Effects of Land Cover on Soil Temperature，Humidity and Moisture in Phoebe bournei Forest

Jiyou WU，Minggao CHEN，Chunying DONG，Xiaofei HUANG，Mingjun HUANG，Yong CHENG，Qiu LlU，Qijun WU

1.Hunan Branch of Chinese Academy of Forestry，Changsha 410004，China；

2.High Quality Material Center of Hunan，Changsha 410004，China；

3.Hunan Jinlin Forestry Co.，Ltd.，Taoyuan 415701，China

Effects of Land Cover on Soil Temperature，Humidity and Moisture in Phoebe bournei Forest

Jiyou WU1，2*，Minggao CHEN1，2，Chunying DONG1，2，Xiaofei HUANG1，2，Mingjun HUANG1，2，Yong CHENG1，2，Qiu LlU1，2，Qijun WU3

1.Hunan Branch of Chinese Academy of Forestry，Changsha 410004，China；

2.High Quality Material Center of Hunan，Changsha 410004，China；

3.Hunan Jinlin Forestry Co.，Ltd.，Taoyuan 415701，China

Under the condition of high temperature，the effects of five cover patterns（clean tillage，film mulching，weed covering，branches and leaves covering and growing grass covering）on soil properties in young Phoebe bournei forest were investigated.The results showed that the five cover patterns all showed significant effects on soil properties in young Phoebe bournei forest under the condition of high temperature.Land cover increased land temperature in Phoebe bournei forest.Under the film mulching，the land temperature was increased most rapidly with the largestincrement.However，weedcovering，branchesandleavescoveringand growing grass covering decreased land temperature.Among them，growing grass covering showed the best cooling effect.The film mulching，weed covering，branches and leaves covering and growing grass covering all increased land humidity.The film mulching showed the best moisture-preserving effect in the early period，but in the late period，the humidity in the film mulching treatment group was lower than that in the clean tillage treatment group.Among the five mulching patterns，moisture loss in the film mulching treatment group was slowest and least，followed by those in the weed covering and branches and leaves covering treatment groups，and moisture loss in the growing grass covering treatment group was fastest and most.

Soil management；Land cover；Land temperature；Land humidity；Soil moisture

P hoebe bournei（Lauraceae: Phoebe）is a large evergreen tree［1］.The trunk of Phoebe bournei is straight，and wood texture is fine.Its whittling section is smooth and beautiful with aroma.Phoebe bournei is a kind of precious timber for senior architecture，furniture，wood carvings and precise wood patterns，and is also endangered and second-class pro tected species in China［2-3］.Therefore，Phoebe bournei has great economic value and development prospects［4］.In recent years，with deepened understanding on value of Phoebe bournei for timber and landscaping，artificial afforestation of Phoebe bournei has attracted more and more attention［5-7］. Li et al.［8］investigated the effect of nutrient content on growth of Phoebe bournei seedlings.Many scholars also conducted studies on seedling technology［9-12］，seedling traits［13-14］and cutting seedling［15-16］of Phoebe bournei.In this study，the effects of land cover on soil temperature，humidity and moisture in Phoebe bournei forest were investigated so as to provide theoretical support for high-yielding cultivation of Phoebe bournei and to promote scientific development of Phoebe bournei forest management.

Land cover，as a regulation technology for soil management，has attracted more and more attention，and many researches have been conducted on this technology.Studies have found that land cover can increase biomass，suppress weeds and increase soil nutrients，thereby improving root environment，promoting plant growth and increasing fruityield，etc［17-23］.Most previous studies have focused on ecological and production efficiency brought by land cover's improving soil environment，but there are rare reports on effects of land cover on soil properties in extreme cases.Soil properties determine soil fertility，directly influencing the growth of plants［24-29］.The studies on effects of land cover on soil properties in extreme cases will help to the adoption of appropriate cover pattern for reducing losses.Total five cover patterns were designed in this study，and theireffects on soilproperties in Phoebe bournei forest were investigated so as to explore the appropriate way for regulating soil environment，protect plant growth and provide scientific reference for further landscaping management.

Materials and Methods

Overview on test site

The test was conducted in the experimentalbase ofHunan Jinlin Forestry Co.，Ltd.located in Pantang Town， Taoyuan County， Hunan Province.The test site has a subtropical monsoon climate with annual average temperature of 16.4℃，annual average relative humidity of 81%，annual average rainfall of 1 480 mm，annual sunshine of 1 531 h and frost-free period of 286 d.The test site，with an altitude of 150 m，has typical hilly topography.The soil is quaternary red clay with moderate fertility，pH of 5.0-6.5 and organic matter content of 0.5%-2%.The soil is suitable for growth of a variety of tree species.The soil conditions were basically the same within the test site.

Test design

Totalfive land coverpatterns（clean tillage （control），film mulching，weed covering，branches and leaves covering and growing grass covering）were designed.There were three replicates for each land cover pattern，and there were three young Phoebe bournei trees for each replicate.

In the clean tillage treatment group，the surface soil beneath the canopies of the Phoebe bournei trees was plowed shallowly and weeded，and covered with nothing.In the film mulching treatment group，the surface soilbeneath the canopies ofthe Phoebe bournei trees was covered with colorless and transparent polyethylene plastic film in the depth of 0.06 mm.In the weed covering treatment group，weed was spread out on the ground around the trunks（6 m（L）× 1.2 m（W）×10 cm（H）for each）.In the branches and leaves covering treatment group，the waste branches and leaves were spread out on the ground around the trunks（6 m（L）×1.2 m（W）×10 cm （H）for each）.In the growing grass covering treatment group，weeds in the Phoebe bournei forest grew arbitrarily（6 m（L）×1.2 m（W）for each）.

The test observation began after a rainstorm on July 20，2013，and ended on August 14，2013.During this period，the weather was all sunny with continued high temperature.

lndicator measurement and methods

The measurement was carried out during 9:00 to 11:00 am every day. The measured indicators included land temperature，land humidity and soil moisture contents at various soil layers.The final data were expressed as the means.Based on the calculated results，the figures were drawn.

Theweathertemperaturewas measured on the ground of the test site.The land temperature and humidity were measured by temperature and humidity measuring instrument（CENTER313，Qunte，Taiwan）；the soil moisture contents（volumetric water content of soil）at the depths of 5，10，15 and 20 cm were determined using soil moisture meter（FieldScout TDR100，USA）.

Data processing and analysis

The processing and analysis of data，as well as drawing of figures，were conducted using Microsoft Office Excel 2007.In addition，correlation analysis was conducted.

Results and Analysis

Effect of different land cover pattern on land temperature in Phoebe bournei forest

As shown in Fig.1，during the test period （26 d），the daily weather temperatures were all higher than 35℃，and the average weather temperature was also up to 36.8℃.In the five land cover treatment groups，the land temperature was all increased continuously.In the film mulching treatment group，the increment of land temperature was fastest and largest.On the 13rd d，the land temperature was increased to 50℃，which was lasted till the end of the test.The average land temperature in the film mulching treatment group （47.6℃）was higher than that in the control group by 6.7℃，and it was also the highest among the five treatment groups.The increment of land temperature in the weed，branches and leaves and growing grass covering treatment groups was relatively slow and small.In the three treatment groups above，the land temperatures were all lower than that in the control group；there was no significant difference in land temperature between the weed and branches and leaves covering treatment groups；the land temperature in the growing grass covering treatment group was lowest.The land temperature in the film mulching treatment group was even higher than the weather temperature，but the land temperatures in the weed，branches and leaves and growing grass covering treatment groups were all lower than the weather temperature.It suggests that under the condition of high temperature，film mulching will increase land temperature，but weed，branches and leaves or growing grass covering will decrease land temperature.

Effect of different land cover pattern on land humidity in Phoebe bournei forest

As shown in Fig.2，during the test period，the land humidities in the branches and leaves，weed and growing grass covering treatment groups were all higher than 60%，and they were all higher than that in the control. In addition，the decrease rates of land humidity in the three treatment groups were also lower than that in the control group.In overall，the land humidities in the three treatment groups ranked as growing grass covering＞branches and leaves covering＞weed covering. In the first 15 d，the land humidity（100%）in the film mulching treatment group was much higher than those in the other treatment groups.Since the 15thd，the land humidity in the film mulching treatmentgroup declined rapidly，and it decreased from 100%tothat lower than that of the control group within only two days.This decline lasted till the end of the test.In the early test period，soil moisture content was higher，and water evaporated rapidly and greatly.However，plastic film is un-permeable，and it blocked the evaporation of water vapor.Thus the humidity beneath the film reached 100%.In the later period，the temperature under the film rose with time.The soil moisture content was reduced，and water evaporation became less.The evaporated water under the film was much more than that supplied by soil.Even worse，the air under the film could not communicate with the outside world.Therefore，the water vapor under the film was reduced greatly，and land humidity was also reduced rapidly to that lower than that in the control group.

Effect of different land cover pattern on soil moisture in Phoebe bournei forest

As shown in Fig.3，the differences in soil moisture among the five land cover patterns became small with the proceeding of the test，which was consistent with the finding of Yamanaka et al［7］.In the late period，soil moisture content was not reduced further，and it was remained at a state of dynamic equilibrium.This was because that soil moisture moved in various forms all the time，and it flows from high-potential position to low-potential position［8］.When soil moisture is in equilibrium，soilhas been under drought stress.At the depth of 0-5 cm，after certain times，the soil in the film mulching（19 d），branches and leaves covering（18 d），weed covering（17 d）and growing grass covering （11 d）treatment groups all entered a drought state.In terms of strength of waterpreserving effect，the five land cover patterns ranked as film mulching＞branches and leaves covering＞wed covering ＞ clean tillage ＞ growing grass covering.In the late period，at the depth of 0-5 cm，the soil moisture contents in the five treatment groups ranked as film mulching＞branches and leaves covering≈ weed covering＞clean tillage＞growing grass covering.The variations in soil moisture content at the depths of 5-10，10-15 and 15-20 cm were similar to that at the depth of 0-5 cm.The longer time the soil requires to reach the equilibrium state is，the slower the soil water loss is.The higher the soil mois-ture content is，the less the water loss is.From a comprehensive point of view，the moisture holding capacities of the five land cover patterns ranked asfilm mulching ＞ branchesand leaves covering＞weed covering＞clean tillage＞growing grass covering.

Conclusions and Discussion

The study results showed that land cover had significant effects on land temperature，land humidity and soil moisture under the condition of high temperature.Film mulching greatly increased land temperature，but branches and leaves covering，weed covering and growing grass covering all decreased land temperature under the condition of high temperature. Among the three treatments，growing grass covering showed the best cooling effect，while there was no significant difference in cooling effect between branches and leaves covering and weed covering.In terms of land humidity，branches and leaves covering，weed covering and growing grass covering all increased soil humidity under the condition of high temperature. Among the three treatments，growing grass covering showed the best moisturizing effect，followed by branches and leaves covering，and weed covering showed relatively weak moisturizing effect.The effect of film mulching on land humidity was complex.In the early period，film mulching showed the best moisturizing effect among the land cover treatments.While in the late period，land humidity in the film mulching treatment group was even lower than that in the control group. Film mulching，branches and leaves covering and weed covering all could delay and reduce soil moisture loss，while growing grass covering accelerated and increased soil water loss. Considering the water retention capacity，the five land cover treatments ranked as film mulching＞branches and leaves covering＞weed covering＞clean tillage＞growing grass covering.In summary，film mulching had high water retention capacity under the condition of high temperature. However，the high airtightness of plastic film led to excessively high temperature beneath plastic film，affecting plant growth.This also confirmed the view that film mulching technique is more suitable for low temperature drylands［30］.Weed covering and branches and leaves covering could increase soil moisture and regulate soil temperature and humidity.These findings were consistent with the study results of a number of foreign scholars［31-33］.In addition，weed covering and branches and leaves covering could also increase soil moisture content and increase crop yield［31-34］.Therefore，weed covering and branches and leaves covering are more adaptable in forestry production.

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Responsible editor：Tingting XU

Responsible proofreader：Xiaoyan WU

地表覆盖对闽楠林地土壤温度、湿度和土壤水分影响

吴际友1，2*，陈明皋1，2，董春英1，2，黄小飞1，2，黄明军1，2，程勇1，2，刘球1，2，吴其军3（1.中国林科院湖南分院，湖南长沙 410004；2.湖南省优质用材工程技术研究中心，湖南长沙410004；3.湖南金淋林业有限公司，湖南桃源415701）

以闽楠幼林林地土壤为对象，研究在高温下5种不同覆盖方式（清耕处理、地膜覆盖、杂草覆盖、枝叶覆盖、生草覆盖）对土壤性状的影响。结果表明，5种覆盖方式在高温下对土壤性状产生了影响：地膜覆盖提高了地表温度，且地膜覆盖下的地表温度上升最快，上升幅度最大，杂草覆盖、枝叶覆盖和生草覆盖则降低了地表温度，生草覆盖的降温效果最好；地膜覆盖、杂草覆盖、枝叶覆盖和生草覆盖都能提高地表湿度，其中地膜覆盖前期保湿效果最好，后期则低于清耕处理；地膜覆盖的土壤水分散失最慢最少，杂草覆盖和枝叶覆盖次之，生草覆盖的水分散失最快最多。

土壤管理；地表覆盖；地表温度；地表湿度；土壤含水量

湖南省林业科技计划项目“闽楠、红椿家具材良种选育与应用”（XLK201406）。

吴际友（1963-），男，湖南桃源人，研究员，博士，主要从事森林培育研究。*通讯作者，E-mail：hnforestry@sina.com。

2015-09-10

SupportedbyForestryScienceandTechnologyProgram ofHunan Province（XLK201406）.

*Corresponding author.E-mail:hnforestry@sina.com

Received:September 10，2015 Accepted:November 10，2015

修回日期 2015-11-10