scholarly journals Direct and Lagged Effects of Spring Phenology on Net Primary Productivity in the Alpine Grasslands on the Tibetan Plateau

2020 ◽  
Vol 12 (7) ◽  
pp. 1223 ◽  
Author(s):  
Zhoutao Zheng ◽  
Wenquan Zhu ◽  
Yangjian Zhang
Keyword(s):  
Tibetan Plateau ◽  
Primary Productivity ◽  
Net Primary Productivity ◽  
Growing Season ◽  
The Tibetan Plateau ◽  
Ecosystem Productivity ◽  
Alpine Grasslands ◽  
Spring Phenology ◽  
Ecosystem Carbon ◽  
Lagged Effects

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.

scholarly journals 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

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.

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

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

&lt;p&gt;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 &lt; 0.1) in the alpine grassland during 2001-2015 while the annual NPP increased significantly at a rate of 1.25 gC/m&lt;sup&gt;2&lt;/sup&gt;/yr (P &lt; 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 &gt; 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 &lt; 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&amp;#8217;t be concluded simply for an annual sum, and their relationships for each separate season are also critical.&lt;/p&gt;

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

2017 ◽  
Vol 232 ◽  
pp. 235-246 ◽  
Author(s):  
Siyuan Wang ◽  
Bing Zhang ◽  
Qichun Yang ◽  
Guangsheng Chen ◽  
Bojuan Yang ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Primary Productivity ◽  
Net Primary Productivity ◽  
The Tibetan Plateau

scholarly journals Growing Season Precipitation Rather than Growing Season Length Predominates Maximum Normalized Difference Vegetation Index in Alpine Grasslands on the Tibetan Plateau

2020 ◽  
Vol 12 (3) ◽  
pp. 968
Author(s):  
Jiang Wei Wang ◽  
Meng Li ◽  
Guang Yu Zhang ◽  
Hao Rui Zhang ◽  
Cheng Qun Yu
Keyword(s):  
Tibetan Plateau ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Growing Season ◽  
The Tibetan Plateau ◽  
Season Length ◽  
Alpine Grasslands ◽  
Vegetation Productivity ◽  
Growing Season Length ◽  
Growing Season Precipitation

Precipitation and growing season length (GSL) are vital abiotic and biotic variables in controlling vegetation productivity in alpine regions. However, their relative effects on vegetation productivity have not been fully understood. In this study, we examined the responses of the maximum normalized difference vegetation index (NDVImax) to growing season precipitation (GSP) and GSL from 2000 to 2013 in 36 alpine grassland sites on the Tibetan Plateau. Our results indicated that NDVImax showed a positive relationship with prolonged GSL (R2 = 0.12) and GSP (R2 = 0.39). The linear slope of NDVImax increased with that of GSP rather than GSL. Therefore, GSP had a stronger effect on NDVImax than did GSL in alpine grasslands on the Tibetan Plateau.

scholarly journals The Restoration Potential of the Grasslands on the Tibetan Plateau

2021 ◽  
Vol 14 (1) ◽  
pp. 80
Author(s):  
Ruijing Wang ◽  
Qisheng Feng ◽  
Zheren Jin ◽  
Tiangang Liang
Keyword(s):  
Tibetan Plateau ◽  
Net Primary Productivity ◽  
Meteorological Data ◽  
Alpine Grassland ◽  
Northwestern Part ◽  
The Tibetan Plateau ◽  
Alpine Grasslands ◽  
Local Conditions ◽  
Grassland Ecosystems ◽  
Restoration Potential

While the alpine grassland ecosystems on the Tibetan Plateau (TP) have generally improved in recent years, some grasslands still suffer from varying degrees of degradation. Studying the restoration potential (R) of the grasslands on the TP is crucial to the conservation and restoration of its alpine grassland ecosystems. Few studies have assessed the restoration value of the alpine grasslands on the TP. We attempt to estimate the actual (ANPP) and potential net primary productivity (PNPP) of the grasslands on the TP. On this basis, we defined R as the “gap” between the current and highest achievable levels of restoration of a grassland. Then, R estimates were yielded for the alpine grasslands on the TP, which we used to analyze the restoration value of these grasslands. Specifically, based on the meteorological data for the period 2001–2019, in conjunction with remote-sensing imagery acquired by a moderate-resolution imaging spectroradiometer for the same period, the Carnegie–Ames–Stanford approach model was selected to produce ANPP estimates for the grasslands on the TP. Then, the Thornthwaite memorial model, the principle of similar habitats, and the Chikugo model, were employed to generate PNPP estimates for these grasslands. In addition, the R of these grasslands was then assessed based on the difference between their PNPP and ANPP. The main results are summarized as follows. (1) A multiyear mean R of 332.33 g C·m–2 (81.59% of the ANPP) was determined for the grasslands on the TP over the period 2001–2019. A notable spatial distribution pattern of high Rs in the southwestern, eastern and middle parts of the TP, and low Rs in the northwestern part of the TP were also identified. Most of the grasslands in areas such as the southern part of Nagqu, the southwestern part of Ngari, Xigaze, Garze Tibetan Autonomous Prefecture, Aba Tibetan and Qiang Autonomous Prefecture, Gannan Tibetan Autonomous Prefecture, Huangnan Tibetan Autonomous Prefecture, Haibei Tibetan Autonomous Prefecture, Guoluo Tibetan Autonomous Prefecture and Yushu Tibetan Autonomous Prefecture were found to have high restoration value. (2) Grasslands with a stable R account were the highest proportion (76.13%) of all the grasslands on the TP, followed by those with a decreasing R (19.62%) and those with an increasing R (4.24%). Grasslands with an increasing R were mainly concentrated in the southern part of Xigaze, and parts of Yushu Tibetan Autonomous Prefecture, Guoluo Tibetan Autonomous Prefecture and Garze Tibetan Autonomous Prefecture. (3) Analysis based on the local conditions of the TP revealed a high restoration value for three types of grassland (i.e., alpine meadows, mountain meadows, and temperate meadow steppes), the grasslands distributed at altitudes of 3000–4000 m, and the grasslands located in the warm temperate zone. The results of this study are expected to provide scientific and theoretical support for the formulation of policies and measures aimed at conserving grasslands, as well as restoring ecosystems and degraded grasslands on the TP.

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