Forest biomass and root–shoot allocation in northeast China

Temperate and boreal forests act as major sinks for atmospheric CO₂. To assess the magnitude and distribution of the sinks more precisely, an accurate estimation of forest biomass is required. However, the determinants of large-scale biomass pattern (especially root biomass) are still poorly understood for these forests in China. In this study, we used 515 field measurements of biomass across the northeast part of China, to examine factors affecting large-scale biomass pattern and root–shoot biomass allocation. Our results showed that, Picea & Abies forest and coniferous & broadleaf mixed forest had the highest mean biomass (178–202 Mg/ha), while Pinus sylvestris forest the lowest (78 Mg/ha). The root:shoot (R/S) biomass ratio ranged between 0.09 and 0.67 in northeast China, with an average of 0.27. Forest origin (primary/secondary/planted forest) explained 31–37% of variation in biomass (total, shoot and root), while climate explained only 8–15%, reflecting the strong effect of disturbance on forest biomass. Compared with shoot biomass, root biomass was less limited by precipitation as a result of biomass allocation change. R/S ratio was negatively related to water availability, shoot biomass, stand age, height and volume, suggesting significant effects of climate and ontogeny on biomass allocation. Root–shoot biomass relationships also differed significantly between natural and planted forests, and between broadleaf and coniferous forests. Shoot biomass, climate and forest origin were the most important predictors for root biomass, and together explained 83% of the variation. This model provided a better way for estimating root biomass than the R/S ratio method, which predicted root biomass with a R² of 0.71.     

Short term soil priming effects and the mineralisation of biochar following its incorporation to soils of different pH

The aim of this work was to determine the magnitude of the priming effect, i.e. short-term changes in the rate (negative or positive) of mineralisation of native soil organic carbon (C), following addition of biochars. The biochars were made from Miscanthus giganteus, a C4 plant, naturally enriched with ¹³C. The biochars were produced at 350 °C (biochar350) and 700 °C (biochar700) and applied with and without ryegrass as a substrate to a clay-loam soil at pH 3.7 and 7.6. A secondary aim was to determine the effect of ryegrass addition on the mineralisation of the two biochars.After 87 days, biochar350 addition caused priming effects equivalent to 250 and 319 μg CO₂-C g⁻¹ soil, in the low and high pH soil, respectively. The largest priming effects occurred at the start of the incubations. The size of the priming effect was decreased at higher biochar pyrolysis temperatures, which may be a way of controlling priming effects following biochar incorporation to soil, if desired. The priming effect was probably induced by the water soluble components of the biochar. At 87 days of incubation, 0.14% and 0.18% of biochar700 and 0.61% and 0.84% of biochar350 were mineralized in the low and high pH soil, respectively. Ryegrass addition gave an increased biochar350 mineralisation of 33% and 40%, and increased biochar700 at 137% and 70%, in the low and high pH soils, respectively. Certainly, on the basis of our results, if biochar is used to sequester carbon a priming effect may occur, increasing CO₂-C evolved from soil and decreasing soil organic C. However, this will be more than compensated for by the increased soil C caused by biochar incorporation. A similar conclusion holds for accelerated mineralisation of biochar due to incorporation of fresh labile substrates. We consider that our results are the first to unequivocally demonstrate the initiation, progress and termination of a true positive priming effect by biochar on native soil organic C.     

基于足迹家族的甘肃省生态文明建设评价

改进了足迹家族法并应用于甘肃省的生态文明建设评价,结果表明:1990—2013年甘肃省生态压力处于中等水平,温室气体(GHG)排放由较低升至中等,水资源压力较高;生态文明建设为中等水平。空间上,生态压力较高的有兰州、白银、嘉峪关,较低的有酒泉、陇南、庆阳、张掖、甘南,其余地区为中等水平;GHG排放较高的是金昌、嘉峪关、兰州,中等的是酒泉、白银和张掖,其余地区较低(临夏为碳汇);水资源压力较低的是甘南、临夏和陇南,中等的是张掖和酒泉,其他9市压力较高;生态文明水平较高的有甘南、临夏、陇南和张掖,较低的是白银、金昌、兰州和嘉峪关,其余地区中等。     

宁夏回族自治区平罗县主要农作物碳足迹研究

农田碳足迹可以全面地反映农作物生产过程中各种因素引起的碳排放效应,是指导农业生产节能减排的重要指标。为探明农作物生产的碳足迹,基于宁夏回族自治区平罗县农田生产的实地调查数据,利用碳足迹的基本理论和方法,测算了该县农作物碳足迹。结果表明,水稻、玉米和小麦的碳足迹分别为1 487.56±164.59,913.03±142.99和809.75±144.99kg Ce/(hm2.a);碳成本分别为0.17±0.05,0.08±0.02g和0.12±0.03kg Ce/kg;化肥的施用量是影响碳足迹的主要因素,而水稻生产过程中灌溉水及育秧过程也是其碳足迹较高的主要原因。为了提高农田固碳减排增汇效益,应压缩水稻种植面积,扩大玉米和小麦种植,同时,建立节肥低碳高效的种植模式是实现平罗县农田节能减排的有效途径。     

Decomposition Dynamics and Nutrient Release Pattern from Leaf Litters of Five Commonly Occurring Homegarden Tree Species in Mizoram,India

Leaf litter decomposition and nutrient release patterns from five common multipurpose tree species—viz., Artocarpus heterophyllus, Mangifera indica, Areca catechu, Citrus sp., and Tamarindus indica, found in homegardens of Mizoram—were evaluated using a litter bag technique. The result of the study indicates a varying pattern of decomposition and nutrient release (N&P) among the species. Citrus sp. and T. indica were found to be the most labile species with comparatively much higher decay constant and faster nutrient release. Initial nitrogen concentration, lignin content, and lignin/N ratio of foliage litter showed significantly higher (p < .01) correlation with the decay coefficient and were found to be the important determinants in the decay process. The initial slow release and immobilization of N in A. heterophyllus and M. indica leaf litter reflect their potential as a source of nitrogen storage and effective mulching material. While litter from T. indica and Citrus sp. can provide the short-term nutrient need, foliage for the other three species may supply the long-term nutrient requirement for the understory crops in such agroforestry systems.     

饥饿与再投喂对方斑东风螺生长、基本营养成分及RNA/DNA比值的影响

在(25.8±1.7)℃条件下,测定了方斑东风螺(5.25±0.53)g在不同时间(7、15、25和40d)饥饿处理后再投饵30d过程中的生长参数、基本营养成分及组织RNA/DNA比值的变化。饥饿状态下,螺体水分含量逐渐上升,第15天时显著高于对照组;脂肪与糖原含量均下降,并分别于饥饿15d、25d时显著低于对照组(P<0.05);而蛋白质含量在不同处理组间无显著性差异(P>0.05);足肌与肝胰脏中RNA/DNA比值均随饥饿时间延长而逐渐降低。恢复生长后,除饥饿40d组含水量显著高于对照组外(P<0.05),该组其余营养成分及其它各组相应指标均恢复至或接近对照组;RNA/DNA比值除在饥饿40d组肝胰脏中仍较低外均接近或显著高于对照组。各组幼螺摄食率(FR)均高于或显著高于对照组(P<0.05),体重增量、食物转化率(FCE)在前3处理组及特殊生长率(SGR)在饥饿7d与25d组均与对照组间无显著差异(P>0.05),而饥饿15d组的SGR显著高于对照组(P<0.05);饥饿40d组尽管FR显著提高,但体重增量、FCE及SGR均显著低于对照组(P<0.05)。结果表明,方斑东风螺幼螺饥饿时主要消耗脂肪与糖原...     

木材固碳量与含碳率研究进展

木材碳学是近年来兴起的一门科学, 其主要研究内容包括木材碳素的储存量、木材储能、人工林木材固碳增汇与优质木材培育技术及木质产品固碳延伸等方面。文中简述了木材碳学研究中木材固碳量与含碳率、木材固碳量的影响因素、木材固碳量与木材热值的关系以及木质材料固碳量和固碳延伸等方面的研究现状, 并对今后的研究方向进行了展望。     

Leucocyte profile and growth rates as indicators of crowding stress in pejerrey fingerlings (Odontesthes bonariensis)

Crowding is one of the most common stressors found in intensive aquaculture, compromising growth rates and immune function. Plasmatic cortisol is a classic stress biomarker for fish, but its quantification is expensive and demands blood volumes that small individuals do not provide, constraining the usage of this technique to assess stress in fingerlings. The leucocyte profile is an alternative methodology to quantify stress with reduced costs and volumes of blood. Stress conditions promote neutrophilia and lymphocytopenia as response to elevated glucocorticoids levels. Considering the difficulties to assess stress imposed by intensive fish farming using measurement of glucocorticoid hormones, this study aimed to evaluate the stress‐induced changes in leucocyte profiles and growth rates imposed by crowding in fingerlings of Odontesthes bonariensis, a promising South‐American candidate for freshwater aquaculture. To meet these objectives, fingerlings (initial weight 0.05 ± 0.06 g and length 1.68 ± 0.13 cm) were reared for 45 days under three rearing densities (1, 5 and 10 fingerlings L^?1). At the end of this period, fish were anaesthetized and euthanized to obtain the leucocyte profile, neutrophil:lymphocyte ratio (N:L) and growth rate. Increasing density promoted: significant reduction in growth (final length, weight and specific growth rate); neutrophilia and lymphocytopenia; and increased N:L ratio. Concluding, the tested rearing densities imposed distinct levels of stress characterized by different N:L ratio, demonstrating that the leucocyte profile is a reliable alternative to measure stress levels in O. bonariensis fingerlings and probably in other fish species.     

Relationship between stable carbon isotope discrimination and water use efficiency under regulated deficit irrigation of pear-jujube tree

To investigate the relationship between stable carbon isotope discrimination (Δ) of different organs and water use efficiency (WUE) under different water deficit levels, severe, moderate and low water deficit levels were treated at bud burst to leafing, flowering to fruit set, fruit growth and fruit maturation stages of field grown pear-jujube tree, and leaf stable carbon isotope discrimination (Δ_L) at different growth stages and fruit stable carbon isotope discrimination (Δ_F) at fruit maturation stage were measured. The results indicated that water deficit had significant effect on Δ_L at different growth stages and Δ_F at fruit maturation stage. As compared with full irrigation, the average Δ_L at different growth stages and Δ_F at fruit maturation stage were decreased by 1.23% and 2.67% for different water deficit levels, respectively. Δ_L and Δ_F among different water deficit treatments had significant difference at the same growth stage (P < 0.05). Under different water deficit conditions, significant relationships between the Δ_L and WUE_i (photosynthesis rate/transpiration rate, P_n/T_r), WUE_n (photosynthesis rate/stomatal conductance of CO_2, P_n/g_s), WUE_y (yield/crop water consumption, Y/ET_c) and yield, or between the Δ_F and WUE_y and yield were found, respectively. There were significantly negative correlations of Δ_L with WUE_i, WUE_n, WUE_y and yield (P < 0.01) at the fruit maturation stage, or Δ_L with WUE_i and WUE_n (P < 0.01) over whole growth stage, respectively. Δ_F was negatively correlated with WUE_y, WUE_n and yield (P < 0.05), but positively correlated with ET_c (P < 0.01) over the whole growth stage. Thus Δ_L or Δ_F can compare WUE_n and WUE_y, so the stable carbon isotope discrimination method can be applied to evaluate the water use efficiency of pear-jujube tree under the regulated deficit irrigation.     

内蒙农牧交错带地区土地利用方式和施肥对土壤碳库的影响

内蒙武川是我国典型的内蒙农牧交错带地区,土地利用方式转变和施肥是影响该地区农业生产和土壤碳储量的重要人类活动。选取内蒙武川地区,针对不同土地利用方式(耕地、退耕还林/还草)和施肥措施(化肥、有机肥)的长期定位试验土壤,分析土壤有机碳(SOC)、土壤无机碳(SIC)和全氮(TN)含量和储量,结合13C和15N稳定同位素方法,研究土地利用方式和施肥措施对于该地区土壤碳氮转化的影响规律。研究表明,退耕还灌/还草后,SOC储量较耕地均有显著提高(提高幅度0.60~0.98 Mg hm-2 a-1),SIC储量也增加或保持相同水平(柠条地除外)。相比不施肥处理,施用有机肥能显著增加SOC(1.08~1.19 Mg hm-2 a-1),施化肥处理则会降低SIC(0.06~0.16 Mg hm-2 a-1),且主要影响次生碳酸盐。施肥SIC中原生碳酸盐比例(0~23%)低于自然土壤(3%~29%)。施肥措施对于土壤碳氮的转化强度远大于土地利用方式的改变。对于内蒙等干旱半干旱地区土壤,土地利用和施肥措施对于土壤有机和无机碳的影响应该在区域固碳管理中给予全面考虑。