Spatial attributes of fire regime in eastern Canada: influences of regional landscape physiography and climate

The characterization of the fire regime in the boreal forest rarely considers spatial attributes other than fire size. This study investigates the spatial attributes of fires using the physiography of the landscape as a spatial constraint at a regional scale. Using the Canadian National Fire Database, the size, shape, orientation and eccentricity were assessed for 1,136 fires between 1970 and 2010 in Quebec’s boreal forest and were summarized by ecodistrict. These spatial metrics were used to cluster 33 ecodistricts into homogeneous fire zones and then to determine which environmental variables (climate, topography, hydrography, and surficial deposits) influence the spatial attributes of fires. Analyses showed that 28 out of 33 ecodistricts belonging to a given fire zone were spatially contiguous, suggesting that factors driving the spatial attributes of fire are acting at a regional scale. Indeed, the orientation and size of fires vary significantly among the zones and are driven by the spatial orientation of the landscape and the seasonal regional climate. In some zones, prevailing winds during periods conducive to fire events parallel to the orientation of the landscape may favour the occurrence of very large fires (>100,000 ha). Conversely, an orientation of the landscape opposite to the prevailing winds may act as a natural firebreak and limit the fire size and orientation. This study highlights the need to consider the synergistic relationship between the landscape spatial patterns and the climate regime over the spatial attributes of fire at supra-regional scale. Further scale-dependant studies are needed to improve our understanding of the spatial factors controlling the spatial attributes of fire.     

Land-use legacies of twentieth-century forestry in the UK: a perspective

Landscape Ecology - Complex interactions between societies and their environment have shaped landscapes across Europe over centuries. Therefore, taking a historical perspective can be important...     

高寒地区引种枣树试验

枣树栽培历史悠久,分布广泛,最低气温不低于-23℃是其分布先决条件,因此形成了北纬43°的分布北线.我们突破此线在新疆北部石河子地区引种枣树成功,在确定适宜北疆地区的栽培品种后,利用其当年萌生枝条能形成花芽并开花结果的特性,配套相应栽培管理技术,通过平茬、密植、修剪、防寒等措施达到早产、丰产,取得理想经济效果.枣树在北疆地区栽培能够安全越冬是管理技术得以应用的基础.因此,采取防寒措施是最关键的步骤.据5年试验结果重点以1997年～1998年冬为例说明枣树越冬防寒措施及其效果.     

Vegetation productivity consequences of human settlement growth in the eastern United States

In this study, we investigated the impact of human settlement growth on vegetation carbon uptake in the eastern United States between 1992/1993 and 2001. Human settlement growth was measured by changes in the density of housing units. Vegetation carbon uptake was estimated with gross primary production (GPP) based on the light-use efficiency approach applied to satellite imagery. Annual GPP was found to increase by approximately 140?g?C?m^?2 on average for the entire study area in 2001 compared to 1992/1993, accompanied by region-wide increases in downward shortwave radiation and minimum daily temperature. Changes in GPP, however, varied significantly by different types of settlement growth. Exurbanized areas, where the rural settlement (less than 0.025?units per acre) converted to exurbs (0.025?C0.6?units per acre), were associated with approximately 157?g?C?m^?2 increase in GPP due to high vegetation proportions. Suburbanization, the conversion from exurban settlement to suburbs (0.6?C4?units per acre), was related with a decline of GPP by 152?g?C?m^?2 due to progressive development of built-up land cover. Results help to understand the potential of carbon mitigation in the human-dominated landscapes using vegetation as a natural store of carbon dioxide. This in turn has implications for the low-carbon development planning along the gradient of human settlement densities.     

Land-use and land-cover dynamics in response to changes in climatic,biological and socio-political forces: the case of southwestern Ethiopia

Few studies of land-use/land-cover change provide an integrated assessment of the driving forces and consequences of that change, particularly in Africa. Our objectives were to determine how driving forces at different scales change over time, how these forces affect the dynamics and patterns of land use/land cover, and how land-use/land-cover change affects ecological properties at the landscape scale. To accomplish these objectives, we first developed a way to identify the causes and consequences of change at a landscape scale by integrating tools from ecology and the social sciences and then applied these methods to a case study in Ghibe Valley, southwestern Ethiopia. Maps of land-use/land-cover change were created from aerial photography and Landsat TM imagery for the period, 1957–1993. A method called `ecological time lines' was developed to elicit landscape-scale explanations for changes from long-term residents. Cropland expanded at twice the speed recently (1987–1993) than two decades ago (1957–1973), but also contracted rapidly between 1973–1987. Rapid land-use/land cover change was caused by the combined effects of drought and migration, changes in settlement and land tenure policy, and changes in the severity of the livestock disease, trypanosomosis, which is transmitted by the tsetse fly. The scale of the causes and consequences of land-use/land-cover change varied from local to sub-national (regional) to international and the links between causes and consequences crossed scales. At the landscape scale, each cause affected the location and pattern of land use/land cover differently. The contraction of cropland increased grass biomass and cover, woody plant cover, the frequency and extent of savanna burning, and the abundance of wildlife. With recent control of the tsetse fly, these ecological changes are being reversed. These complex patterns are discussed in the context of scaling issues and current conceptual models of land-use/land-cover change.     

苹果中氯氟氰菊酯残留降解研究

为了解苹果生产过程中氯氟氰菊酯的残留污染及其在苹果中的降解规律,用气相色谱法动态检测了大田苹果中氯氟氰菊酯残留量。结果表明,最后1次施药后苹果中氯氟氰菊酯的残留量顺序为:37.5g/hm2喷施3次>37.5g/hm2喷施2次≈18.8g/hm2喷施3次>18.8g/hm2喷施2次,喷药总量是影响农药残留的主要因素;施药后到采收前,果皮残留浓度是果肉的9～40倍,氯氟氰菊酯的降解为一级动力学模型,半衰期为17.6d,苹果果肉降解速率(T1/2=22.7d)比果皮(T1/2=16.9d)慢。以37.5g/hm2浓度喷3次,30d后苹果中氯氟氰菊酯残留量(<0.02mg/kg)远低于我国和欧盟等国家的最大残留限量要求。     

黄土高原成龄富士苹果园土壤养分含量标准值研究

2012-2013年,对黄土高原12个主产县区108个典型富士果园养分状况调查分析。结果表明：果园土壤有机质、全氮、全磷、全钾含量分别为11.9、0.63、1.12和13.7 g · kg-1,有效氮、有效磷、有效钾、有效钙、有效镁、有效锌和有效铁含量分别为77.7、26.9、259.7、4 681、121.3、1.24和7.89 mg · kg-1。制定了黄土高原成龄富士苹果园土壤养分含量标准值。土壤养分状况特征为：有机质偏低,全氮、全磷和全钾等全素养分相对适宜,但有效养分偏低;全素养分含量变异较小,有效养分含量变异较大;大量元素变异较小,微量元素变异较大;地域和深度分布不均衡问题较为突出。不同产区间,延安和洛川土壤养分水平较低,分别有9个和5个养分因子处于低值和缺乏水平;而河南陕县养分水平较佳,各养分因子均处于适宜值以上水平。今后果园土壤管理的重点是,因地制宜着力提高土壤有机质和有效养分的含量,并注意适度深施肥,提高20 ~ 60 cm土层的有效养分含量。     

辽东地区杂交榛子产业发展中的问题及对策

杂交榛子是辽宁省经济林研究所利用平榛做母本、欧洲榛作父本杂交培育的[1],1999—2019年共有16个品种先后通过辽宁省林木品种审定委员会审定或认定。截至2020年,在辽东地区(抚顺、本溪、丹东3市)推广种植面积已达1.4万hm²,占全国总面积的20%左右。辽东的优越气候条件非常适合栽植杂交榛子,现已成为我国杂交榛子的主产区。2019—2020年,我们对辽东地区杂交榛子产业的发展现状、存在问题进行调查和分析,并提出发展建议,以期对辽东地区杂交榛子产业发展提供参考。     

Soil seed banks are short-lived and triggered by the first effective rainfalls in the vacant lots of Santiago,Chile

We studied the temporal variation of the soil seed banks in the urban lots of Santiago, Chile. As most of the plants that emerge from the seed banks in lots are also found in open habitats and are easily germinable, we hypothesize that the seed banks in lots are highly dynamic and short-lived, with the bank depleted every year during the germination season to be reloaded with new seeds during the next seed dispersal period. In each 20 lots for two year (2017 and 2018), 9 soil samples were collected. These samples were obtained from three sampling points randomly distributed across the plots. The seed bank was estimated by seed germination in soil samples placed in plastic trays. The samples of all the lots were stratified at 2 °C by 3 months before sowing. In order to record the seed persistence, soil of three lots watered in 2017 for six months were dried and maintained under dark and non-watered conditions until re-sowing in autumn 2018. To determine if the seeds present cold-associated germination triggers, soils of five lots were maintained under dark conditions for 3 months (soils without cold stratification) for comparison with soils with cold stratification of the same lots. The above-ground plants were recorded in all lots for both years. Forty plant species were recorded in soil bank. The total emerged seedling densities ranged between 7,944 (2017) to 3,700 seedlings m^-2 (2018). Species per lot varied between 17 and 7 during 2017, and between 14 and 3 during 2018. In five lots, seedling densities were not statistically different between cold stratified soil at 2 ° C and non-stratified. In three lots with re-sown soil, seedling density of the first sowing (4,096 seedlings m^-2) was significantly higher than second sowing (201 seedlings m^-2). Thirty-seven plant species were recorded in the above-ground vegetation during 2017 and 42 species in 2018. Species frequency of the seed bank was positively correlated with species frequency of above-ground vegetation. Concluding, the bank is highly dynamic, short-lived, and is depleted every year during the germination season, which begins with effective rainfalls, would be reloaded with seeds during the seed dispersal period.     

青藏高原东缘龙胆属藏药植物资源调查

采用查阅文献资料、实地调查和标本采集相结合的方法对青藏高原东缘龙胆属藏药植物资源的种类组成及药用价值进行了调查,以期为龙胆属藏药植物资源的持续利用和合理开发提供科学依据。结果表明:据初步统计,青藏高原东缘龙胆属藏药植物资源丰富,共有16种。     

气候变化背景下陇东塬区‘红富士’苹果始花期研究

【目的】分析苹果始花期对气候变化的响应,提取主要影响气象因子,并提出优势苹果花期预报方法;为苹果开花期气象灾害防御和管理措施的调整提供科学依据。【方法】采用偏最小二乘回归法对西峰农业气象试验站多年观测的苹果始花期与光、热、水气象因子进行分析,并开展了苹果始花期预测。【结果】苹果始花期的早晚与2月下旬至4月上旬的旬平均气温及3月平均气温呈显著负相关;苹果开花日期与积温呈现显著的相关性,≥0℃、≥5℃积温越大或0℃积温越小,花期出现越早,反之则迟;说明气温升高,开花日期出现早,反之则迟。苹果始花期与稳定通过10℃初日接近,较稳定通过5℃初日晚超过20 d。利用偏最小二乘回归模型预报苹果始花期,预测日期与实际日期相符率为97%。【结论】影响陇东苹果开花早晚的主要影响因素是热量因子,日照次之,降水影响最小,气候变暖和高光照使苹果始花期提前。偏最小二乘回归模型预测苹果始花期较传统回归模型和线性分析法预报苹果始花期更为科学。     

渭北旱塬苹果园土壤水分环境效应

塬面苹果园、农田和其它主要土地利用方式的比较研究表明,苹果园的水分环境效应表现为土壤高入渗率、降雨低产流率和强烈的蒸腾耗水作用形成的土壤低湿层,使土壤水库对干旱的调节作用丧失,导致苹果产量随年际降雨呈现较大波动。随着苹果种植面积的扩大,这种水分环境效应将加强土壤、植物、大气间的水分小循环,削弱降雨转化为地表水和地下水的比例,最终影响区域水资源的数量和果业的持续发展。     

豫东地区苹果病虫害发生动态及防治

豫东黄河故道地区苹果栽培面积 36 .47万hm2 (公顷 ) ,是河南省苹果的主要产区。近 1 0年来 ,由于品种结构、栽培管理及病虫防治方法改变 ,苹果园主要病虫害种类、发生特点和为害程度也出现明显的变化。1　苹果主要病虫害得到控制　　 (1 )苹果树腐烂病　通过增施粪肥 ,合理追肥 ,施用磷钾肥 ,合理留果 ,调节好大小年结果 ,加强对削弱树势的病虫害防治 ,控制晚秋肥水 ,使果树及早进入休眠 ;上冻前对主干涂白防寒 ,春季苹果树腐烂病大发生季节突击刮治病部 ,坚持常年巡回刮治 ,刮除烂皮后 ,病疤涂抹 5 %菌毒清水剂 2 5～ 30倍液消毒 ,苹果树…     

Drivers of the dynamics in net primary productivity across ecological zones on the Mongolian Plateau

Understanding the drivers and mechanisms of the dynamics in grassland productivity is prerequisite for studying effective resource institutions and policies that can be used to govern grassland resources sustainably. We present a diagnostic analysis of the major drivers of the dynamics in grassland net primary productivity (NPP) across ecological zones on the Mongolian Plateau. We estimated a spatial panel data model for NPP (1986–2009) as a function of climatic and socioeconomic variables. Static and dynamic spatial panel models were estimated in each of the sub-regions, which were classified based on rural livelihoods and ecological models of grassland dynamics, to identify the major drivers of NPP dynamics. The statistical modeling results indicated that the major drivers of NPP dynamics vary across the six sub-regions. Grain output was the major predictor of NPP dynamics in the farming and farming-grazing zones of Inner Mongolia. Precipitation and livestock populations both had significantly positive relationships with NPP in the two grazing zones of Inner Mongolia. However, in Mongolia, livestock populations was the only significant predictor of NPP in the grazing zone with relatively stable climate, and precipitation was the only significant predictor of NPP in the grazing zone with highly variable climate. Human land-use activities and livestock management behaviors and the bidirectional causal relationships between livestock populations and NPP could explain the positive relationships between livestock population and grassland NPP. The heterogeneous drivers of NPP dynamics across space indicated the necessity of diverse resource polices and institutions for sustainable governance of grassland resources.     

黄土高原苹果农户气候风险的感知脆弱性评估

为测量黄土高原苹果生产的气候风险,使用陕甘宁17个苹果主产县2014年的截面数据,计算农户感知脆弱性指数,区分气温敏感和气温耐受两类农户群体,通过多元回归分别探讨可持续生计框架中各种生计资本指标与两类农户感知脆弱性的关系。结果表明:16个生计资本指标对气温敏感农户的感知脆弱性没有影响;气温耐受农户的感知脆弱性随一个生计资本指标(家庭规模)增加而增大。可持续生计框架对农户感知脆弱性评价作用有限,应该和农户感知、适应行为结合才能更好的区分脆弱人群,有效减小脆弱性。     

A landscape-geochemical approach in insular studies as exemplified by islets of the eastern Baltic Sea

The main objective of our investigations is to find out the primary geochemical properties of insular landscapes in order to ascertain the landscape stability on an area of land uplifting in the conditions of a regressive sea. Therefore we focus our study on the landscapes of Kolga Bay islets, which are located near the Estonian coast in the Gulf of Finland. A landscape-geochemical approach of landscape study improves the mapping of insular landscapes and understanding of processes of landscape development. Besides land use changes, land uplift and marine influence shape the landscape patterns of island through topography and subsurface water. We propose geochemical typology of landscapes based on substance movement (eluvial, superwatery, subwatery), field studies on islands, and chemical analysis of soil and water samples. From a landscape geochemical perspective, types of matter fluxes mainly control stability of an insular landscape. Interactions between geochemical, ecosystem and geomorphic processes reveal that islands behave as systems, rather than merely a sequence of interdependent soil-vegetation complexes along topographic gradients. This revised version was published online in August 2006 with corrections to the Cover Date.     

黄土高原沟壑区苹果树休眠枝条含水量研究

通过对苹果树休眠枝条含水量的比较研究,探讨了黄土高原沟壑区不同地形、不同农艺措施处理对果树枝条受冻害“抽干”程度的影响。结果表明,沟坡地形热量状况最好、果树受冻害程度最轻,台坪次之,塬面受冻害程度最重;生育期灌溉和果园深翻可以明显降低枝条受冻害程度。     

黄土高原干旱地区农田杂草和党参对耕作模式的响应

连续3年在2个不同耕作季节选择免耕、深耕不耙、深耕耙平、旋耕4种耕作方法,研究其对党参田间优势杂草种群的影响以及耕作方式协同杂草作用对党参产量的影响。结果表明:参田中一年生杂草以虫食(Corispermum declinatum Steph.ex Stev.var.declinatum)、荠(Capsella bursapastoris(Linn.) Medic)、灰灰菜(Chenopodium album L.)、狗尾草(Setaria viridis(L.) Beauv.)为优势种群,多年生杂草以田旋花(Convolvulus arvensis L.)、冰草(Agropyron cristatum(Linn.) Gaertn.)为优势种群;免耕参田杂草种类最多,数量最大,党参产量最低;夏季干旱时节深耕耙平参田杂草种类、数量均最少,党参产量最高。夏季高温干旱时节进行深耕耙平能够有效的控制党参田间杂草,提高参田产量,在一定程度上降低了除草成本,可作为党参绿色种植控草技术进行推广应用。     

广西西北部高原地区柿种质资源调查及遗传多样性分析

 调查和研究了广西西北部云贵高原地区柿种质资源状况,并对收集到的柿种质进行表型系统聚类和SCoT遗传多样性分析。结果表明,广西西北部云贵高原地区柿种质资源较丰富,至少拥有柿、油柿和野柿3个种31个不同品种和类型,部分地方仍保存有原始的野生种。不同柿种质在形态和DNA水平上都表现出很大的变异,具有丰富的多样性。35个相对独立的表型性状被用于柿种质的Q型系统聚类分析,在欧氏距离D = 9.8处,31份种质被分为5组,与果形及种质类型在一定程度上相吻合。13条SCoT多态性引物可从31份柿种质中扩增出161个DNA位点,多态性带比例为95.65%;UPGMA聚类分析显示,SCoT标记能将31份柿种质完全区分开,在相似系数0.686的水平将其分为5大类,与表型分析结果基本一致。