Chestnut Orchards Research Articles

Study on yield values of two irrigation systems in adult chestnut trees and comparison with non-irrigated chestnut orchard

Different types of irrigation systems can be used in chestnut orchards. To understand which one grants higher yield values treatments were applied in adult trees: drip system - TI; micro-sprinkler system - SI; non-irrigated system - NI. The study covers two years in the northeast of Portugal. Irrigation was triggered every time stem water potential was lower than -1.2 MPa. The study considers costs with the equipment, water and labour, and the income from the chestnuts’ sale. Due to the hotter conditions of 2016 more water was supplied (93 mm) than in 2015 (47 mm). Little more water was furnished in SI (73 mm) than in TI (67 mm). Production was 27% higher in irrigated (48 kg/tree) than in NI trees (38 kg/tree) and in relation to the canopy’s area (kg/m2) the TI produced 18% and SI 29% more than NI. Annual costs were higher with irrigation (4654, 4549 and 1530 €/ha for SI, TI and NI, respectively) but the higher income (22126, 21984 and 16174 €/ha for TI, SI and NI respectively) made up for the investment. The profits from irrigated trees can be 22% or 37% higher than in non irrigated ones, for 1 ha or 5 ha, respectively.

Entomopathogenic fungi and nematodes against larvae of the chestnut weevil, Curculio elephas (Coleoptera: Curculionidae): a laboratory evaluation

ABSTRACTPest control in chestnut orchards is mainly achieved by chemicals, but there is growing focus on the potential use of biological control agents. The larval susceptibility of the chestnut weevil Curculio elephas L. (Coleoptera: Curculionidae) to different strains/species of entomopathogenic fungi and nematodes was evaluated in laboratory by soil cup bioassays. In the experiments with fungi, a wild strain of Metarhizium anisopliae caused the highest larval mortality (about 90%) compared with a commercial and a wild strain of Beauveria bassiana (80% and 77% respectively). Regarding nematodes, the commercial strain of Heterorhabditis bacteriophora was more effective in the control of chestnut larvae (77% insect mortality) than Steinernema carpocapsae (43%).

The infection process of chestnut rot, an important disease caused by Gnomoniopsis smithogilvyi (Gnomoniaceae, Diaporthales) in Oceania and Europe

Chestnut rot is an important disease of chestnut trees in Oceania (Australia, New Zealand), and Europe (Italy, France, Switzerland, United Kingdom). The causal agent has been identified as the fungus Gnomoniopsis smithogilvyi (Gnomoniaceae, Diaporthales). Koch’s Postulates was demonstrated on nuts from three Australian chestnut varieties with G. smithogilvyi from Australia, New Zealand and Italy. The Australian and New Zealand isolates were pathogenic on all three varieties, however the Italian isolate produced smaller lesions on all three, and was only mildly pathogenic on Decoppi Marone. Infection of chestnut floral and vegetative tissues was investigated during the chestnut phenological stages of flowering (sampled twice over two years), immature nuts and burrs, mature nuts and burrs, and tree dormancy (immature nuts and burrs, mature nuts and burrs, and tree dormancy were sampled once in one year). Gnomoniopsis smithogilvyi was present in all the sampled phenological stages, most frequently from female flowers during the flowering period. In the first year, the fungus infected 82% of female flowers, while in the second year only 10% were infected. Ascospore trapping in a laboratory chamber experiment confirmed ascopores are released in to the air from infected burrs. Ascospore trapping in an Australian chestnut orchard during the flowering period also showed ascospores are released in to the air, with peak trapping times at sunset and the hours following sunset (8-11 pm), and the hours following sunrise (7-9 am). These experiments support the hypothesis that ascospores of G. smithogilvyi infect chestnut trees, particularly the flowers. The fungus then exists as a latent pathogen in reproductive and vegetative tissues, leading to the development of the disease during nut maturity.

Carbon fractions as indicators of organic matter dynamics in chestnut orchards under different soil management practices

Several studies have emphasized the negative impact of the conventional soil management (CT) system on productivity and sustainability of chestnut orchards (Castanea sativa Mill.) when compared to no-tillage with grass cover (NT). However, scarce information is available regarding the effects of these soil management systems on soil organic matter (SOM) dynamics and soil quality. SOM or soil organic carbon is a key component of soil quality and has different fractions with different lability, namely, organic C (POC), active C (AC) and hot-water extractable carbon (HWC). These are considered as indicators of changes in management-induced soil quality. Thus, a study was carried out to evaluate the effects of NT and CT systems applied in the chestnut orchards on: (i) total amount of soil organic C (TOC), including C from both organic and mineral layers; (ii) soil organic C concentration of mineral horizons (OC); (iii) labile soil organic fractions (POC, AC, HWC); (iv) and soil mineral-associated C. The study was developed in two 30-year old chestnut orchards located in Northeast Portugal, that were kept under different soil management systems (NT or CT) during the preceding 17 years. Soil samples were taken at 0–10 and 10–20 cm soil depth. No significant differences in OC concentration were observed between NT and CT, while TOC was significantly higher in NT than in CT (22.54 and 12.17 Mg/ha or 34.16 and 22.90 Mg/ha, considering the organic layer plus mineral layers at 0–10 and 0–20 cm depth (set of two depths). The NT practice led to significantly higher concentration of labile C fractions (POC, AC and HWC) than CT at 0–10 cm soil depth. These results indicate that measurement of labile soil organic C fractions, such as POC, AC and HWC, may provide a sensitive and consistent indication of changes in soil C and SOM dynamics in response to soil management practices. Overall, NT seems to ensure better soil quality than CT in chestnut orchards under Mediterranean climate conditions.

Fungal community in chestnut orchards with different Hypholoma fasciculare aboveground abundance: potential implications for sustainable production

European chestnut (Castanea sativa Mill.) trees have a significant impact in the Portuguese economy, due to the production of chestnuts and wood, and other related activities, such as mushroom collection and hunt. Hypholoma fasciculare (Huds.) is a saprophytic fungus widely distributed in Tras-os-Montes (northeast of Portugal) chestnut groves that displays an in vitro strong antagonistic activity against ectomycorrhizal (EMC) fungi. In this study, the above- and belowground fungal diversity was evaluated in three chestnut orchards, containing distinct H. fasciculare sporocarps abundances in an attempt to better understand the potential of this fungus to attain an improved chestnut tree sustainable productivity. Aboveground analysis was performed based on macrofungi collection during fruiting seasons (spring and autumn) of two consecutive years. Belowground evaluation was based on the metabarcoding of chestnut orchards soil DNA, using the fungal barcode ITS1 and a high-throughput sequencing (454-sequencing) approach. Although all collected fruitbodies were identified as being produced by Basidiomycota fungi, a more diversified fungal community was revealed by the belowground approach. Both approaches have revealed a rich and abundant ECM community in all chestnut orchards. The correlation between the abundance of H. fasciculare fruitbodies and specific fungal guilds fruitbodies/reads suggests that this fungus may affect soil fungal community, mainly ECM and phytoparasites, as well as species composition of fungal communities. Although not conclusive, the results suggest that H. fasciculare presence could be critical for sustainable chestnut ecosystems.

Monitorizar para regar: o caso do castanheiro (Castanea sativa)

It is assumed that chestnut tree benefits from irrigation but it should be managed conscientiously. This article aims to evaluate the relationship between different soil-plant-atmosphere intervenient to guideline de chestnut producer to the best commitment for water management in the chestnut. In 2015, in a chestnut orchard of Judia variety located in Braganca, it was compared watered and no watered trees. It was measured stem water potential, soil moisture and meteorological parameters. Throughout the growing season the stem water potential dropped from -0.6MPa to -1.6MPa, but in watered trees it was kept near -1.2MPa. Soil moisture at 30cm in watered trees varied between 15 and 22% and it was below 13% in non watered trees. The stem water potential is well correlated with soil moisture, but it is floatable with environmental conditions. The yield was 20% higher in watered trees even with deficit irrigation. The producer benefits from the use of equipment that allows automatic and continuous records without destructive methods.

Genetic monitoring of traditional chestnut orchards reveals a complex genetic structure

This study presents the results of a systematic genetic analysis between wild and cultivated chestnuts in an orchard in southern Spain, highlighting a complex structure and considerable genetic diversity and opening the possibility to generalize this approach to other Mediterranean orchards. Tree genetic monitoring offers a good opportunity to evaluate populations and preserve their long-term adaptive evolutionary potential. Chestnut is a multipurpose species of high economic importance in the Mediterranean basin and considered an example of integration between natural and man-driven distribution of diversity under changing environmental and historical conditions. Due to its multipurpose characteristics, man influenced its populations (grafting/sexual propagation) and a complex genetic structure is expected. We monitored the trees of a chestnut orchard for studying the genetic diversity and relationship in grafts and rootstocks and detecting possible response in its adaptive potential. For this, morphological traits and genomic and genic microsatellite markers were used. Chestnut trees showed considerable genetic structure, with high level of clonality in the varieties and genetic diversity in rootstocks. The similarity analysis revealed a different clustering pattern for varieties, detecting higher variability for genomic microsatellite markers. Rootstocks harboured a high level of diversity, not previously described, and not contained in the genetic information from populations and varieties from the same region. Results contribute to understanding the human role in the management of chestnut and demonstrate that rootstocks constitute an unexploited reservoir of variation valuable for conservation strategies against stress factors and future and unpredictable environmental changes.

Genetic diversity of the sweet chestnut (Castanea sativa Mill.) in Central Europe and the western part of the Balkan Peninsula and evidence of marron genotype introgression into wild populations

The sweet chestnut (Castanea sativa Mill.) is a widely spread and important multipurpose tree species in the Mediterranean area, which has played an important role in human history. Natural events, such as glaciations, and human influence played significant roles in the distribution and genetic makeup of the sweet chestnut. In order to better understand how natural and human-mediated past events affected the current genetic diversity and structure of the sweet chestnut, we analysed populations from Central Europe and the western part of the Balkan Peninsula, utilizing ten polymorphic nuclear microsatellite markers. The study revealed the existence of three genetically and, to a large extent, geographically distinct and well-defined groups of sweet chestnut populations. Two not entirely separated groups of populations were detected in the northern part of the studied area and one in the southern. Our results indicate that the genetic structure of sweet chestnut populations in Central Europe and the western part of the Balkan Peninsula is the result of both natural colonization events and significant and lengthy human impact. Furthermore, it has been proven that the gene flow between cultivated/grafted trees’ and wild chestnut stands can influence their genetic structure. However, our results reveal that cultivated-to-wild introgression in the sweet chestnut is dependent on the close proximity of chestnut orchards and naturally occurring populations.

The Research Status and Future Development of a New Chestnut Cultivar “Huaqiao 2”

“Huaqiao 2” is a new chestnut (Castanea mollissima) cultivar developed from seeding tree by Xiangtan Research Institute of Forestry Sciences. It comes into blossom 2-3 years after planting. It has early maturity, good quality and glossy surface. The average mass of fruit is 16.2 g. The yield is 6900 kg·hm﹣2 (yield of test tree), with high and stable yield, and suitable for planting in the neutral to acidic gravel soil. Xiangtan Research Institute of Forestry Sciences has built some successful “Huaqiao 2” chestnut orchards.

Wood biomass recovery from chestnut orchards: results from a case study

Sweet chestnut has been for many centuries essential to human diet in large areas of Southern Europe. Its cultivation was abandoned in the last century, but is at present under restoration for socioeconomic reasons, representing also an opportunity for allocating woody residues to the energy sector. A little is known from the literature about sweet chestnut pruning, and the aim of the study was to assess the biomass yield and quality, the productivity and costs of the system as well as its energetic balance between inputs and outputs. The yield of recovered wood material amounted to between 22.3 tonnes of dry matter per hectare (tdw ha−1) and 33.3 tdw ha−1. Time consumption for pruning has been related to trees’ DBH, so detecting a linear relationship, although weak, between tree size and the time spent for maintenance. Productivity expressed as tdw per hour varied according to the site and the operating systems adopted accordingly. Costs for the whole chain, excluding transport to the plant facility amounted to 113 or to 430 € t dw −1 depending on the terrain relief and the presence of an underbrush to be cleaned. Wood chips distribution in size classes provided a material unsuitable for non-industrial due to the percentage of oversize particles, probably due to the high presence of twigs. The energy ratio resulted of 30:1 and 21:1 for the two sites. Transportation had the main impact in terms of energy, followed by extraction and chipping phases.

A Study on the Xenia Effect in Castanea henryi

The xenia effect results in pollen affecting the setting rate and the appearance and quality of fruits. To further understand this phenomenon, we investigated the xenia effect in Castanea henryi using the cultivars ‘Huali 1’, ‘Huali 2’, ‘Huali 3’, and ‘Huangzhen’ as materials. Twenty combinations of self-, cross-, and natural pollination were undertaken in a chestnut orchard in Chenzhou City, Hunan Province, China. Significant differences were observed among the pollination combinations in terms of the time of fruit ripening, rate of fruit setting, size of the barbed shell and nut, and content of soluble sugars, fats, proteins, amylose, and vitamin C. No significant differences were observed with regard to nut rate, content of total starch, and moisture content. The fruit quality of the 20 pollination combinations was evaluated using a subordinate function method, and showed that Huali 2 × Huali 3 was the best combination, and Huangzhen × Huangzhen was the most ineffective combination. Therefore, we recommend the combination of Huali 2 × Huali 3 for the future production of C. henryi.

Insect Pests Fauna and the Natural Enemy Insects at Eco-friendly and Conventional Chestnut Orchards

Insect Pests Fauna and the Natural Enemy Insects at Eco-friendly and Conventional Chestnut Orchards

Soil DNA pyrosequencing and fruitbody surveys reveal contrasting diversity for various fungal ecological guilds in chestnut orchards.

Fungal diversity in Mediterranean forest soils is poorly documented, particularly when considering saprobic and pathogenic organisms. Next-generation sequencing (NGS) methods applied to soil fungi provide the opportunity to unveil the most inconspicuous functional guilds (e.g. saprobes) and life forms (e.g. Corticiaceae) of this tremendous diversity. We used fruitbody surveys over 2 years and soil 454 metabarcoding in Castanea sativa orchards to evaluate respectively the reproductive (fruitbodies) and vegetative (mycelia) parts of fungal communities in three 100-year-old stands. Analysis of 839 fruitbodies and 210 291 ITS1 reads revealed high fungal diversity, mainly shown by belowground analysis, with high (dominant) abundance of mycorrhizal fruitbodies and reads. Both methods displayed contrasted composition and structure of fungal communities, with Basidio- and Ascomycetes dominating above- and belowground, respectively. For the two dominant fungal guilds (i.e. ectomycorrhizal and saprobic), diversity above- and belowground overlapped weakly. This study is the first assessment of the complementarity of fruitbody surveys and NGS for analysing fungal diversity in Mediterranean ecosystems and shows that belowground methods still need to be completed by fruiting diversity to provide a comprehensive overview of the different fungal guilds. The results shed light on chestnut soil biodiversity and question the spatial distribution and synergies among fungal guilds.

Loss of labile organic carbon from subsoil due to land-use changes in subtropical China

Topsoil carbon (C) stocks are known to decrease as a consequence of the conversion of natural ecosystems to plantations or croplands; however, the effect of land use change on subsoil C remains unknown. Here, we hypothesized that the effect of land use change on labile subsoil organic C may be even stronger than for topsoil due to upward concentration of plantations and crops root systems. We evaluated soil labile organic C fractions, including particulate organic carbon (POC) and its components [coarse POC and fine POC], light fraction organic carbon (LFOC), readily oxidizable organic carbon, dissolved organic carbon (DOC) and microbial biomass down to 100 cm soil depth from four typical land use systems in subtropical China. Decrease in fine root biomass was more pronounced below 20 cm than in the overlying topsoil (70% vs. 56% for plantation and 62% vs. 37% for orchard. respectively) driving a reduction in subsoil labile organic C stocks. Land use changes from natural forest to Chinese fir plantation, Chinese chestnut orchard, or sloping tillage reduced soil organic C stocks and that of its labile fractions both in top and subsoil (20–100 cm). POC reduction was mainly driven by a decrease in fine POC in topsoil, while DOC was mainly reduced in subsoil. Fine POC, LFOC and microbial biomass can be useful early indicators of changes in topsoil organic C. In contrast, LFOC and DOC are useful indicators for subsoil. Reduced proportions of fine POC, LFOC, DOC and microbial biomass to soil organic C reflected the decline in soil organic C quality caused by land use changes. We conclude that land use changes decrease C sequestration both in topsoil and subsoil, which is initially indicated by the labile soil organic C fractions.

Establishment and dissemination of hypovirulent strains of Cryphonectria parasitica in Greece

SummaryChestnut blight caused by Cryphonectria parasitica has been one of the major reasons for the decline of chestnut cultivation in Greece over the last 50 years. A previous detailed study of the vc types of the fungus has revealed only four vc types in the entire country, those of EU‐1, EU‐2 and EU‐10 with the dominant being EU‐12 counting for 88% of the isolates. As the loss in orchard trees reached in some chestnut producing prefectures over 35% of the trees, the decision was taken to apply biological control on a nationwide scale. The project was implemented in 17 prefectures during the period 2007–2009. Hypovirulent (hv) strains of C. parasitica which were infected by the CHV‐1 subtype I (Italian subtype) viruses which occur naturally in Greece were used. The necessary hypovirulent inoculum was prepared at the Forest Research Institute during the period 2007–2009 on a large scale, however, with laboratory care. Three million inoculations were made around accessible developing cankers over three consecutive years by trained personnel. An extensive evaluation conducted in 2011 in the 12 of the 17 treated prefectures, where no natural hypovirulence had been found before, demonstrated not only the successful establishment of hypovirulence but also profound dissemination and healing of non‐inoculated cankers. The extent of dissemination varied significantly among sampling plots and among prefectures. The conclusion is drawn that CHV‐1 subtype I has successfully established and spread into chestnut orchards and coppice forests resulting in a gradual decline of chestnut blight.

Natural occurrence of Fusarium proliferatum on chestnut in Italy and its potential entomopathogenicity against the Asian chestnut gall wasp Dryocosmus kuriphilus

The Asian chestnut gall wasp Dryocosmus kuriphilus (DK) is one of the most important pests of chestnut trees worldwide, and sustainable control measures are urgently required for its control. In this study, the recurring mycoflora associated with DK galls in some Italian chestnut orchards was identified, and two Fusarium proliferatum strains (I3 and I4) were tested for their entomopathogenicity toward DK and their pathogenicity to chestnut in order to evaluate their potential as biocontrol agents. The two F. proliferatum strains, both isolated from the inside of DK galls and often covering dead bodies of larvae, pupae, and adults, caused a natural insect infection of about 4 % and resulted to be non-pathogenic to chestnut plants, while they induced 33 and 97 % of larvae mortality when applied in laboratory experiments to intact DK fresh or sectioned galls, respectively. Both strains infected maize seedlings, used as non-target hosts, and produced fumonisins in vitro. The efficacy in controlling DK in the galls, the absence of pathogenicity to chestnut, and the lower mycotoxin production indicated strain I3 as a promising biocontrol agent of the considered pest.

First Report of Chestnut Blight Caused by Cryphonectria parasitica in a Chestnut Orchard in Andalusia (Southern Spain)

In Europe, chestnut blight caused by Cryphonectria parasitica (Murrill) Barr was first seen in Italy in 1938 (1). In Spain, the disease was first detected in Basque country in 1947 and later in other areas of northern Spain: Galicia, León, Navarra, and Catalonia, and in Trás-os-Montes in Portugal (2). In November 2012, in an orchard (2 ha) in Almonaster la Real (Huelva, Spain), approximately 20 cankered Castanea sativa (sweet chestnut) trees cv. Vazqueño, 40 to 50 years old, were observed. The trees were grafted 2 years before. In May and June 2013, six new disease focuses were detected near the first one. Five focuses were located in the same village and the other in Jabugo (a neighboring village). Diseased trees exhibited sunken cankers, cracked bark with mycelial fan spreads under the bark, and in some cases, orange fungal sporulation was visible on the bark. Samples were collected from two affected trees and symptom-bearing bark pieces were then placed in moist chambers at 20°C for up to 8 days to induce fungal sporulation. Cultures were made from spore masses extruding from the cankered bark and from the edge of necrotic lesions visible in the phloem of cankered bark tissue onto potato dextrose agar (PDA). Monoconidial fungal isolates were obtained from both trees. The morphological structure of two isolated fungi was identical to that described as C. parasitica (3). Species identity was confirmed by analysis of nucleotide sequences of the internal transcribed spacer (ITS) rDNA, using ITS1-ITS4 (4) as primer pairs, respectively. BLAST searches showed a high similarity between collected isolates' DNA sequences and C. parasitica sequences found on GenBank (96% coverage, 99% identity). Our isolates have been included in GenBank as KF220298 and KF220299. The pathogenicity assay of these two isolates was conducted using two cultivars of sweet chestnut (seedlings from Huelva and Granada nurseries). Isolate pathogenicity was tested on 3-year-old chestnut seedlings in a growth chamber at 25°C (day) and 20°C (night) with a 14-h photoperiod. The isolates were cultured on PDA at 25°C for 7 days. Stems were wounded at 10 cm height with a drill. Each isolate was inoculated to 25 replicates per cultivar by placing a mycelia agar plug (4 to 5 mm diameter) in the hole and wrapping the stem with Parafilm. Plants treated identically with sterile agar plugs were used as controls. Plants were then maintained at 100% relative humidity for 2 h. Both isolates induced diseases symptoms and death of seedlings of both cultivars at a mean time of 37.5 days after inoculation. No significant differences between isolates or between cultivars were detected. Twenty control plants similarly treated with sterile PDA discs did not display symptoms. C. parasitica was re-isolated from lesions, confirming Koch's postulates. Andalusia has 14,000 ha of chestnut crops with high commercial value due to their precocity. Dispersion of chestnut blight in this zone can reduce crop productivity. To our knowledge, this is the first report of C. parasitica causing chestnut blight in Andalusia (southern Spain), one of the few areas left in southwestern Europe free of chestnut blight.

A TREE CROP ARCHETYPE

Chestnut trees come very close to representing the archetypal tree crop. They are very long lived; most species of Castanea form very large trees. Examples of Castanea sativa in Italy known to be more than one thousand years old provide annual harvests of delicious, nutritious, easily harvested, easily stored food. Because a mature chestnut orchard resembles a temperate hardwood forest in both structure and function, it provides significant ecological benefits with consequences far beyond merely producing a fruit. The tree offers habitat to myriad animal species and acts as the keystone in its community. It anchors the soils to steep slopes that otherwise would be almost completely unsuitable for any other form of agriculture. The chestnut grove moderates local climate by shading the understory and by transpiring water into the atmosphere. It requires minimal inputs of fertilizers and labor to maintain productivity. The chestnut tree serves as host for symbiotic relationships with fungi, including the choice edible chanterelle and porcini mushrooms whose niches are those of the soil’s great decomposers and recyclers, mobilizing deep soil nutrients and minerals into the humus layers. Agriculture leads to environmental degradation when it depends on the plow to plant annual crops because the plow destroys soil-building processes and causes erosion and the loss of biodiversity. Cropping systems based on perennial plants may mitigate some of the negative ecological impacts of agriculture because in perennial agro-ecosystems, soil-building processes can flourish. Woody plants, especially very long-lived ones like chestnut trees, can be cultivated using methods that mimic natural ecosystems in their stability, productivity and complexity. A grove of ancient chestnut trees resembles an old-growth forest in many ways and it provides ecosystem services with benefits extending past the boundaries of the orchard. The landscape value of the chestnut grove is almost unequalled by that of any other forest type, possibly also because the grove is evocative of a simpler, quieter past, when our relationship with nature was based on the regular cycles of sun and moon and season.

Interaction between Torymus sinensis (Hymenoptera: Torymidae) and T. beneficus, Introduced and Indigenous Parasitoids of the Chestnut Gall Wasp Dryocosmus kuriphilus (Hymenoptera: Cynipidae)

Torymus sinensis is a parasitoid wasp that was introduced from China to Japan to control the invasive chestnut gall wasp Dryocosmus kuriphilus. Interaction between T. sinensis and the indigenous parasitoid T. beneficus has been of interest since T. sinensis was first released in chestnut orchards, as hybridization between them might impede the success of biological control by the introduced parasitoid. Such apprehensions disappeared with the drastic decrease in damage caused by D. kuriphilus. However, the emergence of morphologically intermediate individuals between them after the introduction of the parasitoid has triggered renewed interest in hybridization, specifically on the non-target effects of biological control. In this review, the interaction between both species, specifically hybridization, species composition and species displacement, is surveyed. Molecular markers are used, not only because T. sinensis and T. beneficus are similar morphologically, but also because the latter has two emergence strains (early- and late-spring). Surveys show that 1) T. sinensis has displaced both emergence strains of T. beneficus; 2) hybridization between T. sinensis and early-spring T. beneficus occurs at a low frequency (≤ 1%); but that 3), hybrid F 1 s between T. sinensis and late-spring T. beneficus occur at a much higher frequency (≤ 20%). A study of phylogenetic relationships indicates that the late-spring T. beneficus is closer to the different species T. sinensis than the early-spring T. beneficus. This can partly explain why T. sinensis hybridizes more readily with the late-spring T. beneficus than with the early-spring T. beneficus.

中亚热带山区深层土壤有机碳库对土地利用变化的响应

PDF HTML阅读 XML下载 导出引用 引用提醒 中亚热带山区深层土壤有机碳库对土地利用变化的响应 DOI: 10.5846/stxb201310312630 作者: 作者单位: 湖南农业大学资源环境学院,中国科学院亚热带农业生态研究所,湖南农业大学资源环境学院,湖南农业大学资源环境学院,湖南农业大学资源环境学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目(31100381);湖南省自然科学基金项目(13JJ4066);湖南农业大学引进人才项目(11YJ20) Response of deep soil organic carbon storage to land-use changes in subtropical hilly region of China Author: Affiliation: College of Resources Environment,Hunan Agricultural University,Key Laboratory of Agro-Ecological Processes in Subtropical Region,Institute of Subtropical Agriculture,Chinese Academy of Sciences,College of Resources Environment,Hunan Agricultural University,College of Resources Environment,Hunan Agricultural University,College of Resources Environment,Hunan Agricultural University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:通过对中亚热带丘陵山区4种典型的土地利用方式(天然林以及由此转变而来的杉木人工林、板栗园和坡耕地)1 m深土壤剖面碳储量、δ13C值和细根生物量的研究,结果表明:土地利用变化7a后,土壤剖面(1 m)有机碳储量与天然林相比降低了26%-36%,且40 cm以下深层矿质土壤碳储量下降了19%-45%。1 m深土壤δ13C平均则升高1‰-3‰,说明植物群落的光合类型发生了变化,C4植物种对土壤有机碳的贡献增加。天然林转变后,严重的水土流失、人为扰动和植物物种组成的变化,诱发深层土壤碳输入减少以及碳流失和矿化损失增加,是导致深层土壤碳储量大幅下降的主因。土地利用变化后,60 cm深细根生物量锐减50%-99%,且细根主要集中于表土层。这主要与土壤理化性状劣化、资源有效性大幅降低及天然林转变后植被幼龄化有关,反映土地利用变化后土地生产力大幅退化。上述研究结果揭示在中亚热带山地开发、利用和土地转变过程中,加强天然林保育和中幼林抚育,创新减轻坡土扰动的农艺措施和加强陡坡地退耕,严控水土流失,科学施肥补充损失的土壤有机质和养分,对于维系山地土壤生产力和山区可持续经营具有长远意义。 Abstract:Soil is a major terrestrial carbon pool and most of the soil carbon is stored in the deep soil layers, which contributes to more than half of the total soil carbon storage. Compared with the topsoil carbon storage, carbon reserved in deep soil depth may respond differently to environmental change and land management practices. Thus, it needs to consider the deep soil organic carbon storage in the global carbon cycles. In the subtropical hilly region of China, some soils are deeply weathered and have highly developed profile. These deeply weathered soils may very sensitive to land use changes. Until recently, the dynamics of carbon storage in deep soil, especially its response to land use conversion was largely ignored in the subtropical hilly region of China. In the present study, soil carbon storage at 1 m depth, soil δ13C value and fine root biomass were evaluated within a representative land-use sequence in mid-subtropical China. The purpose was to evaluate the effect of land use change on the storage and resource of deep soil carbon storage. The land-use tpes included natural forest (control treatment), Chinese fir plantation, Chinese chestnut orchard and sloping tillage. Results showed that soil carbon storage at 1 m depth was 112.03, 82.40, 78.83 and 72.29 t/hm2 for natural forest, Chinese fir plantation, Chinese chestnut orchard and sloping tillage, respectively. After the natural forest was converted to other land uses for 7 years, soil carbon storage was decreased by 26%-36% at 1 m depth. Not only the topsoil (27%-34%), but also the deep soil (below 40 cm) showed significant decrease of carbon storage by 19%-45%. The conversion from natural forest to sloping tillage exerted a larger decrease of soil carbon storage than to Chinese fir plantation and Chinese chestnut orchard. In contrast to the decrease of soil carbon storage with land use changes, the average δ13C value at 1 m depth was increased by 1‰-3‰, indicating an increasing contribution of carbon input from C4 plant species to soil. After the land-use conversion, severe human disturbance caused serious topsoil erosion and water loss and shift of plant species composition. This led to the reduction of carbon input to soil and the increment of carbon loss in deep soil, and further to a substantial decrease of deep soil carbon storage. In addition, the fine root biomass at 60 cm depth was reduced by 50%-99% and tended to concentrate in surface soil layer after the land-use changes. It was primarily due to the deterioration of soil physicochemical regime, decrease of available soil resource and juvenile vegetation after the land use conversion. The decrease of fine root biomass also reflected a substantial degradation of land productivity. In conclusion, our study raises concerns about (i) the importance of natural forest preservation and young forest nurture; (ii) innovation of agronomic soil practices as regarding to topsoil disturbance reduction and continue implementation of "grain for green" policy in sloping tillage; and (iii) controlling of topsoil erosion and water loss and supplement of chemical fertilizer after the land-use conversion in hilly region of middle subtropical China. 参考文献 相似文献 引证文献