超高产小麦产量及旗叶生理特性的研究

为给超高产小麦生产能力的进一步提升提供理论依据,以超高产小麦品种温麦6号为对照,在水肥条件较好的高产麦田研究了两个具有超高产潜力的小麦品种洛麦21号和周麦18的产量及生育后期旗叶生理特点。结果表明,与温麦6号相比,洛麦21号和周麦18分别增产13.02%和9.92%,差异达极显著和显著水平。洛麦21号和周麦18每公顷穗数与对照差异不显著,但穗粒数和千粒重均显著高于温麦6号,两品种的经济系数也均高于温麦6号。洛麦21号和周麦18在生育后期都具有较高的光合速率、较大的光合叶面积指数和较高的PSⅡ最大光化学效率(Fv/Fm),并且其光合功能期长,叶绿素含量高;旗叶可溶性糖和可溶性蛋白含量不仅高而且下降缓慢。这些结果说明,改善生育后期旗叶光合性能、延缓叶片衰老进程、增加穗粒数和千粒重,以及提高经济系数可进一步提高超高产小麦品种的产量。     

广州市水稻作物生态系统碳汇功能

根据广州市水稻作物系统的相关资料和实地的观测数据,通过实验分析,研究了广州市水稻作物生态系统的碳汇功能。结果表明：2005年广州市水稻作物生态系统净生产力吸收CO2 1621649t?a-1,其土壤CO2排放1168625t?a-1,吸收大于排放,系统净吸收CO2 总量为453024t?a-1,广州市水稻作物生态系统具有碳汇功能,单位面积CO2吸收量为5.58t?hm-2 a-1,是一个弱的碳汇。     

华北平原主要作物生产的碳效率研究初报

提高农作物生产的碳效率是实现低碳农业的重要途径之一。为探明农业生产中的碳效率,本文以河北吴桥县为例,基于农户生产调查数据,利用投入产出法,对华北平原冬小麦、夏玉米和棉花3种主要作物生产的碳投入、碳产出和碳效率进行了评价。结果表明,冬小麦、夏玉米和棉花生产的碳投入总量分别为943.47±225.14、525.74±134.73和513.60±138.94 kg CE km^-2,其中化肥和电能占总量的大部分,分别约占60%和25%。3种作物碳的产出总量分别为8 430.70±774.45、7 194.50± 754.58和5 486.00±547.69 kg CE hm^-2,其中秸秆约占总量的50%,经济产量约占34%,根约占17%。冬小麦、夏玉米和棉花碳的生产效率分别为7.95±2.55、15.90±4.34和7.60±2.92 kg kg^-1 CE,碳的经济效率分别为13.28±4.56、21.47±5.86和76.70±29.45 CHY kg^-1 CE,碳的生态效率分别为9.59±3.07、14.57±3.98和11.69±4.49 kg C kg^-1 CE,作物间的碳效率差异显著,初步表明在华北平原,夏玉米生产的碳综合效率最高,棉花次之,冬小麦最低。     

Estimating the quadratic mean diameters of fine woody debris in forests of the United States

Most fine woody debris (FWD) line-intersect sampling protocols and associated estimators require an approximation of the quadratic mean diameter (QMD) of each individual FWD size class. There is a lack of empirically derived QMDs by FWD size class and species/forest type across the U.S. The objective of this study is to evaluate a technique known as the graphical estimation (GE) method for estimating FWD QMDs across forests of the U.S. Results indicate tremendous inter- and intra-specific variation in small FWD diameters. In addition, GE model fitting results demonstrated a lack of substantial difference in FWD QMDs between common forest types. It is postulated that the mixing, fracturing, and decay of both tree and shrub downed woody debris in diverse forest types across the U.S. can homogenate FWD QMDs at state/national levels. In the absence of site-specific empirical measurement of FWD QMDs, it is suggested that a general national set of FWD QMDs derived from the GE method be adopted for large-scale FWD monitoring efforts.     

Changes in above- and belowground biomass in early successional tropical secondary forests after shifting cultivation in Sarawak,Malaysia

Uncertainties in the rate of biomass variation with forest ageing in tropical secondary forests, particularly in belowground components, limit the accuracy of carbon pool estimates in tropical regions. We monitored changes in above- and belowground biomass, leaf area index (LAI), and biomass allocation to the leaf component to determine the variation in carbon accumulation rate with forest age after shifting cultivation in Sarawak, Malaysia. Nine plots in a 4-year-old forest and fourteen plots in a 10-year-old forest were monitored for 5 and 7 years, respectively. Forest and plant part biomass were calculated from an allometric equation obtained from the same forest stands. Both above- and belowground biomass increased rapidly during the initial decade after abandonment. In contrast, a much slower rate of biomass accumulation was observed after the initial decade. LAI also increased by approximately double from the 4-year-old to 10-year-old forest, and then gently increased to the 17-year-old forest. We also found that allocation variation in leaf biomass and nitrogen was closely related to the rate of biomass accumulation as a forest aged. During the first decade after abandonment, a high biomass and nitrogen allocation to the leaf component may have allowed for a high rate of biomass accumulation. However, reduction in those allocations to leaf component after the initial decade may have helped to suppress the biomass accumulation rate in older secondary forests. Roots accounted for 14.0–16.1% of total biomass in the 4–17-year-old abandoned secondary forests. We also verified the model predicted values for belowground biomass by Cairns et al. (1997) and Mokany et al. (2006), although both models overestimated the values throughout our data sets by 45–50% in the 10-year-old forest. The low root:shoot ratio in the secondary forests may have caused this overestimation. Therefore, our results suggest that we should modify the models to estimate belowground biomass considering the low root:shoot ratio in tropical secondary forests.     

Forest structure and live aboveground biomass variation along an elevational gradient of tropical Atlantic moist forest (Brazil)

Live aboveground biomass (AGB) is an important source of uncertainty in the carbon balance from the tropical regions in part due scarcity of reliable estimates of live AGB and its variation across landscapes and forest types. Studies of forest structure and biomass stocks of Neotropical forests are biased toward Amazonian and Central American sites. In particular, standardized estimates of aboveground biomass stocks for the Brazilian Atlantic forest are rarely available. Notwithstanding the role of environmental variables that control the distribution and abundance of biomass in tropical lowland forests has been the subject of considerable research, the effect of short, steep elevational gradients on tropical forest structure and carbon dynamics is not well known. In order to evaluate forest structure and live AGB variation along an elevational gradient (0–1100 m a.s.l.) of coastal Atlantic Forest in SE Brazil, we carried out a standard census of woody stems ≥4.8 cm dbh in 13 1-ha permanent plots established on four different sites in 2006–2007. Live AGB ranged from 166.3 Mg ha⁻¹ (bootstrapped 95% CI: 144.4,187.0) to 283.2 Mg ha⁻¹ (bootstrapped 95% CI: 253.0,325.2) and increased with elevation. We found that local-scale topographic variation associated with elevation influences the distribution of trees >50 cm dbh and total live AGB. Across all elevations, we found more stems (64–75%) with limited crown illumination but the largest proportion of the live AGB (68–85%) was stored in stems with highly illuminated or fully exposed crowns. Topography, disturbance and associated changes in light and nutrient supply probably control biomass distribution along this short but representative elevational gradient. Our findings also showed that intact Atlantic forest sites stored substantial amounts of carbon aboveground. The live tree AGB of the stands was found to be lower than Central Amazonian forests, but within the range of Neotropical forests, in particular when compared to Central American forests. Our comparative data suggests that differences in live tree AGB among Neotropical forests are probably related to the heterogeneous distribution of large and medium-sized diameter trees within forests and how the live biomass is partitioned among those size classes, in accordance with general trends found by previous studies. In addition, the elevational variation in live AGB stocks suggests a large spatial variability over coastal Atlantic forests in Brazil, clearly indicating that it is important to consider regional differences in biomass stocks for evaluating the role of this threatened tropical biome in the global carbon cycle.     

Estimation of biomass and carbon stocks in plants,soil and forest floor in different tropical forests

An accurate characterization of tree carbon (TC), forest floor carbon (FFC) and soil organic carbon (SOC) in tropical forest plantations is important to estimate their contribution to global carbon stocks. This information, however, is poor and fragmented. Carbon contents were assessed in patula pine (Pinus patula) and teak (Tectona grandis) stands in tropical forest plantations of different development stages in combination with inventory assessments and soil survey information. Growth models were used to associate TOC to tree normal diameter (D) with average basal area and total tree height (H_T), with D and H_T parameters that can be used in 6–26 years old patula pine and teak in commercial tropical forests as indicators of carbon stocks. The information was obtained from individual trees in different development stages in 54 patula pine plots and 42 teak plots. The obtained TC was 99.6 Mg ha⁻¹ in patula pine and 85.7 Mg ha⁻¹ in teak forests. FFC was 2.3 and 1.2 Mg ha⁻¹, SOC in the surface layer (0–25 cm) was 92.6 and 35.8 Mg ha⁻¹, 76.1 and 19 Mg ha⁻¹ in deep layers (25–50 cm) in patula pine and teak, respectively. Carbon storage in trees was similar between patula pine and teak plantations, but patula pine had higher levels of forest floor carbon and soil organic carbon. Carbon storage in trees represents 37 and 60% of the total carbon content in patula pine and teak plantations, respectively. Even so, the remaining percentage corresponds to SOC, whereas FFC content is less than 1%. In summary, differences in carbon stocks between patula pine and teak trees were not significant, but the distribution of carbon differed between the plantation types. The low FFC does not explain the SOC stocks; however, current variability of SOC stocks could be related to variation in land use history.     

土地利用变化对生态系统碳汇-碳源的影响研究——以河北武安市为例

土地利用变化引起的生态系统类型转变对于区域碳循环有着极其重要的作用。运用1997～2008年土地利用变更数据,煤、石油、天然气燃烧的碳排放量,对河北省武安市碳汇-碳源进行了估算,结果表明1997～2008年武安市碳汇处于不稳定状态,碳源呈明显增加趋势。武安市碳增汇由1997年的绿灯区转变为2008年的红灯区。各乡（镇）碳汇-碳源变化的区域差异显著,其中12个乡（镇）处于红灯区,10个乡（镇）处于绿灯区。笔者根据结果提出增加碳汇,减少碳排放的建议,旨在为区域的减排目标和可持续发展提供借鉴。     

凉山州森林植被碳储量估算及碳密度空间分析

基于凉山州森林分类区划界定成果,利用生物量模型对全州森林植被碳储量进行估算,并进行空间分析。估算结果,全州森林植被碳储量为110.2491 Tg,其中公益林80.888 Tg;商品林29.361 1 Tg;碳储量主要集中在江河两岸和荒漠化及水土流失严重地区两个生态区位,但碳密度相对不高;全州森林植被碳储量分布不均,西北和东北区域碳密度相对较高,中部和南部区域相对较低。     

土壤有机碳储量的估算研究进展

就土壤碳循环与全球变化,人类活动对土壤有机碳库的影响,土壤有机碳库的估算等主要研究进展进行了分析综述,并基于空间尺度对相关估算方法进行了分析和评价。