Tree plantations contribute towards balancing global carbon (C) and nitrogen (N) cycles, with the C:N ratio being a key factor determining soil fertility in plantations. In the present study, we ...investigated how the management practices of Chinese fir (Cunninghamia lanceolata) plantations affect soil organic carbon (SOC), C:N ratio and soil quality. We assessed how these soil properties vary for stands of (1) different ages (up to 97years) within the same rotation and (2) similar ages but in different rotations (up to four). Soil samples were collected and analysed from incremental depths (0–20, 20–40, 40–60, 60–80, and 80–100cm). Continuous replanting of Chinese fir at the same site caused SOC stock and C:N ratio to decline after the second rotation. SOC stock (0–100cm) decreased by 3, 3.6, and 14.3% between the first and second, second and third, and third and fourth rotations, respectively. The SOC concentration and C:N ratio declined from 21- to 40-year-old stands, and then increased in the 97-year-old stand throughout all soil depths. The stratification ratio (SR) index of SOC stock showed that continuous cultivation causes soil quality to decrease with increasing rotation cycle. Approximately 35–45% of equivalent soil mass SOC stocks were distributed in the upper soil layer (0–20cm) in stands of all ages, indicating more organic C accumulation in the surface layer compared to subsurface layers (>20cm). In conclusion, we recommend that (1) cutting cycles of the stands should be increased from 20 to 25years (current practice) to ~30years of age and (2) plantations should only be cultivated to the second rotation to maintain site productivity, which would maximise both the ecological and economic value of this practice to the environment.
•SOC stock and C:N ratio decreased after second rotation.•More organic C accumulation was in the top soil.•Soil quality decreased with each rotation cycle.•Cutting cycles of the stands should be increased to 25–30years.•Successive planting at the same site should be maintained only to the second rotation.
Studies on intra-specific variability in leaf functional traits is important to evaluate adaptation of the species to predicted climate change, and to develop long-term conservation strategy. The ...main objectives were to investigate the relationship between the functional traits leaves and C, N, P stoichiometry of Chinese fir from different geographical provenances and their relationship with the main environmental factors of provenance.
In this study, we measured 12 leaf functional traits on 36-year-old Cunninghamia lanceolata trees from 13 provenances. Analysis of variance (ANOVA) was performed to examine the variability. Redundancy analysis (RA) was computed to examine the relationship between geo-climatic factors of provenance origin and leaf functional traits while Pearson's correlation coefficient was computed to assess inter-trait correlations. The results showed statistically significant differences (P < 0.01) in intraspecific leaf traits among provenances, except leaf P content. The relationships among leaf traits are consistent with the general trend observed in the leaf economic spectrum. Mean annual temperature appeared to be a key factor that influences intraspecific leaf traits variability compared to mean annual precipitation.
These results provide useful insights about adaptation of leaf trait of Chinese fir in a changing climatic condition. Thus, our findings shed light on the importance of interspecific trait variability in Chinese fir and the potential effect of climate change.
Malate dehydrogenase (MDH) genes play vital roles in developmental control and environmental stress tolerance in sessile plants by modulating the organic acid-malic acid level. However, MDH genes ...have not yet been characterized in gymnosperm, and their roles in nutrient deficiency are largely unexplored. In this study, 12 MDH genes were identified in Chinese fir (
), namely,
,
,
,
,
. Chinese fir is one of the most abundant commercial timber trees in China, and low phosphorus has limited its growth and production due to the acidic soil of southern China. According to the phylogenetic analysis, MDH genes were classified into five groups, and Group 2 genes (
,
,
, and
) were only found to be present in Chinese fir but not in
and
. In particular, the Group 2 MDHs also had specific functional domains-Ldh_1_N (malidase NAD-binding functional domain) and Ldh_1_C (malate enzyme C-terminal functional domain)-indicating a specific function of ClMDHs in the accumulation of malate. All
genes contained the conserved MDH gene characteristic functional domains Ldh_1_N and Ldh_1_C, and all ClMDH proteins exhibited similar structures. Twelve
genes were identified from eight chromosomes, involving fifteen
homologous gene pairs, each with a Ka/Ks ratio of <1. The analysis of cis-elements, protein interactions, and transcription factor interactions of MDHs showed that the
gene might play a role in plant growth and development, and in response to stress mechanisms. The results of transcriptome data and qRT-PCR validation based on low-phosphorus stress showed that
and
were upregulated under low-phosphorus stress and played a role in the response of fir to low-phosphorus stress. In conclusion, these findings lay a foundation for further improving the genetic mechanism of the
gene family in response to low-phosphorus stress, exploring the potential function of this gene, promoting the improvement of fir genetics and breeding, and improving production efficiency.
Plantation development stage (forest age sequence) influences environmental conditions and litter inputs, which can modify labile C and N pools. Changes in labile C and N pools during stand ...development could vary considerably with soil parent material. However, empirical evidence is scarce regarding the extent of interactive effects between parent material and stand development stage on labile C and N pools in plantations of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.), the dominant plantation tree in southern China. We examined the concentrations of soil labile C and N (dissolved organic carbon, DOC, dissolved organic nitrogen, DON, dissolved inorganic nitrogen, DIN, microbial biomass carbon, Cmic, microbial biomass nitrogen, Nmic) and basic soil properties within a soil depth of 100 cm for three stand development stages (young, middle-aged and mature) of Chinese fir plantations grown on soils derived from granite or siltstone. The parent material influenced the responses of the DON, DIN and Nmic pools to stand development stage, whereas no interaction effect of parent material and stand on the Cmic and DOC pools was observed. The parent material had a clear effect on the standing pools of labile C and N. Siltstone soils tended to have greater pool sizes of DOC, DON, DIN, and Nmic and greater ratios of Cmic/total carbon (TC) and Nmic/total nitrogen (TN). The stand development stage did not affect the DOC, Cmic and Cmic/TC ratio. The mineral N and Nmic pools increased significantly and the DON and DON/TN ratio declined sharply from young to middle-aged stands in both soil type. The changes in the DON, DIN and Nmic pools and the Nmic/TN ratio from middle-aged to mature stands depend on the parent material. The concentrations of DOC, DON, DIN, Cmic and Nmic were positively correlated with multiple soil parameters, such as the TC, TN, C/N ratio, water-stable aggregates (WSA), and water content, but negatively correlated with the bulk density (BD). DOC, DON, Cmic and Nmic significantly decreased with soil depth, but the extent of the decrease in DOC and DON was greater in course-textured granite soils. Overall, the turnover rates of the labile C pools are higher in the siltstone soils where internal N cycling during a traditional rotation ~25 years maintain the supply of mineral N and improve N incorporation into microbial biomass. These results highlight the need to identify soil physicochemical properties before afforestation. The rotation length and N fertilizer application in Chinese fir plantations should be adjusted based on the soil parent material.
•Labile C pool did not differ with stand development on siltstone and granite sites.•Labile N pools response to stand development stage vary between parent materials.•Labile C and N pools were greater in fine-textured soils from siltstone.•Labile C and N pools relate to multiple soil properties of parent materials.•Recommend parent material as a key factor in managing Chinese fir plantation
Phosphate (Pi) deficiency is one of the most limiting factors for Chinese fir growth and production. Moreover, continuous cultivation of Chinese fir for multiple generations led to the reduction of ...soil nutrients, which hindered the yield of Chinese fir in southern China. Although NAC (NAM, ATAF, and CUC) transcription factors (TFs) play critical roles in plant development and abiotic stress resistance, it is still unclear how they regulate the response of Chinese fir to phosphate (Pi) starvation. Based on Pi-deficient transcriptome data of Chinses fir root, we identified a NAC transcription factor with increased expression under Pi deficiency, which was obtained by PCR and named
. RT-qPCR confirmed that the expression of
in the root of Chinese fir was induced by phosphate deficiency and showed a dynamic change with time. It was positively regulated by ABA and negatively regulated by JA, and
was highly expressed in the roots and leaves of Chinese fir. Transcriptional activation assay confirmed that
was a transcriptional activator. The promoter of
was obtained by genome walking, which was predicted to contain a large number of stress, hormone, and growth-related cis-elements. Tobacco infection was used to verify the activity of the promoter, and the core promoter was located between -1519 bp and -589 bp. We identified 18 proteins bound to the
promoter and 5 ClNAC100 interacting proteins by yeast one-hybrid and yeast two-hybrid, respectively. We speculated that AHL and TIFY family transcription factors, calmodulin, and E3 ubiquitin ligase in these proteins might be important phosphorus-related proteins. These results provide a basis for the further study of the regulatory mechanism and pathways of
under Pi starvation.
Canopy litter is an important component of coarse woody debris (CWD), which affects nutrient and carbon cycling in forest ecosystems. For marcescent plant species (characterized by dead branches and ...leaves remaining in the canopy for several years before abscission), nutrient resorption from senescing leaves is an important nutrient conservation strategy. However, investigating the ecological function of canopy litter is challenging due to its limited accessibility and also the heterogeneous canopy microclimate in terms of light transmission, temperature and moisture. We studied the spatiotemporal distribution of canopy litter mass and seasonal dynamics of leaf nutrients and nutrient resorption during senescence in the canopy along a chronosequence of Chinese fir Cunninghamia lanceolata (Lamb.) Hook plantations in southeast China. The dry mass weight of dead branches and dead leaves in the canopy significantly increased with stand stage (14.6, 14.2, and 17.4 t ha−1 for young, middle-aged, and mature stands respectively), accounting for high proportions of total aboveground litter of 85.7%, 79.1% and 80.0%, respectively, along with annual litterfall production (2.44, 3.75, and 4.34 t ha−1, respectively). The canopy height distribution of dead branches and leaves also increased with stand age, ranging from 0 to 4 m in young stands, 3–8 m in middle-aged stands, to 4–10 m in mature stands. The seasonal pattern of canopy litter mass was the inverse of litterfall production: canopy litter mass peaked, while litterfall production was lowest in winter. Mean N, P, K, and Mg nutrient resorption efficiencies across stands at each stage were 53.8–58.9%, 64.0–68.9%, 85.0–90.2%, and 46.5–56.6%, respectively, while Ca was not retranslocated from senescing leaves. In summary, Chinese fir plantations retain large amounts of dead branches and leaves in the canopy from which at least ~50% of the nutrients N, P, K and Mg are recycled, representing an important nutrient conservation strategy that has evolved to adapt to nutrient-limited habitats. Canopy litter therefore plays an important role in these forest plantation ecosystems and should be protected instead of being removed from the canopy to the forest floor.
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•Canopy litter mass spatiotemporal dynamics varied in a Chinese fir chronosequence.•Canopy litter biomass increased over time, accounting for ~80% aboveground litter.•N, P, K, and Mg concentrations decreased during senescence before litterfall.•N, P, K, and Mg resorption efficiencies varied seasonally and among developmental stages.•Resorption from canopy litter contributes significantly to nutrient cycling.
•Most of the soil properties decreased in their concentration with increase in rotation.•TP, LP-II-C, LP-I-N, and pH identified as key soil quality indicators.•Soil quality of entire soil profile ...decreased with increase in rotation cycle.•Cultivation of Chinese fir should be limited to only two rotations in the same site.
Globally, forest conversion is known to affect soil quality. In the present study, we developed a soil quality index (SQI) to quantify the changes in soil quality due to conversion of native forests into Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) plantations in southern China. We selected 11 Chinese fir stands of different ages (12-, 21-, 40-, and 97-year-old in the first rotation; 1-, 12-, 21-, and 31-year-old stands in the second rotation; 13- and 21-year-old stands in the third rotation; and a 10-year-old stand in the fourth rotation) from sub-tropical forest plantations in Nanping, Fujian Province, China. Soil samples were collected from different depths (0–20, 20–40, 40–60, 60–80, and 80–100 cm) and 20 soil properties were analysed. SQI was computed from the minimum data set derived from principal component analysis (PCA). Although the PCA included many soil properties, we identified total phosphorus (TP) and labile carbon pool II (LP-II-C) as key soil quality indicators, because they contributed 36.2 and 34.9% to SQI, respectively, followed by labile nitrogen pool I (LP-I-N) and soil pH. SQI values showed that continuous replanting of Chinese fir at the same site decreased soil quality significantly at 0–100 cm depth. Increasing rotation cycle (from first to fourth) strongly reduced LP-II-C (48.8%), LP-I-N (56.6%), labile nitrogen-II (70.2%), nitrate-nitrogen (67.7%), and available phosphorus (48.4%), indicating that successive rotation degrades soil quality. Thus, our results demonstrate that Chinese fir cultivation should be limited to only two rotations in the same site to preserve soil quality. We conclude that TP, LP-II-C, LP-I-N, and pH can be used as effective indicators in temporal soil quality monitoring programs under forest plantations.
Sustainable forestry requires adopting more ecosystem-informed perspectives. Tree thinning improves forest productivity by encouraging the development of the understory, which in turn improves ...species diversity and nutrient cycling, thereby altering the ecophysiological environment of the stand. This study aimed to quantify tree growth, understory vegetation, and soil quality of 9- and 16-year-old Chinese fir (
Cunninghamia lanceolata
(Lamb.) Hook.) plantations in South China, 1–7 years after pre-commercial thinning. The quadratic mean diameter (QMD) and individual tree volume were greatly increased and compensated for the reduced stand yield in thinned stands. In 2011, the stand volume in unthinned and thinned stands were 276.33 and 226.46 and 251.30 and 243.64 m
3
ha
−1
, respectively, for young and middle stage. Therefore, we predicted that over time, the stand volume in thinned stands should exceed that in unthinned stands. The composition, diversity, and biomass of understory vegetation of the plantation monocultures significantly increased after thinning. The effects of thinning management on understory development were dynamic and apparent within 1–2 years post-thinning. Some light-demanding plant species such as
Styrax faberi
,
Callicarpa formosana
,
Lophatherum gracile
, and
Gahnia tristis
emerged in the shrub and herb layer and became dominant with the larger gaps in the canopy in thinned stands. The trigger effects of thinning management on understory and tree growth were more pronounced in the young stage. The beneficial effects on soil physical and chemical properties were measurable at later stages (7 years after thinning). The strong positive relationship between understory biomass and volume increment (at the tree and stand levels) indicated that understory improvement after thinning did not restrict productivity within Chinese fir stands but rather, benefited soil water content and nutrient status and promoted tree growth.
Phosphorus is one of the essential elements for plant growth and development, but available phosphorus (Pi) content in many soil types is low. As a fast-growing tree species for timber production, ...Chinese fir is in great demand of Pi, and the lack of Pi in soil restricts the increase of productivity of Chinese fir plantation. Root morphology and the synthesis and secretion of organic acids play an important role in the uptake of phosphorus, but the molecular mechanisms of Chinese fir root responses to Pi deficiency are largely unexplored. In this study, seedlings of Yang 061 clone were grown under three Pi supply levels (0, 5 and 10 mg·L-1 P) and morphological attributes, organic acid content and enzyme activity were measured. The transcriptome data of Chinese fir root system were obtained and the expression levels of phosphorus responsive genes and organic acid synthesis related genes on citric acid and glyoxylate cycle pathway were determined.
We annotated 50,808 Unigenes from the transcriptome of Chinese fir roots. Among differentially expressed genes, seven genes of phosphate transporter family and 17 genes of purple acid phosphatase family were up-regulated by Pi deficiency, two proteins of SPX domain were up-regulated and one was down-regulated. The metabolic pathways of the citric acid and glyoxylate cycle pathway were mapped, and the expression characteristics of the related Unigenes under different phosphorus treatments were analyzed. The genes involved in malic acid and citric acid synthesis were up-regulated, and the activities of the related enzymes were significantly enhanced under long-term Pi stress. The contents of citric acid and malic acid in the roots of Chinese fir increased after 30 days of Pi deficiency.
Chinese fir roots showed increased expression of genes related with phosphorus starvation, citrate and malate synthesis genes, increased content of organic acids, and enhanced activities of related enzymes under Pi deficiency. The results provide a new insight for revealing the molecular mechanism of adaption to Pi deficiency and the pathway of organic acid synthesis in Chinese fir roots.
Available phosphorus (P) scarcity in the highly weathered soils of the subtropical forests in southern China is a serious concern. To ensure whether inoculation of arbuscular mycorrhizal fungi (AMF) ...with Chinese fir (
) under low P stress conditions could promote its growth and P utilization capacity, an indoor pot simulation experiment was carried out with the different P supply treatments and Chinese fir seedlings as the tested material.
The experiment had two P supply treatments, no P supply (P0, 0 mmol·L
KH
PO
) and normal P supply (P1, 1.0 mmol·L
KH
PO
). The seedling in each P supply treatment was inoculated with
(Gi), a widespread species of AMF in the natural environment, and with no AMF inoculation as a control treatment (CK). The Gi infection rate in the root system, root cortex tissue dissolution rate, root morphological indexes and biomass, whole plant P use efficiency, and root P use efficiency of Chinese fir were determined under different treatment conditions.
The results showed that P0 treatment significantly increased the Gi infection rate (
< 0.05). After inoculating AMF with different P supply treatments, the root cortex tissue dissolution rate was considerably enhanced. In contrast, the Chinese fir's root length and surface area were reduced; however, the root volume did not change significantly. The average root diameter in the P0 treatment and inoculated with AMF was significantly more prominent than in the uninoculated treatment (
0.05). The root biomass and root-to-shoot ratio at different P supply treatments were significantly higher in the Gi infection treatment than in the CK group. Under different P supply treatments, root inoculation with Gi promoted root P use efficiency and whole plant P use efficiency. In conclusion, low P stress condition promoted the colonization of AMF in the root system, increased the dissolution of root cortex tissue, root volume, and the average diameter, and promoted root biomass accumulation and P use efficiency.
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