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991.
Beech woodland can be restored by direct planting of beech (Fagussylvatica L.) seedlings in abandoned areas, but this methodis generally avoided in forestry because of the growth difficultiesof beech in full-light conditions. This study tested a methodthat consists of planting beech seedlings in full-light conditionswith silver birch (Betula pendula Roth.) or Scots pine (Pinussylvestris L.) as nurse trees. A total of 65 two-year-old beechseedlings surrounded by either 3, 4, 5 or 6 pine or birch seedlingsor without competitors were planted in bare-soil open-fieldconditions in Central France. Tree growth and light availabilitywere monitored at the end of each of the following 3 years,and soil moisture was also measured the last year. At the endof the experiment, aerial biomass measurements were made onthe beeches. Results showed that relative beech growth in termsof diameter was significantly reduced by the local neighbouringtrees and that this reduction was particularly noticeable inthe pine treatments where there was extensive pine seedlingdevelopment. In contrast, relative beech height did not exhibitany significant variations among the treatments. Light availabilitywas decreased by the neighbouring trees, especially in the pinetreatments. Light reduction was more pronounced in the last2 years and in the middle or lower parts of the canopy of thesubject beech. Soil water content was lower under the pine canopiesthan under the birch canopies, and was positively correlatedto beech relative diameter growth. Specific leaf area, height-to-diameterratio and crown length-to-crown width ratio weakly but significantlyincreased with competition from the neighbours. Beech biomasspartitioning was only weakly affected by the treatments. Thisstudy showed that nurse trees tend to reduce beech growth butimprove form although effects remained weak due to the insufficientlength of the experiment. Further studies are also needed toquantify the effects of the neighbourhood on the growth of competitiveherbaceous vegetation and on changes in the microclimatic conditions. 相似文献
992.
在广东省阳西县开展赤桉和尾叶桉接种10个外生菌根菌的野外试验,根据造林后对树高、地径和胸径的观测,发现菌根菌与树种间存在互作效应,这种效应影响菌根菌接种效果;试验筛选出的菌株:H4461,适于尾叶桉,树高增加2%-21%,胸径增加13%-35%,对赤桉树高生长也有促进作用;H4339,对赤桉1年生内幼树树高生长有显著促进作用, 也改善径生长,也适用于尾叶桉;H4111,对赤桉、尾叶桉的后期生长有效果;E4100、H4331、H4338和H4317,有时对参试树种生长有改善作用;其它参试菌根菌E4070,H4937,H4314,在两树种间表现极不稳定。 相似文献
993.
A dynamic, closed-chamber infrared gas analysis (IRGA) system (DC-1: CIRAS-1, PP-Systems, Hitchin, U.K.) was compared with three other systems for measuring soil CO(2) efflux: the soda lime technique (SL), the eddy correlation technique (EC), and another dynamic, closed-chamber IRGA system (DC-2: LI-6250, Li-Cor, Inc., Lincoln, NE). Among the four systems, the DC-1 systematically gave the highest flux rates. Relative to DC-1, SL, EC and DC-2 underestimated fluxes by 10, 36 and 46%, respectively. These large and systematic differences highlight uncertainties in comparing fluxes from different sites obtained with different techniques. Although the three chamber methods gave different results, the results were well correlated. The SL technique underestimated soil CO(2) fluxes compared with the DC-1 system, but both methods agreed well when the SL data were corrected for the underestimation at higher fluxes, indicating that inter-site comparisons are possible if techniques are properly crosscalibrated. The EC was the only system that was not well correlated with DC-1. Under low light conditions, EC values were similar to DC-1 estimates, but under high light conditions the EC system seriously underestimated soil fluxes. This was probably because of interference by the photosynthetic activity of a moss layer. Although below-canopy EC fluxes are not necessarily well suited for measuring soil CO(2) efflux in natural forest ecosystems, they provide valuable information about understory gas exchange when used in tandem with soil chambers. 相似文献
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Hansen BD Lascelles BD Keene BW Adams AK Thomson AE 《American journal of veterinary research》2007,68(5):468-475
OBJECTIVE:To determine the correlation between activity as measured by an accelerometer and videographic measurements of movement and mobility in healthy dogs. ANIMALS: 4 healthy dogs. PROCEDURES: After determination that accelerometers had good agreement, 5 identical accelerometers were used simultaneously to test their output at 8 locations (rotated among collar, vest, and forelimb stocking locations) on each dog. Movement and mobility for each dog were recorded continuously with a computerized videography system for 7-hour sessions on 4 consecutive days. Accelerometer values were combined into 439 fifteen-minute intervals and compared with 3 videographic measurements of movement and mobility (distance traveled, time spent walking > 20 cm/s, and time spent changing position by > 12% of 2-dimensional surface area during 1.5 seconds). RESULTS: 96% of values compared between the most discordant pair of accelerometers were within 2 SDs of the mean value from all 5 accelerometers. All mounting locations provided acceptable correlation with videographic measurements of movement and mobility, and the ventral portion of the collar was determined to be the most convenient location. CONCLUSIONS AND CLINICAL RELEVANCE: Use of an accelerometer was adequate for at-home activity monitoring, an important end point in clinical trials of treatment for chronic disease, and provided information about daily activity that is unattainable by other methods. 相似文献
998.
Biting midges overwintering in Belgium 总被引:6,自引:0,他引:6
999.
OBJECTIVE: To evaluate metastatic rate and survival times of dogs with chondrosarcoma of nonnasal bony sites treated by wide surgical excision. STUDY DESIGN: Retrospective study. ANIMALS: Dogs (n=31) with chondrosarcoma. METHODS: Medical records were retrospectively reviewed to identify dogs with chondrosarcoma of bone in potentially surgically accessible sites. When complete information was not available in the medical record, owners and referring veterinarians were contacted by telephone to evaluate the course of disease and survival times. When possible, histopathologic diagnosis was confirmed by a single board certified pathologist and tumors were histologically graded. RESULTS: Dogs treated by wide surgical excision (n=18) had a mean survival time of 3097 days and did not reach median survival time. Dogs untreated except for diagnostic biopsy (n =13) had a median survival time of 523 days and a mean survival time of 495 days. Method of treatment and tumor grade predicted survival time (P=.016 and P=.007, respectively). Metastatic rate was 28% for treated dogs and 15% for untreated dogs, with no significant difference between the 2 groups (P=.39). CONCLUSIONS: Wide surgical excision significantly improves survival time for dogs with chondrosarcoma of nonnasal bony sites, but does not affect the likelihood of metastasis. Grade may be prognostic for survival. CLINICAL RELEVANCE: Surgical excision benefits dogs with chondrosarcoma and can result in prolonged survival times. Metastasis still occurs in approximately 1 of 4 dogs even after surgical resection. 相似文献
1000.
Presumptive intraperitoneal envenomation resulting in hemoperitoneum and acute abdominal pain in a dog 下载免费PDF全文