实测了青藏高原植被样带22个地区不同植被类型的地上部分生物量并进行了格局分析。对于未受人为干扰的以常绿阔叶林为基带的亚高山天然植被，随着海拔升高，地上生物量呈递增趋势，在一定海拔高度达最大，海拔继续升高地上生物量则迅速下降。这一垂直分异规律在一定程度上反映了全球地带性森林植被最大生物量分布的纬向分异性。基于Weber定律的回归分析表明，地上生物量与水热因子的相关关系可用Logistic函数拟合，1月平均气温、7月平均气温、年平均气温、年降水量及其组合因子可解释高原植被样带地上生物量变化的28%～53%，其中年降水量及其同年平均气温的组合与地上生物量的相关性最高（R2为0.46～0.53，p

<p>We measured aboveground live-biomass density (ABD) in 22 sites along the Tibetan Alpine Vegetation Transects (TAVT) for different vegetation types including forests, shrublands and grasslands. Pattern analysis indicated that ABD of natural vegetation in the mountain areas increased from lower to higher altitudinal zones until the maximum was reached at some optimum elevation level and then declined as the altitude continued to increase. We believe that the altitudinal patterns to some extent reflect the latitudinal differences of maximum biomass in global forests. Regressions of transformed data based on the Weber^,s law revealed that January, July and annual mean temperatures and annual precipitation, singly or in combination, accounted for 28%-53% of the variation in ABD along the TAVT where annual precipitation and its combination with annual mean temperature had the highest relationship to ABD (R2=0.46-0.53, p<0.001). The relationships between ABD and the climatic factors could be expressed as logistic equations with a maximum ABD of 1 500 Mg DW&middot;hm-2. However, the variations in annual precipitation and mean temperatures could not explain the highest ABD in the alpine fir forest in Sergyemla Mountains because ABD distribution patterns of natural vegetation can be limited by additional climatic factors such as solar radiation, wind, moisture and related water/energy balances.</p>

The accurate simulation and prediction of grassland aboveground biomass (AGB) and theoretical livestock carrying capacity are key steps for maintaining ecosystem balance and sustainable grassland management. The AGB in fenced grassland is not affected by grazing and its variability is only driven by climate change, which can be regarded as the grassland potential AGB (AGB_p). In this study, we compiled the data for 345 AGB field observations in fenced grasslands and their corresponding climate data, soil data, and topographical data on the Qinghai-Tibetan Plateau (TP). We further simulated and predicted grassland AGB_p and theoretical livestock carrying capacity under the climate conditions of the past (2000-2018) and future two decades (2021-2040) based on a random forest (RF) algorithm. The results showed that simulated AGB_p matched well with observed values in the field (R² = 0.76, P < 0.001) in the past two decades. The average grassland AGB_p on the Tibetan Plateau was 102.4 g m^-2, and the inter-annual changes in AGB_p during this period showed a non-significant increasing trend. AGB_p fluctuation was positively correlated with growing season precipitation (R² = 0.57, P < 0.001), and negatively correlated with the growing season diurnal temperature range (R² = 0.51, P < 0.001). The average theoretical livestock carrying capacity was 0.94 standardized sheep units (SSU) ha^-1 on the TP, in which about 54.1% of the areas showed an increasing trend during the past two decades. Compared with the past two decades, the theoretical livestock carrying capacity showed a decreasing trend in the future, which was mainly distributed in the central and northern TP. This study suggested that targeted planning and management should be carried out to alleviate the forage-livestock contradiction in grazing systems on the Tibetan Plateau.

放牧是荒漠草原主要利用方式之一，生物量是生态系统获取能量能力的主要体现。目前对荒漠草原优势植物生物量分配及权衡研究相对缺乏。本研究以内蒙古荒漠草原为研究对象，设置3个不同放牧梯度(轻度放牧，中度放牧，重度放牧)，并以不放牧作为对照，通过对群落特征和4种优势植物短花针茅(Stipa breviflora)、无芒隐子草(Cleistogenes songorica)、冷蒿(Artemisia frigida)、银灰旋花(Convolvulus ammannii)生物量进行分析，揭示不同放牧梯度下优势植物生物量分配特征及生物量权衡机制。结果表明：随着放牧强度增加，荒漠草原群落地上、地下生物量、凋落物、盖度、4种优势植物地上地下生物量呈降低趋势；4种优势植物生物量均表现出向地下权衡，且随着放牧强度增加，权衡值变大；4种优势植物地上地下生物量均与群落盖度和凋落物含量呈显著正相关关系，冷蒿和银灰旋花根冠比均与群落盖度和凋落物含量呈显著负相关关系。本研究为理解地上地下生物量分配提供了一个新的视角和方法。

Grazing is one of the main utilization methods in desert grasslands. Biomass is the main manifestation of the energy acquisition capacity of the ecosystem. At present,there is a relative lack of research on biomass allocation and trade-offs of dominant plants in desert grasslands. In this study,three different grazing gradients (light grazing,medium grazing,and heavy grazing) were set up in Inner Mongolia desert grassland,and no grazing was used as the control. The above-ground and below-ground biomass of four dominant plants (<i>Stipa breviflora</i>,<i>Cleistogenes songorica</i>,<i>Artemisia frigida</i>,<i>Convolvulus ammannii</i>) were analyzed to investigate the biomass distribution characteristics and biomass trade-off of dominant plants under different grazing gradients. The results showed that with the increase of grazing intensity,the above-ground and below-ground biomass,litter,cover,and above and below-ground biomass of the four dominant plants tended to decrease;All four dominant plant biomasses showed a trade-off to the belowground,and the trade-off value became larger as the grazing intensity increased;The above and below-ground biomass of the four dominant plants showed significant positive correlations with community cover and litter content,while the root/shoot ratio of <i>Artemisia frigida</i> and <i>Convolvulus ammannii</i> showed significant negative correlations with community cover and litter content. This study provides a new perspective and method for understanding above- and below-ground biomass distribution.

The dynamics of net primary productivity (NPP) and its partitioning to the aboveground versus belowground are of fundamental importance to understand carbon cycling and its feedback to climate change. However, the responses of NPP and its partitioning to precipitation gradient are poorly understood. We conducted a manipulative field experiment with six precipitation treatments (1/12 P, 1/4 P, 1/2 P, 3/4 P, P, and 5/4 P, P is annual precipitation) in an alpine meadow to examine aboveground and belowground NPP (ANPP and BNPP) in response to precipitation gradient in 2015 and 2016. We found that changes in precipitation had no significant impact on ANPP or belowground biomass in 2015. Compared with control, only the extremely drought treatment (1/12 P) significantly reduced ANPP by 37.68% and increased BNPP at the depth of 20-40 cm by 80.59% in 2016. Across the gradient, ANPP showed a nonlinear response to precipitation amount in 2016. Neither BNPP nor NPP had significant relationship with precipitation changes. The variance in ANPP were mostly due to forbs production, which was ultimately caused by altering soil water content and soil inorganic nitrogen concentration. The nonlinear precipitation-ANPP relationship indicates that future precipitation changes especially extreme drought will dramatically decrease ANPP and push this ecosystem beyond threshold.

草原地上生物量（AGB）是草原调查监测中的重要指标，是草原生态保护和资源合理利用的依据，对草原可持续发展与科学管理具有重要意义。本研究以广西兴安县热性灌草丛为研究对象，结合机载激光雷达数据与高分辨率多光谱卫星影像，利用2021年采集的89个实地样方调查数据，对草原AGB进行了遥感反演研究。结果表明，草层高度信息是草原AGB建模的重要指标。增强型植被指数（EVI）、比值植被指数（RVI）、归一化植被指数（NDVI）中EVI与AGB的相关系数最高（0.666），高度指标中平均草层高度（CHM_mean）与AGB的相关系数最高（0.686），二者结合的指标中RVI×CHM_mean与AGB的相关系数最高（0.735）。模型精度验证结果显示，EVI模型中均方根误差（RMSE）最低，为292.047 g·m^-2，CHM_mean模型中RMSE最低，为245.084 g·m^-2，RVI×CHM_mean模型中RMSE最低为225.872 g·m^-2。结果说明机载激光雷达数据可以有效提取草层高度信息，尽管存在明显的低估现象，但在草原AGB研究中仍具有较大的应用潜力。

Grassland aboveground biomass （AGB） is an important indicator in grassland monitoring. It is an important index when designing strategies for the ecological protection and rational utilization of grassland resources. In addition， it is of great significance for the sustainable development and scientific management of grassland. In this study， shrub grassland in Xing’an County， Guangxi was the subject of the research， and data were obtained from airborne LiDAR data and high-resolution multispectral satellite images. The retrieval of grassland AGB was investigated using data collected from 89 field quadrats in 2021 and five basic regression models. The accuracy of different indicators and models was evaluated by root mean square error （RMSE）， mean absolute error （MAE）， and R-square values. It was found that grass height metrics were very important information for grassland AGB retrieval. We calculated correlation coefficients between pairs of indexes. In terms of vegetation indexes， the highest correlation coefficient was between the enhanced vegetation index （EVI） and AGB （0.666）. In terms of vegetation height indexes， the highest correlation coefficient was between average grass height （CHM_mean） and AGB （0.686）. In terms of combined indexes， the highest correlation coefficient was between the ratio vegetation index （RVI）×CHM_mean and AGB （0.735）. The accuracy and verification results showed that the minimum RMSE of the EVI models was 292.047 g·m^-2， the minimum RMSE of CHM_mean models was 245.084 g·m^-2， and the minimum RMSE of RVI×CHM_mean models was 225.872 g·m^-2. Our results show that grass height information can be effectively extracted from airborne LiDAR data， and although there is an obvious underestimation， it still has great application potential in research on grassland AGB.

Fertilization and enclosure are two important factors affecting plant biomass and diversity of alpine mea-dow. It is of great scientific significance to elucidate the processes and mechanisms underlying how both factors affect plant community for the sustainable development of alpine meadow. In this study, we analyzed the responses of plant community and species richness to fertilization (nitrogen, phosphorus, and potassium) and enclosure (grazing exclusion) in an alpine meadow on the eastern Qinghai-Tibet Plateau, and examined the underlying mechanisms of species loss. The treatments of fertilization and fertilization + enclosure significantly increased community aboveground biomass, while enclosure alone had no such effect. Community light transmittance and species richness significantly decreased in all the three treatments. At the functional group level, changes of aboveground biomass under fertilization and fertilization + enclosure mainly resulted from a significant increase in grass biomass and a significant decrease in sedge biomass. There was no significant difference in miscellaneous forb biomass among different treatments. At the species level, species composition changed significantly under fertilization and fertilization + enclosure treatments, with <em>Elymus nutans</em>&nbsp;and <em>Poa poophagorum</em>&nbsp;gradually replacing <em>Kobresia setschwanensis</em>&nbsp;as the dominant species. There was a significant negative linear relationship between light transmittance and total community biomass and a significant positive linear relationship between community light transmittance and species richness, indicating that the increase of total biomass intensified the light limitation in the lower layer, and then led to the decrease of species richness through light competition. In summary, our results demonstrated that increased light competition caused by the increases of total biomass was an important driver for species loss under fertilization and enclosure conditions, providing a scientific basis for future biodiversity maintenance and management of alpine meadow.<br><div> <br></div>