种植密度对新疆高产棉花群体光合作用、冠层结构及产量形成的影响

 在新疆气候生态条件下,研究了种植密度对棉花（Gossypium hirsutum）群体光合作用、冠层结构和产量形成的影响,探讨了新疆棉花高产的生理机理及进一步提高产量的途径。结果表明：群体光合速率在盛铃期以前随密度增加明显增强,盛铃期以后,低密度6万株·hm-2的群体光合速率仍为最低,高密度30万株·hm-2群体光合速率迅速下降,中密度18万株·hm-2则保持较高水平。叶面积指数的变化与群体光合速率的变化相似,其峰值出现在盛铃期。冠层结构各指标的变化表现为,随密度增加平均叶簇倾角变大,株型变紧凑,但密度过大,群体散射辐射与直射辐射透过系数小,冠层结构不良,造成生育后期群体光合速率较快下降。增加密度能增加单位面积总铃数,但密度过高削弱了棉株个体发育,生育后期群体光合速率下降早,造成单铃重降低。群体总光合物质累积与群体光合速率在各生育时期呈显著正相关,籽棉产量与群体光合速率仅在盛铃期和吐絮期呈显著正相关;生产上要实现棉花高产及超高产,应使棉花生育前期群体光合速率稳定上升,至盛铃期达到高峰值,吐絮期群体光合速率保持较高水平     

集成高分辨率UAV影像与激光雷达点云的亚热带森林林分特征反演

该研究集成高分辨率无人机(UAV)影像和激光雷达(LiDAR)点云数据估算亚热带天然次生林林分基本特征变量。首先, 基于LiDAR点云和反距离加权插值法构建林下高精度数字高程模型(DEM); 然后利用UAV影像对序列构建植被冠层上层三维点云, 并借助DEM进行高度信息归一化, 提取高度和冠层点云密度相关的特征变量; 最后, 构建预测模型并估算Lorey’s高、林分密度、胸高断面积、蓄积量。结果表明: 联合提取的特征变量与Lorey’s高的敏感性最高, 蓄积量次之, 林分密度和胸高断面积最低; 利用UAV灵活快速的手段获取森林冠层信息, 辅以高精度LiDAR数据获取的地形信息, 两者互补实现一种可重复的快速、廉价和灵活的林分特征的反演方式。     

伏牛山自然保护区森林冠层结构对林下植被特征的影响

在伏牛山自然保护区典型地段设立样方,测定了森林生态系统内几种典型群落类型的冠层结构、光环境特征,调查了林下植被的特征,分析了它们之间的相互关系.结果显示:各群落的冠层结构和光环境有一定的差异,单因素方差分析表明,部分群落间的差异性达到显著水平;各群落灌木层物种丰富度、多样性和均匀度均高于草本层,而优势度正相反;线性拟合的结果表明,草本层的物种丰富度、多样性与冠下光合量子通量密度间呈极显著负相关,优势度与冠下光合量子通量密度间呈显著正相关,灌木层各参数与冠层结构特征间相关性不显著.研究表明,冠层结构的变化对草本层(包括更新幼苗)的影响显著高于灌木层.林隙/林窗或林中空地的出现可能对草本物种或其他阳性及先锋物种具有促进作用,而对优势种幼苗的萌发和定植产生负效应.推测在典型的落叶阔叶林生态系统演替进程中,林下光照强度可能不是最主要的限制因素,优势种种子的扩散、萌发和定植限制可能更重要.     

冠层部位对金叶女贞叶片结构的影响

金叶女贞是一种在园林绿化上广泛应用的彩叶植物,上层叶金黄色,下层叶深绿色。本文利用常规植物制片技术,研究了叶绿素缺少的金叶女贞上层金叶和下层绿叶的解剖结构。结果表明:(1)金叶女贞上层金叶和下层绿叶的上表皮无显著差异,但是下层绿叶的下表皮细胞较小,气孔密度较低;(2)下层绿叶的叶肉组织较薄,细胞较大,排列疏松;(3)在下层绿叶中叶绿体类囊体片层排列密集,叶肉组织内单位体积叶绿体数量较少;(4)冠层部位对光合色素的积累有明显影响。叶绿素缺少的金叶女贞叶片结构显著受到冠层部位的影响,光合色素的变化幅度较一般植物更大,不同冠层部位叶片叶色有明显差异,可以作为研究植物冠层部位对叶形态、结构和生理生化影响的好材料。     

沿海基干林带结构调控对林分冠层结构参数及林地土壤的影响

以上海浦东沿海水杉基干林带为研究对象,分析水杉林分间伐以及间伐后林下套种其他树种构建复层林2种结构调控措施下林分冠层及林地土壤的变化。结果表明:间伐和复层林构建可显著促进上层乔木树高和胸径的生长,也有助于林下乔灌木和草本植物的发育;未间伐水杉林带LAI最高,其次为复层林带,间伐林分最低。各林分林隙分数的分布特征与LAI相反;3种林分土壤全N、全P和速效K含量差异不显著,而间伐林和复层林土壤速效P、水解N和有机质含量比未间伐林有进一步改善,但间伐林分和复层林带之间土壤养分状况没有显著差异;林分结构调控增加了0～50cm土壤有机碳储量,其中以0～15cm土层有机碳密度最高。复层林带和间伐林土壤呼吸速率比未间伐林分别提高了42%和33%。     

水稻冠层结构变化对二向反射率的影响

通过对植被二向反射特性的研究,可反演植被冠层结构信息,如叶面积指数、平均叶角、株高、覆盖率等。在大田晚稻（秀水63）移栽后第26、35、41、49、62、67和86d,对水稻冠层结构及二向反射率进行实测,并分析了二向反射率随冠层结构变化规律,结果表明,植被冠层二向反射率对入射角与观测角的敏感性随着植被冠层结构的变化而变化,蕴涵着丰富的植被结构信息。     

关帝山云杉次生林冠层结构对天然更新的影响

冠层结构和林下光环境对天然更新苗的分布和生长具有重要的作用。本研究以关帝山云杉次生林天然更新苗为对象,利用单因素方差分析和泊松相关性检验,分析冠层结构对天然更新苗的影响。结果表明：在林冠开度(CO)为19.5%～24.5%、林下散射光指数为4～5时天然更新株数最多;最适的CO、林下直射光和林下总光照表现为幼苗大于幼树,而最适叶面积指数则幼苗小于幼树;冠层结构及林下光照对于幼苗的生长相关性不显著。幼苗和幼树对于林下光环境有着不同的适应区间,不同密度的更新苗样地间叶面积指数和林下光照存在显著差异,研究结果为理解该地区林分天然更新提供科学依据。     

夏季栾树群落冠层结构对其环境温湿度的调节作用

为探究栾树群落降温增湿作用与其冠层结构参数的相关性在一天中的变化趋势,于天气晴朗的夏季对北京奥林匹克森林公园栾树群落内部和对照点的温度、相对湿度、群落冠层结构参数进行了铡定.结果表明:栾树群落的郁闭度与叶面积指数、平均叶倾角呈显著相关,且叶面积指数与平均叶倾角呈显著相关;在夏季8:00-18:00,栾树群落可降低空气温度0.43～7.53℃,在12:00左右达到降温最大值,增加相对湿度1％ ～ 22％,且在10:00左右增湿作用最显著,而在18:00-次日8:00降温增湿效果不明显;9:00-12:00,郁闭度和叶面积指数显著影响栾树群落的降温增湿作用;12:00-14:00,仅郁闭度与降温增湿作用显著相关;直到18:00,郁闭度和叶面积指数共同决定了栾树群落的降温增湿作用.因此,影响栾树群落降温增湿作用的冠层结构参数在一天中随着时间的推移发生变化.     

新冠疫情对全球生物多样性热点地区森林面积的影响

森林是维持生物多样性的重要保障,森林面积的损失常常会导致区域生物多样性的降低或丧失。为探讨新冠疫情对全球生物多样性的影响,该文利用Image J软件筛选出全球生物多样性热点地区占国土面积超60%的国家作为研究对象,以全球生物多样性热点地区的森林损失面积、生物多样性完整性数据、年度(2020年和2021年)新冠疫情感染数据、国内生产总值(GDP)为研究对象,进行关联分析、线性混合效应模型构建和回归预测。结果表明:虽然新冠病毒的每百万人口感染数量与森林损失面积表现为显著负相关,具体表现为新冠疫情显著减少了因城市和农业大规模扩张而导致的森林损失面积,但在新冠疫情暴发的2年(2020年和2021年)期间,全球生物多样性热点地区的森林损失总量仍然持续上升,主要原因是新冠疫情间接加速了人工林和天然林的采伐。回归模型预测显示,新冠疫情期间,全球生物多样性热点地区的森林损失面积在2020年和2021年分别增加了5.83%和21.78%。综上表明,虽然新冠疫情对生物多样性热点地区的森林损失具有一定的抑制作用,但森林损失面积仍然在增加。该研究结果为制定生物多样性的保护措施提供了数据支撑。     

水平结构配置对冬小麦冠层垂直结构、微环境及产量的影响

作物的冠层结构是影响产量的重要因素,群体微环境反映了作物冠层内小气候的变化,与作物的冠层结构及产量形成密切相关。该研究在大田试验条件下,设置等行距(R₁,20 cm+20 cm)、宽窄行(R₂,12 cm+12 cm+12 cm+24 cm)两种不同行距和低(D₁,120.0 kg·hm^–2)、中(D₂,157.5 kg·hm^–2)、高(D₃,195.0 kg·hm^–2) 3个播量配置组合,分析了不同处理组合下冬小麦(Triticum aestivum)生育后期冠层垂直结构、群体微环境及产量表现,旨在优化小麦绿色栽培措施,在不增加水肥投入情况下,挖掘冬小麦的生产潜力和进一步增产的可能性和可行性。结果表明:冬小麦上、中、下3个层次冠层开度(DIFN)、平均叶倾角(MLA)及叶面积指数(LAI)均表现为R₂大于R₁,且R₂行距上层和中层DIFN、各层次...     

不同林分郁闭度与遥感数据的相关性

林分郁闭度与遥感数据的相关性分析是郁闭度遥感估算的基础,郁闭度遥感是林业遥感的重要方向。以四川省石棉县为例,就不同林分探讨了其郁闭度与陆地资源卫星专题制图仪LANDSAT Thematic Mapper(TM,包括其波段1至7,分别表示为TM1、TM2、TM3、TM4、TM5、TM6和TM7)数据之间的相关性及其受地形校正的影响。建立了地形数据库和基于1994年调查数据的森林资源数据库;对1994年6月26日成像的LANDSAT TM数据进行了几何校正,并与森林资源数据库配准;分别利用Lambert Cosine Correction(LCC)模型和Sun Canopy Sensor(SCS)模型对TM数据进行地形校正,生成TM-LCC和TM-SCS数据;将TM、TM-LCC和TM-SCS各波段数据分别与森林资源数据叠加统计,得到各小班TM、TM-LCC和TM-SCS各波段数据的均值和标准差,并将其添入数据库中,选取标准差较小的小班共1194个作为样本。按优势树种将样本层化为8个林分层,分别计算其郁闭度与TM、TM-LCC和TM-SCS各波段数据间的相关系数,并分析其在不同林分不同波段上的差异及其受地形校正的影响。研究表明:铁杉、冷杉和云杉等林分郁闭度与TM部分波段数据的相关性在0.01的水平上均为显著;而桦木、栎类、桤木、软阔类和云南松等林分郁闭度与TM数据的相关性在0.05的水平上均不显著;TM的LCC校正提高了冷杉、铁杉和软阔等林分郁闭度与TM4和TM5的相关性,TM的LCC校正还提高了软阔类林分郁闭度与TM7的相关性,TM的SCS校正提高了冷杉林分郁闭度与TM4和TM5的相关性,且在0.01的水平上均为显著。TM的LCC和SCS校正未能明显提高桦木、栎类、桤木、云南松和云杉等林分郁闭度与TM数据的相关性。该研究对林分郁闭度遥感具有一定的科学意义和应用价值。     

Pervasive canopy dynamics produce short-term stability in a tropical rain forest landscape

A fundamental property of all forest landscapes is the size frequency distribution of canopy gap disturbances. But characterizing forest structure and changes at large spatial scales has been challenging and most of our understanding is from permanent inventory plots. Here we report the first application of light detection and ranging remote sensing to measurements of canopy disturbance and regeneration in an old-growth tropical rain forest landscape. Pervasive local height changes figure prominently in the dynamics of this forest. Although most canopy gaps recruited to higher positions during 8.5 years, size frequency distributions were similar at two points in time and well-predicted by power-laws. At larger spatial scales (hundreds of ha), height increases and decreases occurred with similar frequency and changes to canopy height that were analysed using a height transition matrix suggest that the distribution of canopy height at the beginning of the study was close to the projected steady-state equilibrium under the recent disturbance regime. Taken together, these findings show how widespread local height changes can produce short-term stability in a tropical rain forest landscape.     

基于机载激光雷达的中亚热带常绿阔叶林林窗特征

机载激光雷达(LiDAR)是一种新型主动式遥感技术,能直接获取多尺度高精度的冠层三维结构信息,将其推广到森林干扰生态学领域,可为林窗研究提供应用支撑.以湖南中亚热带常绿阔叶林为研究对象,利用小光斑LiDAR数据进行林窗识别和几何特征估测.选择合适的分辨率和内插方法生成冠层高程模型,采用计算机图形学方法估测林窗面积、边界木高度和形状指数,并进行野外观测验证.结果表明: 林窗识别率为94.8%,主要影响因素是林窗面积和林窗形成木类型;估测的林窗面积和边界木高与野外观测值呈较强线性相关,R²值分别为0.962和0.878,其中估测的林窗面积平均比野外观测值高19.9%,估测的林窗边界木高度平均比野外观测值低9.9%;区域内林窗密度为12.8个·hm^-2,占森林面积13.3%;林窗面积、边界木高和形状指数的平均值分别为85.06 m²、15.33 m和1.71,区域内多为较小面积、边缘效应不太显著的林窗.
     

Linking canopy leaf area and light environments with tree size distributions to explain Amazon forest demography

Forest biophysical structure – the arrangement and frequency of leaves and stems – emerges from growth, mortality and space filling dynamics, and may also influence those dynamics by structuring light environments. To investigate this interaction, we developed models that could use LiDAR remote sensing to link leaf area profiles with tree size distributions, comparing models which did not (metabolic scaling theory) and did allow light to influence this link. We found that a light environment‐to‐structure link was necessary to accurately simulate tree size distributions and canopy structure in two contrasting Amazon forests. Partitioning leaf area profiles into size‐class components, we found that demographic rates were related to variation in light absorption, with mortality increasing relative to growth in higher light, consistent with a light environment feedback to size distributions. Combining LiDAR with models linking forest structure and demography offers a high‐throughput approach to advance theory and investigate climate‐relevant tropical forest change.     

Estimating below‐canopy light regimes using airborne laser scanning: An application to plant community analysis

Light is a key driver of forest biodiversity and functioning. Light regimes beneath tree canopies are mainly driven by the solar angle, topography, and vegetation structure, whose three‐dimensional complexity creates heterogeneous light conditions that are challenging to quantify, especially across large areas. Remotely sensed canopy structure data from airborne laser scanning (ALS) provide outstanding opportunities for advancement in this respect. We used ALS point clouds and a digital terrain model to produce hemispherical photographs from which we derived indices of nondirectional diffuse skylight and direct sunlight reaching the understory. We validated our approach by comparing the performance of these indices, as well as canopy closure (CCl) and canopy cover (CCo), for explaining the light conditions experienced by forest plant communities, as indicated by the Landolt indicator values for light (L_light) from 43 vegetation surveys along an elevational gradient. We applied variation partitioning to analyze how the independent and joint statistical effects of light, macroclimate, and soil on the spatial variation in plant species composition (i.e., turnover, Simpson dissimilarity, β_SIM) depend on light approximation methodology. Diffuse light explained L_light best, followed by direct light, CCl and CCo (R² = .31, .23, .22, and .22, respectively). The combination of diffuse and direct light improved the model performance for β_SIM compared with CCl and CCo (R² = .30, .27 and .24, respectively). The independent effect of macroclimate on β_SIM dropped from an R² of .15 to .10 when diffuse light and direct light were included. The ALS methods presented here outperform conventional approximations of below‐canopy light conditions, which can now efficiently be quantified along entire horizontal and vertical forest gradients, even in topographically complex environments such as mountains. The effect of macroclimate on forest plant communities is prone to be overestimated if local light regimes and associated microclimates are not accurately accounted for.     

Logging leaves a fingerprint on the number,size, spatial configuration and geometry of tropical forest canopy gaps

Recent advances in remote sensing such as airborne laser scanning have revolutionized our ability to accurately map forest canopy gaps, with huge implications for tracking forest dynamics at scale. However, few studies have explored how canopy gaps vary among forests at different successional stages following disturbances, such as those caused by logging. Moreover, most studies have focused exclusively on the size distribution of gaps, ignoring other key features such as their spatial distribution and shape. Here, we test a series of hypotheses about how the number, size, spatial configuration, and geometry of gaps vary across a logging disturbance gradient in Malaysian Borneo. As predicted, we found that recently logged forests had much higher gap fraction compared to old-growth forests, a result of having both a greater total number of gaps and a higher proportion of large gaps. Regrowing forests, on the other hand, fell at the opposite end of the spectrum, being characterized by both fewer and smaller gaps compared to nearby old-growth forests. Across all successional stages gaps were found to be spatially clustered. However, logging significantly diluted the degree of spatial aggregation and led to the formation of gaps with much more complex geometries. Our results showcase how logging and subsequent regrowth substantially alter not just the number and size of gaps in a forest, but also their spatial arrangement and shape. Linking these emergent patterns to their underlying processes is key to better understanding the impacts of human disturbance on the structure and function of tropical forests.     

山西灵空山天然松栎混交林群落特征与冠层结构

以2011年建设的山西灵空山4 hm²天然松栎混交林森林动态监测样地为研究平台,以400个10 m×10 m样方为测量单元,于2016年进行群落特征研究,采用半球面影像法(DHP)分析冠层结构和林下光照特征.结果表明: 样地内共有乔木5558株,共计25种,分属于10科15属.冠层开阔度(CO)集中在15.0%～25.0%,叶面积指数(LAI)集中在1.5～2.5,林下光环境参数集中在10.0%～30.0%.建群种在样地内的分布对冠层结构和林下光环境影响显著;冠层结构对林下光环境所有参数的影响方向一致,其中采用叶面积指数评价冠层结构动态的效果更佳;冠层开阔度和叶面积指数对林下光环境产生相反的影响,且均对散射光入射率影响程度最大.温性松栎混交林的林冠层整体较为均匀,林下光分布较为集中,林分树种组成与冠层结构对林下光照影响显著.     

Influence of forest structure on density and nest success of mature forest birds in managed landscapes

Managing for forest wildlife requires attention not only to quantity but quality of forests within the landscape. We examined the extent to which local structural attributes and landscape context of forest stands explained variation in density and reproductive success of mature forest birds across 12 sites in southeast Ohio, USA, 2004–2006. Results suggest that several structural characteristics influenced bird–habitat relationships in our study. Densities of 3 songbird species (i.e., ovenbird [Seiurus aurocapilla], cerulean warbler [Setophaga cerulea], and scarlet tanager [Piranga olivacea]) were positively related to canopy openness, which is usually a function of canopy gaps. Habitat attributes described by ground litter, understory density, and canopy height were positively associated with densities of ground (i.e., worm-eating warbler [Helmitheros vermivorum]), or shrub nesting species (i.e., Kentucky and hooded warblers [Geothlypis formosa and Setophaga citrina], respectively). Furthermore, the number of small trees likely drove the positive relationship between density of wood thrush (Hylocichla mustelina), a subcanopy nester. After accounting for temporal variability in daily nest survival rates, the odds of nest survival for all species increased 10.5% for every 1% increase in canopy openness and decreased 1.4% for each 5% increase in understory vegetation density. Habitat–nest survival relationships were not apparent at the level of the individual species. Our results suggest that structural attributes produced by increasing habitat heterogeneity may be necessary for conservation of forest bird communities. © 2012 The Wildlife Society.     

Topography shapes the structure,composition and function of tropical forest landscapes

Topography is a key driver of tropical forest structure and composition, as it constrains local nutrient and hydraulic conditions within which trees grow. Yet, we do not fully understand how changes in forest physiognomy driven by topography impact other emergent properties of forests, such as their aboveground carbon density (ACD). Working in Borneo – at a site where 70‐m‐tall forests in alluvial valleys rapidly transition to stunted heath forests on nutrient‐depleted dip slopes – we combined field data with airborne laser scanning and hyperspectral imaging to characterise how topography shapes the vertical structure, wood density, diversity and ACD of nearly 15 km² of old‐growth forest. We found that subtle differences in elevation – which control soil chemistry and hydrology – profoundly influenced the structure, composition and diversity of the canopy. Capturing these processes was critical to explaining landscape‐scale heterogeneity in ACD, highlighting how emerging remote sensing technologies can provide new insights into long‐standing ecological questions.     

广东省2004—2016年植被冠层降雨截留模拟及时空变化特征

评价植被冠层降雨截留能力,是生态系统水循环的重要研究内容。以广东省中小流域为例,结合地面监测站点的降雨量数据和MODIS叶面积指数遥感数据,利用植被冠层降雨截留模型,定量模拟和分析了广东省流域尺度2004—2016年的地表植被冠层降雨截留能力及其时空变化特征。结果表明:(1)2004—2012年广东省年均植被冠层降雨截留率持续下降,2016年略有上升,并且随着时间的推移,流域之间的植被冠层降雨截留率差异越来越小。(2)广东省植被冠层降雨截留能力呈现山区东西两翼高,山区中部以及沿海地区低的显著空间差异格局,这种空间格局与植被覆盖LAI主要呈现由珠三角向外围递增的圈层空间格局特征密切相关,而与由南向北逐渐递减的降雨空间格局特征相关性不大。(3)森林覆盖对流域植被冠层降雨截留能力有着一定的影响,其中流域内阔叶林占森林面积的比例对这种影响的程度起着最为关键的作用。