Zhao Xueyong

Relationship between fresh leaf traits and leaf litter decomposition of 20 plant species in Kerqin sandy land, China

Abstract 20 plant species (10 monocots and 10 dicots) grown in Kerqin sandy grassland were incubated under indoor conditions to monitor the amount and rate of CO2 release from the leaf litter. 11 traits of mature fresh leaves including caloric value, contents of Mg, P, N, K, C, C/N, N/P, specific leaf area, dry matter content and leaf surface area were measured to determine the relationship between CO2 release and leaf characteristics. All those traits have great variation among the 20 species with over 3 fold differences between the maximum and minimum values, and a few traits such as leaf Mg content reached as high as 9 folds. After 28 ds incubation, the average CO2 release amount from all the species was (4121 ± 1713) μg kg−1 dry soil. The highest level from Chenopodium acuminatum was (8767 ± 177) μg kg−1 dry soil, which was 5 folds higher than the lowest level ((1669 ± 47)μg kg−1 dry soil) from Digitaria sanguinalis. However, CO2 release rate showed the same trend in all the 20 species, i.e., the leaf litter decomposed faster initially (0–4 d), and gradually slowed down during extended cultural periods. Comparison between monocots and dicots showed that these two taxonomic groups had significant differences in terms of the amount and rate of CO2 released from leaf litter, and N and C contents, leaf C/N, and dry matter content of mature leaves. Contents of N, C and dry matter, and C/N of mature leaves are significantly correlated with CO2 release from leaf litter decomposition, which has been revealed by the Pearson correlation test. It can be concluded that these three traits of mature leaves can be used indirectly to predict decomposition rate of the leaf litter.

Biomass allocation response of species with different life history strategies to nitrogen and water addition in sandy grassland in Inner Mongolia

Biomass allocation response of species with different life history strategies to nitrogen and water addition in sandy grassland in Inner Mongolia MAO Wei, LI Yu-Lin, CUI Duo, ZHAO Xue-Yong, ZHANG Tong-Hui, and LI Yu-Qiang Naiman Desertification Research Station, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou 730000, China; and Center for Earth System Science, Tsinghua University, Beijing 100084, China

Variation of Zn content in soils under different land-use types in the Hetao oasis, Inner Mongolia of China

Understanding the status and distribution of the micronutrient Zn in soils is important for managing plant growth and preventing soil pollution for agricultural irrigation systems in arid and semi-arid regions. In this study, a total of 195 soil samples from five soil layers (0–20, 20–40, 40–60, 60–80 and 80–100 cm) in the three land-use types (wasteland, forestland and cropland) after long-term agricultural fertilization and irrigation with Yellow River water were collected in the middle of the Hetao oasis, i.e. the Yongji irrigation sub-oasis. We analyzed the vertical and spatial distributions of Zn content and its relationship with soil properties to determine whether differences of Zn content existed in the soil profiles. The results revealed that the mean content of Zn was 107 mg/kg, 1.9 times higher than the background value (55.7 mg/kg) of the Hetao oasis and much lower than the secondary standard value (300 mg/kg) of the Chinese Environmental Quality Standard for Soils when pH>7.5. Soil Zn contents were not significantly different and the coefficients of variation of Zn contents were less than 50% in the five soil layers. Soil Zn content was similar from southern to northern parts but increased from western to eastern parts in the sub-oasis. Soil Zn contents did not differ significantly among the three land-use types, but soil total nitrogen (TN) contents were significantly higher in the agriculturally managed forestland and cropland than in the wasteland (P<0.05). Zn was significantly and positively correlated with TN (F=36.6, P<0.001). The use of fertilizers may increase the content of Zn in soils, but flooding irrigation may minimize the differences in the spatial distribution of soil Zn content in the whole sub-oasis. This research is of important value for soil pollution control and sustainable land use management in arid and semi-arid regions.

Comparison of soil physico-chemical properties under different land-use and cover types in northeastern China's Horqin Sandy Land

The Horqin Sandy Land of northeastern China was originally a grassland with plenty of water and lush vegetation dominated by palatable grass species along with sparsely scattered woody species. However, it has experienced severe desertification in recent decades due to its fragile ecology together with inappropriate human activities. Currently, the landscape of the Horqin Sandy Land is dominated by irrigated croplands and sand dunes with different degrees of vegetation cover, as the region has become the most important part of the semiarid agro-pastoral ecotone of northern China. In this study, we compared soil physical and chemical properties under different land-use and cover types (irrigated cropland, rainfed cropland, sandy grassland, fixed dunes, and mobile dunes) . We found that soil particle size distribution; organic C, total N, and total mineral element, microelement, and available microelement and nutrient contents; pH; CEC; and bulk density differed significantly among the land-use and cover types. In general, soil quality was highest in the cropland, intermediate in the sandy grassland, and lowest in the dunes. The most important soil quality attribute, soil organic carbon (SOC) storage, decreased in the following order: irrigated cropland (5, 699 g/m 2 ) ＞ sandy grassland (3, 390 g/m 2 ) ＞ rainfed cropland (2, 411 g/m 2 ) ＞ fixed dunes (821 g/m 2 ) ＞ mobile dunes (463 g/m 2 ) . SOC was significantly positively correlated with a large proportion of the other soil physico-chemical parameters. Our results suggest that the key issue in restoration of the degraded soils will be to increase SOC storage, which would also create a high potential for sequestering soil C in desertified areas of the Horqin Sandy Land.

Vertical distribution of Artemisia halodendron root system in relation to soil properties in Horqin Sandy Land, NE China

Root distribution plays an important role in both vegetation establishment and restoration of degraded land through influencing soil property and vegetation growth. Root distribution at 0~60 cm depth of A. halodendron was investigated in Horqin Sandy Land. Soil organic carbon (SOC) and nitrogen (SN) concentration as well as carbon and nitrogen in root biomass and necromass were measured. Root length density (RLD) was estimated. Total root biomass, necromass and the RLD at 0~60 cm depth was 172 g/m 2 , 245 g/m 2 , and 368 m/m 2 , respectively. Both biomass and necromass of A. halodendron roots decreased with soil depth, live roots were mainly at 0~20 cm (76% of biomass and 63% of root length), while 73% of the necromass was within 0~30 cm depth. N concentration of roots (biomass and necromass) was about 1.0% and 1.5%, respectively. There were significant differences in SOC concentration between soil layers, but insignificant for SN. Soil C/N ratio decreased with depth ( P A. halodendron efficiency in soil restoration in sandy land.

Seasonal changes in the relationship between species richness and community biomass in grassland under grazing and exclosure, Horqin Sandy Land, northern China

This study carried out an analysis of seasonal changes in relationships between vegetation cover,plant density,species richness and above-ground biomass in grassland under grazing and exclosure in Horqin Sandy Land.Results showed that in grassland being grazed and fenced,vegetation cover,richness and biomass were lower in April than those in August,while plant density showed a reverse trend.Vegetation cover over the season was higher in fenced grassland than that in grazed grassland;biomass in June and August was higher in fenced grassland than that in grazed grassland,while plant density in April and June and was lower in fenced grassland than that in grazed grassland.In fenced grassland,the relationship between species richness and biomass was significantly negative in August(p0.01);in grazed grassland,the relationship between plant density and biomass was significantly positive in the April(p0.01) and was significantly negative in August(p0.01).The relationship between plant density and total biomass for dominant species varied with seasonal changes under grazing and exclosure.In grassland under grazing,the relationship between plant density of Cleistogenes squarrosa and biomass was significantly positive in April(p0.01) and was significantly negative in August(p0.01);the relationship between plant density of Artemisia scoparia or Setaria viridis and biomass was significantly negative in August(p0.01);the relationship between plant density of Salsola collina and biomass was significantly positive in April and June(p0.01).In fenced grassland,the relationship between plant density of Lesredeza davurica or Salsola collina and biomass was significantly positive in August(p0.01).These results suggest that long-term grazing,seasonal changes and their interaction significantly influence vegetation cover,plant density and biomass in grassland(p0.05).Long-term grazing also affects the seasonal changes of plant density and biomass of dominant species,which further affects the seasonal relationship between plant density and biomass in grassland.Species competition in fenced grassland results in the seasonal changes of relationship between species richness and biomass.

ITS sequence analysis ofArtemisia halodendronin different habitat gradients

The aim of the present study is to investigate the difference between ITS sequences of Artemisia halodendron Turcz. from different habitat gradients in Horqin Sandy Land, with Artemisia depauperata Krasch. selected as the outgroup. Results indicate that the total length of A. halodendron ITS is 696 bp, the lengths of unaligned ITS-1 and ITS-2 sequences varied from 253 to 256 bp and 264 to 269 bp, respectively, and GC content of ITS-1 and ITS-2 sequences ranged from 54.02% to 54.77% and 56.75% to 58.64%, respectively. This indicates a high difference of length and composition of sequences in ITS-1 than ITS-2. The genetic identity between ITS sequences of A. halodendron from nine populations ranged from 85.7% to 99.7% which indicates some genetic differentiation between sequences. In the maximum parsimony (MP) tree, most ITS sequences from A. halodendron show two major clades: Clade I and Clade II, with Clade II older than Clade I. The order is subp4 → subp1 → subp2 → subp3 → subp8 → subp6 → subp7 → subp9 → subp5, and corresponding habitat order is: inter-dune lowlands → semi-mobile dune → mobile dune → semi-fixed dune → fixed dune. This indicates a close relation between the evolutionary processes of A. halodendron and desertification forming processes and ecological restoration processes of Horqin Sandy Land.