基于空地协同采样的植被覆盖度随机森林估算方法

基于无人机高光谱影像, 建立地形复杂地区植被覆盖度的非参数随机森林回归估算模型。为获得构建随机森林模型所需的足够数量的训练样本, 利用低空无人机搭载的光学相机, 在从地面难以到达的山地、水域和植被茂密区, 通过垂直拍摄获得厘米分辨率的航拍影像, 作为对地面样方采样的补充。首先计算地面数码相机照片和无人机可见光影像的红绿蓝植被指数(red-green-blue vegetation index, RGBVI), 然后使用大津分割法提取样方的植被覆盖信息, 得到构建模型所需的训练样本。在此基础上, 基于2018年8月16—18日在内蒙古自治区察右中旗油娄沟矿区获取的GaiaSky-mini2无人机高光谱影像数据, 利用递归特征消除算法优选参与随机森林回归的特征变量集, 利用空地协同获取的训练样本构建植被覆盖度的随机森林回归估算模型。该模型在测试集上的确定系数R2为0.923, 均方根误差为0.087, 优于常用的像元二分模型, 可用于矿区植被动态信息的精细化监测。     

Capybaras (Rodentia: Cavidae) in highlands: environmental variables related to distribution,and herbivory effects on a common plant species

The capybara Hydrochoerus hydrochaeris is one of the largest and most widely distributed herbivores in the Neotropical lowlands. However, as yet, there are no records of its occurrence in highland environments. Our aim was to evaluate the environmental variables related to the capybara’s distribution and monitor the effects of its herbivory on the individuals and on the reproductive phenology of A. polyanthus, a common and important plant species of the high-altitude grasslands. Our results show that capybaras frequently occur in the high-altitude grasslands along the Campo Belo River, but they avoid waterlogged areas, occurring more frequently on the dry rocky areas. Capybara herbivory affected the number of A. polyanthus rosettes in flower, leading to the presence of inflorescence formation anomalies. High-altitude grasslands apparently provide capybaras with the three main components (food, shelter and water) required for their occurrence. However, although they seem to present a seasonal feeding strategy, which also happens in lowlands, their avoidance of the waterlogged areas suggests that in highlands the species may present different environmental preferences from those presented in lowlands. In addition, the impact of capybaras’ herbivory on A. polyanthus individuals indicates the potential impact that capybaras can represent on the plant community of the high-altitude grasslands. This appears to be a great opportunity to study the effect of the arrival of a large herbivore in a new environment and possible impacts on plant assemblages.     

Year-round activity patterns in a hyperdiverse community of rainforest amphibians in Madagascar

Madagascar hosts a high diversity of amphibians estimated at over 500 species, nearly all of them endemic. Surprisingly few data are available on the activity cycles of this fauna, despite its importance for ecological, evolutionary and conservation research. Here we report the results of a year-round survey of amphibians along a transect bordering the Analamazaotra forest near Andasibe in central eastern Madagascar. During 120 transect walks evenly spaced through the year, a total of 2530 individuals of 40 species of anurans was observed. Abundance was higher during the warm/rainy season (December to April) and peaked in February. Of the five climatic predictors measured, only mean temperature and relative humidity showed high importance values, and multi-model averages indicate that these two variables have a strong effect on amphibian abundance along the transect. Species richness showed no evident peak during the study period and was best explained by a model including average temperature and rainfall. Canonical correspondence analysis indicates that Boophis sibilans, B. tephraeomystax, B. boehmei and Plethodontohyla notosticta were more frequently encountered along the transect on cold and humid days while Plethodontohyla mihanika, Gephyromantis boulengeri and Spinomantis aglavei were distinctly more abundant on cold and dry days, and Paradoxophyla palmata on warm and dry days. The results of our study flag a number of species as suitable candidates for future monitoring initiatives and suggest that a simple combination of visual and acoustic surveys can estimate amphibian activity with high sample sizes in Madagascar’s rainforests.     

污染环境下森林发展系统的最优控制

研究了污染环境下一类森林发展系统的最优控制问题。首先,提出所研究的模型并通过Banach不动点定理证明了解的存在唯一性,然后根据凸泛函的性质以及Mazur引理得出最优控制的唯一解。     

水泥窑协同处置生活垃圾的燃烧特性分析优化

针对传统方法难以分析掺烧生活垃圾后的水泥窑复杂燃烧特性的问题,引入数据挖掘技术,以国内某水泥厂为对象,采集相关参数数据,使用稳定性选择算法分析各参数对煤耗与NO_x排量的影响系数,通过随机森林算法建立煤耗与NO_x排量的数学模型,结合K-means聚类算法得出关键优化参数及其最优值。结果表明,该方法能够建立精确的煤耗与NO_x排量模型,挖掘出节能减排的关键优化参数及其最优目标值。通过改善关键优化参数至最优值,能够大大降低煤耗与NO_x排量,可指导水泥厂优化窑内燃烧特性。     

一种自适应谐波叠加的复调音乐主旋律提取新方法

随着音乐数量的迅速增加,对音乐进行数字化的处理已经成为必然趋势.主旋律反映了音乐的主要思想,提取主旋律在制作计算机音乐,检索分类,哼唱识别等领域具有广泛的应用价值.本文提出一种自适应谐波叠加的复调音乐主旋律提取算法.首先,通过声源分离预处理,通过判别基频最小稳定方差改变压缩因子,自适应叠加谐波构建显著函数;然后,对显著函数构建的基频片断采用随机森林模型进行人声检测,组合所有人声帧的最大显著度频率得到音乐的主旋律序列.实验表明,在MIR-1K数据集上得到的结果在高信噪比情况下有显著提升.     

腐烂等级、径级对阔叶红松林木质残体含水率和密度的影响

【目的】含水率和密度是木质残体重要的物理性质。为了更合理地评估森林生态系统养分含量和生产力变化,对阔叶红松林木质残体的含水率和密度进行研究。【方法】以东北典型阔叶红松林中主要树种红松、臭冷杉、枫桦、槭树、椴树、水曲柳、榆树的木质残体为研究对象, 对5个腐烂等级(Ⅰ—Ⅴ)下的3个径级(ⅰ—ⅲ)进行取样, 分析腐烂等级、径级、树种、结构组分(边材、心材)对木质残体含水率、密度的影响。【结果】随腐烂等级的增加, 木质残体含水率显著增加, 密度显著降低; 除腐烂等级Ⅲ和总体木质残体边材密度显著高于心材外, 其余腐烂等级木质残体含水率、密度在边材与心材之间均无显著差异; 除腐烂等级Ⅰ的木质残体心材含水率外, 其余腐烂等级木质残体边材、心材的含水率和密度在部分树种之间均有显著差异。木质残体含水率、密度在径级间均无显著差异; 径级ⅰ的木质残体边材、心材含水率在部分树种间有显著差异, 径级ⅰ、ⅲ的木质残体边材、心材的密度在部分树种间均有显著差异。【结论】受不同因素的影响,阔叶红松林木质残体的含水率、密度有不同的变化规律, 且腐烂等级以及树种是导致木质残体分解过程中引起含水率、密度显著变化的重要因素。     

杨-桤混交林及其凋落物对土壤氮矿化的影响

【目的】研究含氮量中等的立地条件下杨-桤混交林相比于杨树纯林能否增加土壤养分,分析桤木是否为合适的固氮树种,探讨桤木与杨树营造混交林以缓解人工林连栽带来的土地肥力衰退问题。【方法】以苏北地区杨树人工纯林以及杨-桤(1∶1)混交林为研究对象,采用尼龙网袋法观察两种林分下凋落叶质量分解以及养分释放的过程,比较两种凋落物处理(去除凋落物与保留凋落物)对土壤全氮以及碱解氮含量的影响。采用树脂芯田间原位培养法,研究杨-桤混交林与杨树纯林两种林分在两种凋落物处理下,林地土壤氮年净矿化量的变化。【结果】营造杨-桤混交林显著提高了林地土壤全氮和碱解氮含量。杨树纯林凋落物分解时需从周围土壤中吸收更多氮素,且分解速率较慢。杨-桤混交林凋落物分解更快进入氮释放状态,因此去除凋落物后混交林土壤碱解氮显著减少。保留凋落物处理下,杨-桤混交林中每公顷土壤氮年净氨化量显著高于杨树纯林中的,去除凋落物后两者差异不显著。【结论】研究发现,桤木是杨树较合适的伴生树种,营造杨-桤混交林可以起到增加土壤全氮和碱解氮含量的作用,有助于缓解杨树纯林连栽带来的地力下降问题。混交林凋落物分解速率与氮素释放速率更快,有利于人工林生态系统氮循环。保留凋落物处理下,混交林中每公顷土壤氮年净氨化量显著高于杨树纯林的,而每公顷土壤氮年净硝化量没有显著差异,表明混交林凋落物分解释放的氮素主要促进土壤氨化过程,对土壤硝化过程影响较弱。     

不同分解程度木麻黄凋落物的养分特征及微生物功能多样性分析

【目的】通过了解木麻黄凋落物分解过程中的养分变化以及微生物碳源的利用特征,明确凋落物微生物多样性与养分之间的关系。【方法】在海南省海口市桂林洋海滨选取10~15年生木麻黄林,按照“S”形五点取样法,分别采集0~5 cm、≥5~10 cm、≥10~15 cm 等3种不同分解程度的凋落物样品,测定其理化性质,并利用Biolog微孔板法测定凋落物外生菌和内生菌的群落功能多样性,对其进行主成分PCA分析和冗余RDA分析。【结果】①凋落物的分解程度越高,其有机碳、全氮、全磷含量越低。②不同分解程度木麻黄凋落物中外生菌和内生菌功能多样性差异显著,外生菌平均颜色变化率(AWCD)随分解程度增加而增大,而内生菌AWCD则降低。③凋落物分解程度越高,外生菌的Shannon、Simpson指数明显升高,McIntosh指数无显著差异;内生菌的Shannon、Simpson指数也随之增加,而McIntosh指数则明显降低。④外生菌和内生菌对6大类碳源利用强度存在差异,优势碳源分别为糖类和多聚物,分解后期胺类和酚类的利用率均有提高。⑤主成分PCA分析表明,不同分解程度的凋落物外生菌和内生菌对31种碳源的利用均有显著差异;RDA分析表明,碳、氮含量与凋落物外生菌微生物功能多样性指数呈最大相关。【结论】木麻黄凋落物分解程度越大,外生菌碳代谢强度和多样性越高,而内生菌碳代谢强度越低,其多样性越高;凋落物的氮、碳含量是影响凋落物微生物功能多样性的主要因素。因此,外生菌和内生菌在木麻黄凋落物的分解中发挥着不同的作用。