大气CO2浓度升高对春玉米土壤呼吸的影响

为探讨春玉米不同生育期土壤呼吸速率对大气CO₂浓度升高的响应,以黄土高原旱作春玉米为研究对象,通过改进的开顶式气室（OTC）模拟大气CO₂浓度升高的环境,在田间条件下设置自然大气CO₂浓度（CK）、OTC对照（OTC,CO₂浓度同CK）与CO₂浓度升高（OTC+CO₂,OTC系统自动控制CO₂浓度700 μmol/mol）3种处理。研究了旱区覆膜高产栽培春玉米播前（V0）、六叶期（V6）、九叶期（V9）、吐丝期（R1）、乳熟期（R3）、蜡熟期（R5）及完熟期（R6）土壤呼吸速率对大气CO₂浓度升高的响应特征,以及大气CO₂浓度升高对土壤呼吸速率的温度与水分效应的影响。研究发现,OTC+CO₂处理土壤呼吸速率,与CK相比,在R3和R5期分别增加43%、104%（P<0.05）,与OTC相比,R3和R5期分别提升了63%、109%（P<0.05）;OTC处理与CK相比,在整个生育期对土壤呼吸影响不显著;3种处理条件下,土壤温度和水分随生育期变化趋势基本一致,土壤呼吸速率与土壤温度和水分分别呈指数相关和抛物线型相关;结果表明：大气CO₂浓度升高对土壤呼吸的影响因生育期而异,土壤温度和土壤水分是影响旱地农田土壤呼吸的重要因素,CO₂浓度升高会使土壤呼吸温度效应值（Q₁₀）降低,土壤呼吸对土壤水分响应的阈值提高。     

Methane emissions from an Amazon floodplain lake: Enhanced release during episodic mixing and during falling water

Soil respiration rates vary significantly among major plant biomes, suggesting that vegetation type influences the rate of soil respiration. However, correlations among climatic factors, vegetation distributions, and soil respiration rates make cause-effect arguments difficult. Vegetation may affect soil respiration by influencing soil microclimate and structure, the quantity of detritus supplied to the soil, the quality of that detritus, and the overall rate of root respiration. At the global scale, soil respiration rates correlate positively with litterfall rates in forests, as previously reported, and with aboveground net primary productivity in grasslands, providing evidence of the importance of detritus supply. To determine the direction and magnitude of the effect of vegetation type on soil respiration, we collated data from published studies where soil respiration rates were measured simultaneously in two or more plant communities. We found no predictable differences in soil respiration between cropped and vegetation-free soils, between forested and cropped soils, or between grassland and cropped soils, possibly due to the diversity of crops and cropping systems included. Factors such as temperature, moisture availability, and substrate properties that simultaneously influence the production and consumption of organic matter are more important in controlling the overall rate of soil respiration than is vegetation type in most cases. However, coniferous forests had 10% lower rates of soil respiration than did adjacent broad-leaved forests growing on the same soil type, and grasslands had, on average, 20% higher soil respiration rates than did comparable forest stands, demonstrating that vegetation type does in some cases significantly affect rates of soil respiration.     

华北平原地区麦田土壤呼吸特征

2008年4-6月利用LI-8100及LI-6400-09测定了华北平原典型冬小麦田土壤CO_2通量,并分析了麦田土壤呼吸变化规律及其影响机制.结果表明:土壤呼吸日变化呈明显的单峰曲线,最高值出现在12:30-14:30,最低值出现在5:00-6:30;在不同的天气条件下,土壤呼吸速率晴天最高,多云其次,阴天最小;观测期间冠层内各高度CO_2浓度与麦田土壤呼吸速率白天呈显著线性负相关,夜间正相关;土壤呼吸速率与5 cm地温的季节变化趋势基本一致,二者显著指数相关;在田间持水量范围内,土壤呼吸速率与土壤湿度正相关,当土壤相对湿度低于30%时,土壤呼吸受到抑制而通量降低;综合考虑土壤温度与湿度的双因素指数回归模型能较好地解释土壤呼吸的变化情况,土壤温度低于15 ℃时效果更好.

Abstract：

By using LI-8100 and LI-6400-09, the soil CO_2 flux of a winter wheat field in North China Plain was determined from April to June 2008, with its change patterns and affecting fac-tors analyzed. The soil respiration had a single-peak diurnal variation, with the maximum at 12: 30-14:30 and the minimum at 5:00-6:30, and the respiration rate was higher in sunny days than in cloudy or overcast days. There was a significant negative correlation between the CO_2 con-centrations at all canopy heights and the soil respiration rate at daytime, but a significant positive correlation at night. The soil respiration rate presented a seasonal variation similar to the soil tem-perature at 5 cm depth, and had a significant exponential relationship with the soil temperature. Significant correlation was also found between the soil respiration rate and soil humidity when the soil moisture content was within the range of field capacity. Soil humidity less than 30% would limit the soil respiration, inducing a decrease of soil CO_2 flux. A multiple exponential regression model of soil temperature and moisture could better explain the variation of soil respiration, espe-cially when the soil temperature was below 15 ℃.     

旱作农田不同耕作土壤呼吸及其对水热因子的响应

为研究旱作农田春玉米生育期不同耕作土壤呼吸变化特征及其对水热因子的响应情况,在山西省寿阳县旱农试验基地采用红外气体分析法测定了传统耕作(CT)、少耕(RT)和免耕(NT)土壤呼吸速率,并同步测定了各土层土壤水分、温度.研究表明:在春玉米生育期内,土壤呼吸速率均呈单峰型变化趋势,峰值出现在8月;传统耕作与少耕土壤呼吸速率变化趋势基本一致,而免耕土壤与前两者相比波动幅度较大;土壤呼吸峰值与水分、温度之间无明显相关,其余时期土壤呼吸与水分、温度因子具有良好的相关性;双因子模型较单因子模型能更好的描述土壤呼吸与水分、温度之间关系,基于水热双因子(10-20 cm)的指数-幂模型能够解释土壤呼吸变化的81％-87％ (P＜O.01);3种耕作土壤呼吸对水热因子协同影响的敏感性表现为CT＞NT＞RT.     

Soil and total ecosystem respiration in agricultural fields: effect of soil and crop type

A study was made of the effect of soil and crop type on the soil and total ecosystem respiration rates in agricultural soils in southern Finland. The main interest was to compare the soil respiration rates in peat and two different mineral soils growing barley, grass and potato. Respiration measurements were conducted during the growing season with (1) a closed-dynamic ecosystem respiration chamber, in which combined plant and soil respiration was measured and (2) a closed-dynamic soil respiration chamber which measured only the soil and root-derived respiration. A semi-empirical model including separate functions for the soil and plant respiration components was used for the total ecosystem respiration (TER), and the resulting soil respiration parameters for different soil and crop types were compared. Both methods showed that the soil respiration in the peat soil was 2–3 times as high as that in the mineral soils, varying from 0.11 to 0.36 mg (CO₂) m^–2 s^–1 in the peat soil and from 0.02 to 0.17 mg (CO₂) m^–2 s^–1 in the mineral soils. The difference between the soil types was mainly attributed to the soil organic C content, which in the uppermost 20 cm of the peat soil was 24 kg m^–2, being about 4 times as high as that in the mineral soils. Depending on the measurement method, the soil respiration in the sandy soil was slightly higher than or similar to that in the clay soil. In each soil type, the soil respiration was highest on the grass plots. Higher soil respiration parameter values (R_s0, describing the soil respiration at a soil temperature of 10°C, and obtained by modelling) were found on the barley than on the potato plots. The difference was explained by the different cultivation history of the plots, as the potato plots had lain fallow during the preceding summer. The total ecosystem respiration followed the seasonal evolution in the leaf area and measured photosynthetic flux rates. The 2–3-fold peat soil respiration term as compared to mineral soil indicates that the cultivated peat soil ecosystem is a strong net CO₂ source.     

土壤-玉米系统中土壤呼吸强度及各组分贡献

用特殊设计的气体采集箱法对玉米生长期间潮土呼吸强度进行了测定。结果表明,施用150kgNhm^-2的裸地土壤CO2累积排放量是294g C m^-2,约为种植玉米土壤的一半。用根去除法测得的玉米对土壤呼吸的贡献率,苗期小于20％,拔节到收获期波动在30％-70％之间,全生长期平均为46％。玉米生长期间因土壤有机碳分解而释放出的CO2总量为2．94MgChm^-2,大约是0—40cm土层中土壤有机碳总储存量的8％,因此需要输入7．35Mghm^-2的碳含量40％的作物残留物才能平衡土壤中有机碳的损失,约为玉米收获时残留于土壤中根量的一倍,但与残留根量及玉米生长期间根系分泌到土壤的有机物量的总和相当,因此土壤中有机碳总体处于平衡状态。在玉米生长期间,施用氮肥可使土壤CO2排放量降低10％。土壤排放CO2主要受土壤温度的影响,温度效应Q10为1．90-2．88。     

Soil respiration in a poor upland site of Scots pine stand subjected to elevated temperatures and atmospheric carbon concentration

Soil respiration rates under elevated temperature and atmospheric CO₂ concentrations were studied in eastern Finland (62° 47N, 30° 58E, 144 m.a.s.1.) around naturally regenerated 20 – 30 years old Scots pine trees, enclosed in open top chambers. The production of CO₂ varied spatially and temporally, but clearly followed the changes in temperature measured at the soil surface. However, soil respiration in the open control was higher than that in chambers; i.e. the chamber itself changed the conditions by increasing the temperature, altering the movement of water, and thereby soil moisture. Nevertheless, an elevation in the concentration of atmospheric CO₂ raised soil respiration and brought it nearer to the level in the open control. An increase in temperature seemed to inhibit this rise, possibly because of an imbalance between temperature and moisture.     

干旱区荒漠生态系统的土壤呼吸

采用LI-8100土壤碳通量测量系统测定了准噶尔盆地高(B)、低(A)两个盖度级3个典型荒漠植物群落梭梭、盐穗木、假木贼的土壤呼吸速率,比较分析了各样地土壤呼吸的变化特征及水热因子对荒漠土壤呼吸特征的可能影响.结果表明:生长季,土壤呼吸速率存在明显的日变化和季节变化规律,不同盖度和群落类型的荒漠土壤呼吸速率变化形式基本相同.日变化格局最高值出现在12:00～14:00,最低值在8:00或20:00;夏季各月(6、7、8月份)土壤呼吸速率高于秋季月份(9、10月份),春季(5月份)最低.高盖度梭梭群落样地日平均土壤呼吸速率与其他样地存在显著差异.各样地土壤呼吸速率与地表温度呈不同程度的正相关,而与土壤温度的相关性较弱;高盖度盐穗木样地(土壤湿度最高)、梭梭样地(土壤湿度最低)土壤呼吸速率与土壤湿度呈显著负相关.地表温度-土壤湿度的多变量模型能在更大空间尺度解释荒漠土壤呼吸速率时间变化的61.9%.样地间土壤呼吸速率的差异可能主要受土壤湿度影响.高、低盖度的梭梭、盐穗木和假木贼群落的Q10值分别为1.34、1.3、1.65、1.58、1.17和1.31,平均值1.39.     

南京城市公园绿地不同植被类型土壤呼吸的变化

子2007年10月-2008年9月,利用Li-6400便携式光合作用仪配合土壤呼吸气室对南京中山植物园内草坪、疏林和近自然林3种植被类型的土壤呼吸速率的季节变化及其影响因子进行了测定.结果表明:不同植被类型土壤呼吸速率具有明显的季节变化,夏季(8月)较高,近自然林、疏林和草坪类型分别为3.28、4.07和7.58 μmol·m~(-2)·s~(-1),冬季(12月)最低,近自然林、疏林和草坪类型分别为0.82、0.99和1.42 μmol·m~(-2)·s~(-1);不同植被类型的年均土壤呼吸速率有显著差异(P＜0.05),平均土壤呼吸速率大小排序为草坪>疏林>近自然林;不同植被类型的土壤呼吸速率与土壤温度呈显著性指数相关关系,与土壤含水率无显著相关关系;Q_(10)值均随着土层深度的增加而增加;不同植被类型的Q_(10)值存在一定程度的差异,近自然林类型的Q_(10)值大于草坪和疏林类型的Q_(10)值.研究表明,城市如果大量发展草坪可能增加土壤CO_2的排放.

Abstract：

By using Li-6400 portable photosynthetic apparatus connected to soil chamber,the soil respiration rate under three vegetation types(lawn,open woodland,and close-to-nature forest)in Nanjing Zhongshan Botanical Garden was measured from October 2007 to September 2008,with related affecting factors analyzed.The soil respiration rate had obvious seasonal fluctuation,being the highest in summer(August)and the lowest in winter(December).For the close-to-nature forest,open woodland,and lawn,their soil respiration rate in summer was 3.28,4.07,and 7.58μmol·m~(-2)·s~(-1),and that in winter was 0.82,0.99,and 1.42μmol·m~(-2)·s~(-1),respectively.The annual mean soil respiration rate differed significantly with vegetation type(P＜0.05),which was in order of close-to-nature forest＜open woodland＜lawn.The soil respiration rate had significant exponential correlation with soil temperature,but no correlation with soil moisture.The Q_(10) value increased with increasing soil depth,and was larger in close-tonature forest than in open woodland and lawn.Our results indicated that the rapid development of lawn in urban green space could increase the urban soil CO_2 emission.     

不同耕作措施下旱地农田土壤呼吸及其影响因素

为探讨耕作措施对旱地农田土壤呼吸的影响,采用动态气室法在山西寿阳地区对秸秆还田、免耕覆盖、浅旋耕、常规耕作4种耕作措施下玉米生长季土壤呼吸及影响因子进行了测定和分析。结果表明,4种耕作措施下土壤呼吸速率的日和季节变化规律明显,均呈单峰型,呼吸速率的日峰值出现在11:30 13:30,呼吸速率的季节峰值出现在7月上旬至中旬。浅旋耕、秸秆还田、常规耕作、免耕覆盖措施整个生长季平均土壤呼吸速率分别为2.82、2.77、2.64μmolCO.2m-.2s-1和2.49μmolCO.2m-.2s-1,处理间无显著差异。研究结果还显示土壤温度和湿度是影响旱地农田土壤呼吸的主要因子,二者分别解释了土壤呼吸季节变化的55%78%,20%43%。4种措施下土壤呼吸的温度敏感系数Q10值在2.19 3.07之间,大小依次为免耕覆盖浅旋耕秸秆还田常规耕作。对水分的敏感性依次为免耕覆盖秸秆还田浅旋耕常规耕作。     

中国东部亚热带森林土壤呼吸的时空格局

土壤呼吸是陆地碳循环中仅次于全球总初级生产力的第二大碳通量途径, 揭示土壤呼吸的时空格局对整个陆地碳循环具有重要意义。该文在中国东部亚热带季风气候区, 按纬度梯度由南向北选取深圳梧桐山、杨东山十二度水保护区、宁波天童山3个区域作为研究对象, 于2009年8月至2010年10月测定了不同季节各个区域内代表性植被类型的土壤呼吸速率及地下5 cm处土壤温度, 旨在初步了解中国东部亚热带森林地区土壤呼吸的时空格局及其影响因素。结果显示: 3个区域的土壤呼吸速率均存在显著的季节变化, 其变幅为2.64-6.24 μmol CO₂·m ^-2·s^-1, 总体趋势和地下5 cm处土壤温度的季节变化一致, 均为夏季最高冬季最低; 土壤温度的变化可以解释不同样地土壤呼吸季节变化的58.3%-90.2%; 各样地全年的Q₁₀值从1.56到3.27; 通过离样地最近的气象站点的日平均气温与试验样地地下5 cm处土壤温度之间的线性正相关关系推算出日土壤温度的变化, 利用土壤呼吸速率和地下5 cm处土壤温度之间的指数关系, 估算出各样地全年的土壤CO₂通量为1 077-2 058 g C·m^-2·a^-1, 在全球所有生态系统类型中处于较高水平。     

Soil respiration fluxes measured along a hydrological gradient in a Norway spruce stand in south Sweden (Skogaby)

Soil respiration fluxes were measured continuously in order to assess the degree to which they were influenced by spatial and temporal variation in soil moisture. The synergistic effects of the variation in soil moisture with the one in soil temperature, soil organic matter and global radiation on respiration fluxes were also analysed. The measurements were performed using an open chamber system along a hydrological gradient in a Norway spruce forest in south Sweden (Skogaby) for 3 weeks in June 1995. The measured soil respiration fluxes were quite stable and somewhat larger compared with those reported in literature. The experiment took place during the shoot elongation period with intensive nutrient uptake, and it might be that soil respiration was dominated by mycorrhizal activity. Variation in the moisture content of the litter layer accounted for most of the spatial variation in respiration fluxes. This revised version was published online in June 2006 with corrections to the Cover Date.     

川西亚高山粗枝云杉人工林地上凋落物对土壤呼吸的贡献

采用Li-8100土壤碳通量分析仪对川西亚高山典型的粗枝云杉(Picea asperata)人工林土壤呼吸(凋落物去除和对照)及其环境因子进行为期1年的连续观测。结果表明:凋落物去除处理和对照土壤呼吸速率均具有显著的季节动态变化,并呈现一致的动态特征,变动范围分别为0.35—4.39μmol m-2s-1和0.40—5.15μmol m-2s-1。整个观测期间,凋落物去除对土壤温度、水分以及土壤呼吸速率产生的差异均不显著。与对照相比,凋落物去除分别使土壤呼吸速率和土壤水分平均下降了14.21%和4.95%。两种处理的土壤呼吸速率和土壤温度均呈显著指数相关,与土壤水分呈显著线性相关。凋落物去除和对照的土壤温度敏感性(Q10)分别为3.84和4.09。凋落物对土壤呼吸速率的年均贡献率为14.93%,且存在明显季节动态。可见,地表凋落物是亚高山森林土壤呼吸的重要组成部分。     

Soil respiration response to three years of elevated CO2 and N fertilization in ponderosa pine (Pinus ponderosa Doug. ex Laws.)

We measured growing season soil CO₂ evolution under elevated atmospheric [CO₂] and soil nitrogen (N) additions. Our objectives were to determine treatment effects, quantify seasonal variation, and compare two measurement techniques. Elevated [CO₂] treatments were applied in open-top chambers containing ponderosa pine (Pinus ponderosa L.) seedlings. N applications were made annually in early spring. The experimental design was a replicated factorial combination of CO₂ (ambient, + 175, and +350 L L^–1 CO₂) and N (0, 10, and 20 g m^–2 N as ammonium sulphate). Soils were irrigated to maintain soil moisture at > 25 percent. Soil CO₂ evolution was measured over diurnal periods (20–22 hours) in October 1992, and April, June, and October 1993 and 1994 using a flow-through, infrared gas analyzer measurement system and corresponding pCO₂ measurements were made with gas wells. Significantly higher soil CO₂ evolution was observed in the elevated CO₂ treatments; N effects were not significant. Averaged across all measurement periods, fluxes, were 4.8, 8.0, and 6.5 for ambient + 175 CO₂, and +350 CO₂ respectively).Treatment variation was linearly related to fungal occurrence as observed in minirhizotron tubes. Seasonal variation in soil CO₂ evolution was non-linearly related to soil temperature; i.e., fluxes increased up to approximately soil temperature (10cm soil depth) and decreased dramatically at temperatures > 18°C. These patterns indicate exceeding optimal temperatures for biological activity. The dynamic, flow-through measurement system was weakly correlated (r = 0.57; p < 0.0001; n = 56) with the pCO₂ measurement method.     

Soil Respiration in European Grasslands in Relation to Climate and Assimilate Supply

Soil respiration constitutes the second largest flux of carbon (C) between terrestrial ecosystems and the atmosphere. This study provides a synthesis of soil respiration (R _s) in 20 European grasslands across a climatic transect, including ten meadows, eight pastures and two unmanaged grasslands. Maximum rates of R _s ( ), R _s at a reference soil temperature (10°C; ) and annual R _s (estimated for 13 sites) ranged from 1.9 to 15.9 μmol CO₂ m⁻² s⁻¹, 0.3 to 5.5 μmol CO₂ m⁻² s⁻¹ and 58 to 1988 g C m⁻² y⁻¹, respectively. Values obtained for Central European mountain meadows are amongst the highest so far reported for any type of ecosystem. Across all sites was closely related to . Assimilate supply affected R _s at timescales from daily (but not necessarily diurnal) to annual. Reductions of assimilate supply by removal of aboveground biomass through grazing and cutting resulted in a rapid and a significant decrease of R _s. Temperature-independent seasonal fluctuations of R _s of an intensively managed pasture were closely related to changes in leaf area index (LAI). Across sites increased with mean annual soil temperature (MAT), LAI and gross primary productivity (GPP), indicating that assimilate supply overrides potential acclimation to prevailing temperatures. Also annual R _s was closely related to LAI and GPP. Because the latter two parameters were coupled to MAT, temperature was a suitable surrogate for deriving estimates of annual R _s across the grasslands studied. These findings contribute to our understanding of regional patterns of soil C fluxes and highlight the importance of assimilate supply for soil CO₂ emissions at various timescales.     

华南丘陵区不同土地利用方式下土壤呼吸

采用静态箱-气相色谱法对华南丘陵区针叶林和果园土壤呼吸及其主要影响因子进行了观测。结果表明:针叶林和果园含凋落物年均土壤呼吸分别为(1.96±0.09)和(6.56±0.32)kg.m-2.a-1;不含凋落物年均土壤呼吸分别为(1.60±0.07)和(5.30±2.80)kg.m-2.a-1。土地利用方式对土壤呼吸的影响较大,果园土壤呼吸明显大于针叶林(P<0.01)。针叶林和果园土壤呼吸季节变化模式相似,即雨季较高而旱季较低。不同土地利用方式下不同处理土壤呼吸均与地下5cm土壤温度、地表温度和气温呈显著指数相关。利用Q10模型计算出针叶林和果园土壤呼吸Q10值变化范围在1.73～3.30。土壤呼吸与土壤含水量显著相关。温度和土壤含水量能部分解释针叶林和果园土壤呼吸的季节变化。针叶林和果园由凋落物分解释放的CO2对土壤呼吸的贡献分别为18.14%和19.08%。     

内蒙古不同类型草地土壤氮矿化及其温度敏感性

土壤氮矿化(Nitrogen mineralization)是土壤氮循环的重要环节,对土壤氮素供应以及植物生产力的维持具有十分重要的意义。沿中国东北草地样带(Northeastern China Transect, NECT)分别在典型草地、过渡草地及荒漠草地设置了3个实验样地,利用不同温度(5、10、15、20 ℃和25 ℃)和不同水分(30%、60%和90%土壤饱和含水量,Saturated soil moisture, SSM)的室内培养途径,探讨了不同类型草地的土壤氮矿化速率、土壤氮矿化的温度敏感性(Q₁₀)及其主要影响因素。实验结果表明:从典型草地至荒漠草地,土壤全碳、全氮、全磷、微生物生物量碳氮含量均表现为逐渐下降的趋势;类似地,土壤净氮矿化速率、硝化速率也逐渐降低。在20 ℃和60% SSM时,土壤净氮矿化速率表现为典型草地 (0.715 mg N kg^-1 d^-1) > 过渡草地 (0.507 mg N kg^-1 d^-1) > 荒漠草地 (0.134 mg N kg^-1 d^-1);相反,温度敏感性却逐渐升高,温度敏感性与基质质量指数呈负相关。草地类型和水分对于土壤净氮矿化速率、硝化速率具有显著影响,且二者间具有显著的交互效应。包含温度和水分的双因素模型可很好地拟合土壤氮矿化速率的变化趋势(P < 0.0001),二者可共同解释土壤硝化速率92%-96%的变异。土壤氮矿化沿着草地演替呈现出很好的空间格局、并与温度和水分具有密切关系,为解释内蒙古草地空间分布格局提供了理论基础。     

Soil respiration of Alaskan tundra at elevated atmospheric carbon dioxide concentrations

Summary CO₂ efflux from tussock tundra in Alaska that had been exposed to elevated CO₂ for 2.5 growing seasons was measured to assess the effect of long- and short-term CO₂ enrichment on soil respiration. Long-term treatments were: 348, 514, and 683 μll⁻¹ CO₂ and 680 μll⁻¹ CO₂+4°C above ambient. Measurements were made at 5 CO₂ concentrations between 87 and 680 μll⁻¹ CO₂. Neither long- or short-term CO₂ enrichment significantly affected soil CO₂ efflux. Tundra developed at elevated temperature and 680 μll⁻¹ CO₂ had slightly higher, but not statistically different, mean respiration rates compared to untreated tundra and to tundra under CO₂ control alone.     

沙坡头人工植被演替过程的土壤呼吸特征

为探讨人工植被演替过程对土壤呼吸速率的影响,本文利用碱液吸收法同步测定了腾格里沙漠东南缘1956、1964、1981、1987、1989、2007年始植的人工植被区和2007年新铺设的草方格固沙区及流沙区的土壤呼吸速率变化,同时分析了土壤水分和温度对上述不同样地土壤呼吸的影响。结果表明:1) 总体而言,土壤呼吸速率随着人工植被演替时间的延长而逐渐增大。当土壤含水量较高时,不同始植年代人工植被区的土壤呼吸速率具有显著的差异(P<0.05);当土壤含水量较低时,不同始植年代植被区的土壤呼吸速率没有显著的差异(P>0.05)。2)土壤呼吸速率与土壤含水量呈正相关关系,且相关系数随着人工植被演替时间的延长而逐渐增大。3)利用土壤呼吸速率-土壤温度指数函数关系计算得到不同人工植被演替阶段土壤呼吸速率的Q₁₀值均较低(平均值仅为1.02)。土壤温度对1987、1989年人工植被区内的土壤呼吸速率产生了显著影响(P<0.05),而对其他样地的土壤呼吸速率影响不显著 (P>0.05)。综合说明,人工植被的演替过程改变了土壤呼吸速率大小及其对土壤水分和温度的响应。     

Heterotrophic Soil Respiration in Relation to Environmental Factors and Microbial Biomass in Two Wet Tropical Forests

We examined the correlation between fungal and bacterial biomass, abiotic factors such as soil moisture, carbon in the light soil fraction and soil nitrogen to a depth of 0–25 cm and heterotrophic soil respiration using a trenching technique – in a secondary forest (Myrcia splendens, Miconia prasina and Casearia arborea) and a pine (Pinus caribeae) plantation in the Luquillo Experimental Forest in Puerto Rico. Soil respiration was significantly reduced where roots were excluded for 7 years in both the secondary forest and the pine plantation. Microbial biomass was also significantly reduced in the root exclusion plots. In root exclusion treatment, total fungal biomass was on average 31 and 65% lower than the control plots in the pine plantation and the secondary forest, respectively, but the total bacterial biomass was 24 and 8.3% lower than the control plots in the pine plantation and the secondary forest, respectively. Heterotrophic soil respiration was positively correlated with fungal biomass (R²=0.63, R²=0.39), bacterial biomass (R²=0.16, R²=0.45), soil moisture (R²=0.41, R²=0.56), carbon in light fraction (R²=0.45, R²=0.39) and total nitrogen (R²=0.69, R²=0.67) in the pine plantation and the secondary forest, respectively. The regression analysis suggested that fungal biomass might have a greater influence on heterotrophic soil respiration in the pine plantation, while the bacterial biomass might have a greater influence in the secondary forest. Heterotrophic soil respiration was more sensitive to total N than to carbon in the light fraction, and soil moisture was a major factor influencing heterotrophic soil respiration in these forests where temperature is high and relatively invariable.