Material Accumulation And Energy Characteristics Of Coastal Shelterbelts Under Different Human Disturbance Patterns

Coastal shelterbelts were natural barrier to coastal areas, it played an important role to withstandnatural disasters and protect ecological environment of coastal areas. However, because of humandisturbance, the structure and function of coastal shelterbelts was changed, in addition, long-termsuffering of pure forest management caused much ecological problems increasingly demonstrate, suchas soil fertility decline, pests exacerbated, forest aged and incomplete, update difficulty. Materialcycling and energy flow were the two basic processes of ecosystems, which had great significance toreveal the stability and sustainability of ecosystems. This paper took4forests (A: nature secondaryforest which almost not be disturbed; B: mix forest, planting Casuarina and Pinus after selectivecutting nature secondary forest; C: Casuarina plantationⅠ, planting Casuarina and protectingundergrowth after cutting nature secondary forest; D: Casuarina plantationⅡ, planting Casuarina anddisturbing undergrowth frequently after cutting nature secondary forest) with different patterns ofhuman disturbance as material, studied the communities’ biomass、plant carbon content and forestcarbon storage、plant nutrient elements content and forest nutrient elements accumulation contents、thedifference of caloric values among plants and standing crop of energy, and analyze its causes, in orderto provide basic information for the sustainable management of coastal shelterbelts. The resultsshowed that:1. Biomass of layer trees under different human patterns disturbance decreased in the followingorder D>C>A>B, while undergrowth decreased in the following order A>B>C>D, showed that withdisturbance intensity increased, biomass decreased gradually. Biomass of forests decreased in thefollowing order D>A>C>B, biomass of tree layer of plots A was less than the plots C, than biomass ofundergrowth higher than plots C, making the total biomass of plots A higher than plots C. With theintensity of human disturbance increasing, biodiversity of undergrowth increased at first thanreduction. The relationship between biomass and biodiversity of undergrowth was not obvious.2. Combined with analysis of variance shows that the differences of carbon content of differentorgans from the same tree were significan（tP<0.05）, while plants of undergrowth from the same layer were not significant（P>0.05）. The average carbon content of conifer species (49.18%) higher thanbroad-leaved species (45.27%), the average carbon content of evergreen broad-leaved species (45.49%)and deciduous tree species (45.05%) was similar. The carbon content of different layers decreased aslignification decrease, which decreased in the following order: tree layer﹥shrub layer﹥liana layer﹥herbaceous layer.3. The carbon storage of tree layers under different patterns of human disturbance weredecreasing in the order of D>C>A>B. The carbon storage of undergrowth decreased with disturbanceintensity increasing and the trends was A> B> C> D. The chance of carbon storage of forests wassame to tree layers.4. The nutrient elements contents of leaf was the highest among different organs of the same tree,than stem was the lowest and K, Ca, Mg were in center. The characteristics of nutrient elementscontents were that, in large number elements, the content of N was the most, P was the lowest and K,Ca, Mg were in center while the content of Fe and Mn were significantly higher than Cu and Zn oftrace elements. The nutrient elements content of undergrowth were concentrated, and higher than treelayer. The nutrient elements accumulation of N was the highest, about half of total accumulation, Pwas the lowest, account for only about2%, the accumulation of trace elements ranged from1.37%to3.97%.5. N: P of4plots increased with the order of A (15.78)<B (29.09)<C (37.63)<D (41.24),indicating that plant growth by P restriction more and more obvious with disturbance intensityincreasing. The nutrient elements accumulation of forests under different disturbance patternsdecreased in the following order: A>D>C>B. Plots A had the highest accumulation, and2.63times toplots B,2.40times to plot C and2.10times to plot D.6. Combined with analysis of variance shows that leaves had the higher caloric values than otherorgans of the same tree, the difference was significant (P <0.05), than the differences were notsignificant between other organs and plants from the same layer of undergrowth (P>0.05). Caloricvalues of evergreen broad-leaved species were higher than deciduous tree species and coniferousspecies was higher than hardwood species. Caloric values of plantation trees (Casuarina equisetifolia,Pinus elliottii, Acacia crassicarpa）were higher than native tree species, than Litsea glutinosa had thehighest caloric values of native tree species. The caloric values of different layers decreased in thefollowing order: tree layer﹥liana layer﹥shrub layer﹥herbaceous layer. 7. Standing crop energy of plants in the tree layer under different human disturbance patternsdecreased in the following order D> C> A> B, energy of undergrowth decreased with disturbanceintensity increasing. As most of energy concentrated in the tree layer, therefore, the distribution rule ofstanding crop energy of forest was same to tree layers.8. The variation of carbon storage, standing crop energy of undergrowth under different humandisturbance patterns were same to biomass, carbon storage and standing crop energy decreased withdisturbance intensity increasing. The nutrient elements accumulation of forest were effected bybiomass and nutrient elements content, plots A had the highest nutrient elements accumulationrevealed that on the one hand, its plants had higher nutrient elements contents and soil was fertile,nutrient cycling was good, on the other hand it confirmed that issues as soil fertility decline and soildegradation were caused by long-term plant Casuarina equisetifolia.