Method for screening broad-leaved tree species suitable for mixed planting with Chinese fir and application thereof

Abstract

The application provides a method for screening broad-leaved tree species suitable for mixed planting with Chinese fir, and belongs to the technical field of forest management. The Chinese fir and the broad-leaved tree are mixed for afforestation, and a pure Chinese fir forest is simultaneously built as a yield measurement control. By comparing the accumulations of the Chinese fir / broad-leaved tree mixed forest and the pure Chinese fir forest, the growth amounts of the single-tree volume of the Chinese fir in the Chinese fir / broad-leaved tree mixed forest and the single-tree volume of the pure Chinese fir forest, and the yield rates of the large and medium-sized timber species of the Chinese fir in the Chinese fir / broad-leaved tree mixed forest and the pure Chinese fir forest, the broad-leaved tree species suitable for mixed planting with the Chinese fir are finally screened out. The Chinese fir is mixed with the broad-leaved tree species screened out by the method, so that the timber yield and the yield rate of the large and medium-sized timber species of the Chinese fir plantation can be improved, the stand growth is excellent, the production demand for the Chinese fir under the existing condition can be effectively met, the economic benefit and the ecological benefit are high, and the method has a wide application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of forest management, and in particular to a method for screening broadleaf tree species suitable for mixed planting with Chinese fir and application thereof. BACKGROUND

[0002] Chinese fir is the largest wood yield and the highest diameter timber yield of coniferous wood species in southern China. At present, intensive management mode of multiple afforestation in the same afforestation land is generally adopted for Chinese fir. Long-term forestry production practice shows that due to the biological characteristics of Chinese fir and the influence of traditional cultivation methods, continuous planting of Chinese fir pure forest causes land degradation, stand habitat deterioration and other problems. The wood yield and large and medium-sized timber yield of Chinese fir plantations have decreased to varying degrees, which not only reduces the operating income of wood production units, but also exacerbates the wood supply and demand contradiction. Therefore, how to change the traditional management mode of Chinese fir, improve the wood yield and quality of Chinese fir plantations, and realize the sustainable management of Chinese fir plantations has become a technical problem that forestry workers urgently need to solve.

[0003] A large number of studies have shown that establishing Chinese fir / broadleaf mixed forest is a better solution to the problems of wood yield reduction and low quality caused by continuous planting of Chinese fir. Therefore, since the 1980s, many forestry workers have established a large number of different types of Chinese fir / broadleaf mixed forests from the composition of mixed tree species, the proportion of mixed number of trees and the mixed method. However, due to the traditional mixed mode ignoring the differences in ecological characteristics between tree species and many problems in afforestation density and forest management, the mixed effect of Chinese fir / broadleaf mixed forest is not good, and the expected purpose cannot be achieved.

[0004] Selecting broadleaf tree species with mutual benefit or complementary effect and mixing with Chinese fir to establish Chinese fir / broadleaf tree mixed forest, improving the habitat conditions of Chinese fir or reducing the competition intensity of adjacent trees in Chinese fir pure forest through broadleaf trees, and then improving the wood yield and large and medium-sized timber yield ratio of Chinese fir, has become one of the important management measures to solve the problem of wood yield and quality reduction of Chinese fir. However, there is no method for screening broadleaf tree species suitable for mixed planting with Chinese fir. SUMMARY

[0005] The present application provides a method for screening broadleaf tree species suitable for mixed planting with Chinese fir and application thereof, which solves the problem of reduced yield and timber yield of Chinese fir pure forest in the prior art.

[0006] In order to achieve the above-mentioned application purpose, the present application provides the following technical scheme:

[0007] The present application provides a method for screening broadleaf tree species suitable for mixed planting with Chinese fir, comprising the following steps:

[0008] S1. Selecting the afforested land with the position index of Cunninghamia lanceolata of 14 or above;

[0009] S2. Cunninghamia lanceolata and broad-leaved trees are mixed afforested, and Cunninghamia lanceolata pure forest is built as a yield control;

[0010] S3. During the growth of Cunninghamia lanceolata / broad-leaved tree mixed forest, if the crown of broad-leaved tree shields the adjacent Cunninghamia lanceolata crown height more than 1 / 3, Cunninghamia lanceolata and broad-leaved tree are thinned at the same time;

[0011] S4. The rotation period is determined according to the position index of Cunninghamia lanceolata of the afforested land;

[0012] S5. After the Cunninghamia lanceolata / broad-leaved tree mixed forest is harvested at the rotation period, the volume of Cunninghamia lanceolata / broad-leaved tree mixed forest and Cunninghamia lanceolata pure forest is compared;

[0013] If the volume of Cunninghamia lanceolata / broad-leaved tree mixed forest is less than that of Cunninghamia lanceolata pure forest, the broad-leaved tree species is excluded from mixed afforestation with Cunninghamia lanceolata; if the volume of Cunninghamia lanceolata / broad-leaved tree mixed forest is greater than that of Cunninghamia lanceolata pure forest, the following comparison is continued:

[0014] (1) The volume increment of Cunninghamia lanceolata single tree in Cunninghamia lanceolata / broad-leaved tree mixed forest is compared with that of Cunninghamia lanceolata pure forest;

[0015] (2) The yield rate of Cunninghamia lanceolata size material in Cunninghamia lanceolata / broad-leaved tree mixed forest is compared with that of Cunninghamia lanceolata pure forest;

[0016] If the volume increment of Cunninghamia lanceolata single tree in Cunninghamia lanceolata / broad-leaved tree mixed forest is greater than that of Cunninghamia lanceolata pure forest, and the yield rate of Cunninghamia lanceolata size material in Cunninghamia lanceolata / broad-leaved tree mixed forest is increased by 18% and 30% or more compared with that of Cunninghamia lanceolata pure forest, the broad-leaved tree species is determined as a broad-leaved tree species suitable for mixed afforestation with Cunninghamia lanceolata.

[0017] Preferably, the afforested land of S1 is a habitat that can meet the life history of local broad-leaved tree species.

[0018] Preferably, the Cunninghamia lanceolata and broad-leaved tree mixed afforestation is in the form of row mixed afforestation, and the row spacing of Cunninghamia lanceolata and broad-leaved tree is 2.0-2.5 m, and the intra-row spacing is 1.5-2.0 m.

[0019] Preferably, during thinning, the adjacent two rows of Cunninghamia lanceolata and broad-leaved tree are taken as a thinning unit, and through comparison between rows and between trees, small trees are thinned and large trees are left, inferior trees are thinned and superior trees are left, and uniformity is considered, and the tree number retention density after thinning is 45%-50% of the initial afforestation density.

[0020] Preferably, if the position index of Cunninghamia lanceolata of the afforested land is 18 or above, the rotation period is 15-20 years; if the position index of Cunninghamia lanceolata of the afforested land is 16, the rotation period is 20-25 years; if the position index of Cunninghamia lanceolata of the afforested land is 14, the rotation period is 25-30 years.

[0021] Preferably, the large-diameter timber is Chinese fir with a breast diameter of greater than or equal to 22 cm, the medium-diameter timber is Chinese fir with a breast diameter of 16 cm to less than 20 cm, and the small-diameter timber is Chinese fir with a breast diameter of 8 cm to less than 14 cm.

[0022] The application further provides use of the method in Chinese fir planting.

[0023] The application further provides use of the method in improving wood yield of Chinese fir plantations.

[0024] The application further provides use of the method in improving yield of large-diameter timber of Chinese fir plantations.

[0025] By using the above technical scheme, the application has the following beneficial effects: the Chinese fir and broad-leaved trees are mixed for afforestation, and a pure Chinese fir forest is simultaneously established as a yield comparison control. By comparing the accumulations of the Chinese fir / broad-leaved tree mixed forest and the pure Chinese fir forest, the growth amounts of the single-tree volume of the Chinese fir in the Chinese fir / broad-leaved tree mixed forest and the pure Chinese fir forest, and the yield of large-diameter timber of the Chinese fir in the Chinese fir / broad-leaved tree mixed forest and the pure Chinese fir forest, the broad-leaved tree species suitable for mixing with the Chinese fir are finally screened out. Mixing the Chinese fir with the broad-leaved tree species screened out by the method can improve the wood yield and the yield of large-diameter timber of the Chinese fir plantation, and the stand growth is excellent, which can effectively meet the production demand for the Chinese fir under the current situation, and has high economic and ecological benefits, and has a wide application prospect. DETAILED DESCRIPTION

[0026] The application provides a method for screening broad-leaved tree species suitable for mixing with Chinese fir, comprising the following steps:

[0027] S1. selecting afforestation land with a site index of 14 or above and suitable for growth of Chinese fir;

[0028] S2. mixing Chinese fir and broad-leaved trees for afforestation, and simultaneously establishing a pure Chinese fir forest as a yield comparison control;

[0029] S3. during the growth of the Chinese fir / broad-leaved tree mixed forest, if the broad-leaved tree crown shields more than 1 / 3 of the height of the adjacent Chinese fir crown, then the Chinese fir and the broad-leaved tree are thinned;

[0030] S4. determining the rotation period according to the site index of the Chinese fir in the afforestation land;

[0031] S5. after harvesting at the rotation period, comparing the accumulations of the Chinese fir / broad-leaved tree mixed forest and the pure Chinese fir forest;

[0032] If the accumulation of the Chinese fir / broad-leaved tree mixed forest is less than that of the pure Chinese fir forest, then the broad-leaved tree species is excluded from mixing with the Chinese fir for afforestation. If the accumulation of the Chinese fir / broad-leaved tree mixed forest is greater than that of the pure Chinese fir forest, then the following comparison is continued:

[0033] (1)Compare the volume increment of Cunninghamia lanceolata single tree in Cunninghamia lanceolata / broad-leaved tree mixed forest with that in Cunninghamia lanceolata pure forest;

[0034] (2)Compare the yield of standard timber of Cunninghamia lanceolata in Cunninghamia lanceolata / broad-leaved tree mixed forest with that in Cunninghamia lanceolata pure forest;

[0035] If the volume increment of Cunninghamia lanceolata single tree in Cunninghamia lanceolata / broad-leaved tree mixed forest is greater than that in Cunninghamia lanceolata pure forest, and the yield of standard timber of Cunninghamia lanceolata in Cunninghamia lanceolata / broad-leaved tree mixed forest is increased by more than 18% and 30% respectively compared with that in Cunninghamia lanceolata pure forest, then the broad-leaved tree species is determined to be suitable for mixed forest with Cunninghamia lanceolata.

[0036] The application firstly selects the afforestation land for Cunninghamia lanceolata / broad-leaved tree mixed forest, which needs to meet the following conditions at the same time: (1) the afforestation land with Cunninghamia lanceolata position index of 14 or more; (2) the habitat that can meet the life history of local broad-leaved tree species; (3) the afforestation land is not a forested afforestation land. Cunninghamia lanceolata and broad-leaved trees are planted in a row mixed afforestation way, and the row spacing of Cunninghamia lanceolata and broad-leaved trees is 2.0-2.5 m, further preferably 2.1-2.4 m, and more preferably 2.2 m; the intra-row spacing is 1.5-2.0 m, further preferably 1.7-1.9 m, and more preferably 1.8 m. During the growth of Cunninghamia lanceolata / broad-leaved tree mixed forest, if the broad-leaved tree canopy shields more than 1 / 3 of the height of the adjacent Cunninghamia lanceolata canopy, thinning is performed on Cunninghamia lanceolata and broad-leaved trees. When thinning, the adjacent two rows of Cunninghamia lanceolata and broad-leaved trees are taken as a thinning unit, and through comparison between rows and between trees, small trees are thinned and large trees are reserved, inferior trees are thinned and superior trees are reserved, and uniformity is considered. After thinning, the reserved density of tree number is 45%-50% of the initial afforestation density, further preferably 46%-49%, and more preferably 47%. Cunningham lanceolata position index of the afforestation land is used as the criterion for determining the rotation period. For the stand with Cunningham lanceolata position index of 18 or more, the rotation period is 15-20 years, further preferably 16-19 years, and more preferably 18 years; for the stand with Cunningham lanceolata position index of 16, the rotation period is 20-25 years, further preferably 21-24 years, and more preferably 22 years; and for the stand with Cunningham lanceolata position index of 14, the rotation period is 25-30 years, further preferably 26-29 years, and more preferably 28 years. After the rotation, the following indexes are compared:

[0037] 1. Compare the volume increment of Cunninghamia lanceolata single tree in Cunninghamia lanceolata / broad-leaved tree mixed forest with that in Cunninghamia lanceolata pure forest

[0038] The stand volume of Cunninghamia lanceolata / broad-leaved tree mixed forest is the sum of the volume of Cunninghamia lanceolata single tree and the volume of broad-leaved tree single tree in Cunninghamia lanceolata / broad-leaved tree mixed forest; the stand volume of Cunninghamia lanceolata pure forest is the sum of the volume of all Cunninghamia lanceolata single trees in Cunninghamia lanceolata pure forest. The volume of Cunninghamia lanceolata and broad-leaved tree single trees is calculated according to the National Forest Resources Continuous Inventory Technical Regulations (2014).

[0039] If the stand volume of the Chinese fir / broad-leaved tree mixed forest is greater than that of the Chinese fir pure forest, there is a possibility that the Chinese fir and the broad-leaved tree mixed forest can increase the growth of the Chinese fir in the mixed forest, but it cannot be determined that the increase of the stand volume of the Chinese fir / broad-leaved tree mixed forest is caused by ① the increase of the stand volume of both the Chinese fir and the broad-leaved tree; ② the increase of the stand volume of the Chinese fir and the decrease of the stand volume of the broad-leaved tree; or ③ the decrease of the stand volume of the Chinese fir and the increase of the stand volume of the broad-leaved tree. Therefore, it is necessary to further confirm how the interaction between the Chinese fir and the broad-leaved tree affects the growth of the Chinese fir in the mixed forest. Therefore, it is necessary to continue to make the following comparisons:

[0040] (1) Compare the stand volume growth of the Chinese fir in the Chinese fir / broad-leaved tree mixed forest with that of the Chinese fir in the Chinese fir pure forest;

[0041] (2) Compare the yield of the Chinese fir in the Chinese fir / broad-leaved tree mixed forest with that of the Chinese fir in the Chinese fir pure forest;

[0042] 2. Comparison of the stand volume growth of the Chinese fir in the Chinese fir / broad-leaved tree mixed forest with that of the Chinese fir in the Chinese fir pure forest

[0043] The stand volume of the Chinese fir in the Chinese fir / broad-leaved tree mixed forest is the average value of the stand volume of the Chinese fir in the Chinese fir / broad-leaved tree mixed forest, and the stand volume growth is the average value of the stand volume divided by the age of the forest. The stand volume of the Chinese fir in the Chinese fir pure forest is the average value of the stand volume of the Chinese fir in the Chinese fir pure forest, and the stand volume growth is the average value of the stand volume divided by the age of the forest.

[0044] (1) If the stand volume of the Chinese fir / broad-leaved tree mixed forest is greater than that of the Chinese fir pure forest, and the stand volume growth of the Chinese fir in the mixed forest is greater than that of the Chinese fir in the pure forest, it indicates that the broad-leaved tree promotes the growth of the Chinese fir in the Chinese fir / broad-leaved tree mixed forest, or the two have a mutual growth promoting effect, resulting in an increase in the stand volume of the Chinese fir in the Chinese fir / broad-leaved tree mixed forest;

[0045] (2) If the stand volume of the Chinese fir / broad-leaved tree mixed forest is greater than that of the Chinese fir pure forest, but the stand volume growth of the Chinese fir in the mixed forest is less than that of the Chinese fir in the pure forest, it indicates that the broad-leaved tree inhibits the growth of the Chinese fir in the Chinese fir / broad-leaved tree mixed forest, and the increase of the stand volume of the mixed forest is mainly caused by the increase of the stand volume of the broad-leaved tree.

[0046] The stand productivity of the Chinese fir / broad-leaved tree mixed forest is used to evaluate the relationship between the Chinese fir and the broad-leaved tree in the mixed forest.

[0047] The stand productivity of the Chinese fir / broad-leaved tree mixed forest is the actual volume growth of the mixed forest divided by the expected volume growth. When the value is greater than 1, the actual volume growth of the mixed forest is caused by the mutual benefit or complementarity between the Chinese fir and the broad-leaved tree, resulting in an increase in the yield of the Chinese fir; if the value is less than 1, the actual volume growth of the mixed forest is caused by the interspecific competition between the Chinese fir and the broad-leaved tree, resulting in a decrease in the yield of the Chinese fir.

[0048] Further, if the actual volume increment of Cunninghamia lanceolata and broad-leaved trees in the mixed forest is greater than 1, then there is a mutual benefit between Cunninghamia lanceolata and the broad-leaved trees, and the two promote each other to improve the stand volume, and then the broad-leaved tree is the best broad-leaved tree species mixed with Cunninghamia lanceolata; if the actual volume increment of Cunninghamia lanceolata in the mixed forest is greater than 1, and the actual volume increment of the broad-leaved tree is less than 1, then there is a complementary relationship between Cunninghamia lanceolata and the broad-leaved tree, and it can be confirmed that the broad-leaved tree species creates favorable conditions for the growth of Cunninghamia lanceolata, but the growth of itself is inhibited by Cunninghamia lanceolata, and the improvement of the actual volume increment of the mixed forest is caused by the growth of Cunninghamia lanceolata. The tree species that can form a complementary relationship with Cunninghamia lanceolata can also be used as a secondary suitable tree species mixed with Cunninghamia lanceolata.

[0049] By comparing the single-tree volume increment of Cunninghamia lanceolata in Cunninghamia lanceolata / broad-leaved tree mixed forest and Cunninghamia lanceolata pure forest, it can be determined whether the broad-leaved tree species mixed with Cunninghamia lanceolata can promote the volume increment of Cunninghamia lanceolata, but it cannot guarantee whether the yield of the dimension lumber species after processing of the Cunninghamia lanceolata wood is increased accordingly. Only when the yield of the dimension lumber species is increased, can the wood utilization rate be improved. Therefore, it is necessary to compare the yield of the dimension lumber species of Cunninghamia lanceolata in Cunninghamia lanceolata / broad-leaved tree mixed forest and Cunninghamia lanceolata pure forest.

[0050] 3. Comparison of the yield of the dimension lumber species of Cunninghamia lanceolata in Cunninghamia lanceolata / broad-leaved tree mixed forest and the yield of the dimension lumber species of Cunninghamia lanceolata in Cunninghamia lanceolata pure forest

[0051] (1) According to the Cunninghamia lanceolata dimension lumber species standard, the Cunninghamia lanceolata stand is divided into three types of dimension lumber species, i.e. small-diameter lumber [8 cm≤diameter at breast height (DBH) <14 cm], medium-diameter lumber [16 cm≤DBH <20 cm] and large-diameter lumber (DBH≥22 cm);

[0052] (2) According to the Cunninghamia lanceolata volume table, the volumes of the three types of Cunninghamia lanceolata dimension lumber species are calculated respectively;

[0053] (3) The volumes of the small-diameter lumber, the medium-diameter lumber and the large-diameter lumber are divided by the stand volume respectively, and the yield of the dimension lumber species of the small-diameter lumber, the medium-diameter lumber and the large-diameter lumber can be obtained;

[0054] (4) The yields of the dimension lumber species of the large-diameter lumber, the medium-diameter lumber and the small-diameter lumber of Cunninghamia lanceolata in Cunninghamia lanceolata / broad-leaved tree mixed forest and Cunninghamia lanceolata pure forest are compared respectively. If the yields of the dimension lumber species of the large-diameter lumber and the medium-diameter lumber in the Cunninghamia lanceolata / broad-leaved tree mixed forest are increased by more than 18% and 30% respectively, it indicates that the mixed forest indeed promotes the yield of the dimension lumber species of Cunninghamia lanceolata, and improves the wood utilization efficiency of Cunninghamia lanceolata.

[0055] The technical solutions provided by the present application will be described in detail below in combination with the embodiments, but they cannot be understood as limitations to the protection scope of the present application.

[0056] The position index of Chinese fir refers to the average height of dominant Chinese fir trees in a Chinese fir forest at the age of 20 years. When the height of dominant trees is in the interval [13.1, 14.9) m, the position index of the forest land is 14; when the height is in the interval [15.1, 16.9) m, the position index of the forest land is 16; when the height is in the interval [17.1, 18.9) m, the position index of the forest land is 18; and so on.

[0057] If the age of the Chinese fir forest is not 20 years, the position index of Chinese fir is calculated by the method shown in the "Preparation and application of national Chinese fir (seedling forest) position index table" of the Chinese fir cultivation research collaboration group of 14 southern provinces (regions) (1982).

[0058] For afforestation land on which Chinese fir forest has not been planted in the past, but the quality of the afforestation land needs to be evaluated at the time of afforestation, the position index is calculated by the "multiple position index method".

[0059] Example 1

[0060] In the spring of 1999, Chinese fir / broad-leaved tree mixed afforestation was carried out on a Chinese fir clear-cut site in Qingyuan, Zhejiang. The position index of Chinese fir of the afforestation site was 16, and local broad-leaved tree species such as Ziziphus sativa, Schima superba, Melia, Phoebe zheliensis, and Cinnamomum camphora were selected to be mixed with Chinese fir in rows, with a planting density of 2.0 m x 1.5 m. At the same time, Chinese fir pure forest was planted as a yield control.

[0061] In the spring and autumn of 1999 and 2000, under-forest tending was carried out once. Shrubs, herbs, and vines that affect the growth of afforestation seedlings were removed.

[0062] In the spring of 2008, i.e. when the Chinese fir / broad-leaved tree mixed forest was 9 years old, adjacent Chinese fir and broad-leaved trees were taken as a thinning unit, and the growth conditions of Chinese fir and broad-leaved trees in the rows and between the trees were compared for tending and thinning. After thinning, the reserved density of tree number in the mixed forest was about 50% of the afforestation density.

[0063] In the spring of 2024, i.e. when the Chinese fir / broad-leaved tree mixed forest reached the rotation age of 25 years, various growth indicators were measured, and the volume, single-tree volume growth, and size-species out-wood yield of Chinese fir and different tree species pure forest and Chinese fir / broad-leaved tree mixed forest were calculated. At the same time, the relative productivity of Chinese fir / broad-leaved tree mixed forest was calculated using the actual volume growth and the expected volume growth, and the promotion / inhibition effect of the interspecific relationship between Chinese fir and different broad-leaved trees on yield was quantified. The results are shown in Tables 1 and 2.

[0064] Table 1 Comparison of volume, single-tree volume growth, and size-species out-wood yield of Chinese fir and broad-leaved tree pure forest and mixed forest

[0065]

[0066]

[0067] Table 2 Interactions between Cunninghamia lanceolata and broad-leaved species and their effects on yield

[0068]

[0069] As can be seen from Table 1 and Table 2, the stand volume of Cunninghamia lanceolata pure forest is the lowest, the yield of small-diameter timber is more than 70%, the yield of medium-diameter timber is less than 20%, and the yield of large-diameter timber is 0; Cunninghamia lanceolata mixed with Phoebe chekiangensis, Cinnamomum camphora, Ziziphus sativa and Machilus zanthoxyloides will increase the stand volume to different degrees. Cunninghamia lanceolata mixed with Ziziphus sativa and Machilus zanthoxyloides which have competitive relationship, the yield of small-diameter timber is more than 50%, the yield of medium-diameter timber is not more than 25%, and the yield of large-diameter timber is within 9%; Cunninghamia lanceolata mixed with Cinnamomum camphora which has complementary relationship, the yield of small-diameter timber is reduced to 25%, the yield of medium-diameter timber is more than 50%, and the yield of large-diameter timber is increased to more than 18%; Cunninghamia lanceolata mixed with Phoebe chekiangensis which has mutual benefit relationship, the yield of small-diameter timber is reduced to 10%, the yield of medium-diameter timber is close to 60%, and the yield of large-diameter timber is more than 30%. This shows that Cunninghamia lanceolata mixed with broad-leaved species with mutual benefit relationship can significantly increase the yield of stand and the yield of large and medium-diameter timber; Cunninghamia lanceolata mixed with broad-leaved species with complementary relationship is the second, and Cunninghamia lanceolata mixed with broad-leaved species with competitive relationship is the worst.

[0070] In summary, Cunninghamia lanceolata and Ziziphus sativa have competitive relationship, Cunninghamia lanceolata and Machilus zanthoxyloides have competitive relationship, Cunninghamia lanceolata and Cinnamomum camphora have complementary relationship, and Cunninghamia lanceolata and Phoebe chekiangensis have mutual benefit relationship; this shows that Cunninghamia lanceolata mixed with Cinnamomum camphora and Phoebe chekiangensis can increase the timber yield and the yield of large and medium-diameter timber of Cunninghamia lanceolata plantation.

[0071] Example 2

[0072] In spring 2004, Cunninghamia lanceolata / broad-leaved tree mixed forest was planted in broad-leaved tree abandoned land in southern Jiangxi. The Cunninghamia lanceolata site index of the afforestation site was 18, and native broad-leaved tree species Castanopsis hystrix, Dinopanax formosanus, Quercus acutissima and Eucalyptus were selected to be mixed with Cunninghamia lanceolata in row afforestation with a planting density of 2.0 m x 2.0 m. At the same time, Cunninghamia lanceolata pure forest was planted as a yield control.

[0073] In spring and early summer of 2004, 2005 and 2006, the undergrowth vegetation was completely cut, and shrubs, herbs and vines that affected the growth of afforestation seedlings were removed.

[0074] In autumn 2014, when the Cunninghamia lanceolata / broad-leaved tree mixed forest was 8 years old, the adjacent Cunninghamia lanceolata and broad-leaved trees were taken as a thinning unit, and the growth conditions of Cunninghamia lanceolata and broad-leaved trees in rows and between plants were compared for tending and thinning. After thinning, the reserved density of plants in the mixed forest was about 50% of the planting density.

[0075] In the spring of 2024, that is, when the mixed forest of Cunninghamia lanceolata and broad-leaved trees reaches the rotation age of 20 years, various growth indicators are measured, and the accumulations, single-tree volume growth, and size-class timber yield of Cunninghamia lanceolata and different pure forests and mixed forests of Cunninghamia lanceolata and broad-leaved trees are calculated. At the same time, the relative productivity of the mixed forest of Cunninghamia lanceolata and broad-leaved trees is calculated using the actual volume growth and the expected volume growth, and the promotion / inhibition effect of the interspecific relationship between Cunninghamia lanceolata and different broad-leaved trees on the yield is quantified, and the results are shown in Tables 3 and 4.

[0076] Table 3 Comparison of accumulations, single-tree volume growth, and size-class timber yield of Cunninghamia lanceolata and broad-leaved tree pure forests and mixed forests

[0077]

[0078] Table 4 Interspecific interaction between Cunninghamia lanceolata and broad-leaved trees and its effect on yield

[0079]

[0080]

[0081] As shown in Tables 3 and 4, the stand accumulation of the Cunninghamia lanceolata pure forest is the lowest, the small-diameter timber yield rate is more than 70%, the medium-diameter timber yield rate is less than 15%, and the large-diameter timber yield rate is 0; the stand accumulation of the Cunninghamia lanceolata pure forest is far less than that of the mixed forest. In the mixed forest of Cunninghamia lanceolata and broad-leaved trees, the stand accumulation of the mixed forest of Cunninghamia lanceolata and Eucalyptus, which has an interspecific competitive relationship, is the smallest, followed by the mixed forest of Cunninghamia lanceolata and Quercus acutissima, which has an interspecific complementary relationship, and the stand accumulations of the mixed forests of Cunninghamia lanceolata and Castanopsis hystrix and Cunninghamia lanceolata and Machilus thunbergii, which have interspecific mutualistic relationships, are the largest. At the same time, in the mixed forest of Cunninghamia lanceolata and broad-leaved trees with an interspecific mutualistic relationship, the proportion of large-diameter timber yield is more than 23%, the proportion of medium-diameter timber yield is more than 50%, and the proportion of small-diameter timber yield is less than 20%; in the mixed forest of Cunninghamia lanceolata and broad-leaved trees with an interspecific complementary relationship, the proportion of large-diameter timber yield is close to 20%, the proportion of small-diameter timber yield is slightly higher than 45%, and the proportion of small-diameter timber yield is 30%; and in the mixed forest of Cunninghamia lanceolata and broad-leaved trees with an interspecific competitive relationship, the proportion of large-diameter timber yield is only 4%, the proportion of medium-diameter timber yield is less than 45%, and the proportion of small-diameter timber yield is more than 35%.

[0082] In summary, Cunninghamia lanceolata and Eucalyptus have a competitive relationship, Cunninghamia lanceolata and Quercus acutissima have an interspecific complementary relationship, and Cunninghamia lanceolata and Castanopsis hystrix and Cunninghamia lanceolata and Machilus thunbergii have interspecific mutualistic relationships; it is indicated that the mixed forests of Cunninghamia lanceolata and Quercus acutissima, Castanopsis hystrix, and Machilus thunbergii can improve the timber yield and size-class timber yield of Cunninghamia lanceolata plantations.

[0083] As shown in the above examples, the present application provides a method for screening broad-leaved tree species suitable for mixed forest with Cunninghamia lanceolata. The mixed forest of Cunninghamia lanceolata and the broad-leaved tree species screened by the method can improve the timber yield and size-class timber yield of Cunninghamia lanceolata plantations.

[0084] The above merely describes the preferred embodiments of the present application, and it should be pointed out that, for those skilled in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as falling within the protection scope of the present application.

Claims

1. A method for selecting suitable broad-leaved tree species for mixed planting with Chinese fir, characterized in that, Includes the following steps: S1. Select afforestation sites with a Chinese fir status index of 14 or higher; S2. Mixed planting of Chinese fir and broad-leaved trees, while establishing pure Chinese fir forests as a yield control; S3. During the growth of mixed Chinese fir / broadleaf forests, if the canopy of a broadleaf tree shades more than 1 / 3 of the height of the canopy of an adjacent Chinese fir tree, both the Chinese fir and the broadleaf tree shall be thinned out simultaneously. S4. The rotation period is determined based on the cedar status index of the afforestation area; S5. After logging during the rotation period, compare the stock volume of mixed Chinese fir / broadleaf forests and pure Chinese fir forests; If the volume of the mixed forest of Chinese fir / broadleaf trees is less than that of a pure Chinese fir forest, then afforestation of mixed forests of this broadleaf tree species and Chinese fir is excluded; if the volume of the mixed forest of Chinese fir / broadleaf trees is greater than that of a pure Chinese fir forest, the following comparison is continued: (1) Compare the volume of a single Chinese fir tree in a mixed Chinese fir / broadleaf forest with the volume of a single Chinese fir tree in a pure Chinese fir forest; (2) Compare the yield of standard timber species of Chinese fir in mixed Chinese fir / broadleaf forest with that of pure Chinese fir forest; If the volume growth of a single Chinese fir tree in a mixed forest is greater than that of a pure Chinese fir forest, and the timber yield of large-diameter and medium-diameter Chinese fir trees in the mixed Chinese fir / broadleaf forest is increased by more than 18% and 30% respectively compared with the pure Chinese fir forest, then the broadleaf tree species is determined to be a suitable broadleaf tree species for mixed planting with Chinese fir.

2. The method according to claim 1, characterized in that, The afforestation site described in S1 is a habitat that can meet the needs of local native broad-leaved tree species to complete their life cycle.

3. The method according to claim 1, characterized in that, The mixed planting method for Chinese fir and broad-leaved trees is row mixed planting, with a row spacing of 2.0 to 2.5 meters and a plant spacing of 1.5 to 2.0 meters within the row.

4. The method according to claim 1, characterized in that, During thinning, adjacent fir and broad-leaved trees are treated as a single thinning unit. Through comparison between rows and between trees, smaller trees are cut down and larger ones are left, inferior trees are cut down and superior ones are left, and the trees are taken care of evenly. After thinning, the density of trees retained is 45% to 50% of the initial afforestation density.

5. The method according to claim 1, characterized in that, If the status index of Chinese fir in the afforestation area is 18 or above, the rotation period is 15 to 20 years; if the status index of Chinese fir in the afforestation area is 16, the rotation period is 20 to 25 years; if the status index of Chinese fir in the afforestation area is 14, the rotation period is 25 to 30 years.

6. The method according to claim 1, characterized in that, The large-diameter timber is fir with a diameter at breast height (DBH) ≥ 22cm, and the medium-diameter timber is fir with a DBH ≤ 16cm and < 20cm.

7. The application of the method according to any one of claims 1 to 6 in afforestation of Chinese fir.

8. The application of the method according to any one of claims 1 to 6 in increasing timber yield in Chinese fir plantations.

9. The application of the method according to any one of claims 1 to 6 in improving the yield of standard timber species in Chinese fir plantations.

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