沙地樟子松天然林自然落种和土壤种子库的特征   总被引：3，自引：1，他引：2  

闫德仁  杜敏  王玉华  张宝珠  敖文明  乔殿学  阿日根扎 《东北林业大学学报》2009,37(11)

研究了呼伦贝尔沙地3种类型的樟子松天然林内天然母树的自然落种和土壤种子库特征.结果表明:土壤种子库中种子数量的空间分布特征和母树自然落种数量的空间分布规律相同.从树干或林缘向外,随着传播距离的增加,土壤种子库的种子数量和母树自然落种的种子数量均有降低的趋势.从树干或林缘向外4～5m范围内樟子松母树自然落种数量最多,而后随着距离的增加,自然落种数量明显减少.樟子松天然林母树自然落种的传播距离范围可以达到25m,表明在适宜条件下,沙地樟子松天然林通过自然更新,能够迅速扩展林缘,扩大种群.  相似文献   

Release of Carbon in Different Molecule Size Fractions from Decomposing Boreal Mor and Peat as Affected by Enchytraeid Worms     

Mari Lappalainen  Marjo Palviainen  Jussi V.K. Kukkonen  Heikki Setälä  Sirpa Piirainen  Tytti Sarjala  Harri Koivusalo  Leena Finér  Samuli Launiainen  Ari Laurén 《Water, air, and soil pollution》2018,229(7):240

Terrestrial export of dissolved organic carbon (DOC) to watercourses has increased in boreal zone. Effect of decomposing material and soil food webs on the release rate and quality of DOC are poorly known. We quantified carbon (C) release in CO₂, and DOC in different molecular weights from the most common organic soils in boreal zone; and explored the effect of soil type and enchytraeid worms on the release rates. Two types of mor and four types of peat were incubated in laboratory with and without enchytraeid worms for 154 days at +?15 °C. Carbon was mostly released as CO₂; DOC contributed to 2–9% of C release. The share of DOC was higher in peat than in mor. The release rate of CO₂ was three times higher in mor than in highly decomposed peat. Enchytraeids enhanced the release of CO₂ by 31–43% and of DOC by 46–77% in mor. High molecular weight fraction dominated the DOC release. Upscaling the laboratory results into catchment level allowed us to conclude that peatlands are the main source of DOC, low molecular weight DOC originates close to watercourse, and that enchytraeids substantially influence DOC leaching to watercourse and ultimately to aquatic CO₂ emissions.  相似文献   

Farm Forestry Prospects Among Some Local Communities in Rachuonyo District,Kenya   总被引：1，自引：0，他引：1  

Mark Appiah  Ari Pappinen 《Small-Scale Forestry》2010,9(3):297-316

Deforestation and degradation of productive lands are serious threats to the sustainability of forestry/agricultural practices in Kenya. In the last two decades farm forestry (FF) has been promoted through pilot projects among local communities as an example of sustainable land use. However adoption of FF is limited outside the project locations because FF improvement measures focused mainly on biological (e.g. succession, biodiversity and traditional industrial timber production) and technical concerns (e.g. material input delivery such as providing free tree seedlings for field planting) rather than local values, and interests and the constraints facing farmers. This study examined the local farm priorities and constraints and the prospects for the wider implementation of farm-level tree planting in four communities in Rachuonyo District. Using interviews with 597 randomly selected household heads, the study assessed farmer’s production assets and activities, land tenure, priority tree species and the constraints to growing trees on farms. Results show that farm labour is represented by a young population, 56.3% under the age of forty. They are mainly engaged in small-scale mixed cropping integrated with multipurpose trees and some livestock. Tree products contribute about 32% to household cash income, more than any other source (agricultural products, labour sales, etc). Females were more often household heads and had considerable influence over productive activities, making them an important target group in FF development. Farmers preferred exotic tree species due to their ability to provide short-term cash income, fuel and shade. Farmers’ concerns included population pressure on limited farmlands and the problem of credit for agricultural inputs. Given the feeling of secured tenure arrangement and influence of tree products on the household economy, farmers are likely to invest more in efficient land uses such as FF if consideration is given to local priorities.  相似文献   

Duration of vegetative and generative development phases in oat cultivars released since 1921     

Pirjo Peltonen-Sainio  Ari Rajala 《Field Crops Research》2007

Genetic yield improvements in oat (Avena sativa L.) cultivars grown at high latitudes have resulted from marked changes in harvest index and yield components. This study was designed to investigate whether such changes have entailed alterations in duration of different developmental phases: vegetative, generative and grain filling phases and pre-anthesis generative sub-phases such as pre-fertile, pre-abortion, fertile pre-abortion, fertile and abortion sub-phases. We tested 14 oat cultivars released between 1921 and 1988 and 6 breeding lines. Ten randomly sampled plants of each oat entry were collected every 3–4 d (18 times) from seedling emergence until pollination, and apical developmental stages were determined on the most advanced spikelet. Cumulated degree-days (Cdd) for each critical developmental stage and component phases were determined (5 °C as a base temperature). At each measurement the number of leaves, green leaves and tillers on main shoot, apex length (mm) and height to the uppermost node, and stipule (cm) were recorded. Phyllochron (°C d leaf⁻¹) and relative elongation rates (RER) for height characterising traits were calculated. Grain filling was the only period altered by breeding, while no consistent effects on duration of vegetative and generative pre-anthesis phases and sub-phases were detected. Different developmental phases were interrelated: in some cases cultivars with similar duration of pre-anthesis phase, however, differed in duration of some pre-anthesis sub-phases. Their duration was not, however, consistently associated with measured growth and yield parameters. Likely long days that make the northern growing conditions exceptional and unique, substantially narrowed the differences among oat entries in duration of different developmental phases, thereby making their role also less critical in yield determination contrary to the situation in the main global temperate cereal production regions.  相似文献   

Spring wheat response to timing of water deficit through sink and grain filling capacity   总被引：2，自引：0，他引：2  

Ari Rajala  Kaija Hakala  Pirjo Mkel  Susanna Muurinen  Pirjo Peltonen-Sainio 《Field Crops Research》2009,114(2):263-271

Water and nitrogen (N) availability are the main factors influencing crop growth globally. Poorly distributed or insufficient water for crop growth requirements decreases yields in drought-prone areas such as those with a Mediterranean type environment. Cereal grain yield is a complex trait of interrelated components: plants per unit land area, spikes per plant, spikelets per spike, grains per spikelet, and single grain weight (SGW). The effect of water limitation and timing on development of yield components was studied in detail at the spike level in spring wheat (Triticum aestivum L.) cultivar Amaretto. An experiment with three watering treatments (control watering, CONT; drought prior to pollination, DR1 and terminal drought, DR2) was arranged in a large greenhouse (20 m × 30 m), with the use of standard field-trial machinery. Automated blackout curtains were used to control day length, which was set to correspond to that at 40°N. With watering treatments, two N application rates (60 and 120 kg N ha⁻¹) were used to investigate the N effect and potential watering × N interaction on yield formation and realisation. The water deficit effect exceeded the effect of N on fertile floret and grain number and SGW. DR1 strongly reduced the number of fertile florets and grains, whereas terminal drought reduced the number of grains per spike. Resuming the watering at pollination markedly enhanced photosynthesis, and hence grain filling capacity, resulting in the highest SGW in DR1. Enhancement in availability of key resources was associated with reduced rate of fertile floret and grain abortion, which resulted in higher grain to fertile floret ratio in DR1. Spikelets in the mid-section of the spike dominated yield formation in all treatments. In DR1 this was especially emphasised as 53% of the grain yield was produced in spikelets 4–6, whereas in DR2 and CONT this was 45 and 41%, respectively. Grains in proximal position in the spikelets produced about 80% of the spike grain yield, the proportion being slightly higher in stressed plants and plants receiving 60 kg N. No marked N × water deficit treatment interaction occurred for any of the measured parameters.  相似文献   

Mesh selectivity of a sweeping trammel net for Japanese whiting Sillago japonica   总被引：2，自引：0，他引：2  

Ari Purbayanto  Seiji Akiyama  Tadashi Tokai and  Takafumi Arimoto 《Fisheries Science》2000,66(1):97-103

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Potpourri oil toxicity in cats: 6 cases (2000–2007)     

Julie C. Schildt DVM  L. Ari Jutkowitz VMD  DACVECC  Matthew W. Beal DVM  DACVECC 《Journal of Veterinary Emergency and Critical Care》2008,18(5):511-516

Objective – To describe the clinical and laboratory features, treatment, and outcome of cats with a history of potpourri oil exposure. Design – Retrospective study. Setting – Veterinary teaching hospital. Animals – Six client‐owned cats. Measurements and Main Results – The medical records of animals with oral or lingual ulceration and exposure to potpourri oil from January 2000 to December 2007 were reviewed. Information obtained from the medical records included signalment, product to which the animal was exposed, clinical signs, physical examination findings, diagnostic test results, treatment, duration of hospitalization, and outcome. Six cats qualified for inclusion in the study; 3 were castrated males and 3 were spayed females. Age range was 0.3–3.6 years. All cats had severe oral and lingual ulceration. Additional clinical findings included hyperthermia, tachypnea, ptyalism, and lethargy. Treatment of these cats included IV fluids, analgesic therapy, antimicrobial therapy, and gastrointestinal protectants. Two of these cats received an esophagostomy tube for nutritional support. Duration of hospitalization was 0–5 days. All cats survived to discharge. Follow‐up for 3 cats revealed complete healing of the oral ulceration. Conclusions – Potpourri oil toxicity should be considered as a differential diagnosis in any cat with oral and lingual ulceration. Prognosis for recovery is good with supportive care.  相似文献   

The ability of the pine-top weevil to carry spores and infect Scots pine with Endocronartium pini     

A. Pappinen  K. von Weissenberg 《Forest Pathology》1994,24(5):258-263

The pine-top weevil Pissodes piniphilus is known to be often associated with trees infected with resin-top disease. In this paper, the ability of the weevil to carry Endocronartium pini spores in laboratory conditions and its ability to infect pines in the field were studied. The weevil may carry spores and cause infection in healthy pines.  相似文献   

Estimation of dispersal gradients of S- and P-type basidiospores of Heterobasidion annosum     

T. Möykkynen  K. von Weissenberg  A. Pappinen 《Forest Pathology》1997,27(5):291-300

The number of airborne deposits of the root pathogen Heterobasidion annosum was counted with a wood disc method at distances 5–1000 m from one S-type and one P-type infection centre in stands of Picea abies in June, July and August, 1995. The level of background deposition in the area was determined in four healthy control stands. Based on intersterility group determination of deposits, only measurements within 100 m of the infection centres could be used in estimations of dispersal gradients owing to confusion with background deposition. A power law gradient model adequately described the reduction of deposits with increasing distance from the infection centres. Gradients were fairly similar in four directions around the infection centres as the wind speeds were low (3.2m/s) during the collection periods. The gradients were steeper around the P-type centre, probably due to its lower spore production capacity. The background deposition level (2.8 colonies/m²× h) was reached at distances 1255 m and 98 m from the S-type and P-type centre, respectively.  相似文献   

Upside-down swimming behaviour of free-ranging narwhals     

Rune Dietz  Ari D Shapiro  Mehdi Bakhtiari  Jack Orr  Peter L Tyack  Pierre Richard  Ida Grønborg Eskesen  Greg Marshall 《BMC ecology》2007,7(1):1-10

Background

Free-ranging narwhals (Monodon monoceros) were instrumented in Admiralty Inlet, Canada with both satellite tags to study migration and stock separation and short-term, high-resolution digital archival tags to explore diving and feeding behaviour. Three narwhals were equipped with an underwater camera pod (Crittercam), another individual was equipped with a digital archival tag (DTAG), and a fifth with both units during August 2003 and 2004.

Results

Crittercam footage indicated that of the combined 286 minutes of recordings, 12% of the time was spent along the bottom. When the bottom was visible in the camera footage, the narwhals were oriented upside-down 80% of the time (range: 61100%). The DTAG data (14.6 hours of recordings) revealed that during time spent below the surface, the two tagged narwhals were supine an average of 13% (range: 9–18%) of the time. Roughly 70% of this time spent in a supine posture occurred during the descent.

Conclusion

Possible reasons for this upside-down swimming behaviour are discussed. No preference for a clockwise or counter-clockwise direction of roll was observed, discounting the possibility that rolling movements contribute to the asymmetric left-handed helical turns of the tusk.  相似文献