景谷县森林蓄积量遥感估测及其动态变化分析

以云南省景谷县为研究区,基于Landsat5和Landsat8遥感数据,利用2012年和2017年两期全国森林资源连续清查实地调查数据,建立多元逐步回归和随机森林模型对景谷县森林蓄积量进行遥感估测对比研究。结果显示:综合建模精度来看,随机森林法在相同样地数量条件下具有更好的估测效果;从估测结果与林地保护利用规划和林地变更数据结果相比较,随机森林法估测值接近真实值,估测精度较高。     

城市池塘水质时间变化特性--以扬州大学江阳路南校区池塘为例

城市中的池塘是城市水体的重要组成部分,为揭示城市化背景下池塘水体水质的时间变化特性,选取扬州大学江阳路南校区池塘为研究区,对该池塘2018年7月至2019年6月的水质参数蓝绿藻浓度(Phyco)、水温(WT)、溶解氧(DO)、pH与电导率(EC)进行观测,采用变异系数法、单因子水质标识指数法以及多元线性回归法对各参数的变化特性进行评价。结果显示:池塘WT呈季节性变化;观测期间pH变化范围为7.74~9.98,水体呈碱性;DO变化的随机性较强,未表现出明显变化规律;各水质参数变异性及权重从大到小依次为WT>DO>EC>pH;以DO为指标的单因子水质标识指数结果表明:池塘DO达到Ⅲ类水要求的时段占总观测时段的84%;多元线性回归分析结果表明:DO与WT、pH呈正相关,与Phyco呈负相关,Phyco及pH的变化对DO浓度的影响相对于WT大。     

Dissolved oxygen controls summer habitat of Clear Lake Hitch (Lavinia exilicauda chi), an imperilled potamodromous cyprinid

Clear Lake Hitch is an imperilled minnow endemic to Clear Lake, Lake County, California, United States listed as threatened under the California Endangered Species Act (ESA) and a candidate for listing under the United States ESA. It exhibits a potamodromous life cycle whereby adults, which reach up to 6 + years in age and over 350 mm in length, migrate into Clear Lake's ephemeral tributaries briefly during spring to spawn. Conservation and management of Clear Lake Hitch is inhibited, in part, by a lack of information on the lacustrine habitat of nonbreeding individuals within Clear Lake. To address this problem, we sampled Clear Lake Hitch with gill nets in a stratified random sampling design to determine the distribution and habitat associations in early summer 2017 and 2018. We identified abundance-habitat relationships for juveniles and adults using Bayesian zero-inflated negative binomial generalised linear mixed modelling. Results indicated that dissolved oxygen concentration was the most important habitat feature measured; juveniles and adults were substantially more abundant in normoxic (≥2 mg/l) than in hypoxic (<2 mg/l) habitat. Both also exhibited weak positive relationships with chlorophyll fluorescence, suggesting relatively productive habitats may support higher numbers of Clear Lake Hitch. Spatially, juveniles were most abundant in nearshore habitats while adults were ubiquitous, indicating an ontogenetic habitat expansion that may be associated with a resource availability-predation risk trade-off. Management actions undertaken to improve hypoxia problems in Clear Lake would also improve Clear Lake Hitch habitat.     

耕地利用视角下全国粮食生产时空特征演变

为综合考虑耕地数量及各项因素对粮食生产的影响,基于对数平均迪式分解方法(LMDI)将影响粮食产量的因素分解为耕地面积、复种指数、种植结构和粮食单产四大因素,研究1996—2016年其对全国粮食产量变化的作用机制。结果表明:1)我国耕地数量持续减少,空间上呈现南部地区减少、北部地区增加的趋势,导致全国粮食产能重心北移。2)粮食单产、复种指数这些技术因素均是促进因素,其中单产提高对总产量提升贡献最大;期间耕地面积下降与种植结构调整则是粮食产量的抑制因素。研究认为,城市化过程中耕地面积减少不可避免,保证粮食安全不但需要严格保护耕地,而且必须强化"藏粮于技"战略实施,不断提高粮食单产与复种指数,以稳定与优化粮食生产。     

不同玉米品种与大豆带状复种模式氮素吸收利用分析

为科学利用大豆的生物固氮作用,筛选玉米大豆带状复种模式下最佳组合,本试验以‘大丰26’(IC1)、‘大丰30’(IC2)、‘强盛51’(IC3)及‘强盛388’(IC4)为实验材料,采用单因素随机区组长期定位试验测得各玉米品种氮素利用及产量数据。结果表明：玉米大豆带状复种模式下玉米产量及地上部生物量均表现为IC2>IC3>IC4>IC1 (P<0.05)。相比IC1、IC3及IC4处理,IC2处理下年平均氮素积累量、氮素农学利用率、氮素生理利用率及氮素偏生产率分别显著增加了10.8%、11.0%、15.3%;17.3%、32.3%、26.2%;36.8%、34.9%、30.1%;18.8%、20.6%、12.5%,而IC2处理年平均氮素收获指数较IC4处理显著降低4.6个百分点(P<0.05);此外,氮素农学利用率、氮素生理利用率、氮素收获指数与产量呈极显著正相关(P<0.05)。综合表明,‘大丰30’与大豆带状复种能够显著提高作物产量及氮素利用率,可作为山西省最优组合推广。     

基于线性混合模型的蓝点马鲛叉长和体重关系的月间及性别差异

为了研究蓝点马鲛（）生活史特征的异质性，根据2018年10月至2019年3月在东海外海渔场的拖网调查采样数据，对其叉长和体重关系的月间及性别差异进行了研究。依据收集的367尾蓝点马鲛样本，求得其叉长和体重关系（b的估计均值为2.794。本研究构建了广义线性模型和9个线性混合模型，用于研究蓝点马鲛的叉长和体重关系（）在时间及性别上的差异。贝叶斯信息准则（BIC）值和均方根误差值均表明，最复杂的线性混合模型（即月份和性别对两个参数P<0.01）。在最优模型中，a值则与此相反。本研究表明，月份和性别对蓝点马鲛叉长和体重关系具有显著的影响，线性混合模型能把月份和性别的异质性通过随机效应在单个模型中更准确、快速地体现，从而进一步证实了此模型在数据来源异质性研究中的优势。     

Development of a linear mixed-effects individual-tree basal area increment model for masson pine in Hunan Province,South-central China

ABSTRACT

An individual-tree basal area increment model was developed for masson pine based on 26276 observations of 13,138 trees in 987 sample plots from the 7th (2004), 8th (2009), and 9th (2014) Chinese National Forest Inventory in Hunan Province, South-central China. The model was built using a linear mixed-effects approach with sample plots included as random effects since the data have a hierarchical stochastic structure and biased estimates of the standard error of parameter estimates could be a consequence of applying ordinary least square (OLS) for regression. In addition, within-plot heteroscedasticity and autocorrelation were also considered. The final mixed-effects model was determined according to the Akaike information criterion (AIC), Bayesian information criterion (BIC), log-likelihood (Loglik), and the likelihoodratio test (LRT). The results revealed that initial diameter (DBH), the sum of the basal area (m²/ha) in trees with DBHs larger than the DBH of the subject tree (BAL), number of trees per hectare (NT), and elevation (EL) had a significant impact on individual-tree basal area increment. The mixed-effects model performed much better than the basic model produced using OLS. Additionally, the variance structure of the model errors was successfully modeled using the power function. However, the autocorrelation structures were not defined because there was no autocorrelation amongst the data. It is believed that the final model will contribute to the scientific management of the masson pine.     

基于高光谱成像技术识别水稻纹枯病

【目的】利用高光谱成像技术对水稻纹枯病进行早期的快速无损识别,结合判别分析方法建立相应的鉴别模型。【方法】以健康和感染纹枯病的水稻幼苗为研究对象,采集叶片和冠层各180个样本的380~1 030 nm波段的360条高光谱图像,剔除明显噪声部分后,以440~943 nm波段作为水稻样本的光谱范围,分别用不同的方法预处理获得水稻叶片的光谱曲线。采用偏最小二乘–判别分析(PLS-DA)对不同预处理的光谱建模。采用MNF算法对冠层的原始光谱数据进行特征信息提取,并基于特征信息建立线性判别分析(LDA)模型和误差反向传播神经网络(BPNN)判别模型。【结果】标准正态变量变换(SNV)预处理后建立的PLS-DA模型的预测集判别正确率最高,为92.1%。基于特征信息的LAD和BPNN模型的判别结果优于基于全波段的PLS-DA判别模型。基于最小噪声分离变换特征信息提取的BPNN模型取得了最优效果,建模集和预测集正确率分别达99.1%和98.4%。【结论】采用高光谱成像技术对水稻纹枯病生理特征进行无损鉴别是可行的,本研究为水稻纹枯病的识别提供了一种新方法。     

Genetic structuring and diversity patterns along rivers – local invasion history of Ambrosia artemisiifolia (Asteraceae) along the Danube River in Vienna (Austria) shows non‐linear pattern

Ambrosia artemisiifolia is an annual weed from North America that nowadays is invasive in many countries worldwide. In Austria, numerous populations of A. artemisiifolia are located along the Danube River, especially along the ‘New Danube’ (Vienna). This area is characterised by ruderal and riparian sites, which are regularly flooded. To better understand the spread of A. artemisiifolia and its colonising behaviour along the Danube River, we analysed genetic structure and diversity based on 23 populations linearly arranged along the Viennese Danube riverbed and upstream, utilising the Amplified Fragment Length Polymorphism (AFLP) fingerprint method. We generated 284 polymorphic AFLP markers across 446 A. artemisiifolia plants. The genetic diversity within populations was higher (HW = 0.091) than among populations (HB = 0.007). This result indicates A. artemisiifolia introductions from similar mixtures of sources or spread from a single already mixed introduction. Within our local setting, we were unable to identify neither source or sink populations nor an obvious linear genetic structuring. Genetic among‐population differentiation was low to moderate (amova ‐derived F_ST = 0.124). Lack of geographical structuring is indicative of highly dynamic gene flow, which is further supported by the absence of an isolation‐by‐distance pattern. Multiple introductions and non‐directional gene flow are most likely promoted by anthropogenic disturbance and human‐mediated dispersal. Our results demonstrate the ability and speed of A. artemisiifolia to settle in newly disturbed areas and the difficulties to predict invasion directions, as downstream river dispersal was negligible.     

长江中游地区水旱复种轮作模式资源利用率比较研究

为了实现农田资源高效利用,维护农业生态良性循环,优化长江中游地区传统种植模式,本研究于2013年10月—2015年11月,以冬闲连作为对照,分析比较了不同水旱复种轮作模式(冬闲-早稻-晚稻→冬闲-早稻-晚稻、马铃薯-玉米‖大豆-晚稻→蔬菜-花生‖玉米-晚稻、蔬菜-花生‖玉米-晚稻→绿肥-早稻-晚稻、绿肥-早稻-晚稻→油菜-花生-晚稻、油菜-花生-晚稻→马铃薯-玉米‖大豆-晚稻)的光、温、水、土资源利用效率。结果表明:水旱复种轮作模式的冬季、晚季和周年的光能利用率均比冬闲连作处理高,周年光能利用率两年间分别高8.26%~82.50%和2.63%~121.42%,其中均以"蔬菜-花生‖玉米-晚稻→绿肥-早稻-晚稻"轮作模式最高。水旱复种轮作模式的年有效积温利用率均高于冬闲连作模式,两年间分别高12.87%~21.26%和11.17%~25.88%,以"蔬菜-花生‖玉米-晚稻→绿肥-早稻-晚稻"轮作模式最佳。两年间水旱复种轮作模式的冬季、晚季和周年的水分利用率均比冬闲连作处理高,其中周年水分利用率分别高45.36%~83.50%和40.00%~118.75%,以"马铃薯-玉米‖大豆-晚稻→蔬菜-花生‖玉米-晚稻"轮作模式的晚季和周年水分利用率最高,"蔬菜-花生‖玉米-晚稻→绿肥-早稻-晚稻"模式的冬季水分利用率最高。两年间土地利用率均以"绿肥-早稻-晚稻"复种模式最高,平均利用率达96.11%,"蔬菜-花生‖玉米-晚稻→绿肥-早稻-晚稻"轮作模式的土地利用率表现最好。因此,各水旱复种轮作模式的周年光能利用率、年有效积温利用率、水分利用率和土地利用率均高于冬闲对照,其中以"蔬菜-花生‖玉米-晚稻→绿肥-早稻-晚稻"和"绿肥-早稻-晚稻→油菜-花生-晚稻"轮作模式表现较好,适宜在长江中游地区推广应用。