| The State Forestry Administration and the National Development and Reform Commission of China jointly issued the Outline of the 14 th FiveYear Plan for Forestry and Grassland Protection and Development,which clearly stated that " promoting comprehensive management of desertification and rocky desertification scientifically,strengthen restoration of degraded forests,and improving forest quality precisely".Pitaya（Hylocereus undatus）is one of the species selected for ecological management in karst rocky desertification（KRD）areas and plays a significant role in the restoration of degraded ecosystems and regional economy.In recent years,pitaya were found degrading that branches got yellow and decline of growth.So,it is urgent to carry out researches on the internal mechanism and quality-efficiency improvement of pitaya.Which is of great significance to promoting the control of rocky desertification and the development of ecological industry and promoting the revitalization of rural areas in rocky desertification areas.Based on the theories of natural geography and ecology,such as plant functional traits and ecological chemometrics,this paper aimed at the scientific problems and technological demands of degradation characteristics of pitaya,driving factors of degradation,nutrient cycling and limitation,quality and effectiveness,influencing mechanism of fruit quality in karst rocky desertification area.Guanling-Zhenfeng Huajiang was selected as the research area in the Guizhou plateau mountainous region,which represents the overall structure of karst ecological environment in south China.From2019 to 2022,through data collection and analysis,single-factor analysis,principal component analysis,multiple linear regression analysis,Pearson’s correlation analysis,redundancy analysis,and variance decomposition analysis,based on the research of degradation mechanism and improvement of quality and efficiency of pitaya in karst rocky desertification area,key technology research,and application demonstration whole chain designing,integrated deployment and modular promotion system research.This study focused on elucidating the degradation characteristics of pitaya,revealing the internal mechanism of degradation,putting forward quality and efficiency improvement technology of pitaya and carrying out application demonstration and verification,providing scientific and technological reference for ecological control of rocky desertification and sustainable management of ecological industry.（1）The degradation characteristics of pitaya in the rocky desertification area of karst plateau valley in southern China were clarified,and the response patterns of different degraded plant functional traits,soil traits,and fruit quality were revealed.The basic characteristics of the ecological adaptation strategies of different degraded pitaya forests were obtained,and the tree growth showed a degradation trend.The results showed that the twig functional traits（APH,ACW,ATL,ATD,ATT）and root functional traits（RMC,RNC,RKC）generally decreased with the increase of degradation,indicating that the plant’s ability to absorb water and nutrients decreased and showed a growth degradation.The analysis showed that there was a clear differentiation between twig and root functional traits at different stages of degradation,and there was a tradeoff strategy between twig and root functional traits,the whole trait group moved along the positive direction of axis 1 along the principal component axis with the degradation stage.Soil SMC showed an overall increased first and then decrease with the increase of degradation,while soil BD and EC showed an increase and TCP showed a decrease,indicating that soil water deficit and soil structure deterioration may lead to the degradation of pitaya stand growth;soil SOC,TN,TK,AN,and AP showed differences among degradation gradients,indicating that C,N,P,and K elements are one of the nutrient elements affecting pitaya degradation,and the effective state nutrients have an effect on pitaya growth.Soil C and P cycle enzymes generally decreased with the degradation gradient,and N cycle enzymes generally increased,and each soil enzyme showed the characteristic of surface aggregation.The enzyme stoichiometry C:N decreased significantly with degradation,while enzyme C:P,enzyme N:P,and vector length tended to increase and vector angle tended to decrease,indicating a change in soil microbial resource allocation strategy.AP and TN contents were the main drivers of variation in soil enzyme and ecological enzyme stoichiometry,with 47.5% and 24.3% of explanatory variables respectively.FDW showed a decrease across degradation;the overall decreasing trend of nutrient contents such as soluble solids,water content,soluble protein,and proanthocyanidins in LD,MD,and SD stages Compared with ND,the contents of soluble solid moisture content,soluble protein procyanidins and other nutrients in LD MD and SD stages showed a downward trend on the whole,and the comprehensive evaluation of fruit quality also showed a downward trend,indicating that the degradation of pitaya forest significantly reduced the yield and quality characteristics.These revealed the growth response and adaptation characteristics of pitaya at each degradation stage,and it is helpful to understand the degradation of pitaya and its adaptation mechanism to environment.（2）The mechanism of pitaya degradation in the rocky desertification area of karst plateau valley in southern China was elucidated,the relationship of plant,soil and fruit quality was analyzed,and the main driving factors of pitaya growth degradation,soil degradation and fruit quality degradation were derived.The study showed that the differences of C:N and P:K of root in different degradation stages were not significant;C:P,C:K,N:P and N:K showed the same trend,increasing first and then decreasing with increasing degradation（N:K difference was not significant）,indicating that growth degradation caused a disorder of nutrient element ratios in pitaya plants;overall N:P was lower than 14 for each degradation gradient（except LD）,indicating that pitaya growth was limited by N.The RDA and VPA analysis showed that the interaction between CWHC and N:K explained 20.1% of the variables for twig structural traits;while the interaction between SMC,CWHC,NCP,TK,AK and NAG,ACP explained 29.5% of the variables for root functional traits.The results showed that the interaction among soil physical properties（SMC,CWHC,NCP）,soil chemical properties（TK,AK,N:K）,and soil extracellular enzymes（NAG,ACP）was the driving factorof pitaya growth degradation.The overall soil quality decreased first and then increased with the aggravation of degradation,indicating that soil quality decreased due to the degradation of pitaya forest,and improved due to the large accumulation of soil organic residues difficult to decompose and transform later;analysis of soil barrier factors showed that moisture,bulk weight and nutrient contents of nitrogen,phosphorus and potassium were the main factors affecting soil quality,and soil texture needed improvement urgently.The results showed that plant traits promoted fruit quality,and soil traits also promoted or inhibited fruit quality RDA and VPA analyses showed that the explanatory variable of ATL on fruit quality was 16.36%,indicating that ATL was the main plant trait factor for fruit quality variation;while the interaction between CWHC and TK,N:K was the main soil factor affecting fruit quality（14.2% of explanatory variables）.The interaction between soil traits and plant traits explained 40.9% of the variance in fruit quality,indicating that the interaction between soil traits（CWHC,TK,N:K）and plant traits（ATL）was the main driving factors influencing fruit quality variation.This article revealed that the growth of pitaya in karstic rocky desertification areas is limited by N,dissects the relationship of plant functional traits,soil traits,and fruit quality,and identifies the main affecting factors of pitaya growth degradation,soil degradation,and fruit quality degradation,which is beneficial to propose better conservation measures in rocky desertification management and provide a reference for pitaya production management and quality cultivation technology.（3）Constructed the growth control,composite planting,water-saving sprinkler irrigation technology,soil improvement,and integrated planting and raising technology system and demonstration in the rocky desertification area of Karst Plateau Canyon in southern China.Due to the obvious fragility of the nature habitat in the rocky desertification area,forest trees are prone to degradation and limit the productivity of forest.For these reasons,the technical systems of growth regulation,compound planting,soil improvement,water-saving sprinkler irrigation technology,and integration of planting and raising are condensed to improve quality and efficiency.Through the demonstration,the growth control technology can reduce transpiration and prevent excessive competition for resources;the water-saving sprinkler irrigation technology can supplement water to overcome the drought stress in the karst habitat and achieve efficient use of water;the compound planting technology can regulate soil temperature and humidity,assist soil organic reconstruction and cultivate agglomerate structure;the soil improvement and integrated planting technology can cultivate soil fertility and improve soil properties.It effectively coordinates the relationship between light,temperature,water,fertilizer,yield,and quality,improved the flowering,fruiting,and fruiting capacity of twigs,reduced the consumption of nutrients by diseased and weak twigs,and improves the growth,soil,and fruit quality of pitaya obviously.The growth degradation is alleviated and the ecological and economic benefits are improved and increased,which promoteed the precise improvement of forest quality,vegetation restoration,and sustainable development of industry in rocky desertification management,and consolidateed the stability of rocky desertification ecological management and ecological industry. |
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