To assess phosphorus (P) status of forest soil under naturally restored vegetation, P fractions in the 10-cm soil layer were quantified at different successional stages on the clear-cut site of mixed broadleaved and Korean pine forest. Four communities of shrub, softwood broad-leaved forest, softwood and hardwood broad-leaved forest, and hardwood broad-leaved forest represented different successional stages. A soil sample from a primary broad-leaved and Korean pine stand was the control. A sequential P fractionation scheme extracted empirically defined pools of P and path analysis used to partition the direct and indirect contribution of soil P fractions to available P. The results show that available P increased significantly with long-term succession, while both sodium bicarbonate-extractable P (NaHCO3-P) and sodium hydroxide-extractable P (NaOH-P) fractions were reduced in early successional stages and increased in late stages. Compared to the primary forest, concentrations of P fractions in the four stages significantly decreased except for HCl-P, indicating that soil P supplements over the long-term did not return to primary forest levels. The results of related analysis also showed that NaHCO3-Pi levels were significantly related to available phosphorus. According to the path analysis coefficient, NaHCO3-Pi exhibited the highest effect on available P among eight P fractions; the indirect effects of other P fractions via NaHCO3-Pi were larger than those with other P fractions. Overall, this study suggests that soil P bioavailability gradually improved during natural vegetation restoration on clear-cut sites mainly through the increase of NaHCO3-P, where phosphorous is immediately available, and subsequently available phosphorus NaOH-P.
In some urban parks in Tokyo, semi-natural habitat patches are maintained as nature reserves for birds, called bird sanctuaries. Bird censuses and vegetation surveys were conducted in eight urban parks in Tokyo from December 2015 to July 2016 to determine the effectiveness of bird sanctuaries on avian species composition. The relationship between avian species composition and environmental conditions was analyzed by partial redundancy analysis (partial RDA) using vegetation variables, number of visitors, presence or absence of reserves within the same park, area of wooded parts, and normalized difference vegetation index (NDVI) in the surrounding area. The results of the partial RDA are as follows: (1) Area, lower vegetation cover, higher vegetation cover, tree species composition obtained from detrended correspondence analysis (DCA) on vegetation survey data, and NDVI in the surrounding area were considered as covariates and explained 17.4–33.6% of the total variation in bird species composition, (2) The presence or absence of sanctuary significantly explained bird species compositional variation regardless of season, indicating that the sanctuaries were beneficial for urban avoider species not only in the sanctuaries but also in the surrounding wooded area, and (3) Tree coverage within a 100 m range and leaf litter coverage also influenced avian species composition. We concluded that bird sanctuaries and other nature reserves can be beneficial to bird conservation, even within Tokyo. The positive effect of sanctuaries could be due to the limited influence of human presence and the developed vegetation within them. These reserves may play the role of core habitats within the studied urban parks.
Growth traits and genetic diversity of 23 provenances of Quercus rubra introduced from North America were analyzed in a provenance trial established with a randomized block design in Hwaseong, Gyeonggi, South Korea in 1993. Growth variables and survival at age 25 were compared with results from early stages. Height, DBH, volume and stem straightness of Q. rubra was better than those of the domestic oak (Quercus accutissima). Growth of the Dunham Island provenance from New York was the best among the 23 provenances that of the Eagle River provenance from Wisconsin was poorest. Survival rate at age 25 was on average 52%. The longitude of seed origin and growth of provenance were consistently significantly negatively correlated at all ages. Growth of coastal provenances was superior to that of the inland provenances, which were separated by the Appalachian Mountains. Genetic diversity and genetic distance among the provenances were evaluated using microsatellite markers. The allelic frequencies showed high polymorphism in 10 microsatellite loci, and 292 alleles were found. Of 10 loci, two were commonly found in the 23 provenances. The mean allelic diversity and heterozygosity observed among the provenances were similar to those from the native populations of Q. rubra in North America. Nei′s genetic distance among the 23 was estimated and showed that a clear trend between geographic and genetic distances, indicating that some provenances have high genetic diversity with superior growth performance.
Spot fire increase the difficulty of fire-fighting and threaten public safety, and therefore it is important to study ignition probabilities of fuel bed by different firebrands, in order to understand ignition mechanisms and analyze the formation of spot fires. This will provide an important basis for further study to improve the fire-fighting efficiency and reduce casualties. In this study, the ignition probabilities of larch (Larix gmelinii) fuel beds with different moisture levels and packing ratios by diffreent firebrands, including cones and twigs of different sizes, was investigated. Ignition experiments were conducted at different wind speeds generated by fans. The results show that, regardless of moisture content and packing ratio, ignition probability is zero when there is no wind. Both moisture content and wind speed significantly influence ignition probability, while packing ratio has almost no effect. The maximum moisture content at which firebrand ignition occurred was 50%, and ignition probability increased with wind speed and decreased with moisture content. Cones have the highest ignition probability, followed by large twigs and by small twigs. Ignition probability is also affected by firebrand shapes and sizes that determine their potential heat and contact area to the fuel bed. Two empirical models were established to link ignition probability with fuel properties and wind speed. This study will help clarify the mechanism of spot ignition and reduce corresponding losses.
To explore the critical relationships of photosynthetic efficiency and stem sap flow to soil moisture, two-year-old poplar saplings were selected and a packaged stem sap flow gauge, based on the stem-heat balance method, and a CIRAS-2 portable photosynthesis system were used. The results show that photosynthetic rates (P n), transpiration rates (T r), instantaneous water use efficiency (WUE) and the stem sap flow increased initially and then decreased with decreasing soil water, but their critical values were different. The turning point of relative soil water content (W r) from stomatal limitation to nonstomatal limitation of P n was 42%, and the water compensation point of P n was 13%. Water saturation points of P n and T r were 64% and 56%, respectively, and the WUE was 71%. With increasing soil water, the apparent quantum yield (AQY), light saturation point (LSP) and maximum net photosynthetic rate (P nmax) increased first and then decreased, while the light compensation point (LCP) decreased first and then increased. When W r was 64%, LCP reached a lower value of 30.7 µmol m−2 s−1, and AQY a higher value of 0.044, indicating that poplar had a strong ability to utilize weak light. When W r was 74%, LSP reached its highest point at 1138.3 µmol∙m−2 s−1, indicating that poplar had the widest light ecological amplitude and the highest light utilization efficiency. Stem sap flow and daily sap flow reached the highest value (1679.7 g d−1) at W r values of 56% and 64%, respectively, and then declined with increasing or decreasing W r, indicating that soil moisture significantly affected the transpiration water-consumption of poplar. Soil water was divided into six threshold grades by critical values to maintain photosynthetic efficiency at different levels, and a W r of 64–71% was classified to be at the level of high productivity and high efficiency. In this range, poplar had high photosynthetic capacity and efficient physiological characteristics for water consumption. The saplings had characteristics of water tolerance and were not drought resistant. Full attention should be given to the soil water environment in the Yellow River Delta when planting Populus.
Preventing and suppressing forest fires is one of the main tasks of forestry agencies to reduce resource loss and requires a thorough understanding of the importance of factors affecting their occurrence. This study was carried out in forest plantations on Maoer Mountain in order to develop models for predicting the moisture content of dead fine fuel using meteorological and soil variables. Models by Nelson (Can J For Res 14:597–600, 1984) and Van Wagner and Pickett (Can For Service 33, 1985) describing the equilibrium moisture content as a function of relative humidity and temperature were evaluated. A random forest and generalized additive models were built to select the most important meteorological variables affecting fuel moisture content. Nelson's (Can J For Res 14:597–600, 1984) model was accurate for Pinus koraiensis, Pinus sylvestris, Larix gmelinii and mixed Larix gmelinii—Ulmus propinqua fuels. The random forest model showed that temperature and relative humidity were the most important factors affecting fuel moisture content. The generalized additive regression model showed that temperature, relative humidity and rain were the main drivers affecting fuel moisture content. In addition to the combined effects of temperature, rainfall and relative humidity, solar radiation or wind speed were also significant on some sites. In P. koraiensis and P. sylvestris plantations, where soil parameters were measured, rain, soil moisture and temperature were the main factors of fuel moisture content. The accuracies of the random forest model and generalized additive model were similar, however, the random forest model was more accurate but underestimated the effect of rain on fuel moisture.
Five Larix species (L. griffithii, L. speciose, L. himalaica, L. kongboensis, and L. potaninii var. australis), have survived on the Qinghai-Tibet Plateau (QTP) under specific climate conditions for decades. The lack of genomic information seriously hinders research on the evolution, conservation and ecology of these Larix resources. In this study, complete chloroplast (cp) genomes of the 5 species were assembled and compared based on next generation sequencing technology combined with polymerase chain reaction validation. The results show that the 5 cp genomes are relatively conservative in size, gene content and arrangement, and border variation. Phylogenetic analysis showed that the species are closely related as well as to seven other species of the same genus. In addition, the 5 cp genomes contained few simple sequence repeats and relatively low nucleotide variability; thus, 12 candidate polymorphic cp DNA markers will be helpful for further research on relevant population genetics. These results will provide valuable genetic information for the conservation, evolution and ecology of these species and their relatives.
To study the effect of jasmonates (JAs) on the resistance of economic forest plants to insects, Rosa rugosa ‘Plena’ leaves were treated with 1 mmol/L jasmonic acid (JA), methyl jasmonate (MeJA) and Z-jasmone, then the content of tannin and total phenol in leaves and the feeding area of Monolepta hieroglyphica adults on leaves were measured. Changes in the activities of detoxification enzymes in adult M. hieroglyphica that had fed on leaves treated with JAs were also studied. Tannin and total phenol levels in leaves increased significantly after treatment with JAs, and tannin level was 1.36–1.55-fold higher than in the control after treatment with 1 mmol/L MeJA. The total content of phenol in leaves treated with 1.0 mmol/L Z-jasmone increased by 1.33–2.20-fold compared with those of the control. The activities of detoxification enzymes in adults were inhibited to differing degrees: activity of alkaline phosphatase (AKP) first increased, then decreased; the activities of acid phosphatase (ACP), glutathione S-transferases (GSTs) and carboxylesterase (CarE) following treatment with 1 mmol/L MeJA were significantly reduced and were 22%–31%, 11%–26%, and 11%–31% lower than those of the control, respectively. Moreover, the feeding area of adult M. hieroglyphica on the leaves treated with JAs was significantly reduced (P < 0.05). The feeding area of economic forest R. rugosa ‘Plena’ leaves treated with 1 mmol/L MeJA decreased by 17%–43% compared with that of the control. Moreover, the decrease in the adult M. hieroglyphica feeding area was highly positively correlated with the content of tannin and positively correlated with the contents of total phenol of economic forest R. rugosa ‘Plena’ leaves. The reduced feeding area of adult M. hieroglyphica was highly negatively correlated with the activities of AKP and ACP and negatively correlated with those of the GSTs. In conclusion, the use of 1 mmol/L MeJA can noticeably decrease the deleterious effects of adult M. hieroglyphica.
Larch caterpillars are widely distributed in the Great Xing’an boreal forests; however, the relationship between caterpillar defoliation dynamics and climatic factors is poorly understood. The aims of this study are to investigate the primary weather conditions that might influence forest defoliation and to identify the most important life stage of the larch caterpillar at which forest defoliation might be mitigated by incorporating more inhibitory influences from climatic factors. The life cycle of the larch caterpillar was partitioned into four stages and multiple linear regression and mixed effect models were combined with a relative weight analysis approach to evaluate the importance and influence of meteorological variables on defoliation dynamics. The results show that warmer temperatures in growing seasons and overwintering periods can increase the defoliation area, while rainy and humid growing seasons decrease the defoliation area. Total precipitation during the early instar larval period had the greatest power to explain the variance in defoliation dynamics and had a very strong inhibitory effect, followed by the accumulative temperatures of the late instar larval period which had a positive impact, and precipitation during the middle instar larval period which had a negative impact. Weather conditions during the early instar larval period had the greatest influence on the area defoliated and accounted for 40% of the explained variance. This study demonstrates that climatic warming and drying will increase the risk of larch caterpillar outbreaks in the Great Xing’an Mountains.
Coumarate 3-hydroxylase (C3h) genes participate in the synthesis of lignin and may affect the properties of wood that are important for its commercial value. A better understanding of the natural variation in C3h genes and their associations to wood properties is required to effectively improve wood quality. We used a candidate gene-based association mapping approach to identify CfC3h allelic variants associated with traits that affect the wood properties of Catalpa fargesii. We first isolated the full-length CfC3h cDNA (1825 bp), which was expressed at relatively high levels in xylem according to real time-polymerase chain reaction. In totally, 17 common single-nucleotide polymorphisms (minor allele frequency > 5%) were identified through cloning and sequencing the CfC3h locus from a mapping population (including 88 unrelated natural C. fargesii individuals collected from main distribution area). Nucleotide diversity and linkage disequilibrium (LD) in CfC3h indicate that CfC3h has low nucleotide diversity (π t = 0.0031 and θ w = 0.0103) and relatively low LD (within 1800 bp; r 2 ≥ 0.1). An association analysis identified eight common single-nucleotide polymorphisms (SNPs) (false discovery rate, Q < 0.10) and ten haplotypes (Q < 0.10) associated with wood properties, explaining 4.92–12.09% of the phenotypic variance in an association population consisted of 125 unrelated natural individuals (The 88 individuals from the mapping population were comprised in the association population). Our study would provide new insight into C3h gene affecting wood quality, and the SNP markers identified would have potential applications in marker-assisted breeding in the future.
Cold-resistance pathways that operate in model plants such as Arabidopsis thaliana and Oryza sativa have been studied extensively. It has been found that CBF genes play an important role in plant cold resistance. Liriodendron chinense, a tree known for its graceful tree shape and widely spread in south China, has weak cold tolerance. However, little is known about its response to cold. To further study the function of L. chinense CBF gene family, we started by characterizing all members of this gene family in the L. chinense genome and their expression profiling. Phylogenetic analysis found that 14 CBF genes in L. chinense are more closely related to their homologues in woody plants and A. thaliana than those in O. sativa. Cis-acting elements and GO analysis showed that some LcCBF genes participated in the biological process of cold stress response. The transcriptomic and RT-qPCR data showed that most of LcCBF genes displayed an initially increasing and subsequently decreasing trend during cold stress course and the expression profile of each member was different. Some LcCBF genes exhibited a different abundance in callus, root, stem and leaf tissues. The structure and expression characteristics of LcCBF genes imply that they may have similar and different functions in response to cold stress conditions. The identification and analysis of LcCBF gene family have laid the foundation for future studies into L. chinense cold stress mechanisms and for the cultivation of cold-resistance cultivars.
Tree diversity has long been considered a key driver of insect herbivory in forest ecosystems. However, studies have given contradictory results: increased tree diversity can have positive, negative or neutral effects on insect herbivory. Since many issues can complicate the tree-herbivore interactions, the descriptor ‘tree diversity’ per se actually has only limited explanatory power for insect herbivory. Particularly, in addition to the direct bottom-up effects on insect herbivores, tree diversity may have stronger indirect top-down effects via natural enemies of insect herbivores. However, most research has addressed only direct bottom-up impacts. In fact, insect herbivory is the result of complex interactions (food webs) among all the species in a community. Although it is hard to integrate all functionally important species and dynamic information into food webs, the effects of tree diversity on insect herbivory are highly dependent on the dominant species at different trophic levels. It is important and practical to simultaneously consider the characteristics of main trees, herbivores, and natural enemies when attempting to predict the overall effects of forest tree diversity on insect herbivory. In order to ensure comparability between studies, it is necessary to classify them according to the descriptors of insect herbivory and tree diversity, and to compare results within each category. These measures might enhance our understanding of the mechanisms by which tree diversity drives insect herbivory and, in turn, help to develop sustainable pest management strategies for forests.
Plantations have been widely established to improve ecosystem services and functioning. Black locust, Robinia pseudoacacia L. is a common, widely planted species to control soil erosion on the Loess Plateau. Previous studies have focused on economic values but the interactions between soil and plant carbon (C), nitrogen (N) and phosphorus (P) remain unknown. Investigating variations of soil, green and senesced leaf C, N and P levels in R. pseudoacacia along a latitudinal gradient is useful to understanding its ecological functions. The results show that soil C, N and senesced leaf N and P significantly decreased with an increase in latitude, but there were no significant changes in the senesced leaf C and soil P. The resorption efficiency of N was related with latitude and soil N levels, and the relation between green leaf N and soil N was significant. These relations suggest that soil N was the key in affecting green leaf N levels. At higher latitudes, senesced leaves had lower N levels associated with higher N resorption efficiency to maintain a stable N content in green leaves. With a decrease of soil N, R. pseudoacacia can enhance N resorption efficiency to meet the demand of growth. Thus, it is an important species for reforestation, especially in nutrient-poor environments.
In the Original publication of the article, the authors found an error in the text “We recommend CLef of 5 and 12 mmol m−2 POD1 for broadleaved species and conifers, respectively” under the section abstract and conclusion
Intercropping of mulberry (Morus alba L.) and alfalfa (Medicago sativa L.) is a new forestry-grass compound model in China, which can provide high forage yields with high protein. Nitrogen application is one of the important factors determining the production and quality of this system. To elucidate the advantages of intercropping and nitrogen application, we analyzed the changes of physicochemical properties, enzyme activities, and microbial communities in the rhizosphere soil. We used principal components analysis (PCA) and redundancy discriminators analysis to clarify the relationships among treatments and between treatments and environmental factors, respectively. The results showed that nitrogen application significantly increased pH value, available nitrogen content, soil water content (SWC), and urea (URE) activity in rhizosphere soil of monoculture mulberry. In contrast, intercropping and intercropping + N significantly decreased pH and SWC in mulberry treatments. Nitrogen, intercropping and intercropping + N sharply reduced soil organic matter content and SWC in alfalfa treatments. Nitrogen, intercropping, and intercropping + N increased the values of McIntosh diversity (U), Simpson diversity (D), and Shannon–Weaver diversity (H′) in mulberry treatments. However, PCA scatter plots showed clustering of monoculture mulberry with nitrogen (MNE) and intercropping mulberry without nitrogen (M0). Intercropping reduced both H′ and D but nitrogen application showed no effect on diversity of microbial communities in alfalfa. There were obvious differences in using the six types of carbon sources between mulberry and alfalfa treatments. Nitrogen and intercropping increased the numbers of sole carbon substrate in mulberry treatments where the relative use rate exceeded 4%. While the numbers declined in alfalfa with nitrogen and intercropping. RDA indicated that URE was positive when intercropping mulberry was treated with nitrogen, but was negative in monoculture alfalfa treated with nitrogen. Soil pH and SWC were positive with mulberry treatments but were negative with alfalfa treatments. Intercropping with alfalfa benefited mulberry in the absence of nitrogen application. Intercropping with alfalfa and nitrogen application could improve the microbial community function and diversity in rhizosphere soil of mulberry. The microbial community in rhizosphere soil of mulberry and alfalfa is strategically complementary in terms of using carbon sources.