季节性放牧对黄河源区高寒草甸植被耗水量及水分利用效率的影响   总被引：1，自引：0，他引：1  

贺慧丹  杨永胜  祝景彬  李红琴  未亚西  李英年 《冰川冻土》2017,39(1):130-139

研究季节性放牧对植被耗水量、水分利用效率的影响,是探索如何提高高寒草甸水源涵养能力的重要内容之一。以青藏高原三江源高寒草甸季节性放牧样地与自然放牧样地为研究对象,分析了季节性放牧和自然放牧条件下高寒草甸植被耗水量、水分盈亏量、水分利用效率（WUE）的动态变化及其与环境因素的关系。结果表明：在植被生长季（5-9月）,季节性放牧样地和自然放牧样地植被耗水量在5月开始增加, 7月达最高,分别为160.94 mm和145.96 mm,季节性放牧样地植被总耗水量（395.52 mm）比自然放牧样地（348.14 mm）高13.61%。生长季平均来看,季节性放牧样地和自然放牧样地5-9月水分正盈余,分别为13.58 mm和70.96 mm,但在植物生长旺季（8月）略有亏缺。季节性放牧样地和自然放牧样地植被耗水量均与降水量呈弱的正相关关系。季节性放牧样地植被地上净初级生产量（ANPP）、地下净初级生产量（BNPP）和总的净初级生产量（NPP）比自然放牧样地分别高32.54 g·m^-2、5.96 g·m^-2、38.50 g·m^-2,季节性放牧样地ANPP的水分利用效率（WUE）比自然放牧样地高53.85%,而BNPP、NPP的WUE比自然放牧样地分别低13.06%和9.97%。这表明,季节性放牧可提高植被生产量和耗水量,但对高寒草甸WUE的影响因放牧方式不同导致地上、地下生物量分配格局不同而有所差异。  相似文献   

青南退化高寒草甸植被土壤固碳潜力   总被引：4，自引：1，他引：3  

李英年  徐世晓  赵亮  张法伟 《冰川冻土》2012,34(5):1157-1164

青南与青北高寒草甸植被、 土壤、 气候类型相似, 地植被、 土壤碳密度可比性强. 研究表明, 青南高寒草甸植被退化严重, 植被和土壤碳密度随退化程度的加剧而降低, 轻度、 中度、 重度和极度退化植被碳密度分别为921.281、 809.998、 237.974 gC·m^-2和75.972 gC·m^-2, 0~40 cm土壤碳密度分别为16.760、 16.145、 14.360 gC·m^-2和12.945 kgC·m^-2. 在青北未退化草甸植被和0~40 cm层次土壤碳密度分别为1 149.327 gC·m^-2和20.305 kgC·m^-2. 相对青北高寒草甸植被类型而言, 青南高寒草甸轻度、 中度、 重度、 极度退化的植被固碳密度分别增加228.046、 339.329、 911.354 gC·m^-2和1073.355 gC·m^-2, 而对应0~40 cm层次土壤固碳密度可分别增加3.545、 4.160、 5.946 gC·m^-2和7.359 kgC·m^-2. 以青南当地未退化草地而言, 轻度、 中度、 重度和极度退化的高寒草甸0~20 cm层次土壤固碳密度可达1.694、 2.087、 3.537 kgC·m^-2和4.282 kgC·m^-2, 表现出较大的固碳潜力.  相似文献   

2000-2013年浑善达克沙地植被净初级生产力变化研究     

元志辉  池勇峰  雷军  包刚  包玉海  萨楚拉  咏梅 《冰川冻土》2017,39(1):185-199

利用卫星遥感资料和地面气象观测资料,基于CASA模型及其他数理方法估算了浑善达克沙地2000-2013年生长季（4-10月）植被净初级生产力（NPP）,并对其时空变化特征进行了分析,讨论了气候因子和人类活动对植被净初级生产力的影响。结果表明： 14年间,研究区生长季的植被净初级生产力呈波动中增加趋势,多年平均NPP为239.8 gC·m^-2·a^-1。整个研究区表现为高NPP值（大于150 gC·m^-2·a^-1）的植被面积在增加,低NPP值（小于150 gC·m^-2·a^-1）的植被面积在减少。在空间分布上,研究区的北部、中部和南部边缘区域的植被NPP增加趋势较明显,而东部和西部部分区域未发生明显的趋势性变化。总体而言,研究区植被净初级生产力变化趋势与降水量的关系更密切,其相关系数达到0.86,是驱动植被NPP年际波动的最直接因素。而与温度呈负相关,相关系数为-0.42。综合考虑气候因素和人类活动对沙地NPP的影响发现,温度降低、种饲料面积、年末牲畜存栏头数和羊的数量的减少是NPP值提高的关键因素。  相似文献   

不同封育年限高寒草甸植被/土壤碳密度及净生态系统CO2交换量的比较     

刘晓琴  吴启华  李红琴  毛绍娟  李英年 《冰川冻土》2013,35(4):848-856

封育是推广范围最广的草地恢复措施之一. 为研究不同封育年限高寒草甸植被、土壤碳密度变化, 对1 a、6 a和16 a不同封育年限样地监测结果进行分析.结果表明: 不同封育年限高寒草甸植被现存碳密度表现出封育16 a>封育1 a>封育6 a, 分别为1 522.57 gC·m^-2、1 323.12 gC·m^-2和1 148.17 gC·m^-2, 但不同封育年限之间植被现存碳密度差异不显著(P>0.05). 土壤碳密度垂直分布明显, 0~5 cm和5~10 cm土层有机碳密度较高, 随土层深度增加土壤有机碳密度明显下降, 土壤容重上升;不同封育年限之间0~40 cm层次土壤碳密度和土壤容重差异性均不显著, 但仍可表现出土壤碳密度封育1 a>封育6 a>封育16 a, 分别为28 636.32 gC·m^-2、26 570.92 gC·m^-2和26 060.71 gC·m^-2;同时, 土壤容重随封育时间延长而下降. 对7月下旬到10月上旬净生态系统CO₂交换率(NEE)监测来看, 封育1 a植被土壤碳吸收速率显著高于封育16 a(P<0.05);而排放率与封育16 a样地接近, 差异不显著(P>0.05).  相似文献   

2000—2020年祁连山冻土区植被水分利用效率变化特征及其对干旱的响应     

李丽丽  杜军  李亚徽  陈明坤  万斌文  王大为 《冰川冻土》2023,(2):688-698

冻土是冰冻圈要素的重要组成部分,是气候变化最敏感的区域之一,冻土环境变化引起水热条件差异是引发植被生态系统能量交换、水循环和碳循环的重要因素。水分利用效率(WUE)是联系生态系统碳循环与水循环关系的关键,反映了植被生态系统对冻土退化的调整和适应策略。本研究基于MODIS的植被总初级生产力(GPP)和蒸散发(ET)产品,估算并分析了2000—2020年祁连山多年冻土与季节冻土区植被GPP/ET/WUE空间变化特征,并结合自适应帕尔默干旱指数(scPDSI),研究了多年冻土区与季节冻土区植被WUE对干旱的响应。结果表明：2000—2020年祁连山地区植被WUE、GPP和ET的平均值分别为0.56 gC·m^-2·mm^-1,307.79 gC·m^-2和443.02 mm,三者空间分布特征均为东南高、西北低;WUE高于0.8 gC·m^-2·mm^-1的植被主要分布在季节冻土区,WUE低于0.4 gC·m^-2·mm^-1的植被主要分布在多年冻土区。近...  相似文献   

祁连山黑河上游多年冻土区不同植被类型土壤有机碳密度分布特征   总被引：6，自引：3，他引：3  

马素辉  牟翠翠  郭红  张现凯  栗泽苑  张廷军 《冰川冻土》2018,40(3):426-433

山地多年冻土的异质性影响其植被类型的分布特征,且对有机碳的分布也具有重要影响。通过采集黑河上游多年冻土区三种典型植被类型（高寒沼泽草甸、高寒草甸、高寒草原）8个活动层的土壤样品,测定其土壤有机碳密度及其理化性质。结果表明：高寒沼泽草甸土壤有机碳密度最高（49.50 kg·m^-2）,高寒草甸次之（11.22 kg·m^-2）,高寒草原最低（7.30 kg·m^-2）。土壤有机碳密度的剖面垂直分布特征具有差异性,高寒沼泽草甸土壤有机碳密度随深度变化不明显,高寒草原和高寒草甸土壤有机碳密度随深度逐渐减小,存在显著的表层聚集性。有机碳密度与土壤含水率和细粒含量呈显著正相关,与pH值呈显著负相关关系。一般线性模型结果表明土壤含水率、pH值和土壤颗粒组成解释了96.39%的有机碳密度变异,其中土壤含水率贡献了81.53%,pH值和土壤粒度分别贡献了9.33%和4.75%。研究表明多年冻土区不同植被类型土壤有机碳密度分布特征具有明显差异,山地多年冻土土壤含水率是控制有机碳密度分布特征的重要影响因素。  相似文献   

2009/2010年黄河源区高寒草甸下垫面能量平衡特征分析   总被引：1，自引：1，他引：0  

周秉荣  李凤霞  肖宏斌  周万福  颜亮东  李甫  李晓东 《冰川冻土》2013,35(3):601-608

以青藏高原黄河源玛多为实验区, 基于TRM-ZS1气象生态环境监测仪2009年11月1日至2010年10月31日辐射及能量通量观测数据, 采用波文比能量平衡法, 进行了该区域潜热和感热通量的估算, 分析了黄河源区高寒草甸下垫面辐射收支, 潜热、 感热和土壤热通量在不同季节的分配, 对该区域冬季地面加热场强度的变化进行了研究.结果表明: 该区域总辐射、 净辐射较强, 总辐射平均日积分值为18.06 MJ·m^-2·d^-1, 净辐射平均日积分值5.95 MJ·m^-2·d^-1, 曾观测到高达979.5 W·m^-2的净辐射通量.全年地表平均反射率为0.30, 接近于荒漠和半荒漠下垫面的反射率.植物生长季土壤湿度和冬、 春季地面积雪是影响该区域地表反射率的两个最主要因素.该区域感热通量年积分值为742.68 MJ·m^-2·a^-1, 潜热通量年积分值为1 388.58 MJ·m²·a^-1, 全年中地表以潜热方式传递热量为主.分季节分析, 冬季感热潜热强度相当, 春季以感热为主, 夏秋季则以潜热为主.土壤热通量年积分值为38.06 MJ·m^-2·a^-1, 全年热通量在热量平衡中约占1.8%, 但季节分配不平衡, 在冬季, 有|G|>H+LE, 土壤热通量是热平衡最大的分量.该区域地表全年向大气释放热量, 地表对大气而言是热源.  相似文献   

塔里木盆地盐化草甸植被净初级生产力对全球变化的响应          下载免费PDF全文

张宏 《第四纪研究》1998,18(4):372-372

地带性植被净初级生产力(NPP)的形成除受自身的生物生态学特性制约外,主要决定于环境中热量和水分状况的分配及组合。随着全球变化与陆地生态系统研究的开展,以模型为主要手段预测植被生产力对气候变化响应的研究逐步深入,相继提出了一些利用气候指标或指数估算植被净初级生产力的模型,如Miami模型、Chikugo模型和北京模型等。但利用上述模型无法估算盐化草甸植被等非地带性植被的NPP,因为它们的形成不依赖于大气降水,而主要依靠地下水。由于土壤蒸发能综合反映土壤的水热状况,与NPP的形成关系密切。因此,作者利用以阿维扬诺夫公式计算所得的不同地下水埋深的潜水蒸发与实测的盐化草甸植被净初级生产力数据,拟合了  相似文献   

祁连山疏勒河上游多年冻土区高寒草甸土壤CO2通量特征     

赵倩  刘文杰  陈生云  任倩  袁文平  周凌晞 《冰川冻土》2014,36(6):1572-1581

研究青藏高原多年冻土区高寒草甸土壤CO₂通量有助于准确估算该区域的土壤CO₂排放, 对认识高原土壤碳循环及其对全球气候变化的响应具有重要意义. 利用静态箱-气相色谱法和LI-8100土壤CO₂通量自动测量系统对疏勒河上游多年冻土区高寒草甸土壤CO₂通量进行了定期观测, 结合气象和土壤环境因子进行了分析. 结果表明: 整个观测期高寒草甸土壤表现为CO₂的源, 土壤CO₂通量的日变化范围为2.52～532.81 mg·m^-2·h^-1. 土壤CO₂年排放总量为1 429.88 g·m^-2, 年均通量为163.23 mg·m^-2·h^-1; 其中, CO₂通量与空气温度和相对湿度、活动层表层2 cm、10 cm、20 cm、30 cm 土壤温度、含水量和盐分均显著相关. 2 cm土壤温度、空气温度和总辐射、空气温度、2 cm土壤盐分分别是影响活动层表层2 cm土壤完全融化期、冻结过程期、完全冻结期、融化过程期土壤CO₂通量的最重要因子. 在完全融化期、冻结过程期和整个观测期, 拟合最佳的温度因子变化分别能够解释土壤CO₂通量变化的72.0%、82.0%和38.0%, 对应的Q₁₀值分别为1.93、6.62和2.09. 冻融期(含融化过程期和冻结过程期)和完全冻结期的土壤CO₂排放量分别占年排放总量的15.35%和11.04%, 在年排放总量估算中不容忽视.  相似文献   

基于MODIS资料的2000-2004年江河源区陆地植被净初级生产力分析   总被引：18，自引：2，他引：16  

郭晓寅  何勇  沈永平  冯丁 《冰川冻土》2006,28(4):512-518

基于EOS/MODIS卫星遥感资料的分析表明,2000-2004年江河源地区陆地植被平均年NPP为82.04 gC.m-2,相当于同期全国陆地植被年NPP的23%,其中2001年的年NPP最小,只有78.04gC.m-2,2002年最大,为85.44 gC.m-2.根据年NPP分布显示,黄河源区的植被生长状况要好于长江源区,其中在黄河源东南部陆地植被的年NPP>250 gC.m-2,为江河源区植被年生长最大的区域;该地区的植被年NPP最小值的区域分布在长江源的西北部地区,年NPP大部分<50 gC.m-2.江河源地区植被的年NPP表现为显著的年际变化特征,不同地区年NPP的变化特征各不相同;高寒草甸的年NPP为该地区所有陆地植被年NPP中最大,其5 a平均值为89.38 gC.m-2,其次为高寒草原和灌木及草本植被;由于地处高寒地区,温度成为影响该地区陆地植被净初级生产力的主要因素.  相似文献   

青海省植被净初级生产力的模拟研究          下载免费PDF全文

王莉雯  卫亚星 《第四纪研究》2011,31(1):180-188

遥感技术根据植被光谱特征可以有效地估算植被的净初级生产力(NPP).利用遥感数据估算植被NPP,是近10年来NPP的模型研究和估算方法最为突出的特点.文章借鉴了CASA,GLO-PEM,VPM等光能利用率NPP模型的优点,同时充分考虑了研究区域其植被光能利用率和环境因素的典型特点,建立了针对研究区域基于光能利用率原理的...  相似文献   

宁东煤炭基地植被生态特征及矿业开发对其的影响     

杜灵通  徐友宁  宫菲  丹杨  王乐  郑琪琪  马龙龙 《地质通报》2018,37(12):2215-2223

准确评估大型能源基地矿业开发活动对区域植被生态系统影响具有重要的科学意义和实践价值。利用2000—2017年中分辨率成像光谱仪(MODIS)连续观测的生态系统参量,定量研究宁东煤炭基地开发建设以来的植被生态系统时空变化特征,分析矿业开发对植被生态系统的影响。结果表明,随着宁东煤炭基地开采活动的持续,区域植被生态系统的生产力及其与大气之间的水汽交换强度整体增强,归一化植被指数、总初级生产力、净初级净生产力和蒸散的年增长幅度分别为0.0053、5.10g·C/(m2·a-1)、4.10g·C/(m2·a-1)和6.62mm/a;这4种指标在空间像元上也以增长趋势为主,且未来多数像元有持续增强的特征,但生态系统的水分利用效率却在降低。空间分析表明,大尺度植被生态演变受矿业活动影响微弱,其主要受制于气候和区域性的生态治理工程。  相似文献   

Water fluxes and their control on the terrestrial carbon balance: Results from a stable isotope study on the Clyde Watershed (Scotland)     

J.A.C. Barth  H. Freitag  H.J. Fowler  A.P. Smith  C. Ingle  A. Karim 《Applied Geochemistry》2007,22(12):2684

The gradients between precipitation and runoff quantities as well as their water isotopes were used to establish a water balance in the Clyde River Basin (Scotland). This study serves as an example for a European extreme with poorly vegetated land cover and high annual rainfall and presents novel water stable isotope techniques to separate evaporation, interception and transpiration with annual averages of 0.029 km³ a⁻¹, 0.220 km³ a⁻¹ and 0.489 km³ a⁻¹, respectively. Transpiration was further used to determine CO₂ uptake of the entire basin and yielded an annual net primary production (NPP) of 352 × 10⁹ g C (Giga gram) or 185.2 g C m⁻². Compared to other temperate areas in the world, the Clyde Basin has only half the expected NPP. This lower value likely results from the type of vegetation cover, which consists mostly of grasslands. Subtracting the annual heterotrophic soil respiration flux (R_h) of 392 Gg (206.1 g C m⁻² a⁻¹) from the NPP yielded an annual Net Ecosystem Productivity (NEP) of −40 Gg C, thus showing the Clyde Watershed as a source of CO₂ to the atmosphere. Despite the unusual character of the Clyde Watershed, the study shows that areas with predominant grass and scrub vegetation still have transpirational water losses that by far exceed those of pure evaporation and interception. This infers that vegetation can influence the continental water balances on time scales of years to decades.  相似文献   

Application of the <Superscript>137</Superscript>Cs tracer technique to study soil erosion of alpine meadows in the headwater region of the Yellow River     

Y. S. Li  G. X. Wang  Y. J. Ding  L. Zhao  Y. B. Wang 《Environmental Geology》2009,58(5):1021-1028

The ¹³⁷Cs tracer technique was used to study soil erosion of alpine meadow grassland in two small river basins in the headwater region of the Yellow River. The results show that the levels of ¹³⁷Cs in soil samples from this alpine meadow vegetation zone exhibit an exponential distribution, generally within a depth of approximately 20 cm. Due to strong winds, freeze-thaw cycles and water, soil erosion was found to be stronger on the upper slope than on the lower slope, and except for the slope crest, the intensity of soil erosion at other sites was as follows: upslope < midslope < downslope. There was a significant negative correlation between the intensity of soil erosion and the extent of alpine meadow vegetation cover (P < 0.01). The mean soil erosion modulus exhibited a linear reduction trend with an increase in vegetation cover, and the correlation coefficient R ² was ≥ 0.997. The higher the degradation degree of the alpine meadow grassland, the greater is the soil erosion. The mean erosion modulus in the severely degraded meadow zone was 2.23 times greater than the one in the slightly degraded zone, and the maximum erosion modulus reached 2.96 × 10⁶ kg/km²/a.  相似文献   

Algal mat productivity: Comparisons in a salt marsh     

Joy B. Zedler 《Estuaries and Coasts》1980,3(2):122-131

This paper documents the role of salt marsh algal mats in the productivity of a southern California tidal wetland. The productivity of the mats, which are composed of filamentous bluegreen and green algae and diatoms, varies both temporally and spatially in relation to tidal inundation and overstory vegetation. The estimates of net primary productivity (NPP) were highest under the canopy ofJaumea carnosa (Less.) Gray (341 g C m^?2 yr^?1) at low elevation. Elsewhere, NPP appeared to be limited by low light (276 g C m^?2 yr^?1 underSpartina foliosa Trin.) and desiccation (185 g C m^?2 yr^?1 underBatis martima L. and 253 g C m^?2 yr^?1 underMonanthochloe littoralis Engelm). Algal NPP was from 0.8 to 1.4 times that of the vascular plant overstory NPP. It is hypothesized that the arid environment of southern California and resulting hypersaline soils reduce vascular plant cover, which leads to high algal productivity.  相似文献   

Comparison of net primary productivity in karst and non-karst areas: a case study in Guizhou Province,China     

Bing Wang  Shengtian Yang  Changwei Lü  Jing Zhang  Yujuan Wang 《Environmental Earth Sciences》2010,59(6):1337-1347

Green plants play an important role in energy flows and material cycles. The net primary productivity (NPP) reflects the capability of vegetation to convert solar energy into photosynthate (fixed carbon). Understanding the factors that contribute to variations in NPP is of key importance for improving the rock-desertification environment in karst areas. In this paper, the NPP model (Light Use Efficiency model) is modified on the basis of remote sensing data [moderate resolution imaging spectroradiometer (MODIS)], climate data and observed information. Then the model is employed to estimate the spatial–temporal variations of NPP in the Guizhou Province, China. Finally, the NPP differences between karst area and non-karst area, and the relationships between NPP and climate factors are analyzed. The results show that the NPP estimated using MODIS data are reasonable. The mean NPP of territorial vegetation is 421.46 gC m⁻² year⁻¹; the NPP in the non-karst area is 13.3% higher than that in the karst area; the correlation degree between NPP and precipitation is better in southeastern and western districts.  相似文献   

Exploring the effects of water on vegetation change and net primary productivity along the IGBP Northeast China Transect   总被引：2，自引：0，他引：2  

Yujin Zhang  Guangsheng Zhou 《Environmental Earth Sciences》2011,62(7):1481-1490

To understand the mechanisms underlying the effects of climate variation, especially the effects of water on vegetation, vegetation type and distribution as well as climate data and soil type were used to simulate present vegetation distributions and net primary productivity (NPP) under present and future climate scenarios SRES-A2 and SRES-B2. A natural vegetation NPP model was also applied to calculate future vegetation NPP. The results showed that water played a dominant role not only in the distribution of vegetation, but also in the rate of change in the vegetation area. Analysis of NPP showed that precipitation had more effects on the amount of biome NPP than temperature did. Different effects were observed for the rate of change in NPP. In cases where biomes remain unaltered, the variation in annual precipitation could account for 39% of the variation in NPP. In cases where biomes changed, 45% of NPP was caused by temperature variation. Regarding the variation in transect production, −2.85% resulted from the change in vegetation structure when compared with present NPP, and 7.69% from the climate change under scenario SRES-B2; these values were −7.4 and 19.56%, respectively, under scenario SRES-A2. The results showed water served as a dominant factor controlling the vegetation distributions and NPP. However, temperature became determinant where the biomes changed, impacting the rate of change in vegetation NPP when the climate changed. The results also showed that water would have a positive effect on transect production, and the structure of vegetation had a negative effect under the projected future climate.  相似文献   

Net primary production and decomposition of salt marshes of the Ebre delta (Catalonia,Spain)     

Antoni?CurcóEmail author  Carles?Ibà?ez  John?W.?Day  Narcís?Prat 《Estuaries and Coasts》2002,25(3):309-324

Net primary production was measured in three characteristic salt marshes of the Ebre delta: anArthrocnemum macrostachyum salt marsh,A. macrostachyum-Sarcocornia fruticosa mixed salt marsh andS. fruticosa salt marsh. Above-ground and belowground biomass were harvested every 3 mo for 1 yr. Surface litter was also collected from each plot. Aboveground biomass was estimated from an indirect non-destructive method, based on the relationship between standing biomass and height of the vegetation. Decomposition of aboveground and belowground components was studied by the disappearance of plant material from litter bags in theS. fruticosa plot. Net primary production (aboveground and belowground) was calculated using the Smalley method. Standing biomass, litter, and primary production increased as soil salinity decreased. The annual average total aboveground plus belowground biomass was 872 g m⁻² in theA. macrostachyum marsh, 1,198 g m⁻² in theA. macrostachyum-S. fruticosa mixed marsh, and 3,766 g m⁻² in theS. fruticosa biomass (aboveground plus belowground) was 226, 445, and 1,094 g m⁻², respectively. Total aboveground plus below-ground net primary production was 240, 1,172, and 1,531 g m⁻² yr⁻¹. There was an exponential loss of weight during decomposition. Woody stems and roots, the most recalcitrant material, had 70% and 83% of the original material remaining after one year. Only 20–22% of leafy stem weight remained after one year. When results from the Mediterranean are compared to other salt marshes dominated by shrubbyChenopodiaceae in Mediterranean-type climates, a number of similarities emerge. There are similar zonation patterns, with elevation and maximum aboveground biomass and primary production occurring in the middle marsh. This is probably because of stress produced by waterlogging in the low marsh and by hypersalinity in the upper marsh.  相似文献   

Primary production in Long Island sound     

Nicole L. Goebel  James N. Kremer  Christopher A. Edwards 《Estuaries and Coasts》2006,29(2):232-245

Daily and annual integrated rates of primary productivity and community respiration were calculated using physiological parameters measured in oxygen-based photosynthesis-irradiance (P-I) incubations at 8 stations throughout central and western Long Island Sound (cwLIS) during the summer and autumn of 2002 and 2003 and the late spring of 2003. Each calculation takes into account actual variations in incident irradiance over the day and underwater irradiance and standing stock with depth. Annual peak rates, ±95% confidence interval of propagated uncertainty in each measurement, of gross primary production (GPP, 1,730±610 mmol O₂ m⁻² d⁻¹), community respiration (R_c, 1,660±270 mmol O₂ m⁻² d⁻¹), and net community production (NCP, 1,160±1,100 mmol O₂ m⁻² d⁻¹) occurred during summer at the western end of the Sound. Lowest rates of GPP (4±11 mmol O₂ m⁻² d⁻¹), R_c (−50±300 mmol O₂ m⁻² d⁻¹), and NCP (−1,250±270 mmol O₂ m⁻² d⁻¹) occurred during late autumn-early winter at the outer sampled stations. These large ranges in rates of GPP, R_c, and NCP throughout the photic zone of cwLIS are attributed to seasonal and spatial variability. Algal respiration (R_a) was estimated to consume an average of 5% to 52% of GPP, using a literature-based ratio of R_a:R_c. From this range, we established that the estimated R_a accounts for approximately half of GPP, and was used to estimate daily net primary production (NPP), which ranged from 2 to 870 mmol O₂ m⁻² d⁻¹ throughout cwLIS during the study. Annual NPP averaged 40±8 mol O₂ m⁻² yr⁻¹ for all sampled stations, which more than doubled along the main axis of the Sound, from 32±14 mol O₂ m⁻² yr⁻¹ at an eastern station to 82±25 mol O₂ m⁻² yr⁻¹ at the western-most station. These spatial gradients in productivity parallel nitrogen loads along the main axis of the Sound. Daily integrals of productivity were used to test and formulate a simple, robust biomass-light model for the prediction of phytoplankton production in Long Island Sound, and the slope of the relationship was consistent with reports for other systems.  相似文献