神农架国家级自然保护区川金丝猴栖息地的植物群落分类及特征

采用植物社会学调查方法,对神农架国家级自然保护区川金丝猴栖息地植物群落进行了调查,并对127个植物样方调查资料进行了聚类分析。综合数量分类及植物社会学的分类标准,将神农架川金丝猴栖息地植被划分为13个群丛和4个群落;分析了各群丛的结构特征、地理分布特征(海拔、地形等)以及不同群丛的植物组成和食源植物状况,同时对各群丛乔木层的胸径等级和高度进行了分析。结果表明:群丛Ⅰ(华山松-金佛山箬竹-湖北大戟)、群丛Ⅵ(巴山冷杉+红桦-箭竹+兴山五味子-抱茎风毛菊)、群丛Ⅸ(华山松-鄂西绣线菊-中日金星蕨)以及群丛Ⅻ(巴山冷杉+华山松-鞘柄菝葜+鄂西绣线菊-中日金星蕨)4个群丛所含物种数最多,其中群丛Ⅰ、Ⅵ、Ⅸ所含食源植物种数也最多;群丛Ⅳ(红桦-湖北花楸-离舌橐吾)胸径大于30 cm的树木所占比例及乔木层平均高度均最大;这5个群丛是神农架国家级自然保护区川金丝猴栖息地的主要植被类型。该研究可为神农架国家级自然保护区川金丝猴栖息地的植被保护与恢复提供重要参考。     

神农架天然针阔混交林乔木更新的空间格局

为深入了解神农架天然针阔混交林群落乔木树种的更新特征,于神农架国家公园设置1 hm2森林动态监测样地对树种更新进行调查,利用Ripley的L函数分析优势更新树种的空间分布格局、种间空间关联性以及与大树的空间分布关系。结果显示:(1)更新个体共有35 752株,隶属于19科29属45种。更新优势种基本是乔木层优势树种,物种更新数量表现为:巴山冷杉(Abies fargesii Franch.)华山松(Pinus armandii Franch.)四蕊槭(Acer stachyophyllum subsp. tetramerum (Pax) A. E.)华中山楂(Crataegus wilsonii Sarg.),混交林群落更新良好。(2)随着尺度增加,巴山冷杉、华山松更新空间格局由聚集分布向随机分布和均匀分布发展;华中山楂、四蕊槭更新的空间格局在整个尺度上均为聚集分布,表明针叶、阔叶树种更新在空间生态利用策略上出现分化。(3)巴山冷杉与其余3个优势更新树种、华山松与华中山楂更新呈显著正相关,表现出对微生境的共同喜好;四蕊槭分别与华山松、华中山楂更新的空间关系表现为显著负相关,种间竞争激烈。(4)巴山冷杉、华中山楂、四蕊槭的更新个体与大树的空间分布总体为显著正相关,这可能与种子传播限制相关;华山松幼苗、幼树与大树的空间分布在小尺度上呈负相关,存在资源不对称竞争。     

神农架天然针阔混交林乔木更新的空间格局

为深入了解神农架天然针阔混交林群落乔木树种的更新特征,于神农架国家公园设置1 hm²森林动态监测样地对树种更新进行调查,利用Ripley的L函数分析优势更新树种的空间分布格局、种间空间关联性以及与大树的空间分布关系。结果显示：（1）更新个体共有35 752株,隶属于19科29属45种。更新优势种基本是乔木层优势树种,物种更新数量表现为：巴山冷杉（Abies fargesii Franch.） > 华山松（Pinus armandii Franch.） > 四蕊槭（Acer stachyophyllum subsp.tetramerum（Pax）A.E.） > 华中山楂（Crataegus wilsonii Sarg.）,混交林群落更新良好。（2）随着尺度增加,巴山冷杉、华山松更新空间格局由聚集分布向随机分布和均匀分布发展;华中山楂、四蕊槭更新的空间格局在整个尺度上均为聚集分布,表明针叶、阔叶树种更新在空间生态利用策略上出现分化。（3）巴山冷杉与其余3个优势更新树种、华山松与华中山楂更新呈显著正相关,表现出对微生境的共同喜好;四蕊槭分别与华山松、华中山楂更新的空间关系表现为显著负相关,种间竞争激烈。（4）巴山冷杉、华中山楂、四蕊槭的更新个体与大树的空间分布总体为显著正相关,这可能与种子传播限制相关;华山松幼苗、幼树与大树的空间分布在小尺度上呈负相关,存在资源不对称竞争。     

神农架川金丝猴栖息地森林群落的数量分类与排序

在神农架川金丝猴生境典型地段设立样方58块,根据样方资料对神农架川金丝猴栖息地的森林群落用组平均法分类和DCA排序.用组平均法将58块样地分为9个群系,依据《中国植被》的分类原则和系统将研究区植物群落划归为7个植被型.样地的DCA排序较好地揭示了该区森林群落的分布格局与环境梯度的关系;DCA第二轴明显地反映出森林群落的海拔梯度变化,沿DCA第二轴从右到左,海拔逐渐升高;第一轴表现了各植物群落或植物种所在环境的坡度、坡向,即水分和光照因素,沿第一轴从下到上,坡度渐缓、坡向渐向阳.其中海拔梯度是环境因子中对森林群落起决定性作用的因子.研究表明,巴山冷杉+糙皮桦-大齿槭+尾萼蔷薇-高原露珠草+星果草群系发育较好,高大树木占有较大的比例,是神农架川金丝猴最适宜栖息地.7个植被型物种丰富度指数在群落梯度上呈规律性波动.其中针叶林和针叶-阔叶混交林中,物种丰富度指数在群落梯度上的总体趋势表现为灌木层＞草木层＞乔木层;在常绿阔叶林和常绿-落叶阔叶混交林中,该趋势为灌木层＞乔木层＞草本层;在落叶阔叶林中,其丰富度指数的趋势为灌木层＞草本层和乔木层.不同植被类型川金丝猴食源植物种类在群落梯度上的变化趋势与物种丰富度指数相同,但地衣类植物作为川金丝猴冬季的重要食物只在针叶林和针叶-阔叶混交林中生长.本研究为制定栖息地保护计划,更好地保护神农架川金丝猴提供了科学理论依据.     

太白山巴山冷杉林主要树种与开花秦岭箭竹的空间点格局分析

采用单变量和双变量O-ring函数对太白山大熊猫栖息地巴山冷杉林主要树种的空间分布格局、种间关联性及其与林下开花箭竹的空间关联性进行了多尺度分析.结果表明: 巴山冷杉林中,巴山冷杉数量最多,但种群结构衰退,白桦种群相对年轻,种群结构稳定,红桦种群也呈衰退趋势;3个主要树种在小尺度上呈聚集分布,随尺度增加,逐渐表现为随机分布.3个树种的空间关联性主要表现在小尺度范围内,随尺度增加,空间分布格局逐渐表现为不关联;巴山冷杉和白桦与开花秦岭箭竹在大、中尺度内呈现正相关,而红桦与开花秦岭箭竹在大、中尺度上表现出负相关.大熊猫栖息地内乔木和林下秦岭箭竹共同推动森林的动态演替和发展,进而影响秦岭大熊猫栖息地的环境变化.     

神农架巴山冷杉群落更新特点及影响因素

采用样方法对神农架自然保护区巴山冷杉群落更新特性、环境因子对其更新的影响进行了研究.研究表明:(1)林窗更新是巴山冷杉群落重要的更新方式,以红桦为代表的阔叶树种和巴山冷杉等耐荫树种在林窗内外均存在更新差异;(2)巴山冷杉在林窗更新中具有最大优势,3a以下的巴山冷杉幼苗数量占45.7%,随着年龄的增加下降明显,7a以上的幼树数量只占6.3%;(3)用SPSS将影响巴山冷杉更新的四类环境因子进行主成分分析表明,林窗面积、坡向、林窗微环境、乔灌草盖度依次是影响巴山冷杉幼苗生长和分布的主要因子;(4)林窗微环境因子的相关分析表明,在不同的生活史阶段,更新影响因子重要性不同,光照水平和土壤水分分别对幼苗和幼树的生长具有显著影响;(5)坡向和密度的相关分析表明在北坡巴山冷杉更新幼苗数量丰富,灌草层是巴山冷杉更新过程的潜在障碍.     

神农架川金丝猴栖息地优势树种生态位及食源植物

该文采用定量分析法, 研究了湖北神农架千家坪地区川金丝猴 (Rhinopithecus roxellana) 现生栖息地优势树种的生态位宽度、生态位重叠和生态位相似比例, 分析了优势树种生态位对神农架川金丝猴生存的影响。结果如下:1) 在64000m2的样方中, 木本植物255种, 隶属于44科105属, 其中乔木23科51属129种, 灌木22科49属113种, 木质藤本7科9属13种。优势科主要有蔷薇科、樟科、槭树科、忍冬科、壳斗科和四照花科等。2) 生态位宽度在栖息地森林群落乔木层中最高的为红桦 (Betula albo-sinensis) (5.261), 华山松 (Pinus armandii) (4.545) 、巴山冷杉 (Abiesfargesii) (4.289) 和糙皮桦 (Betula utilis) (3.256) 次之;灌木层中最高的为红晕杜鹃 (Rhododendron erubescens) (2.245), 多枝柳 (Salixpolyclona) (2.064) 、华中山楂 (Crataegus wilsonii) (1.508) 和陇东海棠 (Malus kansuensis) (1.453) 次之。3) 主要树种生态位宽度大于1的有30种, 占总数的11.67%, 其中21种是川金丝猴食源植物, 占神农架川金丝猴食源植物总数的10.40%;重要值排名前25位的树种中, 18种为食源植物, 占重要值总和的74.50%。4) 优势种的生态位重叠值在0.4以上的有7对种群;大部分种群的生态位相似性比值在0~0.3之间, 占全部种对的83.82%。结果表明, 神农架川金丝猴栖息地植物组成复杂, 优势种多为食源植物;优势种的生境高度相似、生态位多有重叠、种间竞争较为激烈, 将导致现有栖息地森林群落结构及植物组成发生变化, 食源植物短缺, 甚至栖息地面积缩减等现象, 这些都会影响川金丝猴的生存。因此, 加强保护神农架千家坪川金丝猴现生栖息地森林为川金丝猴创造适宜生存空间迫在眉睫。     

基于阈值法的山区森林常绿、落叶特征遥感自动识别方法——以贡嘎山地区为例

森林的常绿、落叶特征是土地覆被产品的重要属性。由于山区地形复杂,地表遥感辐射信号地形效应明显,导致山区森林常绿、落叶特征遥感自动识别一直是难点。提出了一种基于阈值法的山区森林常绿、落叶特征遥感自动识别简单实用方法。该方法利用多源、多时相遥感影像,选择归一化植被指数(NDVI)为指标,通过统计参考样本的NDVI在生长季和非生长季的差异,自动找出区分常绿、落叶特征的阈值,基于判别规则识别山区森林常绿、落叶特征。以贡嘎山地区为例,分别以多时相Landsat TM影像(简称TM)、多时相环境减灾卫星影像(简称HJ)为单源数据,多时相的HJ、TM组合影像为多源数据,验证该方法的有效性。实验结果表明,该方法能够有效识别山区森林常绿、落叶特征,总体精度达到93.87%,Kappa系数为0.87。该方法适用于山区大面积森林常绿、落叶特征遥感自动提取,已被成功应用于"生态十年"专项西南地区土地覆被数据的生产。     

神农架世界自然遗产地川金丝猴通道设计

旅游公路会带来野生动物致死、生境破碎化、栖息地丧失、基因隔离等一系列生态问题。设计和修建跨公路的野生动物通道作为缓解旅游公路负面效应的一种有效途径。野生动物通道在国外研究较多, 但在我国实际案例较少。作者针对湖北神农架世界自然遗产国家一级保护动物川金丝猴(Rhinopithecus roxellana)被旅游公路隔离的生态问题, 通过实地考察和分析该物种的长期监测结果, 构建了跨公路动物通道的设计方案。神农架川金丝猴通道主要技术参数为: (1) 在遗产地的大龙潭和小龙潭各建川金丝猴上跨式通道1 座, 宽度以80 m 为宜; (2) 通道上铺设土壤, 厚度2.2 m-2.4 m; (3) 通道上种植巴山冷杉(Abies fargesii)、长松萝(Usnea longissimi)、红桦(Betula albosinensis)、千金榆(Carpinus cordata)、猫儿屎(Decaisnea insignis)、米心水青冈(Fagus engleriana)等川金丝猴喜食的植物, 培育形成郁闭度0.7-0.8 的针阔混交林; (4) 在通道入口和中部设立红外监测系统, 并对监测数据进行自动实时传输与分析; (5) 完善配套设施建设, 如在通道入口两侧设立高2.4 m 的栅栏、通道两侧设立有藤蔓植物覆盖的生态保护墙、树立“注意野生动物”、“前方有野生动物通道”警示牌等。通道建成后, 须加强通道维护管理、持续开展科研监测、积极宣传保护理念, 以期实现川金丝猴通道功能高效持久的发挥。     

海南岛尖峰岭12种热带常绿阔叶乔木展叶期与开花期对气候变化的响应

为了探讨我国热带地区植物物候与气候变化的关系, 利用海南岛尖峰岭热带树木园12种热带常绿阔叶乔木植物2003-2011年物候观测资料结合同期月平均气温和降水数据, 运用积分回归分析方法, 筛选出影响海南岛12种乔木(8种本地种、4种引入种)展叶始期与开花始期的气象因素以及不同气象因素月值变化(月平均气温和月降水量)综合作用对这些树种物候期的动态影响, 最终建立积分回归-物候预测模型, 对气候变化背景下我国热带地区植物物候变化趋势进行了预测。结果表明: 海南岛12种热带常绿阔叶乔木展叶始期与开花始期均对气候变化做出较明显的响应, 几乎所有的树种展叶始期与开花始期的发生都受到气温和降水的共同影响。多数树种展叶始期受展叶前冬季及春季气温影响显著, 且在临近展叶始期的月份, 气温的影响更显著。上一年秋季月降水量对各树种开花始期的影响比其他时段显著, 这验证了降水的滞后性假说。本地种展叶始期对气候变化的响应比其开花始期对气候变化的响应更敏感, 引入种则相反。各树种展叶和开花在受气温和降水综合影响最明显的月份(假设其余11个月份月平均气温和月降水量不变), 月平均气温升高0.1 ℃、月降水量增加10 mm可使展叶始期和开花始期提前或推迟1-3天。积分回归分析方法为解释海南岛热带常绿阔叶乔木物候与气温和降水的动态关系提供了有效的途径, 基于气温和降水与物候资料建立的积分回归-物候预测模型具有对气温和降水变化影响下物候响应的解释率和预测精度高(R²≥ 0.943)的优点, 对于预测气候变化影响下的植物物候变化趋势有一定的适用性。     

Winter Feeding Tree Choice in Sichuan Snub-Nosed Monkeys (Rhinopithecus roxellanae) in Shennongjia Nature Reserve,China

We investigated patterns of winter feeding tree choice in 4 groups of Sichuan snub-nosed monkeys (Rhinopithecus roxellanae) in Shennongjia Nature Reserve, China. We collected data during 2 winters from 1998 to 2000. The monkeys used mature forest, young forest and shrub forest, but not grassland. Groups used tree species in a significantly nonrandom pattern. There was a similar composition of preferred tree species between different habitats for each group and among the same habitat types for different groups. They preferred Abies fargesii, Pinus armandii and Salix walliciana for foraging. The 3 species occur in varying degrees of abundance in different habitats and were used differently by the 4 groups. The difference is probably due to interhabitat differences in availability of tree species, in addition to microclimate. The mean circumference of a tree had little effect on its preference score, but preferred species tend to be larger. A Wilcoxon signed-rank test indicated that the percentage of trees used and average number of feeding bites per tree is significantly greater for larger trees. For all trees in a given habitat, the percentage of trees used and average number of bites per tree have a significant positive correlation with average tree circumference. Our results indicate that Rhinopithecus roxellanae prefer to feed in large trees more than small trees in a given habitat, thereby preferring mature forest habitat. There is also a group-size effect; larger groups used higher-quality habitats than those of smaller groups. Both tree species and size are the major determinants of feeding choice, but tree species is more important than tree size. Our results have at least three implications for winter habitat conservation of Sichuan snub-nosed monkeys. Conservation efforts should be focused on mature forest because it is better habitat at Rhinopithecus than young forest, as long as the same tree species are present. Secondly, Pinus armandii, Abies fargesii and Salix walliciana should be conserved as top priority in forest communities. Third, the largest trees in each habitat should be given greatest possible protection.     

川西不同树种人工林对土壤涵水能力的影响

为评价青藏高原东缘不同树种造林对土壤涵水能力的影响,选择立地条件与营林方式相同的4种人工林(连香树(Cercidiphyllum japonicum)、油松(Pinus tabulaeformis)、落叶松(Larix kaempferi)和华山松(Pinus armandii))为研究对象,以落叶阔叶灌丛为对照,比较造林恢复28 a后不同人工林土壤孔隙度及持水性的变化,结合林地凋落物贮量及细根生物量等参数,试图揭示造成不同人工林地土壤涵水能力及潜力差异化的因素。结果显示:营造油松和华山松纯林不仅没能有效改善土壤孔隙状况,反而加剧了土壤涵水功能的退化。相反,连香树和落叶松在代替次生落叶灌丛造林后,土壤容重显著下降,孔隙度增加且小孔隙比例升高,持蓄水能力提高。凋落物及细根特性是不同林地土壤持水性能差异的重要因素。综合分析表明,在对退化生态系统进行造林恢复时,应尽量避免营造高密度针叶纯林,应结合种植有助于土壤结构改良的落叶或阔叶树种。     

Inter-species variation of photosynthetic and xylem hydraulic traits in the deciduous and evergreen Euphorbiaceae tree species from a seasonally tropical forest in south-western China

The objective of the present study was to examine the functional coordination among hydraulic traits, xylem characteristics and gas exchange rates across three deciduous Euphorbiaceae tree species (Hevea brasiliensis, Macaranga denticulata and Bischofia javanica) and three evergreen Euphorbiaceae tree species (Drypetes indica, Aleurites moluccana and Codiaeum variegatum) from a seasonally tropical forest in south-western China. The deciduous tree species were more vulnerable to water stress-induced embolism than the evergreen tree species. However, the deciduous tree species generally had higher maximal rates of sapwood and leaf-specific hydraulic conductivity (K _S and K _L), respectively. Compared with the evergreen tree species, the deciduous tree species, however, possessed a lower density of sapwood and a wider diameter of xylem vessels. Regardless of leaf phenology, the hydraulic vulnerability and conductivity were significantly correlated with sapwood density and mean vessel diameter. Furthermore, the hydraulic vulnerability was positively correlated with water transport efficiency. In addition, the deciduous tree species exhibited higher maximal photosynthetic rates (A _max) and stomatal conductance (g _max), but lower water use efficiency (WUE). Interestingly, the A _max, g _max and WUE were strongly correlated with K _S and K _L across the deciduous and evergreen tree species. These results suggest that xylem structure, rather than leaf phenology, accounts for the difference in hydraulic traits between the deciduous tree species and the evergreen tree species. Meanwhile, our results show that there is a significant trade-off between hydraulic efficiency and safety, and a strong functional correlation between the hydraulic capacity and gas exchange rates across the deciduous and evergreen tree species.     

基于树木年轮定量重建过去50年贵州典型森林优势树种的地上生物量与生产力变化

利用树木年轮宽度结合树木生物量方程,重建了贵州3个地区典型森林(2个常绿与落叶阔叶混交林和1个典型常绿阔叶林)6个优势树种(天龙山:化香树Platycarya strobilacea、安顺润楠Machilus cavaleriei;茂兰:化香树、马尾松Pinus massoniana;雷公山:华山松Pinus armandii、白梓树Pterostyrax psilophyllus)以树木个体为单元的地上生物量(AGB)与地上净初级生产力(ANPP);比较了喀斯特与非喀斯特地区树木AGB与ANPP的差异;并研究了近50年气候变化对ANPP的影响。结果显示,针叶树的平均年轮宽度大于阔叶树,喀斯特地区针叶树和阔叶树的平均树木年轮宽度,分别小于非喀斯特地区针叶树和阔叶树的平均树木年轮宽度。喀斯特地区树木的AGB及其变异幅度均小于非喀斯特地区树木。近50年来,喀斯特地区阔叶树与针叶树的ANPP平均分别为(2.4±1.2) kg a~(-1)株~(-1)和(4.6±4.1) kg a~(-1)株~(-1),显著低于非喀斯特地区阔叶树与针叶树的(5.6±4.8) kg a~(-1)株~(-1)和(12.4±7.7) kg a~(-1)株~(-1)。喀斯特地区树木ANPP的增长趋势与年均温的相关性高于生长季降水,非喀斯特地区树木ANPP与年均温和生长季降水均显著相关,且不管是在喀斯特还是在非喀斯特地区,针叶树ANPP对气候指标的变化比阔叶树更敏感。     

Degree of Humification in Fresh Litter from a Subtropical Mixed Plantation Forest in Southwest China

The humification degree of fresh litter directly controls the accumulation of soil humus derived from plant litter, but very little information on this process is available. Planted forests are well known to restrict soil fertility, which is often indicated by the soil humus level. In this study, fresh litter was collected during different plant phenological stages during 2016 and 2017 in a mixed plantation in Southwest China. The values of hue coefficient ΔlogK (absorbance ratio of 400 nm and 600 nm on a logarithmic scale), optical density E4/E6 (absorbance ratio of 400 nm and 600 nm) and A600/C (absorbance at 600 mm per mg of carbon per ml of extraction) and the concentration of extractable humus carbon (HC) were determined in four litter components (foliar, twigs, reproductive organs and miscellaneous) of the dominant species (Pterocarya stenoptera, Quercus acutissima, Cunninghamia lanceolata and Toxicodendron vernicifluum). All of the litter components exhibited obvious humification characteristics, and showed the highest concentration of extractable HC during the leaf maturation period. The miscellaneous and foliar litters showed greater humification than the other litter types. The components of Pterocarya stenoptera litter exhibited greater degrees of humification than those of the other species, with lower ΔlogK and E4/E6 values and higher A600/C values. The litter from coniferous and evergreen species showed lower humification than that from broad-leaf and deciduous species regardless of the litter component examined. The present results provide new insights into the management of plantations and theoretical data to accurately improve the quality of plantations and maintain soil fertility under a global change.     

Growth,morphology and leaf characteristics after simulated herbivory in Chinese subtropical evergreen saplings

Growth, morphology and leaf characteristics were assessed in late spring following simulated autumnal defoliation in second-year saplings of three Chinese subtropical evergreen tree species.Castanopsis fargesii showed strong compensatory growth in terms of plant biomass after removal of both 50 and 75% of leaf biomass and slight compensatory growth after 90% defoliation. DefoliatedC. fargesii saplings had more leaves per unit shoot length than non-defoliated saplings. New leaves on defoliated plants were smaller and had higher per area nitrogen content than new leaves on non-defoliated plants.Pinus massoniana andElaeocarpus japonicus showed strong and no compensatory growth, respectively, after 50% defoliation. The strong compensatory growth inP. massoniana andC. fargesii may partly explain why these species predominate in the early and late successional phases of evergreen broad-leaved forests     

Independence of stem and leaf hydraulic traits in six Euphorbiaceae tree species with contrasting leaf phenology

Hydraulic traits and hydraulic-related structural properties were examined in three deciduous (Hevea brasiliensis, Macaranga denticulate, and Bischofia javanica) and three evergreen (Drypetes indica, Aleurites moluccana, and Codiaeum variegatum) Euphorbiaceae tree species from a seasonally tropical forest in south-western China. Xylem water potential at 50% loss of stem hydraulic conductivity (P50_stem) was more negative in the evergreen tree, but leaf water potential at 50% loss of leaf hydraulic conductivity (P50_leaf) did not function as P50_stem did. Furthermore, P50_stem was more negative than P50_leaf in the evergreen tree; contrarily, this pattern was not observed in the deciduous tree. Leaf hydraulic conductivity overlapped considerably, but stem hydraulic conductivity diverged between the evergreen and deciduous tree. Correspondingly, structural properties of leaves overlapped substantially; however, structural properties of stem diverged markedly. Consequently, leaf and stem hydraulic traits were closely correlated with leaf and stem structural properties, respectively. Additionally, stem hydraulic efficiency was significantly correlated with stem hydraulic resistance to embolism; nevertheless, such a hydraulic pattern was not found in leaf hydraulics. Thus, these results suggest: (1) that the evergreen and deciduous tree mainly diverge in stem hydraulics, but not in leaf hydraulics, (2) that regardless of leaf or stem, their hydraulic traits result primarily from structural properties, and not from leaf phenology, (3) that leaves are more vulnerable to drought-induced embolism than stem in the evergreen tree, but not always in the deciduous tree and (4) that there exists a trade-off between hydraulic efficiency and safety for stem hydraulics, but not for leaf hydraulics.     

Cambial growth dynamics and climatic control of different tree life forms in tropical mountain forest in Ethiopia

Munessa Forest is a mountain forest in south-eastern Ethiopia experiencing seasonal rainfall variation. We investigated seasonal cambial activity and dormancy from increment rates of four different tree species belonging to varying life forms, namely, evergreen native conifer (Podocarpus falcatus), evergreen introduced conifer (Pinus patula), evergreen broadleaved tree (Prunus africana) and deciduous broadleaved tree (Celtis africana). Measurements of stem radius fluctuations were registered with the help of high-resolution electronic dendrometers. Daily amplitudes of stem diameter variations and daily and monthly net growth rates were determined and related to climatic variables measured at local climate stations. Thin sections of wood collected with a microcorer every 3–6 weeks allowed a visual control of newly formed wood cells during consecutive time intervals. Lack of water availability during the long dry season induced cambial dormancy of 5–7 months depending on life forms. After the onset of the short rainy season, stem swelling started quite synchronously with a variation of only single days in all studied species. Evergreen tree species were able to initiate wood formation during the short rainy season, whereas growth in the deciduous broadleaved species started in the long rainy season. The acquired data provide a basis for delineating the species-specific growth boundaries and the duration of the cambial growing season.     

基于无人机的昆明海口林场宽地坝林区植物群落建群种格局研究

建群种是植物群落优势层中的主要物种,对群落环境有显著控制作用。空间格局是植物种群的基本特征之一,探讨建群种的空间格局是理解生物与生境之间关系和认识群落生态过程的有效途径。空间格局特征包括种群空间关联性及其空间分布型。利用无人机技术,获取昆明海口林场半湿润常绿阔叶林和落叶栎类林的多光谱遥感影像,采用ArcGIS Pro软件进行遥感影像分类并提取滇青冈(Cyclobalanopsis glaucoides)、光叶石栎(Lithocarpus mairei)、滇石栎(L.dealbatus)、栓皮栎(Quercus variabilis)、槲栎(Q.aliena)植株树冠中心点空间坐标。在Programita Febrero 2014软件中进点格局分析。结果表明:各物种10m以下呈均匀分布或随机,随尺度增加,渐渐表现为聚集分布。光叶石栎种群和滇石栎种群空间关联性表现为负相关。     

六种阔叶树种叶片水浸提液对云南松种子萌发生长的化感作用

为了筛选营建云南松抗虫混交林的树种,该研究观察了云南切梢小蠹非寄主植物川滇桤木、缅桂、滇朴、樟树、麻栎和山茶六种阔叶树种叶片不同浓度的水浸提液对云南松种子萌发及幼苗生长的化感作用。结果表明:(1)川滇桤木、滇朴、麻栎和山茶四种阔叶树种叶片的水浸提液对云南松种子萌发和幼苗生长表现出低浓度促进,高浓度抑制效应。(2)在测试浓度范围内,樟树和缅桂叶片水浸提液对云南松种子萌发和幼苗生长存在抑制作用。综上所述,六种阔叶树种对云南松的化感作用敏感性不同,低浓度范围内的川滇桤木、滇朴、麻栎和山茶树叶片水浸提液对云南松生长表现出促进作用,樟树和缅桂叶片水浸提液对云南松生长具有抑制作用。因此,结合营林技术,可选用川滇桤木、滇朴、麻栎等阔叶树种与云南松混交,营建云南松抗虫混交林。