次生栎林和人工松林土壤呼吸对温度敏感性的室内模拟

土壤呼吸对温度的敏感性是影响全球气候变暖不确定性的因素之一.为了解在排除其他生态因子的影响下天然阔叶林和人工针叶林土壤呼吸对温度敏感性的差异,选择了苏南丘陵次生栎林和火炬松人工林为研究对象,采集2种林分0～10cm表层土壤,分别进行了5℃、15℃、25℃和35℃的室内恒温培养实验.用传统的密闭气室碱液吸收法测定它们的CO2释放量的动态变化,并测定土壤理化性质.结果表明:次生栎林对温度的敏感性即Q10值大于火炬松人工林;在5℃、15℃和25℃培养时2种林分土壤呼吸累积释放CO2量的差异不显著,并且土壤释放CO2的动态变化一致,而35℃时,次生栎林显著大于火炬松人工林;在25℃培养时,次生栎林土壤呼吸累积释放CO2量与5℃和15℃相比并没有显著增加,反而低于火炬松人工林;次生栎林的全碳、全氮、全钙、全磷含量以及碳氮比显著大干火炬松人工林.模拟结果表明,在全球气候变暖背景下,天然阔叶林可能比人工针叶林释放更多的CO2.     

次生栎林蒸腾强度与生态因子的关系

采用多元回归分析和灰色关联分析方法,探讨下蜀次生栎林蒸腾强度与生态因子的相关关系。研究认为用二次工咕次多项式回归方程和指数回归方程拟合更能反映各生态因子在整个生长季中与蒸腾强度关系的性质。影响蒸腾强度的主要生态因子是温度和净辐射;其次是空气相对湿度和土壤热流通量;风速和土壤含水率的影响很小。灰色关联分析与多元回归分析的结论一致。研究结果为进一步阐明次生栎林的结构和功能提供了理论基础。     

施石灰对杉木人工林土壤呼吸及其温度敏感性的影响

我国酸沉降主要分布区域与杉木人工林主要分布区域重合,石灰添加是改良酸化土壤的有效措施。为探究酸沉降背景下施石灰对土壤呼吸及其温度敏感性的影响,本研究以杉木人工林土壤为对象,在2018年6月一次性添加0、1和5 t·hm^-2的氧化钙,于2020年6月开始进行为期一年的原位土壤呼吸速率观测。结果表明：与不施石灰相比,施石灰显著提高了土壤pH值和交换性Ca²⁺含量,不同石灰施用量之间无显著差异。杉木人工林土壤呼吸及其组分具有明显的季节差异,表现为夏季最高,冬季最低,施石灰未显著改变其季节动态特征。施石灰显著降低了土壤异养呼吸速率,提高了自养呼吸速率,最终导致施石灰对土壤呼吸无显著影响。土壤呼吸月动态变化与温度月动态变化基本保持一致,土壤呼吸与土壤温度呈显著的指数关系,施石灰后土壤呼吸及自养呼吸的温度敏感性(Q₁₀)呈上升趋势,土壤异养呼吸的Q₁₀呈下降趋势。综上,施石灰提高了杉木人工林土壤自养呼吸,显著降低了土壤异养呼吸,这有利于杉木人工林土壤固碳。     

东灵山地区辽东栎林主要土壤因子的Haar小波分解

小波分解可以区分一维信号的区域变化和局部细节,是进行土壤因子分析的一种有效方法。应用该方法对北京东灵山地区辽东栎林样带中的3个主要土壤因子指标进行Haar小波分解。结果表明：沿山下到山顶样带梯度,土壤含水量呈明显的逐步下降趋势;土壤pH值变化幅度在6.5-6.6之间,表现比较稳定;土壤有机质含量在样带中存在3个较高值区域,具有一定的复杂性。较大水平上3个土壤因子在样带的下部受到的干扰较大,在样带的中、上部受到的干扰较小;在较小水平上,土壤含水量存在不规则的周期性干扰,pH值和有机质含量受干扰的情况较为复杂,规律性不明显。低频近假信号可以有效地揭示出土壤因子在样带中的总体变化规律,高频细节信号主要反映土壤因子受其它因素干扰程度,并可以在样带上定位出现奇异性变化的区域。     

北京山区辽东栎林土壤释放CO_2的模拟实验研究

模拟北京山区辽东栎林群落,对该类型土壤释放ＣＯ２过程进行了连续３ａ的实验研究,结果表明：辽东栎林土壤呼吸强度平均为５．９２±１．３２μｍｏｌＣＯ２ｍ－２ｓ－１,在不同月份中,以８月份最高,１０月最低,依次为８月＞７月＞６月＞９月＞１０月（Ｐ＜０．０５）;１３：００为土壤日呼吸的最高峰。温度为影响土壤呼吸的主要因子,二者存在极显著相关关系（ｒ＝０．５６６８,ｐ＜０．００１,ｎ＝９４）。据３ａ观测的土壤呼吸日平均值计算得出,模拟辽东栎林土壤释放ＣＯ２的通量估计范围为１７１．５～２７５．１ｋｇＣＯ２ｈｍ－２ｄ－１,平均为２２３．３ｋｇＣＯ２ｈｍ－２ｄ－１。     

北亚热带次生栎林与火炬松人工林土壤微生物生物量碳的季节动态

在南京林业大学下蜀森林生态定位研究站次生栎林和火炬松人工林内,采用随机区组设计,连续两年测定了林下土壤微生物生物量碳、土壤温度、土壤湿度和林地凋落物输入量.结果表明:两种林分的土壤微生物生物量碳呈明显的季节性波动,均在植物生长旺季维持在较低水平,而在植物休眠季节维持在较高水平;在0～10 cm土层内,火炬松林和次生栎林土壤微生物生物量碳变幅分别在267.8～459.8 mg·kg-1和278.6～467.8 mg·kg-1;土壤微生物生物量碳与土壤温度之间具有显著的负相关关系,而与森林地上凋落物输入量、土壤湿度无显著相关关系.说明该区域土壤微生物生物量碳的季节波动可能与土壤中有效碳及其它土壤养分的可利用状况、植物根系对营养的竞争以及林木的生长节律有关.     

落叶松人工林生长季节土壤呼吸通量各组分的变化

2010年采用挖壕法,利用Li-8150土壤碳通量全自动观测仪对东北林业大学哈尔滨实验林场落叶松人工林土壤各组分呼吸通量进行昼夜观测,研究土壤呼吸通量的昼夜和月变化特征,以及对土壤温度的敏感性.结果表明:各月份落叶松的枯枝落叶、根和矿质土壤呼吸通量昼夜变化均呈现单峰形态.5-10月各组分土壤呼吸通量昼夜变化幅度分别在3.1％～12.4％、1.9％～8.7％和10.9％ ～67.2％;枯枝落叶和根呼吸的平均值分别占土壤呼吸总量的21.2％、11.1％、13.4％、12.0％、14.2％和10.3％、8.8％、11.6％、10.0％、12.5％,昼夜波动幅度较小,月平均值分别为14.3％和10.6％.矿质土壤呼吸平均值分别占土壤呼吸总量的68.5％、80.2％、75.1％、78.1％和73.3％,昼夜波动幅度较小,月平均值为71.5％.枯枝落叶和矿质土壤呼吸通量对地表下10 cm的温度敏感性(Q10)显著高于地表,且矿质土壤呼吸通量Q10值高于枯枝落叶呼吸通量.根呼吸通量对地表下10 cm处和地表Q10值无显著差异.枯枝落叶和根呼吸Q10值的月变化为低温时较高、高温时较低,而矿质土壤呼吸Q10值则夏季较低、春秋季较高.     

苏南丘陵次生栎林生态系统磷素循环的系统分析与预测

森林生态系统中的养分循环是该系统的主要功能之一 ,历来为许多研究者所重视[1,4 ,5] 。磷是植物生长发育所不可缺少的重要营养元素 ,它对促进林木生长 ,提高林业生产力具有很大作用。以往有关森林生态系统磷素循环的研究 ,大多忽视了根系凋落归还的作用 ,从而影响循环结果及其相应评价。为此 ,研究了苏南丘陵次生栎林生态系统磷素循环 ,并进行系统分析 ,建立生态系统磷素动态模型 ,预测并分析其变化规律 ,为制定合理的经营管理措施 ,保持林业持续发展提供理论依据。1　自然概况与研究方法1.1　自然概况试验地位于江苏省句容县境内 ,东经119…     

中国不同气候带人工林与天然林的土壤呼吸差异

通过国内外文献检索收集了201 条中国森林土壤呼吸及相关环境因子数据, 比较了不同气候带(热带、亚热带、暖温带、中温带和高原气候区)人工林和天然林的土壤呼吸差异。结果表明: 中国森林土壤呼吸沿着气候梯度由南至北呈递减趋势,平均速率为2.67 μmol·m^–2·s^–1。天然林平均土壤呼吸速率(2.89 μmol·m^–2·s^–1)显著高于人工林(2.40 μmol·m^–2·s^–1)。除了暖温带以外, 其它四个气候区的天然林土壤平均呼吸速率均高于人工林。人工林土壤平均呼吸速率依次为: 暖温带(3.17 μmol·m^–2·s^–1)>热带(2.83 μmol·m^–2·s^–1)>亚热带(2.20 μmol·m^–2·s^–1)>中温带(1.97 μmol·m^–2·s^–1)>高原气候区(1.14 μmol·m^–2·s^–1); 其中高原气候区的土壤平均呼吸速率显著低于暖温带、热带和亚热带。天然林的土壤平均呼吸速率依次为: 热带(4.40 μmol·m^–2·s^–1)>暖温带(2.75 μmol·m^–2·s^–1)>亚热带(2.70 μmol·m^–2·s^–1)>高原气候区(2.63 μmol·m^–2·s^–1)>中温带(2.37 μmol·m^–2·s^–1)。不同气候带森林土壤自养呼吸贡献率平均为33.1%(17.1-65.7%), 天然林土壤自养呼吸比例(34.7%)略高于人工林(32.6%)。中国森林土壤呼吸的Q₁₀值平均为2.56(1.46-3.60), 沿气候梯度由南到北逐渐增加。不同气候带的人工林土壤呼吸温度敏感性Q₁₀(2.38)要低于天然林(2.68)。     

杉木人工林去除根系土壤呼吸的季节变化及影响因子

2007年1月至2008年12月,在长沙天际岭国家森林公园内,采用挖壕法研究杉木人工林去除根系后土壤呼吸速率季节动态及其与5 cm土壤温、湿度的相关关系。结果表明:去除根系与对照5 cm土壤温度的差异性不显著(P=0.987),5 cm土壤湿度差异显著(P=0.035)。杉木林去除根系处理后土壤呼吸速率明显降低,2007至2008两年实验期间去除根系与对照处理变化范围分别为0.19-2.01μmol.m-2s-1和0.26-2.61μmo.lm-2s-1,年均土壤呼吸速率分别为0.90μmo.lm-2s-1和1.30μmol.m-2s-1。去除根系土壤呼吸速率降低幅度为9.4%-59.7%,平均降低了30.4%。去除根系和对照的土壤呼吸速率与5 cm土壤温度之间均呈显著指数相关,模拟方程分别为:y=0.120e0.094t(R2=0.882,P=0.000),y=0.291e0.069t(R2=0.858,P=0.000)。Q10值分别为2.56和2.01。     

重庆缙云山两种林分土壤呼吸对模拟氮沉降的季节响应差异性

氮沉降对土壤呼吸的影响仍然存在着争论,需要进一步研究。选择重庆缙云山的马尾松林和柑橘林开展了氮添加实验,分别设置3个氮添加水平(低氮T_5:20 g N m~(-2)a~(-1),中氮T_(10):40 g N m~(-2)a~(-1)和高氮T_(15):60 g N m~(-2)a~(-1))和对照(T_0:0 g N m~(-2)a~(-1))共4个水平的处理,各林分每个处理各9次重复,每个处理量分4次,在每个季度开始各施1次。采用ACE(Automated Soil CO_2 Exchange Station,UK)自动土壤呼吸监测系统测定两林分土壤表层(0—10 cm)的呼吸、温度和湿度,分别在当年的7月、9月、11月、第2年的1月、2月、3月、5月、6月各连续测定4d,每天(8:00—18:00)4次,以揭示两种林分土壤呼吸对模拟氮沉降的季节动态响应及其差异性。结果表明:(1)柑橘林与马尾松林林下土壤表层呼吸表现出一致的季节变化动态趋势:夏季春季秋季冬季,但柑橘林土壤呼吸显著高于马尾松林(P0.05)。(2)总体上氮沉降抑制了2种林分土壤表层呼吸,而N沉降量大抑制程度越高。只在冬季土壤湿度低的马尾松林下氮沉降促进了土壤呼吸。(3)土壤温度与土壤呼吸有极显著的正相关指数关系(P0.01),而土壤水分与土壤呼吸有显著的二次模型拟合关系,但均受到氮沉降量处理的影响。综合分析表明,在亚热带山区2类森林下的典型案例结果支持氮沉降抑制土壤呼吸的认识。     

Annual variation in soil respiration and its components in a coppice oak forest in Central Italy

In order to investigate the annual variation of soil respiration and its components in relation to seasonal changes in soil temperature and soil moisture in a Mediterranean mixed oak forest ecosystem, we set up a series of experimental treatments in May 1999 where litter (no litter), roots (no roots, by trenching) or both were excluded from plots of 4 m². Subsequently, we measured soil respiration, soil temperature and soil moisture in each plot over a year after the forest was coppiced. The treatments did not significantly affect soil temperature or soil moisture measured over 0–10 cm depth. Soil respiration varied markedly during the year with high rates in spring and autumn and low rates in summer, coinciding with summer drought, and in winter, with the lowest temperatures. Very high respiration rates, however, were observed during the summer immediately after rainfall events. The mean annual rate of soil respiration was 2.9 µ mol m^?2 s^?1, ranging from 1.35 to 7.03 µmol m^?2 s^?1. Soil respiration was highly correlated with temperature during winter and during spring and autumn whenever volumetric soil water content was above 20%. Below this threshold value, there was no correlation between soil respiration and soil temperature, but soil moisture was a good predictor of soil respiration. A simple empirical model that predicted soil respiration during the year, using both soil temperature and soil moisture accounted for more than 91% of the observed annual variation in soil respiration. All the components of soil respiration followed a similar seasonal trend and were affected by summer drought. The Q₁₀ value for soil respiration was 2.32, which is in agreement with other studies in forest ecosystems. However, we found a Q₁₀ value for root respiration of 2.20, which is lower than recent values reported for forest sites. The fact that the seasonal variation in root growth with temperature in Mediterranean ecosystems differs from that in temperate regions may explain this difference. In temperate regions, increases in size of root populations during the growing season, coinciding with high temperatures, may yield higher apparent Q₁₀ values than in Mediterranean regions where root growth is suppressed by summer drought. The decomposition of organic matter and belowground litter were the major components of soil respiration, accounting for almost 55% of the total soil respiration flux. This proportion is higher than has been reported for mature boreal and temperate forest and is probably the result of a short‐term C loss following recent logging at the site. The relationship proposed for soil respiration with soil temperature and soil moisture is useful for understanding and predicting potential changes in Mediterranean forest ecosystems in response to forest management and climate change.     

西双版纳热带季节雨林与橡胶林土壤呼吸的季节变化

采用挖壕沟法与红外气体分析法,研究了西双版纳热带季节雨林和人工橡胶林内土壤呼吸包括根系呼吸、异养呼吸的干湿季动态变化.结果表明：季节雨林内土壤呼吸和异养呼吸速率均显著大于橡胶林(P＜0.01),但根系呼吸差异不显著;土壤温湿度是呼吸速率变化的主要影响因子,季节雨林和橡胶林内土壤呼吸和异养呼吸速率均为雨季＞干热季＞雾凉季,但季节雨林内根系呼吸为雨季＞雾凉季＞干热季,而橡胶林内为雾凉季＞雨季＞干热季;季节雨林内根系呼吸对土壤呼吸的贡献率(29%)小于橡胶林(42%,P＜0.01),而季节雨林内异养呼吸对土壤呼吸的贡献率为71%、橡胶林为58%;当5 cm土壤温度在12 ℃～32 ℃范围内变化时,季节雨林内土壤呼吸及根系呼吸、异养呼吸的Q₁₀值均大于橡胶林,且异养呼吸的Q₁₀值最大而根系呼吸的Q₁₀值最小.     

中亚热带杉木人工林和米槠次生林凋落物添加与去除对土壤呼吸的影响

在未来大气CO₂浓度升高的背景下, 植被净初级生产力的增加将促使森林土壤碳输入增多。凋落物是土壤碳库的重要来源, 对土壤呼吸会产生重要影响。为了模拟植物净初级生产力提高、凋落物产量增加情景下凋落物对土壤呼吸和土壤碳库的影响, 2013年1月到2014年12月, 在福建省三明市陈大镇国有林场, 在杉木(Cunninghamia lanceolata)人工林和米槠(Castanopsis carlesii)次生林, 通过设置去除凋落物、添加凋落物和对照(保留凋落物, 不做任何处理)处理, 研究了土壤呼吸和土壤碳库的动态变化。研究发现: 土壤含水量在10%-25%范围内, 土壤呼吸温度敏感性指数(Q₁₀)随着土壤含水量的增加呈递增趋势, 当含水量<10%时, 由于干旱胁迫打破了土壤呼吸与温度之间的耦合, 改变了Q₁₀值, 使得Q₁₀值小于1。土壤呼吸与凋落物输入量呈显著的线性正相关关系, 杉木人工林对照和添加凋落物处理及米槠次生林对照处理, 土壤呼吸与2个月前的凋落物输入量相关性最好。而米槠次生林添加凋落物处理, 土壤呼吸与当月的凋落物输入量相关性最好, 不同林分凋落物呼吸对土壤呼吸的贡献率不同, 米槠次生林凋落物层呼吸年通量明显大于杉木人工林, 分别占各林分土壤总呼吸的34.4%和15.1%, 添加凋落物后, 杉木人工林和米槠次生林的土壤呼吸速率增加, 但添加凋落物处理的土壤呼吸年通量与对照的差值小于年凋落物输入量。因此, 在未来全球CO₂升高背景下, 植被碳储量的增加、凋落物增加并没有引起土壤呼吸成倍增加, 更有利于中亚热带地区土壤碳吸存。     

Site and temporal variation of soil respiration in European beech, Norway spruce, and Scots pine forests

Global warming and changes in rainfall amount and distribution may affect soil respiration as a major carbon flux between the biosphere and the atmosphere. The objectives of this study were to investigate the site to site and interannual variation in soil respiration of six temperate forest sites. Soil respiration was measured using closed chambers over 2 years under mature beech, spruce and pine stands at both Solling and Unterlüß, Germany, which have distinct climates and soils. Cumulative annual CO₂ fluxes varied from 4.9 to 5.4 Mg C ha^?1 yr^?1 at Solling with silty soils and from 4.0 to 5.9 Mg C ha^?1 yr^?1 at Unterlüß with sandy soils. With one exception soil respiration rates were not significantly different among the six forest sites (site to site variation) and between the years within the same forest site (interannual variation). Only the respiration rate in the spruce stand at Unterlüß was significant lower than the beech stand at Unterlüß in both years. Soil respiration rates of the sandy sites at Unterlüß were limited by soil moisture during the rather dry and warm summer 1999 while soil respiration at the silty Solling site tended to increase. We found a threshold of ?80 kPa at 10 cm depth below which soil respiration decreased with increasing drought. Subsequent wetting of sandy soils revealed high CO₂ effluxes in the stands at Unterlüß. However, dry periods were infrequent, and our results suggest that temporal variation in soil moisture generally had little effect on annual soil respiration rates. Soil temperature at 5 cm and 10 cm depth explained 83% of the temporal variation in soil respiration using the Arrhenius function. The correlations were weaker using temperature at 0 cm (r² = 0.63) and 2.5 cm depth (r² = 0.81). Mean Q₁₀ values for the range from 5 to 15 °C increased asymptotically with soil depth from 1.87 at 0 cm to 3.46 at 10 cm depth, indicating a large uncertainty in the prediction of the temperature dependency of soil respiration. Comparing the fitted Arrhenius curves for same tree species from Solling and Unterlüß revealed higher soil respiration rates for the stands at Solling than in the respective stands at Unterlüß at the same temperature. A significant positive correlation across all sites between predicted soil respiration rates at 10 °C and total phosphorus content and C‐to‐N ratio of the upper mineral soil indicate a possible effect of nutrients on soil respiration.     

Influences of forest floor cleaning on the soil respiration and soil physical property of a larch plantation in Northeast China

Aimed to estimate how forest floor cleaning affected the carbon budget and soil physical feature, a 2-yr (2005–2006) measurement on soil respiration, soil bulk density, capillary porosity, soil temperature and soil volumetric moisture was carried out in a larch plantation. Firstly, forest floor cleaning evidently decreased soil respiration. Annual cumulative soil CO₂ efflux decreased from 44.2 μmol·m^?2 a^?1 to 22.4 μmol·m^?2 a^?1. Secondly, cleaning practice slightly increased soil temperature at the growing season, but reduced it at the dominant winter season. It also made soil moisture higher in summer, but lower in spring and autumn. Moreover, the cleaning practice induced more compact soil compared with the uncleaned control. Thirdly, forest floor cleaning of litters and understory shrubs could cause non-respiratory carbon loss of about 175.0 mol·m^?2. This loss decreased from 175.0 mol·m^?2 to 137.4 mol·m^?2 when soil respiratory carbon loss decreased. However, the alteration of soil physical characters in the cleaned plots should be carefully considered since this alteration was not favorable to the growth of larch plantation in a long run.     

施肥对油茶园土壤呼吸和异养呼吸及其温度敏感性的影响

油茶是中国南方重要的木本食用油料树种,研究施肥对油茶园土壤呼吸及其温度敏感性的影响,对于估算中国南方典型种植园林温室气体排放及其对气候变化的响应具有重要意义。设置对照(CK)、施肥(OF)、断根(CK-T)和断根施肥(OF-T)4个处理,采用静态箱-气相色谱法,通过多年观测,分析探讨施肥对油茶园土壤呼吸和异养呼吸及其温度敏感性的影响。结果表明:(1)施肥对油茶园土壤呼吸和异养呼吸无显著影响。研究期间,各处理(OF、CK、OF-T、CK-T)土壤CO_2通量依次为(77.91±2.59)、(73.71±0.97)、(66.82±1.02)mg C m~(-2)h~(-1)和(66.84±3.94)mg C m~(-2)h~(-1);(2)各处理土壤呼吸温度敏感性(Q_(10))表现为OF-T(1.96±0.01)CK-T(1.79±0.03)OF(1.77±0.01)CK(1.75±0.03),其中,OF-T处理下Q_(10)显著高于其他3个处理,即施肥显著增加了断根处理土壤呼吸Q_(10);(3)施肥显著增加了土壤表层NH_4~+-N和NO_3~--N含量,Q_(10)与土壤表层NH_4~+-N和NO_3~--N含量表现出显著的正相关关系。     

Soil respiration in a Mediterranean oak forest at different developmental stages after coppicing

To assess the variation of soil respiration at different forest stages we measured it in a coppiced oak (Quercus cerris L.) chronosequence in central Italy during two campaigns, spanning 2 successive years, in four stands at different stages of the rotation: 1 year (S1), 5 years (S5), 10 years (S10) and 17 years (S17) after coppicing. The contribution of the different components of soil respiration flux (aboveground litter, belowground decomposition soil organic matter and root respiration) was estimated by a paired comparison of manipulative experiments between the recently coppiced stand (S1) and mature stand (S17). Ninety percent of soil respiration values were between 1.7 and 7.8 μmol m^?2 s^?1, with an overall mean (±SD) of 4.0±2.7 μmol m^?2 s^?1. Spatial variation of soil respiration was high (CV=44.9%), with a mean range (i.e. patch size) of 4.8±2.7 m, as estimated from a semivariance analysis. In the absence of limitation by soil moisture, soil respiration was related to soil temperature with the exponential Q₁₀ model (average Q₁₀=2.25). During summer, soil moisture constrained soil respiration and masked its dependence on soil temperature. Soil respiration declined over the years after coppicing. Assuming a linear decline with stand age, we estimated a reduction of 24% over a 20‐year‐rotation cycle. The response of soil respiration to temperature also changed with age of the stands: the Q₁₀ was estimated to decrease from 2.90 in S1 to 2.42 in S17, suggesting that different components or processes may be involved at different developmental stages. The contribution of heterotrophic respiration to total soil respiration flux was relatively larger in the young S1 stand than in the mature S17 stand.