| Soil and water conservation plantation is an important means to control soil erosion.The red soil hilly area in Hunan Province is the main soil erosion area.Studying the soil and water conservation effect of the Melaleuca alternifolia plantation is of great significance for enriching the choice of soil and water conservation plantation.Melaleuca alternifolia has been widely regarded as a plant that can produce essential oils of plants.It has also been introduced in the south of China,but few people pay attention to its soil and water conservation effect.The paper selected the different forest ages of the Phyllostachys pubescens planted in the Ningyuan County of Hunan Province as the research object,and obtained the physical properties of the soil and the biomass of the forest by field sampling and experiment,and applied the one-way analysis of variance and correlation.Analysis,redundancy analysis and factor analysis studied the soil and water conservation effects of the Melaleuca alternifolia plantation,and the main results were as follows:(1)The change of dry water holding capacity,leaf water holding capacity and branch water holding capacity of the Phyllostachys pubescens plantation is consistent with the change of forest age,and increases with the increase of forest age.The total water holding capacity is 7 years old(181.53 t/hm').>5 years old(150.05t/hm')>3 years old(91.15t/hm')>1 year old(29.56t/hm~2),the growth rate is 208.36%,64.62%,20.98%,showing a trend of slowing growth.The changes of water holding capacity,herb water holding capacity and water holding capacity of the shrubs in the Melaleuca alternifolia were consistent with the change of forest age,and increased with the increase of forest age.The total water holding capacity was 7 years old(6.96 t/hrrm~2).5 years old(6.52t/hm~2)>3 years old(5.88t/hm~2)>1 year old(5.14t/hm~2)?the growth rates were 14.4%,10.88%and 6.75%,respectively,showing a trend of slower growth.(2)According to the mean value,with the increase of forest age,the natural moisture content of soil is 23.833%of 1-year-old plantation,and the lowest is 22.667%of 7-year-old plantation.The overall trend is gradually decreasing;soil capillary water holding capacity The performance was 31.611%for the first year and 24.546%for the 7-year-old,which showed a downward trend with the increase of the forest age.The maximum water holding capacity of the soil was 50.568%for the 1-year-old,and the minimum was 37.769%for the 7-year-old.With the increase of forest age,it shows a downward trend,and its decline rate increases with the increase of forest age;the minimum water holding capacity of soil is 50.568%for 1 year,and the smallest is 37.769%for 7 years,with the age of forest.It increases and shows a downward trend,and its rate of decline increases with the increase of forest age.(3)The annual surface runoff produced by the different forest ages of the Melaleuca alternifolia plantation decreased with the increase of the forest age,which was as follows:the maximum annual growth rate was 6.14 t/100 m~2,and the minimum runoff was 7.48 t at 7 years./100m~2,the rate of decreasing with the increase of forest age is 3.91%,10.01%and 15.63%,respectively.The rate of decrease is increasing year by year;the maximum annual output is 154.1 kg/100m~2 for 1 year,followed by 3 years.It is 153.4 t/100 m~2,and the smallest is 101.7 kg/100 m~2 in 7 years.The overall trend shows a decrease with the increase of forest age.The rate of decrease is 3.72%,15.63%and 21.39%,respectively.Increase year by year.(4)With the increase of forest age,the soil bulk density showed an increasing trend.The increase rate of the soil increased with the increase of forest age was 4.97%,3.79%and 5.16%,respectively.The increase rate first decreased and then increased;the total soil porosity continued to increase.The decreasing trend,the rate of decrease with the increase of forest age is 3.74%,5.75%%and 5.79%,respectively,and the rate of decrease is increasing rapidly;the porosity of soil capillary is decreasing,and the rate of decrease increases with the age of the forest.The changes were 1.34%,5.16%and 4.97%,respectively,and the rate of decrease first increased and then decreased;the porosity of soil non-capillary tube showed a downward trend,and the rate of decrease with the increase of forest age was 11.18%,3.19%%and 7.28%,respectively.The rate of decrease of the soil first decreases and then rises;the ratio of soil aggregates to soil sample is 97.557%in 7 years and 87.597%in 3 years,which increases with the increase of forest age,and the 3 years old plantation The decline trend is 4.19%;the soil water stability index shows an increasing trend as a whole,and the rate of increase increases with the increase of forest age-1.76%,34.35%and 12.65%,respectively,and the rate of change rises first and then decreases.;Showed a rising trend of soil permeability as a whole,the rate of its rise with increasing stand age change was 10.43%,17.49%and 11.46%,respectively.(5)RDA showed that the relationship between stand characteristics and stand water holding capacity was significant,and the effect of stand biomass on stand water holding capacity was slightly higher than that of stand growth amount,and the crown width,Tree height,litter biomass and tree biomass have the highest impact on stand water holding capacity.RDA showed that soil bulk density,soil water stability coefficient and annual sand yield,and annual surface runoff correlation were not significantly correlated and negatively correlated.Soil bulk density,soil water stability coefficient was related to soil water holding capacity,soil natural water content,and soil porosity.Insignificant and negative correlation,the soil water holding capacity,soil natural water content,soil porosity and annual sand yield,annual surface runoff correlation were significantly and positively correlated,indicating that the soil physical properties of plantation forest and soil water holding capacity contain a lot of correlation.And the correlation is significant.Overall,the total soil porosity and soil permeability coefficient have the highest impact on soil water holding capacity.(6)According to the factor score,the main component score is calculated,and the comprehensive score is obtained.The 7-year-old plantation has the highest comprehensive score of 3.461,and the 5-year-old plantation has the second comprehensive score of 1.003.The 3-year-old plantation has a comprehensive score again.For-1.571,the 1-year-old plantation had the lowest overall score of-2.989.It shows that with the growth of forest age,the soil and water conservation function of the Melaleuca alternifolia plantation is increasing year by year.The conclusions showed that the Melaleuca alternifolia plantation has strong soil and water conservation effect and can be used as soil and water conservation forest in the red soil hilly area of southern Hunan. |
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