Contents & Foreword, Characterizing And ... - IRRI books

●●●ecosystem classifications are diverse. Surface hydrology and land characteristicshave often been used exclusive of each other.The lack of specific criteria available in the classification systems hasalso hindered the reliable differentiation of the systems. For example, byusing only drought occurrence as a criterion, Ubon (Thailand), Tarlac (Philippines),and Raipur (Madhya Pradesh, India) are classified only as droughtpronerainfed lowlands, despite the vast difference in their biophysical characteristics(soil type, rainfall, amount and pattern of water retention, etc.).Such a classification reflects only the hydrological effect and assumes thatits generic causes are the same across sites, or does not take into account thecauses at all. Because of this, all the areas classified in a particular ecologyappear to be homogeneous in all respects across locations, which is far fromreality. This also indicates (proposes) the application of the same remedialmeasures to overcome the stress across locations.This issue mostly relates to aspects of scale and the spatial heterogeneitythat exists at every level. The issue here really is of the level of understandingthat is possible and needed. A better understanding is always morehelpful and can be achieved only through detailed analysis. Therefore, theanalysis of the spatial pattern of both the nature of occurrence of stress (e.g.,drought in early, mid, and late season or at different crop growth stages) andseverity of stress (e.g., degree of drought and its temporal feature and effecton the crop) should be included in the characterization, which can providemore meaningful interpretations, especially on management aspects, thanonly classification of the site in an ecological class.Unrelated criteria/parameters used in characterization at different levels.Even within a location/site, the parameters used at different levels are notonly different but also generically diverse. In such cases, the analysis at differentlevels cannot be integrated. Table 4 shows an example of parameterdiversity used at different levels. The information in this table also showsthat, in certain types of analysis, there is no direct relationship of any parameterused in one level to the parameters used in the next level. Therefore, theuse of related parameters becomes necessary if the analysis at different levelsis to be integrated.Exclusiveness of the levels of analysis. Unless the analysis at different levelsis done in a continuum, that is, within a given area, ecosystem, oragroecological zone, and by using related (common) parameters, its integrationand synthesis are extremely difficult.Unspecified definitions of rice environmental classes below the subecosystemlevel. There is no classification subdivision below the rice subecosystemlevel in any of the classification systems. Hence, different workers use differentterminologies, such as land management units, production units, riceenvironments, land-use units, etc. This is not a problem, however, if thereare equivalents and these can be specified. Also, from the review in thischapter, it has been noted that, at the higher levels of analysis, such as mega26 Singh et al