The paddy field and forest significantly decreased , while the dry land , barren land and built - up land gradually increased . the further analysis of the change data shows that degree of land use in the study area was still in the developing stage during the year from 1998 to 2000 从变化结果的分析可知，在1998 2000年间，长乐市土地利用变化的主要类型为水田、林地、旱地和未利用地，表现为水田、有林地的明显减少，旱地、未利用地及居民地的大量增加。
Located at yellow river alluvial plain , the soil of heze is very suitable to the growth of many trees , just like poplar , paulownia and so on , so heze has some advantages of natural resources . and now , there are 4 , 000 , 000 mu woodlands , 10 , 820 , 000 mu forests in farmlands , 3800 , 000 mu intercrop of crop and paulownia . the ratio of forest to land is 28 . 6 % 目前,全市有林地面积发展到400万亩,农田林网1082万亩,农桐间作380万亩,林木覆盖率28 . 6 % ;林木蓄积量1320万立方米,约占全省总量的六分之一;林业一、二、三产业总产值100亿元。
Thesis establishes forest volume prediction model of red - birch ' s five - age group and the wooded area prediction model by rolling prediction and multi - step prediction of ann which structures are 5 - 25 - 5 and 4 - 10 - 1 . thesis predicts red - birch ' s five - age group volume and the wooded area of experimental district from 2000 to 2004 . in order to evaluate the precision of the model , the author establishes the gm ( 1 , 1 ) model 论文中应用人工神经网络滚动预测和多步预测方法，分别采用5 - 25 - 5和4 - 10 - 1神经网络结构建立实验区红桦5个龄组的蓄积量预测模型与有林地面积预测模型，预测了实验区2000 2004年红桦各龄组蓄积量以及有林地面积。
The paddy field decreased in 1970s and 1980s and then increased after 1990 , in 1973 , 1990 , and 2002 , the percentage of paddy field in the whole catchment is respectively 18 . 54 % , 15 . 02 % , and 17 . 00 % ; meanwhile , dry field experienced opposite change with the percentage respectively 22 . 41 % , 31 . 02 % , 21 . 23 % 灌木林和其他林地在70 、 80年代经历了较大幅度减少, 1990年后,两者变动均不大。灌草地总量在1973 1990年间变化不大,但转入和转出比较频繁,进入90年代后,灌草地显著增加。有林地、水域和建设用地持续增加。
In quantitative terms , from the year of 1973 to 1990 , the absolute change extent obey the following sequence : dry field ( 8 . 61 % ) > shrub land ( - 7 . 06 % ) > paddy field ( - 3 . 52 % ) > naked land ( 2 . 12 % ) > tea land ( - 1 . 92 % ) > forest land ( 1 . 06 % ) > grassland ( - 0 . 61 % ) > rural settlement ( 0 . 58 % ) > traffic and industrial land ( 0 . 53 % ) > water ( 0 . 1 % ) > urban land ( 0 . 06 % ) ; and from 1990 to 2002 , dry field ( - 9 . 79 % ) > grassland ( 3 . 33 % ) > forest land ( 3 . 18 % ) > paddy field ( 1 . 98 % ) > naked land ( - 1 . 45 % ) > rural settlement ( 0 . 85 % ) > shrub land ( 0 . 73 % ) > water ( 0 . 48 % ) > traffic and industrial land ( 0 . 47 % ) > urban land ( 0 . 27 % ) > tea land ( 0 ) from the year of 1973 through 2002 , the cultivated land increased and then decreased 从数量上来看, 1973 1990年,变化幅度从大到小依次是旱地>灌木林>水田>裸岩地>其他林地>有林地>灌草地>农村居民点>交通工矿用地>水域>城镇用地; 1990 2002年则为旱地>灌草地>有林地>水田>裸岩地>农村居民点>灌木林>水域>交通工矿用地>城镇用地>其他林地。各地类的变化方向和强度存在较大差异。 1973年至2002年,耕地总量经历了先增后减的变化。
