Net Primary Productivity Values Research Articles

Estimation of Net Primary Productivity and Net Annual Assimilation in the Forests of Kumaun Himalaya

Estimation of carbon uptake by the forests is required to measure the carbon flux of a region. In present study, net primary productivity (NPP) and net annual assimilation (NAA) of carbon was estimated in forests of Kumaun Himalaya by integration of field based measurements and information generated using satellite data. Aboveground NPP was estimated by quantification of aboveground biomass increment, root mortality and litterfall. Root mortality value was added to the biomass accumulation of root component to compute the total belowground productivity. Net Annual Assimilation (NAA) was computed as a difference between carbon uptake in NPP and litterfall plus root mortality. NPP values ranged from 5.20 t/ha/yr (degraded sal forest) to 21.38 t/ha/yr (temperate conifer forest). Total estimated values of net annual uptake of carbon and net annual assimilation of carbon in the study area were 748.93 × 10 4 t/yr and 457.27 × 10 4 t/yr, respectively. Estimation of NPP and NAA are useful for further computation of carbon flux to know the status of forest as sink or source of carbon to the atmosphere.

Variability of Net Primary Productivity and Associated Biophysical Drivers in Bahía de La Paz (Mexico)

The use of information of net primary productivity (NPP) from remote ocean color sensors is increasingly common in marine sciences. The resulting information has been used to explain variations in productivity at different spatio-temporal scales and in the presence of climate phenomena, such as the El Niño Southern Oscillation, and global warming. Satellite remote sensing data were analyzed in Bahía de La Paz (BLP), Mexico, to determine the spatio-temporal variation in NPP. In addition, in situ hydrographic data were obtained to characterize the water properties in the bay. The satellite data agree with in situ measurements, validating the satellite observations over this region. The NPP generally presented seasonal variation with maximum values in winter-spring and minimum values in summer–autumn. The variance explained by NPP from the measured variables was ranked as Chl-a < DEN < SST < PAR < WSC. The highest NPP values generally occurred when subtropical subsurface (SsStW) water was relatively shallow. Due to divergence and mixing processes, this water provided nutrients to the euphotic zone, and consequently an increase in NPP and changes in plankton biomass were observed. The annual trends of the variation in hydrographic data with respect to that of remote sensing data were similar; however, it is necessary to increase the number of data validation studies. The remote sensing and in situ measurements allowed for the main biophysical variables that modulate NPP in different time scales to be identified. The satellite-derived NPP data classifies the BLP as a high productivity zone with 432 g C m−2 year−1. The use of satellite NPP data is satisfactory and should be incorporated into marine primary productivity studies.

Evaluating the dynamics of grassland net primary productivity in response to climate change in China

Net primary productivity (NPP) has been considered as a direct indicator to access the terrestrial primary production. However, considerable uncertainties remain toward the response mechanism of NPP to climate change across annual and seasonal scales, especially for grassland ecosystems. In this study, the spatiotemporal dynamics of grassland NPP and its prominent climate-controlling factor were evaluated based on the CASA model and ground-based meteorological data across annual and seasonal scales in China from 1982 to 2016. Results showed that the annual mean grassland NPP was 294.58 gC·m−2·a−1 over the 35 years; the largest annual mean NPP was observed in Alpine sub-alpine meadow (235.72 ± 13.21 gC·m−2·a−1), while the smallest annual mean NPP value occurred in Desert grassland (97.27 ± 9.64 gC·m−2·a−1). Moreover, the multiyear mean grassland NPP showed a decreasing trend from the southeast to the northwest spatially. Temporally, grassland NPP exhibited a significant increasing trend (slope = 2.4 gC·m−2·a−1; p < 0.0001) over the whole study period; an abrupt change point across the grassland NPP time series was observed in 1999. Specially, 66.34% of the grassland area showed an increasing trend in NPP, and the areas with a significant increasing trend were concentrated in Qinghai-Tibet Plateau and the northern area of Xinjiang. Further climate factor analysis with NPP indicated that NPP positively correlated with precipitation and negatively correlated with temperature for the whole grassland area. In particular, the temperature was a dominant driver in NPP variations for Alpine sub-alpine meadow, Slope grassland and Alpine sub-alpine grassland, while precipitation controlled the most in NPP variations for Plain grassland and Desert grassland. The accumulation of grassland NPP in spring and autumn benefits from the increase in temperature, and precipitation promoted the accumulated NPP in summer and winter.

A LIMNOLOGICAL STUDY OF PRIMARY PRODUCTIVITY IN SEASONAL VARIATIONS OF A TYPICAL TROPICAL POND OF BUNDELKHAND REGION, INDIA

The primary productivity of the Mahil pond has been estimated from March 2017 to February 2018 at four different stations. Various physicochemical parameters and phytoplankton were studied. The seasonal variation of primary productivity revealed that maximum and minimum values of Gross primary productivity and community respiration were associated with rainy and summer seasons respectively. The minimum values of Net primary productivity were recorded during rainy season and maximum during winterfor different study stations.

RELATIONSHIP OF NITRATE AND PHOSPHATE CONCENTRATION ON PHYTOPLANKTON PRIMARY PRODUCTIVITY IN DUMAI RIVERS OF RIAU PROVINCE

This research was conducted in January 2020 in the waters of the Sembilan Dumai River which aims to determine the concentration of nitrate and phosphate on the primary productivity of phytoplankton. The research method used in this research is the survey method while the determination of the research station was done by technic purposive sampling. The results showed that the average nitrate concentration ranged from 0.0194 - 0.0749 mg/l and the average phosphate concentration ranged from 0.1452 - 0.8502 mg/l. There are 6 classes of phytoplankton found in the waters of the Sembilan Dumai River, namely Bacillariophyceae, Cocinodiscophyceae, Chroococcophyceae, Cyanophyceae, Cyanobacteria and Xanthophyceae. The results of phytoplankton abundance calculations ranged from 74.07 - 280.09 Ind/L. The primary productivity value of phytoplankton for gross primary productivity ranged from 62.5 - 104.16 mgC/m2/jam, respiration values ​​ranged from 20.83 - 41.66 mgC/m2/jam and the net primary productivity value ranged from 41.67 - 72.91 mgC/m2/jam. The results of the multiple linear regression test for the relationship between nitrate and phosphate on the primary productivity of phytoplankton at each station are shown by the mathematical equation Y = 60.18 + (-233,19,35) x and Y = 60.18 + 30.44x with the coefficient of determination ( R2) = 0.140 and (R2) = 0.226 and the correlation coefficient (r) = 0.631, the mathematical equation states that the relationship between nitrate and phosphate on the primary productivity of phytoplankton is strong.

Spatio-temporal Variation of Net Primary Productivity of Farmland Ecosystem in Central Yunnan Plateau

Based on MODIS data and CASA (Camegie Ames Stanford Approach) model to estimate the net primary productivity (NPP) of farmland ecosystem in the Central Yunnan Plateau from 1982 to 2019, the spatial autocorrelation method and Sen’ s trend analysis were used to analyze the spatial-temporal variation characteristics of farmland NPP and the influence of climate factors for the last 38 years. The results indicated: The annual NPP of farmland varied from 772.43 to 993.72 g C/(m2⋅a) during 1982 - 2019, with the total mean value of 897.50 g C/(m2⋅a), which had the decrease trend during 1982 - 2000 but showed the increase fluctuation from 2001 to 2019. The total values of NPP tended to stabilize during 1982 - 2019. As for the spatial distribution, the farmland NPP in the southwest low-altitude areas were relatively high (>1500 g C/(m2⋅a)), whereas the farmland NPP in the northeast high-altitude regions had the lower values, especially in Kunming and urbans in central Yunnan (<200 g C/(m2⋅a). From the variation trend, the farmland NPP significantly increased in 31.7% of the agricultural area in the Central Yunnan Plateau, with no obvious change and significant decrease in 37.1% and 31.2%, which was observed for obvious increase tendency in the northeast area. The significant positive relationships were observed for 30.0%, 28.2% and 73.0% of mean pixel NPP with precipitation, temperature and SPEI drought index respectively, which indicated that the farmland ecosystem was largely influenced by drought to a certain extent.

STUDIES ON SEASONAL VARIATIONS IN PRIMARY PRODUCTIVITY AND RELATED WATER QUALITY PARAMETERS IN FRESHWATER FISH PONDS IN COASTAL ANDHRA PRADESH, INDIA

The present study was designed to demonstrate the seasonal variations in physico-chemical parameters in sh ponds and carried out for one year at monthly intervals in ten sh ponds. Maximum value of Gross Primary Production (GPP) and Net Primary Production (NPP) is observed during pre-monsoon and subsequently the lower values during monsoon season correspond to the attenuation of light. A signicant variation in seasonal community respiration was noticed during the study period. Seasonal uctuations in gross and net primary production values were quite apparent in surface waters and showed a bimodal type of distribution. The values were generally high during post winter months (March to June) and low during winter (January) and monsoon months (July and August). The dissolved oxygen content and chlorophyll-a were correlated with increase in temperature and light transparency during the pre-monsoon period whereas the phosphate concentrations were measured maximum in monsoon followed by pre-monsoon and post-monsoon suggested the accumulation of inorganic nutrients through terrestrial catchments

基于改进的CASA模型三峡库区NPP时空特征及气候驱动机制

采用改进后的CASA模型对三峡库区2001-2015年的NPP进行了估算。通过Sen斜率的方法，对NPP的年内及年际时空变化趋势及分布特征进行了分析；基于相关性分析方法，深入探讨了气候因子对NPP的驱动机制；并以气候模式模拟结果为输入项，对NPP的未来变化趋势进行了预测，得到如下结论：（1）2001-2015年间，三峡库区NPP的月值呈单峰型季节变化趋势，峰值达到160 gC m^-2月^-1，发生于7月。NPP年际变化呈波动型上升趋势，幅度较小，多年平均值为727 gC m^-2 a^-1。空间分布上，主要表现为库首库尾较高、库腹较低和长江以北高于长江以南的特点。（2） NPP与降水、气温及净辐射等气候因子之间均呈显著正相关，其中与气温的相关性最强，与降水的相关性最弱，植被生产力对气温的变化更为敏感。（3）未来15年NPP多年平均值为859 gC m^-2 a^-1，总体呈微弱减小趋势，幅度为4.14 gC m^-2 10a^-1。与现状对比来看，未来NPP表现出一定程度的增加，总体而言，三峡库区植被长势趋好，呈良性稳定态势发展。;Net primary production (NPP) in the Three Gorges Reservoir Area (TGRA) during 2001-2015 was estimated using a modified parameter CASA model. The spatial and temporal variation and distribution characteristics of the NPP were analyzed on annual and inter-annual scale based on Sen's slope. According to the correlation analysis method, the driving mechanism of climate factors to NPP was discussed. Then, the NPP in the future was predicted with climate model simulation results as input. The results showed that:(1) from 2001 to 2015, the monthly value of NPP in the TRGA presented a single-peak seasonal variation trend, reached its maximum value of 160 gC m^-2 month^-1 in July. The annual variability of NPP showed a rising trend of fluctuation with a small range, and the multiyear average value of NPP was 727 gC m^-2 a^-1. In terms of the spatial distribution, the main features are higher in head and tail of the reservoir, lower belly of the reservoir and higher north of the Yangtze River than south. (2) The NPP was significantly positively correlated with precipitation, temperature and solar radiation, with the strongest correlation with temperature and the weakest correlation with precipitation, indicating that the vegetation productivity was more sensitive to the change of temperature. (3) In the next 15 years, the multiyear average value of NPP was 859 gC m^-2 a^-1, showed a slight decrease trend, with a range of 4.14 gC m^-2 10a^-1. Compared with the current situation, the NPP showed a certain increase in the future. Generally speaking, the vegetation in the TGRA was growing well and developing in a benign and stable way.

基于多源数据的三江源区生态工程建设前后草地动态变化及驱动因素研究

基于2000-2015年的NDVI、NPP和GPP多源数据，并结合人类干扰强度等级的构建，采用线性回归分析和地理加权回归分析方法，对比分析了在不同干扰等级下三江源区生态工程实施前5年和后10年草地的动态变化及其驱动因素。结果表明：（1）人类干扰强度和NDVI、NPP、GPP在空间上具有显著的区域差异，均表现为从西北向东南增加的趋势，且2006-2010年和2011-2015年草地NDVI、NPP和GPP值明显高于2000-2004年；（2）与2000-2004年相比，2006-2010年草地NDVI、NPP和GPP值的草地退化面积均减少，而2011-2015年退化面积又均增加，表明生态工程建设后的5年较前5年草地退化状况得到改善，然而在下一个5年草地又出现退化趋势；（3）在各人类干扰等级下生态工程实施后的5年内70%以上的草地处于改善状态，均出现退化面积比例显著减少，改善面积比例显著增加的趋势，而在2011-2015后5年草地退化面积比例增加，表明生态工程的实施促进了草地生态系统的改善，尤其在重度人类干扰区，草地由2000-2004年的52.71%退化区域到2006-2010年84.95%的改善区域。（4）影响草地动态变化的主要因素为距离道路的距离、距离居民点的距离、人口密度、干旱、温度和坡度等，各影响因素分布具有明显的空间异质性。研究结果将有助于为三江源区草地生态系统恢复、管理和战略制定提供科学指导和决策依据。;Using Normalized Difference Vegetation Index (NDVI), Net Primary Productivity (NPP) and Gross Primary Productivity (GPP) data from 2000 to 2015 and combining with of human interference level, linear regression analysis and geographically weighted regression (GWR) analysis were used to compare and analyze the grassland dynamics and their driving factors in the Three-River headwaters region before and after the implementation of ecological construction projects. Results showed that:(1) spatially, human interference and NDVI, NPP and GPP had significantly regional differences, which all showed increasing trends from northwest to southeast, and the grassland NDVI, NPP and GPP values during 2006-2010 and 2011-2015 were significantly larger than that during 2000-2004. (2) Compared with 2000-2004, the NDVI, NPP and GPP values of grassland have been improved during 2006-2010 after ecological construction project, while NDVI, NPP and GPP values showed degrading tendencies again during 2011-2015. (3) In all human interference levels, 70% of the grassland was improved within 5 years after the implementation of ecological projects, and the area ratio of degraded grassland significantly decreased and that of the improved grassland showed significant increasing trend, indicating that the implementation of ecological projects has contributed to the improvement of grassland ecosystems. Especially in areas of severe human disturbance, grassland changed from 52.71% degraded areas in 2000-2004 to 84.95% improved areas in 2006-2010. (4) The main driving factors affecting the dynamic changes of grassland were distance to roads, distance to settlements, population density, drought, temperature and topographic slope, and the distribution of each influencing factor had obvious spatial heterogeneity. The study will help to provide scientific guidance and decision-making basis for grassland ecosystem restoration, management and strategy formulation in the Three River Source Region.

Determining the Primary Productivity of the Macrophytes in Tamdil Lake, Mizoram, Northeast India

The present investigation has been carried out for determining the net primary productivity (NPP) of the macrophytes found in Tamdil Lake, Mizoram. Both monthly and daily NPP of the macrophytes were evaluated for a period of two years. The findings clearly indicate that Alternanthera philoxeroides has the highest monthly NPP values (range: 2.18 to 24.42 gm–2 month–1; mean value 18.54 ± 2.12 gm–2 month–1), followed by Echinochloa stagnina (range: 0.91 to 10.94 gm–2 month–1; mean value 7.69 ± 1.97 gm–2 month–1), Eichhornia crassipes (range: 0.63 to 15.93 gm–2 month–1; mean value 12.74 ± 3.14 gm–2 month–1) and Kyllinga tenuifolia (range: 0.20 to 8.61 gm–2 month–1; mean value 7.02 ± 1.95 gm–2 month–1). This was followed progressively by Nymphaea pygmaea helvola with values of 1.08 to 17.11 gm–2 month–1. The monthly NPP of ‘other species’ ranged from 0.38 to 8.01 gm–2 month–1 (mean value 6.06 ± 2.08 gm–2 month–1). The monthly NPP of all the species (combined) reported a range of 0.89 to 119.82 gm–2 month–1 (mean value of 63.50 ± 2.99 gm–2 month–1). For estimation of daily NPP of the macrophytes, Alternanthera philoxeroides reported the peak daily NPP (range: 0.15 to 1.26 gm–2 day–1 with mean value of 0.87 ± 1.39 gm–2 day–1), followed closely by Eichhornia crassipes (range: 0.09 to 0.83 gm–2 day–1; mean value of 0.53 ± 1.42 gm–2 day–1, Nymphaea pygmaea helvola (range: 0.09 to 0.81 gm–2 day–1, mean value of 0.49 ± 2.13 gm–2 day–1), Echinochlo astagnina (range: 0.07 to 0.59 gm–2 day–1 with a mean value of 0.27 ± 0.98 gm–2 day–1. It has been found that the daily NPP of ‘other species’ ranged from 0.03 to 0.47 gm–2 day–1 with a mean value of 0.23 ± 0.92 gm–2 day–1.The daily NPP of all species (combined) ranged from 0.05 to 3.46 gm–2 day–1 with a mean value of 2.47 ± 2.28 gm–2 day–1. The macrophyte NPP varied significantly during the study period. Moderately higher daily NPP values of macrophytes indicates that the lake is approaching towards eutrophic status.

Investigating net primary production in climate regions of central Zagros, Iran, using MODIS and meteorological data

Rangeland production is sensitive to climate conditions. In this study, we monitored actual and potential production in the climate zones of Chaharmahal and Bakhtiari province in central Zagros, Iran, from 2000-2016. Net primary production (NPP), light use efficiency (LUE) and rain use efficiency (RUE) were extracted from climatic and MODIS satellite data using the Carnegie-Ames-Stanford approach (CASA) and Miami models. The accuracy of the modeled NPP maps was assessed using regression analysis, based on field data collected at 750 sites under different rangeland conditions. The spatial distribution of NPP and RUE indicated that annual production and photosynthetic efficiency in degraded rangelands with poor and very poor conditions have decreased compared to those of moderate-good classes. The highest relationship between the field and modeled NPP was associated with the Astragalus spp.-Ferula spp. (R2 = 0.865, p &lt; 0.001) in the humid and cold climate zone with good rangeland conditions while the lowest was observed in the annual grasses-annual forbs (R2 = 0.198, p &lt; 0.001) vegetation type with very poor rangeland conditions within the semi-arid and cold climate zone. Furthermore, the highest and lowest NPP values were observed in the Daphne mucronata-Prangos ferulacea (48.38 g C m-2 yr-1) and annual grasses-annual forbs (3.42 g C m-2yr-1) vegetation types with LUE values of 0.13 and 0.02 g C MJ-1 within the humid and cold and the semi-humid and cold climate zones, respectively. According to these findings, remote sensing-based differences between actual and potential NPP can be used as a valuable tool for identification of human impacts on broad rangeland ecosystems.

CO2 fertilization, transpiration deficit and vegetation period drive the response of mixed broadleaved forests to a changing climate in Wallonia

The change in forest productivity was simulated in six stands in Wallonia (Belgium) following different climate scenarios using a process-based and spatially explicit tree growth model. Simulations revealed a strong and positive impact of the CO 2 fertilization while the negative effect of the transpiration deficit was compensated by longer vegetation periods. The site modulated significantly the forest productivity, mainly through the stand and soil characteristics. Forest net primary production (NPP) reflects forest vitality and is likely to be affected by climate change. Simulating the impact of changing environmental conditions on NPP and two of its main drivers (transpiration deficit and vegetation period) in six Belgian stands and decomposing the site effect. Based on the tree growth model HETEROFOR, simulations were performed for each stand between 2011 and 2100 using three climate scenarios and two CO2 modalities (constant vs time dependent). Then, the climate conditions, soils and stands were interchanged to decompose the site effect in these three components. In a changing climate with constant atmospheric CO2, NPP values remained constant due to a compensation of the negative effect of increased transpiration deficit by a positive impact of longer vegetation periods. With time-dependent atmospheric CO2, NPP substantially increased, especially for the scenarios with higher greenhouse gas (GHG) emissions. For both atmospheric CO2 modalities, the site characteristics modulated the temporal trends and accounted in total for 56 to 73% of the variability. Long-term changes in NPP were primarily driven by CO2 fertilization, reinforced transpiration deficit, longer vegetation periods and the site characteristics.

Tuzlu ve Sodik Arazilerde Islah ve Tarımsal Faaliyetler Sonrası Arazi Tahribatının Dengelenmesinin İzlenmesi

Tarım arazilerinin doğal veya insan kaynaklı etkiler ile bozulmasının önlenmesi ve tahrip olan arazilerin geri kazanımı son zamanlarda birçok ülkenin en önemli stratejik hedefleri arasına girmiştir. Bu kapsamda, arazi tahribatının dengelenmesi (ATD) kavramı, arazi bozulması oranının düşürülmesi ve bozulmuş alanların iyileştirilme oranının artırılmasının göstergesi olarak tanımlanmaktadır. Bir bölgede veya karasal ekosistemde verimli arazi alanı ve dolayısıyla sürdürülebilir arazi kullanımı sabit kaldığında veya arttığında ATD’ye ulaşıldığı düşünülebilir. Bu çalışmada, doğal olarak oluşmuş tuzlu/sodik özelliklere sahip merada, ıslah faaliyetleri ve sonrası başlatılan tarımsal üretimin etkileri, ATD çerçevesinde değerlendirilmiştir. ATD’nin değerlendirilmesinde, meranın ıslah sonrası tarımsal faaliyetler altındaki üretkenliği, ıslah öncesi ve ıslah sonrası dönemlere ait normalize edilmiş fark bitki örtüsü indeksi (NDVI), net birincil verimlilik (NPP) ile toprak organik karbon stoku (TOCS) verileri kullanılmıştır. Tüm alanda sulama imkânı bulunmadığından yaklaşık 1200 hektarlık alanda ıslah çalışması yürütülmüştür. Bu kapsamda 2008 ve 2012 yıllarında çalışma alanında 202 noktadan bozulmuş ve bozulmamış toprak örnekleri alınmıştır. Toprak örneklerinin organik madde (OM), hacim ağırlığı, toprak reaksiyonu (pH) ve elektriksel iletkenlikleri (EC) belirlenmiş ve değerlendirilmiştir. Islah kapsamındaki arazilerde başlangıçta ortalama 40.51 ton ha-1 olan TOCS, ıslah ve tarımsal faaliyetler sonrası 44.68 ton ha-1’a çıkmıştır. Islah öncesi -0.044 ile + 0.060 ve 125 ile 250 g C m-2 arasında olan NDVI ve NPP değerleri, ıslah sonrası önemli bir artış göstererek, 2013 ve 2017 yıllarında sırası ile 0.234-0.551 ve 0.419-0.631 ve 200-475 g C m-2 ve 200-407 g C m-2 aralığında kayıt edilmiştir. Islah çalışması yürütülen alanlarda ıslah öncesi ortalama OM değeri % 2.09 iken, ıslah sonrası ortalama % 2.16’ya çıkmıştır. EC değerleri ise 4.08 dS m-1’den 2.26 dS m-1’e düşmüştür. Elde edilen bulgular arazi ıslah çalışmalarında benimsenen arazi yönetim uygulamalarının arazi üretkenliğine dolayısı ile ATD'ye olumlu bir etki yaptığını ortaya koymaktadır. Aynı zamanda bu çalışma, arazi bozulması ve dengelenmesinin izlenmesi için güncel veri tabanlarının önemini de ortaya koymaktadır.

Impact of climate change on net primary production (NPP) in south Iran.

Climate change is a natural hazard which threatens the sustainable development of human health, food security, economic well-being, and natural resources. It also affects photosynthesis, plant respiration, and decomposition of organic matter that contribute to atmospheric carbon flow. The net primary production (NPP) is one of the main components of carbon balance. This study investigated the impact of climatic change on the net production in the Hormozgan county in south Iran. To obtain NPP, MODIS NPP product (MOD17A3) was used and future temperature and precipitation values were obtained using the HadGEM2-ES model under the RCP4.5 scenario. These values were downscaled using the LARSWG 6 statistical model, and precipitation and temperature were simulated for the RCP4.5 scenario. For further analysis, NPP was simulated based on the BIOME-BGC model and compared with the NPP data obtained from the MODIS images. Comparison of the climatic parameters of the basic (2001-2015) and future (2016-2030) periods indicated an increase in precipitation, minimum temperature, and maximum temperature of the study area and subsequently an increase in the NPP value in all biomes (averagely 17.73%) in the future. The highest NPP values were observed in the central and western parts of the region in biomes 4 (mangrove forest cover), 10 (broadleaf forest vegetation), and 6, 5, and 1 (rangeland vegetation), respectively, and the lowest values were observed in the eastern parts. Results showed that the increase in future NPP could be due to the increase in precipitation.

Contribution of unvegetated tidal flats to coastal carbon flux.

Unvegetated flats occupy a large area in the intertidal zone. However, compared to vegetated areas, the carbon sequestration of unvegetated tidal flats is rarely quantified, even though these areas are highly threatened by human development and climate change. We determined benthic maximum gross primary production (GPPm ), net primary production (NPP) and total respiration (TR) during emersion on seven tidal flats along a latitudinal gradient (from 22.48°N to 40.60°N) in winter and summer from 2012 to 2016 to assess the spatial and temporal variability of carbon dioxide flux. In winter, these processes decreased by 89%-104% towards higher latitudes. In summer, however, no clear trend was detected across the latitudinal gradient. Quadratic relationships between GPPm , NPP and TR and sediment temperature can be described along the latitudinal gradient. These curves showed maximum values of GPPm and NPP when the sediment temperatures reached 28.7 and 26.6°C respectively. TR increased almost linearly from 0 to 45°C. The maximum daily NPP across the latitudinal gradient averaged 0.24±0.28gCm-2 day-1 , which was only 10%-20% of the global average of NPP of vegetated coastal habitats. Multiplying with the global area of unvegetated tidal flats, our results suggest that the contribution of NPP on unvegetated tidal flats to the coastal carbon cycle is small (11.04±13.32TgC/year). If the land cover of vegetated habitats is continuously degraded to unvegetated tidal flats, the carbon sequestration capacity in the intertidal zone is expected to reduce by at least 13.10TgC/year, equivalent to 1% of global carbon emissions from land-use change.

Effects of spatial\u2013temporal land cover distribution on gross primary production and net primary production in Schleswig-Holstein, northern Germany

BackgroundAnnual total Gross Primary Production (GPP) and Net Primary Production (NPP) and the annual total stored GPP and NPP are tightly coupled to land cover distributions because the distinct vegetation conditions of different land cover classes strongly affect GPP and NPP. Spatial and statistical analysis tools using Geographic Information Systems (GIS) were used to investigate the spatial distribution of each land cover class and the GPP and NPP based on the CORINE land cover classification in the federal state, Schleswig-Holstein, Germany for the years 2000, 2006 and 2012.Results“Non-irrigated arable land” and “pastures” were the dominant land cover classes. Because of their large area, “non-irrigated arable land” and “pastures” had higher annual total stored GPP and NPP values than the other land cover classes. Annual total GPP and NPP hotspots were concentrated in the central-western part of Schleswig-Holstein. Cold spots were mainly located in the western and eastern Schleswig-Holstein. The distributions of the annual total GPP and NPP hotspots and cold spots were primarily determined by land cover and land cover changes among the investigated years. The average annual total NPP/GPP ratios were 0.5647, 0.5350 and 0.5573 in the years 2000, 2006 and 2012, respectively. The calculated respiration in 2006 was the highest, followed by those in 2012 and 2000.ConclusionsThe land cover classes with high-ability of carbon stocks in 2000, 2006 and 2012 in Schleswig-Holstein were identified in this study. Furthermore, it is recommendable to enhance the annual total GPP and NPP and the annual total stored GPP and NPP in Schleswig-Holstein by replacing the land cover classes showing low carbon stock capabilities with the classes showing high abilities for the purpose of increasing greenhouse gas fixation.

Simulation of climate change and thinning effects on productivity of Larix olgensis plantations in northeast China using 3-PGmix model

Understanding the effects of thinning on forest productivity under climate change is vital to adaptive forest management. In the present study, the 3-PGmix model was applied to simulate the thinning effects on productivity of Larix olgensis plantations under climate change using 164 sample plots collected from the 6th, 7th and 8th National Forest Inventories in Jilin Province, northeast China. Climate scenarios of RCP 4.5 and RCP 8.5 were adopted from 2011 to 2100 with corresponding reference years (1981–2010). We simulated four cutting intensities: no-thinning, NT; low intensity thinning with 10% stem removal, LT; moderate thinning with 20% stem removal, MT and heavy thinning with 30% stem removal, HT for three times with 5- and 10-year thinning intervals. The results indicated that the mean net primary productivity (NPP) during the simulated 90 years was increased under RCP 4.5 and RCP 8.5. The LT and MT had positive but HT had negative effects on the mean NPP for the same climate scenario. Increased thinning intensity facilitated the positive effects of climate change on NPP but without a significant interaction effect. During the simulation, LT had the highest NPP value and HT had the biggest NPP increase under future climate change. We also discussed the management of larch plantations under climate change and advocated low intensity thinning with 10-year thinning interval to gain maximum NPP for mitigating climate change.

Using SMOS soil moisture data combining CO2 flask samples to constrain carbon fluxes during 2010–2015 within a Carbon Cycle Data Assimilation System (CCDAS)

The terrestrial carbon cycle is an important component of the global carbon budget due to its large gross exchange fluxes with the atmosphere and their sensitivity to climate change. Terrestrial biosphere models show large uncertainties in simulating carbon fluxes, which impact global carbon budget assessments. The land surface carbon cycle is tightly controlled by soil moisture through plant physiological processes. Accurate soil moisture observations thereby have the potential to improve the modeling of carbon fluxes in a model-data fusion framework. We employ the Carbon Cycle Data Assimilation System (CCDAS) to assimilate six years of surface soil moisture provided by the SMOS satellite in combination with global-scale observations of atmospheric CO2 concentrations. We find that assimilation of SMOS soil moisture exhibits better performance on soil hydrology modeling at both global and site-level than only assimilating atmospheric CO2 concentrations, and it improves the soil moisture simulation particularly in mid- to high-latitude regions where the plants suffer from water stress frequently. The optimized model also shows good agreements with inter-annual variability in simulated Net Primary Productivity (NEP) and Gross Primary Productivity (GPP) from an atmospheric inversion (Jena CarboScope) and the up-scaled eddy covariance flux product (FLUXNET-MTE), respectively. Correlation between SIF (Solar Induced Fluorescence) and optimized GPP also shows to be the highest when soil moisture and atmospheric CO2 are simultaneously assimilated. In general, CCDAS obtains smaller annual mean NEP values (1.8 PgC/yr) than the atmospheric inversion and an ensemble of Dynamic Global Vegetation Models (DGVMs), but larger GPP values (167.8 PgC/yr) than the up-scaled eddy covariance dataset (FLUXNET-MTE) and the MODIS based GPP product for the years 2010 to 2015. This study demonstrates the high potential of constraining simulations of the terrestrial biosphere carbon cycle on inter-annual time scales using long-term microwave observations of soil moisture.

Influence of climate variations on primary production indicators and on the resilience of forest ecosystems in a future scenario of climate change: Application to sweet chestnut agroforestry systems in the Iberian Peninsula

Abstract Sweet chestnut agroforestry systems make valuable contributions to the landscape and environment, fulfilling fundamental functions and processes. Net primary production (NPP) and carbon use efficiency (CUE) are commonly used as ecological indicators to evaluate the responses of the terrestrial carbon cycle to climate change. Nonetheless, although climate-induced primary production changes have been widely documented at the global scale, few studies have addressed this issue at local scale in relation to sweet chestnut forests. Data from 65 climate maps and MODIS remote-sensed data captured in the Iberian Peninsula between 2000 and 2015 were analysed in this study. Different statistical methods (Linear Regression and Classification and Regression Trees) were used to analyse the potential influence of climate change on sweet chestnut primary production, thus enabling assessment of ecosystem and ecosystem service (ES) supply and of the resilience of these systems in a future scenario of climate change in the Iberian Peninsula. The findings for the whole of the Iberian Peninsula show that NPP and CUE are negatively correlated with temperature variables and positively correlated with latitude. High NPP values mainly corresponded to northern Spain, which is characterised by cold, humid conditions. The CUE values were highest in northern Portugal, mainly in managed, monospecific forest. Overall, the fitted models showed a temporary response in which the monthly variables were particularly important and water availability was more important than temperature. The findings suggest that precipitation is not a limiting factor in Atlantic areas, but that water availability tends to be a limiting factor in Mediterranean areas. However, mean annual temperature (MAT) is also an important driver of sweet chestnut production and may be a limiting factor in a future scenario of climate change. Regions of Provenance (RoP) proved useful for explaining NPP and CUE and classifying the sweet chestnut agroforestry systems. Finally, the study findings also revealed that Iberian sweet chestnut ecosystems and the associated ES supplies are at risk of being seriously affected or even disappearing as a result of climate change, especially in some Mediterranean areas of southern and central Spain.

Scale effects of sediment retention, water yield, and net primary production: A case‐study of the Chinese Loess Plateau

AbstractEcosystem services are generated by ecological processes over a range of scales. Studying the scale effects on ecosystem services is important for exploring the driving mechanisms and conducive to prudent ecological managements. Unfortunately, quantitative testing the scale effects of ecosystem services' associations, as well as identifying the driving mechanisms across scales, has rarely been documented. This study used the Loess Plateau as study area to test the scale effects and the correlations between sediment retention, water yield, and net primary production (NPP) and their driving mechanisms. A model of Integrated valuation of Ecosystem Services and Tradeoff 3.0 and the Carnegie‐Ames‐Stanford Approach were used to assess the services of sediment retention, water yield, and NPP in 2000 and 2008. Canonical correlation analysis (CCA) was used to quantify the driving mechanisms of ecosystem services. The results indicated that the ecosystem services are more varied in spatial patterns at small scale than at large scale. The average values of sediment retention, water yield, and NPP at small scale increased during the period. However, at large scale, the average values of sediment retention and water yield decreased and the NPP value increased simultaneously. Generally, the correlations between ecosystem services weakened when the spatial scale increased. The results from CCA indicated that, at small scale, the natural factors of precipitation, hours of sunshine, and temperature were the principal driving factors underlying ecosystem services. When the scale increased, the socioeconomic factors of population, grain production, and nonfarming production were gradually integrated into the factors driving the patterns of ecosystem services.