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Wang L.D.,Gansu Agricultural University | Wang L.D.,State Key Laboratory Breeding Base of Desertification and Aeolian Sand Disaster Combating | Wang L.D.,Gansu Hexi Corridor Forest Ecosystem National Research Station | Yao T.,Gansu Agricultural University | And 11 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2016

To better understand the changes in soil conditions after agriculture use ceases, we measured and analyzed the changes in three components-soil microbial quantity, soil microbial biomass, and soil enzyme activity-in sample sites where farming had been discontinued for different periods (1, 2, 3, 4, 5, 8, 15, 24 and 31 years), in the lower Shiyang River area. By using the data, the correlations between the three components were also studied in 2012. The three components, respectively, contained 1) bacteria, fungi, and actinomycetes; 2) microbial biomass carbon, microbial biomass nitrogen, and microbial biomass phosphorus; and 3) catalase, sucrase, urease, and phosphatase. Synchronic space investigation was adopted instead of diachronic temporal investigation. Results showed that bacteria were the most abundant of the three soil microorganisms in the nine soil samples taken 31 years after farming ceased, followed by actinomycetes and fungi. Overall, the maximum weighted average of the three soil microbial quantities all occurred in the first 8 years after farming ceased. The quantity of soil microbial biomass carbon initially decreased with increasing time since farming ceased. It gradually increased starting in the 4th year and reached the peak in the 24th year, after which it became stable. The soil microbial biomass nitrogen appeared to increase with time. After the maximum weighted average in the 4th year, there was a steady reduction with large significant differences in soil microbial biomass nitrogen among soil sites of various ages. The weighted average soil microbial biomass phosphorus increased at the same pace as nitrogen at the beginning of the soil restoration period. The biomass phosphorus level climaxed at the 8th year, after which it tended to decline gradually before finally stabilizing. The general trend of soil enzyme activity decreased, but with fluctuations, with increasing soil succession age. Moreover, soil microbial quantity, soil microbial biomass, and soil enzyme activity declined dramatically in all restoration ages with soil depth from 0 to 10 cm, 10 to 20 cm, and 20-30 to 30-40 cm. In addition, the surface soil microbial biomass and soil enzyme activity were the largest among the four soil levels. The changes in soil microbial quantity, soil microbial biomass, and soil enzyme activity were extremely slow. In addition, an interactive process and a feedback response between the three components was observed. Highly significant correlations were found, especially between fungi and actinomycetes, microbial biomass nitrogen and sucrase, actinomycetes and catalase and sucrase, microbial biomass carbon and phosphatase, microbial biomass nitrogen and urease, and microbial biomass phosphorus and sucrose. To summarize, we noted an improvement in the soil conditions in the initial 4-5 years after ceasing agricultural practice, followed by a declining trend in soil fertility. © 2016, Ecological Society of China. All rights reserved.

Zhang J.,Gansu Agricultural University | Zhang J.,Minqin National Research Station for Desert Steppe Ecosystem | Zhang J.,State Key Laboratory Breeding Base of Desertification and Aeolian Sand Disaster Combating | Zhang J.,Desert Research Institute | And 21 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2014

Kumtag desert, China's sixth largest desert, lies in the south-east of the Lop Nur region,and is famous with the unique dune type of Pseudo-feathery dunes in the whole world. Kumtag desert is expanding and threatening to engulf previously productive lands with its arid wasteland character with the speed of 1-4 m eastward annually. Tamarix sand-hillocks is a frequent special biological landform types, with legible age layers structure composited by sand and plant litters, in Kumtag desert. And it is very important for regional environmental evolution research because of noting the desert environmental information diversification. In the present paper, we try to explore desert environmental change process of Kumtag desert based on stable isotope techniques collecting stable carbon isotope sample of Tamarix sand-hillocks from the different habitats and set up the stable carbon isotope series in age layers of four typical Tamarix sand-hillocks, proluvial landforms, wedland landforms, YaDan landforms and valley landforms, meanwhile environmental information and local meteorological data were collected as well. The results showed that the ratio of stable carbon isotope (δ13C), in age layers of Tamarix sand-hillocks, was fluctuated during 40-60 s of twenty century, and had declined since 1980s. The change tendency of stable carbon isotope series was accord with the stable carbon isotope downtrend of tree-ring all over the world. It was indicated that atmospheric CO2 concentration increasing affected the carbon isotope of stable carbon isotope (δ13C) in age layers of Tamarix sand-hillock. The resolution ratio(δ)of stable carbon isotope in age layers of Tamarix sand-hillocks had a similar change trendency to the global climate changes. It was dry and warm climate environment in the recent 120 years, which the resolution ratio(δ)was reduced with the global climate warming. However, the climate environment was colder and moister before the industrial revolution in the nineteenth century, and the resolution ratio(δ)was rosen. There was different response of the solution ratio δof stable carbon isotope in age layers of Tamarix sand-hillocks under different habitats to climatic elements changes. In the high altitude area, the resolution ratio (δ) in age layers was restricted by several climatic factors. e.g. air temperature, humidity, atmospheric pressure, etc. the resolution ratio(δ) composition had significantly relationship with annual air relative humidity, annual precipitation, seasonal atmospheric pressure and seasonal illumination intensity. The resolution ratio(δ) composition was affected by several climatic factors, but the hysteresis effect was not obvious. On the contrary, in the arid desert area in low elevation, the resolution ratio(δ) composition had had greatly sensitivities to annual temperature, seasonal precipitation and seasonal air relative humidity, and the hysteresis effect was obvious.

Han F.,State Key Laboratory Breeding Base of Desertification and Aeolian Sand Disaster Combating | Han F.,Gansu Key Laboratory of Desertification Combating | Han F.,Desert Research Institute | Xu X.,State Key Laboratory Breeding Base of Desertification and Aeolian Sand Disaster Combating | And 14 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2013

Growth and development of plants were always influenced by the combined effects of climate conditions accumulated in the previous periods, which was always explained by the variation of phenological characteristics of plants. With the rapidly increase of average surface temperature over the 20th century, shifts in animal and plant phenology have been widely reported in the northern hemisphere, phenology was now recognized as one of the simplest and most frequently used bio-indicators for studying the climate change. However, there are great differences in the response of plant phenology to the climate change, and which one will be the relatively sensitive meteorological factors to the phenology of plant species, to which time scale the plant species will be responded significantly is still unknown, this make it difficult to accurately predict the responding process of plant species to the climate change. Phenological data of typical herbaceous plants (Lris lacteal) and the corresponding meteorological data were both collected from the Minqin Desert Botanical Garden in 1974- 2007, and phenological characteristics of this species was analyzed and its response to the accumulated precipitation and temperature in different time scales were studied. The conclusions were obtained as follows: (1) The growing season length (difference between the starting date of budding period to the ending date of wilting period) of Lris lacteal was about 201.7 days with an increasing rate of 0.8 days per 10 years, which was not statistically significant during 1974-2007 (P>0.1). (2) Except the starting date (which refers to the time when nearly 50% of the species have experienced a certain phenological event) of the flowering period showed an obvious delay, and was statistically significant, the starting date and the ending date (which refers to the time when most of the species have finished this event) of remaining phenophases all displayed a slight delay, and was not statistically significant. The duration period (days of difference between the starting and ending date of one phenology) of all the phenophases of Lris lacteal varied greatly in different years, in which the duration period of budding period, flowering period and fruiting period all exhibited a decreasing trend, while leafing period and wilting period both showed an increasing trend, all of which were not statistically significant. (3) The extension of growing season lengths of Lris lacteal was attributed to the combined effects of both temperature and precipitation. The starting date of phenophases of this species was greatly influenced by the accumulated temperature from the preceding 3 weeks to 3 months, which was statistically significant at the 95% confidence level, while which has no relations with the accumulated temperature in preceding 1-3 years. Some of the phenophases of this species has a slight response to the accumulated precipitation in short-term and mid-term period, but no influence was found on the accumulated precipitation in the long-term period. (4) Phenophases of Lris lacteal was not only influenced by the local climate change, but also has some relations with its water use mechanisms, climate change in the future may have an great influence on the phenological characteristics of typical herbaceous plants in this desert area.

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