Measurement and modelling of CO2 flux from a drained fen peatland cultivated with reed canary grass and spring barley

Cultivation of bioenergy crops has been suggested as a promising option for reduction of greenhouse gas (GHG) emissions from arable organic soils (Histosols). Here, we report the annual net ecosystem exchange (NEE) fluxes of CO₂ as measured with a dynamic closed chamber method at a drained fen peatland grown with reed canary grass (RCG) and spring barley (SB) in a plot experiment (n = 3 for each cropping system). The CO₂ flux was partitioned into gross photosynthesis (GP) and ecosystem respiration (R_E). For the data analysis, simple yet useful GP and R_E models were developed which introduce plot‐scale ratio vegetation index as an active vegetation proxy. The GP model captures the effect of temperature and vegetation status, and the R_E model estimates the proportion of foliar biomass dependent respiration (R_fb) in the total R_E. Annual R_E was 1887 ± 7 (mean ± standard error, n = 3) and 1288 ± 19 g CO₂‐C m^?2 in RCG and SB plots, respectively, with R_fb accounting for 32 and 22% respectively. Total estimated annual GP was ?1818 ± 42 and ?1329 ± 66 g CO₂‐C m^?2 in RCG and SB plots leading to a NEE of 69 ± 36 g CO₂‐C m^?2 yr^?1 in RCG plots (i.e., a weak net source) and ?41 ± 47 g CO₂‐C m^?2 yr^?1 in SB plots (i.e., a weak net sink). Standard errors related to spatial variation were small (as shown above), but more significant uncertainties were related to the modelling approach for establishment of annual budgets. In conclusion, the bioenergy cropping system was not more favourable than the food cropping system when looking at the atmospheric CO₂ emissions during cultivation. However, in a broader GHG life‐cycle perspective, the lower fertilizer N input and the higher biomass yield in bioenergy cropping systems could be beneficial.     

几种实验动物骨骼肌肌球蛋白ATP酶与SDH酶染色的比较

本文为研究ATP酶和SDH酶两种反应法在骨骼肌分型方面的异同。在兔、豚鼠、大白鼠和小鼠的腓肠肌的恒冷连续切片中,取相邻的两片分别做ATP酶和SDH酶反应,然后选取两片相对应部位做显微摄片,并进行比较。结果显示:两种酶反应中,Ⅰ型纤维的吻合率是83％,Ⅱ型纤维的吻合率为68％。本文认为,ATP酶和SDH酶两种反应所作的分型不能视为等同。     

绿原酸对草鱼鱼种生长、非特异性免疫和肉质的影响

为考察绿原酸对草鱼鱼种生长、非特异性免疫指标和肌肉品质的影响,在基础饲料中分别添加0.00%（对照组）、0.01%、0.02%、0.04%、0.06%、0.08%绿原酸,饲养平均体重（3.190.03） g的草鱼鱼种。经60d饲养,各组草鱼增重率分别为283.1%、305.7%、307.3%、329.6%、308.3%、303.0%,饲料系数分别为1.45、1.33、1.33、1.26、1.30、1.36;与对照组相比,添加0.04%绿原酸显著提高草鱼鱼种增重率,降低了饲料系数（P0.05）,添加0.01%、0.02%、0.06%绿原酸有提高草鱼鱼种增重率的趋势;在饲料中添加0.04%绿原酸可显著提高肝胰脏SOD活性（P0.05）,添加0.08%绿原酸可显著降低血浆天门冬氨酸氨基转移酶活性（P0.05）,各组肝胰脏溶菌酶、血浆碱性磷酸酶和丙氨酸氨基转移酶活性无显著差异（P0.05）。对肌肉成分的分析表明,各组水分、粗脂肪含量无显著差异（P0.05）,但添加0.04%绿原酸可显著提高肌肉粗蛋白、缬氨酸、异亮氨酸、组氨酸、必需氨基酸和总氨基酸含量（P0.05）。添加0.02%绿原酸可显著提高肌肉羟脯氨酸、胶原蛋白含量（P0.05）。综上所述,适量绿原酸能改善草鱼鱼种生长性能、非特异性免疫功能和肌肉品质。草鱼鱼种饲料中绿原酸添加量推荐为0.04%。       

Acquisition and allocation of carbon and nitrogen by Danthonia richardsonii in response to restricted nitrogen supply and CO2 enrichment

Dry weight (DW) and nitrogen (N) accumulation and allocation were measured in isolated plants of Danthonia richardsonii (Wallaby Grass) for 37 d following seed imbibition. Plants were grown at ≈ 365 or 735 μ L L^–1 CO₂ with N supply of 0·05, 0·2 or 0·5 mg N plant^–1 d^–1. Elevated CO₂ increased DW accumulation by 28% (low-N) to 103% (high-N), following an initial stimulation of relative growth rate. Net assimilation rate and leaf nitrogen productivity were increased by elevated CO₂, while N concentration was reduced. N uptake per unit root surface area was unaffected by CO₂ enrichment. The ratio of leaf area to root surface area was decreased by CO₂ enrichment. Allometric analysis revealed a decrease in the shoot-N to root-N ratio at elevated CO₂, while the shoot-DW to root-DW ratio was unchanged. Allometric analysis showed leaf area was reduced, while root surface area was unchanged by elevated CO₂, indicating a down-regulation of total plant capacity for carbon gain rather than a stimulation of mineral nutrient acquisition capacity. Overall, growth in elevated CO₂ resulted in changes in plant morphology and nitrogen use, other than those associated simply with changing plant size and non-structural carbohydrate content.     

三峡库区不同植被类型土壤养分特征

通过三峡库区8个植被类型370个样地的群落调查和土壤分析,研究了不同植被类型、土壤类型、海拔对表层土壤有机质及全氮、速效磷、速效钾含量的影响.结果表明:(1)三峡库区不同植被类型土壤有机质、全氮平均含量规律为阔叶林＞竹林＞针叶林＞灌丛＞草丛,森林土壤有机质及全氮平均含量丰富;速效磷平均含量表现为草丛＞落叶阔叶林＞灌丛＞暖性针叶林＞常绿落叶阔叶混交林＞温性针叶林＞竹林＞常绿阔叶林,草丛与其他植被类型差异显著;速效钾平均含量表现为常绿落叶阔叶混交林＞落叶阔叶林＞灌丛＞针叶林＞竹林＞草丛＞常绿阔叶林,竹林、草丛、常绿阔叶林与常绿落叶阔叶混交林、落叶阔叶林、灌丛、针叶林差异显著.(2)不同土壤类型养分含量差异显著,黄棕壤中有机质、全氮含量高,分别为6.83%、0.44%,紫色土中速效磷含量高,达到54.24mg/kg.(3)随海拔升高,有机质、全氮含量呈明显增加趋势,速效磷、速效钾含量变化趋势不明显.     

羊草草原枯枝落叶积累的研究──自然状态下枯枝落叶的积累及放牧、割草对积累量的影响

在自然状态下,羊草草原枯枝落叶积累季节动态是积累量从５月出现,随着时间推移呈指数形式递增,１０月末出现最大值。当枯枝落叶输入量和分解速率保持恒定时,积累量的年变化,随着时间的进展不断增加,最后达到稳定状态,量大积累量为５７２ｇ／ｍ￣２,达９５％稳定状态时间约为７─８ａ。放牧对枯枝落叶积累有明显的抑制作用,当放牧强度达７．５８羊（只）／ｈｍ￣２时,积累量比非放牧区减少近７４％。割草对枯枝落叶积累的影响也是显著的,随着割草频度增加,积累量明显减少,当一年内刈割３次,积累量减少８３％。刈割时间对积累量的影响表现在割草期的早晚,伴随刈割时间推迟,积累量逐渐减少。     

Below-ground competition between trees and grasses may overwhelm the facilitative effects of hydraulic lift

Under large East African Acacia trees, which were known to show hydraulic lift, we experimentally tested whether tree roots facilitate grass production or compete with grasses for below‐ground resources. Prevention of tree–grass interactions through root trenching led to increased soil water content indicating that trees took up more water from the topsoil than they exuded via hydraulic lift. Biomass was higher in trenched plots compared to controls probably because of reduced competition for water. Stable isotope analyses of plant and source water showed that grasses which competed with trees used a greater proportion of deep water compared with grasses in trenched plots. Grasses therefore used hydraulically lifted water provided by trees, or took up deep soil water directly by growing deeper roots when competition with trees occurred. We conclude that any facilitative effect of hydraulic lift for neighbouring species may easily be overwhelmed by water competition in (semi‐) arid regions.     

草坪草狗牙根中抗逆基因BeDREB的克隆及功能鉴定

DREB(dehydrationresponsiveelementbindingprotein)蛋白是一类在植物中所特有的,能与DRE(dehydrationresponsiveelement)顺式作用元件特异性结合的转录因子,调控与干旱、高盐以及低温等逆境胁迫应答有关基因的表达.根据狗牙根近缘植物的DREB转录因子的AP2EREBP保守结构域的基因序列,通过RTPCR和RACE的方法分别从冷诱导和盐诱导的狗牙根cDNA中扩增到了2个似DREB基因,分别命名为BeDREB1和BeDREB2,并已提交NCBIGenBank,其登录号分别为AY462117和AY462118.这两个基因的编码框均为753个碱基,编码251个氨基酸,具有DREB转录因子的典型特征.两种逆境胁迫下扩增的基因序列同源性很高,达到了97.8%.利用酵母单杂交真核转录激活的方法进行了功能鉴定,证明BeDREB1和BeDREB2蛋白均可以与DRE顺式作用元件结合,激活下游报告基因HIS3的表达.RTPCR结果显示,BeDREB1基因受冷胁迫诱导表达,而BeDREB2受盐胁迫的诱导表达,且随着诱导时间的不同,表达量也在发生变化.上述结果表明,从狗牙根中克隆到的BeDREB1和BeDREB2基因属于DREB转录因子家族的新成员,在狗牙根中分别与冷胁迫和盐胁迫的信号转导有关.     

豚鼠肾小管上皮原代细胞的培养

目的建立一种简便易行的豚鼠原代肾小管上皮细胞培养方法。方法运用筛网分离法和多种酶消化法获取高纯度的肾小管上皮细胞。利用免疫组化法和形态学观察法鉴定培养的肾小管上皮细胞性质及纯度。结果通过肾小管节段贴壁,胶原酶消化组织节段和细胞等方法,有效地促进肾小管原代细胞增殖;胰酶节段消化法的细胞贴壁效果稍差,细胞传代状态不理想;胰酶消化法则细胞贴壁较少,细胞生长状态较差。结论培养豚鼠原代。肾小管上皮细胞是可行的。     

The formation of the brush-sticks: modification of chimpanzees or the by-product of folding?

Based on field research and experimental treatments of trees, we investigated the formation of the brush-like shape of digging sticks used by chimpanzees (Pan troglodytes troglodytes). Evidence obtained in the field consisted of digging sticks found in Mboete, Equatorial Guinea, which is a newly reported locality for this type of tool, and Campo, Cameroon. Digging sticks used by chimpanzees in these areas had a brush-like shape at one end, which was quite different from the other end that was probably used for digging. In our tree-breaking experiment, 8 out of 17 species acquired a typical brush-like shape without human modification when broken off, and the shapes of the stumps were similar to those found in the field. Other species did not acquire the brush-like shape naturally or even after human modifications, and the stumps had different shapes from those found in the field. Our findings suggest that the brush-like shapes of digging sticks are often naturally formed when broken off from trees, depending on the nature of the fibre structure, and that the brush-like end is not used as the digging tool. We conclude that the vegetation surrounding termite mounds might influence how chimpanzees combine different types of tools, i.e., digging stick, brush-stick and fishing tool, for obtaining termites.