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61.
Ekaterina Shorohova Ekaterina Kapitsa Ilkka Vanha-Majamaa 《Forest Ecology and Management》2008,255(10):3606-3612
The wood bulk density, bark mass and decomposition rate constants of cut stumps of the main European boreal tree species were assessed along a 40-year chronosequence of clear-felled sites with and without prescribed burning. Using the single exponential model, the annual decomposition rate constants k of above-ground stumps were calculated as 0.048, 0.052 and 0.068 year−1 for Scots pine (Pinus sylvestris), Norway spruce (Picea abies) and birch (Betula sp.), respectively. Bark decomposed faster than wood and bark fragmentation increased the rate of decomposition. There was a significant negative effect of burning on decomposition rate for pine wood, and for pine and spruce bark but not for spruce and birch wood or for birch bark. The decomposition of bark of all species was slower with larger diameter stumps but only slightly slower in the case of birch wood. Our results suggest (i) using different decomposition rate constants for wood and bark, (ii) taking into account fragmentation as it greatly increases the volume loss, and (iii) adjusting of k in carbon dynamics studies on burned sites. Such refinements to estimates of coarse woody debris decomposition constants could aid in identification of ecosystems and management scenarios necessary to maximize carbon storage and conserve biodiversity. Prescribed burning for restoration purposes decreases decomposition rates and consequently ensures longer persistence of stumps for maintaining biodiversity in intensively managed forests. 相似文献
62.
National inventories of down and dead woody material forest carbon stocks in the United States: Challenges and opportunities 总被引:1,自引:1,他引:0
Concerns over the effect of greenhouse gases and consequent international agreements and regional/national programs have spurred the need for comprehensive assessments of forest ecosystem carbon stocks. Down and dead woody (DDW) materials are a substantial component of forest carbon stocks; however, few surveys of DDW carbon stocks have been conducted at national-scales around the world. This study uses the DDW survey of the United States as a case study to examine the challenges of inventorying DDW at a national scale, reviews how dead wood carbon pools are currently estimated in the National Greenhouse Gas Inventory (NGHGI), and suggests opportunities for improving such inventories. The US currently estimates national DDW carbon stocks using models with standing live tree attributes as predictor variables, calibrated using preliminary DDW field estimates. In recent years, implementation of a national DDW inventory has resulted in inventory-based DDW estimates. National field-based DDW estimates follow the national patterns of DDW carbon dispersion seen in earlier model-based estimates. Although the current DDW inventory provides fairly repeatable measurements within a statistically defensible national sample design for producing national estimates of DDW carbon stocks, improving numerous aspects of the DDW survey would may improve the accuracy and precision of C estimates reported in the NGHGI. 相似文献
63.
晚更新世小江流域泥石流沉积特征及发育规律 总被引:1,自引:0,他引:1
泥石流沉积物作为晚更新世一种特殊沉积类型,是在特定的地质过程和地理环境中形成的。由于特殊的地理环境,泥石流沉积成为晚更新世小江流域主要的沉积类型,本文在研究了青藏高原东缘小江流域蒋家沟附近晚更新世不同时段泥石流沉积剖面沉积特征、化学元素及可溶盐成分的富集规律、CaCO3含量、pH值、有机质含量及植物花粉组合特征后发现,自末次间冰期到末次冰期,沉积物基质中可溶性盐在增多,花粉从以木本为主转变为草本为主,同时泥石流沉积层有变薄的趋势,反映了随气候变冷,泥石流有减少的趋势。 相似文献
64.
Abstract – The links between river flows, water temperature, river regulation and recruitment variability of Golden Perch, Macquaria ambigua oriens, were investigated from the Fitzroy Basin, Queensland. The dominant age classes determined by interpreting growth marks observed in otoliths were variable among rivers. Positive correlations between the age frequency and monthly river flow volumes were greatest in summer (December–March) conversely, autumn, winter and spring river flows correlated poorly for most rivers. Water temperature exhibits strong seasonality across the basin with mean monthly temperatures >23 °C generally occurring between October and April. These data indicate the combination of water temperature and increased river flows are important factors for recruitment. The degree of river regulation is also suspected of contributing to increased variability in dominant age classes within rivers. This assessment highlights the importance of timing of river flows in mitigating the negative effects of river regulation on golden perch populations. 相似文献
65.
降雨泥石流预报的研究 总被引:3,自引:0,他引:3
要准确预报泥石流的发生、到达时间和规模,需要了解流域的基本情况以及泥石流形成的原因和条件。本文以云南省东川蒋家沟为例,以流域降雨产流量为基础,对泥石流暴发,到达时间及暴发规模的预报作了系统的研究。以10min降雨雨强为基本依据,计算10min降雨的产流及形成径流的单宽流量,从而预报泥石流的发生,由此可以计算泥石流的运动速度、预报泥石流的到达时间。以10min激发降雨的产流及形成径流总量,结合泥石流中泥沙体积浓度和流域堵塞系数,计算出泥石流总量,从而预报泥石流的发生规模。 相似文献
66.
泥石流入汇主河淤积规律的水槽试验研究 总被引:1,自引:0,他引:1
以试验为基础,研究了泥石流入汇主河后淤积规律,主要探讨了淤积量及淤积分布问题。通过试验分析认为,泥石流入汇主河后的淤积量基本随流量比的增大而增大,就其淤积速率而言,有先增大后减小的变化规律。淤积量在流量比大约为0.5时出现峰值,在流量比为0.65时出现谷值,淤积量与流量比关系变化曲线以倾斜向上的直线为对称轴,呈倾斜向上的正弦波形。各工况下淤积范围基本不变,但试验中反映出,淤积范围有随交汇角增大而增大的趋势。 相似文献
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