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1.
The diurnal and seasonal dynamics of soil respiration in the A. ordosica shrubland on Ordos Plateau were investigated in the growing season （May-October） of 2006 and their environmental driving factors were also analyzed, Results indicated that diurnal dynamics of soil respiration rate and its temperature dependence showed some discrepancy in two different growth stages （the vegetative growth stage and the reproductive growth stage）. During the vegetative growth stage, the diurnal variation of soil respiration was slight and not correlated with the daily temperature change, but during the reproductive growth stage, the daily respiration variation was relatively large and significantly correlated with the diurnal variation of air and soil temperature. In the growing season, the peak value of soil respiration occurred at July and August because of the better soil water-heat conditions and their optimal deployment in this period. In the shrubland ecosystem, precipitation was the switch of soil respiration pulses and can greatly increase soil respiration rates after soil rewetting. Moreover, the soil respiration rates in the growing season and the air temperature and soil surface water content were closely correlated （p〈0.05） each other. The stepwise regression model indicated that the variation of soil surface moisture accounted for 41.9% of the variation in soil respiration （p〈0.05）.  相似文献   

2.
Carbohydrate represents an important part of the soil labile organic carbon pool. Water soluble carbohydrate drives the C cycle in forest soil by affecting microbial activity and hot water extractable carbohydrate is thought related to soil carbon sequestration due to the association with soil aggregation. In a temperate forest region of northeast China, Changbai Mountain, we investigated the abundance, spacial distribution, and seasonal dynamics of cool and hot-water extractable carbohydrate in soils under mixed broad-leaved Korean pine forest. The concentrations of cool-water extractable carbohydrate (CWECH) in three soil layers (0-5, 5-10, 10-20 cm) ranged from 4.1 to 193.3 g·kg-1 dry soil, decreasing rapidly with soil depth. On an annual average, the CWECH concentrations in soils at depths of 5-10 and 10-20 cm were 54.2% and 24.0%, respectively, of that in the 0-5 cm soil layer. CWECH showed distinct seasonal dynamics with the highest concentrations in early spring, lowest in summer, and increasing concentrations in autumn. Hot-water extractable carbohydrate (HWECH) concentrations in three soil layers ranged from 121.4 to 2026.2 g·kg-1 dry soil, which were about one order of magnitude higher than CWECH. The abundance of HWECH was even more profile-dependent than CWECH, and decreased more rapidly with soil depth. On an annual average, the HWECH concentration in soils 10-20 cm deep was about one order of magnitude lower than that in the top 0-5 cm soil. The seasonality of HWECH roughly tracked that of CWECH but with seasonal fluctuations of smaller amplitude. The carbohydrate concentrations in cool/hot water extracts of soil were positively correlated with UV254 and UV280 of the same solution, which has implications for predicting the leaching loss of water soluble organic carbon.  相似文献   

3.
To analyze the relationship between the management of three forest stand plantations and soil quality in the Dimapur district of the Northeastern Himalayan region,India,three forest soil profiles,covered by different species stands,at three depths were tested for 13 physical and chemical variables.Only four of these variables(electric conductivity,bulk density exchangeable Mg and available P)were included in a minimum data set,after using a varimax rotation algorithm in a principal component analysis,and subsequently used to calculate a soil quality index(SQI).Results showed higher SQIs in the surface layers(0–20 cm depth)than in the deeper ones.Average weighed SQI varied significantly(P<0.05)through the three considered forest sites,with the lowest value at site FS3.These findings reveal that the approach used here is suitable for preliminary screening of the impact of a forestry species on soil,to aid in species selection and improve soil health for afforestation and reforestation projects.  相似文献   

4.
In order to improve the understanding of the role of a canopy opening/gap on the physical environments in a secondary forest in Northeastern China, a case study was conducted in and around a small irregular gap in a montane secondary forest. The secondary forest, which was severely disturbed by human beings about 50 years ago, was dominated by Quercus mongolica and Fraxinus rhynchophyllaan. Temporal variation in photosynthetic photon flux density （PPFD）, air temperature （TA） at 10 cm above the ground, soil temperature （Ts） and soil water content （SWC） at top-layer （0-15 cm） and sub-layer （15-30 cm） were measured from May to September after the second year since the formation of the small gap （the ratios of gap diameter to stand height were less than 0.5） in 2006 respectively. Results indicated that the highest value of PPFD occurred at the northern edge of the gap, particularly at the beginning of the growing season in May. On sunny days, the highest value of PPFD appeared earlier than that on overcast days. Maximum and mean values of TAwere higher in the northern part of the gap, and the minimum values of TAwere at the southern edge of the gap. Soil temperature varied obviously in the gap with the range from 1 to 8 ℃. Maximum values of Ts occurred at the northern part of the gap, which was significantly correlated with the maximum values of TA （R = 0.735, P〈0.05）. SWC was higher in the top-layer （0-15 cm） than that in sub-layer （15-30 cm）, but the difference of them was not significant （p〉0.05）, which might be attributed to the small gap size and the effects of aboveground vegetations. From these results, the maximum of PPFD in the study area occurred at the northern part of the gap, which was consistent with the results observed in north hemisphere, but the occurrence time varied with the differences of the latitudes. The highest values of air and soil temperatures also occurred in the northern part of the gap because they were affected by the radiation. However  相似文献   

5.
Succession rules of soil acidity quality of larch plantations in first rotation at different development stages, succession rules of soil acidity quality of young stand of larch plantations in second rotation and the relationship between soil acidity and various forms of organic phosphorus and inorganic phosphorus were studied in mountainous area of eastern part of Northeastern China. The results showed that active acidity (pH value) inrhizosphere soil decreased continually with stand age increasing from young stand, half-mature stand, near mature stand to mature stand, but active acidity (pH value) in non-rhizosphere soil, exchange acidity, exchangeable aluminium, total hydrolytic acidity, and the ratio of exchange acidity and total hydrolytic acidity in rhizosphere soil and in non-rhizosphere soil increased apparently; total organic P, moderately resistant organic P, and highly resistant organic P in soil decreased at all age stages in larch plantations when soil acidity added. For rhizosphere soil of  相似文献   

6.
In the summer of 2015,hundreds of forest fires burned across the state of Alaska.Several uncontrolled wildfires near the town of Tanana on the Yukon River were responsible for the largest portion of the area burned statewide.In July 2017,field measurements were carried out in both unburned and burned forested areas nearly adjacent to one another,all within 15 miles of the village of Tanana.These surveys were used to first visually verify locations of different burn severity classes,(low,moderate,or high),estimated in 2016 from Landsat images(collected before and after the 2015 Tanana-area wildfires).Surface and soil profile measurements to 30-cm depth at these same locations were collected for evidence of moss layer and forest biomass burning.Soil temperature and moisture content were measured to 30-cm depth,and depth to permafrost was estimated by excavation wherever necessary.Digital thermal infra-red images of the soil profiles were taken at each site location,and root-zone organic layer samples were extracted for further chemical analysis.Results supported the hypothesis that the loss of surface organic layers is a major factor determining post-fire soil water and temperature changes and the depth of permafrost thawing.In the most severely burned forest sites,complete consumption of the living moss organic layer was strongly associated with both warming at the surface layer and increases in soil water content,relative to unburned forest sites.Soil temperatures at both 10-cm and 30-cm depths at burned forest sites were higher by 8-10C compared to unburned sites.Below 15 cm,temperatures of unburned sites dropped gradually to frozen levels by 30 cm,while soil temperatures at burned sites remained above 5C to 30-cm depth.The water content measured at 3 cm at burned sites was commonly in excess of 30%by volume,compared to unburned sites.The strong correlation between burn index values and depth to permafrost measured across all sites sampled in July 2017 showed that the new ice-free profile in severely burned forest areas was commonly 50-cm deeper than in unburned soils.  相似文献   

7.
Determining the physical and mechanical properties of soil and its behavior for engineering projects is essential for road construction operations. One of the most important principles in forest road construction, which is usually neglected, is to avoid mixing organic matter with road materials during excavation and embankment construction. The current study aimed to assess the influence of organic matter on the physical properties and mechanical behaviors of forest soil and to analyze the relation between the amount of organic matter and the behavior of forest soil as road material. A typical soil sample from the study area was collected beside a newly constructed roadbed. The soil was mixed with different percentages of organic matter(control treatment, 5, 10, and 15% by mass) and different tests including Atterberg limits, standard compaction, and California bearing ratio(CBR) tests were conducted on these different soil mixtures. The results showed that soil plasticity increased linearly with increasing organic matter.Increasing the organic matter from 0%(control) to 15%resulted in an increase of 11.64% of the plastic limit and 15.22% of the liquid limit after drying at 110 ℃. Also,increasing the organic matter content reduced the soil maximum dry density and increased the optimum moisture content. Increasing the organic matter from 0 to 15% resulted in an increase of 11.0% of the optimum moisture content and a decrease of 0.29 g/cm~3 of the maximum dry density. Organic matter decreased the CBR, which is used as the index of road strength. Adding 15% organic matter to the soil resulted in a decrease of the CBR from 15.72 to 4.75%. There was a significant difference between the two drying temperatures(60 and 110 ℃) for the same organic matter mixtures with lower water content values after drying at 60 ℃. The results revealed the adverse influence of organic matter on soil engineering properties and showed the importance of organic matter removal before excavation and fill construction.  相似文献   

8.
Trees on sand dunes are more sensitive to environmental changes because sandy soils have extremely low water holding capacity and nutrient availability. We investigated the dynamics of soil respiration(Rs) for secondary natural Litsea forest and plantations of casuarina,pine, acacia and eucalyptus. Results show that significant diurnal variations of Rsoccurred in autumn for the eucalyptus species and in summer for the pine species, with higher mean soil respiration at night. However, significant seasonal variations of Rswere found in all five forest stands. Rschanged exponentially with soil temperatures at the 10-cm depth; the models explain 43.3–77.0% of Rs variations. Positive relationships between seasonal Rsand soil moisture varied with stands. The correlations were significant only in the secondary forest, and the eucalyptus and pine plantations. The temperature sensitivity parameter(Q10 value) of Rsranged from 1.64 in casuarina plantation to 2.32 the in secondary forest; annual Rswas highest in the secondary forest and lowest in the pine plantation. The results indicate that soil temperatures and moisture are the primary environmental controls of soil respiration and mainly act through a direct influence on roots and microbial activity. Differences in root biomass, quality of litter,and soil properties(pH, total N, available P, and exchangeable Mg) were also significant factors.  相似文献   

9.
Extreme droughts can adversely affect the dynamics of soil respiration in tree plantations. We used a severe drought in southwestern China as a case study to estimate the effects of drought on temporal variations in soil respiration in a plantation of Eucalyptus globulus. We documented a clear seasonal pattern in soil respiration with the highest values(100.9 mg C–CO_2 m~(-2)h~(-1)) recorded in June and the lowest values(28.7 mg C–CO_2 m~(-2)h~(-1)) in January. The variation in soil respiration was closely associated with the dynamics of soil water driven by the drought. Soil respiration was nearly twice as great in the wet seasons as in the dry seasons. Soil water content accounted for 83–91% of variation in soil respiration, while a combined soil water and soil temperature model explained 90–99% of the variation in soil respiration. Soil water had pronounced effects on soil respiration at the moisture threshold of 6–10%. Soil water was strongly related to changes in soil parameters(i.e., bulk density, p H,soil organic carbon, and available nitrogen). These strongly influenced seasonal variation in soil respiration. We found that soil respiration was strongly suppressed by severe drought. Drought resulted in a shortage of soil water which reduced formation of soil organic carbon, impacted soil acid–base properties and soil texture, and affected soil nutrient availability.  相似文献   

10.
《林业研究》2021,32(2)
Relationships between stem growth and climatic and edaphic factors,notably air temperatures and soil moisture for different slopes,are not completely understood.Stem radial variations were monitored at the bottom and top slope positions in a Larix principis-rupprechtii plantation during the 2017 and 2018 growing seasons.Total precipitation during the growing season in 2017 and 2018 was 566 mm and728 mm,respectively.Stem contractions typically occurred after mid-morning followed by swelling in the late afternoon in both plots,reflecting the diurnal cycle of water uptake and loss.Trees at the two locations showed the same growth initiation(mid-May) because of the small differences in air and soil temperatures.There were no significant differences in cumulative stem radial growth between the bottom plot(1.57±0.34 mm) and the top plot(1.55±0.26 mm) in 2018.However,in 2017,the main growth period of the bottom plot ceased 17 days earlier than in the top plot,while cumulative seasonal growth of the bottom plot(1.08±0.25 mm)was significantly less than the top plot(1.54±0.43 mm).Maximum daily stem shrinkage was positively correlated with air and soil temperatures,solar radiation,vapor pressure deficits,and negatively correlated with volumetric soil moisture content.The maximum daily shrinkage reflected transpiration rates as affected by environmental factors.Daily radial stem increment was correlated with precipitation and volumetric soil moisture in both years,but with air temperatures only in 2017.The seasonal growth of L.principis-rupprechtii Mayr thus shows interannual dynamics,while precipitation constitutes a key driving factor.  相似文献   

11.
潜在温室气体CO气体通量相关研究很少,多集中于热带、亚热带地区,大兴安岭兴安落叶松林作为我国北方寒温带最大的天然林,研究该森林土壤CO变化特征具有典型性与创新性.于2020年6—9月采用加拿大LGR-N2O∕CO分析仪持续测定大兴安岭兴安落叶松林CO气体通量及土壤温湿度,分析大兴安岭兴安落叶松林土壤CO气体通量的变化特...  相似文献   

12.
本研究对鄂尔多斯高原沙化灌丛群落油蒿土壤呼吸日变化和季节变化进行了野外定位观测,并对其环境驱动因子进行了初步的探讨.结果表明:油蒿群落两个不同生长期土壤呼吸日变化及其对温度因子的响应存在差异.营养生长期,土壤呼吸日变化不明显,且土壤呼吸速率和温度日变化无显著的相关关系;而在生殖生长期,土壤呼吸日变化非常明显,气温及0-10 cm土壤温度日变化与土壤呼吸速率相关显著(P<0.05).整个生长季期间,土壤呼吸高峰期出现在7-8月,与该段时间水热因子条件最佳且配置较好密切相关.荒漠灌丛生态系统中,降雨是土壤呼吸出现激发现象的控制因素.降雨对土壤产生的干湿交替作用能够显著提高土壤呼吸速率.生长季期间,土壤呼吸速率变化与气温及0-10 cm土壤含水量变化的相关性显著(P<0.05).通过逐步回归发现,0-10 cm土壤含水量的变化能够说明生长季土壤呼吸速率变化的41.9% (P<0.05).图3表2参34.  相似文献   

13.
大岗山森林生态站区气象要素分析   总被引：20，自引：0，他引：20       下载免费PDF全文
采用林外对照区与不同林型小气倏定位观测的实验方法,以大岗山森林生态站2001－2002年气象观测数据为基础,从太阳辐射、大气温度、大气湿度、土壤温度、降水量、蒸发量、风速和风向等因子对大岗山森林生态站站区林内与林外对照区气象要素值进行对比分析。结果表明：（1）大气下垫面的性质是影响气象要素变化的重要因子,林内气温、湿度变幅小,且基本处于静风状态;无林地气温、湿度日较差、年较差大,蒸发量相对增加,平均风速增大。（2）林分类型、郁闭度不同对气象要素的变化也有很大影响。  相似文献   

14.
由人类活动所造成的大气中温室气体浓度急剧增加而引起的全球气候变暖和环境变化已引起全世界的广泛关注。氧化亚氮(N2O)是仅次于二氧化碳(CO2)和甲烷(CH4)的一种温室气体,在大气中含量较低却十分稳定,具有较大的增温潜能(其单分子的增温潜能是CO2的310倍)和较快的浓度增加速率(以每年0.25%的速率增加)(IPCC,2007)。N2O可吸收红外线,减少地球表面通过大气向外层空间的热辐射,导致地球表面温度增加。N2O能参与大气中许多光化学反应,破坏臭氧层(Crutzen,1970),导致到达地球表面的紫外线明显增加,给人类健康和生态环境带来多方面的危害。  相似文献   

15.
3种林茶复合系统小气候特征日变化研究   总被引：2，自引：1，他引：2  
对枫香、香樟、栾树与茶树复合的3种模式小气候日变化进行观测.结果表明,大气和土壤温度日变化等表现出与光辐射强度一致单峰变化规律,但峰值出现的时间比太阳辐射强度的峰值迟滞2 h左右;相对湿度的日动态呈"U"型变化;光辐射强度与大气温度和湿度呈极显著的正相关关系,与不同深度土壤温度呈正相关,与土壤湿度呈不显著负相关;光辐射强度、大气和土壤温度是决定各模式小气候特征的重要因子.初步认为,枫香-茶复合系统较其他两种能保持适宜而又稳定的生长环境,更适宜本地推广.  相似文献   

16.
小兴安岭天然针阔混交林择伐后土壤呼吸动态变化   总被引：6，自引：2，他引：4  
采用LI-8100土壤CO2排放通量全自动测量系统,针对小兴安岭带岭林业局东方红林场不同择伐强度的针阔混交林样地,测定林地生长季土壤呼吸速率以及10cm土深处的温度和湿度,探讨生长季土壤呼吸的日变化、季节变化和年通量。结果表明：土壤呼吸日变化动态与土壤温度日变化动态基本一致,呈明显的单峰曲线。采伐强度不同间接影响着土壤呼吸速率。研究表明：针阔混交林土壤呼吸速率均值在0．6—8．2μml·m^-2·s^-1之间,高于同纬度其他地区;雨季（6月、7月、8月、9月）土壤呼吸明显大于旱季（5月、10月、11月）;针阔混交林生态系统土壤呼吸不同月份通量值在1．68～18．82mol·m^-2之间,最大值和最小值分别出现在7月和11月。与北半球温带森林生态系统土壤呼吸变化趋势基本一致。2006年针阔混交林生态系统土壤呼吸通量为84．37mol·m^-2,与朝鲜半岛硬阔混交林土壤呼吸相似,但比一些热带地区的结果偏大。  相似文献   

17.
Respiration of the rhizosphere in a beech (Fagus sylvatica L.) forest was calculated by subtracting microbial respiration associated with organic matter decomposition from daily mean soil CO2 efflux. We used a semi-mechanistic soil organic matter model to simulate microbial respiration, which was validated against "no roots" data from trenched subplots. Rhizosphere respiration exhibited pronounced seasonal variation from 0.2 g C m(-2) day(-1) in January to 2.3 g C m(-2) day(-1) in July. Rhizosphere respiration accounted for 30 to 60% of total soil CO2 efflux, with an annual mean of 52%. The high Q10 (3.9) for in situ rhizosphere respiration was ascribed to the confounding effects of temperature and changes in root biomass and root and shoot activities. When data were normalized to the same soil temperature based on a physiologically relevant Q10 value of 2.2, the lowest values of temperature-normalized rhizosphere respiration were observed from January to March, whereas the highest value was observed in early July when fine root growth is thought to be maximal.  相似文献   

18.
有机覆盖物对城市绿地土壤水分和温度的影响   总被引：7，自引：1，他引：7       下载免费PDF全文
为了解有机覆盖物对城市绿地土壤水分和温度的影响,文章选择城市公园绿地对地表分别进行了覆盖3cm、5cm有机覆盖物和未覆盖空白对照三种处理试验,研究了0~10cm、10~20cm、20~30cm和30~40cm不同土层的水分和温度变化。结果表明:(1)三种覆盖处理土壤含水量的季节变化趋势一致。土壤含水量在0~10cm波动最大,随着土壤深度的增加,这种波动表现得越来越弱。(2)覆盖3cm有机物处理在四个土壤层次均高于空白对照,而在10~20cm和20~30cm的增加量最多;覆盖5cm有机物处理只在0~10cm明显的高于空白对照。(3)不同覆盖处理的土壤温度的季节变化趋势一致。相对于空白对照,覆盖处理的土壤日温变化幅度要明显小于空白对照,其中覆盖3cm和5cm有机物的处理比对照区在炎热的夏季土壤温度分别降低了2.0℃和0.9℃,而在寒冷的冬季升高了0.9℃和1.4℃。同时,覆盖处理也减小了不同土层深度的温度变幅。    相似文献   

19.
研究根据广东和广西(两广)地区森林类型分布图、主要森林类型的年土壤呼吸数据库以及中国日值格点气温、降水数据,建立线性模型预测两广地区主要森林类型的年土壤呼吸速率和年土壤呼吸通量。结果表明,两广地区主要森林类型年土壤呼吸速率为常绿阔叶林864.18 gC/m~2/yr>其他森林811.03 gC/m~2/yr>针叶林791.43 gC/m~2/yr>灌木林780.18 gC/m~2/yr>落叶阔叶林758.80 gC/m~2/yr>竹林731.49 gC/m~2/yr>针阔混交林684.91 gC/m~2/yr。两广地区森林年土壤呼吸通量为204.41 TgC/yr,其中常绿阔叶林最大,为77.41 TgC/yr,针叶林次之,为56.81 TgC/yr,具体为常绿阔叶林>针叶林>灌木林>落叶阔叶林>针阔混交林>竹林>其他森林,顺序与各种森林类型面积大小一致。各森林类型的土壤呼吸通量主要与森林面积有关,森林面积越大土壤呼吸通量越大。  相似文献   

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