格氏栲天然林与人工林土壤异养呼吸特性及动态

通过用静态碱吸收法对中亚热带福建三明格氏栲自然保护区内的格氏栲天然林和33年生的格氏栲人工林及杉木人工林的土壤异养呼吸进行为期2年的定位研究。结果表明，三种森林枯枝落叶层呼吸和无根土壤呼吸速率季节变化均呈单峰曲线，最大峰值出现在5月至6月，最小值出现在12月至1月。格氏栲天然林、格氏栲人工林和杉木人工林枯枝落叶层呼吸速率平均值分别为CO2 79．88、44．37和21．02mgm^-2h^-1，无根土壤呼吸速率平均值分别为CO2 217．4、85．85和94．04mg m^-2h^-1。2002年枯枝落叶层呼吸速率和无根土壤呼吸速率主要受土壤温度影响，但在极端干旱的2003年则主要受土壤湿度的影响。双因素关系模型（R=ae^bTW^c）拟合结果优于仅考虑土壤温度或土壤湿度的单因素关系模型，土壤温度和土壤湿度共同解释不同年份枯枝落叶层呼吸和无根土壤呼吸速率季节变化的82％～85％和85％～92％。不同森林枯枝落叶层呼吸对土壤温度和湿度的敏感性均高于无根土壤呼吸的。格氏栲天然林、格氏栲人工林和杉木人工林枯枝落叶层呼吸年通量分别为C3．76、2．63和1．23t hm^-2a^-1，无根土壤呼吸年通量则分别为C3．44、2．79和1．49t hm^-2a^-1。不同森林土壤异养呼吸通量的差异主要与枯落物数量和质量、土壤有机质数量和质量的差异有关。杉木林枯枝落叶层呼吸对干旱敏感性高于格氏栲（天然林和人工林）的，而人工林（杉木和格氏栲）的土壤有机C对干旱敏感性则要高于格氏栲天然林。     

西双版纳热带季雨林土壤呼吸变化规律及其影响因素

为了探寻西双版纳热带季雨林土壤呼吸变化规律及其影响因素,分别于2014年不同季节测定了土壤呼吸强度及相关环境因子,同时取相应点表土(0—10cm)测定土壤养分,利用指数模型和线性模型分析土壤呼吸与土壤温度和湿度的关系。结果表明:热带季雨林大气温度的日变化趋势均为单峰曲线;落叶季雨林和半常绿季雨林大气湿度日变化均呈"V"字形变化趋势;0—10cm土壤温度与大气温度变化趋势相一致,在14:00左右达到峰值;土壤湿度均呈"V"字形变化趋势,在14:00达到最低,此后有所回升,局部有所波动。在时间尺度上,2种热带季雨林土壤呼吸均表现为单峰型,且峰值出现的时间基本一致,在14:00左右达到最大,最低值出现在早上6:00,相同时间常绿季雨林土壤呼吸速率高于落叶季雨林。2种热带季雨林土壤呼吸季节性差异显著(p0.05),呈先增加后降低的趋势,均表现为秋季夏季冬季春季。2种热带季雨林土壤呼吸与土壤温度之间关系以指数方程拟合最好,土壤温度可以解释土壤呼吸强度的53.7%~71.0%;落叶季雨林土壤呼吸与土壤湿度之间关系以线性方程拟合最好,常绿季雨林土壤呼吸与土壤湿度之间关系以指数方程拟合最好,土壤湿度可以解释土壤呼吸强度的52.1%~62.3%。通过偏相关分析可知,西双版纳热带季雨林土壤呼吸均与有机质和土壤速效养分含量呈极显著的相关关系(p0.01),与土壤全氮含量呈显著的相关关系(p0.05),而与全磷含量并没有显著的相关性(p0.05),其中常绿季雨林的相关系数均高于落叶季雨林。     

喀斯特峡谷不同植被类型土壤的呼吸及其温度敏感性

[目的]了解喀斯特地区植被恢复对土壤碳释放的影响,为精确估计区域土壤碳收支变化提供参考。[方法]以喀斯特峡谷地区典型植被类型(草地、稀灌草丛、灌丛和乔木林地)为研究对象,采用Li-8100便携式土壤呼吸仪对其土壤呼吸、土壤温度和土壤水分进行定位连续观测,系统研究土壤温度(T)和土壤湿度(W)对土壤呼吸速率(Rs)的影响。[结果](1)草地、稀灌草丛、灌丛和乔木林4种植被类型土壤呼吸均呈单峰型季节动态,土壤呼吸速率的最大值均出现在夏季,最小值出现在冬季,其土壤呼吸速率变化范围分别为0.73~1.21,1.20~1.48,1.54~2.41,1.86~2.95μmol/(m2·s);观测期内,土壤呼吸速率均值分别为1.65,2.76,2.45,3.43μmol/(m2·s)。(2)土壤温度是影响土壤呼吸速率的主导因素,单因素指数模型显示土壤温度对土壤呼吸速率变化的解释能力为72.37%;三次项模型表明土壤水分的贡献率为43.9%。双因素关系模型较好地反映了土壤温度、湿度对土壤呼吸的影响,二者可共同解释土壤呼吸变化的81.5%~91.2%。(3)土壤呼吸的温度敏感性指数Q10值与土壤温度和湿度均呈显著负相关(p0.05)。[结论]4种植被类型土壤呼吸及其温度敏感性同时受土壤温度和水分影响,当土壤含水量过低或过高时,土壤温度的主导作用相对减弱,土壤湿度的影响作用加强。     

石质边坡枯枝落叶层的水土保持功能研究

为了解石质边坡枯枝落叶层的水土保持功能,对广东省顺德区大睡牛岗石质边坡枯枝落叶的蓄积量,枯枝落叶持水性能,枯枝落叶减少土壤侵蚀量,枯枝落叶层下土壤理化性质等内容进行了研究。结果表明:大睡牛岗枯枝落叶蓄积量为219.18 g/m²。枯枝落叶层最大持水率为64%～75%。枯枝落叶层厚度及径流深度影响径流流出时间,随着枯枝落叶厚度的增加,径流流出时间延长,随径流深度增大,径流时间缩短。覆盖枯枝落叶层能极显著地提高土壤抗冲性,与未覆盖枯枝落叶的模拟边坡相比,坡度30°,枯枝落叶2 cm,径流深度1 cm条件下,下坡、中坡、上坡枯枝落叶可减少87.80%以上的土壤侵蚀量。大睡牛岗豆科植被较多的坡位（下坡与上坡）其枯枝落叶层下土壤理化性质优于豆科植被较少的坡位（平台与中坡）。     

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。     

不同耕作措施对旱作春玉米农田土壤呼吸影响的研究——土壤温度对土壤呼吸速率的影响

以山西省寿阳县长期耕作试验为基础,采用碱吸收法研究不同耕作土壤呼吸,结果表明,在中国北方旱作玉米地不同耕作土壤呼吸速率动态变化趋势皆与土壤温度季节变化规律一样,呈单峰抛物线型,峰值出现在7月上旬,达C 1 253 mg/(m2·d);不同时期土壤呼吸速率均值,少耕为C 650 mg/(m2·d)和免耕为C 658 mg/(m2·d),分别比传统耕作C 649 mg/(m2·d)高0.1%和1.4%;不同耕作下土壤呼吸速率与土壤温度均呈显著正相关,免耕>传统耕作>少耕;免耕能显著增加土壤呼吸温度敏感性,免耕Q10值为2.26,比传统耕作高出40.1%,与少耕Q10值1.41相比则降低12.6%;15 cm和10 cm土层Q10均值分别为2.05和1.98,比 5 cm 土层Q10值分别显著高出64.7%和59.1%.可以看出,耕作措施改变土壤温度是影响旱作农田CO2排放的重要因素.     

采伐干扰对东北温带次生林土壤碳矿化和活性有机碳的影响

在黑龙江东部的张广才岭选择典型次生杂木林进行不同采伐处理,一个生长季后测定了土壤潜在碳矿化速率和活性有机碳含量.结果表明:在28℃条件下经过90d的培养,土壤潜在碳矿化速率和碳矿化总量在所测定的土层中(0-10 cm,10-20 cm,20-30 cm)均表现为:50%强度采伐>皆伐后农作>25%强度采伐≌对照>皆伐后造林的变化趋势,但各处理间差异不显著.土壤易氧化碳含量在3个土层50%强度采伐均显著高于对照.土壤微生物碳含量在0-10 cm和10-20 cm土层,50%强度采伐显著高于对照.在0-10 cm土层,皆伐后造林显著低于对照.水溶性有机碳含量在0-10 cm和10-20 cm土层,50%强度采伐显著高于对照,在20-30cm土层,皆伐后造林显著低于对照,这说明在东北温带次生林中,较大强度的择伐短期内可增加土壤活性有机碳含量.而皆伐后造林可导致土壤活性有机碳出现下降趋势.     

巴山水青冈林生态系统土壤呼吸作用及与温度的关系

采用定位观测与综合分析相结合、野外实验与模型模拟相结合的方法.利用LI 6400光合仪研究米仓山国家森林公园巴山水青冈原生林地及皆伐13年后林地土壤呼吸特征.结果表明,原生林及皆伐迹地土壤呼吸作用季节变化和日变化均呈单峰曲线.生长季节中,土壤呼吸作用最强的季节是7-8月,最弱季节是4月和11月;昼夜变化中最强呼吸出现在14:00-15:00,凌晨5:00左右土壤呼吸作用最弱.土壤呼吸速率与5 cm深度土壤温度存在显著线性关系,与近地面地表温度存在极显著指数关系.皆伐迹地经过自然恢复后土壤呼吸作用比原生林强.     

森林演替和气候变暖对暖温带天然次生林植物根系呼吸的交互效应

为了揭示森林演替和气候变暖及交互过程对森林土壤自养呼吸和森林不同层次植物根系呼吸的影响,以关帝山不同演替阶段4种天然次生林(杨桦阔叶落叶林、油松针阔混交林、华北落叶松林和云杉林)为研究对象,于2016—2019年利用Li—6400便携式分析仪观测每种林型不同层次植物根系呼吸和土壤自养呼吸生长季的变化规律;同时采用温室加热法,模拟增温对土壤自养呼吸及各组分的影响。结果表明:(1)根系呼吸速率和土壤自养呼吸速率随演替的进行而降低。乔木层根系呼吸对土壤自养呼吸的贡献率随演替进行则显著上升,而灌木层和草本层的贡献率则显著下降。(2)增温显著提高了不同演替阶段自养呼吸速率,提高幅度为8.48%~8.76%,并随演替进行而升高。森林不同层次植物根系呼吸速率对增温的响应程度不同,其中增温显著提高了草本层和灌木层植物根系呼吸速率,提高幅度分别为10.88%~14.00%和8.37%~15.26%,而[JP]对乔木层植物根系呼吸速率作用则不显著。增温降低了土壤自养呼吸和乔木层根系呼吸的贡献率,则提高了草本层根系呼吸对土壤自养呼吸的贡献率。(3)增温和演替没有改变土壤自养呼吸及各组分在生长季变化规律,但演替和增温对土壤自养呼吸、草本层和灌木层植物根系呼吸有显著的耦合效应。综上所述,森林土壤自养呼吸和根系呼吸速率随演替进行具有降低的趋势,土壤自养呼吸速率、灌木层和草本层植物根系呼吸速率对增温响应程度显著,并且对演替和增温的交互过程有显著的耦合效应,为气候变暖背景下森林更新过程对森林土壤碳排放影响的研究提供数据支持和理论依据。     

改变碳输入对南亚热带海岸沙地典型天然次生林土壤呼吸的影响

土壤呼吸是陆地生态系统碳循环的一个重要过程,开展环境因子和改变碳输入对土壤呼吸影响的研究具有重要意义.2015年3月-2016年2月,在南亚热带海岸沙地典型天然次生林中设置去除根系、去除凋落物、加倍凋落物和对照4种处理,采用LI-8100连续观测改变碳输入对土壤呼吸的影响.结果表明:改变碳输入没有显著影响l0cm土壤温度和湿度(P＞0.05);不同处理土壤呼吸速率存在明显的季节变化,表现为夏高冬低,最大值出现在5月或者6月,最小值出现在11月或12月;土壤呼吸速率的年均值为加倍凋落物＞对照＞去除根系＞去除凋落物,不同改变碳输入方式均降低了土壤呼吸的Q10值;矿质土壤呼吸、凋落物呼吸和根系呼吸对土壤总呼吸的贡献分别为41.24％、43.29％和15.45％;不同处理土壤呼吸速率分别与土壤温度和湿度呈显著的指数和线性正相关(P＜0.05),双因子模型能解释土壤呼吸变异的45％ ～ 69％;改变碳输入影响土壤可溶性有机碳和微生物生物量碳,不同处理土壤呼吸速率与可溶性有机碳和微生物生物量碳呈正相关.因此,改变碳输入引起土壤易变碳的变化进而影响土壤呼吸.     

Variation of soil respiration at three spatial scales: Components within measurements, intra-site variation and patterns on the landscape

Soil respiration is an important component of terrestrial carbon cycling and can be influenced by many factors that vary spatially. This research aims to determine the extent and causes of spatial variation of soil respiration, and to quantify the importance of scale on measuring and modeling soil respiration within and among common forests of Northern Wisconsin. The potential sources of variation were examined at three scales: [1] variation among the litter, root, and bulk soil respiration components within individual 0.1 m measurement collars, [2] variation between individual soil respiration measurements within a site (<1 m to 10 m), and [3] variation on the landscape caused by topographic influence (100 m to 1000 m). Soil respiration was measured over a two-year period at 12 plots that included four forest types. Root exclusion collars were installed at a subset of the sites, and periodic removal of the litter layer allowed litter and bulk soil contributions to be estimated by subtraction. Soil respiration was also measured at fixed locations in six northern hardwood sites and two aspen sites to examine the stability of variation between individual measurements. These study sites were added to an existing data set where soil respiration was measured in a random, rotating, systematic clustering which allowed the examination of spatial variability from scales of <1 m to 100+ m. The combined data set for this area was also used to examine the influence of topography on soil respiration at scales of over 1000 m by using a temperature and moisture driven soil respiration model and a 4 km² digital elevation model (DEM) to model soil moisture. Results indicate that, although variation of soil respiration and soil moisture is greatest at scales of 100 m or more, variation from locations 1 m or less can be large (standard deviation during summer period of 1.58 and 1.28 μmol CO₂ m⁻² s⁻¹, respectively). At the smallest of scales, the individual contributions of the bulk soil, the roots, and the litter mat changed greatly throughout the season and between forest types, although the data were highly variable within any given site. For scales of 1-10 m, variation between individual measurements could be explained by positive relationships between forest floor mass, root mass, carbon and nitrogen pools, or root nitrogen concentration. Lastly, topography strongly influenced soil moisture and soil properties, and created spatial patterns of soil respiration which changed greatly during a drought event. Integrating soil fluxes over a 4 km² region using an elevation dependent soil respiration model resulted in a drought induced reduction of peak summer flux rates by 37.5%, versus a 31.3% when only plot level data was used. The trends at these important scales may help explain some inter-annual and spatial variability of the net ecosystem exchange of carbon.     

Response of soil respiration to precipitation during the dry season in two typical forest stands in the forest-grassland transition zone of the Loess Plateau

Forest ecosystems on the Loess Plateau are receiving increasing attention for their special importance in carbon fixation and conservation of soil and water in the region. Soil respiration was investigated in two typical forest stands of the forest-grassland transition zone in the region, an exotic black locust (Robinia pseudoacacia) plantation and an indigenous oak (Quercus liaotungensis) forest, in response to rain events (27.7 mm in May 2009 and 19 mm in May 2010) during the early summer dry season. In both ecosystems, precipitation significantly increased soil moisture, decreased soil temperature, and accelerated soil respiration. The peak values of soil respiration were 4.8 and 4.4 μmol CO₂ m⁻² s⁻¹ in the oak plot and the black locust plot, respectively. In the dry period after rainfall, the soil moisture and respiration rate gradually decreased and the soil temperature increased. Soil respiration rate in black locust stand was consistently less than that in oak stand, being consistent with the differences in C, N contents and fine root mass on the forest floor and in soil between the two stands. However, root respiration (R_r) per unit fine root mass and microbial respiration (R_m) per unit the amount of soil organic matter were higher in black locust stand than in oak stand. Respiration by root rhizosphere in black locust stand was the dominant component resulting in total respiration changes, whereas respiration by roots and soil microbes contributed equally in oak stand. Soil respiration in the black locust plantation showed higher sensitivity to precipitation than that in the oak forest.     

The influence of thinning on the ecological conditions and soil respiration in a larch forest on Hokkaido Island

The effects of cutting on the ecological conditions and soil respiration in larch forests of Japan were studied. The cutting was found to significantly change the soil surface, resulting in the high spatial and temporal variation of the hydrothermal conditions and soil respiration. The influence of a stand’s thinning on the environment and soil respiration is considered using the example of the thinning of a ripening larch stand in the Tomakomai National Forest (Hokkaido Island, Japan). The changes in the hydrothermal conditions (the temperature and moisture of the mineral soil layers and litter) and some other factors (the root and litter density and the C/N ratio) after the thinning of the stands and their influence on the soil respiration were studied. The soil respiration in the thinned forest site did not differ from that on the control plot, whereas the soil temperature was much higher in the former. The moisture of the soil mineral layers and the litter was the same. Despite the latter fact, no significant relationships between the soil respiration and its temperature and moisture were found. In the area covered with the thinned forest, the water content of the litter turned out to be the main microclimatic factor affecting the soil respiration. There, the fine roots and litter density were 18 and 15 % less, respectively. The thinning of the stand induced high variation of the soil respiration and temperature, as well as of the fine roots and the litter density. On the whole, the soil respiration in the larch forest studied in Japan was determined by the litter stock and the C to N ratio.     

Biological changes in northern spruce forest soil after clear-cutting

In northern Finland, reforestation has frequently failed in clear-cut areas of coniferous forests. These failures prompted an investigation of the changes in the invertebrate fauna and in the bacterial populations of such forest soils after clear-cutting. Clear-cut areas in four neighbouring sites of various ages were sampled monthly, and the results were compared with those for samples taken simultaneously from a control site in an untreated spruce stand. After clear-cutting, the total biomass of the invertebrate fauna showed a strong increase, mainly due to an increase of the Enchytraeidae populations. The biomass reached its maximum after 7 yr and returned to the original level by year 13 after clear-cutting. Bacterial counts showed the same pattern as the faunal biomass; the numbers at first increased after clear-cutting, then regressed, and approached the control value after 13 yr. Cellulose degradation and soil respiration behaved in the same way. Bacterial numbers showed a significant seasonal variation at all sites, including the control; counts were maximal after the snow melt in June and decreased during the growing season.     

Nutrient limitations to soil microbial biomass and activity in loblolly pine forests

We performed an assay of nutrient limitations to soil microbial biomass in forest floor material and intact cores of mineral soil collected from three North Carolina loblolly pine (Pinus taeda) forests. We added solutions containing C, N or P alone and in all possible combinations, and we measured the effects of these treatments on microbial biomass and on microbial respiration, which served as a proxy for microbial activity, during a 7-day laboratory incubation at 22 °C. The C solution used was intended to simulate the initial products of fine root decay. Additions of C dramatically increased respiration in both mineral soil and forest floor material, and C addition increased microbial biomass C in the mineral soil. Additions of N increased respiration in forest floor material and increased microbial biomass N in the mineral soil. Addition of P caused a small increase in forest floor respiration, but had no effect on microbial biomass.     

Impact of land degradation on soil respiration in a steppe (Stipa tenacissima L.) semi-arid ecosystem in the SE of Spain

Climate change scenarios predict increases in temperature, changes in precipitation patterns, and longer drought periods in most semi-arid regions of the world. Ecosystems in these regions are prone to land degradation, which may be aggravated by climate change. Soil respiration is one of the main processes responsible for organic carbon losses from arid and semi-arid ecosystems. We measured soil respiration over one year in two steppe ecosystems having different degrees of land degradation under three ground-covers: with vegetation, bare soil, and an intermediate situation between plants and bare soil.The largest differences in soil respiration rates between the sites were observed in spring, coinciding with the highest level of plant activity. The degraded site had drier and hotter soils with less soil water availability and a longer drought period. As a result, vegetation on the degraded site did not respond to spring rainfall events. Soil respiration showed a strong seasonal variability, with average annual rates of 1.1 and 0.8 μmol CO₂ m⁻² s⁻¹ in the natural and degraded sites, respectively. We did not observe significant differences in soil respiration rates associated with ground-cover i.e., the temporal variation was much larger than the spatial variation. At both sites, soil moisture was the controlling driver of soil respiration for most of the year, when temperatures were above 20 °C and constrained the response to temperature for the few months when the temperature was below 20 °C. An empirical model based on soil temperature and soil moisture explained 90% and 72% of the seasonal variability of soil respiration on the natural and degraded sites, respectively. For the first time, this study suggests that land degradation may alter the carbon balance of these ecosystems through changes in the temporal dynamics of soil respiration and plant productivity, which have important negative consequences for ecosystem functioning and sustainability.     

Effects of prescribed fire on rates of decomposition and nitrogen mineralization in a ponderosa pine ecosystem

Summary The effects of a prescribed fire in a ponderosa pine ecosystem on the rates of decomposition and nitrogen mineralization (including ammonification and nitrification) in the forest floor and mineral soil horizons were evaluated. The prescribed fire immediately increased the rates of nitrogen mineralization and nitrification in the forest floor of all burned plots and in the mineral soil of one plot. The rates of decomposition, as measured by CO2 evolution, in both the forest floor and mineral soil were not significantly different immediately after the burn when expressed on an organic matter basis. The rates of nitrogen mineralization in the forest floor and mineral soil were higher 6 and 10 months after the burn. The rate of decomposition (as measured by respiration) was lower in the forest floor but not in the mineral soil 6 and 10 months after the burn. Volatile organics that may inhibit rates of nitrogen mineralization may have been consumed by prescribed fire.     

Modeling soil respiration based on carbon, nitrogen, and root mass across diverse Great Lake forests

The variability in the net ecosystem exchange of carbon (NEE) is a major source of uncertainty in quantifying global carbon budget and atmospheric CO₂. Soil respiration, which is a large component of NEE, could be strongly influential to NEE variability. Vegetation type, landscape position, and site history can influence soil properties and therefore drive the microbial and root production of soil CO₂. This study measured soil respiration and soil chemical, biological and physical properties on various types of temperate forest stands in Northern Wisconsin (USA), which included ash elm, aspen, northern hardwood, red pine forest types, clear-cuts, and wetland edges. Soil respiration at each of the 19 locations was measured six times during 1 year from early June to mid-November. These data were combined with two additional data sets from the same landscape that represent two smaller spatial scales. Large spatial variation of soil respiration occurred within and among each forest type, which appeared to be from differences in soil moisture, root mass and the ratio of soil carbon to soil nitrogen (C:N). A soil climate driven model was developed that contained quadratic functions for root mass and the ratio of soil carbon to soil nitrogen. The data from the large range of forest types and site conditions indicated that the range of root mass and C:N on the landscape was also large, and that trends between C:N, root mass, and soil respiration were not linear as previously reported, but rather curvilinear. It should be noted this function appeared to level off and decline at C:N larger than 25, approximately the value where microbial nitrogen immobilization limits free soil nitrogen. Weak but significant relationships between soil water and soil C:N, and between soil C:N and root mass were observed indicating an interrelatedness of (1) topographically induced hydrologic patterns and soil chemistry, and (2) soil chemistry and root production. Future models of soil respiration should address multiple spatial and temporal factors as well as their co-dependence.     

火烧和保留采伐剩余物对土壤有机碳矿化的影响

采用室内培养法,比较分析了福建三明地区米槠次生林皆伐后火烧、保留采伐剩余物处理对土壤有机碳累积矿化量的影响,分析了土壤有机碳累积矿化量和土壤初始有机碳、微生物生物量碳及可溶性有机碳的关系。结果表明,火烧、保留采伐剩余物处理6个月和18个月后,火烧处理表层0~10 cm土壤有机碳含量较对照处理分别下降了6.0%和1.9%,保留采伐物处理土壤表层有机碳增加了15.6%和25.0%。两次培养中,火烧处理各土层累积矿化量显著低于对照和保留采伐剩余物处理;火烧6个月后,保留采伐剩余物处理各土层累积矿化量显著低于对照,18个月后10~20和20~40 cm土层累积矿化量显著高于对照处理。火烧18个月后,保留采伐剩余物处理各土层累积矿化量显著高于1年前的累积矿化量,分别高57.0%、112.0%和49.9%;火烧和对照处理前后两次培养各土层累积矿化量变化并无明显规律。土壤有机碳累积矿化量与土壤初始有机碳、微生物生物量碳和可溶性有机碳呈显著地线性相关关系(p0.05)。营林活动初期,皆伐后保留采伐剩余物措施较火烧能够增加土壤有机碳库,对土壤肥力及后期林木生长有重要的促进作用。     

重庆缙云山3种林型土壤呼吸及其影响因子

2011年1～12月,采用LI-Cor 8100开路式土壤碳通量测量系统对重庆缙云山保护区3种主要林分类型(针阔混交林、常绿阔叶林和毛竹林)的土壤呼吸速率和林内气温、土壤温度和湿度进行了野外观测。结果表明:针阔混交林、常绿阔叶林和毛竹林的土壤呼吸碳通量分别为654.70、1008.37和910.64 g C m-2a-1;3种林型土壤呼吸速率均呈现显著的季节性变化,且夏季>秋季>春季>冬季,最大值出现在7月,最小值出现在1月;3种林型土壤呼吸速率全年平均值分别为1.73、2.66和2.40μmol m-2s-1;3种林型土壤呼吸速率均与林内气温存在显著正相关关系(P<0.05),且与5 cm土壤温度均存在极显著的指数正相关(P<0.05);与5 cm土壤含水量的相关性不显著(P>0.05),但土壤含水量较低而温度较高时,较低的土壤含水量对呼吸速率具有一定抑制作用;3种林型的土壤呼吸对温度的敏感系数(Q10值)存在差异,全年表现为毛竹林(2.44)>针阔混交林(1.76)>常绿阔叶林(1.72),同时均表现显著的季节差异。