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41.
草畜平衡管理系列研究(1) ——现行草畜平衡管理制度刍议 总被引:6,自引:4,他引:2
对现行草畜平衡的监测和管理制度进行了分析,指出其在预测的时效性、与现行生产体系的适合性以及针对性等方面存在的不足与缺憾。评价了当前草畜平衡管理中的一些误区。基于基层工作的实践经验和资料数据,提出了改进草畜平衡监测和管理的一些建议。 相似文献
42.
中国草地生态系统碳循环研究进展 总被引:7,自引:2,他引:5
草地生态系统碳循环研究在揭示草地碳源/汇功能,提高草地碳管理水平上至关重要。阐述了碳科学的重要意义;对我国草地生态系统碳储量及碳排放量评估结果予以总结比较;探讨工程建设、草原开垦、放牧管理、施肥、草地恢复技术和气候变化及其他自然因素对草地生态系统碳循环的影响;概括并评价目前我国草地生态系统碳评估的研究方法及意义。指出目前我国草地生态系统碳循环研究中存在的主要问题,及未来中国草地生态系统碳循环的研究趋势。 相似文献
43.
A certified organic apple (Malus × domestica Borkh.) orchard was established to study the interaction of ground cover management systems (GMS) and nutrient sources (NS) on nitrogen (N) use efficiency and N surplus in the Southern U.S. for three years. Trees treated with green compost (GC) and wood chips (WC), regardless of the NS, had greater N accumulation and leaf N use efficiency compared to the shredded paper or mow-and-blow treated trees. The WC-treated trees had comparably low N surplus relative to the GC trees that induced more [NO3−] in soil or soil solution in the rooting zone in September in year 3. GC trees had the highest [NO3−] mineralization in the soil during winter. GMS had greater overall effects on the tree response variables than did the NS. 相似文献
44.
民勤绿洲荒漠过渡区辐射特征与热量平衡规律研究 总被引:8,自引:0,他引:8
根据巴丹吉林沙漠与腾格里沙漠交汇处的民勤绿洲荒漠过渡区的长期连续实测资料 ,分析了该地区的辐射特征 ,研究了热量平衡各分量的变化特征及热量平衡规律。在绿洲荒漠过渡区 ,其太阳辐射、净辐射和反射辐射具有明显的日进程和季节变化规律 ;太阳辐射月总量最大值 (12 0 2 3 3kW·m- 2 )出现在 8月份 ,最小值(5 2 0 6 5kW·m- 2 )出现在 11月份 ;流动沙丘表面的反射率高于有植被覆盖的红柳和白刺灌丛沙丘表面的反射率 ,在植被生长季节更为明显 ,反射率日最大值分别为流动沙丘 (37 5 % ) >白刺沙丘 (2 9 7% ) >红柳沙丘 (2 7 9% ) ;流动沙丘表面接受的净辐射是植被覆盖区的 5 0 %~ 70 %左右。在绿洲荒漠过渡区生态系统的热量平衡中 ,占比例最大的是潜热通量 ,其次为感热通量和土壤热通量。随着荒漠化程度的加深 ,生态系统反射率增加 ,净辐射减少 ,而且热量平衡中感热通量和土壤热通量所占比例增加 ,而潜热通量比例减小。 相似文献
45.
Gerhard?WieserEmail author Thomas?Gigele Hans?Pausch 《European Journal of Forest Research》2005,124(1):1-8
We investigated carbon (C) uptake and respiratory losses of an adult Pinus cembra tree at the alpine timberline throughout an entire year by means of an automated, multiplexing gas exchange system. These chamber measurements were then combined with biomass data for scaling up the C budget to the tree level. Integrated over an entire year, the cumulative C gain of the tree under study was 23.5 kg of C in 2002. The daily C balance was negative for 5 months and the estimated total wintertime respiratory losses were 9% of the amount of C fixed during the growing season. The total annual C loss of the tree consumed 55% of the annual net C gain and the remaining surplus was stored in new tissues (36%) and used for fine root growth (9%). Thus, the overall C budget of P. cembra at the upper timberline is balanced fairly well, although the C sink strength in fine roots is strongly limited owing to low root zone temperatures when compared to conifers at lower elevation sites. 相似文献
46.
47.
In this study we determined soil moisture storage, evapotranspiration (ET) and light interception in an agroforestry trial consisting of pine trees grown over (1) control (bare ground), (2) ryegrass/clovers (Lolium perene/Trifolium spp.), (3) lucerne (Medicago sativa), and (4) ryegrass only during the third growing season between 1992 and 1993. The results show that:
相似文献
1. | In the period when rainfall was frequent and exceeded the evaporative demand (Epot), ET and depletion of soil moisture were not affected by the ground cover treatments. During summer when rainfall was less frequent, but with moisture readily available in the soil profile, ET was associated with plant canopy, and was significantly higher for the pasture ground covers than for the control. Therefore, the more rapid growth by lucerne caused higher ET in this ground cover than in the ryegrass/clovers ground cover in which the pasture was slow growing. At the end of the study period, total ET was in the following order: lucerne (757 mm) > ryegrass/clovers (729 mm) > Control (618 mm). |
2. | ET was dominated by pasture transpiration (Ep) during most of the growing season, but by tree transpiration (Et) in winter when large parts of the pasture canopy was shaded. Ep was always at least 16% higher for lucerne than for ryegrass/clovers species as a result of a greater radiation intercepted by the former. |
3. | Fraction of incoming radiation intercepted by the tree crowns was in the following order: control > ryegrass > ryegrass/clovers > lucerne. At the end of the one-year period, fraction of intercepted radiation was 140% greater for control than for lucerne ground cover. |
4. | The control produced the largest tree crowns, which were almost twice the tree crowns in the lucerne ground cover which produced the smallest trees. Accordingly, the trees in the control intercepted more radiation and rainfall, with the former being lost to evaporation, than the trees in the pasture. |
5. | The fractions of radiation intercepted and ET accounted for by the trees and pastures were associated with the proportion of the plot area they occupied. |
48.
This paper summarizes several studies on N recycling in a tropical silvopastoral system for assessing the ability of the system
to increase soil fertility and insure sustainability. We analyzed the N2 fixation pattern of the woody legume component (Gliricidia sepium), estimated the recycling rate of the fixed N in the soil, and measured N outputs in tree pruning and cut grass (Dichanthium aristatum). With this information, we estimated the N balance of the silvopastoral system at the plot scale. The studies were conducted
in an 11-year-old silvopastoral plot established by planting G. sepium cuttings at 0.3 m × 2 m spacing in natural grassland. The plot was managed as a cut-and-carry system where all the tree pruning
residues (every 2-4 months) and cut grass (every 40-50 days) were removed and animals were excluded. No N fertilizer was applied.
Dinitrogen fixation, as estimated by the 15N natural abundance method, ranged from 60-90% of the total N in aboveground tree biomass depending on season. On average,
76% of the N exports from the plot in tree pruning (194 kg [N] ha–1 yr–1) originated from N2 fixation. Grass production averaged 13 Mg ha–1 yr–1 and N export in cut grass was 195 kg [N] ha–1 yr–1. The total N fixed by G. sepium, as estimated from the tree and grass N exports and the increase in soil N content, was about 555 kg [N] ha–1 yr–1. Carbon sequestration averaged 1.9 Mg [C] ha–1 yr–1 and soil organic N in the 0-0.2 m layer increased at a rate of 166 kg [N] ha–1 yr–1, corresponding to 30% of N2 fixation by the tree. Nitrogen released in nodule turnover (10 kg [N] ha–1 yr–1) and litter decomposition (40 kg [N] ha–1 yr–1) contributed slightly to this increase, and most of the recycled N came from the turnover or the activity of other below-ground
tree biomass than nodules.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
49.
非洲菊切花保鲜剂的研究 总被引:15,自引:0,他引:15
本文研究由蔗糖、硝酸银、8-HQ(8-羟基喹啉)配制的不同保鲜剂对非洲菊切花插瓶寿命、水分平衡、鲜重变化及观赏值等指标的影响。结果表明:4%蔗糖 200mg/L硝酸银 200mg/L硫酸铝 320mg/L8-HQ的保鲜效果最好。 相似文献
50.
转基因植物对环境生态平衡的影响 总被引:1,自引:0,他引:1
根据近年来国内外关于转基因植物的研究进展,结合维持生态平衡的3个主要因素,即物种组成、环境因素及信息系统,论述转基因植物对环境生态平衡的影响. 相似文献