Average Annual Net Primary Production Research Articles

A High-Resolution Simulation of Forest Ecosystem Carbon Budget Change with Complex Terrain

Forest ecosystems represent important carbon sinks within terrestrial ecosystems. Simulating carbon budgets in forest ecosystems located within complex terrains forms the foundation for understanding global carbon cycle dynamics. In this study, employing the FORCCHN model and utilizing mountain climate data as forcing parameters, the impact of the terrain factors of the Changbai Mountain Nature Reserve on carbon budget change in 1998–2017 was studied. The dynamics and distribution patterns of carbon fluxes at different slope aspects and elevations were discussed. Findings demonstrated that between 1998 and 2017, the per-unit area gross primary production (GPP), net primary production (NPP), and net ecosystem production (NEP) for the Changbai Mountain Reserve were 839.35, 462.03, and 192.72 gC m −2 a −1 , respectively. The carbon fluxes varied significantly with elevation: the GPP of the north, south, and west and the NPP of the east, south, and west decreased, and the NEP of the south and west increased. The total amount in GPP and NPP of the Changbai Mountain Nature Reserve fluctuated slightly year by year, but the carbon sequestration capacity decreased from year to year. The reserve had an average annual total GPP, NPP, and NEP of 1.62, 0.89, and 0.37 TgC a −1 , respectively. The north was the strongest carbon sink in the study area, contributing 35.98%, 35.88%, and 36.80% to the total amount of GPP, NPP, and NEP, respectively. This study emphasized the significance of precise mountain meteorological data to accurately quantify the carbon fluxes of mountain forest ecosystems.

Regional Contribution and Attribution of the Interannual Variation of Net Primary Production in the Yellow River Basin, China

Net primary production (NPP) serves as a crucial indicator of the ecosystem’s capacity to capture atmospheric CO2. Gaining insights into the dynamics of NPP and its driving mechanisms is pivotal for optimizing ecosystem carbon sink resource management. Since the implementation of the Grain-for-Green Program (GFGP) in 1999, the Yellow River Basin (YRB) has been one of the most significant areas for ecological restoration in China. However, our knowledge regarding the interannual variability (IAV) of NPP and the underlying driving forces in this region remains incomplete. In this study, we utilized a light use efficiency model to assess the spatiotemporal dynamics, IAV, and driving factors of NPP in the YRB during the period from 1999 to 2018. Our findings revealed that the average annual NPP in the YRB approximated 189.81 Tg C. Over the study duration, NPP significantly increased in 79.63% of the basin with an overall increasing rate of 6.76 g C m−2 yr−1. The most prominent increase was observed in the key GFGP implementation area, predominantly in the semi-humid region. Notably, the middle altitude region (1–1.5 km), semi-humid region, and grassland emerged as the primary contributors to the basin’s total vegetation carbon sequestration. However, it is worth emphasizing that there was substantial IAV in the temporal trends of NPP, with the semi-humid region being the most influential contributor (62.66%) to the overall NPP IAV in the YRB. Further analysis of the driving mechanisms unveiled precipitation as the primary driver of NPP IAV in the YRB with a contribution of 62.9%, followed by temperature (23.07%) and radiation (14.03%). Overall, this study deepened our understanding of the IAV and driving mechanisms of NPP in the YRB under ecological restoration, and provided scientific support for optimizing the management of regional carbon sequestration resources.

Dynamic Changes and Driving Mechanisms of Net Primary Production (NPP) in a Semi-Arid Region of China

The objective of this study is to analyze the spatiotemporal dynamics of net primary production (NPP) change combined with land use and to further explore the driving factors of NPP change, allowing us to provide a scientific reference point for optimizing the land-use structure and improving regional carbon sequestration capacity. The average annual NPP ranged from 200 to 300 gC/m2•a in the period of 2001–2020 in our study area. We used trend analysis and linear regression analysis to explore the spatial and temporal dynamic changes in annual NPP and analyzed the driving mechanism in a semiarid region (western Jilin Province) of China in the period of 2001–2020. The results showed that NPP presented a trend of fluctuating growth, and the spatial distribution of NPP showed that NPP values of cultivated land, forest and grassland were generally higher than those of other land-use types. The high value in the southeastern region and low value in the northwestern region were identified because there were large areas of cultivated land distributed in the southeastern part of the study area in the period of 2001–2020. The main driving factors that affected NPP were annual precipitation, CO2 emissions, GDP and hours of sunshine. NPP was positively correlated with annual precipitation, CO2 emissions and GDP, and it had a significant negative correlation with hours of sunshine. Our study provides important support for research into land-use structure and improvements to the regional carbon sequestration capacity, making an important contribution to regional sustainable development.

Spatiotemporal variation of marsh vegetation productivity and climatic effects in Inner Mongolia, China

Net primary productivity (NPP) is a vital ecological index that reflects the ecological function and carbon sequestration of marsh ecosystem. Inner Mongolia has a large area of marshes, which play a crucial role in the East Asian carbon cycle. Under the influence of climate change, the NPP of Inner Mongolian marsh has changed significantly in the past few decades, but the spatiotemporal variation in marsh vegetation NPP and how climate change affects marsh NPP remain unclear. This study explores, for the first time, the spatiotemporal variation of marsh NPP and its response to climatic change in Inner Mongolia based on the MODIS-NPP and climate datasets. We find that the long-term average annual NPP of marsh is 339.85 g⋅C/m2 and the marsh NPP shows a significantly increasing trend (4.44 g⋅C/m2/a; p < 0.01) over Inner Mongolia during 2000–2020. Spatially, the most prominent increase trend of NPP is mainly distributed in the northeast of the region (Greater Khingan Mountains). The partial correlation results show that increasing autumn and summer precipitation can increase the NPP of marsh vegetation over Inner Mongolia. Regarding the temperature effects, we observe a strong asymmetric effect of maximum (Tmax) and minimum (Tmin) temperature on annual NPP. A high spring Tmax can markedly increase marsh NPP in Inner Mongolia, whereas a high Tmin can significantly reduce it. In contrast to spring temperature effects on NPP, a high summer Tmax can decrease NPP, whereas a high Tmin can increase it. Our results suggest different effects of seasonal climate conditions on marsh vegetation productivity and highlight the influences of day-time and night-time temperatures. This should be considered in simulating and predicting marsh carbon sequestration in global arid and semi-arid regions.

NPP Variability Associated with Natural and Anthropogenic Factors in the Tropic of Cancer Transect, China

The regions near the Tropic of Cancer are a latitudinal geographical zone with typical climatic, topographic, and human landscape features. It is necessary to explore the region’s net primary productivity (NPP) dynamics as it combines complex topography, various vegetation types, and intense human activities. The study sets the transect near the Tropic of Cancer (TCT) and uses the Carnegie–Ames–Stanford (CASA) model to estimate the NPP from 2000 to 2020. After using the RESTREND method, the paper calculates and compares the relative contributions of climate variability and anthropogenic activities to NPP changes. Finally, the geographical detector (Geodetector) model is applied to evaluate how anthropogenic and natural factors affect spatial distribution patterns and NPP changes. The results indicated that the average annual NPP is 820.39 gC·m−2·yr−1 during the 21 years. In addition, when the NPP varies, it increases over the entire study area, with a slope of 4.81 gC·m−2·yr−1, particularly in the western region. Across the entire research area, 63.39% and 77.44% of the total pixels positively contribute to climate variability and human activities in NPP, with a contribution of 0.90 and 3.91 gC·m−2·yr−1, respectively. Within the western, central, and eastern regions, anthropogenic activities have a stronger impact on NPP than climate variability, particularly pronounced in the eastern region. Furthermore, vegetation cover is the dominant factor in the spatial patterns and NPP trends across the TCT and the three regions. In contrast, climate factors are shown to be less influential in NPP distribution than in the western region. The results also demonstrated that the effect of population density and the GDP on NPP gradually rises. Two-factor interaction is much larger than any individual factor, with the dominant interaction factor being vegetation cover with climatic factors. Lastly, the findings revealed that anthropogenic activities positively promote NPP accumulation across the TCT, thus highlighting the importance of human activity-led ecological restoration and ecological protection measures that contribute to regional carbon sequestration and carbon balance.

Modeling carbon uptake by vegetation of grassland ecosystems and its associated factors in China based on remote sensing

In order to reveal the spatial variation characteristics and influencing factors of grassland net primary productivity (NPP) in China, this paper uses remote sensing data, land use data and meteorological data to simulate and estimate China’s grassland net primary productivity from 2001 to 2019 using the Carnegie-Ames-Stanford Approach (CASA). The trend analysis and complex correlation analysis were used to analyze the relationship with the temporal and spatial changes of grassland NPP from the perspectives of climate factors, topography, longitude and latitude. The results show that: 1) In the past 19 years, the China’s grassland NPP has generally shown a fluctuating upward trend, the spatial distribution of NPP variation shows a characteristic of low in the west and high in the east, with the increased area accounting for 70.39% of the total grassland area, and the low NPP values are mainly distributed in the northwestern part of Tibet and Qinghai and the central part of Inner Mongolia, the average annual NPP is 257.13 g C·m−2·a−1. 2) The change of mean NPP value of grassland in China is more dependent on precipitation (p) than air temperature (T). 3) Grassland NPP showed a decreasing trend with the increase of altitude, and the NPP on the gradient with DEM between 200 m and 500 m was the highest (483.86 g·C·m−2·a−1); The maximum annual mean value (448.42 g C·m−2·a−1) is fallen over the sharp slope of 35°–45°; the NPP of grassland increases with the slope (from shade to sunny), and the NPP of grassland on the semi-sunny slope increases. The annual average NPP is the highest (270.87 g C·m−2·a−1). 4) The mean value of grassland NPP was negatively correlated with the change of latitude, and showed a “wave-like” downward trend from south to north; the mean value of grassland NPP was positively related to the change of longitude. The correlation relationship shows a “stepped” upward trend from west to east.

Responses of Forest Net Primary Productivity to Climatic Factors in China during 1982-2015.

Forest ecosystems play an important role in the global carbon cycle. Clarifying the large-scale dynamics of net primary productivity (NPP) and its correlation with climatic factors is essential for national forest ecology and management. Hence, this study aimed to explore the effects of major climatic factors on the Carnegie-Ames-Stanford Approach (CASA) model-estimated NPP of the entire forest and all its corresponding vegetation types in China from 1982 to 2015. The spatiotemporal patterns of interannual variability of forest NPP were illustrated using linear regression and geographic information system (GIS) spatial analysis. The correlations between forest NPP and climatic factors were evaluated using partial correlation analysis and sliding correlation analysis. We found that over thirty years, the average annual NPP of the forests was 887 × 1012 g C/a, and the average annual NPP per unit area was 650.73 g C/m2/a. The interannual NPP of the entire forest and all its corresponding vegetation types significantly increased (p < 0.01). The increase in the NPP of evergreen broad-leaved forests was markedly substantial among forest types. From the spatial perspective, the NPP of the entire forest vegetation gradually increased from northwest to southeast. Over the years, the proportions of the entire forest and all its corresponding vegetation types with a considerable increase in NPP were higher than those with a significant decrease, indicating, generally, improvements in forest NPP. We also found climatic factors variably affected the NPP of forests over time considering that the rise in temperature and solar radiation improved the interannual forest NPP, and the decline in precipitation diminished the forest NPP. Such varying strength of the relationship between the interannual forest NPP and climatic factors also varied across many forest types. Understanding the spatiotemporal pattern of forest NPP and its varying responses to climatic change will improve our knowledge to manage forest ecosystems and maintain their sustainability under a changing environment.

Temporal and Spatial Variation of Vegetation in Net Primary Productivity of the Shendong Coal Mining Area, Inner Mongolia Autonomous Region

Coal mining can cause significant local environmental damage while driving the regional economy of an area. The key index of net primary productivity (NPP) measures the amount of energy made available in an ecosystem and serves as a useful metric for understanding vegetation restoration in mining areas. This study used a CASA model to estimate the vegetation NPP of the Ordos area of the Shendong coal fields from 2000 to 2019. Model output, human factors, and regional meteorological data were subjected to trend analysis, significance testing, partial correlation analysis, and residual analysis. The NPP data generated by a CASA model inversion approximated measured data to a reasonable degree. The average annual NPP of the vegetation in the study area from 2000 to 2019 was 44.51 g C/m2 a. In general, NPP showed a fluctuating upward trend, with slower increases before 2011 and more rapid increases after 2011. The trend exhibited considerable spatial heterogeneity. Areas with increasing NPP accounted for 21.54% of the study area and occurred mainly in the Dongsheng District, the Kangbashi District, and areas bordering the Ejin Horo Banner. Analysis detected consistent spatial variation between NPP and each factor in the study area. NPP is positively correlated with precipitation and human activities and negatively correlated with air temperature. The change in vegetation cover depended on both human activity and meteorological conditions. In terms of the strength of influence on vegetation NPP, human activity exceeded climate, followed by temperature and precipitation. Although the NPP of vegetation in the region directly affected by coal mining shows a trend of improvement, it is still lower than that in the natural growing region. In the next step, the ecological restoration of vegetation should be further strengthened to achieve regional ecological balance.

Asymmetric Impacts of Diurnal Warming on Vegetation Carbon Sequestration of Marshes in the Qinghai Tibet Plateau

AbstractAs the world's Third Pole, the Qinghai‐Tibet Plateau has a large area of marshes, which plays an important role in global carbon cycle. The net primary productivity (NPP) of vegetation is a crucial index for measuring the carbon flux of marsh ecosystems. Understanding the change in marsh NPP and its response to climatic change is important for assessing carbon sequestration of marsh ecosystems. Based on MODIS NPP data and climate data from 2000 to 2020, this study analyzed the spatiotemporal change in marsh NPP and determined its relationship with climate factors on the Qinghai‐Tibet Plateau. The results showed that the average annual NPP of marshes on the Qinghai‐Tibet Plateau increased significantly by 11.70 ± 1.07 g C·m−2/10a during 2000–2020, with an average value of about 184.37 ± 11.12 g C·m−2. Spatially, the annual marsh NPP showed obviously increasing trend in the northeast but decreasing trend in the southwest regions. Daytime maximum and nighttime minimum temperatures had asymmetric effects on marsh NPP, with a larger positive effect of minimum temperature. Warmed minimum temperatures in winter and spring significantly increased the annual marsh NPP on the Qinghai‐Tibet Plateau. The increasing maximum and minimum temperatures in the summer obviously promoted the vegetation growth in marshes. Additionally, the increasing spring precipitation could significantly increase the marsh NPP. Our results highlight that the asymmetric impacts of daytime and nighttime temperatures on marsh vegetation should be adequately considered in predicting marsh carbon sequestration on the Qinghai‐Tibet Plateau, especially in the context of global asymmetric diurnal warming.

Monitoring the impacts of cultivated land quality on crop production capacity in arid regions

Cultivated land plays a vital role in human survival and the development of human civilization. The cultivated land quality (CLQ) is of considerable significance for ensuring food security and social stability. Although studies have been conducted to assess CLQ, efforts regarding the quantitative impacts of CLQ on crop production capacity are still scarce, especially in arid regions. Understanding such a question greatly benefits land resources management and sustainable development of oasis agriculture. The objective of this study is to explore the spatiotemporal variations of CLQ and to quantify the impacts of CLQ on crop production capacity via an ordinary linear regression (OLS) model and correction analysis in arid regions. The Delphi-AHP (analytic hierarchy process) method is applied to assess CLQ in this study with the highest accuracy (96.35%). The average score of cultivated land quality (S-CLQ) is 58.75 in the study area. The results further suggest that the quality of decreasing cultivated land (61.53) is much higher than that of increasing cultivated land (57.99). We use net primary productivity (NPP) calculated by the vegetation photosynthesis model (VPM) to simulate the crop production capacity and find that CLQ has a significant positive impact on crop production capacity (R2 = 0.706). The distribution of average annual NPP is similar to that of CLQ. 62.41% of cultivated land shows an increasing trend in annual NPP, whereas 37.57% of cultivated land shows a decreasing trend. Pearson coefficient by intervals is calculated to identify areas where crop production capacity does not match the quality of cultivated land. The results reveal considerable differences in the Pearson coefficient in various intervals (negative correlation in 5 intervals and positive correlation in 10 intervals). This research quantifies the impacts of CLQ on crop production capacity and provides a way to accurately capture the location of cultivated land that needs to be improved in arid regions.

土地利用转变与海拔高度协同作用黄土高原植被固碳变化特征

PDF HTML阅读 XML下载 导出引用 引用提醒 土地利用转变与海拔高度协同作用黄土高原植被固碳变化特征 DOI: 10.5846/stxb202106211643 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 陕西省自然科学基础研究计划项目（2017JZ008） Vegetation carbon sequestration in the Loess Plateau under the synergistic effects of land cover change and elevations Author: Affiliation: 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:全球固碳释碳问题一直是近年来关乎民生的热点话题，区域碳源/碳汇对生态环境的重要性不言而喻。基于CASA模型估算黄土高原1990-2015年植被净初级生产力的年际变化，并分析土地利用变化、海拔高度及两者协同作用对其综合影响，结果表明：（1）黄土高原1990-2015年植被NPP与植被固碳总体呈增加趋势，年均NPP增速2.74 gC m-2 a-1，年均固碳增速1.13 TgC/a，研究区林地年均NPP （619.5 gC m-2 a-1）远超其他用地类型，固碳效果理想；（2）黄土高原年均NPP随高程的增加先降低后升高，年总NPP和固碳量随高程增加变化趋势相反；（3）研究区土地利用转变类型中退耕还林的植被固碳效果最好；而林地变为耕地或草地均不能达到固碳目的，此外，更推荐在研究区海拔低于1500 m变草为耕，海拔高于1500 m退耕还草，海拔高于3000 m变耕、草为林。以期为区域尺度的生态环境建设提供一定的参考和科学依据。 Abstract:Global carbon sequestration and release has been a hotspot issue concerning people's livelihood in recent years. The importance of regional carbon sequestration and release to the ecological environment was self-evident. It is of great theoretical and practical significance to use remote sensing data and appropriate estimation model to quantitatively estimate NPP (Net Primary Productivity) and analyze spatio-temporal pattern of vegetation carbon sequestration and carbon release in the Loess Plateau. Based on the CASA (Carnegie Ames Stanford Approach) model, this paper estimated the annual change of the NPP on the loess plateau from 1990 to 2015, and analyzed the comprehensive effects in the process of Land Use/Land Cover Change (LUCC), elevations and their synergistic effects. It found that:(1) vegetation NPP and carbon sequestration showed an increasing trend in the Loess Plateau from 1990 to 2015. The annual average growth rate of NPP was 2.74 gC m-2 a-1 and the annual average growth rate of carbon sequestration was 1.13 TgC/a. The average annual NPP (619.5 gC m-2 a-1) of forest land in the study area was much higher than that of other land types, which was an ideal means of carbon sequestration. (2) The annual mean NPP of the Loess Plateau increased year by year, but the annual mean annual NPP decreased first and then increased with the increase of elevation, while the annual total NPP and carbon sequestration showed opposite trends with the increase of elevation. (3) In the study area, conversion of cropland to forest contributed the most to vegetation carbon sequestration among all land use changes types, meanwhile, the conversion of forest into cropland or grassland could not achieve carbon sequestration. In addition, it is recommended to convert grassland to cropland when the elevation is lower than 1500 m, return cropland to grassland when the elevation is higher than 1500 m, and convert cropland and grassland to forest when the elevation is higher than 3000 m in the study area. The study focuses on the effect of carbon sequestration under the synergistic effect of land use change and elevations. It is concluded that the development and utilization of land in the study area leads to the increase of carbon sequestration, while the ecological return of land leads to the increase of carbon sequestration; Moreover, it is more suitable to convert cropland to forest at low and high altitude regions than at middle altitude in the study area, in order to provide reference and guidance for the ecological environment in the regional scale. 参考文献 相似文献 引证文献

Contributions of climate change and human activities to vegetation dynamics in Qilian Mountain National Park, northwest China

A series of policies have been implicated in the Qilian Mountain National Park (QLMNP) to combat climate change (CC). Distinguishing the impacts of CC and human activities (HA) on vegetation dynamics in QLMNP is crucial for policies implementation and ecological conservation. Here, we quantify the contributions of CC and HA to net primary productivity (NPP) using partial derivatives and dividing them into six different scenarios. The results indicated that the average annual NPP over the whole park significantly increased (2.14 g C m−2 yr−1) and a major portion of QLMNP (74.39%) exhibited a significant vegetation restoration; only 0.14% of the park underwent significant degradation during 2000–2019. Precipitation was the dominant climatic factor that influenced vegetation dynamics in QLMNP (56.66%), while the influences of temperature and solar radiation account for 28.92% and 14.42%, respectively. The climatic factors were positively correlated with NPP in most regions of the QLMNP. The relative contributions of CC and HA to the increase in NPP were 39.70% and 60.30%, respectively. The HA-dominated (NPP) areas contained most ecological restoration projects. In addition, substantial differences were observed in the CC-dominated and HA-dominated areas; 70.73% of the CC-dominated areas and 29.27% of the HA-dominated areas showed the decrease in NPP. Moreover, CC-dominated areas were mainly distributed in low-value NPP areas, and the precipitation was negatively correlated with NPP in this area. In general, CC and the ecological restoration projects made a positive contribution to the eco-environment of QLMNP.

Decoupling the Effect of Climate and Land-Use Changes on Carbon Sequestration of Vegetation in Mideast Hunan Province, China

Urbanization and global climate change are two important global environmental phenomena in the 21st century. Human activities and climate changes usually increase the uncertainties of the ecosystem functions and structures and can greatly affect regional landscape patterns and the carbon cycle. Consequently, it is critical to understand how various climate and land-use changes influence the carbon dynamics at a regional scale. In this study, we quantitatively analyzed the spatial and temporal changes of net primary productivity (NPP) and the effects of climate factors and human disturbance factors (i.e., land-use changes) on the “Chang–Zhu–Tan” (CZT) urban agglomeration region from 2000 to 2015. The Carnegie–Ames–Stanford Approach (CASA) model was combined with spatially explicit land-use maps, monthly climate data, and MODIS NDVI images to simulate the carbon dynamics in the CZT area. Based on our six different scenarios, we also analyzed the relative roles of climate change and land-use change in total production. Our results indicated that the annual NPP of the study area maintained an upward trend by 7.31 gC•m−2•yr−1 between 2000 and 2015. At the same time, the average annual NPP was 628.99 gC•m−2 in the CZT area. We also found that the NPP was lower in the middle of the north region than in others. In addition, land-use changes could contribute to a positive effect on the total production in the study area by 3.42 T gC. Meanwhile, the effect of climate changes on the total production amounted to −1.44 T gC in the same region and period. Temperature and precipitation had negative effects on carbon sequestration from 2000 to 2015. As forest land constituted over 62.60% of the total land use from 2000 to 2015, the negative effect of carbon sequestration caused by urbanization could be ignored in the CZT area. Although climate and land-use changes had simultaneously positive and negative effects during the period 2000–2015, prioritizing the protection of existing forest land could contribute to increasing carbon sequestration and storage at the regional scale. Our study assists in understanding the impact of climate changes and land-use changes on carbon sequestration while providing a scientific basis for the rational and effective protection of the ecological environment in mid-east Hunan Province, China.

Spatiotemporal Monitoring of a Grassland Ecosystem and Its Net Primary Production Using Google Earth Engine: A Case Study of Inner Mongolia from 2000 to 2020

Grassland ecosystems are a significant part of the global ecosystem and support the livelihoods of millions of people. The Inner Mongolia grassland is the largest temperate grassland in the world, and an important ecological barrier for China, but due to human activities and climate change it has been faced with an ecological crisis in recent years. In this study, a modified Carnegie-Ames-Stanford approach (CASA) model based on the Google Earth Engine platform was used to determine the net primary production (NPP) in the Inner Mongolia grassland from 2000 to 2020. The results show that the average annual NPP of the Inner Mongolia grassland is 278.63 g C/m2, and 83.22% of the total area has shown an increasing trend during the study period. We also analyzed the impact of land-use/cover change (LUCC) and climatic factors on NPP. We found that: (1) the total area of grassland increased from 2000 to 2010 and then decreased from 2010 to 2020. During the whole study period, although the grassland area increased slightly by 4728.69 km2 because of LUCC, the overall effect of LUCC on grassland NPP was negative, with a loss of 17.63 Tg C compared to an increase of 16.38 Tg C. (2) The main meteorological factor affecting the NPP of the Inner Mongolia grassland is precipitation, followed by sunshine duration and temperature. About 97.06% of the grassland shows a positive correlation between NPP and precipitation. (3) The results for NPP and its changing trends are not completely consistent in the long- and short-term study periods. Considering the instability of grassland growth, it is necessary to take the periodic variation of precipitation into account when studying NPP. These results could provide basic information for policy formulation and scientific research into the ecological environment management of grassland areas in the future.

Spatiotemporal variation and driving factors of vegetation net primary productivity in a typical karst area in China from 2000 to 2010

Exploring the spatiotemporal variation in vegetation net primary productivity (NPP) and evaluating the impact of different drivers on NPP are vital for vegetation protection and restoration in Guizhou Province, which is a typical karst area in China. In this study, Cox–Stuart test, linear regression and spatial statistics were used to analyze the spatiotemporal variation in vegetation NPP in Guizhou. Random Forest combined with local spatial autocorrelation analysis was applied to quantify the effects of eight drivers from climate, topography, human activities and vegetation growth status on the NPP from different clusters in different years based on the NPP product from the Global Production Efficiency Model (GLO-PEM). The following results were obtained. (1) The average annual NPP in Guizhou during 2000–2010 showed no significant increasing or decreasing trend. (2) The annual mean NPP in the west was the lowest in the period, but the NPP per year had a rising tendency in the west and a declining one in the east from 2000 to 2010. (3) The NPP in Guizhou showed a significant clustering trend across each year in the period, whereas the clustering degree reflected a downward trend over time. The statistically significant clusters of high values (HH) and clusters of low values (LL) of NPP were mainly distributed in the east and west, respectively, in 2000, 2005 and 2010. (4) The accuracy of the driver analysis of the three NPP cluster types combined (HH + LL, HL + LH, and HH + HL + LH + LL) was higher than that of the other cluster types in Guizhou in 2000, 2005 and 2010. Vegetation growth and human activities show greater effect on the NPP of the three combined types than climate and topography. These findings are valuable in refining the results of the driver analysis and improving their accuracy. This study provides a deeper insight into the effect of different drivers on the NPP from different spatial clusters in Guizhou. Our results indicate that implementing appropriate silvicultural measures and formulating effective management policies are essential to improve the NPP and reduce the adverse effects of human activities on NPP in Guizhou.

河西走廊植被净初级生产力时空变化及其影响因子研究

PDF HTML阅读 XML下载 导出引用 引用提醒 河西走廊植被净初级生产力时空变化及其影响因子研究 DOI: 10.5846/stxb202001130105 作者: 作者单位: 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（41761083）；甘肃省自然科学基金（17JR5RA061） Temporal and spatial change of Net Primary Productivity of vegetation and its determinants in Hexi Corridor Author: Affiliation: Fund Project: National Natural Science Foundation of China;Natural Science Foundation of Gansu Province of China 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:干旱半干旱区植被NPP变化对全球碳循环有重要影响，该区域NPP对气候变化的响应表现出较大的时空异质性，其驱动机制并不十分清楚。选择中国河西走廊，利用随机森林算法估算了2002-2018年的NPP，基于偏导数法计算了气候与人类活动对NPP的影响。结果表明：（1）随机森林算法能较好的适用于干旱半干旱区NPP估算。（2）2002-2018年间河西走廊年NPP的平均值为153.32 gC m-2 a-1，总量为37.468 Tg C/a，呈东南向西北递减的分布特征，研究期间NPP呈2.37 gC m-2 a-1（P=0.09）增长趋势。（3）河西走廊NPP变化52.51%由气候因子贡献，47.49%由人类活动贡献。（4）在气候变化对NPP的影响中，降水主导了该区72.21%的区域，温度对NPP变化量的贡献占73.71%，前者影响着NPP变化格局，后者主导NPP变化数量。升温和增湿均有利于该区NPP增加，随着西北地区气候暖湿化，河西走廊植被会持续改善，该研究有助于理解干旱半干旱区NPP对气候变化的响应机制，为适应气候变化政策制定提供理论依据。 Abstract:The variation of vegetation Net Primary Productivity (NPP) has an important impact on the global carbon cycle in arid and semi-arid regions. The response of NPP to climate change in this region shows great spatial and temporal heterogeneity, while its driving mechanism is not clear. In this study, the Hexi Corridor in China was selected as study area, and the NPP from 2002 to 2018 was estimated using a random forest algorithm. The effects of climate and human activities on NPP were calculated based on the partial derivative method. The results showed that (1) random forest algorithms presented good performance in the NPP estimation in arid and semi-arid areas. (2) The average annual NPP of Hexi Corridor from 2002 to 2018 was 153.32 gC m-2 a-1, and the total amount was 37.468 Tg C/a, which indicated a decreasing distribution pattern from southeast to northwest. During the study period, the NPP showed an increasing trend of 2.37 gC m-2 a-1 (P=0.09). (3) 52.51% of the NPP variation in the Hexi Corridor was contributed by climate factors, and 47.49% was contributed by human activities. (4) For the impact of climate change on the NPP, precipitation dominated 72.21% of the area, and temperature contributed 73.71% of the amount of NPP variation. The former affected the NPP change pattern and the latter dominated the amount of NPP variation. Both warming and humidification are conducive to the increase of NPP in this area. With the warm and humid climate in the Northwest China, the vegetation in the Hexi Corridor will continue to increase. This study is helpful for understanding the response mechanisms of the NPP to climate change in arid and semi-arid areas, and provides a theoretical basis for decision making in adaptation to climate change. 参考文献 相似文献 引证文献

Spatiotemporal distribution of grassland NPP in Gansu province, China from 1982 to 2011 and its impact factors.

The modified Carnegie–Ames–Stanford Approach (CASA) model based on the comprehensive and sequential classification system of grasslands (CSCS, a unique vegetation classification system) was used to determine grassland net primary production (NPP) in Gansu province from 1982 to 2011 and its spatio-temporal variability. The relationship between NPP and climate drivers was analyzed. The results showed that annual NPP of grasslands in Gansu province averaged 139.30 gC m-2 yr -1 during the study period. NPP decreased from southeast to northwest across the province. Grassland NPP showed an increasing trend during the period 1982–2011, and the increase rate over the whole period was 92.91%. The highest NPP appeared in summer with more precipitation and higher cumulative temperature conditions; while the lowest values existed in winter. The largest correlation coefficient was found between the average annual NPP and the average annual precipitation (r = 0.77), followed by annual NPP and solar radiation (r = 0.70) or NDVI (r = 0.69), Annual NPP had no significant correlation with annual cumulative temperature (>0°C) or moisture index (K-value). Thus, precipitation is the major controlling factor on the average annual NPP in Gansu grassland. Solar radiation and NDVI also have important effects on grassland NPP in Gansu. These results may provide basic information for sustainable development and utilization of grassland and for the improvement and protection of the ecological environment as well.

The effects of climate factors and human activities on net primary productivity in Xinjiang.

Net primary productivity (NPP) is an index of the increase in plant biomass. Plant biomass is an important component of the global carbon cycle that indicates the health of an ecosystem. Environmental restoration has recently received much attention in Xinjiang, and it is thus important to quantify the dynamic effects of the drivers of NPP in the region. NPP was calculated for the annual growing season from 1982 to 2013 using the Carnegie-Ames-Stanford Approach (CASA) model. The effects of climate factors on NPP were analyzed, and the relationships between NPP and climate factors as well as human activity were quantified. Additionally, an innovative method based on partial derivatives and residual error was proposed to calculate the contributions of climate factors and human activities. The results show that average annual NPP in Xinjiang was 57.45gCm-2 from 1982 to 2013 and that the average increase in annual NPP was 0.23gCm-2year-1. The average increases in annual NPP due to temperature, precipitation, and solar radiation were 0.0095, 0.2679, and 0.2541gCm-2year-1; the average decreases were respectively - 0.0133, - 0.0521, and - 0.0725gCm-2year-1. Precipitation and solar radiation influence NPP more than temperature. Precipitation had the greatest effect on NPP in the first 19years, but solar radiation became more influential after 2000. Climate conditions were favorable for increase in NPP before 2000. The environmental restoration also occurred in Xinjiang during that period, and human activity slightly decreased NPP. Human activity increased and had a greater effect on NPP after 2000.

Spatial and temporal change patterns of net primary productivity and its response to climate change in the Qinghai-Tibet Plateau of China from 2000 to 2015

The vegetation ecosystem of the Qinghai-Tibet Plateau in China, considered to be the “natural laboratory” of climate change in the world, has undergone profound changes under the stress of global change. Herein, we analyzed and discussed the spatial-temporal change patterns and the driving mechanisms of net primary productivity (NPP) in the Qinghai-Tibet Plateau from 2000 to 2015 based on the gravity center and correlation coefficient models. Subsequently, we quantitatively distinguished the relative effects of climate change (such as precipitation, temperature and evapotranspiration) and human activities (such as grazing and ecological construction) on the NPP changes using scenario analysis and Miami model based on the MOD17A3 and meteorological data. The average annual NPP in the Qinghai-Tibet Plateau showed a decreasing trend from the southeast to the northwest during 2000–2015. With respect to the inter-annual changes, the average annual NPP exhibited a fluctuating upward trend from 2000 to 2015, with a steep increase observed in 2005 and a high fluctuation observed from 2005 to 2015. In the Qinghai-Tibet Plateau, the regions with the increase in NPP (change rate higher than 10%) were mainly concentrated in the Three-River Source Region, the northern Hengduan Mountains, the middle and lower reaches of the Yarlung Zangbo River, and the eastern parts of the North Tibet Plateau, whereas the regions with the decrease in NPP (change rate lower than −10%) were mainly concentrated in the upper reaches of the Yarlung Zangbo River and the Ali Plateau. The gravity center of NPP in the Qinghai-Tibet Plateau has moved southwestward during 2000–2015, indicating that the increment and growth rate of NPP in the southwestern part is greater than those of NPP in the northeastern part. Further, a significant correlation was observed between NPP and climate factors in the Qinghai-Tibet Plateau. The regions exhibiting a significant correlation between NPP and precipitation were mainly located in the central and eastern Qinghai-Tibet Plateau, and the regions exhibiting a significant correlation between NPP and temperature were mainly located in the southern and eastern Qinghai-Tibet Plateau. Furthermore, the relative effects of climate change and human activities on the NPP changes in the Qinghai-Tibet Plateau exhibited significant spatial differences in three types of zones, i.e., the climate change-dominant zone, the human activity-dominant zone, and the climate change and human activity interaction zone. These research results can provide theoretical and methodological supports to reveal the driving mechanisms of the regional ecosystems to the global change in the Qinghai-Tibet Plateau.

Impacts and uncertainties of climate/CO2 change on net primary productivity in Xinjiang, China (2000–2014): A modelling approach

Dryland in Xinjiang, China has been threatened in recent decades by rapid climate change. However, due to large uncertainties in spatial climate datasets, the impacts of climate change and rising CO2 on net primary productivity (NPP) in Xinjiang have remained unclear. These uncertainties in climate will inevitably lead to uncertainties in model estimated NPP in Xinjiang. The uncertainties can be assessed by running an Arid Ecosystem Model (AEM) using multiple climate datasets. Such an approach allows to disentangle the relative contributions of individual climate factors on NPP change using numerical simulations and factorial analysis. The average annual NPP for Xinjiang from 2000 to 2014 was 155.90±2.74 g·C/(m2·year), 189.99±1.80 g·C/(m2·year), 213.04±8.93 g·C/(m2·year) by using the MERRA, ERA-Interim and CFSR datasets respectively to drive AEM. Our multiple simulations show a consistent temporal pattern of the regional NPP during 2000–2014 that increased during 2008–2011, and decreased during 2005–2006 and 2013–2014. However, we found large uncertainties in the spatial pattern of NPP change during this time, particularly in the Taklimakan Desert and northern Xinjiang (except for the Tacheng where NPP increased). All simulations indicated that areas surrounding the Taklamakan Desert and ecosystems at high latitude (>47°) and northwestern Xinjiang were dominated by precipitation change. However, there are large uncertainties in the dominant climate driver in other areas. To assess uncertainties in ecosystem NPP assessment, efforts should be made to improve the confidence in climate data in the northern Xinjiang. This can be achieved by establishing more rain gauges.