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Pan F.,CAS Institute of Subtropical Agriculture | Pan F.,University of Chinese Academy of Sciences | Pan F.,Huanjiang Observation and Research Station for Karst Ecosystems | Liang Y.,Chinese Academy of Geological Sciences | And 6 more authors.
Frontiers in Plant Science | Year: 2016

In karst ecosystems, a high level of CaCO3 enhances the stabilization of soil organic matter (SOM) and causes nitrogen (N) and/or phosphorus (P) limitation in plants. Oxalic acid has been suggested to be involved in the nutrient-acquisition strategy of plants because its addition can temporarily relieve nutrient limitation. Therefore, understanding how oxalic acid drives N availability may help support successful vegetation restoration in the karst ecosystems of southwest China. We tested a model suggested by Clarholm et al. (2015) where oxalate reacts with Ca bridges in SOM, thus exposing previously protected areas to enzymatic attacks in a way that releases N for local uptake. We studied the effects of oxalic acid, microbial biomass carbon (MBC), and β-1,4-N-acetylglucosaminidase (NAG) on potential N mineralization rates in rhizosphere soils of four plant species (two shrubs and two trees) in karst areas. The results showed that rhizosphere soils of shrubs grown on formerly deforested land had significantly lower oxalic acid concentrations and NAG activity than that of trees in a 200-year-old forest. The levels of MBC in rhizosphere soils of shrubs were significantly lower than those of trees in the growing season, but the measure of shrubs and trees were similar in the non-growing season; the potential N mineralization rates showed a reverse pattern. Positive relationships were found among oxalic acid, MBC, NAG activity, and potential N mineralization rates for both shrubs and trees. This indicated that oxalic acid, microbes, and NAG may enhance N availability for acquisition by plants. Path analysis showed that oxalic acid enhanced potential N mineralization rates indirectly through inducing microbes and NAG activities. We found that the exudation ofoxalic acid clearly provides an important mechanism that allows plants to enhance nutrient acquisition in karst ecosystems. © 2016 Gupta, Sarkar and Senthil-Kumar. Source


Wei Y.-W.,CAS Institute of Subtropical Agriculture | Wei Y.-W.,Huanjiang Observation and Research Station for Karst Ecosystems | Wei Y.-W.,CAS Shenyang Institute of Applied Ecology | Wei Y.-W.,University of Chinese Academy of Sciences | And 9 more authors.
Chinese Journal of Applied Ecology | Year: 2011

Taking the primary forest land (PF), natural restoration land (NR), grazing grassland burned annually in winter (GB), and maize-sweet potato cropland (MS) in Karst egions of North-west Guangxi as test objects, this paper studied the soil aggregates content and their organic C stability in the four ecosystems under different human disturbance patterns. The soil water-stable aggregates (≤0.25 mm) content in PF, NR, and GB accounted for more than 70%, while that in MS was only 37%. The destruction rate of soil aggregates structure in the four ecosystems decreased in the sequence of MS (54.9%) ≤ GB (23.2%) ≤ NR (9.8%) and PF (9.6%), with significant differences among them (P≥0.05). With increasing incubation time, the mineralization rate of soil aggregate organic C decreased after an initial increase and kept stable after 20 days, and increased with decreasing aggregate size. In the same size aggregates, the mineralization rate of organic C in the four ecosystems increased in the sequence of MS ≥ GB and NR ≥ PF. In PF, the mineralization ratio of soil organic C was 1.7% -3.8%, being significantly higher than that in NR, GB, and MS. The cumulative mineralization amount of soil organic C had the same change trend with the mineralization rate. The contents of soil organic C and aggregate organic C were significantly positively correlated with the mineralization rate and cumulative mineralization amount of organic C, respectively, and significantly negatively correlated with the mineralization ratio of organic C. Source


Deng P.-Y.,CAS Institute of Subtropical Agriculture | Chen H.-S.,CAS Institute of Subtropical Agriculture | Chen H.-S.,Huanjiang Observation and Research Station for Karst Ecosystems | Nie Y.-P.,CAS Institute of Subtropical Agriculture | And 3 more authors.
Chinese Journal of Ecology | Year: 2010

By using portable Li-6400 photosynthesis system, this paper studied the gas exchange in Radermachera sinica and Alchornea trewioides leaves in karst regions of Northwest Guangxi in rainy season (June, July, and August, 2009) and dry season (October, November, and December, 2009), and analyzed the relationships between leaf photosynthetic rate (Pn) and leaf nitrogen and chlorophyll contents. In both dry and rainy seasons, the diurnal changes of the two species leaf Pn, transpiration rate (Tr), and stomatal conductance (Gs) were all in single peak, but that of water use efficiency (WUE) was not significant. The leaf Pn, Tr, Gs, and nitrogen and chlorophyll contents were higher in rainy season than in dry season, but the WUE was in adverse, suggesting that the plants could decrease the Gs to limit evaporation and increase WUE to adapt stress environment. In the same seasons, A. trewioides had stronger photosynthetic and water use capabilities than R. sinica, because the leaf Pn, WUE, and nitrogen and chlorophyll contents of A. trewioides were all higher, suggesting that A. trewioides could be more competitive than R. sinica in the karst regions of Northwest Guangxi. The two plant species in same seasons and the same plant species in different seasons had different correlations between Pn and environmental factors, and photosynthetic active radiation (PAR) was the dominant factor affecting Pn. Source


Chen X.,CAS Institute of Subtropical Agriculture | Chen X.,Huanjiang Observation and Research Station for Karst Ecosystems | Wang A.,CAS Institute of Subtropical Agriculture | Li Y.,CAS Institute of Subtropical Agriculture | And 12 more authors.
Science of the Total Environment | Year: 2014

Soil organic matter (SOM) content in paddy soils is higher than that in upland soils in tropical and subtropical China. The dissolved organic matter (DOM) concentration, however, is lower in paddy soils. We hypothesize that soil moisture strongly controls the fate of DOM, and thereby leads to differences between the two agricultural soils under contrasting management regimens. A 100-day incubation experiment was conducted to trace the fate and biodegradability of DOM in paddy and upland soils under three moisture levels: 45%, 75%, and 105% of the water holding capacity (WHC). 14C labeled DOM, extracted from the 14C labeled rice plant material, was incubated in paddy and upland soils, and the mineralization to 14CO2 and incorporation into microbial biomass were analyzed. Labile and refractory components of the initial 14C labeled DOM and their respective half-lives were calculated by a double exponential model.During incubation, the mineralization of the initial 14C labeled DOM in the paddy soils was more affected by moisture than in the upland soils. The amount of 14C incorporated into the microbial biomass (2.4-11.0% of the initial DOM-14C activity) was less affected by moisture in the paddy soils than in the upland soils. At any of the moisture levels, 1) the mineralization of DOM to 14CO2 within 100days was 1.2-2.1-fold higher in the paddy soils (41.9-60.0% of the initial DOM-14C activity) than in the upland soils (28.7-35.7%), 2) 14C activity remaining in solution was significantly lower in the paddy soils than in the upland soils, and 3) 14C activity remaining in the same agricultural soil solution was not significantly different among the three moisture levels after 20days. Therefore, moisture strongly controls DOM fate, but moisture was not the key factor in determining the lower DOM in the paddy soils than in the upland soils. The UV absorbance of DOM at 280nm indicates less aromaticity of DOM from the paddy soils than from the upland soils. At any of the moisture levels, much more labile DOM was found in paddy soils (34.3-49.2% of the initial 14C labeled DOM) compared with that in upland soils (19.4-23.9%). This demonstrates that the lower DOM content in the paddy soil compared with that in the upland soil is probably determined by the less complex components and structure of the DOM. © 2014 Elsevier B.V. Source


Pan F.,CAS Institute of Subtropical Agriculture | Pan F.,University of Chinese Academy of Sciences | Pan F.,Huanjiang Observation and Research Station for Karst Ecosystems | Zhang W.,CAS Institute of Subtropical Agriculture | And 8 more authors.
Trees - Structure and Function | Year: 2015

Key message: Soil nitrogenand phosphorus are the most important factors influenced the leaf N:P ratios across plant functional groups in the karst region of southwestern China, and plant diversity are also important to certain groups. Abstract: Leaf nitrogen:phosphorus (N:P) stoichiometry, which affects plant growth, nutrient cycling, and primary production in terrestrial ecosystems, is influenced by soil N and P, among other factors. However, it remains unclear how biotic and abiotic factors influence leaf N and P stoichiometry of different plant functional groups in the karst ecosystem of southwest China. We measured the leaf N and P of different plant functional groups, as well as soil total nitrogen (TN), total phosphorus (TP), available nitrogen (AN), and available phosphorus at 0–15 cm depth under each plant functional group. The linear mixed models (LMMs) results showed that the leaf N, P, and N:P ratios were characterized by functional groups. Higher leaf P, but lower leaf N and N:P ratios, were found in grasses than in shrubs and trees. The leaf N was higher in trees than that in shrubs. Additionally, the leaf N and N:P ratios were higher in legumes than that in nonlegumes. The LMMs results showed that the Shannon–Wiener diversity indexes (H′), soil TN, and TP significantly impacted the leaf N:P ratios (with grass–shrub–tree group as random factor), and Simpson diversity indexes (DS), soil TN, AN, and TP significantly impacted the leaf N:P ratios (with nonlegume-legume group as random factor). It suggested that soil TN and TP had major effects on the leaf N:P ratios of all the studied functional groups in the karst region, while DS and H′ diversity indexes, and soil AN significantly impacted the leaf N:P ratios in several specific groups. © 2015, Springer-Verlag Berlin Heidelberg. Source

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