水蚀风蚀交错区土壤呼吸影响因素及其对土地利用方式变化的响应

为准确评估黄土高原水蚀风蚀交错区土壤呼吸速率季节变化影响因素及其对不同土地利用方式的响应,于2009~2012年植物生长季节,选取6 种当地典型的土地利用类型,应用红外气体分析法对土壤呼吸速率进行测定,并结合土壤水、热与养分因子进行分析。结果表明, 水蚀风蚀交错区退耕会显著改变土壤呼吸强度,该区典型农地的土壤呼吸速率为1.06～1.39 mol/（m2s）,农地转变为裸地的过程中,土壤呼吸速率下降为原来的42%～63%,尤其在植物生长旺季的7、 8、 9 三个月下降明显。 农地弃耕后建设人工草（灌木）地使土壤呼吸速率提高了109%～200%,农田撂荒样地土壤呼吸速率约为农地的79%～179%,农地略高于长芒草地和荒草地。该区土壤呼吸速率变化的主导因子为土壤温度,尤其与10 cm土层的土壤温度相关性最好,土壤呼吸速率与土壤含水量之间拟合优度较差, 但土壤温度与含水量双因子指数模型Rs=aebTc 对该地区土壤呼吸速率的拟合均优于相应的单因子模型。10 cm土层的土壤呼吸温度敏感性系数（Q10值）排序为:无植被生长样地（裸地,2.09）农地（农地、坡地农地,2.07～1.69） 撂荒地（坡地撂荒地、撂荒地、梯田撂荒地,1.71～1.53）草（灌木）地（柠条地、苜蓿地、长芒草地、荒草地,1.51～1.42）,可见随着未来气温的升高,在生态系统土壤呼吸整体有可能增加的背景下,退耕还林（草）会降低土壤呼吸对温度的敏感性,且Q10值随土壤含水量降低而降低。土壤呼吸速率与土壤有机质、全氮之间有极显著的正相关关系。因此,水蚀风蚀交错区土壤呼吸受到土壤温度、水分、养分及土地利用方式的显著影响。     

淮北地区5种不同植物群落土壤呼吸研究

选取河南西平杨树人工林生态系统中5种不同植物群落土地为研究对象,利用Licor-8100土壤呼吸测定系统对其土壤呼吸进行了连续观测,分析、比较5种不同植物群落土壤呼吸的差异及其影响因素。研究结果表明:（1）5种植物群落下土壤呼吸有所差异,但其日变化及年内变化趋势大致相同,均与土壤温度变化趋势一致,呈单峰曲线,其土壤呼吸大小顺序为:8 m行宽林间小藜—牛筋草地 > 2 m行宽林间苍耳地 > 8 m行宽林间水蓼—灰灰菜地 > 8 m行宽林间苍耳地 > 2 m行宽林间裸地;（2）采用土壤温度和湿度单因素模型（R_s=ae^bT_s或R_s=aW+b）进行分析:土壤温度和土壤含水量分别解释了不同植物群落土壤呼吸季节变化的41%~79%和2.3%~21%;而采用双因素模型分析（R_s=ae^bT_sW^c）,土壤温湿度共同解释了土壤呼吸速率季节变化的49.1%~86.7%,表明不同植物群落的土壤呼吸均受土壤温度和土壤含水量的共同影响;（3）运用Q₁₀=e^10b模型分析,Q₁₀值大小顺序为:8 m行宽林间小藜—牛筋草地（2.47） > 2 m行宽林间苍耳地（2.3） > 2 m行宽林间裸地（2.7） > 8 m行宽林间水蓼—灰灰菜地（2.59） > 8 m行宽林间苍耳地（2.22）,且5种不同植物群落下土壤呼吸Q₁₀值均表现为春季 > 冬季 > 秋季 > 夏季,即土壤呼吸温度敏感性随着温度的升高呈现出降低的趋势。     

退耕还林还草过程中不同土地利用方式土壤呼吸作用及其碳收支评估

采用动态密闭气室法对黄土高原水蚀风蚀交错区9种土地利用方式植物生长季节内（2010年6—10月）土壤呼吸速率及其主要影响因子进行测定,分析不同土地利用方式间土壤呼吸的差异性和土壤呼吸对温度、土壤水分、叶面积指数等因子的响应,对7种土地利用方式土壤碳收支进行了估算。结果表明,植物生长季节内,不同土地利用方式下土壤呼吸速率呈多峰型变化趋势。裸地、农地、梯田农地、苜蓿地、撂荒地、长芒草地、荒草地、沙柳地、沙蒿地的土壤呼吸速率季节变化范围分别为0.18～1.05、0.30～2.08、0.50～1.71、0.53～2.78、0.26～1.08、0.39～1.93、0.30～2.27、0.43～1.43、0.39～1.26μmol·m-2·s-1。9种土地利用方式下土壤呼吸速率均与气温和5、10、15cm地温呈显著相关（P〈0.05）或极显著相关（P〈0.01）,而与0～6cm土壤水分相关性不显著。9种土地利用方式下地温对应的Q10值均表现为15cm地温〉10cm地温〉5cm地温。研究区域内土壤呼吸速率与其地上植被叶面积指数呈极显著线性相关关系（r=0.679,P〈0.01）。     

华北低丘山地栓皮栎人工林土壤呼吸变化特征及其与撂荒地的差异

2010年4-10月,采用静态箱-气相色谱法,研究了晴天条件下华北南部低丘山地29a生的栓皮栎人工林林地土壤呼吸变化特征及其与撂荒地的差异。结果表明：（1）撂荒地和栓皮栎林土壤呼吸速率月变化趋势均呈单峰曲线,且土壤呼吸速率最大值均出现在7月份。测定时期内的栓皮栎林土壤呼吸速率平均值为601.69mg·m^-2·h^-1,比撂荒地的1007.96mg·m^-2·h^-1约低40.3%。（2）影响撂荒地和栓皮栎人工林地土壤呼吸速率的主要因子是土壤温度,与土壤湿度的相关性不明显,且撂荒地与栓皮栎林地在土壤5cm深处的Q10分别为2.702、2.573。     

黄土区梯化坡地不同土地利用方式对土壤理化性质的影响

[目的]研究覆膜作物、牧草地和撂荒地模式下梯化坡地不同土地利用方式对土壤理化性质的影响,为黄土区梯化坡地优化农业生产管理提供科学依据。[方法]以黄土区甘肃省陇西县梯化坡地为研究对象,选择5种土地利用方式(玉米地、苜蓿地、撂荒地2 a,撂荒地4 a和荒草地)按不同坡位(挖方段、中间段、填方段)进行土壤取样,对0—40 cm土层土壤理化性质进行研究。[结果]在5种土地利用方式下,土壤含水量、容重均随土层深度增加而增大,其中玉米地土壤含水量最高,容重最小;土壤机械组成均表现为:细砂粒黏粒粉粒粗砂粒;土壤含水量、容重、黏粒和粉粒均表现为:挖方段中间段填方段,而粗砂粒、细砂粒、有机碳、速效钾和水解性氮则呈现相反的趋势。土壤pH值均值变化为苜蓿地最大,撂荒地最小,且方差分析差异不显著(p0.05)。土壤有机碳、速效钾和有效磷均值均表现为玉米地最大,水解性氮均值表现为:苜蓿地玉米地撂荒地2 a荒草地撂荒地4 a。[结论]覆膜玉米地表现出对土壤含水量、容重及养分的促进作用均优于其他土地利用方式,且填方段的土壤更加肥沃,耕作中应注重加强对挖方段的施肥。     

重庆缙云山 4 种典型林分生长季土壤呼吸特征及其与环境因子的关系

2012年4-8月,采用LI-8100开路式土壤碳通量测量系统对重庆缙云山4种典型林分（常绿阔叶林、竹林、针阔混交林和针叶林）的土壤呼吸速率进行测定,并同步测定5和10 cm土壤温度、湿度及pH值,分析4种林分土壤呼吸变化特征及其与环境因子的关系.结果表明：1）4种典型林分土壤呼吸日变化规律不同,5月、7月针阔混交林和针叶林土壤呼吸速率日波动幅度大于常绿阔叶林和竹林;2）各林分土壤呼吸速率均表现出4-7月升高而7-8月降低的月变化规律;3）土壤呼吸速率与5 cm、10 cm土壤温度均呈指数关系,常绿阔叶林的温度敏感性（5 cmQ10=2.054,10cm Q10=2.117）大于其他3种林分;4）常绿阔叶林土壤呼吸速率与土壤湿度无显著相关性,而对其他林分呈二次相关关系;5）常绿阔叶林的土壤呼吸与5 cm、10 cm土壤pH值显著相关,竹林的土壤呼吸仅与5 cm土壤pH值显著相关,其他林分未表现出显著相关关系.     

橡胶林土壤呼吸速率及其与土壤温湿度的关系

利用Li-6400光合仪研究4 a、12 a和19 a橡胶林的土壤呼吸及其各组分(微生物呼吸、根系呼吸、凋落物呼吸)呼吸速率的日变化和年变化特征,探索土壤温度和湿度对土壤呼吸速率的影响。结果表明: 不同树龄橡胶林土壤呼吸速率在全天观测期间,出现最大值和最小值的时刻有很大差异,但在9:00~11:00时刻的测定值均接近日均值;在不同树龄橡胶林中各组分呼吸速率日变化大小虽不一致,但均表现为凋落物呼吸速率最小。4 a、12 a和19 a橡胶林土壤呼吸速率均有明显的月变化,月均值分别是2.45、2.63和2.96 μmol m-2 s-1;最大值出现在7月和8月,最小值出现在2月和3月;不同树龄橡胶林土壤呼吸速率月变化相互间差异不显著;土壤微生物呼吸占土壤呼吸的比例最高(为43.6%),根系呼吸次之(为36.1%),凋落物呼吸较小(为20.4%)。土壤呼吸速率与土壤温度之间具有显著的指数函数关系,但与土壤湿度的相关性不显著,从而得知海南橡胶林土壤温度与土壤呼吸速率有着密切的关系,土壤水分与土壤呼吸速率可能没有直接的关系。     

重庆市缙云山3种森林类型的土壤呼吸特征研究

2010年7—12月,采用LI—COR公司生产的LI-8100土壤碳通量测量系统及土壤温度、湿度传感器对重庆市缙云山自然保护区内的毛竹林、针阔混交林、针叶林的土壤呼吸速率以及地表下5cm处的土壤温度和体积含水量进行测定,最后对3种林地土壤呼吸的时间变化特征及其与土壤温湿度和森林凋落物的关系进行了分析。结果表明：（1）3种林地土壤呼吸速率日内变化特征不明显,白天总体呼吸速率大于夜间。（2）月际变化明显,表现为从7—8月土壤呼吸速率增大,8—12月逐渐减小。3种林分7—12月总体平均土壤呼吸速率表现为毛竹林〉针阔混交林〉针叶林。（3）毛竹林、针阔混交林、针叶林的土壤呼吸速率与5cm土壤温度均存在极显著的指数相关关系（p〈0.01）,温度每升高10℃,土壤呼吸的变化比率Q10值分别为2.67,2.19,2.13。（4）土壤呼吸特征与5cm土壤含水量之间没有明显的相关关系。（5）各林地无凋落物的土壤呼吸速率均小于对应林地有凋落物土壤呼吸速率,各林地无凋落物的Q10值均大于对应林地有凋落物的Q10值。     

强碱土土壤呼吸及其影响因子分析

利用LI-8100土壤碳通量测量仪测定了在自然升温下的强碱土土壤呼吸速率、温度(气温和土壤温度)、湿度(空气相对湿度和土壤湿度)数据,通过分析它们的相关关系,探讨土壤呼吸速率的变化特征及其主要影响因素,建立了相应的回归模型并进行了精度检验。结果表明:(1)各实验土壤呼吸速率的日变化过程均呈单峰型,日间为正呼吸,夜间为负呼吸。(2)平均气温由4.4℃升至15.84℃和17.61℃时,平均土壤呼吸则由-0.07μmol m-2 s-1增加至0.07和0.31μmol m-2 s-1。温度越高,土壤呼吸速率越大。(3)土壤呼吸速率与气温、土壤温度、土壤湿度呈正相关,与空气相对湿度呈负相关,并且随着温度的升高,相关系数均不断增大。实验1中气温与土壤呼吸的相关系数为0.75,实验2、3则增至0.96和0.98。(4)土壤呼吸速率的最主要直接影响因子为气温,土壤湿度通过气温对土壤呼吸速率的间接影响与气温的影响相当。(5)土壤呼吸速率无论与温、湿度中单个因子还是温湿度双因子构建的回归方程,其拟合优度和模型精度均随温度的升高而增大,在气温与土壤呼吸速率构建的方程中,其R2由实验1的0.5544增至实验2、3的0.9284和0.9685,RMSE则由0.7055减至0.3011、0.1560。     

长期施肥对东北中部春玉米农田土壤呼吸的影响

【目的】 探究不同施肥措施对土壤呼吸的影响,为我国东北黑土区固碳减排研究提供科学依据。 【方法】 本研究基于“国家黑土肥力与肥料效益监测基地”长期定位试验,选取不施肥 (CK)、单施化肥 (NPK)、化肥配施秸秆 (NPKS)、化肥配施低量有机肥 (NPKM1)、化肥配施高量有机肥 (NPKM2)5个不同施肥处理。采用Soil-box343土壤呼吸测量系统进行野外监测,并同时观测环境条件。 【结果】 长期不同施肥处理下,农田土壤呼吸速率变化范围为4.12～7.23 μmol/(m2·s),随玉米生长表现出“先升高后降低”的季节变化特征,最高值出现在播种后69天左右,NPKM2处理土壤呼吸速率的峰值显著高于其他处理 (P < 0.05)。监测期内土壤呼吸速率与土壤温度之间呈现显著的正相关关系,土壤温度可以解释土壤呼吸速率变异的41%～77%,土壤温度敏感系数Q ₁₀值的变化范围2.35～3.49。春玉米生长季内农田土壤呼吸总量变化范围为3473～5643 kg/hm2,NPKS处理显著高于CK处理34.2%,而NPKM2处理分别比NPKS、NPK和CK处理高21.0%、26.4%、62.4% (P < 0.05),长期有机无机肥配施处理土壤有机碳含量增加趋势比其他处理明显,截止到2016年,NPKM1和NPKM2处理SOC较初始SOC分别增加了6.01 g/kg和5.55 g/kg。 【结论】 长期施用有机肥能够增加土壤呼吸,提高土壤有机碳含量,有利于农田生产力提高和农田可持续利用。      

黄土丘陵沟壑区人工草地减沙水代价分析

以裸坡农地为对照,根据黄土丘陵沟壑区三大副区人工草地径流小区多年的观测资料,系统分析了黄土丘陵沟壑区人工草地减沙水代价（R_rs）特征及其与各影响因素之间的关系。结果表明:人工草地在不同地区其平均R_rs存在差异,且变化幅度较大,整体上丘陵沟壑第二副区大于第一副区和第三副区;不同牧草轮作下条播草木樨的R_rs最大,较自然草坡高25%,其R_rs表现为:条播草木樨 > 撒播苜蓿 > 草木樨 > 苜蓿 > 自然草坡;草田带状间轮作的R_rs表现为:草木樨/农作物 > 苜蓿/农作物,且草田带状间轮作的R_rs明显高于牧草轮作;人工草地R_rs与汛期降水量、侵蚀模数呈较好的指数反比关系,与最大30 min降雨强度（I₃₀）呈线性反比关系。     

砖红壤区降雨因子对产流产沙的影响

应用三种无量纲化的灰色关联法分析了12个降雨因子对于砖红壤区裸地和桉林地产流的影响,以及15个降雨径流因子对于产沙的影响。结果表明:无量纲处理方法不同将导致因子关联度排序出现变化;复合因子的关联度大多数都高于单因子;与PI₃₀相比,在砖红壤区裸地中PI₅更能代表降雨侵蚀力指标,而桉林地则是PI₁₀;Q_m’H在桉林地比通用的降雨侵蚀力更适于作为坡面降雨侵蚀模型的侵蚀动力因子。研究结果将有助于建立灰色关联法在土壤侵蚀研究中的标准化程序,为建立砖红壤区土壤侵蚀预报模型提供理论支持。     

山西省天龙山弃耕地的根系呼吸及其影响因素

用去除根系法对山西省天龙山自然保护区弃耕地的根系呼吸进行了为期2a的研究。结果表明,弃耕地的根系呼吸速率具有明显的季节变化,与土壤温度的变化趋势相一致,夏季高冬春季低。2007和2008年3—12月的根系呼吸总量(以C计)分别为329.5和392.5g/m2。土壤温度是影响根系呼吸速率的主导因子,可以解释根系呼吸速率季节变化的79%~88%,土壤水分对根系呼吸的影响较小。包括土壤温度和土壤水分两个变量的双因素模型可以解释根系呼吸季节变化的81%~89%;根系呼吸占土壤总呼吸的比例具有明显的季节变化,为24%~54%;2007和2008年3—12月根系呼吸比例的平均值分别为24.9%和30.9%。     

The effect of ground cover or initial organic carbon on soil fungi, aggregation, moisture and organic carbon in one season with oat (Avena sativa) plots

The unique capacity of fungi to efficiently sequester carbon in aerobic conditions, presents a way to maximize OC gain in agricultural systems. Oat (Avena sativa) was planted in the temperate climate of southern Ontario, Canada to study factors affecting soil organic carbon (OC). The plots varied with initial OC from 25 to 68 g kg⁻¹ or with ground cover of differing decomposability (alfalfa (Medicago sativa) growing from seed, dried oat straw, dried hay and compost) on high OC soil (60–70 g kg⁻¹). The soil was analysed for correlation of changes in soil aggregation, moisture, OC, fungal hyphal number and length and distribution of organic matter by mass and OC in density fractions within the growing season. At harvest, soil OC and moisture were increased only in plots with ground cover. Total hyphal length was not significantly different with ground cover treatment at harvest, and did not correlate with soil aggregation and soil OC. However, the number of hyphae with >5 μm diameter (primarily mycorrhizal fungi) correlated with % OC in ground cover plots while the number of hyphae <5 μm (primarily saprophytic fungi) correlated with % OC without ground cover in the gradient of initial soil OC. Mycorrhizal hyphae may be important to the increases in soil OC from surface treatment, although there was no treatment effect of mycorrhizal occurrence on the oat roots. This microcosm study, with growing and dried ground cover, suggests surface management may a simple and inexpensive means in agriculture to increase soil moisture and OC that benefits farmers as well as reducing atmospheric CO₂.     

Wind tunnel simulation of ridge-tillage effects on soil erosion from cropland

In the arid and semi-arid regions, ridge tillage was often used as an alternative practice for wind erosion control on the croplands without sufficient crop residues left during the fallow period. Through wind tunnel experiments, wind erosion rate and vertical mass flux profile of blown sand under the simulated conditions of ridge tillage and flat tillage were studied in 15, 10, 10, 5, 3 min exposures at the wind velocities of 8, 10, 15, 20, 24 m s⁻¹, respectively. The results for the soil tested indicate that the mean rate of wind erosion under flat tillage was 129.89 g m⁻² min⁻¹, while that under ridge tillage were 20–60% less. Under ridge tillage with different structures, average wind erosion rate had a positive correlation with the spacing between adjacent ridges. For the same ridge height, average wind erosion rate decreased with increasing ratio between the height of ridge and the width of furrow. For the same ratio between the height of ridge and the width of furrow, average wind erosion rate increased with increasing height of ridge. Power function relationships were found between wind erosion rate and wind velocity on all the simulated tillage conditions. A wind velocity of 15 m s⁻¹ was the critical velocity, above which wind erosion rate increased rapidly for the soil and simulated tillage conditions tested. Compared with flat tillage, ridge tillage remarkably decreased wind erosion rates when wind velocities were beyond 15 m s⁻¹. Under ridge tillage, the total mass of sand transported at a height of 0–20 cm above soil surface (Q_0–20), and the fraction of that travelling at a height of 0–4 cm (Q_0–4/Q_0–20), were less man mat under flat tillage. For the same ridge height, Q_0–4/Q_0–20 increased with increasing ratio between the height of ridge and the width of furrow. For the same ratio between the height of ridge and the width of furrow, Q_0–4/Q_0–20 decreased with increasing height of the ridge. Sand transport rate under flat tillage decreased with increasing height by a negative exponential function, while negative linear functions were found under ridge tillage. Thus ridge tillage decreased the rate of wind erosion and sand transportation near soil surface, reduced the loss of soil nutrient caused by wind erosion and plant damage caused by blown sand abrasion, which make it an effective agricultural technology for wind erosion control in the arid and semi-arid regions.     

滇东南石漠化山地不同退耕还林模式土壤地力变化初探

通过对滇东南西畴县石漠化山地12种不同退耕还林模式的土壤进行定点观测和地力变化分析,结果表明:土壤物理性状有很大改善,土壤抗蚀性和储水性增强,土壤养分提高,土壤吸收保存养分离子能力增强。对于提高地力而言,墨西哥柏+金银花、花椒+白枪杆、川滇桤木+红三叶、川滇桤木林、花椒+大白脉根和墨西哥柏+紫花苜蓿等6种模式较佳,值得在石漠化山地推广。     

Modelling the effects of temperature and moisture on CO2 evolution from top- and subsoil using a multi-compartment approach

A novel approach, at least for laboratory conditions, for analysis of the dependence of soil C evolution on temperature is presented. A two-component (labile and refractory organic C) parallel first-order model was fitted to CO₂ evolution rates from top- and subsoil, incubated at different combinations of temperature (constant −4, 0.3, 5, 15, 25, weekly fluctuating between −4 and +5°C) and moisture (17, 26, 36 and 50% H₂O for the topsoil and 16, 23, 31 and 41% for the subsoil) and to the evolution of CO₂ after the addition of roots or stubble of Phalaris arundinacea in the topsoil, measured at 25°C and 36% H₂O (Lomander et al., 1998). The size of the pools and their respective first-order rate constants were optimized simultaneously by a least-squares method. The optimization was carried out separately for top- and subsoil. Quadratic functions were fitted to the temperature and moisture responses. For topsoil samples in which roots or stubble were added, a three-component model (labile, refractory and stubble or roots) was used. The initial partitioning of the soil C, the decomposition rate constants for each partition and the temperature and moisture responses were all assumed to be identical to those of pure topsoil, while the initial pool sizes of added roots and straw were measured. The calculated temperature at which CO₂ evolution ceased (T_min) was −0.83°C, and a recalculation to Q₁₀-values resulted in increasing temperature response with decreasing temperature (Q₁₀=2.2 at 25°C and 12.7 at 0.3°C). Simulated CO₂ evolution rates agreed well with the measurements (R_adj²=0.96 and 0.81) for top- and subsoil, respectively. The multi-compartment approach was superior to the single-compartment approach, which gave R_adj²=0.88 and 0.76 for top- and subsoil, respectively. In general, CO₂ evolution rates obtained from the laboratory experiment were higher than those measured in the field, even after differences in temperature and moisture were taken into account. After 300 d in the laboratory at 25°C and 36% H₂O, 99% and 86% of the added straw and roots, respectively, had disappeared according to the described model. The CO₂-evolution rate per unit of soil carbon was about two times higher for topsoil than for subsoil.