Relationship Between Diurnal Changes of Net Photosynthetic Rate and Influencing Factors in Rice under Saline Sodic Stress

The net photosynthetic rate of flag leaves and influencing factors under saline sodic soil conditions were investigated at the full heading stage of rice. The net photosynthetic rate of rice leaves showed a double-peak curve in a day in both non-saline sodic and saline sodic soil treatments. The first peak of the net photosynthetic rate appeared at 9：00-10：00 and 9：00 in the saline sodic and non-saline sodic soil treatments, respectively, whereas the second peak both at 14：00. The midday depression of the net photosynthetic rate always appeared regardless of non-saline sodic or saline sodic soil conditions. In addition, the net photosynthetic rate significantly decreased in all day under saline sodic conditions compared with that under non-saline sodic conditions. Some differences were observed in correlation characters between the net photosynthetic rate and all influencing factors during 9：00-13：00. Under non-saline sodic conditions, the diurnal changes of the net photosynthetic rate in a day were mainly caused by stomatal conductance, and the limitation value and the stomatal factors served as determinants; whereas under saline sodic stress, the diurnal changes of the net photosynthetic rate in a day were mainly caused by non stomatal factors including light intensity and air temperature.

Diurnal variation of gas exchange, chlorophyll fluorescence, and photosynthetic response of six parental lines of maize released in three eras

Over the past seven decades, the grain yield of maize(Zea mays L.) has increased continuously in China, mostly due to hybridization innovations, particularly recent genetic improvements in photosynthesis. In order to reveal photosynthetic characters of elite inbred lines in different ears, a field experiment was conducted at the North China Plain of Shandong Province in China. Six parental lines of maize introduced in three eras(the 1960 s, 1980 s, and 2000 s) were investigated diurnal variation of gas exchange, chlorophyll fluorescence, and photosynthetic response characteristic at the grain filling stage. Compared to earlier parental lines, the 2000 s parental lines always had higher net photosynthetic rate(Pn) throughout the day, especially at noon, and a mid-day depression in Pn did not occur in all hybrids parental lines. Moreover, the stomatal conductance(Gs) and water use efficiency(WUE) of the 2000 s’ lines showed higher value than those of the 1960 s’ and 1980 s’ lines. The inbred lines differences in photosynthetic parameters were partly owing to their different quantum carboxylation efficiencies and light synthase activities. Simultaneously, the 2000 s parental lines exhibited lower light and CO2 compensation points, and their higher apparent quantum yield, and carboxylation efficiency. These suggested that the modern parental lines required lower light intensity and less CO2 to maintain a relatively high photosynthetic capacity, substantially increasing leaf physical quality and stress resistance. It provided crucial information of high photo-efficiency and stress-resistance breeding in maize.

Photosynthetic Diurnal Variation of Soybean Cultivars with High Photosynthetic Efficiency

The photosynthetic characters were investigated among soybean cultivars with high photosynthetic efficiency and high yield. The results indicated that: 1) There were significant differences in photosynthetic rate (Pn) and dark respiration rate (DR) under saturation light intensity and appropriate temperature. 2) There were a little difference in light compensation point among them. Photo flux density (PFD) were about 360μmol/m2·s when Pn tended to zero. 3) When PFD>1 900 μmol/m2·s, photoinhibition occuried a-mong the cultivars. Diurnal variation of Pn was shown a curve with two peaks. 4) The cultivars with high photosynthetic efficiency were subjected less to photoinhibition than that with high yield. Critical temperatures of photoinhibition in high photosynthetic efficiency cultivars were higher than that of high yield.

Relationship Between Net Photosynthetic Rate of Cassava SC205 and Its Physio-ecological Factors

[Objective]The aim was to measure photosynthetic characters of SC 205, a cassava cultivar, and explore the relationships of the net photosynthetic rate （Pn） with physiological and ecological factors. [Method] The diurnal variations of photosyn-thesis in leaves of SC205 were studied by LICOR-6400 portable photosynthesis system, and the relationships of the net photosynthetic rate （Pn） with physiological and ecological factors were studied by simple correlation analysis and path analysis. [Result] The curve of diurnal variation of Pn showed single peak at 10：00 am at 24.07 μ mol CO2 m2/s, without showing midday depression; the diurnal changes of stomatal conductance （Gs）, transpiration rate （Tr）, leaf temperature （Tl）, air tempera-ture （Ta） and photosynthetic active radiation （PAR） al showed single peak curves, and there were positive relationships of Pn with Gs, Tr, Tl, Ta and PAR. The diur-nal variations of intercellular CO2 concentration （Ci）, atmospheric CO2 concentration （Ca）, relative humidity （RH） showed in a U-shape curve. There were highly signifi-cant positive correlation of Pn with Gs and PAR; the diurnal variation of Pn had highly significant negative correlations with Ci and Ca. The direct impact of physio-logical factors on Pn was as fol ows： Ci＆gt;Gs＆gt;Tl＆gt;Tr, and the direct impact of ecologi-cal factors was RH＆gt;PAR＆gt;Ca＆gt;Ta. [Conclusion] The research showed that Ci, Gs and Tr play very important roles in the changes of Pn among the physiological fac-tors, and PAR and Ca affect the changes of Pn among the ecological factors.

Diurnal Variation of Photosynthetic Physiological Characteristics of Kadsura coccinea(Lem.)A.C.Smith

[Objectives]This study was conducted to investigate the diurnal variations of photosynthetic and physiological characteristics in 3-year-old Kadsura coccinea(Lem.)A.C.Smith plants.[Methods]A Li-6400 portable photosynthetic system was used to study the diurnal variations of the photosynthetic physiological characteristics of K.coccinea.[Results]The diurnal variation of the net photosynthetic rate(Pn)of K.coccinea leaves showed a"double peak"curve,and there was a lunch break at noon.The maximum value of Pn[4.51 mmol/(m^(2)·s)]appeared at 10:00,and the daily average Pn was 3.98 mol/(m^(2)·s);and the stepwise regression analysis showed that photosynthetically active radiation(PAR)and stomatal conductance(Gs)were the main factors affecting Pn.The partial correlation analysis and path analysis showed that the order of effects on Pn was Gs>PAR.[Conclusions]This study provides a reference for further research on the development and utilization of K.coccinea.

Diurnal and seasonal variation of glacier meltwater hydrochemistry in Qiyi glacierized catchment in Qilian Mountains, Northwest China: implication for chemical weathering

In glacierized catchments, glacier runoff typically shows a strong diurnal cycle in the ablation season(June-September). To elucidate the effect of these processes on the chemical weathering, fresh snowfall and water samples were collected and studied from the supraglacial river, proglacial river,and gauging site in Qiyi glacierized catchment Qilian Mountains, Northwestern China, in the summer of2011. The pH and electronic conductivity(EC) were determined in the field, and the concentrations of major ions(Na^+, K^+, Mg^(2+), Ca^(2+), Cl^-, SO_4^(2-), NO_3^-) were measured. The results indicated that EC linearly increased with increasing distance from the glacial snout, and the concentrations of major ions increased with increasing water-rock interaction time. Along the flow path of the glacier runoff, Na^+ and Cl^-are more concentrated than other ions in the supraglacial river while Mg^(2+) and SO_4^(2-)are more concentrated than other ions at the gauging site. The discharge, pH, EC,and the concentrations of major ions exhibited significant diurnal variation along the flow path. On the other hand, the amplitude of variation diminished from upstream to downstream along the flow path.The chemical weathering rate(Na^++K^++Mg^(2+)+Ca^(2+))was determined to be 10.9 t/yr/km^2. Moreover,further research indicated that the sampling method influenced the assessment of chemical weathering rates. When the sample was collected randomly in one diurnal cycle of hydrography, the estimated ionic flux could deviate-47%~73% based on estimated hourly data. In contrast, if three samples were collected at peak, base flow and the discharge decreasing rate starts to slow down in one diurnal cycle of hydrography, respectively, the deviation would be less than 15%. The smaller the diurnal variation of discharge, the smaller deviation calculated.

Effects of sea surface temperature,cloud radiative and microphysical processes,and diurnal variations on rainfall in equilibrium cloud-resolving model simulations

The effects of sea surface temperature（SST）,cloud radiative and microphysical processes,and diurnal variations on rainfall statistics are documented with grid data from the two-dimensional equilibrium cloud-resolving model simulations.For a rain rate of higher than 3 mm.h 1,water vapor convergence prevails.The rainfall amount decreases with the decrease of SST from 29℃ to 27℃,the inclusion of diurnal variation of SST,or the exclusion of microphysical effects of ice clouds and radiative effects of water clouds,which are primarily associated with the decreases in water vapor convergence.However,the amount of rainfall increases with the increase of SST from 29℃ to 31℃,the exclusion of diurnal variation of solar zenith angle,and the exclusion of the radiative effects of ice clouds,which are primarily related to increases in water vapor convergence.For a rain rate of less than 3 mm.h 1,water vapor divergence prevails.Unlike rainfall statistics for rain rates of higher than 3 mm.h 1,the decrease of SST from 29℃ to 27℃ and the exclusion of radiative effects of water clouds in the presence of radiative effects of ice clouds increase the rainfall amount,which corresponds to the suppression in water vapor divergence.The exclusion of microphysical effects of ice clouds decreases the amount of rainfall,which corresponds to the enhancement in water vapor divergence.The amount of rainfall is less sensitive to the increase of SST from 29℃ to 31℃ and to the radiative effects of water clouds in the absence of the radiative effects of ice clouds.

Leaf Photosynthetic Rate and Related Influencing Factors in Super High-yield Combination C Liangyou H255

[ Objective] Study on the photosynthesis and influencing factors in super high-yield combination C Liangyou H255. [ Method] The photosynthetic characteristies were measured at a hot and muggy day under natural conditions. [ Result] A respective single peak at 11：30 was observed in diurnal variation curves of net photosynthetic rate （Pn） and transpiration rate（Tr）. Correlation analysis shows that Pn presents an extremely significant correlation with photon flux densities （PFD） of photosynthetically active radiation, in comparison assumes a significant correlation either with stomatal conductance （Gs） or with ambient CO2 concentration （Ca）. [ Conclusion] Gs followed by PFD presented most influence on Pn of super high-yield combination C Liangyou H255.

盐城滨海淡水湿地芦苇光合特性及叶绿素荧光特性日变化研究

[目的]探讨盐城滨海淡水湿地芦苇光合特性和叶绿素荧光特性。[方法]以滨海淡水湿地芦苇为研究对象,测定光合参数和叶绿素荧光参数日变化,并与滨海盐沼湿地芦苇进行比较。[结果]盐城滨海淡水湿地芦苇净光合速率、气孔导度、蒸腾速率和胞间CO_(2)浓度日变化呈双峰型,水分利用效率日变化呈“U”型。电子传递速率日变化整体上呈下降趋势,非光化学淬灭系数和实际光化学量子效率日变化分别呈倒“U”型和“U”型。滨海淡水湿地芦苇净光合速率高于滨海盐沼湿地芦苇,具有更强的光合能力。[结论]盐城滨海淡水湿地芦苇相较于滨海盐沼湿地芦苇具有更强的光合固碳能力。

施氮对河西走廊灌区青贮玉米抽雄期光合日变化、农艺性状及干物质量的影响

【目的】探究施氮对河西走廊灌溉区青贮玉米光合日变化和农艺性状及干物质量的影响,寻求河西走廊灌溉区最佳施氮量。【方法】以青贮玉米金铃67号为研究对象,于2022年在河西走廊灌溉区开展大田试验,设置5种施氮水平N0(0 kg/hm^(2))、N1(218 kg/hm^(2))、N2(249 kg/hm^(2))、N3(280kg/hm^(2))、N4(311 kg/hm^(2)),分析不同施氮水平对青贮玉米抽雄期叶片相对叶绿素含量(SPAD)、光合特性、农艺性状及干物质量的差异。【结果】N3处理下青贮玉米的SPAD相较于N0提高17.56%;N3处理下净光合速率、水分利用率分别提高17.42%、36.56%,N4处理蒸腾速率和气孔导度分别比N0高50.00%、49.14%,胞间二氧化碳N2处理比N0高42.96%,农艺性状及干物质量均以N3处理最高,相比N0株高、基径、叶面积指数、干物质量分别提高10.60%、18.18%、41.05%、34.59%。【结论】河西灌区施氮量280 kg/hm^(2)能够提高抽雄期玉米光合特性、农艺性状及干物质量。

3个油橄榄品种光合特性与同化物分配规律

为研究油橄榄光合特性及同化物分配规律,使用LI-6400XT光合测定系统及13C同位素标记分别测定3个油橄榄品种的光合指标和同化物分配。结果表明,3个品种光合日变化均为典型的双峰型,存在“午休”现象。灰色关联度分析表明,影响净光合速率的主要因子是气孔导度和大气CO_(2)浓度。3个油橄榄品种的光饱和点、光补充点均高于一般阳性植物,为强阳性树种。不同品种间光合及CO_(2)响应曲线特征参数存在差异,‘佛奥’、‘鄂植8号’光合能力较强,对光和CO_(2)的利用范围及利用率高。用13C同位素法标记72 h后,光合同化物主要集中在叶片,分配率为39.52%~49.92%;种仁的光合同化物含量最低,分配率仅为6.67%~8.18%。

6个猕猴桃品种的光合特性分析

为筛选优良猕猴桃品种,以2个泰安市本地主栽品种和4个引进品种为试验材料,测定叶片相关生理指标,使用便携式光合作用测定系统测定6个猕猴桃品种的光合日变化、光合作用光响应(PnPAR),分析净光合速率(Pn)、气孔导度(Gs)、胞间CO_(2)浓度(Ci)、蒸腾速率(Tr)之间的相关性。结果表明,‘徐香’光适应范围为最高,其表观量子效率为0.067,光饱和点为1632μmol/(m^(2)·s),光饱和点与光补偿点差值为1600μmol/(m^(2)·s)。‘泰山1号’净光合速率最大为18.45μmol/(m^(2)·s),光能利用效率最高达到1.26%,均是6个猕猴桃品种中的最高值。综合分析,‘徐香’和‘泰山1号’光合特性最好。以净光合速率、蒸腾速率、气孔导度、胞间CO_(2)浓度作为变量进行相关性分析,发现气孔导度和蒸腾速率对猕猴桃净光合速率的影响呈极显著正相关,胞间CO_(2)浓度和净光合速率呈现显著负相关。

宁夏贺兰山东麓新引酿酒葡萄品种光合特性比较

【目的】对宁夏贺兰山东麓产区种植的酿酒葡萄品种马瑟兰、马尔贝克、小芒森和维欧妮与产区广泛种植的酿酒葡萄品种赤霞珠(CK_(1))和霞多丽(CK_(2))光合生理特征进行研究,筛选适宜该地区种植的新品种。【方法】测定不同品种成熟叶片的光响应曲线、CO_(2)响应曲线以及自然条件下的光合日变化特征。【结果】不同品种光合性状存在显著差异,在光响应曲线特征参数中,马瑟兰的最大净光合速率(P_(m))、光饱和点(LSP)显著高于其他品种,CK_(2)的光补偿点(CCP)和暗呼吸速率(R_(d))最大且表观量子效率(AQY)低于其他品种。由CO_(2)响应曲线特征参数可知,维欧妮的羧化效率(CE)、最大光合能力(A_(max))和光呼吸速率(R_(q))均显著高于其他品种,各品种的CO_(2)饱和点(CSP)变化范围在1 109.98~1 318.83μmol/(m^(2)·s)之间,CK_(2)的CO_(2)补偿点(CCP)最高,为77.74μmol/(m^(2)·s),其次为马尔贝克,维欧妮的最低,为60.18μmol/(m^(2)·s)。不同品种的光合日变化中,马瑟兰和马尔贝克的日P_n呈现双峰曲线,并具有明显的“光合午休”现象,其他4个品种的日P_n呈现单峰曲线,其中,维欧妮的净光合速率日均值最大,马尔贝克的最小。【结论】4个新引品种在贺兰山东麓产区的光合适应性均较好,光合能力大小依次是维欧妮>小芒森>CK_(2)>马尔贝克>马瑟兰>CK1。

遮阴条件下两种短命植物的叶绿素荧光特性及适应性差异

为探明短命植物的光合适应性,本研究以卷果涩芥(Malcolmia scorpioides)和硬萼软紫草(Arnebia decumbens)为试验对象,研究了遮阴率为75%的4个时间梯度(0、1、7、14 d)下两种短命植物叶绿素荧光日变化及遮阴14 d后叶绿素含量和生物量的变化。结果表明:1) 0 d时,两种短命植物最大光化学效率(Fv/Fm),实际光合效率Y (Ⅰ)和Y (Ⅱ)在午间(14:00)明显降低(P <0.05),存在午间光抑。2)遮阴1和7 d,两种短命植物光合效率日变化呈“单峰”型曲线,14:00时上升至峰值,并伴随环式电子传递流量子产量[Y (CEF)]上升,光抑制被改善;14 d时,卷果涩芥PSⅠ受体端限制引起的量子产量[Y (NA)]和PSⅡ非调节性能量耗散的量子产量[Y (NO)]升高,光系统受损,光合活性下降。3)与未遮阴环境相比,遮阴环境的午间14:00卷果涩芥光合活性下降95.3%,光损伤程度增加95.0%,硬萼软紫草光合活性上升4.0%,热耗散效率下降18.6%。4)遮阴14 d后,两种短命植物的叶绿素含量和生物量均下降,且卷果涩芥的下降率高于硬萼软紫草。综上,硬萼软紫草较卷果涩芥耐阴,14 d内的遮阴均可提高硬萼软紫草的光保护能力,改善光抑制,而卷果涩芥的改善效果仅限7 d内,超过7 d时光合利用率降低。

灌水量对玉米抽雄—吐丝期光合特性及干物质积累的影响

【目的】探究灌水量对玉米抽雄—吐丝期光合作用能力的影响,明确光合特性指标与玉米干物质积累的相关性。【方法】以2018年在内蒙古自治区农牧业科学院试验基地开展的长期定位试验为基础,设置315 m^(3)/hm^(2)(W_(1))、645 m^(3)/hm^(2)(W_(2))、945 m^(3)/hm^(2)(W_(3))、1275 m^(3)/hm^(2)(W_(4))、1605 m^(3)/hm^(2)(W_(5))及雨养处理(W_(0))共6个灌水量,研究灌水量对玉米光合特性指标与干物质积累量影响,通过非直角双曲线模型拟合光响应曲线参数,探究不同灌水量下玉米抽雄—吐丝期光合特性指标及其与干物质积累的相关性。【结果】2019年,W_(3)处理叶片SPAD值仅低于W_(4)处理;2020年,W_(3)处理叶片SPAD值显著高于其他处理,较W_(4)、W_(2)、W_(1)、W_(5)、W_(0)处理分别增加3.96%、5.12%、11.10%、12.64%、19.90%;2019、2020年,W_(3)处理平均日净光合速率均最高;2019年,W_(3)处理茎、叶、穗干质量位于第二位,2020年W_(3)处理除穗干质量外其余指标均高于其他处理;W_(4)、W_(5)处理叶片光合作用与W_(3)处理无显著差异。【结论】在内蒙古中西部地区,全生育期降水量>365 mm时,采用945 m^(3)/hm^(2)的灌水量能有效提高玉米抽雄—吐丝期的光合效率,促进干物质积累,提高玉米产量。

盐胁迫条件下竹柳光合作用日变化特征研究

以竹柳盆栽苗木为试验材料,分析其在不同盐分浓度下的净光合速率、气孔导度、蒸腾速率、胞间CO_(2)浓度等光合生理指标的日变化特征。结果表明:竹柳在对照与轻度胁迫条件下,净光合速率的日变化特征表现为双峰型;在中度和重度胁迫条件下,为单峰型曲线,变化趋势表现为先上升后下降。气孔导度在对照与轻度胁迫条件下的日变化特征表现为双峰型;在中度和重度胁迫条件下为单峰型曲线,呈逐渐下降的趋势。蒸腾速率的日变化特征与气孔导度类似。各胁迫处理胞间CO_(2)浓度均较对照高,且随胁迫程度的加剧,胞间CO_(2)浓度也随之上升。

南疆地区4个鲜食枣品种(系)光合特性研究

【目的】探明南疆地区不同鲜食枣品种(系)夏季光合性能及差异,为鲜食枣品种(系)选育与推广栽培提供理论依据。【方法】以冬枣、蟠枣、XLCZ和伏脆蜜为试材,测定光合色素、光合日变化趋势及光合速率-光响应曲线特征参数,比较分析4个鲜食枣品种(系)光合特性。【结果】净光合速率(Pn)日均值分别为冬枣4.21µmol/(m^(2)•s)、蟠枣5.74µmol/(m^(2)•s)、XLCZ 6.02µmol/(m^(2)•s)、伏脆蜜3.41µmol/(m^(2)•s)。XLCZ和蟠枣净光合速率日变化均呈典型的单峰型曲线,无“午休”现象;冬枣和伏脆蜜呈明显的双峰型。4个鲜食枣品种(系)对光合有效辐射的响应曲线基本一致,净光合速率随着光合有效辐射升高而增加,当光照强度达饱和点后,净光合速率增长曲线变化趋于平缓。光补偿点为XLCZ>伏脆蜜>冬枣>蟠枣,光饱和点为XLCZ>伏脆蜜>蟠枣>冬枣。4个鲜食枣品种(系)水分利用率均表现为上午较下午高,且冬枣>伏脆蜜>蟠枣>XLCZ。【结论】冬枣、蟠枣、XLCZ和伏脆蜜4个鲜食枣品种(系)在阿克苏地区均具有较强的光适应能力,其中,冬枣和蟠枣耐阴性相对较好,能更好地利用弱光;伏脆蜜能更好地利用强光。

Leaf gas exchange and photosynthesis curves of Elymus nutans and Potentilla anserina under fencing and grazing conditions in the Qilian Mountains, Northwest China

Potentilla anserina L.and Elymus nutans Griseb.are dominant species in the subalpine meadows of China.Grazing is one of the most important factors that influence community structure and productivity of subalpine meadows.Understanding how grazing changes photosynthetic capability is essential for preservation and restoration of grasslands.However,information about the effects of grazing on photosynthetic capability remains inadequate.Experiments were conducted in fencing and grazing areas in the Qilian Mountains,Northwest China.The leaf gas exchange and photosynthetic curves of P.anserina and E.nutans were measured at different growth stages.Results showed that grazing decreased the values of leaf gas exchange parameters,such as net photosynthetic rate,stomatal conductance,transpiration rate,and intercellular CO2 concentration of P.anserina and E.nutans.In addition,grazing decreased the values of net photosynthetic rate-photosynthetically active radiation(PN-PAR)curve parameters,such as light-saturated net photosynthetic rate,apparent quantum efficiency,light compensation point,light saturation point,and dark respiration rate.Our results demonstrated that grazing was the primary limiting factor for photosynthesis of dominant grassland species in the study area.

Variation of nitric oxide emission potential in plants: a possible link to leaf N content and net photosynthetic activity

Aims Ecological systems,especially soils,have been recently recognized as an important source of atmospheric nitric oxide(No).However,the study on the contribution of plants to atmospheric No budget is significantly lagged.The specific objectives of this study are to reveal the phylogenetic variation in No emission potential existing in various plant species and find out the possible leaf traits affecting No emission potential.Methods We measured No emission potential,leaf N and C content,C:N ratio,specific leaf area,net photosynthetic rate(Pn)and estimated photosynthetic N use efficiency(PNuE)of 88 plant species.Further investigation of the relationships between No emission potential and leaf traits were performed by simple linear regression analysis and pair-wise correlation coefficients analysis.Important Findingsmajor results are as follows:(1)No emission from plant species exhibited large variations,ranging from 0 to 41.7 nmol m^(−2) h^(−1),and the species frequency distributions of No emission potential could be fitted to a log-normal curve.(2)among 88 species,No emission potential was the highest in Podocarpus macrophyllus,but lowest in Zanthoxylum nitidum and Vernicia montana.(3)No emission potential has strong correlation to leaf N content,Pn and PNuE.The variations in No emission potential among diverse plant species may be closely related to leaf N level and net photosynthetic ability.

Characteristics of Soil Respiration of Terraces and Slope Farmland in Loess Hilly and Gully Regions

Soil CO_2 emissions of terraces and slope farmland in loess hilly and gully regions were measured by using Infra Red Gas Analysis(IRGA),and the diurnal variation characteristics of soil respiration rate in different slope positions of terraces and slope farmland were analyzed.The results show that the diurnal variation curves of soil respiration rate of terraces and slope farmland in loess hilly and gully regions had a single peak.The soil respiration rate of terraces reached the peak during 13:00-15:00,while the soil respiration rate of slope farmland reached the peak from 11:00 to13:00,and it was the lowest at next 07:00.The daily average of soil respiration rate in slope farmland was 0.86μmol/(m^2·s),accounting for 93.48% of that of terraces.The daily average of soil respiration rate in different slope positions of terraces and slope farmland is shown as follows:the bottom of the slope>the middle of the slope>the top of the slope.At the top of the slope,the daily averages of soil respiration rate in terraces and slope farmland were the same;at the middle and bottom of the slope,the daily average of soil respiration rate in terraces was larger than that of slope farmland.