Primary Production Measurements Research Articles

Inter‐annual variations over a decade of primary production of the seagrass Posidonia oceanica

AbstractWe acquired quasi‐continuous measurements of community gross primary production (GPP) by mass balance of O2 measured on a mooring, from August 2006 to October 2016 over a Posidonia oceanica meadow (10 m depth) in the Bay of Revellata (Corsica). Over the 2006–2016 period, annual GPP averaged 88 molO2 m−2 yr−1 and ranged from 61 to 108 molO2 m−2 yr−1. The 2 yr with the lowest annual GPP (2007 and 2015) were characterized by a low occurrence of fall–winter storms, probably leading to the accumulation of leaf litter in fall and early winter; we hypothesize this might have led to occultation of benthic macro‐algae. Among the other years, the inter‐annual variability of GPP was related to changes during the February–August period, as GPP was repeatable among years during the September–January period. For the February–August period, inter‐annual variations of GPP were correlated to chlorophyll a (Chl a), solar radiation (SR) and water temperature. Computed phytoplankton GPP corresponded to a small fraction of community GPP, so the relation between GPP and Chl a probably reflected inter‐annual variations of a common driver that we hypothesize to be nutrient inputs. The correlation of GPP with SR shows that light availability contributed to inter‐annual variations of the development of P. oceanica. The positive relation between GPP and temperature was consistent with the fact that the observed temperatures in the Bay of Revellata were during the study period within the comfort range for the growth of P. oceanica, despite an increase of water temperature of 0.7°C.

Seasonal patterns of thermal stratification and primary production in the northern parts of Lake Tanganyika

Abstract Thermal stratification in meromictic Lake Tanganyika weakens during the cool, dry and windy season, allowing intrusions of deeper nutrient-rich waters into the upper mixed layer enhancing primary productivity. The current study examined the seasonal influence of thermal structure on the patterns of primary production in Lake Tanganyika. Two sites (Kigoma Bay and Mahale) were sampled on a monthly basis for 1 year. Water temperature and chlorophyll a fluorescence profiles (0–100 m) were measured using a multisonde. Water samples were taken every 20 m (0–100 m) to measure soluble reactive phosphorus (SRP), chlorophyll a and primary production. Pulse Amplitude Modulated Fluorometry was used for the measurements of primary production. The results show that the dry season coincided with higher wind speeds, elevated SRP and some peaks of chlorophyll a and primary production at both sites. During the wet season, high levels of chlorophyll a and primary production coincided with an increase in the euphotic depth, a deep chlorophyll maximum (DCM) and a contribution from metalimnetic areal production at both sites. Our results suggest that the vertical distribution of primary production in Lake Tanganyika is affected by the lake thermal structure, nutrient availability and the extent of the euphotic zone. In Lake Tanganyika, estimates of areal primary production were significantly affected by DCM and required estimation throughout the entire upper mixed layer and the metalimnion which extended to ~89 m.

A 55-Year Time Series Station for Primary Production in the Adriatic Sea: Data Correction, Extraction of Photosynthesis Parameters and Regime Shifts

In 1962, a series of in situ primary production measurements began in the Adriatic Sea, at a station near the island of Vis. To this day, over 55 years of monthly measurements through the photic zone have been accumulated, including close to 3000 production measurements at different depths. The measurements are conducted over a six-hour period around noon, and the average production rate extrapolated linearly over day length to calculate daily production. Here, a non-linear primary production model is used to correct these estimates for potential overestimation of daily production due to linear extrapolation. The assimilation numbers are recovered from the measured production profiles and subsequently used to model production at depth. Using the recovered parameters, the model explained 87% of variability in measured normalized production at depth. The model is then used to calculate daily production at depth, and it is observed to give on average 20% lower daily production at depth than the estimates based on linear extrapolation. Subsequently, water column production is calculated, and here, the model predicted on average 26% lower water column production. With the recovered parameters and the known magnitude of the overestimation, the time-series of water column production is then re-established with the non-linearly-corrected data. During this 55-year period, distinct regimes were observed, which were classified with a regime shift detection method. It is then demonstrated how the recovered parameters can be used in a remote sensing application. A seasonal cycle of the recovered assimilation number is constructed along with the seasonal cycle of remotely-sensed chlorophyll. The two are then used to model the seasonal cycle of water column production. An upper and a lower bound on the seasonal cycle of water column production based on remotely-sensed chlorophyll data are then presented. Measured water column production was found to be well within the range of remotely-sensed estimates. With this work, the utility of in situ measurements as a means of providing information on the assimilation number is presented and its application as a reference for remote sensing models highlighted.

Produktivitas Primer Fitoplankton pada Daerah Penangkapan Ikan di Taman Wisata Alam Danau Buyan, Buleleng, Bali

This research aims to identify productivity value of phytoplankton’s net primary as well as its relation within parameter of physics, chemistry, and aquatic biology to the productivity value of phytoplankton’s net primary in the waters of Lake Buyan Nature Park. Measurement of primary phytoplankton productivity is conducted by using bright and dark bottle method. The taking of lake water samples for measurement of phytoplankton primary productivity and measurement of supporting parameters namely physics (temperature, brightness, turbidity), chemistry (pH, nitrate, phosphate) and biology (phytoplankton abundance) were carried out at four research stations in the fishing area. Data analysis used in this research is correlation analysis among parameters of physic, chemistry, and aquatic biology to the net primary productivity value of phytoplankton by using the PAST 3.1 application. The obtained result showed that the value of net primary productivity ranged from 76.39 to 211.46 mgC / m3 / day and the parameters of physics, chemistry and aquatic biology have a relationship with net primary productivity of phytoplankton. Brightness, abundance of phytoplankton, nitrate, temperature, dissolved oxygen, pH and phosphate which are positively correlated with net primary productivity of phytoplankton while water turbidity is negatively correlated with it. Parameters that have a strong to very strong relationship with net primary productivity are dissolved oxygen, temperature, nitrate, phytoplankton abundance, and water brightness.

The 13C method as a robust alternative to 14C-based measurements of primary productivity in the Mediterranean Sea.

Due to the increasing constraints on using the radioactive isotope 14C to measure primary productivity (14C-PP), we determined the surface carbon fixation rates in the Mediterranean Sea, using the alternative stable isotope 13C method (13C-PP). Rates obtained (13C-POCp) were compared with simultaneous 14C-POCp measurements in samples of different volumes (72 mL and 1.2 L). We also tested the variation of the percentage of dissolved primary production (PER), to the total productivity using organic and inorganic filters (14C method). 13C-POCp rates ranged from 0.4, in the Ionian basin, to 1.5 mgC m−3 h−1 in the Ligurian region. These results agreed with those found with the 14C-PP in 1.2-L samples (two sample t-test, t = 1.035, df = 22, P = 0.31). However, we found that 14C-POCp rates derived from 72-mL incubations were 46% lower than those measured with 13C-PP. The discrepancy between large and small volume incubations was likely due to differences in the number of large phytoplankton cells within the community. PER values measured with silver membrane filters yielded similar results than those obtained using polycarbonate filters. Our findings showed that when the sample size is carefully chosen, the 13C-PP provide comparable results to 14C-PP even in waters of low productivity in the Mediterranean Sea.

Turbulence simultaneously stimulates small- and large-scale CO2 sequestration by chain-forming diatoms in the sea

Chain-forming diatoms are key CO2-fixing organisms in the ocean. Under turbulent conditions they form fast-sinking aggregates that are exported from the upper sunlit ocean to the ocean interior. A decade-old paradigm states that primary production in chain-forming diatoms is stimulated by turbulence. Yet, direct measurements of cell-specific primary production in individual field populations of chain-forming diatoms are poorly documented. Here we measured cell-specific carbon, nitrate and ammonium assimilation in two field populations of chain-forming diatoms (Skeletonema and Chaetoceros) at low-nutrient concentrations under still conditions and turbulent shear using secondary ion mass spectrometry combined with stable isotopic tracers and compared our data with those predicted by mass transfer theory. Turbulent shear significantly increases cell-specific C assimilation compared to still conditions in the cells/chains that also form fast-sinking, aggregates rich in carbon and ammonium. Thus, turbulence simultaneously stimulates small-scale biological CO2 assimilation and large-scale biogeochemical C and N cycles in the ocean.

A multi-method autonomous assessment of primary productivity and export efficiency in the springtime North Atlantic.

Fixation of organic carbon by phytoplankton is the foundation of nearly all open-ocean ecosystems and a critical part of the global carbon cycle. But quantification and validation of ocean primary productivity at large scale remains a major challenge, due to limited coverage of ship-based measurements and the difficulty of validating diverse measurement techniques. Accurate primary productivity measurements from autonomous platforms would be highly desirable, due to much greater potential coverage. In pursuit of this goal we estimate gross primary productivity over two months in the springtime North Atlantic from an autonomous Lagrangian float using diel cycles of particulate organic carbon derived from optical beam attenuation. We test method precision and accuracy by comparison against entirely independent estimates from a locally parameterized model based on chlorophyll a and light measurements from the same float. During nutrient replete conditions (80% of the study period), we obtain strong relative agreement between the independent methods across an order of magnitude of productivities (r2=0.97), with slight under-estimation by the diel cycles method (-19±5 %). At the end of the diatom bloom, this relative difference increases to -58 % for a six-day period, likely a response to SiO4 limitation, which is not included in the model. In addition, we estimate gross oxygen productivity from O2 diel cycles and find strong correlation with diel cycles-based gross primary productivity over the entire deployment, providing further qualitative support to both methods. Finally, simultaneous estimates of net community productivity, carbon export and particle size suggest that bloom growth is halted by a combination of reduced productivity due to SiO4 limitation and increased export efficiency due to rapid aggregation. After the diatom bloom, high chlorophyll a normalized productivity indicates that low net growth during this period is due to increased heterotrophic respiration and not nutrient limitation. These findings represent a significant advance in the accuracy and completeness of upper ocean carbon cycle measurements from an autonomous platform.

Temporal Variability of Primary Production Explains Marine Ecosystem Structure and Function

Understanding drivers of ecosystem structure and function is a pervasive goal in academic and applied research. We used 24 synthetic ecosystem-level indices derived from trophic models, and independently derived data for Net Primary Productivity, to investigate drivers of ecosystem structure and function for 43 marine ecosystems distributed in all oceans of the world and including coastal, estuaries, mid-ocean islands, open-ocean, coral reef, continental shelf, and upwelling ecosystems. Of these indices, ecosystem Biomass, Primary Production, Respiration, the ratio of Biomass to Total System Throughput (sum of total energy flow into and out of an ecosystem as well as between ecosystem components), the ratio of Production to Biomass, Residence Time (mean time that a unit of energy remains in the ecosystem), Average Trophic Level, and Relative Ascendency (index of organization and complexity of a food web) displayed relationships with measures of Net Primary Productivity (NPP). Across all ecosystems, relationships were stronger with seasonal and interannual variability of NPP as compared to mean NPP. Both measures of temporal variability were combined into multivariate predictive relationships for each ecosystem index, with r2 values ranging from 0.14 to 0.49 and Akaike’s information criteria values from − 8.44 to 3.26. Our results indicate that despite large geographic and environmental differences, temporal variability of NPP is strongly linked to the structure and function of marine ecosystems.

Asymmetric responses of primary productivity to altered precipitation simulated by ecosystem models across three long-term grassland sites

Abstract. Field measurements of aboveground net primary productivity (ANPP) in temperate grasslands suggest that both positive and negative asymmetric responses to changes in precipitation (P) may occur. Under normal range of precipitation variability, wet years typically result in ANPP gains being larger than ANPP declines in dry years (positive asymmetry), whereas increases in ANPP are lower in magnitude in extreme wet years compared to reductions during extreme drought (negative asymmetry). Whether the current generation of ecosystem models with a coupled carbon–water system in grasslands are capable of simulating these asymmetric ANPP responses is an unresolved question. In this study, we evaluated the simulated responses of temperate grassland primary productivity to scenarios of altered precipitation with 14 ecosystem models at three sites: Shortgrass steppe (SGS), Konza Prairie (KNZ) and Stubai Valley meadow (STU), spanning a rainfall gradient from dry to moist. We found that (1) the spatial slopes derived from modeled primary productivity and precipitation across sites were steeper than the temporal slopes obtained from inter-annual variations, which was consistent with empirical data; (2) the asymmetry of the responses of modeled primary productivity under normal inter-annual precipitation variability differed among models, and the mean of the model ensemble suggested a negative asymmetry across the three sites, which was contrary to empirical evidence based on filed observations; (3) the mean sensitivity of modeled productivity to rainfall suggested greater negative response with reduced precipitation than positive response to an increased precipitation under extreme conditions at the three sites; and (4) gross primary productivity (GPP), net primary productivity (NPP), aboveground NPP (ANPP) and belowground NPP (BNPP) all showed concave-down nonlinear responses to altered precipitation in all the models, but with different curvatures and mean values. Our results indicated that most models overestimate the negative drought effects and/or underestimate the positive effects of increased precipitation on primary productivity under normal climate conditions, highlighting the need for improving eco-hydrological processes in those models in the future.

Extraction of Photosynthesis Parameters from Time Series Measurements of In Situ Production: Bermuda Atlantic Time-Series Study

Computing the vertical structure of primary production in ocean ecosystem models requires information about the vertical distribution of available light, chlorophyll concentration and photosynthesis response parameters. Conversely, given information on vertical structure of chlorophyll and light, we can extract photosynthesis parameters from vertical profiles of primary production measured at sea, as we illustrate here for the Bermuda Atlantic Time-Series Study. The procedure is based on a model of the production profile, which itself depends on the underwater light field. To model the light field, attenuation coefficients were estimated from measured optical profiles using a simple model of exponential decay of photosynthetically-available irradiance with depth, which accounted for 97% of the variance in the measured optical data. With the underwater light climate known, an analytical solution for the production profile was employed to recover photosynthesis parameters by minimizing the residual model error. The recovered parameters were used to model normalized production profiles and normalized watercolumn production. The model explained 95% of the variance in the measured normalized production at depth and 97% of the variance in measured normalized watercolumn production. A shifted Gaussian function was used to model biomass profiles and accounted for 93% of the variance in measured biomass at depth. An analytical solution for watercolumn production with the shifted Gaussian biomass was also tested. With the recovered photosynthesis parameters, maximum instantaneous growth rates were estimated by using a literature value for the carbon-to-chlorophyll ratio in this region of the Atlantic. An exact relationship between the maximum instantaneous growth rate and the daily growth rate in the ocean was derived. It was shown that calculating the growth rate by dividing the production by the carbon-to-chlorophyll ratio is equivalent to calculating it from the ratio of the final to the initial biomass, even when production is time dependent. Finally, the seasonal cycle of the recovered assimilation number at the Bermuda Station was constructed and analysed. The presented approach enables the estimation of photosynthesis parameters and growth rates from measured production profiles with only a few model assumptions, and increases the utility of in situ primary production measurements. The retrieved parameters have direct applications in satellite-based estimates of primary production from ocean-colour data, of which we give an example.

PRODUCTIVITY OF DIATOMS IN CULTURE AND IN MARINE HABITATS

The diatom dominated phytoplankton net primary production in different areas of the ocean (from 100-1000 mg C. m-2. day-1) and in estuaries (up to 2000 mg C. m-2. day-1) is compared with the maximum productivity of marine diatoms in culture (50 g C . m-2 . day-1) for Cyclotella cryptica (Centrales, Diatomeae) and 1000 mg C . m-2. day-1 for Coscinodiscus asteromphalus (Centrales, Diatomeae). The rate of C-assimilation as a measure of primary production is critically discussed in relation to the different factors regulating the reproduction of cells and the production of organic material. The evaluation of another parameter for primary production: light dependent protein synthesis (LPS) is proposed, which brings reproduction of phytoplankton cells and the production of organic material closer together. As an example of the requirement for more information about the potential growth and production rate of diatom species, some results on the cultivation of the tropical shallow water diatom Bellerochea yucatanensis V. STOSCH (Centrales, Diatomeae) are presented. At 30 C this species has a specific growth rate (µ max) of = 4.4 divisions per day and 4 divisions per day at 34°C with an average cell size of 34 x 26 ? m. The temperature range of this species is from 12°C (µ = 0.3) to 35°C (µ = 2).

The best incubation time for primary productivity of phytoplankton in Laguna Lake, North Maluku, Indonesia

Yuliana, Irfan M. 2018. The best incubation time for primary productivity of phytoplankton in Laguna Lake, North Maluku, Indonesia. Biodiversitas 19: 1021-1028. Primary productivity of phytoplankton is a source of energy and organic matter utilized by organisms at higher food chain levels. The measurement of the high rate of primary productivity can be done through the incubation of sample water at a particular time and time depending on sunlight intensity. This study aimed to estimate the best incubation time to achieve the highest primary productivity of phytoplankton in Laguna Lake, Ternate City, North Maluku Province, Indonesia in February 2017. The study was conducted at one location with four different levels of depth of 0, 5, 10, and 15 meters, and at three incubation times, i.e., 09:00-13:00, 10:00-14:00, and 11:00-15:00 (Eastern Indonesian Time). The chemical and physical parameters of radiance, temperature, pH, nitrate, and orthophosphate content were measured to estimate water quality of the lake. The results of this study showed that were 10 genera of phytoplankton belonging to Bacillariophyceae (6 genera), Chlorophyceae (4 genera), and Cyanophyceae (2 genera). The Laguna Lake has temperature ranged between 29.0-31.1oC, nitrate content of 0.22-0.58 mg l-1, orthophosphate content of 0.14-0.27 mg l-1, and pH 7. The primary productivity value at incubation time 09:00-13:00; 10:00-14:00; and 11:00-15:00 were of 101,851-258,278; 40,59-351,643; and 76,197-305,754 mgC m-3 hours-1, respectively. The best incubation time that provides the highest value in the measurement of primary productivity of phytoplankton at Laguna Lake was at 10:00 am to 14:00 pm.

Estimating large carnivore populations at global scale based on spatial predictions of density and distribution - Application to the jaguar (Panthera onca).

Broad scale population estimates of declining species are desired for conservation efforts. However, for many secretive species including large carnivores, such estimates are often difficult. Based on published density estimates obtained through camera trapping, presence/absence data, and globally available predictive variables derived from satellite imagery, we modelled density and occurrence of a large carnivore, the jaguar, across the species’ entire range. We then combined these models in a hierarchical framework to estimate the total population. Our models indicate that potential jaguar density is best predicted by measures of primary productivity, with the highest densities in the most productive tropical habitats and a clear declining gradient with distance from the equator. Jaguar distribution, in contrast, is determined by the combined effects of human impacts and environmental factors: probability of jaguar occurrence increased with forest cover, mean temperature, and annual precipitation and declined with increases in human foot print index and human density. Probability of occurrence was also significantly higher for protected areas than outside of them. We estimated the world’s jaguar population at 173,000 (95% CI: 138,000–208,000) individuals, mostly concentrated in the Amazon Basin; elsewhere, populations tend to be small and fragmented. The high number of jaguars results from the large total area still occupied (almost 9 million km2) and low human densities (< 1 person/km2) coinciding with high primary productivity in the core area of jaguar range. Our results show the importance of protected areas for jaguar persistence. We conclude that combining modelling of density and distribution can reveal ecological patterns and processes at global scales, can provide robust estimates for use in species assessments, and can guide broad-scale conservation actions.

Logging disturbance shifts net primary productivity and its allocation in Bornean tropical forests.

Tropical forests play a major role in the carbon cycle of the terrestrial biosphere. Recent field studies have provided detailed descriptions of the carbon cycle of mature tropical forests, but logged or secondary forests have received much less attention. Here, we report the first measures of total net primary productivity (NPP) and its allocation along a disturbance gradient from old-growth forests to moderately and heavily logged forests in Malaysian Borneo. We measured the main NPP components (woody, fine root and canopy NPP) in old-growth (n=6) and logged (n=5) 1ha forest plots. Overall, the total NPP did not differ between old-growth and logged forest (13.5±0.5 and 15.7±1.5 Mg C ha-1 year-1 respectively). However, logged forests allocated significantly higher fraction into woody NPP at the expense of the canopy NPP (42% and 48% into woody and canopy NPP, respectively, in old-growth forest vs 66% and 23% in logged forest). When controlling for local stand structure, NPP in logged forest stands was 41% higher, and woody NPP was 150% higher than in old-growth stands with similar basal area, but this was offset by structure effects (higher gap frequency and absence of large trees in logged forest). This pattern was not driven by species turnover: the average woody NPP of all species groups within logged forest (pioneers, nonpioneers, species unique to logged plots and species shared with old-growth plots) was similar. Hence, below a threshold of very heavy disturbance, logged forests can exhibit higher NPP and higher allocation to wood; such shifts in carbon cycling persist for decades after the logging event. Given that the majority of tropical forest biome has experienced some degree of logging, our results demonstrate that logging can cause substantial shifts in carbon production and allocation in tropical forests.

A Comparative Study on Pelagic Primary Productivity in the Coastal Areas of Eritrean Red Sea

Primary Productivity is the process by which inorganic forms of carbon are synthesized by living organisms into simple organic compounds. Most carbon on Earth is in inorganic oxidized forms such as carbon dioxide (CO2), bicarbonate (HCO3-), and carbonate (CO3). Inorganic carbon must be chemically reduced to form the organic molecules which are the building blocks of life and the mechanism by which energy is stored in living organisms. Eritrea’s coastal and marine ecosystems are characterized by rich and diverse coral reefs, isolated mangrove forests, sea-grass beds, bays, beaches and pristine unpolluted waters that are at the critical juncture between development and conservation. These ecosystems represent a physical resource base for the potentially rich and unexploited marine fisheries. This study is basically aimed at the measurement of primary productivity in relation to fisheries. The study results will also high light the plankton assemblage of a coastal environment and this study will also examine the productivity of the coastal environment.

2001-2014年博斯腾湖流域植被物候时空变化及其驱动因子

PDF HTML阅读 XML下载 导出引用 引用提醒 2001-2014年博斯腾湖流域植被物候时空变化及其驱动因子 DOI: 10.5846/stxb201708071416 作者: 作者单位: 1 新疆师范大学 地理科学与旅游学院,1 新疆师范大学 地理科学与旅游学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（41461006，47164003）；变化环境下干旱区湖泊流域-生态-经济复合系统的协同进化与发展，模式研究（U1703341） Temporal and spatial variation of vegetation phenology and its driving factor analysis in the Bosten Lake Drainage Basin from 2001 to 2014 Author: Affiliation: Xinjinag Normal University,Xinjinag Normal University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:以博斯腾湖流域为研究对象，利用MODIS的MCD12Q2和LST产品、GHCN_CAMS气温观测/再分析资料与气象数据，采取趋势分析与相关性分析法探求了博斯腾湖流域2001-2014年植被物候的时空变化及其影响因素的相对作用，对博斯腾湖流域植被物候分区不同的驱动区域。结果表明：①在研究期内，整个研究区植被物候始期在第76-168天，末期在第172-295天；物候始期自南向北逐渐推迟、而末期逐渐提前，物候的空间分布特征与该区海拔高度的分布保持了较好的一致性；②2001-2014年植被始期和末期有明显提前趋势（提前3-6d），主要分布在流域的盆地和平原绿洲区，表示研究区植被物候受到人类活动的影响。③植被物候始期与末期变化受气候因子驱动影响的区域占比分别为57.10%和51.30%，主要分布在黄水沟流域，清水河流域，孔雀河流域，大尤路都斯盆地和小尤路都斯盆地周围地区；而非气候因子占42.90%和48.70%，主要位于博斯腾湖周围绿洲和库尔勒绿洲等地势较低的区域。④由植被生长季物候与降水、气温的偏相关性关系和复相关性关系可以得出，多年物候始期和末期与气温有关；而且随海拔升高，气温的敏感幅度越高。博斯腾湖流域植被物候的时空变化不仅是受气候变化的影响，还主要受人类活动和海拔高度差异等影响因素的共同作用。 Abstract:Vegetation phenology is widely used as an independent measure and powerful indicator of primary net productivity, crop yields, insect emergence, bird migration, climate change, carbon balance and cycle, and fundamental ecosystem function and is influenced at the local and global scales by climatic factors (including precipitation, temperature) and human activities. Studies of vegetation phenology are important, as solutions are needed to overcome issues such as environmental change, sustainable management, and biodiversity conservation. Hence, an in-depth understanding of the spatio-temporal variations and driving factors of vegetation phenology are important in the currently changing environment. The Bosten Lake Drainage Basin is located in northwest China and covers a vast area with a complicated terrain, including most of the middle Tianshan Mountains in the northwest, whole Yanqi basin, and northeast part of the Tarim basin in the south, which are characterized by distinctive distribution patterns of temperature, precipitation, and human activities. Here, based on the MCD12Q2, GHCN_CAMS air temperature, Digital Elevation Model(DEM), and metrological observed data, we established monthly geographical weighted regression (GWR) models and measured the near surface air temperature. Next, spatio-temporal evolution characteristics and driving factors of vegetation phenology in the Bosten Lake Drainage Basin were studied by determining slope, partial correlation, and multiple correlations. The results demonstrated that:(1) the start of growth season (SOG) was concentrated in 76-168 Julian days, whereas the end of growth season (EOS) was in 172-295 Julian days; the SOG was delayed and EOS was gradually advanced from north to south. Elevation played an important role in the regional differentiation of vegetation phenology; with increasing altitude, SOG was significantly delayed, EOG was advanced, and the length of the growth season (LOG) was significantly shortened. (2) SOG and EOG advanced synchronously in the plane oasis area during 2001 and 2014 because of the influence of human activities. (3) Climatic factors affected the area of SOG and BOG accounted for 57.10% and 51.30%, respectively, and was mainly located in the Huangshuigou river watershed, Qingshui river watershed, Konqi river watershed, Qongyultuz basin, and around the Kiqikyultuz basin. Non-climatic factors affected the area of SOG and BOG, accounting for 42.90% and 48.70%, and were located in low-altitude regions including the oasis around Bosten lake and the Korla oasis. (4) The correlation between vegetation phenology and climatic factors by partial correlation and multiple correlations demonstrated that variations in inter-annual SOG and BOG were mostly affected by air temperature. As altitude increased, vegetation showed obvious sensitivity of phenology to temperature. In summary, spatio-temporal variations in vegetation phenology in the Bosten Lake Drainage Basin are not only influenced by climate change, but are also influenced by the combined effects of human activities and altitude. 参考文献 相似文献 引证文献

基于光合电子传递速率的浮游植物初级生产力测量

基于光合电子传递速率的浮游植物初级生产力测量

Weather-driven change in primary productivity explains variation in the amplitude of two herbivore population cycles in a boreal system.

Vertebrate populations throughout the circumpolar north often exhibit cyclic dynamics, and predation is generally considered to be a primary driver of these cycles in a variety of herbivore species. However, weather and climate play a role in entraining cycles over broad landscapes and may alter cyclic dynamics, although the mechanism by which these processes operate is uncertain. Experimental and observational work has suggested that weather influences primary productivity over multi-year time periods, suggesting a pathway through which weather and climate may influence cyclic herbivore dynamics. Using long-term monitoring data, we investigated the relationships among multi-year weather conditions, measures of primary productivity, and the abundance of two cyclic herbivore species: snowshoe hare and northern red-backed vole. We found that precipitation (rain and snow) and growing season temperatures were strongly associated with variation in primary productivity over multi-year time horizons. In turn, fourfold variation in the amplitude of both the hare and vole cycles observed in our study area corresponded to long-term changes in primary productivity. The congruence of our results for these two species suggests a general mechanism by which weather and climate might influence cyclic herbivore population dynamics. Our findings also suggested that the association between climate warming and the disappearance of cycles might be initiated by changes in primary productivity. This work provides an explanation for observed influences of weather and climate on primary productivity and population cycles and will help our collective understanding of how future climate warming may influence these ecological phenomena in the future.

Spatial variability of photophysiology and primary production rates of the phytoplankton communities across the western Antarctic Peninsula in late summer 2013

Primary production measurements in the Southern Ocean are generally carried out during phytoplankton blooms in the Antarctic summer, whereas information from late summer is scarcer, especially in the northernmost part of the western Antarctic Peninsula (wAP). Here, we present data on phytoplankton photophysiology, chlorophyll-a concentration (Chl a), phytoplankton communities and primary productivity for 3 sub-regions, as follows: Transitional Water with Bellingshausen Sea influence (TBW-dominated sub-region), Transitional Water with Weddell Sea influence (TWW-dominated sub-region), both occupying the Bransfield Strait (BS), and a mixture of both transitional waters in the Gerlache Strait (Gerlache sub-region). Comparisons between these sub-regions have shown that, on average, Chl a, (0.65mgm−3) was lower and upper mixed layer depth (ZUMLD = 52.62m) was deeper in TWW-dominated waters, whereas intermediate Chl a (1.22mgm−3) and moderate ZUMLD (36.46m) values were found in the TBW-dominated sub-region and the lowest ZUMLD (22.33m) and highest Chl a values (1.58mgm−3) were found in the Gerlache sub-region. However, similar values of Fv/Fm were found in the 3 sub-regions, which indicate a high physiological plasticity, even considering different phytoplankton communities. A canonical correspondence analysis highlighted the association between the TBW-dominated sub-region and the dominance of diatoms, coupled with higher photosynthetic carotenoids (especially fucoxanthin), contrasting with the Gerlache sub-region, mainly associated with photoprotective carotenoids (particularly alloxanthin from cryptophytes) and relative lower ZUMLD. Primary production rates estimated from the PAM (Pulse-Amplitude Modulate) fluorometric technique agreed very well with 14C measurements (r2=0.91, n=5, p=0.01). Although higher maximum chlorophyll a specific primary production rates were found in the TWW sub-region (1.91 ± 1.22 mgCmg Chl a−1h−1), the other two areas also showed relatively high assimilation numbers as compared to previous works in the region. In short, despite the large spatial variability of physical water column features, adequate photophysiological traits allowed high primary production rates by those late summer phytoplankton communities in the northern wAP region.

Seasonal oxygen dynamics in a warm temperate estuary: effects of hydrologic variability on measurements of primary production, respiration, and net metabolism.

Seasonal responses in estuarine metabolism (primary production, respiration, and net metabolism) were examined using two complementary approaches. Total ecosystem metabolism rates were calculated from dissolved oxygen time series using Odum's open water method. Water column rates were calculated from oxygen-based bottle experiments. The study was conducted over a spring-summer season in the Pensacola Bay estuary at a shallow seagrass-dominated site and a deeper bare-bottomed site. Water column integrated gross production rates more than doubled (58.7 to 130.9 mmol O2 m-2 d-1) from spring to summer, coinciding with a sharp increase in water column chlorophyll-a, and a decrease in surface salinity. As expected, ecosystem gross production rates were consistently higher than water column rates, but showed a different spring-summer pattern, decreasing at the shoal site from 197 to 168 mmol O2 m-2 d-1 and sharply increasing at the channel site from 93.4 to 197.4 mmol O2 m-2 d-1. The consistency among approaches was evaluated by calculating residual metabolism rates (ecosystem - water column). At the shoal site, residual gross production rates decreased from spring to summer from 176.8 to 99.1 mmol O2 m-2 d-1, but were generally consistent with expectations for seagrass environments, indicating that the open water method captured both water column and benthic processes. However, at the channel site, where benthic production was strongly light-limited, residual gross production varied from 15.7 mmol O2 m-2 d-1 in spring to 86.7 mmol O2 m-2 d-1 in summer. The summer rates were much higher than could be realistically attributed to benthic processes, and likely reflected a violation of the open water method due to water column stratification. While the use of sensors for estimating complex ecosystem processes holds promise for coastal monitoring programs, careful attention to the sampling design, and to the underlying assumptions of the methods, is critical for correctly interpreting the results. This study demonstrated how using a combination of approaches yielded a fuller understanding of the ecosystem response to hydrologic and seasonal variability.