Decadal change and inter-annual variability of net primary productivity on the Tibetan Plateau

Abstract

Net primary productivity (NPP) is an important indicator of plant dynamics and the net carbon exchange between the terrestrial ecosystem and atmosphere. Both the long-term shifts in climate mean (climate change) and short-term variations around the climate mean (climate variability) have impacts on NPP but studies examining both aspects of climate variations are rare especially in the data-scarce regions such as the Tibetan Plateau (TP). Here, we used a dynamic vegetation model to investigate the impacts of the changes and variabilities in temperature, precipitation, cloud cover and CO2 on NPP on the TP. The simulated NPP was evaluated using field and Moderate-Resolution Imaging Spectroradiometer NPP and was found to be reasonable. At monthly time scale, NPP significantly correlated concurrently and at 1-month lag with temperature, precipitation and cloud cover (coefficient of determination, R2, in 0.52–0.77). Annual NPP variability was high (low) where mean annual NPP was low (high). The effects of annual precipitation, cloud cover and temperature variability on annual NPP variability were spatially heterogeneous, and temperature variability appeared to be the dominant factor (R2 of 0.74). Whereas, NPP changes were very similar to CO2 increases across the TP (spatial correlation of 0.60), indicating that long-term changes in NPP were dominated by CO2 increases. For both variability and long-term changes in NPP, temperature was the major factor of influence (highest spatial correlation of 0.67). These findings could assist in making informed mitigation policies on the impacts of climate change and variability on ecosystem and local nomadic communities.

Historical and Future Vegetation Changes in the Degraded Frozen Soil and the Entire Tibetan Plateau and Climate Drivers

“…The increase of NPP over the entire TP is consistent with Zhuang 2010) who found that the TP changed from a small carbon source or neutral state in the early part of the century to a carbon sink later on, which indicates improved ecosystem productivity with time. The great spatial heterogeneity in annual NPP change in the future on the TP is similar to that of the historical period which has been reported by Cuo et al (2021), C. Li et al (2022), andPiao et al (2012). Vegetation productivity change in the DPSZs on the TP is apparently opposite to that in the arctic and subarctic regions in the historical period.…”

“…For soil moisture, all of the correlation coefficients, with the exception of −0.02 at Ngari, are greater than 0.47 and RMSE ranges from 0.01 to 0.09 (Table S2 in Supporting Information ). These analyses and the evaluations conducted in previous studies (Cuo et al., 2016, 2020, 2021) all demonstrate that the performance of LPJ on the TP is in general reasonable.…”

“…The Lunds-Postdam-Jena Dynamic Global Vegetation Model (LPJ) that has been widely applied globally (Beer et al, 2007;Murray, 2014;Sitch et al, 2003;Steinkamp & Hickler, 2015) was used in this study. The LPJ model has been adapted and applied to the TP for studying plant functional types (PFTs), desertification and NPP (Cuo et al, 2016(Cuo et al, , 2020(Cuo et al, , 2021. The model spatial resolution was set at 0.25° in this study and there were 3,978 cells on the TP.…”

Contrasting Trends in Water Use Efficiency of the Alpine Grassland in Tibetan Plateau

“…The precipitation also increased significantly in much of TP (Zhao, Zhang, & Zhou, 2022) except the southern TP, where decreasing trend occurred (Yue et al., 2020). Meanwhile, vegetation greenness (Piao et al., 2015; Wei et al., 2022) and productivity (Cuo et al., 2021; Piao et al., 2012) overall enhanced in most parts of TP since a warmer and wetter climate can promote the growth of alpine plants. Because WUE serves as an integrated functional indicator of ecosystems (Hatfield & Dold, 2019), it is necessary to elucidate how WUE of Tibetan alpine grassland varies and what its major drivers are for a better understanding of the responses and feedbacks of high‐elevation ecosystems to a changing climate.…”

Effects of Environmental Factors on the Changes in MODIS NPP along DEM in Global Terrestrial Ecosystems over the Last Two Decades

“…It is related to life activities such as vegetation growth, development, and reproduction, and it also provides an indispensable material basis for the life activities of other biological members in the entire ecosystem. Most of the studies focus on the spatiotemporal changes in NPP [13,14] and the impact of climate and human activities on NPP [15,16], modeling organic carbon storage with NPP as input data, and changes in carbon sources and sinks of the terrestrial ecosystem [12,[17][18][19]. Studies on the changes in NPP with increasing elevation gradients (EG) are mainly conducted in local regions, and all come from instantaneous surveys [20][21][22][23][24].…”