The establishment of either forest or grassland on degraded cropland has been proposed as an effective method for climate change mitigation because these land use types can increase soil carbon (C) ...stocks. This paper synthesized 135 recent publications (844 observations at 181 sites) focused on the conversion from cropland to grassland, shrubland or forest in China, better known as the ‘Grain‐for‐Green’ Program to determine which factors were driving changes to soil organic carbon (SOC). The results strongly indicate a positive impact of cropland conversion on soil C stocks. The temporal pattern for soil C stock changes in the 0–100 cm soil layer showed an initial decrease in soil C during the early stage (<5 years), and then an increase to net C gains (>5 years) coincident with vegetation restoration. The rates of soil C change were higher in the surface profile (0–20 cm) than in deeper soil (20–100 cm). Cropland converted to forest (arbor) had the additional benefit of a slower but more persistent C sequestration capacity than shrubland or grassland. Tree species played a significant role in determining the rate of change in soil C stocks (conifer < broadleaf, evergreen < deciduous forests). Restoration age was the main factor, not temperature and precipitation, affecting soil C stock change after cropland conversion with higher initial soil C stock sites having a negative effect on soil C accumulation. Soil C sequestration significantly increased with restoration age over the long‐term, and therefore, the large scale of land‐use change under the ‘Grain‐for‐Green’ Program will significantly increase China's C stocks.
Land-use change is widely considered to be a major factor affecting soil carbon (C) sequestration (ΔCs). This paper studied changes to soil C stocks (Cs) following the conversion of farmland to ...forest, shrub and grassland across the key area for implementing China's "Grain for Green"--the Loess Plateau. The results are based on a synthesis of 44 recent publications (including 424 observations at 70 sites) which has allowed us to further refine our understanding of the mechanisms driving the increase in Cs following farmland conversion. This synthesis suggests that the ΔCs potential of the Loess Plateau could reach 0.59 Tg yr(-1) based on an estimated annual average ΔCs rate of 0.29 Mg ha(-1) yr(-1). In the region's different rainfall zones both the main contributing factors and Cs dynamics varied. Across the entire Loess Plateau, Cs showed first an increasing (<5 yr) then a decreasing (6-10 yr) tendency only to increase (>10 yr) yet again. In addition, the ΔCs rates depended primarily on restoration age. This synthesis demonstrates that both the initial s Cs and the average annual temperature have a significant effect on ΔCs while the effect of land-use conversion type, rainfall zone, and average annual precipitation were minimal.
Changes in land use type can lead to variations in soil water characteristics. The objective of this study was to identify the responses of soil water holding capacity (SWHC) and soil water ...availability (SWA) to land use type (grassland, shrubland and forestland). The soil water characteristic curve describes the relationship between gravimetric water content and soil suction. We measured the soil water characteristic parameters representing SWHC and SWA, which we derived from soil water characteristic curves, in the 0-50 cm soil layer at sites representing three land use types in the Ziwuling forest region, located in the central part of the Loess Plateau, China. Our results showed that the SWHC was higher at the woodland site than the grassland and shrubland, and there was no significant difference between the latter two sites, the trend of SWA was similar to the SWHC. From grassland to woodland, the soil physical properties in the 0-50 cm soil layer partially improved, BD was significantly higher at the grassland site than at the shrubland and woodland sites, the clay and silt contents decreased significantly from grassland to shrubland to woodland and sand content showed the opposite pattern, the soil porosity was higher in the shrubland and woodland than that in the grassland, the soil physical properties across the 0-50 cm soil layer improved. Soil texture, porosity and bulk density were the key factors affecting SWHC and SWA. The results of this study provide insight into the effects of vegetation restoration on local hydrological resources and can inform soil water management and land use planning on the Chinese Loess Plateau.
The revegetation of abandoned farmland significantly influences soil organic C (SOC) and total N (TN). However, the dynamics of both soil OC and N storage following the abandonment of farmland are ...not well understood. To learn more about soil C and N storages dynamics 30 years after the conversion of farmland to grassland, we measured SOC and TN content in paired grassland and farmland sites in the Zhifanggou watershed on the Loess Plateau, China. The grassland sites were established on farmland abandoned for 1, 7, 13, 20, and 30 years. Top soil OC and TN were higher in older grassland, especially in the 0-5 cm soil depths; deeper soil OC and TN was lower in younger grasslands (<20 yr), and higher in older grasslands (30 yr). Soil OC and N storage (0-100 cm) was significantly lower in the younger grasslands (<20 yr), had increased in the older grasslands (30 yr), and at 30 years SOC had increased to pre-abandonment levels. For a thirty year period following abandonment the soil C/N value remained at 10. Our results indicate that soil C and TN were significantly and positively correlated, indicating that studies on the storage of soil OC and TN needs to focus on deeper soil and not be restricted to the uppermost (0-30 cm) soil levels.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Severe soil erosion is a serious environmental problem in China. In 1999 the Chinese government implemented the Grain-for-Green Program （herein referred to as the Program）, a well rounded program of ...ecological reconstruction to help control the country＇s soil erosion problems. This study quantitatively analyzed the impacts of the Program using data from 11 Chinese river systems to evaluate the effects of the Program on soil erosion. Results show runoff decreased and the soil erosion significantly decreased because of an increase in the area of farmland-converted forestlands. When comparing two time periods, 2003-2007 and 1998-2002, runoff and soil erosion were reduced by 18% and 45.4%, respectively. Therefore, the Program has the effect of controlling soil erosion while producing ecological benefits.
Hydrogen sulfide (H2S) is emerging as an important signalling molecule that regulates plant growth and abiotic stress responses. However, the roles of H2S in symbiotic nitrogen (N) assimilation and ...remobilization have not been characterized. Therefore, we examined how H2S influences the soybean (Glycine max)/rhizobia interaction in terms of symbiotic N fixation and mobilization during N deficiency‐induced senescence. H2S enhanced biomass accumulation and delayed leaf senescence through effects on nodule numbers, leaf chlorophyll contents, leaf N resorption efficiency, and the N contents in different tissues. Moreover, grain numbers and yield were regulated by H2S and rhizobia, together with N accumulation in the organs, and N use efficiency. The synergistic effects of H2S and rhizobia were also demonstrated by effects on the enzyme activities, protein abundances, and gene expressions associated with N metabolism, and senescence‐associated genes (SAGs) expression in soybeans grown under conditions of N deficiency. Taken together, these results show that H2S and rhizobia accelerate N assimilation and remobilization by regulation of the expression of SAGs during N deficiency‐induced senescence. Thus, H2S enhances the vegetative and reproductive growth of soybean, presumably through interactions with rhizobia under conditions of N deficiency.
Hydrogen sulfide (H2S) is emerging as a signalling molecule implicated in plant growth and abiotic stress response. However, it is unspecified whether H2S plays a pivotal role in nitrogen (N) assimilation and remobilization in plants. In this study, soybean (Glycine max) was chosen as a research object to study the synergistic regulation of H2S and rhizobia on N absorption and transport. During N deficiency‐induced soybean senescence, the synergistic effect of H2S and rhizobia regulated the expression of SAGs, including genes involved in protein degradation, nucleic acid degradation, NAC TFs, and receptor‐like protein kinases, affecting the activities, protein abundances, and transcription levels of N metabolism‐related enzymes. However, an increase in the level of N metabolism promoted the assimilation and remobilization of N in soybean by enhancing the N contents in plant tissues and the NRE of the leaves, which ultimately alleviated leaf senescence, and increased the plant biomass and the yield parameters. Therefore, it was demonstrated that H2S could act synergistically with rhizobia to promote effectively N uptake and transport during N deficiency‐induced soybean senescence, ultimately enhancing the vegetative and reproductive growth of soybean.
Soil water is a key terrestrial water resource, particularly in arid and semi-arid regions of the world such as the Loess Plateau of China. Information on the dynamics of soil moisture following ...vegetation restoration is essential for managing water resources and can be helpful for adjusting relevant government policies. To evaluate the response of soil water storage (SWS) to long-term natural vegetation succession (~160a), we examined the soil moisture for different restoration ages in the Ziwuling forest region, which is located in the central part of the Loess Plateau. Our results showed that the SWS decreased with long-term natural vegetation restoration. The bulk density (BD), soil water content (SWC), and clay and silt content presented similar trends to those of the SWS throughout the entire vegetation succession. The SWS was significantly and positively correlated with the SWC and aeration porosity (P<0.05). The SWC was lower in the upper soils (0–50cm) than in the deeper soils (>50cm) at every restoration stage, as was the SWS; however, the SWS in the 200–300cm soil layer was the highest (164.61–212.80mm) compared to other layers in all restoration stages. These results are expected to help improve the understanding of the response of deep soil water to long-term natural vegetation restoration and to provide insights into the dynamics of deep soil water influenced by vegetation.
•The soil water storage decreased along with the natural vegetation succession.•The soil total porosity and capillary porosity strongly affect the soil water content in the vegetation restoration process.•The soil water storage was highest in the 200–300cm soil layer at each restoration stage.
Land-use change resulting from natural restoration probably enhances the carbon sequestration capacity of terrestrial ecosystems. To explore those factors which foster changes in the soil carbon pool ...in forest restoration, a study comparing soil organic carbon at different vegetation succession stages along a 150-year chronosequence was conducted in the Ziwuling forest region located in the central part of the Loess Plateau, China. It showed that in long-term (~150yr) secondary forest succession the soil organic carbon storage (Cs), soil organic carbon (SOC), total nitrogen (TN), and C/N ratio all increased rapidly and tended to be at their highest at roughly the 50-year restoration mark. From this point onward the values gradually stabilized indicating that the SOC and the TN accumulated mainly in the early restoration stages. The Cs was significantly and positively correlated with the SOC, the TN, and the C/N ratio (P<0.01). The Cs in the soil was higher in the upper rather than the lower soil layers. However, the increments of the Cs mainly changed in the lower soil layers. Soil water storage was not the key factor influencing the Cs. The results suggested that changes to the Cs were the result of the accumulation of the SOC and the TN during forest succession and this capacity has shown to be positively related to forest succession on the Loess Plateau, China.
•Revegetation is recognized as one of the primary contributors to carbon sink.•We examine the effects of long-term revegetation on C stock in soil.•C sequestration mainly occur in lower soil after abandoned farmland.
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