冀北山地阔叶林对降雨再分配的影响

[目的]探讨冀北山地阔叶林林冠层的穿透降雨、冠层截留和树干径流对降雨再分配的影响,为该地区的森林建设、森林结构调整提供依据。[方法]利用SPSS专业统计分析软件对林地降雨的数据进行相关性分析和回归分析。[结果]林分的穿透雨占的比例是最大(占到总比例的70.22%),林冠截留其次(为28.20%),而树干径流占得比例最小(为1.58%);穿透雨量与林外降雨量有比较好的线性关系(R^2=0.997 9),林分在降雨比较小的时候是不会有穿透雨的,当林外降雨量达到0.78mm时开始出现穿透雨。林冠截留在降雨的再分配过程中占有很重要的作用,林冠截留量与林外降雨量有明显的幂函数关系,达到了极显著水平(p<0.01)。树干径流量与林外降雨量呈现正相关的关系(R^2=0.9703),阔叶树林在降雨达到4.88mm时才会出现树干径流,但是树干径流具有一定的时滞性,而时滞性的大小和林木本身及雨量的强弱都有很大的关系,当叶面积指数较小,并且枝干夹角成45%,林木表面光滑则形成比较容易。[结论]林冠层对降雨的再分配过程有重要影响,冀北山地阔叶林林冠层的水文效应与森林健康发展具有一定的关系。     

黄土丘陵区2种典型林分降雨分配特征及其主要影响因素

森林对降雨的分配是森林生态水文和生物地球化学循环中的重要过程之一。通过对黄土丘陵区2种典型林分(刺槐林和辽东栎林)生长季降雨分配过程的实地监测,探究2种林分的降雨分配特征及其主要影响因素。结果表明:试验期间,刺槐林和辽东栎林降雨分配各组[JP]分均表现为穿透雨量(325.0,295.1 mm)＞冠层截留量(39.8,73.6 mm)＞树干径流量(25.8,21.9 mm),同时穿透雨率(83.2%和75.6%)＞冠层截留率(10.2%和18.8%)＞树干径流率(6.6%和5.6%)。次降雨量是影响降雨分配的关键因子,穿透雨量和树干径流量与次降雨量间呈现极显著线性关系,冠层截留量与次降雨量间呈现极显著对数函数关系;穿透雨率和树干径流率与次降雨量间呈现显著对数函数关系,冠层截留率与次降雨量间呈现极显著指数函数关系。刺槐林和辽东栎林产生穿透雨的次降雨阈值分别为1.0,1.3 mm,产生树干径流的次降雨阈值分别为5.9,5.4 mm。刺槐林产生的穿透雨量和[JP]树干径流量均大于辽东栎林,而冠层截留量小于辽东栎林。研究结果为黄土丘陵区森林生态水文过程的研究提供基础数据,对该地区植被恢复过程中植被类型的选择具有指导意义。     

木兰围场华北落叶松林对降雨再分配的影响

为了探究落叶松林对降雨再分配的过程,通过对木兰围场国有林场管理局北沟林场内落叶松林进行穿透降雨、冠层截留和树干径流3个方面进行了监测,结果表明:(1)穿透雨量和林冠截留占林外降雨量的比例比较大,树干径流量的比例则非常小,分别为59.44%,39.20%,1.36%;(2)穿透雨量和林外降雨呈现线性关系(R2=0.988 6),林冠截留量与林外降雨量也具有明显的幂函数关系(R2=0.755 9),树干径流与林外降雨量具有明显的线性相关关系(R2=0.755 9),并且都达到了极显著水平(p0.01);(3)根据穿透雨与林外降雨的方程,当林外降雨量高于1.81mm时会产生穿透雨。依据林外降雨与树干径流的方程,当林外降雨高于5.18mm时会产生树干径流。林冠在降雨再分配过程中起到了很重要的作用,形成了二次降雨。     

大豆冠层对降雨再分配的影响

[目的]研究农作物冠层的降雨再分配特征,为区域水土流失治理和生态环境建设提供科学依据。[方法]以大豆作为研究对象,采取人工模拟降雨法以及喷雾法观测大豆不同生育期(幼苗期、始花期、盛花期、结荚期和始粒期)以及降雨强度(40,80 mm/h)下的茎秆流量、穿透雨量以及冠层截留量,探究大豆全生育期的冠层截留分异特征及叶面积指数和降雨强度对大豆降雨再分配的影响。[结果]大豆生育期内,茎秆流率平均值为15.02%,穿透雨率平均值为83.94%,冠层截留率平均值仅为1.04%。表明冠层截留所占降雨再分配的比例很小,其对降雨空间分异的影响所占比例较小。随着叶面积指数的增加,大豆的茎秆流量及茎秆流率,冠层截留量及冠层截留率均显著增加,然而穿透雨强度及穿透雨率显著减小。当降雨强度由40 mm/h增大到80 mm/h时,大豆的茎秆流量显著增加,但茎秆流率随雨强的变化并无显著差异;穿透雨量随着雨强的增大而增大,且随着雨强的变化存在显著性差异,但穿透雨率随降雨强度的变化并无显著差异。[结论]大豆冠层对降雨的再分配主要体现在茎秆流以及穿透雨,冠层截留所占比例很小,且叶面积指数与降雨强度均对降雨再分配有着重要的影响作用。     

沿坝地区天然次生林对降雨再分配的影响

为了探究天然次生林对降雨再分配的过程,通过对沿坝地区的北沟林场内天然次生林进行穿透降雨、冠层截留和树干径流3个方面进行监测,结果表明:（1）穿透雨量和林冠截留占林外降雨量的比例比较大,树干径流量的比例则非常小,分别为59.46%,37.33%,3.21%。（2）穿透雨量和林外降雨呈现线性关系（R²=0.980 4）,林冠截留量与林外降雨量也具有明显的幂函数关系（R²=0.823 4）,树干径流与林外降雨量具有明显的线性相关关系（R²=0.909 8）,并且都达到了极显著水平（p < 0.01）。（3）根据穿透雨与林外降雨的方程y=0.8034x-1.7939,当林外降雨量高于2.23 mm时会产生穿透雨;依据林外降雨与树干径流的方程y=0.0552x-0.1981,当林外降雨高于3.58 mm时会产生树干径流;林冠在降雨再分配过程中起到了很重要的作用,形成了二次降雨。     

华北土石山区油松林对降雨再分配的影响

森林对大气降雨的再分配有着重要的作用,2010年通过对河北省木兰国营林场油松林穿透降雨、冠层截留量和树干径流的观测,分析了华北土石山区油松林降雨再分配的特征。结果表明:油松林的穿透降雨量、冠层截留量和树干径流量分别占大气降雨量的67.07%,29.79%,3.10%。油松林冠层穿透降雨量和树干径流量与林外降雨量呈明显的线性关系(R2=0.986,R2=0.893),林冠截留量与降雨量成幂函数关系(R2=0.765);根据回归方程,当林外降雨量大于0.264mm时,可发生穿透降雨,当林外降雨量大于4.89mm时,可发生树干径流;林冠在降雨再分配过程中起着主要的作用,在空间和时间上都进行了再分配。     

杨树与小麦间作系统林冠层降雨再分配对地表径流和淋溶的影响

[目的]探讨杨树林冠层降雨再分配对地表径流量、侵蚀量和淋溶量的影响,为农林间作系统削减水土流失提供理论依据。[方法]以太湖流域杨树与小麦作系统为研究对象,通过对2013年全年101场降雨的降雨量、林内穿透雨量、树干径流量的野外观测及对地表径流量、侵蚀量和淋溶量的样品收集进行测定分析。[结果]①总降雨量为943.5 mm,林内总穿透雨量、树干径流量及截留量分别为796.2,7.3和140.0 mm,分别占总降雨量的84.4%,0.8%和14.8%。其中,降雨量10 mm的中、小降雨发生最频繁,占总降雨场次的80.2%;②穿透雨量(R~2=0.993)和树干径流量(R~2=0.748 4)与林外降雨量呈线性正相关关系;当降雨量大于5.5 mm时,树干开始产生径流;林冠截留率与降雨量呈负幂函数相关关系(R~2=0.414 7);除了降雨量外,林冠截留率还与林冠叶面积指数有关;③间作系统林分密度越大,冠层叶面积指数越大,林冠层对径流量和侵蚀量的削减作用就越强。④单株杨树距离树干1.5 m处平均穿透雨量较0.5 m,7.5 m处分别减少了3.2%,9.3%,淋溶水量分别减少了3.5%,10.8%;就单株林木而言,除降雨量外,林冠结构特征对淋溶流失起着重要作用。[结论]①间作系统中杨树林冠层对降雨的再分配作用主要取决于降雨量,降雨量越大林冠层截留效果越不显著;②杨树密度的增大能显著减少系统内地表径流量和侵蚀量;③单株杨树在距离树干1.5 m处的冠层对降雨的削减作用最大,淋溶水量亦最少。     

祁连山青海云杉林冠降雨再分配特征及影响因素

以祁连山排露沟小流域青海云杉林为研究对象,2015年5—9月观测了34场降雨的林外降雨量、穿透雨量和树干茎流量,并同步观测了相关的林外气象因子,分析了青海云杉林冠降雨再分配特征及影响因素。结果表明:(1)青海云杉林的总穿透雨量、树干茎流量和截留量分别为275.9,1.8,90.0mm,分别占总降雨量的75.04%,0.48%和24.48%,并在不同降雨量等级之间存在差异。(2)冠层降雨再分配各组成要素(穿透雨、树干茎流、林冠截留)与降雨量、降雨历时、10min最大雨强、空气相对湿度呈极显著的相关性。随着降雨量和降雨历时的增大,穿透雨量和树干茎流量均不断增大,而穿透雨率、树干茎流率和截留量(率)均逐渐趋于稳定。(3)青海云杉林内产生穿透雨和树干茎流的临界降雨量分别为0.8mm和9.6mm。因此,气象因素是影响冠层降雨再分配的重要因素之一。     

公路石质边坡喷播绿化植被的降雨、灌溉水分分配特征

为提高边坡水分利用效率,通过客土喷播的方式人工模拟公路石质边坡,观测坡体表面土壤裂隙发育情况及地表径流、底层渗漏及土壤储存等水分分配过程,分析灌溉及降雨条件下的坡面水分分配特征。结果表明:坡体表面形成的土壤裂隙分布不均匀,呈现由坡顶至坡底逐渐减少的趋势,且阳坡不同坡位的裂隙总面积均大于阴坡;不同坡向坡体灌溉水分分配特征存在一定差异,阳坡0.02%的水分通过坡上植被蒸散消耗,7.00%的灌溉用水沿着坡面运动形成地表径流,10.00%的灌溉水分转化为底层渗漏量,53.00%的灌溉水分被土壤储存;阴坡植物蒸散、地表径流、底层渗漏及土壤储存水分的比例分别为0.01%,35.00%,0.25%和39.00%;随着植被覆盖度的增加,灌溉产生的地表径流减少,土壤储存水分增大;降雨强度对坡面水分分配特征具有显著影响,在小雨强条件下,约95.00%的降雨被土壤储存,底层渗漏量、地表径流分别在中雨强及大雨强条件下达到最大值;在不同雨强下,阴坡的地表径流是阳坡的1.1~3.0倍,阳坡的底层渗漏量大于阴坡且阳坡较阴坡具有更高的水分利用效率。该结果可为公路边坡植被恢复过程中水分的有效利用提供依据。     

重庆缙云山楠竹林地不同时间尺度降雨量再分配规律研究

楠竹林是缙云山森林生态系统的一种典型植被类型,通过对楠竹林地设置的径流小区2002-2007年水文观测资料研究,定性和定量揭示了该植被类型降雨-径流过程特征的变化规律,并得出降雨过程中,林冠截留、地表径流、地下径流、土壤、枯落物等影响因子对降雨量的分配情况。研究证明,(1)2002-2007年,楠竹林的降雨的年际分布比较稳定;降雨量比较集中出现4-9月,占全年降雨量的72%,峰值出现在7月。(2)地表径流与地下径流与降雨保持密切的响应关系,在对降雨量的分配中,地表径流占30.7%,地下径流占15.2%。(3)楠竹林地的土壤最大分配降雨量为19 mm,枯落物最大分配降雨量为4.6 mm,林冠截留分配降雨量13.2%。本研究旨在为长江流域森林生态水文研究中树种选择、植被建设提供参考与数据支持。     

Agricultural potential of Mediterranean grain and forage legumes: Key differences between and within Vicia species in terms of phenology, yield, and agronomy give insight into plant adaptation to semi-arid environments

In order to identify key adaptive traits which affect productivity in Mediterranean grain and forage legumes and simultaneously determine the agricultural potential of a wide range of Vicia species, germplasm collected from the wild throughout the eastern Mediterranean was grown under semi-arid conditions in Tel Hadya, Syria (313 mm growing season rainfall). These included species currently in use in Mediterranean agriculture, such as V. sativa L., as well as those more widely used in the past-such as V. ervilia L., but also a broad selection from Section Narbonensis (B. Fedtsch. ex Radzhi) Maxted, including V. narbonensis L, V. johannis Tamamsch., V. hyaeniscyamus Mout., V. serratifolia Jacq., and V. kalakhensis Khattab et al. V. faba, a near relative of the taxa in Section Narbonensis, was included as a domesticated control. Where applicable, a representative range of subspecies was used. Accessions were chosen from a wide range of habitats in terms of latitude (31.02–40.72 decimal^o), longitude (27.1–43.17 decimal^o), altitude (20–1510 m), rainfall (180–1700 mm/yr) and soil depth (5–50 cm) in order to maximise diversity within species. Agricultural potential was determined by measuring seed, hay and biological yield, as well as agronomic traits such as harvest index, standing crop height, and seed size. The comparative influence of phenology and key agronomic traits such as plant habit and seed size on productivity varied tremendously between species, depending on their reproductive strategies. In V. sativa and V. ervilia, the smaller seed species which rely on long vegetative phases and growing seasons to accumulate sufficient biomass to set seed, and in which there was comparatively little agronomic variation, phenology had a large impact on yield. In early emerging taxa such as V. ervilia and V. s. subsp. sativa, with built-in long vegetative phases and growing seasons, seed yield was negatively correlated with flower ing (r = –0.86 to –0.88), whereas the opposite was the case for later emerging taxa such as V. s. subsp. nigra (L.) Ehrh. (r = 0.95). Within V. narbonensis and relatives, the larger seeded Vicia species which rely on more conservative reproductive strategies where high seedling vigour associated with large seeds enables the species to enter reproductive phases relatively early, phenology had a much smaller impact on yield than did variation of key traits such as seed weight, plant habit and pod shattering. Among the undomesticated germplasm harvest indices ranged from 0.09–0.31, hay yields from 0.1–3.4 t/ha, seed yield from 0–2.0 t/ha, and dry matter at maturity from 1.6–6.5 t/ha. Sub-specific taxonomy was crucial in determining agronomic potential. V. narbonensis var. aegyptiaca Kornhuber ex Asch. et Schweinf. showed the most potential, combining an upright habit, large seeds (212 mg) and tendency to retain intact pods after maturity, with the highest yield, harvest index and crop height of all the wild Vicia species. V. sativa subsp. sativa, V. ervilia and V. narbonensis var. narbonensis were less productive, but still showed agricultural potential. The smaller seeded V. narbonensis, var. affinis, var. jordanica H. Schäf. and var. salmonea (Mout.) H. Schäf., and their close relatives V. johannis, V. hyaeniscyamus, V. serratifolia and V. kalakhensis have little to offer Mediterranean agriculture on the basis of poor agronomy.     

On the Taxonomy of the Members of ‘Saccharum Complex’

The difficulty and problems encountered in the study of cultivated plants, in general and sugarcane, in particular has been indicated. In order to understand these problems, a brief review on the taxonomy of Saccharum and closely related taxa, namely, Erianthus, Sclerostachya, Narenga and Miscanthus (generally known as ‘Saccharum complex’) has been given. A short account on the important morphological features that are specific to sugarcane has also been stated as classification is commonly based on such morphological characters. A note has been added on the chromosome number, origin, and distribution of the species of ‘Saccharum complex’ members. Taxonomic keys have been devised for identification of the genera of Saccharinae and for the species of Saccharum and Erianthus occurring in India. A new combination, Sclerostachya fallax (Balansa) Amalraj et Balasundaram, has also been proposed.     

Polymorphism of high molecular weight glutenin subunits in three species of Aegilops

A collection of 136 accessions of Aegilops umbellulata (39), Ae. comosa (75) and Ae. markgrafii (22) was analysed for high-molecular-weight (HMW) glutenin subunits composition. The homogeneity of the accessions was studied and 55.1% of the collection was homogeneous for HMW glutenin subunits (29 Ae. umbellulata, 33 Ae. comosa and 14 Ae. markgrafii). The HMW glutenin subunits of Ae. umbellulata are encoded by the Glu-U1 locus; in Ae. comosa results showed that this proteins are encoded at the 1M chromosome, and the locus was named Glu-M1. In Ae. markgrafii it was assumed that HMW glutenin subunits were encoded by an homoeologous locus and it was named Glu-C1. All the accessions of Ae. umbellulata and Ae. markgrafii expressed both, x-type and y-type subunits. Among the Ae. comosa accessions, only one expressed an x-type subunit alone. All the accessions of Ae. umbellulata and some of Ae. comosa had x-type glutenins of higher molecular weights than those commonly present in bread wheat. A total of 8 alleles were detected at the Glu-U1 locus, 11 at the Glu-M1 and 4 at the Glu-C1. The new HMW glutenin variation found in this work suggests their possible utilisation in breeding for wheat quality.     

Effect of agroforestry woody species on earthworm activity and physicochemical properties of worm casts

The effects of five agroforestry woody species (Dactyladenia barteri, Gliricidia sepium, Leucaena leucocephala, Senna siamea andTreculia africana) on the surface aasting activity ofHyperiodrilus africanus were studied in an Alfisol (Oxic Paleustalf) in southwestern Nigeria. Casting activity under the woody species decreased in the following order:Dactyladenia sp. (26.4 Mg ha^-1 year^-1)>Gliricidia sp. (24.4 Mg ha^-1 year^-1)>Treculia sp. (22.9 Mg ha^-1 year^-1)>Leucaena sp. (18.6 Mg ha^-1 year^-1)>Senna sp. (18.3 Mg ha^-1 year^-1). These differences in casting activity were partly explained by microclimatic effects. Irrespective of the woody species, the worm casts were higher in clay and silt contents, bulk density, water-stable aggregates, pH, organic C, exchangeable cations, effective cation exchange capacity, and extractable P levels than the corresponding surface soils. The woody species did affect the physicochemical properties and P sorption of the worm casts. The content of water-stable aggregates of worm casts decreased in the following order:Dactyladenia sp.>Treculia sp.>Senna sp.>Leucaena sp.>Gliricidia sp. Large differences in extractable P levels were observed.Senna sp. was associated with the highest extractable P level (11.5 mg kg^-1) andTreculia sp. the lowest (4.9 mg kg^-1). P sorption was highest on worm casts underDactyladenia sp. and lowest on those underTreculia sp. Without fertilizer application, there were no significant differences in the dry weight of maize grown in the different worm casts. With NPK applications, the dry weight of maize grown in worm casts associated withTreculia sp. was significantly lower than that of maize grown in the other worm casts, mainly due to the low extractable P level. Despite a high organic C and exchangeable K status, maize grown in the worm casts still responded significantly to N and K applications. The N uptake by maize grown in worm casts associated withTreculia sp. was lower than that in the other treatments.     

Genetic diversity of rhizobia associated with indigenous legumes in different regions of Flanders (Belgium)

We investigated the diversity of rhizobia isolated from different indigenous legumes in Flanders (Belgium). A total of 3810 bacterial strains were analysed originating from 43 plant species. Based on rep-PCR clustering, 16S rRNA gene and recA gene sequence analysis, these isolates belonged to Bradyrhizobium, Ensifer (Sinorhizobium), Mesorhizobium and Rhizobium. Of the genera encountered, Rhizobium was the most abundant (62%) and especially the species Rhizobiumleguminosarum, followed by Ensifer (19%), Bradyrhizobium (14%) and finally Mesorhizobium (5%). For two rep-clusters only low similarity values with other genera were found for both the 16S rRNA and recA genes, suggesting that these may represent a new genus with close relationship to Rhodopseudomonas and Bradyrhizobium. Primers for the symbiotic genes nodC and nifH were optimized and a phylogenetic sequence analysis revealed the presence of different symbiovars including genistearum, glycinearum, loti, meliloti, officinalis, trifolii and viciae. Moreover, three new nodC types were assigned to strains originating from Ononis, Robinia and Wisteria, respectively. Discriminant and MANOVA analysis confirmed the correlation of symbiosis genes with certain bacterial genera and less with the host plant. Multiple symbiovars can be present within the same host plant, suggesting the promiscuity of these plants. Moreover, the ecoregion did not contribute to the separation of the bacterial endosymbionts. Our results reveal a large diversity of rhizobia associated with indigenous legumes in Flanders. Most of the legumes harboured more than one rhizobial endosymbiont in their root nodules indicating the importance of including sufficient isolates per plant in diversity studies.     

Phylogenetic relationships of Actinidia and related genera based on micromorphological characters of foliar trichomes

The phylogenetic relationships within the genus Actinidia and among 3 allied genera Clematoclethra, Saurauia, and Sladenia have been very controversial. In order to understand the systematic implication of foliar trichomes in those genera, the micromorphological characteristics of foliar trichomes from 34 taxa were examined by means of light microscopy and scanning electron microscopy (SEM). The observed micromorphological characteristics were classified into eight main types. A phylogenetic analysis of Actinidia and related genera based on 15 micromorphological characters of foliar trichomes was conducted using Wagner parsimony method and Sladenia celastrifolia, Rhododendron hybridum and R. simsii as a complex outgroup. In the resulting phylogenetic tree, Actinidia is shown to be a monophyletic group, and Clematoclethra and Saurauia form another monophyletic group. This study also presents the phylogenetic relationships among 4 sections within the genus Actinidia: the monophyly of sect. Leiocarpae and of sect. Strigosae, and polyphyly of sect. Maculatae and of sect. Stellatae.     

Diversity of native rice (Oryza Poaceae:) species of Costa Rica

We found several populations of wild Oryza species in the lowlands of Costa Rica. The plants showed extensive morphological variation, suggesting the presence of several species. In the morphologic study, 33 traits were scored for plants of all the species. A principal component analysis revealed the significant morphological separation of the different species. The analyses indicated that there are three species, O. grandi­glumis, O. latifolia and O. glumaepatula. Two putative hybrid types were found, both significantly differing in their morphology from the known species and intermediate at several traits. O. grandi­glumis is a new record for Costa Rican flora. Its main population is located in Caño Negro Wildlife Refuge, Los Chiles, Alajuela. O. latifolia is distributed throughout the lowlands of the country and the plants of the Atlantic slope are significantly bigger in general habit than those of the Guanacaste area. During this study a population of O. glumaepatula of hundreds of thousands of plants was discovered in the Medio Queso River wetland, Los Chiles, Alajuela. This population is the most important source of genes for cultivar's improvement from the primary gene pool of rice in Costa Rica. The small ligule and the wide flag leaf characteristic of the two CCDD species separated them from the AA diploid O. glumaepatula. Seed size, ligule size, number of branches in the panicle, plant height and sterile lemma length are all bigger in O. grandi­glumis, and influenced the second factor that separated the CCDD species in two discrete clusters. The species found offer great possibilities for the improvement of rice cultivars and they should be thoroughly studied and appropriately protected.     

Powdery Mildew Resistance in a Collection of Chinese Barley Varieties

One hundred and forty-seven Chinese barley varieties maintained at the Gene Bank of the National Barley Improvement Centre, Zhejiang, and 84 progenies from these varieties were tested at the seedling stage for their reaction to 32 selected pathotypes of Blumeria graminis f. sp. hordei. Eighteen resistance spectra were identified comprising single or combined resistances from eight known (Ml(Bw), Ml(Ch), Mla7, Mla8, Mla9, Mla13, MlaRu4 and Mlg) and six unknown resistance genes. The most frequent gene was Ml(Bw), which was found in 69 varieties and previously detected in only a few European winter barley varieties. The genes Mla8 and Ml(Ch) were also often present, but other resistance genes were rare. After inoculation, considerably fewer pathogen colonies were observed in ‘Aiganqi’ and one line of ‘Tong5’. Twenty varieties were composed of lines with different resistance genes. China is likely to be a region of origin of the genes Ml(Bw), Mla7, as well as three unknown genes found in original landraces and perhaps another three unknown genes detected in cultivars bred in China. The resistances of varieties from the Zhejiang province and those originating from 11 other Chinese provinces were quite different. Unfortunately, none of the varieties are promising sources of resistance to powdery mildew and China does not seem to be a region suitable for identifying such sources.