Does Caragana korshinskii plantation increase soil carbon continuously in a water‐limited landscape on the Loess Plateau, China?

Abstract

Although afforestation of nitrogen‐fixing shrubs, especially Caragana korshinskii in semiarid areas, is expected to improve ecosystem restoration and carbon sequestration, water shortage induced by these thirsty shrubs may negate potential benefits. Yet there is poor understating of the persistence of soil carbon sequestration in nitrogen‐fixing shrub plantations. Here, we selected three C. korshinskii plantations with different ages (10, 20, and 30 years) on the Loess Plateau to evaluate the persistence of soil carbon sink. We examined dynamics of soil carbon, total nitrogen, and soil water, as well as their relationships along the plantation ages. The results showed that soil organic carbon (SOC) and soil total nitrogen (STN) were tightly coupled. SOC, STN, and soil water stocks (0–100 cm) were significantly decreased by 23.9%, 19.9%, and 29.2% from 10 to 30 years, respectively. The reduction of SOC and STN was likely caused by lowered intercanopy herbaceous productivity due to soil drying and intensified competition from shrubs. We present evidence that the positive carbon sequestration by afforestation of leguminous shrub in short term may be further weakened by water shortage, making our ability to restore degraded land in semiarid regions more challenging than previously thought. Therefore, it is essential to improve management of afforestation land such as thinning for maintaining SOC sequestration persistently in water‐limited areas.

Is the Change of Soil Carbon Capacity Persistence Rising or Remain Stable With Maturity of Vegetation Restoration?

“…Some studies have found that afforestation does not necessarily increase SOC stocks, but instead decreases SOC stocks during the later stages of succession (61). Similar findings were reported by a study on a shrub plantation situated on the Loess Plateau, China, during which SOC stocks decreased by almost 25% over a period of afforestation succession of 10-30 years (62). Moreover, a previous study has shown that although forests sequester C in the long term, the soil C stocks of shrubland and grassland had decreased significantly 30 years after having been converted from cropland (63).…”

“…The results of our study suggested that about 30 years of planting, the trend of increasing soil carbon pool was not sustained, and SOC stock decreased slightly as a saturated C state was reached (54). Moreover, previous studies have confirmed that a slight soil carbon stock loss due to a water deficit occurred in some shrublands (62).…”

Effect of using an infiltration hole and mulching in fish‐scale pits on soil water, nitrogen, and organic matter contents: Evidence from a 4‐year field experiment

“…The typical natural vegetation of this region is Stipa bungeana Trin. Since 1999, the Grain for Green Program has been implemented to restore the degraded sloping lands (Chai et al, 2019). The main restored plants are Armeniaca sibirica , Amygdalus davidiana , Hippophae rhamnoides , and Caragana korshinskii .…”

“…The watertable is ca 50 m below the land surface, so the soil water stocks available to plants are only recharged by rainwater (Wang et al, 2015). Precipitation is highly variable, with approximately 71.2% of the total annual precipitation generated during June to September, most of which is in the form of high-intensity rainstorms, so soil erosion predominately occurs during this period (Chai et al, 2019). Soil erosion modulus was 1200 t km À2 yr À1 .…”

Trade-off between soil water maintenance and carbon sequestration during the implementation of ecological restoration programs in semi-arid Loess Plateau

“…Although these results are consistent with our results, few of them take both carbon sequestration and deep soil water consumption into consideration especially under different rainfall zones, and therefore the comprehensive assessment of trade-off between the two vital soil functions was limited. However, recent study suggested that positive carbon sequestration by afforestation in short term may be further weakened by water shortage, making our ability to restore degraded land in semi-arid regions more challenging (Chai et al , 2019). From this perspective, ecological restoration, e.g., tree planting, is not a simple solution and it must be planned carefully and implemented to achieve desired outcomes in the long run particularly in eco-fragile regions (Holl and Brancalion, 2020).…”