Rainfall and temperatures changes have confounding impacts on Phytophthora cinnamomi occurrence risk in the southwestern USA under climate change scenarios

Global change will simultaneously impact many aspects of climate, with the potential to exacerbate the risks posed by plant pathogens to agriculture and the natural environment; yet, most studies that explore climate impacts on plant pathogen ranges consider individual climatic factors separately. In this study, we adopt a stochastic modeling approach to address multiple pathways by which climate can constrain the range of the generalist plant pathogen Phytophthora cinnamomi (Pc): through changing winter soil temperatures affecting pathogen survival; spring soil temperatures and thus pathogen metabolic rates; and changing spring soil moisture conditions and thus pathogen growth rates through host root systems. We apply this model to the southwestern USA for contemporary and plausible future climate scenarios and evaluate the changes in the potential range of Pc. The results indicate that the plausible range of this pathogen in the southwestern USA extends over approximately 200 000 km² under contemporary conditions. While warming temperatures as projected by the IPCC A2 and B1 emissions scenarios greatly expand the range over which the pathogen can survive winter, projected reductions in spring rainfall reduce its feasible habitat, leading to spatially complex patterns of changing risk. The study demonstrates that temperature and rainfall changes associated with possible climate futures in the southwestern USA have confounding impacts on the range of Pc, suggesting that projections of future pathogen dynamics and ranges should account for multiple pathways of climate–pathogen interaction.     

Bioprecipitation: a feedback cycle linking Earth history,ecosystem dynamics and land use through biological ice nucleators in the atmosphere

Landscapes influence precipitation via the water vapor and energy fluxes they generate. Biologically active landscapes also generate aerosols containing microorganisms, some being capable of catalyzing ice formation and crystal growth in clouds at temperatures near 0 °C. The resulting precipitation is beneficial for the growth of plants and microorganisms. Mounting evidence from observations and numerical simulations support the plausibility of a bioprecipitation feedback cycle involving vegetated landscapes and the microorganisms they host. Furthermore, the evolutionary history of ice nucleation‐active bacteria such as Pseudomonas syringae supports that they have been part of this process on geological time scales since the emergence of land plants. Elucidation of bioprecipitation feedbacks involving landscapes and their microflora could contribute to appraising the impact that modified landscapes have on regional weather and biodiversity, and to avoiding inadvertent, negative consequences of landscape management.     

黄土高原西部旱农区不同品种马铃薯集雨限灌效应

通过大田试验研究了集雨限灌对同薯23号和大西洋两个马铃薯品种的补灌效应.结果表明：集蓄雨水在苗期补灌能显著提高旱作马铃薯的产量,且大西洋增产幅度高于同薯23号;在薯块膨大期补灌同薯23号的产量增加不显著,而大西洋减产.低额补灌（补灌45 mm）有利于同薯23号水分利用效率（WUE）和灌水利用效率（IWUE）的提高.大西洋苗期补灌的WUE和IWUE均高于薯块膨大期.补灌提高了同薯23号的大薯率、中薯率和单株薯产量,降低了小薯率, 但绿薯率、烂薯率有所增加;大西洋的大薯率和小薯率增加,中薯率稍有下降,烂薯率增加.     

多年平均降水资源空间变化模拟方法的研究

区域多年平均降水量的研究是集水农业工程规划的基础,也是有限的降水资源合理利用和配置的依据。研究利用ＡＲＣ／ＩＮＦＯ地理信息系统,建立了研究区的栅格数字高程模型（ＤＥＭ）及近３０年的年均降水量空间数据库;采用９种算法（距离权重法、趋势面法、样条函数法、普通Ｋｒｉｇｉｎｇ法、通用Ｋｒｉｇｉｎｇ方法１、通用Ｋｒｉｇｉｎｇ方法２、泰森多边形法、多元回归法和综合方法）,计算并比较分析了研究区多年平均降水量的     

晋西黄土区土地利用对降雨入渗产流模式和优先流分布的影响试验研究

黄土高原退耕还林(草)工程显著改变了河川径流过程,但其作用机制尚不明晰。选取晋西黄土区4种典型下垫面(20年和30年刺槐人工林地、草地、休耕地)分别开展连续3场模拟降雨试验,观测坡面入渗产流过程,并结合染色示踪和图像处理软件技术,分析土地利用类型对坡面降雨入渗产流模式和优先流分布的影响。结果表明：(1)累积入渗量和优先流发育程度均表现为刺槐林地>草地>休耕地,刺槐林地优先流对总入渗的贡献是草地和休耕地的2.5—4.5倍,但优先流贡献均不超过10%,仍以基质流入渗为主。(2)4种用地类型降雨入渗主要补给地表60—70cm土层,前期降雨均匀增加表层土壤含水率,而后期降雨补给深层土壤水分的空间变异性显著增强。(3)刺槐林地产流量及径流系数均显著小于草地和休耕地,且前期含水量对20年刺槐林地的影响较小,而显著影响草地和休耕地径流系数。(4)直径d<1mm的细根显著促进降雨入渗和优先流发育,而d>5mm的粗根与入渗量和基质流量呈显著负相关。较高的土壤初始含水率、容重和粘粒含量会抑制入渗和优先流的发生。研究说明不同土地利用类型将改变降雨入渗产流过程及土壤水运动形式。     

Spatial synchrony in Drosophila suzukii population dynamics along elevational gradients

1. Spotted wing drosophila (SWD; Drosophila suzukii Matsumura, 1931) is a polyphagous invasive crop pest native of Southeast Asia able to attack a wide array of host plant species in both cultivated and natural habitats. SWD is now widespread in several mountain regions, but it is still unclear how the species moves to different elevations across the seasons, and how this depends on environmental conditions and food resources. 2. The temporal dynamics of several SWD populations were studied along elevational gradients in the Alps using a synchrony analysis. Twelve transects were selected, covering an overall elevational gradient of 2100 m. SWD abundance was monitored every 2 weeks during the growing season (from June to November 2015) when cultivated and wild hosts are potentially susceptible (i.e. fruits are ripe). 3. Spotted wing drosophila were widely distributed along all the tested elevations, revealing synchrony in population dynamics across ranges in elevation and geographic distance. Synchronised populations were observed at distances of up to 100 km at sites with similar temperatures. The high dispersal potential of the pest together with the seasonal variation in temperature are likely to be the dominant mechanisms causing the observed spatial synchrony. A factor that seemed to reduce synchrony is the large concentration of host plants (i.e. crop) in lowland agricultural landscapes. 4. The spatial synchrony in pest abundance at large spatial scale indicates that the risk of SWD outbreaks is highly dependent on drivers beyond the control of traditional field‐scale management. These findings could help in developing monitoring and predictive models of SWD population dynamics.     

Forest biomass,productivity and carbon cycling along a rainfall gradient in West Africa

Net Primary Productivity (NPP) is one of the most important parameters in describing the functioning of any ecosystem and yet it arguably remains a poorly quantified and understood component of carbon cycling in tropical forests, especially outside of the Americas. We provide the first comprehensive analysis of NPP and its carbon allocation to woody, canopy and root growth components at contrasting lowland West African forests spanning a rainfall gradient. Using a standardized methodology to study evergreen (EF), semi‐deciduous (SDF), dry forests (DF) and woody savanna (WS), we find that (i) climate is more closely related with above and belowground C stocks than with NPP (ii) total NPP is highest in the SDF site, then the EF followed by the DF and WS and that (iii) different forest types have distinct carbon allocation patterns whereby SDF allocate in excess of 50% to canopy production and the DF and WS sites allocate 40%–50% to woody production. Furthermore, we find that (iv) compared with canopy and root growth rates the woody growth rate of these forests is a poor proxy for their overall productivity and that (v) residence time is the primary driver in the productivity‐allocation‐turnover chain for the observed spatial differences in woody, leaf and root biomass across the rainfall gradient. Through a systematic assessment of forest productivity we demonstrate the importance of directly measuring the main components of above and belowground NPP and encourage the establishment of more permanent carbon intensive monitoring plots across the tropics.     

Are Brazil nut populations threatened by fruit harvest?

Harvest of Brazil nuts from the large, iconic tree Bertholletia excelsa generates substantial income for smallholders, providing a strong incentive to conserve the mature forests where it grows. Although much previous work has focused on the impact of nut harvest on new seedling recruits into B. excelsa populations, the connection between harvest rates and long‐term population stability is still unclear. Moreover, there is additional uncertainty for Brazil nut management in terms of population response to climate change and other anthropogenic influences. We drew on 14 years of research in two sites in Acre, Brazil with different B. excelsa nut harvest intensities (39% and 81%), to produce stochastic and deterministic matrix population models which incorporated parameter uncertainty in vital rates. Adult abundance was projected to remain close to the current observed abundance or higher through the next 50 years. Elasticity analyses revealed that the asymptotic population growth rate (λ) was most sensitive to stasis vital rates in sapling, juvenile, and adult stages. Deterministic transition matrices calculated using diameter growth rates dependent on rainfall yielded average λ values around 1.0 under extreme high, extreme low, and average annual rainfall. While sustained high rates of Brazil nut harvest and climate change could potentially negatively impact B. excelsa populations, changes in human use of the forested landscape are more immediate concern. To reduce the risk of population decline, smallholders and managers of B. excelsa rich forests should focus on conservation of pre‐mature and mature individuals.     

降雨对北方城市5种典型城市绿化树种叶面滞尘的影响

城市树木和森林植被净化大气颗粒污染物的功能受到了广泛的重视,但由于受多种植被特征与环境因素的影响,定量评价城市植被净化大气颗粒污染物功能非常困难。研究了不同降雨条件下大叶黄杨、银杏、栾树、五角枫、杜仲5种我国北方城市绿化典型树种叶面滞尘量的变化特征。在选定的样树冠层分上、中、下3层和东、南、西、北4个方向,采集成熟叶片,采用刷洗样本叶表,抽取水样及分级抽滤并烘干称重的方法,测定这5种树种降雨后12d(夏季累积滞尘量)、14mm降雨后(小雨)、29mm降雨后(中雨)以及室内模拟降雨30mm/h(15mm雨量)后叶片表面不同粒径大气颗粒污染物的滞留量。研究结果表明:降雨对不同粒径颗粒物去除能力有较大差异,除银杏以外,PM10以上颗粒物更容易去除;小雨对颗粒物的冲刷能力有限;中雨可以冲刷掉50%以上总颗粒物;室内模拟强降雨可以冲刷掉90%以上颗粒物,随着降雨增大,各粒径颗粒物随之冲刷量增加;同时叶表结构对抗冲刷能力有显著影响,革质叶片更容易滞尘及冲刷,绒毛结构滞尘能力较低,抗冲刷能力较强;北方大叶黄杨具有综合去除空气中颗粒物优势(小雨TSP冲刷量为(775.06±33.99)mg/m~2),银杏具有去除细颗粒物优势(中雨PM_(2.5)冲刷量为(426.55±40.83.99)mg/m~2)。