•C emissions of stem respiration from 16, 25, 41 years old forest were estimated.•Air temperature and moisture are the primary climatic factor affecting RS.•The general model of RS using Q10 may ...underestimated the RS of young trees.•Q10 of RS peaked at a temperature within the range of 0–5°C.•Temperature-corrected Q10 of RS should be considered to estimate C emissions.
Stem respiration is a critical yet unavailable component of forest ecosystem carbon cycle dynamics. It is therefore necessary to study the variation in stem respiration at different time scales, especially regarding the response of the temporal variation in stem respiration to climatic factors. However, stem respiration is commonly measured only a few times a year during the daytime. In this study, we investigated the stem respiration of Larix principis-rupprechtii Mayr at different time scales, including hours, days, months, and seasons, and in forests of different ages as well as its connection with climatic factors using a soil carbon flux system (Li-8100) in North China during the growing season (May to September) and the non-growing season (October) from 2013 to 2015. The maximum daily stem respiration rate (abbreviated as RS) occurred between 14:00 and 18:00, and the minimum occurred between 4:00 and 8:00 (2.01–4.24, 1.71–4.25 and 1.02–1.72 vs. 10.83–2.93, 1.08–2.28 and 0.51–1.17μmolm−2s−1, respectively) for three forestry ages, which was in accordance with single-peak curves. The seasonal respiration was highest in late July and lowest in late October (3.84 vs. 0.27μmolm−2s−1, respectively). Calculation of RS indicated that the annual CO2 efflux per unit area was ranked by forest age as follows: 25 (11.53±2.08tha−1)>16 (7.45±1.02)>41 (4.87±0.66)years of age. The average annual Q10 values were 3.85 (16 years of age), 3.41 (25), and 2.23 (41). The Q10 value of the 16-year-old forest peaked (9.89) during low temperature (0–5°C) and subsequently decreased with increasing air temperature. These results not only clarify the response of RS to climatic factors at different time scales but also reveal the relationship between stem respiration in forests of different ages and their temperature sensitivity. These results suggest that the sensitivity of RS to temperature is negatively correlated with stand age and air temperature. Methodologically, incorporating stand age and air temperature into the conventional method would improve the accuracy of annual stem respiration estimates.
Journal impact factor (JIF) and journal ranking play essential roles in scholarly publishing and research assessment, but the overuse of these metrics has recently drawn criticism. One topic of major ...debate is that certain objective measurable and controlled variables, including publication delay, journal size and article size, could impact JIF; in addition, journal identity is increasingly becoming a matter of concern. In this study, we focus mainly on the links between publication delays, number of published articles per year, average paper length and JIF and explore the mechanisms of journal ranking levels according to these variables. After a thorough survey of 53 forestry journals, we find that (1) compared to other fields, forestry research has a humble publishing culture with a lower JIF, smaller journal size, longer articles and rather substantial time to accept and publish the original articles in their final form. (2) More published articles per year could help a forestry journal rank in the top 50%. In addition, for non open access journals, a shorter period between manuscript acceptance and the final published version, a longer time between online available and final publication, and more time from articles receiving to online posting positively impact journal ranking; while for open access journals, longer paper length and faster article acceptance has a positive influence on ranking. (3) There is statistical evidence that publication practice preferences exist between different ranking levels. This research provides an objective view for rethinking the overdependence on JIF and journal ranking in research assessment.
The combined cadmium (Cd) and acid rain pollution poses a significant threat to the global ecological environment. Previous studies on the combined adverse effects have predominantly focused on the ...aboveground plant physiological responses, with limited reports on the microbial response in the rhizosphere soil. This study employed Populus beijingensis seedlings and potting experiments to simulate the impacts of combined mild acid rain (pH=4.5, MA) or highly strong acid rain (pH=3.0, HA), and soil Cd pollution on the composition and diversity of microbial communities, as well as the physiochemical properties in the rhizosphere soil. The results showed that Cd decreased the content of inorganic nitrogen, resulting in an overall decrease of 49.10 % and 46.67 % in ammonium nitrogen and nitrate nitrogen, respectively. Conversely, acid rain was found to elevate the content of total potassium and soil organic carbon by 4.68 %-6.18 % and 8.64–19.16 %, respectively. Additionally, simulated acid rain was observed to decrease the pH level by 0.29–0.35, while Cd increased the pH level by 0.11. Moreover, Cd alone reduced the rhizosphere bacterial diversity, however, when combined with acid rain, regardless of its intensity, Cd was observed to increase the diversity. Fungal diversity was not influenced by the acid rain, but Cd increased fungal diversity to some extend under HA as observed in bacterial diversity. In addition, composition of the rhizosphere bacterial community was primarily influenced by the inorganic nitrogen components, while the fungal community was driven mainly by soil pH. Furthermore, “Metabolism” was emerged as the most significant bacterial function, which was markedly affected by the combined pollution, while Cd pollution led to a shift from symbiotroph to other trophic types for fungi. These findings suggest that simulated acid rain has a mitigating effect on the diversity of rhizosphere bacteria affected by Cd pollution, and also alters the trophic type of these microorganisms. This can be attributed to the acid rain-induced direct acidic environment, as well as the indirect changes in the availability or sources of carbon, nitrogen, or potassium.
•Cd decreased the content of inorganic nitrogen, whereas the acid rain increased the total potassium and soil organic carbon.•Cd alone reduced the rhizosphere bacterial diversity; however, it increased the diversity when combined with acid rain.•The rhizosphere bacterial community was primarily influenced byinorganic nitrogen, while the fungal community by soil pH.•Cd pollution led to a shift from symbiotroph to other trophic types for fungi.
•ES was greater near the crown and the root than at the middle stem positions.•Nitrogen was the primary nutrient element affecting ES.•Sapwood width was the primary wood structure affecting ES.•C ...emissions from older tree was underestimated without the vertical variation in ES.•A model of ES for each stem position was established.
Stem CO2 efflux (ES) plays an essential role in the carbon balance of forest ecosystems. Therefore, it is necessary to study the vertical and seasonal variations in ES in forests with different ages, especially in response to factors associated with temperature, nutrients and wood structure. In this study, we investigated ES and its association with temperature factors using a carbon flux system (Li-8100A) at monthly intervals during the growing season (May to September) and the non-growing season (October) from 2013 to 2015. In addition, we collected data on nutrients and wood structure in August 2016 from 16- (young), 25- (immature), and 41-year-old (mature) Larix principis-rupprechtii Mayr stands in North China. Our analysis showed that the ES values at stem positions near the crown and the root system were generally higher than those in the middle and that the minimum ES values in July occurred at 2.0 m (3.61 μmol m−2 s−1), 3.0 m (2.42 μmol m−2 s−1), and 5.0 m (4.03 μmol m−2 s−1) in the young, immature, and mature forests, respectively. Air temperature and wood temperature influenced the vertical variation in ES, as did stem nitrogen concentration and sapwood width. Compared to the method that uses the vertical ES gradient to determine tree-scale CO2 effluxes for 16-, 25- and 41-year-old L. principis-rupprechtii forests, the method that uses the ES value at the 1.3-m stem position underestimated the CO2 effluxes by 5%, 6%, and 24%, respectively. The ES and Q10 models for each stem position for the three forest ages in this study can be used to accurately estimate tree-scale CO2 effluxes. These results not only clarified the relationships between the vertical variation in ES and temperature, nutrient content and wood structure, but also revealed the likely response mechanisms of ES to these factors. Methodologically, incorporating the vertical variation in ES and the associated drivers into conventional models would improve the accuracy of annual ES estimates.
Weeping cypress is an endemic tree species that is widely planted in China, and the simple stand structure and fragile ecosystem of its plantation are common issues. Exploring the effect of different ...gap sizes on the soil bacterial community structure of weeping cypress plantations can provide a theoretical basis for the near-natural management of forest plantations. We, therefore, constructed three kinds of forest gaps with different sizes in weeping cypress plantations, namely, small (50–100 m
2
), medium (100–200 m
2
), and large gaps (400–667 m
2
), for identifying the key factors that affect soil bacterial communities following the construction of forest gaps. The results suggested that the herb layer was more sensitive than the shrub layer, while the Simpson, Shannon, and richness indices of the herb layer in plots with gaps were significantly higher than those of designated sampling plots without any gaps (CK). The presence of large gaps significantly increased the understory plant diversity and the Shannon and Simpson indices of the soil bacterial alpha diversity. There were obvious changes in the community composition of soil bacteria following the construction of forest gaps. The dominant bacterial phyla, orders, and functions were similar across the plots with different gap sizes. Of the indicator bacterial species, the abundance of the nitrogen-fixing bacteria,
Lysobacter_ yangpyeongensis
, and
Ensifer_meliloti
, was significantly different across plots with different gap sizes and accounted for a large proportion of the bacterial population of plots with medium and large gaps. The understory plant diversity was mostly related to the soil bacterial community than to other soil factors. The results of structural equation modeling indicated that the understory plant diversity was the most important environmental factor in driving the composition and diversity of bacterial communities. The construction of forest gaps significantly improved the understory plant diversity, physicochemical properties of the soil, and bacterial diversity in weeping cypress plantations, and the results of the comprehensive evaluation were in the order: large gaps > small gaps > medium gaps > CK. Our results suggested that large gaps are beneficial for the diversity of above-ground plant communities and underground soil bacterial communities.
The decline in forest ecological function caused by pure forest plantations planted in the Yangtze River basin is becoming increasingly serious. To investigate this problem, we selected the local ...low-efficiency weeping cypress plantations for forest gap transformation. Three forest gap sizes, specifically large, medium, and small gaps, were established, and the effects of gap sizes on soil bacterial community structure and diversity in winter and summer were studied compared to no gaps (CK; control). Compared to CK, forest gaps had a significant effect on soil organic carbon (SOC) and soil total nitrogen (TN), and the highest values of SOC and soil TN under two seasons occurred in large forest gaps. The interactions of forest gap sizes and seasons had significant effects on pH, SOC, TN, and alpha diversity indices, including Simpson, Chao1, and ACE indices. Compared to winter, forest gaps significantly increased the soil bacterial community diversity indices in summer. Forest gap sizes significantly affected the composition of the bacterial community, but the composition of the dominant bacteria at the phyla and genera levels was similar. Linear discriminant effect size (LEfSe) analysis showed that there were 32 indicator bacterial species in two seasons. Co-occurrence network analysis revealed that the relationship of the soil bacterial community at the phyla level was complex, and there was a significant positive correlation among bacterial species. Soil bulk density (BD) and soil moisture (SM) significantly affected the soil bacterial alpha diversity indices. The composition of the dominant bacteria at the phyla level was significantly affected by soil microbial carbon (MBC), whereas the composition of dominant bacteria at the genera level was affected by soil hydrolysable nitrogen (AN) and the carbon/nitrogen (C/N) ratio. In this study, compared to the other forest gaps, large forest gaps were more conducive to the accumulation of soil nutrients, thus improving the structure of the soil bacterial community. Importantly, changes in the soil bacterial community structure due to gap formation may have profound effects on soil biogeochemical processes in weeping cypress forest plantations.
The root system architecture (RSA), being a key characteristic of the root economic spectrum, describes the spatial arrangement and positioning of roots that determines the plant's exploration of ...water and nutrients in the soil. Still, it remains poorly understood how the RSA of woody plants responds to the demand for water and nutrients in different soil environments and how the uptake of these resources is optimized. Here we selected single-species plantations of
and determined their topological index (
), revised topological index (
and
), root link length (
), root branching rate (
and
:
), and
soil physicochemical properties to assess which root foraging strategies adopt in different soil environments among Guang'an City (GA), Suining City (SN), Mianyang City (MY), and Deyang City (DY) in China. We also tested the potential effects of different nutrients upon RSA according to its plastic phenotype. Principal component analysis (PCA) showed that levels of soil nutrients were the highest at DY, followed by MY and SN, and lower at GA. A dichotomous branching pattern was observed for GA, SN, and MY, but a herringbone branching pattern for DY. The
was ranked as GA, > SN, > MY > DY. The
of GA, SN, and MY was significantly lower than that of DY (
< 0.05). Among the different city regions, values of
were the largest in different regions and those of
the smallest. The cross-sectional area of the root system did not differ between any two connected branch orders. The
, and
were significantly and negatively correlated with soil's water content, porosity, total nitrogen, total potassium, available nitrogen, and available phosphorus (
< 0.05), whereas they all had significant, positive relationships with soil temperature (
< 0.05). The
was significantly and positively correlated with total potassium in soil (
< 0.05). Redundancy analysis showed that total potassium was the main factor driving variation in RSA. Our results emphasize that the RSA is capable of corresponding plastic alterations by changing its number of internal or external links and the root link length of fine roots
a heterogeneous environment, thereby optimizing the rates of water capture and space utilization.
Fine root anatomy plays an important role in understanding the relationship between fine root function and soil environment. However, in different soil environments, the variation of fine root ...anatomical structure in different root sequences is not well studied. We measured the soil conditions and anatomical structure characteristics (root diameter, cortical tissue, vascular tissue and xylem) of fine roots of
Cupressus funebris
in four experimental sites, and analyzed each level of fine roots separately. We link these data to understand the relationship between fine root anatomy and soil conditions. We found that the anatomical structure of fine roots is closely related to soil environmental factors. The fine roots of lower root order are mainly affected by soil nutrients. Among them, the cortical tissue of first-order fine roots was positively correlated with potassium and phosphorus, but negatively correlated with nitrogen, while second- and third-order fine roots was positively correlated with soil total potassium and negatively correlated with nitrogen and phosphorus. For the fine roots of high root order, the cortical tissue disappeared, and the secondary vascular tissue was mainly affected by soil moisture. In addition, we also found that the division of fine root functional groups is not fixed. On the one hand, the function of third-order fine roots will slip. For example, the decrease of soil moisture will promote the transformation of third-order fine roots into transport roots, and the reduction of nitrogen will promote the transformation of third-order fine roots into absorption roots to fix nitrogen. This transformation strategy can effectively prevent the restriction of soil nutrients on plant growth. On the other hand, with the change of habitat, the first- and second-order fine roots are still the absorbing root, and the fourth- and fifth-order fine roots are still the transport root, but the efficiency of absorption and transport will be affected. In conclusion, our findings emphasize the fine roots in different soil environment to show high levels of plasticity, shows that fine root anatomical structure changes may make plants, and reveals that the fine is just order of reaction and its mechanism in the soil environment.
To address the ecological challenges arising from pure forest plantations and the wood supply–demand imbalance, implementing sustainable forest management is paramount. Accordingly, we studied crop ...trees at three densities (100, 150, and 200 N/ha) in a subtropical Pinus massoniana plantation. Our study revealed that the dominant phyla and genera within the fungal community remained largely consistent, with Basidiomycota and Ascomycota occupying prominent positions. Notably, the β diversity of the fungal community exhibited significant changes. Ectomycorrhizal and saprophytic fungi emerged as crucial functional guilds, and crop-tree thinning contributed to increased complexity within the fungal network, with a prevalence of positive rather than negative correlations among genera. The significant roles played by Camphor plants and ferns were evident in the fungal networks. Additionally, under crop-tree thinning, plant diversity experienced a significant boost, fostering interactions with the fungal community. Herb diversity played a vital role in the fungal community, affecting it either directly or indirectly, by altering the content of total phosphorus or organic matter in the soil. This study underscores the relationship between undergrowth plants and soil fungal communities, offering a scientific basis for evaluating the sustainability of restoring inefficient forest-plantation ecosystems.
As one means of close-to-nature management, forest gaps have an important impact on the ecological service function of plantations. To improve the current situation of P. massoniana plantations, ...three different sizes of forest gaps (large gaps, medium gaps and small gaps) were established to observe whether gap setting can improve the soil fertility and plant diversity of forest plantations. The results showed that compared with the control, the soil organic matter content of different soil layers increased significantly in the medium forest gap and large forest gap. The content of soil organic matter in the surface layer of the middle gap had the largest increase (80.64%). Compared with the control, the content of soil-available potassium between different soil layers decreased significantly by 15.93% to 25.80%. The soil hydrolysable nitrogen reached its maximum under the medium gap. Soil moisture showed significant changes among different gap treatments, different soil layers and their interaction, decreasing significantly in large gaps and small gaps but increasing significantly in medium gaps. The soil bulk density decreased significantly compared with the control, and the surface soil reached the minimum in the medium gap. There were different plant species in forest gaps of different sizes, and shrub layer plants were more sensitive to gap size differences than herb layer plants. The plant diversity indices of the shrub layer increased significantly and showed a maximum under the medium gap. The plant diversity of the herb layer showed the opposite trend, and the Shannon-Wiener index, Simpson index and Pielou index were significantly lower than those of the control. RDA showed that different gap treatments had significant effects on the distribution of plants under the forest. Soil available potassium, soil moisture and soil bulk density affected the distribution and diversity of plants under the forest, serving as the limiting factors of plant growth. In forest management, if we strictly consider the improvement of plant diversity and soil physicochemical properties, these results suggest that a medium gap should be established in a plantation for natural restoration.
PDF