Actual Net Primary Productivity Research Articles

Assessment of ecological restoration projects under water limits: Finding a balance between nature and human needs

Revegetation has significantly contributed to improvements in ecosystem services, such as carbon sequestration and soil retention. Yet, vegetation expansion in water-limited regions may generate conflict of water demand between nature and humans. Present studies are still lacking when it comes to identifying the permissible vegetation capacity, i.e. net primary productivity (NPP) threshold, based on the local water resources limits, and further proposing adjustment and optimization strategies to keep water use balanced in anthropogenic-biological systems. Under such a circumstance, this study assesses the difference between the actual NPP and NPP thresholds at regional and ecosystem scales in China. The results show that 8 out of 31 provinces have their provincial actual NPP above the regional NPP thresholds, mainly concentrated in northern China between 400 and 800 mm iso-precipitation line, i.e. North China Plain (Beijing-Tianjin-Hebei), the middle reaches of the Yellow River Basin (Shaanxi and Henan provinces), and the Northeast China (Heilongjiang, Jilin and Liaoning). Forest ecosystems dominate the difference between the actual total woodland and grassland ecosystems NPP and the permissible NPP thresholds in these regions, ranging from 67% (Beijing) to 99% (Tianjin). If the current vegetation intensity in these regions remains unchanged, the areas of woodland and grassland ecosystems should be optimized 0–48% and 0–100% of their present areas to balance the water demand between the ecosystems and humans, without considering the potential consequence of climate change and soil erosion. Although 23 provinces have their regional actual NPP below their permissible NPP thresholds, 6 out of 23 provinces still have their woodland and grassland ecosystems NPP above the corresponding NPP thresholds, mainly focusing on the Northwestern China north over the 400 mm iso-precipitation line, including Inner Mongolia, Qinghai, Hainan, Shanxi, Gansu and Xinjiang. Forest ecosystems also dominate the negative NPP differences in these regions, ranging from 91% (Inner Mongolia) to 46% (Gansu). These reveal the hidden and potential pressure in the 6 provinces to balance limited water resources in the local anthropogenic-biological system. This study provides a method to assess the water-resources permissible NPP threshold and further proposes the specific adjustment and optimization plans for the areas with actual NPP above the corresponding NPP thresholds, which can provide guidance for ecological restoration program implementations in a more sustainable way.

Ecological Response of the Subsidy and Incentive System for Grassland Conservation in China

The overexploitation of Grasslands without any return-back and compensation is the major cause of degradation and deterioration of the grassland ecosystem. The Subsidy and Incentive System for Grassland Conservation (SISGC) in China aimed to restore grassland ecology by the reduction of overgrazing, promoting carrying capacity, and increasing alternative employment of herders in non-husbandry sectors. However, the ecological response to the SISGC still remains unclear on the national scale. Here, we used systematic sampling, and satellite image time series data revealed a widespread proliferation of major ecological indicators for grasslands, contrasting climate and actual net primary productivity (NPP) before (2004–2010) and after (2011–2017) the implementation of SISGC founded the contributions to policy, as simulated by the Carnegie-Ames-Stanford-Approach (CASA) model. On average, by two-phase comparison, the actual grassland NPP increased by 11.72%. The contribution of policy implementation and climate factors increased grassland NPP by up to 61.14% and 38.86%, respectively, but the response of the NPP growth of various grassland types exhibited divergence, mainly divided into policy-led (contribution rate of 52.28–97.02%) and climate-led (contribution rate of 57.56–96.00%). Hence, the SISGC policies should be renewed for different grassland types.

The Dominant Driving Force of Forest Change in the Yangtze River Basin, China: Climate Variation or Anthropogenic Activities?

Under the combined effect of climate variations and anthropogenic activities, the forest ecosystem in the Yangtze River Basin (YRB) has experienced dramatic changes in recent decades. Quantifying their relative contributions can provide a valuable reference for forest management and ecological sustainability. In this study, we selected net primary productivity (NPP) as an indicator to investigate forest variations. Meanwhile, we established eight scenarios based on the slope coefficients of the potential NPP (PNPP) and actual NPP (ANPP), and human-induced NPP (HNPP) to quantify the contributions of anthropogenic activities and climate variations to forest variations in the YRB from 2000 to 2015. The results revealed that in general, the total forest ANPP increased by 10.42 TgC in the YRB, and forest restoration occurred in 57.25% of the study area during the study period. The forest degradation was mainly observed in the Wujiang River basin, Dongting Lake basin, and Poyang Lake basin. On the whole, the contribution of anthropogenic activities was greater than climate variations on both forest restoration and degradation in the YRB. Their contribution to forest restoration and degradation varied in different tributaries. Among the five forest types, shrubs experienced the most severe degradation during the study period, which should arouse great attention. Ecological restoration programs implemented in YRB have effectively mitigated the adverse effect of climate variations and dominated forest restoration, while rapid urbanization in the mid-lower region has resulted in forest degradation. The forest degradation in Dongting Lake basin and Poyang Lake basin may be ascribed to the absence of the Natural Forest Conservation Program. Therefore, we recommend that the extent of the Natural Forest Conservation Program should expand to cover these two basins. The current research could improve the understanding of the driving mechanism of forest dynamics and promote the effectiveness of ecological restoration programs in the YRB.

A Multi-Perspective Assessment Method with a Dynamic Benchmark for Human Activity Impacts on Alpine Ecosystem under Climate Change

Intense human activities and rapid climate changes both have obvious impacts on alpine ecosystems. However, the magnitudes and directions of the impacts by these two drivers remain uncertain due to a lack of a reasonable assessment method to distinguish between them. The impact of natural resilience is also generally included in the dynamics of a disturbed ecosystem and is liable to be mixed into the impact of human activity. It is urgent that we quantitatively discriminate human activity impacts on the ecosystem under climate change, especially for fast-developing alpine regions. Here, we propose an assessment method to determine human activity impacts under a dynamic climate, taking the potential net primary production (NPP) of an ecosystem as a benchmark. The potential NPP (NPPP) series under the changing climate was retrieved by an improved integrated biosphere simulator based on the initial disturbed ecosystem status of the assessment period. The actual NPP (NPPA) series monitored by remote sensing was considered as the results derived from the joint impacts of climate change, natural resilience and human activity. Then, the impact of human activity was quantified as the difference between the NPPP and NPPA. The contributions of human activity and natural forces to ecosystem NPP dynamics were then calculated separately and employed to explore the dominant driver(s). This assessment method was demonstrated in a typical alpine ecosystem in Northwest China. The results indicate that this method capably revealed the positive impacts of local afforestation and land-use optimization and the negative impacts caused by grazing during the assessment period of 2001–2017. This assessment method provides a quantitative reference for assessing the performances of ecological protections or human damage to alpine ecosystems at the regional scale.

气候变化和人为活动在宁夏草地变化中的相对作用

PDF HTML阅读 XML下载 导出引用 引用提醒 气候变化和人为活动在宁夏草地变化中的相对作用 DOI: 10.5846/stxb202105191307 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 宁夏自然科学基金项目（2018AAC03277）；宁夏农业高质量发展和生态保护科技创新示范项目（NGSB-2021-14-03，NGSB-2021-15-01）；陕西省教育厅项目（20JK0760） Assessment of relative effects of climate change and human activities on grassland dynamic in Ningxia 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:气候变化和人为活动是草地生态系统退化或恢复过程中的两大驱动因素。选取植被净初级生产力（NPP）为衡量指标，利用改进的Carnegie-Ames-Stanford Approach （CASA）模型、Thornthwaite Memorial模型以及残差趋势法分别计算了宁夏草地实际净初级生产力（ANPP）、潜在净初级生产力（PNPP）和人为活动影响的生产力（HNPP）及其变化趋势，定量评估了2001-2019年气候变化和人为活动在宁夏4种类型草地（温性草甸、温性草原、温性荒漠草原和温性草原化荒漠）动态变化中的相对作用。结果表明，2001-2019年宁夏草地实际净初级生产力增加的面积占宁夏草地总面积的97.84%；全区草地潜在净初级生产力均表现为增加趋势，表明气候变化有利于植被恢复。草地恢复过程中，气候变化引起的草地恢复面积占草地恢复总面积的61.68%，气候变化和人为活动共同作用引起的草地恢复面积占38.32%；人为活动是导致草地退化的绝对主导因素。4种类型草地动态变化的驱动因素存在差异，气候变化是促进温性草甸（68.94%）和温性草原化荒漠（70.51%）恢复的主导因素，气候变化和人为活动共同作用是促进温性草原恢复的主导因素（62.30%），温性荒漠草原的恢复是气候变化和人为活动共同作用的结果（97.93%）。水热条件好转，尤其是降水增加是宁夏草地恢复的主导气候因子，生态保护政策的实施是促进草地恢复的主要人为因素，对草地的不合理利用是导致草地退化的主要人为因素。 Abstract:Climate change and human activity are two main factors driving vegetation dynamics during grassland recovery or degradation. In this study, the net primary productivity (NPP) was selected as the index, the improved Carnegie-Ames-Stanford Approach (CASA) model and Thornthwaite Memorial model were used to estimate actual net primary productivity (ANPP) and potential net primary productivity (PNPP) determined by climatic conditions, respectively. The residual trend analysis (RESTREND) method was applied to analyze the residuals of potential and actual net primary productivity and further identify non-climatic effects on vegetation dynamics in four types of natural grassland, including meadow steppe, warm steppe, desert steppe and warm steppe desert of Ningxia. Results showed that the ANPP in 97.84% of the grassland increased from 2001 to 2019 generally. The PNPP of the whole region presented an increasing trend, revealing that climate change had a positive effect on vegetation recovery across the study area. During the grassland restoration, 61.68% of the recovered grassland resulted from climate change, while 38.32% of the recovered grassland from the combined effects of climate change and human activity. Anthropogenic activities were considered as the absolutely dominant influencing factor for vegetation degradation. The driving factors of vegetation dynamic showed differences in the four types of grassland. Climate change was the dominant factor for the recovery of warm meadow (68.94%) and warm steppe desert (70.51%). The combined effects of climate change and human activities were the main factors for the recovery of warm steppe (62.30%). The recovery of warm desert steppe resulted from the combined effects of climate change and human activities (97.93%). The improvement of hydrothermal conditions, especially the increases in precipitation, was the main influencing factor for grassland restoration in Ningxia. The implementation of ecological protection policies produced significantly positive effects on the restoration of grassland, and the unreasonable occupation of grassland was the main anthropogenic factor leading to grassland degradation. 参考文献 相似文献 引证文献

三江源国家公园植被净初级生产力变化趋势及影响因素

PDF HTML阅读 XML下载 导出引用 引用提醒 三江源国家公园植被净初级生产力变化趋势及影响因素 DOI: 10.5846/stxb202106131577 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 第二次青藏高原综合科学考察研究项目（2019QZKK0302）；中国科学院青海省人民政府三江源国家公园联合研究专项专项（LHZX-2020-07） Changes and influencing factors of vegetation net primary productivity in the Sanjiangyuan National Park 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:净初级生产力（NPP）是评估全球气候变化和人类活动下生态系统状况、过程和机制的重要指标之一。研究以中国首批国家公园之一的三江源国家公园为对象，利用GLOPEM-CEVSA耦合模型，以1981-2018年空间插值的气象数据和基于遥感反演的FPAR数据为输入，分别估算仅气候驱动的潜在NPP （NPPCL）和气候遥感共同驱动的现实NPP （NPPRS），以二者之差厘定人类活动影响的NPP （NPPHA），进而探究全球气候变化下人类活动的影响。结果表明：（1）三江源地区NPPRS多年均值为309.70 g C m-2 a-1，占NPPCL的61.65%。其中，黄河源、长江源和澜沧江源园区NPPRS分别为249.88 g C m-2 a-1、140.18 g C m-2 a-1和330.55 g C m-2 a-1。（2）全区NPPRS以2.00 g C m-2 a-1速率显著增加，高于NPPCL（1.74 g C m-2 a-1），其中黄河源、长江源和澜沧江源园区NPPRS增长速率分别占各自NPPCL增长速率的89.13%、90.23%和77.43%，澜沧江源园区整体受人类活动影响最大。（3）气候影响方面，年降水、年平均日最高气温和年平均日最低气温共同可解释全区NPPCL和NPPRS年际变化的51%和73%，可分别解释黄河源、长江源和澜沧江源园区的48%和58%、52%和69%、42%和50%，其中气温对NPP年际变化趋势影响更大。（4）人类活动在大部分区域呈负影响，存在西北向东南负面影响增强的空间分布特征，但2000年前后人类活动对生产力变化趋势呈负影响的面积从79.12%降低到56.34%，NPP变化量从-71.41 Tg C降低到-38.72 Tg C，作为主导因子的变化范围从18.73%增加至38.76%，三江源地区生态保护与恢复等措施促进了植被生产力增加，但需进一步实施生态保护与恢复措施，这是一项长期而艰巨的任务。 Abstract:The Net Primary Productivity (NPP) is an important indicator quantifying ecosystem status, process and undying mechanisms due to global climate change and human activities. The potential NPP (NPPCL) and actual NPP (NPPRS) were estimated through GLOPEM-CEVSA model driven by the only interpolated climate data, and both climate and remote sensing data, respectively, for the near 40 years from 1981 to 2018. The human activities dominated NPP (NPPHA) was defined as the difference between NPPRS and NPPCL. The method was applied in the Sanjiangyuan National Park, one of the first national parks in China, to explore the impacts of human activity under global climate change. The results showed that:(1) the average NPPRS was 309.70 g C m-2 a-1, accounting for 61.65% of the NPPCL for the whole region. For the three sub-parks, the NPPRS were 249.88 g C m-2 a-1, 140.18 g C m-2 a-1 and 330.55 g C m-2 a-1 in the Yellow River headwater, Yangtze River headwater and Lancang River headwater, respectively. (2) The NPPRS was increasing significantly by a speed of 2.00 g C m-2 a-1, which was faster than the NPPCL (1.74 g C m-2 a-1). The speed ratio of NPPRS to NPPCL were 89.13%, 90.23% and 77.43% for the three sub-parks by the above oder, respectively, which meant the Lancang Park was most impacted by human activities. (3) In the terms of climate impact, temperature had a stronger impact on the trend of NPP. Specifically, annual total precipitation, average annual maximum temperature and minimum temperature explained 51% and 73% of the interannual variation of NPPCL and NPPRS in the whole region, which can explain 48% and 58%, 52% and 69%, 42% and 50% of the interannual variability in the NPP timeseries in the Yellow River, Yangtze River and Lancang River sub-park, respectively. (4) Human activities had a negative influence over the most areas and became stronger to the southeast from the northwest. And the area showing a negative influence from human activities on the productivity changes decreased from 79.12% before 2000 to 56.34% after 2000. The total NPP over the whore negative area decreased from -71.41 Tg C to -38.72 Tg C, and the human activity as the dominant factor increased from 18.73% to 38.76% for the same two periods. It illustrated that the ecological protection and restoration of the Three-River Headwaters Region have contributed to an increasing vegetation productivity, but the protection and restoration measures should be further implemented. 参考文献 相似文献 引证文献

Diverse responses of grassland dynamics to climatic and anthropogenic factors across the different time scale in China

An accurate quantification in the separation of the relative contributions of climate change and human activities on grassland dynamics is crucial for controlling grassland degradation. Here, we investigated grassland dynamics in China by using net primary productivity (NPP) as an evaluation indicator from 1982 to 2016. We calculated the human-induced grassland NPP (HNPP) by subtracting the potential NPP (PNPP) from the actual NPP (ANPP) to distinguish the climatic and anthropogenic effects on grassland NPP changes across different time scales. Results indicated that the change in grassland ANPP resulted from different dominated factors in the two periods of 1982–1999 and 2000–2016. An obvious increase of grassland ANPP was observed from 1982 to 1999, which mainly due to a slight increasing trend in grassland PNPP driven by a humid-warm climate and a slight decrease in grassland HNPP from weak human activities. An overall increase in ANPP (69.576%) over its decrease portion (30.424%) was observed from 1982 to 1999. Human activities-induced ANPP increase mainly occurred in Shaanxi, Qinghai and Gansu Provinces and Tibet Autonomous Region for the grassland types of Alpine subalpine meadow, Meadow and Slope grassland. Climate-dominated decrease mainly occurred in Shanxi, Shaanxi and Heilongjiang, especially for Plain and Slope grassland. However, an overall decreasing trend of grassland ANPP was observed from 2000 to 2016, mainly attributed to a decreasing trend in grassland HNPP by human intervention and a warm-dry climate-induced negative effect on grassland growth. Overall, the grassland underwent a decrease than increase in ANPP (58.826% vs 41.174%) during 2000–2016; the contributions of climate factors to grassland ANPP increase was relatively greater than that of human factors in Xinjiang, Qinghai and Inner Mongolia. Human activities-dominated ANPP decrease occupied 23.913%, obviously higher than the decrease dominated by climate change (9.248%), which mainly occurred in Alpine subalpine meadow, Desert grassland and Alpine subalpine grassland. Overall, these findings seem to demonstrate that there are great differences in the temporal and spatial effects of climate change and human activities on different regions and different grassland types in China before and after 1999, and contribute to providing location guidance for future grassland restoration. Meanwhile, this study is expected to improve the understanding of the driving mechanisms of grassland dynamics, and provide support for scientifically evaluating and adjusting ecological restoration policies in China.

Assessing levels, trade-offs and synergies of landscape services in the Iranian province of Qazvin: towards sustainable landscapes

ContextEvidence-based knowledge is crucial for place-based knowledge production and learning towards sustainable landscapes through stewardship and integrated spatial planning.ObjectivesWe focus on the landscape service concept as a tool, and three fundamental challenges for its use: (1) how to monitor benefits provided by different landscapes; (2) to demonstrate trade-offs and synergies among benefits in a landscape; and (3) to discuss how to incorporate results from analyses into landscape stewardship and planning.MethodsAs a case study we chose the Iranian Qazvin province with diverse natural and anthropogenic landscapes, and top-down societal steering. Five landscape services (water yield, water regulation, pollination, actual net primary production (NPPact) and social-cultural connectivity) were assessed and compared.ResultsAll landscape services were significantly correlated. Major trade-offs and synergies among services were between NPPact and water yield and regulation. Trade-off and synergy clusters showed that landscape functions depend on both natural and anthropogenic landscape patterns and processes.ConclusionsProviding transparent data about trade-offs and synergies among landscape services can facilitate learning about which services are important among landscapes. For each of six settings we suggest action plans. We discuss the role of Iranian landscape stewardship and planning, and integrative research needs.

Quantitative Assessment of the Effects of Climate Change and Human Activities on Grassland NPP in Altay Prefecture

Grassland degradation in Altay Prefecture is of considerable concern as it is a threat that hinders the sustainable development of the local economy and the stable operation of the livestock industry. Quantitative assessment of the relative contributions of climate change and human activities, which are considered as the dominant triggers of grassland degradation, to grassland variation is crucial for understanding the grassland degradation mechanism and mitigating the degraded grassland in Altay Prefecture. In this paper, the Carnegie-Ames-Stanford Approach model and the Thornthwaite memorial model were adopted to simulate the actual net primary productivity (NPPA) and potential net primary productivity (NPPP) in the Altay Prefecture from 2000 to 2019. Meanwhile, the difference between potential NPP and actual NPP was employed to reflect the effects of human activities (NPPH) on the grassland. On this basis, we validated the viability of the simulated NPP using the Pearson correlation coefficient, investigated the spatiotemporal variability of grassland productivity, and established comprehensive scenarios to quantitatively assess the relative roles of climate change and human activities on grassland in Altay prefecture. The results indicate three main points. (1) The simulated NPPA was highly consistent with the MOD17A3 dataset in spatial distribution. (2) Regions with an increased NPPA accounted for 70.53% of the total grassland, whereas 29.47% of the total grassland area experienced a decrease. At the temporal scale, the NPPA presented a slightly increasing trend (0.83 g C m–2 yr–1) over the study period, while the trends of NPPP and NPPH were reduced (–1.31 and –2.15 g C m–2 yr–1). (3) Compared with climate change, human activities played a key role in the process of grassland restoration, as 66.98% of restored grassland resulted from it. In contrast, inter-annual climate change is the primary cause of grassland degradation, as it influenced 55.70% of degraded grassland. These results could shed light on the mechanisms of grassland variation caused by climate change and human activities, and they can be applied to further develop efficient measures to combat desertification in Altay Prefecture.

Agroforestry trade-offs between biomass provision and aboveground carbon sequestration in the alpine Eisenwurzen region, Austria

Mountain agroecosystems deliver essential ecosystem services to society but are prone to climate change as well as socio-economic pressures, making multi-functional land systems increasingly central to sustainable mountain land use policy. Agroforestry, the combination of woody vegetation with crops and/or livestock, is expected to simultaneously increase provisioning and regulating ecosystem services, but knowledge gaps concerning trade-offs exist especially in temperate industrialized and alpine regions. Here, we quantify the aboveground carbon (C) dynamics of a hypothetical agroforestry implementation in the Austrian long-term socio-ecological research region Eisenwurzen from 2020 to 2050. We develop three land use scenarios to differentiate conventional agriculture from an immediate and a gradual agroforestry implementation, integrate data from three distinct models (Yield-SAFE, SECLAND, MIAMI), and advance the socio-ecological indicator framework Human Appropriation of Net Primary Production (HANPP) to assess trade-offs between biomass provision and carbon sequestration. Results indicate that agroforestry strongly decreases HANPP because of a reduction in biomass harvest by up to − 47% and a simultaneous increase in actual net primary production by up to 31%, with a large amount of carbon sequestered in perennial biomass by up to 3.4 t C ha-1 yr-1. This shows that a hypothetical transition to agroforestry in the Eisenwurzen relieves the agroecosystem from human-induced pressure but results in significant trade-offs between biomass provision and carbon sequestration. We thus conclude that while harvest losses inhibit large-scale implementation in intensively used agricultural regions, agroforestry constitutes a valuable addition to sustainable land use policy, in particular when affecting extensive pastures and meadows in alpine landscapes.

A Method for Quantifying the Impacts of Human Activities on Net Primary Production of Grasslands in Northwest China

Accurately assessing the impact of human activities on net primary productivity (NPP) of vegetation is of great significance to the achievement of sustainable development. However, it is difficult to disentangle the effects of climate conditions and human activities on NPP, and bridging this knowledge gap largely depends on the calculation of the NPP under natural conditions. Here, we propose a method for calculating natural vegetation NPP (NNPP) based on non-human influence grids, which are obtained according to the consistent rate of climate and actual NPP (ANPP) temporal changes. We selected Northwest China as study area, and we used a light use efficiency (LUE) model to estimate ANPP and used the random forest algorithm (RF) to estimate the NNPP. The results show that NNPP is very close to ANPP, and the human activities on NPP (HNPP) based on NNPP is close to the actual situation of human activities on NPP. From 2001 to 2017, the positive HNPP accounts for 40.28% of the total grassland area, with an average value of 28.65 gC·m−2·yr−1, while the negative HNPP accounts for 59.72% of the total area, with an average value of −31.19 gC·m−2·yr−1. The grassland NPP shows an increasing trend, which is dominated by climate factors. Human activity is the dominant factor for the grassland degradation, accounting for 42.78% of the degraded area, but promoting grassland growth in 11.4% of the restored area. This study provides a new method to estimate the impacts of human activities on vegetation, and the results can be used to evaluate the effectiveness of ecological environmental governance, providing a quantitative basis for scientifically building the harmonious relationship between human and nature.

Dynamics and Drivers of Grasslands in the Eurasian Steppe during 2000–2014

The Eurasian steppe (EAS) is the largest contiguous grassland worldwide. Quantitative evaluations of the relative impacts of climate change and human activities on grasslands are significant for understanding grassland degradation mechanisms and controlling degraded grasslands. In this study, we analyzed the grassland productivity based on multiple forms of net primary productivity (NPP), including climate NPP (CNPP), actual NPP (ANPP), and human-caused NPP (HNPP) during 2000–2014. The results demonstrate that the average value of annual ANPP in the EAS was 47.36 gC/(m2·year), with a weak decrease (−0.02 gC/(m2·year)) during the study period. The area of grassland degradation account for 48.52% of the total grassland area in EAS, while the area of grassland recovery account for 51.48%. Restorative grassland was mainly distributed in Mongolia and China, while worse grassland was mainly distributed in the Kazakh steppe regions. Grassland degradation in China was mainly caused by climate change, whereas it was mainly caused by human activities in Mongolia. Grassland recovery in Kazakh steppe regions was mainly caused by human activities, but in Mongolia, it was mainly caused by climate change. Compared with temperature, precipitation played a more significant role on grassland productivity.

Vegetation Productivity Dynamics in Response to Climate Change and Human Activities under Different Topography and Land Cover in Northeast China

Net primary productivity (NPP) is the total amount of organic matter fixed by plants from the atmosphere through photosynthesis and is susceptible to the influences of climate change and human activities. In this study, we employed actual NPP (ANPP), potential NPP (PNPP), and human activity-induced NPP (HNPP) based on the Hurst exponent and statistical analysis to analyze the characteristics of vegetation productivity dynamics and to evaluate the effects of climate and human factors on vegetation productivity in Northeast China (NEC). The increasing trends in ANPP, PNPP, and HNPP accounted for 81.62%, 94.90%, and 89.63% of the total area, respectively, and ANPP in 68.64% of the total area will continue to increase in the future. Climate change played a leading role in vegetation productivity dynamics, which promoted an increase in ANPP in 71.55% of the area, and precipitation was the key climate factor affecting ANPP. The aggravation of human activities, such as increased livestock numbers and intensified agricultural activities, resulted in a decrease in ANPP in the western grasslands, northern Greater Khingan Mountains, and eastern Songnen Plain. In particular, human activities led to a decrease in ANPP in 53.84% of deciduous needleleaf forests. The impact of climate change and human activities varied significantly under different topography, and the percentage of the ANPP increase due to climate change decreased from 71.13% to 53.9% from plains to urgent slopes; however, the percentage of ANPP increase due to human activities increased from 3.44% to 21.74%, and the effect of human activities on the increase of ANPP was more obvious with increasing slope. At different altitudes, the difference in the effect of these two factors was not significant. The results are significant for understanding the factors influencing the vegetation productivity dynamics in NEC and can provide a reference for governments to implement projects to improve the ecosystem.

Quantitative Assessment of NPP Changes in the Yellow River Source Area from 2001 to 2017

It is of great significance to quantitatively evaluate the ecological degradation and restoration of the Yellow River source area from 2001 to 2017. Net primary productivity (NPP) is the core indicator used to indicate the health of terrestrial ecosystems. Based on the improved CASA (Carnegie-Ames-Stanford Approach) model and MOD17A3 NPP products, 174 measured sample sites were used to validate the NPP simulation results, select the model with higher accuracy as the actual NPP simulation, and using Theil-Sen median trend analysis and Mann-Kendall test to investigate the dynamics of NPP changes. The results are as follows: (1) the accuracy of the CASA model is higher than that of the MOD17A3 NPP product, and it is more suitable for the simulation of the actual NPP in the source area of the Yellow River; (2) the Yellow River Source region has shown a fluctuating upward trend in net primary productivity over the past 17 years, with 50% of the region showing a slight improvement, 36% showing a significant improvement, 13% showing a slight decline, and only 1% showing a significant decline, the average annual growth rate of NPP is 2.6 g C/yr-1. Compared with 2001, the net primary productivity in 2017 increased by 5.24×1012g C.

Impacts of climate change and human activities on net primary productivity of grasslands in Inner Mongolia, China during 1982-2015.

We analyzed the impacts of climate change and human activities on the net primary productivity of grasslands in Inner Mongolia during 1982-2015. The results showed that the growth rates of actual net primary productivity (ANPP) were 1.08 and 1.36 g C · m-2 · a-1 in 1982-1998 and 1999-2015, respectively. Such changes were largely due to restoration, with restoration implementing in 81.6% and 76.3% of the total study area in 1982-1998 and 1999-2015, respectively. The area of degraded grasslands tends to increase. The effects of climate change and human activity varied across different types of grassland. Climate change was the main contributor to grassland restoration over the two periods, with the contribution rates being 79.3% and 94.1%, respectively. The ANPP was positively correlated with precipitation but not with temperature, indicating that precipitation was the main climate factor influencing grassland restoration. Human activities contributed most to grassland degradation over the two periods, with the contribute rate being 83.3% and 87.8%, respectively. Our results suggested that the climate change was the dominant contributor to grassland restoration, while human activities, such as increase in livestock numbers, cultivation and afforestation, accelerated grassland degradation.

Reducing human activity promotes environmental restoration in arid and semi-arid regions: A case study in Northwest China

Human activities have adversely impacted grassland net primary productivity (NPP) across the world, and quantitative estimations of the anthropogenic impacts on NPP (HNPP) can be helpful to improve environmental protection and climate adaptation measures. However, disentangling the effects of climate variability and human activities on NPP is problematic and requires the calculation of potential net primary productivity (PNPP). In this study, we assessed the anthropogenic impacts on NPP in the Shiyang River basin—a typical arid and semi-arid region. We used the seasonal changes in NPP to identify the grids that were not affected by human activity and then proposed a method to calculate PNPP based on the leaf area index (LAI). We estimated the actual net primary productivity (ANPP) using the Carnegie-Ames-Stanford Approach (CASA) model, and the HNPP was then calculated as the difference between ANPP and PNPP. Our results showed that this method for PNPP calculation was reliable. From 2001 to 2016, the positive (90.85 gC·m−2·a−1) and negative effects (−130.21 gC·m−2·a−1) of human activities on NPP accounted for 32.68% and 46.84% of the ANPP, respectively, and the overall average HNPP was −39.36 g C·m2·a−1. The implementation of ecological and environmental protection projects gradually mitigated the negative effects of human activity on NPP at a rate of 4.55 gC·m−2·a−1; however, negative HNPP values still occupied 55.39% of the entire region in 2016. In contrast with the prevailing views that climate change is the main factor accounting for vegetation recovery in arid and semi-arid regions, our results suggest that reducing human activities can significantly promote environmental restoration. The findings of this study suggest that policy makers and stakeholders can restore grassland ecosystems and promote environmental protection by reducing anthropogenic activities in arid and semi-arid regions.

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 < 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 < 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.

RESTREND-based assessment of factors affecting vegetation dynamics on the Mongolian Plateau

The landscape of the Mongolian Plateau (MP) is shaped by both climatic change and human activities. It is noteworthy to monitor regional vegetation dynamics and to discriminate the impacts of climatic and anthropogenic factors on vegetation productivity and diversity. To investigate human- and climate-driven changes in vegetation cover across the MP during 2000−2014, the residual trend analysis (RESTREND) method was applied to analyze the residuals of potential and actual net primary productivity (NPP) and further identify non-climatic effects on vegetation dynamics. Results suggested that the normalized difference vegetation index (NDVI) in growing seasons had been increasing at the rate of 0.002/a in the whole MP during 2000–2015. And potential NPP increased across 71% of the study area, revealed that climate change displayed a generally positive effect on vegetation recovery across the plateau; However, the 53% of the total study area exhibited an decreasing residuals trend, indicated that human activity played a negative role in vegetation recovery. Analysis of the combined effects of climate change and human activities indicated that vegetation recovered in 74% but degraded in 22% of area of the MP. Anthropogenic activity could thus be considered as the main influencing factor of vegetation degradation, while climate change was the main controlling factor of vegetation restoration. Besides, Climatic factors had a similar effect on vegetation dynamics in inner and outer Mongolia, but human activities showed a different pattern with a lesser (greater) effect on vegetation degradation (recovery) in inner Mongolia than in outer Mongolia, respectively.

Assessment the Influence of Climate and Human Activities in Vegetation Degradation using GIS and Remote Sensing Techniques

Vegetation net primary productivity (NPP) reveals the plants capability to transform solar energy to photosynthesis. It can be used as an indicator of status of environmental processes affected by climate changes and human activities, especially in degraded areas such as Gadarif State, Sudan, where vegetation degradation has progressively taken place. In this study, three types of net primary productivity from 2000 to 2017 were used to assess the relative roles of climate variables and human activities on vegetation variability in the eastern part of Sudan (Gadarif State) by ordinary least-square regression technique. The three types of NPP are the actual NPP derived from MODIS data, potential NPP estimated using Thornthwaite memorial model and human-related NPP, the difference between the Potential NPP and actual NPP. The correlations between NPP and climate variables are calculated using Pearson’s correlation coefficient. The results revealed that 91.7% of the study area has experienced vegetation degradation caused by human activities with a variation of 97.95% in NPP. In contrast, 8.3% of the study area has a recovery by 2.05% of increase in NPP favored by climate change. The main driving forces of vegetation degradation are human activities, and the dominant factor for vegetation reversion is climate. No clear interaction between the two factors (climate change and human activities) was observed in the study area throughout the period of study. Thus, we concluded that NPP is a good indicator for assessing the relative roles of climate changes and human activities in vegetation cover dynamics that has obviously occurred in almost all districts of Gadarif, Sudan.

Response of grassland productivity to climate change and anthropogenic activities in arid regions of Central Asia.

BackgroundQuantitative evaluations of the relative impacts of climate change and anthropogenic activity on grasslands are significant for understanding grassland degradation mechanisms and controlling degraded grasslands. However, our knowledge about the effects of anthropogenic activities and climate change on the grassland in a mountain basin system in arid regions of Central Asia is still subject to great uncertainties.MethodsIn this research, we have chosen the net primary productivity (NPP) as an index for revealing grassland dynamics processes. Moreover, the human appropriation of net primary production (NPPH), which was calculated as the potential NPP (NPPP) minus the actual NPP (NPPA), was applied to distinguish the relative influences of climate change and human activities on the grassland NPP variations in a mountain basin system of Central Asia from 2001–2015.ResultsThe results indicated that the grassland NPPA showed an increasing trend (35.88%) that was smaller than the decreasing trend (64.12%). The respective contributions of human activity, climate change and the two together to the increase in the NPPA were 6.19%, 81.30% and 12.51%, respectively. Human activity was largely responsible for the decrease in the grassland NPPA, with the area experiencing human-induced decreases accounting for 98.21% of the total decreased area, which mainly occurred during spring/autumn pasture and winter pasture. Furthermore, the average grazing pressure index (GPI) values of summer pastures, spring/autumn pasture and winter pastures were 1.04, 3.03 and 1.83, respectively, from 2001–2015. In addition, negative correlations between the NPP and GPI occupied most of the research area (92.41%).DiscussionOur results indicate that: (i) anthropogenic activities were the primary cause of the reduction in the grassland NPP, especially grazing activities. (ii) For areas where the grassland NPP has increased, precipitation was the dominant climatic factor over temperature in controlling the grassland NPP changes in the study area. (iii) The findings of the current research indicate that some measures should be taken to reduce livestock pressure, and artificial grasslands can be built along the Irtysh River and the Ulungur River to relieve grazing pressure on spring/autumn pastures and winter pastures. Our results could provide reliable information for grassland management and the prevention of grassland degradation in arid regions of Central Asia.