基于InTEC模型的塔河森林净初级生产力影响因子定量分析

森林净初级生产力(NPP)是反映森林碳源/汇能力的重要参数,其时空变化同时受气象变化(大气温度、降水等)、大气成分变化(CO₂浓度、N沉降)和各种森林干扰的影响.然而,目前影响森林NPP变化的关键因子尚不明确.为了探究这一问题,本研究在综合考虑InTEC模型的干扰和非干扰因子的基础上,重新模拟了不同立地指数下的NPP-林龄关系,并嵌入1987—2015年林火数据,模拟1901—2015年塔河森林平均NPP变化特征,设计9种模拟情景定量分析1961—2015年不同影响因子对塔河森林NPP变化的贡献,并探究塔河森林NPP年际以及年代变化的主要影响因子,为森林经营提供指导性策略.结果表明: 1901—1960年,塔河森林NPP的变化趋势较为平稳,1960年以后NPP随干扰因子变化趋势显著.林火和立地指数(SCI)的引入,均在不同时间对NPP的分布特征产生了不同影响.1960年以后,塔河森林NPP大幅变化的主要原因是森林年龄和林火的干扰,其年际平均贡献率为-49%,其次是降水和CO₂,分别为-28%和17%,气温和氮沉降的平均贡献率分别为5%和1%.     

江西省森林净初级生产力动态变化特征及其驱动因子分析

亚热带森林生态系统具有巨大的固碳潜力。净初级生产力(NPP)在碳循环过程中具有重要的作用, 受到气候变化、大气成分、森林扰动的强度和频度、林龄等因子的综合影响, 然而目前上述各因子对亚热带森林NPP变化的贡献尚不明确, 需要鉴别森林NPP时空变化的主要驱动因子, 以准确认识亚热带森林生态系统碳循环。该文综合气象数据、年最大叶面积指数(LAI)、参考年NPP (BEPS模型模拟)、林龄、森林类型、土地覆盖、数字高程模型(DEM)、土壤质地、CO₂浓度、氮沉降等多源数据, 利用InTEC模型(Integrated Terrestrial Ecosystem Carbon-budget Model)研究亚热带典型地区江西省森林生态系统1901-2010年NPP时空动态变化特征, 通过模拟情景设计, 着重讨论1970-2010年气候变化、林龄、CO₂浓度和氮沉降对森林NPP动态变化的影响。研究结果如下: (1) InTEC模型能较好地模拟研究区NPP的时空变化; (2)江西省森林NPP 1901-2010年为(47.7 ± 4.2) Tg C·a^-1 (平均值±标准偏差), 其中20世纪70年代、80年代、90年代分别为50.7、48.8、45.4 Tg C·a^-1, 2000-2009年平均为55.2 Tg C·a^-1; 随着森林干扰后的恢复再生长, 江西省森林NPP显著上升, 2000-2009年NPP增加的森林面积占森林总面积的60%; (3) 1970-2010年, 仅考虑森林干扰因子和仅考虑非干扰因子(气候、氮沉降、CO₂浓度)情景下NPP分别为43.1和53.9 Tg C·a^-1, 比综合考虑干扰因子和非干扰因子作用下的NPP分别低估7.3 Tg C·a^-1 (低估的NPP与综合考虑干扰因子和非干扰因子作用下NPP的比值为14.5%,下同)和高估3.6 Tg C·a^-1 (7.1%); 气候因子导致平均NPP减少2.0 Tg C·a^-1 (4.7%), 氮沉降导致平均NPP增加4.5 Tg C·a^-1 (10.4%), CO₂浓度变化及耦合效应(氮沉降+ CO₂浓度变化)分别导致平均NPP增加4.4 Tg C·a^-1 (10.3%)和9.4 Tg C·a^-1 (21.8%)。     

甘肃白龙江流域净生态系统生产力时空变化

净生态系统生产力(NEP)是估算区域植被碳源、碳汇的重要指标。以甘肃白龙江流域为研究区,结合MODIS与气象数据对2000—2013年的流域净生态系统生产力时空变化进行了研究,并探讨了典型地形因子对NEP的影响。结果表明:(1)2000—2013年甘肃白龙江流域单位面积NEP平均为226.65 g C m~(-2)a~(-1),碳汇区主要分布在白龙江上游两岸、岷江西岸、白水江南岸、大团鱼河两岸的山地林区,碳源区主要分布在武都区、迭部县北缘的高寒草甸区等。(2)从不同植被类型上看,常绿阔叶林、常绿/落叶阔叶混交林单位面积NEP最高,高寒草地单位面积NEP最小,且耕地单位面积NEP增加最明显,常绿/落叶阔叶混交林单位面积NEP降低最明显。(3)2000—2013年研究区单位面积NEP总体上呈增加的趋势,增加明显的地区分布在流域的中部和西北部,4—9月为流域碳汇季节。(4)地形因子对甘肃白龙江流域NEP有明显影响,海拔4200 m以下多为碳汇区;陡坡区的碳汇能力的增长趋势低于缓坡区;阴坡的碳汇能力高于阳坡区。     

陆地生态系统净第一性生产力对全球变化的响应

陆地生态系统的年净第一性生产力是每年植物通过光合作用固定的碳总量。随着全球变化发生,ＮＰＰ发生相应的变化。传统的方法预测ＮＰＰ的变化是利用气候和植被之间的局地关系建立回归模型,但用此方法预测ＮＰＰ的变化是有条件的。目前国际上出现了一种陆地生态系统的动态模型,它考虑了植物营养元素如氮的有效性,同时利用不同ＧＣＭｓ模型预测的气候因子的变化值和全球变化模拟研究的实验数据,预测全球ＮＰＰ的可能变化及区域分     

1971—2020年盘锦芦苇湿地净生态系统生产力及其影响因子

滨海河口湿地生态系统具有很强的储碳和固碳能力,正确评估其固碳变化及其环境影响因子是滨海河口湿地科学保护与管理的基础。本研究以盘锦芦苇湿地为对象,采用陆地生态系统模型,结合Mann-Kendall突变检验法、统计分析方法和情景模拟试验,分析了1971—2020年芦苇湿地净生态系统生产力(NEP)的变化特征、稳定性、未来趋势以及环境影响因子对NEP的贡献率。结果表明：1971—2020年盘锦芦苇湿地的年均NEP为415.51 g C·m^-2·a^-1,以1.7 g C·m^-2·a^-1的速率稳定增长,且未来仍呈持续增加趋势。NEP在春、夏、秋和冬季的多年均值分别为33.95、418.05、-18.71和-17.78 g C·m^-2·a^-1,增长速率分别为0.35、1.26、0.14和-0.06 g C·m^-2·a^-1。未来春季和夏季的NEP呈增加趋势,而秋季和冬季的NEP呈减少趋势。不同尺度下环境因子对盘锦芦苇湿地NEP...     

内蒙古典型草原不同群落净生态系统生产力的动态变化

净生态系统生产力(net ecosystem productivity,NEP)是反映生态系统碳源汇功能的重要指标。本研究选取内蒙古锡林河流域的贝加尔针茅群落、大针茅群落、克氏针茅群落和羊草群落为对象,利用BIOME-BGC模型模拟了4个草地群落年际间和年内逐日NEP动态变化,分析了4个草地群落对降水量的响应特征和可能机制,并且探讨气候变化背景下4个草地群落水分胁迫系数、降水利用率和碳转化效率的变化规律。结果表明:1954—2012年贝加尔针茅群落、大针茅群落、克氏针茅群落和羊草群落的多年平均NEP分别为11.41、-7.82、-5.03和9.30 g C·m-2·a-1。总体来看,4种草地群落多年平均日NEP的年内季节动态均呈先释放、后固碳、再释放的变化特征。4种草地群落多年平均水分胁迫系数由高到低分别为:贝加尔针茅羊草大针茅克氏针茅;多年平均降水利用效率由高到低分别为:贝加尔针茅克氏针茅大针茅羊草;多年平均碳素转化效率由高到低分别为:贝加尔针茅克氏针茅大针茅羊草。4种草地群落NEP与年降水量均存在显著的相关性,NEP为0时,4种草地群落年降水量平均值为295.76 mm,说明在年降水量大于该值时NEP多为正值,而小于该值时NEP多为负值。     

大气氮沉降对中亚草地生态系统净初级生产力的影响

氮沉降作为除气候变化、CO₂浓度升高以及土地利用变化之外的第四大主要影响陆地生态系统结构和功能的因素,其对碳循环过程的影响研究相对薄弱,同时也是不确定性最大的环节之一。近年来,由于长期高强度的放牧导致草地生态系统的生产力降低,氮成为典型草地植物生长和生态系统净初级生产力的主要限制因子。据研究,亚洲的氮沉降平均增速极有可能高于全球氮沉降平均增速,成为未来氮沉降增加最快的区域。在此背景下,研究大气氮沉降对于中亚草地生态系统的影响具有重要的意义。利用反硝化-分解模型（DNDC）分析1979-2014年中亚地区草地生态系统净初级生产力（NPP）的时空分异,探讨氮沉降对草地NPP影响。结果表明：（1）1979-2014年间,中亚地区平均草地NPP约为（173.10±31.80） g C m^-2 a^-1,草地NPP时空分异明显,各草地类型的NPP从大到小依次为森林草甸、温带草原和荒漠草原,并且草地NPP以（2.67±1.30） g C m^-2 a^-1的速度逐年增长;（2）当前氮沉降情景总体上促进了中亚地区草地NPP的增长,1979-2014年氮沉降使得中亚草地NPP增加了0.42 Pg C。     

三江源地区人工草地的生态系统CO2净交换、总初级生产力及其影响因子

为了揭示三江源区垂穗披碱草(Elymus nutans)人工草地生态系统(100°26′-100°41′ E, 34°17′-34°25′ N, 海拔3 980 m)的净生态系统CO₂交换(NEE), 该研究利用2006年涡度相关系统观测的数据分析了该人工草地的NEE, 总初级生产力(GPP)、生态系统呼吸(R_eco)以及R_eco/GPP的变化特征及其影响因子。CO₂日最大吸收值为6.56 g CO₂·m^-2·d^-1, 最大排放值为4.87 g CO₂·m^-2·d^-1。GPP年总量为1 761 g CO₂·m^-2, 其中约90%以上被生态系统呼吸所消耗, CO₂的年吸收量为111 g CO₂·m^-2。5月的R_eco/GPP略高于生长季的其他月份, 为90%; 6月R_eco/GPP比值最低, 为79%。生态系统的呼吸商(Q₁₀)为4.81, 显著高于其他生态系统。该研究表明: 生长季的NEE主要受光量子通量密度(PPFD)、温度和饱和水汽压差(VPD)的影响, 生态系统呼吸则主要受土壤温度的控制。     

东亚地区陆地生态系统净第一性生产力时空格局

利用植被分类数据、NDVI数据、气象数据以及观测数据,基于CASA生态系统模型,估算了东亚地区(10～70°N,70～170°E)陆地生态系统植被净第一性生产力.结果表明:1982～1999年研究区总NPP呈现波动增加趋势,平均每年增加0.08833PgC.18a间NPP平均值为14.24 PgC,约占全球总NPP的22.6%～23.9%.研究区NPP年变化呈单峰曲线,最大值出现在7月份,达2.98PgC,全年中NPP积累主要发生在4～10月份,该时段内NPP总量占全年总量的86.81%.春、夏、秋、冬四季NPP平均总量分别为:2.31、8.16、2.79、1.10 PgC,分别占全年NPP平均总量的16.20%、57.27%、19.58%、7.73%.将NPP年平均值分成3个范围:低值区(7.82～300gC · m-2)、中值区(301～700 gC · m-2)、高值区(>700 gC · m-2),分别研究了其空间分布特征.     

森林生态系统年净初级生产力和生境复杂度对小型兽类物种多样性影响

本研究主要探讨黄龙自然保护区森林生态系统年净初级生产力水平和栖息地复杂程度对小型兽类物种多样性的影响。将调查区按海拔高度分为4 个调查点,每点的年净初级生产力水平各不相同,分别为: 24.9 MJ / (m²·a) ; 21.5 MJ / (m²·a) ; 17.5 MJ / (m²·a) 和14.1 MJ / (m²·a) 。在选择调查点时,同时考虑栖息地复杂程度,在生产力水平较高的调查点选择栖息地复杂程度较低的地点,而在生产力较低的调查点选择栖息地复杂程度较高的地点调查,以便分析森林生态系统年净初级生产力水平与栖息地复杂程度对小型兽类物种多样性的影响。采用鼠铗捕获小型兽类。结果表明,小型兽类物种多样性与森林生态系统年净初级生产力水平有密切关系,随着海拔升高,森林生态系统年净初级生产力的降低,所捕获的小型兽类生物量随之降低,其物种多样性也随之下降。小型兽类物种多样性也与栖息地复杂程度有关,森林生态系统年净初级生产力水平在一定范围内,大于17.5 MJ / (m²·a) ,栖息地复杂度的增加可以降低年净初级生产力水平对小型兽类物种多样性的影响。然而,森林生态系统年净初级生产力水平降低到一定程度时,小于14.1 MJ / (m²·a) ,生产力水平则为影响小型兽类物种多样性的主要因子。此外,小型兽类的生物量与森林生态系统年净初级生产力和栖息地复杂程度也有类似的关系。     

Is Net Ecosystem Production Equal to Ecosystem Carbon Accumulation?

Net ecosystem production (NEP), defined as the difference between gross primary production and total ecosystem respiration, represents the total amount of organic carbon in an ecosystem available for storage, export as organic carbon, or nonbiological oxidation to carbon dioxide through fire or ultraviolet oxidation. In some of the recent literature, especially that on terrestrial ecosystems, NEP has been redefined as the rate of organic carbon accumulation in the system. Here we argue that retaining the original definition maintains the conceptual coherence between NEP and net primary production and that it is congruous with the widely accepted definitions of ecosystem autotrophy and heterotrophy. Careful evaluation of NEP highlights the various potential fates of nonrespired carbon in an ecosystem.     

Terrestrial Subsidies of Organic Carbon Support Net Ecosystem Production in Temporary Forest Ponds: Evidence from an Ecosystem Experiment

Recent research suggests that secondary production in aquatic systems can be driven by inputs of energy from terrestrial sources. Temporary forest ponds appear to be unproductive ecosystems that are reliant upon allochthonous inputs of energy to support secondary production, but the functioning of these systems has not been well quantified. To assess the metabolic state of this type of ecosystem as well as to quantify the importance of terrestrial subsidies of carbon to ecosystem function, we conducted an experiment in which we manipulated the amount of leaf litter in ponds. Litter was either removed or removed and replaced (that is, control) from the dry basins of ponds immediately after leaf abscission. Once the ponds filled, we monitored net ecosystem production (NEP) on a biweekly basis from 9 April to 27 May 2002. All ponds were consistently net heterotrophic; however, NEP was significantly less negative in removal ponds. Furthermore, removal ponds also had lower levels of respiration (R) and higher dissolved oxygen levels than control ponds. The removal of litter had no effect on gross primary production, indicating that the difference in NEP between treatments was driven by the change in R. Therefore, it appears that terrestrial inputs of organic carbon support heterotrophic respiration in these ponds, and that the endogenous production of carbon is insufficient to support secondary production.     

Effects of Climate Change and Shifts in Forest Composition on Forest Net Primary Production

Forests are dynamic in both structure and species composition, and these dynamics are strongly Influenced by climate.However, the net effects of future tree species composition on net primary production (NPP) are not well understood. The objective of this work was to model the potential range shifts of tree species (DISTRIB Model) and predict their impacts on NPP (PnET-Ⅱ Model) that will be associated with alterations in species composition. We selected four 200 × 200 km areas In Wisconsin, Maine, Arkansas, and the Ohio-West Virginia area, representing focal areas of potential species range shifts. PnET-Ⅱ model simulations were carried out assuming that all forests achieved steady state, of which the species compositions were predicted by DISTRIB model with no migration limitation. The total NPP under the current climate ranged from 552 to 908 g C/m2 per year. The effects of potential species redistributions on NPP were moderate (-12% to 8%) compared with the influence of future climatic changes (-60% to 25%). The direction and magnitude of climate change effects on NPP were largely dependent on the degree of warming and water balance. Thus, the magnitude of future climate change can affect the feedback system between the atmosphere and biosphere.     

Biometric Based Carbon Flux Measurements and Net Ecosystem Production (NEP) in a Temperate Deciduous Broad-Leaved Forest Beneath a Flux Tower

Biometric based carbon flux measurements were conducted over 5 years (1999–2003) in a temperate deciduous broad-leaved forest of the AsiaFlux network to estimate net ecosystem production (NEP). Biometric based NEP, as measured by the balance between net primary production (including NPP of canopy trees and of forest floor dwarf bamboo) and heterotrophic respiration (RH), clarified the contribution of various biological processes to the ecosystem carbon budget, and also showed where and how the forest is storing C. The mean NPP of the trees was 5.4 ± 1.07 t C ha⁻¹ y⁻¹, including biomass increment (0.3 ± 0.82 t C ha⁻¹ y⁻¹), tree mortality (1.0 ± 0.61 t C ha⁻¹ y⁻¹), aboveground detritus production (2.3 ± 0.39 t C ha⁻¹ y⁻¹) and belowground fine root production (1.8 ± 0.31 t C ha⁻¹ y⁻¹). Annual biomass increment was rather small because of high tree mortality during the 5 years. Total NPP at the site was 6.5 ± 1.07 t C ha⁻¹ y⁻¹, including the NPP of the forest floor community (1.1 ± 0.06 t C ha⁻¹ y⁻¹). The soil surface CO₂ efflux (RS) was averaged across the 5 years of record using open-flow chambers. The mean estimated annual RS amounted to 7.1 ± 0.44 t C ha⁻¹, and the decomposition of soil organic matter (SOM) was estimated at 3.9 ± 0.24 t C ha⁻¹. RH was estimated at 4.4 ± 0.32 t C ha⁻¹ y⁻¹, which included decomposition of coarse woody debris. Biometric NEP in the forest was estimated at 2.1 ± 1.15 t C ha⁻¹ y⁻¹, which agreed well with the eddy-covariance based net ecosystem exchange (NEE). The contribution of woody increment (Δbiomass + mortality) of the canopy trees to NEP was rather small, and thus the SOM pool played an important role in carbon storage in the temperate forest. These results suggested that the dense forest floor of dwarf bamboo might have a critical role in soil carbon sequestration in temperate East Asian deciduous forests.     

Biotic, Abiotic, and Management Controls on the Net Ecosystem CO2 Exchange of European Mountain Grassland Ecosystems

The net ecosystem carbon dioxide (CO₂) exchange (NEE) of nine European mountain grassland ecosystems was measured during 2002–2004 using the eddy covariance method. Overall, the availability of photosynthetically active radiation (PPFD) was the single most important abiotic influence factor for NEE. Its role changed markedly during the course of the season, PPFD being a better predictor for NEE during periods favorable for CO₂ uptake, which was spring and autumn for the sites characterized by summer droughts (southern sites) and (peak) summer for the Alpine and northern study sites. This general pattern was interrupted by grassland management practices, that is, mowing and grazing, when the variability in NEE explained by PPFD decreased in concert with the amount of aboveground biomass (BM_ag). Temperature was the abiotic influence factor that explained most of the variability in ecosystem respiration at the Alpine and northern study sites, but not at the southern sites characterized by a pronounced summer drought, where soil water availability and the amount of aboveground biomass were more or equally important. The amount of assimilating plant area was the single most important biotic variable determining the maximum ecosystem carbon uptake potential, that is, the NEE at saturating PPFD. Good correspondence, in terms of the magnitude of NEE, was observed with many (semi-) natural grasslands around the world, but not with grasslands sown on fertile soils in lowland locations, which exhibited higher maximum carbon gains at lower respiratory costs. It is concluded that, through triggering rapid changes in the amount and area of the aboveground plant matter, the timing and frequency of land management practices is crucial for the short-term sensitivity of the NEE of the investigated mountain grassland ecosystems to climatic drivers.     

水分胁迫对成年荔枝不同季节光合速率日变化的影响

以16a生‘糯米糍’荔枝(Litchi chinensis Sonn.cv.Nuomizi)为试材,研究了其在水分胁迫下不同季节的光合速率日变化。结果表明,保湿处理的净光合速率(Pn)日变化在秋、夏季呈单峰曲线,冬、春季为双峰曲线;干旱处理除在冬季出现双峰曲线外,其他季节均呈单峰曲线。两个处理的Pn日变化最大值或第1个峰值出现时间基本一致,冬季为9:00、春季和夏季为10:00、秋季为12:00。保湿处理的日最高Pn变化范围为6.25-8.14μmolm-2s-1,干旱处理的在4.35-6.56μmolm-2s-1;中度水分胁迫对田间成年荔枝树的光合速率具有较大的抑制作用,干旱对日净光合总量的抑制比例分别为:冬季18.6%,夏季21.3%,春季34.1%,秋季34.7%。在光合作用旺盛时段(8:00-16:00)中度水分胁迫导致叶片Pn的降低主要是由气孔因素所致。     

生态因子对森林生态系统稳定性影响的数学分析

本文在对河南省森林生态类型划分的基础上,应用主成分分析、模糊聚类和遂步判别分析的方法,对森林生态系统的稳定性进行了研究,结果表明：影响森林生态系统稳定性的因子主要有6个,即：森林覆被率、人口密度、土壤侵蚀模数、大风日数、降水集中率和地形;河南省森林生态系统按其稳定程度可分为5个等级;应用逐步判别分析是建立稳定性判别模式的较好方法。     

Effects of Soil Abiotic and Biotic Factors on Tree Seedling Regeneration Following a Boreal Forest Wildfire

Ecosystems - Wildfire disturbance is important for tree regeneration in boreal ecosystems. A considerable amount of literature has been published on how wildfires affect boreal forest regeneration....     

子午岭林区生态系统转换对土壤有机碳特征的影响

生态系统转换影响土壤有机碳的动态、循环及环境质量.本研究分析了子午岭林区农田、草地、灌丛和森林不同生态系统土壤总有机碳、活性有机碳和稳定性有机碳含量.结果显示:各生态系统中,表层(0~10 cm)土壤总有机碳含量显著高于深层土壤(40~70 cm).与农田生态系统表层土壤相比,草地、灌丛、森林生态系统土壤总有机碳含量分别增加82.07%、121.67%和183.16%,深层土壤有机碳含量也有类似的趋势;从增加的绝对值来看,表层土壤活性有机碳含量分别增加2.24、4.13和5.43 g/kg,土壤稳定性有机碳含量分别增加4.76、6.23和10.18g/kg.表明农田生态系统转换为林、草生态系统,有利于土壤有机碳的积累.而且,土壤作为碳“汇”的功能增强,更有利于CO2固定和生态环境改善.