Effects of disturbance on regeneration of Abies fabri forests at the upper reaches of the Yangtze River

Mudflow is the principal disturbance in Abies fabri forests. In the Gongga Mountain areas of the upper reaches of the Yangtze River, the intensities and periodicity of different scale mudflows vary. Small-scale mudflows are more frequent, occurring every one or two years while large-scale mudflows may occur once in more than one hundred years. Through a field study of A. fabri forests during different stages of growth, we analyzed their structural characteristics and discovered that after different sizes of mud-flow, poplar and birch often occupy the dominant canopy at the expense of the slow growing A. fabri, for only a small number of saplings are A. fabri that occurs in the first regeneration stage. However, a large number of seed resources can be found in mature A. fabri forests and as a unique regeneration species, A. fabri will gradually replace all the other species and form a stable community of strong shade-tolerant trees. Because of the intimate relationship between growing conditions and soil and water conservation at the upper reaches of the Yangtze River, we should carry out some artificial measurements to control and promote the slow regeneration process of A. fabri.     

Causes and typical control model of wind-drift sandy lands in abandoned channel of the Yellow River

The historical formation and development of the abandoned channel of the Yellow River is reviewed and its causes of formation and present condition of prevention and control are analyzed in this paper. Based on this analysis, some ideas about control, critical problems and countermeasures in the next period are proposed with two typical control models as examples. We suggest that in preventing and controlling the wind-drift sandy lands in the region, the emphasis should be to develop, with a greatly expanded effort, a recycling economy. This should realize a combination of two ideas, i.e. integrate combating desertification with a structural adjustment of agricultural and an increase in the income of farmers.     

Effect of forest vegetation on runoff and sediment production in sloping lands of Loess area

According to fixed-position data for 1985–2003 from nine runoff plots of Caijiachuan watershed which lies in Jixian County of Shanxi Province in Loess area, this paper studied the relationship between vegetation and runoff and sediment production in sloping lands in detail, which helps to provide scientific basis for vegetation re-construction and studies on environmental transformation of water and sediment in watersheds of Loess area. Although, many study results testify that forest vegetation has an important function in soil and water conservation and cutting runoff, the effect of vegetation on runoff and sediment transmission is complicated, and this needs to be studied in depth. The results of the paper showed the following. Firstly, the natural secondary forest performs better function of soil and water conservation than artificial Robinia pseudoacacia forest, and runoff and sediment produced in the former in individual rainfall were 65%–82% and 23%–92% of those produced in the latter. At the same time, better correlative relationship between runoff and sediment production and rainfall and rainfall intensity were testified by multiple regression, but the correlation decreased gradually with the increase of canopy density of forest. Secondly, the difference of runoff and sediment production in several land use types was very distinct, and the amount of runoff and sediment produced from Ostryopsis davidiana forest and natural secondary forest were the least, and runoff and sediment produced from in artificial Robinia pseudoacacia forest and Pinus tabulaeformis forest were 5-fold as much as those from O. davidiana forest. Besides, runoff and sediment produced in mixed planting of apple trees and crops were 16.14-fold and 2.96-fold than those of O. davidiana forest, respectively, but the amount decreased obviously after high-standard soil preparation in the case of the former. Thirdly, based on gray cognate analyses of factors affecting runoff and sediment production in sloping land, the factors of stand canopy density and herb and litter biomass were the most significant ones, whose gray incidence degree exceeded 0.6. Therefore, mixed forest with multi-layer stand structure and shrub forest should be developed in vegetation re-construction of Loess area, which will help to increase coverage and litter thickness in order to cut down the runoff and sediment dramatically in sloping land. __________ Translated from Chinese Journal of Applied Ecology, 2005, 16(9): 1,613–1,617 [译自: 应用生态学报, 2005, 16(9): 1,613–1,617]     

我国水土保持高等教育发展现状与对策

 针对当前国内外水土保持高等教育发展的现状和我国水土保持高等教育面临的问题,提出建立"水利部水土保持教育培训中心"、建立农学门类下的国家一级学科、注重师资队伍建设、建立长期稳定的教学、科研、生产相结合的基地(园区、户外教室)、加强水土保持职业技术教育等对策,以加速我国水土保持高等教育的发展。     

黄土半干旱区油松苗木蒸腾特性与影响因子的关系

 为分析土壤水分与气象因子对油松蒸腾作用的影响程度,提高造林成活率,并为林地水分管理提供科学依据。在2004年生长季典型晴天,采用盆栽试验,人为控制土壤水分,利用针叶Li-1600稳态气孔仪和BP-3400精密天平等仪器,对黄土半干旱区油松苗木的蒸腾特性及其影响因子的关系进行研究。结果表明:在不同的土壤水分条件下,油松蒸腾速率和气孔阻力的日变化曲线分别呈“双峰型”和“W”型;在典型晴天下,蒸腾速率与土壤含水量的关系呈三次曲线相关,7、8和10月份,油松叶片蒸腾速率达到最大值时所对应的土壤含水量分别为17.7%、19.8%和17.5%。蒸腾速率除自身生理特性的影响外,还受土壤水分和气象因子综合影响,当土壤水分充足时,蒸腾速率与气象因子相关性高;当土壤水分产生胁迫时,蒸腾速率与气象因子相关性降低。在严重土壤水分胁迫下,7和8月份气温对蒸腾作用的影响最大,10月份光合有效辐射的影响最大。在土壤充分供水的条件下,7月份空气相对湿度对蒸腾作用的影响最大,8月份是气温,10月份是叶温。     

试论我国水土保持学科的性质与定位——川陕“长治工程”中期评估考察的思考

 以小流域为单元实施山、水、田、林、路、渠综合治理的理论与技术体系是在我国水土保持长期生产实践和科学研究中形成的具有中国特色的水土保持学科体系。通过川陕"长治工程"中期评估考察,分析"长治工程"小流域综合治理的特色与创新,并据此讨论我国水土保持学科的性质与定位。水土保持学科无论从法律地位还是学术地位,均应归属于资源保护与利用的范畴,与环境保护和生态学科的本质区别在于,水土保持更具有突出的生产功能。现阶段水土保持学科仍应首先赋予其防治水土流失,治理江河,提高农业生产综合能力,发展农村经济,改善农村基础设施及农民生活质量的内涵,并努力使之与农村生态建设结合,以不断深化和丰富其内涵,同时应在开发建设项目水土保持、饮用水水源地水土保持等方面拓展其学科外延。     

Dynamics of organic carbon and nitrogen in deep soil profile and crop yields under long-term fertilization in wheat-maize cropping system

Soil organic carbon (SOC) and nitrogen (N) are two of the most important indicators for agricultural productivity. The primary objective of this study was to investigate the changes in SOC and N in the deep soil profile (up to 100 cm) and their relationships with crop productivity under the influence of long-term (since 1990) fertilization in the wheat-maize cropping system. Treatments included CK (control), NP (inorganic N and phosphorus (P) fertilizers), NPK (inorganic N, P and potassium fertilizers), NPKM (NPK plus manure), and M (manure). Crop yield and the properties of topsoil were measured yearly from 2001 to 2009. C and N contents were measured at five different depths in 2001 and 2009. The results showed that wheat and maize yields decreased between 2001 and 2009 under the inorganic fertilizer (NP and NPK) treatments. The average yield between 2001 and 2009 under the NP, NPK, NPKM, and M treatments (compared with the CK treatment) increased by 38, 115, 383, and 381%, respectively, for wheat and 348, 891, 2 738, and 1 845%, respectively, for maize. Different long-term fertilization treatments significantly changed coarse free particulate (cfPOC), fine free particulate (ffPOC), intramicroaggregate particulate (iPOC), and mineral-associated (mSOC) organic carbon fractions. In the experimental years of 2001 and 2009, soil fractions occurred in the following order for all treatments: mSOC>cfPOC>iPOC>ffPOC. All fractions were higher under the manure application treatments than under the inorganic fertilization treatments. Compared to the inorganic fertilization treatments, manure input enhanced the stocks of SOC and total N in the surface layer (0–20 cm) but decreased SOC and N in the deep soil layer (80–100 cm). This reveals the efficiency of manure in increasing yield productivity and decreasing risk of vertical loss of nutrients, especially N, compared to inorganic fertilization treatments. The findings provide opportunities for understanding deep soil C and N dynamics, which could help mitigate climate change impact on agricultural production and maintain soil health.     

基于转录组测序金丝草叶片响应铅胁迫的抗氧化酶相关基因

为了深入揭示植物抗氧化酶的相关基因及其响应重金属胁迫的作用机制,以重金属铅（Pb）超富集植物金丝草[Pogonatherum crinitum（Thunb.）Kunth.]为研究对象,设置Pb浓度0、300、500、1 000 mg·L^-1和2 000 mg·L^-1的水培模拟胁迫试验,测定不同Pb浓度下金丝草叶片的抗氧化酶活性,并对Pb胁迫处理的金丝草叶片进行RNA-Seq测序,将转录组测序得到的Unigenes通过GO与KEGG富集注释,筛选出叶片抗氧化酶相关的DEGs,并利用实时荧光定量聚合酶链反应（qRT-PCR）进行验证。结果表明：随Pb胁迫浓度的增加,金丝草叶片过氧化物酶（POD）、超氧化物歧化酶（SOD）和过氧化氢酶（CAT）活性呈增加趋势,丙二醛（MDA）含量则呈先增加后降低的趋势;转录组测序得到总碱基数为56.34 Gb,各样品碱基质量达到Q20、Q30水平的均大于90%,测序结果可靠;筛选出的DEGs通过GO与KEGG数据库进行对比注释发现,金丝草叶片DEGs在“过氧化物酶体”“氧化还原酶活性”“氧化还原酶活性,作用于CH-OH供体组”“活性氧代谢过程”和“过氧化氢代谢过程”等与抗氧化相关的GO功能条目上显著富集,在“谷胱甘肽代谢”“抗坏血酸和醛糖代谢”“植物激素信号转导”“黄酮类生物合成”和“MAPK信号通路-植物”等与抗氧化相关的KEGG通路上显著富集; Pb胁迫下金丝草叶片抗氧化酶相关基因PcSOD、PcPOD和PcCAT上调表达,qRT-PCR验证结果与转录组测序结果一致,Pb胁迫下这些基因的相对表达量与抗氧化酶活性的变化趋势一致。研究表明,金丝草可通过提高抗氧化酶活性来适应Pb胁迫,抗氧化酶相关基因PcSOD、PcPOD和PcCAT参与了金丝草应对Pb胁迫的调控过程。     

棉区有机肥替代化肥对棉花产量及其构成因子的影响

【目的】研究棉花合理的化肥减施量和有机肥替代量,筛选化肥减施与有机肥替代最佳模式,为新疆南部棉区棉花化肥减施增效技术提供理论依据。【方法】采用田间试验,以不施肥和无机复混肥为对照,分析化肥有机替代比例(20%、40%、100%)对棉花产量构成的影响。【结果】施肥可改善棉花产量构成,提高棉花产量。与无机肥处理(CF)比较,化肥减量20%下施用400 kg有机肥、化肥减量40%下施用800方有机肥处理,通过提高棉花单铃重和衣分,改善棉花产量构成,显著提高棉花产量。处理3、处理4处理棉花产量分别为423.50和403.76 kg/667m ²,比空白处理(CK)增产27.70%、21.75%,比CF处理增产5.81%、0.88%。【结论】新疆南部棉区棉花种植以化肥减量20%、化肥减量40%,即每667 m²基施有机肥400 kg,无机复混肥65.39 kg,追施尿素22.35 kg(每667 m²基肥施用有机肥800 kg,无机复混肥49.04 kg,追肥尿素16.76 kg)较为适宜。处理3、处理4模式(20%、40%的化肥减量)可以推广应用。     

Water-use efficiency of a poplar plantation in Northern China

The water-use efficiency (WUE) of an ecosystem—defined as the gross ecosystem production (GEP) divided by the evapotranspiration (ET)—is an important index for understanding the coupling of water and carbon and quantifying water–carbon trade-offs in forests. An open-path eddy covariance technique and a microclimate measurement system were deployed to investigate the WUE of a poplar plantation ecosystem in the Daxing District of Beijing, China, during the growing seasons in 2006, 2007, and 2008. We found that WUE values changed diurnally, peaking in early morning and showing a minimum between 2 pm and 3 pm. This pattern was regulated by photosynthetically active radiation, saturated vapor pressure deficit, and stomatal opening and closure. WUE had inter-daily variations but no substantial seasonal variation. The WUE decreased with increasing soil water content due to the higher sensitivity of ET than GEP to increased soil moisture. Under moist soil conditions (i.e., relative extractable water content >0.4), GEP was stable and WUE was generally low. These results suggest that the poplar plantation does not effectively use the available soil water for carbon uptake, and that soil moisture is lost to the atmosphere through ET.