河岸带生态系统管理模型研究进展

以河岸带生态系统管理模型REMM为例,介绍了国外河岸带研究的最新成果。河岸带生态系统管理模型(REMM)是一种计算机模拟模型,它可以模拟河岸带的水文、C、N、P营养物质循环、迁移及植被的生长过程。REMM输入的数据是田间的N、P等营养物质、沉积物,输出的是地表径流和浅地表径流及通过渗漏转移溪流和周围水体中的营养物质、沉积物的数量。河岸带包括三个区,REMM允许用户定义每一个区域的不同植被类型组合,以便找出拦截污染物效果较好的缓冲带类型,模型的模拟数据可以为建立植物缓冲带,提供决策依据。最后对REMM模型进行了分析与评价。     

立地条件对拟赤杨人工林木材纤维特性的影响

对不同立地条件拟赤杨人工林木材纤维形态和化学成分进行测定和比较分析,结果表明:不同立地级拟赤杨人工林木材纤维长度的径向变异均属于PanshinⅠ型。拟赤杨人工林木材纤维长度和宽度均随着立地级的升高而增大,而拟赤杨人工林木材纤维长宽比随着立地级的升高而略有减小。拟赤杨人工林木材硝酸—乙醇纤维素含量、Klason木素含量、热水抽出物含量、1%NaOH抽出物含量、苯醇抽出物含量均随着立地级的升高而降低,而戊聚糖含量均随着立地级的升高而提高。对于营造定向培育作为人造板和纸浆原料的拟赤杨人工林宜选择较高立地级的林地栽培。     

保护性耕作示范效果监测研究

分析总结了农业部保护性耕作示范效果(10个县)2003年的监测成果。试验表明，保护性耕作的抗旱、保墒、培肥土壤、增产、增收和防治沙尘暴等都初见成效。尤其在旱地的效果更佳。试验未发现保护性耕作比传统耕作的病虫害严重，但免耕的杂草量比传统耕作的要多，经过施用除草剂可以得到控制。在保护性耕作的实施过程中，需要农艺与农机有机结合，不断创新和完善适合不同类型区的保护性耕作技术模式。     

Revisiting the relationship between common weather variables and loblolly–shortleaf pine seed crops in natural stands

Seed production was monitored during24 years using seed-collection traps inloblolly–shortleaf pine (Pinus taeda L.–P.echinata Mill.) stands located in southeast Arkansas,north-central Louisiana, and southwest Mississippi onthe southeastern Coastal Plain, USA. Sound seedproduction was correlated with mean monthlyprecipitation and temperature from National Oceanicand Atmospheric Administration weather stationslocated near the seed-collection areas to determinethe potential of weather factors in forecasting pineseed crops. Correlations were restricted to threecritical periods in the pine reproductive cycle –strobili primordia differentiation, pollination, andfertilization. The most important (P 0.05)variables correlated with pine seed production for combined locations were cumulative precipitation (r = +0.60) during July, August, and September at 27 to 25 months before seed dispersal and mean temperature (r = –0.45) in August at 26 months before seed dispersal. Because multiple environmental factors can negatively impact pine seed development during the two yearsfollowing strobili primordia differentiation,seed-production forecasts based on weather variablesshould be verified by on-site cone counts during thesummer preceding autumn seed dispersal.     

我国西南山区中小水电站临河(沟)型弃渣场处理措施研究

我国西南地区由于山高坡陡,建设过程中产生了大量的弃土、石、渣(后简称弃渣),这些弃渣如得不到较好的处理将造成严重的水土流失,弃渣处理正慢慢成为水保和环评验收中的制约性因素之一。因此,开发建设项目应充分重视渣场的有效处理。着重探讨西南高山区中小水电开发临河(沟)型渣场的工程措施,包括拦渣堤、排水沟等的设计简化过程。     

甘蓝BoKIN1基因的ploy(A)位点的预测及其频率分析

多聚腺苷酸化(Polyadenylation)是真核生物中一种重要的pre-mRNA加工机制,是mRNA成熟的一个必经过程。为了解甘蓝BoKIN1基因的多聚腺苷酸化加工情况,本研究从甘蓝全基因组数据库中下载得到BoKIN1基因序列,并利用生物信息学手段分析了BoKIN1的基因结构和基因表达。研究结果显示:BoKIN1基因在花器官中表达最高;然后基于EST文库发现了3个ploy(A)位点,并计算了这些ploy(A)位点在premRNA加工过程中被选择的大致频率情况,结果显示BoKIN1基因在pre-mRNA加工过程中至少有6个ploy(A)位点可供选择加尾,其中AP4位点被选择加尾的频率最高,其次是AP5位点。因此选择AP4位点加尾后形成的mRNA是转录后加工的主要产物。通过本研究我们确定了甘蓝类BoKIN1基因6个选择性加尾位点及其3'UTR的主要产物和次要产物,可对于未来进一步利用这些3'UTR奠定基础。     

Biomass and carbon pools of disturbed riparian forests

Quantification of carbon pools as affected by forest age/development can facilitate riparian restoration and increase awareness of the potential for forests to sequester global carbon. Riparian forest biomass and carbon pools were quantified for four riparian forests representing different seral stages in the South Carolina Upper Coastal Plain. Three of the riparian forests were recovering from disturbance (thermal pollution), whereas the fourth represents a mature, relatively undisturbed riparian forest. Above and belowground carbon pools were determined from linear transects established perpendicular to the main stream channels and spanning the width of the riparian area. The objective of this study was to quantify the biomass and carbon pools in severely disturbed, early successional bottomland hardwood riparian forests and to compare these values to those of a less disturbed, mature riparian forest.

Aboveground biomass in all four riparian forests increased during the 2.5-year investigation period. The total carbon pool in these South Carolina Coastal Plain riparian forests increased with forest age/development due to greater tree and soil carbon pools. The mature riparian forest stored approximately four times more carbon than the younger stands. The importance of the herbaceous biomass layer and carbon pool declined relative to total aboveground biomass with increasing forest age. As stands grew older fine root biomass increased, but an inverse relationship existed between percentages of fine root biomass to total biomass. The root carbon pool increased with forest age/development due to a combination of greater fine root biomass and higher root percent carbon.

Aboveground net primary production (NPP) in young riparian forests rapidly approached and exceeded NPP of the more mature riparian forest. As a woody overstory became established (after 8–10 years) annual litterfall rate as a function of NPP was independent of forest age and litterfall amount in the young riparian forests was comparable to mature riparian forests. Biomass in the riparian forest floor and carbon pool declined with increasing riparian forest development. Woody debris in these riparian forests comprised a relatively small carbon pool. An understanding of bottomland hardwood riparian forest carbon pools at different stages of succession allows us to assess how time since disturbance influences these pools, leading to a better understanding of the recovery processes.     

Effect of density of riparian vegetation on effective tractive force

This study aims to clarify the effect of density of riparian vegetation on effective tractive force for various bedload transport conditions. Hydraulic model experiments were performed using a straight channel, and the methods used to calculate the effective tractive force necessary for estimating bedload transport rate in channels with riparian vegetation were studied. An apparatus was developed to directly measure the effective tractive force in a channel with riparian vegetation. Applying the apparatus in a hydraulic experiment allowed accurate direct measurement of effective tractive force, formerly estimated indirectly. Based on the experimental results, the effect of the density of vegetation on the effective tractive force was examined. Then the methods for estimating effective tractive force and bedload transport rate were studied. As a result of the experiment, it was found that the coefficient of velocity U/U_* and the ratio of coefficient of velocity (U/U_*)/(U/U_*) are negatively correlated with the density of vegetation. A very high negative correlation was also obtained between recession coefficient of effective tractive force ( = effective tractive force of a flow with riparian vegetation/effective tractive force of a flow with no riparian vegetation) and the density of vegetation. The friction factor of the channel bed f was positively correlated with the density of vegetation. Methods were presented for accurately estimating effective tractive force using equations including the relationships of the density of vegetation to the coefficient of velocity, the ratio of the coefficient of velocity, and the recession coefficient of effective tractive force. Using the estimated effective tractive force and an existing bedload equation enabled very accurate calculation of bedload transport rate in flows through riparian vegetation. The methods presented in this study have potential to be developed as a tool that can provide guidance in the planning and designing of riparian vegetation that are intended for the prevention and mitigation of floods and resultant sediment transportation.     

Sediment deposition in streams adjacent to upland clearcuts and partially harvested riparian buffers in boreal forest catchments

The rates of fine sediment deposition were compared among three logged and three reference stream reaches 2–3 years before and 3–4 years after logging to assess the environmental impacts of partial harvesting as a novel riparian management strategy for boreal forest streams. The partial-harvest logging resulted in 10, 21 and 28% average basal area removal from riparian buffers at the three logged sites, adjacent to upland clearcut areas. No significant differences from pre-logging or reference-site sedimentation patterns were detected for two of the three logged sites. At the site with the most intense riparian logging (WR2), significant increases of 3–5 times higher than pre-logging or reference levels were detected in fine inorganic sediment (250–1000 μm) load and accumulation in the first year after logging, but no significant change was detected in fine organic sediments or very fine sediments (0.5–250 μm). The increased inorganic sediment deposition at WR2 was temporary with no significant differences from reference or pre-logging levels detectable by summer of the second post-logging year. Logging impacts on fine sedimentation in streams appeared to have been mitigated by careful logging practices including winter harvesting in riparian areas to reduce ground disturbance, and a tendency to avoid immediate (within 3–5 m) stream-side areas. Where it is feasible and advisable to conduct partial harvesting in riparian buffers of boreal forest streams, the logging can be conducted without posing significant risk of increased sediment inputs to streams when careful logging practices are followed.