Shrub Caragana Research Articles

Effects of Caragana Korshinskii Kom. cover on runoff, sediment yield and nitrogen loss

Soil erosion is serious in the Loess Plateau of China. Deposition of the eroded sediment in lakes or rivers may lead to eutrophication, because the sediment carries a lot of nutrients. Field experiments were conducted to study soil erosion and loss of nitrogen (N) from a 15° hillslope with 30% (low) or 80% (high) coverage of the shrub Caragana korshinskii Kom. A bare soil plot was used for the comparison. The results showed that Caragana korshinskii cover significantly reduced runoff and soil erosion. In comparison to the bare soil plot, the vegetation covered plots had about 20% less runoff and 65% less sediment. In general, the concentration of N in both runoff water and the eroded sediment decreased with time and approached a steady value. However, the species of nitrate nitrogen (NO 3) was exceptional which increased with time slightly. The soil erosion caused an N loss of about 250 mg/m 2 for the bare soil plot, the low coverage of Caragana korshinskii reduced the N loss by 20% and the high coverage of Caragana korshinskii reduced the N loss by 40%. Moreover, the amount of total N in eroded sediment was 2 to 3 times higher than the value in runoff water. In the total N loss, the organic N was about 75-80%. Nevertheless, inorganic N in runoff water was 5 to 10 times higher than the value in eroded sediment. The species of NO 3 was obviously higher than the species of ammonium nitrogen (NH 4). NO 3 was the main species of inorganic N loss and was about two thirds of total. The organic N was the main species of N in the eroded sediment.

Characteristics of soil water consumption of typical shrubs (Caragana microphylla) and trees (Pinus sylvestris) in the Horqin Sandy Land area, China

Reforestation is one of the most effective ways to reduce the impacts of desertification. Caragana microphylla Lam. and Pinus sylvestris var. mongolica Litrin have been widely used to stabilize shifting sands in the Horqin sandy land area since the 1980s. However, soil water depletion has been of major concern in C. microphylla and P. ongolica plantations and in many places current soil moisture cannot meet the demand of growing plants. To determine the water budget of C. microphylla and P. mongolica plantations, we studied the effect of plantations on soil moisture and assessed the evapotranspiration in plantations of both species. Investigations were conducted at a fenced plot at Wulanaodu (42°29′N, 119°30′E, 479 m a. s. l), located at the western edge of the Horqin Sandy Land area in Inner Mongolia, northern China. Five year old C. microphylla and seven year old P. mongolica plants were selected from the plantations and transplanted to iron boxes (400 cm×200 cm×120 cm) which can drain extra water. Plant spacing of 1 m×1 m was applied to P. mongolica, and two plant spacings of 1 m×1 m and 1 m×2 m to C. microphylla. The transplanted plants grew for two years in the boxes. Soil moisture from soil surface to a depth 80 cm were measured at 20 cm intervals in boxes every 10 d (2004) or 3 d (2005) during the growing season with a TDR water meter. The evapotranspiration was estimated from a mathematical formula and the characteristics of soil water consumption and evapotranspiration of these two plantations were analyzed. The soil water of P. mongolica was more than that of C. microphylla at the same 1 m×1m spacing. The soil water of C. microphylla with the 1 m×2 m spacing was more than that of the 1 m×1 m spacing. The evapotranspiration ranged from high to low as follows: C. microphylla (1 m×1 m), C. microphylla (1 m×2 m) and P. mongolica (1 m×1 m) during the growing seasons. The evapotranspiration of individual plants ranging from high to low was C. microphylla (1 m×2 m), C. microphylla (1 m×1 m), and P. mongolica (1 m×1 m) during the growing season. C. microphylla grown for five year consumed more water than P. mongolica grown for seven years at the same spacing.

Estimation of transpiration in communities dominated by shrub Caragana microphylla.

Aims Our objectives were to develop an appropriate procedure for scaling up the sap flow from individual stems to the whole shrub and to the plot and to assess the utility of using sap flow gauges to determine the stand-level transpiration of shrub plantations in a semiarid sandy environment. Methods Sap flow rates of stems in a 15-year-old Caragana microphylla shrub in Horqin Sandy Land, China were measured using the stem heat balance techniques in June 2006 to determine transpiration of the C. microphylla plantation. The gauge-equipped stems, ranging in basal diameter from 0.4 to 1 cm, were selected on the basis of statistical analysis within the representative sampling plot for determining the "mean stem". Synchronously, total leaf area of the plant was measured by the basal cross-sectional area method and the leaf area density (LAD) method. We took advantage of the sparse distribution of C. microphylla and the ease of directly measuring LAD for individual shrubs to create a new scaling method based on these direct LAD measurements for shrubs in the study plot. We extrapolated the measurements of water use by individual stems to determine the area-averaged transpiration of the shrubland. The method used for the extrapolation assumed that the transpiration of a shrub was proportional to its leaf area. Important findings We found daily differences of 14.3% between transpiration estimated with sap measurements and with a weighing lysimeter reference, suggesting that the scaling procedure can be used to provide reliable estimates of transpiration from the shrub C. microphylla in Horqin Sandy Land.

Evaluation of water use of Caragana microphylla with the stem heat-balance method in Horqin Sandy Land, Inner Mongolia, China

Transpiration rates of a 15-year-old sand-fixation plantation of the leguminous shrub Caragana microphylla in the Horqin Sandy Land, northeast China, were measured by sap flow gauges throughout the summer of 2006. We extrapolated the measurements of water use by individual plants to determine the area-averaged transpiration ( T s) of the shrubland. The method used for the extrapolation assumes that the transpiration of a shrub was proportional to its leaf area. Similar results were found when comparing transpiration estimated with sap flow measurements to the actual evapotranspiration measured by the weighed lysimeter method, indicating that the scaling procedure can be used to provide reliable estimates of shrub transpiration. Daily sap flow rates and T s were mainly controlled by photosynthetically active radiation ( Q) and vapor pressure deficit ( D), whereas soil moisture had more influence on monthly change in T s. Maximum stand-level transpiration rates for C. microphylla ranged from 1.64 to 1.95 mm day −1, with an average value of 1.19 mm day −1. The seasonal (1 June to 31 August) total transpiration amounted to 109 mm, representing 66% of the incoming precipitation over this period. These results suggest that C. microphylla is highly effective at utilizing scarce water resources in semi-arid environments.

Combined effects of elevated CO2 and soil drought on carbon and nitrogen allocation of the desert shrub Caragana intermedia

Impacts of either elevated CO2 or drought stress on plant growth have been studied extensively, but interactive effects of these on plant carbon and nitrogen allocation is inadequately understood yet. In this study the response of the dominant desert shrub, Caragana intermedia Kuanget H.c.Fu, to the interaction of elevated CO2 (700 ± 20 μmol mol−1) and soil drought were determined in two large environmental growth chambers (18 m2). Elevated CO2 increased the allocation of biomass and carbon into roots and the ratio of carbon to nitrogen (C:N) as well as the leaf soluble sugar content, but decreased the allocation of biomass and carbon into leaves, leaf nitrogen and leaf soluble protein concentrations. Elevated CO2 significantly decreased the partitioning of nitrogen into leaves, but increased that into roots, especially under soil drought. Elevated CO2 significantly decreased the carbon isotope discrimination (Δ) in leaves, but increased them in roots, and the ratio of Δ values between root and leaf, indicating an increased allocation into below-ground parts. It is concluded that stimulation of plant growth by CO2 enrichment may be negated under soil drought, and under the future environment, elevated CO2 may partially offset the negative effects of enhanced drought by regulating the partitioning of carbon and nitrogen.

Water balance change for a re-vegetated xerophyte shrub area/Changement du bilan hydrique d’une zone replantée d’arbustes xérophiles

Water balances for a re-vegetated xerophyte shrub (Caragana korshinskii) area were compared to that of a bare surface area by using auto-weighing type lysimeters during the 1990–1995 growing seasons at the southeast Tengger Desert, Shapotou, China. The six-year experiment displayed how major daily water balance components might vary for a bare and a re-vegetated sand dune area. Evapotranspiration from the C. korshinskii lysimeter represented a major part of the water balance. The average annual ET/P ratios varied between 69 and 142%. No seepage was observed for the vegetated lysimeter. For the bare lysimeter, on the other hand, 48 mm or 27% of observed rainfall per year occurred as seepage. These results suggest that re-vegetating large sandy areas with xerophytic shrubs could reduce soil water storage by transpiration. Also, the experimental results indicate that re-vegetating large sandy areas could significantly change groundwater recharge conditions. However, from a viewpoint of desert ecosystem reconstruction, it appears that natural rainfall can sustain xerophytic shrubs such as C. korshinskii which would reduce erosion loss of sand. However, re-vegetation has to be balanced with recharge/groundwater needs of local populations.

Relationships between pikas (Ochotona, mammalia) and vegetation in Tuva

The burrowing and trophic activities of four pika (Ochotona) species proved to be reflected in the horizontal structure of the biogeocenotic cover. Zoophytochores ofOchotona daurica andO. pallasi pricei burrows correspond to previously described ameboid zoophytochores. Burrows of pikas provide for the growth of pea shrubs (Caragana bungei, C leucophloea), with the formation of specific plant groups under their crowns and on rubble dug out by pikas. In ecosystems of placers, zoophytochores are formed owing to the presence of pika food stores and lavatories, which are the main substrate for vascular plants first appearing among the stones. General ecological (and successional) series characterizing the overgrowing of placers is as follows: (1) separate spots of vegetation with poor floristic composition at the sites of pika food stores (stacklets); (2) groups of spots and simplest complexes; and (3) complex plant communities of pika colonies. Food stores of pikas in Tuva were analyzed.