Responses of net primary productivity to phenological dynamics in the Tibetan Plateau, China

As a key biotic factor, phenology exerts fundamental influences on ecosystem carbon sequestration. However, whether spring phenology affects the subsequent seasonal ecosystem productivity and the underlying resource limitation mechanism remains unclear for the alpine grasslands of the Tibetan Plateau (TP). In this study, we investigated the direct and lagged seasonal responses of net primary productivity (NPP) to the beginning of growing season (BGS) along a precipitation gradient by integrating field observations, remote sensing monitoring and ecosystem model simulations. The results revealed distinct response patterns of seasonal NPP to BGS. Specifically, the BGS showed a significant and negative correlation with spring NPP (R = −0.73, p < 0.01), as evidenced by the direct boosting effects of earlier BGS on spring NPP. Moreover, spring NPP was more responsive to BGS in areas with more annual precipitation. The boosting effects of earlier BGS on NPP tended to weaken in summer compared with that in spring. Sequentially, BGS exhibited stronger positive correlation with autumn NPP in areas with less annual precipitation, which suggested the enhanced lagged suppressing effects of earlier spring phenology on ecosystem carbon assimilation during the later growing season under aggravated water stress. Overall, the strengthened NPP in spring was offset by its decrement in autumn, resulting in no obvious relationship between BGS and annual NPP (R = −0.34, p > 0.05) for the entire grasslands on the TP. The findings of this study imply that the lagged effects of phenology on the ecosystem productivity during the subsequent seasons should not be neglected in the future studies.

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The Change in Environmental Variables Linked to Climate Change Has a Stronger Effect on Aboveground Net Primary Productivity Than Does Phenological Change in Alpine Grasslands

Frontiers in Plant Science ◽

10.3389/fpls.2021.798633 ◽

2022 ◽

Vol 12 ◽

Author(s):

Jiangwei Wang ◽

Meng Li ◽

Chengqun Yu ◽

Gang Fu

Keyword(s):

Climate Change ◽

Tibetan Plateau ◽

Carbon Cycling ◽

Primary Productivity ◽

Environmental Variables ◽

Net Primary Productivity ◽

Growing Season ◽

The Tibetan Plateau ◽

Aboveground Net Primary Productivity ◽

Alpine Grasslands

More and more studies have focused on responses of ecosystem carbon cycling to climate change and phenological change, and aboveground net primary productivity (ANPP) is a primary component of global carbon cycling. However, it remains unclear whether the climate change or the phenological change has stronger effects on ANPP. In this study, we compared the effects of phenological change and climate change on ANPP during 2000–2013 across 36 alpine grassland sites on the Tibetan Plateau. Our results indicated that ANPP showed a positive relationship with plant phenology such as prolonged length of growing season and advanced start of growing season, and environmental variables such as growing season precipitation (GSP), actual vapor pressure (Ea), relative humidity (RH), and the ratio of GSP to ≥5°C accumulated temperature (GSP/AccT), respectively. The linear change trend of ANPP increased with that of GSP, Ea, RH, and GSP/AccT rather than phenology variables. Interestingly, GSP had the closer correlation with ANPP and meanwhile the linear slope of GSP had the closer correlation with that of ANPP among all the concerned variables. Therefore, climate change, mainly attributed to precipitation change, had a stronger effect on ANPP than did phenological change in alpine grasslands on the Tibetan Plateau.

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Net primary productivity and spatial distribution of vegetation in an alpine wetland, Qinghai-Tibetan Plateau

Limnology ◽

10.1007/s10201-007-0205-5 ◽

2007 ◽

Vol 8 (2) ◽

pp. 161-170 ◽

Cited By ~ 12

Author(s):

Mitsuru Hirota ◽

Kiyokazu Kawada ◽

Qiwu Hu ◽

Tomomichi Kato ◽

Yanhong Tang ◽

...

Keyword(s):

Spatial Distribution ◽

Tibetan Plateau ◽

Primary Productivity ◽

Net Primary Productivity ◽

Alpine Wetland

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Influence of spring phenology on seasonal net primary productivity in the alpine grassland on the Tibetan Plateau

10.5194/egusphere-egu2020-12393 ◽

2020 ◽

Author(s):

Zhoutao Zheng ◽

Wenquan Zhu ◽

Yangjian Zhang ◽

Ke Huang ◽

Nan Cong

Keyword(s):

Primary Productivity ◽

Net Primary Productivity ◽

Growing Season ◽

Ecosystem Model ◽

Alpine Grassland ◽

The Tibetan Plateau ◽

Field Observations ◽

Vegetation Phenology ◽

Spring Phenology ◽

The Relationship

<p>Vegetation phenology is recognized to exert crucial influences on carbon sequestration and the role of vegetation phenology in mediating carbon cycle varies with ecosystem type. However, the relationship between vegetation phenology and productivity has not been fully understood in the alpine ecosystem due to a lack of field observations, poor model performances and their complex mechanisms. In this study, we examined the spatio-temporal variation in beginning of growing season (BGS) and net primary productivity (NPP) for the alpine grassland on the Tibetan Plateau (TP) and the regulation effects of spring phenology on seasonal NPP by integrating field observations, remote sensing monitoring and ecosystem model simulation. The ecosystem model performances were improved by optimizing ecosystem parameters from field observations. The results indicated a significant advance in BGS with a rate of 0.31 days/yr (P < 0.1) in the alpine grassland during 2001-2015 while the annual NPP increased significantly at a rate of 1.25 gC/m<sup>2</sup>/yr (P < 0.01). With regard to the relationship between BGS and NPP, large spatial heterogeneities were identified. Overall, a negative but non-significant correlation (R = -0.34, P > 0.1) was observed between BGS and annual NPP for the entire grassland ecosystem on the TP. But responses of NPP to BGS varied with seasons. Specifically, BGS showed significant negative correlation with spring NPP (R = -0.73, P < 0.01), and advanced spring led to increased spring NPP. The positive effects of advanced BGS on NPP tended to weaken in summer. Moreover, BGS was significantly and positively correlated with autumn NPP in some relatively arid zones of the southwestern TP, suggesting the suppressing effects of earlier spring on carbon assimilation during the later growing season in water limited areas. This study improved our understanding on the impacts of biotic factors on carbon cycles of the alpine ecosystem and implies that the effects of phenology can&#8217;t be concluded simply for an annual sum, and their relationships for each separate season are also critical.</p>

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Spatio-Temporal Changes of Vegetation Net Primary Productivity and Its Driving Factors on the Qinghai-Tibetan Plateau from 2001 to 2017

Remote Sensing ◽

10.3390/rs13081566 ◽

2021 ◽

Vol 13 (8) ◽

pp. 1566

Author(s):

Yin Zhang ◽

Qingwu Hu ◽

Fengli Zou

Keyword(s):

Tibetan Plateau ◽

Primary Productivity ◽

Human Activities ◽

Net Primary Productivity ◽

Climatic Factors ◽

Correlation Coefficients ◽

Google Earth ◽

Computing Platform ◽

Positive Effects ◽

Spatio Temporal

The Qinghai-Tibetan Plateau (QTP) is the highest plateau in the world. Under the background of global change, it is of unique significance to study the net primary productivity (NPP) of vegetation on the QTP. Based on the Google Earth Engine (GEE) cloud computing platform, the spatio-temporal variation characteristics of the NPP on the QTP from 2001 to 2017 were studied, and the impacts of climate change, elevation and human activity on the NPP in the QTP were discussed. The mean and trend of NPP over the QTP were “high in the southeast and low in the northwest” during 2001–2017. The trend of NPP was mostly between 0 gC·m−2·yr−1 and 20 gC·m−2·yr−1 (regional proportion: 80.3%), and the coefficient of variation (CV) of NPP was mainly below 0.16 (regional proportion: 89.7%). Therefore, NPP was relatively stable in most regions of the QTP. Among the correlation coefficients between NPP and temperature, precipitation and human activities, the positive correlation accounted for 81.1%, 48.6% and 56.5% of the QTP area, respectively. Among the two climatic factors, the influence of temperature on NPP was greater than that of precipitation. The change of human activities and the high temperature at low altitude had positive effects on the increase of NPP.

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