Trend in seasonal amplitude of northern net ecosystem production:Simulated results from IAP DGVM in CAS-ESM2

北方陆地净生态系统生产力(NEP)具有明显的季节变化特征,这是大气CO_(2)季节变化的关键驱动.研究这些碳循环过程并理解潜在的驱动因素是气候研究的一个关键问题.本文利用第二代中国科学院地球系统模式(CAS-ESM2)中的全球植被动态模型(IAPDGVM),研究了1990-2014年北方NEP(40°-90°N)的季节振幅及其变化趋势.在初始化试验的基础上,本文开展了一个控制试验来评估模拟的北方NEP季节幅度的变化趋势,同时开展了三个敏感性试验来研究气候和大气CO_(2)的贡献.结果表明:1990-2014年,模拟的北方NEP季节振幅显著增加,趋势为9.69万吨碳/月/年,这主要是由于最大NEP增加所致.当分别排除CO_(2)施肥效应和气候效应时,上述增加趋势大大减弱.这些显著的减少表明大气CO_(2)和气候变化对北方NEP的季节性振幅有重要影响.尽管模式存在不确定性,但这些结果有利于进一步提升IAPDGVM对陆地碳循环的精确模拟,也为CAS-ESM研究碳-气候相互作用的应用提供了重要参考.

Assessing the vulnerability of ecosystems to climate change based on climate exposure, vegetation stability and productivity

Background: Global warming has brought many negative impacts on terrestrial ecosystems, which makes the vulnerability of ecosystems one of the hot issues in current ecological research. Here, we proposed an assessment method based on the IPCC definition of vulnerability. The exposure to future climate was characterized using a moisture index(MI) that integrates the effects of temperature and precipitation. Vegetation stability, defined as the proportion of intact natural vegetation that remains unchanged under changing climate, was used together with vegetation productivity trend to represent the sensitivity and adaptability of ecosystems. Using this method, we evaluated the vulnerability of ecosystems in Southwestern China under two future representative concentration pathways(RCP 4.5 and RCP 8.5) with MC2 dynamic global vegetation model.Results:(1) Future(2017–2100) climate change will leave 7.4%(under RCP 4.5) and 57.4% of(under RCP 8.5) of areas under high or very high vulnerable climate exposure;(2) in terms of vegetation stability, nearly 45% of the study area will show high or very high vulnerability under both RCPs. Beside the impacts of human disturbance on natural vegetation coverage(vegetation intactness), climate change will cause obvious latitudinal movements in vegetation distribution, but the direction of movements under two RCPs were opposite due to the difference in water availability;(3) vegetation productivity in most areas will generally increase and remain a low vulnerability in the future;(4) an assessment based on the above three aspects together indicated that future climate change will generally have an adverse impact on all ecosystems in Southwestern China, with non-vulnerable areas account for only about 3% of the study area under both RCPs. However, compared with RCP 4.5, the areas with mid-and highvulnerability under RCP 8.5 scenario increased by 13% and 16%, respectively.Conclusion: Analyses of future climate exposure and projected vegetation distribution indicate widespread vulnerability of ecosystems in Southwestern China, while vegetation productivity in most areas will show an increasing trend to the end of twenty-first century. Based on new climate indicators and improved vulnerability assessment rules, our method provides an extra option for a more comprehensive evaluation of ecosystem vulnerability, and should be further tested at larger spatial scales in order to provide references for regional, or even global, ecosystem conservation works.

应用集合卡尔曼滤波算法对土壤呼吸速率同化及NEP估算

为了对净生态系统生产力(NEP)进行准确估算,以长白山通量观测站观测数据为基础,构建土壤温度、湿度耦合因子的更新模型(线性函数、指数函数、二次式函数),结合集合卡尔曼滤波算法(EnKF)获取高精度土壤呼吸速率数据,应用陆地生态系统碳循环综合模型(InTEC模型)准确估算NEP。结果表明:二次式模型的EnKF算法同化结果估算效果最好,决定系数(R^(2))为0.782,均方根误差为52.90 g·m^(-2)·a^(-1);指数模型EnKF算法同化结果估算值的R^(2)为0.755,均方根误差为56.47 g·m^(-2)·a^(-1);线性模型EnKF算法同化结果估算值的R^(2)为0.742,均方根误差为62.80 g·m^(-2)·a^(-1)。选取二次式模型优化后的土壤呼吸速率数据,InTEC模型模拟长白山通量观测站长时间序列净生态系统生产力的R^(2)为0.900,均方根误差为61.77 g·m^(-2)·a^(-1);InTEC模型模拟东北三省森林生态系统2003—2010年的净生态系统生产力年均值,由初始模拟的30.07 g·m^(-2)·a^(-1),经EnKF算法更新后提升到176.87 g·m^(-2)·a^(-1)。因此,采用EnKF更新土壤温度-湿度耦合因子获取的土壤呼吸速率数据,能够提高InTEC模型估算NEP的精度,为大区域尺度森林生态系统NEP估算提供技术支持。

Quantifying the impacts of fire aerosols on global terrestrial ecosystem productivity with the fully-coupled Earth system model CESM

Fire is a global phenomenon and a major source of aerosols from the terrestrial biosphere to the atmosphere.Most previous studies quantified the effect of fire aerosols on climate and atmospheric circulation,or on the regional and site-scale terrestrial ecosystem productivity.So far,only one work has quantified their global impacts on terrestrial ecosystem productivity based on offline simulations,which,however,did not consider the impacts of aerosol–cloud interactions and aerosol–climate feedbacks.This study quantitatively assesses the influence of fire aerosols on the global annual gross primary productivity(GPP)of terrestrial ecosystems using simulations with the fully coupled global Earth system model CESM1.2.Results show that fire aerosols generally decrease GPP in vegetated areas,with a global total of−1.6 Pg C yr^−1,mainly because fire aerosols cool and dry the land surface and weaken the direct photosynthetically active radiation(PAR).The exception to this is the Amazon region,which is mainly due to a fire-aerosol-induced wetter land surface and increased diffuse PAR.This study emphasizes the importance of the influence of fire aerosols on climate in quantifying global-scale fire aerosols’impacts on terrestrial ecosystem productivity.

Trade-offs and synergies between ecosystem services in Yutian County along the Keriya River Basin,Northwest China

The Keriya River Basin is located in an extremely arid climate zone on the southern edge of the Tarim Basin of Northwest China,exhibiting typical mountain-oasis-desert distribution characteristics.In recent decades,climate change and human activities have exerted significant impacts on the service functions of watershed ecosystems.However,the trade-offs and synergies between ecosystem services(ESs)have not been thoroughly examined.This study aims to reveal the spatiotemporal changes in ESs within the Keriya River Basin from 1995 to 2020 as well as the trade-offs and synergies between ESs.Leveraging the Integrated Valuation of Ecosystem Services and Trade-offs(InVEST)and Revised Wind Erosion Equation(RWEQ)using land use/land cover(LULC),climate,vegetation,soil,and hydrological data,we quantified the spatiotemporal changes in the five principal ESs(carbon storage,water yield,food production,wind and sand prevention,and habitat quality)of the watershed from 1995 to 2020.Spearman correlation coefficients were used to analyze the trade-offs and synergies between ES pairs.The findings reveal that water yield,carbon storage,and habitat quality exhibited relatively high levels in the upstream,while food production and wind and sand prevention dominated the midstream and downstream,respectively.Furthermore,carbon storage,food production,wind and sand prevention,and habitat quality demonstrated an increase at the watershed scale while water yield exhibited a decline from 1995 to 2020.Specifically,carbon storage,wind and sand prevention,and habitat quality presented an upward trend in the upstream but downward trend in the midstream and downstream.Food production in the midstream showed a continuously increasing trend during the study period.Trade-off relationships were identified between water yield and wind and sand prevention,water yield and carbon storage,food production and water yield,and habitat quality and wind and sand prevention.Prominent temporal and spatial synergistic relationships were observed between different ESs,notably between carbon storage and habitat quality,carbon storage and food production,food production and wind and sand prevention,and food production and habitat quality.Water resources emerged as a decisive factor for the sustainable development of the basin,thus highlighting the intricate trade-offs and synergies between water yield and the other four services,particularly the relationship with food production,which warrants further attention.This research is of great significance for the protection and sustainable development of river basins in arid areas.

The Dynamics and Driving Force of Farmland Ecosystem Productivity

Based on the experimental data of crop yield, soil water and fertility of a dryland farming ecosystem in northwest China, asystematic analysis is carried out to study the dynamics of dryland farming ecosystem productivity and its limitingfactors. This paper also discusses which of the two limiting factors, i.e., soil water or fertility, is the primary factor and theirdynamics. The result shows that fertility is the primary limiting factor when the productivity is rather low. As chemicalfertilizer input increases and the productivity promotes, water gradually becomes the primary limiting factor. Chemicalfertilizers and plastic film mulching are the two major driving forces that determine the crop productivity and its stabilityin these areas.

Succession and Enhancement Mechanism of Ecosystem Productivity in the De-farming Area of the Ecotone Between Agriculture and Animal Husbandry in North China

The succession and enhancement mechanism of the ecosystem productivity with the characteristics ot de-tarmlng in me ecotone between agriculture and animal husbandry in North China was discussed in order to provide an ideaology or a technical basis for maintaining the impetus of ecological restoration and economic development in this region. A case study was applied in combination with the theoretical analysis. The results indicated that the biomass productivity of the de-farming subsystem decreased by 38.4-72.3% compared with that of farming subsystem in the ecosystem. The main function of de-farming subsystem was focused on ecological productivity, it caused the ideal beneficial recycling ‘defarming → planting grass → raising animals → earn money＇ difficult to be realized. With the differentiation of de-farming subsystem, the natural and social resources input to the farming subsystem were accumulated. This laid a basis for the new attributes of economic productivity to be upgraded. The case study indicated that the economic productivity of the ecosystem was increased by 8.85-13.35 times due to re-coupling between the de-farming subsystem and the farming subsystem as well as coupling between microhabitat differentiation and crop production in the subsystems, where the microhabitat differentiation could enrich water and fertilizer in the same field. It was concluded that the important mechanisms to enhance the system productivity in the ecotone between agriculture and animal husbandry of North China included structure rebuilding and opening of the de-farming ecosystem and taking the advantage of complementary cooperative production among different regions under the market economy and rebuilding an open agro-pasture production structure,

The Measurement of the Software Ecosystem’s Productivity with GitHub

Software productivity has always been one of the most critical metrics for measuring software development.However,with the open-source community(e.g.,GitHub),new software development models are emerging.The traditional productivity metrics do not provide a comprehensive measure of the new software development models.Therefore,it is necessary to build a productivity measurement model of open source software ecosystem suitable for the open-source community’s production activities.Based on the natural ecosystem,this paper proposes concepts related to the productivity of open source software ecosystems,analyses influencing factors of open source software ecosystem productivity,and constructs a measurement model using these factors.Model validation experiments show that the model is compatible with a large portion of open source software ecosystems in GitHub.This study can provide references for participants of the open-source software ecosystem to choose proper types of ecosystems.The study also provides a basis for ecosystem health assessment for researchers interested in ecosystem quality.

Spatiotemporal variations of ecosystem services and driving factors in the Tianchi Bogda Peak Natural Reserve of Xinjiang,China

Nature reserves play a significant role in providing ecosystem services and are key sites for biodiversity conservation.The Tianchi Bogda Peak Natural Reserve(TBPNR),located in Xinjiang Uygur Autonomous Region,China,is an important ecological barrier area in the temperate arid zone.The evaluation of its important ecosystem services is of great significance to improve the management level and ecological protection efficiency of the reserve.In the present study,we assessed the spatiotemporal variations of four ecosystem services(including net primary productivity(NPP),water yield,soil conservation,and habitat quality)in the TBPNR from 2000 to 2020 based on the environmental and social data using the Integrated Valuation of Ecosystem Services and Trade-offs(InVEST)model.In addition,the coldspot and hotspot areas of ecosystem services were identified by hotspot analysis,and the trade-off and synergistic relationships between ecosystem services were analyzed using factor analysis in a geographic detector.During the study period,NPP and soil conservation values in the reserve increased by 48.20%and 25.56%,respectively;conversely,water yield decreased by 16.56%,and there was no significant change in habitat quality.Spatially,both NPP and habitat quality values were higher in the northern part and lower in the southern part,whereas water yield showed an opposite trend.Correlation analysis revealed that NPP showed a synergistic relationship with habitat quality and soil conservation,and exhibited a trade-off relationship with water yield.Water yield and habitat quality also had a trade-off relationship.NPP and habitat quality were affected by annual average temperature and Normalized Difference Vegetation Index(NDVI),respectively,while water yield and soil conservation were more affected by digital elevation model(DEM).Therefore,attention should be paid to the spatial distribution and dynamics of trade-off and synergistic relationships between ecosystem services in future ecological management.The findings of the present study provide a reference that could facilitate the sustainable utilization of ecosystem services in the typical fragile areas of Northwest China.

How Does the Agricultural Ecosystem Productivity Respond to Climate Fluctuations in the Northern Farming-pastoral Region?

Using meteorological data and mathematical statistics analysis,we take Jungar Banner in the northern farming-pastoral region of China for example,to analyze the fluctuations in the precipitation and average temperature in Jungar Banner during the period 1961-2009.We calculate the NPP of agricultural ecosystem and climatic yield of the main crops in the region during the period 1961-2009,and expound the response of agricultural ecosystem productivity to climate fluctuations in Jungar Banner.Indubitably the climate changes impose great effects on the structure and function of regional ecosystem,and there is a need to take a number of measures to minimize the detrimental effects of climate changes on climatic yield of the main crops.

Assessing the Dynamics of Grassland Net Primary Productivity in Response to Climate Change at the Global Scale

Understanding the net primary productivity(NPP) of grassland is crucial to evaluate the terrestrial carbon cycle. In this study, we investigated the spatial distribution and the area of global grassland across the globe. Then, we used the Carnegie-Ames-Stanford Approach(CASA) model to estimate global grassland NPP and explore the spatio-temporal variations of grassland NPP in response to climate change from 1982 to 2008. Results showed that the largest area of grassland distribution during the study period was in Asia(1737.23 × 104 km^2), while the grassland area in Europe was relatively small(202.83 × 10~4 km^2). Temporally, the total NPP increased with fluctuations from 1982 to 2008, with an annual increase rate of 0.03 Pg C/yr. The total NPP experienced a significant increasing trend from 1982 to 1995, while a decreasing trend was observed from 1996 to 2008. Spatially, the grassland NPP in South America and Africa were higher than the other regions, largely as a result of these regions are under warm and wet climatic conditions. The highest mean NPP was recorded for savannas(560.10 g C/(m^2·yr)), whereas the lowest was observed in open shrublands with an average NPP of 162.53 g C/(m^2·yr). The relationship between grassland NPP and annual mean temperature and annual precipitation(AMT, AP, respectively) varies with changes in AP, which indicates that, grassland NPP is more sensitive to precipitation than temperature.

Variation of net primary productivity and its drivers in China’s forests during 2000-2018

Background:Net primary productivity(NPP)in forests plays an important role in the global carbon cycle.However,it is not well known about the increase rate of China’s forest NPP,and there are different opinions about the key factors controlling the variability of forest NPP.Methods:This paper established a statistics-based multiple regression model to estimate forest NPP,using the observed NPP,meteorological and remote sensing data in five major forest ecosystems.The fluctuation values of NPP and environment variables were extracted to identify the key variables influencing the variation of forest NPP by correlation analysis.Results:The long-term trends and annual fluctuations of forest NPP between 2000 and 2018 were examined.The results showed a significant increase in forest NPP for all five forest ecosystems,with an average rise of 5.2 gC·m-2·year-1 over China.Over 90%of the forest area had an increasing NPP range of 0-161 gC·m-2·year-1.Forest NPP had an interannual fluctuation of 50-269 gC.m-2·year-1 for the five major forest ecosystems.The evergreen broadleaf forest had the largest fluctuation.The variability in forest NPP was caused mainly by variations in precipitation,then by temperature fluctuations.Conclusions:All five forest ecosystems in China exhibited a significant increasing NPP along with annual fluctuations evidently during 2000-2018.The variations in China’s forest NPP were controlled mainly by changes in precipitation.

A process model for simulating net primary productivity (NPP) based on the interaction of water-heat process and nitrogen: a case study in Lantsang valley

Terrestrial carbon cycle and the global atmospheric CO2 budget are important foci in global climate change research. Simulating net primary productivity （NPP） of terrestrial ecosystems is important for carbon cycle research. In this study, a plant-atmosphere-soil continuum nitrogen （N） cycling model was developed and incorporated into the Boreal Ecosystem Productivity Simulator （BEPS） model. With the established database （leaf area index, land cover, daily meteorology data, vegetation and soil） at a 1 km resolution, daily maps of NPP for Lantsang valley in 2007 were produced, and the spatial-temporal patterns of NPP and mechanisms of its responses to soil N level were further explored. The total NPP and mean NPP of Lantsang valley in 2007 were 66.5 Tg C and 416 g？m-2？a-1 C, respectively. In addition, statistical analysis of NPP of different land cover types was conducted and investigated. Compared with BEPS model （without considering nitrogen effect）, it was inferred that the plant carbon fixing for the upstream of Lantsang valley was also limited by soil available nitrogen besides temperature and precipitation. However, nitrogen has no evident limitation to NPP accumulation of broadleaf forest, which mainly distributed in the downstream of Lantsang valley.

Biomass and productivity in sal and miscellaneous forests of Satpura plateau (Madhya Pradesh) India

The paper deals with the biomass and productivity of sal (SF) and miscellaneous forests (MF) of Satpura plateau (Madhya Pradesh) India. These forest types were divided into four sites namely open miscellaneous (OMF, site-I), closed miscellaneous (CMF, site-II), open sal (OSF, site-III) and closed sal (CSF, site-IV). The degree of disturbance followed the order: III (0.70) 109 (III) > 79.80 (I) > 52.69 (II), while for NPPherb, the order of importance was, 109.50 (IV) > 73.27 (I) > (II), 71.75 (III) > 55.71 (II). NPPtotal was highest for closed forest stands than of the open ones. NPPteak was lower for high-disturbed site than of the less disturbed site. Photosynthetic/ non - photosynthetic ratio follows the order: 0.067 (II) > 0.030 (III) > 0.026 (IV) > 0.018 (I). Open forests showed lower values for this ratio. NEP was higher for SF than of the MF. Further closed forests showed higher values of NEP. OSF showed lower values of NEPsal than of the CSF. Disturbances in open forests not only reduced stand biomass of tree species, dominant species in particular, but also declined the tree productivity. So, gap filling plantation in side the forest is suggested to improve the productivity of open forests.

福建省森林植被NEP时空变化及影响因子分析

不断加剧的气候变化和人类活动增加了区域生态系统碳循环研究的不确定性。净生态系统生产力(NEP)能够定量描述陆地生态系统与大气之间的碳交换量,探究区域生态系统NEP的时空变化及对气象、植被等因子的响应有助于明晰区域生态系统碳收支状况和应对气候变化。基于TEC模型和生态系统呼吸模型评估了福建省森林2000-2020年NEP时空格局,并借助地理探测器和贡献率方法探究了福建省NEP时空变化的主要驱动因子。结果表明:(1)2000-2020年福建省森林多年年均NEP为528 g·m^(-2),呈极显著的增强趋势。空间分布规律为“高值主要分布在福建南部的内陆地区,低值主要分布在中北部和南部沿海地区”,约48.3%的地区NEP呈显著上升趋势,主要分布在福建省的中部偏西南地区,而仅有1.00%的地区呈显著下降趋势;(2)空间分布上,影响福建省森林NEP的空间分异的主要因子为植被、地形和气象要素。归一化植被指数对森林NEP空间分布的影响最大,是影响福建省森林NEP空间分异的主要驱动因子,其次是地形和太阳辐射,高程的最适区间为891-1 491 m,而辐射的最适区间为128-130 W·m^(-2)。与单因子相比,双因子间的相互作用均增强了对NEP空间分布的影响,其中归一化植被指数与太阳辐射的交互作用对NEP解释力最强;(3)时间变化上,气候与植被因子综合解释了福建省森林NEP年际变化的46.7%,其中归一化植被指数的升高是NEP多年变化的主导因素,而气象因子的变化均对NEP的上升趋势起到了负抑制作用,这说明在“双碳”建设时需要有效提高植被对气候变化的适应能力。

Sensitivity of Near Real-time MODIS Gross Primary Productivity in Terrestrial Forests Based on Eddy Covariance Measurements

As an important product of Moderate Resolution Imaging Spectroradiometer(MODIS), MOD17A2 provides dramatic improvements in our ability to accurately and continuously monitor global terrestrial primary production, which is also significant in effort to advance scientific research and eco-environmental management. Over the past decades, forests have moderated climate change by sequestrating about one-quarter of the carbon emitted by human activities through fossil fuels burning and land use/land cover change. Thus, the carbon uptake by forests reduces the rate at which carbon accumulates in the atmosphere. However, the sensitivity of near real-time MODIS gross primary productivity(GPP) product is directly constrained by uncertainties in the modeling process, especially in complicated forest ecosystems. Although there have been plenty of studies to verify MODIS GPP with ground-based measurements using the eddy covariance(EC) technique, few have comprehensively validated the performance of MODIS estimates(Collection 5) across diverse forest types. Therefore, the present study examined the degree of correspondence between MODIS-derived GPP and EC-measured GPP at seasonal and interannual time scales for the main forest ecosystems, including evergreen broadleaf forest(EBF), evergreen needleleaf forest(ENF), deciduous broadleaf forest(DBF), and mixed forest(MF) relying on 16 flux towers with a total of 68 site-year datasets. Overall, site-specific evaluation of multi-year mean annual GPP estimates indicates that the current MOD17A2 product works highly effectively for MF and DBF, moderately effectively for ENF, and ineffectively for EBF. Except for tropical forest, MODIS estimates could capture the broad trends of GPP at 8-day time scale for all other sites surveyed. On the annual time scale, the best performance was observed in MF, followed by ENF, DBF, and EBF. Trend analyses also revealed the poor performance of MODIS GPP product in EBF and DBF. Thus, improvements in the sensitivity of MOD17A2 to forest productivity require continued efforts.

Spatiotemporal characteristics and influencing factors of ecosystem services in Central Asia

Land use/land cover(LULC)change and climate change are two major factors affecting the provision of ecosystem services which are closely related to human well-being.However,a clear understanding of the relationships between these two factors and ecosystem services in Central Asia is still lacking.This study aimed to comprehensively assess ecosystem services in Central Asia and analyze how they are impacted by changes in LULC and climate.The spatiotemporal patterns of three ecosystem services during the period of 2000-2015,namely the net primary productivity(NPP),water yield,and soil retention,were quantified and mapped by the Carnegie-Ames-Stanford Approach(CASA)model,Integrated Valuation of Ecosystem Services and Tradeoffs(InVEST)model,and Revised Universal Soil Loss Equation(RUSLE).Scenarios were used to determine the relative importance and combined effect of LULC change and climate change on ecosystem services.Then,the relationships between climate factors(precipitation and temperature)and ecosystem services,as well as between LULC change and ecosystem services,were further discussed.The results showed that the high values of ecosystem services appeared in the southeast of Central Asia.Among the six biomes(alpine forest region(AFR),alpine meadow region(AMR),typical steppe region(TSR),desert steppe region(DSR),desert region(DR),and lake region(LR)),the values of ecosystem services followed the order of AFR>AMR>TSR>DSR>DR>LR.In addition,the values of ecosystem services fluctuated during the period of 2000-2015,with the most significant decreases observed in the southeast mountainous area and northwest of Central Asia.LULC change had a greater impact on the NPP,while climate change had a stronger influence on the water yield and soil retention.The combined LULC change and climate change exhibited a significant synergistic effect on ecosystem services in most of Central Asia.Moreover,ecosystem services were more strongly and positively correlated with precipitation than with temperature.The greening of desert areas and forest land expansion could improve ecosystem services,but unreasonable development of cropland and urbanization have had an adverse impact on ecosystem services.According to the results,ecological stability in Central Asia can be achieved through the natural vegetation protection,reasonable urbanization,and ecological agriculture development.

2000—2020年黄土高原NEP时空格局与驱动力

黄土高原是中国重要的生态屏障。在全球变化的背景下,黄土高原的碳收支平衡备受关注。本研究基于MOD17A3HGF数据,通过GSMSR模型、趋势分析、差异分析以及地理探测器等方法,分析2000—2020年黄土高原的碳源/汇特征,揭示2000—2020年该区域生态系统净生产力(NEP)的时空格局及其驱动因素。同时,将研究区按经度方向划分为西、中、东三个子区域,比较不同区域内驱动因素的差异性。结果表明:(1)近20 a黄土高原49.69%的区域从碳源向碳汇转变;NEP随时间波动上升,在东南部高于西北部,多年平均值为12 g C·m^(-2)·a^(-1)。(2)水分条件是影响NEP空间分布的主要自然因素,而土地利用类型则是影响NEP空间分布的主要人为因素;不同因子间的交互作用对NEP的影响普遍大于单个因子。(3)西、中、东三个子区域NEP的驱动因子存在明显的空间分异特征,中、西部地区受气候影响较多,以降水、湿度等水分条件为主;东部地区受地形、气候、人类活动等因素综合影响,其中,以土地利用类型为代表的人为干扰最强。

Quantification of Ecosystem Services Provided by <i>Pterocarpus lucens</i>Lepr. Ex Guill. and Perrott.: Forage Production, Timber and Carbon Sequestration in the Biosphere Reserve of Ferlo (Northern Senegal)

This study aims at quantifying the most important ecosystem services: forage production, timber production and carbon sequestration provided by Pterocarpus lucens to local communities of Ferlo Biosphere Reserve. The results suggested that the ecological structure of Pterocarpus lucens revealed a bell-shaped form with left dissymmetric distribution indicating a predominance of individuals with small circumference and height. A regression using the software Minitab 16, with circumference and the height as explanatory variables, has allowed a development of predictive models for the estimation of the produced forage and the quantification of the timber supplied by one of the most used plant species in Sahelian pastures. Forage production of Pterocarpus lucens was estimated at 178 kg DM/ha. This large value of forage showed the predominance of this species in animal feed in the Sahel. The quantity of wood produced was 545 kg DM/ha while the quantity of above ground sequestered carbon was 325.35 kg of C/ha. Those estimations are interesting in the implementation context of the Ferlo Biosphere Reserve which aims at matching the productive capacity of ecosystems with the needs of local communities.

Tree diversity effects on forest productivity increase through time because of spatial partitioning

Background: Experimental manipulations of tree diversity have often found overyielding in mixed-species plantations. While most experiments are still in the early stages of stand development, the impacts of tree diversity are expected to accumulate over time. Here, I present findings from a 31-year-old tree diversity experiment(as of2018) in Japan.Results: I find that the net diversity effect on stand biomass increased linearly through time. The species mixture achieved 64% greater biomass than the average monoculture biomass 31 years after planting. The complementarity effect was positive and increased exponentially with time. The selection effect was negative and decreased exponentially with time. In the early stages(≤ 3 years), the positive complementarity effect was explained by enhanced growths of early-and mid-successional species in the mixture. Later on(≥ 15 years), it was explained by their increased survival rates owing to vertical spatial partitioning — i.e. alleviation of self-thinning via canopy stratification. The negative selection effect resulted from suppressed growths of late-successional species in the bottom layer.Conclusions: The experiment provides pioneering evidence that the positive impacts of diversity-driven spatial partitioning on forest biomass can accumulate over multiple decades. The results indicate that forest biomass production and carbon sequestration can be enhanced by multispecies afforestation strategies.