Table of Content

20 May 2009, Volume 20 Issue 05

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Articles

Soil nitrous oxide emission in four temperate forests in northeastern China.

WANG Ying¹;WANG Chuan-kuan¹;FU Min-jie^1,2;LIU Shi¹;WANG Xing-chang¹

2009, 20(05):  1007-1012 . 

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Seasonal dynamics of N2O flux and its controlling factors for four representative temperate forests in northeastern China were examined with a static closed chamber-gas chromatograph technique. These forests were Korean pine (Pinus koraiensis) plantation, Dahurian larch (Larix gmelinii) plantation, Mongolian oak (Quercus mongolica) forest and hardwood broadleaved forest (dominated by Fraxinus mandshurica, Juglans mandshurica, and Phellodendron amurense). The results showed that all ecosystems were overall atmospheric N2O source during the growing season. The N2O flux (μg·m-2·h-1) decreased in order of the hardwood broadleaved forest (210±49)>the pine plantation (176±46)>the larch plantation (98±59)>the oak forest (16±126). Overall, there was no consistent seasonal pattern in N2O flux for the four ecosystems. The N2O flux was significantly positively correlated to soil gravimetric water content (0〖KG-*2〗-〖KG-*7〗10 cm depth) consistently for all ecosystems, but significantly negatively correlated to NO3--N content for each ecosystem. However, the responses of N2O flux to soil temperature and NH4+-N differed among the ecosystems. The N2O fluxes for the coniferous plantations were positively correlated to NH4+-N, but not correlated to the soil temperature at 5 cm depth; while those for the broadleaved forests displayed an opposite trend. The soil water content was the dominator of soil N2O emission for the forests in 2007 perhaps resulting from relative drought in the year. Interactions of vegetation type, environmental factor, and nitrogen availability to soil N2O emission should be further studied in the future.

Comparison of soil C and N in rubber plantation and seasonal rain forest.

ZHANG Min^1,2;ZOU Xiao-ming¹

2009, 20(05):  1013-1019 . 

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With the rubber plantation and seasonal rain forest in Xishuangbanna of Southwestern China as test objectives, a comparative study was conducted on their litter input, soil total C and N contents, and seasonal changes of soil active C and N from 2006 to 2007. Comparing with seasonal rain forest, rubber plantation had lower amount of aboveground litterfall and higher amount of floor mass, reflecting the lower decomposition rate (turnover coefficient, K) of litters, and had higher C/N ratio of litters and soil, indicating that the organic matters in rubber plantation were more resistant to degradation. The surface soil total organic C, labile organic C, and microbial biomass C concentrations in rubber plantation accounted for 60%〖KG-*2〗-〖KG-*7〗70% of those in seasonal rain forest, and the soil NO3--N concentration and pH value in rubber plantation were lower than those in seasonal rain forest, indicating that the conversion from seasonal rain forest to rubber plantation decreased the C and N inputs from aboveground litterfall and the availability of soil C and N, and caused soil acidification. Moderate land management strategies for rubber plantations were needed to prevent the degradation of soil quality and to maintain the productive sustainability.

Temperature sensitivity of organic C mineralization in gray forest soils after land use conversion.

XU Ru-min^1,2;LI Zhong-pei^1,2;CHE Yu-ping¹;ZHANG Chao^1,2

2009, 20(05):  1020-1025 . 

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A laboratory incubation test was conducted to study the organic C mineralization in gray forest soils after land use conversion and the temperature sensitivity of the mineralization. It was shown that after the conversion from wildwood land to farmland, the organic C and total N contents in 0〖KG-*2〗-〖KG-*7〗10 cm and 10〖KG-*2〗-〖KG-*7〗20 cm soil layers decreased by 685% and 768%, and 405% and 444%, and the average mineralization rate and cumulative mineralization of soil organic C in farmland were 244%〖KG-*2〗-〖KG-*7〗432% and 920%〖KG-*2〗-〖KG-*7〗137% of those in wildwood land, respectively. At lower temperature (<25 ℃), there was no significant difference in the temperature sensitivity of soil organic C mineralization between the two land use types; while at higher temperature (>25 ℃), this temperature sensitivity in farmland soil was higher in 0〖KG-*2〗-〖KG-*7〗10 cm layer but significantly lower in 10〖KG-*2〗-〖KG-*7〗20 cm layer, compared with that in wildwood land soil.

Effects of seasonal freeze-thaw on the enzyme activities in Abies faxoniana and Betula platyphylla litters.

DENG Ren-ju^1,2;YANG Wan-qin¹; WU Fu-zhong¹

2009, 20(05):  1026-1031 . 

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To understand the effects of seasonal freeze-thaw on the ecological processes of subalpine forest ecosystem, the enzyme activities in Abies faxoniana and Betula platyphylla litters under freeze-thaw were measured from October 2006 to October 2007 by the method of litter bags. There was an obvious monthly change in the enzyme activities, but the peak time varied with enzymes. Compared to the control, freeze-thaw had significant effects on the activities of invertase, urease, cellulase, and dehydrogenase in the litters (P＜005). Over a growth season, the invertase, cellulase, and urease activities in fir litter increased by 661%, 148%, and 763%, respectively while dehydrogenase activity decreased by 184%, and the invertase activity in birch litter increased by 394% while the urease, cellulase and dehydrogenase activities decreased by 182%, 287% and 156%, respectively. As for the activities of peroxidase and polyphenol oxidase in fir and birch litters, they were less affected by freeze-thaw. All of these revealed that seasonal freez e-thaw had definite effects on the litter decomposition of subalpine forest, which closely related to the kind of litter and its decomposition stage.

Effects of elevated O₃ concentration on anti-oxidative enzyme activities in Pinus tabulaeformis.

RUAN Ya-nan^1,2;HE Xing-yuan²;CHEN Wei²;CHEN Zhen-ju²; SUN Yu²

2009, 20(05):  1032-1037 . 

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An open-top chamber experiment was conducted to study the effects of high concentration O3 (80 nmol·mol-1) on the superoxide anion radical (O2〖SX（B-*3〗-〖〗·〖SX）〗) generation rate, hydrogen peroxide (H2O2) content, activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDHAR) and glutathione reductase (GR), and ascorbic acid content in Pinus tabulaeformis leaves. Under high concentration O3 exposure, the superoxide anion radical generation rate and H2O2 and malondialdehyde (MDA) contents increased, while the ascorbic acid content and the activities of SOD, APX, DHAR, MDHAR, and GR increased in early growth season but decreased then to a level lower than the control, which illustrated that the antioxidant system of P. tabulaeformis did respond in an acclimation way in the early growth season, but could not bear the damage of long-term elevated O3 exposure.

Estimation of carbon emission from forest fires in Zhejiang Province of China in 1991-2006.

YANG Guo-fu¹;JIANG Hong^1,2;YU Shu-quan¹;ZHOU Guo-mo¹;JIA Wei-jiang³

2009, 20(05):  1038-1043 . 

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Forest fire is an important disturbance factor of natural ecosystem, which can release great amount of greenhouse gases. With the persistent global warming, forest fire tends to happen more frequently. Based on the statistical data of forest fires and the biomass data of dominant forest types in Zhejiang Province in 1991〖KG-*2〗-〖KG-*7〗2006, the annual greenhouse gases emission from forest fires in the Province was estimated by using emission factors and emission ratio. The results showed that the annual emissions of CO2, CO, CH4, and non-methane hydrocarbon (NMHC) from forest fires were 127930, 76728, 30987, and 14755 t, and the amounts of annually consumed biomass and carbon were 861481 and 387767 t, respectively, suggesting that forest fire had definite effects on the regional carbon budget.

Effects of light intensity heterogeneity in gaps of broadleaved Korean pine forest in Changbai Mountains on Pinus koraiensis seedlings growth.

WANG Zhuo¹;FAN Xiu-hua²

2009, 20(05):  1044-1050 . 

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By using a Li-6400 portable photosynthesis system, this paper studied the heterogeneity of light intensity in four different size gaps of a broadleaved Korean pine forest in Changbai Mountains, and analyzed the diurnal change of the photosynthesis of Pinus koraiensis saplings in the gaps. In the nine orientations within the gaps, the peak value of the photosynthetically active radiation (PAR) varied in the sequence of west of actual gap, north of extended gap, gap center＞south of actual gap, south of extended gap, east of extended gap, east of actual gap＞west of extended gap, north of actual gap. Light distribution was dissymmetry in the orientations of east-west and south-north, with the variation in west and north being more significant than that in other orientations. There was no significant difference in the average PAR among the positions within specific orientations. The average PAR of the four gaps from I to IV was 2185, 4557, 6602, and 2348 μmol·m-2·s-1, respectively, and the difference was statistically significant (P＜005). PAR had a significant positive correlation with net photosynthetic rate (Pn), and the correlation coefficient increased with increasing PAR. With the increase of gap size, both the PAR and the Pn of P. koraiensis saplings increased first and decreased then, with the maximum values appeared at 267 m2 of gap size .

Seasonal changes of potassium, calcium and magnesium contents and accumulation in Calamagrostis angustifolia in Sanjiang Plain.

SUN Zhi-gao^1,2;LIU Jing-shuang²;YU Jun-bao¹; CHEN Xiao-bing¹

2009, 20(05):  1051-1059 . 

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From May to October 2004, the seasonal changes of K, Ca, and Mg contents and accumulation in Calamagrostis angustifolia, the dominant species in the typical meadow and marsh meadow communities of Sanjiang Plain, were studied. There was a greater difference in the seasonal changes of K, Ca, and Mg contents in different parts of typical meadow C. angustifolia (TMC) and marsh meadow C. angustifolia (MMC). The K content in aboveground parts of the two communities had an overall decreasing trend, according with linear model K=A+Bt, the Ca content had a smaller change in stem but an overall increasing trend in leaf and vagina, being accorded with parabola model Ca=A＋B1t＋B2t2 and exponential growth model Ca=Aexp(t/B1)+B2, respectively, while the Mg content had the greatest change in stem but changed relatively smoothly in leaf and vagina. The differences of K, Ca, and Mg contents in different parts of TMC and MMC were obvious. The K content in aboveground parts of TMC was generally higher than that of MMC, while the Ca and Mg contents in the root and vagina of MMC were higher than those of TMC. The K, Ca, and Mg storage and accumulation in different parts of TMC and MMC also differed. Root had the greatest K, Ca, and Mg storage, occupying 6382±2319%, 7868±15.44%, and 7648±1906% of the total storage in TMC and 8523±920%, 9351±346%, and 9239±322% in MMC, respectively. The aboveground parts of TMC had a higher storage of K, Ca and Mg than those of MMC, while the root was in adverse. Such a difference was mainly due to ecological characteristics of C. angustifolia and its habitat conditions.

Effects of different conservation tillage measures on winter wheat water use in Wuwei oasis irrigated area.

FENG Fu-xue;HUANG Gao-bao;YU Ai-zhong;CHAI Qiang;TAO Ming;LI Jie

2009, 20(05):  1060-1065 . 

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Field experiments were conducted in 2006〖KG-*2〗-〖KG-*7〗2008 to study the effects different conservation tillage measures, including conventional tillage with stubble incorporating (TS), no-tillage without stubble retention (NT), no-tillage with stubble standing (NTSS), no-tillage with stubble retention (NTS), on the soil moisture profile, soil water storage, water use efficiency (WUE), and grain yield of winter wheat in Wuwei oasis irrigated area. Comparing with conventional tillage, NTS and NTSS could significantly increase the water storage in 0〖KG-*2〗-〖KG-*7〗30 cm soil layer from returning green to jointing stage, and increase this storage in 30〖KG-*2〗-〖KG-*7〗150 cm soil layer from returning green till maturity. NTS, NTSS, and NT increased the water storage in whole soil profile (0〖KG-*2〗-〖KG-*7〗150 cm) by 2955〖KG-*2〗-〖KG-*7〗3469 mm, 1732〖KG-*2〗-〖KG-*7〗2179 mm, and 089〖KG-*2〗-〖KG-*7〗1568 mm at sowing, and 3759〖KG-*2〗-〖KG-*7〗3835 mm, 570〖KG-*2〗-〖KG-*7〗2214 mm, and 461〖KG-*2〗-〖KG-*7〗1393 mm at harvesting, respectively. The difference in water storage became more significant with increasing soil depth. NTS, NTSS, NT and TIS increased the grain yield of winter wheat by 1565%〖KG-*2〗-〖KG-*7〗1684%, 698%〖KG-*2〗-〖KG-*7〗1275%, 588%〖KG-*2〗-〖KG-*7〗1174%, and 392%〖KG-*2〗-〖KG-*7〗816%, and the WUE by 1715%〖KG-*2〗-〖KG-*7〗1752%, 775%〖KG-*2〗-〖KG-*7〗965%, 824%〖KG-*2〗-〖KG-*7〗1000%, and 417%〖KG-*2〗-〖KG-*7〗991%, respectively. NTS and NTSS improved the rain water use efficiency and grain yield, being the efficient conservative tillage measures to alleviate the lack of water resource in the study area.

Effects of farmland shelterbelt on photosynthetic characteristics and grain yield of maize in Hexi corridor oasis.

DING Song-shuang;SU Pei-xi

2009, 20(05):  1066-1071 . 

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Farmland shelterbelt is a main component of oasis agro-ecosystem in the Hexi corridor of Gansu Province, which plays an important role in maintaining local agricultural production and ecological balance. This paper studied the photosynthetic characteristics of maize at its grain-filling stage and the grain yield of maize under the protection of the shelterbelt. The results showed that at the same distances east and west of the shelterbelt, maize plants at the east side always intercepted more photosynthetic active radiation (PAR) than those at the west side. Within 20 m from the west side of the shelterbelt, the net photosynthetic rate (Pn) of maize plants was lower because of the serious shading by trees; and within 15 m from the west side, the Pn was lower than that from the east side. The grain yield of maize was decreased within 10 m from the east and 15〖KG-*2〗-〖KG-*7〗20 m from the west side, but increased or not affected in other locations.

Difference in P utilization from organic phosphate between two rice genotypes and its relations with root-secreted acid phosphatase activity.

LI Yong-fu^1,2;LUO An-cheng²;WU Liang-huan²;WEI Xing-hua³

2009, 20(05):  1072-1078 . 

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With two rice genotypes (cv. Zhongbu 51 and Azucena) differing in their root-secreted acid phosphatase activity (APA) under low P condition as test materials, an agar culture experiment was conducted to investigate their P utilization from myo-inositol hexaphosphate (IHP) under conditions of sterilization and inoculating with soil microorganisms. Under sterilization, the shoot dry mass, P absorption and P concentration of test genotypes supplied with hexaphosphate (IHP) as the P source were significantly higher than those with no P supply, but significantly lower than those supplied with inorganic P, indicating that rice plants could partly acquire P from IHP under sterilized condition. The root-secreted APA of the two genotypes was significantly higher under low P than under sufficient P supply, and the higher APA of Zhongbu 51 under low P could be one of the mechanisms of higher P utilization capability of Zhongbu 51 than Azucena under deficient P supply. When supplied with high level IHP (0.96 mmol P·L-1), the shoot dry mass, P absorption and P concentration of both Zhongbu 51 and Azucena were higher than those when supplied with low level IHP (0.16 mmol P·L-1), indicating that substrate availability could be one of the limiting factors to the utilization of phytate by rice. Inoculation with soil microorganisms had no significant effects on the shoot dry mass, P absorption and P concentration of rice plants, regardless of IHP level and rice genotypes, implying that the utilization of IHP by rice could not be improved via inoculation with soil microorganisms.

Effects of low molecular organic acids on nitrogen accumulation, nodulation, and nitrogen fixation of soybean (Glycine max L.) under phosphorus deficiency stress.

WANG Shu-qi^1,2;HAN Xiao-zeng¹;QIAO Yun-fa¹;YAN Jun¹;LI Xiao-hui¹

2009, 20(05):  1079-1084 . 

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A greenhouse sand culture experiment was conducted to study the effects of citric acid, oxalic acid, malic acid, and their mixture on the nitrogen accumulation, nodulation, and nitrogen fixation of soybean. After the application of test low molecular weight organic acids, the nitrogen accumulation in the aboveground part of soybean decreased by 176%〖KG-*2〗-〖KG-*7〗449% at seedling stage, 298%〖KG-*2〗-〖KG-*7〗884% at flowering stage, 918%〖KG-*2〗-〖KG-*7〗696% at podding stage, and 221%〖KG-*2〗-〖KG-*7〗417% at maturing stage). In the meanwhile, the nodule number, nitrogenase activity, and leghemoglobin content decreased by 114%〖KG-*2〗-〖KG-*7〗596%, 805%〖KG-*2〗-〖KG-*7〗917%, and 119%〖KG-*2〗-〖KG-*7〗599%, respectively, resulting in a significant decrease (971%〖KG-*2〗-〖KG-*7〗645%) of nitrogen fixation of soybean, compared with the control. The inhibitory effect of test low molecular weight organic acids increased with their increasing concentration. Oxalic acid had a higher inhibitory effect than citric acid and malic acid, and the mixture of the three organic acids had an enhanced inhibitory effect.

Seasonal variation and related affecting factors of arbuscular mycorrhizal fungi in Caragana korshinskii roots.

LIU Yong-jun^1,2;ZHENG Hong²; HE Lei²;AN Li-zhe²;FENG Hu-yuan²

2009, 20(05):  1085-1091 . 

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With the combination of root staining and PCR-DGGE, the seasonal variation of arbuscular mycorrhizal fungi (AMF) in Caragana korshinskii roots was investigated; and by the methods of principal component analysis and canonical correspondence analysis, the relationships between this variation and soil factors were analyzed. It was found that the total infection rate of AMF and the infection rates of arbuscules and vesicles in C. korshinskii roots as well as the spore density of AMF in soil varied significantly among seasons. From spring to autumn, the total infection rate of AMF had a decreasing trend, whereas the other three indicators were in adverse. A total of nine AMF phylotypes were detected in spring, summer, and autumn, but the community composition and diversity indices of AMF had definite differences among the seasons. The infection rate of vesicles decreased with increasing soil total N, P, and organic C, while the spore density of AMF increased with decreasing soil moisture and available P. The seasonal variation of AMF community composition in C. korshinskii roots was mainly affected by soil total P, available P, and organic C.

Comparison of low temperature-induced proteins in tillering node of winter wheat cultivars with different cold resistance.

YU Jing¹;ZHANG Lin²;CANG Jing¹;HAO Zai-bin¹;YANG Yang¹;LI Zhuo-fu²

2009, 20(05):  1092-1098 . 

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By using two-dimensional electrophoresis and mass spectrometry techniques, the proteomes in the tillering node of cold-resistant winter wheat Dongnongdongmai 1 and cold-susceptible winter wheat Jimai 22 before and after low temperature treatment were comparatively analyzed. It was observed that within the range of pH 4〖KG-*2〗-〖KG-*7〗7, there was a significant difference in the expression level of 55 protein spots in the protein profiles of tillering node before and after low temperature treatment, and 47 of the 55 protein spots were expressed in the two cultivars. After low temperature treatment, the abundance value of 23 protein spots increased, with the absolute abundance being higher in Dongnongdongmai 1 than in Jimai 22, while that of 7 protein spots decreased, with the absolute abundance being lower in Dongnongdongmai 1 than in Jimai 22. The expression level of 8 protein spots specific in Dongnongdongmai 1 was up-regulated. In all of the up-regulated proteins, their expression level in Dongnongdongmai 1 was 21〖KG-*2〗-〖KG-*7〗165 times as high as that in Jimai 22, among which, 10 protein spots had an expression level of 4 times high. In the down-regulated proteins, their expression level in Dongnongdongmai 1 was 01〖KG-*2〗-〖KG-*7〗04 times as high as that in Jimai 22. The differential protein spots were detected by mass spectrometry, and identified by compared with retrieval database. A total of 51 protein spots fingerprints were obtained, among which, 157% were of stress protein, 275% were of metabolism-related protein, 196% were signaling molecules, 98% were of unknown protein, and other proteins took up 274%. These variously expressed proteins might play an important role in the cold resistance of Dongnongdongmai 1.

Dynamic changes of rice (Oryza Sativa L.) tiller angle under effects of photoperiod and effective accumulated temperature.

OUYANG You-nan^1,2;LI Chun-sheng¹;ZHANG Shan-qing¹;WANG Hui-min¹;ZHU Lian-feng¹;YU Sheng-miao¹;JIN Qian-yu¹;ZHANG Guo-ping²

2009, 20(05):  1099-1104 . 

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Using rice variety DI508 as test material, a field experiment of different seeding dates and a test with plant growth chamber were conducted to study the dynamic changes of rice tiller angle under effects of different photoperiod and effective accumulated temperature. Under field condition, the tiller angle of DI508 plants changed gradually into erect after 10〖KG-*2〗-〖KG-*7〗15 days of photoperiod becoming shorter (since the Summer Solstice on 21st June), irrespective of seeding dates (4th April, 5th May, and 4th June). Under controlled photoperiod, the tiller angle changed in the same way as in the field. Shorter lighting treatment (10 hours) advanced the tiller angle change, while longer lighting treatment (14 hours) delayed the change. Effective accumulated temperature had no effects on the tiller angle change of DI508.

Effects of mulching and fertilization on winter wheat field soil moisture in dry highland region of Loess Plateau.

WANG Xiao-feng;TIAN Xiao-hong;CHEN Zi-hui;CHEN Hui-lin;WANG Zhao-hui

2009, 20(05):  1105-1111 . 

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A field experiment was conducted in a winter wheat field in Weibei dry highland region of Loess Plateau to study the effects of different mulching and fertilization treatments on soil moisture regime. The treatments were 1) no fertilization, 2) conventional fertilization, 3) recommended fertilization, 4) recommended fertilization + manure, 5) recommended fertilization + plastic mulch on soil ridges, 6) recommended fertilization + plastic mulch on soil ridges and straw mulch in furrows, and 7) recommended fertilization + straw mulch on entire plot. Soil moisture content was determined regularly with a neutron probe. Among the treatments, recommended fertilization plus plastic mulch on soil ridges and straw mulch in furrows in dry season (spring) resulted in the greatest increase of soil water storage and maintained the storage to the critical stage crops needed, followed by recommended fertilization plus plastic mulch on soil ridges. These two treatments could store more precipitation in field, and would benefit the development of rainfed agriculture in dry highland region of Loess Plateau. As for recommended fertilization plus manure, it had the least increase of soil water storage, with a difference of 482 mm to the recommended fertilization plus plastic mulch on soil ridges and straw mulch in furrows in dry season.

Coupling effects of temperature, moisture, and nitrogen application on greenhouse soil pH and EC.

YUAN Qiao-xia¹;ZHU Duan-wei²;WU Ya-juan²

2009, 20(05):  1112-1117 . 

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A laboratory incubation experiment was conducted to study the effects of temperature (T), moisture (W), nitrogen application (N), and their combinations on the pH and EC of greenhouse soil having cultivated for 5 years. The results showed that with the increase of incubation time, soil pH was decreasing, which could be well described by the first-order kinetic model, and the pH decreasing rate (k) under effects of test factors was in the order of N>W> W×N > T×W. Soil EC increased quickly to the maxima in the first week of incubation, decreased slightly then, and finally reached to a constant (ECsty). The ECsty value was significantly affected by N, W, T×W, T, and W×N. Reducing nitrogen application and rational deficit irrigation could effectively postpone the soil acidification and EC increase. A regression equation of k and ECsty was established, which could be used to predict the changes of soil pH and EC under different conditions of moisture regime and nitrogen application.

Nutrient release characteristics and use efficiency of slow- and controlled release fertilizers.

DUAN Lu-lu^1,2;ZHANG Min¹; LIU Gang²; SHANG Zhao-cong²; YANG Yi²

2009, 20(05):  1118-1124 . 

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Water extraction method and soil incubation method were used to study the nutrient release characteristics of four slow- and controlled release fertilizers (CRF1, CRF2, SCU, and IBDU), and pot experiment was conducted to assess the effects of the release characteristics on the nutrient requirements of canola (Brassica napus L.). The nutrient release curves of test fertilizers in water were S pattern for CRF1 and CRF2, burst pattern for SCU, and reverse L pattern for IBDU. The nutrient release characteristics of the four fertilizers in water and in soil all fitted binomial equations, suggesting that there existed some similarities in the nutrient release in the two media. The nutrient uptake and biomass of canola plants treated with CRF1 and CRF2 were significantly higher than those treated with SCU and IBDU, and CRF2 had the greatest effect. The nutrient release curves of CRF1 and CRF2 accorded more closely with the nutrient requirements of canola.

Selection of landscape metrics for urban forest based on simulated landscapes.

LIU Chang-fu^1,2;LI Jing-ze¹;LI Xiao-ma¹;HE Xing-yuan²;CHEN Wei²

2009, 20(05):  1125-1131 . 

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Based on the existing urban forest landscape of Shenyang, four landscape pattern gradients were simulated, and one existing landscape pattern gradient in accordance with the trend of these gradients was selected. By analyzing the responses of 28 landscape metrics for landscape fragmentation and patch shape complexity to various landscape pattern gradients, preference landscape metrics were selected for describing the degree of the two landscape pattern characteristics. The results showed that patch density (PD) and mean patch area (AREA_MN) regularly responded to the change of landscape fragmentation. The increase of landscape fragmentation resulted in an increase of PD value while a decrease of AREA_MN value. Patch shape complexity of area weighted mean perimeter area ratio (PARA_AM) coincided with the gradients of landscape pattern. PARA_AM value increased with increasing patch shape complexity, which precisely characterized the degree of patch shape complexity.

Application of “overlay-maps” model in prior period research of ecological planning of Shanghai Expo area.

XU Xi^2,3;WANG Xiao-ming^1,3;WANG Tian-hou^1,3;LIU Yi-ning⁴;WANG Kai-yun^2,3

2009, 20(05):  1132-1139 . 

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An ecological planning approach for Shanghai Expo 2010 was constructed based on “overlay-maps” model, and the ecological elements and GIS visualization in Shanghai Expo 2010 area were investigated and analyzed from the aspects of human comfort degree, life health, and sustainable utilization of resources. This approach included the determination of objectives for ecological planning, the selection and in situ investigation of ecological elements, the construction of eco-database, and the integrative analysis of GIS visualization, being indispensable for the prior period research of ecological planning of Expo area. Based on the present situation of soil pollution in the Expo area, a tentative scheme of soil restoration and utilization was brought forward, with the concerns of green space demand and soil secondary pollution avoidance. To protect the wild life habitats in Expo area, a demarcation of conservation areas for plants and original landscape was made. A conception of using landscape elements to optimize air temperature, humidity, and ventilation in the process of urban design was proposed, aimed to promote the human comfort degree under tropical monsoon conditions.

Urban vegetation coverage change inside the Third-Ring Road of Shenyang City, China: A study with linear spectral unmixing technique.

HU Jian-bo^1,2;CHEN Wei¹;LI Xiao-yu¹;HE Xing-yuan¹

2009, 20(05):  1140-1146 . 

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Based on the Landsat TM images of 2001 and 2006, and by using linear spectral unmixing (LSU) technique, the information of urban vegetation coverage inside the Third-Ring Road of Shenyang City was extracted, and the dynamic change of the vegetation coverage in 2001〖KG-*2〗-〖KG-*7〗2006 was analyzed, in combining with a land use map derived from the visual interpretation of a QuickBird image of 2006. The results showed that in 2001〖KG-*2〗-〖KG-*7〗2006, the urban vegetation coverage in study area changed drastically. Urban greening and the cropland encroachment caused by urban sprawl coexisted, and the vegetation gain from urban greening was larger than the vegetation loss from cropland encroachment. The vegetation coverage of road, residence, public facilities, and park and square increased with varying degrees (5%〖KG-*2〗-〖KG-*7〗9%), while industrial land changed little. The spatial distribution of urban greening was relatively reasonable. Though the polarization of vegetation coverage between central city and suburban still existed, this polarization had been mitigated to some extent. With the increase of the distance from city center, the vegetation coverage increased in sequence of park and square (08％·km-1)<residence (15%·km-1)<industrial land (17％·km-1)<public facilities (24％·km-1)<road (29％·km-1). The polarization of vegetation coverage in public facilities and road were still serious, suggesting that more greening programs and strict conservation efforts were needed.

Dynamic changes of Ruoergai Plateau wetland ecosystem service value.

ZHANG Xiao-yun^1,2,3;Lü Xian-guo¹;SHEN Song-ping⁴

2009, 20(05):  1147-1152 . 

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Based on the satellite remote sensing data acquired in 1975 and 2006, and by using the assessment method of ecosystem service value, the dynamic changes of physical production value, gas regulation value, and water storage value of Ruoergai Plateau wetland ecosystem in 1975〖KG-*2〗-〖KG-*7〗2006 were studied. During study period, the total value of the three services decreased from 1959 billion RMB Yuan to 1238 billion Yuan RMB, among which, physical production value increased by 0302 billion RMB Yuan, while the gas regulation and water storage value decreased by 7507 billion RMB Yuan. The benefit from the increase of physical production was much less than the loss of ecosystem degradation. Overgrazing induced the biomass reduction and soil deterioration, resulting in the decline of Ruoergai Plateau wetland ecosystem service value and service capacity.

Spatial patterns of eco-climatic factors on Tibetan Plateau.

ZHAO Dong-sheng¹;WU Shao-hong^1,2;ZHENG Du¹;YANG Qin-ye¹

2009, 20(05):  1153-1159 . 

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Based on the 1966〖KG-*3〗-〖KG-*7〗2005 observation data from 113 meteorological stations on the Tibetan Plateau and its surrounding areas, the spatial patterns of mean temperature of warmest month (TWM), mean temperature of coldest month (TCM), duration of mean daily temperature ≥10 ℃ (DT10), annual precipitation (AP), mean annual potential evapotranspiration (PE), and annual arid index (AI), on the Plateau were analyzed. It was shown that the TWM was 7〖KG-*2〗-〖KG-*7〗20 ℃, which decreased from eastern surrounding area to the central region, while TCM was -184 ℃ to 8 ℃,being decreased from south to north. The DT10 decreased from eastern surrounding area (>150 days) to central region (50 days), and the AP decreased from southeast to northwest. The PE calculated by Thornthwaite model decreased from southeast to northwest, and was 330〖KG-*2〗-〖KG-*7〗750 mm in most parts of the study area. Arid area occupied a larger proportion and mainly located in the northwest of Tibetan Plateau, while humid area was smaller and mainly located in the east and southeast of the Plateau. The vegetation distribution on Tibetan Plateau had good correlations with the test eco-climatic factors, suggesting that these factors could better characterize the vegetation patterns on Tibetan Plateau.

Regional ecological planning and ecological network construction: A case study of “Ji Triangle” Region.

LI Bo¹;HAN Zeng-lin¹;TONG Lian-jun²

2009, 20(05):  1160-1165 . 

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By the methods of in situ investigation and regional ecological planning, the present ecological environment, ecosystem vulnerability, and ecological environment sensitivity in “Ji Triangle” Region were analyzed, and the ecological network of the study area was constructed. According to the ecological resources abundance degree, ecological recovery, farmland windbreak system, environmental carrying capacity, forestry foundation, and ecosystem integrity, the study area was classified into three regional ecological function ecosystems, i.e., east low hill ecosystem, middle plain ecosystem, and west plain wetland ecosystem. On the basis of marking regional ecological nodes, the regional ecological corridor (Haerbin-Dalian regional axis, Changchun-Jilin, Changchun-Songyuan, Jilin-Songyuan, Jilin-Siping, and Songyuan-Siping transportation corridor) and regional ecological network (one ring, three links, and three belts) were constructed. Taking the requests of regional ecological security into consideration, the ecological environment security system of “Ji Triangle” Region, including regional ecological conservation district, regional ecological restored district, and regional ecological management district, was built.

Effects of Dendrolimus punctatus feeding and methyl jasmonate (MeJA)- or terpenes fumigation on abscisic acid and jasmonic acid contents in Pinus massoniana seedling needles.

DENG Wen-hong¹;SHEN Ying-bai^2,3;CHEN Hua-jun¹;LI Zhen-yu⁴;JIANG Xiang-ning^2,3

2009, 20(05):  1166-1170 . 

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Abscisic acid (ABA) and Jasmonic acid (JA) play an important role in inducing the stress-resistance of plants. In this study, parts of the needles on a ring of Pinus massoniana seedling shoots were subjected to 4 hours Dendrolimus punctatus feeding or 4 hours fumigation with 10 μmol·L-1 of methyl jasmonate (MeJA) or terpenes, and the ABA and JA contents in treated needles, untreated neighboring sister needles, and untreated needles above and below the ring were determined by GC/MS. An obvious increase of ABA and JA contents was observed in all of the needles, whether they were treated or not, illustrating that ABA and JA were the vital signaling molecules in the wound signal transduction pathway, and participated in the formation of systematic resistance of P. massoniana seedlings.

Interactive effects of temperature and nitrogen fertilizer on the survival, development, and reproduction of brown planthopper Nilaparvata lugens.

ZHENG Xu-song¹;CHEN Guihua²;XU Hong-xing¹;LÜ Zhong-xian¹

2009, 20(05):  1171-1175 . 

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A laboratory study was made on the interactive effects of temperature (20 ℃, 23 ℃, 26 ℃, 29 ℃, and 32 ℃) and nitrogen fertilization level (0 and 250 kg·hm-2) on the survival, development, and reproduction of brown planthopper (BPH) Nilaparvata lugens. With increasing temperature from 20 ℃ to 29 ℃, the egg hatchability, nymphal survival, and adult fecundity of BPH increased and the developmental duration of all stages shortened; while at 32 ℃, it was in adverse. At all test temperatures, the BPH on rice plants treated with 250 kg N·hm-2 had higher egg hatchability, nymphal survival and adult fecundity, and shorter developmental duration of eggs and nymphs, compared with no nitrogen fertilization, which suggested that high level nitrogen fertilization enhanced the ecological adaptability of BPH to stress conditions. There were significant interactive effects of temperature and nitrogen fertilizer on the egg hatchability, nymphal duration, and adult fecundity of BPH, implying that global warming and long-term high level application of nitrogen fertilizer could be responsible for the outbreaks of BPH in recent years.

Niche of macrozoobenthos in intertidal zone of Jiaojiang Estuary.

ZHAO Yong-qiang;ZENG Jiang-ning;GAO Ai-gen;CHEN Quan-zhen;SHOU Lu;LIAO Yi-bo; HUANG Yi-jun

2009, 20(05):  1176-1183 . 

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The niche width and niche overlap of macrozoobenthos dominant species in the intertidal zone of Jiaojiang Estuary in October 2007 were analyzed based on niche theory, and the effects of natural factors (salinity, water temperature, sediment temperature, beach width, and sediment grain size) and environmental factors (contents of oils and heavy metals) on the environmental heterogeneity as well as the relationships between selected environmental factors and quantitative distribution of various groups of macrozoobenthos were studied by using canonical correspondence analysis method. The macrozoobenthos dominant species in study area were classified into four groups, i.e., burrowing surface predator, surface grazer, subsurface filter feeder, and subsurface swallow feeder, based on their feeding types. There were great differences in the niche widths among the groups, with the maximum of 0428 and the minimum of 0168, which suggested that different groups had different adaptive capacity to the environmental factors. At the level of niche overlap value higher than 06, Macrophthalmus japonicas and M. definitus of Group 1, Lunatica gilva, Bullacta exarata, Decorifera insignis, Assiminea brevicula and Cerithidae ornate of Group 2, and Moerella iridescens, Glauconome chinensis and Potamocorbula laevis of Group 3 had a biologically significant niche overlap, indicating their similar behavior in utilizing natural feeding resources.

Effects of benthic macro-invertebrate on decomposition of Acer buergerianum leaf litter in streams.

JIANG Li-hong;WANG Bei-xin;CHEN Ai-qing;LAN Ce-jie

2009, 20(05):  1184-1189 . 

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By using composite mesh bag method, the effects of benthic macro-invertebrate in an undisturbed stream and an ecologically restored stream on the decomposition process of Acer buergerianum leaf litter from the Purple Mountain of Nanjing in winter were studied. After 112 days of decomposition, the remaining rate of A. buergerianum leaf litter based on ash-free dry mass was 31〖KG-*2〗- 〖KG-*7〗62%, and the decomposition rate followed a declined exponential equation (P<005). In the flowing water of the undisturbed and ecologically restored streams, the decomposition rate of leaf litter was 00064 d-1 and 00030 d-1; while in the still water of the streams, it was 00016 d-1 and 00018 d-1, respectively. The abundance and biomass of benthic macro-invertebrate were significantly higher in the flowing water of undisturbed stream than in that of ecologically restored stream (P<005), but had no significant differences in the still water of the two streams. Shredders (mainly Asellus sp.) had the highest abundance (704%) in the flowing water of undisturbed stream, while filterers (mainly Tanytarsus sp.) were dominant (378%) in the flowing water of ecologically restored stream. The decomposition rate of the leaf litter was significantly correlated with the richness and abundance of shredder species in flowing water (P<001), but had less correlation with the biomass of the shredders, suggesting that the decomposition of A. buergerianum leaf litter in streams in winter was more dependent on the richness and abundance of shredders.

Effects of temperature, salinity, and light intensity on the growth and toxin production of Chattonella marina.

HUANG Juan¹;YANG Wei-dong^1,2;LIU Jie-sheng^1,2;LI Hong-ye¹;LIU Bi-hui¹

2009, 20(05):  1190-1195 . 

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A laboratory experiment with orthogonal design was conducted to study the effects of factors salinity, temperature, and light intensity on the growth and toxin production of Chattonella marina. Three levels of salinity (22, 33, and 45), temperature (20 ℃, 25 ℃, and 30 ℃) and light intensity (2000, 3000, and 4500 lx) were installed. In all treatments, the three factors had no significant effects on the growth of C. marina, but salinity significantly affected the toxin production of C. marina. Under salinity 45, temperature 30 ℃ and light intensity 2000 lx, C. marina had the maximal growth rate; under salinity 22, temperature 20 ℃ and light intensity 4500 lx, the toxin production of C. marina was the maximal. Low salinity was not favorable to the C. marina growth but favorable to its haemolytic toxin production. When the growth of C. marina was limited, its haemolytic toxin production increased.

Labidocera euchaeta: Its distribution in Yangtze River Estuary and responses to global warming.

XU Zhao-li;GAO Qian

2009, 20(05):  1196-1201 . 

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Based on the investigation data from eight oceanographic censuses in Yangtze River Estuary (28°00′〖KG-*2〗-〖KG-*7〗32°00′ N，122°00′〖KG-*2〗-〖KG-*7〗123°30′ E) in four seasons of 1959 and 2002, the seasonal distribution pattern of Labidocera euchaeta in the Estuary and the responses of this zooplankton to global warming were analyzed. In the study area, L. euchaeta had a higher average abundance in winter and spring than in summer and autumn, with the highest occurrence frequency in winter and an obvious aggregation in spring and summer. Water salinity was the key factor determining the horizontal distribution of L. euchaeta. The optimal water temperature and salinity for L. euchaeta were 16 ℃ and 12〖KG-*2〗-〖KG-*7〗20, respectively, indicating that this zooplankton belonged to a warm temperate brackish water species. Comparing with that in 1959, the abundance of L. euchaeta in 2002 decreased obviously, which could be related to global warming and suggested that L. euchaeta could be used as an important indictor species of ocean warming in Yangtze River Estuary. The high abundance of L. euchaeta in spring appeared in the most turbid zone of Yangtze River Estuary, being of significance in maintaining the functions of fishing grounds in the waters.

Isolation, identification and diversity analysis of petroleum-degrading bacteria in Shengli Oil Field wetland soil.

HAN Ping¹;ZHENG Li¹;CUI Zhi-song¹;GUO Xiu-chun^1,2;TIAN Li¹

2009, 20(05):  1202-1208 . 

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The petroleum-degrading bacteria in Shengli Oil Field wetland soil were isolated and identified by traditional experiment methods, and their diversity was analyzed by PCR-DGGE (denaturing gradient gel electrophoresis). A total of thirteen petroleum-degrading bacterial strains were isolated, among which, six strains were found to have the ability of degrading the majority of C12〖KG-*2〗-〖KG-*7〗C26 petroleum hydrocarbon, with a degradation rate of >90%. These petroleum degraders were phylogeneticly identified as the members of Halomonas, Alcanivorax, and Marinobacter, which were all belonged to γ-proteobacteria. The uncultured predominant bacteria in Shengli Oil Field wetland soil were of Sulfurovum, Gillisia and Arcobacter. Among the predominant bacteria, γ-proteobacteria accounted for a larger proportion, followed by α-proteobactiria, ε-proteobactiria, Actinobacteria, and Flavobacteria.

Ecological safety regulation of A/DAT-IAT process for municipal wastewater treatment.

ZHU Shuang¹;HUA Tao¹;ZHOU Qi-xing^1,2;WU Qiong¹

2009, 20(05):  1209-1213 . 

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Four controlling parameters of A/DAT-IAT process for municipal wastewater treatment, i.e., operation period (T), external recycled rate (R1), internal recycled rate (R2), and mixed liquid suspended solid concentration (MLSS), were studied by orthogonal experiments, and the regular and ecotoxicological indicators of the effluents were examined. The results showed that the optimum conditions of regular indicators removal were T=3 h, R1=20%，R2=150%, and MLSS=5000 mg·L-1, and the optimum conditions of ecotoxicological indicators removal were T=3 h, R1=20%，R2=150%, and MLSS=3000 mg·L-1. The reason which caused the difference of the two optimum conditions might be that there were some non-biodegradable organic matters having certain ecological toxic effects and some organic matters whose ecological toxicity increased after hydrolysis and acidification. Adding flocculants and properly choosing controlling parameters were suggested to improve the regular and ecotoxicological indicators of the effluent.

In situ immobilization remediation of heavy metals-contaminated soils: A review.

WANG Li-qun^1,2;LUO Lei^2,3;MA Yi-bing²;WEI Dong-pu²;HUA Luo¹

2009, 20(05):  1214-1222 . 

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In situ immobilization of heavy metals in contaminated soils by adding extraneous active amendments has been considered as a cost-effective measure for contaminated soil remediation. Application of immobilization amendments can decrease the available fractions of heavy metals or change their redox states, and thus, effectively decrease the mobility, bioavailability, and toxicity of the heavy metals in soils. This paper summarized the present researches about the in situ immobilization of heavy metals in soils, including kinds of immobilization amendments, research methods, immobilization indexes, immobilization mechanisms, and relevant environmental risk assessment. The mostly applied amendments include clay minerals, phosphates, organic composts, and microbes. Due to the complexity of soil matrix and the limitations of current analytical techniques, the exact immobilization mechanisms have not been clarified, which could include precipitation, chemical adsorption and ion exchange, surface precipitation, formation of stable complexes with organic ligands, and redox reaction. The prospects and limitations of in situ immobilization of heavy metals in soils were discussed. Future work should focus on the elucidation of immobilization mechanisms at molecular scale, with specific attention be paid to the potential risks of applying immobilization amendments and its long-term effects on field soils.

Research advances in organic nitrogen acquisition by plants.

WANG Wen-ying;LIU Jun-ying

2009, 20(05):  1223-1228 . 

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Since the establishment of plant mineral nutriology, it has been well believed that plants mainly absorb inorganic nitrogen. With the improvement of research means and contents, it was approved that some vascular plants with no mycorrihiza could absorb soluble organic nitrogen, especially small molecular amino acids, which aroused the attentions on plant organic nutrition and its diverse modes. Relative researches suggested that amino acids could be released into soil by various means, while microbes, plants, animals, and their metabolites were the main sources. The contents of amino acids in soil were affected by soil temperature, moisture, applied organic fertilizer, plant species, and their growth stages. The uptake of amino acids by plants was an active process regulated by the carriers, energy status, and media pH and temperature. The mechanisms of amino acid uptake by plants and the related ecological processes are needed to be studied further.

Species diversity and ecological distribution of anaerobic ammonium-oxidizing bacteria.

CHEN Ting-ting;ZHENG Ping;HU Bao-lan

2009, 20(05):  1229-1235 . 

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Anaerobic ammonium oxidation (anammox) is an important discovery in microbiology and environmental sciences, which can simultaneously remove NH4+-N and NO3--N, being valuable in environmental engineering. However, anaerobic ammonium oxidizers are extremely slow-growing, and their population’s doubling time is longer than 11 days, which seriously restricts the application of anammox process. Therefore, the study of anammox bacteria is of significance. It has been proved that besides planctomycetes, the first recognized anammox bacteria, both nitrifying bacteria and denitrifying bacteria are also capable of anaerobic ammonium oxidation. These anammox bacteria have wide-spread habitats, which offered a chance to exploit new bacterial resources for anammox. Nitrifying bacteria and denitrifying bacteria have the function of anammox, and their metabolic diversity provides a basis to speed up the start-up of anammox reactor. It was revealed that anaerobic digestion sludge can present anammox activity, with sulphate as electron acceptor. The new bioreaction lays a foundation for the development of novel N-removal biotechnology, being conducive to the development and application of anammox to get more bacterial resources for anammox and to make clear the ecological distribution of anammox bacteria.

Measurement difference in paddy field nitrogen leakage by using different type lysimeters.

WANG Mi¹;CHEN Zhi-wei¹;YANG Jing-ping²;XU Wei¹;GE Chang-shui³;CHEN Wen-yue³

2009, 20(05):  1236-1242 . 

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Vertical and ‘T’ types of lysimeter were used to measure the concentrations of ammonia N, nitrate N, and total nitrogen (TN) in the leakage of paddy field in rice growth season under different N application levels. For ammonia N, its concentration measured with these two types of lysimeter all ranged in 0〖KG-*2〗-〖KG-*7〗8 mg·L-1 in 2007 and 0〖KG-*2〗-〖KG-*7〗4 mg·L-1 in 2006; for nitrate N, its concentration measured with vertical lysimeter was 0〖KG-*2〗-〖KG-*7〗4 mg·L-1 in 2007 and basically the same in 2006, while that measured with ‘T’ type lysimeter was 0〖KG-*2〗-〖KG-*7〗20 mg·L-1 in 2007 but lower in 2006. The TN concentration in the leakage was 0〖KG-*2〗-〖KG-*7〗60 mg·L-1 in 2007, much higher than that (0〖KG-*2〗-〖KG-*7〗16 mg·L-1) in 2006. In the leakage, nitrate N was the dominant N form. The total leakage loss of N in whole rice growth season in 2007 was 1581 kg·hm-2 of TN and 933 kg·hm-2 of nitrate N when measured with vertical lysimeter, and 721 kg·hm-2 of TN and 425 kg·hm-2 of nitrate N when measured with ‘T’ type lysimeter. Due to the difference in the pathways of ammonia-N and nitrate-N leakage, different methods for calculating N leakage should be employed when using the two types of lysimeter in measurement. The N leakage measured by vertical lysimeter was more close to that estimated by paddy plot-leaching measurement method.

Spatiotemporal dynamics of land use in Langqi Island at Minjiang Estuary.

YAN Shu-jun¹; HONG Wei²

2009, 20(05):  1243-1247 . 

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By using RS and GIS techniques and a series of indices in characterizing the dynamics of land use, the spatiotemporal characteristics of land use in Langqi Island at Minjiang Estuary in 1989, 1996 and 2005 was studied. The results showed that in 1989〖KG-*2〗-〖KG-*7〗2005, the land use types in the Island all changed, but agricultural landscape was always the main land type. The single land use dynamics of water area was the largest, which reached 785% from 1989 to 2005. The annual change rate of comprehensive land use was 190%, the cultivation rate decreased rapidly, while the forest coverage and the construction land use rate increased. The comprehensive index of land use degree in the study area decreased, which indicated that the land use type tended to be diversification.

Effects of illumination and seed-soaking reagent on seed germination of Solanum nigrum.

YANG Chuan-jie^1,2;WEI Shu-he¹;ZHOU Qi-xing^1,3;HU Ya-hu^1,2;NIU Rong-cheng^1,2

2009, 20(05):  1248-1252 . 

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To explore a rapid seed germination method for hyperaccumulator Solanum nigrum, a germination experiment with different illumination and seed-soaking treatments was conducted in constant temperature box and greenhouse, with filter as burgeon base. Under illumination, the germination rate was about 5 times high of that without illumination (P<005), indicating that illumination was one of the prerequisites for the seed germination of S. nigrum. All test seed-soaking reagents could significantly improve the germination rate of S. nigrum (P<005), with the best effect of H2O2. The seeds treated with H2O2 had the shortest germination time. The germination rate of seeds soaked but without cleaning was 2〖KG-*2〗-〖KG-*7〗3 times as high as that of seeds soaked and cleaned with water.

Factors affecting citations: A comparison between Chinese and English journals in ecology.

XIAO Hong¹;YUAN Fei²;WU Jian-guo^2,3

2009, 20(05):  1253-1262 . 

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Citations to journal papers in eight ecological journals at home and abroad were analyzed to identify key contributing factors and compare the difference between the selected Chinese and English journals. The results indicated that the annual average citations of English journals were much higher than those of Chinese journals. Percentage of single-authored papers was also higher in English journals than in Chinese journals. Co-authored papers accounted for a large proportion of papers published in all journals, indicating the significance of collaboration in modern ecological research. A positive correlation was observed between the number of authors and citation rate, but the relationship was weak in general. On an average, papers in English journals were longer than those in Chinese journals, and the annual average citations increased with paper length. By tracking the citation dynamics of papers, we found that the most cited papers in English journals had higher increasing citation rates. This suggested that they had a stronger persistence effect than those in Chinese journals. These results will provide some useful guidance for authors and editors in ecology.