南疆植被总初级生产力对区域降水的响应规律

为研究总初级生产力(Gross primary productivity,GPP)对区域降水的响应规律,本研究通过对南疆地区喀什、阿克苏、和田3个市2000—2014年的GPP进行分析,得出GPP的时空分布规律,进而与2000—2011年同期的降水进行耦合分析,以探寻植被GPP与降水之间的响应关系,从而为南疆地区植被生态保持和可持续发展提供依据。结果表明:1)从时间尺度来看,GPP呈现出与季节相关的波动性,年均GPP的极值点基本出现在每年的7月;2)在空间分布上,和田地区的GPP在空间上呈现北低南高的空间格局,阿克苏地区的GPP呈现北高南低的空间格局,并且在数值上存在较大的差异性,喀什地区的GPP呈现北高南低的空间格局,西北部GPP分布比较集中并有较高的值;3)变化趋势上,和田地区呈现上升趋势、阿克苏地区整体比较稳定、喀什地区呈现上升的趋势;4)研究区域内GPP与降水之间均为正相关关系。当降水滞后1个月时,和田及喀什GPP与降水之间的相关系数显著提高,但是阿克苏地区没有表现出时滞性,说明响应关系更加明显。     

内蒙古苏木山华北落叶松生物量及碳储量研究

森林生物量、碳储量是评价森林生长状况的重要指标。通过野外样地调查及室内烘干称重等方法,研究了苏木山林场不同林龄华北落叶松人工林乔木层、灌木层、草本层生物量以及乔木层净生产力、碳储量积累特点和变化趋势。结果表明:幼龄林、中龄林、近熟林平均木的生物量分别为26.41 kg、32.70 kg、107.81 kg;林分生物量分别为43.66 t·hm^-2、79.88 t·hm^-2、125.83 t·hm^-2;灌木层和草本层生物量之和分别为1.44 t·hm^-2、1.19 t·hm^-2、0.95 t·hm^-2;乔木层净第一生产力分别为2.56 t·hm^-2·a^-1、3.07 t·hm^-2·a^-1、3.40 t·hm^-2·a^-1,碳储量分别为22.20 t·hm^-2、40.55 t·hm^-2、63.80 t·hm^-2。苏木山华北落叶松人工林生物量、碳储量随林龄增加而增大,各器官碳储量从大到小依次为干>根>枝>皮>叶。     

运用植被指数时序特征对落叶松人工林分类

为探究植被指数时序特征是否有利于落叶松人工林提取,以孟家岗林场为研究试验区域,根据落叶松人工林季相和物候特征,利用Landsat8OLI影像数据提取研究区内5种植被的归一化植被指数(I NDV)、差值植被指数(I DV)、比值植被指数(I RV)、增强型植被指数(I EV),构建相应的植被指数时序特征。采用最大似然和随机森林两种方法对单一时相影像和加入植被指数时序特征的影像进行对比试验。结果表明:影像中加入植被指数时序特征后,最大似然算法的分类总体精度为89.53%,Kappa系数为0.87,比单一时序特征的影像分类精度提高了13.35%;随机森林算法的森林类型分类总体精度为93.22%,Kappa系数为0.92,比单一时序特征的影像分类精度提高了19.8%。因此,加入植被指数时序特征后能得到更高的落叶松人工林提取精度。     

建德市公益林生态系统服务价值评价

对公益林生态系统服务功能和价值评估进行研究,为建德市公益林保护、规划和管理提供科学指导和理论依据。本文依据《生态系统服务功能评估规范》,结合涵养水源、保育土壤等8项指标,评价建德市公益林生态系统服务价值。结果表明,建德市公益林生态系统服务总价值81.64亿元,其中涵养水源效益25.22亿元,固土保肥效益4.43亿元,固碳释氧效益12.53亿元,积累营养效益0.48亿元,森林游憩效益22.19亿元,净化大气效益3.21亿元,生物多样性保护效益12.13亿元,森林防护效益1.45亿元。公益林生态系统服务价值远高于其直接利用价值,表明应继续实施生态补偿政策,努力提高生态补偿标准。     

基于机器学习算法的土壤有机质 质量比估算

为快速高效地估测干旱、半干旱地区土壤有机质(soil organic matter, SOM)质量比,提出了一种结合竞争适应重加权法(CARS)和随机森林(RF)的估测模型.以内陆干旱区艾比湖流域为研究区,测定土壤高光谱反射率和SOM质量比,经预处理后,利用CARS对原始光谱(R)、一阶导数(R′)、吸光度(log(1/R))及吸光度一阶导数［log(1/R)］′4种光谱变量的可见-近红外光谱进行筛选,并结合RF算法,建立全谱段RF模型与CARS-RF模型.结果表明,基于CARS方法对光谱进行变量筛选后,得出4种光谱变量的优选变量集个数分别为35,26,34和121;在4种光谱变量中,R′和［log(1/R)］′的SOM估测模型精度较高,以［log(1/R)］′为基础数据获得的模型精度最高;CARS-RF模型精度优于全谱段RF模型,模型验证集决定系数(R²)、均方根误差(RMSE)、相对分析误差(RPD)分别为0.881,6.438 g/kg和2.177.该研究在预处理的基础上通过变量优选,应用较少的变量个数获得较高的估测精度,为干旱、半干旱区SOM高光谱估测提供了适宜高效的方法.     

Artificial neural network modeling of microbial community structures in the Atlantic Forest of Brazil

Microbial communities vary across the landscape in forest soils, but prediction of their biomass and composition is a difficult challenge due to the large numbers of variables that influence their community structures. Here we examine the use of artificial neural network (ANN) models for extraction of patterns among soil chemical variables and microbial community structures in forest soils from three regions of the Atlantic Forest of Brazil. At each location, variations in soil chemical properties and FAME profiles of microbial community structures were mapped at 20 × 20 m intervals within 10 ha parcels. Geostatistical analyses showed that spatial variability in soil physical and chemical variables could be mapped at scale distances of 20 m, but that FAME profiles representing the microbial communities were highly variable and had no spatial dependence at the same scale in most cases. RDA analysis showed that FAME signatures representing different microbial groups were positively associated with soil pH, OM, P and base cations concentrations, whereas microbial biomass was negatively associated with the same environmental factors. In contrast, ANN models revealed clear relationships between microbial community structures at each parcel location, and generated verifiable predictions of variations in FAME profiles in relation to soil pH, texture, and the relative abundances of base cations. The results suggest that ANN modeling provides a useful approach for describing the relationships between microbial community structures and soil properties in tropical forest soils that were not able to be captured using geostatistical and RDA analyses.     

铲头堆砂白蚁原始繁殖蚁形成的周期

铲头堆砂白蚁Cryptotermes declivis Tsai et Chen是破坏木材及木制品的重要干木白蚁,其有翅成虫通过分飞配对后建立新群体,是其重要繁殖扩散途径。本文对铲头堆砂白蚁原始繁殖蚁形成周期进行了研究。以似桂木Paratocarpus sp.、团花Anthocephalus chinensis(Lam.) Rich. et Walp.和球花豆Parkia sp.作为该种白蚁食料,研究其原始繁殖蚁配对后从新建群体的形成到产生下一代的原始繁殖蚁,完成1个世代生活周期。结果表明,铲头堆砂白蚁在室温下,新建群体的形成、发展、发育至下一代原始繁殖蚁形成的周期约5 a,不同寄主材料对铲头堆砂白蚁生活周期没有显著性影响,但与群体数量多少显著相关。本研究首次明确了铲头堆砂白蚁群体发育成熟的周期,对该害虫的检疫与防控研究具有重要参考价值。     

白三叶与不同禾草混播群落17年稳定性经较研究

在适度放牧条件下开展了白三叶与多年生黑麦草、紫羊茅、草地早熟禾和无芒雀麦的两两豆禾混播群落的种间相容性、群落生产力和稳定性的研究。17年的研究结果表明,白三叶 紫羊茅组合的年均干物质产量502g/m2,显著高于其他组合(P<0.05),但前期以白三叶 多年生黑麦草最高(P<0.05)。在时间序列混播比例的变化上,白三叶逐渐增加,然后维持在一定的范围;多年生黑麦草第1年最高,后逐渐下降;紫羊茅和草地早熟禾变化不大,而无芒雀麦减少最快,并最终消失;白三叶 紫羊茅组合的比例动态变化最小,组分稳定,而且群落抵抗力最强,年均杂草侵入量仅为2.4 g/m2,极显著地低于其他处理(P<0.01)。参试禾本科牧草与白三叶的种间相容性为紫羊茅>多年生黑麦草≥草地早熟禾>无芒雀麦。种间相容性是混播群落长期稳定性的重要决定因素。时间梯度上的群落生产力变化趋势,白三叶 紫羊茅和白三叶 草地早熟禾呈平稳略升,而白三叶 多年生黑麦草和白三叶 无芒雀麦呈前高后低模式。对混播群落稳定性的判断存在时间尺度和空间尺度。     

Protective effect of butylated hydroxylanisole against hydrogen peroxide-induced apoptosis in primary cultured mouse hepatocytes

Butylated hydroxyanisole (BHA) is a synthetic phenolic compound consisting of a mixture of two isomeric organic compounds: 2-tert-butyl-4-hydroxyanisole and 3-tert-butyl-4-hydroxyanisole. We examined the effect of BHA against hydrogen peroxide (H₂O₂)-induced apoptosis in primary cultured mouse hepatocytes. Cell viability was significantly decreased by H₂O₂ in a dose-dependent manner. Additionally, H₂O₂ treatment increased Bax, decreased Bcl-2, and promoted PARP-1 cleavage in a dose-dependent manner. Pretreatment with BHA before exposure to H₂O₂ significantly attenuated the H₂O₂-induced decrease of cell viability. H₂O₂ exposure resulted in an increase of intracellular reactive oxygen species (ROS) generation that was significantly inhibited by pretreatment with BHA or N-acetyl-cysteine (NAC, an ROS scavenger). H₂O₂-induced decrease of cell viability was also attenuated by pretreatment with BHA and NAC. Furthermore, H₂O₂-induced increase of Bax, decrease of Bcl-2, and PARP-1 cleavage was also inhibited by BHA. Taken together, results of this investigation demonstrated that BHA protects primary cultured mouse hepatocytes against H₂O₂-induced apoptosis by inhibiting ROS generation.     

Evaluation of embryonic age and the effects of different proteases on the isolation and primary culture of chicken intestinal epithelial cells in vitro

The present study evaluates the effects of embryonic age and proteolytic enzymes on the isolation and primary culture of chicken enterocyte and to establish an effective technique for chicken intestinal epithelial cell (IEC) cultivation. Fourteen‐day‐old, 16‐day‐old and 18‐day‐old embryos (average weight: 52.23 ± 0.76 g, 50.86 ± 0.99 g, 48.98 ± 1.03 g) were the source for preparation of enterocyte culture, and trypsin‐ethylene diamine tetraacetic acid, collagenase, thermolysin and combination of collagenase and thermolysin were used for digestion medium. Optimal culture protocols were determined by qualitative assays of proliferation. Cells isolated by using 14‐day‐old embryo and collagenase obtain the best attachment and growth in culture, and the production of continuously growing IEC cultures. Thus, we conclude that the use of collagenase as a dissociating enzyme and 14‐day‐old embryo as a source can be advantageously applied to the isolation of chicken IEC and this method may be useful for various applications and basic studies of the intestinal tract concerning such objects as physiology, immunology and toxicology.