct after one week of frost whereas D. octaedra much better tolerated frost conditions. Earthworms of both species which survived frosts were characterized by a significant body weight decrease during the period of frosts and fast recovery in spring suggesting a different pattern of individual resource expenditure as compared with constant +2 °C winter regime. Contrasting trends in the population dynamics of L. rubellus and D. octaedra during the frost-free period and during winter suggest that in the long-term temperature fluctuations contribute to the coexistence of decomposer species of similar trophic position in the forest litter. The results are discussed in context of consequences of climate change for the functioning of soil systems.     

1960-2012年山东省近地面和高空相对湿度时空变化特征

[目的]探讨近地面和高空相对湿度的时空变化特征及其与气温和降水的关系,为研究山东省气候波动过程提供依据.[方法]基于山东省1960-2012年探空和地面观测资料,采用回归分析、IDW空间插值、Mann-Kendall单调趋势检验法以及敏感性分析等方法研究了相对湿度变化特征.[结果]1960-2012年,山东省近地面年均相对湿度呈下降趋势,变化速率为-0.23％/10 a(p＞0.05).其中,春季、秋季和夏季相对湿度下降速率大小依次为-0.45％/10 a,-0.42％/10 a和-0.18％/10 a,而冬季相对湿度却呈增加趋势(0.10％/10 a).空间上,近地面相对湿度从东部沿海向西部内陆递减,而下降趋势呈现“东快西慢”的特点.高空相对湿度也呈下降趋势,而且对流层中下层的变化趋势比上层明显.近地面相对湿度季节变化对年变化的贡献率由大到小依次为:秋季＞春季＞冬季＞夏季,对流层中下层各季的贡献率大小依次为:秋季＞冬季＞春季＞夏季,而对流层上层各季贡献率由大到小为:夏季＞秋季＞冬季＞春季.[结论]敏感性分析表明,干旱指数变化1％,将引起近地面和高空相对湿度分别变化-1.55％和-1.95％,而气温或降水变化1％,将导致相对湿度变化在-0.15％～0.09％.     

The abundance and efficacy of Rhizobium leguminosarum bv. viciae in cultivated soils of the eastern Canadian prairie

For optimum production, the use of commercial rhizobial inoculant on pea (Pisum sativum L.) at seeding is necessary in the absence of compatible rhizobial strains or when rhizobial soil populations are low or symbiotically ineffective. Multiple site experiments were conducted to characterize the abundance and effectiveness of resident populations of Rhizobium leguminosarum bv. viciae (Rlv) in eastern Canadian prairie soils. A survey of 20 sites across a broad geographical range of southern Manitoba was carried out in 1998 and was followed by more intensive study of five of the sites in 1999 and 2000. Appreciable nodulation of uninoculated pea was observed at all sites which had previously grown inoculated pea. However, uninoculated pea grown at two sites, which had not previously grown pea, had negligible nodulation. Likewise, wild Lathyrus sp. and Vicia sp. plants collected from uncultivated areas adjacent to agricultural sites were poorly nodulated. In the more intensively studied sites, there was a tendency towards higher nodulation in pea plants receiving commercial inoculant containing Rlv strain PBC108 across all site-years (e.g., 4.7% in nodulation and 22% in nodule mass), but the effect was significant at only 2 of 10 site-years. Despite a relatively high range of soil pH (6-8), regression analysis indicated that decreasing soil pH resulted in lower nodulation rates. Likewise, electrical conductivity (EC) was correlated to nodulation levels, however the effect of EC was likely more indicative of the influence of soil texture and organic matter than salinity. As with nodulation, commercial inoculation tended to increase above-ground dry matter (DM) and fixed-N (estimated by the difference method) at the early pod-filling stage, but again the effects were significant at only 2 of 10 site-years. Specifically, above-ground DM and fixed-N levels were up to 29 and 51% greater, respectively, in inoculated compared to non-inoculated treatments at these sites. Addition of N-fertilizer at a rate of 100 kg N ha⁻¹ decreased nodulation at almost all site-years (by as much as 70% at one site), but rarely resulted in increases in above-ground DM compared to inoculated plots. The study indicates for the first time that populations of infective, and generally effective strains of Rlv occur broadly in agricultural soils across the eastern Canadian prairie, but that there is a tendency for increased symbiotic efficiency with the use of commercial inoculant.