Increased Precipitation and Nitrogen Alter Shrub Architecture in a Desert Shrubland: Implications for Primary Production

Abstract

Shrublands are one of the major types of ecosystems in the desert regions of northern China, which is expected to be substantially more sensitive to global environmental changes, such as widespread nitrogen enrichment and precipitation changes, than other ecosystem types. However, the interactive effects of nitrogen and precipitation on them remain poorly understood. We conducted a fully factorial field experiment simulating three levels of precipitation (ambient, +20%, +40%) and with two levels of nitrogen deposition (ambient, 60 kg N ha-1 yr-1) in a desert shrubland in the Mu Us Desert of northern China. We used plant architectural traits (plant cover, volume, twig size and number) as proxies to predict aboveground net primary productivity (ANPP) of the dominant shrub (Artemisia ordosica Krasch), and assessed the responses of plant productivity and architectural traits to water and nitrogen addition. We found significant differences in twig size and number of A. ordosica under water and nitrogen treatments but not in shrub cover/volume, which suggest that twig size and number of the shrub species were more sensitive to environmental changes. The productivity of the overall community was sensitive to increased precipitation and nitrogen, and shrubs played a more important role than herbaceous plants in driving productivity in this ecosystem. Precipitation- and nitrogen-induced increases in vegetation production were positively associated with increases in twig size and number of the dominant shrub. Water addition enhanced the twig length of A. ordosica, while nitrogen addition resulted in increased twig density (the number of twigs per square meter). Water and nitrogen interacted to affect twig length, but not twig number and shrub ANPP. The trade-off, defined as negative covariance between twig size and number, was likely the mechanism underlying the responses of twig length and shrub ANPP to water and nitrogen interactions. Our results highlight the sensitivity of twig size and number as indicators to estimate shrub production and the mechanism underpinning desert shrub ANPP response to global environmental changes.

Benefactor facilitation and beneficiary feedback effects drive shrub‐dominated community succession in a semi‐arid dune ecosystem

“…This shows that the shrub twig number is highly sensitive to biotic environmental change and complements the conclusion of She et al. (), who proposed that the twig number is a good indicator of abiotic environmental changes.…”

“…The method used for the annual growth measurements of the shrub ( A. ordosica ) followed She, Zhang, Qin, Wu, and Bai (). We considered the dry biomass of the current year's twigs as a proxy for shrub annual growth (AG); these twigs were easily recognized by their colour and structure (Jobbágy & Sala, ).…”

Nitrogen enrichment alters nutrient resorption and exacerbates phosphorus limitation in the desert shrub Artemisia ordosica

“…Shrub ( A. ordosica ) ANPP (g/m 2 ) was estimated by a nondestructive method based on twig size and number, following the methodologies outlined in She et al. ().…”

“…Our experiment was design followed that described in She, Zhang, Qin, Wu, and Bai (2016), with minor adjustments as follows. In October 2014, four experimental blocks, each containing six 5 m × 5 m plots, were established in an A. ordosica shrubland.…”

Plasticity in Meristem Allocation as an Adaptive Strategy of a Desert Shrub under Contrasting Environments

“…This study was conducted at Yanchi Research Station (37°04′–38°10′N, 106°30′–107°41′E, 1530 m a.s.l), which is located on the southwestern edge of the Mu Us Desert, Ningxia, China. This region has a semiarid continental monsoon climate with an average annual temperature of 8.1°C and a mean annual precipitation of 284.8 mm (1955–2013) ( She et al, 2016 ). Soil type is characterized by quartisamment based on the US Soil Taxonomy ( Gao et al, 2014 ).…”