邊坡(po)生態防(fang)護(hu)的中(zhong)(zhong)使用的植物(wu)采(cai)用最多的是豆科、禾本(ben)科等(deng)，對灌木(mu)(mu)、喬木(mu)(mu)等(deng)木(mu)(mu)本(ben)植物(wu)研(yan)究(jiu)較少，實踐中(zhong)(zhong)也不(bu)太(tai)成功，但(dan)木(mu)(mu)本(ben)植物(wu)在生態防(fang)護(hu)中(zhong)(zhong)有自己的優勢。

   1、生(sheng)(sheng)(sheng)態(tai)防(fang)護(hu)(hu)的理論體系(xi)：生(sheng)(sheng)(sheng)態(tai)防(fang)護(hu)(hu)的目(mu)(mu)(mu)(mu)標之一是使植(zhi)(zhi)物存活(huo)(huo)(huo)并(bing)正(zheng)常生(sheng)(sheng)(sheng)長(chang)。然而長(chang)期以來，人們(men)僅把不(bu)良自(zi)然條件(jian)下(xia)樹或草(cao)坪的成(cheng)活(huo)(huo)(huo)作為(wei)研究(jiu)目(mu)(mu)(mu)(mu)的，并(bing)在栽培方面獲得(de)了(le)(le)很(hen)大成(cheng)功(gong)，形(xing)成(cheng)了(le)(le)一系(xi)列在不(bu)同(tong)條件(jian)下(xia)的施(shi)工(gong)(gong)工(gong)(gong)藝或技(ji)術，如(ru)植(zhi)(zhi)生(sheng)(sheng)(sheng)袋(dai)、土工(gong)(gong)網(wang)、三維(wei)網(wang)、草(cao)袋(dai)、保(bao)水劑(ji)、生(sheng)(sheng)(sheng)根粉(fen)等(deng)。現代(dai)生(sheng)(sheng)(sheng)態(tai)防(fang)護(hu)(hu)工(gong)(gong)程(cheng)則不(bu)能僅以植(zhi)(zhi)物存活(huo)(huo)(huo)為(wei)研究(jiu)目(mu)(mu)(mu)(mu)的。大量的施(shi)工(gong)(gong)實(shi)踐證(zheng)明，邊坡防(fang)護(hu)(hu)施(shi)工(gong)(gong)后，有的看似達到了(le)(le)生(sheng)(sheng)(sheng)態(tai)防(fang)護(hu)(hu)的目(mu)(mu)(mu)(mu)的，表(biao)面上植(zhi)(zhi)被恢復了(le)(le)，水土流失也得(de)到了(le)(le)一定的控制，但時(shi)間一長(chang)，由于植(zhi)(zhi)物長(chang)勢逐漸減弱，群落開始逆行演替，剛剛恢復植(zhi)(zhi)被覆蓋的土地又會退化為(wei)裸地，形(xing)成(cheng)水土流失現象。

   為發揮植(zhi)物持續永久的(de)綜合生態(tai)功能，應運用生態(tai)學原理構建(jian)一(yi)個(ge)和諧有序(xu)、穩定(ding)的(de)植(zhi)物群落，這(zhe)一(yi)點(dian)非常(chang)重要，其關鍵是護(hu)坡植(zhi)物的(de)選(xuan)擇。下面研究(jiu)在不同的(de)邊(bian)坡上(shang)制定(ding)物種配方應遵循的(de)原則(ze)。

   1.1  遵從植(zhi)(zhi)(zhi)物(wu)(wu)生(sheng)(sheng)(sheng)(sheng)(sheng)態(tai)習(xi)(xi)性(xing)，因地(di)制宜植(zhi)(zhi)(zhi)物(wu)(wu)的(de)(de)(de)生(sheng)(sheng)(sheng)(sheng)(sheng)態(tai)習(xi)(xi)性(xing)是指植(zhi)(zhi)(zhi)物(wu)(wu)生(sheng)(sheng)(sheng)(sheng)(sheng)長對環境條(tiao)(tiao)件(jian)的(de)(de)(de)要求，包(bao)括氣候(hou)生(sheng)(sheng)(sheng)(sheng)(sheng)態(tai)條(tiao)(tiao)件(jian)、土壤(rang)生(sheng)(sheng)(sheng)(sheng)(sheng)態(tai)條(tiao)(tiao)件(jian)、生(sheng)(sheng)(sheng)(sheng)(sheng)物(wu)(wu)生(sheng)(sheng)(sheng)(sheng)(sheng)態(tai)條(tiao)(tiao)件(jian)等。氣候(hou)生(sheng)(sheng)(sheng)(sheng)(sheng)態(tai)條(tiao)(tiao)件(jian)（光照、濕度(du)(du)、溫(wen)度(du)(du)等）影響植(zhi)(zhi)(zhi)物(wu)(wu)的(de)(de)(de)生(sheng)(sheng)(sheng)(sheng)(sheng)長繁殖，決(jue)定植(zhi)(zhi)(zhi)物(wu)(wu)能(neng)否順利越冬(dong)、越夏；土壤(rang)生(sheng)(sheng)(sheng)(sheng)(sheng)態(tai)條(tiao)(tiao)件(jian)（養(yang)分(fen)、肥力、結構、PH值、鹽分(fen)等）與植(zhi)(zhi)(zhi)物(wu)(wu)的(de)(de)(de)生(sheng)(sheng)(sheng)(sheng)(sheng)長密切相(xiang)關；生(sheng)(sheng)(sheng)(sheng)(sheng)物(wu)(wu)生(sheng)(sheng)(sheng)(sheng)(sheng)態(tai)條(tiao)(tiao)件(jian)關系著(zhu)植(zhi)(zhi)(zhi)物(wu)(wu)的(de)(de)(de)生(sheng)(sheng)(sheng)(sheng)(sheng)長發育。如果(guo)外界環境不(bu)能(neng)滿足植(zhi)(zhi)(zhi)物(wu)(wu)的(de)(de)(de)生(sheng)(sheng)(sheng)(sheng)(sheng)態(tai)習(xi)(xi)性(xing)，植(zhi)(zhi)(zhi)物(wu)(wu)生(sheng)(sheng)(sheng)(sheng)(sheng)長就要受(shou)到阻礙甚至發生(sheng)(sheng)(sheng)(sheng)(sheng)退(tui)化。因此，在選配(pei)植(zhi)(zhi)(zhi)物(wu)(wu)時應綜合(he)(he)考慮環境條(tiao)(tiao)件(jian)，因地(di)制宜合(he)(he)理種植(zhi)(zhi)(zhi)。

   1.2  保持物(wu)(wu)(wu)(wu)種(zhong)(zhong)(zhong)(zhong)多(duo)(duo)樣性(xing)(xing)(xing)，建立自然(ran)群(qun)(qun)(qun)落(luo)(luo)結構(gou)。目(mu)前，學術界就物(wu)(wu)(wu)(wu)種(zhong)(zhong)(zhong)(zhong)多(duo)(duo)樣性(xing)(xing)(xing)在(zai)(zai) 生(sheng)態系統中的(de)(de)(de)(de)(de)作(zuo)用提出了很多(duo)(duo)假設，如冗余種(zhong)(zhong)(zhong)(zhong)假設、零(ling)假設、特異反應假設、鉚釘假設等，對這個問題的(de)(de)(de)(de)(de)看法還沒有完全一(yi)致的(de)(de)(de)(de)(de)認識(shi)。多(duo)(duo)數(shu)生(sheng)態學家認為，物(wu)(wu)(wu)(wu)種(zhong)(zhong)(zhong)(zhong)多(duo)(duo)樣性(xing)(xing)(xing)是群(qun)(qun)(qun)落(luo)(luo)穩定(ding)的(de)(de)(de)(de)(de)一(yi)個重(zhong)要尺度(du)，物(wu)(wu)(wu)(wu)種(zhong)(zhong)(zhong)(zhong)多(duo)(duo)樣性(xing)(xing)(xing)指數(shu)高的(de)(de)(de)(de)(de)群(qun)(qun)(qun)落(luo)(luo)，物(wu)(wu)(wu)(wu)種(zhong)(zhong)(zhong)(zhong)之間往(wang)(wang)往(wang)(wang)形(xing)成(cheng)比較復雜的(de)(de)(de)(de)(de)關系，植(zhi)(zhi)物(wu)(wu)(wu)(wu)鏈或植(zhi)(zhi)物(wu)(wu)(wu)(wu)網更(geng)加趨于復雜，當面(mian)對來自外界環(huan)境的(de)(de)(de)(de)(de)變化或群(qun)(qun)(qun)落(luo)(luo)內(nei)部種(zhong)(zhong)(zhong)(zhong)群(qun)(qun)(qun)的(de)(de)(de)(de)(de)波動時，群(qun)(qun)(qun)落(luo)(luo)有一(yi)個較強(qiang)的(de)(de)(de)(de)(de)反饋系統，可以(yi)緩沖干擾。當某一(yi)物(wu)(wu)(wu)(wu)種(zhong)(zhong)(zhong)(zhong)發(fa)生(sheng)病(bing)蟲(chong)害時，不(bu)可能侵(qin)染所有的(de)(de)(de)(de)(de)物(wu)(wu)(wu)(wu)種(zhong)(zhong)(zhong)(zhong)，即病(bing)蟲(chong)害不(bu)易(yi)傳播。植(zhi)(zhi)物(wu)(wu)(wu)(wu)的(de)(de)(de)(de)(de)自然(ran)群(qun)(qun)(qun)落(luo)(luo)結構(gou)是草、灌、喬三位一(yi)體的(de)(de)(de)(de)(de)多(duo)(duo)層次的(de)(de)(de)(de)(de)復雜結構(gou)，物(wu)(wu)(wu)(wu)種(zhong)(zhong)(zhong)(zhong)多(duo)(duo)樣性(xing)(xing)(xing)指數(shu)高，在(zai)(zai)一(yi)般的(de)(de)(de)(de)(de)情(qing)況下抗(kang)外界干擾的(de)(de)(de)(de)(de)能力強(qiang)，即使群(qun)(qun)(qun)落(luo)(luo)中一(yi)種(zhong)(zhong)(zhong)(zhong)或幾種(zhong)(zhong)(zhong)(zhong)植(zhi)(zhi)物(wu)(wu)(wu)(wu)受到(dao)病(bing)蟲(chong)害的(de)(de)(de)(de)(de)危(wei)害而死亡，其他(ta)的(de)(de)(de)(de)(de)植(zhi)(zhi)物(wu)(wu)(wu)(wu)也(ye)會填補其留下的(de)(de)(de)(de)(de)空白。

   1.3  遵從生(sheng)(sheng)(sheng)態(tai)位原則，優化(hua)(hua)植(zhi)(zhi)(zhi)物(wu)配(pei)(pei)置基(ji)于(yu)物(wu)種多樣性(xing)的(de)考慮，在利用(yong)植(zhi)(zhi)(zhi)物(wu)進行(xing)邊坡防(fang)護(hu)時采用(yong)的(de)植(zhi)(zhi)(zhi)物(wu)種類較多，這(zhe)就要求擬定一(yi)個合(he)(he)理的(de)配(pei)(pei)方，因自然群落(luo)中(zhong)的(de)物(wu)種、種群不是(shi)偶然的(de)組(zu)合(he)(he)，而(er)是(shi)生(sheng)(sheng)(sheng)態(tai)上(shang)的(de)協調與組(zu)合(he)(he)。綠化(hua)(hua)植(zhi)(zhi)(zhi)物(wu)的(de)選(xuan)配(pei)(pei)除了要考慮它(ta)(ta)們的(de)生(sheng)(sheng)(sheng)態(tai)習性(xing)外(wai)，實(shi)際(ji)上(shang)還取決于(yu)生(sheng)(sheng)(sheng)態(tai)上(shang)的(de)協調與組(zu)合(he)(he)。這(zhe)是(shi)生(sheng)(sheng)(sheng)態(tai)防(fang)護(hu)工(gong)作關鍵的(de)一(yi)步，它(ta)(ta)直接(jie)關系(xi)到系(xi)統(tong)生(sheng)(sheng)(sheng)態(tai)功能的(de)發揮和(he)景觀價值(zhi)的(de)提(ti)高。因此，在選(xuan)配(pei)(pei)植(zhi)(zhi)(zhi)物(wu)時，應(ying)充(chong)分(fen)考慮植(zhi)(zhi)(zhi)物(wu)在群落(luo)中(zhong)的(de)生(sheng)(sheng)(sheng)態(tai)位的(de)特性(xing)，從空間(jian)(jian)、時間(jian)(jian)和(he)資(zi)源生(sheng)(sheng)(sheng)態(tai)位上(shang)的(de)分(fen)異來合(he)(he)理選(xuan)配(pei)(pei)植(zhi)(zhi)(zhi)物(wu)種類，使所選(xuan)擇植(zhi)(zhi)(zhi)物(wu)生(sheng)(sheng)(sheng)態(tai)位盡量錯(cuo)開，從而(er)避免種間(jian)(jian)的(de)直接(jie)競爭。

   1.4  遵從(cong)互(hu)惠共(gong)(gong)生(sheng)(sheng)(sheng)的(de)原理，協同植物(wu)(wu)(wu)之間的(de)關系在(zai)植物(wu)(wu)(wu)生(sheng)(sheng)(sheng)長(chang)(chang)(chang)(chang)(chang)發(fa)育(yu)(yu)過(guo)程中(zhong)，根系作為植物(wu)(wu)(wu)和土壤的(de)重(zhong)要界面，不僅是重(zhong)要的(de)吸收(shou)和代謝器官，而且是重(zhong)要的(de)分(fen)泌(mi)器官。它一(yi)方(fang)(fang)面從(cong)生(sheng)(sheng)(sheng)長(chang)(chang)(chang)(chang)(chang)介(jie)質(zhi)中(zhong)攝取養分(fen)和水分(fen)，另一(yi)方(fang)(fang)面也(ye)向生(sheng)(sheng)(sheng)長(chang)(chang)(chang)(chang)(chang)介(jie)質(zhi)中(zhong)分(fen)泌(mi)離子和大(da)量(liang)的(de)有(you)機物(wu)(wu)(wu)質(zhi)。當(dang)(dang)一(yi)些(xie)植物(wu)(wu)(wu)的(de)生(sheng)(sheng)(sheng)長(chang)(chang)(chang)(chang)(chang)發(fa)育(yu)(yu)有(you)利(li)時(shi)，它們互(hu)惠共(gong)(gong)生(sheng)(sheng)(sheng)，相(xiang)互(hu)促進生(sheng)(sheng)(sheng)長(chang)(chang)(chang)(chang)(chang)，如皂莢與七里香在(zai)一(yi)起生(sheng)(sheng)(sheng)長(chang)(chang)(chang)(chang)(chang)時(shi)，互(hu)相(xiang)都有(you)促進作用(yong)；當(dang)(dang)一(yi)些(xie)植物(wu)(wu)(wu)的(de)分(fen)泌(mi)物(wu)(wu)(wu)對其(qi)(qi)他植物(wu)(wu)(wu)的(de)生(sheng)(sheng)(sheng)長(chang)(chang)(chang)(chang)(chang)發(fa)育(yu)(yu)不利(li)時(shi)，就會影響其(qi)(qi)生(sheng)(sheng)(sheng)長(chang)(chang)(chang)(chang)(chang)。群落中(zhong)植物(wu)(wu)(wu)的(de)分(fen)泌(mi)物(wu)(wu)(wu)對其(qi)(qi)他植物(wu)(wu)(wu)的(de)生(sheng)(sheng)(sheng)長(chang)(chang)(chang)(chang)(chang)發(fa)育(yu)(yu)有(you)很大(da)的(de)影響，在(zai)選(xuan)配植物(wu)(wu)(wu)種時(shi)應高(gao)度重(zhong)視。

   2、生(sheng)(sheng)(sheng)(sheng)態(tai)(tai)(tai)防護(hu)的(de)(de)(de)(de)(de)現狀：目前，在(zai)生(sheng)(sheng)(sheng)(sheng)態(tai)(tai)(tai)防護(hu)中草(cao)(cao)(cao)(cao)(cao)坪應用比較(jiao)廣泛。根據草(cao)(cao)(cao)(cao)(cao)種(zhong)(zhong)(zhong)(zhong)(zhong)對氣候的(de)(de)(de)(de)(de)適應性(xing)(xing)，可將草(cao)(cao)(cao)(cao)(cao)種(zhong)(zhong)(zhong)(zhong)(zhong)分為(wei)冷(leng)(leng)季(ji)型(xing)(xing)(xing)草(cao)(cao)(cao)(cao)(cao)種(zhong)(zhong)(zhong)(zhong)(zhong)（早(zao)熟禾屬(shu)(shu)(shu)(shu)(shu)、羊茅屬(shu)(shu)(shu)(shu)(shu)、黑麥(mai)(mai)草(cao)(cao)(cao)(cao)(cao)屬(shu)(shu)(shu)(shu)(shu)、胡枝子(zi)屬(shu)(shu)(shu)(shu)(shu)、薹草(cao)(cao)(cao)(cao)(cao)屬(shu)(shu)(shu)(shu)(shu)、三葉(xie)草(cao)(cao)(cao)(cao)(cao)屬(shu)(shu)(shu)(shu)(shu)、百(bai)脈根屬(shu)(shu)(shu)(shu)(shu)等）暖(nuan)季(ji)型(xing)(xing)(xing)草(cao)(cao)(cao)(cao)(cao)種(zhong)(zhong)(zhong)(zhong)(zhong)（狗(gou)(gou)牙根屬(shu)(shu)(shu)(shu)(shu)、狼尾草(cao)(cao)(cao)(cao)(cao)屬(shu)(shu)(shu)(shu)(shu)、地(di)毯草(cao)(cao)(cao)(cao)(cao)屬(shu)(shu)(shu)(shu)(shu)、鈍(dun)葉(xie)草(cao)(cao)(cao)(cao)(cao)屬(shu)(shu)(shu)(shu)(shu)、假儉(jian)(jian)草(cao)(cao)(cao)(cao)(cao)屬(shu)(shu)(shu)(shu)(shu)、馬蹄金(jin)屬(shu)(shu)(shu)(shu)(shu)、畫眉草(cao)(cao)(cao)(cao)(cao)屬(shu)(shu)(shu)(shu)(shu)等）、過(guo)(guo)渡型(xing)(xing)(xing)草(cao)(cao)(cao)(cao)(cao)種(zhong)(zhong)(zhong)(zhong)(zhong)（野牛(niu)草(cao)(cao)(cao)(cao)(cao)屬(shu)(shu)(shu)(shu)(shu)、結縷草(cao)(cao)(cao)(cao)(cao)屬(shu)(shu)(shu)(shu)(shu)等）。在(zai)邊(bian)坡(po)防護(hu)工(gong)(gong)程中大都選(xuan)擇一(yi)些(xie)根系(xi)發達(da)(da)、固(gu)土能(neng)(neng)力強的(de)(de)(de)(de)(de)草(cao)(cao)(cao)(cao)(cao)種(zhong)(zhong)(zhong)(zhong)(zhong)，如早(zao)熟禾、黑麥(mai)(mai)草(cao)(cao)(cao)(cao)(cao)、羊毛草(cao)(cao)(cao)(cao)(cao)、狗(gou)(gou)牙根、假儉(jian)(jian)草(cao)(cao)(cao)(cao)(cao)、鈍(dun)葉(xie)草(cao)(cao)(cao)(cao)(cao)、馬蹄金(jin)等，然后采用合理的(de)(de)(de)(de)(de)施工(gong)(gong)技(ji)術播種(zhong)(zhong)(zhong)(zhong)(zhong)，并精心(xin)呵護(hu)以(yi)保證一(yi)定(ding)(ding)的(de)(de)(de)(de)(de)成活(huo)率(lv)。早(zao)期，種(zhong)(zhong)(zhong)(zhong)(zhong)子(zi)發芽(ya)(ya)率(lv)高、出芽(ya)(ya)整齊，如黑麥(mai)(mai)草(cao)(cao)(cao)(cao)(cao)，播種(zhong)(zhong)(zhong)(zhong)(zhong)7天后，發芽(ya)(ya)率(lv)可達(da)(da)到90%以(yi)上(shang)(shang)，1個月后原來裸露的(de)(de)(de)(de)(de)邊(bian)坡(po)就披上(shang)(shang)了(le)(le)綠裝。表面上(shang)(shang)看植(zhi)(zhi)被恢復了(le)(le)，水土流失(shi)(shi)得(de)到了(le)(le)控(kong)制，生(sheng)(sheng)(sheng)(sheng)態(tai)(tai)(tai)環境得(de)到了(le)(le)改善，但這種(zhong)(zhong)(zhong)(zhong)(zhong)好(hao)景不長(chang)(chang)，短則一(yi)年半載(zai)，長(chang)(chang)則2~3年就會發生(sheng)(sheng)(sheng)(sheng)衰退現象(xiang)。如華南地(di)區引進的(de)(de)(de)(de)(de)多(duo)年生(sheng)(sheng)(sheng)(sheng)黑麥(mai)(mai)草(cao)(cao)(cao)(cao)(cao)，不耐高溫、不能(neng)(neng)越(yue)夏，在(zai)夏天很快就消(xiao)失(shi)(shi)，不能(neng)(neng)完成世代交替，但麥(mai)(mai)草(cao)(cao)(cao)(cao)(cao)在(zai)初期生(sheng)(sheng)(sheng)(sheng)長(chang)(chang)非常(chang)旺盛(sheng)，有競爭優(you)勢。為(wei)達(da)(da)到四(si)(si)(si)季(ji)常(chang)青的(de)(de)(de)(de)(de)效(xiao)(xiao)(xiao)果，在(zai)邊(bian)坡(po)工(gong)(gong)程中還(huan)常(chang)常(chang)采取(qu)冷(leng)(leng)季(ji)型(xing)(xing)(xing)草(cao)(cao)(cao)(cao)(cao)和暖(nuan)季(ji)型(xing)(xing)(xing)草(cao)(cao)(cao)(cao)(cao)混播的(de)(de)(de)(de)(de)措施，但因暖(nuan)季(ji)型(xing)(xing)(xing)草(cao)(cao)(cao)(cao)(cao)在(zai)冬天枯萎后常(chang)阻礙(ai)冷(leng)(leng)季(ji)型(xing)(xing)(xing)草(cao)(cao)(cao)(cao)(cao)的(de)(de)(de)(de)(de)發芽(ya)(ya)、繁殖，冷(leng)(leng)季(ji)型(xing)(xing)(xing)草(cao)(cao)(cao)(cao)(cao)在(zai)夏天又阻礙(ai)暖(nuan)季(ji)型(xing)(xing)(xing)草(cao)(cao)(cao)(cao)(cao)的(de)(de)(de)(de)(de)發芽(ya)(ya)、繁殖，還(huan)是(shi)很難達(da)(da)到四(si)(si)(si)季(ji)常(chang)青的(de)(de)(de)(de)(de)效(xiao)(xiao)(xiao)果。究其原因，我們認為(wei)這種(zhong)(zhong)(zhong)(zhong)(zhong)生(sheng)(sheng)(sheng)(sheng)態(tai)(tai)(tai)防護(hu)工(gong)(gong)程旨在(zai)利(li)用人工(gong)(gong)的(de)(de)(de)(de)(de)方法加快植(zhi)(zhi)被恢復過(guo)(guo)程，往往違背了(le)(le)自然演替規律，在(zai)選(xuan)配植(zhi)(zhi)物時，大多(duo)只考慮單個物種(zhong)(zhong)(zhong)(zhong)(zhong)的(de)(de)(de)(de)(de)生(sheng)(sheng)(sheng)(sheng)態(tai)(tai)(tai)習性(xing)(xing)，欠考慮物種(zhong)(zhong)(zhong)(zhong)(zhong)間的(de)(de)(de)(de)(de)競爭關系(xi)，忽略了(le)(le)物種(zhong)(zhong)(zhong)(zhong)(zhong)多(duo)樣性(xing)(xing)對生(sheng)(sheng)(sheng)(sheng)態(tai)(tai)(tai)系(xi)統功能(neng)(neng)的(de)(de)(de)(de)(de)貢獻。另外，草(cao)(cao)(cao)(cao)(cao)本植(zhi)(zhi)物在(zai)水土保持(chi)功能(neng)(neng)上(shang)(shang)也有一(yi)定(ding)(ding)的(de)(de)(de)(de)(de)缺陷(xian)：一(yi)是(shi)根系(xi)較(jiao)淺，固(gu)坡(po)護(hu)坡(po)效(xiao)(xiao)(xiao)果差；二(er)是(shi)群落易發生(sheng)(sheng)(sheng)(sheng)衰退，二(er)次恢復很困難；三是(shi)管理費用高；四(si)(si)(si)是(shi)外來物種(zhong)(zhong)(zhong)(zhong)(zhong)的(de)(de)(de)(de)(de)大量(liang)采用，對生(sheng)(sheng)(sheng)(sheng)態(tai)(tai)(tai)安(an)全有很大風險(xian)。

   3、灌(guan)木(mu)在生(sheng)態護(hu)(hu)坡(po)(po)中的(de)(de)(de)(de)作(zuo)用(yong)(yong)我(wo)國的(de)(de)(de)(de)邊坡(po)(po)坡(po)(po)度(du)一(yi)般為45°，有的(de)(de)(de)(de)甚至達到(dao)(dao)60°以(yi)上，單純(chun)用(yong)(yong)草(cao)本(ben)(ben)植物(wu)(wu)雖然覆(fu)蓋度(du)大、美觀，初(chu)期植被均勻整齊，但防護(hu)(hu)效果不太(tai)理想，而栽植喬木(mu)又(you)會提高(gao)坡(po)(po)面(mian)負載，在風力作(zuo)用(yong)(yong)下極易造(zao)成坡(po)(po)面(mian)的(de)(de)(de)(de)不穩定或坍塌。隨著實踐經驗的(de)(de)(de)(de)提高(gao)，人(ren)們(men)逐(zhu)漸認識到(dao)(dao)灌(guan)木(mu)綠化具有的(de)(de)(de)(de)優(you)勢(shi)。灌(guan)木(mu)不僅具有良好的(de)(de)(de)(de)抗(kang)(kang)旱、保(bao)水、保(bao)土(tu)、防風沙、降(jiang)塵土(tu)、抗(kang)(kang)鹽堿等優(you)點，而且生(sheng)長(chang)快、耐貧瘠、對(dui)土(tu)壤(rang)(rang)要求不高(gao)，和(he)草(cao)本(ben)(ben)植物(wu)(wu)相比，優(you)勢(shi)相當(dang)明顯：一(yi)是(shi)灌(guan)木(mu)類木(mu)本(ben)(ben)植物(wu)(wu)根系的(de)(de)(de)(de)先端部位能(neng)向(xiang)土(tu)壤(rang)(rang)母(mu)質內部延伸，增強邊坡(po)(po)的(de)(de)(de)(de)穩定性。二(er)是(shi)維(wei)護(hu)(hu)管理作(zuo)業(ye)量(liang)(liang)小，灌(guan)木(mu)對(dui)水、肥的(de)(de)(de)(de)需求量(liang)(liang)少，適應(ying)性強。三是(shi)對(dui)小氣候(hou)的(de)(de)(de)(de)改善(shan)作(zuo)用(yong)(yong)明顯，能(neng)緩和(he)陽(yang)光的(de)(de)(de)(de)熱(re)輻射，使酷熱(re)的(de)(de)(de)(de)天氣降(jiang)溫、失(shi)燥(zao)，給(gei)人(ren)以(yi)舒適的(de)(de)(de)(de)感(gan)覺。同時(shi)由(you)于(yu)灌(guan)木(mu)的(de)(de)(de)(de)生(sheng)物(wu)(wu)量(liang)(liang)比草(cao)本(ben)(ben)植物(wu)(wu)大，進(jin)行光合(he)作(zuo)用(yong)(yong)吸(xi)收(shou)的(de)(de)(de)(de)二(er)氧化碳(tan)多，吸(xi)滯煙灰粉塵，稀釋、分解、吸(xi)收(shou)和(he)固定大氣中的(de)(de)(de)(de)有毒有害物(wu)(wu)質也較多，能(neng)更好的(de)(de)(de)(de)凈(jing)化空(kong)氣。但單一(yi)的(de)(de)(de)(de)灌(guan)木(mu)群(qun)落(luo)也易產生(sheng)表土(tu)侵蝕，對(dui)初(chu)期的(de)(de)(de)(de)保(bao)水不利。因此，在邊坡(po)(po)防護(hu)(hu)過程中，植物(wu)(wu)的(de)(de)(de)(de)選擇以(yi)草(cao)本(ben)(ben)植物(wu)(wu)與灌(guan)木(mu)配合(he)為宜，二(er)者結合(he)，可起到(dao)(dao)快速持久的(de)(de)(de)(de)護(hu)(hu)坡(po)(po)效果，有利于(yu)生(sheng)態系統的(de)(de)(de)(de)正向(xiang)演(yan)替。

   但采用草(cao)本植(zhi)(zhi)物(wu)種子(zi)和灌木(mu)種子(zi)混播時，有時會不盡人意(yi)，常常形成(cheng)稀樹草(cao)原的格局，這是因為草(cao)本植(zhi)(zhi)物(wu)一(yi)般發(fa)(fa)芽早、成(cheng)坪快，往往扼殺剛剛發(fa)(fa)芽的灌木(mu)幼苗。所(suo)以(yi)在(zai)今天的綠化施(shi)工中，一(yi)般先(xian)種植(zhi)(zhi)生長(chang)速度快、成(cheng)坪快的先(xian)鋒(feng)草(cao)本植(zhi)(zhi)物(wu)，以(yi)達(da)到快速恢(hui)復(fu)植(zhi)(zhi)被，控制早期水土流失(shi)的目的，然后(hou)因地制宜栽植(zhi)(zhi)灌木(mu)。