Effects of converting natural grasslands into planted grasslands on ecosystem respiration: a case study in Inner Mongolia, China

Abstract

With increasingly intensifying degradation of natural grasslands and rapidly increasing demand of high quality forages, natural grasslands in China have been converted into planted grasslands at an unprecedented rate and the magnitude of the conversion in Inner Mongolia is among the national highest where the areal extent of planted grasslands ranks the second in China. Such land-use changes (i.e., converting natural grasslands into planted grasslands) can significantly affect carbon stocks and carbon emissions in grassland ecosystems. In this study, we analyzed the effects of converting natural grasslands into planted grasslands (including Medicago sativa, Elymus cylindricus, and M. sativa+E. cylindricus) on ecosystem respiration (F eco) in Inner Mongolia of China. Diurnal F eco and its components (i.e., total soil respiration (F ts), soil heterotrophic respiration (F sh) and vegetation autotrophic respiration (F va)) were measured in 2012 (27 July to 5 August) and 2013 (18 July to 25 July) in the natural and planted grasslands. Meteorological data, aboveground vegetation data and soil data were simultaneously collected to analyze the relationships between respiration fluxes and environmental factors in those grasslands. In 2012, the daily mean F eco in the M. sativa grassland was higher than that in the natural grassland, and the daily mean F va was higher in all planted grasslands (i.e., M. sativa, E. cylindricus, and M. sativa+E. cylindricus) than in the natural grassland. In contrast, the daily mean F ts and F sh were lower in all planted grasslands than in the natural grassland. In 2013, the daily mean F eco , F ts and F va in all planted grasslands were higher than those in the natural grassland, and the daily mean F sh in the M. sativa+E. cylindricus grassland was higher than that in the natural grassland. The two-year experimental results suggested that the conversion of natural grasslands into planted grasslands can generally increase the F eco and the increase in F eco is more pronounced when the plantation becomes more mature. The results also indicated that F sh contributed more to F eco in the natural grassland whereas F va contributed more to F eco in the planted grasslands. The regression analyses show that climate factors (air temperature and relative humidity) and soil properties (soil organic matter, soil temperature, and soil moisture) strongly affected respiration fluxes in all grasslands. However, our observation period was admittedly too short. To fully understand the effects of such land-use changes (i.e., converting natural grasslands into planted grasslands) on respiration fluxes, longer-term observations are badly needed.

Soil organic matter on arid saline-alkali land drives greenhouse gas emissions from artificial and natural grasslands in different directions

“…For A*B, GWP were affected by SOM, NO 3 − , TN, and salinity. This is consistent with previous reports that showed that Bro has a higher salt and alkali tolerance; therefore, it is mainly regulated by soil nutrients, whereas Alf has less nutrient limitation due to nitrogen fixation, and A*B is regulated by nutrient competition and salinity (Figure 5) (Lucero et al, 2000;Zhang et al, 2017;Jia et al, 2018). Regarding NG and artificial grasslands, SOM had different effects on GWP (Figure 5).…”

“…In contrast, non-legume wheatgrass exhibits better drought and salinity tolerance than purple prairie clover (Gong et al, 2015;Jia et al, 2018), which may explain why Alf had lower FCO 2 and higher SOM levels (Li et al, 2012). The higher emissions and lower carbon storage in mixed-species grasslands could be attributed to the complementary competition among different species (Figures 2D, 4E) (Lucero et al, 2000;Zhang et al, 2017). The mixture of legumes and grasses promotes better nutrient supply, and competition among plants stimulates rhizosphere effects by producing more types of root exudates, consequently jointly promoting respiration intensity in the soil layer.…”

Soil Carbon Dioxide Emission: Soil Respiration Measurement in Temperate Grassland, Nepal

“…However, soil carbon pool dynamics can be altered with the factors like climate change [40], land use [41] [42] [43] and management practices [21] [44] [45] [ 46]. Research indicated that global soil carbon dioxide emissions are in the range of 98 ± 12 Pg•y −1 (1 Pg = 10 15 g), with annual increases of 0.1 Pg that is suggested to be temperature-associated [47].…”

“…Geographical distribution of grassland is expansive throughout the world [38] and it is one of the principal ecotypes in the terrestrial ecosystem situated mostly in areas with more severe eco-environment where neither the forest growth nor the farmland reclamation is appropriate. Carbon in grasslands originates from below-ground biomass [14] [21] [52], primarily roots [53] [54] that increase with the age [55] and micro-organisms [43]. Approximately above 40% land area of the global terrestrial ice-free surface is covered by grasslands [56].…”

Sustainable Forest Development in the Digital Era: The Impact of Internet Use on the Happiness of Forest Farmers’ Families in Ecologically Fragile Ethnic Areas of China

“…Existing measures of happiness mainly adopt univariate scoring measures of individual or family life satisfaction, but since happiness is difficult to directly observe, scoring measures are also susceptible to the influence of actual interview bias and respondents' emotional changes, resulting in distorted results of happiness and leading to measurement bias. Therefore, in light of the happiness measurement methods and research definitions of Xing [7], Tan et al [48], and Zhang et al [49], and based on the availability of research data and the sustainability of forest resource utilization, this study deconstructs the happiness of forest farmers' families into five dimensions: family environment, economic status, educational conditions, public services, and developmental resilience. Among them, family environment measures the basic living conditions and water security of forest farmers' families; economic condition evaluates the subjective feeling of forest farmers regarding family income and local socio-economic development; educational condition measures the perception of social education and the degree of education of forest farmers' families; public services targets the subjective perception of forest farmers regarding local social recreation, employment, and basic public service security; and developmental resilience embodies the forest farmers' families in terms of natural disasters, epidemic shocks, and the prevention of returning to poverty (Table 1).…”